248
Ind. Eng. Chem. Process Des. Dev. 1903, 22, 248-257
due to the difficulties of vanadium and sulfur removal from asphaltenes. Figure 13 shows that the degree of the contribution of the two removal reactions to the cracking relates to the mechanism of the reaction; i.e., each of three feedstocks has a respective type of asphaltene cracking as follows: Boscan crude is mainly related to vanadium removal (because conversions are ranked in order: cracking < desulfurization < vanadium removal); Athabasca bitumen is equally related to the removal of vanadium and sulfur; and Khafji vacuum residue is mainly related to desulfurization at low conversion and to vanadium removal at higher conversion.
Conclusion The features of asphaltene cracking are summarized as follows: (1)the removal of vanadium and sulfur from asphaltenes; (2) the decrease of molecular weight of remaining asphaltene; (3) the decrease of unit number and no change of unit sheet weight; (4)no change of asphaltene macrostructure in the stacking portion (cracking occurring at the nonstacked portion); ( 5 ) no major change of asphaltene particle size, (6) the change of vanadyl association type in remaining asphaltenes from “free” to “bound” state and the decrease of the dissociation energy of the vanadyl. According to these features, the model of asphaltene ciacking previously proposed was confirmed, where the main reactions are the destruction of asphaltene micelles caused by vanadium removal and the depolymerization of asphaltene molecules by removal of heteroatoms such as
sulfur. By comparing the model with the reactivities and selectivities, it is shown that the contribution of the two reactions in the model for asphaltene cracking depends on the kinds of feedstocks. Acknowledgment We would like to thank Dr. T. Tatsumi and Professor H. Tominaga of Tokyo University for their assistance in the ESR measurement. Grateful appreciation is expressed to the memory of Dr. Akiyoshi Tamaki, the former president of Chiyoda Chemical Engineering & Construction Co., La., deceased in June 1981. We are indebted to him for his leadership and assistance in the present work. Registry No. Vanadium, 7440-62-2. Literature Cited Dlckie, J. P.; Yen, T. F. Anal. Chem. 1987, 39, 1847. Dlckson, F. E.; Kunnesh, C. J.; McGlnnls, E. L.; Petrakls, L. Anal. Chem. 1972, 4 4 , 978. Haiey, G. A. Anal. Chem. IS71 4 3 , 371. Kim, ti.; Long, R. B. Id.Eng. Chem. Fundam. 1979, 18, 60. Nakamura, M.; Shiroto, Y.; Takahashi, H. Nlppon Kagaku Kabhi 1980, 1037. Pollack, S. A.; Yen, T. F. Anal. Chem. 1970, 42, 623. Shiralshl, M.; Sanada. Y. hvppon Kagaku Kaishi. 1978, 153. Takeuchl, C.; Nakamura, M.; Shlroto Y. ACS/CSJ Joint Meeting, Prepr. Div. Pet. CY”.,Am. Chem. Soc. 1979a 2 4 . 666. Takeuchl. C.; Nakamura, M.; Shiroto, Y. Paper presented at 62nd Canadian Chemical Conference 8 Exhlbltlon, Sect. Novel Chem. Processes, Vancower, June 6, 1978b. Tynan, E. C.; Yen T. F. Fuel 1989, 43. 191. Yen, T. F.; Erdman, J. Q.: Pollack, S. S. Anal. Cbem. IS81 33, 1587.
Received for review March 12, 1982 Accepted August 26, 1982
Asphaltme Cracking in Catalytic Hydrotreating of Heavy Oils. 3.‘ Characterization of Products from Catalytic Hydroprocessing of KhafJiVacuum Residue Yoshbnl Shlroto,’ Shlnlchl Nakata, Yoshlo Fukul, and Chkato Takeuchl Chiyo& Chemical Engineering & Construction Co., LM., 313, Morlya-cho, Kanagawa-ku, Yokohama 221, Japan
Technologies for upgrading heavy residual oils for transportation fuels are becoming increasingly important. The asphattenic Bottom Cracking (ABC) process developed by Chiyoda is one of the new upgrading technologies. ABC is the process of asphaitenes converslon by catalytic hydrotreatingfor petroleum heavy ends. The combination of ABC and solvent deasphalting (SDA) is the effective route for the complete conversion of asphaitenic bottoms. This report presents the characterlzatlons of various products from Khafji vacuum residue by the pilot plant test of ABC combined with an SDA. One typlcal feature of product oils is to show good qualities (gravity: >20° API; metals:
