The conversion of acetone derived from biomass to isobutene has attracted extensive attentions.In comparison with Brønsted acidic catalyst,Lewis acidic catalyst could exhibit a better catalytic performance with a...The conversion of acetone derived from biomass to isobutene has attracted extensive attentions.In comparison with Brønsted acidic catalyst,Lewis acidic catalyst could exhibit a better catalytic performance with a higher isobutene selectivity.However,the catalyst stability remains a key problem for the long-running acetone conversion and the reasons for catalyst deactivation are poorly understood up to now.Herein,the deactivation mechanism of Lewis acidic Y/Beta catalyst during the acetone to isobutene conversion was investigated by various characterization techniques,including acetone-temperature-programmed surface reaction,gas chromatography-mass spectrometry,in situ ultraviolet-visible,and ^(13)C cross polarization magic angle spinning nuclear magnetic resonance spectroscopy.A successive aldol condensation and cyclization were observed as the main side-reactions during the acetone conversion at Lewis acidic Y sites.In comparison with the low reaction temperature,a rapid formation and accumulation of the larger cyclic unsaturated aldehydes/ketones and aromatics could be observed,and which could strongly adsorb on the Lewis acidic sites,and thus cause the catalyst deactivation eventually.After a simple calcination,the coke deposits could be easily removed and the catalytic activity could be well restored.展开更多
Isolated cationic Pd species encapsulated in MFI zeolite,i.e.,Pd@MFI,have been successfully prepared via in situ hydrothermal route followed by oxidative treatment.The as-prepared Pd@MFI samples are investigated as pr...Isolated cationic Pd species encapsulated in MFI zeolite,i.e.,Pd@MFI,have been successfully prepared via in situ hydrothermal route followed by oxidative treatment.The as-prepared Pd@MFI samples are investigated as promising catalysts in the reaction of methane combustion.Typically,Pd@H-ZSM-5 shows remarkable activity in methane catalytic combustion with a low apparent activation energy value of 70.7 kj/mol as well as good catalytic stability even in excess water vapor.Detailed characterization results demonstrate the strong interaction between Pd sites and zeolite framework in Pd@ZSM-5 and the efficient stabilization of isolated Pd sites by zeolite thereof.Spectroscopy analyses reveal that the presence of BrΦnsted acid sites is beneficial to methane adsorption and its subsequent activation on adjacent Pd sites,constructing cooperation between Bronsted acid sites and Pd sites within the confined space of MFI zeolite toward high-efficiency methane catalytic combustion.The reaction mechanism of methane combustion catalyzed by Pd@H-ZSM-5 model catalyst is finally discussed.展开更多
Propane dehydrogenation(PDH)provides an alternative route to non-petroleum based propylene and eligible catalysts with good overall performance are still being explored.Herein,we report the construction of zeolite sta...Propane dehydrogenation(PDH)provides an alternative route to non-petroleum based propylene and eligible catalysts with good overall performance are still being explored.Herein,we report the construction of zeolite stabilized Pt-Zn catalysts Pt-Zn/Si-Beta for PDH.Characterization results from transmission electron microscopy(TEM),ultraviolet-visible(UV-vis)and Fourier transform infrared(FTIR)spectroscopy reveal that highly-dispersed Zn species are stabilized by the silanols from zeolite framework dealumination,which then act as the anchoring sites for Pt species.The close contact between Pt-Zn species and the electronic interaction thereof make Pt-Zn/Si-Beta robust PDH catalysts.Under optimized conditions,a high propylene production rate of 4.11 molmol_(Pt)^(-1)s^(-1),high propylene selectivity of 98% and a sustainable deactivation rate of~0.02 h^(-1)can be simultaneously achieved at 823 K.Coke deposition is not the key reason for the catalytic deactivation,while the loss of Zn species and the resulting aggregation of Pt species under high temperatures are responsible for the irreversible deactivation of Pt-Zn/Si-Beta catalyst in PDH reaction.展开更多
The selective dehydrogenation of ethanol to acetaldehyde is a promising route for acetaldehyde production.Although Cu-based catalysts exhibit high activity in ethanol dehydrogenation,a rapid deactivation due to Cu sin...The selective dehydrogenation of ethanol to acetaldehyde is a promising route for acetaldehyde production.Although Cu-based catalysts exhibit high activity in ethanol dehydrogenation,a rapid deactivation due to Cu sintering always occurs.In this study,highly dispersed Cu species were stabilized using the silanol defects in Beta zeolite(denoted as Beta)resulting from dealumination,and applied as robust catalysts for ethanol-to-acetaldehyde conversion.Typically,a long catalyst lifetime of 100 h with an acetaldehyde yield of^70%could be achieved over 5%Cu/Beta.The presence of Cu^+and Cu0 species and the agglomeration of Cu particles after a long-term reaction for 180 h were revealed by transmission electron microscopy,thermogravimetric analysis,and CO-diffuse-reflectance infrared Fourier transform spectroscopy,and were responsible for the deactivation of the Cu/Beta catalyst in the ethanol-to-acetaldehyde conversion.展开更多
Oxygen vacancy plays vital roles in regulating the electronic and charge distribution of the oxygen deficient materials.Herein,abundant oxygen vacancies are created during assembling the two-dimensional(2D)ultra-thin ...Oxygen vacancy plays vital roles in regulating the electronic and charge distribution of the oxygen deficient materials.Herein,abundant oxygen vacancies are created during assembling the two-dimensional(2D)ultra-thin Bi_(2)MoO_(6) nanoflakes into three dimensional(3D)Bi_(2)MoO_(6) nanospheres,resulting in significantly improved performance for photocatalytical conversion of CO_(2) into liquid hydrocarbons.The increased performance is contributed by two primary sites,namely the abundant oxygen vacancy and the exposed molybdenum(Mo)atom induced by oxygen-migration,as revealed by the theoretical calculation.The oxygen vacancy(Ov)and uncovered Mo atom serving as dual binding sites for trapping CO_(2) molecules render the synchronous fixation-reduction process,resulting in the decline of activation energy for CO_(2) reduction from 2.15 eV on bulk Bi_(2)MoO_(6) to 1.42 eV on Ov-rich Bi_(2)MoO_(6).Such a striking decrease in the activation energy induces the efficient selective generation of liquid hydrocarbons,especially the methanol(C_(2)H_(5) OH)and ethanol(CH_(3) OH).The yields of CH_(3) OH and C_(2)H_(5) OH over the optimal Ov-Bi_(2)MoO_(6) is high up to 106.5 and 10.3μmol g^(-1) respectively,greatly outperforming that on the Bulk-Bi_(2)MoO_(6).展开更多
Bimetallic Cr-In/H-SSZ-13 zeolites were prepared by wet impregnation and investigated for selective catalytic reduction of nitric oxide by methane(CH4-SCR).Reduction-oxidation treatments led to close contact and inter...Bimetallic Cr-In/H-SSZ-13 zeolites were prepared by wet impregnation and investigated for selective catalytic reduction of nitric oxide by methane(CH4-SCR).Reduction-oxidation treatments led to close contact and interaction between Cr and In species in these zeolites,as revealed by transmission electron microscopy and X-ray photoelectron spectroscopy.Compared to monometallic Cr/H-SSZ-13 and In/H-SSZ-13,the bimetallic catalyst system exhibited dramatically enhanced CH4-SCR performance,i.e.,NO conversion greater than 90%and N2 selectivity greater than 99%at 550°C in the presence of 6%H2O under a high gas hourly space velocity of 75 000/h.The bimetallic Cr-In/H-SSZ-13 showed very good stability in CH4-SCR with no significant activity loss for over 160 h.Catalytic data revealed that CH4 and NO were activated on the In and Cr sites of Cr-In/H-SSZ-13,respectively,both in the presence of O2 during CH4-SCR.展开更多
The generation of multifunctional isolated active sites in zeolite supports is an attractive method for integrating multistep sequential reactions into a single‐pass tandem catalytic reaction.In this study,bifunction...The generation of multifunctional isolated active sites in zeolite supports is an attractive method for integrating multistep sequential reactions into a single‐pass tandem catalytic reaction.In this study,bifunctional TiSn‐Beta zeolite was prepared by a simple and scalable post‐synthesis approach,and it was utilized as an efficient heterogeneous catalyst for the tandem conversion of alkenes to 1,2‐diols.The isolated Ti and Sn Lewis acid sites within the TiSn‐Beta zeolite can efficiently integrate alkene epoxidation and epoxide hydration in tandem in a zeolite microreactor to achieve one‐step conversion of alkenes to 1,2‐diols with a high selectivity of>90%.Zeolite confinement effects result in high tandem rates of alkene epoxidation and epoxide hydration as well as high selectivity toward the desired product.Further,the novel method demonstrated herein can be employed to other tandem catalytic reactions for sustainable chemical production.展开更多
The self-aldol condensation of aldehydes was investigated with rare-earth cations stabilized by[Si]Beta zeolites in parallel with bulk rare-earth metal oxides.Good catalytic performance was achieved with all Lewis aci...The self-aldol condensation of aldehydes was investigated with rare-earth cations stabilized by[Si]Beta zeolites in parallel with bulk rare-earth metal oxides.Good catalytic performance was achieved with all Lewis acidic rare-earth cations stabilized by zeolites and yttrium appeared to be the best metal choice.According to the results of several complementary techniques,i.e.,temperature-programmed surface reactions,in situ diffuse reflectance infrared Fourier transform spectroscopy,ultraviolet-visible diffuse reflectance spectroscopy,the reaction pathway and mechanism of the aldehyde self-aldol condensation over Y/Beta catalyst were studied in more detail.Density functional theory calculations revealed that aldol dehydration was the rate-limiting step.The hydroxyl group at the open yttrium site played an important role in stabilizing the transition state of the aldol dimer reducing the energy barrier for its hydration.Lewis acidic Y(OSi)(OH)2 stabilized by zeolites in open configurations were identified as the preferred active sites for the self-aldol condensation of aldehydes.展开更多
The selective catalytic hydrogenation of carboxylic acids is an important process for alcohol production,while efficient heterogeneous catalyst systems are still being explored.Here,we report the selective hydrogenati...The selective catalytic hydrogenation of carboxylic acids is an important process for alcohol production,while efficient heterogeneous catalyst systems are still being explored.Here,we report the selective hydrogenation of carboxylic acids using earth‐abundant cobalt oxides through a reaction‐controlled catalysis process.The further reaction of the alcohols is completely hindered by the presence of carboxylic acids in the reaction system.The partial reduction of cobalt oxides by hydrogen at designated temperatures can dramatically enhance the catalytic activity of pristine samples.A wide range of carboxylic acids with a variety of functional groups can be converted to the corresponding alcohols at a yield level applicable to large‐scale production.Cobalt monoxide was established as the preferred active phase for the selective hydrogenation of carboxylic acids.展开更多
Solid-state NMR(ssNMR)spectroscopy is a powerful technique for characterizing the surface sites of solid acids and organic intermediates formed during the acid catalyzed reaction.As a very useful probe molecule,ammoni...Solid-state NMR(ssNMR)spectroscopy is a powerful technique for characterizing the surface sites of solid acids and organic intermediates formed during the acid catalyzed reaction.As a very useful probe molecule,ammonia is often utilized to determine the density of solidacids’surface sites by ssNMR spectroscopy.The present mini-review summarizes some of the latest research developments on the quantitative characterization of the acid sites and carbenium ions during the zeolite catalytic reaction by ammonia probe-assisted ssNMR spectroscopy.展开更多
Herein,Co_(2)P nanorods(NRs)with exposure to high-index facets(HIFs)were prepared by a special assembly-calcination method using thioacetamide(TAA)as a structure-directing reagent.The analysis of adsorption energies o...Herein,Co_(2)P nanorods(NRs)with exposure to high-index facets(HIFs)were prepared by a special assembly-calcination method using thioacetamide(TAA)as a structure-directing reagent.The analysis of adsorption energies of S atoms on different facets as well as the surface energies of Co_(2)P indicate that the HIFs become more stable after adsorbing S atoms.With rich unsaturated sites on HIFs,the photochemical reduction rate of CO_(2)over Co_(2)P NRs is 14.5 mmol h^(-1)g^(-1)for the production of CO within 3 h.The analysis of electron transfer,bond lengths,bond angles and adsorption energies indicate that the CO_(2)molecules are more easily adsorbed and activated on the HIFs.The free energy calculations and d band theory demonstrate that the HIFs are conducive to reducing the formation energy barriers as well as improving the stability of the intermediate^(*)COOH,then enhancing the catalytic performance of CO_(2)reduction.展开更多
Synthesis of value-added chemicals from biomass is an essential strategy to mitigate the global dependency on fossil resources and achieve the aim of carbon neutrality. Thereinto, ethanol and acetic acid are crucial b...Synthesis of value-added chemicals from biomass is an essential strategy to mitigate the global dependency on fossil resources and achieve the aim of carbon neutrality. Thereinto, ethanol and acetic acid are crucial biomass-derived platform molecules.Recently, catalytic upgrading ethanol and acetic acid into C4 energy-intensive fuels and chemicals via the elongation of carbon backbone has received widespread attention. The primary focus of this review is to systematically describe the recent breakthrough in the conversion of ethanol or acetic acid to C4 chemicals including 1,3-butadiene, n-butenes, isobutene or n-butanol.Special attentions will be given to heterogeneous catalyst design strategies, reaction parameters on the catalytic performance along with the relevant mechanism investigations, as well as their future challenges and opportunities. The present review will provide the detailed insights into the synthesis of C4 chemicals from biomass-derived ethanol and acetic acid and shed a light on the development of highly efficient catalysts.展开更多
Zeolite is one of the most important heterogeneous catalysts in acid catalytic reactions.Considering that the catalytic behaviors of zeolites are mostly related to their acidic characteristics,extensive attention has ...Zeolite is one of the most important heterogeneous catalysts in acid catalytic reactions.Considering that the catalytic behaviors of zeolites are mostly related to their acidic characteristics,extensive attention has been attracted to the measurements of acid type,strength and concentration in zeolites.Numerous techniques including Fourier-transform infrared(FTIR)spectroscopy,probe-assisted^(1)H,^(13)C and^(31)P magic angle spinning nuclear magnetic resonance spectroscopy(MAS NMR)as well as temperature programmed desorption of ammonia(NH_(3)-TPD)have been developed for determining the acid sites.Nevertheless,a single approach is defective to characterize the acid sites comprehensively.Herein,combining the probe-assisted(e.g.,NH_(3)and CD_(3)CN)^(1)H MAS NMR and NH_(3)-TPD,the acid sites in different zeolites including the acid type,density and strength were determined.The commonly utilized NH_(3)-TPD to determine the acid strength of zeolite samples with different topologies should be rigorously considered owing to zeolite confinement effect.Controlling the desorption temperature of NH_(3)probe molecules,the acid type(Le.,Brønsted acid sites(BAS)and Lewis acid sites(LAS))and the corresponding density could be determined by NH_(3)probe-assisted^(1)H MAS NMR spectroscopy,while the acid strength could be investigated via CD_(3)CN probe-assisted^(1)H MAS NMR spectroscopy.展开更多
Wastewater management and energy/resource recycling have been extensively investigated via photo(electro)catalysis.Although both operation processes are driven effectively by the same interfacial charge,each system is...Wastewater management and energy/resource recycling have been extensively investigated via photo(electro)catalysis.Although both operation processes are driven effectively by the same interfacial charge,each system is practiced separately since they require very different reaction conditions.In this review,we showcase the recent advancements in photo(electro)catalytic process that enables the wastewater treatment and simultaneous energy/resource recovery(WT-ERR).Various literatures based on photo(electro)catalysis for wastewater treatment coupled with CO_(2)conversion,H_(2)production and heavy metal recovery are summarized.Besides,the fundamentals of photo(electro)catalysis and the influencing factors in such synergistic process are also presented.The essential feature of the catalysis lies in effectively utilizing hole oxidation for pollutant degradation and electron reduction for energy/resource recovery.Although in its infancy,the reviewed technology provides new avenue for developing next-generation wastewater treatment process.Moreover,we expect that this review can stimulate intensive researches to rationally design photo(electro)catalytic systems for environmental remediation accompanied with energy and resource recovery.展开更多
Herein,we prepa red novel three-dimensional(3D)gear-s haped Co3O4@C(Co3O4 modified by amorphous carbon)and sheet-like SnO2/CC(SnO2 grow on the carbon cloth)as anode and cathode to achieve efficient removal of 4-nitrop...Herein,we prepa red novel three-dimensional(3D)gear-s haped Co3O4@C(Co3O4 modified by amorphous carbon)and sheet-like SnO2/CC(SnO2 grow on the carbon cloth)as anode and cathode to achieve efficient removal of 4-nitrophenol(4-NP)in the presence of peroxymonosulfate(PMS)and simultaneous electrocatalytic reduction of CO2,respectively.In this process,4-NP was mineralized into CO2 by the Co3O4@C,and the generated CO2 was reduced into HCOOH by the sheet-like SnO2/CC cathode.Compared with the pure Co0.5(Co3O4 was prepared using 0.5 g urea)with PMS(30 mg,0.5 g/L),the degradation efficiency of 4-NP(60 mL,10 mg/L)increased from 74.5%-85.1%in 60 min using the Co0.5 modified by amorphous carbon(Co0.5@C).Furthermore,when the voltage of 1.0 V was added in the anodic system of Co0.5@C with PMS(30 mg,0.5 g/L),the degradation efficiency of 4-NP increased from 85.1%-99.1%when Pt was used as cathode.In the experiments of 4-NP degradation coupled with simultaneous electrocatalytic CO2 reduction,the degradation efficiency of 4-NP was 99.0%in the anodic system of Co0.5@C with addition of PMS(30 mg,0.5 g/L),while the Faraday efficiency(FE)of HCOOH was 24.1%at voltage of-1.3 V using the SnO2/CC as cathode.The results showed that the anode of Co3O4 modified by amorphous carbon can markedly improve the degradation efficiency of 4-NP,while the cathode of SnO2/CC can greatly improve the FE and selectivity of CO2 reduction to HCOOH and the stability of cathode.Finally,the promotion mechanism was proposed to explain the degradation of organic pollutants and reduction of CO2 into HCOOH in the process of electrocatalysis coupled with advanced oxidation processes(AOPs)and simultaneous CO2 reduction.展开更多
In this article,we present our research results on chemical fixation of CO_(2) using organobismuth compounds.We fabricated bismuth biphenoate complex,Zn-Mg-Al composite oxides,and SBA-15 or Al-SBA-15 immobilized hydro...In this article,we present our research results on chemical fixation of CO_(2) using organobismuth compounds.We fabricated bismuth biphenoate complex,Zn-Mg-Al composite oxides,and SBA-15 or Al-SBA-15 immobilized hydroxyl ionic liquid for CO_(2) cycloaddition onto epoxides.The hypervalent bismuth compounds show good ability for association and dissociation with CO_(2).The bismuth biphenolate complexes are catalytically effective for the cycloaddition reaction.The heterogeneous catalysts,viz.Zn-Mg-Al oxides and SBA-15 or Al-SBA-15 immobilized ionic liquid,are efficient for the synthesis of cyclic carbonate from CO_(2) and epoxide.It is found that the presence of a trace amount of water can improve the catalytic activity of the immobilized ionic liquid.展开更多
Multifunctional heteroatom zeolites have drawn broad attentions due to the possible synergistic effects in the catalytic reactions.Remarkable achievements have been made on the synthesis,characterization and catalytic...Multifunctional heteroatom zeolites have drawn broad attentions due to the possible synergistic effects in the catalytic reactions.Remarkable achievements have been made on the synthesis,characterization and catalytic applications of multifunctional heteroatom zeolite,while a review on this important topic is still missing.Herein,current research status of multifunctional heteroatom zeolites is briefly summarized,aiming to boost further researches.First,the synthesis strategies toward heteroatom zeolites are introduced,including the direct synthesis and postsynthesis routes;then,the spectroscopic techniques to identify the existing states of heteroatom sites and the corresponding physiochemical properties are shown and compared;finally,the catalytic applications of multifunctional heteroatom zeolites in various chemical reactions,especially in one-step tandem reactions,are discussed.展开更多
文摘The conversion of acetone derived from biomass to isobutene has attracted extensive attentions.In comparison with Brønsted acidic catalyst,Lewis acidic catalyst could exhibit a better catalytic performance with a higher isobutene selectivity.However,the catalyst stability remains a key problem for the long-running acetone conversion and the reasons for catalyst deactivation are poorly understood up to now.Herein,the deactivation mechanism of Lewis acidic Y/Beta catalyst during the acetone to isobutene conversion was investigated by various characterization techniques,including acetone-temperature-programmed surface reaction,gas chromatography-mass spectrometry,in situ ultraviolet-visible,and ^(13)C cross polarization magic angle spinning nuclear magnetic resonance spectroscopy.A successive aldol condensation and cyclization were observed as the main side-reactions during the acetone conversion at Lewis acidic Y sites.In comparison with the low reaction temperature,a rapid formation and accumulation of the larger cyclic unsaturated aldehydes/ketones and aromatics could be observed,and which could strongly adsorb on the Lewis acidic sites,and thus cause the catalyst deactivation eventually.After a simple calcination,the coke deposits could be easily removed and the catalytic activity could be well restored.
文摘Isolated cationic Pd species encapsulated in MFI zeolite,i.e.,Pd@MFI,have been successfully prepared via in situ hydrothermal route followed by oxidative treatment.The as-prepared Pd@MFI samples are investigated as promising catalysts in the reaction of methane combustion.Typically,Pd@H-ZSM-5 shows remarkable activity in methane catalytic combustion with a low apparent activation energy value of 70.7 kj/mol as well as good catalytic stability even in excess water vapor.Detailed characterization results demonstrate the strong interaction between Pd sites and zeolite framework in Pd@ZSM-5 and the efficient stabilization of isolated Pd sites by zeolite thereof.Spectroscopy analyses reveal that the presence of BrΦnsted acid sites is beneficial to methane adsorption and its subsequent activation on adjacent Pd sites,constructing cooperation between Bronsted acid sites and Pd sites within the confined space of MFI zeolite toward high-efficiency methane catalytic combustion.The reaction mechanism of methane combustion catalyzed by Pd@H-ZSM-5 model catalyst is finally discussed.
基金supported by the Municipal Natural Science Foundation of Tianjin(18JCJQJC47400,18JCZDJC37400)the National Postdoctoral Program for Innovative Talent(BX20200171)the Fundamental Research Funds for the Central Universities。
文摘Propane dehydrogenation(PDH)provides an alternative route to non-petroleum based propylene and eligible catalysts with good overall performance are still being explored.Herein,we report the construction of zeolite stabilized Pt-Zn catalysts Pt-Zn/Si-Beta for PDH.Characterization results from transmission electron microscopy(TEM),ultraviolet-visible(UV-vis)and Fourier transform infrared(FTIR)spectroscopy reveal that highly-dispersed Zn species are stabilized by the silanols from zeolite framework dealumination,which then act as the anchoring sites for Pt species.The close contact between Pt-Zn species and the electronic interaction thereof make Pt-Zn/Si-Beta robust PDH catalysts.Under optimized conditions,a high propylene production rate of 4.11 molmol_(Pt)^(-1)s^(-1),high propylene selectivity of 98% and a sustainable deactivation rate of~0.02 h^(-1)can be simultaneously achieved at 823 K.Coke deposition is not the key reason for the catalytic deactivation,while the loss of Zn species and the resulting aggregation of Pt species under high temperatures are responsible for the irreversible deactivation of Pt-Zn/Si-Beta catalyst in PDH reaction.
基金supported by the National Natural Science Foundation of China(21872072,21573113)Municipal Natural Science Foundation of Tianjin(18JCZDJC37400)Sinopec(417012)~~
文摘The selective dehydrogenation of ethanol to acetaldehyde is a promising route for acetaldehyde production.Although Cu-based catalysts exhibit high activity in ethanol dehydrogenation,a rapid deactivation due to Cu sintering always occurs.In this study,highly dispersed Cu species were stabilized using the silanol defects in Beta zeolite(denoted as Beta)resulting from dealumination,and applied as robust catalysts for ethanol-to-acetaldehyde conversion.Typically,a long catalyst lifetime of 100 h with an acetaldehyde yield of^70%could be achieved over 5%Cu/Beta.The presence of Cu^+and Cu0 species and the agglomeration of Cu particles after a long-term reaction for 180 h were revealed by transmission electron microscopy,thermogravimetric analysis,and CO-diffuse-reflectance infrared Fourier transform spectroscopy,and were responsible for the deactivation of the Cu/Beta catalyst in the ethanol-to-acetaldehyde conversion.
基金financially supported by the National Natural Science Foundation of China(Grants 52072165,52070092,51662031)。
文摘Oxygen vacancy plays vital roles in regulating the electronic and charge distribution of the oxygen deficient materials.Herein,abundant oxygen vacancies are created during assembling the two-dimensional(2D)ultra-thin Bi_(2)MoO_(6) nanoflakes into three dimensional(3D)Bi_(2)MoO_(6) nanospheres,resulting in significantly improved performance for photocatalytical conversion of CO_(2) into liquid hydrocarbons.The increased performance is contributed by two primary sites,namely the abundant oxygen vacancy and the exposed molybdenum(Mo)atom induced by oxygen-migration,as revealed by the theoretical calculation.The oxygen vacancy(Ov)and uncovered Mo atom serving as dual binding sites for trapping CO_(2) molecules render the synchronous fixation-reduction process,resulting in the decline of activation energy for CO_(2) reduction from 2.15 eV on bulk Bi_(2)MoO_(6) to 1.42 eV on Ov-rich Bi_(2)MoO_(6).Such a striking decrease in the activation energy induces the efficient selective generation of liquid hydrocarbons,especially the methanol(C_(2)H_(5) OH)and ethanol(CH_(3) OH).The yields of CH_(3) OH and C_(2)H_(5) OH over the optimal Ov-Bi_(2)MoO_(6) is high up to 106.5 and 10.3μmol g^(-1) respectively,greatly outperforming that on the Bulk-Bi_(2)MoO_(6).
文摘Bimetallic Cr-In/H-SSZ-13 zeolites were prepared by wet impregnation and investigated for selective catalytic reduction of nitric oxide by methane(CH4-SCR).Reduction-oxidation treatments led to close contact and interaction between Cr and In species in these zeolites,as revealed by transmission electron microscopy and X-ray photoelectron spectroscopy.Compared to monometallic Cr/H-SSZ-13 and In/H-SSZ-13,the bimetallic catalyst system exhibited dramatically enhanced CH4-SCR performance,i.e.,NO conversion greater than 90%and N2 selectivity greater than 99%at 550°C in the presence of 6%H2O under a high gas hourly space velocity of 75 000/h.The bimetallic Cr-In/H-SSZ-13 showed very good stability in CH4-SCR with no significant activity loss for over 160 h.Catalytic data revealed that CH4 and NO were activated on the In and Cr sites of Cr-In/H-SSZ-13,respectively,both in the presence of O2 during CH4-SCR.
文摘The generation of multifunctional isolated active sites in zeolite supports is an attractive method for integrating multistep sequential reactions into a single‐pass tandem catalytic reaction.In this study,bifunctional TiSn‐Beta zeolite was prepared by a simple and scalable post‐synthesis approach,and it was utilized as an efficient heterogeneous catalyst for the tandem conversion of alkenes to 1,2‐diols.The isolated Ti and Sn Lewis acid sites within the TiSn‐Beta zeolite can efficiently integrate alkene epoxidation and epoxide hydration in tandem in a zeolite microreactor to achieve one‐step conversion of alkenes to 1,2‐diols with a high selectivity of>90%.Zeolite confinement effects result in high tandem rates of alkene epoxidation and epoxide hydration as well as high selectivity toward the desired product.Further,the novel method demonstrated herein can be employed to other tandem catalytic reactions for sustainable chemical production.
文摘The self-aldol condensation of aldehydes was investigated with rare-earth cations stabilized by[Si]Beta zeolites in parallel with bulk rare-earth metal oxides.Good catalytic performance was achieved with all Lewis acidic rare-earth cations stabilized by zeolites and yttrium appeared to be the best metal choice.According to the results of several complementary techniques,i.e.,temperature-programmed surface reactions,in situ diffuse reflectance infrared Fourier transform spectroscopy,ultraviolet-visible diffuse reflectance spectroscopy,the reaction pathway and mechanism of the aldehyde self-aldol condensation over Y/Beta catalyst were studied in more detail.Density functional theory calculations revealed that aldol dehydration was the rate-limiting step.The hydroxyl group at the open yttrium site played an important role in stabilizing the transition state of the aldol dimer reducing the energy barrier for its hydration.Lewis acidic Y(OSi)(OH)2 stabilized by zeolites in open configurations were identified as the preferred active sites for the self-aldol condensation of aldehydes.
文摘The selective catalytic hydrogenation of carboxylic acids is an important process for alcohol production,while efficient heterogeneous catalyst systems are still being explored.Here,we report the selective hydrogenation of carboxylic acids using earth‐abundant cobalt oxides through a reaction‐controlled catalysis process.The further reaction of the alcohols is completely hindered by the presence of carboxylic acids in the reaction system.The partial reduction of cobalt oxides by hydrogen at designated temperatures can dramatically enhance the catalytic activity of pristine samples.A wide range of carboxylic acids with a variety of functional groups can be converted to the corresponding alcohols at a yield level applicable to large‐scale production.Cobalt monoxide was established as the preferred active phase for the selective hydrogenation of carboxylic acids.
基金the National Natural Science Foundation of China(21972069)the Fundamental Research Funds for the Central Universities(Nankai University).
文摘Solid-state NMR(ssNMR)spectroscopy is a powerful technique for characterizing the surface sites of solid acids and organic intermediates formed during the acid catalyzed reaction.As a very useful probe molecule,ammonia is often utilized to determine the density of solidacids’surface sites by ssNMR spectroscopy.The present mini-review summarizes some of the latest research developments on the quantitative characterization of the acid sites and carbenium ions during the zeolite catalytic reaction by ammonia probe-assisted ssNMR spectroscopy.
基金financially supported by the National Natural Science Foundation of China(52072165,51662031 and 51720105001)the general project of science and technology research of Jiangxi Provincial Department of Education(DA202102160)+1 种基金the project funded by China Postdoctoral Science Foundation(2019M653583)the starting research fund(EA202102179)。
文摘Herein,Co_(2)P nanorods(NRs)with exposure to high-index facets(HIFs)were prepared by a special assembly-calcination method using thioacetamide(TAA)as a structure-directing reagent.The analysis of adsorption energies of S atoms on different facets as well as the surface energies of Co_(2)P indicate that the HIFs become more stable after adsorbing S atoms.With rich unsaturated sites on HIFs,the photochemical reduction rate of CO_(2)over Co_(2)P NRs is 14.5 mmol h^(-1)g^(-1)for the production of CO within 3 h.The analysis of electron transfer,bond lengths,bond angles and adsorption energies indicate that the CO_(2)molecules are more easily adsorbed and activated on the HIFs.The free energy calculations and d band theory demonstrate that the HIFs are conducive to reducing the formation energy barriers as well as improving the stability of the intermediate^(*)COOH,then enhancing the catalytic performance of CO_(2)reduction.
基金supported by Scientific Research Project of Tianjin municipal Education Commission (2022KJ078)。
文摘Synthesis of value-added chemicals from biomass is an essential strategy to mitigate the global dependency on fossil resources and achieve the aim of carbon neutrality. Thereinto, ethanol and acetic acid are crucial biomass-derived platform molecules.Recently, catalytic upgrading ethanol and acetic acid into C4 energy-intensive fuels and chemicals via the elongation of carbon backbone has received widespread attention. The primary focus of this review is to systematically describe the recent breakthrough in the conversion of ethanol or acetic acid to C4 chemicals including 1,3-butadiene, n-butenes, isobutene or n-butanol.Special attentions will be given to heterogeneous catalyst design strategies, reaction parameters on the catalytic performance along with the relevant mechanism investigations, as well as their future challenges and opportunities. The present review will provide the detailed insights into the synthesis of C4 chemicals from biomass-derived ethanol and acetic acid and shed a light on the development of highly efficient catalysts.
基金supported by the National Natural Science Foundation of China(22272083)the Fundamental Research Funds for the Central Universities(Nankai University).
文摘Zeolite is one of the most important heterogeneous catalysts in acid catalytic reactions.Considering that the catalytic behaviors of zeolites are mostly related to their acidic characteristics,extensive attention has been attracted to the measurements of acid type,strength and concentration in zeolites.Numerous techniques including Fourier-transform infrared(FTIR)spectroscopy,probe-assisted^(1)H,^(13)C and^(31)P magic angle spinning nuclear magnetic resonance spectroscopy(MAS NMR)as well as temperature programmed desorption of ammonia(NH_(3)-TPD)have been developed for determining the acid sites.Nevertheless,a single approach is defective to characterize the acid sites comprehensively.Herein,combining the probe-assisted(e.g.,NH_(3)and CD_(3)CN)^(1)H MAS NMR and NH_(3)-TPD,the acid sites in different zeolites including the acid type,density and strength were determined.The commonly utilized NH_(3)-TPD to determine the acid strength of zeolite samples with different topologies should be rigorously considered owing to zeolite confinement effect.Controlling the desorption temperature of NH_(3)probe molecules,the acid type(Le.,Brønsted acid sites(BAS)and Lewis acid sites(LAS))and the corresponding density could be determined by NH_(3)probe-assisted^(1)H MAS NMR spectroscopy,while the acid strength could be investigated via CD_(3)CN probe-assisted^(1)H MAS NMR spectroscopy.
基金financially supported by the National Natural Science Foundation of China(Nos.52000097,51878325,51868050 and 51938007)the Natural Science Foundation of Jiangxi Province(Nos.20192BAB213011 and 20192ACBL21046)+1 种基金the Ph.D.research startup foundation of Nanchang Hangkong University(No.EA201802367)the Open Project Program of the State Key Laboratory of Photocatalysis on Energy and Environment(No.SKLPEE-KF202106),Fuzhou University。
文摘Wastewater management and energy/resource recycling have been extensively investigated via photo(electro)catalysis.Although both operation processes are driven effectively by the same interfacial charge,each system is practiced separately since they require very different reaction conditions.In this review,we showcase the recent advancements in photo(electro)catalytic process that enables the wastewater treatment and simultaneous energy/resource recovery(WT-ERR).Various literatures based on photo(electro)catalysis for wastewater treatment coupled with CO_(2)conversion,H_(2)production and heavy metal recovery are summarized.Besides,the fundamentals of photo(electro)catalysis and the influencing factors in such synergistic process are also presented.The essential feature of the catalysis lies in effectively utilizing hole oxidation for pollutant degradation and electron reduction for energy/resource recovery.Although in its infancy,the reviewed technology provides new avenue for developing next-generation wastewater treatment process.Moreover,we expect that this review can stimulate intensive researches to rationally design photo(electro)catalytic systems for environmental remediation accompanied with energy and resource recovery.
基金the National Natural Science Foundation of China(Nos.51878325,51868050,51622806,51378246 and 51720105001)the Natural Science Foundation of Jiangxi Province(Nos.20162BCB22017,20165BCB18008,20171ACB20017,20133ACB21001 and 20171BAB206049)the Graduate Innovation Fund of Jiangxi Province(No.YC2018-S360)。
文摘Herein,we prepa red novel three-dimensional(3D)gear-s haped Co3O4@C(Co3O4 modified by amorphous carbon)and sheet-like SnO2/CC(SnO2 grow on the carbon cloth)as anode and cathode to achieve efficient removal of 4-nitrophenol(4-NP)in the presence of peroxymonosulfate(PMS)and simultaneous electrocatalytic reduction of CO2,respectively.In this process,4-NP was mineralized into CO2 by the Co3O4@C,and the generated CO2 was reduced into HCOOH by the sheet-like SnO2/CC cathode.Compared with the pure Co0.5(Co3O4 was prepared using 0.5 g urea)with PMS(30 mg,0.5 g/L),the degradation efficiency of 4-NP(60 mL,10 mg/L)increased from 74.5%-85.1%in 60 min using the Co0.5 modified by amorphous carbon(Co0.5@C).Furthermore,when the voltage of 1.0 V was added in the anodic system of Co0.5@C with PMS(30 mg,0.5 g/L),the degradation efficiency of 4-NP increased from 85.1%-99.1%when Pt was used as cathode.In the experiments of 4-NP degradation coupled with simultaneous electrocatalytic CO2 reduction,the degradation efficiency of 4-NP was 99.0%in the anodic system of Co0.5@C with addition of PMS(30 mg,0.5 g/L),while the Faraday efficiency(FE)of HCOOH was 24.1%at voltage of-1.3 V using the SnO2/CC as cathode.The results showed that the anode of Co3O4 modified by amorphous carbon can markedly improve the degradation efficiency of 4-NP,while the cathode of SnO2/CC can greatly improve the FE and selectivity of CO2 reduction to HCOOH and the stability of cathode.Finally,the promotion mechanism was proposed to explain the degradation of organic pollutants and reduction of CO2 into HCOOH in the process of electrocatalysis coupled with advanced oxidation processes(AOPs)and simultaneous CO2 reduction.
基金The financial supports of the National Natural Science Foundation of China(Grant Nos.20507005 and 20873038)Outstanding Young Research Award of National Natural Science Foundation of China(Grant No.E50725825)Hong Kong Baptist University(FRG/08-09/II-09)。
文摘In this article,we present our research results on chemical fixation of CO_(2) using organobismuth compounds.We fabricated bismuth biphenoate complex,Zn-Mg-Al composite oxides,and SBA-15 or Al-SBA-15 immobilized hydroxyl ionic liquid for CO_(2) cycloaddition onto epoxides.The hypervalent bismuth compounds show good ability for association and dissociation with CO_(2).The bismuth biphenolate complexes are catalytically effective for the cycloaddition reaction.The heterogeneous catalysts,viz.Zn-Mg-Al oxides and SBA-15 or Al-SBA-15 immobilized ionic liquid,are efficient for the synthesis of cyclic carbonate from CO_(2) and epoxide.It is found that the presence of a trace amount of water can improve the catalytic activity of the immobilized ionic liquid.
基金supported by Municipal Natural Science Foundation of Tianjin(Grant No.18JCJQJC47400)the National Natural Science Foundation of China(Grant No.21773127)the Fundamental Research Funds for the Central Universities.
文摘Multifunctional heteroatom zeolites have drawn broad attentions due to the possible synergistic effects in the catalytic reactions.Remarkable achievements have been made on the synthesis,characterization and catalytic applications of multifunctional heteroatom zeolite,while a review on this important topic is still missing.Herein,current research status of multifunctional heteroatom zeolites is briefly summarized,aiming to boost further researches.First,the synthesis strategies toward heteroatom zeolites are introduced,including the direct synthesis and postsynthesis routes;then,the spectroscopic techniques to identify the existing states of heteroatom sites and the corresponding physiochemical properties are shown and compared;finally,the catalytic applications of multifunctional heteroatom zeolites in various chemical reactions,especially in one-step tandem reactions,are discussed.
