Upgrading heavy oil using slurry processes

Abstract

There is a growing interest in processes capable of converting heavy feedstocks (petroleum residues and heavy oils) into lower boiling products of high quality. The operational problems of upgrading heavy feeds relate to the presence of sulfur, nitrogen, metals, and considerable amounts of Conradson carbon residue. An efficient residue conversion process must be able to reduce the molecular weight of the feedstocks to material with boiling points below 550 C, increase the H-to-C ratio of the refined product, and remove heteroatoms and metals. Whereas the molecular weight reduction is normally achieved by C-C bond cracking above 400 C, often in the presence of acid catalysts, a higher H-to-C ratio can be obtained by either the rejection of carbon (as in coking) or the addition of hydrogen (as in hydrogenation processes). Slurry processes combine the flexibility of the carbon rejection with the high performance of the hydrogen addition processes. The origin of slurry processes is the Bergius-Pier technology (1920--1930) for the conversion of heavy oils and coal into distillates. Whereas the original Bergius-Pier technology did not use a catalyst, small amounts of inexpensive additives or finely dispersed hydrogenation catalysts can be used to increase the rates of the desired reactions. Catalystsmore » can also inhibit coke formation by physically interfering with the coalescence of mesophase, which is the precursor of solid coke. Catalysts are used to reduce the severity of the process and to improve the quality of the products. Most of the research carried out in the past decade in the field of slurry processes has dealt with the identification of more effective and/or less expensive catalysts and the technological problems related to their use. Here the authors discuss both subjects, describing the path from the fundamental chemistry of dispersed catalytic systems to the development and initial commercialization of slurry processes.« less