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Dimethyl ether (DME) is the simplest ether and a major by-product of methanol-to-olefins production from coal.Its residue can lead to severe catalyst poisoning in subsequent hydrogenation or polymerization processes,reducing reaction efficiency and polyolefin product quality.Therefore,the deep removal of DME is critical for ensuring the performance of hydrogenation and polymerization reactions.This article introduces removal technologies for trace DME in light olefins streams,including washing,distillation,adsorption,catalysis,and combined technologies.The principles,application status,advantages,and disadvantages of different removal technologies are analyzed and compared.Among them,molecular sieve adsorption is the most effective approach for removing oxygen-containing compounds such as DME,featuring low energy consumption and high impurity removal efficiency.It is particularly suitable for the fine removal of trace impurities in olefin feedstocks.By regulating the topology,acid site distribution,pore structure,and ion exchange type of molecular sieves,the adsorption capacity for DME can be increased,adsorption performance improved,and the selectivity and yield of light olefins enhanced.This is of great significance for the future development of the methanol to olefins industry.
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With the rapid development of industrial and agricultural technologies,a vast array of novel industrial pollutants are being released into the environment,posing severe threats to human health.Among these issues,water pollution stands out as particularly critical.The increasingly severe environmental problems have become global challenges,necessitating innovative green solutions.Photocatalysis,an eco-friendly and clean energy technology,holds promising prospects for degrading and mineralizing organic pollutants in water.However,its practical application is constrained by several limitations,including low light utilization efficiency,difficulty in catalyst recovery,and low degradation rates.To overcome these drawbacks,novel photocatalytic coupling technologies have emerged.These technologies enhance the light response range,resulting in higher light utilization efficiency.Additionally,they offer advantages such as high surface active sites,high quantum yields,low costs,and ease of recovery,making them a cutting-edge green technology that has garnered significant attention from researchers.This article provides a detailed overview of the advantages and mechanisms of various photocatalytic coupling techniques.It also delves into the key issues surrounding their application in wastewater treatment today and offers insights and future perspectives on research trends in this field.
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Paracetamol (PCT), as an emerging organic pollutant widely present in aquatic environments, has attracted considerable attention due to its environmental persistence and potential ecological toxicity.Traditional water treatment technologies often fail to achieve its complete removal. Photocatalysis (PC) and photoelectrocatalysis (PEC) technologies, which utilize the photoelectric properties of semiconductor materials to induce the generation of strongly oxidizing reactive oxygen species (ROS) through photogenerated charge carriers, provide highly promising solutions for the efficient degradation of PCT.This review systematically summarizes the reaction mechanisms of PC and PEC technologies for PCT degradation, with a focus on analyzing the performance of conventional catalysts such as TiO2, ZnO, WO3, and BiVO4.Meanwhile, key challenges facing current technologies, such as insufficient catalyst stability, are pointed out.Finally, the paper discusses future research directions in this field, emphasizing the importance of enhancing catalyst stability in real water environments and conducting techno-economic assessments to promote engineering applications.
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As a critical medium in power equipment,transformer oil serves three primary functions:insulation,cooling,and arc-extinguishing.During its use,due to the synergistic effects of heat,oxygen,electric arcs,and microorganisms,transformer oil gradually ages and deteriorates,ultimately leading to increased acidity,impurity accumulation,and significant performance degradation,resulting in the simultaneous decommissioning of the transformer.As a petrochemical resource,waste transformer oil can be further processed and utilized as valuable products,which not only helps prevent environmental pollution but also generates significant economic benefits.This paper first systematically analyzes the types and degradation causes of transformer oil.It then summarizes the high-value utilization pathways and regeneration treatment processes for waste transformer oil.Finally,it outlines future research directions for waste transformer oil regeneration,providing some technical references for its high-value utilization.
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As an important chemical raw material, sodium 3-aminobenzene sulfonate is mainly produced through catalytic hydrogenation of sodium 3-nitrobenzene sulfonate.This study investigated the catalytic performance of 5%Pd/C catalysts modified with different additives in the hydrogenation of the nitro group on the benzene ring to the amino group, and compared it with unmodified catalysts.The catalysts were characterized by XRD, XPS, BET, and metal dispersion analysis.The results showed that the 5%Pd/C catalyst modified with additives exhibited superior catalytic performance.
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Selective catalytic reduction (SCR) technology is the mainstream process for removing nitrogen oxides (NOx).The core of this technology is the catalyst.In actual operation,the activity of the catalyst is easily interfered with by H2O and SO2,leading to a decrease in its activity,and causing the denitrification ability of the SCR system to weaken.This paper investigated the modification effects of Cr and CrCu on Fe-based denitration catalysts,and explored their improvement on the activity and anti-poisoning performance of the FeSO4/HY denitration catalyst.The results showed that the introduction of Cr and CrCu promoters significantly enhanced both the anti-poisoning performance and the activity of the catalyst.The characterization test results of X-ray diffraction (XRD),scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) method indicated that the catalyst possessed a relatively stable molecular sieve structure,a uniform pore distribution,and a large specific surface area.Compared to the FeSO4/HY denitration catalyst,the addition of Cr and Cu increased the outer-layer d-band holes of the FeSO4/HY denitration catalyst,thereby enhancing its catalytic activity,lowering the active temperature,and improving the denitration efficiency.
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Quinoline selective hydrogenation holds particular significance in synthesizing organic intermediates,pharmaceutical molecules,and agrochemicals.A series of carbon/nitrogen dual-vacancy sites modified carbon nitride supports were synthesized via secondary high-temperature treatment and ammonium carbonate treatment,and the performance of the corresponding Pd-based catalysts in quinoline hydrogenation was evaluated.It was found that Pd/MAC-3 exhibited the highest activity and stability,over which quinoline can be converted completely within 3 h under 40 ℃ and 0.4 MPa H2 pressure,and the selectivity to Py-THQ was up to 100%.The characterization results of X-ray diffraction (XRD),scanning transmission electron microscopy (STEM),X-ray photoelectron spectroscopy (XPS),quinoline adsorption,hydrogen activation and spillover showed that the introduction of carbon/nitrogen dual-vacancy sites enhances the interaction between Pd species and the support.This results in improved Pd dispersion and inhibits Pd particle aggregation during the hydrogenation process.Meanwhile,the modification of carbon/nitrogen dual-vacancy sites also improves the quinoline molecule adsorption and hydrogen spillover on the catalyst surface,which may be the main factors affecting the catalytic hydrogenation activity of Pd/MAC-3.
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Ce-based multi-component composite oxide catalysts were prepared via the citric acid complexation method,and the effects of calcination temperature and Fe doping on their NH3-SCR denitrification performance were systematically investigated.The results indicated that calcination temperature significantly influenced the catalytic activity.The sample calcined at 600 ℃ exhibited optimal performance,achieving a NOx conversion efficiency exceeding 90% within the temperature range of 265-550 ℃.The introduction of Fe shifted the operating temperature window towards lower temperatures,enhancing low-temperature activity,though it led to a decline in high-temperature performance.XRD characterization indicated that the main phases of the catalysts calcined between 550-650 ℃ were TiO2,SnO2,and Ce-Zr oxide solid solution,while the Ce4W9O33 impurity phase appeared upon calcination at 700 ℃.Fe doping was found to inhibit grain growth and reduce the crystallinity of catalyst particles.This study provides valuable insights for the design and preparation of Ce-based composite SCR catalysts.
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A series of Ni-Co-rare earth metals (La,Ce,Pr,and Y) ternary metal catalysts with varying Ni/Co molar ratios were prepared via the co-precipitation-hydrothermal method and applied in the hydrogenation of FA for the production of 1,5-pentanediol (1,5-PDO).The 3Ni2Co-2.5Ce catalyst with a metal ratio of 3∶2∶2.5 exhibited the highest activity for the conversion of FA to 1,5-PDO.Under optimal reaction conditions (180 ℃,4 MPa H2,8 h),this catalyst achieved a 1,5-PDO yield of 59.9% and remained stable after five cycles.The excellent selectivity for 1,5-PDO was attributed to the synergistic effect of NiCo bimetallic active sites and the interfacial NiCo-Ov-Ce4+ sites.
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Dicyclopentadiene (DCPD) resin is widely used in adhesives,coatings,and electronics packaging due to its excellent mechanical properties and chemical resistance.However,the presence of numerous unsaturated double bonds in the traditional DCPD resin molecular structure results in insufficient weather resistance,thermal stability,and dielectric properties,limiting its application in high-end sectors.In this study,a novel preparation method for a high-performance DCPD resin hydrogenation catalyst was designed using a multi-effect synergistic catalytic system.This was achieved by constructing a "mesoporous-macroporous" hierarchical pore support,introducing electronic promoters to modulate the electronic environment of nickel,and combining this with a citric acid surface treatment process.Various characterization results demonstrate that the prepared catalyst exhibits excellent hydrogenation activity,selectivity,and stability,indicating significant potential for industrial application.
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This study compares the performance differences and deactivation mechanisms of Karstedt catalyst and Speier catalyst during the isomerization of allyl polyethers.Experiments showed that the Karstedt catalyst follows the Herzfeld-Laidler mechanism at low concentrations;however,when the concentration exceeds 120×10-6,the reaction rate reached an upper limit.TEM analysis reveals its dual equilibrium states involving dissolution equilibrium and dissociation equilibrium:limitations in ligand solubility lead to partial formation of catalyst emulsions,while dissolved platinum centers can dissociate and aggregate into inactive platinum black.For the Speier catalyst,the time-conversion profile deviated from the Herzfeld-Laidler mechanism and exhibited significant deactivation.This is attributed to the gradual reduction of highly active Pt(Ⅳ) to less active Pt(Ⅱ) and inactive Pt(0) during the reaction.Solvent comparison experiments further confirmed that reducing solvents accelerate the reduction of Pt(Ⅳ),resulting in decreased catalytic activity.Based on ligand solubility and metal valence evolution,this study elucidates the deactivation kinetics of the two platinum catalysts in homogeneous catalytic systems,providing a theoretical basis for the selection and process optimization of industrial catalysts.
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α-Porous alumina carriers were prepared using alumina trihydrate and pseudo-boehmite as the main raw materials.The influence of different calcination temperatures on the structure and properties of the carriers was investigated using XRD and SEM.Subsequently,ethylene epoxidation catalysts with different silver loading amounts were prepared,and the effect of silver content on their initial performance was evaluated.The results showed that the mechanical strength and specific surface area of the carriers changed significantly after exceeding 1 000 ℃,accompanied by a phase transformation into α-Al2O3.Furthermore,when the silver loading was 26%,the initial selectivity of the catalyst can reach 83.5%.
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A series of MnCe composite oxides were prepared by co-precipitation method,and the samples were applied in the thermal desorption treatment of the naphthalene contaminated soil.XRD,BET,H2-TPR,Raman,and NH3-TPD were used to characterize the physicochemical properties of the MnCe composite oxides.The results showed that the increase of the amount of CeO2 of the MnCe composite oxide could lead to the improvement of the pore structure of the sample.Meanwhile,the redox property,chemical adsorbed oxygen,and acidity of the sample would also enhanced with the increase of the CeO2 content.The addition of MnCe composite oxide was favorable to the thermal desorption of naphthalene.MC-3 sample,as the Mn/Ce molar ratio was 1∶2,exhibited the best promoting effect on the thermal desorption of naphthalene.Under thermal desorption at 280 ℃ for 5 min,the removal rate of naphthalene reached 81.8%.Under thermal desorption at 280 ℃ for 15 min,the removal rate of naphthalene reached 95.7%.Besides,the thermal desorption processes of naphthalene with or without the addition of MC-3 were fitted by exponential decay kinetic model.
