------------- ---- U. S. Department of Commerce Research Paper RP1830 National Bureau of Standards Volume 39, O ctober 1947 Part of the Journal of Research of the Nationa l Bureau of Standards Alkylbenzenes in the Ca Fraction From Five Different Catalytic Petroleum Refining Processesl 2 3 By Anton J. Streiff 4 and Frederick D. Rossini This repor t gives the resul ts of the a na lysis, by measurement s of freezing p oin ts of ap­ propriate mixtures, supplemented by analytical distillat ion, of the four individual Os alkyl­ ben zenes (ethylbenzene, a-xylene, m-xylene, and p-xylene) occu lTing in the product from t he following fi ve different catalytic petroleum refinin g processes: (1) H ydrofo rming, (2) T wo-pass Fixed Bed, (3) Three-p ass F ixed Bed, (4) Low- temperat ure F luid, a nd (5) High­ temperatul'e Fluid. The data indica te that th e relative a moun ts by volume of the fou r Os alkylbenzenes are not greatly d ifferent in t he fi ve different products bein g, on the average, as fo ll o\\'s: ethylbenzene, 12; a-xylene, 21; m-xy lene, 48; p-xylene, 19. These amo unts correspond substan tia lly to t hose called fo r in chemical t hermod ynamic eq uili brium for the op erating temperatures in vo lved . I. Introduction the name of the company that supplied the sample, the approximate temperature and pressure in the As part of its war research program, the Ameri­ reaction zone, and the charging stock. can P etroleum Institute R esearch Project 6 at The process labeled hydroforming is one in the N ational Bureftu of Standards was requested which material of the gasoline range is reformed, to analyze the individual alkylbenzenes in the Cg in thc presence of a catalyst and hydrogen , to give fraction from five differen t catalytic petroleum material of nearly the same boiling range but of refining proces es. The investigation was com­ appreciably higher aromaLic cOll Le nt. pleted early in 1943, and the res ults on the com­ The process labeled t wo-pass fixed bed is a position were correla ted, by appropria te other catalytic-cracking one of Houdry des ign, in which laboratories, wi th manufacturing conditions and material of the gas oil or h eavier distillate rangc with engine performance, to improve the utility is cracked in the presence of a catalyst in a fixed of these ma terials as componen ts for aviation fu el. bcd, with the gasoline fraction from th e first opera­ This report gives the results of the analysis of the tion repassed through a similar operation . amounts of ethylbenzene, o-xylene, m-xylene, and The process labeled Three-pass Fixed B cd is also p-xylene in the product from these five different a catalytic cracking process of Houdry design and catalytic petroleum refining processes. is operated similarly. The charging stock for this II. Materials Analyzed process was h eavy naphtha accumulated from the two-pass fixed bed process . The five lots of ma terial that were analyzed in The process labeled Low-temperature Fluid and this investigation are listed in table 1, which gives the one labeled High-temperature Fluid arc cata­ the name of the process tha t produced the material, lytic cracking processes in which a fluid catalyst 1 '['his investiga.tion was performed as part or the work of the American is moved continuously through the reaction zone, P etroleum Institute Research P roject 6 at the ra ti onal Bureau of Standards on the Analysis, Purification, and Properties of H ydrocarbons. with th e ca talyst being reactivated in continuous 2' 'rhis paper is a revision or a restricted report of the Ameri can P etroleum flow through a separate chamber. The charging Institute Researcb Project 6 at the Kational Bu reau of Standards issued under dete of J uly 31, 1943, with the title " Analysis of the Aromatic H ydrocarbons stock here is kerosine or gas oil. in the C, Fractions of High Aromatic Stocks from Five Different Plant All of th e foregoing processes have been de­ Processes. n 3 P resented before the Division of Petroleum Chemistry of the American scribcd many times in technical articles in the Chemical Society at the meeting at Atlantic e ll )', N. J., in April 1947. petroleum journals, and readers will readily find • Research _~ ssociate on tbe American P etroleum I nstitute Research P roject 6. them under the names given abov e or the follow- Alkylbenz enes in the Cg Fraction 303 758745- 47- - 2 TABLE 1. I nfoTmation conceTning the sam ples analyzed Catalytic petroleum refini ng I Temperature in reaction Pressure in process Supplier zone (a pproximate) reaction zone Charging stock --- - - - ---------------------I-------c------.---I------.---I--------------- lb/in.' OF °c 0 K (gage) aim H ydroforming ................... numble Oil and Refining Co., Hous· 925 496 769 215 15.6 Selected naphtha. ton, rr cx. Two,pa3sfixcd bed ......... _..... SUIl Oil Co., Marcus Hook, Pa ....... _ 850 454 727 50 4.4 Gas oil plus heavy distillate from l'vrid· continent and Gulf coast crudes. Three·pass fixed bed ........... Socony·YaclJu m Oil Co. , Paulsboro, 875 468 741 33 3.2 Heavy naphtha frolll two·pass fixed N. J. bed catalytic process. Low·tcmperaturc fluid ... Standard Oil Development Co., SOD 427 700 ____ __ __________ Mirando kerosine. Elizabeth. N. J. H igh·temperature fluid ._........ Standard Oil De,clorment Co., 975 524 797 . ..... _ ........ Southwest Louisiana gas oiL Elizabeth, N.!. ing: Hydroforming pctrolewn refining process; by adsorption [l p. The amount of material Houdry catalytic cracking process; fluid catalytic processed in the adsorption experiment is selected cracking process. so as to produce not less than 15 ml of a portion Each of the fiv e materials analyzed may be that contains all the aromatics, with only a small described as that part of the product of the given amount or none of the nonaromatic hydro­ plant process containing all of the four Cs aro­ carbons. The res ults of the analytical adsorption matic hydrocarbons, which have normal boiling cxperimen t on the sample from the Hydroforming points as follows: Ethylbenzene, 136.19° C; process are shown in figure 1, and the correspond­ a-xylenc, 144.42° C; m-xylene, 139 .10° C; p-xylene, ing results on the sample from the High-tempera­ 138.35° C. Each sample was prepared by the ture Fluid proccss are shown 6 in figure 2. ,mpplier by distillation of the whole product from (b) Using the aromatic portion obtained as the given plant process. A small amount of described in (a), experiments are made to deter­ toluene (at 110.62° C) and a small amount of mine the lowering of the freezing point of samples isopropylbenzene (at 152.40° C) and higher Cg of "pure" ethylbenzene, p-xylene, m-xylene, and alkylbe.nzenes wcre included in the material a-xylene, respectively, produced by the addition of blended to form the sample for analysis in the small measured amounts (in the range 5 to 7 per­ present investigation, in order to insurc the pres­ cent) of the given unknowns to the given "pure" ence in the given sample of substantially all of the compounds. E ach such m easurement of the Cs aromatic hydrocarbons from the original stock. lowering of the freezing point produces a value of B ecause some of the samples were prepared so as the amount of the given hydrocarbon in the un­ to include more C7 and Cg aromatics than others, known mixture. This procedure requires that the the r elative amounts of the C7 and C9 aromatics molecular weight of the unknown be known. If to thc Cs aromatics have no significance . Like­ it is not known, a determination of the molecular wise, the aromatic contcnt of the original material weight may be made by measuring the lowering of as submitted for analysis would depend upon how the freezing point produced by the addition of a much of the C7 and Cg hydrocarbons (aromatics small measured amount of the given unknown to plus paraffins and naphthenes) was included. "pure" benzene (provided benzene is known not The data that havc an important significance to be a component of the unknown). This method are the relative amounts of thc four Cs alkylben­ of determining individual hydrocarbons in mix­ zenes in the five samplcs. tures of hydrocarbons by measurement of freezing points is described in detail in reference [2l. The III. Method of Analysis " unknown" sample for which complete data are The method of analysis developed for this 1l1- , Figures in brackets indicate the literature references at the end of this paper. vestigation is as follows: • rr, as may be probable, there is no significant difference between the rela· (a) A sample of the material is subjected to an tive amounts of the four C, aromatic hydrocarbons at the frout and back ends of the Momatic plateau from the adsorpt ion experiment, t hen the aromatic analytical determination of the aromatic content portion may be taken substa ntially Ireeof nonaromatic compounds. 304 Journal of Research '.50 and the removal from the aromatic hydrocarbons of methanol by extraction with water and of 1.49 pen tane by distillation. The use of this procedlll'e is also described in reference [5] . The aromatic content was determined not only 1.48 by the simple adsorption procedure described under (a) above, but also by comparison of the 1.41 refractive index of the original material with the refractive index of mixtures made by remixing A known amounts of the aromatic portion and the 1.46 I I nonaromatic portion, obtained as described in the ..