literature Cited
Akhmetshina, 11. N., Levinter, hI. E., Tanatarov, M. A., Nochalov, Y. D., Seftepererab. Neftekhim. (hIoscow), 1969 (81, 10. Andrew, J. AI., Ind. Eng. Chem., 51, 507 (1959). Blanding, F. H., ibid., 45, 1186 (1953). Campbell, D. It., Wojciechowski, B. W., Can. J . Chem. Eng., 47, 413 (1969). Eberly, P. E., Kimberlin, C. N., Miller, W.H., Drushel, H. V., I n d . Eng. Cheni. Process Des. Develop., 5 , 193 (1966). Fitzgerald, 31. E., hIoirano, J. L., Morgan, H., Cirillo, V. A,, Appl. Spectrosc., 24, 106 (1970). Froment, G. F., Bischoff, K. B., Chem. Eng. Sci., 16, 189 (1961). Froment, G. F., Bischoff, K. B., ibid., 17, 105 (1962). Narquardt, D. W., J . SOC.Appl. Math., 11,431 (1963). Masamune, S., Smith, J. AI., AIChE J., 12, 384 (1966). Ozawa, Y., Bischoff, K. B., Ind. Eng. Chem. Process Des. Develop., 7, 73 (1968). Reif. H. E.. Kress. R. F.. Smith, J. S..Petrol. Refiner, 40 ( 5 ) 237 (1961). ’ Sagara, Y., LIasamune, S., Smith, J. 11.,AIChE J., 13, 1226 (1967).
Shnaider, G. S., Khim. Tekhnol. Topk. Masel, 1969 (5), 5. Shnaider, G. S., Mukhin, I. I., Chueva, M. A., Kogan, Y. S., ibid., 1969 ( l ) ,10. Szepe, S., Levenspiel, O., European Federation of Chemical Engineers, Symposium on Reaction Engineering, Brussels, Se tember 1968. Vooriies, A., Ind. Eng. Chem., 37, 318 (1945). Waterman, H. I., Boelhowuer, C., Huibers, D. T. A., “Process Characterization,” Elsevier, Amsterdam, Netherlands, 1960. Weekman, V. W.,Ind. Eng. Chem. Process Des. Develop., 7, 90 (1968). Weekman. 5’. W.. ibid.. 8- z. 38R .- . . . . .- - 11969). I
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Weekman: 1’.W.: ru’ace, D . M., AIChE J., 16,397 (1970). White, P. J., Hydrocarbon Process. Petrol. Refiner, 47,103 (1968a). White. P. J.. PreDrint No. 24-68, API Division of Refining, - 33rd Mid-Year Megting, Philadelphia, May 1968b. Wojciechowski, B. W., Can. J . Chem. Eng., 46, 48 (1968). Wojciechowski, B. W., Juusola, J. A,, Downie, J., ibid., 47, 338 ( 1969). RECEIVED for review October 29, 1970 ACCEPTEDMay 3, 1971
Application of a Kinetic Model for Catalytic Cracking Some Correlations of Rate Constants Sterling E. Voltz,l Donald M. Nace, and Vern W. Weekman, Jr. Research Department, X o b i l Research and Development Corp., Paulsboro, N . J . 08066
The rate constants from a kinetic model for catalytic cracking have been correlated with the molecular compositions of a wide variety of gas oils. The catalyst decay constant and rate constants for gas oil cracking and gasoline formation can b e quantitatively related to the ratio of aromatics/naphthenes in virgin gas oils. The corresponding rate constants for recycle and coker feedstocks deviate from the correlations. Some relationships between the rate constants and coke formation have also been observed.
N u m e r o u s studies have been made of the reaction mechmisins and kinetics of pure hydrocarbons over acidic cracking RIost of the results are consistent wit,h the concept that catalytic cracking occurs primarily through carbonjuni ioii ~nechaiiisnis.The catalyt,ic cracking of gas oils is complicated by t’he lireseiice of thousands of different molecules; eac811 ttype has specific rates of adsorption and reaction. Fort~unatrly,many of the catalytic reactions of hydrocarbons can lie described both mechanist’ically and kinetically in terms of the behavior of cert,ain classes of hydrocarbons. During the past decade, there has been considerable progress reported 011 analytical methods to determine various classes of hydrocarbons in gas oils and development of quantit#ativerelationslii~isbetweell molecular composit,ion of charge stocks and product yields in catalytic cracking. (’roroll and Jaquay (1960) pointed out the necessity to considrr the differences in the cracking behavior of major hydror a r l m i tylies in charge stocks to accurately predict product’ yields iii catalyt,ic cracking. They described the relat,ive cracking rates of saturates (paraffins and naphthenes) and To whom correspondence should be addressed. 538
Ind. Eng. Chern. Process Des. Develop., Vol. 10, No. 4, 1971
unsaturates. In the same year, Service (1960) discussed t h e detailed charact,erization of feedstocks for catalytic cracking including the various correlation methods to determine carbon atom distributions. He also recognized the utility of mass spect,ronietry to elucidate classes of hydrocarbons in cracking feedstocks. Reif et al. (1961) developed correlation equations to predict, yields and properties based on the det.ailed characterization of a wide variety of cracking feedstocks and cracking data from a pilot plant unit. Their equations were based to a large degree on the carbon atom distributions in t.he feedstocks. One of the most comprehensive studies relating feed composit,ion with product yields in catalytic cracking was made by White (1968). He developed a regression correlation model to predict product yields based on nine different hydrocarbon types in the feedstocks. The detailed analytical methods for the gas oil charact~erizationwere recently reported by Fit’zgerald et al. (1970). Their analysis included distillation, separations by molecular sieves, mass spect,rometry, and ultraviolet spectroscopy. Shnaider et al. (1969) recently developed a kinetic model for cat,alytic cracking and utilized it to analyze the catalytic
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