Study On Preparation And Catalytic Performance Of Zinc Sulfide Supported Metalloporphyrins

Metalloporphyrins are a kind of important biomimetic catalysts, which have been employed in the catalytic oxidation of alkanes widely. However, metalloporphyrins have some disadvantages in homogeneous system, such as self-oxidation, dimerization and unstability. Supported metalloporphyrins not only improve the stability and reusability but also enhance catalytic activity of metalloporphyrins, so they have arosen widely attention of relevant scholars. In this thesis, tetrakis(4-carboxyl phenyl)metalloporphyrins supported on zinc sulfide were prepared for the first time and used for catalytic oxidation of cyclohexane with oxygen. The catalytic performance of the supported metalloporphyrins was investigated. And the hypothetic mechanism was also discussed.The main contents of this thesis are as follows:1. Three kinds of metalloporphyrin compounds, manganese tetrakis(4-carboxyl phenyl)porphyrin[Mn TCPP], cobalt tetrakis (4-carboxyl phenyl) porphyrin[Co TCPP] and iron tetrakis(4-carboxyl phenyl) porphyrin[Fe TCPP] have been synthesized. They were respectively supported on zinc sulfide to prepare three kinds of supported metalloporphyrins, Mn TCPP/ZnS, Co TCPP/ZnS and Fe TCPP/ZnS.2. The synthesized catalysts were characterized using some techniques such as UV-Vis, FT-IR, XRD, TG and TEM and so on.3. The above three kinds of supported metalloporphyrins (Mn TCPP/ZnS, Co TCPP/ZnS and Fe TCPP/ZnS) were respectively used for the catalytic oxidation of cyclohexane in absence of any solvent, reductants and photochemical techniques. Effects of various parameters such as reaction temperature, air pressure, amount of metalloporphyrin and reaction time on the catalytic performance were explored to determine the best reaction conditions. Through the comparision, we can make conclusions that the catalytic activity order of the three kinds of supported catalysts is Co TCPP/ZnS>Fe TCPP/ZnS>Mn TCPP/ZnS, and that the catalytic activity of the supported catalysts is higher than those of the corresponding unsupported metalloporphyrins.4. Under the best reaction conditions, reusabilities for the catalytic oxidation over the three kinds of supported catalysts were investigated. This research results show that the supported catalysts can be reused for the oxidation more than three times. However, the unsupported metalloporphyrins are one-off used.5. By analyzing the experimental data and refering the relevant literatures, a hypothetic mechanism for the catalytic oxidation of cyclohexane over zine sulfide supported tetrakis(4-carboxyl phenyl)metalloporphyrins is suggested to be a free radical reaction.