ON THE PRODUCTION OF LOW SULFUR FUELS FROM PETROLEUM RESIDUAL OILS.

Environmental regulations to prevent air pollution will become stricter in the future. As a sufficiently low sulfur level of fuel oils, for such regulations, cannot be achieved by the present direct hydrodesulfurizers, investigations are being made into a deep direct hydrodesulfurization. Even in this case, atmospheric residual oils containing a large amount of heavy metals are difficult to desulfurize because of the catalyst poisoning by the metals. Therefore, in order to desulfurize such atmospheric residual oils to a 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. In this paper, catalytic cracking as well as thermal cracking of vacuum residual oils to obtain feed oils for indirect hydrodesulfurizers are reviewed.