CO_2催化氢化研究——REY负载双金属催化剂的催化作用

Catalytic Hydrogenation of Carbon Dioxige and Characterrization of Rey Supported Bimetal Catalysits.

用高压釜实验评价了用离子交换法制备的负载于REY和ZSM-5分子筛上的多种过渡金属对CO_2加氢合成醇和甲烷化的催化活性。实验结果表明,双金属催化剂的活性按下列顺序降低,CO_2甲烷化:Ru>NiRu>NiPd>Nilr;合成醇:NiCu>Ni>NiMn>NiCo。用2％Ru/REY催化剂,在473K、3.9MPa、CO_2/H_2=1/5、反应时间20h条件下,76％的CO_2转化为甲烷。反应温度、压力和溶剂等条件对NiCu/REY催化剂的活性和选择性影响的实验结果表明,在较低温度时(443-473K),醇的选择性高(约100％),增加温度和压力降低了醇的选择性,而增加了甲烷和CO_2的选择性。此外溶剂极性对反应产物和催化活性也有较大影响。催化剂用红外光谱进行了表征。

This work primarily concerned with the REY and ZSM -5 supported bimetal catalysts for the hydrogenation of carbon dioxide by autoclave experiments. The catalytic properties of the catalysts were tested and the activities decreased in the following order: for carbon dioxide methanation, Ru/RE Y > NiRu/REY > NiPd/REY > Ni-Ir/REY;for synthesis of alcohols:NiCu/REY>Ni/REY > NiMn/REY > NiCo/REY. The conversion of carbon dioxide to methane is up to 76% over the 2% Ru/REY catalyst at 473 K,3. 9 MPa,ratio of hydrogen gas/carbon dioxide = 5, in a 20 hour run. The influence of reaction conditions on the NiCu/REY indicated that the selectivity for alcohols is high from 443 - 473 K. The increase of temperature and pressure of the reaction lowered the selectivity for alcohols and increased the selectivity for methane and carbon monoxide. Experiments for the investigation of the effect of solvents on carbon dioxide hy-drogenation indicated that poloar solvents such as triethy-lamine promoted the reaction more effectively than less polar solvents. FT -IR spectra indicated that the intensity of the 1400 and 1437 cm-1bands of the REY supported catalysts are higher than that of ZSM -5 supported catalysts. The peaks at 1400,1437 and 1636 cm-1 might be assigned to the absorption of NH3 coordinated to the metal ion center in the form of [Ni(NH3)6]2+ and/or [Ni (NH3)5NO3]+.