物理化学学报2022，Vol.38Issue(3)：56-65,10.DOI:10.3866/PKU.WHXB202002017
以类水滑石为前驱体的Cu/ZnO/Al2O3催化剂用于COx加氢合成甲醇:CO在反应混合物中的作用
Methanol Synthesis by COx Hydrogenation over Cu/ZnO/Al2O3 Catalyst via Hydrotalcite-Like Precursors:the Role of CO in the Reactant Mixture
摘要
Abstract
Catalytic hydrogenation of CO2 to methanol has attracted considerable attention due to its potential in alleviating global warming and mitigating the dependence on fossil fuels.Cu-based catalysts are widely used in industry because of their high activity for methanol production.However,the reaction still suffers from low methanol selectivity because of the generation of CO as a by-product via the reverse water gas shift reaction(RWGS).The formation of another by-product H2O leads to inevitable Cu sintering,which decreases the methanol production rate.It is well known that CO can alter competitive molecular adsorption on the surface and the redox behavior of the active sites;hence,CO doping in feed gas might not only inhibit the RWGS but also minimize surface poisoning by the adsorbed oxygen.On the other hand,CO2 hydrogenation to methanol over Cu-based catalysts is a structure-sensitive reaction,and a change in the precursor can have a remarkable influence on the structure and morphology of the catalyst,and ultimately,the catalytic performance.In this work,Cu/ZnO/Al2O3 catalysts have been prepared via a hydrotalcite-like precursor(CHT-CZA)and a complex phase precursor(CNP-CZA)using co-precipitation and ammonia evaporation methods.Subsequently,the performance of the two types of catalysts with different CO contents(CO2∶ CO ∶H2∶N2=x∶(24.5-x)∶ 72.5 ∶ 3)is compared at 250℃and 5 MPa in order to explore the role of CO.The evaluation results show that both catalysts follow a similar trend in the conversion of CO and CO2 as well as the space-time-yield(STY)of MeOH and H2O.The conversions of CO2 and STYH2O decrease gradually with an increase in the CO volume,but STYMeOH is positively correlated with the CO volume.Furthermore,X-ray photoelectron spectroscopy(XPS)analysis reveals that the amount of reduced Cu species on the surface increases with increasing CO content.Judging from these results,the introduction of CO inhibits the RWGS and enhances the methanol yield for both catalysts by removing the surface oxygen as the reducing agent and thereby facilitating the exposure of the active reduced Cu species.On the other hand,transmission electron microscopy(TEM)observations indicate the doped CO may cause agglomeration of particles due to over-reduction,leading to gradual catalyst deactivation.Compared with the traditional CNP-CZA,the catalyst derived from hydrotalcite-like compounds exhibits better activity and long-term stability under all atmospheres,at different CO doping levels.This is because the hydrotalcite-like layer structure helps maintain the active metal state and confine the structure by limiting the agglomeration of Cu species.关键词
CO2氢化/甲醇合成/Cu/ZnO/Al2O3催化剂/CO掺杂/水滑石前驱体Key words
CO2 hydrogenation/Methanol synthesis/Cu/ZnO/Al2O3 catalyst/CO doping/Hydrotalcite-like precursors分类
化学化工引用本文复制引用
刘影,刘晓放,夏林,黄超杰,吴兆萱,王慧,孙予罕..以类水滑石为前驱体的Cu/ZnO/Al2O3催化剂用于COx加氢合成甲醇:CO在反应混合物中的作用[J].物理化学学报,2022,38(3):56-65,10.基金项目
This work was supported by the National Natural Science Foundation of China(21776296,21905291),National Key Research and Development Program of China(2017YFB0602203),Strategic Priority Research Program of the Chinese Academy of Sciences(XDA21090201),the Chinese Academy of Sciences(ZDRW-ZS-2018-1-3),and the Shanghai Sailing Program,China(19YF1453000).国家自然科学基金(21776296,21905291),国家重点研发计划(2017YFB0602203),中国科学院战略性先导科技项目(XDA21090201),中国科学院(ZDRW-ZS-2018-1-3)和上海市扬帆计划(19YF1453000)资助项目 （21776296,21905291）
