Study On Activation Regulation Of Cu-Based Catalyst And The Reaction Performance Of CO₂ Hydrogenation To Methanol

The catalytic conversion of CO₂to high value-added chemicals and fuels is of strategic significance to alleviate the energy crisis and achieve the goal of"dual carbon".The"green hydrogen"based on renewable energy has industrial application prospects for CO₂hydrogenation to methanol.Cu-based catalysts are widely used in CO₂hydrogenation to methanol due to their advantages of low price,suitable reaction temperature and high activity.The current research on Cu-based catalysts focuses on how to improve their stability,which is also a bottleneck restricting the development of CO₂hydrogenation to methanol technology.However,Cu-based catalysts are easily deactivated in the reaction process due to the nature of copper species and the formation of by-product water accelerating the agglomeration of particles.The results show that the catalyst activation process plays an important role in catalyst activity and stability as a link between catalyst preparation and performance evaluation.The activation of Cu-based catalysts is usually the reduction of Cu O to the active Cu species（Cu⁰,Cu⁺,etc.）using a reducing gas.It is worth noting that the activation process of Cu-based catalyst is a strong exothermic process accompanied by the generation of a large amount of water vapor,which will inevitably affect the physical and chemical properties of the copper catalyst,directly determining the reaction performance of the catalyst.Cu Zn O/Si O₂（CZS）catalyst with better performance was selected and reduced in a activation atmosphere of 10 vol%H₂/N₂.By adjusting the activation gas speed,the effects of activation on the performance and physical and chemical properties of catalyst on CO₂hydrogenation to methanol were investigated.In this study process,it was found that the activated microenvironment（water vapor,etc.）also had a great influence on the reaction performance of the catalyst.Therefore,on this basis,the influence of different activation atmosphere（pure N₂;pure H₂;10 vol%H₂/N₂）on the CZS catalyst performance was further explored.The main conclusions are as follows:（1）The effect of activation process on the physicochemical properties of CZS catalyst and the reaction performance of CO₂hydrogenation to methanol was studied by adjusting the activation gas speed.From the evaluation results of catalytic performance,the change of activation gas velocity can significantly affect the activity and stability of the catalyst.Combined with XRD,TEM,H₂-TPR,XPS,H₂-TPD and CO₂-TPD characterization results,the activation reconstructed Cu particle size,the distribution of Cu species in different valence states and Cu-Zn O interaction in CZS catalyst.Compared with inactive catalysts,the dispersity of Cu species in activated catalysts was significantly increased,and the stability of activated catalysts was increased by tens of times.This result was closely related to the strong Cu-Zn O interaction stimulated by activation,indicating that activation had obvious advantages in improving the stability of CZS catalysts.（2）Under the optimal activation gas speed of 120 m L/min,the effects of the activation atmosphere（pure N₂,pure H₂,10 vol%H₂+N₂）on Cu species during the activation and reaction were investigated.The results of catalyst performance evaluation showed that CZS catalyst reduced in 10 vol%H₂+N₂atmosphere had the highest stability while CZS catalyst reduced in N₂atmosphere had the highest activity.XRD and TEM results showed that CZS catalyst reduced in 10 vol%H₂+N₂atmosphere can not only inhibit the sintering of CZS catalyst during the activation process and reaction process,but also maintain the stability of Cu⁺/（Cu⁺+Cu⁰）ratio,thus improving the stability of the catalyst.H₂-TPD and XPS results showed that CZS catalyst reduced in N₂atmosphere had a high activation capacity of H₂and a high concentration of Cu⁺,which contributed to its high activity.