Ce助剂对V/SiO2催化CO2氧化乙苯脱氢性能的影响

通过N₂吸附、X射线衍射(XRD)、X射线光电子能谱(XPS)、H₂程序升温还原(H₂-TPR)、CO₂程序升温脱附(CO₂-TPD)和热重分析(TGA)等多种表征手段和催化反应性能评价，研究了铈助剂的添加对V/SiO₂催化CO₂氧化乙苯脱氢性能的影响. 结果表明，Ce助剂不仅提高了催化剂活性组分分散性和氧化还原性能，抑制了钒物种的深度还原，而且增强了催化剂碱性和CO₂吸附能力，减缓了积炭生成，从而显著提高了V-Ce/SiO₂对CO₂氧化乙苯脱氢反应的催化活性和稳定性. 在本实验中，V(0.8)-Ce(0.25)/SiO₂催化剂表现出最佳的催化性能，苯乙烯(ST)收率可达55.6%，选择性为98.5%，反应12 h 后，催化剂活性基本不变，与惰性N₂气氛比较，CO₂明显促进了乙苯脱氢反应，归因于CO₂能保持催化剂表面钒物种的高价态.

Effect of Ce Promoter on Catalytic Performance of V/SiO2 in Oxidative Dehydrogenation of Ethylbenzene with Carbon Dioxide

The effect of a Ce promoter on the catalytic properties of V/SiO₂ was investigated for the oxidative dehydrogenation of ethylbenzene (EB) to styrene (ST) with CO₂ (CO₂-ODEB). The catalysts were characterized by nitrogen adsorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), H₂ temperature-programmed reduction (H₂-TPR), CO₂ temperature-programmed desorption (CO₂-TPD), and thermogravimetric analyses (TGA). It was found that incorporation of Ce into V/SiO₂ increased the dispersion of active V species, enhanced the redox properties of the system, and inhibited deep V reduction of V⁵⁺ to V³⁺ . The Ce promoter also improves the basicity of V/SiO₂ and CO₂ adsorption on the catalyst, and suppresses coke formation. The addition of a Ce promoter greatly improves the catalytic activity and stability of V/SiO₂ towards CO₂-ODEB. The ST yield and selectivity reach 55.6% and 98.5%, respectively, for CO₂-ODEB over the most efficient catalyst, V(0.8)Ce(0.25)/SiO₂, at 550℃, and a CO₂/EB molar ratio of 20. Moreover, after reaction for 12 h, the V(0.8)Ce(0.25)/SiO₂ still shows stable catalytic activity. The ST yield in CO₂ is higher than that in an inert N₂ atmosphere, showing the significant promoting effect of CO₂ on EB dehydrogenation; this is because CO₂ is a soft oxidant and can effectively keep/regain the high valence of V for high activity with CO₂-ODEB.