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
Recently designated as a new special economic zone in China,Zhoushan Archipelago is going through a rapid land use change that is expected to have significant impacts on ecosystem services.However,there is no baseline...Recently designated as a new special economic zone in China,Zhoushan Archipelago is going through a rapid land use change that is expected to have significant impacts on ecosystem services.However,there is no baseline of ecosystem service value(ESV)of the Zhoushan Archipelago up to date,making it impossible to assess any impacts of land use changes.In this study,we adopted the concept of“equivalent value per unit area of ecosystem services in China”and computed the ESV for 2006,2012,and 2020 of a representative district,Dinghai,on the Zhoushan Archipelago.We then analyzed the spatial and temporal patterns of land use changes and their impacts on ESV.The results indicated that the ESV of Dinghai District declined by 59.3 M Chinese yuan($9.5 M US dollars)from 2006 to 2012 and would further decrease by an additional 30.9 M yuan($5 M US dollars)by 2020 according to its planned land uses.These declines in ESV were primarily due to increases in buildup areas and losses in wetland,farmland,and water areas.The results imply that more attention should be paid to controlling urban growth and protecting coastal wetlands in order to preserve valuable ecosystem services of the Archipelago.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This research was financially supported by the National One-Thousand-Talent Program,the National Natural Science Foundation of China(no.41401404)Preparation of this manuscript was partially supported by the Fundamental Research Funds for the Central Universities(2015QNA4039)the Asian Pacific Network funded project(ARCP2013-FP25-Wu).
文摘Recently designated as a new special economic zone in China,Zhoushan Archipelago is going through a rapid land use change that is expected to have significant impacts on ecosystem services.However,there is no baseline of ecosystem service value(ESV)of the Zhoushan Archipelago up to date,making it impossible to assess any impacts of land use changes.In this study,we adopted the concept of“equivalent value per unit area of ecosystem services in China”and computed the ESV for 2006,2012,and 2020 of a representative district,Dinghai,on the Zhoushan Archipelago.We then analyzed the spatial and temporal patterns of land use changes and their impacts on ESV.The results indicated that the ESV of Dinghai District declined by 59.3 M Chinese yuan($9.5 M US dollars)from 2006 to 2012 and would further decrease by an additional 30.9 M yuan($5 M US dollars)by 2020 according to its planned land uses.These declines in ESV were primarily due to increases in buildup areas and losses in wetland,farmland,and water areas.The results imply that more attention should be paid to controlling urban growth and protecting coastal wetlands in order to preserve valuable ecosystem services of the Archipelago.
