Nano-catalysts containing copper–cobalt oxides(Cu–Co–O) have been synthesized by the citric acid(CA) complexing method. Copper(II) nitrate and Cobalt(II) nitrate were employed in different molar ratios as the start...Nano-catalysts containing copper–cobalt oxides(Cu–Co–O) have been synthesized by the citric acid(CA) complexing method. Copper(II) nitrate and Cobalt(II) nitrate were employed in different molar ratios as the starting reactants to prepare three types of nano-catalysts. Well crystalline nano-catalysts were produced after a period of 3 hours by the calcination of CA–Cu–Co–O precursors at 550 °C. The phase morphologies and crystal composition of synthesized nano-catalysts were examined using Scanning Electron Microscope(SEM), Energy Dispersive Spectroscopy(EDS) and Fourier Transform Infrared Spectroscopy(FTIR) methods. The particle size of nano-catalysts was observed in the range of 90 nm–200 nm. The prepared nano-catalysts were used to formulate propellant samples of various compositions which showed high reactivity toward the combustion of HTPB/AP-based composite solid propellants. The catalytic effects on the decomposition of propellant samples were found to be significant at higher temperatures. The combustion characteristics of composite solid propellants were significantly improved by the incorporation of nano-catalysts. Out of the three catalysts studied in the present work, Cu Co-I was found to be the better catalyst in regard to thermal decomposition and burning nature of composite solid propellants. The improved performance of composite solid propellant can be attributed to the high crystallinity, low agglomeration and lowering the decomposition temperature of oxidizer by the addition of Cu Co-I nano-catalyst.展开更多
Supported metal nanoparticles(NPs)as an important heterogeneous catalyst have been widely applied in various industrial processes.During the catalytic reaction,size of the particles plays an important role in determin...Supported metal nanoparticles(NPs)as an important heterogeneous catalyst have been widely applied in various industrial processes.During the catalytic reaction,size of the particles plays an important role in determining their catalytic performance.Generally,the small particles exhibit superior catalytic activity in comparison with the larger particles because of an increase in lowcoordinated metal atoms on the particle surface that work as active sites,such as edges and corner atoms.However,these small NPs are typically unstable and tend to migrate and coalescence to reduce their surface free energy during the real catalytic processes,particularly in high-temperature reactions.Therefore,a means to fabricate stable small metal NP catalysts with excellent sinter-resistant performance is necessary for maintaining their high catalytic activity.In this study,we have summarized recent advances in stabilizing metal NPs from two aspects including thermodynamic and kinetic strategies.The former mainly involve preparing uniform NPs(with an identical size and homogeneous distribution)in order to restrain Ostwald ripening to achieve stability,while the latter primarily involves fixing metal NPs in some special confinement materials(e.g.,zeolites,mesoporous silica and mesoporous carbons),encapsulating NPs using an oxide-coating film(e.g.,forming core-shell structures),or constructing strong metal-support interactions to improve stability.At the end of this review,we highlight our recent work on the preparation of high-stability metal catalysts via a unique interfacial plasma electrolytic oxidation technology,that is,metal NPs are well embedded in a porous MgO layer that has both high thermal stability and excellent catalytic activity.展开更多
Environmental pollution caused by the presence of aromatic aldehydes and dyes in wastewater is a serious global concern. An effective strategy for the removal of these pollutants is their catalytic conversion, possibl...Environmental pollution caused by the presence of aromatic aldehydes and dyes in wastewater is a serious global concern. An effective strategy for the removal of these pollutants is their catalytic conversion, possibly to valuable compounds. Therefore, the design of efficient, stable and long-lifetime catalysts is a worthwhile research goal. Herein, we used nanofibrous carbon microspheres (NCM) derived from the carbohydrate chitin present in seafood waste, and characterized by interconnected nanofibrous networks and N/O-containing groups, as carriers for the manufacture of a highly dispersed, efficient and stable Pd nano-catalyst (mean diameter ca. 2.52 nm). Importantly, the carbonised chitin’s graphitized structure, defect presence and large surface area could promote the transport of electrons between NCM and Pd, thereby endowing NCM supported Pd catalyst with high catalytic activity. The NCM supported Pd catalyst was employed in the degradation of some representative dyes and the chemoselective hydrogenation of aromatic aldehydes;this species exhibited excellent catalytic activity and stability, as well as applicability to a broad range of aromatic aldehydes, suggesting its potential use in green industrial catalysis.展开更多
采用溶胶凝胶法和浸渍法制备了以陶瓷颗粒为骨架的纳米级V2O5-WO3/TiO2(C)催化剂,并用X射线衍射(X-ray diffraction,XRD)和扫描电子透镜(transmission electron microscopy,TEM)表征了催化剂的晶型和形貌。研究了TiO2凝胶热处理温度和WO...采用溶胶凝胶法和浸渍法制备了以陶瓷颗粒为骨架的纳米级V2O5-WO3/TiO2(C)催化剂,并用X射线衍射(X-ray diffraction,XRD)和扫描电子透镜(transmission electron microscopy,TEM)表征了催化剂的晶型和形貌。研究了TiO2凝胶热处理温度和WO3负载量等重要参数对催化剂在以NH3为还原剂的选择性催化还原(selectivecatalytic reduc-tion,SCR)系统中的反应温度窗口、抗硫性的影响。最后考察了催化剂在不同NH3/NO比、O2含量、空速等因素下的性能指标。结果表明,在260～420℃的温度范围内,以陶瓷为骨架的负载型纳米V2O5-WO3/TiO2催化剂具有较高的SCR催化活性,且性能稳定;TiO2以锐钛形式存在的催化剂表现出高的抗硫性能,而TiO2以锐钛和金红石混晶形式存在时,抗硫性能比较差,但硫的中毒是可逆的,可再生;WO3负载量的增加提高了催化剂的活性。展开更多
文摘Nano-catalysts containing copper–cobalt oxides(Cu–Co–O) have been synthesized by the citric acid(CA) complexing method. Copper(II) nitrate and Cobalt(II) nitrate were employed in different molar ratios as the starting reactants to prepare three types of nano-catalysts. Well crystalline nano-catalysts were produced after a period of 3 hours by the calcination of CA–Cu–Co–O precursors at 550 °C. The phase morphologies and crystal composition of synthesized nano-catalysts were examined using Scanning Electron Microscope(SEM), Energy Dispersive Spectroscopy(EDS) and Fourier Transform Infrared Spectroscopy(FTIR) methods. The particle size of nano-catalysts was observed in the range of 90 nm–200 nm. The prepared nano-catalysts were used to formulate propellant samples of various compositions which showed high reactivity toward the combustion of HTPB/AP-based composite solid propellants. The catalytic effects on the decomposition of propellant samples were found to be significant at higher temperatures. The combustion characteristics of composite solid propellants were significantly improved by the incorporation of nano-catalysts. Out of the three catalysts studied in the present work, Cu Co-I was found to be the better catalyst in regard to thermal decomposition and burning nature of composite solid propellants. The improved performance of composite solid propellant can be attributed to the high crystallinity, low agglomeration and lowering the decomposition temperature of oxidizer by the addition of Cu Co-I nano-catalyst.
基金financially supported by the National Natural Science Foundation of China (Nos.51601032, 51971059,5197010432)the Fundamental Research Funds for the Central Universities (Nos.N170204015,N180204014)the Provincial Science and Technology Project/Doctor Start Fund (No. 20170520385).
文摘Supported metal nanoparticles(NPs)as an important heterogeneous catalyst have been widely applied in various industrial processes.During the catalytic reaction,size of the particles plays an important role in determining their catalytic performance.Generally,the small particles exhibit superior catalytic activity in comparison with the larger particles because of an increase in lowcoordinated metal atoms on the particle surface that work as active sites,such as edges and corner atoms.However,these small NPs are typically unstable and tend to migrate and coalescence to reduce their surface free energy during the real catalytic processes,particularly in high-temperature reactions.Therefore,a means to fabricate stable small metal NP catalysts with excellent sinter-resistant performance is necessary for maintaining their high catalytic activity.In this study,we have summarized recent advances in stabilizing metal NPs from two aspects including thermodynamic and kinetic strategies.The former mainly involve preparing uniform NPs(with an identical size and homogeneous distribution)in order to restrain Ostwald ripening to achieve stability,while the latter primarily involves fixing metal NPs in some special confinement materials(e.g.,zeolites,mesoporous silica and mesoporous carbons),encapsulating NPs using an oxide-coating film(e.g.,forming core-shell structures),or constructing strong metal-support interactions to improve stability.At the end of this review,we highlight our recent work on the preparation of high-stability metal catalysts via a unique interfacial plasma electrolytic oxidation technology,that is,metal NPs are well embedded in a porous MgO layer that has both high thermal stability and excellent catalytic activity.
基金This work was supported by the Guizhou Provincial Science and Technology Foundation(Grant No.[2020]1Y212)the Science and Technology Top Talent Project of Guizhou Province(Grant No.[2021]029)+6 种基金the National Natural Science Foundation of China(Grant Nos.52063008 and 52103124)the Graduate Education Innovation Project of Guizhou Province(Grant No.[2020]099)the Guizhou Province Science and Technology Plan Project(Grant No.ZK[2021]Key 050)the Guizhou Key Laboratory of Inorganic Nonmetallic Functional Materials(Grant No.[2022]012)the Hundred Talents Project of Guizhou Province(Grant No.[2016]5673)the Lightweight Materials Engineering Research Center of the Education Department of Guizhou(Grant No.[2022]045)the Guizhou Province Science and Technology Support Plan(Grant Nos.[2020]4Y063 and[2021]04).
文摘Environmental pollution caused by the presence of aromatic aldehydes and dyes in wastewater is a serious global concern. An effective strategy for the removal of these pollutants is their catalytic conversion, possibly to valuable compounds. Therefore, the design of efficient, stable and long-lifetime catalysts is a worthwhile research goal. Herein, we used nanofibrous carbon microspheres (NCM) derived from the carbohydrate chitin present in seafood waste, and characterized by interconnected nanofibrous networks and N/O-containing groups, as carriers for the manufacture of a highly dispersed, efficient and stable Pd nano-catalyst (mean diameter ca. 2.52 nm). Importantly, the carbonised chitin’s graphitized structure, defect presence and large surface area could promote the transport of electrons between NCM and Pd, thereby endowing NCM supported Pd catalyst with high catalytic activity. The NCM supported Pd catalyst was employed in the degradation of some representative dyes and the chemoselective hydrogenation of aromatic aldehydes;this species exhibited excellent catalytic activity and stability, as well as applicability to a broad range of aromatic aldehydes, suggesting its potential use in green industrial catalysis.
文摘采用溶胶凝胶法和浸渍法制备了以陶瓷颗粒为骨架的纳米级V2O5-WO3/TiO2(C)催化剂,并用X射线衍射(X-ray diffraction,XRD)和扫描电子透镜(transmission electron microscopy,TEM)表征了催化剂的晶型和形貌。研究了TiO2凝胶热处理温度和WO3负载量等重要参数对催化剂在以NH3为还原剂的选择性催化还原(selectivecatalytic reduc-tion,SCR)系统中的反应温度窗口、抗硫性的影响。最后考察了催化剂在不同NH3/NO比、O2含量、空速等因素下的性能指标。结果表明,在260～420℃的温度范围内,以陶瓷为骨架的负载型纳米V2O5-WO3/TiO2催化剂具有较高的SCR催化活性,且性能稳定;TiO2以锐钛形式存在的催化剂表现出高的抗硫性能,而TiO2以锐钛和金红石混晶形式存在时,抗硫性能比较差,但硫的中毒是可逆的,可再生;WO3负载量的增加提高了催化剂的活性。
