With ongoing global warming and increasing energy demands,the CH_(4)-CO_(2)reforming reaction(dry reforming of methane,DRM)has garnered significant attention as a promising carbon capture and utilization technology.Ni...With ongoing global warming and increasing energy demands,the CH_(4)-CO_(2)reforming reaction(dry reforming of methane,DRM)has garnered significant attention as a promising carbon capture and utilization technology.Nickel-based catalysts are renowned for their outstanding activity and selectivity in this process.The impact of metal-support interaction(MSI),on Ni-based catalyst performance has been extensively researched and debated recently.This paper reviews the recent research progress of MSI on Ni-based catalysts and their characterization and modulation strategies in catalytic reactions.From the perspective of MSI,the effects of different carriers(metal oxides,carbon materials and molecular sieves,etc.)are introduced on the dispersion and surface structure of Ni active metal particles,and the effect of MSI on the activity and stability of DRM reactions on Ni-based catalysts is discussed in detail.Future research should focus on better understanding and controlling MSI to improve the performance and durability of nickel-based catalysts in CH_(4)-CO_(2)reforming,advancing cleaner energy technologies.展开更多
Photothermal catalytic methane dry reforming(DRM)technology can convert greenhouse gases(i.e.CH_(4)and CO_(2))into syngas(i.e.H_(2)and CO),providing more opportunities for reducing the greenhouse effect and achieving ...Photothermal catalytic methane dry reforming(DRM)technology can convert greenhouse gases(i.e.CH_(4)and CO_(2))into syngas(i.e.H_(2)and CO),providing more opportunities for reducing the greenhouse effect and achieving carbon neutrality.In the DRM field,Ni-based catalysts attract wide attention due to their low cost and high activity.However,the carbon deposition over Ni-based catalysts always leads to rapid deactivation,which is still a main challenge.To improve the long-term stability of Ni-based catalysts,this work proposes a carbon-atom-diffusion strategy under photothermal conditions and investigates its effect on a Zn-doped Ni-based photothermal catalyst(Ni_(3)Zn@CeO_(2)).The photothermal catalytic behavior of Ni_(3)Zn@CeO_(2)can maintain more than 70 h in DRM reaction.And the photocatalytic DRM activity of Ni_(3)Zn@CeO_(2)is 1.2 times higher than thermal catalytic activity.Density functional theory(DFT)calculation and experimental characterizations indicate that Ni_(3)Zn promotes the diffusion of carbon atoms into the Ni_(3)Zn to form the Ni_(3)ZnC0.7 phase with body-centered cubic(bcc)structure,thus inhibiting carbon deposition.Further,in-situ diffuse reflectance infrared Fourier transform(DRIFT)spectroscopy and DFT calculation prove Ni_(3)Zn@CeO_(2)benefits the CH_(4)activation and inhibits the carbon deposition during the DRM process.Through inducing carbon atoms diffusion within the Ni_(3)Zn lattice,this work provides a straightforward and feasible strategy for achieving efficient photothermal catalytic DRM and even other CH_(4)conversion implementations with long-term stability.展开更多
The hydrogenation of petroleum resin(PR)is an effective process to prepare high value-added hydrogenated PR(HPR).However,the preparation of non-noble metal-based catalysts with high catalytic activity for PR hydrogena...The hydrogenation of petroleum resin(PR)is an effective process to prepare high value-added hydrogenated PR(HPR).However,the preparation of non-noble metal-based catalysts with high catalytic activity for PR hydrogenation still remains a challenge.Herein,a La promoted Ni-based catalyst is reported through the thermal reduction of quaternary Ni La Mg Al-layered double hydroxides(Ni La Mg Al-LDHs).The incorporation of La is beneficial to the reduction and stability of Ni particles with reduced particle size,and the increased alkalinity effectively mitigates the breakage of molecular chains of PR.As a result,the La promoted Ni-based catalyst exhibits high catalytic activity and excellent stability for PR hydrogenation.A hydrogenation degree of 95.4%and 96.1%can be achieved for HC_(5)PR and HC_(9) PR with less reduced softening point,respectively.Notably,the hydrogenation degree still maintains at 92.7%even after 100 hours’reaction,much better than that without La incorporation or prepared using conventional impregnation method.展开更多
Highly active and selective Ni-based catalysts for partial oxidation of methane (POM) to syngas (CO/H,) have been studied and developed. Spectroscopic characterization by XRD, XPS, EPR, etc. demonstrated that under th...Highly active and selective Ni-based catalysts for partial oxidation of methane (POM) to syngas (CO/H,) have been studied and developed. Spectroscopic characterization by XRD, XPS, EPR, etc. demonstrated that under the POM reaction conditions, the Ni-components of the catalysts investigated were reduced and enriched on the surface to form metallic Ni0-phase. A comparative study of the first series of transition-metals showed that only Ni and Co have a high POM activity and selectivity, whereas the others (including Mn, Fe, Cu, etc. ) give mainly complete combustion products, Co, and H2O. The results favor the following viewpoints: the PoM activity is related with the rapidly changeable valence transitionmetal sites, M0/M2+ (e. g. Ni0/Ni2+ ), on the surface of the functioning catalysts;the transition-metal sites in zero-valence state seem to be responsible for the activation and dehydrogenation of methane by homolytic splitting of its C-H bonds on these sites. and the nature of rapidly changeable valence of the active sties is requisite for activation and rapid conversion of dioxygen.展开更多
A series of Ni/SBA-15 catalysts with Ni contents from 5 wt%–20 wt%and CaO-12.5%Ni/SBA-15 catalysts with CaO contents from 1.4 wt%– 9.8 wt%have been prepared.The structure of the catalysts was characterized using X-r...A series of Ni/SBA-15 catalysts with Ni contents from 5 wt%–20 wt%and CaO-12.5%Ni/SBA-15 catalysts with CaO contents from 1.4 wt%– 9.8 wt%have been prepared.The structure of the catalysts was characterized using X-ray diffraction（XRD）,N2 adsorption-desorption,transmission electron microscopy（TEM）and X-ray photoelectron spectroscopy（XPS）.The performance of catalytic steam reforming of the poplar leaves to the hydrogen-rich syngas was tested in a fixed-bed reactor.The results indicate that the 7.0wt%CaO-12.5wt%Ni/SBA-15 catalyst exhibits the best performance for the catalytic steam reforming of poplar leaves to hydrogen-rich syngas.The ratio of H2：CO can reach ca 5：1 in the hydrogen-rich syngas.The yield of H2 can reach 273.30 mL/g（poplar leaves）.In the CaO-Ni/SBA-15 catalyst,Ni active component mainly fills the role of catalytic steam reforming of the poplar leaves,and CaO active component mainly plays the role as water-gas shift and CO2 sorbent.展开更多
Kaolin as a raw material for mesoporous support was firstly modified by calcination,acid treatment,and then was used to prepare nickel catalysts.The amount of alumina which was activated in kaolin during thermal treat...Kaolin as a raw material for mesoporous support was firstly modified by calcination,acid treatment,and then was used to prepare nickel catalysts.The amount of alumina which was activated in kaolin during thermal treatment and then leached out in the acid was different.XRD pattern of the kaolin calcined at 600°C or 900°C exhibited only the diffraction peaks for amorphous silica and quartz while that calcined at 1100°C showed obvious peaks forγ-Al2 O3.Therefore,the nickel-based catalysts exhibited different physic-chemical properties.Atmospheric syngas methanation over the catalysts clarified an activity order of CA-1100 N CA-900 N CA-1400 N CA-600 N KA≈0 at temperatures of 350–650°C and a space velocity of 120 L·g-1·h-1.Metallic nickel with small diameter which has medium interaction with the modified kaolin and is well dispersed on the support would have reasonably good activity and carbon-resistance for syngas methanation.展开更多
Ligand modification of Ni-based catalysts by coordination of dicyandiamide to Ni metal leads to enhanced selectivity for the selective hydrogenation of halonitroaromatics.The selectivity of above 99.9%to aromatic halo...Ligand modification of Ni-based catalysts by coordination of dicyandiamide to Ni metal leads to enhanced selectivity for the selective hydrogenation of halonitroaromatics.The selectivity of above 99.9%to aromatic haloamines can be achieved at the conversion of 100%.The results of H_2-TPD and FT-IR experiments show that Ni^-H~＋ species possessing the properties of Lewis acid site on the surface of Raney Ni could be responsible for the hydrodehalogenation.When Raney Ni was treated by dicyandiamide,Ni^-H~＋ species interacted with N atom from the dicyandiamide.This interaction was stable even at reaction temperature,which reduced the possibility to form the intermediate state of Ar-Cl...H~＋Ni^-.And then C-Cl bond could not be polarized and activated.The hvdrodechlorination process was suppressed effectively.展开更多
Perovskites as host structures of cations were used in order to generate in situ active and stable catalysts for ethanol steam reforming. For this purpose,La_(1-x)Mg_xAl_(1-y)Ni_yO_3(x = 0.1; y = 0,0.1,0.2,0.3) perovs...Perovskites as host structures of cations were used in order to generate in situ active and stable catalysts for ethanol steam reforming. For this purpose,La_(1-x)Mg_xAl_(1-y)Ni_yO_3(x = 0.1; y = 0,0.1,0.2,0.3) perovskites were synthetized by the citrate method.Ni segregation is evident for a substitution level higher than 0. 2. The segregation of Ni as NiO generated species interacts with different metal-support after the reduction step. The y = 0.1 catalyst presents the highest H_2 yield value about 85% during reaction time,with low mean values of CH_4 and CO selectivities of 3.4% and 11%,respectively and a low carbon formation. The better performance of y = 0.1 catalyst could be attributed to the minor proportion of segregated phases,thus a controlled expulsion of Ni is successfully reached.展开更多
A series of Ni based catalysts with different supports and basic additives were prepared by sequential impregnation method. The catalysts were characterized by XRD, BET, H2-TPR and CO2-TPD techniques. It was found tha...A series of Ni based catalysts with different supports and basic additives were prepared by sequential impregnation method. The catalysts were characterized by XRD, BET, H2-TPR and CO2-TPD techniques. It was found that the introduction of basic additives enhanced the basicities of catalyats and promoted the dispersities of Ni particles by strong interaction between Ni2＋ and basic additives. Among the Ni based catalysts, 10%Ni/10%La203/ZrO2 showed the superior performance in sorbitol hydrogenolysis. The synergistic effect of Ni and La203 was proven to play an essential role in selective synthesis of EG and 1,2-PG. In the optimal reaction condition, the catalyst presented 100% sorbitol conversion and over 48% glycols （EG and 1,2-PG） yield. The kinetics study of polyols （sorbitol, xylitol and glycerol） hydrogenolysis showed that polyols with more hydroxyl number have higher activity and products distribution was final results of kinetic balance, which could give us some inspiration abeut how to change the products selectivity.展开更多
Co-precipitation method was selected for the preparation of Ni/Al_2O_3, Ni/ZrO_2 and Ni/CeO_2 catalysts, and their performances in methanation were investigated in this study. The structure and surface properties of t...Co-precipitation method was selected for the preparation of Ni/Al_2O_3, Ni/ZrO_2 and Ni/CeO_2 catalysts, and their performances in methanation were investigated in this study. The structure and surface properties of these catalysts were characterized by BET, XRD, H_2-TPD, TEM and H_2-TPR. The results showed that the catalytic activity at low temperature followed the order: Ni/Al_2O_3>Ni/ZrO_2>Ni/CeO_2. Ni/Al_2O_3 catalyst presented the best catalytic performance with the highest CH_4 selectivity of 94.5%. The characterization results indicated that the dispersion of the active component Ni was the main factor affecting the catalytic activity and the one with higher dispersion gave better performance.展开更多
The CO2reforming of CH4is studied over MgO‐promoted Ni catalysts,which were supported on alumina prepared from hydrotalcite.This presents an improved stability compared with non‐promoted catalysts.The introduction o...The CO2reforming of CH4is studied over MgO‐promoted Ni catalysts,which were supported on alumina prepared from hydrotalcite.This presents an improved stability compared with non‐promoted catalysts.The introduction of the MgO promoter was achieved through the‘‘memory effect’’of the Ni‐Al hydrotalcite structure,and ICP‐MS confirmed that only0.42wt.%of Mg2+ions were added into the Ni‐Mg/Al catalyst.Although no differences in the Ni particle size and basicity strength were observed,the Ni‐Mg/Al catalyst showed a higher catalytic stability than the Ni/Al catalyst.A series of surface reaction experiments were used and showed that the addition of a MgO promoter with low concentration can promote CO2dissociation to form active surface oxygen arising from the formation of the Ni‐MgO interface sites.Therefore,the carbon‐resistance promotion by nature was suggested to contribute to an oxidative environment around Ni particles,which would increase the conversion of carbon residues from CH4cracking to yield CO on the Ni metal surface.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.展开更多
A method of synthesizing Ni-based catalysts supported on α-Al2O3-based foams was developed. The foams were impregnated with aqueous solutions of metal chlorides under an air atmosphere using an aerosol route. Separat...A method of synthesizing Ni-based catalysts supported on α-Al2O3-based foams was developed. The foams were impregnated with aqueous solutions of metal chlorides under an air atmosphere using an aerosol route. Separate procedures involved calcination to form oxides and drying to obtain chlorides on the foam surface. The synthesized samples were subsequently reduced with hydrogen. With respect to the Ni/Al2O3 catalysts, the chloride reduction route enabled the formation ofa Ni coating without agglomerates or cracks. Further research included catalyst modification by the addition of Pd, Cu, and Fe. The influences of the additives on the degree of reduction and on the low-temperature reduction effectiveness （533 and 633 K） were examined and compared for the catalysts obtained from oxides and chlorides. Greater degrees of reduction were achieved with chlorides, whereas Pd was the most effective modifier among those investigated. The reduction process was nearly complete at 533 K in the sample that contained 0.1wt% Pd. A lower reduction temperature was utilized, and the calcination step was avoided, which may enhance the economical and technological aspects of the developed catalyst production method.展开更多
RE-doped Ni-based catalysts were prepared by sol-gel method.These catalysts were applied to the reaction of CO2 reforming CH4 to syngas.The studies reveal that RE-doped ( RE = La, Ce, Sm, Yb) Ni-based catalysts show h...RE-doped Ni-based catalysts were prepared by sol-gel method.These catalysts were applied to the reaction of CO2 reforming CH4 to syngas.The studies reveal that RE-doped ( RE = La, Ce, Sm, Yb) Ni-based catalysts show higher catalytic activity than undoped Ni-based catalyst, and with the increasing of RE-doped quantity, the catalytic activity of catalysts exhibits regular changes.When RE-doped quantity is 0.2% ( molar ratio), the catalysts show the best catalytic activity.展开更多
Nickel-based catalysts have emerged as crucial components in alkaline oxygen evolution reactions(OER)due to their exceptional catalytic performance and unique structural properties.However,the understanding of their c...Nickel-based catalysts have emerged as crucial components in alkaline oxygen evolution reactions(OER)due to their exceptional catalytic performance and unique structural properties.However,the understanding of their catalytic mechanisms remains incomplete.This review systematically explores the various types of Ni-based catalysts,including metal-organic frameworks(MOFs),perovskites,and layered double hydroxides(LDHs),while emphasizing their performance metrics.We critically assess the application of advanced in situ characterization techniques,such as in situ Raman spectroscopy and X-ray absorption spectroscopy(XAS),in elucidating the structural evolution and active species during the OER process.By addressing the interplay between catalyst structure and performance,this review aims to provide insights that drive future research efforts toward the optimization of Ni-based catalysts for sustainable hydrogen production.Key areas for potential research advancements are also identified.展开更多
The microstructure of single crystal superalloy is relatively simple,consisting primarily ofγdendrites andγ/γ′eutectics.During the directional solidification process of Ni-based single crystal superalloys,withdraw...The microstructure of single crystal superalloy is relatively simple,consisting primarily ofγdendrites andγ/γ′eutectics.During the directional solidification process of Ni-based single crystal superalloys,withdrawal rate is a critical parameter affecting the spatial distribution ofγ/γ′eutectic along gravity direction.The results show that theγ/γ′eutectic fraction of the upper platform surface is always higher than that of the lower one,regardless of withdrawal rate.As the withdrawal rate decreases,there is a significant increase inγ/γ′eutectic fraction on the upper surface,while it decreases on the lower surface.The upward accumulation ofγ/γ′eutectic becomes more severe as the withdrawal rate decreases.It is also found that the percentage of Al+Ta is positively correlated with theγ/γ′eutectic fraction.Thermo-solute convection of Al and Ta solutes in the solidification front is the prime reason for the non-uniform distribution of eutectic.The non-uniform distribution ofγ/γ′eutectic cannot be eliminated even after subsequent solution heat treatment,resulting in excess eutectic on the upper surface and thus leading to the scrapping of the blade.展开更多
The microstructure evolution and deformation mechanism of a DZ125 superalloy during high-temperature creep were studied by means of microstructure observation and creep-property tests.The results show that at the init...The microstructure evolution and deformation mechanism of a DZ125 superalloy during high-temperature creep were studied by means of microstructure observation and creep-property tests.The results show that at the initial stage of high-temperature creep,two sets of dislocations with different Burgers vectors move and meet inγmatrix channels,and react to form a quadrilateral dislocation network.Andγ′phases with raft-like microstructure are generated after the formation of dislocation networks.As creep progresses,the quadrilateral dislocation network is gradually transformed into hexagonal and quadrilateral dislocation networks.During steady stage of creep,the superalloy undergoes deformation with the mechanism that a great number of dislocations slip and climb in the matrix across the raft-likeγ′phases.At the later stage of creep,the raft-likeγ′phases are sheared by dislocations at the breakage of dislocation networks,and then alternate slip occurs,which distorts and breaks the raft-likeγ′/γphases,resulting in the accumulation of micropores at the raft-likeγ′/γinterfaces and the formation of microcracks.As creep continues,the microcracks continue to expand until creep fracture occurs,which is the damage and fracture mechanism of the alloy at the later stage of creep at high temperature.展开更多
The effect of carbon content on the microstructures and stress rupture properties of a newly developed polycrystalline Ni-based superalloy with high Cr content has been studied.It was observed that both grain size and...The effect of carbon content on the microstructures and stress rupture properties of a newly developed polycrystalline Ni-based superalloy with high Cr content has been studied.It was observed that both grain size and the number of carbides increased with an increase in carbon content.After heat treatment,granular M_(23)C_(6)carbides were dispersed around MC carbides along grain boundaries and inside grains.The quantity of granular M_(23)C_(6)carbides increased while their sizes decreased.These findings can be verified with the results of thermodynamic calculation and differential scanning calorimetry analysis.The stress rupture times(975℃/225 MPa)increased from 13.3 to 25.5 h with the carbon content increased from 0.1 to 0.2 wt.%.The improvement can be attributed to two primary factors.Firstly,grain boundary is typically weak region during deformation process and the grain size increased as carbon content increased in the alloy.Secondly,carbides act as hindrances to impede dislocation movement,leading to dislocation entanglement.As carbon content rose,the quantity of carbides in interdendritic regions and grain boundaries increased,providing a certain degree of strengthening effect and resulting in a longer stress rupture time.展开更多
The creep behavior of two PM superalloys,U720Li and RR1000,each alloyed with trace amount of Sc,was systematically investigated.Findings reveal that RR1000 alloy with 0.064 wt.%Sc(R-0.064)demonstrates superior creep r...The creep behavior of two PM superalloys,U720Li and RR1000,each alloyed with trace amount of Sc,was systematically investigated.Findings reveal that RR1000 alloy with 0.064 wt.%Sc(R-0.064)demonstrates superior creep resistance compared to U720Li alloy with 0.043 wt.%Sc(U-0.043),at 650℃ and 1000 MPa,and the primary creep mechanisms in both alloys are identified as dislocation shearing and precipitate bypassing.When tested at 700℃ and 700 MPa,the U-0.043 alloy predominantly exhibits micro-twinning and dislocation bypassing,while the R-0.064 alloy engages in extended stacking fault shearing ofγ'precipitate,dislocation bypassing and climb.At 750℃ and 460 MPa,dislocation bypassing and climb emerge as the main creep mechanisms for both alloys.展开更多
The performance of welded Ni-based superalloys at high temperatures is essential to be evaluated due to their particular service environment for aero-engines and high-speed aircrafts.The tensile properties and related...The performance of welded Ni-based superalloys at high temperatures is essential to be evaluated due to their particular service environment for aero-engines and high-speed aircrafts.The tensile properties and related microstructural evolutions such as the carbide precipitate and grain of a laser-welded Ni-based alloy were experimentally and numerically investigated at different temperatures(20,300,500,800℃).The results show that at room temperature,the strength of the Base Material(BM)was slightly smaller,with a difference of less than 1%,than the Welded Material(WM),which can be attributed to the more uniformly distributed needle-shaped carbide precipitates in the WM than those nonuniformly coarser spherical ones in the BM.While at 300℃ and 500℃,the strength of WM decreased more obviously compared with that of BM due to the more apparent growth of grain:13.52%loss in yield strength in WM alloys as compared with BM alloys at 300℃,and 16.57% at 500℃.At 800℃,the strength of BM and WM both decreased to a similar level due to Dynamic Recrystallization(DRX).However,a much higher elongation was observed for the BM than WM(less than 50%of BM),which can be attributed to the enhanced dislocation accumulation capability of the large spherical carbides along grain boundaries on the fracture surface in BM.Furthermore,a unified model considering the welding effects on both microstructures(dislocation,carbides,and grain)and mechanical properties evolutions at different temperatures was developed and validated.Based on this model,the key temperature ranges(20–600℃)where apparent weakening of strength and uniform plasticity occurs for welded structures were identified,providing a direct guidance for potential structure and process design.展开更多
基金supported by the Natural Science Foundation of Shanxi Province(202203021221155)the Foundation of National Key Laboratory of High Efficiency and Low Carbon Utilization of Coal(J23-24-902)。
文摘With ongoing global warming and increasing energy demands,the CH_(4)-CO_(2)reforming reaction(dry reforming of methane,DRM)has garnered significant attention as a promising carbon capture and utilization technology.Nickel-based catalysts are renowned for their outstanding activity and selectivity in this process.The impact of metal-support interaction(MSI),on Ni-based catalyst performance has been extensively researched and debated recently.This paper reviews the recent research progress of MSI on Ni-based catalysts and their characterization and modulation strategies in catalytic reactions.From the perspective of MSI,the effects of different carriers(metal oxides,carbon materials and molecular sieves,etc.)are introduced on the dispersion and surface structure of Ni active metal particles,and the effect of MSI on the activity and stability of DRM reactions on Ni-based catalysts is discussed in detail.Future research should focus on better understanding and controlling MSI to improve the performance and durability of nickel-based catalysts in CH_(4)-CO_(2)reforming,advancing cleaner energy technologies.
文摘Photothermal catalytic methane dry reforming(DRM)technology can convert greenhouse gases(i.e.CH_(4)and CO_(2))into syngas(i.e.H_(2)and CO),providing more opportunities for reducing the greenhouse effect and achieving carbon neutrality.In the DRM field,Ni-based catalysts attract wide attention due to their low cost and high activity.However,the carbon deposition over Ni-based catalysts always leads to rapid deactivation,which is still a main challenge.To improve the long-term stability of Ni-based catalysts,this work proposes a carbon-atom-diffusion strategy under photothermal conditions and investigates its effect on a Zn-doped Ni-based photothermal catalyst(Ni_(3)Zn@CeO_(2)).The photothermal catalytic behavior of Ni_(3)Zn@CeO_(2)can maintain more than 70 h in DRM reaction.And the photocatalytic DRM activity of Ni_(3)Zn@CeO_(2)is 1.2 times higher than thermal catalytic activity.Density functional theory(DFT)calculation and experimental characterizations indicate that Ni_(3)Zn promotes the diffusion of carbon atoms into the Ni_(3)Zn to form the Ni_(3)ZnC0.7 phase with body-centered cubic(bcc)structure,thus inhibiting carbon deposition.Further,in-situ diffuse reflectance infrared Fourier transform(DRIFT)spectroscopy and DFT calculation prove Ni_(3)Zn@CeO_(2)benefits the CH_(4)activation and inhibits the carbon deposition during the DRM process.Through inducing carbon atoms diffusion within the Ni_(3)Zn lattice,this work provides a straightforward and feasible strategy for achieving efficient photothermal catalytic DRM and even other CH_(4)conversion implementations with long-term stability.
基金financially supported by the National Natural Science Foundation of China(22078064)Natural Science Foundation of Fujian Province for Distinguished Young Scholar(2018J06002)。
文摘The hydrogenation of petroleum resin(PR)is an effective process to prepare high value-added hydrogenated PR(HPR).However,the preparation of non-noble metal-based catalysts with high catalytic activity for PR hydrogenation still remains a challenge.Herein,a La promoted Ni-based catalyst is reported through the thermal reduction of quaternary Ni La Mg Al-layered double hydroxides(Ni La Mg Al-LDHs).The incorporation of La is beneficial to the reduction and stability of Ni particles with reduced particle size,and the increased alkalinity effectively mitigates the breakage of molecular chains of PR.As a result,the La promoted Ni-based catalyst exhibits high catalytic activity and excellent stability for PR hydrogenation.A hydrogenation degree of 95.4%and 96.1%can be achieved for HC_(5)PR and HC_(9) PR with less reduced softening point,respectively.Notably,the hydrogenation degree still maintains at 92.7%even after 100 hours’reaction,much better than that without La incorporation or prepared using conventional impregnation method.
文摘Highly active and selective Ni-based catalysts for partial oxidation of methane (POM) to syngas (CO/H,) have been studied and developed. Spectroscopic characterization by XRD, XPS, EPR, etc. demonstrated that under the POM reaction conditions, the Ni-components of the catalysts investigated were reduced and enriched on the surface to form metallic Ni0-phase. A comparative study of the first series of transition-metals showed that only Ni and Co have a high POM activity and selectivity, whereas the others (including Mn, Fe, Cu, etc. ) give mainly complete combustion products, Co, and H2O. The results favor the following viewpoints: the PoM activity is related with the rapidly changeable valence transitionmetal sites, M0/M2+ (e. g. Ni0/Ni2+ ), on the surface of the functioning catalysts;the transition-metal sites in zero-valence state seem to be responsible for the activation and dehydrogenation of methane by homolytic splitting of its C-H bonds on these sites. and the nature of rapidly changeable valence of the active sties is requisite for activation and rapid conversion of dioxygen.
基金supported by the National Basic Research Program of China(No.2005CB221405)the National"863"Project of China(No.2006AA10Z425)
文摘A series of Ni/SBA-15 catalysts with Ni contents from 5 wt%–20 wt%and CaO-12.5%Ni/SBA-15 catalysts with CaO contents from 1.4 wt%– 9.8 wt%have been prepared.The structure of the catalysts was characterized using X-ray diffraction（XRD）,N2 adsorption-desorption,transmission electron microscopy（TEM）and X-ray photoelectron spectroscopy（XPS）.The performance of catalytic steam reforming of the poplar leaves to the hydrogen-rich syngas was tested in a fixed-bed reactor.The results indicate that the 7.0wt%CaO-12.5wt%Ni/SBA-15 catalyst exhibits the best performance for the catalytic steam reforming of poplar leaves to hydrogen-rich syngas.The ratio of H2：CO can reach ca 5：1 in the hydrogen-rich syngas.The yield of H2 can reach 273.30 mL/g（poplar leaves）.In the CaO-Ni/SBA-15 catalyst,Ni active component mainly fills the role of catalytic steam reforming of the poplar leaves,and CaO active component mainly plays the role as water-gas shift and CO2 sorbent.
基金Supported by the National Natural Science Foundation of China(21161140329)the National High Technology Research and Development Program of China(2015AA050502).
文摘Kaolin as a raw material for mesoporous support was firstly modified by calcination,acid treatment,and then was used to prepare nickel catalysts.The amount of alumina which was activated in kaolin during thermal treatment and then leached out in the acid was different.XRD pattern of the kaolin calcined at 600°C or 900°C exhibited only the diffraction peaks for amorphous silica and quartz while that calcined at 1100°C showed obvious peaks forγ-Al2 O3.Therefore,the nickel-based catalysts exhibited different physic-chemical properties.Atmospheric syngas methanation over the catalysts clarified an activity order of CA-1100 N CA-900 N CA-1400 N CA-600 N KA≈0 at temperatures of 350–650°C and a space velocity of 120 L·g-1·h-1.Metallic nickel with small diameter which has medium interaction with the modified kaolin and is well dispersed on the support would have reasonably good activity and carbon-resistance for syngas methanation.
基金the National Basic Research Program of China(973 Program)(No 2011CB710800)the National Natural Science Foundation of China(No20976164)
文摘Ligand modification of Ni-based catalysts by coordination of dicyandiamide to Ni metal leads to enhanced selectivity for the selective hydrogenation of halonitroaromatics.The selectivity of above 99.9%to aromatic haloamines can be achieved at the conversion of 100%.The results of H_2-TPD and FT-IR experiments show that Ni^-H~＋ species possessing the properties of Lewis acid site on the surface of Raney Ni could be responsible for the hydrodehalogenation.When Raney Ni was treated by dicyandiamide,Ni^-H~＋ species interacted with N atom from the dicyandiamide.This interaction was stable even at reaction temperature,which reduced the possibility to form the intermediate state of Ar-Cl...H~＋Ni^-.And then C-Cl bond could not be polarized and activated.The hvdrodechlorination process was suppressed effectively.
文摘Perovskites as host structures of cations were used in order to generate in situ active and stable catalysts for ethanol steam reforming. For this purpose,La_(1-x)Mg_xAl_(1-y)Ni_yO_3(x = 0.1; y = 0,0.1,0.2,0.3) perovskites were synthetized by the citrate method.Ni segregation is evident for a substitution level higher than 0. 2. The segregation of Ni as NiO generated species interacts with different metal-support after the reduction step. The y = 0.1 catalyst presents the highest H_2 yield value about 85% during reaction time,with low mean values of CH_4 and CO selectivities of 3.4% and 11%,respectively and a low carbon formation. The better performance of y = 0.1 catalyst could be attributed to the minor proportion of segregated phases,thus a controlled expulsion of Ni is successfully reached.
基金This work was supported by the National Natural Science Foundation of China （No.51376185 and No.51106108）, the National Basic Research Program of China （No.2012CB215304）, the National High Technology Research and Development Program of China （No.2012AA101806）, and the Natural Science Foundation of Guangdong Province （No.$2013010011612）.
文摘A series of Ni based catalysts with different supports and basic additives were prepared by sequential impregnation method. The catalysts were characterized by XRD, BET, H2-TPR and CO2-TPD techniques. It was found that the introduction of basic additives enhanced the basicities of catalyats and promoted the dispersities of Ni particles by strong interaction between Ni2＋ and basic additives. Among the Ni based catalysts, 10%Ni/10%La203/ZrO2 showed the superior performance in sorbitol hydrogenolysis. The synergistic effect of Ni and La203 was proven to play an essential role in selective synthesis of EG and 1,2-PG. In the optimal reaction condition, the catalyst presented 100% sorbitol conversion and over 48% glycols （EG and 1,2-PG） yield. The kinetics study of polyols （sorbitol, xylitol and glycerol） hydrogenolysis showed that polyols with more hydroxyl number have higher activity and products distribution was final results of kinetic balance, which could give us some inspiration abeut how to change the products selectivity.
基金financial support from the National Science and Technology Supporting Plan through contract (2015BAD15B06)the National Natural Science Foundation of China (51661145011)
文摘Co-precipitation method was selected for the preparation of Ni/Al_2O_3, Ni/ZrO_2 and Ni/CeO_2 catalysts, and their performances in methanation were investigated in this study. The structure and surface properties of these catalysts were characterized by BET, XRD, H_2-TPD, TEM and H_2-TPR. The results showed that the catalytic activity at low temperature followed the order: Ni/Al_2O_3>Ni/ZrO_2>Ni/CeO_2. Ni/Al_2O_3 catalyst presented the best catalytic performance with the highest CH_4 selectivity of 94.5%. The characterization results indicated that the dispersion of the active component Ni was the main factor affecting the catalytic activity and the one with higher dispersion gave better performance.
基金supported by the National Natural Science Fundation of China(U1361202,51276120)~~
文摘The CO2reforming of CH4is studied over MgO‐promoted Ni catalysts,which were supported on alumina prepared from hydrotalcite.This presents an improved stability compared with non‐promoted catalysts.The introduction of the MgO promoter was achieved through the‘‘memory effect’’of the Ni‐Al hydrotalcite structure,and ICP‐MS confirmed that only0.42wt.%of Mg2+ions were added into the Ni‐Mg/Al catalyst.Although no differences in the Ni particle size and basicity strength were observed,the Ni‐Mg/Al catalyst showed a higher catalytic stability than the Ni/Al catalyst.A series of surface reaction experiments were used and showed that the addition of a MgO promoter with low concentration can promote CO2dissociation to form active surface oxygen arising from the formation of the Ni‐MgO interface sites.Therefore,the carbon‐resistance promotion by nature was suggested to contribute to an oxidative environment around Ni particles,which would increase the conversion of carbon residues from CH4cracking to yield CO on the Ni metal surface.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.
基金financially supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia and is a result of projects No. 34033 and No. 34023
文摘A method of synthesizing Ni-based catalysts supported on α-Al2O3-based foams was developed. The foams were impregnated with aqueous solutions of metal chlorides under an air atmosphere using an aerosol route. Separate procedures involved calcination to form oxides and drying to obtain chlorides on the foam surface. The synthesized samples were subsequently reduced with hydrogen. With respect to the Ni/Al2O3 catalysts, the chloride reduction route enabled the formation ofa Ni coating without agglomerates or cracks. Further research included catalyst modification by the addition of Pd, Cu, and Fe. The influences of the additives on the degree of reduction and on the low-temperature reduction effectiveness （533 and 633 K） were examined and compared for the catalysts obtained from oxides and chlorides. Greater degrees of reduction were achieved with chlorides, whereas Pd was the most effective modifier among those investigated. The reduction process was nearly complete at 533 K in the sample that contained 0.1wt% Pd. A lower reduction temperature was utilized, and the calcination step was avoided, which may enhance the economical and technological aspects of the developed catalyst production method.
文摘RE-doped Ni-based catalysts were prepared by sol-gel method.These catalysts were applied to the reaction of CO2 reforming CH4 to syngas.The studies reveal that RE-doped ( RE = La, Ce, Sm, Yb) Ni-based catalysts show higher catalytic activity than undoped Ni-based catalyst, and with the increasing of RE-doped quantity, the catalytic activity of catalysts exhibits regular changes.When RE-doped quantity is 0.2% ( molar ratio), the catalysts show the best catalytic activity.
基金supported by the Fundamental Research Funds for the Central Universities(20822041H4082).
文摘Nickel-based catalysts have emerged as crucial components in alkaline oxygen evolution reactions(OER)due to their exceptional catalytic performance and unique structural properties.However,the understanding of their catalytic mechanisms remains incomplete.This review systematically explores the various types of Ni-based catalysts,including metal-organic frameworks(MOFs),perovskites,and layered double hydroxides(LDHs),while emphasizing their performance metrics.We critically assess the application of advanced in situ characterization techniques,such as in situ Raman spectroscopy and X-ray absorption spectroscopy(XAS),in elucidating the structural evolution and active species during the OER process.By addressing the interplay between catalyst structure and performance,this review aims to provide insights that drive future research efforts toward the optimization of Ni-based catalysts for sustainable hydrogen production.Key areas for potential research advancements are also identified.
基金Shenzhen Science and Technology Program(JSGG20220831092800001)。
文摘The microstructure of single crystal superalloy is relatively simple,consisting primarily ofγdendrites andγ/γ′eutectics.During the directional solidification process of Ni-based single crystal superalloys,withdrawal rate is a critical parameter affecting the spatial distribution ofγ/γ′eutectic along gravity direction.The results show that theγ/γ′eutectic fraction of the upper platform surface is always higher than that of the lower one,regardless of withdrawal rate.As the withdrawal rate decreases,there is a significant increase inγ/γ′eutectic fraction on the upper surface,while it decreases on the lower surface.The upward accumulation ofγ/γ′eutectic becomes more severe as the withdrawal rate decreases.It is also found that the percentage of Al+Ta is positively correlated with theγ/γ′eutectic fraction.Thermo-solute convection of Al and Ta solutes in the solidification front is the prime reason for the non-uniform distribution of eutectic.The non-uniform distribution ofγ/γ′eutectic cannot be eliminated even after subsequent solution heat treatment,resulting in excess eutectic on the upper surface and thus leading to the scrapping of the blade.
基金Guizhou Province Science and Technology Plan Project(QKHJC-ZK[2024]yiban604)Guizhou Province Science and Technology Plan Project(CXTD[2021]008)+4 种基金Bijie City Science and Technology Project(BKLH[2023]9)Technology Project of Bijie City(BKLH[2023]36)Natural Science Research Project of Guizhou Higher Education Institutions of China(QJJ[2023]047)Science and Technology Project of Guizhou Department of Transportation(2022-121-011)Sanmenxia City Science and Technology Bureau Science and Technology Research Project(2022002005)。
文摘The microstructure evolution and deformation mechanism of a DZ125 superalloy during high-temperature creep were studied by means of microstructure observation and creep-property tests.The results show that at the initial stage of high-temperature creep,two sets of dislocations with different Burgers vectors move and meet inγmatrix channels,and react to form a quadrilateral dislocation network.Andγ′phases with raft-like microstructure are generated after the formation of dislocation networks.As creep progresses,the quadrilateral dislocation network is gradually transformed into hexagonal and quadrilateral dislocation networks.During steady stage of creep,the superalloy undergoes deformation with the mechanism that a great number of dislocations slip and climb in the matrix across the raft-likeγ′phases.At the later stage of creep,the raft-likeγ′phases are sheared by dislocations at the breakage of dislocation networks,and then alternate slip occurs,which distorts and breaks the raft-likeγ′/γphases,resulting in the accumulation of micropores at the raft-likeγ′/γinterfaces and the formation of microcracks.As creep continues,the microcracks continue to expand until creep fracture occurs,which is the damage and fracture mechanism of the alloy at the later stage of creep at high temperature.
基金supported by the National Natural Science Foundation of China(No.52303394)the National Key Research and Development Program of China(No.2022YFB3705000)+1 种基金the Natural Science Foundation of Liaoning Province(No.2023-BS-015)the Science Center for Gas Turbine Project(No.P2022-C-IV-002-001).
文摘The effect of carbon content on the microstructures and stress rupture properties of a newly developed polycrystalline Ni-based superalloy with high Cr content has been studied.It was observed that both grain size and the number of carbides increased with an increase in carbon content.After heat treatment,granular M_(23)C_(6)carbides were dispersed around MC carbides along grain boundaries and inside grains.The quantity of granular M_(23)C_(6)carbides increased while their sizes decreased.These findings can be verified with the results of thermodynamic calculation and differential scanning calorimetry analysis.The stress rupture times(975℃/225 MPa)increased from 13.3 to 25.5 h with the carbon content increased from 0.1 to 0.2 wt.%.The improvement can be attributed to two primary factors.Firstly,grain boundary is typically weak region during deformation process and the grain size increased as carbon content increased in the alloy.Secondly,carbides act as hindrances to impede dislocation movement,leading to dislocation entanglement.As carbon content rose,the quantity of carbides in interdendritic regions and grain boundaries increased,providing a certain degree of strengthening effect and resulting in a longer stress rupture time.
基金supported by the Natural Science Foundation of China(No.52074366)the Top Ten Science and Technology Projects in Hunan Province,China(No.2024GK1080)+4 种基金the Aero Engine Corporation of China(No.HFZL2022CXY029)the Young Elite Scientists Sponsorship Program by CAST,China(No.2022QNRC001)the Natural Science Foundation of Hunan Province,China(No.2021JJ40757)the Science and Technology Innovation Program of Hunan Province,China(No.2021RC3131)the High Performance Computing Center of Central South University,and the Project supported by State Key Laboratory of Powder Metallurgy,Central South University,China.
文摘The creep behavior of two PM superalloys,U720Li and RR1000,each alloyed with trace amount of Sc,was systematically investigated.Findings reveal that RR1000 alloy with 0.064 wt.%Sc(R-0.064)demonstrates superior creep resistance compared to U720Li alloy with 0.043 wt.%Sc(U-0.043),at 650℃ and 1000 MPa,and the primary creep mechanisms in both alloys are identified as dislocation shearing and precipitate bypassing.When tested at 700℃ and 700 MPa,the U-0.043 alloy predominantly exhibits micro-twinning and dislocation bypassing,while the R-0.064 alloy engages in extended stacking fault shearing ofγ'precipitate,dislocation bypassing and climb.At 750℃ and 460 MPa,dislocation bypassing and climb emerge as the main creep mechanisms for both alloys.
基金co-supported by the financial support from the Fundamental Research Funds for the Central Universities,China(Nos.YWF-23-L-1012,YWF-22-L-1017)the National Natural Science Foundation of China(No.52005020)。
文摘The performance of welded Ni-based superalloys at high temperatures is essential to be evaluated due to their particular service environment for aero-engines and high-speed aircrafts.The tensile properties and related microstructural evolutions such as the carbide precipitate and grain of a laser-welded Ni-based alloy were experimentally and numerically investigated at different temperatures(20,300,500,800℃).The results show that at room temperature,the strength of the Base Material(BM)was slightly smaller,with a difference of less than 1%,than the Welded Material(WM),which can be attributed to the more uniformly distributed needle-shaped carbide precipitates in the WM than those nonuniformly coarser spherical ones in the BM.While at 300℃ and 500℃,the strength of WM decreased more obviously compared with that of BM due to the more apparent growth of grain:13.52%loss in yield strength in WM alloys as compared with BM alloys at 300℃,and 16.57% at 500℃.At 800℃,the strength of BM and WM both decreased to a similar level due to Dynamic Recrystallization(DRX).However,a much higher elongation was observed for the BM than WM(less than 50%of BM),which can be attributed to the enhanced dislocation accumulation capability of the large spherical carbides along grain boundaries on the fracture surface in BM.Furthermore,a unified model considering the welding effects on both microstructures(dislocation,carbides,and grain)and mechanical properties evolutions at different temperatures was developed and validated.Based on this model,the key temperature ranges(20–600℃)where apparent weakening of strength and uniform plasticity occurs for welded structures were identified,providing a direct guidance for potential structure and process design.
