Chapter 14 Role of Asphaltenes in Petroleum Cracking and Refining

Publisher Summary Asphaltenes, which are concentrated in heavy crude oils, are the most troublesome fractions for efficient processing. This chapter describes characteristics of heavy oils, structure of asphaltenes, and the processing difficulties caused by asphaltenes, thermal decomposition of asphaltenes, asphaltene hydroconversion, hydrodesulfurization of heavy oils, and asphaltene conversion to lower-boiling produce. Considerable portions of asphaltenes are converted to hydrocarbon-soluble materials only by thermal treatment and asphaltenes begin to dissociate slightly at moderate temperatures of 190–200 ° C. Asphaltenes may be converted to distillate oils mainly by hydrogenation and hydrocracking, depending on the reaction conditions and the catalyst selected. Multistage hydrodesulfurization process converts a residual oil containing asphaltenes, metals, and sulfur to a substantially asphaltene-free oil without a distillation or solvent extraction step for removal of asphaltenes. The final stage effluent may be employed as the entire stream to a fluidized catalytic cracking (FCC) process.