催化剂表面硅烷化改性对甲醇合成反应的影响

Influence of catalyst surface silanization modification on methanol synthesis reaction

为了减少甲醇合成催化剂(CuO/ZnO/Al_2O_3)载体Al_2O_3表面羟基与甲醇羟基形成氢键发生吸附,用γ-(甲基丙烯酰氧)丙基三甲氧基硅烷偶联剂对催化剂进行改性,并用FTIR,SEM对改性催化剂的结构特征和形貌进行表征评价。结果表明:Al_2O_3表面羟基与硅烷偶联剂发生缩合反应,实现了催化剂表面羟基的修饰改性;未经改性的氧化铝单体之间发生明显的团聚,而改性氧化铝颗粒之间聚集效应减弱;改性催化剂对甲醇、异丙醇和仲丁醇的吸附量明显少于未改性催化剂的吸附量。在固定床中考察催化剂改性对甲醇合成反应的影响,发现异丙醇和仲丁醇溶剂中改性催化剂的甲醇生成速率明显比未改性催化剂的甲醇生成速率快,气相甲醇条件下改性催化剂的甲醇合成速率是未改性催化剂的1.2倍。

To reduce forming hydrogen bond between hydroxyl of methanol synthesis catalyst and hydroxyl of methanol,the catalyst was modified by silane coupling agent,and the structure and morphology of the modified catalyst was evaluated using FTIR and SEM. The results show that condensation reaction happened between the surface hydroxyl of alumina and the silane coupling agent,the unmodified alumina particles clusters each other,while aggregation of the modified alumina particles was reduced. Experiments were conducted to investigate methanol,isopropanol and 2-butanol adsorption/desorption isotherm at elevated temperature. Results show that adsorbing capacity of solvent in the modified catalyst less than that of in the catalyst without modified. In addition,the catalytic performance of the modified catalyst was investigated in a fixed bed reactor,it shows that the methanol reaction rate with the modified catalyst is 1. 2 times of that with the unmodified catalyst.