Study On CuO-ZrO₂/SAPO-34 Catalysts For The One-step Synthesis Of Light Olefins From Syngas

As an important basic raw material of organic chemical industry,light olefines have been obtained via the petroleum route for a long time.Due to the shortage of oil resources,the route of syngas has gained increasing attention.In recent years,one-step synthesis of light olefins from syngas developed rapidly.In this paper,CuO-ZrO₂ catalyst?abbreviated as CZ?was prepared by solid-state grinding,and then combined with SAPO-34 molecular sieves to obtain bifunctional catalyst for one-step synthesis of light olefines from syngas.The main works and results are as follows:?1?The effects of Cu/Zr ratio on the CZ catalyst were investigated.The results show that when the mole ratio of Cu/Zr is 5:5,the activity of the catalyst is the maximum.CZ?5:5?catalyst has the largest surface area,the highest dispersion of copper,and the most active sites in the catalytic hydrogenation of CO.The amount of weak acid in CZ?5:5?/SAPO-34 bifunctional catalyst is high,which results in a high selectivity of light olefins.?2?The effects of complexing agents?citric acid,oxalic acid,acetylacetone?on CZ catalyst were studied.The ZrO₂ prepared with citric acid and oxalic acid as the complexing agent appears in a tetrahedral phase,while the ZrO₂ prepared with acetylacetone is monoclinic phase.In addition,the CZ catalyst prepared with citric acid as complexing agent exhibits a high dispersion of Cu.Moreover,the content of Cu on the surface of catalyst is the highest.Therefore,the catalyst prepared by citric acid shows the highest activity.?3?The effects of promoter?Ga,Zn,Mn?on CZ catalyst were studied.The addition of Ga increases the concentration of Cu on the surface of the catalyst,improves the dispersion of Cu and promotes the dissociation and activation of H2.Moreover,the doping of Ga produces more oxygen vacancy,which is favorable for the dissociation and activation of CO.Appropriate amount of Zn can effectively improve the dispersion of copper,promote the desorption of H2 and increase the conversion of CO.However,excessive amount of Zn leads to excessive hydrogenation of CO and results in a low selectivity of light olefins.The catalytic activity of CZ-Zn10/SAPO-34 bifunctional catalyst shows the highest activity among the CZ-Zn catalysts.Mn can significantly improve the selectivity of light olefins because Mn depresses the reducibility of CuO and decreases the dicossiation and activiation of H2,and further decrease the hydrogenation degree of CO.CZ-Mn40 catalyst shows the highest catalytic activity.?4?The effects of calcination temperature on the CZ-Mn catalyst were investigated.Increasing the calcination temperature decreases the surface area of the catalyst and increases the concentration of oxygen vacancy simultaneously.There is no significant change in the catalytic activity and products selectivity with the calcination temperature ranging from 400 to 520 ?.