固载化阳离子金属卟啉/杂多阴离子复合催化剂在分子氧氧化乙苯过程中的催化特性

以交联聚苯乙烯微球(CPS)为基质载体, 采用同步合成与固载的方法, 简捷地制得了固载化阳离子苯基卟啉, 继而通过与钴盐的配合反应, 制备了固载化阳离子钴卟啉. 在此基础上, 以Keggin 型杂多酸磷钨酸(HPW)及磷钼酸(HPMo)为试剂, 凭借阳离子钴卟啉(CoP)与杂多阴离子之间的静电相互作用, 制备与表征了固载化的由阳离子钴卟啉与杂多阴离子复合而成的固体催化剂CoPPW-CPS和CoPPMo-CPS. 将两种复合催化剂用于分子氧氧化乙苯的氧化反应, 考察研究了催化特性. 结果表明: 在分子氧氧化乙苯的氧化反应中, 复合催化剂具有很高的催化活性, 可使乙苯高选择性地转化为苯乙酮, 反应12 h, 苯乙酮的产率达30.1%; 复合催化剂的催化活性比单纯的固载化钴卟啉高75%; CoPPW-CPS的催化活性高于CoPPMo-CPS. 在复合催化剂结构组分中, 固载化的杂多阴离子并无催化活性, 起催化作用的组分是钴卟啉; 但是, 杂多阴离子可有效保护钴卟啉, 使其免于被氧化失活, 从而使其保持稳定的高催化活性. 复合催化剂具有最适宜的投加量, 过量催化剂的加入, 会抑制钴卟啉的催化活性. 复合催化剂还具有良好的循环使用性能.

Characterization of Immobilized Composite Catalysts of Cationic Metalloporphyrin and Heteropoly Anion in Oxidation of Ethyl Benzene by Molecular Oxygen

An immobilized cationic phenyl porphyrin was prepared with crosslinked polystyrene (CPS) microspheres as carriers via synthesis and immobilization. A kind of immobilized cationic cobalt porphyrin was obtained through a coordination reaction between the immobilized cationic phenyl porphyrin and the cobalt salt. In the composite reactions, phosphotungstic acid (HPW) and phosphomolybdic acid (HPMo) with Keggin structures were used as reagents, respectively, and the combination of the cationic cobalt porphyrin (CoP) with the heteropoly anions by electrostatic interaction led to the formation of the immobilized composite catalysts of CoPPW-CPS and CoPPMo-CPS. We then characterized these immobilized composite catalysts. The immobilized composite catalysts were used in the oxidation of ethylbenzene by molecular oxygen, and their catalytic characters were investigated. The results show that the immobilized composite catalysts possess high catalyst activity. They can transform ethyl benzene into acetophenone with high selectivity, and the yield of acetophenone after 12 h reaches 30.1%. The catalytic activity of the immobilized composite catalysts is 75% higher than that of the immobilized cobalt porphyrin. The catalytic activity of CoPPW-CPS is higher than that of CoPPMo-CPS. The cobalt porphyrin in the composite is the catalyst component as the heteropoly has no catalytic activity. However, the heteropoly anion has a protective effect on the metalloporphyrin against its deactivation during the catalytic reaction. In the oxidation reaction, there is an optimum addition for catalyst, and adding excessive catalyst inhibits its activity. The composite catalysts show good recycle properties.