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Abstract

A method of deeply desulfurizing a fossil fuel which contains a variety of organic sulfur compounds, some of which are labile to hydrodesulfurization (HDS) and some of which are refractory to HDS, comprising the steps of (a) subjecting the fossil fuel to HDS or a similar method of desulfurizing labile organic sulfur compounds, and (b) subjecting the fossil fuel to biocatalytic desulfurization (BDS) using a biocatalyst which is capable of selectively liberating sulfur from HDS-refractory organic sulfur compounds. In this manner, a fossil fuel is produced which does not generate sufficient levels of hazardous, sulfur-containing combustion products that it requires post-combustion desulfurization when it is burned. Moreover, the deeply desulfurized fossil fuel can be produced using only a mild HDS treatment, rather than requiring conditions which may be severe enough to be detrimental to the fuel value of the desired product. The biocatalyst employed in the BDS stage of the instant invention is capable of catalyzing the sulfur-specific, oxidative cleavage of organic carbon-sulfur bonds in sulfur-bearing aromatic heterocyclic molecules such as dibenzothiophene. A particularly preferred biocatalyst is a culture of Rhodococcus rhodocrous bacteria, ATCC No. 53968.

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First Claim