Immobilization Of Metalloporphyrins On CeO₂@SiO₂with A Core-shell Structure As A New Catalyst For Selective Oxidation Of Cyclohexane And Diphenylmethane

According to the structure properties of enzyme, to develop supportedmetalloporphyrin catalysts with high activity and selectivity is very important toachieve a inviroment-friendly indusrial process. In this work, we synthesized nanoMxOy@SiO₂（MxOyis CeO₂, Fe₂O₃, Co_3O4, Mn₃O₄and TiO₂） with core-shell structureand used it as supports to graft metalloporphyrin. In the end, mimetic catalysts withhigh catalytic performance for selective oxidation of alkanes were obtained. First ofall, we refine the synthesis process of carboxyl porphyrin and synthesized ferrel（iron）,cobalt and manganese porphyrin. In addition, two kinds of supports with core-shellstructure were prepared. In the end, metalloporphyrin catalysts anchored on nanoMxOy@SiO₂were achieved and the catalytic performance for the oxidation ofcyclohexane and dibenzylmethane over these catalysts was investigated. The work isas following.1. Synthesis of carboxyl porphyrin was refined. Carboxyl porphyrin andmetalloporphyrin were synthesized by one-pot method and characterized by Mass,UV-Vis and FT-IR.2. Metallopotphyrin supported on organosilicon microspheres mixed with CeO₂wassynthesized and characterized by UV-Vis, FT-IR, SEM and TEM. The results showthat CeO₂cluster was mixed with organosilicon microspheres with particle size of30nm and metalloporphyrin is grafted on organosilicon microspheres by amidebond. The catalyst exhibits excellent catalytic performance for oxidation ofcyclohexane by molecular oxygen without solvent in a sealed autoclave reactor.The conversion of cyclohexane and the selectivity of cyclohexanol+cyclohexanone reached14.21%and54.60%, respectively. After repeated reuse,the conversion of cyclohexane and the selectivity of cyclohexanol+cyclohexanone were still kept at about13.10%and61.90%, respectively. Thecooperative effect among the metalloporphyrin, organosilicon microspheres andceria can smartly enhance the catalytic performance of the catalysts.3. Metallopotphyrin was immobilized on CeO₂@SiO₂with core-shell structure by themodification of CeO₂and one-time coating of SiO₂. The as-prepared catalysts wascharacterized by UV-Vis, FT-IR, SEM and TEM. The results show thatCeO₂@SiO₂with core-shell structure has formed and the particle size is about50 nm. In addition, metalloporphyrin is grafted on the surface of CeO2@SiO2byamide bond. The catalyst shows excellent catalytic performance for oxidation ofdiphenylmethane by molecular oxygen. After ran for24h, the conversion andselectivity of diphenylmethane are41.65%and95.00%, respectively.4. Metallopotphyrin grafted on M_xO_y@SiO₂（M_xO_yis CeO₂, Fe₂O₃, Co₃O₄, Mn₃O₄and TiO₂） with core-shell structure was synthesized by the modification of CeO₂and dual-time coating of SiO₂. The catalysts were characterized by UV-Vis, FT-IR,SEM, TEM, XRD, TG and N₂absorption and desorption. The results show that theformation of CeO₂@SiO₂with core-shell structure has appeared and the particlesize is about400-500nm. In addition, the catalyst shows excellent catalyticperformance for oxidation of diphenylmethane by molecular oxygen withoutsolvent. After ran for24h, the conversion and selectivity of diphenylmethane are70.00%and95.00%, respectively. As for ligand metals in metalloporphyrin, theturn of activity is as following: Mn＞Fe＞Co. And as for the metals in the core,the turn of activity is: CeO₂＞Co₃O₄＞Fe₂O₃＞Mn₃O₄TiO₂.