碱金属离子对PtSn/Al_2O_3催化剂丙烷脱氢活性的影响

用吡啶吸附-红外光谱和热重法研究了La^+、Na^+、K^+碱金属离子对负载型PtSn/Al_2O-3催化剂在丙烷脱氢中活性的影响。结果表明,碱金属离子对催化剂表面酸性有调变作用,提高了PtSn/Al_2O_3催化剂脱氢选择性,引入适量的Li^+和Na^+可减少催化剂的积碳量,改善催化剂的稳定性,提高丙烷转化率和丙烯收率;而引入K^+可减少催化剂的积碳量,但丙烷转化率和丙烯收率大幅下降。

Preparation, Characterization, Hydrodesulfurization and Hydrodenitrogenation Activities of Alumina-supported Tungsten Phosphide Catalysts

Two series of WP/Al2O3 catalyst precursors with WP mass loading in the range 18.5%—37.1% were prepared using the impregnation method and mixing method, respectively, and the catalysts were then obtained by temperature-programmed reduction of supported tungsten phosphate (precursor of WP/Al2O3 catatlysts) in H2 at 650℃ for 4h. The catalysts were characterized by XRD, BET, TG/DTA , XPS and 31P MAS-NMR. The activities of these catalysts were tested in the hydrodenitrogenation (HDN) of pyridine and hydrodesulfurization (HDS) of thiophene at 340℃ and 3.0MPa. The results showed that owing to the stronger interaction of the support with the active species, the precursor of WP/Al2O3 catalyst was more difficultly phosphided and a greater amount of W spe- cies was in a high valence state W6+ on the surface of the catalyst prepared by the impregnation method than that by the mixing method. 31P MAS-NMR results indicated that 31P shift from 85% H3PO4 of 2.55×10-4 for WP and 2.57 ×10-4 for WP/γ-Al2O3 catalysts prepared by mixing method. Such WP/Al2O3 catalysts showed higher HDN activi- ties and lower HDS activities than those prepared by the impregnation method under the same loading of WP. WP/γ-Al2O3 catalysts with weak interaction between support and active species were favorable for HDN reaction while the WP/γ-Al2O3 catalysts with strong interaction were favorable for HDS reaction.

Influence of Alumina Content on Catalytic Performance of PtSn/Al_2O_3/SBA-15 Catalysts for Propane Dehydrogenation

The alumina-modified SBA-15 （A12OJSBA-15） zeolite was prepared in a non-aqueous system by using toluene as the solvent, and was used to support the PtSn-based catalyst for propane dehydrogenation. The BET surface area mea- surements, hydrogen chemisorption, FT-IR spectroscopy, NH3-TPD, XPS and TPO techniques were used to characterize the catalysts. Test results showed that the addition of alumina not only could modify the acid function of the support but also the structure of the metallic phase, thus affecting their catalytic properties. Among these catalysts studied, the PtSn/AI203 （5%）/ SBA-15 catalyst exhibited a best catalytic performance in terms of propane conversion and selectivity to propene. The high catalytic performance might be attributed to the relatively good Pt metal dispersion and/or the strong interaction between Pt and Sn species.

Effect of Ga Addition on Catalytic Performance of PtSnNa/ZSM-5 Catalyst for Propane Dehydrogenation

PtSnNaGa/ZSM-5 catalysts with different contents of Ga were prepared and characterized by X-ray diffraction (XRD), nitrogen adsorption, hydrogen chemisorption, ammonia temperature-programmed desorption (NH3-TPD), hydrogen temperature-programmed reduction (H2-TPR), and temperature-programmed oxidation (TPO) techniques. The performances of these catalysts for propane dehydrogenation were investigated. The test results indicated that the addition of Ga not only could improve the catalytic stability and propene selectivity, but also could effectively prevent the catalysts from coking. It was found that the PtSnNaGa(0.5 m%)/ZSM-5 catalyst exhibited the best performance in terms of propene selectivity and propane conversion. The high catalytic performance was most probably attributed to the presence of Ga that could strength- en the interaction between metals and the support to stabilize the catalytic active sites.

Synthesis and characterization of a tetradentate PNCP iridium complex for catalytic alkane dehydrogenation

A novel hydrido iridium chloride complex supported by a tetradentate PNCP ligand has been synthesized and characterized. Upon activation with NaOtBu, the PNCP-IrHC1 complex is active for transfer dehydrogenation of cyclic and linear alkanes.