Process for producing hydrogen from synthesis gas containing cos

Abstract

Process for treating synthesis gas to recover a purified essentially sulfur-free hydrogen-rich stream. The novel sequence of operations employed comprises initially removing from the feed gas, such as from a synthesis gas derived from partial oxidation of coal or oil, the bulk of contained H.sub.2 S and a substantial part of the contained COS, by physical absorption in a suitable solvent. The gas from the initial absorption is then subjected to water-gas shift reaction over a sulfur-resistant shift catalyst under conditions such that in addition to the conversion of CO to CO.sub.2 most of the contained COS hydrolyzed to H.sub.2 S. The gaseous shift product is then subjected to a second treatment with suitable solvent to remove by physical absorption essentially all of the remaining sulfur, which is then present as H.sub.2 S. The thus desulfurized gas mixture is then sent to a CO.sub.2 absorber, from which a H.sub.2 -rich gas effluent is withdrawn. The H.sub.2 S bearing solvent from the second treatment is used in the initial absorbtion. H.sub.2 S is stripped from the initial rich absorption bottoms liquid to recover a Claus gas effluent of high H.sub.2 S content, while the stripped liquid bottoms are recycled for further use in the process.