"Review of Mid- to High-Temperature Sulfur Sorbents for Desulfurization of Biomass- and Coal-derived Syngas
This review examines state-of-the-art mid- and high-temperature sulfur sorbents that remove hydrogen sulfide (H2S) from syngas generated from coal gasification and may be applicable for use with biomass-derived syngas. Biomass feedstocks contain low percentages of protein-derived sulfur that is converted primarily to H2S, as well as small amounts of carbonyl sulfide (COS) and organosulfur compounds during pyrolysis and gasification. These sulfur species must be removed from the raw syngas before it is used for downstream fuel synthesis or power generation. Several types of sorbents based on zinc, copper, iron, calcium, manganese, and ceria have been developed over the last two decades that are capable of removing H2S from dry coal-derived syngas at mid- to high-temperature ranges. Further improvement is necessary to develop materials more suitable for desulfurization of biomass-derived syngas because of its hydrocarbon, tar, and potentially high steam content, which presents different challenges as compared to desulfurization of coal-derived syngas."
Note: "These sulfur species must be removed from the raw syngas before it is used for downstream fuel synthesis ...".
And, that for "two decades" we have had materials "that are capable of removing H2S from dry coal-derived syngas".
In earlier posts we have cited research confirming that gasoline, and other liquid fuels, derived from coal are, or can be, virtually sulfur-free. And, sulfur, as herein can be effectively extracted during coal gasification, as part of an indirect coal liquefaction process, is a product of commercial value which could help to offset the cost of coal conversion, if it were to be recovered in a marketable form.
Perhaps more to the point: Other research attests that sulfur is a contaminant that can "poison" some coal indirect liquefaction catalysts. It seems clear, though they don't, unsurprisingly, say so, that these scientists weren't just working to reduce pollution; they were working to enhance the economy and reliability of one variant of coal liquefaction technology.