Hydrocarbons(HCs)exert toxic effects on the activity of Cu-based zeolite catalysts for NH_(3)-SCR on diesel vehicles.This study inve stigated the hydrocarbon resistance of both fresh and hydrothermally aged high-silic...Hydrocarbons(HCs)exert toxic effects on the activity of Cu-based zeolite catalysts for NH_(3)-SCR on diesel vehicles.This study inve stigated the hydrocarbon resistance of both fresh and hydrothermally aged high-silica Cu-SSZ-16 catalysts.It was found that low-temperature activity of Cu-SSZ-16 catalyst decreased after C_(3)H_(6) poisoning,which was mainly due to the blockage of pore channels and the coverage of Cu active sites as well as acid sites by the formation of carbon deposits.Additionally,[Cu(OH)]^(+)-Z was proposed to be more easily affected by C_(3)H_(6) poisoning than Cu^(2+)-2Z.Hydrothermally aged Cu-SSZ-16 presented better C_(3)H_(6) resistance than the fresh catalyst since less carbon deposits were accumulated and[Cu(OH)]^(+)-Z species were partially transformed to more-stable Cu^(2+)-2Z in the aged sample.This was probably because of the reduction of acid sites and the formation of CuO_(x),which enhanced the oxidation of C_(3)H_(6),thereby inhibiting the formation of carbon deposits.In addition,the coverage of the active Cu species also influenced the adsorption and oxidation of NO,causing a decrease in low-temperature activity.Thus,the low-temperature activity could be fully recovered by hydrothermal treatment at 500℃due to the removal of carbon deposits and recovery of Cu active sites as well as acid sites.In summary,high-silica CuSSZ-16,with high resistance to HCs and excellent hydrothermal stability,is a competitive candidate as a catalyst for the NH_(3)-SCR reaction in practical application.展开更多
Cu-SSZ-13 small-pore zeolites have been commercialized for NO_(x) abatement in diesel engines,while they still suffer fromhydrothermal deactivation.To identify the changes occurring in catalysts during the whole hydro...Cu-SSZ-13 small-pore zeolites have been commercialized for NO_(x) abatement in diesel engines,while they still suffer fromhydrothermal deactivation.To identify the changes occurring in catalysts during the whole hydrothermal aging(HTA)process,the selective catalytic reduction by ammonia(NH3-SCR)performance of hydrothermally aged catalysts was investigated until total deactivation occurred.Through precisely identifying the alterations in the zeolite framework and active Cu sites during HTA,three stages were distinguished under progressively more severe HTA conditions,which were dealumination/transformation of active Cu species,CuO_(x) accumulation,and structural collapse.These three stages were found to cause a slight decrease,serious attenuation,and total deactivation of the deNO_(x) efficiency,which stemmed from the loss of Bronsted acid sites,reduction in the number of active Cu ion sites and structural collapse,respectively.This work also depicted simulated deactivation curves of Cu-SSZ-13 with various compositions during the HTA process,which helps in understanding the hydrothermal aging limits of catalysts with various Si/Al ratios and Cu loadings.展开更多
In this work,the characterizations of Cu-SSZ-13 after hydrothermal aging(HTA)and thermal aging(TA)at different temperatures(750,800,and 850°C)are compared,and the differences between those two serious aged sample...In this work,the characterizations of Cu-SSZ-13 after hydrothermal aging(HTA)and thermal aging(TA)at different temperatures(750,800,and 850°C)are compared,and the differences between those two serious aged samples are analyzed.With this data,the effect of steam on catalysts deactivation during hydrothermal aging is analyzed.The TA at 750 and 800°C causes the dealumination and the agglomeration of Cu^(2+)ions to Cu O,resulting in the activity loss of Cu-SSZ-13.The presence of steam upon HTA at750 and 800°C aggravates the catalyst deactivation by increasing the Al detachment and the Cu^(2+)agglomeration.The structure and cupric state are almost the same in the Cu-SSZ-13 after TA and HTA at 850°C,respectively,indicating that the steam has little influence on the deactivation.The formation of CuAl_(2)O_(4) spinel is the primary reason for the deactivation after both HTA and TA at 850°C,probably attributed to the strong interaction between Cu^(2+)ions and framework Al sites at high temperatures.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
To reveal how cerium stabilizes Cu/SAPO-34 at low-temperature hydrothermal aging,various amounts of cerium were introduced into Cu/SAPO-34 via impregnation method and treated at 70℃with RH 80%for 96 h.Cerium as Ce^(3...To reveal how cerium stabilizes Cu/SAPO-34 at low-temperature hydrothermal aging,various amounts of cerium were introduced into Cu/SAPO-34 via impregnation method and treated at 70℃with RH 80%for 96 h.Cerium as Ce^(3+)and CeO_(2)nanoparticle is located on the surface of Cu/SAPO-34,and Ce^(3+)plays a vital role on gradually decreasing surface acidity and blocking defect sites with an increase of Ce loading.After hydrothermal aging,Cu/SAPO-34 with high Ce loading shows the superior SCR activity comparable to fresh samples.It is proven that the surface acidity determines the stability of the structure during hydrothermal aging process,and lower surface acidity prevents the number of Cu(Ⅱ)ions from decreasing significantly.Furthermore,the structure's stability helps the recovery of Cu(Ⅱ)ions and renders an outstanding regene ration ability.Our finding paves the way for the design of new Cu/SAPO-34catalysts with good SCR activity and long-term stability in real application.展开更多
This study was aimed to investigate the effects of hydrothermal aging, propene and SO<sub>2</sub> poisoning on the ammonia-selective catalytic reduction (NH<sub>3</sub>-SCR) performance of both...This study was aimed to investigate the effects of hydrothermal aging, propene and SO<sub>2</sub> poisoning on the ammonia-selective catalytic reduction (NH<sub>3</sub>-SCR) performance of both Cu-SAPO-34 and Cu-ZSM-5. The catalytic activities of fresh, aged and poisoned samples were tested in ammonia-selective catalytic reduction (NH<sub>3</sub>-SCR) of NO<sub>x</sub> conditions. The XRD, TG and N<sub>2</sub>-desorption results showed that the structures of the Cu-SAPO-34 and Cu-ZSM-5 remained intact after 750˚C hydrothermally aged, SO<sub>2</sub> and propene poisoned. After hydrothermal aging at 750˚C for 12 h, the NO reduction performance of Cu-ZSM-5 was significantly reduced at lower temperatures, while that of Cu-SAPO-34 was less affected. Moreover, Cu-SAPO-34 catalyst showed high NO conversion with SO<sub>2</sub> or propene compared to Cu-ZSM-5. However, Cu-ZSM-5 showed a larger drop in catalytic activity with SO<sub>2</sub> or propene compared to Cu-SAPO-34 catalyst. The H<sub>2</sub>-TPR results showed that Cu<sup>2 </sup> ions could be reduced to Cu<sup> </sup> and Cu<sup>0</sup> for Cu-ZSM-5, while no significant transformation of copper species was observed for Cu-SAPO-34. Meanwhile, the UV-vis DRS results showed that CuO species were formed in Cu-ZSM-5, while little changes were observed for the Cu-SAPO-34. Cu-SAPO-34 showed high sulfur and hydrocarbon poison resistance compared to Cu-ZSM-5. In summary, Cu-SAPO-34 with small-pore zeolite showed higher hydrothermal stability and better hydrocarbon and sulfur poison resistant than Cu-ZSM-5 with medium-pore.展开更多
The fluctuations of storage temperature and humidity detrimentally affect the bamboo quality and longevity,making it crucial to investigate.Herein,we explored the physical and mechan-ical properties of moso bamboo(Phy...The fluctuations of storage temperature and humidity detrimentally affect the bamboo quality and longevity,making it crucial to investigate.Herein,we explored the physical and mechan-ical properties of moso bamboo(Phyllostachys edulis)subjected to 100-day moist heat cycling aging(MHCA-1:transitioning from low-temperature/high-humidity to high-temperature/low-humidity;MHCA-2:transitioning from low-temperature/low-humidity to high-temperature/high-humidity;CHT:25℃-constant temperature and 60%relative humidity)alongside a control group.Employing a multiscale characterization and Random Forest(RF)modeling,we evaluated the im-pacts of temperature and humidity fluctuations on the bamboo quality,and the influence mech-anism of storage conditions on its physical and mechanical properties were elucidated.Results indicated that elevated temperature and humidity led to remarkable fluctuation in bamboo mois-ture(from−20.36%to 32.99%),weight gain(from−32.69%to 6.19%),and dimensional expan-sion(from−5.37%to 2.38%).Conversely,high-temperature and low-humidity drying conditions resulted in moisture loss and dimensional shrinkage.Total color difference(TCD)of bamboo cor-tex followed the order:MHCA-2(7.46)<CHT(12.24)<MHCA-1(20.10)<control(22.63).The TCD of bamboo pith positively was related with storage temperature.Periodic moist heat aging induced the permanent deformation in bamboo,reducing its elastic modulus by 30.05%-43.79%.Under moist heat aging conditions,the characteristic hemicellulose functional groups,including hydroxyl(−OH),carbonyl(C=O),ether(C-O-C),and aromatic C=C moieties exhibited re-markable structural modifications,i.e.,peak weakening,shifting,or morphological alterations in Fourier transform infrared(FT-IR)spectra.Additionally,these conditions elevated the thermal decomposition onset temperature of cellulose while decreasing its peak intensity.Overall,the RF modeling approach demonstrated a high accuracy in predicting bamboo behavior under varying moisture-heat conditions.It improved bamboo storage and recycling by supporting sorting and grading with reliable long-term data.展开更多
This study introduces a novel core-shell structured composite,Cu/SSZ-13@CeO_(2),designed to boost the catalyst’s resistance to hydrothermal conditions.Characterization results reveal that encapsulating Cu/SSZ-13 with...This study introduces a novel core-shell structured composite,Cu/SSZ-13@CeO_(2),designed to boost the catalyst’s resistance to hydrothermal conditions.Characterization results reveal that encapsulating Cu/SSZ-13 with a ceria(CeO_(2))shell markedly enhances hydrothermal stability by maintaining the functionality of[Cu(OH)]+active sites and averting their deactivation.Furthermore,the CeO_(2) shell substantially prevents the loss of crucial Lewis and Bronsted acid sites,essential for effective SCR performance.A significant finding is the formation of a"Ce-O-Al"bond between the CeO_(2) shell and the Cu/SSZ-13 core,which plays a crucial role in reinforcing the structural stability of the zeolite framework.These insights contribute significantly to the development of robust anti-hydrothermal aging catalysts for mobile SCR applications,heralding the advancement of more efficient SCR catalyst technologies.展开更多
In this work,silica-alumina mixed oxides with different SiO_(2)contents(5%and 30%)were adopted as acidic supports for platinum catalysts for soot oxidation.The obtained catalysts were hydrothermally aged in 10%H_(2)0/...In this work,silica-alumina mixed oxides with different SiO_(2)contents(5%and 30%)were adopted as acidic supports for platinum catalysts for soot oxidation.The obtained catalysts were hydrothermally aged in 10%H_(2)0/air at 750℃for 20 h.The catalysts were characterized by X-ray diffraction(XRD),N_(2)adsorption,inductively coupled plasma(ICP),CO chemisorption,NH3temperature-programmed desorption(TPD),infrared(IR)spectroscopy of CO adsorption,temperature-programmed oxidation(TPO)of NO,and TPD of NO_(x).The surface acidity of catalyst was positive correlated with the content of SiO_(2),which kept platinum in metallic and partially oxidized states in an oxidizing atmosphere.Compared with sulfation treatment on the alumina support,the application of SiO_(2)-Al_(2)O_(3)mixed oxides does not result in the coverage of Pt active sites and the prepared catalysts exhibit excellent activity for NO oxidation.They promote NOxpreferential adsorption on soot and decomposition of surface oxygenated compounds(SOCs)as the sulfated Pt/Al_(2)O_(3)catalyst does.展开更多
A series of Pd/La-Al2O3（PLA） catalysts with La-Al2O3（LA） support calcined at different temperatures（500, 700, 900 and 1050 oC） were prepared using an incipient wetness impregnation method. The activity of the fr...A series of Pd/La-Al2O3（PLA） catalysts with La-Al2O3（LA） support calcined at different temperatures（500, 700, 900 and 1050 oC） were prepared using an incipient wetness impregnation method. The activity of the fresh and hydrothermally aged PLA catalysts were tested for total oxidation of CO and C3H8. The activity of the fresh PLA catalysts for CO and C3H8 oxidation increased with increasing calcination temperature of the support, while the activities of the aged catalysts declined and became essentially the same. CO chemisorption results revealed that the suppressed activities of the aged catalysts were mainly due to the decline of palladium dispersion. The turnover frequency（TOF） of CO oxidation increased with increasing reduction ability of the catalysts, with a fresh catalyst calcined at 1050 oC having the highest value（0.048 s–1）. However, the TOF of C3H8 total oxidation was affected by not only the redox properties of catalysts but also the size of Pd particle, and large Pd particles possessed higher TOF value of C3H8 oxidation, with the highest value（0.125 s–1） being obtained on an aged catalyst calcined at 500 oC.展开更多
Ceria-stabilized tetragonal zirconia(Ce-TZP)has become an interesting alternative for the widely used yttria-stabilized zirconia(Y-TZP),whereas efforts are needed to control its microstructure in order to im-prove the...Ceria-stabilized tetragonal zirconia(Ce-TZP)has become an interesting alternative for the widely used yttria-stabilized zirconia(Y-TZP),whereas efforts are needed to control its microstructure in order to im-prove the strength of Ce-TZP ceramics.In this work,CaO was used to co-dope Ce-TZP ceramics.More specifically,0.2-2.0 mol%Ca(NO_(3))_(3)·4H_(2)O precursor-based CaO was used to dope 10 mol%ceria-stabilized zirconia.Sintering was performed at 1300,1350,or 1400℃,which is lower than the temperatures commonly applied for zirconia ceramics.The microstructure and mechanical properties were investigated and correlated,revealing that 0.2 mol%CaO-doped CeO_(2)-stabilised zirconia sintered at 1350℃ exhibited a fully dense fine-grained tetragonal ZrO_(2) microstructure with high toughness(10.4 MPa m1/2)and biax-ial bending strength(1210±43 MPa),and a narrow strength distribution(weibull modulus of 32.5).1.5 and 2.0 mol% CaO-doping resulted in excellent biaxial bending strength but wider strength distribution and lower fracture resistance.The homogeneously distributed Ca(NO_(3))_(3)·4H_(2)O precursor prevented cubic zirconia-phase formation for CaO-doping up to 2.0 mol%.CaO-doped(≥0.2 mol%)10Ce-TZP sintered at 1350℃ also highly resisted hydrothermal degradation.Furthermore,CaO-doping enabled to make Ce-TZP ceramics as translucent as different commercially available 3Y-TZP ceramics,opening possibilities to use Ce-TZP for dental restorations.展开更多
Structural modification of three dimensional(3D)materials for the application of dielectric loss-based microwave absorbing materials(MAMs)usually relies on intricate synthesis process and can pose challenges in terms ...Structural modification of three dimensional(3D)materials for the application of dielectric loss-based microwave absorbing materials(MAMs)usually relies on intricate synthesis process and can pose challenges in terms of scalability and mass production for practical application.In this work,we reported a successful attempt in modifying the 3D structure of mesoporous lanthanum oxide(La_(2)O_(3))for effective broadband MAMs candidate via simple co-precipitation process.The inclusion of cetyltrimethylammonium bromide(CTAB)and hydrothermal aging treatment result in a significant transformation of La_(2)O_(3)particles from their original polygonal form to a 3D coral-like and nano needle-like structure.The utilization of CTAB and hydrothermal aging results in the increase of surface area and a two-fold increase in pore volume of the resulting La_(2)O_(3).Due to its unique 3D structure,the 3D coral-like and nano needle-like La_(2)O_(3)materials possess a broadband electromagnetic(EM)wave absorption characteristic with the effective absorption bandwidth(EAB)covering the C-band frequency range.Specifically,in the La_(2)O_(3)C-H sample(with CTAB-with hydrothermal),it exhibits strong EM wave absorption with a reflection loss(RL)value of-33.07 dB which equals to 99.95%EM wave absorption at a thickness of only 1.50 mm.The detailed analysis of EM wave absorption properties reveals that the improvement of La_(2)O_(3)materials to attenuate EM wave energy arises from the dielectric loss phenomenon,the enhanced interfacial polarization,multiple reflections mechanism,and conduction loss mechanism induced by the 3D structural formation of the La_(2)O_(3)structure.This work proposes a novel and efficient approach in synthesizing and modifying 3D materials for effective broadband EM wave absorption.展开更多
The single fiber fragmentation test （SFFT） was used to measure the interracial shear strength （IFSS） of sized and unsized CF800/epoxy resin monofilament composite in order to evaluate the effect of sizing respecti...The single fiber fragmentation test （SFFT） was used to measure the interracial shear strength （IFSS） of sized and unsized CF800/epoxy resin monofilament composite in order to evaluate the effect of sizing respectively. Besides, the interfacial reinforcing mechanism was explored by analyzing the surface morphology of the carbon fibers, the wettability between the carbon fibers and the epoxy resin, and the chemical characteristics of the fiber surface. Moreover, the effect of sizing on heat and humidity resistance of interface was investigated by aging test. The results show that sizing improves IFSS of CF800/epoxy resin monofilament composite by 59% through increasing the functional groups containing oxygen and through enhancing wettability, while after sizing the heat and humidity resistance of interface is decreased.展开更多
Two new complexes [Ag（bix）]n·n NAA·n H2O（1） and [Cd（NAA）（phen）2（H2O）]2· 2CH3COO-·H2O（2）（bix = 1,4-bis（imidazol-1-ylmethyl）benzene,HNAA = α-naphthylacetic acid,phen = 1,10-phenanthro...Two new complexes [Ag（bix）]n·n NAA·n H2O（1） and [Cd（NAA）（phen）2（H2O）]2· 2CH3COO-·H2O（2）（bix = 1,4-bis（imidazol-1-ylmethyl）benzene,HNAA = α-naphthylacetic acid,phen = 1,10-phenanthroline） have been successfully synthesized under hydrothermal conditions.Their structures have been determined by elemental analyses,IR spectroscopy,TG and single-crystal X-ray diffraction analysis.The intermolecular hydrogen bonding or π-π stacking interactions extend the complexes into a 3D supramolecular structure.Moreover,the luminescent properties of complex 2 have been investigated in the solid state.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52225004,22402220,and 52200136)the National Key R&D Program of China(Nos.2022YFC3704400 and 2022YFC3701804)the Construction Project of National New Material Production and Application Demonstration Platform(No.TC220H06N)。
文摘Hydrocarbons(HCs)exert toxic effects on the activity of Cu-based zeolite catalysts for NH_(3)-SCR on diesel vehicles.This study inve stigated the hydrocarbon resistance of both fresh and hydrothermally aged high-silica Cu-SSZ-16 catalysts.It was found that low-temperature activity of Cu-SSZ-16 catalyst decreased after C_(3)H_(6) poisoning,which was mainly due to the blockage of pore channels and the coverage of Cu active sites as well as acid sites by the formation of carbon deposits.Additionally,[Cu(OH)]^(+)-Z was proposed to be more easily affected by C_(3)H_(6) poisoning than Cu^(2+)-2Z.Hydrothermally aged Cu-SSZ-16 presented better C_(3)H_(6) resistance than the fresh catalyst since less carbon deposits were accumulated and[Cu(OH)]^(+)-Z species were partially transformed to more-stable Cu^(2+)-2Z in the aged sample.This was probably because of the reduction of acid sites and the formation of CuO_(x),which enhanced the oxidation of C_(3)H_(6),thereby inhibiting the formation of carbon deposits.In addition,the coverage of the active Cu species also influenced the adsorption and oxidation of NO,causing a decrease in low-temperature activity.Thus,the low-temperature activity could be fully recovered by hydrothermal treatment at 500℃due to the removal of carbon deposits and recovery of Cu active sites as well as acid sites.In summary,high-silica CuSSZ-16,with high resistance to HCs and excellent hydrothermal stability,is a competitive candidate as a catalyst for the NH_(3)-SCR reaction in practical application.
基金supported by the National Key R&D Program of China(No.2023YFC3707201)the National Natural Science Foundation of China(No.52270112)the National Energy-Saving and Low-Carbon Materials Production and Application Demonstration Platform Program(No.TC220H06N).
文摘Cu-SSZ-13 small-pore zeolites have been commercialized for NO_(x) abatement in diesel engines,while they still suffer fromhydrothermal deactivation.To identify the changes occurring in catalysts during the whole hydrothermal aging(HTA)process,the selective catalytic reduction by ammonia(NH3-SCR)performance of hydrothermally aged catalysts was investigated until total deactivation occurred.Through precisely identifying the alterations in the zeolite framework and active Cu sites during HTA,three stages were distinguished under progressively more severe HTA conditions,which were dealumination/transformation of active Cu species,CuO_(x) accumulation,and structural collapse.These three stages were found to cause a slight decrease,serious attenuation,and total deactivation of the deNO_(x) efficiency,which stemmed from the loss of Bronsted acid sites,reduction in the number of active Cu ion sites and structural collapse,respectively.This work also depicted simulated deactivation curves of Cu-SSZ-13 with various compositions during the HTA process,which helps in understanding the hydrothermal aging limits of catalysts with various Si/Al ratios and Cu loadings.
基金supported by the National Key Research and Development Program of China (2018YFC0214103)the National Natural Science Foundation of China (22006044)the Scientific Research Funds of Huaqiao University (605-50Y200270001)。
文摘In this work,the characterizations of Cu-SSZ-13 after hydrothermal aging(HTA)and thermal aging(TA)at different temperatures(750,800,and 850°C)are compared,and the differences between those two serious aged samples are analyzed.With this data,the effect of steam on catalysts deactivation during hydrothermal aging is analyzed.The TA at 750 and 800°C causes the dealumination and the agglomeration of Cu^(2+)ions to Cu O,resulting in the activity loss of Cu-SSZ-13.The presence of steam upon HTA at750 and 800°C aggravates the catalyst deactivation by increasing the Al detachment and the Cu^(2+)agglomeration.The structure and cupric state are almost the same in the Cu-SSZ-13 after TA and HTA at 850°C,respectively,indicating that the steam has little influence on the deactivation.The formation of CuAl_(2)O_(4) spinel is the primary reason for the deactivation after both HTA and TA at 850°C,probably attributed to the strong interaction between Cu^(2+)ions and framework Al sites at high temperatures.
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the National Natural Science Foundation of China for Youths(21908207)National Key R&D Program of China(2021YFB3503200)+3 种基金the Key R&D project of Shandong Province(2021CXGC010703)China Postdoctoral Science Foundation(2020M670659)Shanxi Province Science Foundation for Youths(201901D211224)Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(2019L0575)。
文摘To reveal how cerium stabilizes Cu/SAPO-34 at low-temperature hydrothermal aging,various amounts of cerium were introduced into Cu/SAPO-34 via impregnation method and treated at 70℃with RH 80%for 96 h.Cerium as Ce^(3+)and CeO_(2)nanoparticle is located on the surface of Cu/SAPO-34,and Ce^(3+)plays a vital role on gradually decreasing surface acidity and blocking defect sites with an increase of Ce loading.After hydrothermal aging,Cu/SAPO-34 with high Ce loading shows the superior SCR activity comparable to fresh samples.It is proven that the surface acidity determines the stability of the structure during hydrothermal aging process,and lower surface acidity prevents the number of Cu(Ⅱ)ions from decreasing significantly.Furthermore,the structure's stability helps the recovery of Cu(Ⅱ)ions and renders an outstanding regene ration ability.Our finding paves the way for the design of new Cu/SAPO-34catalysts with good SCR activity and long-term stability in real application.
文摘This study was aimed to investigate the effects of hydrothermal aging, propene and SO<sub>2</sub> poisoning on the ammonia-selective catalytic reduction (NH<sub>3</sub>-SCR) performance of both Cu-SAPO-34 and Cu-ZSM-5. The catalytic activities of fresh, aged and poisoned samples were tested in ammonia-selective catalytic reduction (NH<sub>3</sub>-SCR) of NO<sub>x</sub> conditions. The XRD, TG and N<sub>2</sub>-desorption results showed that the structures of the Cu-SAPO-34 and Cu-ZSM-5 remained intact after 750˚C hydrothermally aged, SO<sub>2</sub> and propene poisoned. After hydrothermal aging at 750˚C for 12 h, the NO reduction performance of Cu-ZSM-5 was significantly reduced at lower temperatures, while that of Cu-SAPO-34 was less affected. Moreover, Cu-SAPO-34 catalyst showed high NO conversion with SO<sub>2</sub> or propene compared to Cu-ZSM-5. However, Cu-ZSM-5 showed a larger drop in catalytic activity with SO<sub>2</sub> or propene compared to Cu-SAPO-34 catalyst. The H<sub>2</sub>-TPR results showed that Cu<sup>2 </sup> ions could be reduced to Cu<sup> </sup> and Cu<sup>0</sup> for Cu-ZSM-5, while no significant transformation of copper species was observed for Cu-SAPO-34. Meanwhile, the UV-vis DRS results showed that CuO species were formed in Cu-ZSM-5, while little changes were observed for the Cu-SAPO-34. Cu-SAPO-34 showed high sulfur and hydrocarbon poison resistance compared to Cu-ZSM-5. In summary, Cu-SAPO-34 with small-pore zeolite showed higher hydrothermal stability and better hydrocarbon and sulfur poison resistant than Cu-ZSM-5 with medium-pore.
基金support from the National Key R&D Program in the 14th Five-Year Plan of China(No.2023YFD2201202).
文摘The fluctuations of storage temperature and humidity detrimentally affect the bamboo quality and longevity,making it crucial to investigate.Herein,we explored the physical and mechan-ical properties of moso bamboo(Phyllostachys edulis)subjected to 100-day moist heat cycling aging(MHCA-1:transitioning from low-temperature/high-humidity to high-temperature/low-humidity;MHCA-2:transitioning from low-temperature/low-humidity to high-temperature/high-humidity;CHT:25℃-constant temperature and 60%relative humidity)alongside a control group.Employing a multiscale characterization and Random Forest(RF)modeling,we evaluated the im-pacts of temperature and humidity fluctuations on the bamboo quality,and the influence mech-anism of storage conditions on its physical and mechanical properties were elucidated.Results indicated that elevated temperature and humidity led to remarkable fluctuation in bamboo mois-ture(from−20.36%to 32.99%),weight gain(from−32.69%to 6.19%),and dimensional expan-sion(from−5.37%to 2.38%).Conversely,high-temperature and low-humidity drying conditions resulted in moisture loss and dimensional shrinkage.Total color difference(TCD)of bamboo cor-tex followed the order:MHCA-2(7.46)<CHT(12.24)<MHCA-1(20.10)<control(22.63).The TCD of bamboo pith positively was related with storage temperature.Periodic moist heat aging induced the permanent deformation in bamboo,reducing its elastic modulus by 30.05%-43.79%.Under moist heat aging conditions,the characteristic hemicellulose functional groups,including hydroxyl(−OH),carbonyl(C=O),ether(C-O-C),and aromatic C=C moieties exhibited re-markable structural modifications,i.e.,peak weakening,shifting,or morphological alterations in Fourier transform infrared(FT-IR)spectra.Additionally,these conditions elevated the thermal decomposition onset temperature of cellulose while decreasing its peak intensity.Overall,the RF modeling approach demonstrated a high accuracy in predicting bamboo behavior under varying moisture-heat conditions.It improved bamboo storage and recycling by supporting sorting and grading with reliable long-term data.
基金financially supported by the National Natural Science Foundation of China(No.22176216)the National Engineering Laboratory for Mobile Source Emission Control Technology(No.NELMS2020A13)the National Key Research and Development Program of China(No.SQ2022YFB3500058).
文摘This study introduces a novel core-shell structured composite,Cu/SSZ-13@CeO_(2),designed to boost the catalyst’s resistance to hydrothermal conditions.Characterization results reveal that encapsulating Cu/SSZ-13 with a ceria(CeO_(2))shell markedly enhances hydrothermal stability by maintaining the functionality of[Cu(OH)]+active sites and averting their deactivation.Furthermore,the CeO_(2) shell substantially prevents the loss of crucial Lewis and Bronsted acid sites,essential for effective SCR performance.A significant finding is the formation of a"Ce-O-Al"bond between the CeO_(2) shell and the Cu/SSZ-13 core,which plays a crucial role in reinforcing the structural stability of the zeolite framework.These insights contribute significantly to the development of robust anti-hydrothermal aging catalysts for mobile SCR applications,heralding the advancement of more efficient SCR catalyst technologies.
基金financially supported by the National Key R&D Program of China(No.2017YFC0211102)the National Natural Science Foundation of China(No.21906091)the Mobile Source Emission Control Technology(No.NELMS2020A08)。
文摘In this work,silica-alumina mixed oxides with different SiO_(2)contents(5%and 30%)were adopted as acidic supports for platinum catalysts for soot oxidation.The obtained catalysts were hydrothermally aged in 10%H_(2)0/air at 750℃for 20 h.The catalysts were characterized by X-ray diffraction(XRD),N_(2)adsorption,inductively coupled plasma(ICP),CO chemisorption,NH3temperature-programmed desorption(TPD),infrared(IR)spectroscopy of CO adsorption,temperature-programmed oxidation(TPO)of NO,and TPD of NO_(x).The surface acidity of catalyst was positive correlated with the content of SiO_(2),which kept platinum in metallic and partially oxidized states in an oxidizing atmosphere.Compared with sulfation treatment on the alumina support,the application of SiO_(2)-Al_(2)O_(3)mixed oxides does not result in the coverage of Pt active sites and the prepared catalysts exhibit excellent activity for NO oxidation.They promote NOxpreferential adsorption on soot and decomposition of surface oxygenated compounds(SOCs)as the sulfated Pt/Al_(2)O_(3)catalyst does.
基金Project supported by National Natural Science Foundation of China(21173195,21203167)
文摘A series of Pd/La-Al2O3（PLA） catalysts with La-Al2O3（LA） support calcined at different temperatures（500, 700, 900 and 1050 oC） were prepared using an incipient wetness impregnation method. The activity of the fresh and hydrothermally aged PLA catalysts were tested for total oxidation of CO and C3H8. The activity of the fresh PLA catalysts for CO and C3H8 oxidation increased with increasing calcination temperature of the support, while the activities of the aged catalysts declined and became essentially the same. CO chemisorption results revealed that the suppressed activities of the aged catalysts were mainly due to the decline of palladium dispersion. The turnover frequency（TOF） of CO oxidation increased with increasing reduction ability of the catalysts, with a fresh catalyst calcined at 1050 oC having the highest value（0.048 s–1）. However, the TOF of C3H8 total oxidation was affected by not only the redox properties of catalysts but also the size of Pd particle, and large Pd particles possessed higher TOF value of C3H8 oxidation, with the highest value（0.125 s–1） being obtained on an aged catalyst calcined at 500 oC.
基金the China Scholarship Council(CSC No.201806460096)for financial supportthe Scientific Research-Flanders(FWO-Vlaanderen)for her post-doctoral fellowships(grant Nos.12S8418N and 12S8421N)supported by the Research Fund of KU Leuven project No.C2-17-00402 and the Fund for Scientific Research-Flanders(FWO-Vlaanderen)(grant Nos.G.0431.10N and G.0959.20N).
文摘Ceria-stabilized tetragonal zirconia(Ce-TZP)has become an interesting alternative for the widely used yttria-stabilized zirconia(Y-TZP),whereas efforts are needed to control its microstructure in order to im-prove the strength of Ce-TZP ceramics.In this work,CaO was used to co-dope Ce-TZP ceramics.More specifically,0.2-2.0 mol%Ca(NO_(3))_(3)·4H_(2)O precursor-based CaO was used to dope 10 mol%ceria-stabilized zirconia.Sintering was performed at 1300,1350,or 1400℃,which is lower than the temperatures commonly applied for zirconia ceramics.The microstructure and mechanical properties were investigated and correlated,revealing that 0.2 mol%CaO-doped CeO_(2)-stabilised zirconia sintered at 1350℃ exhibited a fully dense fine-grained tetragonal ZrO_(2) microstructure with high toughness(10.4 MPa m1/2)and biax-ial bending strength(1210±43 MPa),and a narrow strength distribution(weibull modulus of 32.5).1.5 and 2.0 mol% CaO-doping resulted in excellent biaxial bending strength but wider strength distribution and lower fracture resistance.The homogeneously distributed Ca(NO_(3))_(3)·4H_(2)O precursor prevented cubic zirconia-phase formation for CaO-doping up to 2.0 mol%.CaO-doped(≥0.2 mol%)10Ce-TZP sintered at 1350℃ also highly resisted hydrothermal degradation.Furthermore,CaO-doping enabled to make Ce-TZP ceramics as translucent as different commercially available 3Y-TZP ceramics,opening possibilities to use Ce-TZP for dental restorations.
基金Project supported by National Research and Innovation Agency through Rumah Program Organisasi Riset Nanoteknologi dan Material Maj u(ORNM)2024Indonesia Ministry of Finance through the competitive research program of RISPRO Kompetisi(PRJ-68/LPDP/2023)。
文摘Structural modification of three dimensional(3D)materials for the application of dielectric loss-based microwave absorbing materials(MAMs)usually relies on intricate synthesis process and can pose challenges in terms of scalability and mass production for practical application.In this work,we reported a successful attempt in modifying the 3D structure of mesoporous lanthanum oxide(La_(2)O_(3))for effective broadband MAMs candidate via simple co-precipitation process.The inclusion of cetyltrimethylammonium bromide(CTAB)and hydrothermal aging treatment result in a significant transformation of La_(2)O_(3)particles from their original polygonal form to a 3D coral-like and nano needle-like structure.The utilization of CTAB and hydrothermal aging results in the increase of surface area and a two-fold increase in pore volume of the resulting La_(2)O_(3).Due to its unique 3D structure,the 3D coral-like and nano needle-like La_(2)O_(3)materials possess a broadband electromagnetic(EM)wave absorption characteristic with the effective absorption bandwidth(EAB)covering the C-band frequency range.Specifically,in the La_(2)O_(3)C-H sample(with CTAB-with hydrothermal),it exhibits strong EM wave absorption with a reflection loss(RL)value of-33.07 dB which equals to 99.95%EM wave absorption at a thickness of only 1.50 mm.The detailed analysis of EM wave absorption properties reveals that the improvement of La_(2)O_(3)materials to attenuate EM wave energy arises from the dielectric loss phenomenon,the enhanced interfacial polarization,multiple reflections mechanism,and conduction loss mechanism induced by the 3D structural formation of the La_(2)O_(3)structure.This work proposes a novel and efficient approach in synthesizing and modifying 3D materials for effective broadband EM wave absorption.
文摘The single fiber fragmentation test （SFFT） was used to measure the interracial shear strength （IFSS） of sized and unsized CF800/epoxy resin monofilament composite in order to evaluate the effect of sizing respectively. Besides, the interfacial reinforcing mechanism was explored by analyzing the surface morphology of the carbon fibers, the wettability between the carbon fibers and the epoxy resin, and the chemical characteristics of the fiber surface. Moreover, the effect of sizing on heat and humidity resistance of interface was investigated by aging test. The results show that sizing improves IFSS of CF800/epoxy resin monofilament composite by 59% through increasing the functional groups containing oxygen and through enhancing wettability, while after sizing the heat and humidity resistance of interface is decreased.
基金supported by the Science and Technology Development Project of Jilin Provincial Science&Technology Department(201205080)the Science and Technology Research Projects of the Education Office of Jilin Province(No.2013.384)
文摘Two new complexes [Ag（bix）]n·n NAA·n H2O（1） and [Cd（NAA）（phen）2（H2O）]2· 2CH3COO-·H2O（2）（bix = 1,4-bis（imidazol-1-ylmethyl）benzene,HNAA = α-naphthylacetic acid,phen = 1,10-phenanthroline） have been successfully synthesized under hydrothermal conditions.Their structures have been determined by elemental analyses,IR spectroscopy,TG and single-crystal X-ray diffraction analysis.The intermolecular hydrogen bonding or π-π stacking interactions extend the complexes into a 3D supramolecular structure.Moreover,the luminescent properties of complex 2 have been investigated in the solid state.
