CH LORINATED PLAT1NUM-A LUMINA LOW TEMPERATURE ISOMERIZATION CATALYSTS J O S E P H P. G I A N N E T T I A N D RAYNOR T. SEBULSKY Gulf Research & Development Co., Pittsburgh, Pa. 15230 Low temperature paraffin isomerization catalysts can be prepared by reaction of a platinum-alumina with various chlorinating agents. Thionyl chloride, sulfuryl chloride, sulfur monochloride, and a mixture of sulfur dioxide and chlorine can be employed a t elevated temperatures to chlorinate the catalyst. Increased catalyst activity is obtained if the platinum-alumina is treated with hydrogen chloride prior to the sulfur chloride treatment. These chlorinated platinum-aluminas are capable of isomerizing butane, pentane, and hexane to near their equilibrium isomer distributions a t temperatures below 3503 F. In addition to the chlorination sequence, the alumina and its platinum content play major roles in determining catalyst activity.
PARAFFIN isomerization is an excellent means of obtaining high octane gasoline components. Hexane can be isomerized to the higher octane dimethylbutanes and methylpentanes, while butane can be isomerized to isobutane (2-methylpropane), which can be alkylated with olefins to give the highly branched, high octane C6 to C, compounds. Thermodynamic equilibrium favors branched paraffins a t low temperatures. Accordingly, maximum isomerization catalyst activity is desired to permit isomerization processes to operate a t minimum temperatures. The use of Friedel-Crafts catalysts such as anhydrous aluminum chloride and aluminum bromide, singly or in combination with other halides, a t low temperatures, has been known for a long time (Egloff et cd.,1942; Thomas, 1941). However, these catalysts are corrosive, easily deactivated, difficult to handle, and unselective in the reactions which they catalyze. In addition, the aluminum halides are often employed as slurries or sludges which add mechanical problems. Within the past few years several active solid low temperature isomerization catalysts have been reported by workers a t Texaco (Riordan and Estes, 1966) and British Petroleum (Goble and Haresnape, 1964; Goble and Lawrence, 1964; O'May, 1963). The key to their activity is the introduction of chlorine into platinum-alumina by reaction with carbon chlorides. Carbon tetrachloride is particularly effective. I n addition, active catalysts have been prepared by reaction of thionyl chloride with platinum-alumina (Goble and Haresnape, 1965). Our studies have shown that there is a chlorinating sequence for platinum-aluminas which gives catalysts with greatly enhanced low temperature true isomerization activity. In addition, we have extended previous work with thionyl chloride to other chlorine-containing sulfur compounds. Experimental
Materials. The thionyl chloride (SOCL), sulfuryl chloride (S02C12),and sulfur monochloride (S2C12)were obtained 356
I & E C PRODUCT RESEARCH A N D D E V E L O P M E N T
from the Eastman Kodak Co. and used as received. The sulfur dioxide, hydrogen chloride, and chlorine were obtained from the Matheson Chemical Co. and also used as received. The hexane and butane were Phillips Petroleum Co. technical grade and pure grade, respectively. The butane contained 0.35 isobutane and 0.3': pentanes, while the hexane contained 0.45 methylpentanes and 2.1% methylcyclopentane. Both were dried and desulfurized over Linde 13X molecular sieves. Hydrogen was supplied by the Air Reduction Co. and was deoxygenated and dried prior to use. With the exception of catalysts specifically made to study different supporting aluminas, the catalysts were prepared from Sinclair Baker platinum-alumina. The alumina used as the support in the study of platinum level was also obtained from Sinclair Baker. Other aluminas and platinum-aluminas were obtained from various manufacturers. A silica-alumina and a palladium-containing silica-alumina were also evaluated. Where the metal was not present on the support, platinum was added by slurrying the support with an aqueous solution of chloroplatinic acid and oven drying a t 250°F. Catalyst Preparation. All the supports (12- to 20-mesh size, U. S. sieve series) were calcined in air a t 500°F. overnight and then a t 900°F. for 2 hours. They were reduced in H 2 a t 900" F. and atmospheric pressure employing 1.6-standard cubic foot H 2 per hour per 100 grams of support for 2 hours. A 170-ml. charge of the calcined platinum-alumina was placed in an electrically heated 1-inch-i.d. glass reactor equipped with a glass thermowell. The temperature was raised to the 900" F . hydrogen reduction temperature under a small flow of nitrogen. Following reduction with hydrogen, they were brought to the treatment temperature in nitrogen. Where the hydrogen chloride pretreatment and posttreatment were employed, it was added downflow over the platinum-alumina. Hydrogen (1.20-standard cubic foot H ? per hour per 100 grams of platinum-alumina in most cases) was used as a carrier gas in the hydrogen chloride pretreatment. The liquid activating agents
(SOCl,, SO?Cl,, and SKL) were added dropwise from a buret and allowed to vaporize into the approprihte carrier stream (air, nitrogen, or hydrogen a t usually 0.40 standard cubic foot per hour per 100 grams of platinum-alumina). When the activating agents were sulfur dioxide and chlorine, the two gases were combined prior to the reactor and added as a single gas stream. Apparatus. The isomerization experiments were conducted in a 1-inch i.d. carbon steel fixed-bed high pressure reactor. Butane or hexane was combined with hydrogen, preheated, and passed downflow through a 100-ml. bed of catalyst. I n the butane runs the total gaseous products leaving the reactor were depressurized, passed through a dry gas meter, and. collected in a vessel by salt water displacement. For the hexane runs the effluent from the reactor was divided into gas and liquid portions in a high pressure separat'or. The liquid product was collected in a vessel, while the gaseous product was passed through a wet gas meter. Analyses. The chlorine content of the catalyst was determined by an automatic potentiometric procedure. The sample was first slurried in water and the hydrochloric acid resulting from the hydrolysis of the chlorinecontaining catalyst titrated potentiometrically with a standard base to p H 7. All the chlorine from the catalyst was removed. The chlorine results reported were corrected for the chlorine initially present on the platinum-alumina0.50 weight 'C chlorine on the Sinclair Baker platinumalumina, for example--and thus represent only the chlorine added in the activation procedures. Surface areas were determined by nitrogen adsorption. The sulfur content of the catalyst was determined by a high temperature combustion method. The catalyst was heated in oxygen to convert the sulfur into sulfur dioxide. This stream was passed into an acidic solution of potassium iodide and starch indicator. A small amount of potassium iodate was added to develop a blue color. As the SO, stream reacted with this solution, potassium iodate was added to maintain the blue color. T h e sulfur content was calculated from the amount of potassium iodate added. Certain catalysts were analyzed for hydroxyl group content by both infrared (Perkin Elmer 421 dual gradient spectrophotometer) and nuclear magnetic resonance (Varian Associates V4500 wide-line N M R spectrometer) techniques. The catalysts were evaluated for hexane isomerization a t 225" or 280"F., 2!50 or 400 p.s.i.g., 1 LHSV (liquid hourly space velocity defined as milliliters of hydrocarbon feed per milliliter of catalyst per hour), and 2.5 to 1 hydrogen-hexane mole ratio. Butane runs were conducted a t 350" F., 800 p.s.i.g., 1 LHSV, and 2.5 to 1 hydrogenbutane mole ratio. The hydrocarbon samples were analyzed on a Fisher-Gulf Partitioner using a column packed with 10% isoquinoline on Gas Chrom R , 45- to 60-mesh, obtained from the Applied Sciences Laboratory. For isomerizing both hexane and butane, the reaction was over 98% selective to branched hexanes and isobutane, respectively. I n the case of hexane, the selectivity to the 2,2-dimethylbutane isomer is also presented. This was calculated by div:iding the amount of the 2,2dimethylbutane in the product by the hexane conversion. This particular isomer has a high octane rating (106 Research octane nurnber + 3 ml. of tetraethyllead) and is present in high concentrations in an equilibrium hexane mix a t low temperatures.
R e s u l t s and D i s c u s s i o n
Reaction of Thionyl Chloride with Platinum-Alumina. Platinum-alumina reacted with thionyl chloride (SOClJ a t 350", 560", 800", and 1050" F. with a nitrogen carrier gas. I n all but the 1050°F. preparation, a hot spot of from 75. to 150°F. traveled down through the bed as the catalyst was activated. The catalysts were evaluated for hexane isomerization. Figure 1 compares the activity of the catalysts, expressed as hexane conversion and 2,2dimethylbutane selectivity, with their surface areas and chlorine contents. For comparison, equilibrium hexane conversion and 2,2-dimethylbutane selectivity a t 225" F. are about 91 and 40 weight ' C , respectively (Evans et a l , 1962; Ridgeway et al.. 1959). The catalyst prepared a t 1050" F. has the highest activity, but rather surprisingly, the lowest surface area and chlorine content. The highest surface area and chlorine content were obtained on the catalyst prepared a t 350" F., yet this catalyst is inactive for hexane isomerization. Therefore, merely adding chlorine to the platinum-alumina is not sufficient for activity. Analysis of the catalysts prepared a t 800" and 350'F. by infrared and nuclear magnetic resonance techniques (Basila, 1965) provides a partial explanation for this activity difference. For the active catalyst prepared a t 800"F., all the surface hydroxyl groups of the alumina were replaced by chlorine. For the inactive catalyst prepared a t 350°F., only about 6OCcof the surface hydroxyl groups were replaced by chlorine. The effect of varying the amount of thionyl chloride used in the reaction with the platinum-alumina was determined. Thionyl chloride in quantities of 0.09, 0.18, 0.35,
9
1 350
8 -
u ' N
I'
7 -
300
3 P;
6 -
250 5 -
fa
200
4 -
300
550
800
1050
CATALYST PREPARATION TEMPERATURE: "F
Figure 1. Effect of temperature of thionyl chloride reaction with platinum-alumina on catalyst properties and activity 0.36 mole SOClr/100 g. platinum-alumino over 45 min. with Nr diluent. Hexane isomerization at 225' F., 250 p.s.i.g., 1 LHSV, 2.5:l Hz-hexane mole ratio
VOL. 8 N O . 4 D E C E M B E R 1 9 6 9
357
and 0.54 mole per 100 grams of platinum-alumina reacted over a 45-minute period a t 560°F. The chlorine content and surface area of the catalysts and their activity for hexane conversion and 2,2-dimethylbutane selectivity are presented in Figure 2. Results show an increase in the hexane conversion and 2,2-dimethylbutane selectivity with increasing amounts of thionyl chloride, matched by an increase in the chlorine content and a decrease in the surface area of the catalysts. Therefore, the most active catalyst employed the greatest amount of thionyl chloride in the preparation. However, as the amount of thionyl chloride increased, the efficiency-i.e., fraction of available chlorine retained by the catalyst-decreased, as shown by the numbers in parentheses next to the chlorine content. Continued increases in available chlorine would probably not produce a catalyst containing appreciably more chlorine and having greater activity. Nitrogen was used as the carrier gas during these reactions between thionyl chloride and platinum-alumina, T o see if the type of carrier gas influences the final catalyst, the reaction was also performed with oxygen and hydrogen (Table I). Oxygen and nitrogen produce catalysts with generally comparable properties and activities. The catalyst made with a hydrogen carrier was low in chlorine, high in surface area, and very low in activity. This is in agreement with reported results showing that a reducing atmosphere causes the loss of carbon chlorides (Goble and Haresnape, 1964) and thionyl chloride (Goble and Haresnape, 1965) by converting to hydrogen chloride. Hydrogen Chloride Treatment of Platinum-Alumina Prior to Thionyl Chloride Reaction. Maclver, Tobin, and Barth (1963) have shown that the state of hydration of aluminas
loo
80
f
c
a-@I
* 40
/ONVERSION
s I-
a
P
L
r
z
$
8
z
>
6 20
14 I /
c
,o-
1
l o ' 10
1
x I
lo
0
I
I
127 WT.%I
Carrier Gas Type Catalyst analyses Surface area, sq. m./g. Chlorine, wt. % Hexane conversion, wt. 70 2,2-Dimethylbutane selectivity, wt. %
Nz
02
H2
298 8.2 83.0 24.1
301 8.8 81.2 26.6
325 4.5 7.3
7 -
s
6 -
200 0.W
can affect their catalytic properties. Generally, the lower the state of hydration the more active the alumina for the usual acid-catalyzed reactions. T o see the effect of low hydration states of the alumina prior t o thionyl chloride reaction on the resultant catalyst properties, the platinum-alumina was given a 1050"F. treatment with hydrogen chloride, followed by the 560" F. thionyl chloride treatment. The resultant catalyst had lower chlorine content and lower surface area than the catalyst prepared with thionyl chloride alone. But, surprisingly, this catalyst had considerably more activity for butane isomerization than the nonpretreated catalyst. T o show that this was not an additive effect, a hydrogen chloride-treated platinum-alumina without subsequent reaction with thionyl chloride was tested and found to be inactive (Table 11). The exact function of the hydrogen chloride pretreatment is not known. However, infrared and N M R studies (Basila, 1965) have shown that the hydrogen chloride treatment removes about 30% of the hydroxyl groups on the alumina surface. The thionyl chloride then reacts with the remaining hydroxyl groups. The temperature of the reaction with hydrogen chloride has a pronounced effect on the activity obtained after the subsequent thionyl chloride reaction (Figure 3). The greatest activity for the hydrogen chloride-thionyl chloride catalyst occurs when the hydrogen chloride pretreatment temperature is 950°F. and above. Thus, 46 to 47 weight % butane conversion is obtained for the 950" and 1050" F. hydrogen chloride-treated catalysts, while 36 to 37 weight % conversion results from the catalysts treated a t 400" and 800" F. Since a catalyst activated with only the thionyl chloride (hydrogen chloride pretreatment omitted) also
0.18
I
I
0.27
0.36
I
0.45
I 0.54
0.30 mole HCl/hr./100 g. platinum-alumina at 1050' F. for 3 hr. with H, diluent 0.36 mole SOCL/lOO g. platinum-alumina at 560" F. over 45 min. with diluent Butane isomerization at 350" F., 800 p.s.i.g., 1 LHSV, 2.5:l Hzbutane mole ratio
MOLE SOCIz/lW 0 . PLATINUM-ALUMINA
f:igure 2. Effect of amount of thionyl chloride n reaction with platinum-alumina on catalyst iroperties and activity i 0 C h a t 5 6 0 ° F . over 4 5 min. with N2 diluent. Hexane somerizatian a t 225" F., 2 5 0 p.s.i.g., 1 LHSV, 2.5:l-hexane mole ratio
358
...
Table 11. Hydrogen Chloride Pretreatment Prior to Thionyl Chloride Reaction with Platinum-Alumina on Catalyst Properties and Activity
IL
u
0.36 mole SOCl,/lOO g. platinum-alumina a t 56W F. over 45 min. Hexane isomerization a t 225" F., 250 p.s.i.g., 1 LHSV, 2.5:l H2hexane mole ratio.
-1
*i z
Table I. Carrier Gas Type during Thionyl Chloride Reaction with Platinum-Alumina on Catalyst Properties and Activity
l & E C PRODUCT RESEARCH A N D DEVELOPMENT
Catalyst analyses Surface area, sq. m.1 g. Chlorine, wt. 5 Butane conversion, wt.
HCI
SOCI?
HC1 + SOCl,
175 1.3 0
298 8.2 36
145 3.9 47
"Equilibrium butam conversion to isobutane at 350" F . , 61 ut. 5'1.
2
5
0
w
l
,
I
After HCI
E
6
+ SOClz
,
,
l
l
1
l
l
J
1
-U
5
2 0
I 4w
M)O
l
HYDROGEN CHLORIDE ADDITION TEMPERATURE
'
'
I
0-@ 1
0 '
i
'
'
I
!
I
1
l
1wo
800
0-@-After HCI
OF
Figure 3. Effect of temperature of hydrogen chloride pretreatment prior to thionyl chloride reaction with platinum-alumina on catalyst properties cind activity
Figure 4. Effect of contact time of hydrogen chloride pretreatment prior to thionyl chloride reaction with platinum-alumina on catalyst properties and activity 00.90 mole HC1/100 g. platinum-alumina at 1050" F. with H:, diluent (amount constant, rate varied)
00.30 mole HCl/hr./100 g. platinum-alumina a t 1050" F. with HL diluent
0.30 mole HCl/hr./100 g. platinum-alumina for 3 hr. with Hz diluent 0.36 mole SOCI:/lOO g. platinum-alumina at 560" F. over 45 min. with NL diluent Butane isomerization at 350" F., 800 p.s.i.g., 1 LHSV, 2.5:l Hi-butane
(rate constant, amount varied)
mole ratio
mole ratio
gives 36 weight 'C conversion, no significant activity increase is derived from the 800°F.and lower hydrogen chloride treatments. The 400" and 800" F. pretreatments result in more chlorine on the catalyst after both the hydrogen chloride treatments and thionyl chloride reaction than the 950" F.+pretreatments. Thus the chlorine added by the low temperature hydrogen chloride treatments had no promotional effect. Also, the catalysts prepared with the lower temperature pretreatments have higher surface areas than those prepared with the higher temperature treatments. The hydrogen chloride contact time has also a pronounced effect on the catalyst properties and activity. This was tested by adding both different amounts of hydrogen chloride a t a constant rate and a constant amount of hydrogen chloride at different addition rates. The effect of the changes in the contact time by these two procedures is shown in Figure 4 . Generally, both procedures give the same results, with the shorter contact times being the more effective pretreatments. When followed by the standard thionyl chloride reaction, the catalysts given a hydrogen chloride pretreatment of an hour or less give about 6 weight ' C higher conversion than those with the longer treatments. The shorter hydrogen chloride treatments also do not reduce the surface area of the platinumalumina as much. Best results are obtained when the catalyst is not held a t the high pretreatment temperature any longer than necessary. The variables studied for the reaction of thionyl chloride with the platinum-alumina were again investigated with
the hydrogen chloride pretreated platinum-alumina. First the platinum-alumina was given a 3-hour, 1050" F.hydrogen chloride pretreatment. Then the thionyl chloride reaction temperature, amount, and addition time were studied. There were no significant differences in catalyst properties or activity over the ranges studied. These results differ considerably from the thionyl chloride variations with the unpretreated platinum-alumina, where there were effects of reaction temperature and amounts of thionyl chloride employed. The hydrogen chloride pretreatment, although in itself ineffective for making an active low temperature isomerization catalyst, apparently mo6ifies the surface such that all subsequent thionyl chloride treatments resulted in maximum activity. Other Sulfur-Chlorine A4ctivatingAgents. In addition to thionyl chloride, other activating agents were tested: sulfuryl chloride, sulfur monochloride, and a mixture of sulfur dioxide and chlorine. The platinum-alumina was first pretreated with the hydrogen chloride. A few changes were made from the thionyl chloride preparations. The catalysts were purged with nitrogen a t 800" to 850°F. immediately after reaction with the sulfur-chlorine compounds. This treatment lessens the possibility of unreacted material remaining on the catalyst surface. Also, the catalysts were treated with hydrogen chloride a t 400"F. following the nitrogen purge. This step increased the initial catalyst activity of thionyl chloride-activated catalysts by about 3 weight 5 butane conversion. The results obtained with these catalysts are presented in Table 111. The catalysts contained from 3.4t o 3.9 weight '-c chlorine,
0 0 . 3 6 mole SOClr/100 g. platinum-alumina at 560" F. over 45 min. with N! diluent following either of above treatments Butane isomerization at 35OCF. 800 p.s.i.g., 1 LHSV, 2.5:l H r b u t a n e
VOL. 8 NO. 4 DECEMBER 1969
359
~~~~
~
~
~
~
~~
Table 111. Properties and Activity of Catalysts Prepared with Various Sulfur-Chlorine Compounds
0.30 mole HCl/hr./100 g. platinum-alumina for 3 hr. with H, diluent a t 1050" F. prior to and 400" F. following sulfur-chlorine compound addition Hexane isomerization at 280" F., 400 p.s.i.g., 1 LHSV, 2.5:1 H,-hexane mole ratio Butane isomerization at 350" F.. 800 p.s.i.g., 1 LHSV, 2.5:l H2-butane mole ratio
CatalyTt Anal,yses Chlorine. Surface area, ut ( I ).sq m g
Sulfur-Chlorine Compounds SOKL (0.23 mole SOX1, added over 3 hr. a t 600" F.) SO! + Clz (2.1 moles SO, + 2.1 moles C1, added over 10 hr. at 600" F.) SX1, (0.35 mole SZCL added over 3 hr. at 600" F.)
3.9
155
3.9
155
3.4
161
Catal)).stA C ~ Z L Z ~ Y 89.2'~ hexane conversiono 32.4'1, 2,2-dimethylbutane selectivity 89.05 hexane conversion" 31.95 2,2-dimethylbutane selectivity 46.0% butane conversion
'Equilibrium hexane conuersion at 28'0" F. is about S I C c (Ridgeway a d Schoen, 1959)
had surface areas from 155 to 161 sq. meters per gram, and were active for either butane or hexane isomerization. The catalyst inspections and activities are what would generally be expected for the corresponding thionyl chloride catalysts. The above catalysts were also analyzed for their sulfur content (Massoth, 1967). Where thionyl chloride was used in the catalyst preparation, no sulfur in any form was found. This was also true with the sulfur monochloridetreated catalyst, provided oxygen was employed either during or after the sulfur monochloride treatment or a high temperature nitrogen purge-e.g., 900" F.-followed the sulfur monochloride treatment. The catalysts prepared with sulfuryl chloride or a mixture of sulfur dioxide and chlorine resulted in from 0.7 to 1.5 weight % sulfur. I t
46
4.1 WT.% CI
/
44
0
f
0-0
0
3.9 WT.% CI
3.9 W.%C I
4.6 WT.% C I
42
2 Ln
: 8 2
is likely that this sulfur is present as sulfate from the reaction of a portion of the sulfur trioxide liberated from these activating agents and the alumina. I n the case of the thionyl chloride, sulfur dioxide is liberated, which does not react with the alumina. Variations in Platinum Content. Although we believe the main function of the platinum is to hydrogenate any coke precursors, it also has an effect on activity. Catalysts were prepared with platinum contents ranging from 0 to 0.58 weight 70. Analyses showed the catalysts all contained from 3.9 to 4.6 weight % chlorine. However, the activities of the catalysts varied from 37 to 46 weight ;'C (Figure 5 ) . Platinum levels of about 0.3 weight % or higher give the same butane conversion. Variations in Platinum-Alumina. A series of commercial aluminas containing from 0.35 to 0.71 weight % platinum was treated with hydrogen chloride and thionyl chloride. The results (Table IV) indicate a wide range of activities and catalyst properties. Obviously, variations in the manufacture of the aluminas play a major role in the properties of the chlorinated catalysts. No attempt has been made to correlate alumina preparation and properties t o the activity of the chlorinated platinum-aluminas. We merely wish to illustrate the variation in catalyst properties and activity by varying the alumina source. In addition to these aluminas, two silica-aluminas were similarly treated and tested. Although, after treatment,
40
I?
Table IV. Properties and Activity of Catalysts Prepared with Aluminas from Other Manufacturers
m
38
0
0
4.4 WT.%
CI
4.1 WT.% CI
36 1
0
1
0.2
1 0.4
l
0.30 mole HCl/hr./100 g. platinum-alumina for 3 hr. with H2 diluent 0.36 mole SOClz/1O0 g. platinum-alumina a t 560" F. over 45 min. with N2diluent Butane isomerization a t 350" F., 800 p.s.i.g., 1 LHSV, 2.5:1 Hzbutane mole ratio
0.6
PLATINUM CONTENT WT.%
Manufacturer Figure
5. Effect of platinum level on catalyst activity
0.30 mole HCl/hr./100 g. platinum-alumina at 1050°F. for 3 hr. with H2 diluent 0.36 mole SOCI2/100 g. platinum-alumina a t 560" F. over 45 min. with Nz diluent Butane isomerization at 350°F., 800 p.s.i.g., 1 LHSV, 2.5:1 H2butane mole ratio
360
l & E C PRODUCT RESEARCH A N D DEVELOPMENT
A B C D
E F
Chlorine, Wt. cc
Surface Area, Sq. M . i G .
Butane Conversion, %
3.4 3.9 3.8 5.1 4.5 4.6
145 169 145 176 175 171
37 22 20 18 9 2
wt.
these catalysts contained 19.8 and 5.4 weight % chlorine, respectively, they were inactive for isomerization a t our conditions. A probable explanation for their inactivity is that most of the h,ydroxyl groups in silica-aluminas are attached to silicon rather than aluminum atoms (Basila et al., 1964). Chlorination occurs, with the replacement of these hydroxyl groups leading to silicon-chlorine bonds, instead of aluminum-chlorine bonds obtained when alumina is chlorinated. Goble and Lawrence (1964) suggest that activity stems largely from the Lewis acid sites on the chlorinated aluminas which have extreme electronattracting capacity. Acknowledgment
We acknowledge the valuable assistance of M. R . Basila, F. E. Lutinski, and ’W.L. Kehl in the instrumental analyses and of K. I. Miller in the catalyst preparation. literature Cited
Basila, M. R., Gulf Research & Development Co., Pittsburgh, Pa., private communication, 1965. Basila, M. R., Kantner, T. R., Rhee, K . H., J . Phys. Chem. 68, No. 11, 31917 (1964).
Egloff, G., Hulla, G., Komarewsky, V. I., “Isomerization of Pure Hydrocarbons,” p. 28, Reinhold, Kew York, 1942. Evans, H. D., Fountain, E. B., Ross, W. E., Preprints 27th Midyear Meeting, API Division of Refining, San Francisco, 1962. Goble, A. G., Haresnape, J. N. (to British Petroleum Co.), Brit. Patent 953,187 (March 25, 1964). Goble, A. G., Haresnape, J. N. (to British Petroleum Co.), U. S. Patent 3,218,267 (Nov. 16, 1965). Goble, A. G., Lawrence, P. A., Preprints, Proceedings, Third International Congress on Catalysis, Amsterdam, 1964. MacIver, D. S., Tobin, H. H., Barth, R . T., Catalysis 2, 485 (1963). Massoth, F. E., Gulf Research & Development Co., Pittsburgh, Pa., private communication, 1967. O’May, T. C., Sixth World Petroleum Conference, Section 111, Paper 4, FrankfurtlMain, 1963. Ridgeway, J. A., Schoen, W., Preprints of Division of Petroleum Chemistry, 4, 2A, Boston, 1959. Riordan, M. D., Estes, J. H. (to Texaco), U. S. Patent 3,242,228 (March 22, 1966). Thomas, C. A., “Anhydrous Aluminum Chloride in Organic Chemistry,” p. 787, Reinhold, New York, 1941. RECEIVEDfor review May 9, 1969 ACCEPTED September 17, 1969
HYDROCRACKING OF n-HEXANE AND CYCLOHEXANE OVER ZEOLITES ALEXIS
VO O R H I E S ,
JR.,
A N D
Louisiana State University, Baton Rouge, La.
WI L L I A M
J.
HATCHER,
JR.’
70821
The lhydrocracking reaction, scission of carbon-to-carbon bonds plus hydrogenation, w a s investigated, using n-hexane and cyclohexane as reactants. Two crystalline aluminosilicate catalysts were studied: the hydrogen, or acid, form of synthetic faujasite and mordenite. Both catalysts were extremely active for hydrocracking. Integral reactor data were correlated using a conventional Langmuir-Hinshelwood model. The reaction rate constant w a s found to be a n Arrhenius function of temperature with activation energies comparable to catalysts with much larger pore diameters. The model was first-order with respect to the hydrocarbon, and the effect of increasing the hydrogen partial pressure w a s compatible with a “dual-site” mechanism. Typical reaction conditions were 500’ to 800’ F., 750 p.s.i.g., 10 moles of hydrogen per mole of hydrocarbon reactant, and liquid hourlly space velocities of 1 to 8.
THE,hydrocracking
of low-octane naphtha is a scheme being considered for producing liquefied petroleum gas (LPG) in areas lacking; natural gas. Commercial plants have been installed in some areas. Typical hydrocracking catalysts for this type of operation, and other feedstocks as well, have been composed of dispersed metals or metal
’ Present address, Chemical Engineering Department, University of Alabama, Tuscaloosa, Ala. 35486
sulfides on conventional supports such as silica-alumina. This paper describes the results of an investigation of two zeolite catalysts for hydrocracking: the hydrogen, or acid, form of synthetic faujasite and synthetic mordenite. Both catalysts were impregnated with palladium. Pure hydrocarbons, n-hexane and cyclohexane, were used as reactants, chosen since they represent some typical molecular structures found in naphtha. VOL. 8 N O . 4 DECEMBER 1969
361
