以尿素为沉淀剂,采用均相沉淀法成功制备了层状Cu/Zn/Al水滑石化合物.将前驱体材料经焙烧、还原后得到Cu/ZnO/Al_2O_3催化剂,并将其用于CO_2加氢合成甲醇反应.采用X射线衍射(X-ray diffraction,XRD)、热重(thermogravimetric,TG)分析、...以尿素为沉淀剂,采用均相沉淀法成功制备了层状Cu/Zn/Al水滑石化合物.将前驱体材料经焙烧、还原后得到Cu/ZnO/Al_2O_3催化剂,并将其用于CO_2加氢合成甲醇反应.采用X射线衍射(X-ray diffraction,XRD)、热重(thermogravimetric,TG)分析、扫描电镜(scanning electron microscope,SEM)、X射线荧光(X-ray fluorescence,XRF)分析、N_2吸附、H_2程序升温还原(H_2-temperature program reduction,H_2-TPR)、氧化亚氮(N_2O)反应吸附、CO_2程序升温脱附(CO_2-temperature program desorption,CO_2-TPD)技术对所制备的样品进行表征.结果表明,相对于传统共沉淀法,以尿素作为沉淀剂,通过均相沉淀法所制备的前驱体的结晶度更高、催化剂比表面积更大、金属Cu的分散度更好.另外,采用回流处理可以获得更好的效果.活性评估结果表明,O_2转化率随金属Cu比表面积的增大而增加,而甲醇选择性则与催化剂表面碱性位的分布有关.因此,采用尿素回流处理均相沉淀法制备的Cu/ZnO/Al_2O_3催化剂的甲醇收率最高.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
An effective catalytic transfer hydrogenation (CTH) process of bio-based levulinate esters into γ-valerolactone (GVL) was explored over ternary Cu/ZnO/Al2O3 catalyst which was prepared by coprecipitation method and c...An effective catalytic transfer hydrogenation (CTH) process of bio-based levulinate esters into γ-valerolactone (GVL) was explored over ternary Cu/ZnO/Al2O3 catalyst which was prepared by coprecipitation method and could be sustainably used. As a result, quantitative conversion of ethyl levulinate (EL) and 99.0% yield of GVL were obtained in the CTH process using i-PrOH as hydrogen donor. The Cu/ZnO/Al2O3 catalyst with high-surface-area could be reused at least four times without the loss of catalytic activity. Furthermore, the structure and properties of Cu/ZnO/Al2O3 catalyst was characterized through XRD, BET, SEM, TEM and H2-TPR. Also, the influence of different support oxides and calcination temperatures was investigated.展开更多
A modified co-precipitation method for the production of Cu/ZnO/Al2O3 complex was studied. The modification was that part of Al was introduced by adding Al^（3＋） into Cu^（2＋）/Zn^（2＋） solution, and the rest of ...A modified co-precipitation method for the production of Cu/ZnO/Al2O3 complex was studied. The modification was that part of Al was introduced by adding Al^（3＋） into Cu^（2＋）/Zn^（2＋） solution, and the rest of Al was added after co-precipitation step in the form of pseudo-boehmite. The prepared samples were characterized by different techniques such as X-ray diffraction, N2 adsorption, H2-N2O titration, temperature programmed reduction and scanning electron microscopy. X-ray diffraction characterizations revealed that Al^（3＋） can be doped in aurichalcite lattice, and the maximum doping amount of Al^（3＋） was 5.0% of total Cu and Zn atoms. The Cu/ZnO/Al2O3 sample produced by the modified method, in which co-precipitated Al^（3＋） was 2.5% of total Cu and Zn atoms showed much better activity and stability in water-gas shift reaction than commercial sample. The high Cu surface area（26.1 m^2/g） obtained by decompositon of doped aurichalcite is believed to be responsible for the activity enhancement. The stability was enhanced mainly because of the support effect of γ-Al2O3, which was decomposed from pseudo-boehmite in the calcination step.展开更多
A novel coprecipitation-reduction process has been proposed for preparing highly selective Cu/ZnO/Al 2O 3 catalysts for methanol synthesis from CO 2 hydrogenation. Compared to the catalysts prepared by the conventiona...A novel coprecipitation-reduction process has been proposed for preparing highly selective Cu/ZnO/Al 2O 3 catalysts for methanol synthesis from CO 2 hydrogenation. Compared to the catalysts prepared by the conventional method, the new catalysts prepared via the new method exhibit much higher BET surface area and pore size, much smaller crystallite size and higher catalytic activity and selectivity in CO 2 hydrogenation to methanol. It is also found that the molar ratio of Cu + to Cu 0 on the surface of the catalyst obtained by coprecipitation-reduction is much higher than that on the reduced catalyst obtained by the conventional method, which could be crucial for its high activity and selectivity for catalytic hydrogenation of CO 2 to methanol.展开更多
We demonstrate for the first time that a short time of microwave irradiation on the oxide precursor of a Cu/ZnO/Al2O3 catalyst can provide unique opportunity for tailoring the microstructure and activity of the cataly...We demonstrate for the first time that a short time of microwave irradiation on the oxide precursor of a Cu/ZnO/Al2O3 catalyst can provide unique opportunity for tailoring the microstructure and activity of the catalyst for methanol steam reforming. It is shown by in situ XRD that a considerable increase in the microstrain of Cu nanocrystals could be achieved in the catalysts processed by microwave irradiation for 310 min, which correlates well with the enhanced CH3OH conversion as observed on the corresponding samples. The present work also confirms that although the high specific surface area of Cu is a prerequisite for catalytic activity, it does not account for the observed changes in activity and selectivity alone without taking bulk microstructural changes into account.展开更多
Hydrogen production by catalytic steam reforming of methanol over a series of coprecipitated Cu/ZnO/Al2O3 catalysts under atmospheric pressure in a microreactor has been studied Effects of catalyst composition...Hydrogen production by catalytic steam reforming of methanol over a series of coprecipitated Cu/ZnO/Al2O3 catalysts under atmospheric pressure in a microreactor has been studied Effects of catalyst composition, reaction temperature and activation conditions on the catalytic activity have been investigated Crystal phases of catalysts were analyzed by XRD The results showed that Cu/ZnO/Al2O3 catalysts displayed high activity and selectivity for hydrogen and stability The optimized molar ratio is Cu/Zn=10, a maximum methanol conversion of 994?mol%, hydrogen selectivity of 999?mol% and CO molar fraction of 0007% were obtained in the steam reforming reaction with the catalyst containing 45?mol% copper XRD results showed that the diffraction peaks of CuO in the catalyst were clearly lower and broaden It indicated that high dispersion of small copper crystallites on the catalyst surface was formed under the calcination conditions It is suggested that the good performance of Cu/ZnO/Al2O3 catalysts partly resulted from well dispersed展开更多
文摘以尿素为沉淀剂,采用均相沉淀法成功制备了层状Cu/Zn/Al水滑石化合物.将前驱体材料经焙烧、还原后得到Cu/ZnO/Al_2O_3催化剂,并将其用于CO_2加氢合成甲醇反应.采用X射线衍射(X-ray diffraction,XRD)、热重(thermogravimetric,TG)分析、扫描电镜(scanning electron microscope,SEM)、X射线荧光(X-ray fluorescence,XRF)分析、N_2吸附、H_2程序升温还原(H_2-temperature program reduction,H_2-TPR)、氧化亚氮(N_2O)反应吸附、CO_2程序升温脱附(CO_2-temperature program desorption,CO_2-TPD)技术对所制备的样品进行表征.结果表明,相对于传统共沉淀法,以尿素作为沉淀剂,通过均相沉淀法所制备的前驱体的结晶度更高、催化剂比表面积更大、金属Cu的分散度更好.另外,采用回流处理可以获得更好的效果.活性评估结果表明,O_2转化率随金属Cu比表面积的增大而增加,而甲醇选择性则与催化剂表面碱性位的分布有关.因此,采用尿素回流处理均相沉淀法制备的Cu/ZnO/Al_2O_3催化剂的甲醇收率最高.
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the financial support from the State Key Program of the National Natural Science Foundation of China(No.21436007)the support from the central laboratory of SESE in SJTU
文摘An effective catalytic transfer hydrogenation (CTH) process of bio-based levulinate esters into γ-valerolactone (GVL) was explored over ternary Cu/ZnO/Al2O3 catalyst which was prepared by coprecipitation method and could be sustainably used. As a result, quantitative conversion of ethyl levulinate (EL) and 99.0% yield of GVL were obtained in the CTH process using i-PrOH as hydrogen donor. The Cu/ZnO/Al2O3 catalyst with high-surface-area could be reused at least four times without the loss of catalytic activity. Furthermore, the structure and properties of Cu/ZnO/Al2O3 catalyst was characterized through XRD, BET, SEM, TEM and H2-TPR. Also, the influence of different support oxides and calcination temperatures was investigated.
基金the National Natural Science Foundation of China(51572201)
文摘A modified co-precipitation method for the production of Cu/ZnO/Al2O3 complex was studied. The modification was that part of Al was introduced by adding Al^（3＋） into Cu^（2＋）/Zn^（2＋） solution, and the rest of Al was added after co-precipitation step in the form of pseudo-boehmite. The prepared samples were characterized by different techniques such as X-ray diffraction, N2 adsorption, H2-N2O titration, temperature programmed reduction and scanning electron microscopy. X-ray diffraction characterizations revealed that Al^（3＋） can be doped in aurichalcite lattice, and the maximum doping amount of Al^（3＋） was 5.0% of total Cu and Zn atoms. The Cu/ZnO/Al2O3 sample produced by the modified method, in which co-precipitated Al^（3＋） was 2.5% of total Cu and Zn atoms showed much better activity and stability in water-gas shift reaction than commercial sample. The high Cu surface area（26.1 m^2/g） obtained by decompositon of doped aurichalcite is believed to be responsible for the activity enhancement. The stability was enhanced mainly because of the support effect of γ-Al2O3, which was decomposed from pseudo-boehmite in the calcination step.
文摘A novel coprecipitation-reduction process has been proposed for preparing highly selective Cu/ZnO/Al 2O 3 catalysts for methanol synthesis from CO 2 hydrogenation. Compared to the catalysts prepared by the conventional method, the new catalysts prepared via the new method exhibit much higher BET surface area and pore size, much smaller crystallite size and higher catalytic activity and selectivity in CO 2 hydrogenation to methanol. It is also found that the molar ratio of Cu + to Cu 0 on the surface of the catalyst obtained by coprecipitation-reduction is much higher than that on the reduced catalyst obtained by the conventional method, which could be crucial for its high activity and selectivity for catalytic hydrogenation of CO 2 to methanol.
文摘We demonstrate for the first time that a short time of microwave irradiation on the oxide precursor of a Cu/ZnO/Al2O3 catalyst can provide unique opportunity for tailoring the microstructure and activity of the catalyst for methanol steam reforming. It is shown by in situ XRD that a considerable increase in the microstrain of Cu nanocrystals could be achieved in the catalysts processed by microwave irradiation for 310 min, which correlates well with the enhanced CH3OH conversion as observed on the corresponding samples. The present work also confirms that although the high specific surface area of Cu is a prerequisite for catalytic activity, it does not account for the observed changes in activity and selectivity alone without taking bulk microstructural changes into account.
文摘Hydrogen production by catalytic steam reforming of methanol over a series of coprecipitated Cu/ZnO/Al2O3 catalysts under atmospheric pressure in a microreactor has been studied Effects of catalyst composition, reaction temperature and activation conditions on the catalytic activity have been investigated Crystal phases of catalysts were analyzed by XRD The results showed that Cu/ZnO/Al2O3 catalysts displayed high activity and selectivity for hydrogen and stability The optimized molar ratio is Cu/Zn=10, a maximum methanol conversion of 994?mol%, hydrogen selectivity of 999?mol% and CO molar fraction of 0007% were obtained in the steam reforming reaction with the catalyst containing 45?mol% copper XRD results showed that the diffraction peaks of CuO in the catalyst were clearly lower and broaden It indicated that high dispersion of small copper crystallites on the catalyst surface was formed under the calcination conditions It is suggested that the good performance of Cu/ZnO/Al2O3 catalysts partly resulted from well dispersed
