Metal oxide catalysts are widely employed in propane dehydrogenation(PDH)for propylene synthesis,requiring sequential reduction-reaction-regeneration cycles.However,the eff ect of water present in the inlet gas or rea...Metal oxide catalysts are widely employed in propane dehydrogenation(PDH)for propylene synthesis,requiring sequential reduction-reaction-regeneration cycles.However,the eff ect of water present in the inlet gas or reactor on the catalytic per-formance of various metal oxides remains insuffi ciently understood.This study examines the infl uence of water on supported metal oxide catalysts,specifi cally CoO x/Al_(2)O_(3),VO x/Al_(2)O_(3),and an industrial analog CrO x/Al_(2)O_(3) catalyst.By combining titration experiments,in situ Fourier transform infrared spectroscopy,kinetic analysis,and isotopic techniques,we demon-strate that even trace amounts of water can markedly suppress PDH performance via dissociative adsorption on the oxide surface.Methanol pretreatment eff ectively scavenges adsorbed water,recovering Lewis acid-base sites and consequently restoring PDH activity.This work underscores the profound inhibitory role of trace water in PDH over metal oxide catalysts and illustrates the potential of methanol pretreatment as an effective strategy to mitigate this limitation.展开更多
Summary of main observation and conclusion Novel and technologically important processes and phenomena arise at water surfaces in the presence of electric fields.However,experimental measurements on water surfaces are...Summary of main observation and conclusion Novel and technologically important processes and phenomena arise at water surfaces in the presence of electric fields.However,experimental measurements on water surfaces are challenging,and the results are scarce and inconclusive.In this work,the constant potential molecular dynamics method,in which the electrode charges are allowed to fluctuate to keep the electric potential fixed,was implemented in the study of a near-electrode water surface systems.This simulation system was set up with a vapor/liquid-water/vapor slab and two electrodes under different sets of applied electrostatic potential,yielding i)a detailed characterization of the external E-field dependent electrostatic potential/density/dipole moment density profiles,and ii)the relationship between the water surface width and the applied electrode voltage differences which has been rarely reported.The adjustments in the number density profiles in the vicinity of water surfaces due to external E-fields were observed,while the capillary interfacial widths for the surfaces near both cathode and anode were found with different increment rates under increasing E-fields.By examining dipole density profiles across the water surfaces,we found that external E-field induced polarization occurs in both bulk and surface regimes,yet the surface polarization densities vary asymmetrically with respect to the increasing E-fields.Detailed discussions were carried out to explain the correlation between water surface tension and surface widths,as well as the interplay between the surface polarization densities and the hydrogen bond network structure.We conclude that the mechanical and structural properties of the water surfaces could be tuned by both magnitude and direction of the strong external E-fields.We also recognize that more surface properties with application value,such as dielectric permittivity tensor or surface potential,could also be regulated by the external E-fields.展开更多
基金supported by the National Key R&D Program of China(No.2023YFA1507800)the National Science Foundation of China(Nos.22121004,22122808,22478279,and 22108201)+1 种基金the Haihe Laboratory of Sustainable Chemical Trans-formations,the Program of Introducing Talents of Discipline to Uni-versities(No.BP0618007)the XPLORER PRIZE.
文摘Metal oxide catalysts are widely employed in propane dehydrogenation(PDH)for propylene synthesis,requiring sequential reduction-reaction-regeneration cycles.However,the eff ect of water present in the inlet gas or reactor on the catalytic per-formance of various metal oxides remains insuffi ciently understood.This study examines the infl uence of water on supported metal oxide catalysts,specifi cally CoO x/Al_(2)O_(3),VO x/Al_(2)O_(3),and an industrial analog CrO x/Al_(2)O_(3) catalyst.By combining titration experiments,in situ Fourier transform infrared spectroscopy,kinetic analysis,and isotopic techniques,we demon-strate that even trace amounts of water can markedly suppress PDH performance via dissociative adsorption on the oxide surface.Methanol pretreatment eff ectively scavenges adsorbed water,recovering Lewis acid-base sites and consequently restoring PDH activity.This work underscores the profound inhibitory role of trace water in PDH over metal oxide catalysts and illustrates the potential of methanol pretreatment as an effective strategy to mitigate this limitation.
基金YY acknowledge Fundamental Research Funds for the Central Universities,funding from the Chinese National Science Foundation[Grant Nos.11504110,11874147]the Science and Technology Project of Shanghai Science and Technology Commission(18DZ1112700)ECNU Multifunctional Platform for Innovation(001).
文摘Summary of main observation and conclusion Novel and technologically important processes and phenomena arise at water surfaces in the presence of electric fields.However,experimental measurements on water surfaces are challenging,and the results are scarce and inconclusive.In this work,the constant potential molecular dynamics method,in which the electrode charges are allowed to fluctuate to keep the electric potential fixed,was implemented in the study of a near-electrode water surface systems.This simulation system was set up with a vapor/liquid-water/vapor slab and two electrodes under different sets of applied electrostatic potential,yielding i)a detailed characterization of the external E-field dependent electrostatic potential/density/dipole moment density profiles,and ii)the relationship between the water surface width and the applied electrode voltage differences which has been rarely reported.The adjustments in the number density profiles in the vicinity of water surfaces due to external E-fields were observed,while the capillary interfacial widths for the surfaces near both cathode and anode were found with different increment rates under increasing E-fields.By examining dipole density profiles across the water surfaces,we found that external E-field induced polarization occurs in both bulk and surface regimes,yet the surface polarization densities vary asymmetrically with respect to the increasing E-fields.Detailed discussions were carried out to explain the correlation between water surface tension and surface widths,as well as the interplay between the surface polarization densities and the hydrogen bond network structure.We conclude that the mechanical and structural properties of the water surfaces could be tuned by both magnitude and direction of the strong external E-fields.We also recognize that more surface properties with application value,such as dielectric permittivity tensor or surface potential,could also be regulated by the external E-fields.
