咪唑修饰硅胶配位固载锰(Ⅲ)卟啉对环己烷空气氧化的催化作用

Catalysis of Manganeseporphyrin Supported on Imidazole-modified Silica Gel for Cyclohexane Oxidation with Air

应用 3 -氯丙基三甲氧基硅烷和咪唑成功地对硅胶表面进行了修饰 ,并通过咪唑基纵轴配位方式固载了四苯基锰 ( )卟啉 .在无任何外加溶剂及共还原剂的条件下 ,应用此高分子金属卟啉作为催化剂 ,选择性地催化空气氧化环己烷为环己酮和环己醇 .研究结果表明 ,与未固载金属卟啉相比 ,固载金属卟啉具有更高的催化活性和催化选择性 ,反应具有更高的酮醇比 ,催化剂的稳定性有了较大的提高 ,便于回收和重复使用 .另外还探讨了载体在此催化体系中对催化性能的影响 .

One of the most interesting trends in oxidation of hydrocarbons with metalloporphyrins as the catalysts is oxidation of alkanes in Lyons system with molecular oxygen. Great achievements made in this field showed that supported metalloporphyrins possessed important application prospects. In order to enhance the stability of the catalyst and make it be used repeatedly, simple manganese tetraphenylporphyrin was successfully supported on silica gel modified with 3-chloropropyltrimethoxysilane and imidazole. This macromolecular metalloporphyrin was used as the catalyst for the first time for cyclohexane oxidation to cyclohexanol and cyclohexanone with air in the absence of additives or solvents. The reaction catalyzed by the modified silica gel-supported manganeseporphyrin still gave yield of 7.1% and selectivity above 90% to cyclohexanol and cyclohexanone for the fourth time use. The results also showed that the molar ratio of cyclohexanone to cyclohexanol was enhanced from 1.35 to 1.76 after the supported catalyst was used for the reaction. The stability of the manganeseporphyrin was obviously improved and can be easily recovered for reuse. The effect of the support on the catalytic activity in this catalysis system has been discussed.