FeOx-SiO2 catalysts prepared by a sol-gel method were studied for the selective oxidation of methane by oxygen. A single-pass formaldehyde yield of 2.0% was obtained over the FeOx-SiO2 with an iron content of 0.5 wt% ...FeOx-SiO2 catalysts prepared by a sol-gel method were studied for the selective oxidation of methane by oxygen. A single-pass formaldehyde yield of 2.0% was obtained over the FeOx-SiO2 with an iron content of 0.5 wt% at 898 K. This 0.5 wt% FeOx-SiO2 catalyst demonstrated significantly higher catalytic performances than the 0.5 wt% FeOx/SiO2 prepared by an impregnation method. The correlation between the catalytic performances and the characterizations with UV-Vis and H2-TPR suggested that the higher dispersion of iron species in the catalyst prepared by the sol-gel method was responsible for its higher catalytic activity for formaldehyde formation. The modification of the FeOx-SiO2 by phosphorus enhanced the formaldehyde selectivity, and a single-pass formaldehyde yield of 2.4% could be attained over a P-FeOx-SiO2 catalyst (P/Fe = 0.5) at 898 K. Raman spectroscopic measurements indicated the formation of FePO4 nanoclusters in this catalyst, which were more selective toward formaldehyde formation.展开更多
Methane is the main constituent of natural gas, coal-bed gas, landfill gas and methane hydrate resources. These resources may be used more efficiently as clean fuels or as chemical feedstocks if methane can be effecti...Methane is the main constituent of natural gas, coal-bed gas, landfill gas and methane hydrate resources. These resources may be used more efficiently as clean fuels or as chemical feedstocks if methane can be effectively transformed into liquid fuels or chemicals. However, methane only possesses C-H bonds and is a very stable organic molecule hard to functionalize. The C-H activation, particularly the selective functionalization of C-H bonds in saturated hydrocarbons, remains a difficult challenge in chemistry. The present technology for chemical utilization of methane involves the steam reforming of methane to synthesis gas and the subsequent transformation of synthesis gas to methanol or hydrocarbon fuels via methanol synthesis or Fischer-Tropsch synthesis. However, the steam reforming of methane is a high-cost process. The development of more efficient and economical processes for methane transformation is a dream of all chemists and chemical engineers. I think that this is also one of the most important themes of the Journal of Natural Gas Chemistry.展开更多
Oscillations in temperatures of catalyst bed as well as concentrations of gas phase species at the exit of reactor were observed during the partial oxidation of methane to synthesis gas over Ru/Al2O3 in the temperatur...Oscillations in temperatures of catalyst bed as well as concentrations of gas phase species at the exit of reactor were observed during the partial oxidation of methane to synthesis gas over Ru/Al2O3 in the temperature range of 600 to 850℃. XRD, H2-TPR and in situ Raman techniques was used to characterize the catalyst. Two types of ruthenium species, i.e. the ruthenium species weakly interacted with Al2O3 and that strongly interacted with the support, were identified by H2-TPR experiment. These species are responsible for two types of oscillation profiles observed during the reaction. The oscillations were the result of these ruthenium species switching cyclically between the oxidized state and the reduced state under the reaction condition. These cyclic transformations, in turn, were the result of temperature variations caused by the varying levels of the strongly exothermic CH4 combustion and the highly endothermic CH4 reforming (with H2O and CO2) reactions (or the less exothermic direct partial oxidation of methane to CO and H2), which were favored by the oxidized and the metallic sites, respectively. The major pathway of synthesis gas formation over the catalyst was via the combustion-reforming mechanism.展开更多
Catalytic conversion of synthesis gas (CO+H2) into hydrocarbons, also known as Fischer-Tropsch (FT) synthesis, is a crucial reaction for the translbrmation of non-petroleum carbon resources such as coal, natural ...Catalytic conversion of synthesis gas (CO+H2) into hydrocarbons, also known as Fischer-Tropsch (FT) synthesis, is a crucial reaction for the translbrmation of non-petroleum carbon resources such as coal, natural gas, shale gas, coal-bed gas and biogas, as well as biomass into liquid fuels and chemicals. Many factors can influence the catalytic behavior of a FT catalyst. This review highlights recent advances in understanding some key catalyst factors, including the chemical state of active phases, the promoters, the size and the microenvironment of active phase, which determine the CO conversion activity and the product selectivity, particularly the selectivity to C5 + hydrocarbons.展开更多
A series ofnanosized cobalt oxide catalysts modified with phosphorus have been synthesized by the solgel method and investigated in the oxidative dehydrogenation of propane to propene. With the addition of phosphorus,...A series ofnanosized cobalt oxide catalysts modified with phosphorus have been synthesized by the solgel method and investigated in the oxidative dehydrogenation of propane to propene. With the addition of phosphorus, the crystallite size of the catalyst was largely decreased, while the P species in the catalyst were highly dispersed. Compared to pure cobalt oxide, the P-modified samples showed higher propane conversion and enhanced propene selectivity. Over the PCoO catalyst with a P/Co atomic ratio of 0.05, the maximal propene yields of 15.7% with a propane conversion of 28.3% were obtained at 520 ℃.展开更多
Selective oxidation or oxidative functionalization of methane and ethane by both homogeneous and heterogeneous catalysis is presented concerning: (1) selective oxidation of methane and ethane to organic oxygenates by ...Selective oxidation or oxidative functionalization of methane and ethane by both homogeneous and heterogeneous catalysis is presented concerning: (1) selective oxidation of methane and ethane to organic oxygenates by hydrogen peroxide in a water medium in the presence of homogeneous osmium catalysts, (2) selective oxidation of methane to formaldehyde over highly dispersed iron and copper heterogeneous catalysts, (3) selective oxidation of ethane to acetaldehyde and formaldehyde over supported molybdenum catalysts, and (4) oxidative carbonylation of methane to methyl acetate over heterogeneous catalysts containing dual sites of rhodium and iron.展开更多
Hydrogenation of methyl p-hydroxyphenylacetate has been used for the synthesis of p-hydroxyphenyl ethanol.The reaction was catalyzed by Cu_(i)Zr_(j)-x%(mass fraction)carbon nanotubes(CNTs)catalysts.Incorporation of a ...Hydrogenation of methyl p-hydroxyphenylacetate has been used for the synthesis of p-hydroxyphenyl ethanol.The reaction was catalyzed by Cu_(i)Zr_(j)-x%(mass fraction)carbon nanotubes(CNTs)catalysts.Incorporation of a minor amount of CNTs into Cu_(i)Zr_(j) oxide can visibly increase the catalytic activity for the synthesis of p-hydroxyphenyl ethanol.The yield of p-hydroxyphenyl ethanol reaches 94.2%over a co-precipitated catalyst of Cu_(3)Zr_(1) oxide with 11.0%CNTs.Its catalytic activity shows no obvious decrease after three cycles.This is much better than the CNT-free co-precipitated catalyst with a good yield of 81.1%,Cu_(3)Zr_(1)-0%CNTs.展开更多
Carbon nanotube (CNT)-supported Ru nanoparticles with mean sizes ranging from 2.3 to 9.2 nm were prepared by different post-treatments and studied for Fischer-Tropsch (FT) synthesis. The effects of Ru particle siz...Carbon nanotube (CNT)-supported Ru nanoparticles with mean sizes ranging from 2.3 to 9.2 nm were prepared by different post-treatments and studied for Fischer-Tropsch (FT) synthesis. The effects of Ru particle size on catalytic behaviors were investigated at both shorter and longer contact times. At shorter contact time, where the secondary reactions were insignificant, the turnover frequency (TOF) for CO conversion was dependent on the mean size of Ru particles; TOF increased with the mean size of Ru particles from 2.3 to 6.3 nm and then decreased slightly. At the same time, the selectivities to C5+ hydrocarbons increased gradually with the mean size of Ru particles up to 6.3 nm and then kept almost unchanged with a further increase in Ru particle size. At longer contact time, C10-C20 selectivity increased significantly at the expense of C21+ selectivity, suggesting the occurrence of the selective hydrocracking of C21+ to C10-C20 hydrocarbons.展开更多
基金supported by the National Natural Science Foundation of China (Nos.20625310,20773099 and 20873110)the National Basic Programof China (No. 2005CB221408)the National Science Fund for Talent Training in Basic Science (No.J0630429)
文摘FeOx-SiO2 catalysts prepared by a sol-gel method were studied for the selective oxidation of methane by oxygen. A single-pass formaldehyde yield of 2.0% was obtained over the FeOx-SiO2 with an iron content of 0.5 wt% at 898 K. This 0.5 wt% FeOx-SiO2 catalyst demonstrated significantly higher catalytic performances than the 0.5 wt% FeOx/SiO2 prepared by an impregnation method. The correlation between the catalytic performances and the characterizations with UV-Vis and H2-TPR suggested that the higher dispersion of iron species in the catalyst prepared by the sol-gel method was responsible for its higher catalytic activity for formaldehyde formation. The modification of the FeOx-SiO2 by phosphorus enhanced the formaldehyde selectivity, and a single-pass formaldehyde yield of 2.4% could be attained over a P-FeOx-SiO2 catalyst (P/Fe = 0.5) at 898 K. Raman spectroscopic measurements indicated the formation of FePO4 nanoclusters in this catalyst, which were more selective toward formaldehyde formation.
文摘Methane is the main constituent of natural gas, coal-bed gas, landfill gas and methane hydrate resources. These resources may be used more efficiently as clean fuels or as chemical feedstocks if methane can be effectively transformed into liquid fuels or chemicals. However, methane only possesses C-H bonds and is a very stable organic molecule hard to functionalize. The C-H activation, particularly the selective functionalization of C-H bonds in saturated hydrocarbons, remains a difficult challenge in chemistry. The present technology for chemical utilization of methane involves the steam reforming of methane to synthesis gas and the subsequent transformation of synthesis gas to methanol or hydrocarbon fuels via methanol synthesis or Fischer-Tropsch synthesis. However, the steam reforming of methane is a high-cost process. The development of more efficient and economical processes for methane transformation is a dream of all chemists and chemical engineers. I think that this is also one of the most important themes of the Journal of Natural Gas Chemistry.
基金supported by the Ministry of Science and Technology of China (2005CB221401)the National Natural Science Foundation of China(20873111)the Key Science & Technology Specific Projects of Fujian Province (2009HZ10102)
文摘Oscillations in temperatures of catalyst bed as well as concentrations of gas phase species at the exit of reactor were observed during the partial oxidation of methane to synthesis gas over Ru/Al2O3 in the temperature range of 600 to 850℃. XRD, H2-TPR and in situ Raman techniques was used to characterize the catalyst. Two types of ruthenium species, i.e. the ruthenium species weakly interacted with Al2O3 and that strongly interacted with the support, were identified by H2-TPR experiment. These species are responsible for two types of oscillation profiles observed during the reaction. The oscillations were the result of these ruthenium species switching cyclically between the oxidized state and the reduced state under the reaction condition. These cyclic transformations, in turn, were the result of temperature variations caused by the varying levels of the strongly exothermic CH4 combustion and the highly endothermic CH4 reforming (with H2O and CO2) reactions (or the less exothermic direct partial oxidation of methane to CO and H2), which were favored by the oxidized and the metallic sites, respectively. The major pathway of synthesis gas formation over the catalyst was via the combustion-reforming mechanism.
基金the National Basic Research Program of China(No.2013CB933100)the National Natural Science Foundation of China(No.21173174,No.21161130522,No.21033006and No.20923004)the Program for Changjiang Scholars and Innovative Research Team in University(No.IRT1036)
文摘Catalytic conversion of synthesis gas (CO+H2) into hydrocarbons, also known as Fischer-Tropsch (FT) synthesis, is a crucial reaction for the translbrmation of non-petroleum carbon resources such as coal, natural gas, shale gas, coal-bed gas and biogas, as well as biomass into liquid fuels and chemicals. Many factors can influence the catalytic behavior of a FT catalyst. This review highlights recent advances in understanding some key catalyst factors, including the chemical state of active phases, the promoters, the size and the microenvironment of active phase, which determine the CO conversion activity and the product selectivity, particularly the selectivity to C5 + hydrocarbons.
基金supported by the National Basic Research Program of China(Nos.2010CB732303 and 2013CB933102)the National Natural Science Foundation of China(Nos.21073148 and 21033006)the Program for Innovative Research Team of the Ministry of Education of China(No.IRT1036)
文摘A series ofnanosized cobalt oxide catalysts modified with phosphorus have been synthesized by the solgel method and investigated in the oxidative dehydrogenation of propane to propene. With the addition of phosphorus, the crystallite size of the catalyst was largely decreased, while the P species in the catalyst were highly dispersed. Compared to pure cobalt oxide, the P-modified samples showed higher propane conversion and enhanced propene selectivity. Over the PCoO catalyst with a P/Co atomic ratio of 0.05, the maximal propene yields of 15.7% with a propane conversion of 28.3% were obtained at 520 ℃.
基金Financial support by the National Natural Science Foundation of China (Grant Nos. 20433030, 20625310, 20773099 and 20873110)the National Basic Program of China (Grant Nos. 2005CB221408 and 2010CB732303)+1 种基金the Key Scientific Project of Fujian Province (2009HZ0002-1)the Program for New Century Excellent Talents in Fujian Province (to Q. Z.)
文摘Selective oxidation or oxidative functionalization of methane and ethane by both homogeneous and heterogeneous catalysis is presented concerning: (1) selective oxidation of methane and ethane to organic oxygenates by hydrogen peroxide in a water medium in the presence of homogeneous osmium catalysts, (2) selective oxidation of methane to formaldehyde over highly dispersed iron and copper heterogeneous catalysts, (3) selective oxidation of ethane to acetaldehyde and formaldehyde over supported molybdenum catalysts, and (4) oxidative carbonylation of methane to methyl acetate over heterogeneous catalysts containing dual sites of rhodium and iron.
基金This work was supported by the National Natural Science Foundation of China(No.21773196).
文摘Hydrogenation of methyl p-hydroxyphenylacetate has been used for the synthesis of p-hydroxyphenyl ethanol.The reaction was catalyzed by Cu_(i)Zr_(j)-x%(mass fraction)carbon nanotubes(CNTs)catalysts.Incorporation of a minor amount of CNTs into Cu_(i)Zr_(j) oxide can visibly increase the catalytic activity for the synthesis of p-hydroxyphenyl ethanol.The yield of p-hydroxyphenyl ethanol reaches 94.2%over a co-precipitated catalyst of Cu_(3)Zr_(1) oxide with 11.0%CNTs.Its catalytic activity shows no obvious decrease after three cycles.This is much better than the CNT-free co-precipitated catalyst with a good yield of 81.1%,Cu_(3)Zr_(1)-0%CNTs.
基金supported by the National Basic Research Program of China (No. 2013CB933100)the National Natural Science Foundation of China (21173174, 21161130522, 21033006 and 20923004)+1 种基金the Program for Changjiang Scholars and Innovative Research Team in University (No. IRT1036)the Research Fund for the Doctoral Program of Higher Education (No. 20090121110007)
文摘Carbon nanotube (CNT)-supported Ru nanoparticles with mean sizes ranging from 2.3 to 9.2 nm were prepared by different post-treatments and studied for Fischer-Tropsch (FT) synthesis. The effects of Ru particle size on catalytic behaviors were investigated at both shorter and longer contact times. At shorter contact time, where the secondary reactions were insignificant, the turnover frequency (TOF) for CO conversion was dependent on the mean size of Ru particles; TOF increased with the mean size of Ru particles from 2.3 to 6.3 nm and then decreased slightly. At the same time, the selectivities to C5+ hydrocarbons increased gradually with the mean size of Ru particles up to 6.3 nm and then kept almost unchanged with a further increase in Ru particle size. At longer contact time, C10-C20 selectivity increased significantly at the expense of C21+ selectivity, suggesting the occurrence of the selective hydrocracking of C21+ to C10-C20 hydrocarbons.