气相酯交换法合成碳酸甲丙酯负载型催化剂的研究

考察了负载型金属氧化物催化剂对碳酸二甲酯和丙醇气相酯交换合成碳酸甲丙酯的催化性能,并采用BET、XRD、CO2-TPD方法对催化剂进行了表征.结果表明,TiO2/Al2O3对反应具有较高的催化活性和稳定性.随着TiO2负载量的增加,催化剂的比表面积减小,而催化性能则随Ti负载量的增加先增加后减小,在Ti负载量为5%(wt)时活性达到最高,当Ti负载量低于5%(wt)时,TiO2可能以非晶态形式分散在Al2O3表面,而当Ti负载量高于5%(wt)时,TiO2以微晶的形式存在.CO2-TPD研究表明,负载量的改变对催化剂的碱性影响不明显.

Study on the Supported Catalysts Used for the Synthesis of Methyl Propyl Carbonate via Gas-phase Transesterification

The performances of the supported metal oxide catalysts used for transesterification of dimethyl carbonate (DMC) with propanol to synthesize the methyl propyl carbonate (MPC) were studied in a continuous flow fix-bed reactor. The results show that among those catalysts studied, the TiO2 /Al2O3 catalyst has relatively higher activity and stability, and then the characteristics of the TiO2 /Al2O3 were studied via XRD, BET and CO2 -TPD, respectively. From the XRD spectra, it is found that when the Ti loading is below 5%(wt), there is no peak of anatase observed and it seems that the TiO2 is spread on the surface of the Al2O3 supporter in the form of noncrystalline, and when the Ti loading is over 5%(wt), the peaks of anatase appear and the peaks will become stronger as the Ti loading is higher. The BET method shows that the specific area of the catalyst decreases with the increase of the Ti loading. The CO2 -TPD profiles of TiO2 /Al2O3 catalysts indicate that the amount of Ti loading has no apparent effect on the strength of base sites. Finally, the experiments show that the TiO2 /Al2O3 catalyst with 5%(wt) Ti loading has the highest activity and selectivity for the synthesis of MPC.