Cs~+取代的Keggin型杂多酸上丙烷选择氧化制丙烯酸的研究

以沉淀法制备了不同数目Cs+取代的杂多酸HxCs3-xPMo12O40(x=0-3),以及部分Cs+取代的十二磷钨酸Cs2 5H0 5PW12O40,考察了铯离子取代数以及杂多酸不同结构原子对丙烷选择催化性能的影响。对磷钼系列杂多酸,当Cs+取代数为2 5时,样品具有最高的催化活性,而对磷钨杂多酸,Cs+取代对目标反应产物不显活性。最佳平衡离子取代还可显著改变催化剂的比表面积与结构稳定性,也改变了性能 反应温度的相互关系,从而对催化性能产生直接影响。如何抑制丙烯、丙烯酸(包括丙烯醛)的深度氧化是提高丙烯酸选择性及收率的关键。

Partial Oxidation of Propane to Acrylic Acid on the Cs+ Substituted Keggin Type Heteropoly Compounds

The partial oxidation of propane with molecular oxygen to acrylic acid on the Keggin type P-Mo and P-W serial heteropoly compounds was investigated. Substitution of H~+ with Cs~+ in the H_3PMo_(12)O_(40) and H_3PW_(12)O_(40) and its influence on the physico-chemical propeties of the samples were studied in detail. It was found that the type of coordinating (structural) atom in the heteropolyanions is the key factor determining the catalytic behavior of the HPCs for the target reaction, and appropriate acidity of the catalysts is also vital for achieving better performance. Optimized substitution of H~+ with Cs~+ can not only significantly increase the surface area of the samples but also notably improve the structural stability of the HPCs, therefore alter the temperature dependence of the catalytic performance and have a direct impact on overall reaction behavior. It is apparent that effectively suppressing the deep oxidation of propylene, acrylic acid as well as acrolein is essential to achieve high selectivity and yield of acrylic acid on this type of catalytic materials.