A feed gas comprising CO2, H2S and H2 is treated to produce an H2-enriched product and a CO2 product. The feed gas is separated by pressure swing adsorption to provide a stream of the H2-enriched product, and two streams of sour gas depleted in H2 and enriched in H2S and CO2 relative to the feed gas. One of the streams of sour gas is processed in an H2S to elemental sulfur conversion system, in which H2S in the sour gas is converted to elemental sulfur order to obtain a stream of sweetened gas, from which the CO2 product is formed. The other of said streams of sour gas is processed in an oxidation system, in which H2S in the sour gas is oxidized to SOx(SO2 and SO3) which is introduced into the H2S to elemental sulfur conversion system.