Cu-ZnO/γ-Al₂O₃ Bifunctional Catalysts For Dimethyl Ether Steam Reforming To Produce Hydrogen

Hydrogen is a clean and reproducible energy with advantages of high energy storage capacity as well as wide applications.Hydrogen fuel cells are optimal running power supplies for new energy automobile.Oxygenated hydrocarbons steam reforming（SR）is suitable for small-scale H₂ production on mobile fuel cell applications.Dimethyl ether（DME）is a prefered material due to non-toxicity,high H/C and convenient transportion.DME SR is a tandem reaction,and the applied catalysts need to be coupled by a solid acid catalyst and a reforming catalyst.The most commonly used solid acid catalyst isγ-Al₂O₃.And the Cu-based catalysts are the most frequently used catalysts in DME SR due to their high activity and CO₂selectivity in the MSR step.However,it is a great challenge to achieve efficient catalysts with ultra-high Cu dispersion at high reaction temperatures.The coupling mode of bifunctional catalysts need optimize to break down the mass transfer barrier.The Cu/γ-Al₂O₃ catalysts with different Cu content were prepared by impergnation method.The effect of Cu loading on DME SR was studied in detail.The activity tests results show that the catalyst with the Cu content of 3 wt%exhibits the best catalytic activity and is not significant agglomerated after DME SR.However,the catalyst with the Cu content of 9 wt%is heavily sintering during DME SR process,and the pores of the catalyst are seriously blocked.After obtaining the optimal Cu loading by the impregnation method,we synthesized Cu/γ-Al₂O₃catalyst with about 3 wt%Cu loading by a novel sputtering method.We observed that it was sintering at high reaction temperatures.To improve the sintering resistance,we synthesized Cu-Zn O/γ-Al₂O₃catalyst by a bimetallic sputtering method.By contrast,the Cu-Zn O/γ-Al₂O₃ catalyst exhibits higher Cu dispersion and thermal stability,which due to the interaction between Cu species and Zn O.Moreover,the Cu-Zn O/γ-Al₂O₃ catalyst exhibits ultra-high utilization efficiency of Cu species and optimally couples acidic sites and metallic sites.It effectively inhibits methanol decomposition.Furthermore,Cu species of the sputtered catalysts are only anchored on the external of theγ-Al₂O₃,which greatly improve the mass transfer.It effectively inhibits reverse water gas shift.Based on the above improvements,the Cu-Zn O/γ-Al₂O₃ catalyst exhibits ultra-low CO selectivity.