40
Ind. Eng. Chem. Prod. Res. Dev. 1903, 22, 40-44
action temperature, which was quantified by the titration with hydrochloric acid, was 3.2% of the total imidazole group of the catalyst. The dehydrochlorinated product in a pulse of ECH corresponds to 1.9% of the total 2methylimidazole group, that is 60% of the free base, indicating that the free base produced thermally from MImzHCl can be the active site for the reaction and the recovery of dry hydrogen chloride can be achieved. Thus, the reaction scheme over MImzHCl catalysts can be summarized by eq 3. The thermal decomposition of the hy, & T
/-
"ILr-2P"
~
7 7
z
drochloride may allow the recovery of hydrogen chloride and can be a rate-determining step, leading to the zero order in the reactant. Thus, the pulse intervals are strongly
influential in the catalytic activity. A reactor accompanied with the catalyst regeneration unit instead of a continuous flow one should be designed for a practical purpose. Registry No. ECH, 107-07-3; HCl, 7647-01-0; EO, 75-21-8; PCH, 78-89-7; PO, 75-56-9; PA, 123-38-6; acetone, 67-64-1.
Literature Cited Burwell, R., Jr. CHEMTECH 1974, 370. Kokes, R. J.; Tobln. H.; Emmett, P. H. J. A m . Chem. SOC. 1955, 7 7 , 5860. Leal, 0.:Anderson, D.; Bowman, R.; Basolo, F.; Burwell, R., Jr. J Am. Chem. SOC. 1975, 9 7 , 5125. Mochida, I.; Yoneda, Y. J. Catal. 1967, 7 , 386. Mochida, I.: Anju, Y.; Koto, A.; Seiyama, T. Bull. Chem. SOC.Jpn. 1972, 4 5 , 1635. Mochida, I.; Watanabe, H.; Fujltsu, H.; Takeshita, K. J , Chem. SOC.,Chem. Commun. 1980, 793. MochMa, I.; Watanabe, H.; Uchino, A.; Fujitsu. H.: Takeshita, K.; Furuno, M.; Sakura, T.: Nakajima, H. J. Mol. Catal. 1981, 72,359.
Received for review December 21, 1981 Accepted September 27, 1982
Effects of Phosphorus on Nickel-Molybdenum Hydrodesulfurizat ion/H ydrodenitrogenation Catalysts of Varying Metals Content Carl W. Fitr, Jr.,' and Howard F. Rase' DepaHment of Chemical Engineering, The University of Texas, Austin, Texas 78712
Five Ni-Mo catalysts were studied having varying amounts of Mo and P and a constant Ni/Mo ratio. A catalyst with low metals and medium phosphorus content was found to be best for hydrodesulfurization while a highmetaldhigh-phosphorus catalyst gave the best performance and lowest hydrogen consumption for nitrogencontaining feeds. The phosphorus-containing catalysts were less susceptible to coking and produced a more
hydrogen-rich coke.
Hydrotreating catalysts based on Co-Mo or Ni-Mo deposited on a y-alumina carrier are not only fascinating systems but they are also essential in the commercial production of low-sulfur products from petroleum and coal-derived liquids. It is not surprising, therefore, that studies aimed a t both further understanding of these rather complex catalysts and improving their performance continue to stimulate interest in laboratories throughout the world. One area of interest, common to all catalysts, has been the use and performance of promoters in improving activity, selectivity, and catalyst life. One such promoter for Co-Mo and Ni-Mo catalysts, phosphorus, has been investigated and recommended over a period of three decades and is now used in a number of merchant catalysts. The investigation reported here had as its purpose the study of the effect of phosphorus on activity and selectivity in relation to metals content of a group of similarly prepared Ni-Mo/A1203 catalysts. Interesting differences were observed, and some insights on the mode of phosphorus interaction were realized.
Previous Observations Because of the commercial interest in improving hydrotreating catalysts, the patent literature is a major source of information on discoveries and observations on phosPhillips Petroleum Co., Bartlesville, OK 74004.
phorus as a promoter. As early as 1953 Haresnape and Morris (1953) of the Anglo-Iranian Oil Co. claimed that adding phosphorus in the form of cobalt phosphomolybdate or (NH4)3P04.12M003increased the hydrodesulfurization (HDS) activity. The relative activity for a catalyst containing 2.85% COO,15.6% Moo3, and 1.14% P205was 115 compared to an activity of 100 for a similar catalyst with no phosphorus. The promoting effect of phosphorus in improving hydrogenation activity was confirmed in a patent by Housam and Lester of British Petroleum Co. (1959) for both Co-Mo/Al,O, and Ni-W/ Al,O, catalysts. A single-step impregnation procedure using phosphoric acid was proposed by Colgan and Chomitz (1966) of American Cyanamid. Phosphoric acid was found to act as a stabilizing and solubilizing agent, allowing a high concentration of metal to be impregnated uniformly. They recommended a phosphoric acid to molybdenum mole ratio of about 0.4:1, yielding about 1to 5 wt % phosphorus on the catalyst. Larger amounts of phosphorus tend to mask the active areas and reduce the activity of the catalyst. A catalyst containing 14.5% MOO,, 3.5% NiO, and 3.8% H P 0 3 was shown to have an HDS activity of 127 and an HDN activity of 149 when compared to a similar catalyst without phosphorus. Phosphorus also provides increased strength and heat stability. According to Hilfman of UOP (1971), the function of phosphorus is to inhibit the formation of nickel aluminate
0196-4321/83/1222-0040$01.50/0 0 1983 American Chemical Society
Ind. Eng. Chem. Prod. Res. Dev., Vol. 22, No. 1, 1983 41 Table I. Inspections on Prepared Ni-Mo/Al,O, Catalysts designation no. 450 measured composition Ni, wt % Mo, wt % P, wt % measured atomic ratios Ni/Mo P/Mo specific Mo concentration, (g of M O / ~ Z ) ( ~ O ~ ) surface area, mz/g surface area based on A Z O , content only, mz/g pore volume, cm3/g pore volume based on Al,O, content only, cm3/g particle density, g/cm3
no. 451
no. 452
no. 453
no. 454 3.34 13.5
2.34 8.8
2.26 9.3 1.49
2.12 9.1 2.60
2.89 13.0 4.46
0.435 0 5.0
0.397 0.496 6.3
0.381 0.885 6.5
0.363 1.06 11.7
172.6 147.5
146.8 141.0
139.8 137.8
110.4 119.2
0.4 04 9.3 145.5 132.9
0.571 0.587
0.508 0.561
0.502 0.548
0.389 0.474
0.544 0.53
1.1
1.28
1.33
1.60
1.36
to below 0.1 wt % . If formed, nickel aluminate would tie up the nickel atoms and reduce activity. Boron has been mentioned in the literature as also inhibiting the formation of nickel aluminate (Lafitau et al., 1976). Kerns and Larson of Gulf Research and Development Co. (1969) claim that while phosphorus provides substantial improvement for nickel-containing catalysts, no gain is exhibited with a cobalt-containing catalyst in hydrotreating of furnace-oil distillate. Specifically, a furnace-oil distillate was tested which contained 2.03 wt % sulfur and 340 ppm nitrogen. At operating conditions of 650 OF, 1000 psi, 3.0 LHSV, and 4000 scf of hydrogenlbbl of charge stock, an umpromoted Ni-Co-Mo catalyst lowered the nitrogen content to 9 ppm; an Ni-Mo catalyst lowered the nitrogen content to 14 ppm, and an Ni-W catalyst lowered it to 15 ppm. However, when 0.5% phosphorus was added to each catalyst the nitrogen content was increased to 14 ppm for the Ni-Co-Mo catalyst, decreased to 2.8 ppm for the Ni-Mo, and decreased to 13 ppm for the Ni-W catalyst. Some of the most extensive work available in the patent literature is by Mickelson of Union Oil Co. of California (1973a-e). He claims that the function of phosphorus is to provide a more stable impregnating solution and thus better disperse the metals on the catalyst. The use of phosphorus allows an amorphous colloidal film to be deposited on the surface instead of large crystalline aggregates. To achieve this dispersive effect the pH of the solution must be kept in the range of 1 to 2 and the P/ Moo3 ratio in the product should be about 0.12 to 0.23. In a series of tests of Ni-Mo/Al,O, catalysts containing varying amounts of Mo (16.0-21.7 Moo3) and P (1.3-3-58), the catalysts with medium amounts of Mo and P were the most active in hydrodenitrogenation.
Experimental Plan In order to simplify the feed system with the usual goal of reducing the number of variables, pure component feeds were used composed of thiophene and cyclohexene and thiophene/cyclohexene/piperidine. Thiophene was selected as the simplest member of ring compounds containing sulfur that are more difficult to convert than most other types of organic sulfur compounds. Cyclohexene is an intermediate in the benzene-cyclohexene conversion. It can either dehydrogenate to benzene or hydrogenate to cyclohexane depending upon conditions and catalyst characteristics. Piperidine is also an intermediate that occurs in the hydrodenitrogenation of pyridine. It ultimately forms pentane and ammonia in this reaction sequence. Since the
experiments were planned for atmospheric pressure where equilibrium favors pyridine and the hydrogenation of pyridine to piperidine is not significant, piperidine was selected as a means of observing any inhibiting effects on other reactions by an organonitrogen compound (piperidine) and ammonia. Five different catalysts as shown in Table I were prepared having varying amounts of Mo and P and essentially a constant Ni/Mo ratio. Activities relative to the lowmetals catalyst with no phosphorus were determined for both feeds. Catalyst surface areas, pore volumes, and coke characteristics were also compared.
Experimental Equipment and Procedures Reactor System. The microreactor system described by Harrison et al. (1965) was used with improved analytical equipment and mass flowmeters. Analysis. The samples were analyzed by a HewlettPackard Model 5750 gas chromatograph equipped with a thermal conductivity detector. The chromatograph contained two 6 ft X in. stainless steel columns packed with 20% Carbowax 20M treated with 2 % KOH on acidwashed 60/80 mesh Chromosorb W. The output signal from the chromatograph was recorded on a Honeywell recorder which was equipped with a disk chart integrator. Oven temperature was 80 "C and the helium flow rate was 60 cm3/min. The column was calibrated using known samples. Conversions for the runs without piperidine were in the ranges of 23-44% thiophene, 9-1590 cyclohexene to cyclohexane, and 2.5 to 5.5% cyclohexene to benzene. For the feed containing piperidine these same conversions were 4-990, 0.3-1.290, and 0.1 to 0.7%. Piperidine conversion was in the range of 9-30%. Operating Procedure. Before a particular catalyst could be tested, the feed mixture had to be prepared. Two different feeds were used, the first consisting of 92 wt 90 cyclohexene and 8 wt % thiophene and the second consisting of 86 wt % cyclohexene, 8 w t % thiophene, and 6 wt % piperidine. A charge of 0.72 g of sample catalyst was used for each test. This amount completely filled the reactor for the least dense catalyst. After the catalyst was charged it was settled by lightly tapping the assembly against the table top. In the case of the most dense catalyst, glass beads were added to occupy the void volume at the top. A circle of Refrasil cloth was placed above and below the catalyst bed and the entire microreactor was assembled and placed in the sand bath. The reactor was then heated over a period of 30 min from room temperature to about 304 "C with a nitrogen
42
Ind. Eng. Chem. Prod. Res. Dev., Vol. 22, No. 1, 1983
flow of approximately 10 cm3/min. The catalyst was then calcined under these conditions for 1 h. After calcining, the catalyst was sulfided for 4 h with a mixture of 11.3% H2Sin H2 at the same temperature and flow rate. This flow corresponds to a gas velocity of about 1000 vol gas/vol reactor/h. By this procedure the lowmetals catalysts was exposed to at least 6 ''theories'! of sulfur and the high-metals catalysts to at least 4 "theories" of sulfur. A theory of sulfur is defined as the stoichiometric amount of sulfur required to convert the bulk Ni to Ni2S3 and the bulk Mo to MoS2. This sulfiding technique assured reproducible sulfiding, but no claim to complete sulfiding of Mo and Ni oxides is made. The procedure employed is a common one in applications work on hydrodesulfurization catalysts and has been successful in relating results to large-scale units. After sulfiding, the reactor was heated from 304 to 389 "C over a period of 30 to 45 min with a 5 cm3/min nitrogen flow. The liquid feed and hydrogen were then started and the actual activity test begun. Sampling began 30 min after the feed was added and contined every half hour until the run was ended, usually after 6 h. The reactor was then allowed to cool under a small nitrogen flow. Catalyst Preparation. The catalyst samples were prepared by Exxon Research and Development Laboratories in Baton Rouge using a wet impregnation technique. Properties of the five catalysts are summarized in Table I. In the catalyst preparation the alumina support was calcined at 538 "C for 1 h. Next the alumina was exposed over water and subsequently water wetted. Then the support was impregnated by a solution of ammonium molybdate in deionized water. Subsequently, hydrogen peroxide was added to stabilize the solution which was then air dried for 8-10 h followed by oven drying at 1038 "C for 6 h. It was then calcined at 538 "C for 1 h in air. Next the catalyst was again air exposed over water, wetted a second time, and impregnated with a mixture of about the same amount of ammonium molybdate and hydrogen peroxide as before. The previous sequence of drying steps was then repeated. Finally, the catalyst was air exposed over water and wetted a third and final time. It was then impregnated with nickel nitrate and dried as before with the final temperature lowered to 454 "C. The catalyst samples containing phosphorus were prepared in basically the same way except whenever hydrogen peroxide was added phosphoric acid was also added.
Results Effect on Surface Area and Pore Volume. BET surface area and average pore-volume measurements are assembled in Table I for the five catalysts. Since these data are reported on a per gram of extrudate basis, it is helpful for comparative purposes to calculate as a limiting case the areas and pore volumes that would be expected if only the Al,03 contributed to these two properties. The simplistic assumption for this limiting case would be that the added components simply covered A1203 surfaces without changing the area or porosity. In making these calculations the masses other than A1203were assessed as Moo3, NiO, and an equal mixture of H2P03and PO. The rationale for this later assumption is based on the possible nature of the P-A1203interaction presented in the section on coking. If we examine the observed areas and those calculated based on A1203alone as given in Table I, it becomes apparent that both the low-metals and high-metals catalysts without phosphorus produced greater surface areas than
4 5 i - l ~ f e r m e d i a t ePhosphorus
P I PER I D 1 N E CONTAIN I N G F E E D
! g Mo/M21(104)
Figure 1. Thiophene conversion (389 O C , 1 atm, W / F = 36 g of cat./(mol of liquid feed/h), molar ratio H2:oil = 8.6). 4 5 1 - I n t e r m e d i a t e Phosphorus 10501~
454 0
NO PIPERIDINE 453
NoU r-S 452
c--
I O 891
_--------. H i g h Phosphorus
(' 06)
P I P E RID1 N E C O N T A l N I NG FEED
( g Mo / M21 ( I O 4 )
Figure 2. Cyclohexane formation (same conditions as for Figure 1).
I
lo50124 5 1 - l n t e , i e d i o t e Phosphorus 452
High Phosphorus
b---
*Ot
I O 891
453
-------e (
061
P I P E R I D I N E C O N T A I N I N G FEED
( g M o / M 2 ) 1I O 4 )
Figure 3. Benzene formation (same conditions as in Figure 1).
that provided by the A1203content alone, while two of the catalysts containing phosphorus produced close to the same values as that based on the A1203 content alone. The high-metals catalyst with phosphorus had an area that was significantly less. Similar data show that the two sets of pore volumes for each of the nonphosphorus-containing catalysts were approximately unchanged while the actual values for the phosphorus-containing samples were 10 to 20% below those based on A1203alone. These observations suggest that phosphorus additions cause pore plugging, particularly for the high-metals case in which phosphorus is also high. The increased surface area for the nonphosphorus-containing catalysts may be produced by highly porous aggregates of metal oxides in large pores and on exterior surfaces. Activity Comparisons. Using the low-metals, nophosphorus catalyst as a base case relative activity com-
Ind. Eng. Chem. Prod. Res. Dev., Vol. 22, No. 1, 1983 43 Table 11. Relative Activity for Piperidine Conversion4 ~-~ ~
no.450 low metals no P
relative activity
1.0
no. 451 no. 452 no. 453 no. 454 low high high low metals metals metals metals inter- high P high P no P mediate P 0.82
0.33
0.99
0.55
Operating conditions: 389 "C; 1 atm; W / F = 36 g of cat./(mol liquid feed/h); molar ratio H,:oil = 8.6.
parisons are plotted in Figures 1-3 for the several reactions in order to facilitate comparison. Since space velocities and operating conditions were identical in all tests,relative activities, a,were defined as a =
[ ;1
(&)CAT (&)REF]
[
BET surface areas (REF) BET surface area (CAT)
1
where CAT refers to the catalyst being considered and REF to the reference catalyst, No. 450; x is the observed linned-out conversion. These activities are plotted vs. a Mo concentration expressed as g of Mo/m2 cat. I t was not expected that the area correction would produce a single correlation, for there is clear evidence that such a correlation would be unlikely (Tauster et al., 1980; Tauster and Riley, 1981). It is not unreasonable, however, to suggest separate correlations for nonphosphorus-containing catalysts and high-phosphorus catalysts as a convenient means for presenting the data, particularly when it is realized that sulfiding and other pretreatment procedures were identical in each case. By referring to Figure 1-3 one can reasonably conclude that for nitrogen-free feed a low metals/medium phosphorus catalyst (451) is superior for hydrodesulfurization of thiophene at the conditions studied. This catalyst apparently contains the optimum ratio of phosphorus to metals. The catalyst with the same metals content (no. 452) and high phosphorus was inferior as was the high metals/high phosphorus catalyst. With piperidine in the feed the HDS activity is greatly reduced, and all catalysta give comparable performance except the low metals/high phosphorus catalyst (no. 452), which was decidedly inferior. Satterfield et al. (1975) has postulated two types of sites involved in HDS/HDN interaction. One is suggested to be very active for HDS but sensitive to nitrogen poisoning. The other type is less active for HDS but less susceptible to poisoning by nitrogen compounds. It is quite possible that under the relatively mild conditions of these studies the first type predominates, but its activity is destroyed by the nitrogen compounds and only the lower-activity sites remain to produce the low activity observed.
In some feed systems low hydrogenation/dehydrogenation activity is preferred. It was possible to observe both these phenomena because the conditions of test were far from equilibrium to cyclohexane. Although equilibrium favors benzene, hydrogenation was faster than dehydrogenation, and cyclohexane was also produced at the high space velocities used. Figures 2 and 3 indicate that high phosphorus loadings reduce hydrogenation/dehydrogenation activity as indicated, respectively, by cyclohexane and benzene formation. In the case of nitrogen-containing feed the high metals/high phosphorus catalyst (no. 453) has the highest HDS activity and the lowest hydrogenation/dehydrogenation activity. It also appears to be a good HDN catalyst as indicated in Table I1 for conversion of piperidine. One can assume that at high H2 pressures it will be equally as effective in converting pyridine to piperidine. Coking Characteristics. The catalysts for the thiophenecyclohexene test runs were analyzed for carbon and hydrogen content and the results are given in Table 111. All the catalyst samples analyzed were tested for 6-h run times under similar conditions except for catalyst no. 453, which was tested only 4.5 h. A blank pellet (one which had never been tested) of catalyst no. 450 was analyzed in order to ascertain the amount of carbon and hydrogen present on an uncoked catalyst. This base amount was subtracted from the values for the coked sample to give the adjusted analysis. The mole ratio of carbon to hydrogen was then computed. As one can see, the lowest carbon buildup appears to have occurred on the catalysts containing phosphorus. The low-metals/medium-P and the low-metals/ high-P both contained 0.57% carbon, significantly less than the lowmetals/no-P catalyst. The high-metals/no-P catalyst contained by far the greatest carbon buildup. The carbon analysis of the two separate test runs of catalyst no. 450 give an idea of the variability of the data. The hydrogen analysis of the coked catalysts indicates that as the phosphorus content of the catalyst increased the amount of hydrogen in the coke increased slightly. This is the opposite of the trend exhibited in carbon buildup. The coke from high-metals loaded catalysts contained much more hydrogen than the low-metals loaded catalyst. The mole ratio of hydrogen to carbon in the coke very clearly demonstrates a difference in phosphorus- and nonphosphorus-containing catalysts. For both low-metals and high-metals loading the catalysts with no P produced coke low in hydrogen content with a H/C mole ratio of about 1.2 to 1.4. Coke produced on phosphorus-containing catalysts is much richer in hydrogen, possessing an H/C ratio of 2.1 to 2.3 for low-metals/medium and high-P catalysts. A possible explanation for the effect of phosphorus on the degree of coking lies in the fate of the phosphoric acid on the final catalyst. y-Alumina is an acidic support
Table 111. Coke Analysis of Used Catalysts. Thiophene-Cyclohexene FeedQ
fresh catalyst low metals/no P low metalslno P low metalslmed. P low metals/high P high metalslhigh P high metals/no P
cat. desig. blank 4 50-1 450-2 451 452 453 454
raw anal., w t % C
0.10 0.89 0.92 0.67 0.67 0.81 1.40
H 0.35 0.54 0.51 0.57 0.55 0.67 0.63
adj. anal., wt % C
0.0 0.79 0.82 0.57 0.57 0.71 1.30
Note: All catalysts were tested for 6 h except catalyst no. 453, which was tested for 4.5 h.
H/Cmole
H
ratio
0.0 0.19 0.16 0.22 0.20 0.32 0.28
0.0 1.4 1.2 2.3 2.1 2.7 1.3
44
Ind. Eng. Chem. Prod. Res. Dev., Vol. 22, No. 1, 1983
a I
1x1
1
LO?.
C
I
I Ai
AI
Figure 4.
Reaction hydroxide groups.
of phosphoric acid w i t h alumina surface-
0 I
D
Figure 5. Reactions of phosphoric acid w i t h m u l t i p l e surfacehydroxide groups.
containing exposed aluminum atoms, which may act as Lewis acid sites, and hydroxide groups bonded to tetrahedral A1 ions, which act as Bronsted acid sites. The phosphoric acid molecule is also tetrahedral in structure, containing three hydroxide groups and one lone oxygen atom. As shown in Figure 4,an acid-base reaction may occur between a hydroxide group bonded to the alumina surface and one of the hydroxide groups of the phosphoric acid molecule. Either one of these groups may donate a hydrogen ion to the other, split out a water molecule, and result in the formation of an oxygen bond between the alumina support and the phosphoric acid. If the phosphoric acid molecule bonds to the alumina at only one point, the surface acidity will increase, since the one available acidic hydrogen from the surface hydroxide group has been replaced by two available acidic hydrogens from the phosphoric acid. However, the phosphoric acid molecule should be capable of multiple bonding, as shown in Figure 5 , where as many as three bonds may be formed with three different surface hydroxide groups. The formation of the maximum of three bonds would result in the loss of three acidic hydrogens, and the formation of two bonds would result in the loss of one acidic hydrogen. When phosphoric acid is first added to the catalyst, most likely a large number of multiple bonds are formed with the alumina support. These multiple bond formations rapidly decrease the availability of unreacted surface hydroxide groups, and the addition of more phosphoric acid would result in the formation of a higher percentage of single bonds. This type of phenomena is supported by the surface area measurements given in Table I. The initial 1.5% phosphorus caused a great decrease in surface area (26 m2/g) perhaps blocking micropores by virtue of the
multiple-bond attachment. An additional 1% phosphorus acid may have been predominately attached by single bonds. Based on the proposed bonding of phosphoric acid to alumina, one would expect a decrease in surface acidity with increasing phosphorus content until a minimum surface acidity is reached. At concentrations above this particular phosphorus level the surface acidity would begin to rise because only single bonds would be formed. Whether such a level was reached is not discernible from the data. Surface acidity is important to coking because of the effect it has on carbonium ions. Coke is believed to be formed via a carbonium-ion mechanism, and the higher the surface acidity the greater the production of carbonium ions. Consequently, as the phosphorus content increases, the degree of coking decreases. Since coking is one of the primary mechanisms of hydrotreating catalyst deactivation, the lower coking level due to phosphorus is highly significant.
Conclusions For a Ni-Mo catalyst prepared by multiple impregnations and based on model feed mixtures of two and three components, the following conclusions are apparent. For HDS service alone the optimum catalyst recipe is a low-metals formulation with medium phosphorus content. For nitrogen-containing feeds the high-metalslhighphosphorus catalyst gives the best performance and lowest hydrogenation/dehydrogenation activity. The possibility of lower hydrogen consumption in feeds containing aromatics is attractive. Phosphorus-containing catalysts are less susceptible to coke formation and produce a more hydrogen-rich coke. The phosphorus addition apparently reduces the acidity of the alumina carrier. These observations suggest that phosphorus in hydrotreating catalysts is an active ingredient in the catalytic process and that the optimum catalyst recipe for a particular feed system should include specific instructions on phosphorus content relative to other ingredients. Literature Cited Colgan, J. D.; Chomitz, N. U.S. Patent 3287280, 1966. Haresnape, J. N.; Morris, J. E. British Patent 701 217, 1953. Harrison, D. P.; Hall, J. W.; Rase, H. F. I n d . Eng. Chem. 1065, 5 7 , 18. Hilfman, L. U.S. Patent 3617528, 1971. Housam, E. C.; Lester, R. British Patent 807 583, 1959. Kerns, 8. A.; Larson, 0. A. U.S. Patent 3446730, 1969. Laftau, H.; Ned, E.; Clement, J. C. I n "Preparation of Catalysts"; Delmon, B.; Jacobs, P. A,; Poncelet, Ed.; Elsevier: Amsterdam, 1976. Mickelson, G. A. U S . Patent 3 749 663, 1973a. Mickelson, G. A. U S . Patent 3 755 196, 1973b. Mickelson, G. A. U S . Patent 3755 150, 1973c. Mickelson, G. A. U S . Patent 3755 148, 1973d. Mickelson. G. A. U.S. Patent 3 749 664, 1973e. Satterfieid, C. N.; Modell, M.; Mayer, J. F. AIChE J . 1075, 2 1 , 1100. Tauster, S. J.; Peroraro, T. A,; Chianeili, R. R. J . Cafal. 1080, 6 3 , 515. Tauster, S.J.; Riley, K. L. J . Catal. 1081, 67,250.
Received f o r review June 1, 1982 Accepted O c t o b e r 1, 1982
