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Hydrogen,as a zero-carbon and high-energy-density fuel,shows broad prospects in replacing fossil fuels for power generation and in the utilization of clean energy.However,the production,transportation and storage of hydrogen still face significant challenges.Ammonia,as a highly promising hydrogen storage medium,has significant advantages such as high hydrogen content,large energy density,and no carbon emissions during the decomposition process,which has promoted in-depth research on ammonia decomposition hydrogen production technology.The current key bottleneck in this field lies in how to utilize cost-effective catalysts to achieve complete ammonia conversion under a relatively high space velocity[approximately 30 000 mL/(gcat·h)] and at low-temperature conditions (approximately 350 ℃).This paper systematically reviews recent experimental and theoretical advances in ammonia decomposition,and summarizes four key catalyst design strategies:size effect,alkalinity modulation,metal-support interactions,and alloying effect,with their respective mechanisms for promoting the reaction elucidated accordingly.In addition,this paper briefly surveys the technical features of various ammonia decomposition reactors in recent years and discusses the influence of different energy input methods and reactor configurations on catalyst performance,thereby providing a relatively comprehensive reference framework for subsequent research and facilitating the transition of ammonia-to-hydrogen technology from theory to practical application.
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The selective oxidation of ethylbenzene to acetophenone (OEB-AP) is a pivotal reaction in the fine chemical industry for synthesizing high-value-added oxygenated compounds.Its green and economical profile makes it an ideal alternative to traditional Friedel-Crafts acylation and the Hock process.However,this reaction faces challenges such as difficult C—H bond activation,low conversion and selectivity,necessitating the development of highly efficient catalysts.Cobalt-based catalysts,leveraging their multivalent nature (Co2+/Co3+) and exceptional redox properties,have demonstrated significant advantages in the OEB-AP reaction.This article provides a systematic review of recent advances in heterogeneous cobalt-based catalysts for this reaction.In contrast,heterogeneous systems have achieved optimized performance through carrier design (e.g.,SiO2,CeO2,carbon materials) and structural modulation (e.g.,single-atom catalysts and MOF-derived catalysts).Among these,the synergistic effect between oxygen vacancies in CeO2 carriers and cobalt species,heteroatom doping (N/S) in carbon-based materials,and MOF-derived Co-N-C catalysts have shown particularly promising performance.Future research should focus on suppressing benzoic acid byproduct formation,reducing the severity of reaction conditions,and elucidating the interaction mechanisms between cobalt active centers and carriers to facilitate industrial application.
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This paper reviews the recent progress and current status of the oligomerization of high-carbon α-olefins catalyzed by metallocene catalysts.The effects of α-olefins on performance of catalytic systems and the properties of various metallocene poly-α-olefins (mPAOs) are systematically analyzed.Furthermore,the factors such as catalyst structures,substituent effects,reaction conditions,and catalyst modification strategies were carefully studied,and a relationship between these factors and the molecular chain structure of mPAOs,product selectivity and property was established.Finally,the future prospects of the mPAO field are illustrated,which may provide guidance significance for designing and developing high-performance and differentiated mPAO products.
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Nanozymes are a class of functional nanomaterials with enzyme-like catalytic activities.Owing to their high stability,large-scale production capability,and low cost,nanozymes have shown great potential in the field of biomedicine,particularly in tumor catalytic therapy.In recent years,organic selenium nanosheet materials,as an emerging type of nanozyme,have attracted widespread attention due to their unique selenium-active centers,tunable electronic structures,and excellent photothermal conversion performance.Studies have demonstrated that organic selenium nanosheet nanozymes (OSe-NS-NZs) exhibit outstanding performance in catalytic therapy,chemodynamic therapy,sonodynamic therapy,photothermal therapy,and synergistic immune therapy by mechanisms such as antioxidative stress,induction of tumor cell apoptosis,and autophagy.They can also significantly enhance the efficacy of radiotherapy and chemotherapy.This article primarily reviews the design and synthesis methods of organic selenium nanolayer-based nanozymes,explores their anticancer mechanisms,elucidates the structure-activity relationships of these organic selenium nanolayer nanozymes,and highlights the synergistic enhancement mechanism of their multimodal imaging and therapeutic functions.It provides new insights for the construction of theranostic nanoplatforms.Although challenges remain in targeted delivery,in vivo metabolism,and clinical translation,but future efforts in optimizing structure-activity control,developing smart-responsive and multifunctional integrated nanozymes are expected to advance this technology toward clinical application.
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As global petroleum reserves continue to decline,crude oil compositions are becoming increasingly complex.The resulting rise in arsenic levels in subsequent oil products not only complicates downstream processing,but also poses severe environmental risks.In this study,a three-dimensionally cubic KIT-6 zeolite was used as a support,and aluminum was incorporated in a one-step synthesis using aluminum isopropoxide to obtain Al-KIT-6 support.The metal active component MnO2 was then loaded onto this support,yielding a highly efficient arsenic-removal catalyst Mn/Al-KIT-6.Surface acid sites on the catalyst promote the catalytic oxidation of As(Ⅲ) to As(Ⅴ),while MnO2 simultaneously adsorbs the resulting As(Ⅴ),enabling the effective removal of various arsenic species.The results show that when the Si/Al ratio is 50,the Al-KIT-6 support achieves its maximum arsenic-removal efficiency of 62.57%.Further optimization of the Mn loading reveals that the 12%Mn/Al-KIT-6 catalyst delivers the highest efficiency of 99.85%.Over seven consecutive cycles,the catalyst maintains an arsenic-removal efficiency above 80%,demonstrating excellent performance and outstanding recyclability.
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Organic amine absorption-regeneration is a mature route for carbon dioxide capture after combustion,but its engineering application is limited by the high energy consumption of solvent regeneration and solvent degradation.In order to reduce the energy consumption of thermal regeneration of amine solution and improve the desorption rate,we studied the desorption efficiency of single amine and complex amine,developed a heterogeneous solid acid catalyst based on porous carbon supporting SO42-/ZrO2 and other active components,and explored its promotion effect on the catalytic regeneration of amine-rich solution.The catalysts were prepared under different calcination temperatures,loading amounts and synthesis sequences,and characterized by N2 adsorption-desorption,TEM,XRD and NH3-TPD.The effects of catalysts on desorption rate,desorption efficiency and cycle stability were evaluated by cyclic desorption tests.The experimental results showed that the heterogeneous catalyst with optimized preparation conditions could significantly increase the CO2 desorption rate and improve the cycle stability under mild desorption conditions,while showing a tendency to inhibit the formation of by-products and long-term degradation of solvents.This work provides an experimental basis for material design ideas and process verification for low-energy regeneration of CO2 capture by amine method,and provides preliminary data support for subsequent scale-up tests and economic evaluation.
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P-modified HZSM-5 (P/HZSM-5) and transition metal-supported M-P/HZSM-5 (M=Fe,Co,Ni,Mo) catalysts were prepared via the incipient wetness impregnation method.The structure and surface properties of the catalysts were characterized by X-ray diffraction(XRD),N2 adsorption-desorption(BET),temperature-programmed desorption of ammonia(NH3-TPD) and other techniques.The in-situ catalytic cracking performance of different catalysts for pyrolysis volatiles of Hongliulin bituminous coal was systematically investigated in a fixed-bed pyrolysis reactor.Results indicate that P species and transition metals are uniformly dispersed on the HZSM-5 support with mutual interactions.After modification,the framework structure of the catalyst remains intact,but the specific surface area and pore volume decrease slightly,the number of surface acidic sites reduces,and the strong acidic sites disappear completely.M-P/HZSM-5 catalysts exhibit excellent catalytic cracking activity for Hongliulin coal pyrolysis volatiles.The content of heavy components in pyrolysis tar is significantly reduced with a maximum reduction of 10.4 percentage points,while the contents of each fraction of light components are improved to varying degrees.Among them,the Mo-P/HZSM-5 catalyst shows the best catalytic performance and coke resistance,which is mainly attributed to its balanced surface acidity and appropriate pore structure distribution.
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Hydrogen production from electrolytic water splitting has become one of the hot research topics due to its potential application in solving the global energy crisis and environmental contamination.In this study,nickel-cobalt-copper (Ni-Co-Cu) polyalloy catalysts with different tungsten (W) doping concentrations were prepared by the hydrogen bubble template method,and their hydrogen evolution reaction (HER) performances in 1 mol/L KOH alkaline electrolyte were systematically investigated.The prepared catalysts were characterized by SEM,EDS,XRD,Raman spectra and XPS.The results show that tungsten doping can effectively regulate the alloy catalysts’ surface morphology,electronic structure,and active site distribution.When the concentration of tungsten ions in the electrodeposition solution was 5.0 g/L,a uniform three-dimensional porous structure was formed on the catalyst’s surface,with a significant increase in the specific surface area,enhanced lattice distortion,and abundant active sites exposed.Electrochemical tests showed that the catalyst exhibited optimal hydrogen precipitation performance in 1 mol/L KOH,with an overpotential of only 37 mV,a Tafel slope of 54 mV/dec,and excellent stability (potential fluctuation of only 8 mV after 12 h of electrolysis).The moderate doping of tungsten enhanced the catalytic activity by optimizing the electronic synergistic effect and surface roughness,but the excessive doping led to the blockage of active sites.
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Cu2O particles were prepared via a liquid-phase reduction method using copper sulfate,sodium hydroxide,and glucose as raw materials,and subsequently modified by an impregnation process to obtain the Ag-Cu2O catalyst.The structural features and photoelectrochemical properties of the resulting catalyst were characterized and evaluated through a series of measurements,based on which a photo-Fenton degradation mechanism was proposed.Experimental results show that Ag-Cu2O exhibits favorable photocatalytic activity,achieving a degradation efficiency of 73.2% toward levofloxacin in aqueous solution.This enhanced performance can be mainly attributed to the introduction of Ag,which facilitates the separation of photogenerated electron-hole pairs and promotes visible-light absorption.In addition,Ag accelerates the decomposition of H2O2,leading to the generation of more reactive radicals that further boost the degradation of levofloxacin.This work offers a promising approach toward greener and more efficient removal of antibiotics from water.
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This study investigates the effects of different synthesis conditions on the crystallinity and morphology of ZSM-5 zeolites,as well as the impact of morphology on their catalytic performance.Results indicate that silica gel properties significantly influencethe synthesis of zeolites.Specifically,products synthesized from Hailing silica gel exhibit higher crystallinity.In a sodium system,when using n-butylamine as a template,varying the crystallization conditions allows for the preparation of zeolites with diverse morphologies and sizes.When other raw materials and crystallization conditions remain unchanged,simply changing the aluminum source results in ZSM-5 zeolites with different morphologies.Meanwhile,when hexamethylenediamine is used as the template,altering the crystallization conditions or aluminum source has little effect on the morphology and grain size of the zeolites.Additionally,the presence of both n-butylamine and hexamethylenediamine simultaneously influences the physicochemical properties and morphology of the product,obtaining ZSM-5 zeolites of high crystallinity.Catalytic evaluation data show that catalysts containing small-grain ZSM-5 zeolites exhibit better selectivity for light olefins.
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Propane dehydrogenation (PDH) is a key petrochemical process for producing propylene.Dimethyl ether present in propane feedstock can cause deactivation of Pt-based dehydrogenation catalysts.To ensure catalyst activity and normal operation of production facilities,adsorption technology is used to remove dimethyl ether,and continuous operation is achieved through regeneration.Industrial application data indicates that the fixed-bed adsorption method for removing dimethyl ether can reduce the dimethyl ether content in propane feedstock to below 1.0×10-6(ϕ),fully meeting the purification requirements for propane feedstock in the unit.The successful application of this technology in the facility has enabled the resource-efficient utilization of by-product propane in propylene production,reduced propane costs,and provided a feasible pathway for raw material diversification in China’s PDH facilities.
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The large-size diffusion pore required for the residue hydrodemetallization catalyst and guard was taken as the research object.A bimodal pore tooth spherical support of catalyst guard with macro-mesoporous structure was prepared through extrusion molding and granulation process using a water-soluble polymer soft template as macro-mesoporous structure-directing agent and long glass fiber as structure-supporting agent under low water to powder ratio condition.The pore structure of support was characterized by mercury intrusion porosimetry.The results showed that the addition of long glass fiber significantly increased the proportion of pore with pore size >500 nm (21.86%) in the support,meeting the requirement of the catalyst guard support for the proportion of macroporous.The indicators meet the requirements of industrial applications after testing the crushing,bed porosityvoid fraction and abrasion rateratio of the guard tooth spherical support reinforced with glass fiber.
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To determine the optimal low temperature for enhancing the corrosion resistance of bridge pile foundation concrete,the corrosion performance of bridge pile foundation concrete was studied under dry wet cycles in a low temperature and high salt environment.Main raw materials such as cement,fly ash,and crushed stone were selected to prepare concrete specimens B-1,B-2,and B-3 in a dry wet cycle machine at -15 ℃,-10 ℃,and -5 ℃.Under low temperature and high salt environments,the three specimens were tested for corrosion depth,compressive strength,and relative dynamic displacement to find the bridge pile foundation concrete specimens with the best corrosion resistance performance.The experiment showed that the sulfate ion concentration of specimen B-3 was below 1.5%,which was at a lower level compared to the other two specimens.And the compressive strength and corrosion resistance coefficients of the specimens are all greater than 84.1%,and the relative mass loss is less than 3.2%,indicating that the bridge pile foundation concrete B-3 has better corrosion resistance performance in wet dry cycle under high salt environment of -5 ℃.
