Pd-Cu/ZrO2催化CO2加氢制甲醇的性能

Catalytic Performance of Pd-Cu/ZrO2 Catalyst for Hydrogenation of Carbon Dioxide to Methanol

采用溶胶-凝胶法制备了n(Cu)∶n(Zr)=1∶1、1∶2、1∶4和1∶8的Cu/ZrO2催化剂。实验结果表明,当n(Cu)∶n(Zr)=1∶4时,催化剂表现出较高的CO2转化率(8.0%)和甲醇选择性(59.5%),为了增加CO2的转化率,提高甲醇选择性,在n(Cu)∶n(Zr)=1∶4的催化剂中添加质量分数1%的Pd,采用浸渍法制备了Pd-Cu/ZrO2催化剂。在250℃、2MPa、12000mL/(g·h)和V(H2)∶V(CO2)=3∶1的反应条件下,CO2转化率和CH3OH收率相比Cu/ZrO2催化剂(n(Cu)∶n(Zr)=1∶4)分别提高了40.0%和80.9%。通过X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FT-IR)、N2吸附-脱附(BET)、X射线光电子能谱仪(XPS)和程序升温还原化学吸附仪(H2-TPR)等仪器表征证明Pd的添加提高了催化剂的分散性和比表面积。催化剂中Pd和Cu之间强相互作用,使Cu2p轨道结合能向低处偏移,还原温度的降低,说明Pd-Cu/ZrO2催化剂还原能力增强,使得CO2加氢活性提高。

Cu/ZrO2 catalysts with the Cu/Zr molar ratio of 1∶1,1∶2,1∶4 and 1∶8 were prepared by the sol-gel method.When n(Cu)∶n(Zr)=1∶4,a high CO2 conversion(8.0%)with methanol selectivity of 59.5% was achieved.To increase CO2 conversion and CH 3 OH selectivity,Pd-Cu/ZrO2 catalyst with the Cu/Zr molar ratio of 1∶4 and 1% mass fraction of Pd was synthesized by the impregnation method.The results showed that CO2 conversion and CH3OH yield over the Pd-Cu/ZrO2 catalyst were 40.0% and 80.9% higher than that over the Cu/ZrO2 catalyst at 250℃,2 MPa,12000 mL/(g·h)and V(H 2)∶V(CO2)=3∶1.Powder X-ray diffraction(XRD),Fourier transform infrared spectroscopy analysis(FT-IR),N2 adsorption-desorption(BET),X-ray photoelectron spectroscopy(XPS)and temperature-programmed reduction of H2(H2-TPR)results indicated that addition of Pd improved the dispersion and surface area of the catalyst.The strong interaction between Pd and Cu species leads to the shift of Cu2p to low binding energies and decreases the catalyst reduction temperature,which exhibits high catalytic performance for hydrogenation of CO2.