In the methanol-to-hydrocarbons(MTH)process,C1 species,including methanol,dimethyl ether,and surface methoxy species(SMS),play crucial roles in the evolution of organic species and the construction of reaction network...In the methanol-to-hydrocarbons(MTH)process,C1 species,including methanol,dimethyl ether,and surface methoxy species(SMS),play crucial roles in the evolution of organic species and the construction of reaction networks.Understanding the roles of C1 species throughout the entire MTH process is both essential and challenging.Herein,the dynamic evolution of organic species and unique variation of C1 species during the real-time MTH process were observed by operando diffused reflectance Fourier transform infrared spectroscopy and ex-situ 13C cross polarization/magic-angle spinning nuclear magnetic resonance experiments.Importantly,density functional theory calculations thoroughly illustrated that methanol and SMS serve as key C1 species,in the form of not only methylation agents but also hydride acceptors,and their contributions vary across different reaction periods.Initially,SMS acts as the preferential C1 surface intermediate,methylating with hydrocarbons to propagate C–C bond,while also accepting hydrides to generate precursors for active hydrocarbon pool species.As reaction progresses,the role of SMS gradually diminishes,and thereby methanol becomes the predominant C1 species,in methylation for efficient product formation,meanwhile in hydride-transfer causing catalyst deactivation.Additionally,it was demonstrated that the confined zeolite microenvironment modified by large organics affects methanol adsorption and SMS formation,also accounting for the absence of SMS during the later period of reaction.This work provides a comprehensive and systematic understanding of the dynamic roles of C1 species throughout the MTH process,beyond the role as reactants.展开更多
Porous molecular sieve catalysts,including aluminosilicate zeolites and silicoaluminophosphate(SAPO)molecular sieves,have found widespread use in heterogeneous catalysis and are expected to play a key role in advancin...Porous molecular sieve catalysts,including aluminosilicate zeolites and silicoaluminophosphate(SAPO)molecular sieves,have found widespread use in heterogeneous catalysis and are expected to play a key role in advancing carbon neutrality and sustainable development.Given the ubiquitous presence of water during catalyst synthesis,storage,and application,the interactions between water and molecular sieves as well as their consequent effects on frameworks and catalytic reactions have attracted considerable attention.These effects are inherently complex and highly dependent on various factors such as temperature,water phase,and partial pressure.In this review,we provide a comprehensive overview of the current understanding of water-molecular sieve interactions and their roles in catalysis,based on both experimental and theoretical calculation results.Special attention is paid to water-induced reversible and irreversible structural changes in aluminosilicate and SAPO frameworks at the atomic level,underscoring the dynamic and labile nature of these frameworks in water environments.The influence of water on catalytic performance and reaction kinetics in molecular sieve-catalyzed reactions is discussed from two perspectives:(1)its participation in reaction through hydrogen bonding interactions,such as competitive adsorption at active sites,stabilization of ground and transition states,and proton transfer bridge;(2)its role as a direct reactant forming new species via reactions with other vip molecules.Recent advancements in this area provide valuable insights for the rational design and optimization of catalysts for water-involved reactions.展开更多
文摘In the methanol-to-hydrocarbons(MTH)process,C1 species,including methanol,dimethyl ether,and surface methoxy species(SMS),play crucial roles in the evolution of organic species and the construction of reaction networks.Understanding the roles of C1 species throughout the entire MTH process is both essential and challenging.Herein,the dynamic evolution of organic species and unique variation of C1 species during the real-time MTH process were observed by operando diffused reflectance Fourier transform infrared spectroscopy and ex-situ 13C cross polarization/magic-angle spinning nuclear magnetic resonance experiments.Importantly,density functional theory calculations thoroughly illustrated that methanol and SMS serve as key C1 species,in the form of not only methylation agents but also hydride acceptors,and their contributions vary across different reaction periods.Initially,SMS acts as the preferential C1 surface intermediate,methylating with hydrocarbons to propagate C–C bond,while also accepting hydrides to generate precursors for active hydrocarbon pool species.As reaction progresses,the role of SMS gradually diminishes,and thereby methanol becomes the predominant C1 species,in methylation for efficient product formation,meanwhile in hydride-transfer causing catalyst deactivation.Additionally,it was demonstrated that the confined zeolite microenvironment modified by large organics affects methanol adsorption and SMS formation,also accounting for the absence of SMS during the later period of reaction.This work provides a comprehensive and systematic understanding of the dynamic roles of C1 species throughout the MTH process,beyond the role as reactants.
文摘Porous molecular sieve catalysts,including aluminosilicate zeolites and silicoaluminophosphate(SAPO)molecular sieves,have found widespread use in heterogeneous catalysis and are expected to play a key role in advancing carbon neutrality and sustainable development.Given the ubiquitous presence of water during catalyst synthesis,storage,and application,the interactions between water and molecular sieves as well as their consequent effects on frameworks and catalytic reactions have attracted considerable attention.These effects are inherently complex and highly dependent on various factors such as temperature,water phase,and partial pressure.In this review,we provide a comprehensive overview of the current understanding of water-molecular sieve interactions and their roles in catalysis,based on both experimental and theoretical calculation results.Special attention is paid to water-induced reversible and irreversible structural changes in aluminosilicate and SAPO frameworks at the atomic level,underscoring the dynamic and labile nature of these frameworks in water environments.The influence of water on catalytic performance and reaction kinetics in molecular sieve-catalyzed reactions is discussed from two perspectives:(1)its participation in reaction through hydrogen bonding interactions,such as competitive adsorption at active sites,stabilization of ground and transition states,and proton transfer bridge;(2)its role as a direct reactant forming new species via reactions with other vip molecules.Recent advancements in this area provide valuable insights for the rational design and optimization of catalysts for water-involved reactions.
