查看更多>>摘要：A strategy combing homogeneous precipitation and hydrothermal treatment was proposed to prepare Keggin-type(NH4)Cu_(0.2)H_(2.8)PMonVO_(40)for selective oxidation of methacrolein(MAL)to methacrylic acid(MAA).The effects of the preparation conditions on the catalyst properties and catalytic performance were investigated.Compared with traditional precipitation,homogeneous precipitation could provide a homogenized supersatu-ration for crystal initial nucleation,while the subsequent hydrothermal treatment process under high pressure could promote crystal led self-assembly growth of rectangular sediments.Benefiting from the advantages of this new method,the as-prepared(NH4)Cu_(0.2)H_(2.8)PMonVO_(40)with high surface area and regular morphology had a large number of active species(VO~(2+))and acidic sites,thereby enhancing the catalytic performance of the catalyst.The MAL conversion and MAA selectivity over the optimum catalysts prepared at the hydrothermal temperature of 120 ℃ and for a time of 4 h reached above 80%.It is believed that this work offers a new strategy for the preparation of an effective catalyst for the oxidadon reaction.
查看更多>>摘要：The development of macrostructured catalysts for remediation processes is a key step towards the sustainability of multi-phase environmental systems,such as the catalytic reduction of inorganic contaminants.The advances towards practical applications faces great challenges regarding the availability of active centers on catalysts surface.To improve the catalytic activity of macrostructured bimetallic catalysts,it is crucial to understand which are the properties that most influence the catalytic activity of materials deposited on macrostructured supports.This work presents a systematic study on the design of macrostructured bimetallic catalysts with enhanced catalytic activity and selectivity.These materials were tested for selective NO3 conversion to N2.The adoption of different synthesis methodologies allowed a higher metal-metal interaction,which is an important property influencing the efficiency of the bimetallic catalyst.Metal phase distribution through coating layers proved to be a key-step for the synthesis of more active and N2 selective structured catalysts.
查看更多>>摘要：A ternary nanocomposite comprising phosphotungstic acid(PW_(12)),polyethyleneimine(PEI),and graphene oxide(GO),i.e.,PW_(12)-PEI/GO,was developed as a precursor to obtain the W2C/N-rGO catalyst upon in-situ carbonization.W2C/N-rGO was applied in the deep oxidative desulfurization(ODS)of liquid fuel,and exhibited extraordinary performance due to the ultrafine W2C nanoparticles(~ 3-5 nm)evenly dispersed on N-rGO and the electron-donating effect of N-rGO on W2C 4000 ppm of DBT in model oil could be completely removed within only 10 min with a remarkably high turnover frequency(168 h~(-1))and the lower activation energy(30.9 kJmol~(-1)).Radical experiments and density functional tneory calculations indicate that the ODS reaction proceeds mainly via a HO· radical mechanism.Moreover,W2C/N-TGO could be recycled for 6 successive cycles with no obvious loss of performance.
查看更多>>摘要：Transfer hydrogenation of anisole in 2-PrOH has been studied as a model reaction for lignocellulose processing.The reaction was studied over high-loaded Ni-based catalysts synthesized via supercritical antisolvent precipitation of a Ni precursor and sols of four oxides:Al2O3,SiO2,TiO2,and ZrC>2.It was demonstrated that the oxide support significantly affects the structure of the catalysts,their activity,and selectivity.The best performance in the transfer hydrodeoxygenation of anisole was shown by Ni supported on alumina at 250 ℃,which was explained by the highest dispersion of Ni° particles in this catalyst and by the highest concentration of acid centers.
查看更多>>摘要：Over the past few decades,biological hazards and organic pollution have become major environmental concerns.Photocatalysis has been found to be effective in minimizing the negative impacts of these issues in air and water.Lozenge shape Ag/AgCl/ZnTiO3 photocatalysts were fabricated by a facile two-step synthesis method,including hydrothermal and coprecipitation.The physicochemical characteristics and morphological properties of the structures were comprehensively described taking advantage of a multi-technique approach.The prepared photocatalysts offered excellent nitrophenol mineralization(>90%)after 90 min of visible light irradiation.Based on the spin-trapping ESR technique,·O_2~-was recognized as the eminent reactive species during the photocatalytic process.Interestingly,the plasmonic Ag/AgCl/ZnTiO3 photocatalyst presented promising CO2 to CO/CH4 conversion with a production rate of 95.0/18.5 μmol.g~(-1).h~(-1)under visible light irradiation,which is about 1.6 times higher than that of ZnTiO3,implying the synergetic effects due to Ag/AgCl in the ternary construction.In addition to the investigation of antibacterial activity,the prepared photocatalysts were successfully applied to treat the hazardous biological waste bearing U87-MG cancer cells under visible light for the first time.Several as-related analytical techniques were served to demonstrate the activity and interaction pathways.This work may hone a new insight into designing highly efficacious ternary photocatalytic materials.
查看更多>>摘要：This work investigated the effects of support and CO2 co-feeding on the activity and coke formation over gallium-based catalysts for propane dehydrogenation(PDH).The prepared catalysts were characterized by XRD,NH3-TPD,CO2-TPD,O2-TPO,pyridine-IR,Raman and tested in CO2 assisted propane dehydrogenation.The results revealed Ga/HZSM-5 as a highly active and carbon resistant catalyst,more so in the presence of CO2.The structure of coke species was investigated and found to be different over these gallium based catalysts as characterized by O2-TPO and Raman techniques.Coke formation behavior is shown to be directly related to the acid density and strength as well as the topological structure of the support.Moreover,the introduction of CO2 leads to an increase in propane conversion and a decrease in coke selectivity over Ga/HZSM-5 catalysts,although coke species become more graphitic in nature.Lastly,PDH reaction with different co-feeding agents(H2,CO2 and O2)were performed and the results indicate CO2 co-feeding yields the highest propane conversion and lower coke deposition,exhibiting a good application prospect.
查看更多>>摘要：Low-temperature selective catalytic reduction with NH3(LT-SCR)is a promising approach for NOx remediation.This work utilized bimetallic metal-organic frameworks(MOFs)to prepare CeMOx(M=Ti,Cu)catalysts allowing the homogeneous distribution of promoters to investigate LT-SCR explicitly.The strong interfacial interaction between nanoscale-mixed components was characterized on CeTiOx by HRTEM,micro-Raman,and XPS,resulting in high acidity and good redox properties with abundant Ce~(3+)and Ti~(4+).It obtained over 80% conversion from 180 ℃ to 300 ℃ with 100% N2 selectivity,and maintained stable performance in SO2/H2O at a high GHSV of 150,000 L~(-1).In situ DRIFTS reveals that NH3 adsorption was promoted on CeTiOx,which accelerated reaction between NOx and adsorbed NH3 via Eley-Rideal mechanism.Meanwhile,the aliovalent substitution of ceria by Cu~(2+)was observed on CeCuOx,forming oxygen vacancies.Its high redox properties enhanced NOx conversion by Langmuir-Hinshelwood mechanism,but triggered NH3 peroxidation,leading to poor N2 selectivity.
查看更多>>摘要：The issue of loaded Ni/ZrO2 catalyst deactivation has limited the further development of biomass tar reforming.To reduce sintering and coke deposition by optimizing the catalyst,the effects of core-shell structure and cobalt doping coupling on coke deposition in Ni/ZrO2 catalyst are investigated.The Ni/ZrO2 catalyst was deactivated by coke deposition and sintering after 150 min of CO2 reforming of tar.The Ni8Co/ZrO2@SiO2 catalyst exhibited high stability and efficiency of hydrogen conversion(Ch)(50-67 %)and carbon conversion(Cc)(40-60 %)in the toluene reforming,and the Ch(65-81 %)and Cc(73-100 %)in the acetone reforming within 300 min due to the larger specific surface area and richer pore structure.The characterization on the used catalysts showed diat only filamentous coke without encapsulated coke was observed after the reforming of different type of tars reaction.The NigCo/ZrO2@SiO2 catalyst yielded only 6 % and 0.2 % filamentous coke after toluene and acetone reforming reactions.
查看更多>>摘要：The catalytic selective oxidation of isobutane to methacrolein(MAC)and methacrylic acid(MAA)is known to proceed via a Mars-Van Krevelen mechanism.When the reaction is performed in a common reactor with co-feeding of the reactant and oxygen,reactive oxygen species are present on the catalyst surface whereby nonselective oxidation reactions occur.In this work,we studied the possibility to decouple the redox mechanism meaning to separate the reactant oxidation step and the catalyst re-oxidation step for the selective oxidation of isobutane(IBAN)to MAC and MAA.For this purpose,two reactor configurations were employed:a periodic reactor and a two-zone fluidized bed reactor(TZFBR).Whereas the periodic reactor allows the temporal separation of the two steps,the TZFBR enables the spatial separation.A Cs-based Keggin type heteropolycompound was employed as catalyst and characterized before and after reaction by XRD,Raman and XPS to better understand the structural and chemical changes during the periodic operation.The effect of the oxygen/IBAN concentration on the performance was studied.For the periodic reactor it was found that the conversion of isobutane and the formation of products decreased with the consumption of available oxygen species in the catalyst during a period.For the whole periodic tests,low concentration of oxygen injected into the reoxidation part of the cycles led to a high selectivity to the desired products(MAC+MAA).
查看更多>>摘要：We distinguish rates at which carbon deposition occurs during initiation,rates at which catalytic centers are lost during deactivation,and paraffin-to-olefin ratio during propagation as benchmarks that distinguish 5 wt% Cu/H-BEA and H-BEA(Si/Al = 13.5)catalysts during dimethyl ether(DME)homologation in the presence of hydrogen.Studies that systematically vary initial DME contact time(210,94,and 45 mo1_(H+),initial s(mol c)~(-1)),DME pressure(4 and 22 kPa),and H2 pressure(1,24,and 48 kPa)reveal that Cu enables lower carbon deposition rates(on a per proton basis)in the induction period,increases the effluent paraffin-to-olefin ratio during propagation,and decreases instantaneous site-loss yields during termination by 1.5-2×(moles of active sites lost per mole of DME)thus augmenting the degree of product saturation and catalyst stability during DME homologation.These results provide mechanistic insights revealing the critical role of Cu in facilitating DME homologation to high value,high-octane gasoline-range hydrocarbons with higher cumulative turnovers than proton form H-BEA.
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