Yiquan Yang

Study of the supported K2MoO4 catalyst for methanethiol synthesis by one step from high H2S-containing syngas

ESR and XPS are used to study the Mo-based catalysts MoO3/K2CO3/SiO2 and K2MoO4/SiO2 prepared with two kinds of precursors, (NH4)6Mo7O24⋅4H2O and K2MoO4. The catalytic properties of the catalysts for methanethiol synthesis from high H2S-containing syngas are explored. The activity assay shows that the two catalysts have much the same activity for the reaction. By the ESR characterization of both functioning catalysts, the resonant signals of “oxo-Mo(V)” (g=1.93), “thio-Mo(V)” (g=1.98) and S (g=2.01 or 2.04) can be detected. In the catalyst MoO3/SiO2 modified with K2CO3, as increasing amounts of K2CO3 are added, the content of “oxo-Mo(V)” increases, but “thio-Mo(V)” decreases. The XPS characterization indicates that Mo has mixed valence states of Mo4+, Mo5+ and Mo6+, and that S includes three kinds of species: S2− (161.5 eV), [S–S]2− (162.5 eV) and S6+ (168.5 eV). Adding K2CO3 promoter to the catalysts, the Mo species of high valence state is easily sulphided and reduced to Mo2S and “oxo-M(V)”, and the derivation of [S–S]2− and S2− species from S is promoted simultaneously. The methanethiol synthesis is favored if the mole ratio of (Mo6+ + Mo5+)/Mo4+ ≤ 0.8 and S2−/[S–S]2− is kept at a value of about 1.

The catalytic properties of supported K2MoS4/SiO2 catalyst for methanethiol synthesis from high H2S‐content syngas

Methanethiol has been synthesized by one‐step catalytic reaction from H2S‐content syngas on K2MoS4/SiO2 catalyst with selectivity over 95% under the optimum reaction conditions of 563 K, 2.0–3.0 MPa and 5–6% H2S content in the feed syngas. The results of XRD and XPS showed that Mo–S–K phase on the surface of the catalyst K2MoS4/SiO2 was responsible for the high activity and selectivity to methanethiol, and which may be restrained by the existence of (S–S)2- species.

On methanethiol synthesis from H2S-containing syngas over K2MoS4/SiO2 catalysts promoted with transition metal oxides

The catalysts K2MoS4/SiO2 promoted with transition metal oxides Fe2O3, CoO, NiO and MnO2 were prepared and used to catalyze the synthesis of methanethiol from H2S‐containing syngas. The results of activity assay show that the catalysts promoted with Fe2O3, CoO and NiO can remarkably increase the hour space yield of methanethiol. Nevertheless, MnO2 was found to have a disadvantageous effect on the selectivity of methanethiol. The results of XRD and XPS characterization indicate that the addition of the transition metal oxides promoters is in favor of the formation of a Mo–S–K active phase and also retards the decomposition of K2MoS4 to MoS2, thereby suppressing both the deep reduction of Mo species and the formation of (S–S)2 species, which are reflected by the increment of the concentration ratios of both Mo6+/Mo4+ and S2/(S–S)2.

Structure aspects and hydroformylation performance of water-soluble HRh(CO)[P(m-C6H4SO3Na)3]3 complex supported on SiO2

Abstract The solution NMR ( 31 P and 1 H ) and FTIR spectroscopies were employed to investigate the structure information of water-soluble complex HRh(CO)[P(m-C6H4SO3Na)3]3 (1) [P(m-C6H4SO3Na)3: trisodium salt of tri-(m-sulfophenyl)-phosphine, TPPTS] supported on SiO2 (1/SiO2). The 31 P ( 1 H ) NMR spectra showed that a pair of new twin-peak at about 31.5, 32.1xa0ppm while no typical twin-peak at 44.0, 44.7xa0ppm for the phosphorus species ascribed to the complex 1 were observed at 1/SiO2. However, the typical phosphorus peaks for the complex 1 appeared in the case of using TPPTS or Na2CO3-preimpregnated SiO2 as supports. Moreover, the immobilization caused a considerable oxidation of the liberated TPPTS to OTPPTS (OTPPTS, i.e. OP(m-C6H4SO3Na)3: trisodium salt of tri-(m-sulfophenyl)-phosphine oxide) species as evidenced by 31 P ( 1 H ) NMR spectroscopy. The phosphorus-31 peaks at 31.5, 32.1xa0ppm at 1/SiO2 were found to be unchanged before and after the propene hydroformylation. The FTIR results revealed that the CO band appeared at about 1870xa0cm−1 for the 1/SiO2 catalyst, which was lower than that for the precursor complex 1. It is concluded that there exists a strong interaction between the complex 1 and the acidic support of SiO2, resulting in the deformation of the Rh–phosphine complex containing less than three TPPTS ligands, which further transformed by dehydrogenation and dimerization under evacuation to form a species likely [Rh(CO)(TPPTS)2]2 as a main surface complex species at the catalyst 1/SiO2.