花束状CeO_2的制备及其催化CO_2与甲醇直接合成碳酸二甲酯

Preparation of Bouquet-Like CeO_2 and Catalytic Performance for the Direct Synthesis of Dimethyl Carbonate from CO_2 and Methanol

以硝酸铈和尿素为原料,在表面活性剂十六烷基三甲基溴化铵的作用下,采用水热合成法成功制备了新型花束状CeO2催化剂,表征了催化剂的物理化学性质与其活性间的构效关系,并将其用于催化CO2与甲醇直接合成碳酸二甲酯(DMC)。SEM表征结果显示,所制备的花束状CeO2催化剂的形貌良好;TEM及HRTEM表征结果显示,花束状CeO2催化剂中存在一些晶格缺陷并具有较多的(110)晶面;NH3-TPD和CO2-TPD表征结果显示,花束状CeO2催化剂中存在较多的酸性位和碱性位。实验结果表明,花束状CeO2催化剂具有较高的活性,在0.1 g催化剂、15 m L甲醇、CO2初始压力5 MPa、反应温度140℃、反应时间3 h的条件下,DMC收率为4.8 mmol/g(基于每克催化剂)。花束状CeO2催化剂暴露的(110)活性晶面及较多的酸性位和碱性位有利于DMC的生成。

A new bouquet-like CeO2 catalyst for the synthesis of dimethyl carbonate（DMC） from CO2 and methanol was prepared from cerium nitrate and urea with cetyl trimethyl ammonium bromide as the surfactant through hydrothermal method, and was characterized by means of SEM, TEM, HRTEM, NH3-TPD and CO2-TPD. The SEM images showed that the bouquet-like CeO2 exhibited good morphology. The TEM and HRTEM images displayed that the bouquet-like CeO2 had many （110） crystal faces and some crystal defects. The NH3-TPD and CO2-TPD results showed that there were considerable acidic and basic sites on the bouquet-like CeO2. The bouquet-like CeO2 exhibited the high catalytic activity in the synthesis of DMC from CO2 and methanol. The yield of DMC reached 4.8 mmol/g（based on per gram catalyst） under the conditions of 0.1 g catalyst, 15 mL methanol, CO2 initial pressure 5 MPa, 140 ℃ and 3 h. The characterization results are favorable for the formation of DMC on the catalyst.