The size of the nanoparticles and the number of oxygen vacancies have a significant effect on the catalytic activity of copper-based catalysts used for the synthesis of methanol from syngas.In this study,the authors p...The size of the nanoparticles and the number of oxygen vacancies have a significant effect on the catalytic activity of copper-based catalysts used for the synthesis of methanol from syngas.In this study,the authors prepared a series of catalysts CuO/ZnO/Al_(2)O_(3)/CeO_(2)(CZAC)with CuO particles of different sizes and varying number of oxygen vacancies on the surface by changing the added volume of CeO2 by using the co-precipitation method.The properties of the catalysts were characterized and their activity was evaluated by using high-pressure fixed-bed reaction equipment.The results showed that the addition of CeO_(2)to CuO/ZnO/Al_(2)O_(3)not only influenced the size of the CuO particles and metal-metal interactions,but also had an effect on the concentrations of oxygen vacancies and strongly basic sites.The presence of CuO particles of small sizes and a large numbers of oxygen vacancies on the surface of the catalyst were beneficial to its activity for the synthesis of methanol.The catalyst CZAC,when modified by 5%of CeO_(2),recorded CuO particles of the smallest size(8.9 nm),strong intermetallic interactions,and the highest concentrations of oxygen vacancies and strongly basic sites.It also exhibited the highest catalytic activity,with a space-time yield of methanol of 0.315 g/(h·g)that was higher than that of the enterprise RK-5 catalyst[0.215 g/(h·g)].展开更多
Developing deNO_(x)catalysts with lower activity temperatures range significantly reduces NH_(3)selective catalytic reduction(SCR)operating costs for low-temperature industrial flue gases.Herein,a novel FeVO_(4)/CeO_(...Developing deNO_(x)catalysts with lower activity temperatures range significantly reduces NH_(3)selective catalytic reduction(SCR)operating costs for low-temperature industrial flue gases.Herein,a novel FeVO_(4)/CeO_(2)catalyst with great low-temperature NH_(3)-SCR and nitrogen selectivity was synthesized using a dipping method.Characterization techniques such as X-ray diffraction,Raman spectroscopy,specific surface and porosity analysis,H2 temperature-programmed reduction,NH_(3)temperature-programmed desorption,X-ray photoelectron spectroscopy,and the in situ diffused reflectance infrared Fourier transform spectroscopy were used to investigate the catalytic mechanism.An appropriate addition for FeVO_(4)in the catalyst was 5 wt.%from the results,and the active substance content reached the maximum dispersal capacity of the carrier.The NO_(x)conversion exceeded 90%,and the nitrogen selectivity was more than 98%over this catalyst at 200–350°C.The activity was kept at 88%after 7.5 h of reaction at 200°C for 7.5 h in 35 mg m^(-3)SO_(2)gas.The remarkable deNO_(x)activity,nitrogen selectivity,and sulphur resistance performances are attributed to the low redox temperature,the abundance of medium-strong acid and strong acid sites,the sufficient adsorbed oxygen,and the superior Fe^(2+)content on the surface.The Langmuir–Hinshelwood mechanism was observed on the FeVO_(4)/CeO_(2)catalyst in the NH_(3)selective catalytic reduction of NO_(x).展开更多
CeO2 was synthesized via sol-gel process and used as supporter to prepare CuO/CeO2, Cu/CeO2 catalysts by impregnation method. The catalytic properties and characterization of CeO2, CuO/CeO2 and Cu/CeO2 catalysts were ...CeO2 was synthesized via sol-gel process and used as supporter to prepare CuO/CeO2, Cu/CeO2 catalysts by impregnation method. The catalytic properties and characterization of CeO2, CuO/CeO2 and Cu/CeO2 catalysts were examined by means of a microreactor-GC system, HRTEM, XRD, TPR and XPS techniques. The results show that CuO has not catalytic activity and the activity of CeO2 is quite low for CO oxidation. However, the catalytic activity of CuO/CeO2 and Cu/ CeO2 catalysts increases significantly. Furthermore, the activity of CuO/CeO2 is higher than that of Cu/CeO2 catalysts.展开更多
Cu/CeO2-ZrO2 catalysts for water-gas shift （WGS） reaction were prepared with co-precipitation method, and the influence of ZrO2 content on the catalytic structure and properties was investigated by the techniques of...Cu/CeO2-ZrO2 catalysts for water-gas shift （WGS） reaction were prepared with co-precipitation method, and the influence of ZrO2 content on the catalytic structure and properties was investigated by the techniques of N2 physical adsorption analysis, XRD and H2-TPR. The results indicate that the BET surface areas of the catalysts are increased in varying degrees due to the presence of ZrO2. With increasing ZrO2 content, the pore size distribution is centered on 1.9 nm. ZrO2 can efficiently restrain the growth of Cu crystal particles. The appropriate amount of ZrO2 in the Cu/CeO2 catalysts can help the catalyst keep better copper dispersion in the WGS reaction, which can lead to both higher catalytic activity and better thermal stability. When ZrO2 content is 10% （atom fraction）, Cu/CeO2-Zr02 catalyst reaches a CO conversion rate of 73.7% at the reaction temperature of 200℃.展开更多
气氛环境下原位研究催化剂的烧结行为,能够为理解催化剂在预处理以及反应条件下的烧结机理和高稳定催化剂的设计提供重要的实验依据。本文以Au/CeO_(2)模型纳米催化剂为研究对象,利用环境透射电子显微镜原位观察其在O_(2)与CO气氛下的...气氛环境下原位研究催化剂的烧结行为,能够为理解催化剂在预处理以及反应条件下的烧结机理和高稳定催化剂的设计提供重要的实验依据。本文以Au/CeO_(2)模型纳米催化剂为研究对象,利用环境透射电子显微镜原位观察其在O_(2)与CO气氛下的高温动态烧结过程。实验发现,负载在CeO_(2)上的Au纳米颗粒在O_(2)与CO气氛环境中表现出不同的烧结行为,其在O_(2)气氛下具有较高的烧结速度,同时存在颗粒迁移与聚集长大(particle migration and coalescence,PMC)和奥斯特瓦尔德熟化(Ostwald ripening,OR)两种烧结过程;在CO气氛下烧结速度较慢,烧结过程以OR为主。对比不同气氛环境下烧结后催化剂的表面结构可知,CO增加了CeO_(2)表面台阶的数量以及表面氧空位浓度,增强了载体对Au颗粒的锚定作用,从而提升Au/CeO_(2)催化剂的稳定性。展开更多
基金supported by the Nature Science Foundation of China(Grant 22262006,22068009)the Supported by Guizhou Provincial Science and Technology Projects(ZK[2023]ordinary 050,[2023]General 403)+4 种基金the Science and Technology Support Plan Projects of Guizhou Province(Grant(2018)2192)the Scientific and Technological Innovation Talents Team of Guizhou(2018-5607)the Science and Technology Foundation of Guizhou Province(20177254)the One hundred Person Project of Guizhou Province(No.20165655)the Innovation Group Project of Education Department in Guizhou Province(No.2021010)。
文摘The size of the nanoparticles and the number of oxygen vacancies have a significant effect on the catalytic activity of copper-based catalysts used for the synthesis of methanol from syngas.In this study,the authors prepared a series of catalysts CuO/ZnO/Al_(2)O_(3)/CeO_(2)(CZAC)with CuO particles of different sizes and varying number of oxygen vacancies on the surface by changing the added volume of CeO2 by using the co-precipitation method.The properties of the catalysts were characterized and their activity was evaluated by using high-pressure fixed-bed reaction equipment.The results showed that the addition of CeO_(2)to CuO/ZnO/Al_(2)O_(3)not only influenced the size of the CuO particles and metal-metal interactions,but also had an effect on the concentrations of oxygen vacancies and strongly basic sites.The presence of CuO particles of small sizes and a large numbers of oxygen vacancies on the surface of the catalyst were beneficial to its activity for the synthesis of methanol.The catalyst CZAC,when modified by 5%of CeO_(2),recorded CuO particles of the smallest size(8.9 nm),strong intermetallic interactions,and the highest concentrations of oxygen vacancies and strongly basic sites.It also exhibited the highest catalytic activity,with a space-time yield of methanol of 0.315 g/(h·g)that was higher than that of the enterprise RK-5 catalyst[0.215 g/(h·g)].
基金supported by the National Natural Science Foundation of China(52204332 and 52174290)the Outstanding Youth Fund of Anhui Province(2208085J19)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(21KJB450002).
文摘Developing deNO_(x)catalysts with lower activity temperatures range significantly reduces NH_(3)selective catalytic reduction(SCR)operating costs for low-temperature industrial flue gases.Herein,a novel FeVO_(4)/CeO_(2)catalyst with great low-temperature NH_(3)-SCR and nitrogen selectivity was synthesized using a dipping method.Characterization techniques such as X-ray diffraction,Raman spectroscopy,specific surface and porosity analysis,H2 temperature-programmed reduction,NH_(3)temperature-programmed desorption,X-ray photoelectron spectroscopy,and the in situ diffused reflectance infrared Fourier transform spectroscopy were used to investigate the catalytic mechanism.An appropriate addition for FeVO_(4)in the catalyst was 5 wt.%from the results,and the active substance content reached the maximum dispersal capacity of the carrier.The NO_(x)conversion exceeded 90%,and the nitrogen selectivity was more than 98%over this catalyst at 200–350°C.The activity was kept at 88%after 7.5 h of reaction at 200°C for 7.5 h in 35 mg m^(-3)SO_(2)gas.The remarkable deNO_(x)activity,nitrogen selectivity,and sulphur resistance performances are attributed to the low redox temperature,the abundance of medium-strong acid and strong acid sites,the sufficient adsorbed oxygen,and the superior Fe^(2+)content on the surface.The Langmuir–Hinshelwood mechanism was observed on the FeVO_(4)/CeO_(2)catalyst in the NH_(3)selective catalytic reduction of NO_(x).
基金Projected supported by the National Natural Science Foundation of China (20271028) and Tianjin Natural Science Foundation(033602511)
文摘CeO2 was synthesized via sol-gel process and used as supporter to prepare CuO/CeO2, Cu/CeO2 catalysts by impregnation method. The catalytic properties and characterization of CeO2, CuO/CeO2 and Cu/CeO2 catalysts were examined by means of a microreactor-GC system, HRTEM, XRD, TPR and XPS techniques. The results show that CuO has not catalytic activity and the activity of CeO2 is quite low for CO oxidation. However, the catalytic activity of CuO/CeO2 and Cu/ CeO2 catalysts increases significantly. Furthermore, the activity of CuO/CeO2 is higher than that of Cu/CeO2 catalysts.
文摘Cu/CeO2-ZrO2 catalysts for water-gas shift （WGS） reaction were prepared with co-precipitation method, and the influence of ZrO2 content on the catalytic structure and properties was investigated by the techniques of N2 physical adsorption analysis, XRD and H2-TPR. The results indicate that the BET surface areas of the catalysts are increased in varying degrees due to the presence of ZrO2. With increasing ZrO2 content, the pore size distribution is centered on 1.9 nm. ZrO2 can efficiently restrain the growth of Cu crystal particles. The appropriate amount of ZrO2 in the Cu/CeO2 catalysts can help the catalyst keep better copper dispersion in the WGS reaction, which can lead to both higher catalytic activity and better thermal stability. When ZrO2 content is 10% （atom fraction）, Cu/CeO2-Zr02 catalyst reaches a CO conversion rate of 73.7% at the reaction temperature of 200℃.
文摘气氛环境下原位研究催化剂的烧结行为,能够为理解催化剂在预处理以及反应条件下的烧结机理和高稳定催化剂的设计提供重要的实验依据。本文以Au/CeO_(2)模型纳米催化剂为研究对象,利用环境透射电子显微镜原位观察其在O_(2)与CO气氛下的高温动态烧结过程。实验发现,负载在CeO_(2)上的Au纳米颗粒在O_(2)与CO气氛环境中表现出不同的烧结行为,其在O_(2)气氛下具有较高的烧结速度,同时存在颗粒迁移与聚集长大(particle migration and coalescence,PMC)和奥斯特瓦尔德熟化(Ostwald ripening,OR)两种烧结过程;在CO气氛下烧结速度较慢,烧结过程以OR为主。对比不同气氛环境下烧结后催化剂的表面结构可知,CO增加了CeO_(2)表面台阶的数量以及表面氧空位浓度,增强了载体对Au颗粒的锚定作用,从而提升Au/CeO_(2)催化剂的稳定性。
