403 (1970). JuvInaII, R. A,, Kessie, R. W., Steindler. M. J.. ANL-7683, National Technical Information Service, Springfield, Va., 1970. Kunii, D.. Levenspiel, O., "Fluidization Engineering", Chapter 6, Wiley, New York, N.Y., 1969. Levich, V. G., "Physiochemicai Hydrodynamics", Prentice-Hall, Englewood Cliffs, N.J.. 1962. Labine, R. A.. Chem. Eng.. 67, 96 (1960). Liu, Y. H.. Whitby, K. T.. Yu, H. H. S., J. Rech. Atmos., 3, 397 (1966). Lurie, Y. S., Portland Cement, (1959) McCarthy, D.. M.S.Ch.E. Thesis, University of Idaho, Moscow, 1974. Meissner. H. P., Mickley, H. S., ind, Eng. Chem., 41, 1238 (1949). Paretsky, L., Theodore, L., Pfeffer, R., Squires, A. M., J. Air Poll. Control Assoc., 21, 204 (1971). Patterson, R. G., Jackson, M. L.. Paper No. 22b, annual meeting, American Institute of Chemical Engineers. Los Angeles, Calif., Nov 18, 1975. Pilney, J. P., Erickson, E. E.. J. Air Poll. Control Assoc., 18, 684 (1968). (A detailed account is given in Department of Interior, Bureau of Mines, Contract No. 14-69-0070-375, multilih). Ranz, W. E., Wong, J. B.. ind, Eng. Chem., 44, 1371 (1952). Rush, D., Russell, J. C., Iverson, R. E., J. Air Poll. Control Assoc., 23, 98 (1973). Scott, D. S., Guthrie, D. A., Can. J. Chem. Eng., 37, 200 (1959). Squires, A. M., Pfeffer, R., J. Air PoU. Control Assoc., 20, 534 (1970). Stairmand, C. J., Trans. lnst. ofchem. Eng., 28, 130 (1950). Thomas, J. W., Yoder, R. E., Arch. lnd. Health, 13, 545, 550 (1956). Toei. E., Chem. Eng. (Japan), 20, 551, 695 (1956). Tomaides, M., Liu, 6. Y. H., Whitby, K. T., Aerosol Sci., 2,39 (1971). White, F. S., Kinsalla. E. L.. Mining Engineering, 4, 903 (1952). Yankel, A. J., M.S.Ch.E. Thesis, University of Idaho, Moscow, 1972. Yoon, P.. Thodos, G.. A.LCh.€. J., 19, 625 (1973). Zahradnik, R. L., Anyigbo, J., Steinberg, R . A,. Toor, H. L., Environ. Sci. rechnoi., 4, 663 (1970).
N = number concentration of aerosol, cm-3, N1 entering,
N Zleaving
P = fractional penetration per stage, = (1- E') U = superficial gas velocity in bed, cmlsec Uo = initial particle velocity, cmhec U , = superficial gas velocity at minimum fluidization,
-
cmlsec = solids fraction in bed 1 target efficiency per granule, % p = gas viscosity, P p m = micrometers CY
Literature Cited Anderson, D. M., Silverman, L., Air Cleaning Laboratory, Harvard University, to the U S . Atomic Energy Commission, NYO-4615, 1956. Behie, L. A., Kehoe, P., A.l.Ch.E. J., 19, 1070(1973). Black, C. H.. Boubel. R. W., lnd. Eng. Chem., Process Des. Dev., 8, 573 (1969). Blasewitz, A. G., Judson, B. F.. Chem. Eng. Prog., 51, 6-7J (Jan 1955). Boubel, R. W.. Junge, D. C., 64th annual meeting, A.I.Ch.E., San Francisco, Calif.. 1971. Cook, C. C.. Swany, G. R., Colpitts, J. W., J. AirPoll. ControiAssoc., 21, 479 (1971). Fawcett, H., Gardner, G., lnd. Eng. Chem.. 50, 87A (1958). Friedlander, S. K.. A.l.Ch.E. J., 3,43 (1957). Friedlander, S. K., hd. Eng. Chem., 50, 1161 (1958). Friedlander, S. K., J. Collokfhterfac. Sci., 23, 157 (1967). Godel, A., Chem. Eng., 55, 110 (1948). Grace, J. R.,Harrison, D., Chem. ProcessEng., 51, 127(1970). Jackson, M. L.. Patterson, R. G.. A.l.Ch.€., Symp. Ser., No. 747, 47 (1975). Jackson, M. L.. J. Air Poll. ControlAssoc., 24, 569 (1974a). Jackson, M. L., A.l.Ch.E. Symp. Ser. No. 741, 70, 82(1974b). Jugel. W., Reher, E. D.. Grobler, R., Tittman. A,, Chem. Tech. (Leipig), 22,
Received for reuiew May 5, 1975 Accepted October 28,1975
Thermodynamic Equilibria of Selected Heterocyclic Nitrogen Compounds with Their Hydrogenated Derivatives Joseph F. Cocchetto and Charles N. Satterfleld' Department of Chemical Engineering, Massachusetts lnstitute of Technology, Cambridge, Massachusetts 02 739
In the catalytic hydrodenitrogenation of liquid fuels the heterocyclic nitrogen compounds are those most resistant to removal. Thermodynamic analysis of the principal steps in the reaction of representative compounds (pyridine, pyrrole, quinoline, isoquinoline, indole, acridine, and carbazole) reveals that under some significant reaction conditions the overall rate may be at least partly governed by the equilibrium of the first step, the hydrogenation of the N-containing ring. There is no significant thermodynamic limitation on the principal subsequent steps or on the reaction as a whole. Unusual kinetic behavior that has been observed, such as the existence of a maximum in rate with increased temperature, can be well interpreted in terms of a thermodynamic limitation to the allowable concentration of the hydrogenated heterocyclic compound coupled with hydrogenolysis of the C-N bond being the rate-limiting step.
The removal of undesirable nitrogen compounds from petroleum and synthetic crudes derived from coal and oil shale is best achieved by catalytic hydrodenitrogenation (HDN).Most of this nitrogen is in the form of heterocyclic nitrogen compounds, which are the most resistant to HDN. Hydrodenitrogenation of heterocyclic nitrogen compounds proceeds in general via saturation of the heterocyclic ring, followed by ring fracture and subsequent removal of the nitrogen as ammonia. This HDN mechanism is exemplified below for pyridine (McIlvried, 1971; Sonnemans et al., 1972). 272
Ind. Eng. Chem., Process Des. Dev., Vol. 15, No. 2, 1976
3
=&
CsH~iNHz
cjHlz
+ "3
(l)
H Through experimental studies of both model nitrogen compounds and actual or simulated feedstocks, investigators have attempted to elucidate HDN mechanisms and to determine the kinetics of the various steps, as well as the kinetics of overall nitrogen removal. Little has been reported, however, about possible thermodynamic limitations
on HDN reactions in general though there is evidence that this could have significant implications. Sonnemans et al. (1972)estimated the equilibrium constants for the steps in pyridine HDN and found that the vapor-phase hydrogenation of pyridine to piperidine is reversible under representative operating conditions, the equilibrium favoring pyridine at higher temperatures. Sonnemans and coworkers (1973,1974) in more recent papers discuss the mechanistic implications of this hydrogenation equilibrium for pyridine HDN. In experimental work a t 11.1 atm and temperatures of 200 to 500 "C (Satterfield et al., 1975; Satterfield and Cocchetto, 1975) we have observed a maximum in the rate of catalytic HDN of pyridine with increased temperature which seems to be associated with this thermodynamic limitation. If pyridine hydrogenation in eq 1 is rate-limiting, the piperidine will undergo hydrogenolysis (crack) (step 2) as fast as it is formed so that the position of the hydrogenation equilibrium does not influence the rate of denitrogenation. If, on the other hand, piperidine hydrogenolysis is rate-limiting the hydrogenation equilibrium can be established. Increased temperature shifts this equilibrium to the left (toward pyridine), decreasing the partial pressure of piperidine in the system. This can lower the rate of cracking and therefore the rate of denitrogenation, resulting in a decrease in pyridine conversion with increasing temperature. The objective of this study was to extend these conclusions concerning the implications of thermodynamics to consideration of various steps involved in HDN of a group of representative heterocyclic nitrogen compounds found in natural and synthetic liquid fuels.
Table I. Representative Heterocyclic Nitrogen Compounds
Heterocyclic Nitrogen Compounds in Petroleum and Synthetic Crudes
Piperidine
The heterocyclic nitrogen in petroleum and synthetic crudes is incorporated in five- or six-membered rings, most of which are unsaturated. Some representative compounds are shown in Table I. These can be either basic or nonbasic. Pyridines and saturated heterocyclic ring compounds (indoline, hexahydrocarbazole) are generally basic, while pyrroles tend to be nonbasic. The small quantities of nonheterocyclic nitrogen compounds present in liquid fuels include anilines, aliphatic amines, and nitriles. These compounds are generally easier to denitrogenate by catalytic hydrogenation than the relatively unreactive heterocyclic compounds, so they are not a serious problem. Qader et al. (1968)reported that pyridines, quinolines, pyrroles, indoles, and carbazoles are the principal heterocyclic nitrogen structures present in low-temperature coal tars. Indoles, pyridines, and their higher benzologs were reported in a California petroleum (Snyder, 1970). In this same study it was found that the nitrogen content increases with increasing boiling point (molecular weight) of the petroleum fractions. One- and two-ring heterocyclic compounds (pyridines, quinolines) predominate in the lighter fractions while the large multi-ring structures accumulate in the heavier fractions. Similar observations have resulted from studies of shale oils. Dinneen (1962)found that the nitrogen content of Colorado shale oil fractions increases from about 1%(by weight) in naphtha to over 2% in residuum. Pyridines and pyrroles account for most of the nitrogen in the naphtha fraction; pyridines, indoles, quinolines, tetrahydroquinolines, and more complex ring compounds are present in the heavier gas oil fraction. The general conclusion from HDN kinetic studies that the multiring heterocyclic compounds are more difficult to denitrogenate than the lower molecular weight single- and double-ring compounds indicates that the higher boiling
Name F'yrrole
Indole Carbazole Pyridine
Formula
Structure
KJ H
m m H
H
Q
Quinoline Isoquinoline Acridine F'yrrolidine
Q H
Indoline
Hexahydrocarbazole
1,2,3,4-Tetrahydroquinoline
1,2,3,4-Tetrahydroisoquinoline
9,lO-Dihydroacridine
fractions which contain the most nitrogen also contain it in a form which is most difficult to remove.
Hydrodenitrogenation Mechanisms In present commercial practice hydrodenitrogenation proceeds incidentally to catalytic hydrodesulfurization a t elevated temperatures and pressures. Most experimental work on HDN has been done a t temperatures from 300 to 450 "C (570-850 O F ) and pressures of 250-6000 psig. In general, hydrodenitrogenation of heterocyclic nitrogen compounds proceeds via saturation of the heterocyclic ring, followed by ring fracture a t a carbon-nitrogen bond. Nitrogen is then removed from the resulting amine or aniline as ammonia. Ideally, HDN should selectively hydrogenate only the heterocyclic rings, avoiding saturation of desirable aromatics and olefins and minimizing hydrogen consumption. Postulated HDN mechanisms of representative heterocyclic nitrogen compounds are shown in Table 11. The mechanisms proposed for the following compounds are supported by experimental work; pyrrole (Smith, 1957), pyridine (McIlvried, 1971; Sonnemans et al., 1972, 1973, 1974)indole (Aboul-Gheit and Abdou, 1973;Hartung et al., 1961),quinoline (Aboul-Gheit and Abdou, 1973;Doelman and Vlugter, 1963;Madkour et al., 19691,and isoquinoline (Doelman and Vlugter, 1963; Madkour et al., 1969). Side Ind. Eng. Chem.. Process Des. Dev.. Vol. 15, No. 2, 1976
273
Table 11. Postulated HDN Mechanisms of Representative Heterocyclic Nitrogen Compounds
H
5 H
% C4HJH2
+H
C,H,
+ NH,
H
Calculation Procedures Based on the proposed HDN mechanisms for the heterocyclic nitrogen compounds considered in this study, the thermodynamic equilibrium constants for the stepwise and overall HDN reactions were calculated from the corresponding standard free energy changes. All species were taken to be in the gas phase and the ideal gas law was assumed. Details of the calculations are given by Cocchetto (1974). In most cases the free energies of formation of the relevant compounds were not available in the literature, so they were estimated, using the group contribution methods of Benson et al. (1969) and van Krevelen and Chermin (1951). The van Krevelen method resulted in direct estimation of the standard free energy of formation of a compound as a function of temperature AGfO = A S B T
The constants A and B are assumed to be additive functions of the atomic groups comprising the compound. Several of the original van Krevelen group contributions were rederived from more recent data to improve the accuracy of the estimations. Benson's method estimates the standard heat of formation and the corresponding standard entropy change. The standard free energy of formation was then found as
+H
H
H
AGfO = AHfo- TASfO
C,H,
+ NH:,
+
",
reactions also occur. Sonnemans et al. (1972) reported disproportionation reactions in pyridine HDN and that with multi-ring compounds aromatic ring saturation may occur, sometimes followed by ring fracture. Scission of the saturated heterocyclic ring at a carbon-carbon or "anilinetype" carbon-nitrogen bond rather than at the weaker naphthenic carbon-nitrogen bond is also possible. Interconversion between quinoline and indole can even occur. The formation of 0-cyclohexylethylamine, n-octylamine, N-ethylcyclohexylamine, 0-phenylethylamine, and quinoline from indole HDN (Hartung et al., 1961) can be attributed to such side reactions. The mechanisms proposed for carbazole and acridine are the ideal HDN mechanisms for these compounds, but they must be regarded as tentative. Horne and MaAfee (1960) consider the denitrogenation of carbazole to biphenyl plausible, but also indicate that saturation of an aromatic ring prior to nitrogen removal is a possibility. Flinn et al. (1963) suggest that one of the carbazole aromatic rings is hydrogenated and cracked to form an alkylated indole or indoline, which then denitrogenates by the usual mechanism. No information on the mechanism of acridine HDN was found. 274
(2)
Ind. Eng. Chem.. Process Des. Dev., Vol. 15, No. 2, 1976
(3)
where AHfo. = standard heat of formation of a compound and AS,' = standard entropy change for the formation of a compound from its elements. Benson's method is generally more accurate than the method of van Krevelen and is preferred for this reason. Unfortunately, Benson's method was not entirely applicable to all of the compounds encountered in this study, so some estimates had to be based primarily on van Krevelen's method. As much relevant thermodynamic data as could be found was compared with estimated values to determine the reliability of results.
Estimates of Reliability Single-Ring Compounds. Standard heats and free energies of formation, at temperatures up to 1000 K, for pyridine, pyrrole, their hydrogenated derivatives, and ammonia are available in the literature. These data were used to calculate the thermodynamic equilibrium constants for the major steps in the pyridine and pyrrole HDN mechanisms and for the overall reactions. We estimate the absolute errors in the logarithms of the equilibrium constants for the hydrogenation steps (step 1)to vary from about 0.4 a t 298 K to 0.1 a t 1000 K. Equilibrium constants for the overall reactions are more accurate since the free energies of formation for ammonia and the normal hydrocarbons do not introduce any significant errors in the results. The data for the aliphatic amines, however, are of questionable accuracy. Comparison of these data with the free energies of formation estimated from the methods of Benson et al. (1969) and van Krevelen and Chermin (1951) suggests that the literature values may be high by several kcal/mol. Thus the equilibrium constants calculated for the hydrogenolysis reactions (step 2) could be low by one or two orders of magnitude, while those for the denitrogenation reactions (step 3) could be high to the same degree. Multi-Ring Compounds. The calculations for the multi-ring heterocyclic compounds are based primarily upon estimated standard free energies of formation since these data could not be found for most of the relevant compounds. Standard free energies of formation for ammonia and the hydrocarbon products, with the exception of di-
T ,'C I
600 I I
300
I
I
i =
0
100 1
I
0
HYDROGEN PARTIAL P R E S S U R E = I O O ATM HYDROGEN PARTIAL PRESSURE 11 ATM i
0"'
60
TEMPERATURE,' C
Figure 3. Calculated pyridine/piperidine equilibrium. T.'C 600
1 -10.0
1 J 1.o
1
I
2 .o
3.0
I 4.0
12.0 14.'
L
1
1
300
'
100
1
1
4
I
I
I
1
~
1000 I T , ' K - '
Figure 1. Thermodynamicsof pyridine HDN. T,OC 600
100
300
-13.0
10
23
30
.~
li
1000 / T , ' K ~ '
Figure 4. Thermodynamics of quinoline HDN.
1 3 ) C,H,NH,+H, 14) ~
8.0i - - - - - - - l 10
~~
0* 4 H,
C,H,
* NH3
=z C,~,,*hH3
H
75
30
40
1000 / T I ' K
Figure 2. Thermodynamicsof pyrrole HDN. phenylmethane, were found in the literature and were used in preference to less reliable estimations. The results are generally less reliable than those for the single-ring compounds. Errors in the estimated free energies of formation for diphenylmethane and the amine intermediates are about 1 kcal/mol over the temperature range considered. These estimates are based on the relatively accurate Benson method which unfortunately is not completely applicable to the unsaturated and saturated heterocyclic nitrogen compounds. Free energy of formation estimates for these compounds, based on a modified van Krevelen method, could be in error by several kcal/mol. As a result, calculated equilibrium constants for the hydrogenolysis reactions (step 2) and the overall HDN reactions could be in error by one order of magnitude at 1000 K and two orders of magnitude a t 500 K. The equilibrium constants for the denitrogenation reac-
tions (step 3) are more accurate, being within an order of magnitude a t 500-1000 K, since heterocyclic nitrogen compounds are not involved. Estimated equilibrium constants for the ring-saturation reactions, on the other hand, could be in error by two to three orders of magnitude at 500 K and one to two orders of magnitude a t 1000 K, depending on the heterocyclic compounds considered. The results for quinoline and isoquinoline are more reliable than the results for indole and the three-ring compounds, due to better estimates of the free energies of formation.
Results and Discussion Single-Ring Compounds. Figures 1 and 2 present the common logarithms of the equilibrium constants for pyridine and pyrrole HDN, respectively, as a function of the reciprocal of the absolute temperature. The equilibrium constants in both figures always decrease with increasing temperature, consistent with the fact that all the reactions are exothermic. For both pyridine and pyrrole, the equilibrium constants for the initial ring-saturation steps are favorable ( K > 1, log K > 0) a t low temperatures but become unfavorable ( K < 1, log K < 0) above approximately 225 O C . The equilibrium constants for all the other reactions are favorable even at temperatures approaching 500 "C. There is generally a change in the total number of moles Ind. Eng. Chem., Process Des. Dev., Vol. 15, No. 2, 1976
275
600
12,0
600 400
I
100
300
'C
T,
T."C
I-
'
1
1
1
200 I /
100
1
'
::I
10.0
80
L
20
i
- 14 0 10
-
20
30
'0001-
80
40
O K - '
Figure 7. Thermodynamics of acridine HDN.
-100
(41 @ @ ? q + 4 H 2 e
c H1
*NH,
1
1
1
I
10
20
30
40
-120
1000 / T ,
T.'C
OK-'
Figure 5. Thermodynamics of isoquinoline HDN.
T,OC 600 1 1
1
100
300 I
I
I
14.0
Y
1
-40
Y
-1
0
-100 10
3 0
20
1000iT
,
40
O K - '
Figure 8. Thermodynamics of carbazole HDN.
-
12.0
1.0
2 0
1000 i T ,
3.0
4 .O
OK-'
Figure 6. Thermodynamics of indole HDN.
upon reaction, so pressure as well as temperature can affect the equilibria. Elevated pressure shifts the ring-saturation equilibria to the right (toward saturation) since the corresponding reactions are accompanied by a reduction in number of moles. Figure 3 shows, for example, the effect of temperature and pressure on the pyridine/piperidine equilibrium, which emphasizes the importance of hydrogen pressure. Multi-Ring Compounds. Calculated thermodynamic 276
Ind. Eng. Chem., Process Des. Dev., Vol. 15, No. 2, 1976
equilibrium constants for the overall reactions and the steps in the HDN mechanisms of quinoline, isoquinoline, indole, acridine, and carbazole are presented in Figures 4 through 8. These are analogous to Figures 1 and 2 for the single-ring compounds. Qualitatively, the results for both the two- and the three-ring compounds are similar to the results for the single-ring compounds (note that the mechanism proposed for carbazole HDN does not include an initial ring-saturation step). The equilibrium constants for the ring saturation reactions are favorable only at low temperatures; those for the hydrogenolysis, denitrogenation, and overall reactions are favorable a t temperatures as high as 500 "C. The relatively large uncertainties in some estimated equilibrium constants do not significantly affect these qualitative conclusions. The only exception is the equilibrium constant for the initial step in the proposed csrbazole
HDN mechanism (see Figure 8). This reaction involves the hydrogenolysis of a resonance-stabilized pyrrole ring rather than a saturated or a t least partially saturated heterocyclic ring, as in the other compounds considered. This initial step appears to be easier thermodynamically than ring saturation, but it is questionable whether the pyrrole ring in carbazole can be broken under HDN conditions prior t o some degree of saturation. If the carbazole HDN mechanism involves some initial saturation of the aromatic rings, the equilibrium for this saturation step should be similar to the equilibria for the saturation steps in the HDN of the other heterocyclic compounds. Effect of Operating Conditions. Increasing total pressure does not improve the denitrogenation equilibria, since there is no change in the number of moles upon reaction, but the equilibrium constants are very large even a t 500 OC so the equilibria are completely to the right. T h e equilibrium constants for the hydrogenolysis steps and the overall HDN reactions are all very large a t lower temperatures, but some decrease to about unity (log K = 0 ) as the temperature increases to 500 OC. At this temperature only moderate pressure (10 atm) shifts these equilibria completely to the right. Thus the overall reactions and the hydrogenolysis and denitrogenation steps in the HDN mechanisms for the compounds considered are irreversible within the relevant range of temperature and pressure. The initial heterocyclic ring-saturation step, however, is reversible; that is, appreciable quantities of both the saturated and the unsaturated heterocyclic compounds can be present a t equilibrium. Decreasing the temperature or increasing the pressure shifts this equilibrium to the right, toward saturation. The extent to which increased pressure can be used to overcome an unfavorable equilibrium constant depends, of course, on the number of moles of hydrogen consumed in the ring saturation step. Saturation of pyridine to piperidine requires three moles of Hz while hydrogenation of indole to indoline requires only one. For an unfavorable equilibrium constant of say, 0.001 and a hydrogen partial pressure of 100 atm, the equilibrium piperidinelpyridine mole ratio is 1000, the indoline/indole ratio is only 0.1. Thus the elevated hydrogen pressure shifts the pyridinelpiperidine equilibrium completely to the right but fails to make the indolelindoline equilibrium favorable for hydrogenation. Since the slope of the log K vs. 1/T curve is proportional to the enthalpy change on reaction, the exothermicity per mole of heterocyclic compound also increases with the number of moles of hydrogen consumed in the hydrogenation step. Consequently, the equilibrium concentration of the initial hydrogenated species is most sensitive to both pressure and temperature for those heterocyclic compounds consuming the greatest amount of hydrogen in the initial step.
Conclusions The mechanism for the hydrodenitrogenation of heterocyclic nitrogen compounds involves reactions in series.
Only the first step in this reaction sequence is difficult thermodynamically. As a result, the effect of thermodynamics on overall HDN depends on the kinetics of the various steps in the mechanism. If the initial heterocyclic ring-hydrogenation step is ratelimiting, the hydrogenated heterocyclic compound reacts as soon as i t is formed and the position of the hydrogenation equilibrium for the initial step does not affect the overall HDN rate. If hydrogenolysis (cracking) (step 2) is rate-limiting, the reversible initial step can achieve equilibrium. The partial pressure of the saturated heterocyclic compound (the reactant for step 2) then depends on the position of the saturation equilibrium. The overall HDN rate in this case is the rate of hydrogenolysis, which in a simplified model depends on a temperature-dependent kinetic rate constant and on the partial pressure of the saturated heterocyclic compound, governed by the equilibrium of the first step. An increase in temperature increases the kinetic rate constant but decreases the equilibrium constant for the first step, decreasing the partial pressure of the reactant for the hydrogenolysis reaction. Thus the rate may go through a maximum with increased temperature. A potential thermodynamic limitation exists in most HDN mechanisms under those sets of circumstances in which hydrogenolysis of the C-N bond is slower than the rate of hydrogenation of the original heterocyclic ring and the equilibrium concentration of the hydrogenated compound is substantially limited.
Literature Cited Aboul-Gheit. A. K., Abdou, I. K., J. lnst. Petrol., London, 59, 188 (1973). Benson, S. W., Cruickshank. F. R., Golden, D. M.. Haugen. G. R.. O'Neal, H. E., Rodgers, A. S., Shaw, R., Waish, R., Chem. Rev., 69, 279 (1969). Cocchetto, J. F.. S.M. Thesis, Massachusetts Institute of Technology, Cambridge, Mass., 1974. Dinneen, G. U., Proc. Am. Petrol. Inst., 42(8), 41 (1962). Doelman, J., Vlugter, J. C., "Proceedings, Sixth World Petroleum Congress," Section Ill, pp 247-257, The Hague, Netherlands, 1963. i i n n , R. A,. Larson, 0. A,, Beuther, H., Hydrocarbon Process. Pet. Refiner, 42(9), 129 (1963). Hartung, G. K.. Jewell, D. M., Larson. 0. A., Flinn, R . A,, J. Chem. Eng. Data, 6, 477 (1961). Horne, W. A,, McAfee, J., "Advances in Petroleum Chemistry and Refining," K. A. Kobe and J. J. McKetta, Jr., Ed., Vol. 3, p 228, interscience. New York N Y 1960 Madkoir. M M , Mahmoud, B H , Abdou, I K , ViuGer, J C , J lndran Chem SOC 46. 720 (19691 Mcllvried, H. G., ind. Eng. Chem., Process Des. Dev., I O , 125 (1971). Qader. S. A,, Wiser, W. H., Hili, G. R.. lnd. Eng. Chem., Process Des. Dev., 7 , 390 (1968). Satterfield. C. N.. Modell, M., Mayer, J. F., AlChE J . , 21, 1100 (1975). Satterfield, C. N., Cocchetto. J. F., AIChE J., 21, 1107 (1975). Smith, H. A,, "Catalysis," Vol. V, pp 231-234, P. H. Emmett, Ed., Reinhold. New York, N.Y., 1957. Snyder, L. R.,Am. Chem. SOC.Div. Petrol. Chem. Prepr., 4(2), C43 (1970). Sonnemans, J.. Goudriaan, F.. Mars, P.. "Fifth International Congress on Catalysis," Palm Beach, Fla. Paper 76, 1972. Sonnemans, J., van den Berg, G. H., Mars, P., J. Catal., 31, 220 (1973). Sonnemans, J., Neyens, W. J., Mars, P.. J. Catal., 34, 230 (1974). van Krevelen, D. W., Chermin, H. A. G., Chem. Eng. Sci., 1, 66 (1951).
Received for review M a y 20, 1975 Accepted November 13,1975
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