不同形貌HZSM-5的合成及其在催化二氧化碳加氢制备二甲醚中的应用

Preparation of HZSM-5 of Different Morphologies and Its Application in the Catalytic Synthesis of Dimethyl Ether from CO_2 Hydrogenation

以正硅酸乙酯为硅源,四丙基氢氧化铵为模板剂,司盘80和吐温80为活化剂,分别制备了六棱柱状、纳米颗粒和类蜂窝状的HZSM-5型分子筛,用XRD、SEM、BET和NH3-TPD对合成的分子筛进行了表征,结果表明,类蜂窝状的HZSM-5型分子筛具有较大的比表面积和较强的酸性。将合成的分子筛与甲醇合成催化剂Cu OZn O-Al2O3机械混合,制得CO2加氢一步合成二甲醚的双功能催化剂。在反应温度270℃、反应压力3 MPa、空速1 800 m L/(gcat·h)、V(CO2)∶V(H2)=1∶3、m(Cu O-Zn O-Al2O3)∶m(类蜂窝HZSM-5)=1∶1的反应条件下,CO2的单程转化率和二甲醚的产率分别达到了45.4%和20.1%。

Hexagonal-prism-shaped nanoparticles and honeycomb-like HZSM-5 were synthesized using tetraethylsilicate and tetrapropylammoniumoxide as template agents,and Span-80 and Tween-80 as active agents.The synthesized molecular sieves were characterized by the methods of XRD,SEM,BET and NH3-TPD.The results show that the honeycomb-like HZSM-5 has larger specific surface area and higher acidity than others.The bifunctional catalysts Cu O-Zn O-Al2O3/HZSM-5 were prepared by mechanical mixing Cu O-Zn O-Al2O3 and HZSM-5.Its catalytic activity for carbon dioxide hydrogenation to synthesize dimethyl ether was investigated.Under the reaction pressure of 3.0 MPa,space velocity of 1 800 m L/（gcat·h）,volume ratio of CO2/H2 at 1 ∶3 and temperature at 270 ℃,the conversion of CO2 and the yield of dimethyl ether were 45.4% and 20.1%,respectively.