Synthesis of acetic acid by direct oxidation of ethylene on Pd-H4SiW12O40-based catalysts was studied in a fixed-bed integral reactor and a pulse differential reactor. From the performance of the catalysts with differ...Synthesis of acetic acid by direct oxidation of ethylene on Pd-H4SiW12O40-based catalysts was studied in a fixed-bed integral reactor and a pulse differential reactor. From the performance of the catalysts with different compositions and configurations, it is proposed that acetic acid is predominantly produced via an intermediate of acetaldehyde. This can be easily confirmed by comparing the product distributions in the integral and the differential reactors. The active sites for acetic acid formation are considered to exist mainly at the boundaries between the H4SiW12O40 and the Pd particles. The Pd-based catalysts reduced by H2/N2 have higher activities than those reduced by hydrazine, as explained by the degree of Pd dispersion obtained from the characteristics of hydrogen chemical adsorption. It was found that the Pd-Se-SiW12/SiO2 catalyst with selenium tetrachloride as a precursor was more active than that with potassium selenite, and that the acetic acid yield can be greatly increased by adding a suitable amount of dichloroethane (C2H4C12/C2H4 mole ratio=0.03) to the reactants.展开更多
通过阳极化处理玻碳电极,吸附法制备H_(3)PMo_(12)O_(40)修饰电极,研究H_(3)PMo_(12)O_(40)修饰电极在不同支持电解质、扫描速度下对酪氨酸酶的电化学传感。结果表明:以0.1 mol/L H 2 SO 4为支持电解质效果最佳,超纯水效果最差,并且该...通过阳极化处理玻碳电极,吸附法制备H_(3)PMo_(12)O_(40)修饰电极,研究H_(3)PMo_(12)O_(40)修饰电极在不同支持电解质、扫描速度下对酪氨酸酶的电化学传感。结果表明:以0.1 mol/L H 2 SO 4为支持电解质效果最佳,超纯水效果最差,并且该电化学反应属于表面与扩散的共同控制过程;在温和条件下,V(0.1 mol/L H 2 SO 4)∶V(0.5 mol/L Na 2 SO 4)=2∶8混合溶液作为支持电解质,该多酸修饰电极在100 mV/s扫描速度下对酪氨酸酶具有良好的催化作用,氧化还原峰明显,检出限(S/N=3)达15.76 U/mL。展开更多
4,6-Diarylpyrimidin-2(1H)-one derivatives have been synthesized from three-component one-pot condensation of acetophe-none derivatives,aldehydes and urea in the presence of trimethylsilyl chloride and a catalytic amou...4,6-Diarylpyrimidin-2(1H)-one derivatives have been synthesized from three-component one-pot condensation of acetophe-none derivatives,aldehydes and urea in the presence of trimethylsilyl chloride and a catalytic amount of HPMoOunder solvent-free conditions.展开更多
Novel spiro[dibenzo[a,i]xanthene-14,3＇-indoline]-2＇,8,13-triones were prepared by the three-component reaction ofβ-naphthol, isatins,and 2-hydroxy-1,4-naphoquinone in the presence of a catalytic amount of H_4SiW_...Novel spiro[dibenzo[a,i]xanthene-14,3＇-indoline]-2＇,8,13-triones were prepared by the three-component reaction ofβ-naphthol, isatins,and 2-hydroxy-1,4-naphoquinone in the presence of a catalytic amount of H_4SiW_（12）O_（40）.This protocol provides a simple one-step procedure with the advantages of easy work-up,mild reaction conditions and environmentally benign.展开更多
A novel solid Bronsted-Lewis acid catalyst La-PW-SiO_(2)/SWCNTs(single-wall carbon nanotubes)was synthesized from the synergistic modification of H_(3)PW_(12)O_(40)(HPW)by single-walled carbon nanotubes functionalized...A novel solid Bronsted-Lewis acid catalyst La-PW-SiO_(2)/SWCNTs(single-wall carbon nanotubes)was synthesized from the synergistic modification of H_(3)PW_(12)O_(40)(HPW)by single-walled carbon nanotubes functionalized with sidewall hydroxyl groups(SWCNTs–OH)and La^(3+) via sol–gel method.The freshly prepared catalyst was characterized by several methods,and the catalytic activity and stability of it were studied from the esterification of oleic acid and methanol.Results showed that the highest conversion of oleic acid was 93.1%(mass)and maintained as high as 88.7%(mass)after six cycles of La-PW-SiO_(2)/SWCNTs.The high catalytic activity and stability of La-PW-SiO_(2)/SWCNTs can be attributed to the strong electron withdrawing effect of La^(3+) on π bond of SWCNTs,because it can facilitate the formation of a large number of strong Lewis acid sites.Therefore,the reduction of catalytic activity of a solid acid catalyst due to the fact that hydration reaction of its Bronsted acid sites can be effectively reduced.La-PW-SiO_(2)/SWCNTs can be an efficient and economical catalyst,because it shows good catalytic activity and stability.展开更多
文摘Synthesis of acetic acid by direct oxidation of ethylene on Pd-H4SiW12O40-based catalysts was studied in a fixed-bed integral reactor and a pulse differential reactor. From the performance of the catalysts with different compositions and configurations, it is proposed that acetic acid is predominantly produced via an intermediate of acetaldehyde. This can be easily confirmed by comparing the product distributions in the integral and the differential reactors. The active sites for acetic acid formation are considered to exist mainly at the boundaries between the H4SiW12O40 and the Pd particles. The Pd-based catalysts reduced by H2/N2 have higher activities than those reduced by hydrazine, as explained by the degree of Pd dispersion obtained from the characteristics of hydrogen chemical adsorption. It was found that the Pd-Se-SiW12/SiO2 catalyst with selenium tetrachloride as a precursor was more active than that with potassium selenite, and that the acetic acid yield can be greatly increased by adding a suitable amount of dichloroethane (C2H4C12/C2H4 mole ratio=0.03) to the reactants.
文摘通过阳极化处理玻碳电极,吸附法制备H_(3)PMo_(12)O_(40)修饰电极,研究H_(3)PMo_(12)O_(40)修饰电极在不同支持电解质、扫描速度下对酪氨酸酶的电化学传感。结果表明:以0.1 mol/L H 2 SO 4为支持电解质效果最佳,超纯水效果最差,并且该电化学反应属于表面与扩散的共同控制过程;在温和条件下,V(0.1 mol/L H 2 SO 4)∶V(0.5 mol/L Na 2 SO 4)=2∶8混合溶液作为支持电解质,该多酸修饰电极在100 mV/s扫描速度下对酪氨酸酶具有良好的催化作用,氧化还原峰明显,检出限(S/N=3)达15.76 U/mL。
基金Islamic Azad University of Khorram Abad Council for the financial support
文摘4,6-Diarylpyrimidin-2(1H)-one derivatives have been synthesized from three-component one-pot condensation of acetophe-none derivatives,aldehydes and urea in the presence of trimethylsilyl chloride and a catalytic amount of HPMoOunder solvent-free conditions.
基金the financial support from Xinxiang Medical University
文摘Novel spiro[dibenzo[a,i]xanthene-14,3＇-indoline]-2＇,8,13-triones were prepared by the three-component reaction ofβ-naphthol, isatins,and 2-hydroxy-1,4-naphoquinone in the presence of a catalytic amount of H_4SiW_（12）O_（40）.This protocol provides a simple one-step procedure with the advantages of easy work-up,mild reaction conditions and environmentally benign.
基金supported by the National Natural Science Foundation of China(21766009)Program of Qingjiang Excellent Young Talents(Jiangxi University of Science and Technology)。
文摘A novel solid Bronsted-Lewis acid catalyst La-PW-SiO_(2)/SWCNTs(single-wall carbon nanotubes)was synthesized from the synergistic modification of H_(3)PW_(12)O_(40)(HPW)by single-walled carbon nanotubes functionalized with sidewall hydroxyl groups(SWCNTs–OH)and La^(3+) via sol–gel method.The freshly prepared catalyst was characterized by several methods,and the catalytic activity and stability of it were studied from the esterification of oleic acid and methanol.Results showed that the highest conversion of oleic acid was 93.1%(mass)and maintained as high as 88.7%(mass)after six cycles of La-PW-SiO_(2)/SWCNTs.The high catalytic activity and stability of La-PW-SiO_(2)/SWCNTs can be attributed to the strong electron withdrawing effect of La^(3+) on π bond of SWCNTs,because it can facilitate the formation of a large number of strong Lewis acid sites.Therefore,the reduction of catalytic activity of a solid acid catalyst due to the fact that hydration reaction of its Bronsted acid sites can be effectively reduced.La-PW-SiO_(2)/SWCNTs can be an efficient and economical catalyst,because it shows good catalytic activity and stability.
