Preparation Of M-N-C/SiO₂as A New Catalyst For Selective Oxidation Of Ethylbenzene Oxidation

Compared with homogeneous catalysts, supported catalysts can solve the issuessuch as separation, recovery and reuse of catalysts. And supported catalysts canalsopossess benefit such as the well dispersion of active metal sites, reduction of theamount of transition metal. In particular, Inorganic supports have attracted attentionfor rich source, low cost, good mechanical strength and excellent thermal stability.Wherein, the silica-based materials are often chosen as supports, because there are alot of hydroxyl groups on their surfaces or pores, some silane functionalized organicmolecules can be easily immobilized via condensation reactions with the hydroxylgroups of supports.In this work, we synthesized several inorganic supported catalysts byimpregnation method. And the catalytic activity for the selective oxidation ofethylbenzene over these catalysts using oxygen as oxygen source was investigated.The detail work is described as following.First, SiO2nanoparticleshave been synthesized by St ber method modified withorganic amino silicon. Cobalt dichloride and cobalt porphyrins as metal precursors aresupported onto the surface of modified SiO2nanospheres. After heated at800oC in N2atmosphere, supported catalysts are obtained. The catalytic performance of thecobalt-based catalyst for oxidation of ethylbenzene in the absence of any solvent wereinvestigated. As a result, the catalyst using cobalt porphyrin as metal precursor showshigher catalytic performance than that using cobalt dichloride. For example, theconversion of ethylbenzene and selectivity to acetophenone and phenyl alcohol are15.8%and78%, respectively. Moreover, and the catalyst maintain a higher catalyticactivity after3times reuse.Second, supported cobalt-based catalysts have been prepared by impregnationmethod. Cobalt porphyrins as metal precursor were supported on modified silicananospheres. The influence of heat treatment of the catalysts in N2atmosphere wasinvestigated for ethylbenzene oxidation in the absence of solvent system by molecularoxygen. Consequently,500oC is found to possess the best performance of thecatalytic oxidation of ethylbenzene in comparison with other heat temperatures suchas300oC,400oC,600oC and700oC. The conversion of ethylbenzene and selectivityto acetophenone and phenyl alcohol over the catalyst are30.3%and74.2%,respectively. Third, the influence of different metalloporphyrin precursors (i.e. MTPP, M=Mn, Fe, Co) were studied for ethylbenzene oxidation in the absence of solvent systemby molecular oxygen. The results show that different metalloporphyrin precursorsplay a crucial role in the catalytic performance of the catalysts. The catalytic activityof the catalysts prepared by different metalloporphyrin precursors increases asfollowing: MnTPPCl＞FeTPPCl＞CoTPP.Forth, The influence of supports (i.e. CeO2, Fe3O4, Al2O3) is studied forethylbenzene oxidation in the absence of solvent system by molecular oxygen. Theresult shows that supports exert an important effect on the catalytic performance ofthe catalyst for ethylbenzene oxidation. Due to for the different interaction betweenactive centers and supports, the catalytic activity of the catalysts elevates as following:CeO2＞Fe3O4＞Al2O3.