Abstract
Utilization of bottom-of-the-barrel petroleum products like heavy fuel oils (HFO) derived from vacuum residue oils (VRO) is essential for the sustainable use of crude oil. The high sulfur content and asphaltenes with metallic impurities of these products, such as vanadium and nickel, lead to the production of criteria pollutants and inorganic ash upon combustion, which has limited their widespread use in many industries and jurisdictions. Industrially mature thermo-chemical conversion technologies (e.g., cracking, pyrolysis, partial oxidation (POx), and gasification) have been utilized to upgrade and convert oil residues like HFO into cleaner fuels such as syngas and hydrogen. Among these processes, commercial POx and gasification typically proceed via catalyst free-operations. However, the novel variants of gasification processes that can improve the utilization of heavy oil residues can be benefited from using catalysts. That is because not only can catalysts facilitate the reactions within a smaller reactor, but also they can provide better control over the product composition. Nevertheless, the typical characteristics of high carbon, impurities, and sulfur content lead to the deactivation of the solid-state catalysts mainly due to the coking and poisoning. The use of molten salts, metal/metal oxide as catalysts or oxygen carriers, and hydrogen peroxide as a gasifying agent in the gasification of heavy hydrocarbons are identified to offer significant potential to overcome these challenges, albeit introducing alternative difficulties. This paper surveys and briefly discusses the state-of-the-art thermo- and catalytic chemical conversion technologies for petroleum residue derived fuels, focusing on the use of molten catalysts, oxygen carriers, and hydrogen peroxide as oxidizing agents. The paper also briefly reviews methane pyrolysis, dry reforming with molten metal catalysts, and liquid chemical looping gasification to find similarities and know-how that can be used for gasifying heavy oil residues with the molten metal/metal oxides being used as either catalyst or reaction medium.