Bi-functional catalysts,which can be traced back to 1960s,are widely applied in energy conversion and chemical transformation[1].Generally,the enhanced performance of the bi-functional catalyst comes from the local ge...Bi-functional catalysts,which can be traced back to 1960s,are widely applied in energy conversion and chemical transformation[1].Generally,the enhanced performance of the bi-functional catalyst comes from the local geometry or electron density change after the second component introduced.These changes facilitate the reaction at the structure or electron density level[2].In fact,it is a great challenge to understand and control those effects[3].展开更多
A series of mesoporous Ta and Ta-W oxides have been prepared and employed as solid acid catalysts for the dehydration of fructose and glucose to 5-hydroxymethylfurfural(HMF).Solid state 31 P MAS NMR spectroscopic resu...A series of mesoporous Ta and Ta-W oxides have been prepared and employed as solid acid catalysts for the dehydration of fructose and glucose to 5-hydroxymethylfurfural(HMF).Solid state 31 P MAS NMR spectroscopic results using trimethylphosphine(TMP)as a probe molecule show that the acid strength and the ratio of Br?nsted to Lewis acid sites increase gradually with the addition of tungsten in tantalum oxide.It is found that high sugar conversion and HMF selectivity are achieved over catalyst with relatively high ratios of Br?nsted to Lewis acid sites.Unexpected stoichiometric excess of formic acid relative to levulinic acid can be observed mainly because of direct decomposition of fructose over Lewis acid sites.The addition of 2-butanol leads to the increase of sugars conversion and the HMF selectivity,especially for the catalyst with high ratio of Br?nsted to Lewis acid sites.Among them,Ta7W3 oxide catalyst shows 54%HMF selectivity and good reusability with the addition of 2-butanol by extracting HMF from aqueous phase and removing humins deposed on the surface of the catalyst.展开更多
Deoxygenative upgrading of 5-hydromethylfurfural(HMF)into valuable chemicals has attracted intensive research interest in recent years,with product selectivity control remaining an important topic.Herein,TiO_(2) suppo...Deoxygenative upgrading of 5-hydromethylfurfural(HMF)into valuable chemicals has attracted intensive research interest in recent years,with product selectivity control remaining an important topic.Herein,TiO_(2) supported gold catalysts coated with a thin N-doped porous carbon(NPC)layer were developed via a polydopamine-coating-carbonization strategy and utilized for pathway-specific conversion of HMF into 5-methylfurfural(5-MF)with the use of renewable formic acid(FA)as the deoxygenation reagent.The as-fabricated Au/TiO_(2)@NPC exhibited excellent catalytic performance with a high yield of 5-MF(>95%).The catalytic behavior of Au@NPC-based catalysts was shown to be correlated with the suitable combination of highly dispersed Au nanoparticles and favorable interfacial interactions in the Au@NPC core-shell hetero-nanoarchitectures,thereby facilitating the preferential esterification of HMF with FA and suppressing unproductive FA dehydrogenation,which promoted the selective formylation/decarboxylation of hydroxy-methyl group in HMF in a pathway-specific manner.The present NPC/metal interfacial engineering strategy may provide a potential guide for the rational design of advanced catalysts for a wide variety of heterogeneous catalysis processes in terms of the conversion of biomass source.展开更多
TiO_(2)nanosheets with dominant{001}facets,coupled with Cs_(2.5)H_(0.5)PW_(12)O_(40),were successfully synthesized by a one-step hydrothermal reaction.The photocatalytic activity of nanocatalysts was evaluated by the ...TiO_(2)nanosheets with dominant{001}facets,coupled with Cs_(2.5)H_(0.5)PW_(12)O_(40),were successfully synthesized by a one-step hydrothermal reaction.The photocatalytic activity of nanocatalysts was evaluated by the degradation of Rhodamine B under UV light irradiation.The results showed that both the addition of Cs_(2.5)H_(0.5)PW_(12)O_(40)and the exposed{001}facets of TiO_(2)have a positive effect on the photocatalytic activity.The improved photoactivity of nanocomposites in comparison with that of TiO_(2)nanosheets could be attributed to the synergistic effect between Cs_(2.5)H_(0.5)PW_(12)O_(40)and TiO_(2)which facilitates the separation of photo-induced hole-electron pairs.展开更多
MgO nanosheets with exposed（111） facets were obtained through the preparation of Mg（OH）2 precursor by a hydrothermal method in the presence of oleylamine and subsequent calcination in air. The different preferred ...MgO nanosheets with exposed（111） facets were obtained through the preparation of Mg（OH）2 precursor by a hydrothermal method in the presence of oleylamine and subsequent calcination in air. The different preferred orientational assemblies of Mg O nanosheets, achieved by adjusting the polarity of dispersing solvents（ethanol and cyclohexane） during the sample preparation, show different structural and spectral features.展开更多
Anatase TiO2 samples with different ratios of {101} to {001} facets were prepared with hydrothermal method and further treated under three specific calcination atmospheres (air,H2,N2).The characterization results indi...Anatase TiO2 samples with different ratios of {101} to {001} facets were prepared with hydrothermal method and further treated under three specific calcination atmospheres (air,H2,N2).The characterization results indicate that {001} facets may generate more oxygen vacancies and more Ti3+ species than {101} facets.展开更多
A series of mesoporous Nb and Nb-W oxides were employed as highly active solid acid catalysts for the con- version of glucose to 5-hydroxymethylfurfural （HMF）. The results of solid state 31p MAS NMR spectroscopy wit...A series of mesoporous Nb and Nb-W oxides were employed as highly active solid acid catalysts for the con- version of glucose to 5-hydroxymethylfurfural （HMF）. The results of solid state 31p MAS NMR spectroscopy with adsorbed trimethylphosphine as probe molecule show that the addition of W in niobium oxide increases the number of Bronsted acid sites and decreases the number of Lewis acid sites. The catalytic performance for Nb-W oxides varied with the ratio of Bronsted to Lewis acid sites and high glucose conversion was observed over NbsW5 and NbTWs oxides with high ratios of Bronsted to Lewis acid sites. All Nb-W oxides show a relatively high selectivity of HMF, whereas no HMF forms over sulfuric acid due to its pure Bronsted acidity. The results indicate fast isom- erization of glucose to fructose over Lewis acid sites followed by dehydration of fructose to HMF over Bronsted acid sites. Moreover, comparing to the reaction occurred in aqueous media, the 2-butanol/H2O system enhances the HMF selectivity and stabilizes the activity of the catalysts which gives the highest HMF selectivity of 52% over NbTW3 oxide. The 2-butanol/H2O catalytic system can also be employed in conversion of sucrose, achieving HMF selectivity of 46% over Nb5W5 oxide.展开更多
A series of Ce-promoted 6.7%Ni-containing mesoporous silica(Ce-Ni-Si O2)with varying Ce content(0.5%–4.8%)was prepared using the evaporation-induced self-assembly method.The characterization results showed that Ce an...A series of Ce-promoted 6.7%Ni-containing mesoporous silica(Ce-Ni-Si O2)with varying Ce content(0.5%–4.8%)was prepared using the evaporation-induced self-assembly method.The characterization results showed that Ce and Ni species were homogeneously incorporated into the mesoporous silica matrix.The catalytic properties of these samples in the dry reforming of methane reaction revealed that the catalysts(e.g.,1.2%Ce-Ni-Si O2)containing highly dispersed small Ni particles exhibited excellent catalytic activity and long-term stability,which is attributed to the anchoring effect of the Ce and its ability to increase surface oxygen species concentration.展开更多
基金supported by the National Natural Science Foundation of China(91645201 and 21673046)the Ministry of Science and Technology(2017YFB0602204)。
文摘Bi-functional catalysts,which can be traced back to 1960s,are widely applied in energy conversion and chemical transformation[1].Generally,the enhanced performance of the bi-functional catalyst comes from the local geometry or electron density change after the second component introduced.These changes facilitate the reaction at the structure or electron density level[2].In fact,it is a great challenge to understand and control those effects[3].
文摘A series of mesoporous Ta and Ta-W oxides have been prepared and employed as solid acid catalysts for the dehydration of fructose and glucose to 5-hydroxymethylfurfural(HMF).Solid state 31 P MAS NMR spectroscopic results using trimethylphosphine(TMP)as a probe molecule show that the acid strength and the ratio of Br?nsted to Lewis acid sites increase gradually with the addition of tungsten in tantalum oxide.It is found that high sugar conversion and HMF selectivity are achieved over catalyst with relatively high ratios of Br?nsted to Lewis acid sites.Unexpected stoichiometric excess of formic acid relative to levulinic acid can be observed mainly because of direct decomposition of fructose over Lewis acid sites.The addition of 2-butanol leads to the increase of sugars conversion and the HMF selectivity,especially for the catalyst with high ratio of Br?nsted to Lewis acid sites.Among them,Ta7W3 oxide catalyst shows 54%HMF selectivity and good reusability with the addition of 2-butanol by extracting HMF from aqueous phase and removing humins deposed on the surface of the catalyst.
文摘Deoxygenative upgrading of 5-hydromethylfurfural(HMF)into valuable chemicals has attracted intensive research interest in recent years,with product selectivity control remaining an important topic.Herein,TiO_(2) supported gold catalysts coated with a thin N-doped porous carbon(NPC)layer were developed via a polydopamine-coating-carbonization strategy and utilized for pathway-specific conversion of HMF into 5-methylfurfural(5-MF)with the use of renewable formic acid(FA)as the deoxygenation reagent.The as-fabricated Au/TiO_(2)@NPC exhibited excellent catalytic performance with a high yield of 5-MF(>95%).The catalytic behavior of Au@NPC-based catalysts was shown to be correlated with the suitable combination of highly dispersed Au nanoparticles and favorable interfacial interactions in the Au@NPC core-shell hetero-nanoarchitectures,thereby facilitating the preferential esterification of HMF with FA and suppressing unproductive FA dehydrogenation,which promoted the selective formylation/decarboxylation of hydroxy-methyl group in HMF in a pathway-specific manner.The present NPC/metal interfacial engineering strategy may provide a potential guide for the rational design of advanced catalysts for a wide variety of heterogeneous catalysis processes in terms of the conversion of biomass source.
基金This work was supported by the National Natural Science Foundation of China(Nos.21371035,21173050).
文摘TiO_(2)nanosheets with dominant{001}facets,coupled with Cs_(2.5)H_(0.5)PW_(12)O_(40),were successfully synthesized by a one-step hydrothermal reaction.The photocatalytic activity of nanocatalysts was evaluated by the degradation of Rhodamine B under UV light irradiation.The results showed that both the addition of Cs_(2.5)H_(0.5)PW_(12)O_(40)and the exposed{001}facets of TiO_(2)have a positive effect on the photocatalytic activity.The improved photoactivity of nanocomposites in comparison with that of TiO_(2)nanosheets could be attributed to the synergistic effect between Cs_(2.5)H_(0.5)PW_(12)O_(40)and TiO_(2)which facilitates the separation of photo-induced hole-electron pairs.
基金supported by the National Natural Science Foundation of China (Nos. 21673046, 21473036, 21371035, 91645201)
文摘MgO nanosheets with exposed（111） facets were obtained through the preparation of Mg（OH）2 precursor by a hydrothermal method in the presence of oleylamine and subsequent calcination in air. The different preferred orientational assemblies of Mg O nanosheets, achieved by adjusting the polarity of dispersing solvents（ethanol and cyclohexane） during the sample preparation, show different structural and spectral features.
基金This work was supported by the National Natural Science Foundation of China (Nos. 21673046, 91645201)the National Key R&D Program of China (No. 2017YFB0602204).
文摘Anatase TiO2 samples with different ratios of {101} to {001} facets were prepared with hydrothermal method and further treated under three specific calcination atmospheres (air,H2,N2).The characterization results indicate that {001} facets may generate more oxygen vacancies and more Ti3+ species than {101} facets.
文摘A series of mesoporous Nb and Nb-W oxides were employed as highly active solid acid catalysts for the con- version of glucose to 5-hydroxymethylfurfural （HMF）. The results of solid state 31p MAS NMR spectroscopy with adsorbed trimethylphosphine as probe molecule show that the addition of W in niobium oxide increases the number of Bronsted acid sites and decreases the number of Lewis acid sites. The catalytic performance for Nb-W oxides varied with the ratio of Bronsted to Lewis acid sites and high glucose conversion was observed over NbsW5 and NbTWs oxides with high ratios of Bronsted to Lewis acid sites. All Nb-W oxides show a relatively high selectivity of HMF, whereas no HMF forms over sulfuric acid due to its pure Bronsted acidity. The results indicate fast isom- erization of glucose to fructose over Lewis acid sites followed by dehydration of fructose to HMF over Bronsted acid sites. Moreover, comparing to the reaction occurred in aqueous media, the 2-butanol/H2O system enhances the HMF selectivity and stabilizes the activity of the catalysts which gives the highest HMF selectivity of 52% over NbTW3 oxide. The 2-butanol/H2O catalytic system can also be employed in conversion of sucrose, achieving HMF selectivity of 46% over Nb5W5 oxide.
基金supported by the National Basic Research Program of China(2009CB623506)the National Natural Science Foundation of China(21371035,21173050)the Shanghai Leading Academic Discipline Project(B108)
文摘A series of Ce-promoted 6.7%Ni-containing mesoporous silica(Ce-Ni-Si O2)with varying Ce content(0.5%–4.8%)was prepared using the evaporation-induced self-assembly method.The characterization results showed that Ce and Ni species were homogeneously incorporated into the mesoporous silica matrix.The catalytic properties of these samples in the dry reforming of methane reaction revealed that the catalysts(e.g.,1.2%Ce-Ni-Si O2)containing highly dispersed small Ni particles exhibited excellent catalytic activity and long-term stability,which is attributed to the anchoring effect of the Ce and its ability to increase surface oxygen species concentration.
