Acetol is a major light oxygenate and readily produced from staged or fast pyrolysis of lignocellulose biomass. Herein we report that acetol can be selectively converted to methyl pyruvate, an important fine chemical,...Acetol is a major light oxygenate and readily produced from staged or fast pyrolysis of lignocellulose biomass. Herein we report that acetol can be selectively converted to methyl pyruvate, an important fine chemical, through oxidative esterification over Au-based catalysts. Detailed experimental studies showed that Au on amphoteric supports with appropriate strength and balanced ratio of acid and base sites can facilitate the desired oxidative-esterification pathway without accelerating undesired aldol-condensation or Cannizzaro reactions. In particular, hydroxyapatite (with a Ca/P ratio of 1.62) supported Au achieved 87% selectivity to methyl pyruvate at an acetol conversion of 62%.展开更多
Supported Pd catalysts with varied Pd loadings(x=0.5 wt%, 2.0 wt%, 5.0 wt%, 7.5 wt%, 15.0 wt%) were prepared by the incipient wetness impregnation method using a ZnAl_(2)O_(4) spinel support.We found that ZnAl_(2)O_(4...Supported Pd catalysts with varied Pd loadings(x=0.5 wt%, 2.0 wt%, 5.0 wt%, 7.5 wt%, 15.0 wt%) were prepared by the incipient wetness impregnation method using a ZnAl_(2)O_(4) spinel support.We found that ZnAl_(2)O_(4) supported Pd catalysts with low Pd loadings(e.g., 0.5 wt%) are very selective in syngas conversion to methanol and dimethyl-ether(DME).XRD and TEM characterization shows that,after reduction at350℃,PdZnβ phase with Pd:Zn molar ratio of 1:1 is favored to form predominantly on the spinel support at relatively low Pd loadings,i.e.less than 5.0 wt%, while Pd-rich PdZnα alloy phase exists at Pd loadings above 5.0 wt%.A higher reduction temperature such as 500℃ can facilitate the transformation from PdZnα to PdZnβ phase in those catalysts with high Pd loading.We further found that catalysts with predominant PdZnβ phase are selective in the methanol and DME production from syngas,while the presence of PdZnα phase leads to the notable formation of alkanes byproducts,resulting in reduced methanol and DME selectivity.DME formation from dehydration of methanol depends on the acidity of catalysts,which was found to increase with Pd loading,probably due to the formation of isolated Al_(2)O_(3) as a result of Zn migrating from ZnAl_(2)O_(4) spinel phase to form the PdZn phases with Pd.展开更多
Catalytic fast pyrolysis （CFP） is deemed as the most promising way to convert biomass to transportation fuels or value added chemicals. Most works in literature so far have focused on the in situ CFP where the catal...Catalytic fast pyrolysis （CFP） is deemed as the most promising way to convert biomass to transportation fuels or value added chemicals. Most works in literature so far have focused on the in situ CFP where the catalysts are packed or co-fed with the feedstock in the pyrolysis reactor. However, the ex situ CFP with catalysts separated from the pyrolyzer has attracted more and more attentions due to its unique advantages of individually optimizing the pyrolysis conditions and catalyst performances. This review compares the differences between the in situ and ex situ CFP operation, and summarizes the development and progress of ex situ CFP applications, including the rationale and performances of different catalysts, and the choices of suitable ex situ reactor systems. Due to the complex composition of bio-oil, no single approach was believed to be able to solve the problems completely among all those existing technologies. With the increased understanding of catalyst performances and reaction process, the recent trend toward an integration of biomass or bio-oil fractionation with subsequent thermo/biochemical conversion routes is also discussed.展开更多
Out-of-time-ordered correlation(OTOC)functions have been used as an indicator of quantum chaos in a lot of physical systems.In this work,we numerically demonstrate that zero temperature OTOC can detect quantum phase t...Out-of-time-ordered correlation(OTOC)functions have been used as an indicator of quantum chaos in a lot of physical systems.In this work,we numerically demonstrate that zero temperature OTOC can detect quantum phase transition in the anisotropic Dicke model.The phase diagram is given with OTOC.The finite-size effect is studied.Finally,the temperature effect is discussed.展开更多
基金supported by the National Natural Science Foundation of China(91545114,91545203,and 21576227)the 985 Program of the Chemistry and Chemical Engineering disciplines of Xiamen University~~
文摘Acetol is a major light oxygenate and readily produced from staged or fast pyrolysis of lignocellulose biomass. Herein we report that acetol can be selectively converted to methyl pyruvate, an important fine chemical, through oxidative esterification over Au-based catalysts. Detailed experimental studies showed that Au on amphoteric supports with appropriate strength and balanced ratio of acid and base sites can facilitate the desired oxidative-esterification pathway without accelerating undesired aldol-condensation or Cannizzaro reactions. In particular, hydroxyapatite (with a Ca/P ratio of 1.62) supported Au achieved 87% selectivity to methyl pyruvate at an acetol conversion of 62%.
基金supported by the Major Research Plan of National Natural Science Foundation of China(No.91545114 and No.91545203)the National Natural Science Foundation of China(No.21576227)。
文摘Supported Pd catalysts with varied Pd loadings(x=0.5 wt%, 2.0 wt%, 5.0 wt%, 7.5 wt%, 15.0 wt%) were prepared by the incipient wetness impregnation method using a ZnAl_(2)O_(4) spinel support.We found that ZnAl_(2)O_(4) supported Pd catalysts with low Pd loadings(e.g., 0.5 wt%) are very selective in syngas conversion to methanol and dimethyl-ether(DME).XRD and TEM characterization shows that,after reduction at350℃,PdZnβ phase with Pd:Zn molar ratio of 1:1 is favored to form predominantly on the spinel support at relatively low Pd loadings,i.e.less than 5.0 wt%, while Pd-rich PdZnα alloy phase exists at Pd loadings above 5.0 wt%.A higher reduction temperature such as 500℃ can facilitate the transformation from PdZnα to PdZnβ phase in those catalysts with high Pd loading.We further found that catalysts with predominant PdZnβ phase are selective in the methanol and DME production from syngas,while the presence of PdZnα phase leads to the notable formation of alkanes byproducts,resulting in reduced methanol and DME selectivity.DME formation from dehydration of methanol depends on the acidity of catalysts,which was found to increase with Pd loading,probably due to the formation of isolated Al_(2)O_(3) as a result of Zn migrating from ZnAl_(2)O_(4) spinel phase to form the PdZn phases with Pd.
文摘Catalytic fast pyrolysis （CFP） is deemed as the most promising way to convert biomass to transportation fuels or value added chemicals. Most works in literature so far have focused on the in situ CFP where the catalysts are packed or co-fed with the feedstock in the pyrolysis reactor. However, the ex situ CFP with catalysts separated from the pyrolyzer has attracted more and more attentions due to its unique advantages of individually optimizing the pyrolysis conditions and catalyst performances. This review compares the differences between the in situ and ex situ CFP operation, and summarizes the development and progress of ex situ CFP applications, including the rationale and performances of different catalysts, and the choices of suitable ex situ reactor systems. Due to the complex composition of bio-oil, no single approach was believed to be able to solve the problems completely among all those existing technologies. With the increased understanding of catalyst performances and reaction process, the recent trend toward an integration of biomass or bio-oil fractionation with subsequent thermo/biochemical conversion routes is also discussed.
文摘Out-of-time-ordered correlation(OTOC)functions have been used as an indicator of quantum chaos in a lot of physical systems.In this work,we numerically demonstrate that zero temperature OTOC can detect quantum phase transition in the anisotropic Dicke model.The phase diagram is given with OTOC.The finite-size effect is studied.Finally,the temperature effect is discussed.
