Decomposition of hydrogen sulfide into elements in the cyclic chemisorption-catalytic regime

The research was devoted to experimental study of low-temperature cyclic chemisorption-catalytic process for H2S decomposition, including the identification of optimal chemisorbent-catalysts and quantitative investigation of process characteristics. The study involved sulfides of transient metals (Fe, Co and Ni) both in bulk and supported forms. The highest efficiency was achieved with bulk sulfides NiS, CoS and especially FeS. Sorption capacity of up to 10 % by weight is observed for these systems, while all the hydrogen sulfide is absorbed irreversibly. It was shown that at elevated temperatures (250-600 degrees C) the reaction can proceed in a quasi stationary mode, in which the conversion of hydrogen sulfide and the yield of hydrogen are observed almost unchanged during rather long period of time. In this case, the conversion of H2S and the yield of H-2 significantly exceed the equilibrium values for direct H2S decomposition reaction, thus indicating a noticeable contribution of chemisorption processes. In the optimal temperature range (350-400 degrees C), the hydrogen yield on these systems varies from 11 to 95 % with an average value of 26-34 % per cycle.