Catalytic Properties Of Metal Modified Molybdenum Carbide Catalysts For Reverse Water Gas Shift Reaction

The utilization of carbon dioxide （CO₂） has been a research highlight in the field of environment and energy, while the reverse water gas shift （RWGS） reaction is the key process to accomplish the capture, conversion and utilization （CCU） of carbon dioxide. CO₂ can be converted to carbon monoxide, which is a kind of more valuable chemicals, through this reaction. The RWGS reaction also plays an important role in methanol synthesis reaction and Fischer-Tropsch synthesis reaction in which carbon dioxide is taken as source of feed.P-Mo2C and molybdenum carbide supported metal （Cu/Ni） catalysts were synthesized by temperature-programmed reaction in this paper. These samples were characterized by XRD, H2-TPR; catalytic performance was investigated for RWGS reaction in laboratory scale; we also explored the RWGS reaction mechanisum over β-Mo2C,1% Cu/β-Mo2C and 1% Ni/β-Mo2C catalysts.The main results were summarized as follows:1. The addition of metal （Cu/Ni） will affect the reduction property of MoO3, and then have an effect on the preparation of molybdenum carbide catalysts. The carbonization temperature is decreased obviously as the increasing of metal loading in the oxide precedures. Moreover, there are strong interactions between metal species and MoO3 support, the reduction behaviors of metal loaded oxide was modified compared to their parent samples.2. P-Mo2C catalyst has catalytic activity in RWGS reaction, but the addition of Cu and Ni component improves its catalytic activity apparently, especially at the low temperature. The CO₂ conversion over β-Mo2C,1% Cu/(3-Mo2C and 1% Ni/β-Mo2C catalysts is 0.98%, 12.34% and 12.03%, respectlly, at WHSV=300000 mL/g/h and 350℃.1% Cu/β-Mo2C and 1% Ni/β-Mo2C catalysts showed stable activity for the RWGS reaction at 600℃ within 40 h stability test.3. The mechanisum of RWGS reaction was studied over these molybdenum carbide catalysts. The results show that the ability of carbon dioxide dissociation over P-Mo2C,1% Cu/β-Mo2C and 1% Ni/β-Mo2C was different, following the order of 1% Ni/β-Mo2C≈1% Cu/β-Mo2C>β-Mo2C. This is in consistent with the results of activity evaluation, indicating that the ability for CO₂ dissociation has a great influence on the catalytic activity for RWGS reaction.