Coke formation is the primary cause of zeolite deactivation in industrial catalysis,yet the structural identity,spatial location and molecular routes of polycyclic aromatic hydrocarbons(PAHs)within confined zeolite po...Coke formation is the primary cause of zeolite deactivation in industrial catalysis,yet the structural identity,spatial location and molecular routes of polycyclic aromatic hydrocarbons(PAHs)within confined zeolite pores remain elusive.Here,by coupling matrix-assisted laser desorption/ionization Fourier-transform ion cyclotron resonance mass spectrometry with multi-dimensional chemical imaging,we unveil a channel-passing growth mechanism for PAHs in ZSM-5 zeolites during methanol conversion through identifying the molecular fingerprints of larger PAHs,pinpointing and visualizing their 3D location and spatiotemporal evolution trajectory with atomic resolution and at both channel and single-crystal scales.Confined aromatic entities cross-link with each other,culminating in multicore PAH chains as the both thermodynamically favorable and kinetically trapped host-vip entanglement wrought and templated by the defined molecular-scale constrained microenvironments of zeolite.The mechanistic concept proves general across both channel-and cage-structured zeolite materials.Our multiscale deactivating model based on the full-picture coke structure-location correlations—spanning atom,molecule,channel/cage and single crystal scales—would shed new light on the intertwined chemical and physical processes in catalyst deactivation.This work not only resolves long-standing puzzles in coke formation but also provides design principles for coke-resistant zeolites.The methods and insights would rekindle interest in confinement effects and host-vip chemistry across broader chemistry fields beyond catalysis and carbon materials.展开更多
Separation and capture technology for small molecules is of great significance,including for the goal of adsorbing and separating CO2.Accurately controlling the pore size to achieve separation of molecules with simila...Separation and capture technology for small molecules is of great significance,including for the goal of adsorbing and separating CO2.Accurately controlling the pore size to achieve separation of molecules with similar sizes remains a challenging task in rigid porous materials,such as inorganic zeolites.We propose precise pore size engineering of“larger pore”faujasite(FAU)zeolite by depositing carbon atoms inside its framework.Low-dose electron microscopy with high spatial resolution is used to visualize the carbon deposition process and the corresponding evolution of pore size.Pore size changes as a function of carbon deposition time are also studied by gas adsorption using N_(2).The carbon-modulated FAU samples with optimized pore sizes exhibit excellent gas separation of CO_(2) relative to other small molecules.For a 50/50 H_(2)/CO_(2) mixture,the separation factor was increased by 31%with a breakthrough time difference over 1200 s/g as compared to the neat FAU.We thus tailor the gas adsorption of FAU through partial filling of pores with deposited carbon and note that this can be generalized for the pore size engineering of many porous materials for use in industrial gas separation applications.展开更多
文摘Coke formation is the primary cause of zeolite deactivation in industrial catalysis,yet the structural identity,spatial location and molecular routes of polycyclic aromatic hydrocarbons(PAHs)within confined zeolite pores remain elusive.Here,by coupling matrix-assisted laser desorption/ionization Fourier-transform ion cyclotron resonance mass spectrometry with multi-dimensional chemical imaging,we unveil a channel-passing growth mechanism for PAHs in ZSM-5 zeolites during methanol conversion through identifying the molecular fingerprints of larger PAHs,pinpointing and visualizing their 3D location and spatiotemporal evolution trajectory with atomic resolution and at both channel and single-crystal scales.Confined aromatic entities cross-link with each other,culminating in multicore PAH chains as the both thermodynamically favorable and kinetically trapped host-vip entanglement wrought and templated by the defined molecular-scale constrained microenvironments of zeolite.The mechanistic concept proves general across both channel-and cage-structured zeolite materials.Our multiscale deactivating model based on the full-picture coke structure-location correlations—spanning atom,molecule,channel/cage and single crystal scales—would shed new light on the intertwined chemical and physical processes in catalyst deactivation.This work not only resolves long-standing puzzles in coke formation but also provides design principles for coke-resistant zeolites.The methods and insights would rekindle interest in confinement effects and host-vip chemistry across broader chemistry fields beyond catalysis and carbon materials.
基金supported by the National Natural Science Foundation of China(Nos.T2322019(B.S.)and 22275133(B.S.))Suzhou Science and Technology Development Plan(No.ZXL2023179(B.S.))+2 种基金Science Foundation of Jiangsu Province(No.BK20220484(B.S.))Suzhou Key Laboratory of Functional Nano&Soft Materials,Collaborative Innovation Center of Suzhou Nano Science&Technologythe 111 Project,Joint International Research Laboratory of Carbon-Based Functional Materials and Devices,and the Institute for Basic Science(IBS-R019-D1)of Republic of Korea.
文摘Separation and capture technology for small molecules is of great significance,including for the goal of adsorbing and separating CO2.Accurately controlling the pore size to achieve separation of molecules with similar sizes remains a challenging task in rigid porous materials,such as inorganic zeolites.We propose precise pore size engineering of“larger pore”faujasite(FAU)zeolite by depositing carbon atoms inside its framework.Low-dose electron microscopy with high spatial resolution is used to visualize the carbon deposition process and the corresponding evolution of pore size.Pore size changes as a function of carbon deposition time are also studied by gas adsorption using N_(2).The carbon-modulated FAU samples with optimized pore sizes exhibit excellent gas separation of CO_(2) relative to other small molecules.For a 50/50 H_(2)/CO_(2) mixture,the separation factor was increased by 31%with a breakthrough time difference over 1200 s/g as compared to the neat FAU.We thus tailor the gas adsorption of FAU through partial filling of pores with deposited carbon and note that this can be generalized for the pore size engineering of many porous materials for use in industrial gas separation applications.
