The kinetics of CO hydrogenation for the synthesis of C_2 oxygenates overRh-Mn-Li-Fe/SiO_2 was investigated. Kinetic parameters for the formation of ethanol, acetaldehyde,C'2 oxygenates, methanol and methane were ...The kinetics of CO hydrogenation for the synthesis of C_2 oxygenates overRh-Mn-Li-Fe/SiO_2 was investigated. Kinetic parameters for the formation of ethanol, acetaldehyde,C'2 oxygenates, methanol and methane were obtained. The activation energy. H_2 and CO dependenceorders for ethanol and acetaldehyde formation differed greatly, the large difference seemed to implythat they were formed through different intermediates.展开更多
Copper-based catalysts were widely used in the heterogeneous selective hydrogenation of ethylene carbonate(EC),a key step in the indirect conversion of CO_(2) to methanol.However,a high H_(2)/EC molar ratio in feed is...Copper-based catalysts were widely used in the heterogeneous selective hydrogenation of ethylene carbonate(EC),a key step in the indirect conversion of CO_(2) to methanol.However,a high H_(2)/EC molar ratio in feed is required to achieve favorable activity and the methanol selectivity still needs to be improved.Herein,we fabricated a series of Pt-modulated Cu/SiO_(2) catalysts and investigated their catalytic performance for hydrogenation of EC in a fixed bed reactor.By modulating the Pt amount,the optimal 0.2Pt-Cu/SiO_(2) catalyst exhibited the highest catalytic performance with99%EC conversion,over 98%selectivity to ethylene glycol and 95.8%selectivity to methanol at the H_(2)/EC ratio as low as 60 in feed.In addition,0.2Pt-Cu/SiO_(2) catalyst showed excellent stability for 150 h on stream over different H_(2)/EC ratios of 180-40.It is demonstrated a proper amount of Pt could significantly lower the H_(2)/EC molar ratio,promote the reducibility and dispersion of copper,and also enhance surface density of Cu+species.This could be due to the strong interaction of Cu and Pt induced by formation of alloyed Pt single atoms on the Cu lattice.Meanwhile,a relatively higher amount of Pt would deteriorate the catalytic activity,which could be due to the surface coverage and aggregation of active species.These findings may enlighten some fundamental insights for further design of Cu-based catalysts for the hydrogenation of carbon–oxygen bonds.展开更多
Product selectivity and reaction pathway are highly dependent on surface structure of heterogeneous catalysts.For vapor-phase hydrogenation of dimethyl oxalate(DMO),"EG route"(DMO→methyl glycolate(MG)ethyle...Product selectivity and reaction pathway are highly dependent on surface structure of heterogeneous catalysts.For vapor-phase hydrogenation of dimethyl oxalate(DMO),"EG route"(DMO→methyl glycolate(MG)ethylene glycol(EG)→ethanol(ET))and"MA route"(DMO→MG→methyl acetate(MA))were proposed over traditional Cu based catalysts and Mo-based or Fe-based catalysts,respectively.Herein,tunable yield of ET(93.7%)and MA(72.1%)were obtained through different reaction routes over WO_(x) modified Cu/SiO_(2) catalysts,and the corresponding reaction route was further proved by kinetic study and in-situ DRIFTS technology.Mechanistic studies demonstrated that H_(2) activation ability,acid density and Cu-WO_(x) interaction on the catalysts were tuned by regulating the surface W density,which resulted in the different reaction pathway and product selectivity.What's more,high yield of MA produced from DMO hydrogenation was firstly reported with the H_(2) pressure as low as 0.5 MPa.展开更多
Recycling performance of heterogeneous catalysts is of crucial importance especially for a batch reaction system.In this work,we demonstrate a strategy for enhancing recycling performance of Ir-Re/SiO_(2) catalyst syn...Recycling performance of heterogeneous catalysts is of crucial importance especially for a batch reaction system.In this work,we demonstrate a strategy for enhancing recycling performance of Ir-Re/SiO_(2) catalyst synergized with amberlyst-15 in glycerol hydrogenolysis to produce 1,3-propanediol.Comprehensive characterization results reveal that the Re sites in the Ir-Re/SiO_(2) catalyst undergo irreversible segregation and oxidation.These hinder the formation of active ReAOH species and thus contribute to a complete and irreversible deactivation.However,the introduction of amberlyst-15 into the reactant mixture can restrain the oxidation process of Re sites and favor the formation of ReAOH species,and thus significantly enhance the catalytic recycling performance.The results demonstrated here could guide the development of excellent bimetallic catalysts with the desirable recycling performances for the reaction.展开更多
Oxidative coupling of methane(OCM)is a catalytic partial oxidation process that directly converts methane into C_(2) products.For this high temperature reaction,understanding the radical behavior through experimental ...Oxidative coupling of methane(OCM)is a catalytic partial oxidation process that directly converts methane into C_(2) products.For this high temperature reaction,understanding the radical behavior through experimental investigation is important in correlating the catalytic activity and the products.In this work,a spatial resolution online mass spectrometry(MS)system was developed and applied to a Mn-Na_(2)WO_(4)/SiO_(2) catalyzed OCM system.In addition to the residue gas analysis,the system obtained the distribution information of the reactants and products in the reactor.At various setting temperatures,all species online MS signals were collected at different positions,mapping the reaction activity covering parameters including temperature,time and space.The distribution behavior of the catalytic activity,selectivity,and apparent activation energy were kinetically analyzed.Selectivity and additional carbon balance analysis strongly supported the radical coupling model of OCM and indicated that after the catalytic bed layer,there is a significant length in the reactor(>2 mm)filled with radicals.Based on the result,a designed new method by tuning the temperature field in the reactor was found effectively to improve the catalytic activity,especially the C_(2) yield from 702 to 773℃.展开更多
New Ge/SiO_2 glasses have been synthesized by heating the GeO_2/SiO_2 dry gels under H_2gas at 700℃. The resulting fluorescence spectra show that this kind of Ge/SiO_2 glasses emit strongphotoluminescence at 392 nm (...New Ge/SiO_2 glasses have been synthesized by heating the GeO_2/SiO_2 dry gels under H_2gas at 700℃. The resulting fluorescence spectra show that this kind of Ge/SiO_2 glasses emit strongphotoluminescence at 392 nm (3.12 eV), medium strong photoluminescence at 600 nm (2.05 eV)and weak photoluminescence at 770 nm (1.60 eV) respectively. Possible photoluminescencemechanisms are also discussed based on the results of X-ray diffraction (XRD) and X-rayphotoelectron spectra(XPS).展开更多
基金This work was financially by the Chinese Science and Technology Ministry (Grant No.G1999022404)
文摘The kinetics of CO hydrogenation for the synthesis of C_2 oxygenates overRh-Mn-Li-Fe/SiO_2 was investigated. Kinetic parameters for the formation of ethanol, acetaldehyde,C'2 oxygenates, methanol and methane were obtained. The activation energy. H_2 and CO dependenceorders for ethanol and acetaldehyde formation differed greatly, the large difference seemed to implythat they were formed through different intermediates.
基金supported by the National Natural Science Foun-dation of China(22022811,U21B2096 and 21938008)the National Key Research&Development Program of China(2018YFB0605803).
文摘Copper-based catalysts were widely used in the heterogeneous selective hydrogenation of ethylene carbonate(EC),a key step in the indirect conversion of CO_(2) to methanol.However,a high H_(2)/EC molar ratio in feed is required to achieve favorable activity and the methanol selectivity still needs to be improved.Herein,we fabricated a series of Pt-modulated Cu/SiO_(2) catalysts and investigated their catalytic performance for hydrogenation of EC in a fixed bed reactor.By modulating the Pt amount,the optimal 0.2Pt-Cu/SiO_(2) catalyst exhibited the highest catalytic performance with99%EC conversion,over 98%selectivity to ethylene glycol and 95.8%selectivity to methanol at the H_(2)/EC ratio as low as 60 in feed.In addition,0.2Pt-Cu/SiO_(2) catalyst showed excellent stability for 150 h on stream over different H_(2)/EC ratios of 180-40.It is demonstrated a proper amount of Pt could significantly lower the H_(2)/EC molar ratio,promote the reducibility and dispersion of copper,and also enhance surface density of Cu+species.This could be due to the strong interaction of Cu and Pt induced by formation of alloyed Pt single atoms on the Cu lattice.Meanwhile,a relatively higher amount of Pt would deteriorate the catalytic activity,which could be due to the surface coverage and aggregation of active species.These findings may enlighten some fundamental insights for further design of Cu-based catalysts for the hydrogenation of carbon–oxygen bonds.
基金supported by National Natural Science Foundation of China (No.22102147 and 22002151)State Key Laboratory of Chemical Engineering (No.SKL-ChE-22A02)+2 种基金Zhejiang Provincial Natural Science Foundation of China under Grant No.LQ21B030009the Strategic Priority Research Program of the Chinese Academy of Sciences (No.XDA29050300)Qinchuang Yuan high-level innovation and entrepreneurship talents implementing project (No.QCYRCXM-2022-177)。
文摘Product selectivity and reaction pathway are highly dependent on surface structure of heterogeneous catalysts.For vapor-phase hydrogenation of dimethyl oxalate(DMO),"EG route"(DMO→methyl glycolate(MG)ethylene glycol(EG)→ethanol(ET))and"MA route"(DMO→MG→methyl acetate(MA))were proposed over traditional Cu based catalysts and Mo-based or Fe-based catalysts,respectively.Herein,tunable yield of ET(93.7%)and MA(72.1%)were obtained through different reaction routes over WO_(x) modified Cu/SiO_(2) catalysts,and the corresponding reaction route was further proved by kinetic study and in-situ DRIFTS technology.Mechanistic studies demonstrated that H_(2) activation ability,acid density and Cu-WO_(x) interaction on the catalysts were tuned by regulating the surface W density,which resulted in the different reaction pathway and product selectivity.What's more,high yield of MA produced from DMO hydrogenation was firstly reported with the H_(2) pressure as low as 0.5 MPa.
基金supported by Ministry of Science and Technology of the People’s Republic of China,under the Research Fund for National Key R&D Program of China(2018YFB0604700)the Natural Science Foundation of China(22008067,22008074,22008072,21991103)+1 种基金the China Postdoctoral Science Foundation(2020M681202 and 2021T140204)Natural Science Foundation of Shanghai(20ZR1415700)。
文摘Recycling performance of heterogeneous catalysts is of crucial importance especially for a batch reaction system.In this work,we demonstrate a strategy for enhancing recycling performance of Ir-Re/SiO_(2) catalyst synergized with amberlyst-15 in glycerol hydrogenolysis to produce 1,3-propanediol.Comprehensive characterization results reveal that the Re sites in the Ir-Re/SiO_(2) catalyst undergo irreversible segregation and oxidation.These hinder the formation of active ReAOH species and thus contribute to a complete and irreversible deactivation.However,the introduction of amberlyst-15 into the reactant mixture can restrain the oxidation process of Re sites and favor the formation of ReAOH species,and thus significantly enhance the catalytic recycling performance.The results demonstrated here could guide the development of excellent bimetallic catalysts with the desirable recycling performances for the reaction.
文摘Oxidative coupling of methane(OCM)is a catalytic partial oxidation process that directly converts methane into C_(2) products.For this high temperature reaction,understanding the radical behavior through experimental investigation is important in correlating the catalytic activity and the products.In this work,a spatial resolution online mass spectrometry(MS)system was developed and applied to a Mn-Na_(2)WO_(4)/SiO_(2) catalyzed OCM system.In addition to the residue gas analysis,the system obtained the distribution information of the reactants and products in the reactor.At various setting temperatures,all species online MS signals were collected at different positions,mapping the reaction activity covering parameters including temperature,time and space.The distribution behavior of the catalytic activity,selectivity,and apparent activation energy were kinetically analyzed.Selectivity and additional carbon balance analysis strongly supported the radical coupling model of OCM and indicated that after the catalytic bed layer,there is a significant length in the reactor(>2 mm)filled with radicals.Based on the result,a designed new method by tuning the temperature field in the reactor was found effectively to improve the catalytic activity,especially the C_(2) yield from 702 to 773℃.
文摘New Ge/SiO_2 glasses have been synthesized by heating the GeO_2/SiO_2 dry gels under H_2gas at 700℃. The resulting fluorescence spectra show that this kind of Ge/SiO_2 glasses emit strongphotoluminescence at 392 nm (3.12 eV), medium strong photoluminescence at 600 nm (2.05 eV)and weak photoluminescence at 770 nm (1.60 eV) respectively. Possible photoluminescencemechanisms are also discussed based on the results of X-ray diffraction (XRD) and X-rayphotoelectron spectra(XPS).
