Catalytic Synthesis of Methanethiol from H 2 S-rich Syngas Over Sulfided SiO 2 -supported Mo-based Catalysts
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Catalytic Synthesis of Methanethiol from H2S-rich Syngas Over Sulfided SiO2-supported Mo-based Catalysts Ai Ping Chen Æ Qi Wang Æ Ying Juan Hao Æ Wei Ping Fang Æ Yi Quan Yang
Received: 11 September 2007 / Accepted: 22 October 2007 / Published online: 6 November 2007 Ó Springer Science+Business Media, LLC 2007
Abstract The synthesis of methanethiol from H2S-rich syngas was investigated over sulfided Mo-based catalysts supported on SiO2. At CO/H2/H2S = 1/1/2, 0.2 MPa, 3,000 h-1, and 300 °C, mainly CH3SH, COS, and CO2 were formed, along with small amounts of hydrocarbons and thioethers over potassium-promoted Mo-based catalysts. Studies of the reaction pathway show that COS is a primary product, which is hydrogenated to CH3SH and H2O. Most of CO2 originates from water-gas shift reaction. The hydrocarbons and thioethers originate from the hydrogenation of CH3SH. Keywords Methanethiol synthesis Hydrogen sulfide Syngas Mo-based catalysts
1 Introduction Supported Mo-based catalysts have been extensively studied in Fischer–Tropsch (F–T) reaction for the synthesis of mixed alcohols from syngas (CO + H2) [1–6]. In contrast, the studies of the reactions of the syngas in the existence of H2S are very limited. Previously, we have studied the effects of H2S concentration in syngas on the performance of Mo-based catalysts. In this case, we accidentally found that mixed alcohols disappeared and methanethiol became the dominant product when the concentration of H2S in the syngas was over 1.6% [7, 8]. Methanethiol, also referred to as methyl mercaptan, is a
A. P. Chen Q. Wang Y. J. Hao W. P. Fang Y. Q. Yang (&) College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P.R. China e-mail: [email protected]
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well-known intermediate used in the synthesis of organosulfur compounds, such as methionine, dimethyl sulfoxide, and dimethyl sulfone [9]. Methanethiol is industrially produced by the reaction of methanol and hydrogen sulfide over supported metal oxide catalysts, such as K2WO4/ Al2O3 and Cs2WO4/Al2O3 [10]. Obviously, compared to the CH3OH-H2S route for the production of methanethiol, it would be attractive and promising if a simple feedstock, such as H2S-rich syngas (i.e., high H2S-containing syngas or CO/H2/H2S mixtures), could be used. Based on different product distribution and catalysts, different pathways for the synthesis of methanethiol have been proposed. Based on results of the co-adsorption of CO and H2S over anatase and rutile, Beck et al. [11] proposed a reaction pathway for the formation of CH3SH from the hydrogenation of carbonyl sulfide (COS), which proceeded via a thioformic acid (HSCHOads) and a surface methylthiolate (CH3Sads) intermediate. Moreover, Barrault et al. [12] investigated the synthesis of methanethiol from carbon oxides (CO and CO2), H2S and H2 over tungsten-based catalysts. They proposed that carbon oxides react with H2S to produce COS and that COS was hydrogenated to CH3SH. Recently, Mul et al. [13] reported a similar pathway for the CH3SH synthesis from C
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