G.Ali Mansoori 1, H. Lindsey Barnes 2, Glenn M. Webster3

Chapter 19, Pages 525-556, 2003 Manual 37 - Fuels and Lubricants Handbook: Technology, Properties, Performance, and Testing ASTM Manual Series: MNL37WCD ______P.O. Box C700, ASTM International, West Conshohocken, PA 19428-2959 ______WAXES ARE USUALLY SOLID AT ROOM TEMPERATURE because they contain linear paraffinic with carbon chains of various lengths. Waxes can vary in consistency from easily try as a gelling agent for organic solvents·and as a raw mate­ kneadable to brittle. They exhibit relatively low viscosity at rial used. in lipstick formulations for the cosmetic market. temperatures slightly above their melting point. The Carnauba is recognized generally as safe by the United ap­pearance of waxes Can vary from translucent. to opaque, States Food and Drug Administration. but they are not glassy. The consistency (i.e., hardness) and is harvested from the shrubs Eurplwrbiea solu­bility of waxes depends on the temperature at which they antisiphilitica, E. cerifera, and Pedilanthuspavonis in Mexico are observed. and southwest Texas. The candelilla wax is recovered after The use of waxes dates back more than 5000 years. As early the entire mature plant is uprooted and immersed in acidi­ as 4200 B.C. the Egyptians extracted a waxy �ubstance from fied boiling water. During the immersion, the candelilla wax the honeycomb of bees and used it to satw:ite · linen floats to the surface and is skimmedoff. The primarymarket wrap­pings of mummies [!]. The spulptured porittaffof the for candelilla wax is cosmetics where it is a component in lip­ de­ceased decorating a coffin cover was often modeled stick formulations. The chemical composition of carnauba in and painted with pigmented beeswax. Another use and candelilla wax is listed in Table 2. of wax was in the preparation of erasable writing tablets. Synthetic waxes are derivedfrom either the Fischer-Trop­ Fas­tening together several tablets with fiber produced sch process [7] or by ethylene based polymerization pro­ forerun­ners. of the modernbook [2]. cesses [8]. The Fischer-Tropsch (F-T) process originated in Waxes are classified by the matter from which they are de­ Germany inthe 1920s and is illustratedschematically in Eq rived: insect, vegetable, synthetic, and mineral [3]. Beeswax is I. The F-T process was developed to synthesize hydrocarbons an example of insect wax. The chemical composition of and oxygenatedcompounds froma mixtureof hydrogen and beeswax is. unique and its characteristics vary with the carbonmonoxide. DuringWorld War II, the F-T process was species of the honeybee. Apis mellifera is the most common · used by Germanyto produce fuelsfrom coal-derived gas. The cultured bee in the world and will provide a chemical first commercial plant in South Africa started in 1955 at gener­alization of composition of wax for this species [ 4 ]. Sasolburg,using coal as a feedstock.The so-calledSasol pro­ Beeswax is secreted in eight glands on the underside of the cess is illustratedin Fig. I [9]. This plant produces waxes, fu­ worker bee. Bees are believed to secrete one pound of wax £Or els, pipeline gases (i.e., ethylene, methane), and other prod­ every eight pounds of honey they produce. Since secreted ucts using a fixed bed catalyst F-T process. During the F-T beeswax read­ily absorbs color, the final color of the beeswax process, carbon monoxide, which is generated from coal is influenced by the source of the pollen. A typical composition gasification, is reacted under fixed-bed conditions using ° analysis of beeswax is provided in Table I. Beeswax is high-pressure at approximately 220 C in the presence of an extracted by melt­ing or boiling the honeycomb in water and iron catalyst to produce synthetic waxes, as has applications in pharmaceuticals and cosmetics, and is the shownin Eq1. Typicalreaction products that may be derived primarycom­ponent of religious . from the F-T process are listedin Table 3. Vegetable waxes are extracted from the leaves, bark, and berries (seeds) of plants and trees. Abnost all multi-cellular 2nH2 + nCO ->Cn H2n + nHzO (1) plants are covered by a layer of wax [5]. Only a few species Poly(ethylene) waxes may be prodticed by the industrial grown in semiarid climates produce enough wax to be com­ polymerization of ethylene using high or low pressure ethy­ mercially viable for recovery. Carnauba and candelilla wax lene polymerizationtechnology [10], or as thermal decompo­ are two of the most common vegetable waxes that are com­ sition products of the polyethylene polymers. The molecular mercially marketed [6]. is removed from the weights and melting points of the synthetic waxes as com­ dried leaves (fronds) of palm trees grown in the northeast pared with the Fischer-Tropsch waxes are listed in Table 4. re­gion of Brazil. Carnauba is utilized in the polish paste The market stability of pricing and availability of insect indus- and vegetable waxes is affected by climate conditions and naturaldisasters. With the advent of the petroleumindustry, 1 University of Illinois at Chicago, Chicago, IL 60607-7052. the waxes from mineral and synthetic sources surpassedthe 2 CITGO Petr. Corp., H.W. 108 S., P.O. Box 1578, Lake Charles, LA annual production of the combined total of the other two wax 70602. categories. Waxes frominse ct and vegetable sources are mix­ 3 63 Rocklege Rd., Hartsdale,NY 10530. tures of long chain fatty acids, esters of aliphatic alcohols, and hydrocarbons. Waxes from mineral origins are chemi- 525 Petroleum Waxes G.Ali Mansoori, H. Lindsey Barnes, Glenn M. Webster Chapter 19, Pages 525-556, 2003, Manual 37 - Fuels and Lubricants Handbook: Technology, Properties, Performance, and Testing, ASTM Manual Series: MNL37WCD ______526

TABLE I-Compositionalanalysis of beeswax. TABLE3-Products derivedfrom the Fischer-Tropsch process. Component Amount in wt. % Approx. Typical Monoesters, C1sli.31COOC3oH61;C2s Hs1COOC30�1 55-65 Product Yield (wt.%) Diesters, triesters, hydroxydiesters 8-12 Paraffins (i.e., methane,ethane, propane, 7.2 Free fatty acids,C23COOH-C 31COOH 9.5-10.5 andbutane) Free fattyalcohols, C340H-C360H 1-2 Olefins(i.e., methylene, ethylene, propylene, 5.6 Hydroxy-monoesters,C 14H29CH(OH)COOC26H61 8-10 andbutylene) r a Hydrocabons , C2sHs2-C31H64 12-15 Gasoline (Cs-Cu) 18.0 Moistureand mineralimpurities 1-2 Diesel (C,2-C") 14.0 C19 to C23 7.0 aHydrocarbons most commonly found in beeswax include nonacosane Medium Wax (C24-C3s) 20.0 (C2�) and nentriacontane (C31H64). HardWax (>C,s) 25.0 Water soluble non-acidchemicals 3.0 Water soluble acids 0.2

TABLE 2--Chem.ical¢-, composition of camauba andcandelilla wax. Component Carnauba (wt.%) Candelilla (wt.%) TABLE 4-Comparisonof Fischer-TroJ)Schwaxes withother Monoesters 83-88% 28-30% synthetic waxes. Fattyalcohols 2-3 2-3 Free fatty acids 3-4 Type of Wax MolecularWeight Melting�oints; °C Hydrocarbonsa 1.5-3.0 7-9 Fischer-Tropschwax 500-1200 85-110 Resins 4--6 49-574--6 Low Pressurepolyethylene 900-3000 90-125 Moistureand inorganic residue 0.5-1 2-3 wax High Pressurepolyethylene 500-4000 85-130 aHydrocarbons commonly found in camauba and candelilla wax are prin­ wax cipally hentriacontane (C31l¼) and tritriacontane (C33f4s). Pyrolysisa waxes 1000-3000 90-130 aPyrolysis waxes arederive

cally inert and are primarily composed of straighfchain P0WER WATER COAL PLANT (paraffinic)hydrocarbons. STEAM Petroleum wax may vary compositionally over a wide range of molecular weight, up to hydrocarbon chain lengths AIR of approximately CS0-C60. It is typically a solid at room temperature and is derived from relatively high boiling petroleum fractions during the refining process. Petroleum waxes are a class of mineral waxes that arenaturally occur­ NH, MWCAS TARACID PIJBI1'JCAIION ring in various fractions of crude petroleum. They have a COz+lfiS wide range of applications that include: coating of drinking 1lREGAS cups; an adhesives additive; production of candlesand rub­ ber; as components of hot melts, inks, and coatings forpaper; and they can be used in asphalt, caulks, and binders. This chapter will provide a review of petroleum waxes including history,production, types, chemical composition, molecular structure, and property testing.

w: 0 DISCUSSION f---+CO,

C, C,IC, Classification of Crude Oils and Chemical .------, Structure of Ingredients OILS Petroleum crude oil, commonly referred to as crude oil, is a complex mixture of hundreds of compounds including solids, liquids, and gases that are separated by the refining process. Solid. components at room temperature iriclude asphalt / bitumen and inorganics. Liquids of increasing vis­ C,, cosity vary from gasoline, kerosene, diesel oil, and light and heavy lubricating stockoils. Alsoinclud ed are themajor com­ FIG. 1-Generalized Sasol Plant for hydrocarbon synthesis . ponents of natural gas, which include methane, ethane, by the_ Fischer-Tropsch Process. propane, and butane (11). An elemental analysis of crude oil shows that it consists of primarily two elements: hydrogen (11-14%) and carbon CHAPTER 19: PETROLEUMWAXES 527

TABLE 5-Crudeoil content. Crude Type Solvent NeutralOil BaseOil Wax.Content Sulfurand Nitrogen Asphalt APIGravity" ASTM Test Method Paraffinic base Yes Yes <10% Low No >40 E-1519 Naphthenicbase No Yes No Low No <33 D-2864 Intermediatebase No Yes <6% Low Yes 33-40 D-8 Asphaltic base No Yes 0% High Yes <10 D-1079 aAmerican PetroleumInstitute gravityis an arbitraryscale expressing the densityof liquid petroleumproducts. The measuringscale is calibratedin terms of degreeAPI (0API) andcan be calculatedin termsof the formula:0 AP[= 141.5/(SGL[60°F)) - 131.5 whereSG L stands forliquid specificgravity with respect to wa­ ter. The higher the value of API gravity, the more fluidthe liquid.

(83-87%). Crudeoil hydrocarbons contain long hydrocarbon TABLE6-ASTM test methods used forsampling, separation, and chains (saturated and unsaturated), branch structures, and classification of various oil samples and the proceduresused. ring structures,with each having specificphysical and chem­ Test Method Procedureand Application ical properties. Small quantities of other compounds con­ D4057 Practice for manual sampling of petroleum and taining sulfur, oxygen, nitrogen, carbon, and hydrogen are petroleum products frequently present in crudeoils. D270 Sampling of petroleum and petroleum products Crude oils are generally classifiedbased on their predomi­ D4007 Centrifuge method for determination of water and sediment in crudeoil nant hydrocarbon structure type, as shown in Table 5. The D86 Distillationof petroleumproducts types are :['.eferred to as paraffi.nic, naphthenic, intennediate D2007 Clay-gel absorptionchromatography for oil- samples (mixture of paraffinic and naphthenic crude), and asphaltic of initial boiling point of at least 260°C (500°F} into base crude (12]. the hydrocarbon types of polar compounds, aro­ matics and saturates, andrecovery of representa­ Paraffinic hydrocarbon fractions are saturated linear or tive fractionsof these types branched . Naphthenic fractions containfive and six D2425 Mass· spectrometryfor classification of hydrocarbon carbon cyclic (alicyclic) structures. Naphthenes are typ'es-in middle-distillate monocyclic inthe lower-boiling fractions (i.e., gasoline) and D2549 Elution chromatography for separation of represen­ polycyclic in the higher-boiling fractions(i.e., lubricatingoils) tative aromatics and non-aromatics fractions of high-boiling oils, between 232 aod 538°C (450 aod (13]. The asphaltic crudes contain unsaturated aromatic 1000°F) structures containing rings of five and six member carbon D2786 High ionizing voltage mass spectrometryfor hydro­ atoms. Aromaticsare definedas those classes of organic com­ carbon types analysis of gas-oil saturate fractions pounds that behave chemicallylike benzene. Theyare cyclic, D2887 Gas chromatography for boiling range distribution ofpetroleum fractions unsaturated organiccompounds that can sustain an induced D3239 High ionizing voltage mass spectrometry for aro­ electronic ring current due to delocalization of electrons matic typesanalysis of gas-oil aromatic fractions around the ring.Aromatic base oils contain 20-25% aromatic D3279 Titration for determination of the weight percent of compounds. A constituent of asphalticcrudes is asphaltene. asphaltenes as defined by insolubility in normal Asphaltenes are defined as the high molecular weight non­ heptane solvent hydrocarbon fractionof crudeoil precipitated by a designated paraffinicnaphtha solvent at a specifiedtemperature and sol­ vent-oil ratio (14]. Like the naphthenic crude, the aromatic tallinewax. Those formed from naphtenes are knownas mi­ ringsare monocyclic in the lower boiling fractions and poly­ crocrystallinewax. A hydrocarbonin pure state has definite cyclic in the higher boiling fractions. Various ASTM test boiling and freezing (or melting) points, whichcan be mea­ methods listedin Table. 6 are used forsampling, separation, sured in the laboratory(16]. Knowingthe intermolecular en­ and characterization of petroleum fractions. ergy parameters or critical properties and acentric factor Petroleum waxes are derived fromboth paraffinic and in­ and/orrefractive index of hydrocarbons, one can predict their termediate crude oils and are composed of threebasic carbon boiling point using vapor pressure correlations or equations structures (i.e., linear, branched, and ring) that are charac­ of state as discussed in Section I of thisreport. However, such teristic of the crude oil. methods are not capable· of predicting pure hydrocarbon freezingpoints. There are other methods that can be used to Production, Transportation, and Refining of Waxy predict hydrocarbonand wax freezing(melting) point, which Petrolenm Crndes] include but are not limited to variational statisticalmechani­ cal theory (17] and cell-lattice theories(18]. The majorityof crude oils produced aroundthe worldcontain substantial amounts of . These compounds, Waxy Crude Oil sparingly soluble in solution components of the crude oils, A waxycrude usually consists of: (a) a varietyof light and in­ crystallizeat lower temperatures andare the major contribu­ termediate hydrocarbons (paraffins, aromatics, naphtenic, tors to petroleum wax deposits [IS]. The wax present in etc.); (b) wax as defined above; and (c) a variety of other petroleum crudes primarilyconsists of paraffinhydrocarbons heavy organic (non-hydrocarbon) compounds, even though (C18-C36), known as paraffinwax, and naphtenic hydrocar­ at very low concentrations they include resins, asphaltenes, bons (C30-C60). Hydrocarbon components of wax can exist diamondoids, organometallics, etc. Whenthe temperature of in various states of matter (gas, liquid, or solid) depending on a waxy crude oil is lowered to its cloud point, first the heav­ their temperature and pressure. When these hydrocarbons ier fractions of its wax content start to freezeout. ,Upon low­ freeze, they form crystals, which are known as macrocrys- ering of the temperature of a crude oil to its pour point al- ---;,_;:_ --

528 MANUAL37: FUEI.SAND LUBRICANTS HANDBOOK

most all the fractions of its wax content will freeze out. A waxy crude is characterized by its cloud point and pour point, which are measured according to ASTM Test Methods D 2500 and D 97, respectively, as they are dis.cussed later in thisreport. A clean waxy crude is definedas a crude oilin which there exists only hydrocarbons and wax as its only heavy organic constituent. As the clean waxy crude flows through a cold ·pipe or conduit (with a wall temperature below the cloud · point of the crude) wax crystalsmay be formed on the wall, which could then growuntil possibly the whole inner wall is covered with the encapsulating oil �ide the wax layers. As the wax thickness increases, pressure drop across the pipe needs to be increased to maintain a constant flow rate. As a result, the power requirement forthe crudetransport will in­ crease. The arterial blockage problems of clean waxy crude can be efficientlycontrolled by insulation and heating of the pipe to a temperature above its cloud point. Most of the ex­ isting wax depositionproblems of the clean waxy crudes are due to the lack of proper insulation and heating systems. As FIG. 2-Pipeline petroleum transport plugging due to a result, application of chemical anti-foulants and frequent wax and other heavy organics depositions (Courtesy of use of pigging operationshave become necessary[15]. Regu­ Phillips Petroleum Company). lar paraffinic or waxycrudes are widespread.The majorcom­ plex systems problems relatedto the production, processing, and transportation of these medium-gravityfluids is not just To predict the deposition as a functionof time, principlesof en­ crystallization of their wax content at low temperatures, but ergy and mass conservation,the Jaws of diffusion,and the prin­ the formationof deposits that do not disappearupon heating, ciples,of phase transitionsneed to be considered [21,22]. In or­ and will not be completely removed bypigging. der to prevent or remediate arterial blockage/fouling and Regular waxy crudesare not clean and, in additionto wax, facilitate the production of regularwaxy crudes, many issues they contain other heavy organics such as asphaltene, resin, must be undertaken: (a} detailedfluid properties charact eriza­ etc. [1 SJ. Asphaltenesdo not generallycrystallize upori cooling tion, (b} production scheme alternatives, (c} retrograde con­ and, for the most part, they may not have definite freezing densationand depositionbehavior prediction, (d) onsets of de­ points. Depending on theirnatures, theseother heavy organics positionstudies, (e) equipment and facilityoptions, (f) design will have different interactions with wax, which could either and use of chemical anti-foulants and/or pour-point depres­ prevent wax crystal formation or enhance it. Existence of sants and blending alternatives, (g} performancespecification branched paraffins, aromatics, naphtenes, and resins in and maintenance planning, and (h) transportation, storage, petroleum,however, contributeless to µtesedeposits, but mod­ and blending studies[23,24]. ify their crystallization behavior. However, asphaltene pres­ ence in the crude oil could prevent or erihancewax deposition PetroleumRefining . depending in the microscopic natureof asphaltene [19 ,20]. Crude oil is first desalted if salty, deasphalted if asphaltenic, The precipitation of wax frompetroleum fluids during pro­ and dewaxed if highly waxy, beforeit is distilledin an atmo­ duction and transportation maygive rise to a varietyof prob­ spheric distillation unit to separate light ends (gases}, naph­ lems [17]. One ofthe main problems observedis depositionof tha, gasoline, jet, kerosene, gas oil distillate, and residuum solid material on well and pipe walls as demonstratedin Fig. (resid) (see Fig. 3). The residuum (resid) remaining afterthe 2. This happensif (a} the temperatureof the wall is below the atmospheric distillation is then further fractionated in a vac­ cloud point of the oil, {b) a negative radial temperaturegradi­ uum distillation unit into fractions that are distinguishable ent is present in the flow, (c} the wall frictionis high enough by viscosity for further processing into lubricating oil base for wax crystalsto stick to the wall, and (d} asphaltene present stocks. Wax is concentrated in the distillate stream and the in the crude oil has already deposited and has increased the residuum fraction is used to produce the base oils forlubri­ frictionof the wall (changed of wettability) and acting as mor­ cant formulation. Both the distillate and residual lube frac­ tar for the sticking together of wax crystals. Wax crystalliza­ tions (stock) contain unde.sirable constituents such as aro­ tion may cause three problems: (a} higher viscosity, which maticsthat must be removed by extraction to yield baseoils leads to pressure losses, (b) high yield stressfor restartability that arethermally stable with a sufficientlyhigh viscosity in­ of flow, and (c} fouling of petroleum flowarteries [15]. dex• product. The distillate fraction is extracted with a sol- To predict wax deposition tendency of a crude oil it is im­ portant to know its composition forparaffin wax and the other 4 Viscosity Index is defined as V.I. = (µL - µx)/(µL - µH), where µL components is the viscosity at 100°F of the zero-V.I. oil, µH is the viscosity at present in, or added to, the crude oil; their com­ ° ° position distributions; and the pressureand temperatureof the 100 F of thel00 V.I. oil, and µxis theviscosity at-100 F of the un­ known (test) oil. See ASTM D 567 and D 2270 for further detail. A system. Thermodynamics and statistical mechanics of phase measure of the magnitude of viscosity changes in lubricating oils transitionsin polydisperse mixturescan be utilizedto develop withchanges in temperature.The higherthe viscosity index number, predictive models forwax deposition in petroleumfluids [17]. the more resistantthe oil is to changein viscosity. CHAPTER19: PETROLEUMWAXES 529 vent (such as furlural) that has a greater solubility (selective point (i.e., the temperature where the oil ceases to be fluid)is solvent) forthe components having a low viscosityindex. The reduced. residuum fractionis extractedwith propane to remove bitu­ men (asphalt) and resinous material. The desirable oil and wax component is solubilized for further processing. SolventDewaxing Process The nonsoluble portion of the distillate extraction and the The solvent dewaxing process can be divided into three dis­ soluble portion of the residuum fraction are referred to as the tinct sections: (a) crystallizationof the wax components by di­ raffinate phase and both contain the more paraffinic oil. lutionand chllling, (b) filtrationof the wax from thesolution Wax, which typicallyex hibits a hlgh viscosityindex, remains of dewaxed oil and solvent, and (c) recovery of the solvent in the raffinatephase forfurther processing. Because the raf­ fromthe dewaxed oil and wax products [25]. To overcome the finate produced from the extraction process contains wax, hlgh pour point, a solvent dewaxing process has been devel­ whlch crystallizes at relatively hlgh temperatures (> IS°F = oped to remove the wax fromlubricating oil basestocks, as -9.4°C), the fluidityof the base oil that exhibits a hlgh pour shown in Fig. 4. The most widely used solvent dewaxing pro-

Water

Desaldng Naplrta

Nater Gasoline, Jet, Kerosene Crude Storage Tank Distillate Dewaxed Oil v&ccum Dis�on

FIG. 3-Schematlc Illustration of various possible locations of wax production in petroleum refining.

OilyWax Receiving Product Shipped

mended Product

OilyWax 1----..-C.,,stallization ...... Storage ......

-- Wu: a .Fliall sai... t Oil S!an,p

Stop W.XIB'Faall 01 Prailllc!Wu: FIG. 4-Solvent dewaxing process for the removalof wax from lubri­ cating oil slackwax basestocks. 530 MANUAL 37: FUELSAND LUBRICANTSHANDBOOK

90 dewaxing process. The major process variables include: 1) 80 solvent composition, 2) feedstockcomposition, 3) solvent di­ 70 lution procedure, 4) filtration temperature, 5) filtration pro­ 00 cedure, and 6) solvent recovery method. - 50 1. Ketone based solvents are excellent solvents foroils at low �- 40 temperatures necessary to remove the wax by filtering. Di­ 'S 30 luting the raffinatewith too much ketone-based solventcan ·15 20 "" cause the oil to separateinto a distinctl ayer. Oilphase sep­ 1 10 arationwill adverselyaffect the yield of wax and result in s 0 OilPhase the wax portion having an undesirable higher oil content. u Sepa�tion •IO The likelihood of oil phase separation can be determined -20 experimentally by maintaining a constantsolvent dilution - 30 ratio andchanging the percentageof ketone content. -40 2. If the raffinate feedstock contains a high proportion of .50 paraffinic content, it will have a high viscosity or viscosity 30 40 50 00 W 80 90 � index. An oil phase separation can occur when a ketone­ % MEK ContentIn DewuSolvent based dilution solventis mixed with the raffinate. FIG. 5-lllustration of the effect of the ratio of MEK to the 3. The amount of dilution with the solvent can affect the oil petroleum fraction being dewaxed on the resulting cloud point content of the wax. Using a solventdilution greater than 2 of the mixture. partssolvent to 1 partraffinate will result in a re.ductionof theoil content of thewax. 4. The cooling temperatureused to crystallizethe wax during the filtration process can affect the oil content of the wax cesses are based on solvent mixtures of methyl ethyl ketone and the desired physical properties such as melting point . andtoluene, methyl ethyl ketone and methylisobutyl ketone, and hardness.If thedilution solvent is too cold or low cool­ or methyl isobutylketone itself. Figure 5 illustratesthe effect ing temperatures areused, the crystalsize of the waxformed of the ratio of MEK to the petroleumfraction being dewaxed on the surfaceof the rotaryfilter will be small and will re­ on the resulting cloud point of the mixture. In the dewaxing tain more oil. As the dewaxing temperature is reduced, process, the raffinate (feedstock) is diluted with solvent and , softer and lower melting point wax fractions will increase heated 15-20°F (-8-11 °C), above the cloud point of the raffi­ the overall production yield. As illustrated in Table 7, as a nate/solvent mixture( or slurry)and chilled at controlledrates in double-pipe scraped-surface heat exchangers and chillers. The slurry is chilled to 5-20°F ( -3-11°C) below the desired pour point of the oil.When the wax/solventsolution is cooled, wax crystals precipitate from the solution, which are then removed by filtrationusing a rotary vacuum filter. The crys­ i 40. tallized wax formsas a layer (cake) on the surfaceof the rotary - vacuum filter. The wax cake (filtrate) is washed with a spray I 30 of a cold solvent to remove any residual oil beforebeing dis­ a charged from the primary filters. At this point, the wax 6 contains10--40% oil and is referredto as "slack wax"if it is de­ M '20 rived from the distillate lube fraction, or "petrolatum" if it is I derivedfrom the residual lube fraction.Figure 6 illustratesthe effect of solvent dilution ratio on the amount of residual oil 10 content in the slack wax. To produce waxes with lower oil contents ( <5%), an addi­ tional dewaxing processis performed.The waxcake fromthe 0 primary filteris diluted with additionalsolvent and filteredin �· 2;I 3'I 4:1 5;1 6;1 a second (repulp) rotary vacuum filter using the same oper­ ating conditions as the primary filters to obtain the desired FIG. 6-lllustration of the --effect of solvent dilution ratio on wax oil content. the amount of residual oil content in the slack wax. The solvent is recovered from the dewaxed oil filtrate by flash vaporization and distillation. The solvent is recycled for future use in the dewaxing process. Residual solvent in the TABLE7-Effect of dewax temperatureon wax. waxis recovered by flashvaporization andis recycled forfu ­ ture process use. WaxNeedle Dewax Wax Wax Melt.Point Penetration Temperature Yield (ASTM D 127) @ 77°F (25°C) ("F) ("C) (%) ("F) ("C) (ASTM D 1321) DewaxingProcess Variables 60 15.6 62 141 60.6 11 Wax production yield, oil content of the wax, and the pour 55 12.8 67 139 59.4 13 point of base oil are directly affected by variables of the so 10.0 72 137 58.3 16 CHAPTER 19: PETROLEUM WAXES 531

lower dewaxing temperature is used, wax yield increases tween 1 and 3%. Petrolatums are derived from the residual and the melting point and softness change. lubricantfractions with oilcontents between10 and30% 5. The dewaxing process is performed to maximize the re­ coveryof the waxwith the desired oil content and physical Compositional and Molecular Characteristics of properties such as melting point and hardness. This re­ Petroleum Wax quires maintaining a uniform thickness(less than2.5 cm) Paraffinwaxes consist predominately of a mixtureof straight of the wax cake on the rotaryfilter by controlling the pro­ chain saturated hydrocarbon molecules (normal-alkanes) cess temperatures and rotational speed of the filter.Apply­ with the chemical formula C,,H + with n e: 16 [27,28]. In ing wash solvents (forreducing oil content) uniformlypre­ 20 2 orderto demonstrate the physical properties of straightchain vents cracking of the wax cake. Diluting with adequate saturated hydrocarbon molecules, Table 8 is reported as repulp solvent is necessaryto provide a sufficiently fluid taken from Ref 28. In this table the molecular weights, melt­ raffinate. ° ing points, latent heats of fusion, densities (at 20 C), specific heats in solid and liquid states, and boiling points of the nor­ The Wax Finishing Process mal alkanes from C1 to C100, all at atmospheric conditions, arereported. According to this table, the firstfour alkanes of The last step in producing petroleum waxes is the finishing the series, (from methane, CH., up to butane, C4H ) are process. This process involves the removalof odor and ques­ 10 gaseous at room temperature and atmosphericpressure. The tionable color. In addition, the finishingprocess mayinvolve alkanes between Cs and C17 are liquids and alkanes with steps to reduce the polycyclic hydrocarbons to a level that more than 17 carbon atoms are waxy solids at room temper­ meetsthe Food and Drug Administrationregulations forfood ature. The melting points and heats of fusion of alkanes in­ contact.5 crease with their number of carbonatoms. In additionto the Wax color removal may be performed by flowing wax n-alkanes, paraffin waxes may contain varying amounts of through a static bed of activated clay orbauxite. There is a iso- and cyclo-alkanes (i.e., branched chains and aliphatic production loss in the amount of wax after completing the rings).Typically, paraffin waxes contain carbonatom chains___ clay or bauxite contact process. ThiS loss is attributed tO ab­ of C18 to C44. Their macrocrystallinestructure is illustratedin sorption of the wax on the clay or bauxite medium and the Fig. 7. Their plate-like crystal structuresare illustratedby an production loss is greater for darker colored waxes. Newer atomic force microscopeimage given in Fig. 8. Their molec­ finishing process technology is based on hydrofinishing ular weights areusually less than 450 and their kinematicvis­ (fixed bed catalytic process ° ° usinghydrogen) and doesn't re­ cosity at 100 C (212 F) will usually be less than six centis­ quire any filtering medium. Hydrofinishing has the advan­ tokes. Being derivedfrom distillate fractions, paraffin waxes tage of processing waxes with negligible product loss [26]. have distinct boiling point curves that consist of a minimum If the wax exhibits a questionable odor (such as extraction andmaximum value. or dewaxing solvent odor), the wax may be steam stripped Microcrystalline waxes contain higher proportions of iso­ (distilled) to remove traces of processing solvent. Hydrofin­ and cyclo-alkanes (naphthenic) than paraffin waxes. Micro­ ishing may alsobe used to produce odor freewaxes. After the rystalllinewaxes exhibit molecular weights between 500 and wax has completed the finishing process step, it can be 700 with carbon atom chains rangingtypically from C23 to shipped to consumers; either in solid form (i.e., 22 kg car­ C85 in length. Their microcrystalline structure is illustrated tons) or as a molten liquid (in specialized tankswith electri­ in Fig. 9. Microcrystallinewaxes (microwaxes) exhibit kine­ calheaters or steam coils). ° matic viscosities greater than 10 centistokes at 100 C (212°F). Because microcrystalline waxes are derived from Types of Petroleum Waxes residual fractions, they do not havea distinct boiling range. Physical properties of microcrystalline waxes vary with the There are twogeneral types of petroleum waxesthat are pro­ typeof crude oil and processing conditions used to produce duced during the dewaxing process. Wax that is obtained the wax. Typically, m.icrocrystalline, naphthenic waxes ex­ from the distillate lubricating oil fractions is known as hibit needle-like microstructures. macrocrystalline wax (paraffin wax), and wax derived from Intermediate wax properties are intermediate between the residual distillatelubricating oil fraction is referred to as those exhibited by paraffin and microcrystallinewaxes. They microcrystalline wax (microwax). This nomenclature is generally exhibit viscosities between 6 and 10 centistokes at based on the crystal structure of the wax as seen through a 100°c (212°F) and a melting point between 155-165°F microscope (microstructure). A paraffin wax can be distin­ ( -68-7 4°C). Intermediate waxes are derived from the highest guished from a microwax by its larger c:rystal structure. boiling distillate lubricating oil fraction and like paraffin Paraffin waxes usually exhibit plate-like crystal structures waxes, they exhibit a distinct boiling point range. while microwaxesexhibit needle-like crystalstructures. Petrolatums are soft, unctuous products having a melting The composition, nomenclature,and physical properties of point between !00--149°F (-38-o5 °C). The term "unctuous" petroleum are related to the refinery process used in their means "smoothand greasy" in texture. Petrolatums aregener­ production. Slack wax is a refineryterm for distillate-derived ally produced from the same residual oil fraction as micro­ waxes that have oil contents ranging from3-40% by weight crystalline waxes and can be prepared by controlled blending oil. Scale wax is a distillate wax that has an oil content be- of microcrystallinewith wax . Petrolatumsgenerally exhibit oil contents greater than 10% and are marketed with colorsthat vary from dark brownto white .. Table 9 lists the gen­ 5 FDA regulations forwaxes, 21 CFR172.886 and 21 CFR 178.3710. eral physicalproperties of the differentpetroleum waxes. 532 MANUAL 37: FUELS AND LUBRICANTS HANDBOOK

TABLE 8---Physicalproperties of n-Alkanes (28]. Specific Heat (/mol K) Latent Heat No.of MeltingPt of Fusion Density at 20°C Solidat Liquid at Boiling Pt AlkaneS CAtoms Mol. Wt (K) (kJ/kg) (kg/m3) 298K 353K (K) Methane 1 16 90.68 58 0.658 (g) 116.6 Ethane 2 30 90.38 95 0.124 (g) 184.6 Propane 3 44 85.47 80 1.834 (g) 231.1 Butane 4 58 134.79 105 2.455 (g) 272.7 Pentane 5 72 143.45 117 621 (I) 0167.2 309.0 Hexane 6 86 177.83 152 655 (I) 195.4 341.9 Heptane 7 100 182.55 141 679 (I) 225.0 371.6 Octane 8 114 216.37 181 699 (I) 254.2 398.8 Nonane 9 128 219.65 170 714 (I) 284.5 424.0 Decane 10 142 243.50 202 726 (I) 314.5 447.3 Undecane 11 156 247.55 177 737 (I) 345.0 469.1 Dodecane 12 170 263.55 216 745 (I) 376.0 489.5 Tridecane 13 184 267.75 196 753 (!) 406.9 508.6 Tetradecane 14 198 278.95 227 759 (I) 438.5 526.7 Pentadecane 15 212 283.05 207 765 (!) 470.0 543.8 Hexadecane 16 226 291.25. 236 770 (!) ---,__ 501.5 560.0 Heptadecane 17. 240 295.05 214 775 (s) 534.3 575.2 Octadecane 18 254 301.25 244 779 (s) 485.4 564.4 589.5 Nonadecane 19 268 305.15 222 782 (s) • 514.6* 618* 603.1 Eicosane 20 282 309.75 248 785 (s) 544.3 658* 617.0 Heneicosane 21 296 313.35 213 788 (s) 570.7* 698* 629.7 Docosane 22 310 317.15 252 791 (s) 598.1 * 739.0 641.8 Tricosane 23 324 320.65 234 793 (s) 625.0* 772.0 653.4 Tetracosane 24 338 323.75 255 796 (s) 651.4* 805.0 664.5 Pentacosane 25 352 326.65 238 798 (s) 670.4* 815.9 675.1 Hexacosane 26 366 329.45 250 800 (s) 677.8 870.0 685.4 Heptacosane 27 380 331.95 235 802 (s) 728.1* 928* 695.3 Octacosane 28 394 334.35 254 803 (s) 752.8* 937.0 704.8 Nonacosane 29 408 336.35 239 805 (s) 777.2* 1001* 714.0 Triacontane 30 422 338.55 252 806 (s) 801.2* 1037* 722.9 Hentriacontane 31 436 341.05 242 808 (s) 824.5* 1073* 731.2 Dotriacontane 32 450 342.85 266 809 (s) 867.4 1095 740.2 Tritriacontane 33 464 344.55 256 810 (s) 871.0* 1113 748.2 Tetratriacontane 34 478 346.25 268 811 (s) 887.4 1149 755.2 Pentatriacontane 35 492 347.85 257 812 (s) 916.0 1210* 763.2 Hexatriacontane 36 506 349.35 269 814 (s) 937.5* 1206 770.2 Heptatriacontane 37 520 350.85 259 815 (s) 959.1 * 1276* 777.2 Octatriacontane 38 534 352.15 271 815 (s) 980.4* 1305* 784.2 Nonatriacontane 39 548 353.45 271* 816 (s) 1001* 1341* 791.2 Tetracontane 40 562 354.65 272 817 (s) 1022* 1411 795.2 Dotetracontane 42 590 357.32 273 817 (s) 1062* 1435 804.2 Tritetracontane 43 604 358.65 273* 819* (s) 1085* 1465* 813.2 Tetrateracontane 44 618 359.55 274 820* (s) 1102* 1495* 818.2 Hextetracontane 46 646 361.45 276 822* (s) 1140* 1553* 829.2 Octatetracontane 48 674 363.45 276 823 (s) 1177 1595 838.2 Pentacontane 50 702 365.15 276 825* (s) 1213* 1665* 848.2 Hexacontane 60 842 372.15 279 831*(s) 1380* 1916* 888.2 Heptacontane 70 982 378.65 281* 836* (s) 1526* 2131* 919.2 Hectane 100 1402 388.40 285* 846* (s) 1869* 2598* 935.2 (*)Predictedvalue.

(a) X'200 (b) FIG. 7-A scanning electron microscopic illustration of a macrocrystallinestructure wax (a= 200 X; b = 1000 X). CHAPTER 19: PETROLEUM WAXES 533

FIG. 8-An atomic force microscope image of the spiral growthof paraffin crys­ tal (measuring approximately 15 microns across). Inset shows orthorhombic ar­ rangement (0A9 nm x 0.84 nm) of chain ends of one of the crystalterraces (cour­ tesy of Professor M.J. Miles).

(a) X 200 X 1000 (b) FIG. 9-A scanning electron microscopic illustration of a microstructural characteriza­ tion of a refined paraffin wax (a. = 200 X; b = 1000 X).

TABLE9-Physical properties of petroleumwaxes. Property ParaffinWax Intermediate Microcrystalline Petrolatum Melt. Point (0F) 110-155 150-165 14Q..a195 110-180 Molecular Wt. 320--450 450-550 450-700 450-700 CrystalStructure Plates Needles Needles Needles Color White White-Yellow White-Dark Brown White-DarkBrown

Crystal Structure occurs when the wax crystal structurerotates from a hexag­ onal to orthorhombic form as the wax solidifies from a Paraffinwaxes exhibit several crystalline structures depend­ molten state. Paraffinswith carbon atom chains above C37 do ing on their carbon chain length. Odd number carbonchains not exhibit a transition point due to the wax solidifyingdi­ between C,9 and C29 exhibit an orthorhombic type crystal rectly into an orthorhombic crystal structure. Microcrys­ structure. Even numbered carbon chains between C18 and talline and intermediate typewaxes do not exhibit any tran­ C26 exhibit a triclinic structure. Even numbered carbon sition pOiht because they contain higher amounts of chains between C28 and C36 exhibit a monoclinic structure. branched alkanes. All paraffins with carbon chains between C20 and C3• have a Because of the steric effects caused by the arrangement of distinct transition point ( change in crystal form) lower than atoms in the molecule there is a difference between alkanes the temperature at which they solidify. The transitionpoint with odd and even numbers of carbon atoms. The even-num- 534 MANUAL 37: FUELSAND LUBRICANTS HANDBOOK

bered homologs have higher latent heat than the odd-num­ in the solid state at about 2-S'K below the meltingpoint. The bered homologs. Humphries [29] showed that alkanes with an difference between the transition temperature and melting even number of carbonatoms (between 20 and 32) and alka­ temperature becomes smaller with increasing molecular nes with odd number of carbon atoms (higher than 7) exhibit weight and finallydisappears for alkanes with more than 36 a latticetransition in the solid state. The even-numbered car­ carbon atoms [25,28] as demonstrated inFig. 10. The heat as­ bon atom alkanes exhibit this transition closer to theirmelt­ sociated with this solid-solid transitionis subtracted fromthe ing point than the odd-numberedalkanes, as demonstratedin lattice heat of melting. Figures 11 and 12 show variations of Fig. 10. The boiling point of normal-alkanes forthe tempera­ thelatent heat of melting, melting point, and densityof nor­ ture range on the figure are also shown in Fig. 10. mal alkanes versus increasing number of carbon atoms in The lattice transition in alkanes is accompanied by the re­ their structure. According to these figures, while the melting lease of heat of transition. Generally,lattice transitionoccurs point and density versus the number of carbon atoms have _

500 MP 2"-450 TrT I! 400 "& BP � 350

300

250

- 200

150

100 5 10 15 20 25 30 35 40 Number of carbon atoins FIG. 10-Variationof melting point (MP), transition temperature (TrT), and boiling point (BP) of normal alkanes with their number of carbon atoms [28].

-300

� 250 :

�200

150

100 0 20 40 60 . 80 100 Number of carbon atoms FIG. 11-Variation of the latent heat of melting of normal alkanes with the number of car­ bon atoms in alkanes and exhibition of the steric effect [28].

l CHAPTER 19: PETROLEUM WAXES 535

40,n-r------�1000 it is necessary to be able to predict thermodynamic proper­ Q' ties of wax. In this section we present fiveequations of state, a which are used for prediction of molar volumes, vapor pres­ j0 -� sures, and supercritical solubilities of alkanes[32]. ..p.. 800 ,.Q :------7 "'::I The simplest and one of the most widely knownequations o.0300 of state is that of van der Waals. However, this equation of -� state is not accurate enough to predict thermodynamic prop­ ] � - 600 erties of most fluids.Inspired by the vander Waalsmodel, in­ ::E · _e, vestigatorshave proposed several equationsof state through 200 -� the years.Almost every equation of state has been claimed. to 400 ! Table 10-Chemicalcomposition and thennophysical propertiesof Suntech P1!6 100 ParaffinWax (30]. 200 Hydrocarbon Weight�% -0-MP _._ DENSITY n-C-20 2.0 n-C-21 5.5 n-C-22 14.0 0 0 n-C-23 23.0 0 20 40 60 80 .. 100 n-C-24 22.0 n-C-25 14.0 Number of carbon atoms n-C-26 6.5 FIG. 12-Variation of the melling point and densily (@ 20'C) n-C-27 3.0 of normal alkanes with the number of carbon atoms in alkanes n-C-28 2.5 n-C-29 2.0 [28]. n-C-30 1.7 n-C-31 1.5 n-C-32 1.3 Meltingrange 316-329K smooth variations, the latent heat of melting goes through Heat of fusion 266 kJ/kg Liquid specificheat 2.51 kJ/kgK fluctuations. Because of the steric effects (the solid-solid Solid specificheat 2.95 kJ/kgK phase transitionsmentioned above) the latent heats of melt­ Liquid thennal conductivity 0.24W/mK ing of twoconsecutive alkanesdo not always increase with in­ Solid thermalconductivity 0.24 W/mK creasing number ofcarbon atoms, as demonstratedin Fig. 11. Liquid density 760 kg/m3 3 Each even-numbered alkane (with eight carbon atoms or Solid density 818kg/m Liquid viscosity J.90kg/ms more) exhibit a lower latent heat than the odd numbered Molecularweight 332 g/mol alkane having one carbon atom less than it. This fluctuation of the latent heat of melting vanishes as the number of carbon atoms approaches 40, and after that the latent heat increases smoothly withincrease of the number of carbon atoms. 2" As an example, the composition and thermophysical data of a paraffinwax sample (Suntech Pll6) [30], which contains •• almost 100% normal alkanes, is reported in Table 1_0. Ac­ �0 20 cording to this table, the hydrocarbons with 20--32 carbon atoms constitute 99% of the mixture and the ones withmore than 32 carbon atoms constitute the remaining 1 %. Paraffin waxes are generallypolydisperse compounds for which poly­ 15 disperse solution (continuous ntixture) theoriesmay be used • • for characterization [31]. Figure 13 is the graphic represen­ tation of the composition data of Suntech Pl16 paraffin wax 10_ reported in Table 10. Wax can be crystallized out of a solution by lowering its temperature.Varying the temperature gradientcauses a tran­ • 5 sition betweenthe growthof wax plates and growth of a tree­ • likestructure with regular branches as it is shown on Fig. 14. • •• Also shown on Fig. 14 is the bandedgrowth of wax due to ad­ • . • • • dition of a crystallization inhibitor. 20 21 .22 23 24 25 26 27 28 29 30 31 32 Number of carbon atoms Equations of State FIG. 13-The distribution of n-alkanes in Suntech P116 In order to characterize thepetroleum wax and performvar­ paraffin wax as a function of the number of carbon-atoms ious operations on wax mixtures, such as.wax fractionation, (28]. CHAPTER 19: PETROLEUM WAXES 535

400------1000 it is necessary to be able to predict thermodynamic proper­ $2' ties of wax. In thissection we present five equations of state, � a which are used for prediction of mol:tr volumes, vapor pres­ .s0 -.... sures, and supercriticalsolubiliti es of alkanes [32]. p.. 800 ,.Q- The simplest and one of the most widely known equations = 01) 300 of state is that of van der Waals. However, this equation of :E -� state is not accurate enough to predict thermodynamicprop­ - � ertiesof most fluids.Inspired by the van der Waalsmodel, in­ 600 �- _e, vestigators have proposed several equations of state through .... the years.Almost everyequation of state has been claimed to 200 � 400 � Table 10---Chemicalcomposition and thermophysicalproperties of SuntechPl 16 100 ParaffinWax [30]. 200 Hydrocarbon Weight�% -0-- MP _._ DENSITY n-C-20 2.0 n-C-21 5.5 n-C-22 14.0 0 0 n-C-23 23.0 0 20. 40 60 80 . .100 n-C-24 22.0 Number of carbonatoms n-C-25 14.0 n-C-26 6.5 FIG. 12-Variation of the melting point and density(@ 20°C) n-C-27 3.0 of normal alkanes with the number of carbon atoms in alkanes n-C-28 2.5 (28]. n-C-29 2.0 n-C-30 1.7 n-C-31 1.5 n-C-32 1.3 Melting range 316-329K smooth variations, the latent heat of melting goes through Heat of fusion 266 kJ/kg Liquid specificheat 2.51 kJ/kgK fluctuations. Because of the steric effects ( the solid-solid Solidspecific heat 2.95 kJ/kgK phase transitions mentioned above) the latent heats of melt­ Liquid thermal conductivity 0.24 W/rriK ing oftwo consecutive alkanes do not always increase within� Solid thermalconductivity 0.24 W/rriK creasing number of carbon atoms, as demonstratedin Fig. 11. Liquid density 760kg/m3 3 Each even-numbered alkane (with eight carbon atoms or Solid density 818 kg/m Liquid viscosity 1.90 kg/ms more) exhibit a lower latent heat than the odd numbered Molecularweight 332 g/mol alkane having one carbon atom less than it. This fluctuation of the latent heat of melting vanishes as the number ofcarbon atoms approaches 40, and after that the latent heat increases smoothlywith increase of thenumber of carbon atoms. 25 As an example, thecomposition and thermophysical data ,, ofa paraffinwax sample (SuntechP116) [30], which contains • • almost 100% normal alkanes, is reported in Table 10. Ac­ � cording to this table, the hydrocarbons with 20-32 carbon 20 atoms constitute99% of the mixture and theones with more 'iii than 32 carbon atoms constitute the remaining I%. Paraffin 3:: waxes are generally polydisperse compounds for which poly­ 15 dispersesolution (continuous mixture) theories may be used • • for characterization [31]. Figure 13 is the graphic represen­ tation of the composition data of Suntech Pl 16 paraffinwax reported in Table 10. 1C Wax can be crystallized out of a solution by lowering its temperature.Varying the temperaturegradient causes a tran­ • 5 sition between the growth of wax plates and growth of a tree­ • like structurewith regular branches as it is shown on Fig. 14. • J .• • Alsoshown on Fig. 14 is thebanded growth of wax due to ad­ • • • • • dition of a crystallizationinhibitor. ) 20 21 .22 23 24 25 26 27 28 29 30 31 32 Number of carbon atoms Equations of State FIG. 13-The distribution of n-<>lkanes in Suntech P116 In order to characterize thepetroleum wax and perform var­ paraffin wax as a function of the number of carbon-atoms ious operations on wax mixtures, such as wax fractionation, (28]. 536 MANUAL 37: FUELSAND LUBRICANTSHANDBOOK

PR, and SRK are three-constant-parameterequations. All in the above-mentioned fiveequations of state can be written the following generalizedform [32 ]: = _ v+ -yb av/RT Z (2) v-b T"(v+1JC)(v+Ac) 2 2 a +•) c wherea = lJ,, R T/ IP, and b = = 0,,,f3 RT, IP,. nw constants,Parameters while {Jb,and 11 'l, andare A component-dependent are component-independent con­ a f3 stants, and their numerical values for various equations of states are given in Table I I. In extending the equations of a, c arm state= to mixtures,Cm parameters b, and are replacedwith b and withthe followingexpressions (mixing rules):

(a) = RK, PR, SRK,RM -I: llm LLYiY;ll;;i j (3) = Cm = LYibii bm i llm = LL 3M: i i YiY;llij (4) = (3 + Cm = L,yibii bm � i LI,y,y;b.;; J . i iy,b,,)14 i RM in For the equation thereis anotheralternative ern extend­cm ing it to mixturesby replacing T, and P, with T and P as given below: = T T RM-2: (:ff Y cj)I( cj), (b) T cm i)l; ;,;P f't'Y;Y; cij P 2 = FIG. 14-(a) An atomic force microscope image of wax T P T P (5) Pcm (tfY;Y; ;;; c1;)i(tfYiY; ,,; c1;) "trees" growth in a lowering temperature solidification of wax _ from solution. Varyingthe temperature gradient causes a tran­ sition between the growth of wax plates and growth of a R'/:i = tree-like structure with regular branches; (b) An atomic force LLYiY;Riji j microscope image of banded growth of wax due to addition of crystallization inhibitors( courtesyof Prof. J.L. Hutter). These equations of state can be used to calculate properties of wax,its components,i.e., vaporpressure, and molar volumes of liquidat saturated-, sub--cooledand supercritical-conditions in as well as the solubilityof wax insupercritical solvents. be superior some respects to the earlier ones. The Redlich­ To perform phase equilibrium and other saturated prop­ Kwong (RK) equation that is a modification of the van der ertycalculations for wax in liquid and vapor states, we need Waals equation, wasa considerable improvement over other to perform equality of pressures and fugacity calculations equations of relatively simple forms at the timeof its intro­ [32]. The fugacitycoefficient of a componentof theis wax in a 0 5 mixture (4>l')?derivedfrom the generalized Eq I in the fol- duction. In the Soave-Redlich-Kwong· (SRK) equation, the temperature-dependent term of aJT of the RK equation is replaced by a function denoted by a that depends on the acentric factor(PR) of the compound and temperature. The Peng­ Robinson equationis another cubic equation of state in­ TABLEIt-Parameters of theg eneralizede quationof state. volving acentricb factor. Riazi and Mansoori [33] modifiedthe Eq. State-+ parameter of the RK equation by introducing a function, P.µ-ametersof -1. RK MMM RM PR SRK denoted by?, that depends on the refractiveindex of the com­ 1' 0 1.3191 0 0 0 1 1 1 pound. They showed that the resultingequati on is quite ac­ 1J 1 +../2 0 0 0 0 1-../2 0 curate in the prediction of hydrocarbon densities. Mohsen­ .\ e 0.5 0.5 0.5 0 0 Nia et al. [34] proposed that the 3M equation in which the 0.42748 0.487480 0.42748 0.45724 0.42748 repulsive part of the RK equation is modified based on the n. 0.08664 0.064462 0.08664 0.07780 0.08664 statistical mechanics improved the thermodynamic predic­ !ls 1 1 1 "PR "SRK " 1 1 1 1 tions appreciably. This equation is shown to be more accu­ {3 f3RM rate forheavy hydrocarbon phase behavior calculation than apR = [1 + (0.37464 + 1.524226w - 0.26992w2)(1 - �·5)]2 5 2 most of the other equations of state. RK and 3M equations aSRK = [1 + (0.48508 + 1.55171w - 0.15613.:J)(l - �- )] (/3RM)-• - I+ [0.02(1 - 0.92 exp(-J,OOOIT0 - 11)] - 0.035 (Tc - l)}(R* - I) are two-constant-parameter equationsof state,while the RM, CHAP'I'ER 19: PETROLEUM WAXES 537 lowing form[32): erence system, SG = specific gravity, Tb = normal boiling point, in degrees Rankine, a = 1 - Tb I Tg, Y = (I 'l'i[a :�t�n, - ln(v - bmlv)] gr v correction and correction factor. The criticalvolume (in cubic feet per pound mole) is given by the following expressions [37) a,,, v a(nc,,,) - -In z [ + + ] 2 C e + mRT(l+e) (v 'f/Cm)(v ACm) � V = l/g[(1 2fv)f(1 - 2 fv)J (8)

where 2 fv =

TABLE 12-The average deviations of various equations of state in predicting saturated liquid molar volumes of pl.lre compounds compared with those calculatedusin g the hankinsonand thomson (1979) correlation. AAD%

Compound T,. Range RK 3M RM PR SRK co, 0.71-1.00 19.5 8.8 19.5 4.7 14.7 CR, 0.48-0.99 4.5 13.9 4.5 8.6 4.5 C2H6 0.33-0.99 10.3 11.8 6.4 6.0 9.2 C3Hs 0.35-0.98 11.2 10.8 3.9 5.3 9.2 n-C4H10 0.36-0.96 13.3 9.0 3.0 3.6 10.3 n-CsH12 0.47-0.99 16.8 7.5 2.4 3.4 12.5 n-C6H14 0.39-0.99 19.9 6.9 2.2 2.2 14.8 n-C1H16 0.41-0.99 22.3 7.4 1.4 2.7 16.0 n-CsH1s 0.41-0.99 24.7 6.9 1.2 4.2 17.7 n-C,,H,o 0.42-0.98 26.8 7.8 0.8 5.1 18.7 n-C10H22 0.43-0.98 29.9 10.5 0.7 7.0 20.8 n-C11H24 0.55-0.78 31.1 10.5 0.3 7.4 21.3 n-C12H26 0.54-0.89 35.3 14.7 0.4 10.1 24.3 n-C13H28 0.56-0.80 37.6 16.5 0.2 11.4 25.8 n-C1�30 0.54-0.85 42.8 21.4 1.2 15.0 29.9 n-C1sH32 0.58-0.82 45.8 24.1 1.2 16.7 31.8 n-C16H34 0.56-0.81 49.7 26.9 1.8 19.7 35.1 n-C11H36 0.59-0.83 56.2 32.9 3.9 24.3 40.3 n-C1sH3s 0.55-0.84 59.5 35.5 4.0 26.9 43.1 n-C19Rw 0.56-0.85 63.5 39.0 4.4 29.6 46,1 n-C20�2 0.57-0.85 67.9 42.9 4.8 32.2 49.0 n-C22Ri6 0.55-0.81 57.6 31.8 4.5 25.1 40.6 n-C24Hso 0.56-0.82 66.2 39.2 2.9 31.1 47.2 n-C2sHss 0.58-0.84 62.9 36.4 l!.2 27.7 43.1 Overall 36.5 19.7 3.6 13.8 26.1

TABLE 13-The average deviationsof various equation of state in predicting molarvolumes of liquids in sub-cooled and supercritical conditions compared with experimental data. AAD% ExperimentalData Compound T,. Range P,. Range RK 3M RM PR SRK No. of Data Pts. Ref co, 0.7-2.2 1.0-13.6 5.0 4.8 5.0 2.9 6.1 447 a CR, 0.5-2.6 0.0-15.2 2.0 11.1 2.0 7.4 2.4 459 b C2H6 0.3-2.3 0.0-14.3 3.8 11.2 1.7 5.6 4.1 474 C C3Hs 0.2-1.9 0.0-16.5 5.9 9.6 1.8 4.2 5.9 533 d n-C4H10 0.3-1.7 0.0-18.5 8.4 8.4 1.6 3.8 7.9 638 n-CsH12 0.4-0.7 0.0-71.3 11.2 7.6 0.8 2.5 9.4 880 ef n-C6H14 0.4-0.7 0.0-332 14.7 5.8 2.0 2.5 12.6 510 f n-�H16 0.6-1.1 1.8-183 14.5 5.6 2.3 3.3 13.5 70 f,g n-C9H20 0.5-1.0 2.2-218 18.8 3.1 2.2 5.1 17.1 66 g n-C11H24 0.5-0.9 2.6-259 25.1 3.1 2.6 10.4 23.1 70 g n-CnH2s 0.4-0.9 3.0-303 32.3 7.9 3.2 16.7 30.1 70 g n-C11H36 0.4-0.8 4.1-410 48.5 19.8 7.2 31.0 45.9 60 g n-C2olf42 0.4-0.8 5.0-500 59.9 28.6 9.9 41.1 57.1 g n-C3oH62 0.4-0.8 6.8-682 62.7 28.9 6.8 43.5 59.8 so g · Overall 22.3 11.1 3.5 12.8 21.0 4377so a Anguset al., 1976. 1,Goodwin, 1974. c Goodwin and Roder, 1976. d Goodwin and Haynes, 1982. eHaynesandGoodwin, 1976. f Frenkelet al., 1997a. 8 Doolittle, 1964. CHAPTER 19: PETROLEUM WAXES 539

TABLE 14-The average deviations of various equations of state in predicting vapor pressures of pure compounds compared with the experimental data. AAD% ExperimentalData g Compound Tr Ran e RK 3M RM PR SRK No. of Data Pts. Ref co, 0.71-1.00 19.1 4.0 19.1 0.8 0.5 47 b,ca CH, 0.48-0.99 17.2 50.0 17.2 0.7 2.9 84 C,H,; 0.33-0.99 11.5 36.3 11.9 3.0 2.6 114 b,d C3Hs 0.35--0.98 19.8 39.5 8.3 3.0 1.9 101 b,e n-C.JI10 0.36--0.96 43.2 32.4 7.0 5.6 1.9 130 b,f n-CsH12 0.47--0.99 63.4 19.2 9.9 0.8 1.5 91 b,h n-C6H14 0.39--0.99 >100 15.8 16.5 3.1 1.9 88 b,h n-C1H16 0.41--0.99 >100 11.0 20.7 2.4 1.2 80 b,h n-CsH1a 0.41--0.99 >100 18.5 28.9 2.7 1.2 87 b,h n-CgH20 0.42--0.98 >100 33.2 33.3 2.1 1.5 82 c,h n-C10H22 0.43--0.98 >100 51.4 37.4 3.1 1.2 86 b,g,h n-C11H24 0.55--0.78 >100 81.7 37.7 6.6 4.4 27 b n-C12H26 0.54--0.89 >100 89.9 31.7 2.9 0.4 40 b,g,h n-C13H2s 0.56--0.80 >100 >100 28.8 3.3 0.5 27 b n-C1.µl30 0.54--0.85 >100 >100 30.3 5.8 2.5 42 b,g,h n-C1sH32 0.58-0.82 >100 >100 23.4 4.0 0.6 27 b n-C1�34 0.56--0.81 >100 >100 29.3 5.6 0.9 45 b,g,h n-C11H36 0.59--0.83 >100 >100 23.9 6.2 1.6 43 b n-C1sH3s 0.55--0.84 >100 >100 30.2 9.2 3.0 44 b,g n-C19llio 0.56--0.85 >100 >100 30.4 10.4 3.6 42 b,g n-C20H42 0.57--0.85 >100 >100 33.0 8.8 2.4 42 b,g n-C22l46 0.55--0.81 >100 >100 69.1 18.6 1.2 21 b,g n-Cz.µ!50 0.56--0.82 >100 >100 79.4 24.7 1.5 22 b,g n-CzsHss 0.58-0.84 >100 >100 57.9 33.9 1.7 23 b,g n-C29H60 0.54--0.84 >100 >100 82.5 42.S 2.7 12 b n-C3off62 0.54--0.84 >100 >100 75.8 44.5 2.7 12 b n-C32H66 0.55-0.85 >100 >100 61.5 48.9 3.2 12 b n-C3�6s 0.55--0.85 >100 >100 56.9 51.8 3.9 12 b Overall -2100 -650 35.4 12.7 2.0 1483 a Anguset al., 1979. b Frenkelet al., 1997a. c Goodwin, 1974. d Goodwinand Roder, 1976. e Goodwinand Haynes, 1982. £Haynesand Goodwin, 1976. 8 Morgan and Kobayashi, 1994. h Salemo et al., 1986.

this figure, the 3M and RM equations are capable of predict­ ning the experimentby supplying heat with the main heaters, ing supercritical solubilities accurately. In all these cases the while heating the temperature difference (

-4 .------'-----� -<�------� -5 .5 -6 -6 -7 S.a-7 ·:&»..g �-9 "!10 -10 -11 -11 -12 RK -12 SRK -13 ...... __ .,_ __ .,_ __ _,__..-.J -13 .___ .,_ __ .,_ __.,_ __, _ . I 2 Pr 3 4 0 2 Pr 3 4

O O 0 ; r---=:;e::e�;::=o:::� -st-6-4��C57 -6 -7 -7 Ss �9 -t ':lo -11 ·11 -12 MMM -12 PR -13 ,___ .,_ ____ ..._ _,_ __ _, -13 ,___ .,______,_ ..._ _, __ 0 2 3 4 0 I 4 Pr

�r---;;:;;::o:e::e==o===i-6 �-6 r---�::o:e;:e==o===i -7 -7 Ss S.a J9 �-9 -10 �10 -11 -11 -12 �----' RM-1 :12 �-'--' RM-2 -13 .___ __,.______,_ __._ __ _J -13 .___ ,______, _,_ _,__ 0 4 2 Pr 3 0 2 Pr 3 4 FIG. 15-Solubility of n-tritriacontane (n-C.3H68) in supercritical carbon dioxide at 308 K as predicted by various equations of stateand comparedwith the experimental solubil­ ity data[32]. of the sample will be trace shown by Fig. 17 demonstrates the decrease in crys­ Heat x Temperature tallinity as the melting point of the wax increases. The ther­ malanalysis procedure for this work wasstarted at -50°C for APUM= Ttime X Mass Q.T (12) 0.M optimum crystallization of the wax. The wax sample was ° Typically, the actual unitsof !J.Hr are (joules · Kelvin · sec­ heated at a controlled rate to + 150 C. The point at which onds_, · grams-1). Typically, the APUM is divided by the there is a deflection in the base line is the temperature that heatingrate (K/s)of the DCS experiment used to collect the the wax begins to melt. The point at which the peakscan re­ data. This will simplify the expression to yield the specific turnedto the base line is the temperature the wax sample is heat.of melting: completely melted. The peak area represents the amount of energy used to melt thewax sample and is calculated as de­ T scribed above. In addition, an estimate on the expected melt­ 0.MQ. APUM Q (13) ing point can be distinguished. The experienced technologist Heating Rate = T = M could tell by lookingat the shape of a DSC traceif the wax is e a paraffin, intermediate, or microwax. Paraffin waxes typi­ Since the mass of the samplethat was analyzed is known,it cally exhibit sharp peaks as shown in Fig. 16a, DSC peak is then multipliedby the heat emitted/gram of sample toyield shapes forintermediate waxes are less sharpas shown in Fig. the amount of heat given off( Q) duringthe meltingprocess. 16b, and microwaxes exhibiteven less sharp peaks, typically like the peak shown in Fig. 16c. QXM=MM (14) It should be noted that there is a characteristicsmall tran­ Figure 16 illustrates the DSC traces for three different sitionpeak in the DSC tracefor a macrocrystalline paraffinic petroleum waxes; one foreach wax type- paraffin(Fig. 16a), wax as illustratedin Fig. 16a. The transition that is indicated intermediate (Fig. 16b), and microwax (Fig. 16c). The DSC is a solid-solid phase ch;mge ( orthorhombic to hexagonal TABLE 15-Interactionparameter (k 12) of some systems. AAD% T p k,, System RM-2 SRK RM-1 RM-2 [K] [bar] RK 3M PR RK 3M PR Cz� - n-C2sHss 308.2 56-240 -0.4638 -0.2099 0.0807 -0.0553 -0.0189 -0.1283 46.2 27.0 14.4 38. C2� - n-C291¾0 308.2 65-240 -0.4146 -0.1618 0.1215 -0.0131 0.0260 -0.0701 53.1 29.9 23.9 48. C,H6 - n-C,oH.2 308.2 66-200 -0.4777 -0.2066 0.1025 -0.0571 -0.0206 -0.1121 25.0 22.8 57.2 22. 313.2 66-136 -0.4738 -0.2137 0.0901 -0.0517 -0.0139 -0.1233 13.9 30.8 29.7 18. C2H6 - n-C32�6 308.2 66-240 -0.5124 -0.2259 0.1020 -0.0707 -0.0297 -0.1214 46. 43.0 56.2 41. 313.2 66-200 -0.5011 -0.2264 0.1050 -0.0658 -0.0263 -0.1131 24.4 34.5 40.2 20. 318.2 80-240 -0.5248 -0.2438 0.0966 -0.0762 -0.0347 -0.1142 45.2 17.7 22.8 32. 319.2 80-136 -0.4872 -0.2241 0.1087 -0.0565 -0.0157 -0.1219 23.6 37.4 39.3 28. C,H,; - n-C33H,;8 308.2 65-240 -0.4632 -0.1933 0.1100 -0.0286 0.0137 -0.0779 50.2 34.4 50.7 43. 313.2 65-202 -0.4459 -0.1845 0.1433 -0.0240 0.0193 -0.0580 39.6 21.5 28.9 25. 318.2 65-240 -0.4506 -0.1918 0.1433 -0.0203 0.0228 -0.0530 45.7 24.2 28.0 42. CO2 - n-CzsHss 307.2 123-181 -0.3458 -0.0936 0.2487 0.0110 0.0507 0.0211 51.0 7.5 34.4 45. 308.2 80-240 -0.3161 -0.0901 0.2477 0.0296 0.0708 0.0194 52.3 18.3 35.0 49. 313.2 90-275 -0.2910 -0.0835 0.2532 0.0365 0.0765 0.0286 46.7 25.0 44.5 39. 318.2 100-250 -0.2915 -0.0867 0.2504 0.0359 0.0746 0.0232 64.7 13.4 31.0 47. 318.6 119-284 -0.3067 -0.0859 0.2531 0.0347 0.0736 0.0278 53.7 8.2 33.2 45. 323.4 125-327 -0.2973 -0.0869 0.2552 0.0385 0.0764 0.0314 62.5 5.8 28.9 53. 325.2 121-284 -0.2946 -0.0867 0.2540 0.0321 0.0690 0.0287 64.2 7.3 22.6 45. CO2 - n-C29H60 308.2 100-240 -0.2751 -0.0530 0.2782 0.0645 0.1075 0.0670 71.8 21.5 12.9 67. 318.2 100-240 -0.1961 -0.0540 0.2789 0.0818 0.1451 0.0672 81.2 22.2 6.9 76. CO2 - n-C3oH62 308.2 90-250 -0.3254 -0.1141 0.2481 0.0327 0.0779 0.0084 69.6 17.1 28.8 66. 318.2 105-250 -0.3125 -0.1197 0.2439 0.0273 0.0700 -0.0005 67.5 8.3 28.7 57. CO2 - n-C32H66 308.2 120-240 -0.4140 -0.1500 0.2448 -0.0162 0.0316 c-0.0139 59.5 8.1 24.1 54. 318.2 140-240 -0.3913 -0.1462 0.2483 -0.0035 0.0426 -0.0092 67.3 6.7 22.3 55. 328.2 140-240 -0.3777 -0.1345 0.2596 0.0044 0.0477 0.0104 57.5 9.2 27.1 40. CO2 - n-C33H6s 308.2 120-240 -0.3461 -0.1051 0.2825 0.0262 0.0754 0.0496 68.4 25.0 11.3 64. 318.2 140-240 -0.3384 -0.1043 0.2832 0.0280 0.0872 0.0494 65.0 22.9 4.8 61. 328.2 140-240 -0.3057 -0.0990 0.2878 0.0428 0.0876 0.0557 67.4 18.5 3.5 60. Overall 60.0 20.3 28.3 46. a Kalagaand Trebble, 1997. b Moradiniaand Teja, 1986. c Suleimanand Eckert, 1995. d Moradiniaand Teja, 1988. "McHugh et al., 1984 fReverchonetal., 1993. 8 Chandler et al., 1996.

"' " ...."' -n =- ,.. -·-� - i, ... -- gu "'l- ... I:: ,.."' ,.."-' ...... ,.. " -('(:)"' ... "' ...... ""

-·------,�n= -� uw ... -�- w { ... j j ,..3--�-.,__----j ,..,-'1------'--I ...,-1------' 45.G 0.0 2!.G 50,0 .'1511 llU nu . WQ

FIG. 16-The heat of fusion (Mt,) calculation from the DSC melting transition peak by measuring the total area under the peak, (a) paraffin, (b) intermediate, (c) microwax. 542 MANUAL37: FUELSAND LUBRICANTSHANDBOOK

respectively. Referring again to Fig. 16a (paraffin wax), the 85.0 ° 80.0 endotherm is started at -50 C for optimum crystallization I of the wax. The wax sample is heated at a controlled rate to 75.0 l 1 S0'C. The point at which there is a deflection in the base 70.0 + r' line is the temperature that the wax begins to melt. The 65.0 I" { ,I,.! point at which the peak scan returned to the base line is the - fo.O 1· temperature the wax sample is completely melted. The peak ss.o area represents the amount of energy used to melt the wax so.o I sample as discussed above. Figure 17 illustrates that as the .. 45;0 I I melting point of paraffin wax increases, the heat of fusion i 4M decreases because of the higher content of less crystalline 35.0 f, � branched alkane structures. Microcrystalline waxes have a 30.0 lower heat of fusion than paraffin wax that is directly re­ 25.0 lated to the greater amount of branched alkanes (less crys­ -so.o -25.0 0.0 25.0 SO.0 75.0 100.0 125.0 tso.0 talline microstrucfure). Listed in Table 16 are the typical heats of fusion data for both paraffin and microcrystalline Temperature('CJ waxes. FIG. 17-The heat of fusion (AH,) calculation from the DSC melting transition peak by measuring the total area under the Effect of Additives peak of several paraffins demonstrating the decrease in crys­ tallinity as the melting point of the wax increases. In the petroleumwax industry;it is oftennecessary touse ad­ ditives to improve the processabilityof wax or wax mixtures by modifying their physical properties. This may be accom­ crystal structure). As the wax crystal continues to absorb en­ plished by the addition of additives that may include stearic ergy,a larger peak is recorded and then actual melting occurs acid, polyethylene, ethylene-vinyl acetate copolymer or a Fis­ witha returnto the base line as the temperature continuesto cher-Tropsch wax. For example, stearic acid may be added to increase. a paraffinwax to increase firmness,reduce melting point, aid In addition, there is a bimodality indicated in the DSC in mold release, prevent candles from losing their shape in trace peak shapes for intermediate (Fig. 16b) and microcrys­ warm weather, etc. Polyethylene is another additive that may talline (Fig. 16c) waxes. Bi-modal shape is related to the be used. Polyethylene may be added to a paraffin wax to breadth of the wax composition. Bimodal peak shape is not harden the wax structure, modifyburning rate, and improve related to transition. The apparent bimodalityindicates that strength and gloss. In addition to physical property modifi­ the wax has not been made a narrowdistillation cut. The as cation, additives also could alter the microstructureof waxes meltingpoint of wax is in the DSC area that the curve begins as demonstrated by Fig. 14. to return to the base line (downward slope) as the tempera­ ture increases. The squat DSC peak shape of the microwax shown inFig. 16c indicates that it is less crystallineand has Test Procedures for PetroleumWax a broader melting.The apparent bimodality of the microwax Characterization is related to the different melting fractionsthat appearin this particular wax. There are three properties used to characterize petroleum Determinationof the heat of fusion of a wax is of practical waxes: (I) physical properties, (2) chemical properties, and significance for a number of reasons. For example, the (3) functional properties. changes of shape of a DSC trace to that of known waxesmay indicate that a wax has been contaminated or altered. This PhysicalProperty Determination may be confirmed by comparing the heat of fusion of a pre­ Melting Point - Test Methods ASTM -87,D D 3944, and D 127- viously purchased paraffinwax with the suspect wax. For ex­ Melting point is a wax propertythat is of interest to the con­ ample, a historical value for heat of fusion of a wax may be sumer and can be an indication of the perlormance proper­ 200 Jigand a newly purchased paraffin wax may have a heat ties of the wax being tested. The melting point of a wax is of fusion of 180 Jig. This variation confirms that the two defined as the temperature at which the melted petroleum waxes exhibit different properties. wax first shows a minimum rate of temperature change when Another application of the heat of fusion could be for the allowed to cool under prescribed conditions. comparisonof properties of nominally similar waxes offered Test Method D 87 is one of the most commonly utilized by two different suppliers. The higher the heat of fusion, the tests for melting point determination for petroleum waxes. more crystalline the wax is. For some applications, like can­ Paraffin waxes are often marketed based on melting point dles, high crystallinityis desirable to aid in the mold release data produced by D 87. This test method is performed by properties due to shrinkage upon cooling. Low crystalline placing a specimen of molten wax in a test tube equipped waxes do not shrinkas much as highcrystalline products. with a thermometer as illustratedin Fig. !Sa. The test tube is ASTM Test Method D 4419 has been developed to char­ acterize petroleum waxes and measurement of their transi­ tion temperatures by Differential Scanning Calorimetry TABLE 16--Typicalheats of fusion(Jig). (DSC). Figures 16a, 16b, and 16c are DSC endothermic FullyRefined Paraffin wax 180-210 scans of a paraffin, intermediate, and microcrystalline wax, Microcrystallinewax 140-190 CHAPTER19: PETROLEUMWAXES 543

. �·

..- ,...::

'c!!

1 51' ID I d30) .I (a) Dimensionsin inches (millimeters)

..

aK. �

r

(b) Time-+ (c) FIG. 18-{a)Apparatus for ASTM Test Method D 87. Cooling curvefor: (b) a paraffin wax, (c) for intermediate wax, microwax, petrolatum, or waxes containing a high percentage (>50%) of branchedalkanes 544 MANUAL37: FUELSAND LUBRICANTSHANDBOOK then placed in an air bath that is immersed in a water bath Method D 3944, which is a "solidificationpoint" method (Fig. and held at 16-28°C (-61-82°F). Temperature readings are 19a), can be used formelting point determination. The solid­ taken periodically until the wax, solidifies under specified ification point of a petroleum wax is: the temperature in the conditions. During solidification, the rate of temperature de­ cooling curve of the wax where the slope of the curve first creases and produces a plateau in the cooling CUIVe, which is changes significantly as the waxsample changes from a liq­ obtained by plotting the temperatureversus elapsed time as, uid to a solid state. This is illustratedin Fig. 19b, which is a illustratedin Fig. 18b. Thetemperature where the plateau oc­ typicalcooling curve forsolidification point measurement of curs is definedas the meltingpoint. (Note: The thermometer a petroleumwax. used for this workshall conform to ASTM SpecificationE-1.) Test Method D 3944 is performedby heating 50 mg of sam­ Test Method D 87 is not applicable for microcrystalline ple in a test tube above the solidificationtemperature. Once wax, intermediate wax, petrolatum, or waxes containing a the waxis melted, Fig. 20a, a thermocouple (connected to a high percentage (> 50%) of branched alkanes, because a tem­ recorder) is placed in the sample, as illustrated in Fig. 20b, peratureplateau willnot occur with such type of waxesas il­ and allowed to cool to ambient temperature. As the sample lustrated in Fig. 18c and because these type of waxes have a cools, a plot of temperature versus time (Fig. 18a) is ob­ much broader melting distribution (characterized by DSC) tained. This test method is based on the same methodology than paraffin waxes. For non-paraffin type waxes, Test as D 87 with the exception that automated test equipment is

'i'o Jli!:c:ordcr

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so mg (a) wax sample

· Temperatw:et Heat turned ot.l . I

Sol.idification Point

(b)

FIG. 19-(a)Apparatus for determination of melting (solidification) point (cooling curve) of non-paraffin type waxes used in ASTM Test Method D 3944; (b) A typical cooling curve for melting (solidification) point measurement of non-paraffin type waxes.

548 MANUAL 37: FUELS AND LUBRICANTSHANDBOOK

Sample Reference Resistance Thermometer Heater

(a) Nitrogen��� AT-Signal

First-Order Transition: Apex - TlA onset. 20 --r .tnd -2E 'r Second Order-Transition: l I Apex - Tu I I Onset -T10 E nd - TlE I I

� l '2A

(b) FIG. 24-(a) Differentialscanning calorimetry (DSC) experimental set up; {b) Schematic of petroleum wax DSC curve {heating cycle) sample determined to have solid-liquidand solid-solid transitions. This figureis similar to Fig. 16a.

method for petrolatum, which may also be used forsofter gram. DSC can differentiate the type of petroleumwax being waxes. The cone penetration value is more of a measure of evaluated by its melting and crystallization property. Figure finnness or consistency rather than hardness.) 24b (which is similar to Fig. 16a) is the schematic of a Transition Temperatures by DifferentialScanning Calorime­ petroleum wax DSC curve exhibiting solid-liquid and solid­ try(DSC )-Test Method D 4419-Test Method D 4419 is a rapid solidtransitions (Heating Cycle) andthe calculation of such and convenient methodfor determiningthe temperature lim..: temperatures. Paraffinwaxes being derived fromthe distilla­ its governingthe change a wax undergoes fromsolid to liquid tion process have sharp peak shapes, while microcrystalline or as a solid-solid transition. This test method measures the waxes being derived from residual fractions have broader transition temperatures of petroleum waxes, including mi­ peak shapes. This is shown in Fig. 16 (Note: Refer to Stan­ crocrystalline waxes, by differential scanning calorimetry dard TerminologyE 473 for additional information). (DSC) as shown in Fig. 24a. The normal operating tempera­ I turerange extends from 1Sc-150°C. DSC is a technique that Chemical PropertyDetennination measures the difference in energy inputs into a substance Petroleum waxes being composed of hydrocarbonsare rela­ and a referencematerial using a controlled-temperature pro- tively inert but they can undergo compositional chemical CHAPTER 19: PETROLEUM WAXES 549

changes when exposedto elevated temperatures in the pres­ wax and placing approximately 10 g of thin shavings on odor­ ence of oxygen due to oxidation. Waxes can degrade in the freepaper or glassine. Individual test specimens are then eval­ presence of heat and oxygen. The degradation process in­ uated for odor by each panel member and assigneda number volves breaking a bond between a carbon and a hydrogen according to the odor scale shown in Table 18 thatbest fitsthe atom to make a free radical. The free radicals quickly form intensity of the odor. As an alternative procedure, the wax peroxides initially and further react to form acids. The shavings are placed in bottles with each panel member mak­ changes in composition can possibly be detected by testing ing an odor determination between 10 and 60 min after the for color and odor. Antioxidants are added to petroleum shavings are placed into the bottles. The average of the panel waxes to chemically stabilize themfrom the heatdegradation ranking is reported as the odor rating of thesample. process [ 41]. Composition byGas Chromatography-Test MethodD 5442- Color - Test Methods D 156 and D 1500-The color of Test MethodD 5442 is applicable to petroleum derivedwaxes, petroleum waxes can indicate the degree of refinement or including blends of waxes.This test method covers the quan­ possible contamination. Color is not always a reliable pa­ titative determination of the carbon number distribution of rameter for determining quality and should be used judi­ petroleumwaxes in the range of n-Cl 7 throughn-C44 by gas ciously as a specification. There are two methods for deter­ chromatography usinginternal standardization. In addition, mining the color of petroleum waxes: Test Methods D 156 the content of normal and non-normal hydrocarbonsfor each and D 1500, and both are subjective and measure the empir­ carbon number is also determined. Material with a carbon ical value based on visual observation of the wax in the number above n-C44 is determined by difference from 100 molten state. mass% and reported as C 45 +. (Note: Standard Practice E 260 Test Method D 156 is the Saybolt Chronometer Method for provides further information on gas chromatography and quantifying the color of petroleum products such as a StandardPractice E 355 provides informationrelating to gas petroleum wax. Saybolt color is anempirical definition of the chromatographyterms and relationships.) color of a clear petroleum liquid based on a scale of -16 Test Method D 5442 is not applicable to oxygenatedwaxes, (darkest) to + 30 (lightest). The number is derivedby finding such as synthetic polyethylene glycols (i.e., Carbowax), or theheight of a column that visually matches the appropriate natural products such as beeswax or carnauba. This test one of three glass standards and referring to Table 1 of Test method is not directly applicable to waxes with oil content Method D 156. Tiris is done using a Sayboltchronometer (see greater than 10% as determined by Test Method D 721. Fig. 25), which consists of a sample and standard tubes, op­ tical system, light source, and ASTM color standards. Functional Property Determination While Test Method D 156 is used to determine the degree The following methods are for the evaluation of wax base of whiteness of a wax,Test MethodD 1500 is used to measure coatings intended for paper and paperboard. The methods thecolor of waxes that have a tint darker than off-white.Test were developed in concert with the Technical Association of Method D 1500 is conducted using a standard light source, Pulp and Paper Industries. with liquid sample placed into a standard glass container Specular Gloss - Test Method D 1834-Specular gloss is (sample jar) (see Fig. 26) and compared with colored glass defined as the degree to whicha swface simulates a mirror disks ranging in value from0.5--8.0 with 0.5 increments. in its capacity to reflect incident light. Test Method D 1834 CarbonizableSubstances - Test Method D 612-Test Method is a method designed to determine the capacity of a wax D 612 is applicaj,le to paraffin waxes for pharmaceutical use coated surface to simulate a mirror in its ability to reflect an as defined in the United States National Formulary. Molten incident light beam using a glossmeter such as that illus­ wax is treatedwith sulfuric acid and the acidic layer is com­ trated in Fig. 28. Surface gloss is desirable for some waxed pared visually with a colorimetric reference standard to de­ paper applications. For determining the gloss of book pa­ termine if it passes the conformancecriteria for refined wax per, reference should be made to Test Method D 1223. For using the color comparator shownin Fig. 27. very high gloss paper refer to Wink et al. [ 42]. Peroxide Number- Test Method D 1832-Waxes are heat Gloss Retention - Test Method D 2895-This test is intended sensitive and they are susceptible to the action of the oxida­ to correlate with the conditions that are likely to occur in the tion process. The detection of peroxides is the firstindication storage and handling of wax-coated paper and paperboard. that a wax has begun to deterioratein terms of oxidation sta­ Test Method D 2895 is intended primarily to measure the bility. Petroleumwaxes should not have any measurable per­ gloss retention, which is defined as the percent of original oxide values. Deterioration of petroleum wax results in the gloss retained by a test specimen after aging under specified formation of peroxides and other oxygen-carrying com­ conditions. It is calculated as the final gloss divided by the pounds that will oxidize potassium iodide. Peroxide content initial gloss multipliedby 100. The initial gloss of waxed pa­ is reflectedby the peroxide number that is definedas the mil­ per or paperboard is measured in accordance with Test liequivalents of constituents per 1000 g of wax that will oxi­ Method D 1834, then remeasured after aging the sample in ° ° dize potassium iodide. an oven at 40 C (104 F) for 1 and 7 days. The !-day test is Odor - Test Method D 1833-Insome end-use applications, conducted to observe trends whilethe 7-day test is the stan­ such as food packaging, the intensityof the odor is an impor­ dard test duration. tant characteristic. Odors can be an indication of the degree Surface Wax - Test MethodsD 2423, D 3521, and D 3522- of refining,contamination, or oxidation.Test Method D 1833 Wax coatings are applied to provide a better moisture bar­ describes how to rate the odor intensitybased on a subjective rier, appearance, and abrasion resistance. These perlor­ evaluation using a multiple-member test panel. This test is mance features are influencedby the amount of wax present conducted by preparingodor test specimens frompetroleum on the surface. Test Method D 2423 is used to determine the 550 MANUAL 37: FUELSAND LUBRICANTfiHANDBOOK

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Saybolt Chromometer Tube Heater Adapter FIG. 25-ASTMStandard Test Method D 156 Saybolt Chromometer and artificial daylight lamp. CHAPTER 19: PETROLEUM WAXES 551

amount of wax present on the surface of the substrate, but Test Method D 3521 also determinesthe amount of wax that not the absorbed wax. Test methods that determine theap­ is present on the surface of corrugated paperboard. This plied wax by solvent extraction(such as Test Method D 3344) method is applicable to a board on which wax has been ap­ do not clifferentiate between the wax present at thesurface plied by curtain coating, roll coating, or other methods. The and to that which penetrated the substrate. substrate board may or may not contain impregnating(satu­ ration) wax withinits structure. Ifit is known that the speci­ men has coating wax only, with no internal saturating wax, then Test Method D 3344 may determinethe total coating wax . ' applied. Determination of the total amount of waxpresent by I I, I I I ASTM D 3521 involves delamination of the coated facing to I obtaina ripple-freesheet, then scraping offthe wax using a ra­ I ' ' zor blade and calculatingthe amount of waxremoved. I I ' I Test Method D 3522 is used to determine the amount of I I wax that has been applied to the inclividual layers of the cor­ • • rugated paperboard and the amount of the impregnating -....,..._, 0 • • (saturation) waxin the same facing.This is accomplished by 0 • peeling the coated facing fromthe mecliumand then splitting • U2-'·3U ••-a 0 it into two layers; one bearing the coating on waxed fibers � '. ., only and the other containingwaxed fibers only. The layers I • are extractedseparately, collectingboth fibers and wax. This ' will permit the calculation of the applied surfacecoating and I I' the amount of impregnating wax. • •I I -,<-- ' I •' • ..______... i TABLE 18-0dor intensityscale . NumericalRating Odor Description FIG. 26-Standard 0 None glass sample jar used 1 Slight in Test Method D 1500 2 Moderate to measure the color of 3 Strong waxes. 4 Verystrong

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TEST TUBE FIG. 27-Colorcomparator used in Standard Test Method D 612 for measurement of car­ bonizable substances in paraffin waxes for pharmaceutical use. 552 MANUAL 37: FUELS AND LUBRICANTS HANDBOOK

disruption occurs across 50% of the waxed paper surface when the test strips areseparated. The temperatureat which the firstfilm disruption occurson the waxed paper when the test strips are separated is the wax picking point. Test Specimen Method D 1465 is used to determine the temperature at which two strips of wax-coated paper will adhere to each other. Surface disruption of wax coatings at relatively low ambient temperatures is a performance problem for low melting point waxes. If the surface of a waxed paper is blocked together, then surface gloss and barrier properties will be altered. Two stripsof wax-coated paper areplaced on I a calibrated temperature gradient plate for 17 h and re­ moved, cooled, and peeled apart to determinethe block point temperature. Figure 29 illustrates a Type A and a Type B blockingplate used forthese measurements. Coefficient of Kinetic Friction - Test Method D 2534-A coated surface under load is pulled at a uniform rateover a

I second coated surface. This is done experimentally by preparing a "sled" with a weight and then pulling it over the surface to be tested using a horizontal plane and pulley as­ sembly. The forcerequired to movethe load is measured, and the coefficientof kinetic friction(JL 0 is calculated as follows: I (15) Where A = the average scale reading from the electronic load cell-typetension tester for 1 SO mm ( 6in) of uniform slid­ ing and B = sled weight (g). The value obtained is related to the slip property of the wax coating. High slip property val­ \- ues may not be desirable formany commercial articles that have been coated with petroleumwax. Abrasion Resistance - Test Method D 3234-This test method is designed to helppredict the resistance in change of gloss that coatingsmay be subject to during the normal han­ dling of coated paper and paperboard products.Abrasion re­ sistance is the resistance to change in gloss when that coat­ ing has been subjected to an abrading action by an external object. Test Method D 3234 is conducted by dropping 60 g of FIG. 28-Diagram of relative positions of essential elements sand on a verysmall area of a coating under fixedconditions. of Glossmeter used in Standard Test Method D 1834. The abrasion resistance test apparatus is illustrated in Fig. 30. Gloss is measured with a 20° specular glossmeter illus­ trated in Fig. 28 beforeand after the abradingaction by the falling sand. Hot Tack - Test Method D 3706-Hot tack is definedas the Total Wax Content - TestMethod D 3344--Manyof the func­ cohesive strength during the cooling stage before solidifica­ tional propertiesofa wax-treatedpaperboard are dependent on tionof a heat sealbond formedby a wax-polymerblend. Flex­ theamount of waxthat is present. Test Method D 3344 deter­ ible packaging materialsare formed into finished packages by mines the totalamount of wax ina sample of wax-treated cor­ joining surfaces with heat sealedbonds. Thebonding process rugatedpaperboard by extraction.It is applicable to specimens is performed on high-speed packaging lines and the applica­ that have been waxedby either impregnation (saturation) op­ tion pressureused to hold the surfacestogether is released be­ erationsor coatingoperations, or combinations of the two. fore the bond has completely solidified. The wax-polymer Weight of Wax Applied During Coating - Test Method D blend must have enough hot tack while still in a molten stage 3708-Test Method D 3708 is used to determinethe weight of to hold the sealed areas together until the blend has cooled. a hot melt coating applied to corrugated board by curtain In Test Method D 3706, flexible packaging specimens are coating.This method is intended foruse as a routine process heat-sealed together over a series of temperatures and dwell control in the plant. The amount of wax applied is deter­ times. Immediately aftereach seal is formedand beforeit has mined by attaching a foldedsheet of paper to production cor­ started to cool, a force tending to separate the specimens is rugated board,running the combination through the curtain applied by a calibrated spring. If the hot tack of the blend is coater, and subsequently determining the applied weight of strongenough, the seal remainsclosed untilit has solidified; wax on the sheet of paper. if not, the sealseparates. Thus each spring forceand test con­ BlockingPoint - Test MethodD 1465-The blockingpoint of dition eitherpasses or fails.The pattern of pass/fail results is a wax is defined as the lowest temperature at which a film plotted to the blend characteristics. CHAPTER 19: PETROLEUM WAXES 553

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Spotl lght Source 500 111 Separatory funnel

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Acknowledgments D721 Test Methodfor Oil Content of Petroleum Waxes D937 Test Method forCone Penetration of Petrolatum The authors thank Dr. George Totten for his helpful advice D938 Test Method for Congealing Point of Petroleum and guidance in the preparationof this chapter and Dr. Sony Waxes, including Petrolatum Oyekan, Dr. Chen-Hwa Chiu, Dr. Sang J. Park. and Mr. D 1168 Test Method for Hydrocarbon Waxes Used for Adrian D'Sousa for their technical assistance. ElectricalInsulation D 1298 Test Method forDensity, Relative (Specific Grav­ ity)or APIGravity of Crude Petroleumand Liquid ASTM STANDARDS Petroleum Products by Hydrometer Method D 1223 Test Method forSpecular Glossof Paper and Pa­ No. Title perboard D87 Test Method forMelting Point of PetroleumWax D 1321 Test Method forNeedle Penetration of Petroleum I D97 Test Methodfor Pour Point of PetroleumProducts Waxes I D 127 Test Method forDrop Melting Point of Petroleum D 1465 Test Method for Blocking and Picking Points of Wax Including Petrolatum Petroleum Wax D 156 Test Method for Color, Saybolt, of Petroleum D 1500 Test Method forColor, ASTM, of Petroleum Prod­ Products ucts (ASTM Color Scale) D287 Test Method forGravity, API, of Crude Petroleum D 1832 Test Method for Peroxide Number of Petroleum and PetroleumProducts (Hydrometer Method) Wax D445 Test Method forKinematic Viscosity of Transpar- D1833 Test Method for Odor of PetroleumWax ent and OpaqueLiquids D 1834 Test Method for20 ° Specular Gloss of Wax Paper D 612 Test Method for Carbonizable Substances in D2423 Test Method for SurfaceWax on Waxed Coated ParaffinWax Paper CHAPTER 19:PETROIEUM WAXES 555

D2500 Test Method for Cloud Point of Petroleum ISO 1392 Determination of crystallizing point­ Products General method D2534 Test Method for Coefficient of Kinetic Friction ISO 2207 Petroleum waxes-Determination of forWax Coating congealing point D2669 Test Method forApparent Viscosity of Petroleum ISO 3016 Petroleum products-Determination of WaxesCompounded with Additives (Hot Melts) pour point D2895 Test Methodfor Gloss Retention of Waxed Paper ISO 3841 Method for determination of melting and Paperboard after Storage at40 ° C (104 ° F) point of petroleum wax ( cooling curve) D3234 Test Method for Abrasion Resistance of nsKo0-64 Testing methods for melting points of PetroleumWax Coatings chemical products D3235 Test Method for Solvent Extractables in nsKo0-65 Test methods forfreezing point of chem­ PetroleumWaxes ical products D3236 Test Method forApparent Viscosity of Hot Melt NFT60-114 Petroleum products-Melting point of Adhesives and CoatingsMaterials paraffins D3344 Test Method forTotal Wax Content of Corrugated NFT20-051 Chemical products for industrial use. Paperboard Determinationof meltingpoint. Method D3451 Standard Practices for Testing Polymeric Pow­ for the determination of crystallizing ders and Powder Coatings point (freezing point). D3521 Test Method forSurface Wax Coating on Corru­ gated Board D3522 Test Method for Applied Wax Coating and Im­ REFERENCES pregnating (Saturating) Wax in Corrugated Board Facing [1] Hackett,W. J., Maintenance Chemical Specialties, ChemicalPllb­ D 3706 Test Method forHot Tack of Wax-Polymer Blends lishingCo., Inc., NY, 1972. by Flat Spring Test [2) Warth,A. H.,Chemistry and Technologyof Waxes, ReinholdPub­ D 3708 Test Method for Weight of Wax Applied During lishing Corp.,NY, 1956. CurtainCoating Operation [3) Bennet, H., Industrial Waxes, Vol. 1, Chemical Publishing Com­ D4419 Test Method for Transition Temperatures of pany,Inc., NY, 1963. Petroleum Waxes by Differential Scanning [4] Puleo,S. L., "Beeswax," Cosmetics and Toiletries, Vol. 102, Al- Calorimetry lured Publishing Company, Inc., Chicago, 1987. T [5] Warth,A. H., Chemistryand Technology of Waxes, ReinholdPub ­ D 5442 est Method for Analysis of Petroleum Waxes by lishingCorp., NY, 1956. Gas Chromatography [6) Letcher, C. S., 'Waxes,"Kirk-Othmer: Encyclopedia ofChemical El Specificationfor ASTM Thermometers Technology,Vol. 24, 3"' ed.,1984, pp. 466-481. E260 Practice for Packed Column Gas Chromatogra­ [7] Dcy, M. E., "Sasol's Fischer-Tropsch_Experience," Hydrocarbon phy Processing, August,1982, pp. 121-124. E355 Practice for Gas Chromatography Terms and [8] Erchak,Jr. , M., "Process forthe Oxidation of High Molecular Relationships Weight Aliphatic Waxes and Product 880kb, U. S. Patent E473 Standard Terminology Relating to Thermal 2,504,400, WashingtonDC, April 18, 1950. Analysis [9) Haggin, J., "Fischer-Tropsch: New Life for Old Technology," E537 Test Method for Assessing the Thermal Stability Chemical and EngineeringNews, October 1981, pp. 22-32. [10] Caraculacu,A., Vasile,C., Caraculacu,G., "Polyethylene Waxes, of Chemicalsby Methods of ThermalAnalysis Structure,and Thermal Characteristics," Acta Polymerica, Vol. 35,No. 2, 1984,pp. 130-134. [11) Brooks,B. T.,Boord, C. E.,Kurtz, S. S.,and Schmerling,L., The OTHER STANDARDS Chemistry of Petroleum Hydrocarbons,Vol. 1, Reinhold Publish­ ing Corp.,NY, 1954. nd No. [12) Gruse, W. A., Chemical Technology ofPetroleum, 2 ed., Mc­ Title Graw-HillCompany, NY, 1942. BS4633 &4634 Method forthe determination of crystal­ [13] Mazee, w. M., "Petroleum Waxes," ModernPetroleum Technol­ lizing point. Method for the determina­ "' ogy, 4 ed., 1973,pp. 782-803. tion of melting point and/or melting [14] Vasquez, D. and Mansoori,G. A., "Identification and Measure­ range ment of Petroleum Precipitates,"Journal of Pe troleum &ience BS4695 Method for determination of melting and Engineering, Vol. 26,Nos. 1-4,2000, pp. 49-56. point of petroleumwax (cooling curve) [15] Misra. S., Baruah,S., and Singh,K, ParaffinProble ms in Crude DIN 53175 Binders forpaints, varnishes and similar Oil Production and Transportation: A Review, SPE Production coating materials; determination of the andFacilities, Society of PetroleumEngineers, Richardson,TX, solidification point (titer) of fatty acids Feb. 1995,pp.50-54. (method accordingto Dalican) [16) Holder, G. A. and Winkler,J., 'Wax Crystallization fromDistil­ late Fuels," Journalof the Institute of Petroleum,Vol. 51,No. 499, DIN 53181 Bindersfor paints, varnishesand similar 1965,pp. 228-243. coating materials; determination of the [17) Mansoori,G. A. and Canfield,F. B., "Variational Approach to melting interval of resins by the capil­ Melting,"Journal of Chemical Physics, Vol. 51,No. 11, 1969, pp. lary method 4967-4972. 556 MANUAL37: FUELS AND LUBRICANTSHANDBOOK

[18] Pourgheysar,P., Mansoori,G. A., and Modarress,H., "A Single­ Minimization and Phase Rule," Chemical Engin.eeri.ng Commu­ Theory Approach to the Prediction of Solid-Liquid and Liq­ nication, Vol. 54, 1987, pp. 139-148. uid-VaporPhase Transitions,"Journal of Chemical Physics, Vol. [32] Hartono, R., Mansoori,G. A., and Suwono, A., "Prediction of 105, No. 21, 1996, pp. 9580-9587. Molar Volumes, Vapor Pressures and SupercriticalSolubilities [19] Park, S. J. and Mansoori,G. A., "Aggregation and Deposition of of Alkanes by Equations of 5-tate," Chemical Engin.eeri.ng Com­ HeavyOrganics in Petroleum Crudes," InternationalJo urn.al of munications, Vol. 173, 1999. pp. 23--42. EnergySources, Vol. 10, 1988, pp. 109--125. [33] Riazi,M. R. and Mansoori, G. A. "Simple Equationof State Ac­ [20] Branco, V. A. M., Mansoori, G. A., De Almeida Xavier, L. C., curately Predicts Hydrocarbon Densities," Oil & Gas Journal, Park, S. J., and Manafi,H., "AsphalteneFloccuiation and Col­ 1993,pp. 108-111. J lapse fromPetroleum Fluids," Journalof PetroleumScience and [34] Mohsen-Nia, M., Modarress,H., and Ml\fisoori,G. A., "A Simple Engineering, Vol. 32, 2001, pp. 217-230. Cubic Equation of State for Hydrocarbons and Other Com­ [21] Svendsen,J. A., "Mathematical Modeling of WaxDeposition in pounds," SPE Paper No. 26667, Proceedings of the 1993 Annual Oil Pipeline Systems," AIChE Journal, Vol. 39, No. 8, 1993, pp. SPE Meeting, Societyof Petroleum Engineers,Ric />ardson,TX, 1377-1388. 1�� [22] Brown,T. S., Nielsen, V. G., and Erickson,D. D., "Measurement [35] NikitinE. D., Pavlov, P.A., and Bessanova,N. V., "CriticalCon­ and Prediction of the Kinetics of ParaffinDeposition," Journal stantsof n-Alkaneswith from 17 to 24 Carbon Atoms," Journal of Petroleum Technology, April 1995, pp. 328-329. of ChemicalTh ennodynamics, Vol. 26, 1994, pp. 177-182. [23] Noll, L., "Treating Paraffin Deposits in Producing Oil Wells," [36] Frenkel, M., Gadalla, N. M., Hall,K. R., Hong,X., and Mar sh, K. TopicalReport NIPPER-551 (DE92001010),Bartelsville Project N., TRC Thermodynamic Tables-Hydrocarbon; Nim-Hydrocar­ Office,U.S. Department of Energy, Bartelsville,OK, 1992. bon, R. C. Wilhoit, Ed., ThermodYilamicResearch Center, The [24] Sanchez,J. H. P. and Mansoori, G. A., "InSitu Remediationof Texas A & M UniversitySystem, College Station,TX, 1997. Heavy Organic Deposits Using Aromatic Solvents," Paper # [37] Twu, C.H., "An InternallyConsistent Correlationfor Predicting 38966, Proceedings of the 68th Annual SPE Western Regional the CriticalProperties and MolecularWeights of Petroleumand Meeting, Bakersfield, CA, May 1998. Coal-Tar Liquids," Fluid Phase Equlibrium, Vol. 16, 1984, pp. [25] Paraffin Products: Properties, Technology, Applications, G. Y. 137-150. Mozes, Ed., Elsevier, NY, 1982. [38] Edalat, M., Mansoori, G. A., and Bozar-Jomehri, R. B., ''Vapor [26] Murad,K. M., Lal,M., Agarwal,R. K., and Bhattacharyya, K. K., Pressure of Hydrocarbons, Generalized Equation," Encyclope­ "ImproveQuality of Waxby Hydrofinishing,"Petroleum Hydro­ dia of Chemical Processing and Design - 61, Marcel Dekker,Inc., carbons, Vol. 7, No. 2, 1972, pp. 144--7. NY, 1997,pp.362-365. [27] Ferris,S. W., "Characterization of Petroleum Waxes Tappi," [39] Letoffe, J. M., Claudy, P., Garcin, M., and Volle, J. L., ''Evalua­ TAPPI Special Technical Association Publication No. 2, 1963, tionof CrystallizedFractions of Crude Oils by DifferentialScan­ pp. 1-19. ning Calorimetry, Correlation With Gas Chromatography,'' [28] Himran,S., Suwono, A., and Mansoori,G. A., "Characterizationof Fuel, Vol. 74, No. 1, 1995, pp. 92-5. AlkanesAnd ParaffinWaxes for Application as Phase Change En­ [40] Braun, R., '!Limits in Differential Thermoanalysis of Waxes," ergyStorage Medium," EnugySources,Vol. 16, 1994,pp.117-128. Fene SeifenAnstrichm,Vol. 82, No. 2, 1980, pp. 76-81. [29] Humphries, W. F., Performance of Finned Thermal Capacitors, [41] Handbook on Anti.oxidants and Anti.ozonants, Goodyear Chemi­ NASA TND-7690, Washington; D.C., 1974. cals, Akron,OH, 1977. [30] Haji-Sheikh, A., Eftekhar,J. and Lou, D. Y. S., "Some Thermo­ [42] Wink,W. A., Delevanti, C.H.,and Van den Akker, J. A.,Instru­ physical Properties Of Paraffin Wax as a Thermal Storage mentation Studies IXXVII, Study on Gloss I, A Goni.ophotomet­ Medium," Progress in Astronatics and Aeronautics 86, 1983, pp. ricStudy ofHigh GlossPapers, TAPPI, Technical Association of 241-253. the Pulp and Paper Industry, Vol.35, December 1953, p. 163A. '"' [31] Du, P. C. and Mansoori,G. A., "Phase Equilibrium of Multi­ [43] Tomsic, J., Dictionary of Materials and Testing, 2 ed., SAE In­ component Mixtures: Continuous Mixture Gibbs Free Energy ternational,Warrendale, PA, 2000, p. 205.

Petroleum Waxes

G.Ali Mansoori, H. Lindsey Barnes, Glenn M. Webster Chapter 19, Pages 525-556, 2003, Manual 37 - Fuels and Lubricants Handbook: Technology, Properties, Performance, and Testing, ASTM Manual Series: MNL37WCD ______