Two series of ZSM-5 and beta zeolites were pretreated in 1.0 mol/L HNO3 solution at room temper-ature for various time periods. The catalytic performances of their Fe-exchanged products in N2O decomposition were evalu...Two series of ZSM-5 and beta zeolites were pretreated in 1.0 mol/L HNO3 solution at room temper-ature for various time periods. The catalytic performances of their Fe-exchanged products in N2O decomposition were evaluated. The Fe-zeolite catalysts were characterized using N2 adsorp-tion-desorption, inductively coupled plasma optical emission spectroscopy, X-ray diffraction, ultra-violet-visible spectroscopy, temperature-programmed desorption of NH3, and scanning and trans-mission electron microscopies. For the ZSM-5 zeolite, acid leaching primarily takes place on the crystal surface and the particle size is reduced, therefore the pore channels are shortened. However, because of the good stability of MFI zeolites, the acid does not greatly penetrate the pore channels and new mesopores are not created. For the beta zeolite, because the amorphous material is in-clined to dissolve(deagglomerate), some of the micropores are slightly dilated. The improved cata-lytic activities can be explained by the increased active Fe loading as a result of structural changes.展开更多
A reaction-coupling strategy is often employed for CO_(2)hydrogenation to produce fuels and chemicals using oxide/zeolite bifunctional catalysts.Because the oxide components are responsible for CO_(2)activation,unders...A reaction-coupling strategy is often employed for CO_(2)hydrogenation to produce fuels and chemicals using oxide/zeolite bifunctional catalysts.Because the oxide components are responsible for CO_(2)activation,understanding the structural effects of these oxides is crucial,however,these effects still remain unclear.In this study,we combined In_(2)O_(3),with varying particle sizes,and SAPO‐34 as bifunctional catalysts for CO_(2)hydrogenation.The CO_(2)conversion and selectivity of the lower olefins increased as the average In_(2)O_(3)crystallite size decreased from 29 to 19 nm;this trend mainly due to the increasing number of oxygen vacancies responsible for CO_(2) and H_(2) activation.However,In_(2)O_(3)particles smaller than 19 nm are more prone to sintering than those with other sizes.The results suggest that 19 nm is the optimal size of In_(2)O_(3)for CO_(2)hydrogenation to lower olefins and that the oxide particle size is crucial for designing catalysts with high activity,high selectivity,and high stability.展开更多
Co2C‐based catalysts with SiO2,γ‐Al2O3,and carbon nanotubes(CNTs)as support materials were prepared and evaluated for the Fischer‐Tropsch to olefin(FTO)reaction.The combination of catalytic performance and structu...Co2C‐based catalysts with SiO2,γ‐Al2O3,and carbon nanotubes(CNTs)as support materials were prepared and evaluated for the Fischer‐Tropsch to olefin(FTO)reaction.The combination of catalytic performance and structure characterization indicates that the cobalt‐support interaction has a great influence on the Co2C morphology and catalytic performance.The CNT support facilitates the formation of a CoMn composite oxide during calcination,and Co2C nanoprisms were observed in the spent catalysts,resulting in a product distribution that greatly deviates from the classical Anderson‐Schulz‐Flory(ASF)distribution,where only 2.4 C%methane was generated.The Co3O4 phase for SiO2‐andγ‐Al2O3‐supported catalysts was observed in the calcined sample.After reduction,CoO,MnO,and low‐valence CoMn composite oxide were generated in theγ‐Al2O3‐supported sample,and both Co2C nanospheres and nanoprisms were identified in the corresponding spent catalyst.However,only separated phases of CoO and MnO were found in the reduced sample supported by SiO2,and Co2C nanospheres were detected in the spent catalyst without the evidence of any Co2C nanoprisms.The Co2C nanospheres led to a relatively high methane selectivity of 5.8 C%and 12.0 C%of theγ‐Al2O3‐and SiO2‐supported catalysts,respectively.These results suggest that a relatively weak cobalt‐support interaction is necessary for the formation of the CoMn composite oxide during calcination,which benefits the formation of Co2C nanoprisms with promising catalytic performance for the sustainable production of olefins via syngas.展开更多
CoCu/TiO_2 catalysts promoted using alkali metals(Li, Na, K, Rb, and Cs) were prepared by the homogeneous deposition-precipitation method followed by the incipient wetness impregnation method. The influences of the ...CoCu/TiO_2 catalysts promoted using alkali metals(Li, Na, K, Rb, and Cs) were prepared by the homogeneous deposition-precipitation method followed by the incipient wetness impregnation method. The influences of the alkali metals on the physicochemical properties of the CoCu/TiO_2 catalysts and the catalytic performance for CO_2 hydrogenation to long-chain hydrocarbons(C_(5+))were investigated in this work. According to the characterization of the catalysts based on X-ray photoelectron spectroscopy, X-ray diffraction, CO_2 temperature-programmed desorption(TPD), and H_2-TPD, the introduction of alkali metals could increase the CO_2 adsorption and decrease the H_2 chemisorption, which could suppress the formation of CH_4, enhance the production of C_(5+), and decrease the hydrogenation activity. Among all the promoters, the Na-modified CoCu/TiO_2 catalyst provided the maximum C_(5+) yield of 5.4%, with a CO_2 conversion of 18.4% and C_(5+) selectivity of42.1%, because it showed the strongest basicity and a slight decrease in the amount of H_2 desorption;it also exhibited excellent catalytic stability of more than 200 h.展开更多
基金supported by Natural Science Foundation of China(U22B20136,91945301,22202230)National Key R&D Program of China(2021YFF0500702)+3 种基金Natural Science Foundation of Shanghai(22JC1404200)Program of Shanghai Academic/Technology Research Leader(20XD1404000)the“Transformational Technologies for Clean Energy and Demonstration”Strategic Priority Research Program of Chinese Academy of Sciences(XDA21020600)。
基金supported by the National Basic Research Program of China (973 Program 2011CBA00501)+2 种基金Shanghai Municipal Science and Technology Commission China (11DZ1200300)the Foundation of State Key Laboratory of Coal Conversion (11‐12‐610)~~
基金supported by the National Natural Science Foundation of China (21307144,21307007)Science of Technology Development Plan of Jilin Province of China (20140520150JH)~~
文摘Two series of ZSM-5 and beta zeolites were pretreated in 1.0 mol/L HNO3 solution at room temper-ature for various time periods. The catalytic performances of their Fe-exchanged products in N2O decomposition were evaluated. The Fe-zeolite catalysts were characterized using N2 adsorp-tion-desorption, inductively coupled plasma optical emission spectroscopy, X-ray diffraction, ultra-violet-visible spectroscopy, temperature-programmed desorption of NH3, and scanning and trans-mission electron microscopies. For the ZSM-5 zeolite, acid leaching primarily takes place on the crystal surface and the particle size is reduced, therefore the pore channels are shortened. However, because of the good stability of MFI zeolites, the acid does not greatly penetrate the pore channels and new mesopores are not created. For the beta zeolite, because the amorphous material is in-clined to dissolve(deagglomerate), some of the micropores are slightly dilated. The improved cata-lytic activities can be explained by the increased active Fe loading as a result of structural changes.
基金supported by the National Natural Science Foundation of China(21403278)China Shenhua Coal to Liquid and Chemical Company Limited+1 种基金Shanxi Lu'an Coal Corporation LimitedShell Global Solutions International B.V~~
文摘A reaction-coupling strategy is often employed for CO_(2)hydrogenation to produce fuels and chemicals using oxide/zeolite bifunctional catalysts.Because the oxide components are responsible for CO_(2)activation,understanding the structural effects of these oxides is crucial,however,these effects still remain unclear.In this study,we combined In_(2)O_(3),with varying particle sizes,and SAPO‐34 as bifunctional catalysts for CO_(2)hydrogenation.The CO_(2)conversion and selectivity of the lower olefins increased as the average In_(2)O_(3)crystallite size decreased from 29 to 19 nm;this trend mainly due to the increasing number of oxygen vacancies responsible for CO_(2) and H_(2) activation.However,In_(2)O_(3)particles smaller than 19 nm are more prone to sintering than those with other sizes.The results suggest that 19 nm is the optimal size of In_(2)O_(3)for CO_(2)hydrogenation to lower olefins and that the oxide particle size is crucial for designing catalysts with high activity,high selectivity,and high stability.
文摘Co2C‐based catalysts with SiO2,γ‐Al2O3,and carbon nanotubes(CNTs)as support materials were prepared and evaluated for the Fischer‐Tropsch to olefin(FTO)reaction.The combination of catalytic performance and structure characterization indicates that the cobalt‐support interaction has a great influence on the Co2C morphology and catalytic performance.The CNT support facilitates the formation of a CoMn composite oxide during calcination,and Co2C nanoprisms were observed in the spent catalysts,resulting in a product distribution that greatly deviates from the classical Anderson‐Schulz‐Flory(ASF)distribution,where only 2.4 C%methane was generated.The Co3O4 phase for SiO2‐andγ‐Al2O3‐supported catalysts was observed in the calcined sample.After reduction,CoO,MnO,and low‐valence CoMn composite oxide were generated in theγ‐Al2O3‐supported sample,and both Co2C nanospheres and nanoprisms were identified in the corresponding spent catalyst.However,only separated phases of CoO and MnO were found in the reduced sample supported by SiO2,and Co2C nanospheres were detected in the spent catalyst without the evidence of any Co2C nanoprisms.The Co2C nanospheres led to a relatively high methane selectivity of 5.8 C%and 12.0 C%of theγ‐Al2O3‐and SiO2‐supported catalysts,respectively.These results suggest that a relatively weak cobalt‐support interaction is necessary for the formation of the CoMn composite oxide during calcination,which benefits the formation of Co2C nanoprisms with promising catalytic performance for the sustainable production of olefins via syngas.
文摘CoCu/TiO_2 catalysts promoted using alkali metals(Li, Na, K, Rb, and Cs) were prepared by the homogeneous deposition-precipitation method followed by the incipient wetness impregnation method. The influences of the alkali metals on the physicochemical properties of the CoCu/TiO_2 catalysts and the catalytic performance for CO_2 hydrogenation to long-chain hydrocarbons(C_(5+))were investigated in this work. According to the characterization of the catalysts based on X-ray photoelectron spectroscopy, X-ray diffraction, CO_2 temperature-programmed desorption(TPD), and H_2-TPD, the introduction of alkali metals could increase the CO_2 adsorption and decrease the H_2 chemisorption, which could suppress the formation of CH_4, enhance the production of C_(5+), and decrease the hydrogenation activity. Among all the promoters, the Na-modified CoCu/TiO_2 catalyst provided the maximum C_(5+) yield of 5.4%, with a CO_2 conversion of 18.4% and C_(5+) selectivity of42.1%, because it showed the strongest basicity and a slight decrease in the amount of H_2 desorption;it also exhibited excellent catalytic stability of more than 200 h.