Ce-encapsulated Beta zeolite was synthesized by a one-pot hydrothermal method with citric acid complexing Ce in the absence of Na species.Additional citric acid can effectively prevent the deposition of Ce species dur...Ce-encapsulated Beta zeolite was synthesized by a one-pot hydrothermal method with citric acid complexing Ce in the absence of Na species.Additional citric acid can effectively prevent the deposition of Ce species during the hydrothermal synthesis of zeolites,leading to uniform distribution of Ce cluster in the framework of Beta zeolites.Moreover,the sodium-free synthesis system resulted that the Brønsted acid sites were mainly located on the straight channels and external surface of Beta zeolites,improving the utilization of Brønsted acid sites.In addition,Ce encapsulated Beta zeolites showed enhanced activity and robust stability in the alkylation of benzene with 1-dodecene based on the synergistic effect between Ce species and Brønsted acid sites,which pave the way for its practical application in the production of alkylbenzene.展开更多
The fabrication of suitable MFI zeolites to effectively produce para-xylene through the alkylation between toluene and methanol is highly desired.Here,the two-dimensional pillared MFI zeolite was modified by silicalit...The fabrication of suitable MFI zeolites to effectively produce para-xylene through the alkylation between toluene and methanol is highly desired.Here,the two-dimensional pillared MFI zeolite was modified by silicalite-1,and its morphology and structure were systematically investigated by tuning the concentration of Si species during the secondary crystallization process.The MFI zeolites were characterized by X-ray diffraction,transmission electron microscopy,pyridine-infrared and N_(2) adsorption-desorption isotherms.The characterization results showed that the external Brønsted acid sites of surface passivated P-MFI-x samples have been successfully shielded.Interestingly,the P-MFI-23 showed long lifetime and high selectivity of para-xylene(about 35%)based on the cooperation between opened interlamellar structure and passivated silicalite-1 layer.It was found that the accumulated hard coke in the interior of MFI zeolites not only blocked the channels of zeolites but also covered the acidic sites,resulting in the deactivation of catalyst.Furthermore,the highest selectivity of para-xylene(about 48%)can be achieved for P-MFI-30 under harsh reaction condition,which also exhibited excellent regeneration property in the alkylation reaction between toluene and methanol.The strategy described in present research may open a window for the design of other advanced materials.展开更多
基金supported by the National Natural Science Foundation of China(22278090,21978055)Natural Science Foundation of Guangdong Province,China(2022A1515012088)the Science and Technology Planning Project of Guangdong Province,China(2022A0505030073,2022A0505030013).
文摘Ce-encapsulated Beta zeolite was synthesized by a one-pot hydrothermal method with citric acid complexing Ce in the absence of Na species.Additional citric acid can effectively prevent the deposition of Ce species during the hydrothermal synthesis of zeolites,leading to uniform distribution of Ce cluster in the framework of Beta zeolites.Moreover,the sodium-free synthesis system resulted that the Brønsted acid sites were mainly located on the straight channels and external surface of Beta zeolites,improving the utilization of Brønsted acid sites.In addition,Ce encapsulated Beta zeolites showed enhanced activity and robust stability in the alkylation of benzene with 1-dodecene based on the synergistic effect between Ce species and Brønsted acid sites,which pave the way for its practical application in the production of alkylbenzene.
基金supported by the National Natural Science Foundation of China(Grant Nos.22278090,21978055)the Natural Science Foundation of Guangdong Province(Grant No.2022A1515012088)the Science and Technology Program of Guangdong Province(Grant No.2022A0505050073).
文摘The fabrication of suitable MFI zeolites to effectively produce para-xylene through the alkylation between toluene and methanol is highly desired.Here,the two-dimensional pillared MFI zeolite was modified by silicalite-1,and its morphology and structure were systematically investigated by tuning the concentration of Si species during the secondary crystallization process.The MFI zeolites were characterized by X-ray diffraction,transmission electron microscopy,pyridine-infrared and N_(2) adsorption-desorption isotherms.The characterization results showed that the external Brønsted acid sites of surface passivated P-MFI-x samples have been successfully shielded.Interestingly,the P-MFI-23 showed long lifetime and high selectivity of para-xylene(about 35%)based on the cooperation between opened interlamellar structure and passivated silicalite-1 layer.It was found that the accumulated hard coke in the interior of MFI zeolites not only blocked the channels of zeolites but also covered the acidic sites,resulting in the deactivation of catalyst.Furthermore,the highest selectivity of para-xylene(about 48%)can be achieved for P-MFI-30 under harsh reaction condition,which also exhibited excellent regeneration property in the alkylation reaction between toluene and methanol.The strategy described in present research may open a window for the design of other advanced materials.
