Selective and durable fixed‐bed catalysts are highly desirable for developing eco‐efficient HPPO(hydrogen peroxide propylene oxide)process.The powder titanosilicate catalysts must be shaped before being applied in i...Selective and durable fixed‐bed catalysts are highly desirable for developing eco‐efficient HPPO(hydrogen peroxide propylene oxide)process.The powder titanosilicate catalysts must be shaped before being applied in industrial processes.As the essential additives for preparing formed catalysts,binders are usually the catalytically inert components,but they would cover the surface and pore mouth of zeolite,thereby declining the accessibility of active sites.By recrystallizing the binder(silica)/Ti‐MWW extrudates with the assistance of dual organic structure‐directing agents,the silica binder was converted into MWW zeolite phase to form a structured binder‐free Ti‐MWW zeolite with Si‐rich shell,which enhanced the diffusion efficiency and maintained the mechanical strength.Meanwhile,due to the partial dissolution of Si in the Ti‐MWW matrix,abundant silanol nests formed and part of framework TiO4 species were transferred into open TiO_(6)ones,improving the accumulation and activation ability of H_(2)O_(2)inside the monolith.Successive piperidine treatment and fluoridation of the binder‐free Ti‐MWW further enhanced the H_(2)O_(2)activation and oxygen transfer ability of the active Ti sites,and stabilized the Ti‐OOH intermediate through hydrogen bond formed between the end H in Ti‐OOH and the adjacent Si‐F species,thus achieving a more efficient epoxidation process.Additionally,the side reaction of PO hydrolysis was inhibited because the modification effectively quenched numerous Si‐OH groups.The lifetime of the modified binder‐free Ti‐MWW catalyst was 2400 h with the H_(2)O_(2)conversion and PO selectivity both above 99.5%.展开更多
The rechargeable aluminum-sulfur(Al-S)battery is a promising alternative-energy storage device with high energy density and made of cheap raw materials.However,Al-S batteries face several obstacles,especially the shut...The rechargeable aluminum-sulfur(Al-S)battery is a promising alternative-energy storage device with high energy density and made of cheap raw materials.However,Al-S batteries face several obstacles,especially the shuttle effect.Herein,a binder-free S@Ti_(3)C_(2)T_(x)sandwich structure film with uniform sulfur dispersion was designed.The two-dimensional(2D)layered material Ti_(3)C_(2)T_(x) not only has the function of binder and conductive agent but also is a promising host for sulfur anchoring.As a result,S@Ti_(3)C_(2)T_(x)film showed an initial capacity of 489 mA h g^(−1)at 300 mA g^(−1) and retained the value at 415 mA h g^(−1)after 280 stable cycles,with an average Coulombic efficiency of~95%.The film displayed higher capacity and stability than the S+Ti_(3)C_(2)T_(x)cathode prepared by the slurry-coating method(the initial capacity was 317 mA h g^(−1)and then decayed to 222 mA h g^(−1) after 160 cycles).The main capacity of S@Ti_(3)C_(2)T_(x) film in the Al-S battery came from the reversible redox reaction of S^(2−) and S.This new 2D material combined with a controllable electrode structure design paves the way for the development of Al-S batteries.展开更多
文摘Selective and durable fixed‐bed catalysts are highly desirable for developing eco‐efficient HPPO(hydrogen peroxide propylene oxide)process.The powder titanosilicate catalysts must be shaped before being applied in industrial processes.As the essential additives for preparing formed catalysts,binders are usually the catalytically inert components,but they would cover the surface and pore mouth of zeolite,thereby declining the accessibility of active sites.By recrystallizing the binder(silica)/Ti‐MWW extrudates with the assistance of dual organic structure‐directing agents,the silica binder was converted into MWW zeolite phase to form a structured binder‐free Ti‐MWW zeolite with Si‐rich shell,which enhanced the diffusion efficiency and maintained the mechanical strength.Meanwhile,due to the partial dissolution of Si in the Ti‐MWW matrix,abundant silanol nests formed and part of framework TiO4 species were transferred into open TiO_(6)ones,improving the accumulation and activation ability of H_(2)O_(2)inside the monolith.Successive piperidine treatment and fluoridation of the binder‐free Ti‐MWW further enhanced the H_(2)O_(2)activation and oxygen transfer ability of the active Ti sites,and stabilized the Ti‐OOH intermediate through hydrogen bond formed between the end H in Ti‐OOH and the adjacent Si‐F species,thus achieving a more efficient epoxidation process.Additionally,the side reaction of PO hydrolysis was inhibited because the modification effectively quenched numerous Si‐OH groups.The lifetime of the modified binder‐free Ti‐MWW catalyst was 2400 h with the H_(2)O_(2)conversion and PO selectivity both above 99.5%.
基金supported by the National Natural Science Foundation of China(51272155,21875061,21975066 and 21901157)the Open Research Fund Program of Science and Technology on Aerospace Chemical Power Laboratory(STACPL 120201B05)the National Key R&D Program of China(2021YFC2100100)。
文摘The rechargeable aluminum-sulfur(Al-S)battery is a promising alternative-energy storage device with high energy density and made of cheap raw materials.However,Al-S batteries face several obstacles,especially the shuttle effect.Herein,a binder-free S@Ti_(3)C_(2)T_(x)sandwich structure film with uniform sulfur dispersion was designed.The two-dimensional(2D)layered material Ti_(3)C_(2)T_(x) not only has the function of binder and conductive agent but also is a promising host for sulfur anchoring.As a result,S@Ti_(3)C_(2)T_(x)film showed an initial capacity of 489 mA h g^(−1)at 300 mA g^(−1) and retained the value at 415 mA h g^(−1)after 280 stable cycles,with an average Coulombic efficiency of~95%.The film displayed higher capacity and stability than the S+Ti_(3)C_(2)T_(x)cathode prepared by the slurry-coating method(the initial capacity was 317 mA h g^(−1)and then decayed to 222 mA h g^(−1) after 160 cycles).The main capacity of S@Ti_(3)C_(2)T_(x) film in the Al-S battery came from the reversible redox reaction of S^(2−) and S.This new 2D material combined with a controllable electrode structure design paves the way for the development of Al-S batteries.
