钒氧化物催化CO2氧化异丁烷脱氢的研究

采用溶胶-凝胶法制备了一系列钒氧化物催化剂，并用于CO₂氧化异丁烷脱氢反应. 采用X射线衍射、低温N₂吸附-脱附、O₂程序升温氧化、程序升温表面反应和原位傅里叶变换红外光谱等方法研究了催化剂的性质. 反应结果表明，尽管所有钒氧化物催化剂的丁烯选择性都大于85%，但随着催化剂组成和制备方法的改变，催化活性和稳定性差异显著. 其中，12 wt% V₂O₅/Ce_0.6Zr_0.4O₂（7 wt%）-Al₂O₃的催化活性最高，而6 wt% V₂O₅-Ce_0.6Zr_0.4O₂（7 wt%）-Al₂O₃的稳定性最佳. 关联分析催化反应结果与催化剂表征表明，钒氧化物的催化活性取决于VO_x物种的结晶度和分散度，而催化剂表面所积重质焦炭的特性是决定催化剂稳定性的关键. 非稳态反应和原位光谱结果确认，CO₂氧化异丁烷脱氢遵循Mars-van Krevelen氧化还原机理.

Insights into the vanadia catalyzed oxidative dehydrogenation of isobutane with CO2

Vanadia-based catalysts were prepared using the sol-gel method and were subjected to the oxidative dehydrogenation of isobutane with CO₂. The materials were extensively characterized by using X-ray diffraction, N₂ adsorption-desorption, O₂-temperature programmed oxidation, temperature programmed surface reaction, and in situ Fourier transform infrared techniques. Catalytic results indicate that a high selectivity toward total C₄ olefins over 85% was obtained over all of the catalysts. On the contrary, the highest conversion of isobutane was observed over 12 wt% V₂O₅/Ce_0.6Zr_0.4O₂(7 wt%)-Al₂O₃, and a more stable performance was achieved over 6 wt% V₂O₅-Ce_0.6Zr_0.4O₂(7 wt%)-Al₂O₃. The catalytic activity for the titled reaction was found to be dependent on the dispersion and crystallinity of the VO_x species over the catalyst, and the deposition of the heavier coke over the catalyst was revealed to be the main reason for the catalyst deactivation. Moreover, the benefit of CO₂ toward the titled reaction was clearly revealed from TPSR results, and the reaction was confirmed to follow the redox mechanism.