Effect of calcination temperature on catalytic performance of ZnGaZrOx/SAPO-34
In the hydrogenation of CO2 to low-carbon olefins(C2=-C4=),the calcination temperature of the bifunctional cata-lyst has significant effects on its catalytic performance.Based on this,ZnGaZrOx oxides were prepared by co-precipitation method and SAPO-34 molecular sieves were prepared by hydrothermal method,and then both of them were milled to pro-duce ZnGaZrOx/SAPO-34 bifunctional catalysts,and the effects of calcination temperature on the physicochemical proper-ties and catalytic performance of ZnGaZrOx and SAPO-34 were investigated.It was found by XRD,XPS,H2/CO2/NH3-TPD,SEM,N2 adsorption-desorption and in situ DRIFTS characterization that during the preparation of ZnGaZrOx,when the cal-cination temperature was 650℃,ZnGaZrOx had the strongest activation ability of H2 and CO2 adsorption,and it could effec-tively increase the rate and concentration of the generation of HCOO* and CH3O* to promote the methanol product genera-tion.During the preparation of SAPO-34,when the calcination temperature was 450℃,the molecular sieve had the largest specific surface area,the smallest grain size,and the weakest acidity of the strong acid site,which could effectively avoid the secondary hydrogenation of low-carbon olefins,thus obtaining higher selectivity of low-carbon olefins.The ZnGaZrOx/SAPO-34 bifunctional catalysts synthesized under the optimal conditions showed a CO2 conversion of 28.3%,a CO selectiv-ity of only 44.6%,a C2=-C4= selectivity of 84.4%,a C2=-C4= yield of as high as 13.2%at a reaction temperature of 390℃,a pressure of 3 MPa,and an airspeed of 3 600 mL/(g·h).And the catalytic performance did not decay significantly within 100 h of reaction.This work provided a new research idea for the modification of bifunctional catalysts.
CO2 hydrogenationlight olefinscalcination temperatureoxygen vacancyacidity
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