GASOLINE PROCESSING Acknowledgment
(6) Helmers, C. J., and Brooner, G. M., Petroleum Processing, 3 , 133 _ _ _ I1 948). (7) Hoog, H.. Klinkert, H. G., Schaafsma, A., Petroleum Refiner, \ - - - - I
The authors wish to thank J. Crocoll, S. W.Kapranos, E. C. Mertz, and R. G. Walton for their participation in the work reported here. We would also like t o express our gratitude t o t h e Shell Oil Co. for permitting publication of this work.
Literature Cited Anderson, J., Mchllister, S. H., Derr, E. L., and Peterson, W. H., IND.ENG.CHEM.,40, 2295 (1948). (2) Berg, C., Bradley, W. E., Stirton, R. I., Fairfield, R. G., Leffert, C. B., and Ballard, J. H., C h e m . Eng. Progr., 1, 1-12 (1947). (3) Byrns, A. C., Bradley, W. E., and Lee, M. W., IXD.ENG. CHEW,35, I160 (1943). (4) Cole, R. M., and Davidson, D. D., Ibid.,41, 2711 (1949). (5) Groennings, S.,IND. EKQ.CHEM.,ANAL.ED., 17, 361 (1945).
(1)
32, Ao. 5, 137-41 (1953). (8) Ipatieff, V. N., Monroe, G. S., and Schaad, R. E., Division of Petroleum Chemistry, 115th Meeting ACS, San Francisco, March, 1949. (9) Kalichevsky, V. A., Petroleum Re$ner, 30, No. 5, 117-22 (1951). (10) Petroleum Processing, 7, 467-9 (1952). (11) Ryan, J. G., IND.ENG.CHEM.,34, 824 (1942). (12) Voorhies, A., Jr., Smith, W. M., Hemminger, C. E., Ibid., 33, 1104 (1947). (13) Yabroff, D. L., and Border, L. E., Refiner A'atural Gasoline M f r . , 18, 171-6, 203 (1939). (14) Young, W. G., Meier, R. L., Tinograd, J . , Bollinger, H., Kaplan, L.. and Linden, S.L., J . Ant. Chem. SOC.,69,2046 (1947). R E C E I + E fDo i review Derember 8, 1954
ACCEPTED
January 28, 1955
(SELECTIVE HYDROTREATING OVERTUNGSTEN NICKEL SULFIDE CATALYST)
Studies with Mixtures of Pure Compounds W. K. MEERBOTT
AND
G. P. HINDS, JR.
Shell Oil Co., P. 0.Box 2527, Houston 7 , rex.
Studies of hydrotreating of cracked gasolines for desulfurization and stability improvement indicated that olefin isomerization also occurred: In order to establish the nature of this isomerization as well as the other reactions involved in the process, experiments were carried out with mixtures of pure compounds. At optimum hydrotreating conditions, only isomerization via double-bond shifting occurs over regenerated tungsten nickel sulfide. At the longer contact times required for skeletal isomerization, extensive olefin saturation results. The presence of sulfur compounds in the feed inhibits mono-olefin saturation but not diolefin hydrogenation. Qualitative evidence was obtained which indicates that n-olefins saturate faster than branched olefins.
I
K THE previous paper (4)the prsctical aspects of selective hydrotreating of cracked gasolines were discussed. The questions of reaction mechanism and reaction rates were not taken into consideration. However, it was shown earlier that as much as 20% olefin saturation occurred during the process with no loss in product octane number, while achieving 60% desulfurization and 90% conjugated diolefin removal. Data were presented indicating that isomerization of olefins off sets the octane number loss due to saturation. Ilon-ever, because of the coniplexity of the feed stock, i t was uncertain whether olefin isomerization involved more than double-bond shifts. Several investigators ( 2 , 5, 6, 6) have shown that n-olefins can be isomerized to branched-chain olefins. However, all these instances of olefin isomerization occurred over acid treated or acidic catalysts with low activity for the competing saturation reaction. Tungsten nickel sulfide (W/Ni/S) catalyst is a n active hydrogenation catalyst which has not been considered acidic, nor does it have the large surface area generally associated with aluminas and cracking catalysts. T o understand more clearly the isomerization reaction, as well as the other reactions involved in hgdrotreating, a series of experiments was made with mixtures of pure compounds over regenerated tungsten nickel sulfide catalyst. This paper presents the results of this investigation with synthetic feeds and offers a qualitative comparison of the several reactions involved in hydrotreating. The experimental work was carried out in a laboratory unit with essentially the same flow scheme as that presented in the previous paper (4). Operating conditions for these experiments April 1955
were similar to those used in the selective hydrotreating of thermally cracked gasoline: namely, 600" F., 75 pounds per square inch gage, 2I-L:oil mole ratio, and varying space velocities from 1.4 to 8.3. The catalyst was regenerated tungsten nickel sulfide. The liquid charge was a mixture of equal weights of n-heptane and I-octene to which other compounds were added. This standard blend, with about a 70 bromine number, was used in practically all experiments. The sulfur compounds were generally blended one part by weight of n-butyl mercaptan t o two parts of thiophene t o produce the desired sulfur concentration. The liquid products were not caustic washed for hydrogen sulfide removal t o avoid removing mercaptans along with the hydrogen sulfide. Potentiometric titration was used t o analyze for hydrogen sulfide, and the total sulfur was corrected for this amount of reaction product. Liquid recoveries in all the experiments were 99 t o 100 wt. yo of the charge. Practically no cracking or gas make occurred during the process. The materials used in these experiments, their sources, and purities were:' I-Octene n-Heptane n-Octane Thiophene n-Butyl mercaptan tert-Butylphenol Z-MethyI-l,3-pentadiene
99 % 99 % 99 % c P. C.P.
Practical C.P
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
Connecticut Hard Rubber Co. Westvaco Chlorine Products Co. Connecticut Hard Rubber Co Eastman Kodak Co. Eastman Kodak Co. Eastman Kodak Go. Commercial Solvents Corp.
749
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT Calculations:
The degree of selectivity obtainable with the mixture of n-heptane and I-octene containing 0.30 wt. yo sulfur at % Olefin reduction = Br2 No. of rharge" - Br2 No. productt"x 100 600' F., 75 pounds per square inch gage, 2Ha:oil mole ratio Brz No. of chargea and space velocities from 2.7 t o 8.2 over regenerated tungsten nickel sulfide catalyst is shown in Figure 2. For comCorrected for diolefins parism, results obtained from selective hydrosulfur % wt. of charge - sulfur % wt. of product % Sulfur reduction = X 100 treating of thermally cracked gasoline (pressure sulfur yo xt.of charge distil1atetops)overthesamecatiystandat similar operating conditions are also given. It is apparent from these Resuits and D i s c u s s i o ~ results that the lower selec.tivity of the synthetic feed is due primarily t o greater olefin hydrogenation at comparable sulfur Since olefin aaturettion generally mmrts in hss of octane reduction. This is further iIIustrated in Figure 3, which shows nurnbm, it is necessary in selective hydratreating t o minimize the effect of space velocity on oIefin reduction for both feed Two this reaction and to offset it by isomerizatian of the d&s. stocks at a comparable sulfur level. These data indicate that types of olefin isomerization are pwsible: 25 to 35% greater saturation mcurred with 1-octene than with 1. Double-bond shift toward the center of the d e c u l e . the olefins from thermaIEy cracked gasoline. Two explanations 2. Chain branching. Both types of isomerizatian may occur for this observation a p p w r reasonabIe but neither has been sucduring the'process and would be very desirable €oa octane imcessfully substantiated in the current experiments. It is possible provement. Tungsten nickel sulfide catalyst is not eonsidered an that comporients present i n pressure distillate tops inhibit olefin active isomerization catalyst, yet evidence was presented for hydrogenation and/or the n-olefin may hydrogenate more olefin double-bond shift. Because of t h e camplexiky of the gasorapidly than the o l e h p m m m t in the cracked gasoline (Table I ) line feed, it was not certain whether skeletal isomerization occurred under the processing conditions tested. Therefore, a series of experiments was carried out over regenerated tungsten nickel sulfide catalyst with the synthetic f e d consisting of 1-octene and n-heptane containing 0.30 wt. yosulfur to determine the nature of the olefin isomerization. 100
I
I
I
I
-601 80
- OCTENE
L
Table I.
Olefin Typm irr Thermally Cracked Gasoline. Total Olefins, Vol. % ' a-Type olefins R-CH=CHz RF-C=CW~ @-Typeolefins R-CH=CHR R-CH=CHR RaC=CHR
33 7 ( hrrns)
(cis)
Other olefins
9 4 16
31
40
0
I 0
I
2 4 LIQUID HOURLY SPACE
I 6
I
a
VELOCITY, vol/vol/hr
Figure 1. Effect of space velocity on olefin type in selective hydrotreating over regenerated tungsten nickel sulfide catalyst
I
Operating conditions were in the range of those considered optimum for hydrotreating thermally cracked gasoline-i.e., 600' F., 75 pounds per square inch gage, 2H2:oil mole ratio, 2.7-8.2 space velocity. The products were analyzed by infrared spectroscopy (7) to determine the olefin types. These data are summarized in Figure 1, and show that less than 5y0 of the 1octene in the charge remained unconverted. The isomerized olefins were essentially 2-octene but some 3- and 4-octenes were obtained. No tertiary or branched-chain olefins were found. Distillation followed by infrared analysis of selected cuts, and hydrogenation followed by distilIation and inspection of the product obtained a t 8 liquid hourly space velocity (LHSV), verified the absence of skeletal isomerization. Hence, it may be concluded that only double-bond shift isomerization occurs over the tungsten nickel sulfide catalyst under the conditions considered optimum for selective hydrotreating.
150
Figure 2. Selective hydrotreating of p t e s s u ~distillate tops and synthetic feed over tungsten nickel sulfide catalyst
Since neither diolefins nor' dkfrl ph@n& were included in the standard synthetic feed, but both Were ptssent in the thermally cracked gasoline, tests were made with hkrtds containing 2 wt, % 2-methyl-1,a-pentadiene or 0.2 wt. % led-butglphenol, T h e results are given in Figure 4 and indicate E h t n&her 66 these materials had any inhibiting effect on olefin h y d r o g e ~ ~ t l o n The . hydrogenation of the diolefin was extremely rapid! kitl 8.1 liquid hourly space velocity, the maleic anhydride' v a l h (h4AV) of the feed was reduced from 22 to 1, whereas at* Ibwei. space velocities the maleic anhydride value of the producf was zero.
I N D U S T R I A L AND E N G I N E E R I N G CHEMISTRY
Vol. 47, No 4
GASOLINE PROCESSING 100
I
-SynMc Feed 80
-
t
z 0
0
Synthehc Feed containing Z%w
A
Synthetic Feed cmoininq 0 . 2 % ~ t- butyiphenol
60
e
2
40
I-
z O w
E
20
1
0
1
I
I
2 4 6 8 LIQUID HOURLY SWCE VELOCITY, vol/vd/hr
20
Figure 3. Effect of sulfur and olefin type on selectivity in-selective hydrotreating over regenerated tungsten nickel sulfide catalyst
Table II. Isomerization of 1-Octene" over HCI Treated Alorco H-40 Alumina under Hydrotreating Conditions Temperature, ' F. Pressure, lb./sq. inch gage Hz: oil mole ratio
R u n No. WLHSV Olefin reduction, % Olefin distribution, Total olefin on charge Basis,
n-Octane 1-Ootene Sulfur Bromine No.
76 4.0 10
0
a
83 7 90
B
terl Total a
2-methyl-I,
i//
IO
8a
pentodiene
600
75 2 77 2.7 13
0
78 9 87
-
78 1.3 13
79 0.67 , 18
0 74 13 87
0 68
-
40 PERCENT SULFUR
60
80
10
REDUCTION
Figure 4. Effect of dienes and alkylphenols on selective hydrotreating over tungsten nickel sulfide catalyst
-olefin saturation would predominate and prevent the desired skeletal isomerization. A series of runs was made t o determine the extent of olefin saturation in a sulfur-free charge stock. The experimental results plotted in Figure 3 show about 30% more hydrogenation of 1-octene when sulfur is absent from the feed. Sulfur compounds exert a pronounced inhibitory effect on olefin saturation. This might be attributed to a more successful competition for the active catalyst centers by the organic sulfur compounds.
14 __ 82
Wt. % 42 58 0.27 79
These experiments, in agreement with those of Anderson and coworkers ( 1 ) and Young and coworkers ( 8 ) , show the ease and SYNTHETIC F E E 0 ' selectivity with which diolefins can be hydrogenated in comparison with mono-olefin saturation and desulfurization. A O.i3%wS An indication that the least-branched olefins saturate faster, 0 0 3o%w s over tungsten nickel sulfide catalyst, than the more highly 0 0.4 0 % ~S branched compounds was obtained from work with pressure I distillate tops. The saturate portions of a charge and a hydrotreated product were separated by chromatography from the remainder of the gasoline. F-2 octane ratings of the saturate 00 LIQUID 2 HOURLY4 SPACE VELOCITY, vd/vol/hr I0 O fractions show a small loss in octane number (1.1 units) of the hydrotreated product material. The opposite result would have Figure 5. Effect of sulfur concentration on desulbeen expected if the concentration of branched paraffins had furization in selective hydrotreating over tungsten been increased. nickel sulfide catalyst Attempts to accomplish skeleta1 isomer*lzationunder hydrotreating conditions were carried Table 111. Effect of Sulfur Concentration on Hydrotreating Selectivity out over acid treated carriers. Typical experimental results Temperature, F 600 Pressure, Ib /sq inch gage 75 obtained using a hydrochloric H2: oil mole ratio 2 acid treated Alorco H-40 aluCharge Charge mina catalyst are shown in Run N o Wfor 32-34 32 33 34 for 36-38 36 37 38 LHSV 8 3 5 5 2 7 8.3 5.5 2.7 Table 11. These data indicate Br2 N o . 69 49 43 30 73 50 45 29 Olefin reduction, % 29 38 57 32 0 06 38 0 04 60 0 02 that at conditions necessary for 0 40 0 19 0 16 0 08 0 13 Sulfur, w t % appreciable chain branching to Sulfur reduction, % 52 60 80 54 70 85 occur-i.e., low space velocities
2ot-
April 1955
INDUSTRIAL AND ENGINEERING CHEMISTRY
751
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT with a blend of 0.34 wt. % sulfur in n-heptane show 5 to 7% more desulfurization than comparable runs with olefins present. However, this advantage is lost a t a liquid hourly space velocity of 8. These results (Figure 6) would indicate that olefins have, a t most, only a small inhibitory effect on the desulfurization process. I n all these experiments, mercaptan sulfur was completely converted to hydrogen sulfide, while part of the thiophenic sulfur remained unreacted.
z u
B a a J
w
Acknowledgment
40
0 0
IW z
OLEFIN-FREE
FEED, 0.34%~S
The aut.hors wish to express their appreciation t o Shell Oil Co. for permission to publish this work. Acknowledgment is also gratefully accorded t o A. F. Sartor and S. W. Kapranos for assistance in the experiments.
OLEFIN-CONTAINING FEED, 0.30%~ S
20
0
literature Cited 0
Figure 6.
2
6 8 LlOUlD HOURLY SPACE VELOCITY, vd/vol/hr
10
(1) Anderson, J., NIcAllister, S. H., Derr, E. L., and Peterson, W. H., IND.
Desulfurization over tungsten nickel sulfide catalyst in absence of olefins
ENG.CHEM., 4 0 , 2 2 9 5 (1948).
( 2 ) Berg, L., Sumner, G. L., Jr., and Montgomery, C. W. (Gulf Research and Development Co.), U. 5.Patent 2,397,639 (.lpril 2 , 1946).
Additional experiments were performed to define more clearly the effect of sulfur concentration of olefin hydrogenation and extent of desulfurization. Two charges containing 0.13 or 0.40 wt. % sulfur, respectively, were prepared and tested over tungsten nickel sulfide catalyst. The results are given in Table 111 and show essentially the same level of olefin saturation as that obtained at 0.30 wt. % sulfur level. The sulfur reductions for the 0.30 and 0.40 wt. % sulfur charges were approximately the same (Figure 5 ) . However, for the feed containing 0.13% sulfur, about 10% greater desulfurization was obtained. I n the absence of olefins, sulfur compounds appear t o hydrogenate slightly faster a t the lower space velocities, Runs made
(3) (4) (5)
Berg, L., Sumner, G. L., Jr., and Montgomery, C. W., ISD. ENG. CHEM.,3 8 , 7 3 4 (1946). Casagrande, R. AT., Neerbott, W. K.. Sartor, 4.F., and Tramor, R. P., IND. ENG.CHEM.,4 7 , 744 (1955). Egloff, G., Morrell, J. C.. Thomas, C. L., and Bloch, H. S.,J .
Am. Chem. Soc., 6 1 , 3 5 7 1 ( 1 9 3 9 ) . (6) Hay, R. G., Montgomery, C. W.,and Coull, J., IND.ESG. (7)
' (8)
CHEM.,3 7 , 3 3 5 (1945). Johnston, R. W. B., Appleby, W. G., and Baker, If.O., A,iaZ. Chem., 2 0 , 8 0 5 (1948).
Young, W. G., Meier, R. L., Vinograd, J., Bollinger, H., Xaplan, L., and Linden, S. L., J . Am. Chem. Soc., 6 9 , 2046 ( 1 9 4 7 ) .
RECEIVED for review December 8, 1954.
QCCEPTED December 30, 1954.
Polymerization of light Olefins over Nickel Oxide-Silica-Alumina J. P. HOGAN, R. L. BANKS, W. C. LANNING,
AND
ALFRED CLARK
Phillips Pefroleum Co., Burflesville, Oklo.
Refinery cracked gas contains significant quantities of ethylene which are not recoverable by polymerization over catalysts now in commercial use. Nickel oxide on silica-alumina has been found to be highly active for this reaction, even at high ethylene dilution; the present paper describes its use for conversion of ethylene and propylene to motor fuel. The separate olefins were polymerized in continuous-flow experiments at 40' to 95' C. to investigate reaction kinetics and product compositions. In the polymerization of mixed olefins in a cracked gas, the activity and life of the catalyst were improved markedly by the recycle of butane as liquid diluent.
T
HE literature describes a number of catalysts for the polymerization of propylene to gasoline range hydrocarbons. Phosphoric acid, supported on kieselguhr (4)or quartz sand (Q), and copper pyrophosphate ( 1 1 ) are among the most important. Silica-alumina polymerizes propylene less readily and only a t relatively high temperature (15). However, none of these catalysts gives appreciable conversion of ethylene a t the process conditions ordinarily used. Ethylene has been polymerized at 250' to 350" C. in the presence of phosphoric acid ( 7 ) to give
752
products which indicate conjunct polymerization of a type different from that obtained in thermal polymerization (8, 7 , 1 2 ) . Cobalt-charcoal catalysts have been used for the dimerization of ethylene (5). Bailey and Reid (1 ) discovered that silica-alumina promoted with mckel oxide possessed high activity for the polymerization of ethylene, even a t room temperature, and was more active for propylene polymerization than silica-alumina alone. Furthermore, the order of decreasing rate of reaction of normal olefins,
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 47, No. 4
