Formation of a p–n heterojunction rather than p-type or n-type semiconductors can enhance the separation of photogenerated electrons and holes and increase the quantum efficiency of photocatalytic reactions owing to ...Formation of a p–n heterojunction rather than p-type or n-type semiconductors can enhance the separation of photogenerated electrons and holes and increase the quantum efficiency of photocatalytic reactions owing to the difference of the electric potential in the inner electric field near the junction,pointing from n toward p. n-Ag3PO4/p-Ag2CO3 p–n heterojunction composites are prepared through a facile coprecipitation process. The obtained Ag3PO4/Ag2CO3 p–n heterojunctions exhibit excellent photocatalytic performance in the removal of rhodamine B（RhB） compared with Ag3PO4 and Ag2CO3. The 40%-Ag3PO4/Ag2CO3 composite photocatalyst（40 mol% Ag3PO4 and 60 mol% Ag2CO3） exhibits the best photocatalytic activity under visible light,demonstrating the ability to completely degrade RhB within 15 min. Transient photovoltage characterization and an active species trapping experiment further indicate that the formation of a p–n heterojunction structure can greatly enhance the separation efficiency of photogenerated carriers and produce more free h＋active species,which is the predominant contributor for RhB removal.展开更多
TiO2-coated activated carbon surface （TAs） composites were prepared by a sol-gel method with supercritical pretreatment. The photocatalytic degradation of acid yellow （AY） was investigated under UV radiation to es...TiO2-coated activated carbon surface （TAs） composites were prepared by a sol-gel method with supercritical pretreatment. The photocatalytic degradation of acid yellow （AY） was investigated under UV radiation to estimate activity of catalysts and determine the kinetics. And the effects of parameters including the initial concentration of AY, light intensity and TiO2 content in catalysts were examined. The results indicate that TAs has a higher efficiency in decomposition of AY than P25, pure TiO2 particles as well as the mixture of TiO2 powder and active carbon. The photocatalytic degradation rate is found to follow the pseudo-first order kinetics with respect to the AY concentration. The new kinetic model fairly resembles the classic Langmuir-Hinshelwood equation, and the rate constant is proportional to the square root of the light intensity in a wide range. However, its absorption performance depends on the surface areas of catalysts. The model fits quite well with the experimental data and elucidates phenomena about the effects of the TiO2 content in TAs on the degradation rate.展开更多
Steam reforming （SR） of dimethyl ether （DME） was investigated for the production of hydrogen for fuel cells. The activity of a series of solid acids for DME hydrolysis was investigated. The solid acid catalysts we...Steam reforming （SR） of dimethyl ether （DME） was investigated for the production of hydrogen for fuel cells. The activity of a series of solid acids for DME hydrolysis was investigated. The solid acid catalysts were ZSM-5 [Si/A] = 25, 38 and 50： denoted Z（Si/Al）] and acidic alumina （γ-Al2O3） with an acid strength order that was Z（25）〉Z（38）〉Z（50）〉γ-Al2O3. Stronger acidity gave higher DME hydrolysis conversion. Physical mixtures containing a CuO-ZnO-Al2O3-ZrO2 catalyst and solid acid catalyst to couple DME hydrolysis and methanol SR were used to examine the acidity effects on DME SR. DME SR activity strongly depended on the activity for DME hydrolysis. Z（25） was the best solid acid catalyst for DME, SR and gave a DME conversion〉90% IT= 240℃,n（H20）/n（DME） = 3.5, space velocity = 1179 ml.（g cat）^-1.h^-1, and P= 0.1MPa]. The influences of the reaction temperature, space velocity and feed molar ratio were studied. Hydrogen production significantly depended on temperature and space velocity. A bifunctional catalyst of CuO-ZnO-Al2O3-ZrO2 catalyst and ZSM-5 gave a high H2 production rate and CO2 selectivity.展开更多
This paper describes the preparation and evaluation of a micro-sphere catalytic complex for the hydrogen production in a Reactive Sorption Enhanced Reforming （ReSER） process. The catalytic complex made by a spray te...This paper describes the preparation and evaluation of a micro-sphere catalytic complex for the hydrogen production in a Reactive Sorption Enhanced Reforming （ReSER） process. The catalytic complex made by a spray technique has a dual function containing Ni as a catalytic material and CaO as an adsorption material used in the ReSER process. The attrition characteristics of the catalytic complex are acceptable for the commercial used. The nano GaCO3 material used as a precursor of CaO showed a desirable durability with a CO2 sorption capacity of 0.6 mol CO2/kg after 10 repeating cycles under the carbonation temperature of 600 ℃, a CO2 partial pressure of 0.02 MPa, and a calcination temperature of 750 ℃ in N2 measured by a thermal gravimetric analyzer. The testing of the catalytic complex for ReSER showed a hydrogen yield of over 95 % （v/v） in the laboratory fixed fluidized bed reactor. The catalytic system has an attractive prospect in the ReSER process for hydrogen production, especially in the fluidized mode where reactor and regenerator combined in a cycling process.展开更多
Syngas to aromatics(STA)over bifunctional catalysts has attracted much attention in recent years,but the mechanism underlying the formation of aromatics remains controversial.The critical reaction intermediates,carbox...Syngas to aromatics(STA)over bifunctional catalysts has attracted much attention in recent years,but the mechanism underlying the formation of aromatics remains controversial.The critical reaction intermediates,carboxylates,were first identified and then confirmed to essentially promote aromatization in the syngas conversion over a ZnCrAlO_(x)&H-ZSM-5 composite catalyst.This study provides evidence that the carboxylates can be formed during the reactions of formate species and olefins.In addition,it is shown that the carboxylates favor the formation of aromatics over H-ZSM-5 even in the presence of H2.A novel mechanism for the formation of aromatics via the generation and transformation of carboxylate intermediates is proposed,and the transformation of carboxylates to aromatics via methyl-2-cyclopenten-1-one(MCPO)intermediates is indeed likely.A better understanding of the formation mechanism of aromatics would help optimize the composite catalyst.展开更多
A novel metal-free photocatalyst--sulfur/graphene （S/GR） composite--has been synthesized using a facile one-pot, two-step hydrothermal method with thiosulfate and graphene oxide （GO） as precursors. A green reducta...A novel metal-free photocatalyst--sulfur/graphene （S/GR） composite--has been synthesized using a facile one-pot, two-step hydrothermal method with thiosulfate and graphene oxide （GO） as precursors. A green reductant--L-ascorbic add--was used to transform GO to GR under mild conditions. The photocatalyst powders were characterized by Fourier transform infrared spectroscop, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and energy dispersive spectroscopy. Experimental tests were conducted on the photocatalytic decomposition of methyl orange （MO） by different catalysts. Compared to pure oL-S, the as-prepared S/GR composite showed much enhanced photocatalytic activity for the degradation of MO under both UV and solar light. The presence of GR also greatly increased the hydrophilicity and adsorption capacity of the catalyst material. The results indicate that the incorporation of GR with a-S results in a synergistic effect for the S-based photocatalysts offering more effective environmental applications.展开更多
基金supported by the National Natural Science Foundation of China(2100705351302241)+1 种基金the Education Department of Henan Province(2012GGJS-174)Xuchang University Science Research Foundation(2015011)~~
文摘Formation of a p–n heterojunction rather than p-type or n-type semiconductors can enhance the separation of photogenerated electrons and holes and increase the quantum efficiency of photocatalytic reactions owing to the difference of the electric potential in the inner electric field near the junction,pointing from n toward p. n-Ag3PO4/p-Ag2CO3 p–n heterojunction composites are prepared through a facile coprecipitation process. The obtained Ag3PO4/Ag2CO3 p–n heterojunctions exhibit excellent photocatalytic performance in the removal of rhodamine B（RhB） compared with Ag3PO4 and Ag2CO3. The 40%-Ag3PO4/Ag2CO3 composite photocatalyst（40 mol% Ag3PO4 and 60 mol% Ag2CO3） exhibits the best photocatalytic activity under visible light,demonstrating the ability to completely degrade RhB within 15 min. Transient photovoltage characterization and an active species trapping experiment further indicate that the formation of a p–n heterojunction structure can greatly enhance the separation efficiency of photogenerated carriers and produce more free h＋active species,which is the predominant contributor for RhB removal.
基金Project(50802034) supported by the National Natural Science Foundation of ChinaProject(11A093) supported by the Key Project Foundation by the Education Department of Hunan Province,China
文摘TiO2-coated activated carbon surface （TAs） composites were prepared by a sol-gel method with supercritical pretreatment. The photocatalytic degradation of acid yellow （AY） was investigated under UV radiation to estimate activity of catalysts and determine the kinetics. And the effects of parameters including the initial concentration of AY, light intensity and TiO2 content in catalysts were examined. The results indicate that TAs has a higher efficiency in decomposition of AY than P25, pure TiO2 particles as well as the mixture of TiO2 powder and active carbon. The photocatalytic degradation rate is found to follow the pseudo-first order kinetics with respect to the AY concentration. The new kinetic model fairly resembles the classic Langmuir-Hinshelwood equation, and the rate constant is proportional to the square root of the light intensity in a wide range. However, its absorption performance depends on the surface areas of catalysts. The model fits quite well with the experimental data and elucidates phenomena about the effects of the TiO2 content in TAs on the degradation rate.
基金Supported by the Ministry of Science and Technology （G1999022408） and the National Natural Science Foundation of China （20773075）.
文摘Steam reforming （SR） of dimethyl ether （DME） was investigated for the production of hydrogen for fuel cells. The activity of a series of solid acids for DME hydrolysis was investigated. The solid acid catalysts were ZSM-5 [Si/A] = 25, 38 and 50： denoted Z（Si/Al）] and acidic alumina （γ-Al2O3） with an acid strength order that was Z（25）〉Z（38）〉Z（50）〉γ-Al2O3. Stronger acidity gave higher DME hydrolysis conversion. Physical mixtures containing a CuO-ZnO-Al2O3-ZrO2 catalyst and solid acid catalyst to couple DME hydrolysis and methanol SR were used to examine the acidity effects on DME SR. DME SR activity strongly depended on the activity for DME hydrolysis. Z（25） was the best solid acid catalyst for DME, SR and gave a DME conversion〉90% IT= 240℃,n（H20）/n（DME） = 3.5, space velocity = 1179 ml.（g cat）^-1.h^-1, and P= 0.1MPa]. The influences of the reaction temperature, space velocity and feed molar ratio were studied. Hydrogen production significantly depended on temperature and space velocity. A bifunctional catalyst of CuO-ZnO-Al2O3-ZrO2 catalyst and ZSM-5 gave a high H2 production rate and CO2 selectivity.
基金supports from Sinopec of China and from National Science Foundation of China (NSFC) under contracts No.20676119supports from Sinopec of China and from National Science Foundation of China (NSFC) under contracts No. 20876142 respectively
文摘This paper describes the preparation and evaluation of a micro-sphere catalytic complex for the hydrogen production in a Reactive Sorption Enhanced Reforming （ReSER） process. The catalytic complex made by a spray technique has a dual function containing Ni as a catalytic material and CaO as an adsorption material used in the ReSER process. The attrition characteristics of the catalytic complex are acceptable for the commercial used. The nano GaCO3 material used as a precursor of CaO showed a desirable durability with a CO2 sorption capacity of 0.6 mol CO2/kg after 10 repeating cycles under the carbonation temperature of 600 ℃, a CO2 partial pressure of 0.02 MPa, and a calcination temperature of 750 ℃ in N2 measured by a thermal gravimetric analyzer. The testing of the catalytic complex for ReSER showed a hydrogen yield of over 95 % （v/v） in the laboratory fixed fluidized bed reactor. The catalytic system has an attractive prospect in the ReSER process for hydrogen production, especially in the fluidized mode where reactor and regenerator combined in a cycling process.
文摘Syngas to aromatics(STA)over bifunctional catalysts has attracted much attention in recent years,but the mechanism underlying the formation of aromatics remains controversial.The critical reaction intermediates,carboxylates,were first identified and then confirmed to essentially promote aromatization in the syngas conversion over a ZnCrAlO_(x)&H-ZSM-5 composite catalyst.This study provides evidence that the carboxylates can be formed during the reactions of formate species and olefins.In addition,it is shown that the carboxylates favor the formation of aromatics over H-ZSM-5 even in the presence of H2.A novel mechanism for the formation of aromatics via the generation and transformation of carboxylate intermediates is proposed,and the transformation of carboxylates to aromatics via methyl-2-cyclopenten-1-one(MCPO)intermediates is indeed likely.A better understanding of the formation mechanism of aromatics would help optimize the composite catalyst.
文摘A novel metal-free photocatalyst--sulfur/graphene （S/GR） composite--has been synthesized using a facile one-pot, two-step hydrothermal method with thiosulfate and graphene oxide （GO） as precursors. A green reductant--L-ascorbic add--was used to transform GO to GR under mild conditions. The photocatalyst powders were characterized by Fourier transform infrared spectroscop, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and energy dispersive spectroscopy. Experimental tests were conducted on the photocatalytic decomposition of methyl orange （MO） by different catalysts. Compared to pure oL-S, the as-prepared S/GR composite showed much enhanced photocatalytic activity for the degradation of MO under both UV and solar light. The presence of GR also greatly increased the hydrophilicity and adsorption capacity of the catalyst material. The results indicate that the incorporation of GR with a-S results in a synergistic effect for the S-based photocatalysts offering more effective environmental applications.
