负载型TiO2催化苯酚和草酸二甲酯酯交换反应

使用负载型TiO2/SiO2催化苯酚和草酸二甲酯酯交换反应合成草酸二苯酯.通过对TiO2/SiO2催化剂进行XRD、BET化学吸附、NH3-TPD、XPS等表征以及活性测试,结果表明在苯酚和草酸二甲酯酯交换反应中,负载型TiO2的催化性能与TiO2在载体表面的分散状态和催化剂的弱酸性密切相关.微晶态TiO2的产生会导致催化性能的下降.确定了较佳的焙烧温度为550℃,以该温度焙烧的TiO2/SiO2为催化剂,TiO2负载量为13%时,草酸二甲酯的转化率、甲基苯基草酸酯与草酸二苯酯的收率分别为53.1%、38.3%、14.5%.初步探讨了该反应条件下催化剂的失活.

Supported Titanium Oxide Catalysts for Transesterification of Dimethyl Oxalate with Phenol

The transesterification of dimethyl oxalate (DMO) with phenol to produce methyl phenyl oxalate (MPO) and diphenyl oxalate (DPO) was carried out on the TiO2/SiO2 catalyst. By means of X-ray diffraction (XRD), BET specific surface area, temperature-programmed desorption of ammonia (NH3-TPD), and X-ray photoelectron spectroscopy (XPS) analyses, it can be concluded that the catalytic activities of the supported titania catalyst are closely related with the high dispersion of TiO2 on the supporter and the weak acid sites on the catalyst surface. The TiO2 species in the form of amorphism is more responsible than that of the crystalline TiO2 for the synthesis of MPO and DPO. Under the reaction conditions, the optimal calcination temperature for TiO2/SiO2 is 550oC. Thus, 53.1% conversion of DMO, 72.1% and 27.3% selectivity to MPO and DPO, respectively, can be obtained in the presence of TiO2/SiO2 with 13% TiO2 loading. The deactivation experimental results suggest that the reduced catalytic activity is possibly due to the lose of the active catalytic center and carbon deposition.