Passive NO_(x) adsorbers(PNAs)were proposed to address the NO_(x) emissions during the cold start phase.Here we show a novel Ce-based BEA zeolite,as a noble-metal-free passive NO_(x)adsorber.The NO_(x) adsorption capa...Passive NO_(x) adsorbers(PNAs)were proposed to address the NO_(x) emissions during the cold start phase.Here we show a novel Ce-based BEA zeolite,as a noble-metal-free passive NO_(x)adsorber.The NO_(x) adsorption capacity of Ce/BEA reaches 36μmol/g in the feed gas close to realistic exhaust conditions,and the NO_(x) desorption temperature,which is around 290℃,is ideal for diesel exhaust after-treatment systems.Ce/BEA also behaves notable stability of high temperature CO exposure conditions.Multiple characterizations were performed to explore the NO_(x) adsorption chemistry of Ce/BEA.The Ce(Ⅳ)species in the BEA zeolite serves as the active center for NO_(x) adsorption.The bidentate nitrate species is responsible for the observed NO_(x) storage capacity,and the active oxygen around Ce(Ⅳ)plays a critical role in its formation.Considering the significantly better cost efficiency of Ce compared to Pd,Ce/BEA presents an enormous potential for the PNA applications and provides a novel formulation for the noblemetal choice of PNA materials.展开更多
Nonuniform flow distribution along the radial direction usually exists in a Z-flow type radial flow adsorber,which will decrease the utilization of adsorbent and the switching time and may result in operating safety p...Nonuniform flow distribution along the radial direction usually exists in a Z-flow type radial flow adsorber,which will decrease the utilization of adsorbent and the switching time and may result in operating safety problems in cryogenic air separation.In order to improve the uniformity of the flow distribution along the radial direction in the adsorber,a differential equation is derived through pressure drop analysis in the Z-flow type radial adsorber with a cone in the middle of the central pipe.The differential equation determines the ideal cross-sectional radii of the cone along the axis.The result shows that the cross-sectional radius of the cone should gradually decrease from 0.3 m to zero along the axis to ensure that the process air is distributed uniformly in the Z-flow type radial flow adsorber and the shape of the cone is a little convex.The flow distribution without the cone in the central pipe is compared under different bed porosities.It is demonstrated that the proposed differential equation can provide theoretical support for designing Z-flow type radial flow adsorbers.展开更多
Due to the increasing global demand for industrial gas, the development of large-scale cryogenic air separation systems has attracted considerable attention in recent years. Increasing the height of the adsorption bed...Due to the increasing global demand for industrial gas, the development of large-scale cryogenic air separation systems has attracted considerable attention in recent years. Increasing the height of the adsorption bed in a vertical radial flow adsorber used in cryogenic air separation systems may efficiently increase the treatment capacity of the air in the adsorber. However, uniformity of the flow distribution of the air inside the adsorber would be deteriorated using the height-increasing method. In order to reduce the non-uniformity of the flow distribution caused by the excessive height of adsorption bed in a vertical radial flow adsorber, a novel parallel connection method is proposed in the present work. The experimental apparatus is designed and constructed; the Computational Fluid Dynamics(CFD) technique is used to develop a CFD-based model, which is used to analyze the flow distribution, the static pressure drop and the radial velocity in the newly designed adsorber. In addition, the geometric parameters of annular flow channels and the adsorption bed thickness of the upper unit in the parallelconnected vertical radial flow adsorber are optimized, so that the upper and lower adsorption units could be penetrated by air simultaneously. Comparisons are made between the height-increasing method and the parallel connection method with the same adsorber height. It is shown that using the parallel connection method could reduce the difference between the maximum and minimum radial static pressure drop by 86.2% and improve the uniformity by 80% compared with those of using the height-increasing method. The optimal thickness ratio of the upper and lower adsorption units is obtained as 0.966, in which case the upper and lower adsorption units could be penetrated by air simultaneously, so that the adsorbents in adsorption space could be used more efficiently.展开更多
Ce/BEA has the potential to be applied as a novel passive NO_(x)absorber(PNA)in the after-treatment of vehicles due to its considerable NO_(x)storage capacity.However,as a vehicle exhaust after-treatment material,it m...Ce/BEA has the potential to be applied as a novel passive NO_(x)absorber(PNA)in the after-treatment of vehicles due to its considerable NO_(x)storage capacity.However,as a vehicle exhaust after-treatment material,it must withstand the test of long-term hydrothermal aging.This work examined the deactivation mechanism of Ce/BEA during hydrothermal aging.3.0 wt%Ce/BEA was prepared using the ionexchange method,and then subjected to hydrothermal treatment at 650℃with 10%H_(2)O for 1-12 h to obtain samples with different aging extent.For comparison,the H-BEA support was aged under the same conditions.Brunauer-Emmett-Teller(BET)method,X-ray diffraction(XRD),NH_(3)temperature programmed reduction(NH_(3)-TPD),^(27)Al MAS nuclear magnetic resonance(^(27)Al MAS NMR),H_(2)temperature programmed reduction(H_(2)-TPR),and high resolution-transmission electron microscopy(HR-TEM)were performed to characterize the changes in PNA performance,structure,Ce species,and acidity.The HR-TEM and H_(2)-TPR results show that CeO_(x)particles appear after hydrothermal aging,which results from the detachment and aggregation of active Ce species.Based on the^(27)Al MAS NMR results,we conclude that BEA zeolite dealumination leads to the loss of acidic sites and the transformation of active Ce species on the acidic sites into the less active CeO_(x).This is the primary reason for the hydrothermal aging deactivation of Ce/BEA.展开更多
Due to the technology limitation and inferior deNO_(x) efficiency of urea selective catalytic reduction (SCR) catalysts at low temperatures, passive NO_(x) adsorber (PNA) for decrease of NO_(x), CO and hydrocarbons (H...Due to the technology limitation and inferior deNO_(x) efficiency of urea selective catalytic reduction (SCR) catalysts at low temperatures, passive NO_(x) adsorber (PNA) for decrease of NO_(x), CO and hydrocarbons (HCs) during “cold start” of vehicles was proposed to meet the further tighten NO_(x) emission regulations in future. Among them, Pd modified zeolite PNA materials have received more attention because of their excellent NO_(x) storage capacity, anti-poisoning and hydrothermal stability and since Pd/zeolite PNA was proposed, a variety of advanced characterization methods have been applied to investigate its adsorption behavior and structure-performance relationship. The comprehension of the active sites and adsorption chemistry of Pd/zeolite PNA was also significantly improved. However, there are few reviews that systematically summarize the recent progress and application challenges in atomic-level understanding of this material. In this review, we summarized the latest research progress of Pd/zeolite PNA, including active adsorption sites, adsorption mechanism, material physicochemical properties, preparation methods, storage and release performance and structure-performance relationships. In addition, the deactivation challenges faced by Pd/zeolite PNA in practical applications, such as chemical poisoning, high temperature hydrothermal aging deactivation, etc., were also discussed at the micro-level, and some possible effective countermeasures are given. Besides, some possible improvements and research hotspots were put forward, which could be helpful for designing and constructing more efficient PNA materials for meeting the ultra-low NO_(x) emission regulation in the future.展开更多
The paper deals with the modeling of the effect of maldistribution in pollutant abatementtrichloroethylene（TCE）concerning low concentration(10<sup>-5</sup>-10<sup>-8</sup>kg·m<sup>...The paper deals with the modeling of the effect of maldistribution in pollutant abatementtrichloroethylene（TCE）concerning low concentration(10<sup>-5</sup>-10<sup>-8</sup>kg·m<sup>-3</sup>)adsorption in an adsorber.Such a concentration range is rather typical in many an environmental application.Isotherms andbreakthrough curves for TCE adsorption are obtained both for a commercial activated carbonSorbonorit 4 and a laboratory adsorber of d<sub>B</sub>/d<sub>P</sub>=11.Two two-dimensional nonequilibrium isothermalmodels are developed to describe the mass transfer in the fixed bed taking into account the effect ofmaldistribution.It is found the simulation results with maldistribution are in very good agreementwith the experimental findings.Low concentration TCE adsorption in a fixed bed of activated carbonis found to be strongly influenced by maldistribution.The non-uniform distributions of concentrationand loading of the pollutant in the adsorber are predicted by the model.Maldistribution and its ef-fect on the initial breakthrough of TCE in展开更多
Theoretical considerations on diffusion modes of adsorbates in diffusion-cell adsorbers are being investigated. By studying the effects of the operating and model parameters on the response curves calculated by surfac...Theoretical considerations on diffusion modes of adsorbates in diffusion-cell adsorbers are being investigated. By studying the effects of the operating and model parameters on the response curves calculated by surface diffusion model and pore diffusion model, and noting the differences in the results, the following conditions are recommended for the prediction of the prevailing diffusion mode in diffusion-cell experimentsλ≤0.1,BiB≥100,and N≥1The theoretical prediction thus obtained checks well with experimental data taken from literature. New solutions are also presented for the surface diffusion model and the pore diffusion model with rectangular adsorption isotherm.展开更多
A series of transition metal Mn,Cu,Ce and Fe were loaded on TiO_(2) by sol-gel method with noble metal Pd as promotor for the application of passive NO_(x) absorber.Experiments on adsorption and desorption of NO_(x) w...A series of transition metal Mn,Cu,Ce and Fe were loaded on TiO_(2) by sol-gel method with noble metal Pd as promotor for the application of passive NO_(x) absorber.Experiments on adsorption and desorption of NO_(x) were conducted and characterization methods such as X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),transmission electron microscopy(TEM)and in situ Fourier transform infrared spectroscopy(in situ DRIFTS)were involved.The experimental results show that Mn-contained catalysts,Mn-Ti and Pd-Mn-Ti,performed excellent NO_(x) adsorbing ability and appropriate desorption temperature window.On the other hand,Ce-and Cu-contained samples were not suitable for the purpose of PNA.In addition to the low adsorption capacity,these two series of catalysts released massive amount of NO below 150℃.Characterization results indicated that Pd was highly dispersed on all catalysts.The loading of Pd lowered not only the valence states of transition metals but surface oxygen percentage as well.From in situ DRIFTS tests,the Pd had little influence on the types of adsorbed substances for Mn,Ce and Cu series.However,the storage forms of NO_(x) were obviously different on Pd-Fe-Ti and Fe-Ti.展开更多
P-nitrophenol（PNP） adsorption in batch and fixed bed adsorbers was studied. The homogeneous surface diffusion model（HSDM） based on external mass transfer and intraparticle surface diffusion was used to describe th...P-nitrophenol（PNP） adsorption in batch and fixed bed adsorbers was studied. The homogeneous surface diffusion model（HSDM） based on external mass transfer and intraparticle surface diffusion was used to describe the adsorption kinetics for PNP in stirred batch adsorber at various initial concentrations and activated carbon dosages. The fixed bed model considering both external and internal mass transfer resistances as well as axial dispersion with non-linear isotherm was utilized to predict the fixed bed breakthrough curves for PNP adsorption under the conditions of different flow rates and inlet concentrations. The equilibrium parameters and surface diffusivity（Ds） were obtained from separate experiments in batch adsorber. The obtained value of Ds is 4.187×1012 m2/s. The external film mass transfer coefficient（kf） and axial dispersion coefficient（DL） were estimated by the correlations of Goeuret and Wike-Chang. The Biot number determined by HSDM indicated that the adsorption rate of PNP onto activated carbon in stirred batch was controlled by intraparticle diffusion and film mass transfer. A sensitivity analysis was carried out and showed that the fixed bed model calculations were sensitive to Ds and kf, but insensitive to DL. The sensitivity analysis and Biot number both confirm that intraparticle diffusion and film mass transfer are the controlling mass transfer mechanism in fixed bed adsorption system.展开更多
Air flow distribution in radial flow adsorber was numerically investigated using computational fluid dynamics(CFD)method,which was proved to be applicable to study the problem of non-uniform distribution in radial flo...Air flow distribution in radial flow adsorber was numerically investigated using computational fluid dynamics(CFD)method,which was proved to be applicable to study the problem of non-uniform distribution in radial flow adsorber.Results showed that the degree of non-uniformity was more serious in desorption process than that is adsorption process.Therefore,it was considered that the non-uniform distribution of flow in a radial flow adsorber was mainly manifested in the desorption process.Optimum design of distributor parameters can improve the flow distribution in adsorber.Meanwhile,three different structures of distributor and the effect of breathing valve were analyzed.Results revealed that truncated cone is more effective than tubular and conical distributors in flow distribution.By inserting the truncated cone in central channel,desorption uniformity was increased by 6.56%and the breakthrough time of CO_(2)was extended from 564s to 1138s in the adsorption process.The“dead zone”problem at the top of adsorber during the desorption process was solved by opening breathing valve,which prolonged the working life of adsorber and was proved to have less effect on the uniform of airflow.展开更多
Separations of mixtures in fixed-bed adsorbers are influenced by factors such as(1)selectivity of adsorption,Sads,(2)diffusional time constants,Đi/rc 2,and(3)diffusion selectivity,Đ1/Đ2.In synergistic separations,intr...Separations of mixtures in fixed-bed adsorbers are influenced by factors such as(1)selectivity of adsorption,Sads,(2)diffusional time constants,Đi/rc 2,and(3)diffusion selectivity,Đ1/Đ2.In synergistic separations,intracrystalline diffusion of vip molecules serves to enhance the selectivities dictated by thermodynamics of mixture adsorption.In antisynergistic separations,intracrystalline diffusion serves to reverse the hierarchy of selectivities dictated by adsorption equilibrium.For both scenarios,the productivities of the desired product in fixed-bed operations are crucially dependent on diffusional time constants,Đi/rc 2;these need to be sufficiently low in order for diffusional influences to be effective.Also,the ratioĐ1/Đ2 should be large enough for manifestation of synergistic or antisynergistic influence.Both synergistic and antisynergistic separations have two common,distinguishing characteristics.Firstly,for transient uptake within crystals,the more mobile component attains supraequilibrium loadings during the initial stages of the transience.Such overshoots,signifying uphill diffusion,are engendered by the cross-coefficientsΓij(i≠j)of thermodynamic correction factors.Secondly,the component molar loadings,plotted in composition space,follow serpentine equilibration paths.If cross-coefficients are neglected,no overshoots in the loadings of the more mobile component are experienced,and the component loadings follow monotonous equilibration paths.The important takeaway message is that the modeling of mixture separations in fixed-bed adsorbers requires the use of the Maxwell−Stefan equations describing mixture diffusion employing chemical potential gradients as driving forces.展开更多
The design and operation of radial flow adsorber are crucial in large-scale industrial oxygen production,which necessitate accurate prediction of gas-solid transfer behavior.In this work,a developed Computational Flui...The design and operation of radial flow adsorber are crucial in large-scale industrial oxygen production,which necessitate accurate prediction of gas-solid transfer behavior.In this work,a developed Computational Fluid Dynamics-Discrete Element Method(CFD-DEM)model combined with the adsorption model is proposed.The developed CFD-DEM model is validated by comparing simulated results with experimental data and empirical correlation.Subsequently,the effect of particle packing structure and particle shapes on the dynamic adsorption process are analyzed in detail.The results reveal the mechanism of particle packing structure affecting axial velocity distribution,showing that uneven distribution of resistance on the outer flow channel side leads to uneven axial velocity distribution in the bed.Compared to cylindrical adsorbents,the use of spherical adsorbents results in a more uniform axial velocity distribution,consequently reducing bed pressure drop.The study holds significant potential for optimizing gas distribution and improving separation efficiency in future industrial applications.展开更多
Lignin,the most abundant natural aromatic polymer globally,has garnered considerable interest due to its rich and diverse active functional groups and its antioxidant,antimicrobial,and adhesive properties.Recent resea...Lignin,the most abundant natural aromatic polymer globally,has garnered considerable interest due to its rich and diverse active functional groups and its antioxidant,antimicrobial,and adhesive properties.Recent research has significantly improved the performance of lignin-based hydrogels,suggesting their substantial potential in fields such as biomedicine,environmental science,and agriculture.This paper reviews the process of lignin extraction,systematically introduces synthesis strategies for preparing lignin-based hydrogels,and discusses the current state of research on these hydrogels in biomedical and environmental protection fields.It concludes by identifying the existing challenges in lignin hydrogel research and envisioning future prospects and development trends.展开更多
Resourceful food waste treatment is essential for promoting the sustainable development of anaerobic digestion and realizing a circular economy.In this study,biogas residue(BR)was used as a feedstock to produce highva...Resourceful food waste treatment is essential for promoting the sustainable development of anaerobic digestion and realizing a circular economy.In this study,biogas residue(BR)was used as a feedstock to produce highvalue-added products(gas,tar,and char-derived high-performance adsorbents)using pyrolysis technology(at 400–800℃).CaCO_(3),the major component of ash,significantly improved the quality of the pyrolysis product by decomposing into CO_(2) and CaO.The gasification reaction of CO_(2) with coke generated substantial CO and facilitated the formation of a rich pore structure in the char.CaO improved tar quality by contributing to secondary cracking reactions and reducing water content.The composite material formed exhibited excellent performance in wastewater treatment,with a maximum methylene blue adsorption capacity of 969.30 mg/g.The maximum adsorption of heavy metals Cu^(2+),Pb^(2+),and Cd^(2+)was 175.44,244.93,and 199.50 mg/g,respectively.The ash fraction on the ash-biochar composite material adsorbent surface enhanced pollutant removal by providing an alkaline adsorption environment and more oxygen-based n-π interaction sites.The economic analysis showed that the high value-added products obtained from the pyrolysis of BR make this process more productive than land use.展开更多
The increasing need for efficient,sustainable,and environmentally friendly adsorbent materials has driven interest in bio-based alternatives.Conventional silica-based adsorbents,while effective,are often brittle and e...The increasing need for efficient,sustainable,and environmentally friendly adsorbent materials has driven interest in bio-based alternatives.Conventional silica-based adsorbents,while effective,are often brittle and energy-intensive to produce.In contrast,wood offers a renewable and low-energy option with natural porosity suitable for adsorption.This study investigated the fabrication of wood sponge from tropical balsa(Ochroma bicolor)and pulai(Alstonia scholaris)wood through a dual-stage delignification process as a novel bio-based adsorbent.The process involved alkaline treatment using sodium sulfite(Na_(2)SO_(3))and sodium hydroxide(NaOH)at 100℃for 8,9,and 10 h,followed by bleaching process using hydrogen peroxide(H_(2)O_(2))at 100℃for 1,2,and 3 h.The treated samples were then rinsed to neutral pH,frozen at−20℃for 24 h,and freeze-dried at−50℃for 48 h.The results revealed a notable reduction in density and specific gravity,accompanied by increased weight loss and pore diameter size with prolonged delignification process.Optical changes showed increased translucency and layered structures,particularly in balsa wood.FTIR analysis confirmed a reduction in lignin and hemicellulose content,validating the chemical modification within the treated samples.The resulting wood sponges exhibited good porosity and adsorption capacity,ranging from 1.3 to 5.7 g/g.The optimal treatment—10 h of alkaline delignification followed by 3 h of H_(2)O_(2)bleaching—demonstrated the highest performance,highlighting the potential of tropical wood species as efficient,biodegradable,and eco-friendly adsorbent materials.展开更多
Selective extraction of precious metals from urban mines plays a crucial role in mitigating the risk of depletion of precious metal resources and reducing waste pollution.However,a major obstacle in precious metal ext...Selective extraction of precious metals from urban mines plays a crucial role in mitigating the risk of depletion of precious metal resources and reducing waste pollution.However,a major obstacle in precious metal extraction lies in the difficulty of distinguishing the subtle differences in the physicochemical characteristics between them,especially gold and palladium.Herein,a proton-driven separation system was presented for cascade recovery of gold and palladium from waste-printed circuit boards(W-PCBs)leachate using poly(amidoxime)(PAO)hydrogel.This exhibits an ultra-high capacity,extra-fast rate,and excellent selectivity for the extraction of Au(Ⅲ)and Pd(Ⅱ).Notably,the separation of Au(Ⅲ)and Pd(Ⅱ)can be achieved with high selectivity at pH=0,resulting in a remarkable separation factor of k_(Au(Ⅲ)/Pd(Ⅱ))=36.5.This was demonstrated to originate from the differential mechanism of PAO hydrogel for the capture of Au(Ⅲ)and Pd(Ⅱ)under proton-mediated conditions.Drawing inspiration from the mechanism,the proton-driven cascade recovery system demonstrates remarkable efficiency in sequentially recovering 99.92%of gold and 99.05%of palladium from W-PCBs acid leachate.This research opens up a strategy to precisely separate and recover precious metals from e-waste of urban mines.展开更多
Density functional theory(DFT)has helped propel the advance of electrocatalysis in the past two decades.In view of its massive use,it is worth asking how reliable DFT is for the prediction of adsorption energies,which...Density functional theory(DFT)has helped propel the advance of electrocatalysis in the past two decades.In view of its massive use,it is worth asking how reliable DFT is for the prediction of adsorption energies,which are paramount in computational electrocatalysis models.Here,we provide an experimental-computational approach to break down overall adsorption-energy errors into separate gas-phase and adsorbed-phase contributions.The method is evaluated using experimental data and various exchange-correlation functionals and materials for C-and O-containing species.Our main conclusion is that no functional is simultaneously accurate for adsorbates and molecules,as adsorbed-phase errors are visibly different from gas-phase errors.Importantly,total,gas-phase,and adsorbed-phase errors are correlated,revealing intrinsic DFT limitations and enabling the elaboration of swift correction routines.To illustrate the benefits of our approach,we deconvolute and correct all errors in CO_(2)electroreduction to CO and find an agreement with experiments close to chemical accuracy for numerous transition-metal electrodes and all scrutinized functionals.展开更多
Hospital wastewater contains complex pollutants,including residual organic dyes and antibiotic-resistant pathogens,posing severe risks to ecosystems and human health.Conventional adsorbents,constrained by monopolar fu...Hospital wastewater contains complex pollutants,including residual organic dyes and antibiotic-resistant pathogens,posing severe risks to ecosystems and human health.Conventional adsorbents,constrained by monopolar functional groups and limited surface sites,fail to remove both pollutants simultaneously.Here,we report an intelligent responsive polyurethane microsphere adsorbent doped with diallyl dimethylammonium chloride modified carbon nanotubes,termed as PUCD microspheres.The PUCD integrates bipolar adsorption sites,tunable micrometer-scale pores,and a near-infrared(NIR)-triggered in situ capture mechanism within a single platform,which achieves up to 98.3%dye removal,maintains strong adsorption performance across a wide pH range and retains 83.3%efficiency for rhodamine B after five cycles.Notably,the PUCD employs a temperature-responsive phase transition:under NIR irradiation,the microspheres undergo shrinkage,reducing the pore size to generate a‘polymer trap',enabling in situ capture of bacteria with>99%efficiencies for both Staphylococcus aureus and Escherichia coli.By immobilizing live bacteria,the PUCD microspheres substantially reduces the risk of pathogen desorption and toxin release.This promising platform offers a safe,efficient,and single-stage strategy for hospital wastewater purification,enabling the simultaneous elimination of dyes and pathogenic bacteria.展开更多
In order to prevent the emission of NO_(x) from diesel engines during the cold-start period,a NO_(x) adsorption selective catalytic reduction(AdSCR)catalyst was prepared by combining a selective catalytic reduction(SC...In order to prevent the emission of NO_(x) from diesel engines during the cold-start period,a NO_(x) adsorption selective catalytic reduction(AdSCR)catalyst was prepared by combining a selective catalytic reduction(SCR)catalyst with an NO_(x) adsorbent.In this study,CeO_(2)/Al_(2)O_(3)(Ce/Al)was employed as the NO_(x) adsorbent,combined with WO_(3)/CeZrO_(x)(W/CZ)as a promising SCR catalyst,to prepare an AdSCR catalyst.The characterization results demonstrate that the synergistic effects of the combined catalyst significantly enhance the activated oxidation of NO_(x) in comparison to the individual catalysts.The addition of Ce/Al enhances the adsorption of NO_(x) on the catalysts,which is then reduced to N_(2) and H_(2)O by NH_(3) under the action of W/CZ catalysts.The results of the NH_(3)-SCR activity test indicate that an excess of Ce/Al results in a reduction in SCR performance,suggesting that there is a balance between the SCR component and the NO_(x) adsorbent.The optimal combination of 20 wt%Ce/Al+W/CZ(20CA-W/CZ)catalyst demonstrates enhanced NO_(x) adsorption-storage performance while maintaining the exceptional NH_(3)-SCR performance.The NO_(x) complete storage time of the 20CA-W/CZ catalyst is 125 s,which is nearly twice as long as that of the Ce/Al and W/CZ catalysts.Furthermore,the NO_(x) conversion of the 20CA-W/CZ catalyst at low temperatures is approximately 10%higher than that of the W/CZ catalyst.The findings of this study offer a promising s trategy for the design of high-performance AdSCR catalysts in the future.展开更多
Currently,the solid adsorbents with porous structure have been widely applied in CO_(2)capture.However,the unmodified MgO-ZrO_(2)adsorbents appeared to be low adsorption capacity of CO_(2).The solid adsorbent material...Currently,the solid adsorbents with porous structure have been widely applied in CO_(2)capture.However,the unmodified MgO-ZrO_(2)adsorbents appeared to be low adsorption capacity of CO_(2).The solid adsorbent materials were successfully synthesized by loading TEPA onto the pore MgO/ZrO_(2)carriers in the paper.The pore structure and surface characteristic of the samples were analyzed by using XRD,BET,FT-IR and SEM.The adsorbent materials exhibited microcrystalline state,and the crystallinity of all samples gradually decreased as the increase of TEPA content.The pore structure analysis indicated that the modification of MgO-ZrO_(2)adsorbents with TEPA led to the decrease of the specific surface areas,but the narrow micro-mesopore size distributions ranging from 1.8-12 nm in the adsorbents still were maintained.FT-IR spectrum results further verified the successful loading of TEPA.The adsorption capacity of the adsorbents for CO_(2)were tested by using an adsorption apparatus equipped with gas chromatography.The results indicated that when the TEPA loading reached 50%,the sample exhibited the maximum adsorption value for CO_(2),reaching 4.07 mmol/g under the operation condition of 75℃and atmospheric pressure.This result could be assigned to not only the base active sites but also the coexistence of both micropore and mesopore in the adsorbent.After three cycles tests for CO_(2)capture,the adsorption value of the sample for CO_(2)can also reached 95%of its original adsorption capacity,which verified the excellent cyclic operation stability.展开更多
基金supported by the National Key R&D Program of China(2021YFB3503200)the Major Science and Technology Programs of Yunnan Province(202002AB080001-1)。
文摘Passive NO_(x) adsorbers(PNAs)were proposed to address the NO_(x) emissions during the cold start phase.Here we show a novel Ce-based BEA zeolite,as a noble-metal-free passive NO_(x)adsorber.The NO_(x) adsorption capacity of Ce/BEA reaches 36μmol/g in the feed gas close to realistic exhaust conditions,and the NO_(x) desorption temperature,which is around 290℃,is ideal for diesel exhaust after-treatment systems.Ce/BEA also behaves notable stability of high temperature CO exposure conditions.Multiple characterizations were performed to explore the NO_(x) adsorption chemistry of Ce/BEA.The Ce(Ⅳ)species in the BEA zeolite serves as the active center for NO_(x) adsorption.The bidentate nitrate species is responsible for the observed NO_(x) storage capacity,and the active oxygen around Ce(Ⅳ)plays a critical role in its formation.Considering the significantly better cost efficiency of Ce compared to Pd,Ce/BEA presents an enormous potential for the PNA applications and provides a novel formulation for the noblemetal choice of PNA materials.
基金Supported by the Major State Basic Research Development Program of China（2011CB706501）the National Natural Science Foundation of China（51176164）
文摘Nonuniform flow distribution along the radial direction usually exists in a Z-flow type radial flow adsorber,which will decrease the utilization of adsorbent and the switching time and may result in operating safety problems in cryogenic air separation.In order to improve the uniformity of the flow distribution along the radial direction in the adsorber,a differential equation is derived through pressure drop analysis in the Z-flow type radial adsorber with a cone in the middle of the central pipe.The differential equation determines the ideal cross-sectional radii of the cone along the axis.The result shows that the cross-sectional radius of the cone should gradually decrease from 0.3 m to zero along the axis to ensure that the process air is distributed uniformly in the Z-flow type radial flow adsorber and the shape of the cone is a little convex.The flow distribution without the cone in the central pipe is compared under different bed porosities.It is demonstrated that the proposed differential equation can provide theoretical support for designing Z-flow type radial flow adsorbers.
基金Supported by the National Key R&D Program of China(2017YFB0603702)the Natural Science Foundation of Zhejiang Province(Y15E060014)+1 种基金the National Natural Science Foundation of China(51636007)Shanghai Young Teachers Development Program(10-16-301-801)
文摘Due to the increasing global demand for industrial gas, the development of large-scale cryogenic air separation systems has attracted considerable attention in recent years. Increasing the height of the adsorption bed in a vertical radial flow adsorber used in cryogenic air separation systems may efficiently increase the treatment capacity of the air in the adsorber. However, uniformity of the flow distribution of the air inside the adsorber would be deteriorated using the height-increasing method. In order to reduce the non-uniformity of the flow distribution caused by the excessive height of adsorption bed in a vertical radial flow adsorber, a novel parallel connection method is proposed in the present work. The experimental apparatus is designed and constructed; the Computational Fluid Dynamics(CFD) technique is used to develop a CFD-based model, which is used to analyze the flow distribution, the static pressure drop and the radial velocity in the newly designed adsorber. In addition, the geometric parameters of annular flow channels and the adsorption bed thickness of the upper unit in the parallelconnected vertical radial flow adsorber are optimized, so that the upper and lower adsorption units could be penetrated by air simultaneously. Comparisons are made between the height-increasing method and the parallel connection method with the same adsorber height. It is shown that using the parallel connection method could reduce the difference between the maximum and minimum radial static pressure drop by 86.2% and improve the uniformity by 80% compared with those of using the height-increasing method. The optimal thickness ratio of the upper and lower adsorption units is obtained as 0.966, in which case the upper and lower adsorption units could be penetrated by air simultaneously, so that the adsorbents in adsorption space could be used more efficiently.
基金supported the National Key R&D Program of China(2021YFB3503200)the Innovative Research Groups of the National Natural Science Foundation of China(51921004)+1 种基金Young Elite Scientists Sponsorship Program by CAST(2021QNRC001)the Key R&D Project of Shandong Province(2021CXGC010703,2022CXGC020311)。
文摘Ce/BEA has the potential to be applied as a novel passive NO_(x)absorber(PNA)in the after-treatment of vehicles due to its considerable NO_(x)storage capacity.However,as a vehicle exhaust after-treatment material,it must withstand the test of long-term hydrothermal aging.This work examined the deactivation mechanism of Ce/BEA during hydrothermal aging.3.0 wt%Ce/BEA was prepared using the ionexchange method,and then subjected to hydrothermal treatment at 650℃with 10%H_(2)O for 1-12 h to obtain samples with different aging extent.For comparison,the H-BEA support was aged under the same conditions.Brunauer-Emmett-Teller(BET)method,X-ray diffraction(XRD),NH_(3)temperature programmed reduction(NH_(3)-TPD),^(27)Al MAS nuclear magnetic resonance(^(27)Al MAS NMR),H_(2)temperature programmed reduction(H_(2)-TPR),and high resolution-transmission electron microscopy(HR-TEM)were performed to characterize the changes in PNA performance,structure,Ce species,and acidity.The HR-TEM and H_(2)-TPR results show that CeO_(x)particles appear after hydrothermal aging,which results from the detachment and aggregation of active Ce species.Based on the^(27)Al MAS NMR results,we conclude that BEA zeolite dealumination leads to the loss of acidic sites and the transformation of active Ce species on the acidic sites into the less active CeO_(x).This is the primary reason for the hydrothermal aging deactivation of Ce/BEA.
基金financial support from the National Natural Science Foundation of China (No. 52000084)the China Postdoctoral Science Foundation (No. 2019M662630)National Engineering Laboratory for Mobile Source Emission Control Technology (No. NELMS2018A08)。
文摘Due to the technology limitation and inferior deNO_(x) efficiency of urea selective catalytic reduction (SCR) catalysts at low temperatures, passive NO_(x) adsorber (PNA) for decrease of NO_(x), CO and hydrocarbons (HCs) during “cold start” of vehicles was proposed to meet the further tighten NO_(x) emission regulations in future. Among them, Pd modified zeolite PNA materials have received more attention because of their excellent NO_(x) storage capacity, anti-poisoning and hydrothermal stability and since Pd/zeolite PNA was proposed, a variety of advanced characterization methods have been applied to investigate its adsorption behavior and structure-performance relationship. The comprehension of the active sites and adsorption chemistry of Pd/zeolite PNA was also significantly improved. However, there are few reviews that systematically summarize the recent progress and application challenges in atomic-level understanding of this material. In this review, we summarized the latest research progress of Pd/zeolite PNA, including active adsorption sites, adsorption mechanism, material physicochemical properties, preparation methods, storage and release performance and structure-performance relationships. In addition, the deactivation challenges faced by Pd/zeolite PNA in practical applications, such as chemical poisoning, high temperature hydrothermal aging deactivation, etc., were also discussed at the micro-level, and some possible effective countermeasures are given. Besides, some possible improvements and research hotspots were put forward, which could be helpful for designing and constructing more efficient PNA materials for meeting the ultra-low NO_(x) emission regulation in the future.
文摘The paper deals with the modeling of the effect of maldistribution in pollutant abatementtrichloroethylene（TCE）concerning low concentration(10<sup>-5</sup>-10<sup>-8</sup>kg·m<sup>-3</sup>)adsorption in an adsorber.Such a concentration range is rather typical in many an environmental application.Isotherms andbreakthrough curves for TCE adsorption are obtained both for a commercial activated carbonSorbonorit 4 and a laboratory adsorber of d<sub>B</sub>/d<sub>P</sub>=11.Two two-dimensional nonequilibrium isothermalmodels are developed to describe the mass transfer in the fixed bed taking into account the effect ofmaldistribution.It is found the simulation results with maldistribution are in very good agreementwith the experimental findings.Low concentration TCE adsorption in a fixed bed of activated carbonis found to be strongly influenced by maldistribution.The non-uniform distributions of concentrationand loading of the pollutant in the adsorber are predicted by the model.Maldistribution and its ef-fect on the initial breakthrough of TCE in
文摘Theoretical considerations on diffusion modes of adsorbates in diffusion-cell adsorbers are being investigated. By studying the effects of the operating and model parameters on the response curves calculated by surface diffusion model and pore diffusion model, and noting the differences in the results, the following conditions are recommended for the prediction of the prevailing diffusion mode in diffusion-cell experimentsλ≤0.1,BiB≥100,and N≥1The theoretical prediction thus obtained checks well with experimental data taken from literature. New solutions are also presented for the surface diffusion model and the pore diffusion model with rectangular adsorption isotherm.
基金Project(52106173)supported by the National Natural Science Foundation of ChinaProject(2020TQ0187)supported by the Postdoctoral Research Foundation of China。
文摘A series of transition metal Mn,Cu,Ce and Fe were loaded on TiO_(2) by sol-gel method with noble metal Pd as promotor for the application of passive NO_(x) absorber.Experiments on adsorption and desorption of NO_(x) were conducted and characterization methods such as X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),transmission electron microscopy(TEM)and in situ Fourier transform infrared spectroscopy(in situ DRIFTS)were involved.The experimental results show that Mn-contained catalysts,Mn-Ti and Pd-Mn-Ti,performed excellent NO_(x) adsorbing ability and appropriate desorption temperature window.On the other hand,Ce-and Cu-contained samples were not suitable for the purpose of PNA.In addition to the low adsorption capacity,these two series of catalysts released massive amount of NO below 150℃.Characterization results indicated that Pd was highly dispersed on all catalysts.The loading of Pd lowered not only the valence states of transition metals but surface oxygen percentage as well.From in situ DRIFTS tests,the Pd had little influence on the types of adsorbed substances for Mn,Ce and Cu series.However,the storage forms of NO_(x) were obviously different on Pd-Fe-Ti and Fe-Ti.
基金Funded by the Research Fund of the Guangdong Provincial Laboratory of Green Chemical Product Technology(China)the Science Foundation for Young Teachers of Wuyi University(No.2013zk11)
文摘P-nitrophenol（PNP） adsorption in batch and fixed bed adsorbers was studied. The homogeneous surface diffusion model（HSDM） based on external mass transfer and intraparticle surface diffusion was used to describe the adsorption kinetics for PNP in stirred batch adsorber at various initial concentrations and activated carbon dosages. The fixed bed model considering both external and internal mass transfer resistances as well as axial dispersion with non-linear isotherm was utilized to predict the fixed bed breakthrough curves for PNP adsorption under the conditions of different flow rates and inlet concentrations. The equilibrium parameters and surface diffusivity（Ds） were obtained from separate experiments in batch adsorber. The obtained value of Ds is 4.187×1012 m2/s. The external film mass transfer coefficient（kf） and axial dispersion coefficient（DL） were estimated by the correlations of Goeuret and Wike-Chang. The Biot number determined by HSDM indicated that the adsorption rate of PNP onto activated carbon in stirred batch was controlled by intraparticle diffusion and film mass transfer. A sensitivity analysis was carried out and showed that the fixed bed model calculations were sensitive to Ds and kf, but insensitive to DL. The sensitivity analysis and Biot number both confirm that intraparticle diffusion and film mass transfer are the controlling mass transfer mechanism in fixed bed adsorption system.
基金The project is funded by the Fundamental Research Funds for the Central Universities with No.3082017NS2017005.
文摘Air flow distribution in radial flow adsorber was numerically investigated using computational fluid dynamics(CFD)method,which was proved to be applicable to study the problem of non-uniform distribution in radial flow adsorber.Results showed that the degree of non-uniformity was more serious in desorption process than that is adsorption process.Therefore,it was considered that the non-uniform distribution of flow in a radial flow adsorber was mainly manifested in the desorption process.Optimum design of distributor parameters can improve the flow distribution in adsorber.Meanwhile,three different structures of distributor and the effect of breathing valve were analyzed.Results revealed that truncated cone is more effective than tubular and conical distributors in flow distribution.By inserting the truncated cone in central channel,desorption uniformity was increased by 6.56%and the breakthrough time of CO_(2)was extended from 564s to 1138s in the adsorption process.The“dead zone”problem at the top of adsorber during the desorption process was solved by opening breathing valve,which prolonged the working life of adsorber and was proved to have less effect on the uniform of airflow.
文摘Separations of mixtures in fixed-bed adsorbers are influenced by factors such as(1)selectivity of adsorption,Sads,(2)diffusional time constants,Đi/rc 2,and(3)diffusion selectivity,Đ1/Đ2.In synergistic separations,intracrystalline diffusion of vip molecules serves to enhance the selectivities dictated by thermodynamics of mixture adsorption.In antisynergistic separations,intracrystalline diffusion serves to reverse the hierarchy of selectivities dictated by adsorption equilibrium.For both scenarios,the productivities of the desired product in fixed-bed operations are crucially dependent on diffusional time constants,Đi/rc 2;these need to be sufficiently low in order for diffusional influences to be effective.Also,the ratioĐ1/Đ2 should be large enough for manifestation of synergistic or antisynergistic influence.Both synergistic and antisynergistic separations have two common,distinguishing characteristics.Firstly,for transient uptake within crystals,the more mobile component attains supraequilibrium loadings during the initial stages of the transience.Such overshoots,signifying uphill diffusion,are engendered by the cross-coefficientsΓij(i≠j)of thermodynamic correction factors.Secondly,the component molar loadings,plotted in composition space,follow serpentine equilibration paths.If cross-coefficients are neglected,no overshoots in the loadings of the more mobile component are experienced,and the component loadings follow monotonous equilibration paths.The important takeaway message is that the modeling of mixture separations in fixed-bed adsorbers requires the use of the Maxwell−Stefan equations describing mixture diffusion employing chemical potential gradients as driving forces.
基金financially supported by the National Key R&D Program of China(grant No.2019YFB1505000).
文摘The design and operation of radial flow adsorber are crucial in large-scale industrial oxygen production,which necessitate accurate prediction of gas-solid transfer behavior.In this work,a developed Computational Fluid Dynamics-Discrete Element Method(CFD-DEM)model combined with the adsorption model is proposed.The developed CFD-DEM model is validated by comparing simulated results with experimental data and empirical correlation.Subsequently,the effect of particle packing structure and particle shapes on the dynamic adsorption process are analyzed in detail.The results reveal the mechanism of particle packing structure affecting axial velocity distribution,showing that uneven distribution of resistance on the outer flow channel side leads to uneven axial velocity distribution in the bed.Compared to cylindrical adsorbents,the use of spherical adsorbents results in a more uniform axial velocity distribution,consequently reducing bed pressure drop.The study holds significant potential for optimizing gas distribution and improving separation efficiency in future industrial applications.
基金supported by the National Natural Science Foundation of China(21706052,22278114)Natural Science Foundation of Henan Province(242300421575).
文摘Lignin,the most abundant natural aromatic polymer globally,has garnered considerable interest due to its rich and diverse active functional groups and its antioxidant,antimicrobial,and adhesive properties.Recent research has significantly improved the performance of lignin-based hydrogels,suggesting their substantial potential in fields such as biomedicine,environmental science,and agriculture.This paper reviews the process of lignin extraction,systematically introduces synthesis strategies for preparing lignin-based hydrogels,and discusses the current state of research on these hydrogels in biomedical and environmental protection fields.It concludes by identifying the existing challenges in lignin hydrogel research and envisioning future prospects and development trends.
基金supported by the National Natural Science Foundation of China(Nos.52192684,52270136,and U2340214).
文摘Resourceful food waste treatment is essential for promoting the sustainable development of anaerobic digestion and realizing a circular economy.In this study,biogas residue(BR)was used as a feedstock to produce highvalue-added products(gas,tar,and char-derived high-performance adsorbents)using pyrolysis technology(at 400–800℃).CaCO_(3),the major component of ash,significantly improved the quality of the pyrolysis product by decomposing into CO_(2) and CaO.The gasification reaction of CO_(2) with coke generated substantial CO and facilitated the formation of a rich pore structure in the char.CaO improved tar quality by contributing to secondary cracking reactions and reducing water content.The composite material formed exhibited excellent performance in wastewater treatment,with a maximum methylene blue adsorption capacity of 969.30 mg/g.The maximum adsorption of heavy metals Cu^(2+),Pb^(2+),and Cd^(2+)was 175.44,244.93,and 199.50 mg/g,respectively.The ash fraction on the ash-biochar composite material adsorbent surface enhanced pollutant removal by providing an alkaline adsorption environment and more oxygen-based n-π interaction sites.The economic analysis showed that the high value-added products obtained from the pyrolysis of BR make this process more productive than land use.
基金This work was supported by Riset dan Inovasi untuk Indonesia Maju(RIIM)Kompetisi scheme(Grant number:48/II.7/HK/2025)RP ORNM 2025,National Collaborative Research/RiNa(No.499/2023)Penelitian Dosen Pemula grant from the Ministry of Higher Education,Science and Technology,Republic of Indonesia(1483az/IT9.2.1/PT.01.03/2025).
文摘The increasing need for efficient,sustainable,and environmentally friendly adsorbent materials has driven interest in bio-based alternatives.Conventional silica-based adsorbents,while effective,are often brittle and energy-intensive to produce.In contrast,wood offers a renewable and low-energy option with natural porosity suitable for adsorption.This study investigated the fabrication of wood sponge from tropical balsa(Ochroma bicolor)and pulai(Alstonia scholaris)wood through a dual-stage delignification process as a novel bio-based adsorbent.The process involved alkaline treatment using sodium sulfite(Na_(2)SO_(3))and sodium hydroxide(NaOH)at 100℃for 8,9,and 10 h,followed by bleaching process using hydrogen peroxide(H_(2)O_(2))at 100℃for 1,2,and 3 h.The treated samples were then rinsed to neutral pH,frozen at−20℃for 24 h,and freeze-dried at−50℃for 48 h.The results revealed a notable reduction in density and specific gravity,accompanied by increased weight loss and pore diameter size with prolonged delignification process.Optical changes showed increased translucency and layered structures,particularly in balsa wood.FTIR analysis confirmed a reduction in lignin and hemicellulose content,validating the chemical modification within the treated samples.The resulting wood sponges exhibited good porosity and adsorption capacity,ranging from 1.3 to 5.7 g/g.The optimal treatment—10 h of alkaline delignification followed by 3 h of H_(2)O_(2)bleaching—demonstrated the highest performance,highlighting the potential of tropical wood species as efficient,biodegradable,and eco-friendly adsorbent materials.
基金supported by the National Natural Science Foundation of China grant nos.52470149(P.H.Shao)and 52125002(X.B.Luo)the National Key Research and Development Program of China grant no.2023YFC3905903(P.H.Shao)Nanchang Hangkong University Doctoral Start-up Fund grant no.EA202502100(Y.Y.Zhou).
文摘Selective extraction of precious metals from urban mines plays a crucial role in mitigating the risk of depletion of precious metal resources and reducing waste pollution.However,a major obstacle in precious metal extraction lies in the difficulty of distinguishing the subtle differences in the physicochemical characteristics between them,especially gold and palladium.Herein,a proton-driven separation system was presented for cascade recovery of gold and palladium from waste-printed circuit boards(W-PCBs)leachate using poly(amidoxime)(PAO)hydrogel.This exhibits an ultra-high capacity,extra-fast rate,and excellent selectivity for the extraction of Au(Ⅲ)and Pd(Ⅱ).Notably,the separation of Au(Ⅲ)and Pd(Ⅱ)can be achieved with high selectivity at pH=0,resulting in a remarkable separation factor of k_(Au(Ⅲ)/Pd(Ⅱ))=36.5.This was demonstrated to originate from the differential mechanism of PAO hydrogel for the capture of Au(Ⅲ)and Pd(Ⅱ)under proton-mediated conditions.Drawing inspiration from the mechanism,the proton-driven cascade recovery system demonstrates remarkable efficiency in sequentially recovering 99.92%of gold and 99.05%of palladium from W-PCBs acid leachate.This research opens up a strategy to precisely separate and recover precious metals from e-waste of urban mines.
基金financial support from MICIU/AEI/10.13039/501100011033by the European Union,and grant MOE-T2EP10222-0007 from the Ministry of Education,Singapore。
文摘Density functional theory(DFT)has helped propel the advance of electrocatalysis in the past two decades.In view of its massive use,it is worth asking how reliable DFT is for the prediction of adsorption energies,which are paramount in computational electrocatalysis models.Here,we provide an experimental-computational approach to break down overall adsorption-energy errors into separate gas-phase and adsorbed-phase contributions.The method is evaluated using experimental data and various exchange-correlation functionals and materials for C-and O-containing species.Our main conclusion is that no functional is simultaneously accurate for adsorbates and molecules,as adsorbed-phase errors are visibly different from gas-phase errors.Importantly,total,gas-phase,and adsorbed-phase errors are correlated,revealing intrinsic DFT limitations and enabling the elaboration of swift correction routines.To illustrate the benefits of our approach,we deconvolute and correct all errors in CO_(2)electroreduction to CO and find an agreement with experiments close to chemical accuracy for numerous transition-metal electrodes and all scrutinized functionals.
基金financially supported by the National Natural Science Foundation of China(Nos.52473139 and U21A2098)。
文摘Hospital wastewater contains complex pollutants,including residual organic dyes and antibiotic-resistant pathogens,posing severe risks to ecosystems and human health.Conventional adsorbents,constrained by monopolar functional groups and limited surface sites,fail to remove both pollutants simultaneously.Here,we report an intelligent responsive polyurethane microsphere adsorbent doped with diallyl dimethylammonium chloride modified carbon nanotubes,termed as PUCD microspheres.The PUCD integrates bipolar adsorption sites,tunable micrometer-scale pores,and a near-infrared(NIR)-triggered in situ capture mechanism within a single platform,which achieves up to 98.3%dye removal,maintains strong adsorption performance across a wide pH range and retains 83.3%efficiency for rhodamine B after five cycles.Notably,the PUCD employs a temperature-responsive phase transition:under NIR irradiation,the microspheres undergo shrinkage,reducing the pore size to generate a‘polymer trap',enabling in situ capture of bacteria with>99%efficiencies for both Staphylococcus aureus and Escherichia coli.By immobilizing live bacteria,the PUCD microspheres substantially reduces the risk of pathogen desorption and toxin release.This promising platform offers a safe,efficient,and single-stage strategy for hospital wastewater purification,enabling the simultaneous elimination of dyes and pathogenic bacteria.
基金Project supported by the National Natural Science Foundation of China(22072098)the Sichuan Science and Technology Program(2022ZHCG0125)。
文摘In order to prevent the emission of NO_(x) from diesel engines during the cold-start period,a NO_(x) adsorption selective catalytic reduction(AdSCR)catalyst was prepared by combining a selective catalytic reduction(SCR)catalyst with an NO_(x) adsorbent.In this study,CeO_(2)/Al_(2)O_(3)(Ce/Al)was employed as the NO_(x) adsorbent,combined with WO_(3)/CeZrO_(x)(W/CZ)as a promising SCR catalyst,to prepare an AdSCR catalyst.The characterization results demonstrate that the synergistic effects of the combined catalyst significantly enhance the activated oxidation of NO_(x) in comparison to the individual catalysts.The addition of Ce/Al enhances the adsorption of NO_(x) on the catalysts,which is then reduced to N_(2) and H_(2)O by NH_(3) under the action of W/CZ catalysts.The results of the NH_(3)-SCR activity test indicate that an excess of Ce/Al results in a reduction in SCR performance,suggesting that there is a balance between the SCR component and the NO_(x) adsorbent.The optimal combination of 20 wt%Ce/Al+W/CZ(20CA-W/CZ)catalyst demonstrates enhanced NO_(x) adsorption-storage performance while maintaining the exceptional NH_(3)-SCR performance.The NO_(x) complete storage time of the 20CA-W/CZ catalyst is 125 s,which is nearly twice as long as that of the Ce/Al and W/CZ catalysts.Furthermore,the NO_(x) conversion of the 20CA-W/CZ catalyst at low temperatures is approximately 10%higher than that of the W/CZ catalyst.The findings of this study offer a promising s trategy for the design of high-performance AdSCR catalysts in the future.
基金supported by Shanxi Provincial Key Research and Development Project(202102090301026)Graduate Education Innovation Project of Taiyuan University of Science and Technology(SY2023024)。
文摘Currently,the solid adsorbents with porous structure have been widely applied in CO_(2)capture.However,the unmodified MgO-ZrO_(2)adsorbents appeared to be low adsorption capacity of CO_(2).The solid adsorbent materials were successfully synthesized by loading TEPA onto the pore MgO/ZrO_(2)carriers in the paper.The pore structure and surface characteristic of the samples were analyzed by using XRD,BET,FT-IR and SEM.The adsorbent materials exhibited microcrystalline state,and the crystallinity of all samples gradually decreased as the increase of TEPA content.The pore structure analysis indicated that the modification of MgO-ZrO_(2)adsorbents with TEPA led to the decrease of the specific surface areas,but the narrow micro-mesopore size distributions ranging from 1.8-12 nm in the adsorbents still were maintained.FT-IR spectrum results further verified the successful loading of TEPA.The adsorption capacity of the adsorbents for CO_(2)were tested by using an adsorption apparatus equipped with gas chromatography.The results indicated that when the TEPA loading reached 50%,the sample exhibited the maximum adsorption value for CO_(2),reaching 4.07 mmol/g under the operation condition of 75℃and atmospheric pressure.This result could be assigned to not only the base active sites but also the coexistence of both micropore and mesopore in the adsorbent.After three cycles tests for CO_(2)capture,the adsorption value of the sample for CO_(2)can also reached 95%of its original adsorption capacity,which verified the excellent cyclic operation stability.
