On the Production of Low Sulfur Fuels from Petroleum Residual Oils

Abstract

Environmental regulations to prevent air pollutions will become stricter in the future. As the sulfur level of fuel oils low enough for such regulations cannot be achieved by the present direct hydrodesulfurizers, the investigations are being made on the deep direct hydrodesulfurization. Even in these cases, atmospheric residual oils containing much heavy metals are difficult to be desulfurized, because of poisoning of catalysts by the metals. Therefore, in order to desulfurize such atmospheric residual oils to the satisfactory low sulfur level, it is necessary to employ an indirect desulfurization which removes sulfur from the vacuum gas oil without blending it with the vacuum residual oil. As a result, the amount of the vacuum residual oil thus by-produced in 1977 is estimated to reach as much as thirty million tons per year. For the purpose of utilizing this vacuum residual oil, many studies have been reported.In this paper, catalytic cracking as well as thermal cracking of vacuum residual oils for obtaining feed oils to indirect hydrodesulfurizers will be reviewed.