Study On Catalyic Performance Of Metal Tetrakis(P-Carboxylphenyl) Porphrin Grafted On Chitosan

A great attention has been paid by more and more scholars to aerobic oxidation of cyclohexane over biomimetic catalysts, metaloporphyrins, with increasing need of environmental friendly production of cyclohexanone and cyclohexanol. However, it is pity that metaloporphyrins in homogeneous system are unable to be recycled further, resulting in high production cost in practical industry, because they are easy to be destructed by O2in hydrocarbon oxidation. While, catalytic performances of supported metaloporphyrins can be usually promoted by supports, and the above shortcomings can be overcomed. Therefore, in this work, tetrakis(p-carboxylphenyl)metaloporphyrins grafted on chitosan were prepared and used as heterogeneous catalysts, to explore their catalytic performances and recyclability for aerobic oxidation of cyclohexane, and compare their catalytic activities with those of three corresponding ungrafted metaloporphyrins. A possible catalytic reaction mechanism for the oxidation of cyclohexane over chitosan-grafted metaloporphyrins is suggested.The main contents in this thesis are as follows:1. Advance for study on porphyrins, metaloporphyrins and grafted metaloporphyrins and oxidation of cyclohexane over related catalysts is briefly introduced.2. Metaloporphyrins(M TCPPs) were synthesized according to literature methods and porous/imperforate chitosan-grafted metaloporphyrins (M TCPPs/p-/imp-CTS) were prepared by self-designed methods. M TCPP/p-CTS were characterized by Ultraviolet-visible (UV-Vis) and Fourier transform infrared spectroscopies (FT-IR), Thermogravimetric analysis (TG) and X-ray Diffraction (XRD), Transmission electron microscope (TEM) and BET surface area analysis technique and so on. Linkages between chitosan and metaloporphyrins were analyzed, deduced and determined according to characterization data.3. Effects of various factors which were amount of metalloporphyrins, reaction temperture, air pressure and reaction time on cyclohexane oxidation over M TCPPs/p-CTS were investigated. Catalytic ability and reusability for the oxidation of cyclohexane over M TCPPs/p-CTS under preferable reaction conditions were researched, and then compared with those over the corresponding M TCPPs/imp-CTS and metal porphyrins. Catalytic efficiency of three M TCPPs/p-CTS for the cyclohexane oxidation was compared each other as well.4. Experimental results show that the larger surface area of the metaloporphyrins grafted on chitosan is, the better catalytic performance, there is an active order in same metal catalysts for oxidation of cyclohexane, i.e. M TCPPs/p-CTS>M TCPPs>M TCPPs/imp-CTS. High stability catalyst materials, M TCPPs/p-CTS were prepared by salt linkage and coordination of chitosan to tetrakis(p-carboxylphenyl), this improves recyclability of metaloporphyrins, a quantity of grafted catalysts(containing1.0or1.5mg of metaloporphyrins) can be reused8times at least for the oxidation, on average, their catalytic efficiency were higher than those of ungrafted metaloporphyrins. In addition, the stronger the coordination of chitosan to metal ion of metaloprphyrin is, the higher the catalytic activity, i.e. Fe TCPP/p-CTS>Co TCPP/p-CTS>Mn TCPP/p-CTS.5. Based on analysis of experimental data and reference of related literature, the aerobic oxidation of cyclohexane over chitosan grafted metalloporphyrins is suggested as a radical reaction process.