Study On Catalytic Activity Of Metal Tetra(P-Carboxylphenyl) Porphyrins Immobilized On Graphene Oxide Via π-π Interactions

Cytochrome P-450 enzyme is a biocatalyst which widely exists in nature.The Cytochrome P-450 is a bio-enzyme which consists of protein and protoporphyrin.This biocatalyst offers a good model for the green biomimetic catalyst.Metal porphyrins were immobilized on various supports via different forms to mimick some functions of Cytochrome P-450 enzyme,and increase the catalytic activity of metalloporphyrin for understanding how were the catalytic activities of metalloporphyrins supported increased,via the coordination between metal porphyrins and ligands,and the enlargement of BET area of supports.The results show that the ligand-coordination to metal ion in metalloporphyrin changed the electron cloudy densities(ECD)of the metal ion and it-around elements.The ECD changes promoted the catalytic activity of metal porphyrin,and did so the larger surface area of supports.Therefore,in this work,graphene oxide with special Lewis base structure(π electron structure),large specific surface and thermostability was used as support for immobilizing metal porphyrins via π-π interaction,regulating the positive charge of metal ions in metalloporphyrins and efficienctly scattering the metal centre ion on it.The immobilized materials were used to be catalysts for toluene oxidation to explore the catalytic activities.The contents in this work are as followings:1.The research progress of metal porphyrin,graphene oxide,and toluene catalytic oxidation is introduced.2.Graphene oxide(GO),metal tetrakis(p-carboxylphenyl)porphyrins(M TCPP)and GO-supported M TCPP via π-π interactions were synthesized.The catalyst materials were characterized by Fourier Transform Infrared Spectrometry(FT-IR),ultraviolet spectroscopy(UV-vis),X-ray photoelectron spectroscopy(XPS),scanning electron microscope(SEM),thermogravimetric analysis(TG),specific surface area analyzers(BET),and by this way,the structures,immobilized form,and thermostability of catalyst materials are confirmed.3.The catalytic activities of the catalyst materials for toluene oxidation was studied in single variable factors which are reaction temperature,pressure,reaction time and catalyst amount respectively,and from which made sure out the optimum oxidation conditions.Under the optimum conditions,three supported catalyst materials were reused for toluene oxidation,and then the relationships between catalytic performance and their structure were explored.4.The experiment results show that the conversion,yield and TON of toluene oxidation over the unsupported tetrakis(p-carboxylphenyl)porphyrins(M TCPP Cl)are lower than the supported catalyst materials.They were exhaused in one time for use in the oxidation.However,the supported catalyst materials can be reused in the oxidation for four recycles.The averaged conversion and yield of the toluene oxidation over Co TCPP Cl/GO are higher 2.80%and 0.73%,respectively,compared with those from Co TCPP Cl.Under the optimum conditions,The conversion and yield of toluene oxidaiton over Co TCPP Cl/GO used in first,are higher 1.79%and 1.03%,respectively,compared with those from Co TCPP Cl.In summary,the catalytic activity size order for the supported catalyst materials are:Mn TCPP Cl/GO>Co TCPP Cl/GO>Fe TCPP Cl/GO.5.According to the experimental results and relevant references,a possible mechanism for the catalytic oxidation of toluene over three support materials is proposed as a free radical reaction.