Desulfurization of Heavy Oil with Iron Oxide-based Catalysts Using Steam

Desulfurization of heavy oil using steam was examined by catalytic cracking of atmospheric residual oil (AR) with iron oxide-based catalyst. The yield of hydrogen sulfide increased with higher ratio of steam to feedstock, whereas hydrogen sulfide was little produced in AR cracking without steam. Sulfur concentration of oil decreased to half that of feedstock, and some sulfur compounds were deposited on the catalyst. Oxidative cracking of heavy oil using oxygen species derived from steam produced hydrogen species from steam, so part of the hydrogen species reacted with heavy sulfur compounds on the catalyst to produce hydrogen sulfide, light sulfur compounds, and hydrocarbons. Some oxygen species could be transferred to sulfur dioxide. Therefore, hydrogenation and oxidation by the hydrogen and oxygen species derived from steam can cause desulfurization of AR. Cyclic sulfur compounds containing a thiophene ring in heavy oil are less reactive than acyclic sulfur compounds, so the reactivity of cyclic sulfur compounds was examined by catalytic cracking of dibenzothiophene. Dibenzothiophene was decomposed with the catalyst to produce carbon dioxide and hydrogen sulfide. Therefore, both acyclic and cyclic sulfur compounds can be decomposed with the catalyst and steam.