Highly active CNT-promoted co-precipitated Cu-ZnO-Al_2O_3 catalysts,symbolized as Cu_iZn_jAl_k-x%CNTs, were prepared, and their catalytic activity for once-throughmethanol synthesis from syngas was investigated. The r...Highly active CNT-promoted co-precipitated Cu-ZnO-Al_2O_3 catalysts,symbolized as Cu_iZn_jAl_k-x%CNTs, were prepared, and their catalytic activity for once-throughmethanol synthesis from syngas was investigated. The results illustrated that, under the reactionconditions (at 493 K, 5.0 MPa, the volume ratio of H_2/CO/CO_2/N_2= 62/30/5/3, GHSV= 4000 h^(-1),the observed single-pass CO-conversion and methanol-STY over a Cu_6Zn_3Al_1-12.5%CNTs catalystreached 64% and 1210 mg/(h-g), which was about 68% and 66% higher than those (38% and 730 mg/(h·g))over the corresponding CNT-free catalyst, Cu-6Zn_3Al_1, respectively. The characteristic studies ofthe catalysts revealed that appropriate incorporation of a minor amount of the CNTs into theCu_iZn_jAl_k brought about little change in the apparent activation energy of the methanol synthesisreaction, however, led to a considerable increase in the catalyst's active Cu surface area andpronouncedly enhanced the stationary-state concentration of active hydrogen-adspecies on the surfaceof the functioning catalyst, which would be favorable to increasing the rate of the COhydro-genation reactions. Moreover, the operation temperature for methanol synthesis over theCNT-promoted catalysts can be 10-20 degrees lower than that over the corresponding CNT-free contrastsystem, which would contribute considerably to an increase in equilibrium CO-conversion andCH_3OH-yield.展开更多
The low-heat-value cornstalk gas produced in the down-flow fixed bed gasifier was tentatively used for methanol synthesis. The cornstalk gas was purified and the technical procedures such as deoxygenation, desulfuriza...The low-heat-value cornstalk gas produced in the down-flow fixed bed gasifier was tentatively used for methanol synthesis. The cornstalk gas was purified and the technical procedures such as deoxygenation, desulfurization, catalytic cracking of tar, purification and hydrogenation were studied. The catalytic experiments of methanol synthesis with cornstalk syngas were carried out in a tubular-flow integral and isothermal reactor. The effect of reaction temperature, pressure, catalysttypes, catalyst particle size, syngas flow at entering end and composition of syngas was investigated. The optimum process conditions and yield of methanol from cornstalk syngas were obtained. The experimental results indicated that the proper catalyst of the synthetic reaction was C301 and the optimum catalyst size （φ） was 0.833 mm×0.351 mm. The optimum operating temperature and pressure were found to be 235℃ and 5 Mpa, respectively. The suitable syngas flow 0.9-1.10 mol/h at entering end was selected and the best composition of syngas were CO 10.49%, CO2 8.8%, N2 37.32%, CnHm 0.95% and H2 40.49%. The best methanol yield is 0.418 g/g cornstalk. The study provided the technical support for the industrial test of methanol production from biomass （cornstalk）gas.展开更多
From the chemical catalysis viewpoint,the excellent performance of CNTs in adsorption-activation of H2 and in promoting spillover of adsorbed H-species is very attractive,in addition to their nanosize channels,sp2-C c...From the chemical catalysis viewpoint,the excellent performance of CNTs in adsorption-activation of H2 and in promoting spillover of adsorbed H-species is very attractive,in addition to their nanosize channels,sp2-C constructed surfaces,and high thermal/electrical conductivity.This review examines some recent progresses of CNTs as a novel support or promoter of catalysts for certain hydrogenation or dehydrogenation reactions,e.g.,hydrogenation-conversion of syngas to yield alcohols and decomposition or steam-reforming of methanol to generate H2,mainly based on recent work carried out in our laboratory.展开更多
Methanol synthesis catalysts based on Cu, Zn and Al were prepared by three methods and subsequently mixed with H-ferrierite zeolite in an aqueous suspension to disperse the catalysts over the support. These materials ...Methanol synthesis catalysts based on Cu, Zn and Al were prepared by three methods and subsequently mixed with H-ferrierite zeolite in an aqueous suspension to disperse the catalysts over the support. These materials were characterized by X-ray diffraction, N2 adsorption, transmission electron microscopy, temperature programmed reduction, NH3 and H2 temperature-programmed desorption, and X-ray photoelectron spectroscopy. They were also applied to the CO hydrogenation reaction to produce dimethyl ether and hydrocarbons. The catalysts were prepared by coprecipitation under low and high supersaturation conditions and by a homogeneous precipitation method. The preparation technique was found to affect the precursor structural characteristics, such as purity and crystallinity, as well as the particle size distribution of the resulting catalyst. Low supersaturation conditions favored high dispersion of the Cu species, increasing the methanol synthesis catalyst＇s metallic surface area and resulting in a homogeneous particle size distribution. These effects in turn were found to modify the zeolite properties, promoting both a low micropore volume and blockage of the zeolite acid sites. The effect of the methanol synthesis catalyst on the reaction was verified by the correlation between the Cu surface area and the CO conversion rate.展开更多
基金This work Supported by National Nat. Sci. Foundation (No. 50072021) Fujian Provincial Nat. Sci. Foundation (No. 2001H017) of China.
文摘Highly active CNT-promoted co-precipitated Cu-ZnO-Al_2O_3 catalysts,symbolized as Cu_iZn_jAl_k-x%CNTs, were prepared, and their catalytic activity for once-throughmethanol synthesis from syngas was investigated. The results illustrated that, under the reactionconditions (at 493 K, 5.0 MPa, the volume ratio of H_2/CO/CO_2/N_2= 62/30/5/3, GHSV= 4000 h^(-1),the observed single-pass CO-conversion and methanol-STY over a Cu_6Zn_3Al_1-12.5%CNTs catalystreached 64% and 1210 mg/(h-g), which was about 68% and 66% higher than those (38% and 730 mg/(h·g))over the corresponding CNT-free catalyst, Cu-6Zn_3Al_1, respectively. The characteristic studies ofthe catalysts revealed that appropriate incorporation of a minor amount of the CNTs into theCu_iZn_jAl_k brought about little change in the apparent activation energy of the methanol synthesisreaction, however, led to a considerable increase in the catalyst's active Cu surface area andpronouncedly enhanced the stationary-state concentration of active hydrogen-adspecies on the surfaceof the functioning catalyst, which would be favorable to increasing the rate of the COhydro-genation reactions. Moreover, the operation temperature for methanol synthesis over theCNT-promoted catalysts can be 10-20 degrees lower than that over the corresponding CNT-free contrastsystem, which would contribute considerably to an increase in equilibrium CO-conversion andCH_3OH-yield.
基金Project supported by the Foundation of Science and Technology of Henan Province (No. 0324210047).
文摘The low-heat-value cornstalk gas produced in the down-flow fixed bed gasifier was tentatively used for methanol synthesis. The cornstalk gas was purified and the technical procedures such as deoxygenation, desulfurization, catalytic cracking of tar, purification and hydrogenation were studied. The catalytic experiments of methanol synthesis with cornstalk syngas were carried out in a tubular-flow integral and isothermal reactor. The effect of reaction temperature, pressure, catalysttypes, catalyst particle size, syngas flow at entering end and composition of syngas was investigated. The optimum process conditions and yield of methanol from cornstalk syngas were obtained. The experimental results indicated that the proper catalyst of the synthetic reaction was C301 and the optimum catalyst size （φ） was 0.833 mm×0.351 mm. The optimum operating temperature and pressure were found to be 235℃ and 5 Mpa, respectively. The suitable syngas flow 0.9-1.10 mol/h at entering end was selected and the best composition of syngas were CO 10.49%, CO2 8.8%, N2 37.32%, CnHm 0.95% and H2 40.49%. The best methanol yield is 0.418 g/g cornstalk. The study provided the technical support for the industrial test of methanol production from biomass （cornstalk）gas.
基金supported by the National Basic Research Program of China(2011CBA00508)the National Natural Science Foundation of China(20923004)the Program for Changjiang Scholars and Innovative Research Team in University(IRT1036)
文摘From the chemical catalysis viewpoint,the excellent performance of CNTs in adsorption-activation of H2 and in promoting spillover of adsorbed H-species is very attractive,in addition to their nanosize channels,sp2-C constructed surfaces,and high thermal/electrical conductivity.This review examines some recent progresses of CNTs as a novel support or promoter of catalysts for certain hydrogenation or dehydrogenation reactions,e.g.,hydrogenation-conversion of syngas to yield alcohols and decomposition or steam-reforming of methanol to generate H2,mainly based on recent work carried out in our laboratory.
文摘Methanol synthesis catalysts based on Cu, Zn and Al were prepared by three methods and subsequently mixed with H-ferrierite zeolite in an aqueous suspension to disperse the catalysts over the support. These materials were characterized by X-ray diffraction, N2 adsorption, transmission electron microscopy, temperature programmed reduction, NH3 and H2 temperature-programmed desorption, and X-ray photoelectron spectroscopy. They were also applied to the CO hydrogenation reaction to produce dimethyl ether and hydrocarbons. The catalysts were prepared by coprecipitation under low and high supersaturation conditions and by a homogeneous precipitation method. The preparation technique was found to affect the precursor structural characteristics, such as purity and crystallinity, as well as the particle size distribution of the resulting catalyst. Low supersaturation conditions favored high dispersion of the Cu species, increasing the methanol synthesis catalyst＇s metallic surface area and resulting in a homogeneous particle size distribution. These effects in turn were found to modify the zeolite properties, promoting both a low micropore volume and blockage of the zeolite acid sites. The effect of the methanol synthesis catalyst on the reaction was verified by the correlation between the Cu surface area and the CO conversion rate.
