The Promoting Effect of Tellurium on K 2 MoO 4 /SiO 2 Catalyst for Methanethiol Synthesis from High H 2 S-Containing Syn
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The Promoting Effect of Tellurium on K2MoO4/SiO2 Catalyst for Methanethiol Synthesis from High H2S-Containing Syngas Aiping Chen Æ Qi Wang Æ Yinjuan Hao Æ Weiping Fang Æ Yiquan Yang
Received: 4 June 2007 / Accepted: 29 June 2007 / Published online: 25 July 2007 Springer Science+Business Media, LLC 2007
Abstract Tellurium used as promoter was investigated in the preparation of K2MoO4/SiO2 catalyst for methanethiol synthesis from high H2S-containing syngas. The experimental results showed that the addition of Te to K2MoO4/ SiO2 improved the activity of catalysts and the selectivity of methanethiol. ESR results reveal that the addition of Te decreases the content of ‘‘oxo-Mo5+’’ species and increase that of the ‘‘oxysulfo-Mo5+’’ species, simultaneously increase the low valence states of sulfur species. XPS results reveal that the addition of Te to K2MoO4/SiO2 increase the amount of low valence states of molybdenum and sulfur species, which are related to the formation of methanethiol. Keywords Tellurium Methanethiol Mo-based catalyst Syngas ESR XPS
600 h–1, and the optimized methanethiol yield amounts to 0.35 mmolh–1 g–1cat. Zhang et al. [2, 3] have reported the synthesis route of methanethiol from the reaction of CO/H2/H2S over a-Al2O3 at 340 C, 2.0 MPa, 200 h–1, and the selectivity of methanethiol was reported to be over 98%. However, the silica-supported K–Mo catalysts were found to be the most excellent catalysts for direct synthesis of methanethiol at relative low reaction temperature (300 C) and high space velocity (3000 h–1), rare-earth oxides and transition metal oxides used as promoters were investigated [4–6]. Nonmetallic tellurium is often added as a promoter to Mo–V-based catalysts for allylic selective oxidation and ammoxidation of olefins [7, 8]. In the present study, Te was introduced into the K2MoO4/SiO2 catalyst and the performance of the catalysts was investigated. ESR and XPS were used to characterize the modified catalysts.
1 Introduction As an important chemical raw material and organic synthesis intermediate, methanethiol is extensively used in the synthesis of methionine, pesticide, medicine, plastics etc. At present, it is made commercially by the reaction of methanol with hydrogen sulfide, which requires the synthesis of methanol from syngas. Obviously, one-step synthesis of methanethiol from H2S-containing syngas is very promising in industrial application. Very recently, Mul et al. [1] have investigated the synthesis of methanethiol from CO and H2S over sulfided vanadium catalysts based on TiO2 and Al2O3 at 340 C, 1.0 MPa, A. Chen Q. Wang Y. Hao W. Fang Y. Yang (&) College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P.R. China e-mail: [email protected]
2 Experimental 2.1 Catalysts Preparation The Te-promoted K2MoO4/SiO2 catalysts were prepared by multi-step impregnation. Firstly, a given quantity of telluric acid (H6TeO6) was dissolved under heating and stirring to produce an aqueous solution, with which 5.00 g of SiO2 (SBET = 260 m2/
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