液固相同晶取代法制备Sn-NaY催化环己酮Baeyer-Villiger氧化

以微孔分子筛NaY为载体,SnCl_4·5H_2O为锡源,通过液固相同晶取代法制备催化材料Sn-NaY,研究了脱铝预处理和焙烧两个因素对制备Sn-NaY的影响.采用FT-IR、UV-Vis、XRD、N_2物理吸附、ICP、NH_3-TPD、吡啶红外、激光拉曼等手段对催化材料进行了表征.结果表明:对载体进行脱铝预处理有利于分子筛在催化剂制备过程中保持良好的骨架结构,焙烧有利于进入分子筛骨架中的Sn(Ⅳ)与硅羟基成键,从而形成有催化活性的四配位的Sn(Ⅳ),而空气氛围下焙烧容易产生骨架外SnO_2物种.Sn-NaY催化环己酮Baeyer-Villiger氧化结果表明,在环己酮0.03 mol,n(H_2O_2)∶n(酮)=1.5∶1,0.35 g催化剂,15 mL乙腈,70℃反应24 h的工艺条件下,N_2氛围焙烧的同晶取代脱铝催化剂性能最好,环己酮的转化率可达44%,己内酯的选择性为62%.

Preparation of Sn-NaY by Liquid-Solid Isomorphous Substitution for Baeyer-Villiger Oxidation of Cyclohexanone

The molecular sieve catalysts of Sn-NaY were prepared by liquid-solid isomorphous substitution method using NaY as a support and SnCl4 · 5H2O as a tin source.The influence of dealumination pretreatment and calcination on the structure and active sites amount of Sn-NaY were discussed and the samples were characterized by FT-IR,UV-Vis,XRD,N2 physical adsorption,ICP,NH3-TPD,pyridine adsorption IR and Laser Raman.The results show that the dealumination pretreatment contributes to the well-maintained zeolite structure of NaY molecular sieve during the preparation process.Calcination is beneficial for incorporation of tin into the zeolite framework as tetrahedrally coordinated active Sn through bonding with silanols in the framework.Calcination in air atmosphere is responsible for the formation of SnO2.The catalytic properties of Sn-NaY in Baeyer-Villiger oxidation of cyclohexanone were investigated.Catalytic activity results show that under the reaction condition of 0.03 mol of cyclohexanone,n(H2O2) ∶ n(Cyclohexanone) =1.5∶1,0.35 g catalyst,15 mL acetonitrile,at 70 ℃ for 24 h,the catalyst through isomorphous substitution of dealuminated zeolites calcinated in N2 atmosphere shows the best catalytic performance,the conversion of cyclohexanone and the selectivity of ε-caprolactone reach 44％ and 62％,respectively.