Abstract:

CO₂ hydrogenation directly producing value added chemicals over Fe based catalysts is an important approach to achieve its resource-oriented utilization. In this work, ZSM-5 supported iron catalysts with different ratios of Si/Al (25, 70, 150) were prepared by conventional impregnation method and the effects of supports with different Si/Al ratios on the catalytic performance were investigated. The catalyst activity increased first, then decreased with the increase of Si/Al ratio, and the optimal ratio of Si/Al was 70. With the combination of CO₂-DRIFTS and CO₂-TPD, it was found that ZSM-5 (Si/Al=70) zeolite supported Fe catalyst possessed more and stronger basic sites, which promoted the dissociative activation of CO₂. The evolution of catalysts structure was explored using multiple techniques such as H₂-TPR, XRD and Raman spectroscopy. After reduction, Fe2O3 on the catalyst surface was converted into metallic iron, which was then transferred to Fe₃O₄ and FeC_x during the reaction. It was also found that the discrepancy in the interaction between Fe and C under different coordination environments (Si/Al) affects the formation of FeC_x, thereby affecting the activity and products selectivity of CO₂ hydrogenation.

Key words: CO₂ hydrogenation, Fe based catalysts, ZSM-5, Si/Al ratio, catalysis, catalyst support, phase change

摘要：

CO₂加氢在铁基催化剂上直接制取高附加值化学品是实现其资源化利用的重要途径。通过等体积浸渍法制备了不同硅铝比（25，70，150）的ZSM-5负载的铁基催化剂，考察硅铝比对铁基催化剂上CO₂加氢性能的影响。结果表明，随着硅铝比的升高，催化剂活性先升高后降低，最优化硅铝比为70。CO₂-DRIFTS和CO₂-TPD结果显示，硅铝比为70的ZSM-5载体制备的催化剂具有较多且较强的表面碱性位，促进CO₂分子的活化解离。通过H₂-TPR、XRD、Raman等表征揭示了催化剂结构的演变过程。还原后催化剂的活性金属以单质Fe形式存在，反应过程中单质Fe向Fe₃O₄和FeC_x物种转化。不同硅铝比配位环境影响Fe与C的相互作用，影响FeC_x的生成，从而影响CO₂加氢的活性和选择性。

关键词: CO₂加氢, Fe基催化剂, ZSM-5, 硅铝比, 催化, 催化剂载体, 相变