Ligong Zhou

Study on hydrodesulfurization of thiophene over Mo/Al2O3 catalyst presulfided by thiosulfate ammonium

Abstract Ammonium thiosulfate as a novel sulfiding agent was used for presulfidation of hydrodesulfurization (HDS) catalysts. The presulfided Mo/Al 2 O 3 catalysts with different molar ratios of S/Mo were prepared by impregnating Mo/Al 2 O 3 catalysts with an aqueous solution of ammonium thiosulfate, followed by drying. Their characteristics of crystal phases, activation, and surface compositions were examined by X-ray diffraction, thermogravimetric analysis, and X-ray photoelectron spectroscopy. The S 2− and S 6+ in ammonium thiosulfate play different roles during the activation of presulfided catalysts. The S 2− sulfides Mo and S 6+ reacts with Al 2 O 3 support, decreasing the interaction of support with the active metal. The collaboration between S 2− and S 6+ ions improves the sulfidation of MoO 3 . The best HDS performance was observed for the presulfided catalyst with S/Mo = 3. Its thiophene HDS activity is 17% higher than that of Mo/Al 2 O 3 catalyst sulfided with H 2 S.

Hydrodesulfurization of thiophene over Mo/AC catalyst presulfided by ammonium thiosulfate

Through the impregnation of Mo/AC catalyst with an aqueous solution of ammonium thiosulfate (ATS), the ex-situ presulfided Mo/AC-ATS catalyst was prepared; the influence of activation temperature and time on the catalytic performance in the hydrodesulfurization (HDS) of thiophene as a probe reaction was investigated. The result indicated that under the optimized activation conditions, viz., 300°C and 0.5 h, the conversions of thiophene over the presulfided Mo/AC-ATS catalyst are 34% and 42% higher than those obtained over the Mo/AC catalysts sulfided with traditional DMDS and CS2 sulfiding agents, respectively. The XPS, TPR-MS and TEM results demonstrated that the presulfided Mo/AC-ATS has a high content of Mo4+, which may contribute to its high activity in HDS.

Enhanced visible-light-induced photocatalytic activity of anatase TiO2 nanocrystallite derived from CMK-3 and tetrakis(dimethylamino)titanium

Titanium dioxide is a typical photocatalyst in terms of green chemistry, and extending the excitation light to the visible light range has attracted great attention. In this work, we successfully synthesized TiO2 nanocrystallites enriched in oxygen vacancies and traces of N-dopants by a nanocasting method from functionalized mesoporous carbon sieves CMK-3 and tetrakis(dimethylamino)titanium (TDMAT), in which the functionalized CMK-3 acted as both reactant and hard-template. The obtained TiO2-600 was well characterized by means of XRD, BET, Raman scattering, XPS, HRTEM, and EPR. Results demonstrated that TiO2 nanoparticles possessed uniform particle size (5.0 nm), anatase phase and large surface areas (228 m2 g−1) due to the space-confinement effect of mesopores in CMK-3. Rhodamine B (RhB) was used as a representative organic pollutant to evaluate the photocatalytic activity under visible light irradiation. Results showed that the as-prepared TiO2-600 had enhanced photocatalytic activity compared to commercial P25 and the degradation rate was calculated as 4.8 times higher than that of P25 under visible light irradiation. The increased photocatalytic activity of the TiO2 catalyst can be attributed to the synergistic effect between oxygen vacancies and N-dopants.

An environmentally friendly route to prepare graphene oxide using concentrated ozone with improved catalytic performance

An environmentally friendly approach for the synthesis of graphene oxide (GO) from graphite powder using concentrated ozone as the oxidant is reported. Oxygen was produced as the by-product during the oxidizing process, which could be considered as an entirely green route. Furthermore, the GO sheets show fascinating catalytic activity for the oxidation of benzyl alcohol.