The direct synthesis of dimethyl carbonate(DMC)from CO_(2)and methanol has attracted much attention as an environmentally benign and alternative route for conventional routes.Herein,a series of cerium oxide catalysts ...The direct synthesis of dimethyl carbonate(DMC)from CO_(2)and methanol has attracted much attention as an environmentally benign and alternative route for conventional routes.Herein,a series of cerium oxide catalysts with various textural features and surface properties were prepared by the one-pot synthesis method for the direct DMC synthesis from CO_(2)and methanol,and the structure-performance relationship was investigated in detail.Characterization results revealed that both of surface acid-base properties and the oxygen vacancies contents decreased with the rising crystallinity at increasingly higher calcination temperature accompanied by an unexpectedly volcano-shaped trend of DMC yield observed on the catalysts.In situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)studies indicated that the adsorption rate of methanol is slower than that of CO_(2)and the methanol activation state largely influences the formation of key intermediate.Although the enhanced surface acidity-basicity and oxygen vacancies brought by low-temperature calcination could facilitate the activation of CO_(2),the presence of excess strongly basic sites on low-crystallinity sample was detrimental to DMC synthesis due to the preferred formation of unreactive mono/polydentate carbonates as well as the further impediment of methanol activation.Moreover,with the use of 2-cyanopyridine as a dehydration reagent,the DMC synthesis was found to be both influenced by the promotion from the rapid in situ removal of water and the inhibition from the competitive adsorption of hydration products on the same active sites.展开更多
MoS_2 samples with controllable morphologies and structures were synthesized using surfactantassisted hydrothermal processes.The effects of surfactants（PEG,PVP,P123,SDS,AOT,and CTAB）on the morphologies and structure...MoS_2 samples with controllable morphologies and structures were synthesized using surfactantassisted hydrothermal processes.The effects of surfactants（PEG,PVP,P123,SDS,AOT,and CTAB）on the morphologies and structures of MoS_2 samples were investigated.The results revealed that spherical,bulk-like,and flower-like MoS_2 particles assembled by NH4~＋-intercalated MoS_2 nano-sheets were synthesized.The morphologies of the MoS_2 samples and their structures（including the slab length and the number of stacked layers） of MoS_2 nano-sheets in these samples could be controlled by adjusting the surfactants.Mono-dispersed spherical MoS_2 particles could be synthesized with PEG via the creation of MoS_2 nano-sheets with slab lengths shorter than 15 nm and fewer than six stacked layers.Possible formation mechanisms of these MoS_2 samples created via surfactant-assisted hydrothermal processes are proposed.Further,the catalytic activities of MoS_2 samples for anthracene hydrogenation were evaluated in a slurry-bed reactor.The catalyst synthesized with the surfactant PEG exhibited the highest catalytic hydrogenation activity.Compared with the other catalysts,it had a smaller particle size,mono-dispersed spherical morphology,shorter slab length,and fewer stacked layers;these were all beneficial to exposing its active edges.This work provides an efficient approach to synthesize transition metal sulfides with controllable morphologies and structures.展开更多
Pt/activated carbon （Pt/AC） catalyst combined with base works efficiently for lactic acid production from glycerol under mild conditions. Base type （LiOH, NaOH, KOH, or Ba（OH）2） and base/glycerol molar ratio sig...Pt/activated carbon （Pt/AC） catalyst combined with base works efficiently for lactic acid production from glycerol under mild conditions. Base type （LiOH, NaOH, KOH, or Ba（OH）2） and base/glycerol molar ratio significantly affected the catalytic performance. The corresponding lactic acid selectivity was in the order of LiOH〉NaOH〉KOH〉Ba（OH）2. An increase in LiOH/glycerol molar ratio ele‐vated the glycerol conversion and lactic acid selectivity to some degree, but excess LiOH inhibited the transformation of glycerol to lactic acid. In the presence of Pt/AC catalyst, the maximum selec‐tivity of lactic acid was 69.3% at a glycerol conversion of 100% after 6 h at 90 °C, with a Li‐OH/glycerol molar ratio of 1.5. The Pt/AC catalyst was recycled five times and was found to exhibit slightly decreased glycerol conversion and stable lactic acid selectivity. In addition, the experimental results indicated that reaction intermediate dihydroxyacetone was more favorable as the starting reagent for lactic acid formation than glyceraldehyde. However, the Pt/AC catalyst had adverse effects on the intermediate transformation to lactic acid, because it favored the catalytic oxidation of them to glyceric acid.展开更多
The present study reports a novel strategy to fabricate nanocrystal-assembled hierarchical MOR zeolites. This is the first demonstration of hierarchical MOR without preferential growth along the c-axis, which facilita...The present study reports a novel strategy to fabricate nanocrystal-assembled hierarchical MOR zeolites. This is the first demonstration of hierarchical MOR without preferential growth along the c-axis, which facilitates mass transfer in the 12-membered ring channels of MOR zeolite for the conversions involving bulky molecules. The facile method involves the combined use of tetraethylammonium hydroxide （TEAOH） and commercial surfactants, in which TEAOH is essential for the construction of nanocrystal assemblies. The surfactant serves as a crystal growth-inhibiting agent to further inhibit nanocrystalline particle growth, resulting in enhanced mesoporosity. The hierarchical MOR assembled particles, constructed of 20-50-nm crystallites, exhibit superior catalytic properties in the alkylation of benzene with benzyl alcohol compared with the control sample, as the hierarchical MOR possesses a larger external surface area and longer c-axis dimension. More importantly, the material shows improved activity and stability in the dimethyl ether carbonylation to methyl acetate reaction, which is a novel route to produce ethanol from syngas.展开更多
Significant progress has been made in the development of non-precious metal electrocatalysts （NPMEs） during the past decade. Correspondingly, there is an urgent demand for an appropriate measurement method to be est...Significant progress has been made in the development of non-precious metal electrocatalysts （NPMEs） during the past decade. Correspondingly, there is an urgent demand for an appropriate measurement method to be established for the reliable evaluation of NPMEs. In this study, platinum and graphite counter electrodes were used to investigate the impact of counter electrode material on the accelerated durability testing （ADT） of NPMEs in acidic medium. Platinum used as the coun- ter electrode in a traditional three-electrode electrochemical cell was found to dissolve in acidic medium and re-deposit on NPME coated on the working electrode during ADT. Such re-deposition causes the oxygen reduction reaction （ORR） performance of NPMEs to remarkably improve, and thus will seriously mislead our judgment of NPMEs if we are unaware of it. The phenomenon can be avoided using a graphite counter electrode.展开更多
文摘The direct synthesis of dimethyl carbonate(DMC)from CO_(2)and methanol has attracted much attention as an environmentally benign and alternative route for conventional routes.Herein,a series of cerium oxide catalysts with various textural features and surface properties were prepared by the one-pot synthesis method for the direct DMC synthesis from CO_(2)and methanol,and the structure-performance relationship was investigated in detail.Characterization results revealed that both of surface acid-base properties and the oxygen vacancies contents decreased with the rising crystallinity at increasingly higher calcination temperature accompanied by an unexpectedly volcano-shaped trend of DMC yield observed on the catalysts.In situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)studies indicated that the adsorption rate of methanol is slower than that of CO_(2)and the methanol activation state largely influences the formation of key intermediate.Although the enhanced surface acidity-basicity and oxygen vacancies brought by low-temperature calcination could facilitate the activation of CO_(2),the presence of excess strongly basic sites on low-crystallinity sample was detrimental to DMC synthesis due to the preferred formation of unreactive mono/polydentate carbonates as well as the further impediment of methanol activation.Moreover,with the use of 2-cyanopyridine as a dehydration reagent,the DMC synthesis was found to be both influenced by the promotion from the rapid in situ removal of water and the inhibition from the competitive adsorption of hydration products on the same active sites.
基金中国博士后科学基金(2021M693125)大连市高层次人才创新支持计划(2019RT09)+1 种基金中国科学院洁净能源创新研究院合作基金(DNL202016,DNL202019)中国科学院洁净能源创新研究院-榆林学院联合基金(YLU-DNL Fund 2021002,YLU-DNL Fund 2021009).
基金supported by the National Natural Science Foundation of China(21303186)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA07020300)~~
文摘MoS_2 samples with controllable morphologies and structures were synthesized using surfactantassisted hydrothermal processes.The effects of surfactants（PEG,PVP,P123,SDS,AOT,and CTAB）on the morphologies and structures of MoS_2 samples were investigated.The results revealed that spherical,bulk-like,and flower-like MoS_2 particles assembled by NH4~＋-intercalated MoS_2 nano-sheets were synthesized.The morphologies of the MoS_2 samples and their structures（including the slab length and the number of stacked layers） of MoS_2 nano-sheets in these samples could be controlled by adjusting the surfactants.Mono-dispersed spherical MoS_2 particles could be synthesized with PEG via the creation of MoS_2 nano-sheets with slab lengths shorter than 15 nm and fewer than six stacked layers.Possible formation mechanisms of these MoS_2 samples created via surfactant-assisted hydrothermal processes are proposed.Further,the catalytic activities of MoS_2 samples for anthracene hydrogenation were evaluated in a slurry-bed reactor.The catalyst synthesized with the surfactant PEG exhibited the highest catalytic hydrogenation activity.Compared with the other catalysts,it had a smaller particle size,mono-dispersed spherical morphology,shorter slab length,and fewer stacked layers;these were all beneficial to exposing its active edges.This work provides an efficient approach to synthesize transition metal sulfides with controllable morphologies and structures.
基金supported by the National Natural Science Foundation of China(21176236)~~
文摘Pt/activated carbon （Pt/AC） catalyst combined with base works efficiently for lactic acid production from glycerol under mild conditions. Base type （LiOH, NaOH, KOH, or Ba（OH）2） and base/glycerol molar ratio significantly affected the catalytic performance. The corresponding lactic acid selectivity was in the order of LiOH〉NaOH〉KOH〉Ba（OH）2. An increase in LiOH/glycerol molar ratio ele‐vated the glycerol conversion and lactic acid selectivity to some degree, but excess LiOH inhibited the transformation of glycerol to lactic acid. In the presence of Pt/AC catalyst, the maximum selec‐tivity of lactic acid was 69.3% at a glycerol conversion of 100% after 6 h at 90 °C, with a Li‐OH/glycerol molar ratio of 1.5. The Pt/AC catalyst was recycled five times and was found to exhibit slightly decreased glycerol conversion and stable lactic acid selectivity. In addition, the experimental results indicated that reaction intermediate dihydroxyacetone was more favorable as the starting reagent for lactic acid formation than glyceraldehyde. However, the Pt/AC catalyst had adverse effects on the intermediate transformation to lactic acid, because it favored the catalytic oxidation of them to glyceric acid.
基金supported by the National Natural Science Foundation of China(21101150,21476228,21473182)~~
文摘The present study reports a novel strategy to fabricate nanocrystal-assembled hierarchical MOR zeolites. This is the first demonstration of hierarchical MOR without preferential growth along the c-axis, which facilitates mass transfer in the 12-membered ring channels of MOR zeolite for the conversions involving bulky molecules. The facile method involves the combined use of tetraethylammonium hydroxide （TEAOH） and commercial surfactants, in which TEAOH is essential for the construction of nanocrystal assemblies. The surfactant serves as a crystal growth-inhibiting agent to further inhibit nanocrystalline particle growth, resulting in enhanced mesoporosity. The hierarchical MOR assembled particles, constructed of 20-50-nm crystallites, exhibit superior catalytic properties in the alkylation of benzene with benzyl alcohol compared with the control sample, as the hierarchical MOR possesses a larger external surface area and longer c-axis dimension. More importantly, the material shows improved activity and stability in the dimethyl ether carbonylation to methyl acetate reaction, which is a novel route to produce ethanol from syngas.
基金supported by the Fundamental Research Funds for the Central Universities(DUT15RC(3)001,DUT15ZD225)the Program for Liao-ning Excellent Talents in University(LR2015014)+1 种基金the Liaoning BaiQianWan Talents Program(201519)Dalian Excellent Young Scientific and Technological Talents(2015R006)
文摘Significant progress has been made in the development of non-precious metal electrocatalysts （NPMEs） during the past decade. Correspondingly, there is an urgent demand for an appropriate measurement method to be established for the reliable evaluation of NPMEs. In this study, platinum and graphite counter electrodes were used to investigate the impact of counter electrode material on the accelerated durability testing （ADT） of NPMEs in acidic medium. Platinum used as the coun- ter electrode in a traditional three-electrode electrochemical cell was found to dissolve in acidic medium and re-deposit on NPME coated on the working electrode during ADT. Such re-deposition causes the oxygen reduction reaction （ORR） performance of NPMEs to remarkably improve, and thus will seriously mislead our judgment of NPMEs if we are unaware of it. The phenomenon can be avoided using a graphite counter electrode.
