Study On Catalytic Performance And Preparation Of Novel Copper-based Catalyst For CO₂ Hydrogenation To Methanol

Hydrogenation of CO₂ to methanol is an important route to realize CO₂ resource utilization.As a platform molecular in chemistry industry,methanol can be further converted into low carbon hydrocarbons,low carbon mixed alcohols,aromatics,gasoline and other high value-added chemicals.Cu-based catalysts have been widely studied in methanol synthesis from CO₂ hydrogenation due to their high catalytic activity and mild reaction conditions.The catalytic performance of Cu-based catalysts is closely related to Cu surface area and strong Cu-support interaction.Cu-based catalysts prepared by the traditional methods have the problems of less exposed Cu surface and weak interaction between Cu and support,and low methanol yield in CO₂ hydrogenation to methanol reaction.Coordination polymers（CPs）are often used as precursors for the preparation of supported catalysts with high activity because of their high specific surface area,adjustable structure and functionalization of structure.Based on the coordination effect of ligands with metal ions,in this paper,we adopted one-step self-assembly and post-synthetic strategies to build polymetallic coordination polymers,and regulated metal Cu specific surface area and Cu-ZnO interaction of Cu-based catalysts by the introduction of different promoters,and evaluated catalytic performance of Cu-based catalysts derived from different polymetallic coordination polymers and explored their structure-activity relationships.The main results are as follows:（1）Highly dispersed Cu/ZnO/Y₂O₃ catalyst（named as Cu/ZnO/Y₂O₃-cit）was synthesized by the citric acid-assisted mothed.The effect of doping amount of Y₂O₃ on the performance of Cu/ZnO catalyst for CO₂ hydrogenation to methanol was investigated.Y₂O₃increaes Cu surface area of Cu/ZnO catalyst,promotes the formation of Cu-ZnO interface,and enhances Cu-ZnO interaction.The optimized Cu/ZnO/Y₂O₃-cit catalyst did not deactivate after 100 h operation,and its space-time yield of methanol(STY_{Me OH})was 345.3 g _{Me OH} kg_cat^-1 h^-1.（2）On the basis of citric acid-assisted strategy,a two-dimensional layered Zn-based CPs（named as Zn-HMT）with unsaturated ligands was synthesized using methenamine（HMT）and Zn（OAc）₂ as raw materials.Two-dimensional Cu,Zr@Zn-HMT polymer as catalyst precursor was constructed by post-synthetic strategy.Further,highly dispersed Cu/ZnO/Zr O₂ catalyst（named Cu/ZnO/Zr O₂-CAS）was prepared by calcination of the catalyst precursor.Using Cu,Zr@Zn-HMT polymer as catalyst precursor can improve the dispersion of metal Cu and enhance the interaction between Cu-ZnO-Zr O₂.STY_{Me OH} of the developed Cu/ZnO/Zr O₂-CAS catalyst was 426.9 g _{Me OH} kg_cat^-1 h^-1,and showed good stability.（3）Based on the idea of constructing two-dimensional polymer as catalyst precursor,polymetallic Cu Zn Al-BTC MOFs as catalyst precursor were synthesized by one-step self-assembly strategy using Cu（NO₃）₂,Zn（NO₃）₂,Al（NO₃）₃ and trimesic acid as raw materials,and Cu/ZnO/Al₂O₃ catalyst(named as Cu-ZnO^MOF（?）Al₂O₃^AN)was prepared by one-step calcination of Cu Zn Al-BTC MOFs precursor.The catalytic performances of MOFs-derived catalysts were optimized by adjusting the composition of catalysts,calcination temperature and types of Al sources added in MOFs procursor.STY_{Me OH} of the optimized MOF-derived Cu-ZnO^MOF（?）Al₂O₃^AN catalyst was 488.4 g _{Me OH} kg_cat^-1h^-1.Compared with the developed Cu/ZnO/Y₂O₃-cit catalyst and Cu/ZnO/Zr O₂-CAS catalyst,the optimized MOF-derived Cu-ZnO^MOF（?）Al₂O₃^AN showed the higher catalytic stability of CO₂hydrogenation to methanol reaction at 300 h continuous operation.