Al-MCM-41分子筛的制备及其催化合成聚甲氧基二甲醚

采用水热合成法制备了不同Al含量的Al-MCM-41介孔分子筛,考察了分子筛催化甲醇和多聚甲醛合成聚甲氧基二甲醚(PODEn,n为聚合度)的性能;采用XRD、FTIR、N2吸附-脱附、ICP-OES、SEM、NH3-TPD等方法分析了分子筛的孔结构和酸性质对产物分布的影响,并对PODEn的合成工艺条件进行了优化.实验结...

Preparation of Al-MCM-41 zeolite and its catalytic performance in the synthesis of polymethoxy dimethyl ether

Al-MCM-41 mesoporous zeolite with different Al contents were synthesized by the hydrothermal method.The catalytic performances of Al-MCM-41 zeolite in the synthesis of polyoxymethylene dimethyl ethers(PODEn,n represents degree of polymerization)with methanol and paraformaldehyde were investigated.XRD,FTIR,N2 adsorption-desorption,ICP-OES,SEM,and NH3-TPD techniques were used to analyze the pore structure and acid properties of Al-MCM-41,whose influence on the product distribution was discussed.The synthesis process conditions of PODEn were further optimized.The results show that the prepared Al-MCM-41 has an ordered two-dimensional hexagonal mesoporous structure.The doping of Al causes the specific surface area,pore volume and pore size of the zeolite decrease,while effectively increases the amount of medium-strong acid in zeolite which promotes the formation of high polymerization products.When the molar ratio of Si/Al is 40,the Al-MCM-41(40)zeolite shows the best catalytic performance.The optimal synthesis condition for PODEn is that the reaction temperature being 135℃,reaction time being 5 h,the ratio molar of methanol to paraformaldehyde being 1.5,and the amount of catalyst being 2%(w).Under the optimal condition,the conversion of methanol reaches 74.5%and the selectivity to PODE3-5 is up to 31.3%.Al-MCM-41(40)zeolite catalyst exhibited good catalytic activity after being reused for 5 times.