October, 1946
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
sample of retene; 12.9 and 0.9 xcight ,;! respectively, of crystalline extract fractions had refractive indices (n':') of 1.6120 and 1.6018; and 32.4 weight % of raffinate, nZ: 1.5019. The chief reaction is dehydrogenation to retene. Yields calculated from refractive index data, assuming the absence of intermediate products, are about 53 mole 7 of retene and 45% of unreacted charge. DIAMYLDECAHYDROSAPHTHALISE. Dehydrogenation of diamyldecahydronaphthalene (b.p. 124-152", 0.5-0.4 mm.), in a feries of four experiments a t 4.50' and 400" C., yielded liquid products. Cracked material boiling below 300" ranged from 4.5 t o 0.5 weight % of the naphthene charged and consisted almost exclusively of pentane-pentene mixtures. Sulfur dioxide extracts of t h e residues above 300" had refractive indices (n2:) ranging from 1.5575 t o 1.5824; this showed the presence of material of index higher than diamylnaphthalene-for example, amylnaphthalene by side chain cleavage. Some material other than unreacted djamyldecahydronaphthalene was left in the raffinates since the refractive indices of the latter ( n S )ranged from 1.4909 t o 1.4997. PARAFFIN DEHY DROGLXATION S
Table 111 presents results of the dehydrogenation of t h e sixreen-carbon paraffins, cetane and dihydrotetraisobut,ylene. ;Ippreciablc percentages of cracked products were noted. Of These, the lower boiling fractions vere highly unsaturated, and the unsaturation decreased markedly z r t h e boiling range increased. I n the case of cetane not more than traces of the cracked product distilled below 75' C., and the noncondensable gas contained 92-95 mole yo of hydrogcan. The high refractive index
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of the sulfui dioxide extract, n2: 1.5541, indicated that arumatization had occurred. The index (n':) of the raffinate was 1.4454. K i t h dihydrotetraisobutylene the low boiling distillate included substantial quantities of C, hydrocarbons (chiefly iso' butylene). The noncondensable gas contained 16-17 mole % of paraffins having a carbon index (average number of carbon atoms per molecule) of 1.4-1.6. I n t h e two tests refractive indices (n2t) of the extracts and raffinates were 1.50-1.48 and 1.4399-1.4397, respectively; these values indicated t h a t the raffinate mas virtually unreacted charging stock. ACKNOWLEDGMEIVT
The authors express their appreciation t o V. N. Ipatieff for his interest in the work; t o John Grover, James E. Kidder, and J. J. Ottcns for assistance; t o R. R. Moehl for t h e carbon and hydrogen analyses; and t o Herman Pines for supplying the polycyclic nnphthenes. LITERATURE CITED (1) (2)
Braun. Ju!im v . . and Rath, Eiich, Ber., 61, 956-63 (1928). Cameron. J . SX. L.. Cook, J . W., and Graham, Walter, J . Chem.
SOC.,1945, 256-9. ( 3 ) Coulson, Edward. .1.,Ibid., 1937, 1298-1305.
(4) Grosse,
;1 V.,and Mavity, J. SI., Div. of Petroleum Chem.. A.C.S., Boston, 1939. ' 5 ) Grosse, -4.Y., Norrell, J. C., and Mattox, I T . J., IND.EXG.CHEM., 32. 628 (1840), Universal Oil Products Co., Booklet 241.
(6) Kagehira, Ituo, Bull. Chem. SOC.J a p a n , 6 , 241-54 (1931). ( i )Mattox, K. J., and Grosse. A . V.,J . A m . Chem. Soc., 67, 84 (1945). (8) COP Laboratoiy Test Methods for Petroleum and Its Products, Method G-84-40, p. G-33 1.1940). (9) I M . , Zlethod H-44-40, p . H-25.
Polytreating of Catalytically Cracked Gasolines YIADIMIR HAENSEL AND V. Pi. IPATIEFF Cnicersnl Oil Products Coinpany, RiGerside, I l l . T h e treating of first-pass catalj-tically cracked gasolines in the presence of solid phosphoric acid catalyst has been investigated. This process, called "polytreating", results in the formation of gasolines having a low olefin content and an increased lead Susceptibility. The process employs temperatures from about 400" to 560" F. and pressures in excess of 400 pounds per square inch gage, with the preferred operating pressure about 600 pounds. The reduction in bromine number of a given gasoline is primarily a function of temperature and space velocity. Pressure has a minor effect, provided t h e operation is carried out under sufficient pressure to maintain a liquid phase.
T
HE refining of cracked gnsoliries using clays, zinc chloride, and various acids is an old and established practice ( 2 ) . I n most cases the purpose of such treatment is to remove highly unsaturated components, such as diolefins, and thus decrease the tendency t o n a r d gum formation. Since the mono-olefinic constituents of thermally cracked gasolines usually have a higher octane number than the paraffinic and naphthenic components, there is no reason for removing thcsc olefins by a more severe refining treatment. With the advent of catalytic cracking, this viewpoint ~iccesearily changed. The high lcxled octane numbers of catalpticnlly
cracked fuels are due primarily to the presence of branched paraffinic and aromatic compounds; the olefinic constituents, by virtue of their low lead susceptibility, are considered less desirable. -4 number of methods have been proposed for the removal of olefins from catalytically cracked base stocks. These include further processing of the base stock over the cracking catalyst a t conditions approximating those used for the primary cracking step, hydrogenation of olefins, and acid treating. -4nother method for improving the quality of catalytically cracked gasolines is "polytreating", or processing the stock over solid phosphoric acid catalyst. The present paper deals with this particular process. The exploratory work on the process was done in the laboratory; no attempt n-ill be made to discuss at length the considerable amount of data. obtained in pilot plant operation. The laboratory unit (Figure 1 ) consists of a high pressure pump, a reaction tube equipped with a short preheater section, and a catalyst bed with a capacity of 100 cc. Standard G.O.P. KO. 2 solid phosphoric acid catalyst (3j'1p-inch size) was used in a11 experiments. A constant temperature was maintained by means of an automatically controlled electric furnace. The effluent from the reaction tube vas distilled using a six-plate column to remove a gasoline fraction which had the same end point as the charge. Engler distillations, bromine number, and octane number determinations were made on the product. The high boiling
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Table I indicates that, as the operating ternpcraturc is iricreased, the yield of the gasoline fraction is decreased. This io (1000 pounds per square inch gage. 2.2-2.6 LHSV, 12-15 hour runs) accompanied by a decrease in olefin content and an increase in 352 405 Temp. F. Charge 430 451 489 532 octane number. The reaction takes place t o a considerable ex1 0 0 . 0 79.2 7 6 . 2 7 5 . 0 7 4 . 5 7 3 . 9 71.7 GssoliAe, % b y wt. 18 16 17 13 tent even at 352" F.; a considerable improvement is obtained by 52 25 18 Bromine No. Octane No. increasing the temperature to 405' F., b u t further increases in F-2 + 4 c c . T E L " 89:6 9 2 . 1 9 3 . 1 9 3 . 7 9 3 . 8 9 3 . 9 94.2 F-3 + 4 cc. T E L b 90.5 . . . . . . -Blend 98.3-* temperature produce less significant change until 532" F. is Reid vapor pressure, lb. 8.4 7.8 7.5 8.1 8 . 0 5.1 8.9 reached. At this higher temperature two effects begin t o parCarbon on catalyst, wt. % of catalyst ... 0 . 8 4 0 . 6 1 0 . 8 1 0 . 6 9 0 . 6 4 1 . 2 1 ticipate in the reaction. The first is t h a t a mixed phase instead 5 A.S.T.11. Standard Method of T e s t for Knock Characteristics of XIotor of a predominantly liquid phase, which exists a t lower temperaFuels D35i-45 ( T E L tetraethyllead). b A.S.T.M. Tentatlve Method of Test for Knock Characteristics of Aviatures, is attained. The presence of the mixed phase does not tion Fuels D614-44T. permit a complete washing of the catalyst, so that some of the high-boiling polymeric material is left on the catalyst. .-it 532" F EFFECT O F PRESSURE OX POLTTRLATISG TABLE 11. approximately twice as much carbon is formed on the catalyst (518' F. 1.9-2.2 LHSV, 14-18 hour runs) as at 489" F. The second effect is t h a t higher temperatures pro400 600 1000 Pressure, Ib./sq. in. gage Charge 200 mote the reaction of depolymerization t o lower hydrocarbons 83.3 8 1 . 6 83.7 Gasoline, % b y wt. 100.0 90.4 16 22 19 28 Bromine X o . 50 Since the conditions used are those favoring hydrogen transfer, 20 18 17 Aromatics To 16 97:3 Q i . 8 97.3 95.8 Octane Nd., F-3 + 4 cc. T E L 92.6 the lover hydrocarbons formed are primarily paraffinic. Thus, 7.5 8.7 8.7 9.4 8.2 Reid vapor pressure, lb. increasing temperatures result in a product possessing a higher Carbon on catalyst, wt. % of charge . . . 0.075 0.078 0 , 0 2 0 0 . 0 6 8 vapor pressure. Table I1 s h o w t h a t pressures in the range of 400 to 1000 pounds per square inch gage produce a satisfactory increase in material produced in polytreating was collected and subjected to the leaded octane number and a good reduction in bromine catalytic cracking. number, whereas a pressure of 200 pounds is much less effective Furthermore, the results show t h a t the aromatic constituents of DISCUSSION OF RESULTS the gasoline undergo virtually no change during the polytreating The essential features of the polytreating operation are liquidreaction. This isbighly desirable since the alkylation of a& phase treatment, pressures ranging from 400 t o 800 pounds per niatics by olefins would not only remove valuable components square inch gage, temperatures from about 350" t'o 550" F., and from the gasoline b u t would also result in :ippreciabig lower liquid hourly space velocities (LHSV) from 0.5 t o 10. yields of the gasoline. The reactions which take place in polytreating are numerous To determine the active life of the catalyst, a run m s made at and can be classified as those of "conjunct polymerization" (1). 500" F., 1000 pounds per square inch gage, and 5 LHST'. The They involve (a)polymerization of olebns t o higher olefins, ( b ) run was continued until the equivalent of 48.7 gallons of charge cyclization of higher olefins to naphthenes, (c) dehydrogenation was processed over 1 pound of catalyst. Table I11 shows the of naphthenes (produced in reaction b ) t o aromatics, (d) hydroproperties of the charge and of the t,wo products; t'hc first prodgenation of olefins present in the original gasoline to paraffins, uct was obtained during the first 6 hours of operation, and the by hydrogen produced in reaction c. The net result of the operasecond, during the last 6 hours. The entire life test lasted 70 tion is that, a gasoline-fraction is produced having a lorn olefin hours. The life test indicates that the olefin cont'ent of rhe final gasw content, since steps a and d both decrease the olefin content of h i e is increased slightly during the processing of about 50 gallon? the original gasoline. Tables I and I1 show the effect of temperature and pressure of charge per pound of catalyst. The yield of gasoline with upon t.he polytreating of a cat'alytically cracked gasoline. The 300" F. end point is increased a-ith time, since a smaller amount of olefins is removed due to a slight decrease in t,he activity of the gasoline was obtained by cracking a gas oil in at fluid cracking catalyst over the length of the life test. The life test \vas m:ide unit using a synthetic silica-alumina catalyst. Unless otherat a space velocit,y of 5. Other experiments showed that space wise specified, the charging stock used had an end point of 300" I;. velocities ranging from 0.5 t o 10 can be used satisfactorily, whereas space velocities above 10 THERMOCOUPLE result in insufficient reduction in olefin content. The data presented in Table I contain both TE M PER AT U RE F-2 and F-3 octane numbers. It was found th:tt polytreating produces larger increascs ir; F-3 octane numbers than in the corresponding Motor Method values. This is due to the fact t,hat the leaded F-3octane numbers are affected to a greater extent by olefin content than art. the Motor Method octane numbers. Thus, a reduction in olefin content produccs a larger increase in the leaded F-3 octane numbers than in the corresponding Motor ?\Icthod values. STAIN LESS From the beginning of the viork on pulyS T E E L PIPE treating, i t was believed that the molecular weight of the olefinic compounds prescnt. in gasoline had a considerable effect upon the susceptibility of the gasoline to polytreating. In order to obtain some information or> this point, a gasoline of 300" F. end point VALVE was separated into two fractions, one boiling Figure 1. L a b o r a t o r y IJnit Used to Polytreat Catalytically Cracked Gasolines up to 200" F. and the other from 200" to OF TEVPERATURE ON POLYTREATIXG TABLE I. EFFECT
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October, 1946
TABLE 111. POLTTREATIXG LIFE TEST (500" F., 1000 pounds per equare inch gage, 5 LHSV Product Charge First G hr. Last 6 hr: iOO.0 77.6 82.0 Gasoline 5 by nt. 23 28 52 Rromine'ho. Qotane KO.,F-2 4 cc. TEL 89.6 92.6 91.9 Carbon on catalyst .. 2.83 Wt. 70of catalyst
