Gas-phase synthesis of glycolide(GL)from methyl glycolate(MG)is of great significance for producing biodegradable polyglycolic acid.Here,we report a detailed thermodynamics study for the gas-phase synthesis of GL from...Gas-phase synthesis of glycolide(GL)from methyl glycolate(MG)is of great significance for producing biodegradable polyglycolic acid.Here,we report a detailed thermodynamics study for the gas-phase synthesis of GL from MG,which involves complex reaction pathways,by utilizing the Gibbs free energy minimization method.The results indicate that the decompositions of MG and GL and the polymerization of MG are thermodynamically favorable as compared with the target pathway,i.e.,the cyclization of MG.Effects of the reaction conditions including temperature,pressure and feed composition on the formation of GL and linear polymers have also been addressed,which demonstrate that the higher temperature and lower pressure can effectively inhibit the formation of linear methyl ester dimer and improve the selectivity to GL.In addition,the higher N_(2)/MG ratio is beneficial for the formation of GL in the process promoted by catalysts.These thermodynamics results indicate that the process promoted by catalysts would benefit from the kinetics control by high-performance catalysts and the operation at high temperature,low pressure and high N_(2)/MG ratio to enhance the yield of targeted GL.The insights demonstrated here from thermodynamics are valuable for guiding the design of catalysts and/or optimization of reaction conditions for the gas-phase synthesis of GL from MG.展开更多
This study develops a CFD-ML integrated framework to achieve multi-objective optimization for the partial oxidation of n-butane to maleic anhydride(MA).A reactor-pellet coupled model was established to investigate the...This study develops a CFD-ML integrated framework to achieve multi-objective optimization for the partial oxidation of n-butane to maleic anhydride(MA).A reactor-pellet coupled model was established to investigate the effects of four key operating parameters,revealing that inlet temperature dominates reactor performance by increasing MA yield from 35.0%to 37.6%while sharply raising hotspot temperatures by 42 K.The coupled model was then employed to generate 621 cases for training machine learning models,among which the Gaussian Process Regression(GPR)model exhibits superior accuracy.The GPR model was further integrated with the genetic algorithm to generate Pareto-optimal sets.The results indicate that a critical inflection point is identified on the Pareto front,and once this point is exceeded,even a slight increase in MA yield could lead to a sharp rise in the reactor hotspot temperature,thereby increasing the risk of thermal runaway.展开更多
Essentially clearing the structure-activity relationship between iron carbide catalysts involving multiple active centers to understand the reaction mechanism of CO hydrogenation conversion process is still a great ch...Essentially clearing the structure-activity relationship between iron carbide catalysts involving multiple active centers to understand the reaction mechanism of CO hydrogenation conversion process is still a great challenge.Here,two main micro-environment factors,namely electronic properties and geometrical effects were found to have an integrated effect on the mechanism of CO hydrogenation conversion,involving active sites on multiple crystal phases.The Bader charge of the surface Fe atoms on the active sites had a guiding effect on the CO activation pathway,while the spatial configuration of the active sites greatly affected the energy barriers of CO activation.Although the defective surfaces were more conducive to CO activation,the defective sites were not the only sites to dissociate CO,as CO always tended to dissociate in a wider area.This synergistic effect of the micro-environment also occurred during the CO conversion process.Surface C atoms on relatively flat configurations were more likely to form methane,while the electronic properties of the active sites could effectively describe the C-C coupling process,as well as distinguish the coupling mechanisms.展开更多
Understanding carbon-supported Pt-catalyzed oxygen reduction reaction(ORR)from the perspective of the active sites is of fundamental and practical importance.In this study,three differently sized carbon nanotube-suppo...Understanding carbon-supported Pt-catalyzed oxygen reduction reaction(ORR)from the perspective of the active sites is of fundamental and practical importance.In this study,three differently sized carbon nanotube-supported Pt nanoparticles(Pt/CNT)are prepared by both atomic layer deposition(ALD)and impregnation methods.The performances of the catalysts toward the ORR in acidic media are comparatively studied to probe the effects of the sizes of the Pt nanoparticles together with their distributions,electronic properties,and local environments.The ALD-Pt/CNT catalysts show much higher ORR activity and selectivity than the impregnation-Pt/CNT catalysts.This outstanding ORR performance is ascribed to the well-controlled Pt particle sizes and distributions,desirable Pt^04f binding energy,and the Cl-free Pt surfaces based on the electrocatalytic measurements,catalyst characterizations,and model calculations.The insights reported here could guide the rational design and fine-tuning of carbon-supported Pt catalysts for the ORR.展开更多
Carbon mediated catalysis has gained an increasing attention in both areas of nanocatalysis and nanomaterials. The progress in carbon nanomaterials provides many new opportunities to manip-ulate the types and properti...Carbon mediated catalysis has gained an increasing attention in both areas of nanocatalysis and nanomaterials. The progress in carbon nanomaterials provides many new opportunities to manip-ulate the types and properties of active sites of catalysts through manipulating structures, function-alities and properties of carbon surfaces. The present review focuses on progresses in carbon medi-ated oxidative dehydrogenation reactions of ethylbenzene, propane, and butane. The state-of-the-art of the developments of carbon mediated catalysis is discussed in terms of fundamental studies on adsorption of oxygen and hydrocarbons, reaction mechanism as well as effects of carbon nano-material structures and surface functional groups on the catalytic performance. We highlight the importance and challenges in tuning of the electron density of carbon and oxygen on carbon surfac-es for improving selectivity in oxidative dehydrogenation reactions.展开更多
Heterogeneously catalyzed hydrolytic dehydrogenation of ammonia borane is a remarkable structure sensitive reaction. In this work, a strategy by using polyoxometalates(POMs) as the ligands is proposed to engineer the ...Heterogeneously catalyzed hydrolytic dehydrogenation of ammonia borane is a remarkable structure sensitive reaction. In this work, a strategy by using polyoxometalates(POMs) as the ligands is proposed to engineer the surface and electronic properties of Pt/CNT catalysts toward the enhanced hydrogen generation rate and durability. Three kinds of POMs, i.e., silicotungstic acid(STA), phosphotungstic acid(PTA)and molybdophosphoric acid(PMA), are comparatively studied, among which the STA shows positive effects on the catalytic activity and durability. A catalyst structure-performance relationship is established by a combination of kinetic and isotopic analyses with multiple characterization techniques, such as HAADF-STEM, EDS, Raman spectroscopy and XPS. It is shown that the STA compared to the other two POMs can increase the Pt binding energy and thus promote the reaction. The insights demonstrated here could open a new avenue for boosting the reaction by employing the POMs as the ligands to engineer the catalyst electronic properties.展开更多
Heteroatom-doping of carbocatalysts has been a powerful strategy to remarkably enhance the catalytic performance.Herein,the underlying nature of N promotional effects on peroxymonosulfate(PMS)activation for phenol rem...Heteroatom-doping of carbocatalysts has been a powerful strategy to remarkably enhance the catalytic performance.Herein,the underlying nature of N promotional effects on peroxymonosulfate(PMS)activation for phenol removal is understood by combining kinetics analysis with multiple techniques.A strategy using mixed acid oxidation of carbon nanotube(CNT)followed by NH3 treatment is employed to yield a series of catalysts with different N-doping contents but similar fraction of sp^(2)-hybridized carbon and defective degree,endowing with a chance to discriminate the dominant N-containing active sites.The multi-sites kinetics analysis suggests the graphitic N-containing sites as the dominant active sites.The mechanism of the surface-bound reactive species is also discriminated as the dominant reaction mechanism.The insights reported here could provide the methodology to fundamentally understand the heteroatom-doping effects of carbocatalysis.展开更多
Exploration of cost-effective Pt/C catalysts has been a significant issue for electrochemical hydrogen evolution reaction(HER) toward sustainable energy conversion and storage.Herein,we report a fabrication strategy b...Exploration of cost-effective Pt/C catalysts has been a significant issue for electrochemical hydrogen evolution reaction(HER) toward sustainable energy conversion and storage.Herein,we report a fabrication strategy by employing platelet carbon nanofibers(p-CNF) as the support to immobilize Pt-CoO HER electrocatalyst using atomic layer deposition method.The edge-rich p-CNF support is found to act as the anchoring sites of Pt nanoparticles and favorably capture electrons from Pt to yield electron-deficient Pt surfaces for the boosted HER.Additionally,the sequential growth of CoO onto the Pt/p-CNF catalyst elaborately constructs the Pt-CoO interface and facilitates the electron transfer from Pt to CoO,which further enhances the HER activity.These advantages endow the fabricated Pt-CoO/p-CNF catalyst with the superior HER activity,e.g.,a very low overpotential of 26 mV at the current density of 10 mA·cm-2 and a mass activity of 4.42 A·mgPt-1at the overpotential of 30 mV,18.8 times higher than that of the commercial20 wt% Pt/C catalyst.The insights reported here could shed light on for the fabrication of cost-effective Pt-based composite HER catalysts.展开更多
Direct propylene epoxidation with H2 and O2,an attractive process to produce propylene oxide(PO),has a potential explosion danger due to the coexistence of flammable gases(i.e.,C3 H6 and H2)and oxidizer(i.e.,O2).The u...Direct propylene epoxidation with H2 and O2,an attractive process to produce propylene oxide(PO),has a potential explosion danger due to the coexistence of flammable gases(i.e.,C3 H6 and H2)and oxidizer(i.e.,O2).The unknown explosion limits of the multi-component feed gas mixture make it difficult to optimize the reaction process under safe operation conditions.In this work,a distribution method is proposed and verified to be effective by comparing estimated and experimental explosion limits of more than 200 kinds of flammable gas mixture.Then,it is employed to estimate the explosion limits of the feed gas mixture,some results of which are also validated by the classic Le Chatelier’s Rule and flammable resistance method.Based on the estimated explosion limits,process optimization is carried out using commercially high and inherently safe reactant concentrations to enhance reaction performance.The promising results are directly obtained through the interface called gOPT in gPROMS only by using a simple,easy-constructed and mature packed-bed reactor,such as the PO yield of 13.3%,PO selectivity of 85.1%and outlet PO fraction of 1.8%.These results can be rationalized by indepth analyses and discussion about the effects of the decision variables on the operation safety and reaction performance.The insights revealed here could shed new light on the process development of the PO production based on the estimation of the explosion limits of the multi-component feed gas mixture containing flammable gase s,inert gas and O2,followed by process optimization.展开更多
Direct epoxidation of propylene with H_(2)/O_(2),being the dream reaction for propylene oxide(PO)production,has raised wide scientific and industrial interests.Fundamentally understanding the formation mechanism of ac...Direct epoxidation of propylene with H_(2)/O_(2),being the dream reaction for propylene oxide(PO)production,has raised wide scientific and industrial interests.Fundamentally understanding the formation mechanism of acrolein,as the main by-product of this epoxidation process,is very important to achieve the high yield of PO.In this study,we perform the spin-polarized density functional theory(DFT)calculations to investigate the reaction pathway from propylene to acrolein over two representative Au surfaces,that is,Au(111)and Au(100),which incorporates propylene adsorption,methyl hydrogen activation and acrolein formation.The results show that the oxygenated species(mainly O^(*),OH^(*)and OOH^(*))are able to stabilize the adsorption of propylene to decrease the energy barrier for its activation.It is demonstrated that the OOH^(*)on Au(111)surface emerges as the most easily formed oxygenated species via the H-assisted O_(2) dissociation,which is also the most active for the cleavage of methyl CAH bond in propylene.Furthermore,three pathways of acrolein formation activated by O^(*)/OH^(*)/OOH^(*)are analyzed,in which O^(*)is found as the key species to form acrolein.Finally,Bader charge analysis was conducted to explore the reasons behind the promotion effect of the oxygenated species.The insights reported here could be valuable in the design and optimization of gold catalysts for the direct epoxidation of propylene.展开更多
Dry reforming of methane(DRM) is an attractive technology for utilizing the greenhouse gases(CO_(2) and CH_(4)) to produce syngas. However, the catalyst pellets for DRM are heavily plagued by deactivation by coking, w...Dry reforming of methane(DRM) is an attractive technology for utilizing the greenhouse gases(CO_(2) and CH_(4)) to produce syngas. However, the catalyst pellets for DRM are heavily plagued by deactivation by coking, which prevents this technology from commercialization. In this work, a pore network model is developed to probe the catalyst deactivation by coking in a Ni/Al_(2)O_(3) catalyst pellet for DRM. The reaction conditions can significantly change the coking rate and then affect the catalyst deactivation. The catalyst lifetime is higher under lower temperature, pressure, and CH_(4)/CO_(2) molar ratio, but the maximum coke content in a catalyst pellet is independent of these reaction conditions. The catalyst pellet with larger pore diameter, narrower pore size distribution and higher pore connectivity is more robust against catalyst deactivation by coking, as the pores in this pellet are more difficult to be plugged or inaccessible.The maximum coke content is also higher for narrower pore size distribution and higher pore connectivity, as the number of inaccessible pores is lower. Besides, the catalyst pellet radius only slightly affects the coke content, although the diffusion limitation increases with the pellet radius. These results should serve to guide the rational design of robust DRM catalyst pellets against deactivation by coking.展开更多
A millimeter scale butterfly-shaped reactor was proposed based on sizing-up strategy and fabricated via femtosecond laser engraving. An improvement of mixing performance and residence time distribution was realized by...A millimeter scale butterfly-shaped reactor was proposed based on sizing-up strategy and fabricated via femtosecond laser engraving. An improvement of mixing performance and residence time distribution was realized by means of contraction and expansion of the reaction channel. The liquid holdup was greatly increased through connection of multiple mixing units. Structure optimization of the reactor was carried out by computational fluid dynamics simulation, from which the effect of reactor internals on mixing and the influence of parallel branching structure on heat transfer were discussed. The UV–vis absorption spectroscopy was used to determine the residence time distribution in the reactor, and characteristic parameters such as skewness and dimensionless variance were obtained. Further, a chained stagnant flow model was proposed to precisely describe the trailing phenomenon caused by fluid stagnation and laminar flow in small scale reactors, which enables a better fit for the experimental results of the asymmetric residence time distribution. In addition, the heat transfer performance of the reactor was investigated, and the overall heat transfer coefficient was 110–600 W m^(-2)K-1in the flow rate range of 10–40 m L/min.展开更多
Taming the electron transfer across metal–support interfaces appears to be an attractive yet challenging methodology to boost catalytic properties.Herein,we demonstrate a precise engineering strategy for the carbon s...Taming the electron transfer across metal–support interfaces appears to be an attractive yet challenging methodology to boost catalytic properties.Herein,we demonstrate a precise engineering strategy for the carbon surface chemistry of Pt/C catalysts—that is,for the electron-withdrawing/donating oxygencontaining groups on the carbon surface—to fine-tune the electrons of the supported metal nanoparticles.Taking the ammonia borane hydrolysis as an example,a combination of density functional theory(DFT)calculations,advanced characterizations,and kinetics and isotopic analyses reveals quantifiable relationships among the carbon surface chemistry,Pt charge state and binding energy,activation entropy/enthalpy,and resultant catalytic activity.After decoupling the influences of other factors,the Pt charge is unprecedentedly identified as an experimentally measurable descriptor of the Pt active site,contributing to a 15-fold increment in the hydrogen generation rate.Further incorporating the Pt charge with the number of Pt active sites,a mesokinetics model is proposed for the first time that can individually quantify the contributions of the electronic and geometric properties to precisely predict the catalytic performance.Our results demonstrate a potentially groundbreaking methodology to design and manipulate metal–carbon catalysts with desirable properties.展开更多
In this work,a trickle-bed reactor coupled with catalyst pellet model is employed to understand the effects of the temperature and catalyst pellet structures on the reaction-diffusion behaviors in gas oil hydrodesulfu...In this work,a trickle-bed reactor coupled with catalyst pellet model is employed to understand the effects of the temperature and catalyst pellet structures on the reaction-diffusion behaviors in gas oil hydrodesulfurization(HDS).The non-isothermal reactor model is determined to be reasonable due to non-negligible temperature variation caused by the reaction heat.The reaction rate along the reactor is mainly dominated by the temperature,and the sulfur concentration gradient in the catalyst pellet decreases gradually along the reactor,leading to the increased internal effectiveness factor.For the fixed catalyst bed volume,there exists a compromise between the catalyst reaction rate and effectiveness factor.Under commonly studied catalyst pellet size of 0.8-3 mm and porosity of 0.4-0.8,an optimization of the temperature and catalyst pellet structures is carried out,and the optimized outlet sulfur content decreases to 7.6 wppm better than the commercial level at 0.96 mm of the catalyst pellet size and 0.40 of the catalyst porosity.展开更多
Understanding the nature of Pt active sites is of great importance for the structure-sensitive base-free oxidation of glycerol. In the present work, the remarkable Pt particle size effects on glycerol conversion and p...Understanding the nature of Pt active sites is of great importance for the structure-sensitive base-free oxidation of glycerol. In the present work, the remarkable Pt particle size effects on glycerol conversion and products formation from the oxidation of the primary and the secondary hydroxyl groups are understood by combining the model calculations and DFT calculations, aiming to discriminate the corresponding dominant Pt active sites. The Pt(100) facet is demonstrated to be the dominant active sites for the glycerol conversion and the products formation from the two routes. The insights revealed here could shed new light on fundamental understanding of the Pt particle size effects and then guiding the design and optimization of Pt-catalyzed base-free oxidation of glycerol toward targeted products.展开更多
Structure-performance relationship is a complex issue in iron-catalyzed Fischer-Tropsch synthesis,and it is not easy to elucidate it by experimental investigations.First-principle calculation is a powerful method for ...Structure-performance relationship is a complex issue in iron-catalyzed Fischer-Tropsch synthesis,and it is not easy to elucidate it by experimental investigations.First-principle calculation is a powerful method for explaining experimental results and guiding catalyst design.In this study,we investigated the reaction mechanisms of CH_(4)formation and C-C coupling on fourχ-Fe_(5)C_(2)surfaces and established the kinetic equations to compare the rates of CH_(4)formation and C_(1)+C_(1)coupling reactions and determine the CH_(4)/C_(2+)selectivity.The results show that the geometry of theχ-Fe_(5)C_(2)surfaces has little effect on the formation rate of CH_(4);however,the C_(1)+C_(1)coupling reactions are significantly affected by the surface geometry.The C_(1)+C_(1)coupling reaction rates on the terraced-like(510)and(021)surfaces are much higher than those on the stepped-like(001)and(100)surfaces.Based on these results,we established a Brùnsted-Evans-Polanyi(BEP)relationship between the effective barrier difference for CH_(4)formation and C_(1)+C_(1)coupling(ΔE_(eff))and the adsorption energy of C+4H(ΔE_(C+4H))onχ-Fe_(5)C_(2)surfaces.ΔE_(C+4H)can be used as a descriptor for CH_(4)/C_(2+)selectivity on different surfaces ofχ-Fe_(5)C_(2).展开更多
In this study, a bulk composite material symbolized as NiCo LDH-rGO/Ni F was developed by a solvothermal process for the first time. This material was fabricated through simultaneous growth of nickel-cobalt layered do...In this study, a bulk composite material symbolized as NiCo LDH-rGO/Ni F was developed by a solvothermal process for the first time. This material was fabricated through simultaneous growth of nickel-cobalt layered double hydroxide(NiCo LDH) and reduced graphene oxide(rGO) on nickel foam. This bulk composite can be used directly as a binder-free electrode for supercapacitors(SCs). The physicochemical properties of this composite were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The electrochemical properties of the composite were measured by the cyclic voltammetry and galvanostatic charge-discharge. The results show that this composite had a hierarchical structure and exhibited a significantly enhanced specific capacitance of up to 3383 F/g at 1 A/g. The asymmetric SC using this composite as a positive electrode had a high energy density of 40.54 Wh/kg at the power density of 206.5 W/kg and good cycling stability. Owing to the synergies between the metal oxides and the rGO, the preparation method of in situ growth and its hierarchical structure, this bulk composite displayed excellent electrochemical performance and had a promising application as an efficient electrode for high-performance SCs.展开更多
The structures of electrode meso-macropore and the solvent polarity are the crucial factors dominating the performance of the electric double layer capacitors(EDLCs),but their impacts are usually tangled and difficult...The structures of electrode meso-macropore and the solvent polarity are the crucial factors dominating the performance of the electric double layer capacitors(EDLCs),but their impacts are usually tangled and difficult to decouple and quantitate.Here the effects of electrode meso-macropore structure and solvent polarity on the specific capacitance of an EDLC are quantitatively investigated using a steady-state continuum model.The simulation results indicate the specific capacitances are significantly affected by the meso-macropore surface structure.The specific capacitances significantly decrease for both convex surface structures but obviously increase for both concave surface structures,with the increase of curvature radius from 1 to 20 nm.As for solvents,the polar solvent with high saturated dielectric permittivity improves the capacitance performance.Moreover,the electrode meso-macropore structure is of more concern compared with solvent polarity when aiming at enhancing the specific capacitance.These results provide fundamentals for the rational design of porous electrodes and polar electrolytes for EDLCs.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
基金supported by the National Natural Science Foundation of China(22478106,22178102,and 22332003)Shanghai Rising-Star Program(23QA1401900)+1 种基金Young Elite Scientists Sponsorship Programby CAST(2023QNRC001)the Open Project of Yunnan Precious Metals Laboratory Co.,Ltd(YPML-2023050272).
文摘Gas-phase synthesis of glycolide(GL)from methyl glycolate(MG)is of great significance for producing biodegradable polyglycolic acid.Here,we report a detailed thermodynamics study for the gas-phase synthesis of GL from MG,which involves complex reaction pathways,by utilizing the Gibbs free energy minimization method.The results indicate that the decompositions of MG and GL and the polymerization of MG are thermodynamically favorable as compared with the target pathway,i.e.,the cyclization of MG.Effects of the reaction conditions including temperature,pressure and feed composition on the formation of GL and linear polymers have also been addressed,which demonstrate that the higher temperature and lower pressure can effectively inhibit the formation of linear methyl ester dimer and improve the selectivity to GL.In addition,the higher N_(2)/MG ratio is beneficial for the formation of GL in the process promoted by catalysts.These thermodynamics results indicate that the process promoted by catalysts would benefit from the kinetics control by high-performance catalysts and the operation at high temperature,low pressure and high N_(2)/MG ratio to enhance the yield of targeted GL.The insights demonstrated here from thermodynamics are valuable for guiding the design of catalysts and/or optimization of reaction conditions for the gas-phase synthesis of GL from MG.
基金financially supported by the National Natural Science Foundation of China(22408098 and 22393952)the China Postdoctoral Science Foundation(2024M750908)the National Key Research and Development Program of China(2024YFA1509903)。
文摘This study develops a CFD-ML integrated framework to achieve multi-objective optimization for the partial oxidation of n-butane to maleic anhydride(MA).A reactor-pellet coupled model was established to investigate the effects of four key operating parameters,revealing that inlet temperature dominates reactor performance by increasing MA yield from 35.0%to 37.6%while sharply raising hotspot temperatures by 42 K.The coupled model was then employed to generate 621 cases for training machine learning models,among which the Gaussian Process Regression(GPR)model exhibits superior accuracy.The GPR model was further integrated with the genetic algorithm to generate Pareto-optimal sets.The results indicate that a critical inflection point is identified on the Pareto front,and once this point is exceeded,even a slight increase in MA yield could lead to a sharp rise in the reactor hotspot temperature,thereby increasing the risk of thermal runaway.
基金supported by the Research Fund for National Key Research and Development Program of China(2022YFA1503804,2021YFA1501403)the Natural Science Foundation of China(22208094,21922803,92034301,22008066 and 21776077)+2 种基金the China Postdoctoral Science Foundation(BX20190116)the Innovation Program of Shanghai Municipal Education Commission(17ZR1407300)the Program of Shanghai Academic/Technology Research Leader(21XD1421000).
文摘Essentially clearing the structure-activity relationship between iron carbide catalysts involving multiple active centers to understand the reaction mechanism of CO hydrogenation conversion process is still a great challenge.Here,two main micro-environment factors,namely electronic properties and geometrical effects were found to have an integrated effect on the mechanism of CO hydrogenation conversion,involving active sites on multiple crystal phases.The Bader charge of the surface Fe atoms on the active sites had a guiding effect on the CO activation pathway,while the spatial configuration of the active sites greatly affected the energy barriers of CO activation.Although the defective surfaces were more conducive to CO activation,the defective sites were not the only sites to dissociate CO,as CO always tended to dissociate in a wider area.This synergistic effect of the micro-environment also occurred during the CO conversion process.Surface C atoms on relatively flat configurations were more likely to form methane,while the electronic properties of the active sites could effectively describe the C-C coupling process,as well as distinguish the coupling mechanisms.
基金financially supported by the Natural Science Foundation of China(21922803 and 21776077)the Shanghai Natural Science Foundation(17ZR1407300 and 17ZR1407500)+3 种基金the Program for the Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learningthe Shanghai Rising-Star Program(17QA1401200)the State Key Laboratory of Organic-Inorganic Composites(oic-201801007)the Open Project of State Key Laboratory of Chemical Engineering(SKLChe-15C03)。
文摘Understanding carbon-supported Pt-catalyzed oxygen reduction reaction(ORR)from the perspective of the active sites is of fundamental and practical importance.In this study,three differently sized carbon nanotube-supported Pt nanoparticles(Pt/CNT)are prepared by both atomic layer deposition(ALD)and impregnation methods.The performances of the catalysts toward the ORR in acidic media are comparatively studied to probe the effects of the sizes of the Pt nanoparticles together with their distributions,electronic properties,and local environments.The ALD-Pt/CNT catalysts show much higher ORR activity and selectivity than the impregnation-Pt/CNT catalysts.This outstanding ORR performance is ascribed to the well-controlled Pt particle sizes and distributions,desirable Pt^04f binding energy,and the Cl-free Pt surfaces based on the electrocatalytic measurements,catalyst characterizations,and model calculations.The insights reported here could guide the rational design and fine-tuning of carbon-supported Pt catalysts for the ORR.
基金supported by the Natural Science Foundation of China (21306046)the Open Project of State Key Laboratory of Chemical Engineering (SKL-Che-15C03)+2 种基金the Fundamental Research Funds for the Central Universities (WA1514013)the 111 Project of Ministry of Education of China (B08021)supported by the China Scholarship Council (CSC) for the research at Norwegian University of Science and Technology (NTNU)
基金financial supports from the Norwegian Research Councilthe 111 299 Project of Ministry of Education of China (B08021)the European Commission FP-7 Project FREECATS (Grant agreement no.: 280658) are gratefully acknowledged.
文摘Carbon mediated catalysis has gained an increasing attention in both areas of nanocatalysis and nanomaterials. The progress in carbon nanomaterials provides many new opportunities to manip-ulate the types and properties of active sites of catalysts through manipulating structures, function-alities and properties of carbon surfaces. The present review focuses on progresses in carbon medi-ated oxidative dehydrogenation reactions of ethylbenzene, propane, and butane. The state-of-the-art of the developments of carbon mediated catalysis is discussed in terms of fundamental studies on adsorption of oxygen and hydrocarbons, reaction mechanism as well as effects of carbon nano-material structures and surface functional groups on the catalytic performance. We highlight the importance and challenges in tuning of the electron density of carbon and oxygen on carbon surfac-es for improving selectivity in oxidative dehydrogenation reactions.
基金supported by the National Natural Science Foundation of China(21776077)the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning+3 种基金the Shanghai Rising-Star Program(17QA1401200)the Open Project of SKLOCE(SKL-Che-15C03)the Shanghai Natural Science Foundation(17ZR1407300 and 17ZR1407500)the State Key Laboratory of Organic-Inorganic Composites(oic201801007)。
文摘Heterogeneously catalyzed hydrolytic dehydrogenation of ammonia borane is a remarkable structure sensitive reaction. In this work, a strategy by using polyoxometalates(POMs) as the ligands is proposed to engineer the surface and electronic properties of Pt/CNT catalysts toward the enhanced hydrogen generation rate and durability. Three kinds of POMs, i.e., silicotungstic acid(STA), phosphotungstic acid(PTA)and molybdophosphoric acid(PMA), are comparatively studied, among which the STA shows positive effects on the catalytic activity and durability. A catalyst structure-performance relationship is established by a combination of kinetic and isotopic analyses with multiple characterization techniques, such as HAADF-STEM, EDS, Raman spectroscopy and XPS. It is shown that the STA compared to the other two POMs can increase the Pt binding energy and thus promote the reaction. The insights demonstrated here could open a new avenue for boosting the reaction by employing the POMs as the ligands to engineer the catalyst electronic properties.
基金supported by the Natural Science Foundation of China(21922803 and 21776077)the Shanghai Natural Science Foundation(17ZR1407300 and 17ZR1407500)+3 种基金the China Postdoctoral Science Foundation(BX20190116)the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning,the Shanghai Rising-Star Program(17QA1401200)the State Key Laboratory of Organic-Inorganic Composites(oic-201801007)the Open Project of State Key Laboratory of Chemical Engineering(SKLChe-15C03 and SKL-ChE-16C05).
文摘Heteroatom-doping of carbocatalysts has been a powerful strategy to remarkably enhance the catalytic performance.Herein,the underlying nature of N promotional effects on peroxymonosulfate(PMS)activation for phenol removal is understood by combining kinetics analysis with multiple techniques.A strategy using mixed acid oxidation of carbon nanotube(CNT)followed by NH3 treatment is employed to yield a series of catalysts with different N-doping contents but similar fraction of sp^(2)-hybridized carbon and defective degree,endowing with a chance to discriminate the dominant N-containing active sites.The multi-sites kinetics analysis suggests the graphitic N-containing sites as the dominant active sites.The mechanism of the surface-bound reactive species is also discriminated as the dominant reaction mechanism.The insights reported here could provide the methodology to fundamentally understand the heteroatom-doping effects of carbocatalysis.
基金financially supported by the National Natural Science Foundation of China (21922803 and 21776077)the Shanghai Natural Science Foundation (17ZR1407300 and 17ZR1407500)+3 种基金the Program for the Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learningthe Shanghai Rising-Star Program (17QA1401200)the State Key Laboratory of Organic-Inorganic Composites (oic-201801007)the Open Project of State Key Laboratory of Chemical Engineering (SKLChe15C03)。
文摘Exploration of cost-effective Pt/C catalysts has been a significant issue for electrochemical hydrogen evolution reaction(HER) toward sustainable energy conversion and storage.Herein,we report a fabrication strategy by employing platelet carbon nanofibers(p-CNF) as the support to immobilize Pt-CoO HER electrocatalyst using atomic layer deposition method.The edge-rich p-CNF support is found to act as the anchoring sites of Pt nanoparticles and favorably capture electrons from Pt to yield electron-deficient Pt surfaces for the boosted HER.Additionally,the sequential growth of CoO onto the Pt/p-CNF catalyst elaborately constructs the Pt-CoO interface and facilitates the electron transfer from Pt to CoO,which further enhances the HER activity.These advantages endow the fabricated Pt-CoO/p-CNF catalyst with the superior HER activity,e.g.,a very low overpotential of 26 mV at the current density of 10 mA·cm-2 and a mass activity of 4.42 A·mgPt-1at the overpotential of 30 mV,18.8 times higher than that of the commercial20 wt% Pt/C catalyst.The insights reported here could shed light on for the fabrication of cost-effective Pt-based composite HER catalysts.
基金Supported by the National Natural Science Foundation of China(91434117,21776077)the Shanghai Rising-Star Program(17QA1401200)+1 种基金the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learningthe Open Project of State Key Laboratory of Chemical Engineering(SKL-Che-15C03).
文摘Direct propylene epoxidation with H2 and O2,an attractive process to produce propylene oxide(PO),has a potential explosion danger due to the coexistence of flammable gases(i.e.,C3 H6 and H2)and oxidizer(i.e.,O2).The unknown explosion limits of the multi-component feed gas mixture make it difficult to optimize the reaction process under safe operation conditions.In this work,a distribution method is proposed and verified to be effective by comparing estimated and experimental explosion limits of more than 200 kinds of flammable gas mixture.Then,it is employed to estimate the explosion limits of the feed gas mixture,some results of which are also validated by the classic Le Chatelier’s Rule and flammable resistance method.Based on the estimated explosion limits,process optimization is carried out using commercially high and inherently safe reactant concentrations to enhance reaction performance.The promising results are directly obtained through the interface called gOPT in gPROMS only by using a simple,easy-constructed and mature packed-bed reactor,such as the PO yield of 13.3%,PO selectivity of 85.1%and outlet PO fraction of 1.8%.These results can be rationalized by indepth analyses and discussion about the effects of the decision variables on the operation safety and reaction performance.The insights revealed here could shed new light on the process development of the PO production based on the estimation of the explosion limits of the multi-component feed gas mixture containing flammable gase s,inert gas and O2,followed by process optimization.
基金financially supported by the Research Fund for National Key Research and Development Program of China (2021YFA1501403)the National Natural Science Foundation of China (22208094,22038003,21922803,22178100)+1 种基金the Innovation Program of Shanghai Municipal Education Commission,the Program of Shanghai Academic/Technology Research Leader (21XD1421000)the Shanghai Science and Technology Innovation Action Plan (22JC1403800)。
文摘Direct epoxidation of propylene with H_(2)/O_(2),being the dream reaction for propylene oxide(PO)production,has raised wide scientific and industrial interests.Fundamentally understanding the formation mechanism of acrolein,as the main by-product of this epoxidation process,is very important to achieve the high yield of PO.In this study,we perform the spin-polarized density functional theory(DFT)calculations to investigate the reaction pathway from propylene to acrolein over two representative Au surfaces,that is,Au(111)and Au(100),which incorporates propylene adsorption,methyl hydrogen activation and acrolein formation.The results show that the oxygenated species(mainly O^(*),OH^(*)and OOH^(*))are able to stabilize the adsorption of propylene to decrease the energy barrier for its activation.It is demonstrated that the OOH^(*)on Au(111)surface emerges as the most easily formed oxygenated species via the H-assisted O_(2) dissociation,which is also the most active for the cleavage of methyl CAH bond in propylene.Furthermore,three pathways of acrolein formation activated by O^(*)/OH^(*)/OOH^(*)are analyzed,in which O^(*)is found as the key species to form acrolein.Finally,Bader charge analysis was conducted to explore the reasons behind the promotion effect of the oxygenated species.The insights reported here could be valuable in the design and optimization of gold catalysts for the direct epoxidation of propylene.
基金financially supported by the National Natural Science Foundation of China (22078090 and 92034301)the Shanghai Rising-Star Program (21QA1402000)+1 种基金the Natural Science Foundation of Shanghai (21ZR1418100)the Open Project of State Key Laboratory of Chemical Engineering (SKL-ChE-21C02)。
文摘Dry reforming of methane(DRM) is an attractive technology for utilizing the greenhouse gases(CO_(2) and CH_(4)) to produce syngas. However, the catalyst pellets for DRM are heavily plagued by deactivation by coking, which prevents this technology from commercialization. In this work, a pore network model is developed to probe the catalyst deactivation by coking in a Ni/Al_(2)O_(3) catalyst pellet for DRM. The reaction conditions can significantly change the coking rate and then affect the catalyst deactivation. The catalyst lifetime is higher under lower temperature, pressure, and CH_(4)/CO_(2) molar ratio, but the maximum coke content in a catalyst pellet is independent of these reaction conditions. The catalyst pellet with larger pore diameter, narrower pore size distribution and higher pore connectivity is more robust against catalyst deactivation by coking, as the pores in this pellet are more difficult to be plugged or inaccessible.The maximum coke content is also higher for narrower pore size distribution and higher pore connectivity, as the number of inaccessible pores is lower. Besides, the catalyst pellet radius only slightly affects the coke content, although the diffusion limitation increases with the pellet radius. These results should serve to guide the rational design of robust DRM catalyst pellets against deactivation by coking.
基金funded by the National Natural Science Foundation of China (Nos. 21991103, 21991104, 22008074, 22008072)Natural Science Foundation of Shanghai (No. 20ZR1415700)China Postdoctoral Science Foundation (Nos. 2020M671025,2019TQ0093)。
文摘A millimeter scale butterfly-shaped reactor was proposed based on sizing-up strategy and fabricated via femtosecond laser engraving. An improvement of mixing performance and residence time distribution was realized by means of contraction and expansion of the reaction channel. The liquid holdup was greatly increased through connection of multiple mixing units. Structure optimization of the reactor was carried out by computational fluid dynamics simulation, from which the effect of reactor internals on mixing and the influence of parallel branching structure on heat transfer were discussed. The UV–vis absorption spectroscopy was used to determine the residence time distribution in the reactor, and characteristic parameters such as skewness and dimensionless variance were obtained. Further, a chained stagnant flow model was proposed to precisely describe the trailing phenomenon caused by fluid stagnation and laminar flow in small scale reactors, which enables a better fit for the experimental results of the asymmetric residence time distribution. In addition, the heat transfer performance of the reactor was investigated, and the overall heat transfer coefficient was 110–600 W m^(-2)K-1in the flow rate range of 10–40 m L/min.
基金the Natural Science Foundation of China(21922803,92034301,22008066,and 21776077)the China Postdoctoral Science Foundation(BX20190116)+1 种基金the Innovation Program of Shanghai Municipal Education Commission,the Program of Shanghai Academic/Tech-nology Research Leader(21XD1421000)111 Project of the Min-istry of Education of China(B08021)。
文摘Taming the electron transfer across metal–support interfaces appears to be an attractive yet challenging methodology to boost catalytic properties.Herein,we demonstrate a precise engineering strategy for the carbon surface chemistry of Pt/C catalysts—that is,for the electron-withdrawing/donating oxygencontaining groups on the carbon surface—to fine-tune the electrons of the supported metal nanoparticles.Taking the ammonia borane hydrolysis as an example,a combination of density functional theory(DFT)calculations,advanced characterizations,and kinetics and isotopic analyses reveals quantifiable relationships among the carbon surface chemistry,Pt charge state and binding energy,activation entropy/enthalpy,and resultant catalytic activity.After decoupling the influences of other factors,the Pt charge is unprecedentedly identified as an experimentally measurable descriptor of the Pt active site,contributing to a 15-fold increment in the hydrogen generation rate.Further incorporating the Pt charge with the number of Pt active sites,a mesokinetics model is proposed for the first time that can individually quantify the contributions of the electronic and geometric properties to precisely predict the catalytic performance.Our results demonstrate a potentially groundbreaking methodology to design and manipulate metal–carbon catalysts with desirable properties.
基金supported by the National Key R&D Program of China(2018YFB0604500)the National Natural Science Foundation of China(21922803 and 21776077)+4 种基金the Shanghai Natural Science Foundation(17ZR1407300 and 17ZR1407500)the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learningthe Shanghai Rising-Star Program(17QA1401200)the Open Project of SKLOCE(SKL-Che-15C03)the 111 Project of the Ministry of Education of China(B08021)。
文摘In this work,a trickle-bed reactor coupled with catalyst pellet model is employed to understand the effects of the temperature and catalyst pellet structures on the reaction-diffusion behaviors in gas oil hydrodesulfurization(HDS).The non-isothermal reactor model is determined to be reasonable due to non-negligible temperature variation caused by the reaction heat.The reaction rate along the reactor is mainly dominated by the temperature,and the sulfur concentration gradient in the catalyst pellet decreases gradually along the reactor,leading to the increased internal effectiveness factor.For the fixed catalyst bed volume,there exists a compromise between the catalyst reaction rate and effectiveness factor.Under commonly studied catalyst pellet size of 0.8-3 mm and porosity of 0.4-0.8,an optimization of the temperature and catalyst pellet structures is carried out,and the optimized outlet sulfur content decreases to 7.6 wppm better than the commercial level at 0.96 mm of the catalyst pellet size and 0.40 of the catalyst porosity.
基金financially supported by the Natural Science Foundation of China (21776077)the Shanghai Natural Science Foundation (17ZR1407300 and 17ZR1407500)+5 种基金the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learningthe Shanghai Rising-Star Program (17QA1401200)the Open Project of State Key Laboratory of Chemical Engineering (SKLChe-15C03)the State Key Laboratory of Organic– Inorganic Composites (oic-201801007)the Fundamental Research Funds for the Central Universities (222201718003)the 111 Project of the Ministry of Education of China (B08021)
文摘Understanding the nature of Pt active sites is of great importance for the structure-sensitive base-free oxidation of glycerol. In the present work, the remarkable Pt particle size effects on glycerol conversion and products formation from the oxidation of the primary and the secondary hydroxyl groups are understood by combining the model calculations and DFT calculations, aiming to discriminate the corresponding dominant Pt active sites. The Pt(100) facet is demonstrated to be the dominant active sites for the glycerol conversion and the products formation from the two routes. The insights revealed here could shed new light on fundamental understanding of the Pt particle size effects and then guiding the design and optimization of Pt-catalyzed base-free oxidation of glycerol toward targeted products.
基金financially supported by the Natural Science Foundation of China(21922803 and 21776077)the Program for the Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning+1 种基金the State Key Laboratory of Organic-Inorganic Composites(oic-201801007)the Open Project of State Key Laboratory of Chemical Engineering(SKLChe-15C03)。
文摘Structure-performance relationship is a complex issue in iron-catalyzed Fischer-Tropsch synthesis,and it is not easy to elucidate it by experimental investigations.First-principle calculation is a powerful method for explaining experimental results and guiding catalyst design.In this study,we investigated the reaction mechanisms of CH_(4)formation and C-C coupling on fourχ-Fe_(5)C_(2)surfaces and established the kinetic equations to compare the rates of CH_(4)formation and C_(1)+C_(1)coupling reactions and determine the CH_(4)/C_(2+)selectivity.The results show that the geometry of theχ-Fe_(5)C_(2)surfaces has little effect on the formation rate of CH_(4);however,the C_(1)+C_(1)coupling reactions are significantly affected by the surface geometry.The C_(1)+C_(1)coupling reaction rates on the terraced-like(510)and(021)surfaces are much higher than those on the stepped-like(001)and(100)surfaces.Based on these results,we established a Brùnsted-Evans-Polanyi(BEP)relationship between the effective barrier difference for CH_(4)formation and C_(1)+C_(1)coupling(ΔE_(eff))and the adsorption energy of C+4H(ΔE_(C+4H))onχ-Fe_(5)C_(2)surfaces.ΔE_(C+4H)can be used as a descriptor for CH_(4)/C_(2+)selectivity on different surfaces ofχ-Fe_(5)C_(2).
基金supported by the National Key Basic Research Program of China ("973" Program, No. 2014CB239702)the National Natural Science Foundation of China (No. 21676082)
文摘In this study, a bulk composite material symbolized as NiCo LDH-rGO/Ni F was developed by a solvothermal process for the first time. This material was fabricated through simultaneous growth of nickel-cobalt layered double hydroxide(NiCo LDH) and reduced graphene oxide(rGO) on nickel foam. This bulk composite can be used directly as a binder-free electrode for supercapacitors(SCs). The physicochemical properties of this composite were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The electrochemical properties of the composite were measured by the cyclic voltammetry and galvanostatic charge-discharge. The results show that this composite had a hierarchical structure and exhibited a significantly enhanced specific capacitance of up to 3383 F/g at 1 A/g. The asymmetric SC using this composite as a positive electrode had a high energy density of 40.54 Wh/kg at the power density of 206.5 W/kg and good cycling stability. Owing to the synergies between the metal oxides and the rGO, the preparation method of in situ growth and its hierarchical structure, this bulk composite displayed excellent electrochemical performance and had a promising application as an efficient electrode for high-performance SCs.
基金financially supported by the National Basic Research Program of China(2014CB239702)the National Natural Science Foundation of China(21676082,22008067)the China Postdoctoral Science Foundation(2020M681202,2021T140204)。
文摘The structures of electrode meso-macropore and the solvent polarity are the crucial factors dominating the performance of the electric double layer capacitors(EDLCs),but their impacts are usually tangled and difficult to decouple and quantitate.Here the effects of electrode meso-macropore structure and solvent polarity on the specific capacitance of an EDLC are quantitatively investigated using a steady-state continuum model.The simulation results indicate the specific capacitances are significantly affected by the meso-macropore surface structure.The specific capacitances significantly decrease for both convex surface structures but obviously increase for both concave surface structures,with the increase of curvature radius from 1 to 20 nm.As for solvents,the polar solvent with high saturated dielectric permittivity improves the capacitance performance.Moreover,the electrode meso-macropore structure is of more concern compared with solvent polarity when aiming at enhancing the specific capacitance.These results provide fundamentals for the rational design of porous electrodes and polar electrolytes for EDLCs.
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.
