CO-Catalyzed Conversion of H₂S to H₂ + S. 1. Reaction between CO and H₂S

Abstract

The first step in the two-step CO-catalyzed conversion of H2S to H2 and sulfur, reactions 1 and 2, has been studied in order to establish the optimal experimental conditions for the reaction. Without a catalyst, H2S conversions of the order of only 1−2% could be achieved. NiS on alumina proved to be an efficient catalyst, and at 267 °C, H2S conversions reached 52% or 100% of the thermodynamic limit. Small amounts of CO2 and CS2 have also been detected among the products. In comparative experiments using CoS on alumina as the catalyst, up to 67% conversion, representing 100% of the thermodynamic equilibrium H2 yield, could be achieved at a substantially lower temperature, 177 °C. Furthermore, formation of CO2 and CS2 was found to be negligible (<1%) at this low temperature, eliminating the need for the suppression of the COS disproportionation reaction.

Correlation of H2S and COS in the hot coal gas stream and its importance for high temperature desulfurization

“…The reactions (1) and (2) have been discussed in the literature [2][3][4][5][7][8][9]12,[14][15][16] and catalyzed reaction (1) has also been studied [3,17]. Other possible reactions discussed in the literature [3,8] involving the two sulfur species in the hot coal gas streams at different temperatures include: Reactions (4) to (9) usually take place at temperatures above 1,000 o C. Reaction (10) may take place at low temperatures in the presence of MoS 2 catalyst [18].…”

“…Therefore, the most important reaction that determines the concentration of COS and H 2 S in the hot coal gas stream is reaction (1). Some thermodynamic data are available in the literature [2,[6][7][8]16]. The data cover a temperature range from room temperature to 1,200 o C. The reaction is slightly exothermic with the reaction heat of −2.58 kcal/mol and equilibrium constant of 0.53 at room temperature [2].…”

“…Some thermodynamic data are available in the literature [2,[6][7][8]16]. The data cover a temperature range from room temperature to 1,200 o C. The reaction is slightly exothermic with the reaction heat of −2.58 kcal/mol and equilibrium constant of 0.53 at room temperature [2]. Hot coal gas desulfurization is usually carried out at temperatures between 350 o C and 700 o C, while the Claus furnace is usually operated above 950 o C. The relationship of free energy ∆G and equilibrium constant K eq versus temperature is illustrated in Fig.…”

“…The concentration of the rest is negligible. Thermodynamically, the concentration of H 2 S and COS is strongly correlated [2] through reaction (1) and may be affected by the conditions of the system such as temperature and the presence of catalysts.…”

“…In the gasification coal gas stream, the COS content was usually found to be 10-15% of the H 2 S content and formation of COS from H 2 S is certainly taking place [5]. In the literature [2,[6][7][8][9], it has been generally agreed that reaction (1) is responsible for the formation of COS in the hot coal gas stream from H 2 S while the following reaction plays little role.…”