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[Objective]To meet the strict pollution control requirement for treating flue gas in scenarios like gas turbines and coalbed methane power generation,the development of efficient SCR catalysts that can perform well under high temperatures (>500℃) becomes very urgent,mainly due to the evident activity loss caused by serious sintering and aggravated NH3 over-oxidation for the commercial catalysts of V2O5-TiO2.[Methods]A systematic review was conducted on two categories of high-temperature catalysts:zeolite-based and metal oxide-based.Preparation methods performance optimization strategies,and reaction mechanisms were analyzed.In-situ FTIR and poisoning resistance experiments were employed to investigate NH_3-SCR pathways,hydrothermal stability,and resistance to sulfur/alkal metal poisoning under high temperatures.[Results]For zeolite-based catalysts,Fe/SSZ-13 and Cu-SSZ-13 exhibited outstanding performance due to isolated metal sites and synergistic acid-redox properties.Among oxide-based catalysts,WO_3-FeO?and sulfated CeO_2 achieved high efficiency by enhancing surface acidity,oxygen vacancies,and suppressing NH_3 oxidation.Poisoning resistance studies revealed that ZrO_2 doping improved sulfur tolerance,while Ce doping mitigated alkali metal poisoning.[Conclusion]Zeolite-and oxide-based catalysts demonstrate potential for high temperature denitration,yet require further optimization in anti-deactivation mechanisms.Future research should focus on elucidating microstructural degradation under high temperatures;dynamic sulfur salt behavior and alkali meta trapping strategies;multi-pollutant synergistic control and practical adaptation of monolithic catalysts.
[Objective]Methanol, a key industrial chemical, can be synthesized via CO_2 hydrogenation using renewable hydrogen, serving as an effective pathway toward carbon neutrality. This study aims to optimize the process conditions of ZnZrO? solid solution catalysts for CO_2 hydrogenation to methanol, focusing on temperature, pressure, space velocity,H_2/CO_2 ratio, and the role of a hydrophobic agent, providing guidance for industrial applications. [Methods]ZnZrO ?catalysts were prepared via ball milling. Catalytic performance was evaluated in a fixed-bed reactor under varied conditions(temperature, pressure, space velocity, H_2/CO_2molar ratio). In situ diffuse reflectance infrared Fourier transform spectroscopy was employed to analyze reaction intermediates. Additionally, hydrophobic polydivinylbenzene was physically mixed with the catalyst to enhance water removal and methanol synthesis. [Results]Optimal conditions were determined as 320 °C, 5 MPa, and 24 000 mL/(g_(cat)·h), achieving a CO_2 conversion of 5.1%, methanol selectivity of72.2%, and maximum methanol yield. Increasing the H_2/CO_2 ratio from 3 to 9 improved CO_2 conversion to 12.9% and methanol yield by 145.8%, with DRIFTS revealing accelerated formate intermediate formation. Introducing PDVB(mass ratio 1: 1) facilitated water removal, boosting methanol yield to 414.0 mg/(g_(cat)·h) at 320 ° C. [Conclusions]The ZnZrO?catalyst exhibited high efficiency under optimized conditions, while PDVB integration further enhanced methanol productivity. This study offers valuable insights for industrial CO_2 utilization and catalyst design in sustainable chemical synthesis.
[Objective]The aim of this paper is to systematically sort out the preparation technology of plant-based activated carbon,analyse the influence of key process parameters such as carbonisation,activation and modification on its performance,and assess its application potential through economic analysis in order to promote its large-scale application in the field of power generation.[Methods]Focusing on the preparation process of plant-based activated carbon,we systematically compare the effects of different carbonisation methods,such as direct carbonisation hydrothermal carbonisation and microwave carbonisation,and different activation methods,such as physical,chemical physicochemical,microwave-assisted chemical and catalytic activation,on the pore structure,specific surface area and adsorption performance of the activated carbon;we also explore the regulation mechanism of surface functional groups and selectivity by physical,chemical and metal-loaded modification methods;we elaborate its specific application scenarios based on the needs of the power generation field.The study also discusses the modulation mechanism o surface functional groups and selectivity by physical,chemical and metal loading modification methods.[Results]The study shows that (1) direct carbonisation is faster than hydrothermal carbonisation,but with higher energy consumption,but hydrothermal carbonisation has lower energy consumption and wider characteristics of activated carbon,so it has a wider application;(2) physical activation can effectively reduce the activation temperature by using O_2 as an activator.Chemical activation and physicochemical activation mainly regulate the surface properties and pore size distribution of activated carbon,respectively;microwave-assisted and catalytic activation can improve the activation reaction process to a certain extent;microwave-assisted activation can reduce the surface acidity of activated carbon,and catalytic activation can regulate the pore size distribution of activated carbon to a certain range according to the difference in the sizes of the metal-oxide catalyst particles;(3) the economic analysis shows that combining the gasification with the gasification can reduce the energy consumption.heating/power generation can reduce energy consumption,and the production cost of plant-based activated carbon can be reduced by 30%～50%compared with coal-based,and it's more economical (4) in the field of power generation,plant-based activated carbon can adsorb dioxin with an efficiency of more than 99%and can be desulphurised and denitrified at the same time;as a catalyst carrier for electrolysis of water,it can increase the rate of hydrogen production by 45%;and as a supercapacitor material,it can achieve an energy density of 136.6 W·h/kg,which is significantly better than traditional materials.[Conclusion]Plant-based activated carbon,with its high specific surface area,adjustable pore structure and rich surface functional groups,shows a broad application prospect in the fields of flue gas treatment,electrocatalysis and energy storage in power plants.In the future,it is necessary to further optimise the energy efficiency and economy of the preparation process,and to promote its technical large-scale development,so as to help the low-carbon development of the power industry.
[Objective]This study aims to elucidate the microscopic reaction mechanism of Ni-Na_2ZrO_3 bifunctional material in sorption-enhanced methane steam reforming,addressing the challenges of high energy consumption in CO_2separation and severe carbon deposition in traditional methane reforming.By optimizing material design through theoretical simulations,it provides a scientific basis for developing efficient and low-energy bifunctional materials,promoting the large-scale application of hydrogen energy and achieving carbon neutrality goals.[Methods]Based on density functional theory,a Ni-Na_2ZrO_3 surface model was constructed to systematically analyze the adsorption energies and competitive adsorption characteristics of 21 adsorbates (including CH_x,CH_xOH,CO,CO_2,etc.) at different adsorption sites.Transition state calculations were performed to determine the energy barriers of 34 elementary reactions,investigating the kinetic pathways of methane dissociation,intermediate conversion,and CO_2 formation.Key steps and rate-limiting stages of carbon conversion were identified by integrating surface energy,adsorption energy,and reaction barrier data.Furthermore,the CO_2 adsorption-desorption performance of Na_2ZrO_3 and Ni-Na_2ZrO_3 was compared to evaluate the impact of Ni doping on material regenerability.[Results]The results indicate that the absolute adsorption energy of CH?and CH_xOH increases significantly with dehydrogenation,C adsorption energy:-8.69 eV vs.CH_4:-0.45 eV,demonstrating enhanced interaction between dehydrogenated species and the surface.Among the products,H_2 exhibits weak adsorption,facilitating its desorption,while CO_2 remains stably adsorbed,enabling in-situ separation.The optimal methane dissociation pathway follows direct dehydrogenation (CH_4→CH_3→CH_2→CH),with CH_3→CH_2+H as the ratelimiting step (energy barrier:1.59 eV).The intermediate CH generates CO via the CHOH pathway (barrier:1.38 eV),and CO is further oxidized to CO_2 with O atoms provided by OH dissociation.Ni doping significantly enhances regenerability:the adsorption energy of ZrO_2 on Ni-Na_2CO_3 increases to-9.74 eV,and the CO_2 desorption barrier decreases from 4.90 eV to 2.05 e V,drastically reducing regeneration energy consumption.[Conclusion]The Ni-Na_2ZrO_3 bifunctional material demonstrates high carbon conversion efficiency and exceptional cyclic stability in SESMR.The optimal reaction pathway(CH_4→CO_2) is achieved through coupling direct dehydrogenation and the CHOH pathway,with clearly defined rate-limiting steps.Ni incorporation strengthens the adsorption interface and lowers desorption barriers,significantly improving CO_2capture and material regeneration.This study establishes a theoretical framework for designing dual-function materials with high catalytic activity and regenerability,offering critical insights for advancing low-energy hydrogen production and carbon capture technologies.
[Objective] In order to improve the efficiency of electrocatalytic reduction of CO_2 emitted by the thermal power industry to formic acid(HCOOH) and reduce the emission level of CO_2 in the atmospheric environment,[Methods] In this paper, the improvement direction of high-efficiency Bi-based catalysts was proposed by analyzing the pathways of electrochemical carbon dioxide reduction reaction(ECO2RR) and the electrocatalytic effects of Bi metalbased catalysts under different control strategies. [Results] Studies have shown that Bi-based catalysts can achieve a Faraday efficiency greater than 85% when the stable operation time in the electrolytic cell is greater than 100 h. Bibased ECO2RR catalysts can be regulated from four aspects : surface morphology design, surface modification, defect engineering and component regulation. The surface morphology design can provide more active sites, but it cannot meet the practical application requirements of commercial scale HCOOH production. Surface modification can have beneficial effects on selectivity and activity, but there are problems such as stability, cost and mechanism. Defect engineering can optimize the charge transfer in the reaction and the bonding strength of the intermediate, but the controllability and mechanism of defects need to be studied. Component regulation can be carried out from three aspects: Element doping, alloying, and heterostructure construction. It is an important way to optimize the Bi-based ECO2RR reaction, but it also needs to supplement the test and calculation that are more in line with industrial development. [Conclusion] Bi-based catalysts have outstanding potential in the industrial application of electroreduction of CO_2 to HCOOH. More in-depth improvement and mechanism research can accelerate the industrialization of CO_2-derived chemicals.
[Objective]The coal combustion process releases various heavy metal elements, which are easily concentrated on the easy-to-escape fine particles. By placing a heterogeneous agglomeration system in the flue before the electrostatic precipitator(ESP), the heavy metal elements in the flue gas can be effectively absorbed to make it from the fine particle state, the gas state to the coarse particle state, thereby improving the removal efficiency of these elements by ESP. [Methods]In this paper, Monte Carlo method is adopted to simulate the agglomeration process, and the particle group balance equation is used to solve the adsorption process of the agglomeration adsorbent on the particulate heavy metal, and the distribution of heavy metal arsenic in the particulate matter before and after the adsorption under different flow rates of the coagulation adsorbent is obtained. [Results]The results show that after coagulation, the content of heavy metals on fine particles below 1 μm decreases continuously, and the peaks of particles and heavy metals appear between 4.3～10 μm. At the same time, with the increase in the flow rate of the adsorbent, the heavy metals on the fine particles decrease significantly, and the peak value of the coarse particle segment continues to rise. It can be calculated that when the condensed adsorbent content reaches 8ml/m~3, the adsorption efficiency of fine particles was as high as 89.51%, and the adsorption efficiency of fine particulate arsenic reached 92.33%. In addition,the increase in residence time and coagulant injection rate can enhance the effect of coagulation and adsorption,thereby improving the removal efficiency of ESP and realizing the efficient removal of heavy metals in the tail flue gas of coal-fired power plants. [Conclusion]The conclusion can provide theoretical guidance for the transformation of the tail gas of coal-fired power plants with ultra-low emission of heavy metals.
[Objective] In response to the surge of emergency cooling demand of combined heat and power(CHP)system under peak load or extreme environment, the low energy storage density of traditional water storage technology,and the insufficient thermal conductivity of organic phase change materials, the present study is aimed at developing a composite phase change material(CPCM) with suitable phase change temperature, high latent heat, and high thermal conductivity in order to enhance the thermal management efficiency and energy utilization of the system. [Methods]Using octanoic acid(OA) and lauric acid(LA) as substrates, we calculated the binary eutectic ratios based on Schrader's equation theory, and screened the eutectic matrix suitable for the temperature range of 5~8 ℃ by combining the stepcooling curve method, the differential scanning calorimetry(DSC) method, and the melting-solidification cycle experiments;and we further used the adsorption property of expanded graphite(EG) to prepare the OA-LA/EG composites, and systematically analyzed their phase change temperature and thermal conductivity. Further, the porous structure of expanded graphite(EG) was used to prepare OA-LA/EG composites, and the phase transition temperature, latent heat,thermal conductivity and cycling stability were systematically analyzed. [Results] The results show that the phase transition temperature of the eutectic matrix with 80:20 OA-LA mass ratio is 5.4 ℃, and the latent heat is 158.8 J/g. With the addition of 12 wt% EG, the phase transition temperature of the composites is stabilized at 5.2 ℃, and the latent heat is145.8 J/g, and the thermal conductivity is increased to 2.23 W/(m·K), which is 6 times higher than that of the pure OA-LA,and the supercooling phenomenon has been suppressed.(supercooling degree ≤ 0.2 ℃). After 1000 cycles, the latent heat decay rate is only 13.2%, showing excellent cycling stability. [Conclusion] OA-LA/EG composites provide an efficient emergency cooling solution for cogeneration systems by virtue of their adaptable phase change temperature, high energy storage density and fast thermal response, which is of great value for improving the stability of the system and the efficiency of the comprehensive use of energy.