Abstract:In the process of waste resource utilization for the goal of"double carbon",waste plastic gasification syngas has become the focus of emerging technologies due to its rich hydrocarbon characteristics and negative carbon potential.Compared with the carbon resource dissipation and secondary pollution caused by traditional incineration or landfill,gasification technology converts polyolefin waste into high-purity syngas,which has the advantages of low pollution,high economic benefits and strong flexibility.It provides a key path for high-value utilization of waste and green hydrogen co-production,and has a significant effect in realizing resource recycling and reducing environmental pollution.To address challenges such as inadequate syngas quality and catalyst deactivation in conventional gasification processes,a staged chemical looping gasification(SCLG)process is proposed.A typical perovskite-type LaFeO3 oxygen carrier,synthesized via the sol-gel method,is employed in gasification experiments using polypropylene in a fixed-bed reaction system.The influence of pyrolysis temperature,gasification temperature,and the mass ratio of LaFeO3(OC)to polypropylene(PP)on the gasification performance of the LaFeO3 oxygen carrier is systematically investigated.In this process,the feedstock and oxygen carrier are physically separated,thereby effectively avoiding issues of catalyst contamination by solid residues,char,and tar that are commonly encountered in single-stage gasification.Furthermore,the staged reaction mechanism fully utilizes the partial oxidation capacity of the oxygen carrier and the catalytic cracking ability of the reduced metal,leading to a notable improvement in both the yield and quality of syngas.Results indicate that the pyrolysis temperature exerts limited influence on gasification performance,whereas appropriately elevated gasification temperatures are found to significantly enhance the process.An optimal m(OC)∶m(PP)ratio is identified to effectively balance the two-step reactions of oxidative reforming and catalytic cracking,resulting in improved gasification outcomes.Under conditions of a pyrolysis temperature of 600℃,a gasification temperature of 850℃,and an m(OC)∶m(PP)ratio of 1∶1,the optimal gasification performance is achieved:a syngas yield of 143 mmol/g,a carbon conversion rate of 82%,CO selectivity of 80%,and satisfactory cycling stability are obtained.Guidance is provided for the scaling of efficient and stable gasification technology and the resource utilization of waste plastics.

Abstract:To address phosphorus pollution in water bodies,biochar(BC-700)is derived from highland barley straw as a carbon-based material.Magnetic biochar material(MBC-700)is developed by immobilizing iron-based compounds onto BC-700 surfaces through co-precipitation.Adsorption performance of MBC-700 is systematically investigated under varying conditions,including pH,dosage,initial phosphate concentration,and contact time.Characterization techniques(SEM-EDS,XRD,XPS,FTIR,and VSM)combined with kinetic and isothermal adsorption models are employed to elucidate the adsorption mechanism.Results demonstrate that MBC-700 exhibits a porous structure with iron species(FeOOH and Fe3O4)effectively immobilized on its surface,where Fe3O4 contributes to its strong magnetic properties.Post-adsorption analysis reveals phosphate retention primarily as FePO4 precipitates and Fe—O—P complexes.The adsorption process follows spontaneous monolayer chemisorption kinetics,influenced by intraparticle diffusion,surface heterogeneous diffusion,and boundary layer diffusion,achieving a theoretical maximum adsorption capacity of 5.97 mg/g.MBC-700 maintains effective phosphate removal across a broad pH range(3-7),with enhanced performance in acidic conditions and inhibition in alkaline environments.Notably,coexisting anions(CO32-and HCO3-)promote adsorption,while magnetic recovery achieves>98%efficiency.Mechanistic studies identify pore filling,electrostatic attraction,ligand exchange,precipitation,and complexation as dominant adsorption pathways.This work provides scientific insights and technical support for addressing phosphorus pollution and advancing biochar recovery technologies.

Abstract:To address the high nitrogen and oxygen content in bio-oil and catalyst deactivation during catalytic pyrolysis of algal biomass,this study investigated the pyrolysis characteristics of spirulina catalyzed by a molten salt-coupled zeolite/cerium-based catalyst system.The denitrification and deoxygenation effects of the coupled system on Spirulina pyrolysis bio-oil were examined,and the mechanism by which molten carbonate inhibits catalyst deactivation was thoroughly investigated.The results demonstrate that molten carbonate effectively reduces the yield of nitrogen and oxygen elements in bio-oil by 25.90%and 28.53%,respectively.Compared with catalytic pyrolysis alone,the molten carbonate coupled with H-β(Si/Al=26)and NiCe/Al2O3 reduced the content of oxygen/nitrogen-containing compounds in bio-oil by 71.49%/31.20%and 53.14%/39.50%,respectively,while increasing aromatic compound content during single pyrolysis by only 4.02%and 11.02%.After coupling with molten carbonate,the coke deposition mass on H-β(Si/Al=26)decreased by 31.60%,and that on NiCe/Al2O3 decreased by 20.97%after single pyrolysis.Molten carbonate inhibits coke formation by removing oxygen-containing compounds and nitrogen-containing heterocycles from volatiles,while its reaction with basic amides/amines prevents deactivation of active sites.Additionally,molten salt suppresses condensation reactions related to carbon double bonds and amino groups,enhances the saturation of heavy components,and inhibits their further polymerization into coke.Owing to the improved catalyst stability from molten carbonate,the aromatic compound content in bio-oil obtained after 5 cycles using the coupled system increased by over 48%compared to conventional catalytic pyrolysis.

Abstract:The dual functional materials can be formed by combining CO2 adsorbent CaO with specific ethane oxidative dehydrogenation catalyst Cr/SBA-15(mass ratio 1∶1)to achieve integrated CO2 capture and utilization to produce ethylene.This study addresses the insufficient catalytic activity in dual functional materials by modifying Cr/SBA-15 through acid leaching,systematically investigating the effects of citric acid and nitric acid treatments on catalyst structure and performance.The catalysts with 3%Cr loading were synthesized by incipient wetness impregnation,followed by acid leaching at solid-liquid ratio 1∶20,80℃stirring for 4h.After washing and drying,the catalysts were mechanically mixed with CaO to prepare the dual functional material.Ultraviolet-visible spectroscopy results demonstrated that acid leaching enhanced Cr dispersion on the SBA-15 support surface.Microscopic surface morphology further confirmed uniform Cr distribution on the carrier.X-ray diffraction analysis revealed that acid treatment increased the proportion of Cr6+on the catalyst surface,promoting oxidation of Cr3+during calcination.N2 adsorption-desorption tests showed that acid leaching enlarged the specific surface area and pore volume of the material.Solid state nuclear magnetic resonance results elucidated that acid leaching created framework vacancies by breaking Si-O bonds,enabling Cr anchoring to the carrier through silanol nests.Cr dispersion on the support depended on the availability of silanol nest hydroxyl groups,which were increased by acid treatment.Isothermal adsorption-catalysis experiments demonstrated significant performance improvement of the modified materials.Experimental results showed that after citric acid and nitric acid modifications,ethylene yield increased from 26%to 29%and 33%respectively,while ethane conversion rate improved from 37.19%to 47.17%.Combined catalyst characterization indicated that performance enhancement correlated with material property changes,where Cr valence state,dispersion degree,and specific surface area played crucial roles in catalytic activity improvement.

Abstract:Nitric acid demonstrates the ability to rapidly depolymerize lignin,thereby facilitating the value-added utilization of papermaking black liquor via hydrothermal liquefaction(HTL).Using alkaline lignin(AL)as the raw material,the characteristics of the lignin hydrothermal process under different reaction times,temperatures and initial pressures in the presence of nitric acid were investigated.Additionally,the migration process of carbon elements and the reaction mechanism of hydrothermal process were explored.The study indicates that the nitric acid-assisted AL hydrothermal reaction process consists of debranching reactions(10%-15%),acid-induced precipitation aggregation(65%-70%),and depolymerization(15%-20%).Hydrothermal products are predominantly influenced by temperature and initial pressure,exhibiting relatively low sensitivity to reaction time.An increase in hydrothermal temperature can promote debranching reactions of hydrothermal carbon and inhabit the acid-induced precipitation aggregation of AL to form hydrothermal carbon,reducing the proportion of carbon in solid products from 77.0%to 51.6%,and increasing the proportion of carbon in gaseous products from 0.6%to 14.2%.Elevating the initial reaction pressure can inhaibit depolymerization and promote the acid-induced precipitation aggregation of AL to form hydrothermal carbon,leading to a decrease in the proportion of carbon in liquid products from 17.6%to 4.1%,whereas the proportion of carbon in solid products increases from 50.8%to 64.9%.The primary gaseous products of lignin hydrothermal decomposition are CO2 and a minor amount of CO,which originate from the cleavage of carbonyl,carboxyl,and ether bonds during the hydrothermal process.Liquid products primarily consist of monomers,dimers,and phenolic oligomers derived from the depolymerization of AL,resulting from partial depolymerization catalyzed by acid and subsequent repolymerization of the depolymerization products.Hydrothermal carbon is mainly composed of hydrophobic amorphous intermediates formed through the softening and adhesion of AL in an acidic environment,which adsorb partially depolymerized lignin fragments and undergo cross-linking carbonization.According to the carbon distribution among the three-phase products,the optimal operational parameters are determined as a reaction time of 4 hours,a reaction temperature of 180  ℃ and an initial pressure of 0 MPa.Under these conditions,the solid products accounts for 50.8%of the total carbon content and the liquid products contributes 17.6%.

Abstract:Under the global"dual carbon",biomass,as the most abundant renewable carbon resource in nature,has a sustainable large-scale supply capacity and advantages such as carbon neutrality,wide sources and strong economic adaptability.It is regarded as an ideal alternative to fossil resources and an important cornerstone of a sustainable energy and chemical industry system.However,due to the influence of its multi-component interweaving,three-dimensional cross-linked structure and the characteristics of various types of chemical bonds,the efficient utilization of biomass still faces challenges such as complex conversion paths,insufficient reaction selectivity and high energy consumption.Although traditional thermal catalytic methods can achieve a relatively high conversion rate,they often rely on high temperature and high pressure conditions,making it difficult to precisely control the product distribution,and are prone to causing side reactions such as carbon deposition and coking.For this reason,it is urgent to develop green catalytic strategies that can achieve highly selective and efficient conversion under mild conditions.Photoelectrocatalytic biomass conversion is a process that utilizes photocatalysts to absorb light energy and excite electron-hole pairs.Photogenerated holes can selectively oxidize highly reactive functional groups in biomass molecules on the anode side,while photogenerated electrons participate in reduction reactions on the cathode side.Through the precise regulation of the band structure and interface engineering design,the efficiency of carrier separation and migration can be optimized,the occurrence of side reactions can be suppressed,and the selective breaking of specific chemical bonds in biomass and the precise retention of functional groups can be achieved.Thus,high-value chemicals such as gluconic acid and aromatic compounds can be efficiently synthesized under mild conditions.Based on the composition and structural characteristics of biomass,this paper classifies and reviews the research progress of photoelectrocatalytic conversion of cellulose,lignin and their derivatives.For the comprehensive cellulose part,the transformation pathways,product distribution characteristics and influencing factors of typical platform molecules such as glucose and glycerol in the photoelectrocatalytic system were elaborated with emphasis.For the lignin component,it is classified and summarized from two dimensions:the selective cleavage of C-O bonds and C-C bonds in the structure.It covers the application of different photoelectrocatalytic systems in lignin depolymerization and the synthesis of high-value chemical products,and analyzes the advantages of emerging technologies such as dye sensitization systems and three-chamber photoelectrobiochemical systems in improving conversion efficiency and product selectivity.Based on this,the core principles of photocatalyst design were summarized,and effective strategies for enhancing catalytic activity and stability,such as interface engineering,defect control,and doping modification,were discussed.Finally,this paper summarizes the current challenges faced by photoelectrocatalytic biomass conversion in terms of raw material complexity,reaction selectivity and energy matching,and looks forward to future research directions such as high-value utilization of all components of primary biomass and bipolar synergistic catalysis,providing theoretical support and technical references for the study of the mechanism of biomass photoelectrocatalytic conversion and the screening and optimization of catalysts.

Abstract:Graphene has shown promising prospects in the fields of electronics,new energy,and new materials due to its excellent physicochemical properties.The preparation of graphene from bituminous coal not only expands the range of graphene raw materials but also reduces carbon emissions from coal chemical processes.In this study,graphene was prepared from ShenDong bituminous coal using an improved Hummer's method.The crystal structure,morphology,and thickness of the graphene and its intermediates during the preparation process were characterized qualitatively and quantitatively using X-ray diffraction(XRD),Raman spectroscopy,scanning electron microscopy(SEM),transmission electron microscopy(TEM),and atomic force microscopy(AFM).The influence of the particle size of the coal powder raw material on the structure of the prepared graphene was also investigated.The results showed that bituminous coal of different particle sizes could form highly ordered graphite crystal structures through high-temperature graphitization,and thus be successfully converted into graphene.The XRD patterns exhibited distinct graphene characteristic diffraction peaks,and the Raman spectra showed typical graphene defects and sp2 hybridization plane features.As the particle size of bituminous coal increased,the defects in the prepared graphene increased.The graphene samples obtained from coal with a particle size of 46.89 μm had small graphene microcrystalline stacking thickness and high defect levels.SEM,TEM,and AFM characterizations revealed that the prepared coal-based graphene nanosheets had wrinkled surfaces and were 1-2 layers thick,meeting the standard of few-layer graphene.This study provided new ideas for the high-value utilization of bituminous coal,and helped to promote the transformation of fuel coal to material coal and the realization of the dual-carbon goals.

Abstract:Gasification agents significantly affect H2 yield during biomass gasification process.To systematically compare the hydrogen production efficiency of different gasification agents,this study established a process simulation model for hydrogen production from corn straw gasification using Aspen Plus software.Different gasification agents(air,oxygen,air-steam,oxygen-steam)were used to simulate the H2 production process of corn stover gasification.The effects of temperature,equivalence ratio,and steam to biomass ratio on H2 production were systematically analyzed,and economic evaluations on different gasification schemes were further conducted.The results indicated that,compared to using air or oxygen alone as the gasification agent,the combined gasification with steam addition promoted the production of H2.Under all gasification conditions,as the gasification temperature increased,the volume fraction of H2 increased and remained stable at 900℃.The increase in temperature led to a continuous decrease in the volume fraction of CO2 and CH4,while LHV and H2 yields continued to increase.As the equivalence ratio increased(0.25-0.34),the molar ratio of H2 to CO increased,while the proportion of H2 and LHV showed a decreasing trend.The most significant decrease in H2 volume fraction was observed under oxygen-steam conditions.As the steam to biomass ratio increased(0-0.8),the volume fraction of H2 and CO2 increased,LHV significantly increased,and the volume fraction of CO and CH4 decreased.The overall volume fraction of H2 under oxygen-steam combined gasification conditions was higher than that under air-steam combined gasification conditions.Overall,under the same conditions,oxygen-steam combined gasification had the best hydrogen production effect.When the gasification temperature was 900℃,the equivalence ratio was 0.28,and the steam to biomass ratio was 0.6,the volume fraction and yield of H2 could reach 56%and 126 g/kg,respectively.According to the economic analysis,although oxygen-steam gasification has a greater hydrogen production efficiency,its equipment and oxygen preparation costs are relatively high.In contrast,air-steam gasification offers economic advantages due to its lower operating costs.Its levelized hydrogen production cost can be as low as 11.7 yuan/kg,indicating good potential for industrial application.

Abstract:Agricultural and forestry residues,as vital biomass resources,are recognized for their potential in high-value energy conversion,providing an effective pathway toward sustainable development and dual-carbon goals.A cascade conversion model integrating photo-fermentative biohydrogen production with microwave pyrolysis is developed to overcome the limitations of single conversion technologies.By coupling biological and thermochemical processes,efficient stepwise utilization of all biomass components is achieved.Five representative lignocellulosic residues(wheat straw,rose stem,bamboo,cotton stalk,and peanut stem)are employed as feedstocks to investigate the cascade hydrogen production process under conditions of 20 g feedstock,20 min pyrolysis time,and 800 W microwave power.Gas chromatography(GC),Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),thermogravimetric analysis(TGA),and nitrogen adsorption(BET)surface area analysis are applied to elucidate the mechanisms of material transformation,residue composition evolution,and product distribution during hydrogen production.Results indicate that,under light-driven anaerobic conditions,carbohydrates are degraded and dehydrogenated by the photosynthetic bacterial consortium through nitrogenase-and hydrogenase-mediated pathways,yielding 7.994 to 21.211 mL/g of hydrogen.The post-photo-fermentation residues are primarily enriched in recalcitrant lignin,along with residual cellulose and hemicellulose.Subsequent microwave pyrolysis further converts the remaining organic matter into hydrogen(87.970 to 226.905 mL/g)via thermal cracking,decarboxylation,and aromatization reactions.Bamboo shows the highest total hydrogen yield(242.235 mL/g),corresponding to a 422.35%increase compared with single-stage photo-fermentation.In addition,microwave pyrolysis demonstrates strong potential for carbon resource valorization,exemplified by a biochar yield of 54.640%from rose stem residue,and for methane production,with bamboo residue generating 44.812 mL/g.

Abstract:CO2 capture,utilization,and geological storage(CCUS)serve as a foundational technology for large-scale emission reduction in the fossil energy and industry sectors.To quantify the carbon abatement potential and contribution to carbon neutrality for high-emission enterprises in Hainan driven by CCUS,we constructed a high-precision research framework that integrates enterprise-level carbon emission accounting,block-level storage site screening,techno-economic characterization of CCUS projects,source-sink matching via pipeline cost surface modeling,and carbon abatement prediction.This framework enables kilometer-scale CCUS integrated analysis,achieving the first multi-dimensional assessment of Hainan's CCUS technologies.It covers storage capacity,site suitability,techno-economics,cluster deployment,and carbon neutrality pathways.Findings show that the Fushan Sag in Hainan possesses geological conditions for CO2 geological utilization and storage in oil-gas reservoirs and saline aquifers.Key emitters can achieve 90%abatement of total captured CO2 at a levelized cost of<400 CNY/ton via CO2 saline aquifer storage.CCUS technologies are projected to yield a cumulative net abatement of 540 million tons for Hainan's enterprises by 2060,with CO2-EOR and CO2-EWR applications peaking in 2040 and 2045,respectively.This study provides critical support for Hainan's CCUS planning toward carbon neutrality and offers a reference for South-South and island nations to integrate CCUS into their decarbonization and industrial development strategies.

Abstract:As the issue of carbon emissions in the global aviation industry becomes increasingly severe,sustainable aviation fuel(SAF)derived from biomass has emerged as a crucial development direction for carbon reduction in this sector,owing to its low-carbon characteristics during production and use.However,the production cost of existing biomass-based SAF is significantly higher than that of traditional fossil jet fuel.Therefore,a comprehensive assessment of the resource consumption,environmental impact,and economic benefits associated with the production process of biomass-based SAF is crucial for optimizing SAF production technology.This will help reduce production costs and facilitate the large-scale production of low-carbon jet fuel.This article provides a systematic review of recent advancements in the life cycle assessment(LCA)and techno-economic analysis(TEA)of biomass-based SAF production processes.It conducts a comparative analysis of various technological pathways from the perspectives of resources,environmental impact,and economic viability,highlighting their respective advantages and disadvantages.Among the life cycle assessment methods,the carbon footprint assessment for biomass-based SAF production is the most common and is widely used in a variety of SAF production processes.The statistical analysis results indicate that although the carbon reduction effectiveness of various production processes exhibits considerable variation,all demonstrate significantly lower carbon emissions compared to conventional fossil-based jet fuel,with carbon emission reduction percentages ranging from 17.4%to 96.8%.Moreover,LCA is employed to evaluate other environmental impacts besides carbon emissions in biomass-derived jet fuel production systems.The LCA results for the gasification Fischer-Tropsch(G-FT)process and aqueous phase reforming(APR)process revealed that,in addition to carbon emissions,these two production pathways emerged as predominant contributors to acidification potential and human toxicity potential,respectively.Sensitivity analysis shows that changes in land use,hydrogen production methods and power sources have significant impacts on carbon footprint.Furthermore,the LCA based on Analytic Hierarchy Process(AHP)and exergic analysis significantly expand the evaluation dimensions of conventional LCA.The AHP-based approach enables comprehensive quantification of environmental impacts through multi-perspective weighting,while the exergic analysis method elucidates the relationship between energy utilization efficiency and resource consumption from a thermodynamic standpoint.The techno-economic analysis revealed that feedstock costs and production scale constitute the predominant determinants influencing the market price of biomass-derived sustainable aviation fuel.Expanding the production scale can,to a certain extent,distribute capital investment and reduce raw material costs.Sensitivity analysis further demonstrates that the fluctuation of biomass prices exhibits the most significant impact on the economy,and the production process of bio-jet fuel is affected by multiple uncertainties.Additionally,the exergic economic analysis incorporating life cycle thinking demonstrates that the self-powering scheme significantly reduces environmental costs while enhancing economic benefits by decreasing fossil energy dependence.Future research should focus on further optimizing the raw material supply chain,improving conversion efficiency,and promoting the application of green hydrogen.Additionally,it is recommended that governments strengthen policy support by implementing well-designed differentiated carbon tax and subsidy schemes.The multi-dimensional assessment provides a theoretical foundation for both technological optimization and large-scale application of biomass-based SAF production processes,helping the aviation industry reduce carbon emissions and increase efficiency,and achieve sustainable development.

Abstract:5-Hydroxymethylfurfural(HMF),a key biomass-derived platform molecule,can be selectively oxidized to 2,5-diformylfuran(DFF),an important intermediate for bio-based polymers,fine chemicals,and functional materials.Compared to the full oxidation of HMF to 2,5-furandicarboxylic acid(FDCA),the selective formation of DFF requires precise oxidation of the hydroxymethyl group while suppressing overoxidation of the aldehyde group,posing significant challenges in catalyst design and reaction control.This review provides a comprehensive overview of recent progress in the thermal catalytic oxidation of HMF to DFF,with emphasis on the mechanistic pathways,including oxygen source selection,solvent effects,reactive oxygen species generation,and their interplay with active sites.Advances in noble metal catalysts,transition metal oxides,and carbon-based materials are discussed in terms of structural modulation,structure-activity relationships,and catalytic performance.The advantages and limitations of different catalytic systems are critically compared.Finally,key challenges such as selectivity tuning,catalyst stability,mechanistic elucidation,and the development of green,scalable processes are outlined to guide future research on efficient thermal catalytic systems for DFF production.

Abstract:As a clean and renewable energy,biomass has great significance in optimizing energy structure and reducing carbon emissions.As a large agricultural country,China has abundant biomass resources.These biomass materials have high alkali metal content relative to coal,causing the problem of slagging,corrosion and damage to boiler equipment.To investigate the alkali metal release characteristics,the pyrolysis experiments of 6 mm spherical lotus wood particles were carried out.Research was conducted in a turbulent environment from 200℃to 900℃using a four-fan opposed furnace.SEM-EDS,ICP-OES,IC and other detection methods were adopted to investigate the alkali metal accumulation,release and transformation mechanisms.The results showed that Na accounted for 86%of the alkali metal content in the wood,with water-soluble Na dominating,followed by Ca,K,and Mg.During the pyrolysis process,NaNO3 was released firstly and reached the maximum release at 400℃.With the temperature further increasing,NaCl and Na2CO3 were released,and the release peaks were positively correlated with their melting points.The ammonia-soluble Na would be converted to water-soluble Na during the release of water-soluble Na.The total Na release proportion were 58.25%,65.15%and 71.13%at 600℃,800℃and 900℃,respectively.Comparing the Na release under natural convection and turbulent pyrolysis,it was found that the Na release rates under turbulent pyrolysis were always higher than those under natural convection.It was attributed to the fact that the faster particle heating and significant increase in porosity under turbulent pyrolysis conditions.However,the final release rate of Na in both turbulent and natural convective environments at the same temperature exhibited no significant difference,indicating reaction temperature is the determining factor for the final release rate of alkali metals.

Abstract:The anaerobic digestion-gasification coupled technology,as an innovative pathway for efficient biomass conversion,significantly enhances biomass treatment and conversion efficiency.This technology demonstrates broad application prospects in the context of achieving the"dual carbon"goals.In this study,machine learning methods were employed to integrate traditional anaerobic digestion models with gasification process models.A dynamic simulation system for the coupled anaerobic digestion-gasification process of biomass was constructed.The dynamic evolution patterns of key products throughout the entire process from anaerobic digestion to gasification were systematically revealed.Simulation and experimental validation results indicated that the coupled model achieved an average prediction accuracy of 91.3%for the concentrations of major gas products(including H2,CO,CH4,CO2)during the gasification stage.Compared with traditional single gasification models,the prediction accuracy was improved by 12.5%,demonstrating excellent generalization and prediction capabilities.In the initial stage of anaerobic digestion(0-6 days),the system exhibited high methanogenic activity.Volatile fatty acids were rapidly degraded,and the cumulative methane production increased rapidly to 136.4 mL/g,marking the main methanogenic phase of the digestion system.As anaerobic digestion progressed,significant changes were observed in the physicochemical properties of the digestate.The contents of C and O elements showed an overall decreasing trend:C decreased from 34.14%to 29.11%,and O decreased from 30.05%to 20.10%.These results reflected the decomposition of organic components and their conversion into CO₂ and CH₄.The N element content increased from 2.15%to 2.57%,primarily due to the relative nitrogen enrichment resulting from the degradation of carbon-containing components.In terms of carbon emission reduction benefits,the CO2 emission equivalent per unit of biomass input initially increased and then decreased with digestion time.The CO2 emission equivalent of the coupled system reached its highest value(0.069 4 gCO2eq)on the third day of anaerobic digestion,indicating the optimal carbon reduction performance of the system at this time point.This study provides critical theoretical support for the engineering application of biomass cascade utilization technology.

Abstract:Molten salt heat storage is one of the important technologies for the flexibility modification of coal-fired power plants,but there are few comprehensive technical and economic evaluations on their integrating strategies.In this study,Aspen Plus was used to simulate the system,nine schemes were proposed for the integration of a 315 MW coal-fired power plant and molten salt heat storage unit.Taking the peak shaving performance,thermodynamic performance,power supply coal consumption rate,carbon emission and economy as indicators,the comprehensive evaluation of each heat storage scheme was investigated.The optimal scheme was determined using the Technique for Order Preference by Similarity to Ideal Solution(TOPSIS)method.It was found that in the heat storage process,with increasing the heat storage duty,the peaking and thermodynamic performance of the integrated system was improved,of which extracting the re-heating steam as the heat source led to the highest thermal of the integrated system.In the heat releasing process,the thermodynamic performance of the integrated system deteriorated under higher heat storage duty,of which using the hot molten salt to heat the condensate water at the inlet of No.2 high pressure heater caused the optimal peaking and thermodynamic performance of the couple system.In terms of economy analysis,the operation and maintenance cost accounted for the highest ratio of the integrated system,and the compensation income of the heat storage unit provided the highest income of the integrated system.Based on the TOPSIS analysis,the optimal integrating scheme was determined as follows:heat storage duty of 20 MW,using reheat steam as heat source in the heat storage process,heating the condensate water at the inlet of No.2 high pressure heater in heat release process.The relevant research conclusions could provide theoretical and data support for building a coal-fired power plant integrated with molten salt heat storage peaking system.

Abstract:Pressurized fluidized bed coal catalytic hydrogasification technology demonstrates broad application prospects in the coal-to-natural gas field due to its high carbon conversion rate and methane yield.The fluidization number,as a key parameter affecting the performance of fluidized bed gasification,plays a significant role in regulating particle motion,mixing,and gas-solid mass and heat transfer processes within the bed,thereby influencing the temperature distribution,carbon conversion rate,and methane yield in the gasifier.However,systematic research on the fluidization number remains scarce,and a deeper understanding of its mechanism in the flow-transfer-reaction process of gasification is crucial for optimizing process parameters and reactor design.This study,based on computational fluid dynamics(CFD)simulation and employing the multiphase particle-in-cell(MP-PIC)model,investigates the effects of four fluidization numbers(2.0,3.5,5.0 and 8.0)on the coal catalytic hydrogasification performance.The results reveal that smaller bubble sizes generated under lower fluidization numbers effectively enhance carbon-hydrogen mass transfer efficiency,intensify the hydrogasification reaction process,and elevate the hot spot temperature in the bed.The peak hot spot temperature under the 2.0 fluidization number condition reaches 1 555 K,exceeding the melting temperature of coal ash.An increase in the fluidization number promotes particle diffusion and movement within the bed,leading to a more dispersed and reduced hot spot temperature,with the maximum temperatures under the other three fluidization number conditions below 1 300 K.Considering both reaction intensification and hot spot control,a fluidization number of 3.5 is identified as a recommended choice.Furthermore,this study tracks representative particles of different sizes,analyzing their motion trajectories,temperature evolution,and reactivity.It is found that particles with an initial diameter of 196 gm exhibit the best hydrogasification reaction characteristics under the synergistic effects of the high-temperature zone and the small-bubble-enhanced mass transfer region.Particles that are either too large or too small tend to accumulate at the bottom of the bed or become entrained into the dilute phase region,negatively impacting their reactivity.The corresponding results can provide theoretical guidance for the design and optimization of fluidized bed coal gasifiers.

Abstract:The environmental crisis triggered by the dramatic surge in anthropogenic CO2 emissions has accelerated the development of carbon neutrality technologies.Among these,CO2 hydrogenation to methanol has garnered significant attention due to its triple potential for carbon emission reduction,green hydrogen energy storage,and high-value-added chemical conversion.However,its industrial application remains constrained by the development of efficient catalysts and comprehensive understanding of reaction mechanisms.This review systematically focuses on non-noble metal catalytic systems with promising industrial prospects,summarizing the latest advances in their thermodynamic pathways,catalyst material design,and reaction mechanisms.Key findings reveal that Cu-based catalysts demonstrate enhanced active site density and oxygen vacancy regeneration through optimized active site configuration and interface engineering.In2O3-based catalysts exhibit superior performance owing to their exceptional oxygen vacancy stability and anti-sintering characteristics.Zr-based solid solution catalysts,meanwhile,optimize electronic structures via the synergistic effect of lattice stress and oxygen vacancies,overcoming the performance limitations of single-component catalysts.Moreover,key optimization directions have been identified:specific surface area and Lewis acid-base sites of supports,selection of promoters and their electron transfer functions,and preparation strategies for precise regulation of metallic active sites.Mechanistic studies combining experimental and theoretical approaches unveil a competitive relationship between the formate pathway(dominated by*HCOO intermediates)and the reverse water-gas shift-carbonylation pathway(governed by*COOH dissociation),with pathway dominance strongly correlated to catalyst structural characteristics.By integrating multiscale catalyst design with interfacial properties and kinetic behavior analysis,this review provides theoretical guidance for constructing efficient CO2-to-methanol conversion systems.It advances the integration of carbon cycling technologies with green hydrogen economy,offering valuable insights for developing energy-environment synergistic technologies under carbon neutrality objectives.

Abstract:Sewage sludge and coal slime were collected from sewage treatment plant and coal washing plant in the same area,respectively.The effects of combustion temperature,combustion time and mixing ratio on the migration and transformation characteristics of arsenic(As),selenium(Se)and lead(Pb)during co-combustion of sewage sludge with coal slime were investigated by a temperature-programmed tubular furnace and a sequential chemical extraction method.In addition,two acid leaching methods were used to investigate the environmental effects of As,Se and Pb in the combustion products of sewage sludge and coal slime.The release ratios of As,Se and Pb in sewage sludge and coal slime increased with the increase of combustion temperature and the final release ratio order is Se＞As＞Pb.Moreover,the release ratios of As,Se and Pb increase with the increase of sewage sludge mixing ratio.The release ratios of As,Se and Pb in sewage sludge and coal slime increase rapidly with the combustion time and then tend to be stable.The time required to reach the maximum release ratio is Pb＞As＞Se from high to low.Under the constant temperature combustion conditions,the release rates of As,Se and Pb in sewage sludge and coal slime at 1 200 ℃ are faster than those at 900 ℃,and the release rates of As,Se and Pb in coal slime at the initial stage of combustion are slightly faster than that of sewage sludge.The speciation distribution characteristics of As,Se and Pb in sewage sludge and coal slime are the main factors affecting the release behavior.As,Se and Pb in sewage sludge and coal slime mainly exist in inorganic bound states,and the proportions of inorganic bound As,Se and Pb in sewage sludge are higher than those in coal slime.Organic bound state As,Se and Pb in sewage sludge and coal slime are mainly released together with volatile matter when the combustion temperature is below 500 ℃.In the combustion temperature range of 800 ℃ to 1 200 ℃,the content of carbonate+sulfate+oxide and sulfide bonded As in sewage sludge and coal slime is significantly reduced.The main release temperature ranges of carbonate+sulfate+oxide and sulfide bonded Pb is slightly delayed to 900 ℃ and 1 200 ℃,respectively.In the acid leaching environment,the leaching ratios of Se in the sewage sludge and coal slime combustion products are the highest,which are in the medium risk area.However,the leaching ratios of Pb are the lowest,which are basically in the low risk area.

Abstract:Capacitive deionization(CDI)is an emerging desalination technology that utilizes electric field forces to drive the adsorption of charged ions.Due to its low energy consumption and environmentally friendly nature,CDI exhibits significant potential for application in the field of water treatment.Electrode materials are a key component of CDI systems,and their electronic conductivity and interfacial wettability have a significant impact on desalination efficiency.Herein,short-cut pitch-based carbon fibers(PCF)with high electrical conductivity were used as raw materials.They are successively activated by KOH and nitric acid,which effectively increased the specific surface area and surface wettability of the prepared material(KN-PCF).KN-PCF not only exhibits a specific surface area as high as 583.83 m2/g,but also shows a significant reduction in contact angle to 65° and a decrease in interfacial energy to 34.6 mN/m(a reduction of 60.1％),while still maintaining excellent electrical conductivity(with a conductivity of approximately 13.7 S/cm).Under a 1.4 V voltage applied in CDI,the KN-PCF electrode demonstrates a desalination capacity of 25.5 mg/g,an energy consumption of 0.77 Wh/g,and a desalination capacity retention rate of 96.7％.Density functional theory calculations reveal that the oxygen-containing functional groups on the KN-PCF surface effectively enhance the ion capture ability and improve the interfacial charge transfer efficiency through a dual mechanism of reducing the Na+adsorption energy barrier and narrowing the HOMO-LUMO energy gap.In addition,the three-dimensional multi-physics field simulation designed through COMSOL software confirm that the uniformity of the electric field between the KN-PCF electrode and the electrolyte interface is significantly improved.This research provides theoretical and technical support for the high-value utilization of low-value pitch-based carbon fibers.

Abstract:To prepare coal-based carbon anode materials with high-performance sodium storage from coal and coal derivative pitch,a stepwise construction method of closed-pore structure through medium-temperature activation of coal and high-temperature co-carbonization with pitch was proposed.The study focused on the formation of high-volume porous carbon through medium-temperature activation with NaOH,followed by mixing with pitch and high-temperature co-carbonization to produce coal-based carbon anode materials with a high-volume closed-pore structure.The results indicated that the high-temperature co-carbonization of pitch with porous carbon inhibited the formation of long-range ordered carbon microcrystalline structures during the high-temperature carbonization of pitch alone,and effectively converted the open-pore structure of porous carbon into a closed-pore structure.The resulting carbon anode material exhibited a high closed-pore volume of 0.252 cm3/g,while the specific surface area was only 6.09 m2/g.Further investigation into the effects of the ratio of NaOH to coal,the ratio of pitch to porous carbon,and the carbonization temperature revealed that the optimal structure and sodium ion storage performance of the closed-pore carbon(AC/ZL-1400)were achieved when medium-temperature activation was conducted at 700 ℃ with a mass ratio of NaOH to coal of 1∶1,and high-temperature carbonization was performed at 1 400 ℃ when the ratio of asphalt to porous carbon is 2∶1.AC/ZL-1400 exhibited a sodium storage capacity of up to 360.1 mAh/g at 30 mA/g,with a first-cycle coulombic efficiency of 81.27％.Additionally,after 400 long cycles at 150 mA/g,the capacity of AC/ZL-1400 remained at 182.50 mAh/g.This method provides a new approach for the high-value utilization of coal derivative pitch and low-rank coal.