摘要
开发CO_(2)加氢制甲醇高效Cu基催化剂对循环利用该温室气体具有重要意义。工作通过共沉淀、后浸渍法制备了系列助剂(Mn,In,Mo,Mg,Zr)改性的Cu/ZnO/Al_(2)O_(3)(CZA)催化剂,并用固定床反应器评价了其CO_(2)加氢制甲醇催化性能。采用CO_(2)-TPD、X射线衍射(XRD)、X射线光电子能谱(XPS)和H_(2)-TPR研究了金属改性助剂对CZA物理化学性质的影响。此外,通过原位红外漫反射光谱表征揭示了CO_(2)加氢制甲醇反应机理。结果表明,Mn改性CZA催化剂具有良好的还原性能、优异的CO_(2)吸附能力和适宜的Cu^(+)/Cu^(0)比,恰当的Cu^(+)/Cu^(0)比例可促进甲氧基的稳定与转化,从而产生更多的甲醇。金属改性有助于增强铜与载体的相互作用,促进催化剂还原,抑制活性铜组分聚集。与未经处理的CZA催化剂相比,Mn改性催化剂表面具有更多中强碱性位点,有助于吸附更多的CO_(2),进一步加氢形成甲酸盐、甲氧基等中间体。CZA和改性CZA上CO_(2)加氢生成甲醇反应机理遵循甲酸盐途径,甲氧基是关键中间体。Mn改性CZA催化剂由于较强的金属-载体相互作用,催化剂表面Cu纳米颗粒解离H_(2)能力得到提高,载体中存在的间隙H有助于甲酸盐物种的产生,消耗的间隙H由表面Cu纳米颗粒解离出的H原子补充。改性催化剂中的间隙H存在和解离H_(2)能力提升加速了中间物种的形成与转化,促进甲醇的生成。
Development of effective copper-based catalyst for CO_(2) hydrogenation to methanol is of great significance,considering the utilization of this greenhouse gas.In this work,a series of surface promoter-modified(Mn,In,Mo,Mg,Zr)catalyst were synthesized by coprecipitation-post impregnation method and evaluated for CO_(2) hydrogenation to methanol in fixed-bed reactor.The role of metal modifier on the physicochemical properties of Cu/ZnO/Al_(2)O_(3)(CZA)were investigated through CO_(2)-TPD,XRD,XPS and H_(2)-TPR.In addition,the catalytic mechanism for CO_(2)-to-methanol hydrogenation was revealed by employing in situ IR.The results showed that the Mn-modified CZA with good reduction behavior,excellent CO_(2) adsorption capacity and suitable Cu^(+)/Cu^(0) ratio exhibited the best performance.The metal element loaded on catalyst strengthened the interactions between the copper and support,suppressing the growth of Cu.The appropriate Cu^(+)/Cu^(0) ratio facilitates the stabilization and conversion of methoxy,resulting in increased methanol production.Compared to the untreated CZA catalyst,the Mn-modified catalyst has more medium strong base sites on the surface,which helps to adsorb more CO_(2) for further hydrogenation to form formate,methoxyl and other intermediates.The incorporation of metal component in CZA facilitated the catalyst reduction ability.The catalytic mechanism follows the formate pathway and the methoxyl species is the crucial intermediate.The Cu nanoparticles on the catalyst surface showed an increased capacity for H_(2) dissociation when using Mn-modified CZA catalysts.This is due to stronger metal-carrier interactions.The presence of interstitial H in the carriers contributed to the generation of formate species.The dissociated H atoms from the surface Cu nanoparticles replenished the consumed interstitial H.The modified catalyst's interstitial H presence and enhanced H2 dissociation ability accelerated the formation and conversion of intermediate species,promoting methanol generation.
作者
杨强
王刚
李春山
Qiang YANG;Gang WANG;Chunshan LI(Chengdu Institute of Organic Chemistry,Chinese Academy of Sciences,Chengdu,Sichuan 610041,China;University of Chinese Academy of Sciences,Beijing 100049,China;State Key Laboratory of Mesoscience and Engineering,CAS Key Laboratory of Green Process and Engineering,Beijing Key Laboratory of Ionic Liquids Clean Process,Institute of Process Engineering,Chinese Academy of Sciences,Beijing 100190,China;Huizhou Institute of Green Energy and Advanced Materials,Huizhou,Guangdong 516083,China)
出处
《过程工程学报》
CAS
CSCD
北大核心
2024年第10期1166-1176,共11页
The Chinese Journal of Process Engineering
基金
国家重点研发专项(编号:2020YFA0710202)
国家杰出青年自然科学基金项目(编号:22025803)。
关键词
Cu基催化剂
金属-载体相互作用
甲醇合成
表面改性
反应机理
Cu-based catalyst
metal-support interaction
methanol synthesis
surface modification
reaction mechanism
