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
A number of nanostructured carbon materials were proposed as new effective promoters for preparing modified Cu/ZnO/Al 2O 3 catalyst system for efficient hydrogen production from methanol steam reforming. Compared to t...A number of nanostructured carbon materials were proposed as new effective promoters for preparing modified Cu/ZnO/Al 2O 3 catalyst system for efficient hydrogen production from methanol steam reforming. Compared to the catalysts modified by other type of carbon materials, the ACF-promoted catalyst prepared via carbonate-coprecipitation method exhibit the highest performance in the low-temperature steam reforming of methanol. It was suggested that the intrinsic high surface area nature of ACF material may favor the generation of modified catalysts with a high surface area and improved component dispersion, thus leading to improved performance for methanol steam reforming.展开更多
In view of not uniformity in conventional coprecipitation preparation, urea was used as the precursor of precipitator to prepare Cu/ZnO/Al2O3 catalysts for methanol synthesis. In the method, urea was dissolved in nitr...In view of not uniformity in conventional coprecipitation preparation, urea was used as the precursor of precipitator to prepare Cu/ZnO/Al2O3 catalysts for methanol synthesis. In the method, urea was dissolved in nitrate solution and hydrolyzed to produce OH- as precipitator after the solution was heated to 90℃. After 6h, the precipitation was accomplished. The evaluation results of the catalyst activity showed that this catalyst had comparable catalytic activities to the industrial catalyst, and reached its maximum activity at 250℃. At reaction conditions of 250℃, 3MPa,and SV=7600h-1, the STY of methanol was 0.38g/（mL·h） with syngas compositing of H2,CO, CO2, and N2 atmolar ratio of 65.9∶27.1∶2.9∶4.1. X-ray Diffraction （XRD） revealed that the particle size of CuO and ZnO was about 200nm, and Al existed in the form of ZnAl2O4 spinel in the catalysts.展开更多
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
文摘A number of nanostructured carbon materials were proposed as new effective promoters for preparing modified Cu/ZnO/Al 2O 3 catalyst system for efficient hydrogen production from methanol steam reforming. Compared to the catalysts modified by other type of carbon materials, the ACF-promoted catalyst prepared via carbonate-coprecipitation method exhibit the highest performance in the low-temperature steam reforming of methanol. It was suggested that the intrinsic high surface area nature of ACF material may favor the generation of modified catalysts with a high surface area and improved component dispersion, thus leading to improved performance for methanol steam reforming.
文摘In view of not uniformity in conventional coprecipitation preparation, urea was used as the precursor of precipitator to prepare Cu/ZnO/Al2O3 catalysts for methanol synthesis. In the method, urea was dissolved in nitrate solution and hydrolyzed to produce OH- as precipitator after the solution was heated to 90℃. After 6h, the precipitation was accomplished. The evaluation results of the catalyst activity showed that this catalyst had comparable catalytic activities to the industrial catalyst, and reached its maximum activity at 250℃. At reaction conditions of 250℃, 3MPa,and SV=7600h-1, the STY of methanol was 0.38g/（mL·h） with syngas compositing of H2,CO, CO2, and N2 atmolar ratio of 65.9∶27.1∶2.9∶4.1. X-ray Diffraction （XRD） revealed that the particle size of CuO and ZnO was about 200nm, and Al existed in the form of ZnAl2O4 spinel in the catalysts.
