Product selectivity and reaction pathway are highly dependent on surface structure of heterogeneous catalysts.For vapor-phase hydrogenation of dimethyl oxalate(DMO),"EG route"(DMO→methyl glycolate(MG)ethyle...Product selectivity and reaction pathway are highly dependent on surface structure of heterogeneous catalysts.For vapor-phase hydrogenation of dimethyl oxalate(DMO),"EG route"(DMO→methyl glycolate(MG)ethylene glycol(EG)→ethanol(ET))and"MA route"(DMO→MG→methyl acetate(MA))were proposed over traditional Cu based catalysts and Mo-based or Fe-based catalysts,respectively.Herein,tunable yield of ET(93.7%)and MA(72.1%)were obtained through different reaction routes over WO_(x) modified Cu/SiO_(2) catalysts,and the corresponding reaction route was further proved by kinetic study and in-situ DRIFTS technology.Mechanistic studies demonstrated that H_(2) activation ability,acid density and Cu-WO_(x) interaction on the catalysts were tuned by regulating the surface W density,which resulted in the different reaction pathway and product selectivity.What's more,high yield of MA produced from DMO hydrogenation was firstly reported with the H_(2) pressure as low as 0.5 MPa.展开更多
Catalytic upgrading of bio-ethanol to 1,3-butadiene(1,3-BD,ETB)is a renewable and low-carbon technology for the bulk chemical production.Exploring robust catalysts and getting in-depth understanding of the relationshi...Catalytic upgrading of bio-ethanol to 1,3-butadiene(1,3-BD,ETB)is a renewable and low-carbon technology for the bulk chemical production.Exploring robust catalysts and getting in-depth understanding of the relationship between the structure of catalytic sites and reaction selectivity are of great significance for ETB process applications.In this study,we constructed a robust Cu-Zr/SiO_(2) catalyst by an ammonia evaporation and post-impregnation method.Over the optimal 2%Cu-8%Zr/SiO_(2) catalyst,superior performance of 69.6%1,3-BD selectivity and 71.2%ethanol conversion were obtained.Systematic characterizations revealed that three types of Cu-Zr-Si active sites were probably constructed on the Cu-8%Zr/SiO_(2) catalysts as varying the Cu loadings from 0.5 to 20%,affording greatly different activity and selectivity in the ETB process.The 1,3-BD productivity over the(SiO)_(2)(CuO)Zr-OH sites was 8.2 and 77.2 times higher than that of(CuO)_(2)-Zr-(OSi)2 and Cu-(O)_(2)-Zr-(OSi)2 sites,respectively,attributed to the high activities and good balance among the reactions of dehydrogenation,aldol condensation,and MPVO reduction.展开更多
In situ quick X-ray absorption spectroscopy(QXAFS) at the Cu and Zn K-edge under operando conditions has been used to unravel the Cu/Zn interaction and identify possible active site of CuO/ZnO/Al_2O_3 catalyst for met...In situ quick X-ray absorption spectroscopy(QXAFS) at the Cu and Zn K-edge under operando conditions has been used to unravel the Cu/Zn interaction and identify possible active site of CuO/ZnO/Al_2O_3 catalyst for methanol synthesis. In this work, the catalyst, whose activity increases with the reaction temperature and pressure, was studied at calcined, reduced, and reacted conditions. TEM and EDX images for the calcined and reduced catalysts showed that copper was distributed uniformly at both conditions. TPR profile revealed two reduction peaks at 165 and 195 °C for copper species in the calcined catalyst. QXAFS results demonstrated that the calcined form consisted mainly of a mixed Cu O and Zn O, and it was progressively transformed into Cu metal particles and dispersed Zn O species as the reduction treatment. It was demonstrated that activation of the catalyst precursor occurred via a Cu^+intermediate, and the active catalyst predominantly consisted of metallic Cu and Zn O evenunder higher pressures. Structure of the active catalyst did not change with the temperature or pressure, indicating that the role of the Zn was mainly to improve Cu dispersion.This indicates the potential of QXAFS method in studying the structure evolutions of catalysts in methanol synthesis.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
Nanometer SnO2 particles were synthesized by sol-gel dialytic processes and used as a support to prepare CuO supported catalysts via a deposition-precipitation method. The samples were characterized by means of TG-DTA...Nanometer SnO2 particles were synthesized by sol-gel dialytic processes and used as a support to prepare CuO supported catalysts via a deposition-precipitation method. The samples were characterized by means of TG-DTA, XRD, H2-TPR and XPS. The catalytic activity of the CuO/TiO2-SnO2 catalysts was markedly depended on the loading of CuO, and the optimum CuO loading was 8 wt.% （Tloo = 80 ℃）. The CuO/TiO2-SnO2 catalysts exhibited much higher catalytic activity than the CuO/TiO2 and CuO/SnO2 catalysts. H2-TPR result indicated that a large amount of CuO formed the active site for CO oxidation in 8 wt.% CuO/TiO2-SnO2 catalyst.展开更多
The CuO/γ-Al2O3/cordierite catalyst, after being sulfated by sulfur dioxide (SO2) at 673 K, exhibits high activities for selective catalytic reduction (SCR) of nitrogen oxide (NO) with ammonia (NH3) at 573-723 K. The...The CuO/γ-Al2O3/cordierite catalyst, after being sulfated by sulfur dioxide (SO2) at 673 K, exhibits high activities for selective catalytic reduction (SCR) of nitrogen oxide (NO) with ammonia (NH3) at 573-723 K. The intrinsic kinetics of SCR of NO with NH3 over CuO/γ-Al2O3/cordierite catalyst has been measured in a fixed-bed reactor in the absence of internal and external diffusions. The experimental results show that the reaction rate can be quantified by a first-order expression with activation energy Eá of 94.01 kJ·mol-1 and the corresponding p re-exponential factor A′ of 3.39×108 cm3·g-1·s-1 when NH3 is excessive. However, when NH3 is not enough, an E ley-Rideal kinetic model based on experimental data is derived with Ea of 105.79 kJ·mol-1, the corresponding A of 2 .94×109 cm3·g-1·s-1, heat of adsorption-Hads of 87.90 kJ·mol-1 and the corresponding Aads of 9.24 cm3·mol-1. The intrinsic kinetic model obtained was incorporated in a 3D mathematical model of monolithic reactor, and the agreement of the prediction with experimental data indicates that the present kinetic model is adequate for the reac-tor design and engineering scale-up.展开更多
Three series of CeO2/CuO samples were prepared by impregnation method and characterized by XRD, N2 adsorption-desorption, temperatureprogrammed reduction （TPR）, XPS and TEM techniques. In comparison with the samples...Three series of CeO2/CuO samples were prepared by impregnation method and characterized by XRD, N2 adsorption-desorption, temperatureprogrammed reduction （TPR）, XPS and TEM techniques. In comparison with the samples prepared with CuO as initial support, the samples with Cu（OH）2 as initial support have higher reducibilities and smaller relative TPR peak areas, and also larger specific surface areas at calcina- tion temperatures of 400 ℃--600 ℃. As a result, Cu（OH）2 is better than CuO as initial support for preferential oxidation of CO in excess H2 （CO-PROX）. The best catalytic performance was achieved on the sample calcined at 600 ℃ and with an atomic ratio of Ce/Cu at 40%. XPS analyses indicate that more interface linkages Ce-O-Cu could be formed when it was calcined at 600 ℃. And the atomic ratio of Ce/Cu at 40% led to a proper reducibility for the sample as illustrated by the TPR measurements.展开更多
基金supported by National Natural Science Foundation of China (No.22102147 and 22002151)State Key Laboratory of Chemical Engineering (No.SKL-ChE-22A02)+2 种基金Zhejiang Provincial Natural Science Foundation of China under Grant No.LQ21B030009the Strategic Priority Research Program of the Chinese Academy of Sciences (No.XDA29050300)Qinchuang Yuan high-level innovation and entrepreneurship talents implementing project (No.QCYRCXM-2022-177)。
文摘Product selectivity and reaction pathway are highly dependent on surface structure of heterogeneous catalysts.For vapor-phase hydrogenation of dimethyl oxalate(DMO),"EG route"(DMO→methyl glycolate(MG)ethylene glycol(EG)→ethanol(ET))and"MA route"(DMO→MG→methyl acetate(MA))were proposed over traditional Cu based catalysts and Mo-based or Fe-based catalysts,respectively.Herein,tunable yield of ET(93.7%)and MA(72.1%)were obtained through different reaction routes over WO_(x) modified Cu/SiO_(2) catalysts,and the corresponding reaction route was further proved by kinetic study and in-situ DRIFTS technology.Mechanistic studies demonstrated that H_(2) activation ability,acid density and Cu-WO_(x) interaction on the catalysts were tuned by regulating the surface W density,which resulted in the different reaction pathway and product selectivity.What's more,high yield of MA produced from DMO hydrogenation was firstly reported with the H_(2) pressure as low as 0.5 MPa.
基金supported by the National Natural Science Foundation of China(21721004,22108274)“Transformational Technologies for Clean Energy and Demonstration”Strategic Priority Research Program of the Chinese Academy of Sciences(XDA 21060200).
文摘Catalytic upgrading of bio-ethanol to 1,3-butadiene(1,3-BD,ETB)is a renewable and low-carbon technology for the bulk chemical production.Exploring robust catalysts and getting in-depth understanding of the relationship between the structure of catalytic sites and reaction selectivity are of great significance for ETB process applications.In this study,we constructed a robust Cu-Zr/SiO_(2) catalyst by an ammonia evaporation and post-impregnation method.Over the optimal 2%Cu-8%Zr/SiO_(2) catalyst,superior performance of 69.6%1,3-BD selectivity and 71.2%ethanol conversion were obtained.Systematic characterizations revealed that three types of Cu-Zr-Si active sites were probably constructed on the Cu-8%Zr/SiO_(2) catalysts as varying the Cu loadings from 0.5 to 20%,affording greatly different activity and selectivity in the ETB process.The 1,3-BD productivity over the(SiO)_(2)(CuO)Zr-OH sites was 8.2 and 77.2 times higher than that of(CuO)_(2)-Zr-(OSi)2 and Cu-(O)_(2)-Zr-(OSi)2 sites,respectively,attributed to the high activities and good balance among the reactions of dehydrogenation,aldol condensation,and MPVO reduction.
基金supported by the National Basic Research Program of China(973 Program,2013CB933104)the National Natural Science Foundation of China(Nos.11275258 and 11135008)
文摘In situ quick X-ray absorption spectroscopy(QXAFS) at the Cu and Zn K-edge under operando conditions has been used to unravel the Cu/Zn interaction and identify possible active site of CuO/ZnO/Al_2O_3 catalyst for methanol synthesis. In this work, the catalyst, whose activity increases with the reaction temperature and pressure, was studied at calcined, reduced, and reacted conditions. TEM and EDX images for the calcined and reduced catalysts showed that copper was distributed uniformly at both conditions. TPR profile revealed two reduction peaks at 165 and 195 °C for copper species in the calcined catalyst. QXAFS results demonstrated that the calcined form consisted mainly of a mixed Cu O and Zn O, and it was progressively transformed into Cu metal particles and dispersed Zn O species as the reduction treatment. It was demonstrated that activation of the catalyst precursor occurred via a Cu^+intermediate, and the active catalyst predominantly consisted of metallic Cu and Zn O evenunder higher pressures. Structure of the active catalyst did not change with the temperature or pressure, indicating that the role of the Zn was mainly to improve Cu dispersion.This indicates the potential of QXAFS method in studying the structure evolutions of catalysts in methanol synthesis.
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.
基金supported by the National Natural Science Foundation of China (20771061 and 20871071)the 973 Program (2005CB623607)Science and Technology Commission Foundation of Tianjin (08JCYBJC00100 and 09JCYBJC03600)
文摘Nanometer SnO2 particles were synthesized by sol-gel dialytic processes and used as a support to prepare CuO supported catalysts via a deposition-precipitation method. The samples were characterized by means of TG-DTA, XRD, H2-TPR and XPS. The catalytic activity of the CuO/TiO2-SnO2 catalysts was markedly depended on the loading of CuO, and the optimum CuO loading was 8 wt.% （Tloo = 80 ℃）. The CuO/TiO2-SnO2 catalysts exhibited much higher catalytic activity than the CuO/TiO2 and CuO/SnO2 catalysts. H2-TPR result indicated that a large amount of CuO formed the active site for CO oxidation in 8 wt.% CuO/TiO2-SnO2 catalyst.
基金Supported by the National Natural Science Foundation of China （20821004 20736001 21076008） the Research Fund for the Doctoral Program of Higher Education of China （2090010110002）
文摘The CuO/γ-Al2O3/cordierite catalyst, after being sulfated by sulfur dioxide (SO2) at 673 K, exhibits high activities for selective catalytic reduction (SCR) of nitrogen oxide (NO) with ammonia (NH3) at 573-723 K. The intrinsic kinetics of SCR of NO with NH3 over CuO/γ-Al2O3/cordierite catalyst has been measured in a fixed-bed reactor in the absence of internal and external diffusions. The experimental results show that the reaction rate can be quantified by a first-order expression with activation energy Eá of 94.01 kJ·mol-1 and the corresponding p re-exponential factor A′ of 3.39×108 cm3·g-1·s-1 when NH3 is excessive. However, when NH3 is not enough, an E ley-Rideal kinetic model based on experimental data is derived with Ea of 105.79 kJ·mol-1, the corresponding A of 2 .94×109 cm3·g-1·s-1, heat of adsorption-Hads of 87.90 kJ·mol-1 and the corresponding Aads of 9.24 cm3·mol-1. The intrinsic kinetic model obtained was incorporated in a 3D mathematical model of monolithic reactor, and the agreement of the prediction with experimental data indicates that the present kinetic model is adequate for the reac-tor design and engineering scale-up.
文摘Three series of CeO2/CuO samples were prepared by impregnation method and characterized by XRD, N2 adsorption-desorption, temperatureprogrammed reduction （TPR）, XPS and TEM techniques. In comparison with the samples prepared with CuO as initial support, the samples with Cu（OH）2 as initial support have higher reducibilities and smaller relative TPR peak areas, and also larger specific surface areas at calcina- tion temperatures of 400 ℃--600 ℃. As a result, Cu（OH）2 is better than CuO as initial support for preferential oxidation of CO in excess H2 （CO-PROX）. The best catalytic performance was achieved on the sample calcined at 600 ℃ and with an atomic ratio of Ce/Cu at 40%. XPS analyses indicate that more interface linkages Ce-O-Cu could be formed when it was calcined at 600 ℃. And the atomic ratio of Ce/Cu at 40% led to a proper reducibility for the sample as illustrated by the TPR measurements.
