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INDUSTRIAL AND ENGINEERING CHEMISTRY
helices. The distillation data, after the bulk of the n-pentane had been removed, are shown in Figure 3A. That fraction of the distillate (13ml.) intermediate between the benzene and p-cymene plateaus, indicated in Figure 3B, was examined by ultraviolet spectrophotometry with the following results (in per cent) : benzene, 33.1; toluene, 32.8;p-cymene, 33.3; other material, 0.8, The following volumes of various products were found in fraction B: saturated nonbenzenoid hydrocarbons, 567 ml. (Figure 1); benzene, 84.3 ml. (Figure 3A); toluene, 4.3 ml. (spectrophotometric analysis); loss, 114.4ml. (by difference).
543
ACKNOWLEDGMENT
We are pleased to acknowledge the kind cooperation of Wojciech Swietoslawski and William L. Glowacki, both of Mellon Institute. We are also grateful to B. E. Stewart and Frank C. Lauer of Jones and Laughlin Steel Corporation, for furnishing the samples, and to Alberta 5.Jones, who assisted with some of the crystallizations. The spectrophotometric analyses were kindly made by N. D. Coggeshall and M. Muskat, of Gulf Research & Development Company. LITERATURE CITED
DISCUSSION
Since the purpose of this work was to characterize only the saturated nonbeneenoid hydrocarbon impurities, fraction B was not analyzed for thiophene, bromine number, or acid-wash color. However, the behavior of that fraction in the adsorption column (unlike a blank run on the same lot of adsorbent), the large quantity of sludge and acid-wash color$ developed during treatment of the so-called aromatic portion, and the large amount of unrecovered material suggest the presence of unidentified impurities; some of these are believed to be unsaturated hydrocarbons. Fraction B was obtained from 28.5 liters of sample A by purification of the latter through a change of solidifying point equal to 1.18” C. I n the absence of a better method of calculation, this information and the volumes of products recovered from fraction B may be used to estimate the order of magnitude of the amounts of impurities in the original nitration benzene. Our estimate (in volume per cent) follows: saturated nonbeneenoid hydrocarbons, 0.6; toluene, 0.004;unidentified, 0.1,
(1) Altieri, V. J., “Gas Chemists’ Book of Standards for Light Oils and Light Oil Products”, New York, Am. Gas Assoc., 1943. (2) Campbell and Wagner, U.S.Patent 1,991,844(Feb. 19,1935). (3) Collins, W. D.,et al., IND. ENGI.CHEM.,ANAL. ED., 4, 347 (1932). (4) Mair and Forziati, J. Research Natl. Bur. Standards, 32, 151 (1944). (5) Ibid., 32, 165 (1944). (6) Morton, H. A., “Laboratory Technique in Organic Chemistry”, p. 61,New York, McGraw-Hill Book Co., 1938. (7) Rossini, Mair, Forziati, Glasgow, and Willingham, Oil Gas J., 41, 106 (1942); Petroleum Rejiner, 21,73 (1942). (8) Stinzendarfer, Oel u. Kohle, 38, 193 (1942). (9) U.S. Bur. Mines, B d l . 412 (1938). (10) Whitmore, F. C., “Organic Chemistry”, p. 698, New York, D.Van Nostrand Co., 1937. TAKBIN in part from a Ph.D. thesis submitted by J. R. Anderson to the University of Pittsburgh. Contribution 652 of the Department of Chemistry, University of Pittsburgh. J. R. Anderson holds an Industrial Fellowship of the Pittsburgh Steel Company a t Mellon Institute.
Reactions of Hydrocarbons in the Presence of Cracking Catalysts J
POLYMERIZATION OF GASEOUS OLEFINS’ CHARLES L. THOMAS Universal Oil Products Company, Riverside, 111.
T
HE synthetic cracking catalysts are capable of accelerating a variety of hydrocarbon reactions. The type of reaction depends on the hydrocarbon involved and the thermodynamic conditions applied to the system containing the hydrocarbon and the catalyst. It has already been shown that the synthetic cracking catalysts readily sever carbon-carbon bonds in olefins such t\9 octene and hexadecene at atmospheric pressure and 350500’ C. to produce olefins of lower molecular weight (9). I n one sense this cracking of olefins can be regarded as depolymerization. A classical catalyst-that is, a substance that hastens equilibrium-should be capable of accelerating the reverse reaction, polymerization, if the appropriate changes in thermodynamic conditions are made. I n the work reported here, several different synthetic catalysts which had been shown to be active wwking catalysts were studied. Gaseous olefins have already been polymerized by masses containing silica and alumina. The natural clay known 9a. floridin or Florida earth has been studied extensively. Apparently Gurvich (8) was the first to observe that it would polymerize gaseous olefins. This clay is a hydrosilicate of alumina containing 1
The four previous articles in thie seriea appeared in J . Am. Chem. SOC.,
61, 3671 (1939); 66, 1686, 1689, 1694 (1944).
both iron and magnesium compounds. This and numerous similar clays, either with or without acid treatment, have received considerable scientific (2, 16, 16, 21, 82, 84, 86) and technical (7,10,16,14, 19,10, 26) study MI polymerization catalysts. I n general the polymers resulting were dimers, trimers, and tetramers, although small proportions of still higher polymers may have been formed. Isobutylene was especially easy to polymerize. Floridin is capable of polymerizing isobutylene at temperatures as low as -100’ C. (16,82). The molecular weight of the isobutylene polymers was found to increase as the temperature was lowered, The higher-molecular-wcight polymers were elastomers. Apparently Gayer (6) ww the first to report work on a synthetic silica-alumina catalyst for the polymerization of gaseous olefins, His catalyst was prepared by the hydrolytic adsorption of alumina on a silica xerogel. The resulting catalyst contained about 1% alumina. This catalyst produced mainly dimers and trimers under the conditions studied. The same type of catalyst was investigated in considerable detail by Hoog, Smittenberg, and Visser (9) and KazanskiY and Rosengart (19). Related synthetic silica-alumina catalysts have been described for olefin polymerization (1,4,6, ff,18).
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INDUSTRIAL AND ENGINEERING CHEMISTRY ~-
Synthetic silica-alumina catalysts as prepared for catalytic cracking will polymerize propylene and the butylenes. Synthetic silica-zirconia catalysts will polymerize butylenes. The three-component synthetic cracking catalysts, silica-zirconia-alumina and silica-alumina-thoria, are active for polymerizing butylenes. The polymers in all cases are liquids boiling mostly within the gasoline range. A Ca fraction, when hydrogenated, had an octane number of 95.3.
N2
A
Figure 1. Apparatus for Polymerizing Gaseous Olefins
Vol. 31, No. 6
He did not record any connection between this acid nature and the ccitalytic activity. LABORATORY AND PIulT PLANT TESTS
In the laboratory work a number of catalysts were tested to show the presence or absence of polymerizing activity. The pilot plant tests were made on a synthetic silica-alumina cracking catalyst. They provided a suilicient quantity of polymer for rather complete inspection tests. CATALYSTS.The general methods used in preparing the catalysts have already been described (f7,bS). I n the present work the precipitated and washed catalysts were dried, formed into 2 X 2 mm. cylinders, and calcined at 500" C. LABORATORY APPARATUS. The catalyst was placed in a steel tube mounted in a thcrmostated metal block furnace. The liquefied charging stock was drawn from a calibrated pressurc vessel equipped with a sightglass. Small copper tubes were used to connect the charger with the catalyst tube. A needle valve was mounted on the exit of the catalyst tube to control the flow rate. Receivers, a flowmeter, and a wet test meter completed the equipment. Figure 1 is a diagram of the apparatus. The catalyst and silica chips were placed in the catalyst tube, and the tube was put in the block furnace at reaction temperature. The pressure fittings were then attached to the catalyst tube, and the assembly was tested for leaks with nitrogen at operating pressure. Nitrogen a t operating pressure was left in the apparatus. The flow from the charger was then started, and tho rate of exit gas was controlled to give an approximately constant flow as indicated by the flowmeter. The charge was determined from the change in level in the pressure charger. The outlet gas was measured by the wet test meter. The polymer product was stabilized to a distillalion temperature of 10' C. to remove dissolved C, hydrocarbons. PILOT PLANT EQUIPMENT.The same principle was followed which wv&8used for the laboratory apparatus. The pilot plant was somewhat more complicated in that it was equipped with a pump to feed the liquid charge, an automatic pressure control, and a continuous stabilizer. CHARGINQ STOCKS. For practical rcasons technical gas rnixtures (stabilizer reflux from a Dubbs thermal cracking unit) were chosen as the source of the olefins. The analyses follow:
The Gayer catalyst is not particularly active as a cracking catalyst. I n this work it seemed desirable to investigate the polymerizing ability of synthetic silica-alumina catalysts specially prepared to have a high cracking activity. In addition, synthetic silica-zirconia, silica-alumina-zirconia, and silicaalumina-thoria cracking catalysts and the components silica, alumina, and zirconia were investigated. Mole Per Cent The cause or seat of the catalytic activity of either natural or Hydrocarbon For laboraFor pilot Constituent tory testa plant tests the synthetic catalysts is not clear. The synthetic catalysts are noncrystalline, while the natural clay catalysts are crystalline to CaHi CaHs x-rays. When properly prepared the synthetic catalysts are more ISO-C4Hs n-CaHs artive than the natural catalysts. The synthetic catalysts Is0 + n-CaEI1o are known to have surface areas of about 300 to 600 Rquare CS meters per gram. This would lead us to classify them as adsorption catalysts. Indeed TABLE I, LABORATORY POLYMERIZATION OF C4 FRACTION the catalysts are highly ad(45 kg./sq. om.; 165' C.; 60-eo. catalyst volume) sorptive; however, the silica 1OOSiO1- 1OOSiOP lOOSiO22A120a5AlzOaxerogels without alumina or 1OOSiOrllAlnOr 5OZrOs 0.5Th02 Catalyst type4 12Zr02 Si0,b AhOaC ZrO# zirconia are equally adsorptive. Fresh Regen. Fresh Fresh Fresh Fresh Fresh Fresh 28.7 28.7 38.0 25.2 35.7 25 49.8 05.9 I t was observed (6, 21) that 7.28 7.83 7.75 6.86 8.36 0.7 0.6 7.7 silica xerogel is not a catalyst 12 12 12 3 14 for the polymerization of olefins. 45.7 51.8 43.2 Negligible! 36.6 64.3 This caused Gayer (6) to mako 0 . 7 0.6 0 . 8 0.7 0.7 tests on an acid-treated alumina, 3.7 3.5 3.6 from which he concluded that 2.1 1.5 3.6 34.6 23.4 28.6 31.8 30.7 the alumina W&PJ the real cata04.9 01.5 19.2 70.6 02.4 lyst and the silica was merely a The catalyst type indicates composition as a ratio of the number of moles of constituents. b Silica xerogel was prepared in the aame wa an were the other catalysts but without the addition of other oxides. a support to distribute the 0 Activated alumina from Aluminum Ore dbmpany. d Prepared from ZrOClt.8HzOjust as if a oatalyat were being made but in the absence of the silica hydrogel. alumina. Gayer also observed * This polymer yield was calcuJated from the C4H: disappearance; in most inatancea the polymer recovery was that a drop of indicator placed somewhat smaller due to mechanical loama. I When no olymer wan formed a t 165. C. with sirconia, the temperature was gradually railed to 300- C. while on his 1% aluminmn-silica maintaining t f e charging stock flow. No polymer formation wan observed. ratalyst gave an aridic rcartion.
21
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INDUSTRIAL AND ENGINEERING CHEMISTRY
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TABLE 11. PILOT PLANT POLYMERIZATION OF CI FRACTION 175' C,: 100 silica-8 alumina, 456 gram) Polymer Ratio % Removal:Q./B. Time Isof xs0 i - to ~ in , ~Gas, , Standard Liters *dvcatalyst/ Houri CiHi n-C4Hi Polymer6 Charged Recovered liter& hr. 0-24 89.5 31.2 1.67 29,800 22,200 22.54 1.62 24-48 86.6 25.2 2.0 17,750 13.600 12.67 0.855 48-7Ic 76 20.8 2.1 15,600 12,600 8.S85 0.60 Calrulated from analysis of inlet and outlet gases. 6 The yield of polymer calculated from the inlet and outlet gases is someyhat higher. The difference between the calculated polymer and the recovered polymer 10 presumed to be due to handlin losaes At the end of 7l%ours ;he catalyst weight had increased 4.6%. (60 kg./sq.cin.:
545
Again the isobutylene polymerized faster than the n-butylenes. As the catalyst aged, it seemed to losc its ability to polymerize n-butylenes faster than its ability to polymerize isobutylene, As the catalyst agcd, there was less tendency to form polymers boiling outside the gasoline range. That is, there waa a greater tendency for tho catalyst to produce dimers rather than higher polymers. The antiknock quality of the olefinic polymcr compared favorably with that produced by othcr polymeriration catalysts. The quality Of the fraction improvcc' on hydrogenation. This is B property associated with dimers of isobutylcne.
Exploratory tcsts wcre madc on the pilot plant with a, propane-propylene fraction containing 18% propylenr. TEST Raising the temperature to 250-300" C. at 50 kg. per aq. cm. Time, hours 0-16 24-48 48-71 16-24 Vol., liters 15.68 6.96 12.676 ~ ~ m ncaunad the silica-alumina catalyst to polymerize some of the Sp. gr., d:O 0 7365 0.7267 0.7313 0.7343 propylene. The activity of the catalyst seemed to decline faster A.S.T.M. distillation, ' C. under those conditions than in the butylene tests. The polymer Initial b.p. 37 38 made under these conditions contained about 10% dimers and 93 98 115 116 snmc 60% trimers. It will be recalled that Gaycr (6) and 127 133 Hoog el al. (8) obtained polyniers containing over 50% dimer hy 7 0 176 170 ' 00 258 233 polymerizing propylene. A more detailed study of the propylenr End point 2Q4 25 1 polymerization by these catalysts was not made because of t,lrc 6 Contains 52.2% C s hydroonrhons. A.S.T.M. Motor htetliod octane numbere: crude polymer = 85.3: Cd frnrtion (95-1309 C.1 = Rh.3 C'I rapid dccline in catalyst activity owing to the carbonaceous drfraction hydrogenated 86.3. positr on the catalyst. It, w s thought that the rapid decline of tho catalyst activity under these conditions migltt prevent, thv catalyNt from competing with othcr polymerization catalybts that EXPLORATORY LABORATORY RESULTS are known to be able to polymerize propylene while maintaining activity ovcr much longer perio(1.q of time. Preliminary tests wore madc to see if the catalysts would act as polymerization catalysts and to seek usable reaction conditions. LITERATURE CITED These tests ehowed that polymerization took place a t 165' C.,at. Atidowon and D'Ouville, U. S. Patent 2,288,872 (July 7, 1942). a pressure of 45 kg. per sq.cm., and at a feed rate corresponding to Dohronravov and Frost, J . Gen. Chem. (U.S.S.R.). 6, 1796 about 7 volumes of liquefied charge per hour per gross volume of (1936). catalyst. Egloff, Morrell, Thomas. and Rlorh, J . Am. Chcm. Soc.. 61, These conditions were used for tests on a number of catalyst8s. 3571 (1939). Free and von Fuener, U. 5. Patent 2,334,871 (Nov. 23, 1943). Table I is a summary of the results. From the experience gained Fulton and Cross,Canadian Patent 411,606 (April 0, 1943). in these tests the following observations have been made: Gayer, IND. ENU.Cnm., 25, 1132 (1933); U. S. Patent 2,0BS,016 (Jan. 19, 1937). The silica-alumina, silica-zirconia, silica-alumina-thoria, and Gray, U. 5. Patent 2,034,575 (March 17, 1936). silica-alumina-zirconia masses were polymerization catalysts. Gurvich, J . Rues. Phys. Chem. SOC.,47, 827 (1915); 2. physik. Individually the silica, alumina, and zirconia did not act as Chem., A107, 235 (1923). polymerization catalysts. Hoog, Smittenberg, and Visser, Proc. dnd World Pdroleirm The catalysts lost activity with use, apparently because of the Congr. Paris. 2, 489 (1937). de osition of carbonaceous material on them. Houdry, U. 8. Patent 2,035,478 (March 31, 1936). !he catalysts could be regenerated by air at 450-500' C. Hyman, Zbid., 2,197,862 (April 23, 1940). The regenerated catalysts were as -active or more active than I. G. Farbenindustrie, A.-G., Brit. Patent 316,951 (1930) the fresh catalyst. Kazanskil and Rosengart, Bull. acad. sci. U.R.S.S., 1941, 115; The catalysts of Table I had different polymerizing activities. J . Gen. Chem. (U.S.S.R.), 12, 246 (1942), 13, 304 (1943): The method of catalyst preparation seems to be just as important Natl. Petroleum News, 36, R-643 (1944). as chemical composition in preparing active catalysts. Both a Kirn and Fragen, U. S. Patent 2,301,052 (Nov. 3, 1942). suitable preparation method and a suitable com osition are necLebedev and Borgman, J . Gen. Chem. (U.S.S.R.),5, 1695 essary to roduce an active polymerization catagst. (1935) As mi& have been expected from its known activity, isoLebedev, et d.,Rer.. 58, 163 (1925), 63, 1432 (1930); J . Crn. butylene polymerized more readily than ?a-butylenesunder these Chem. (U.S.S.R.), 5, 1589 (1935). conditions. Lee and Ahlherg, U. 9. Patents 2.289.918-19 (July 14, 1942). MaKinney, U.8.Patents 2,142,324 (Jan. 3, 1939) and 2,147,986 PILOT PLANT RESULTS (Feb. 21, 1939). Ocon and Ocon, U. S. Patent 2,289,063 (July 7, 1942); But. Larger scale tests were made so that the process and the prodPatent 624,613 (1940). Osterstrom, st al., U. 8. Patcents 2,056,978-9 (Oct. 13. 19.76). uct could be studied in more detail. The conditions of tempera2,121,258 (June 21, 1938). ture and pressure were nearly the same as those used in the Slobodin, J . Applied Chem. (U.S.S.R.), 8, 35 (1935); SILT. laboratory. The initial feed rate was 8.7 volumes of liquid charge ForGign Petroleum Literattire, Translation 5 3 2 5 (Oct. 29, per hour per gross volume of catalyst, but as the activity of the 1943). Staudinger, Berger, and Fischer, J . prakt. Chem., 160,95 (1842). catalyst declined, the feed was reduced so that i t was 4.5 at thc Thomas et al., U. S. Patents 2,216,284-5 (Oct. 1, 1940), 2,239.end of the test. Table I1 is a summary of the results. Liquid 353 (Jan. 21 19411, 2.242 553 (May 20. 1941): 2,249,583 product inspections are listed in Table 111. From the data in (July 15, 1941). these two tables the following observations have been made: (24) Van Winkle, J . Am. Pharm. Assoc., 17, 544 (1928). (25) Wagner, U. 8. Patents 1,838,943 and 1,938,945 (Dec. 12, 1933). (26) Waterman and Jamin, J . Znst. Petroleum Tech., 12, 510 (1926). The polymerization occurred on the ilot plant scale, very much aa would have been expected from tEe laboratory reaults. The catalyst lost activity with use. During the first 24 hours PRELIENTSD aa part of the Bymposium on Catalysis in the Petroleum Induathe polymer production rate was about 2.5 times as fast as during try before the Division of Petroleum Chemistry at the 108th Meeting of the the 48-71 hour period. AMERICAN CBEMICAL Socrew in New York. N. Y.
TABLE111. PKoPEirrrrcs
OF Cc POLYMER FROM
-
-
-
PrLor PI,AN'~
