Gold catalysts supported on Mg-Al mixed oxides for oxidative esterification of methacrolein are prepared by impregnation.Effects of the support particle size,concentration of HAuCl4 solution and Mg/Al ratio on gold lo...Gold catalysts supported on Mg-Al mixed oxides for oxidative esterification of methacrolein are prepared by impregnation.Effects of the support particle size,concentration of HAuCl4 solution and Mg/Al ratio on gold loading and catalytic properties are investigated.The catalysts are characterized by CO_(2)-TPD,EDS,XPS,STEM and XRD techniques.Catalysts with smaller support particle size show more uniform gold distribution and higher gold dispersion,resulting in a higher catalytic performance,and the uniformity of gold and the activity of the catalysts with larger support particle size can be improved by decreasing the concentration of HAuCl4 solution.The Mg/Al molar ratio has significant effect on the uniformity of gold and the activity of the catalyst,and the optimum Mg/Al molar ratio is 0.1–0.2.This study underlines the importance of engineering support particle size,concentration of HAuCl4 solution and density of adsorption sites for efficient gold loading on support by impregnation.展开更多
The ditheion coefficients(Dapp) and the heterogeneous electron-transfer rate constan(ks)for ferrocene in MPEG/salt electrolytes were determined by using Steady-stae voltammetry. The temperature dependence of the two p...The ditheion coefficients(Dapp) and the heterogeneous electron-transfer rate constan(ks)for ferrocene in MPEG/salt electrolytes were determined by using Steady-stae voltammetry. The temperature dependence of the two parameters obeys the Arrhenius equstion. The effect of the ionic size of sir supporting electrolytes on diffusion and electron transfer dynamics of fermcene was discussed展开更多
The deactivation behavior by crystallite growth of nickel nanoparticles on various supports（carbon nanofibers, zirconia, Si C, α-Al2O3 and γ-Al2O3） was investigated in the aqueous phase reforming of ethylene glyco...The deactivation behavior by crystallite growth of nickel nanoparticles on various supports（carbon nanofibers, zirconia, Si C, α-Al2O3 and γ-Al2O3） was investigated in the aqueous phase reforming of ethylene glycol. Supported Ni catalysts of ~10 wt% were prepared by impregnation of carbon nanofibers（CNF）,Zr O2, SiC, γ-Al2O3 and α-Al2O3. The extent of the Ni nanoparticle growth on various support materials follows the order CNF ~ ZrO2〉 SiC 〉 γ-Al2O3〉〉 α-Al2O3 which sequence, however, was determined by the initial Ni particle size. Based on the observed nickel leaching and the specific growth characteristics; the particle size distribution and the effect of loading on the growth rate, Ostwald ripening is suggested to be the main mechanism contributing to nickel particle growth. Remarkably, initially smaller Ni particles（~12 nm） supported on α-Al2O3 were found to outgrow Ni particles with initially larger size（~20 nm）. It is put forward that the higher susceptibility with respect to oxidation of the smaller Ni nanoparticles and differences in initial particle size distribution are responsible for this behavior.展开更多
Traditional classification algorithms perform not very well on imbalanced data sets and small sample size. To deal with the problem, a novel method is proposed to change the class distribution through adding virtual s...Traditional classification algorithms perform not very well on imbalanced data sets and small sample size. To deal with the problem, a novel method is proposed to change the class distribution through adding virtual samples, which are generated by the windowed regression over-sampling (WRO) method. The proposed method WRO not only reflects the additive effects but also reflects the multiplicative effect between samples. A comparative study between the proposed method and other over-sampling methods such as synthetic minority over-sampling technique (SMOTE) and borderline over-sampling (BOS) on UCI datasets and Fourier transform infrared spectroscopy (FTIR) data set is provided. Experimental results show that the WRO method can achieve better performance than other methods.展开更多
Interactions between metals and supports are of fundamental interest in heterogeneous catalysis, Noble metal particles supported on transition metal oxides (TMO) may undergo a so-called strong metal-support interactio...Interactions between metals and supports are of fundamental interest in heterogeneous catalysis, Noble metal particles supported on transition metal oxides (TMO) may undergo a so-called strong metal-support interaction via encapsulation. This perspective addresses catalytic properties of the metal catalysts in the SMSI state which can be explained on the basis of complementary studies. The electronic geometric and bifunctional effects originating from strong metal-support interactions (SMSI) that are responsible for the catalyst’s activity, selectivity, and stability are key factors that determine performance. A series of Pd-Sb supported on different metal oxide (<em>i.e.</em> SiO<sub>2</sub>, <em>γ</em>-Al<sub>2</sub>O<sub>3</sub>, TiO<sub>2</sub>, and ZrO<sub>2</sub>) were prepared by the impregnation method. The catalysts were characterized by N<sub>2</sub> adsorption (BET-SA and pore size distribution), TEM (transmission electron microscope), TPR (temperature-programmed reduction), CO-chemisorption, the structural characterization of Pd (dispersity, surface area), interaction between Pd and Sb<sub>2</sub>O<sub>3</sub> and also the influence of the nature of the support were investigated. SiO<sub>2</sub> supported Pd catalyst exhibited the highest surface area (192.6 m<sup>2</sup>/g) and pore volume (0.542 cm<sup>3</sup>/g) compared to the other supported oxides catalysts. The electron micrographs of these catalysts showed a narrow size particle distribution of Pd, but with varying sizes which in the range from 1 to 10 nm, depending on the type of support used. The results show almost completely suppressed of CO chemisorption when the catalysts were subjected to high temperature reduction (HTR), this suppression was overcome by oxidation of a reduced Pd/MeOx catalysts followed by re-reduction in hydrogen at 453 K low temperature reduction (LTR), almost completely restored the normal chemisorptive properties of the catalysts, this suppression was attributed by SbOx species by a typical SMSI effect as known for other reducible supports such as TiO<sub>2</sub>, ZrO<sub>2</sub>, CeO<sub>2</sub>, and Nb<sub>2</sub>O<sub>5</sub>.展开更多
基金Open Project of Yunnan Precious Metals Laboratory Co.,Ltd(YPML-2023050269)the Fundamental Research Funds for the Central Universities(226-2023-00085,226-2023-00057).
文摘Gold catalysts supported on Mg-Al mixed oxides for oxidative esterification of methacrolein are prepared by impregnation.Effects of the support particle size,concentration of HAuCl4 solution and Mg/Al ratio on gold loading and catalytic properties are investigated.The catalysts are characterized by CO_(2)-TPD,EDS,XPS,STEM and XRD techniques.Catalysts with smaller support particle size show more uniform gold distribution and higher gold dispersion,resulting in a higher catalytic performance,and the uniformity of gold and the activity of the catalysts with larger support particle size can be improved by decreasing the concentration of HAuCl4 solution.The Mg/Al molar ratio has significant effect on the uniformity of gold and the activity of the catalyst,and the optimum Mg/Al molar ratio is 0.1–0.2.This study underlines the importance of engineering support particle size,concentration of HAuCl4 solution and density of adsorption sites for efficient gold loading on support by impregnation.
文摘The ditheion coefficients(Dapp) and the heterogeneous electron-transfer rate constan(ks)for ferrocene in MPEG/salt electrolytes were determined by using Steady-stae voltammetry. The temperature dependence of the two parameters obeys the Arrhenius equstion. The effect of the ionic size of sir supporting electrolytes on diffusion and electron transfer dynamics of fermcene was discussed
基金the support of the Smart Mix Program of The Netherlands Ministry of Economic Affairs, Agriculture and Innovation and The Netherlands Ministry of Education, Culture and Science (Grant no. 053.70.011)
文摘The deactivation behavior by crystallite growth of nickel nanoparticles on various supports（carbon nanofibers, zirconia, Si C, α-Al2O3 and γ-Al2O3） was investigated in the aqueous phase reforming of ethylene glycol. Supported Ni catalysts of ~10 wt% were prepared by impregnation of carbon nanofibers（CNF）,Zr O2, SiC, γ-Al2O3 and α-Al2O3. The extent of the Ni nanoparticle growth on various support materials follows the order CNF ~ ZrO2〉 SiC 〉 γ-Al2O3〉〉 α-Al2O3 which sequence, however, was determined by the initial Ni particle size. Based on the observed nickel leaching and the specific growth characteristics; the particle size distribution and the effect of loading on the growth rate, Ostwald ripening is suggested to be the main mechanism contributing to nickel particle growth. Remarkably, initially smaller Ni particles（~12 nm） supported on α-Al2O3 were found to outgrow Ni particles with initially larger size（~20 nm）. It is put forward that the higher susceptibility with respect to oxidation of the smaller Ni nanoparticles and differences in initial particle size distribution are responsible for this behavior.
文摘Traditional classification algorithms perform not very well on imbalanced data sets and small sample size. To deal with the problem, a novel method is proposed to change the class distribution through adding virtual samples, which are generated by the windowed regression over-sampling (WRO) method. The proposed method WRO not only reflects the additive effects but also reflects the multiplicative effect between samples. A comparative study between the proposed method and other over-sampling methods such as synthetic minority over-sampling technique (SMOTE) and borderline over-sampling (BOS) on UCI datasets and Fourier transform infrared spectroscopy (FTIR) data set is provided. Experimental results show that the WRO method can achieve better performance than other methods.
文摘Interactions between metals and supports are of fundamental interest in heterogeneous catalysis, Noble metal particles supported on transition metal oxides (TMO) may undergo a so-called strong metal-support interaction via encapsulation. This perspective addresses catalytic properties of the metal catalysts in the SMSI state which can be explained on the basis of complementary studies. The electronic geometric and bifunctional effects originating from strong metal-support interactions (SMSI) that are responsible for the catalyst’s activity, selectivity, and stability are key factors that determine performance. A series of Pd-Sb supported on different metal oxide (<em>i.e.</em> SiO<sub>2</sub>, <em>γ</em>-Al<sub>2</sub>O<sub>3</sub>, TiO<sub>2</sub>, and ZrO<sub>2</sub>) were prepared by the impregnation method. The catalysts were characterized by N<sub>2</sub> adsorption (BET-SA and pore size distribution), TEM (transmission electron microscope), TPR (temperature-programmed reduction), CO-chemisorption, the structural characterization of Pd (dispersity, surface area), interaction between Pd and Sb<sub>2</sub>O<sub>3</sub> and also the influence of the nature of the support were investigated. SiO<sub>2</sub> supported Pd catalyst exhibited the highest surface area (192.6 m<sup>2</sup>/g) and pore volume (0.542 cm<sup>3</sup>/g) compared to the other supported oxides catalysts. The electron micrographs of these catalysts showed a narrow size particle distribution of Pd, but with varying sizes which in the range from 1 to 10 nm, depending on the type of support used. The results show almost completely suppressed of CO chemisorption when the catalysts were subjected to high temperature reduction (HTR), this suppression was overcome by oxidation of a reduced Pd/MeOx catalysts followed by re-reduction in hydrogen at 453 K low temperature reduction (LTR), almost completely restored the normal chemisorptive properties of the catalysts, this suppression was attributed by SbOx species by a typical SMSI effect as known for other reducible supports such as TiO<sub>2</sub>, ZrO<sub>2</sub>, CeO<sub>2</sub>, and Nb<sub>2</sub>O<sub>5</sub>.
