Synthesis, Characterization And Catalytic Properties Of Sn-Containing MCM-41 For Baeyer-Villiger Oxidation Of Cyclohexanone

ε-Caprolactone is an important organic intermediate and monomer with wide application. At present time,ε-caprolactone is produced by Baeyer-Villiger oxidation of cyclohexanone with peroxide organic acid as oxidant which is explosive and convents to byproduct-organic acid in industry. Using low concentration of hydrogen peroxide(27%) instead of peroxide organic acid as oxidant in Baeyer-Villiger oxidation is an environment-friendly process, which has higher atom economy. So, it can meet the requirement of green chemistry's developing more strictly. But, the water solution of hydrogen peroxide(27%) is a kind of oxidant with low activity. Therefore, research and development of more active and high-performance catalysts become the most chanllenge problem of Baeyer-Villiger oxidation of cyclohexanone.At the first part of this thesis, Si-MCM-41 is synthesized by direct hydrothermal synthesis method (DHT) under low template concentration and weak base condition. The samples are characterized by XRD, N2 adsorption-desorption, and FT-IR technics. Effects of charging sequence, crystallization, crystallization time and calcination on the synthesis are inverstigated. The charging sequence and the optimal crystallization time are confirmed. Secondly, Sn-containing MCM-41 molecular sieves with a hexagonal and well-ordered structure are sythensized by direct hydrothermal synthesis method(DHT) and template-ion exchange method(TIE) based on the reasearch of synthesizing Si-MCM-41 by DHT method.The physico-chemical properties of Sn-containing MCM-41 molecular sieves are characterized in detail by XRD, N2 adsorption-desorption, FT-IR, ICP-AES and TEM techniques. The results show that Sn species is mainly incorporated into the framework of Sn-MCM-41 molecular sieves synthesized by DHT method, while Sn species is mainly existed on the wall surface of Sn/MCM-41 molecular sieves synthesized by TIE method.The catalytic properties of Sn containing MCM-41 molecular sieves in Baeyer-Villiger oxidation of cyclohexanone have been studied. The effect of process conditions such as temperacture, the amont of catalyst, the mole ratio of reactant, reaction time, and solvent on reaction are discussed detailedly. Catalytic activity result shows that Sn-MCM-41 obtained by DHT method are superior in catalytic activity for Baeyer-Villiger Oxidation of cyclohexanone than Sn/MCM-41 prepared by TIE method. The physical properties of Sn-containing MCM-41 molecular sieves catalysts have little effect on catalytic activity. The catalytic activity dependents on the concentration of Sn species incorporated into the framework of Sn-containing MCM-41, while the Sn species which locate the wall surface go against the main reaction. The best reaction condition is 0.1mol cyclohexanone, 0.2mol 27%H2O2, 1g Sn-MCM-41(50), 30g dioxane, under 70℃for 4h. Under this condition, the conversion of cyclohexanone and the selectivity ofε-caprolactone can reach 28.73% and 58.92%, respectively.With respect to catalyst life, some deactivation occurs during the reaction when the same Sn-MCM-41(50) catalyst is recycled four times.But the high activity can almost be keeped at three times recycling. The loss of catalytic activity can be mostly attributed to leaching of some unstable Sn. The main byproducts are investigated by GC-MS qualitative anyalysis. Those are 2-cyclohexen-1-one, 2-hydroxy-cyclohexanone, 6-hydroxy-hexanoic acid and et al. The acidity of 27%H2O2 water solutions is considered the main cause of hydrolysis ofε-caprolactone to the corresponding hydroxy acid.