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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 ... I preceding paragraph . 0 1.45 I X I 1. 50 '"0 I I I I I I ~ 1.44 I UJ ~ L > I >= I u 1.49 - -

1.47 1. 41 r-I 1 - I w 1 I I- I 1 1.37 a:: 1.4 6 f- A - I-"" ...J I 1 .... I 1.36 35 .... I 0 0 1.45 r-' I - VO LUME OF FILTRATE IN ML x 1 w 1 0 I FIG URE I.- Results oj the analytical ads01'ption experi ment z I I on the samplejro'ln the Hydroj01'lning process. 1.44 w f-I - > I 1'he refracti ve index of the fi ltrate is given as a fUllction of its Yolnme. 'rhe f= I volume represented by A measures the aromatic content of the material. (,) I 'rho volu me constituted by S shows the material that is to be mixed to co n­ I ....""a:: 1. 43 f-I - stitute the samnle of aromatic hydrocarbons (after the ethyl alco hol at the w I a:: 1 tail end is removed by washing). I I I given in ta,ble 1 of [2] is the Two-pass Fixed-Bed 1. 4 2 f- I I - sample listed in table 1 of this report. I 1 Although the foregoing represen ts the procedure lJJI s 1I -1 finally selected as being the best for analyses of the 1.41 r-I .-l i - kind described, actuftlly mftny more observations - of other kinds were made on the materials in order 1-1 1.37 1-, i l - to work out the simplest and most reliable method I I 1 of analysis. For example, in order to obtain larger 1.3 6 I I I I I i~ quantities of the aromatic portion than are recom­ o 10 15 20 25 30 mended above, the separation of the nona,romatic VOLUME OF FILTR ATE I N ML hydrocarbons from the aromatic h.ydrocarbons was FIGURE 2. - Results of the analytical adsorption experiment also performed by a method previously described on the sample f rom the High-temperature Fluid catalytic [3]. This method involves separation of the non­ cracking process. aromatic hydrocarbons from the aromatic hydro­ The refractive ind ex of the filtrate is gh' en as a fun ction of its volume. 'l'he carbons in the adsorption column by displacement volume represented by A measures th e aromatic content of the material. with pentane, the subseq llent removal of the hydro­ The volume constituted by S shows the materi al that is to be mixed to con­ stitute the sample of aromatic hydrocarbons (a fter the ethyl alcohol at the carbons from the adsorption column with methanol tail end is removed by washing).

Alkylbenzenes in the Cs Fraction 305 The amounts of toluene, of the sum of etl1yl­ The amounts of 0 7, 0 8, and 0 9 aromatic hydro­ benzene plus p-xylene plus m-xylene, of o-xylene, carbons in the aromatic portion of each material,

and of the 0 9 aromatics in the aromatic portion, as determined from the analytical distillations, are were determined by an analytical distillation of given in table 3. This table al'So gives values for about 180 ml of the aromatic portion at a high the molecular weight of the aromatic portion as reflu x ratio in a rectifying column of high efficiency calculated from the data from the analytical dis­ and low hold-up, using n-clecane or diethyl-benzene tillation and as determined from measurements of as a "chaser". These distillations were performed, the lowering of the freezing point in benzene. under the supervision of O. B . Willingham, in In table 4 are given values of the amounts of distilling columns identical with still No. 2 each 0 8 aromatic hydrocarbon determined to be in described in table 1 of reference [4]. The results the aromatic portion by means of measurements of of these distillations (except for the relative fre67:ing points, and t he sum of the amounts of the amounts of the components) were similar to the four 0 8 aromatic hydrocarbons as so determined . results presented in figures 8 to 14, inclusive, of It is interesting to note the good accord between reference [6] . the values given in tIle last column of table 4 with The molecular weights of the given aromatic the corresponding values given in the third column portions were calculated from the relative amounts of table 3.

of the 0 7, 0 8, and 0 9 aromatic hydrocarbons as In table 5 is given a comparison of the content of determined from the di stillation and also from T ABLE 3.- Amounls of th e C7, Cs, and C9 aromatic hydro­ measurements of the lowering of freezing point in carbons in the aromatic portion, and the molecular weight benzene, as described in (b) above. of the aromatic port1·on IV. Results Amounts (% hy volume) of Molecular !1 romat.ic hyd rocarhons- weight of the ar­ The values of the bromine number, and the Sam pie omatic portiona. content of olefins, aromatics, and paraffins plus C7 C, C, II naphthenes, for the materials as received , are ------_._------given in table 2. gj mole gj mole H ydroform iog ______O. 7± O. 3 94 . 4± 0. 5 4. 9± 0 ..J 106. 65 107. 56 Two-pass fixed hcd ______3. 3± . 5 85. 0± .5 11. 7± .5 107.06 107.31 TABLE 2.- Content of olefin, aromatic, and pamffin plus Three-pass fi xed bed _____ 2. 9± .5 94. 2± . 5 2.9± .5 106.05 105. 18 naphthene hydrocarbons in the samples a s received Low-temperature flnid ___ O.5± .3 9i.3± .5 2.2± .5 106. 34 105. 90 High-temperature fl uid __ 0.5± .3 97. 9± .5 1. 6± . 5 106. 27 106. 04 Contont of nl'Omine Conten t of Content of paramn s Sample plus nR ph­ a Deterrniocd independently in two ways, column I giving values calcu­ number a olefin s b R. romatics c thcnes (by c1 itTercncc) lated from the distillation data, and column II giving values determined from the lowcring of the freezi ng point in benzene, as described in part III of refer­ ------_._------~------.------_.- ence [ ~l . The molecular wcight of a C, aromatic is 106.16. Percentage Perceniage P ercertt(lge y/i OO g by I'OZ. by vol . by vol. B ydroforming ______0. 50 O.4±O. 1 (I ) 91.8± 0.5 8. O± O. 4 T A BLE 4.--Amounts of the four Cs alkylbenzenes in the (II) 91.3± .5 aromatic portion, as deterrnined from free zing-point M ean 91.6± .4 'r wo-pass fi xed bed ___ _ 1. 59 1.4± . 2 (I ) 55 .2± .5 43. 3± . 4 rnea.nlremenis (II) 55.5± .5 M ean 55.3± .4 Eth Yl- I I I Total of Three-pass fi xed bcd ___ I. J.o I.O± . 2 (I) 85.3± .5 1:J.2± . 4 Samplc benzenc p-Xylcne m-Xylene o-Xylene I C. ar o- matICS (Il) 86.3± .5 M ean 85.8± .4 - Low-temperature flu id _ 3.84 3.5± . 3 (I ) 77.2±1.0 IS. 4± . 8 P ercentage by yolume' (II) 79.0± 1.0 Mean 78. 1± .7 TT ydroforming ______II i g h -t.e m p e r a t ur e 15.0G 13.5±1.0 (I) 78.4±1.0 i .I±1. 2 11. 2±1.2 17. 2± 1. 2 45. H I. 2 23. 5±1. 2 97. O± 2. 4 Two-pass fixed bed ____ 2 4 fln id. (II) 80A±1.0 11. 4± 1. 16. 4± 1.2 41.4±1. 2 16. 9± 1. 2 86. 1± 2. Thrce-pass fixed bed __ .'I1can i9.4± .7 8.0±1. 2 IS. 9± 1. 2 48. 5± 1. 2 17.6±1.2 93.0±2. 4 Low-temperature Iluid_ 12. 9± 1.2 17.5±1.2 45. 7± 1. 2 24 .3±1. 2 100. 4± 2. 4 H ig h-tem p e r a tu r e • Determined by .R . C. Hardy, Section 3.5, National Burea u of Standards. fl uid ______12. 4±1. 2 19. 4± 1. 2 48.G±1. 2 17. 7± 1. 2 98. 1± 2. " b Calculatcd assuming the olefin s to be C,ll., and the ratio of the density of the aromatics to the olefin s to be 1.1 8. c D etermined iudependenily ill two ways, (1) giving values obtained by the • T he uncertainty of ± 1.2 pcrccnt aSS igned to the amount of cach (', aro­ Simple adsorption experiments (performed by B . J . Mair) described in this matic hydrocarbon in the aromatic portion is the resultan t of an estimatrd report, and (II) gh -in g values obtained by refractive index measurements on uncertainty of ± 1.0 perccnt in the determination of t he lowering of the the original m aterial and appropriate mixturcs of the aromatic and non­ freez iu g point and of ± O.. 1 perce nt in the dctermination of the molecular aromatic portions of the original material. weight of the u nknown mixture.

306 Journal of Research

L ------_. ---

o-xylene in the five materials as determined by In tabJe 6 arc gIv en valu es for t Ile relative measurements of freezing points and as deter­ amounts of the Cs aromatic hydroca.rbons in eacb mined from j,he data of the analytical distillation. of the fi ve different maLerials, as cl eterminocl from measurements of the lowering of the freezing T AB LE 5. - Comparison of the content of o-xylene in the point. At the bottom of table 6 are also given for aromatic portion as determined (1) fr om the measurements of freezing points and (II) from the analytical distillation each compound, for the five samples, (a) the mean value, (b) the average difference between the mean A mo unt of o-xylene and the individua.l values, and (c) the maximum Sample difference bet.ween the mean and the individual Il values. ------1·------. Percentage Percentage v. Discussion by vol. by vol. IIydroform illg .... ______.. ______. __ . 23.5± 1. 2 n.6± 1. 0 In 'rwo-pass fixed bed ______._ Hi. 9± 1. 2 17. 6±1. 0 .t n connection with tIle results obtained this Tbree·pass fi xed bed _. ______17. 6±1. 2 18.0± 1.0 investigation, the fo llowing conclusions may be Low·temperature !l uid ______. ______. ___ 2·1. 3±1. 2 23.8±1. 0 IIigh-temperature lIuid ______•.•. ___ _ 17.7± 1.2 17.6± 1.0 drawn : (a) Tlle relative amounts of tll8 foUl' Cs alkyl­ T ABLE 5. - Relative amounts of the four Cs alkylbenzenes as benzenes are nearly the same in the prod uct from dete"mined fTom freezing-point measurements· fl11 £lve of the catalytic petroleum refining proc­ esses. This is clearly shown by the results in SalJlpic I;~;~{~~ I Zl.XYlen+ ,XYlenel o-Xylene I Tolal t.able 6, which gives the following for the 111eflll ------value flnci for the average difl' erence between the }"'rrccnL:1gc hy \'oiu ITIC mean and the individual values: Ethylbenzene,

H ydroforming .. _. __ .. _____ 11.0± l. O 17. i ± I. O 46.5± 1.0 24.2± 1. 0 100 1l.8, ± 1. 3; p-xylene, 18.8, ± l.0; ?Ii-xylene, 48.4, ~l~wo-pass fixed bed ______13.2±1.0 19. 1± 1.0 48. ]± 1.0 19.0± 1.0 )00 ± 2.0 ; o-"'ylene, 2l.0, ± 2.G. Three·pass fix ed b ~ d __ . ___ 8. G±l. 0 20. 3±1. 0 52. 2± 1. 0 18. 9± l.O 100 Low·tem pera ture fluid . -- 12.9± l.O 17.4± 1.0 45 ..1 ± 1. U 24 . 2± 1. 0 100 (b) The relative amounts of th(' four alkyl­ H igh·temperature f1uid ___ 12.0± 1.0 19.8±1.0 49. 6± 1. 0 18. O± 1. 0 100 bell7.enes are, on the average, wit'lin the estimated ------Mean value ______11 .8 lS.8 48.4 21. 0 ------limits of uneertainty, equal to the relative amou n ts Average diO'ereuce be· that would be expected at thermodynamic equi­ tween the mean 3nd the individual v al ues ______± 1. 3 ± 1. 0 ± 2.0 ± 2.G ------librium at the temperature at which tl)e material l\1aximum d iffcfence be· was produced . This is clearly shown by the tween t he m ean and the individual yalues ..... __ -3. 2 + 1.5 +3.S +3.2 ------results given in table 7, which gives for each -- process the temperature, the actual amount, and • T he "a.lues gh'cn in this tahle arc those from table 4 recalculated to make calculated equilibrium amount for each of the tl\r sum of the amounts of the' fOUf ('8 aromatics cqual to 100 percent. The assigned uncertnin ty a ri ses only from t he d etennillation of the lowering of the foUl' Cs alkylbenzenes. The calculated values for frcC'zin g point, since all u llceftainty in the molecula r weight of the unknown thermodynamic equilibrium given in table 7 are mixturc of aroma tic h ydro c arbon ~ docs not afTrct the relative amounts of the fOllr Cs aromatic hydrocarbons. taken from reference [7] .

T ABLE 7.- Compan·son of th e actual composition with that calculated for thermodynamic equilibrium at the given tem perature (Acl1wl values Font table 6 of this re port; calculated values F OIn reference [7])

Rclali\'e Amounts of the Four C, Alkylbenzenes --_. I Tempera· Samplo LlIre Ethylbenzcne p-Xylcne m·Xylcnc Q·Xyleno ------Actual Calculated Actual Calculated Actual Calcul ated ACLual Ca lcu lated ------o J( Hydroforming_.. ___ . _. __ .... __ . . _ --. --- 769 11. 0±1. a 10. 0±1. 5 17. 7±1. 0 20. 9±3. 5 46. 5±1. a 46. 4±5. a 24. 2±1. a 22. 7±3. 5 Two·pass fixed bed __ .. ___ .. ______------727 13. 2±1. a 9.0± 1. 5 19.1± 1. a 21. 2± 3. 5 4S.1 ± 1.0 47. 3±5. a 19. 6± 1. a 22. 5±3. 5 Three·pass fixed bed ____ ...... ____ .. 741 S.O±J.O 9.4±1. 5 20. 3±1. a 21. 1±3. 5 52. 2± J. a 40. 9± 5. 0 lS.9± LO 22. 6±3. 5 Low-temporatu re tlui <.L ____ . ______---- 700 12. 9± 1. a S.3± 1.5 17. 4± LO 21. 5± 3. 5 45. 5± J. 0 47. S±5. 0 24 . 2± L a 22. 4±3. 5 Righ-temperatl1lc fluid ______797 12.6± 1.0 10. 7±1. 5 19.8±1. 0 20. G± 3. 5 49. 6± 1. 0 45.9,1:5. a 18. 0± 1. a 22. 8±3. 5

Alk ylbenzenes in the Cs Fraction 307 VI. References Petroleum lnst. 23, III, 7 (1942); Oil Gas J. 41, No. 27, 106 (1942); Petroleum Refin er 21, No. 11 , [1] B. J . Mair, J. R esearch N BS 34, 435 (1945) RP1652. 73 (1942). [2] A. J . Streiff and F. D . Rossini, J . R escarch NBS 32, 16] A. F. Forziati, C. B. Willingham, B. J. Mair, and F. D. 185 (1944) RP1584. Rossini, J. Research N BS 32, 11 (1944) RP1571 ; [3] B. J. Mair and A. F . Forziati, J . R esearch NBS 32, Proc. Am. Petroleum I nst. 2<1. III, 34 (1943) . 165 (1944) RP1583. [7] W. J . Taylor, D . D. vVagman, :VI. G. Williams, Ie S. [4] C. B. Willingham and F. D. Rossini , J. Research Pit zer, and F. D . Rossini, J . R esearch NBS 37, NBS 37,15 (1946) RP1724. 95 (1946) RP1732. [5] F. D . Rossini, B. J . Mair, A. F. Forziat i, A. R. Glasgow, Jr. and C. B. Willingham, Proc. Am. WASHINGTON, JANUARY 24,1947.

308 Journal of Research

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