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As a kind of non-CO2 greenhouse gases,hydrofluorocarbons (HFCs) have a global warming potential (GWP) ranging from hundreds to tens of thousands of times higher than that of CO2.Consequently,it is urgent to develop effective emission reduction measures to mitigate HFCs emissions.However,direct elimination methods fail to fully recover and utilize the valuable fluorine (F) resources contained in HFCs.As fourth-generation refrigerants,hydrofluoroolefins (HFOs) are characterized by shorter atmospheric lifetime and significantly lower GWP,making them superior alternatives to HFCs.Simultaneously,HFOs serve as critical feedstocks for high-value fluorochemical products,including fluorinated electronic chemicals and fluoropolymers.The gas-solid phase catalytic dehydrofluorination (DHF) process,which converts HFCs into environmentally friendly HFOs,represents the most promising approach.The success of this technology hinges on catalyst development.Current research focuses on four catalyst categories: non-metal catalysts (e.g.,activated carbon-based materials) offer low-cost advantages but suffer from poor regeneration efficiency and stability.Cr-based catalysts demonstrate exceptional dehydrofluorination activity but face environmental concerns due to excessive acidity and potential Cr leaching.Mg-based catalysts show high selectivity,though their complex synthesis processes hinder scalability.Al-based catalysts stand out for their tunable acidity,environmental benignity,and balanced performance,making them the current research priority.Future advancements should prioritize catalyst design with optimized acidity,hierarchical porosity,and enhanced resistance to coking,aiming to achieve high activity,longevity,and industrial applicability to effectively promote the control of HFCs emissions and their resource utilization.
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Under the background of accelerated green and low-carbon transformation of the fluorine chemical industry worldwide.1,2,3,3,3-Pentafluoropropene (HFO-1225ye,CF3—CF══CHF),a member of HFOs,can be utilized as a potential replacement refrigerant,as a key raw material for synthesizing the fluoropolymers and the high-value-added halogenated olefins.Specially,in the fluorine electronic gas fields,it also provides a key raw material for the special fluorine electronic gas synthesis and has a wide range of high-tech applications such as semiconductor manufacturing and the photovoltaic industry.However,the high cost of the synthesis process and the catalyst deactivation problems seriously limit the large-scale application.In this review,we classified and summarized the approaches for HFO-1225ye according to different raw materials and catalysts,and compared them with the advantages and technical difficulties.Further,for the critical dehydrofluorination reaction,we summarized the reaction mechanism and catalyst deactivation factors,then through the regulation of the catalyst active sites and the rationalization of structure,we discussed how to improve the catalyst activity and stability to establish a high-efficiency catalytic system.Finally,we look forward to the prospects of machine learning-assisted catalyst development,and co-promote the industrialization and commercialization of HFO-1225ye.
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The biomimetic catalytic epoxidation process of cyclohexene under mild conditions has been developed using galactose oxidase model CuⅡL as catalyst,acetaldehyde as co-substrate,and oxygen as oxidant.The effects of co-substrate structure,acetaldehyde dosage,catalyst amount,and reaction time on cyclohexene epoxidation were investigated.Under the optimized reaction conditions (1.0 mmol cyclohexene,2.0 mmol acetaldehyde,0.04 mol% CuⅡL,2.0 mL 1,2-dichloroethane,oxygen at atmospheric pressure,40 ℃,12 h),the conversion rate of cyclohexene was 98.6%,and the selectivity of cyclohexane epoxide was 84.3%.The mechanism of biomimetic catalytic epoxidation of cyclohexene was analyzed using UV-vis-NIR spectrometer and Electron Paramagnetic Resonance (EPR) spectrometer,and the catalytic reaction mechanism of biomimetic catalytic epoxidation of cyclohexene was proposed based on experimental results.Mechanism studies have shown that the peroxide radical pathway is the dominant pathway for epoxidation.
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A series of Mn-CoOx composite oxide catalysts were prepared by the sol-gel method.The CO oxidation performance of the Mn-CoOx composite oxide catalysts with and without assistance by electric field was investigated at a space velocity of 90 000 mL/(g·h).The results show that the Mn-CoOx catalysts exhibit better low-temperature CO oxidation activity in the electric field.Among them,the T50 (the temperature corresponding to 50% CO conversion) of Mn1Co5Ox under electric field assistance is 13 ℃ lower than that under conventional conditions (without electric field) (CO complete conversion at 110 ℃).The characterization results of the catalysts reveals that the introduction of an electric field can optimize the pore structure of the catalyst samples,promote electron transfer in the catalyst,and activate lattice oxygen to enhance the redox ability.
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In this study,a porous micron spherical Ce1WaOx catalyst was successfully synthesized via hydrothermal method,and the influence of W/Ce molar ratio on the deNOx performance of the catalyst was systematically investigated.The results indicated that the deNOx activity of the catalyst exhibits a trend of initially increasing and then decreasing with the rise of the W/Ce molar ratio.The Ce1W0.2Ox catalyst demonstrates excellent deNOxperformance across a broad temperature window,maintaining deNOx efficiency above 90% within the temperature range of 175~475 ℃.Additionally,stability tests of the catalyst under high-humidity and high-sulfur environment demonstrated its excellent resistance to water (H2O) and sulfur (SO2) poisoning.The results revealed that the catalyst maintained efficient deNOx performance when H2O content ranged from 5%~10% (volume fraction),and its deNOx activity rapidly recovered after stopping the introduction of SO2 or water vapor.The superior characteristics of the Ce1W0.2Ox catalyst endow it with exceptional durability and reliability in practical flue gas treatment processes,making it highly suitable for deep deNOxof complex flue gases.This study thus provides a theoretical basis for developing deNOx catalysts with high efficiency,stability,and broad temperature windows.
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The Cu modified CoCu/ZnO catalysts were successfully synthesized by the co-precipitation method using oxalic acid as the precipitant.The effect of calcination temperature on the glycerol (GL) selective hydrolysis properties of the CoCu/ZnO catalysts was investigated.And the as-synthesized samples were systematically characterized by the N2 adsorption-desorption,XRD,H2-TPR,SEM and FT-IR.The results show that with the increase of calcination temperature,the dispersion of Cu species in the catalyst improves.However,when temperature further increased to 650 ℃,the dispersion of Cu species decreased instead.Meanwhile,high-temperature calcination promotes the heterogeneous existence of Co species in the catalyst.In addition,the chemical interaction between Co and Cu gradually increased,further affecting the structural features and the catalytic performance for GL selective hydrolysis.GL was completely converted,and the yield of 1,2-PL was as high as 95% in presence of the CoCu/ZnO-350 catalyst.When the calcination temperature was further increased to 500 ℃,the conversion rate of GL decreased,the yield of 1,2-PL decreased,and the yield of 1,3-PL increased.Particularly,the yield of 1,2-PL over the CoCu/ZnO-650 catalyst achieved only 73%,the yield of EG was 20%,and the yield of 1,3-PL was 7.0%.The structure-activity relationship of CoCu/ZnO catalyst reveals that the chemical interaction between Co and Cu species and the surface co-active sites concentration determine their catalytic performance,rather than the Co and Cu species dispersion.
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Microflower-structured MoS2 catalysts,both pure and doped with transition metals (Fe or Mn),were successfully synthesized via a one-step hydrothermal method for the hydrogen evolution reaction (HER).The morphology,composition and structure of the material were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD),and its hydrogen evolution performance during water electrolysis was studied.Results confirm the successful incorporation of Fe or Mn atoms into the MoS2 lattice.At a current density of 10 mA/cm2,the Fe-doped catalyst (Fe-MoS2-1∶10) exhibited the HER overpotential of 482 mV and the Tafel slope of 148 mV/dec,which were lower than those of pure MoS2,demonstrating excellent electrocatalytic hydrogen evolution performance.Notably,the Mn-doped catalyst (Mn-MoS2) achieved the lowest Tafel slope of 101 mV/dec,indicating the most favorable HER kinetics.
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Appropriate boron doping has been reported to significantly enhance the catalytic performance of Ni/MgAl2O4 catalyst in the dry reforming of methane (DRM), however the underlying reaction mechanism remains unclear.In this work,density functional theory (DFT) calculations were employed to systematically investigate the mechanistic differences between Ni/MgAl2O4 and B-doped Ni/MgAl2O4 catalytic systems during the DRM process.The results indicate that the introduction of boron markedly modifies the geometric configuration and electronic structure of Ni clusters.Strong orbital hybridization between the B p orbitals and Ni d orbitals is observed,leading to a reduced d-state density near the Fermi level.Such electronic regulation enhances the adsorption of CH4 while weakening the adsorption strength of CO2,and significantly lowers the dissociation energy barriers of both reactants.Consequently,the overall catalytic activity of the B-doped Ni/MgAl2O4 system is effectively improved.This study provides theoretical insights into the role of boron doping and offers guidance for the rational design and structural optimization of high-performance DRM catalyst.
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For the exterior wall engineering of construction projects,modified silica superhydrophobic coatings was prepared by the Stober method using hydroxyl terminated polydimethylsiloxane and ammonia water as raw materials.Their hydrophobicity,self-cleaning and durability were analyzed by using contact angle tester and adhesion tester.The results show that the modified silica particles with moderate particle size can be obtained when the dosage of anhydrous ethanol is 180 mL,the amount of ammonia is 10 mL,the amount of ethyl orthosilicate is 10 mL and the modification time is 2.5 h.The amount of modified silica has a significant effect on the hydrophobic and self-cleaning properties of the coating.When the amount of modified silica is 6%,the coating shows the best hydrophobic and self-cleaning properties,and can maintain a high static contact angle and a low sliding angle under long-term water impact.When the mass ratio of modifier hydroxy-terminated polydimethylsiloxane to modified silica is 3∶3,the hydrophobic degree of the coating reaches the highest value.Appropriate increase of silane coupling agent can significantly improve the durability of the coating,and the optimal dosage is 20% (by mass fraction).
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With the continous expansion of the development scale of gas turbine generating units,the issue of nitrogen oxide (NOx) emissons has become the focus of control in air pollution prevention and control.Gas turbines usually use selective catalytic reduction (SCR) technology to control the NOx emission concentration in the exhaust flue gas.The development of high-activity,low-pressure drop catalyst that can be adapted to the denitrification of flue gas from gas-fired units is crucial for promoting the development of the denitrification industry of gas turbine units.Based on improving the preparation strategy from the traditional vanadium-tungsten/titanium catalyst formulation,more vanadium active components were introduced on the TiO2 to produce highly active nanocatalysts by means of selective implantation of active substances,and 45-hole thin-wall molds were combined with highly active nanocatalysts to produce thin-wall honeycomb-type SCR catalyst.The microcosmic composition of the catalyst were analyzed by means of X-ray diffraction (XRD),X-ray fluorescence (XRF),and Brunauer-Emmett-Teller (BET),and the catalyst was tested for denitrification efficiency,unitasker reactivity,compressive strength,and wear rate.The results show that the catalyst exhibits high activity and low pressure drop during the reaction process,and all the performance indexes are excellent.The catalyst shows great potential in the field of NOx flue gas control in gas turbines.
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Wastewater often contains various complex organic compounds and heavy metal ions,making it difficult for a single catalyst to efficiently degrade all pollutants.By preparing nano TiO2-SiO2 composite photocatalysts,the degradation principle of organic pollutants in wastewater by composite photocatalysts was revealed,providing a reliable solution for wastewater treatment.Based on TiO2 and SiO2 powder,nano TiO2-SiO2 composite photocatalysts with different mass ratios were prepared by the sol-gel method.Simulate wastewater with different pH values,and set different experimental conditions to test the performance of the prepared catalysts.Among the performance comparison results of catalysts with different mass ratios,A4 catalyst showed the largest degradation rate of 65.12% in wastewater with different pH values.During the analysis of catalyst performance under different light conditions,G006 condition could significantly reduce the concentration of pollutants in wastewater,with a degradation rate of 85.15%.When the light intensity is 200 mW/cm2 and the light exposure time is 90 min,the composite photocatalyst with 75% TiO2 mass fraction and 20% SiO2 mass fraction has the best application performance in wastewater degradation treatment.
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In view of the failure problems of branch pipes in the southeast of Jiangsu Province in the low CO2 partial pressure environment,such as corrosion,perforation and severe pitting.The physicochemical properties of the failure trunk pipe A of Sudong XX station were systematically analyzed by means of macroscopic morphology,metallographic structure,chemical composition and corrosion product analysis,and the failure causes were analyzed by combining corrosion simulation,ash correlation degree and response surface.The results show that the areas with serious corrosion are located at the gas-liquid interface and the liquid-phase area.Among them,the gas-liquid interface zone has corrosion perforation due to the mutual scouring effect of gas and liquid,while the under-deposit corrosion existing in the liquid phase area forms pitting pits.
