The effect of Mo/HZSM-5 pretreatment at 973 K in inert(He), oxidizing(artificial air), and carburizing(CH4/He mixture) atmospheres on its performance in non-oxidative methane dehydroaromatization(MDA) was investigated...The effect of Mo/HZSM-5 pretreatment at 973 K in inert(He), oxidizing(artificial air), and carburizing(CH4/He mixture) atmospheres on its performance in non-oxidative methane dehydroaromatization(MDA) was investigated. The effect of post-synthesis silylation on deactivation of external acid sites was also studied. Precarburization resulted in increased aromatic selectivity and improved catalyst stability. The benzene selectivity was the highest for the silylated Mo/HZSM-5 catalyst(benzene + naphthalene selectivity after 1 h on stream was close to 100%). The deactivation of precarburized zeolites was less pronounced than that of zeolites heated in air or He. During heating in air or He, larger fractions of the molybdenum oxide species diffused into the micropores than during heating in methane. Carburization of the molybdenum oxide species in the micropores during MDA resulted in the formation of molybdenum carbide particles, and these contributed to pore blocking, making the Brnsted acid sites inaccessible. The formation of molybdenum carbides during heating in methane resulted in a less mobile Mo phase. It is argued that the presence of molybdenum carbide particles in the micropores contributes to rapid catalyst deactivation, in addition to the formation of hard coke on the external surface.展开更多
Controlling the interaction between metal nanoparticles and the support is a means to tune catalytic activity and stability.Herein we investigated the influence of the morphology of hematite on the performance of gold...Controlling the interaction between metal nanoparticles and the support is a means to tune catalytic activity and stability.Herein we investigated the influence of the morphology of hematite on the performance of gold for CO oxidation.Nanosphere and nanorod forms of hematite,α-Fe_(2)O_(3)(S)andα-Fe_(2)O_(3)(R)respectively,were used to support gold nanoparticles.The surface ofα-Fe_(2)O_(3)(R)was more corrugated than that ofα-Fe_(2)O_(3)(S).These defects provide anchoring sites for gold nanoparticle deposition and stabilization.Due to the stronger gold-support interactions,Au/α-Fe_(2)O_(3)(R)contained smaller and more hemispherical gold particles than Au/α-Fe_(2)O_(3)(S).Au/α-Fe_(2)O_(3)(R)was not only more active in CO oxidation but also much more stable as evident from the small change in gold particle size during reaction.The higher reducibility of Au/α-Fe_(2)O_(3)(R)also contributed to the higher CO oxidation activity.展开更多
Density functional theory calculations were carried out to investigate the influence of doping transition metal(TM) ions into the ceria surface on the activation of surface lattice oxygen atoms. For this purpose, the ...Density functional theory calculations were carried out to investigate the influence of doping transition metal(TM) ions into the ceria surface on the activation of surface lattice oxygen atoms. For this purpose, the structure and stability of the most stable(111) surface termination of CeO2 modified by TM ions was determined. Except for Zr and Pt dopants that preserve octahedral oxygen coordination, the TM dopants prefer a square-planar coordination when substituting the surface Ce ions. The surface construction from octahedral to square-planar is facile for all TM dopants, except for Pt(1.14 e V) and Zr(square-planar coordination unstable). Typically, the ionic radius of tetravalent TM cations is much smaller than that of Ce4+, resulting a significant tensile-strained lattice and explaining the lowered oxygen vacancy formation energy. Except for Zr, the square-planar structure is the preferred one when one oxygen vacancy is created. Thermodynamic analysis shows that TM-doped CeO2 surfaces contain oxygen defects under typical conditions of environmental catalysis. A case of practical importance is the facile lattice oxygen activation in Zr-doped CeO2(111), which benefits CO oxidation. The findings emphasize the origin of lattice oxygen activation and the preferred location of TM dopants in TM-ceria solid solution catalysts.展开更多
Mixed Ga–Zn oxynitrides were synthesized using coprecipitation, wet-precipitation, and sol-id-solution methods. The oxynitrides were used as supports for Rh nanoparticle catalysts in photo-catalytic water splitting, ...Mixed Ga–Zn oxynitrides were synthesized using coprecipitation, wet-precipitation, and sol-id-solution methods. The oxynitrides were used as supports for Rh nanoparticle catalysts in photo-catalytic water splitting, CO oxidation, and H2 oxidation. Mixed Ga–Zn oxynitrides produced by wet precipitation and nitridation had good visible-light-absorption properties and high surface areas, so they were used to support uniformly sized poly(vinylpyrrolidone)-stabilized Rh nanoparticles. The nanoparticle size range was 2–9 nm. These catalysts had negligible activity in photocatalytic H2 production by water splitting with methanol as a sacrificial agent. Other mixed Ga–Zn oxynitrides were also inactive. A reference sample provided by Domen also showed very low activity. The in-fluence of particle size on Rh-catalyzed oxidation of CO and H2 was investigated. For CO oxidation, the activities of small particles were higher for particles with higher Rh oxidation degrees. The op-posite holds for H2 oxidation.展开更多
Heterogeneous single-atom catalysts(SACs)hold the promise of combining high catalytic performance with maximum utilization of often precious metals.We extend the current thermodynamic view of SAC stability in terms of...Heterogeneous single-atom catalysts(SACs)hold the promise of combining high catalytic performance with maximum utilization of often precious metals.We extend the current thermodynamic view of SAC stability in terms of the binding energy(E_(bind))of singlemetal atoms on a support to a kinetic(transport)one by considering the activation barrier for metal atom diffusion.A rapid computational screening approach allows predicting diffusion barriers for metal-support pairs based on Ebind of a metal atom to the support and the cohesive energy of the bulk metal(E_(c)).展开更多
Fischer–Tropsch Synthesis(FTS) constitutes catalytic technology that converts synthesis gas to synthetic liquid fuels and chemicals.While synthesis gas can be obtained from any carbonaceous feedstock,current industri...Fischer–Tropsch Synthesis(FTS) constitutes catalytic technology that converts synthesis gas to synthetic liquid fuels and chemicals.While synthesis gas can be obtained from any carbonaceous feedstock,current industrial FTS operations are almost exclusively based on natural gas.Due to the energy structure of China where cheap coal is abundant,coal to liquids(CTL) technology involving coal gasification,FTS and syncrude upgrading is increasingly being considered as a viable option to convert coal to clean transportation fuels.In this brief paper,we review some pertinent issues about Fe-and Co-based FTS catalysts.Fe is better suited to convert synthesis gas derived from coal gasification into fuels.The authors limit themselves to noting some important trends in the research on Fe-based catalysts.They focus on the preparation of phase-pure carbides and innovative cheap synthesis methods for obtaining active and stable catalysts.These approaches should be augmented by(1) computational investigations that are increasingly able to predict not only mechanism,reaction rates and selectivity but also optimum catalyst composition,as well as(2) characterization of the catalytic materials under conditions close to the operation in real reactors.展开更多
基金supported by the Advanced Research Center for Chemical Building Blocks,ARC CBBC,which is co-founded and co-financed by the Netherlands Organization for Scientific Research(NWO)and the Netherlands Ministry of Economic Affairs。
基金financially supported by the Mitrphol group, the Vidyasirimedhi Institute of Science and Technologythe Srimedhi royal scholarship from HRH Princess Maha Chakri Sirindhorn+3 种基金the National Research Council of Thailand (Mid-career Scholar Research 2023)funded by the National Research Council of Thailand (NRCT) and Vidyasirimedhi Institute of Science and Technology: VISTEC (N42A660307)financial support from Thailand Science Research and Innovation (TSRI, FRB660004/0457)funding support from the NSRF via the Program Management Unit for Human Resources & Institutional Development, Research and Innovation (B39G660027)。
基金supported by the European Union through the EU-FP7 NEXT-GTL consortium(NMP3-LA-2009-229183)
文摘The effect of Mo/HZSM-5 pretreatment at 973 K in inert(He), oxidizing(artificial air), and carburizing(CH4/He mixture) atmospheres on its performance in non-oxidative methane dehydroaromatization(MDA) was investigated. The effect of post-synthesis silylation on deactivation of external acid sites was also studied. Precarburization resulted in increased aromatic selectivity and improved catalyst stability. The benzene selectivity was the highest for the silylated Mo/HZSM-5 catalyst(benzene + naphthalene selectivity after 1 h on stream was close to 100%). The deactivation of precarburized zeolites was less pronounced than that of zeolites heated in air or He. During heating in air or He, larger fractions of the molybdenum oxide species diffused into the micropores than during heating in methane. Carburization of the molybdenum oxide species in the micropores during MDA resulted in the formation of molybdenum carbide particles, and these contributed to pore blocking, making the Brnsted acid sites inaccessible. The formation of molybdenum carbides during heating in methane resulted in a less mobile Mo phase. It is argued that the presence of molybdenum carbide particles in the micropores contributes to rapid catalyst deactivation, in addition to the formation of hard coke on the external surface.
文摘Controlling the interaction between metal nanoparticles and the support is a means to tune catalytic activity and stability.Herein we investigated the influence of the morphology of hematite on the performance of gold for CO oxidation.Nanosphere and nanorod forms of hematite,α-Fe_(2)O_(3)(S)andα-Fe_(2)O_(3)(R)respectively,were used to support gold nanoparticles.The surface ofα-Fe_(2)O_(3)(R)was more corrugated than that ofα-Fe_(2)O_(3)(S).These defects provide anchoring sites for gold nanoparticle deposition and stabilization.Due to the stronger gold-support interactions,Au/α-Fe_(2)O_(3)(R)contained smaller and more hemispherical gold particles than Au/α-Fe_(2)O_(3)(S).Au/α-Fe_(2)O_(3)(R)was not only more active in CO oxidation but also much more stable as evident from the small change in gold particle size during reaction.The higher reducibility of Au/α-Fe_(2)O_(3)(R)also contributed to the higher CO oxidation activity.
基金supported by The Netherlands Organization for Scientific Research(NWO)through a Vici grant and Nuffic fundingfunding from the European Union’s Horizon 2020 research and innovation programme under grant No.686086(Partial-PGMs)。
文摘Density functional theory calculations were carried out to investigate the influence of doping transition metal(TM) ions into the ceria surface on the activation of surface lattice oxygen atoms. For this purpose, the structure and stability of the most stable(111) surface termination of CeO2 modified by TM ions was determined. Except for Zr and Pt dopants that preserve octahedral oxygen coordination, the TM dopants prefer a square-planar coordination when substituting the surface Ce ions. The surface construction from octahedral to square-planar is facile for all TM dopants, except for Pt(1.14 e V) and Zr(square-planar coordination unstable). Typically, the ionic radius of tetravalent TM cations is much smaller than that of Ce4+, resulting a significant tensile-strained lattice and explaining the lowered oxygen vacancy formation energy. Except for Zr, the square-planar structure is the preferred one when one oxygen vacancy is created. Thermodynamic analysis shows that TM-doped CeO2 surfaces contain oxygen defects under typical conditions of environmental catalysis. A case of practical importance is the facile lattice oxygen activation in Zr-doped CeO2(111), which benefits CO oxidation. The findings emphasize the origin of lattice oxygen activation and the preferred location of TM dopants in TM-ceria solid solution catalysts.
基金the financial support by the Royal Netherlands Academy of Sciences and Arts and the Chinese Ministry of Science and Technology as part of the Program Strategic Scientific Alliances (PSA)supported by ESRF
文摘Mixed Ga–Zn oxynitrides were synthesized using coprecipitation, wet-precipitation, and sol-id-solution methods. The oxynitrides were used as supports for Rh nanoparticle catalysts in photo-catalytic water splitting, CO oxidation, and H2 oxidation. Mixed Ga–Zn oxynitrides produced by wet precipitation and nitridation had good visible-light-absorption properties and high surface areas, so they were used to support uniformly sized poly(vinylpyrrolidone)-stabilized Rh nanoparticles. The nanoparticle size range was 2–9 nm. These catalysts had negligible activity in photocatalytic H2 production by water splitting with methanol as a sacrificial agent. Other mixed Ga–Zn oxynitrides were also inactive. A reference sample provided by Domen also showed very low activity. The in-fluence of particle size on Rh-catalyzed oxidation of CO and H2 was investigated. For CO oxidation, the activities of small particles were higher for particles with higher Rh oxidation degrees. The op-posite holds for H2 oxidation.
基金This work has received funding from the European Union’s Horizon 2020 research and innovation programme under grant No 686086(Partial-PGMs)Y.W.,K.A.,and D.G.V.acknowledge support by the RAPID manufacturing institute,supported by the Department of Energy(DOE)Advanced Manufacturing Office(AMO),award number DE-EE0007888-9.5.
文摘Heterogeneous single-atom catalysts(SACs)hold the promise of combining high catalytic performance with maximum utilization of often precious metals.We extend the current thermodynamic view of SAC stability in terms of the binding energy(E_(bind))of singlemetal atoms on a support to a kinetic(transport)one by considering the activation barrier for metal atom diffusion.A rapid computational screening approach allows predicting diffusion barriers for metal-support pairs based on Ebind of a metal atom to the support and the cohesive energy of the bulk metal(E_(c)).
文摘Fischer–Tropsch Synthesis(FTS) constitutes catalytic technology that converts synthesis gas to synthetic liquid fuels and chemicals.While synthesis gas can be obtained from any carbonaceous feedstock,current industrial FTS operations are almost exclusively based on natural gas.Due to the energy structure of China where cheap coal is abundant,coal to liquids(CTL) technology involving coal gasification,FTS and syncrude upgrading is increasingly being considered as a viable option to convert coal to clean transportation fuels.In this brief paper,we review some pertinent issues about Fe-and Co-based FTS catalysts.Fe is better suited to convert synthesis gas derived from coal gasification into fuels.The authors limit themselves to noting some important trends in the research on Fe-based catalysts.They focus on the preparation of phase-pure carbides and innovative cheap synthesis methods for obtaining active and stable catalysts.These approaches should be augmented by(1) computational investigations that are increasingly able to predict not only mechanism,reaction rates and selectivity but also optimum catalyst composition,as well as(2) characterization of the catalytic materials under conditions close to the operation in real reactors.
