A series of CeO_(2)-TiO_(2)mixed oxides supports with various Ce/Ti molar ratio were synthesized by modified coprecipitation method. The corresponding Pt loaded(0.5 wt% Pt) catalysts were prepared by electronless depo...A series of CeO_(2)-TiO_(2)mixed oxides supports with various Ce/Ti molar ratio were synthesized by modified coprecipitation method. The corresponding Pt loaded(0.5 wt% Pt) catalysts were prepared by electronless deposition method and evaluated for the deep oxidation of n-hexane as a model VOCs. The results show that the CeO_(2)and TiOxnanoparticles can highly disperse into each other and form Ce_(2)Ti_(2)O_(7)solid solution with appropriate Ce/Ti molar ratio, which significantly improves their redox ability by enhancing the interaction between CeO_(2)and TiO_(x). The dispersibility of Pt species can also be adjusted by altering the Ce/Ti molar ratio, and Pt/CeTi-2/1 catalyst with Ce/Ti molar ratio of 2:1 exhibits the best Pt dispersibility that Pt species mainly exist as Pt single atoms. The high dispersion of Pt species in the Pt/CeO_(2)-TiO_(2)catalysts would promote the catalytic activity of VOCs oxidation with low T90% values(1000 ppm, GHSV = 15,000 h^(-1)), such as for n-hexane degradation with T90% of 139℃. The characterizations reveal that the superior activity is mainly related to possessing the more Pt2+species,adsorbed oxygen species and higher low-temperature reducibility owing to the strong interaction between highly dispersed Pt species and CeO_(2)-TiO_(2)as well as the promoted migration of lattice oxygen by the formation of more Ce_(2)Ti_(2)O_(7)species. Furthermore, the Pt/CeTi-2/1 catalyst also exhibits excellent stability for chlorinated and other non-chlorinated VOCs oxidation, making it very promising for real application under various operating conditions.展开更多
A series of(Ce,Cr)xO2/Nb2O5 catalysts with different(Ce,Cr)xO2 to Nb2O5 mass ratios were synthesized by the deposition-precipitation method for use in deep catalytic oxidation of 1,2-dichloroethane(DCE), which is one ...A series of(Ce,Cr)xO2/Nb2O5 catalysts with different(Ce,Cr)xO2 to Nb2O5 mass ratios were synthesized by the deposition-precipitation method for use in deep catalytic oxidation of 1,2-dichloroethane(DCE), which is one of the typical chlorinated volatile organic compound pollutants. The textural properties were characterized by X-ray diffraction, N2 adsorption/desorption isotherms, UV-Raman spectroscopy, and scanning electron microscopy. The surface acidity and the redox properties were characterized by ammonia temperature-programmed desorption and H2 temperature-programmed reduction, respectively. The results show that the addition of a proper amount of(Ce,Cr)xO2 over Nb2O5 significantly improves the intrinsic catalytic activity towards the deep oxidation of DCE, and only a very small amount of C2H3Cl is detected as the byproduct of the oxidation process. Further study reveals the existence of an obvious synergistic effect between Nb2O5, with abundant strong acid sites, and(Ce,Cr)xO2, with strong oxidation sites, as the strong acid sites of Nb2O5 promote the adsorption and dehydrochlorination of DCE, while the strong oxidation sites of(Ce,Cr)xO2 contribute to the deep oxidation of the reactant, intermediates, and byproducts.展开更多
Influence of three different preparation methods, i.e. impregnation, coprecipitation, and inverse coprecipitation, on the preferential oxidation of CO in excess hydrogen （PROX） over CuO-CeO2 catalysts has been inves...Influence of three different preparation methods, i.e. impregnation, coprecipitation, and inverse coprecipitation, on the preferential oxidation of CO in excess hydrogen （PROX） over CuO-CeO2 catalysts has been investigated and CuO-CeO2 catalysts are characterized using BET, XPS, XRD, UV Raman, and TPR techniques. The results show that the catalysts prepared by coprecipitation have smaller particle sizes, well-dispersed CuOx species, more oxygen vacancies, and are more active in the PROX than those prepared by the other methods. However. the inverse coprecipitation depresses the catalytic performance of CuO-CeO2 catalysts and causes the growth of CuO-CeO2 because of different pH value in the precipitation process.展开更多
High performance CuO-CeO2 catalysts for selective oxidation of CO in excess hydrogen were prepared by a hydrothermal method under different preparation conditions and evaluated for catalytic activities and selectiviti...High performance CuO-CeO2 catalysts for selective oxidation of CO in excess hydrogen were prepared by a hydrothermal method under different preparation conditions and evaluated for catalytic activities and selectivities. By changing the ^nCTAB/^nCe ratio and hydrothermal aging time, the catalytic activity of the CuO-CeO2 catalysts increased and the operating temperature window, in which the CO conversion was higher than 99%, was widened. XRD results showed no peaks of CuOx species and Cu-Ce-O solid solution were observed. On the other hand, Cu＋ species in the CuO-CeO2 catalysts, which was associated with a strong interaction between copper oxide clusters and cerium oxide and could be favorable for improving the selective oxidation performance of CO in excess H2, were detected by H2-TPR and XPS techniques.展开更多
CuO-CeO2 catalyst prepared with co-precipitation showed high catalytic performance for the preferential oxidation of CO in excess hydrogen（PROX）.Influence of pH values in the preparation of CuO-CeO2 on its catalytic...CuO-CeO2 catalyst prepared with co-precipitation showed high catalytic performance for the preferential oxidation of CO in excess hydrogen（PROX）.Influence of pH values in the preparation of CuO-CeO2 on its catalytic performance was investigated in this work.The CuO-CeO2 catalyst prepared at pH = 13.03 had the smallest particle size（5.4 nm）,the largest surface areas（138m 2/g） and the highest activity with CO conversion of 99.6% at 130 ℃.The CuO-CeO2 catalyst was characterized using BET,XRD and TPR techniques.The results showed that when the pH value of the mixed solution containing Cu and Ce species was properly adjusted,both the adsorption layers and diffusion layers of the formed colloidal particles in hydroxide precursor of CuO-CeO2 were modified,resulting in the better catalytic performance for PROX on the final CuO-CeO2 catalyst展开更多
In the present study, we have investigated the reducibility of CuO species on CuO-CeO2 catalysts and the influence of CuO species on the catalytic performance for CO preferential oxidation （CO PROX） in excess hydrog...In the present study, we have investigated the reducibility of CuO species on CuO-CeO2 catalysts and the influence of CuO species on the catalytic performance for CO preferential oxidation （CO PROX） in excess hydrogen. It is revealed that the smaller the difference of reduction temperature （denoted as ？T） for two adjacent CuO species is, the higher the catalytic activity of CuO-CeO2 for the PROX in excess hydrogen may be obtained. It means that if the reduction energy of Cu0-Cu2＋ pairs matched better, the reduction-oxidation recycle of Cu0-Cu2＋ pairs would go on more easily, then the transferring energy of Cu0-Cu2＋ pairs would be lesser. Therefore, the CuO-CeO2 catalysts will be largely improved in their catalytic performance if the different CuO species on the catalysts have matched the reduction energy, which would allows them to cooperate effectively.展开更多
Doping of different rare-earth metals （Pr, Nd, Y and La） had an evident influence on the catalytic performance of CuO-CeO2 for the preferential oxidation （PROX） of CO in excess hydrogen. As for Pr, the doping enha...Doping of different rare-earth metals （Pr, Nd, Y and La） had an evident influence on the catalytic performance of CuO-CeO2 for the preferential oxidation （PROX） of CO in excess hydrogen. As for Pr, the doping enhanced the catalytic activity of CuO-CeO2 for PROX. For example, the CO conversion over the above catalyst for PROX was higher than 99% at 120 °C. Especially, the doping of Pr widened the temperature window by 20 °C over CuO-CeO2 with 99% CO conversion. For Nd, Y, and La, the doping depressed the catalytic activity of CuO-CeO2 for PROX. However, the doping of transition metals markedly improved the selectivity of CuO-CeO2 for PROX.展开更多
Pt/Al_(2)O_(3) catalysts with smaller size of Pt nanoparticles were prepared by ethylene glycol reduction method in two different way and their oxidation activities for three typical VOCs(volatile organic compounds)we...Pt/Al_(2)O_(3) catalysts with smaller size of Pt nanoparticles were prepared by ethylene glycol reduction method in two different way and their oxidation activities for three typical VOCs(volatile organic compounds)were evaluated.The catalyst prepared by first adsorption and then reduction procedure is denoted as L-Pt/Al_(2)O_(3) while the catalyst prepared by first reduction and then loading procedure is defined as R-Pt/Al_(2)O_(3).The results show that L-Pt/Al_(2)O_(3) with the stronger interaction between Pt species and Al_(2)O_(3) exhibit smaller size of Pt nanoparticles and favorable thermal stability compared with R-Pt/Al_(2)O_(3).L-Pt/Al_(2)O_(3) is favor of the formation of more adsorbed oxygen species and more Pt^(2+)species,resulting in high catalytic activity for benzene and ethyl acetate oxidation.However,R-Pt/Al_(2)O_(3) catalysts with higher proportion of Pt^(0)/Pt^(2+)and bigger size of Pt particles exhibits higher catalytic activity for n-hexane oxidation.Pt particles in R-Pt/Al_(2)O_(3) were aggregated much more serious than that in L-Pt/Al_(2)O_(3) at the same calcination temperature.The Pt particles supported on Al_(2)O_(3) with~10 nm show the best catalytic activity for n-hexane oxidation.展开更多
The catalytic behavior of a catalyst for chlorine-containing volatile organic compounds(CVOCs) oxidation largely depends on the synergistic interaction between the oxidizing and acidic sites.In the present work,two ca...The catalytic behavior of a catalyst for chlorine-containing volatile organic compounds(CVOCs) oxidation largely depends on the synergistic interaction between the oxidizing and acidic sites.In the present work,two catalysts with different distributions of CeO_(2) on the inner and outer surfaces of 4.0Ce-USY-ex and 4.0Ce-USY-dp(USY zeolite) were prepared respectively by ion exchange and deposition methods,with a purpose of finding out how the location of the oxidation sites(CeO_(2)) influence its synergistic effect with the acidic sites of zeolite.The results show that 4.0Ce-USY-ex is much more active for catalytic degradation of 1,2-dichloroethane(DCE),while 4.0Ce-USY-dp catalyst exhibit higher catalytic degradation activity for other structured CVOCs(dichloromethane(DCM),trichloroethylene(TCE),chlorobenzene(CB)).CeO_(2) in 4.0Ce-USY-ex catalyst mainly disperses in the pore channels of USY zeolite,and there are many strong acid centers on the surface,which is conducive to the dechlorination conversion of CVOCs.However,CeO_(2) in 4.0Ce-USY-dp catalyst is mainly distributed on the outer surface of USY and has strong oxidation ability,which contributes to the deep oxidation of CVOCs.Moreover,the presence of a large number of strong acid centers on the catalyst surface of 4.0Ce-USY-ex catalysts leads to severe accumulation of surface carbon species and significantly decreases its stability towards DCE.However,a large number of active oxygen species on the surface of 4.0Ce-USY-dp and CeO_(2) catalysts are beneficial to the deep oxidation of DCE,reducing the formation of surface carbon and thus improving the stability of the catalyst.Thus,the influence of the location of the oxidation sites on its synergistic effect with the acidic sites was established in the present work,which could provide some new ideas for the rational design of CVOCs degradation catalyst with appropriate distribution of active sites.展开更多
Different zeolites supported Pt catalystswithmicro-mesoporous structurewere prepared by organic base tetrapropylammonium hydroxide(TPAOH)treatment and their catalytic oxidation activity for various volatile organic co...Different zeolites supported Pt catalystswithmicro-mesoporous structurewere prepared by organic base tetrapropylammonium hydroxide(TPAOH)treatment and their catalytic oxidation activity for various volatile organic compounds(VOCs)were evaluated.The results reveal that the synergistic effect between Pt nanoparticles and surface acid sites plays an important role in VOCs low-temperature removal.The small size and high dispersion of Pt nanoparticles on the surface of the zeolites would promote the catalytic oxidation of aromatics and alkanes over the Pt/zeolite catalysts,while strong acidity and abundant acid sites of catalysts are in favour of the oxidation of the VOCs containingNandOheteroatoms.In addition,it was found that Pt/ZSM-5 catalyst exhibits the highest oxidation activity for various VOCs low-temperature removal amongst all the catalysts due to the balance of both Pt dispersion and abundant acid sites in the catalyst.This comprehensive consideration should be very helpful when designing and preparing novel catalysts for the low-temperature removal of VOCs.展开更多
Series of Cu-USY zeolite catalyst with different Cu loading content were synthesized through simple impregnation method.The obtained catalysts were subjected to selective catalytic reduction of NOxwith NH_(3)(NH_(3)-S...Series of Cu-USY zeolite catalyst with different Cu loading content were synthesized through simple impregnation method.The obtained catalysts were subjected to selective catalytic reduction of NOxwith NH_(3)(NH_(3)-SCR) performance evaluation,structural/chemical characterizations such as X-ray diffraction (XRD),N2adsorption/desorption,H_(2)temperature-programmed reduction (H_(2)-TPR),NH_(3)temperature-programmed desorption (NH_(3)-TPD) as well as detailed in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments including CO adsorption,NH_(3)adsorption and NO+O_(2)in situ reactions.Results show that Cu-USY with proper Cu loading (in this work 5Cu-USY with5 wt.%Cu) could be promising candidates with highly efficient NH_(3)-SCR catalytic performance,relatively low byproduct formation and excellent hydrothermal stability,although its SO_(2)poisoning tolerability needs alleviation.Further characterizations reveal that such catalytic advantages can be attributed to both active cu species and surface acid centers evolution modulated by Cu loading.On one hand,Cu species in the super cages of zeolites increases with higher Cu content and being more conducive for NH_(3)-SCR reactivity.On the other hand,higher Cu loading leads to depletion of Br?nsted acid centers and simultaneous formation of abundant Lewis acid centers,which facilitates NH_(4)NO_(3)reduction via NH_(3)adsorbed on Lewis acid centers,thus improving SCR reactivity.However,Cu over-introduction leads to formation of surface highly dispersed CuOx,causing unfavorable NH_(3)oxidation and inferior N2selectivity.展开更多
A series of Pt-Pd bimetallic catalysts supported on CeO_(2)-ZrO_(2)-La_(2)O_(3) mixed oxides were synthesized through the conventional impregnation method.Three-way catalytic performance evaluations along with detaile...A series of Pt-Pd bimetallic catalysts supported on CeO_(2)-ZrO_(2)-La_(2)O_(3) mixed oxides were synthesized through the conventional impregnation method.Three-way catalytic performance evaluations along with detailed physio-chemical characterizations were carried out to establish possible structure-activity correlations.Results show that on the one hand,different Pt/Pd ratios can strongly affect the TWC behaviors of Pt-Pd/CZL catalysts by modulating the synergistic effect between Pt and Pd.On the other hand,higher Pt/Pd ratio also favors better dispersion of precious metals.Such improved precious metals(PM)dispersion can promote the metal-support interaction and increase the surface oxygen vacancies concentration,thereby raising the dynamic oxygen storage/release capacity,improving the redox ability as well as enha ncing the thermal stability of the Pt-Pd/CZL catalyst.Moreover,the stro ng metal-support interaction can augment surface oxygen vacancy concentration,thereby benefiting low temperature CO and NO reaction via augmented NOxadsorption and nitrate conversion.展开更多
A series of CrOx–CeO2/Ti-PILC(PILC is pillared interlayered clay)catalysts for n-butylamine oxidation were prepared using an impregnation method,and the structures,surface acidity distributions,and redox properties o...A series of CrOx–CeO2/Ti-PILC(PILC is pillared interlayered clay)catalysts for n-butylamine oxidation were prepared using an impregnation method,and the structures,surface acidity distributions,and redox properties of the catalysts were characterized using X-ray diffraction,X-ray photoelectron spectroscopy,transmission electron microscopy,H2temperature-programmed reduction,and NH3temperature-programmed desorption.The results show that addition of an appropriate amount of CeO2enhances the interactions between Cr and Ce,and this increases the acid strength and mobility of active oxygen species on the catalyst.8CrCe(6:1)/Ti-PILC(12,20)exhibits the best catalytic performance and control of NOxin n-butylamine oxidation.展开更多
Micro-mesoporous ZSM-5 zeolites were obtained by the post-treatment of tetrahydroxy ammonium hydroxide(TPAOH) solution with different concentration.The hierarchical pore structure formed during the desilication proces...Micro-mesoporous ZSM-5 zeolites were obtained by the post-treatment of tetrahydroxy ammonium hydroxide(TPAOH) solution with different concentration.The hierarchical pore structure formed during the desilication process facilitates the dispersion of Pt nanoparticles and Pt/ZSM-5 catalysts exhibit rather high catalytic activity for the deep oxidation of various VOCs at low temperature.The catalyst treated with TPAOH of 0.1 mol/L(Pt/ZSM-5(0.1)) shows the lowest degradation temperature(T90%) of 128 and 142℃, respectively for benzene and n-hexane.Compared with the untreated Pt/ZSM-5 catalyst, the abundant mesopores, small Pt particle size and finely dispersed Pt contribute to the superior catalytic activity and stability of the Pt/ZSM-5 catalysts for VOCs removal.More importantly, the existence of H_(2)O in the feed gases hardly affected the activity of Pt/ZSM-5(0.1) catalyst at the low reaction temperature of 128℃, which is very important for VOCs low-temperature removal in the future practical applications.展开更多
Pd/Ce0.67Zr0.33O2 catalyst was pretreated in different atmosphere respectively, and characterized by CO chemical adsorption, XPS, HR-TEM, H2-TPR, Raman, OSC and in situ DRIFTS to investigate the effect of the structur...Pd/Ce0.67Zr0.33O2 catalyst was pretreated in different atmosphere respectively, and characterized by CO chemical adsorption, XPS, HR-TEM, H2-TPR, Raman, OSC and in situ DRIFTS to investigate the effect of the structure properties of PdOx species on the catalytic performance for CO, HC and NOx elimination. The results show that Pd/CZ catalyst pretreated in air atmosphere has higher oxidation activity of HC due to having high Pd dispersion and strong interaction between PdOx and CZ support. Pd/CZ-H catalyst pretreated in reducing atmosphere exhibits better catalytic performance of NOx elimination because of having relatively big Pd particle size, more Pd species in metallic state and higher concentration of oxygen vacancies. While for the Pd/CZ-RG catalyst pretreated in reactant atmosphere, strong adsorption of HC species on the surface of catalysts would lead to a part of active sites being covered, which inhibits HC and NO conversions.展开更多
CeO2-TiO2 catalysts prepared by different methods were investigated for deep oxidation of 1,2-dichloroethane(DCE),as a typical representative of the chlorinated volatile organic compounds(CVOCs).Characterization analy...CeO2-TiO2 catalysts prepared by different methods were investigated for deep oxidation of 1,2-dichloroethane(DCE),as a typical representative of the chlorinated volatile organic compounds(CVOCs).Characterization analysis reveals that CeO2-TiO2 catalysts prepared by sol-gel and coprecipitation methods exhibit higher specific area,CeO2 and TiO2 particles are highly dispersed into each other and the reducibility and mobility of active oxygen species are obviously promoted due to the strong interaction between the two catalysts CeO2 and TiO2,resulting in higher catalytic activity for DCE oxidation to and less chlorinated byproduct.The high calcination temperature would lead to the formation of a new monoclinic phase Ce0.3Ti0.7O2 and sintering,which is the main reason for the catalytic activity for DCE oxidation markedly decreases.展开更多
A series of transition metals(Fe,Co,Ni,Cu,Cr and Mn)-doped CeO_(2)-TiO_(2) catalysts were prepared by the sol-gel method and applied for the catalytic removal of 1,2-dichloroethane(DCE) as a model for chlorinated VOCs...A series of transition metals(Fe,Co,Ni,Cu,Cr and Mn)-doped CeO_(2)-TiO_(2) catalysts were prepared by the sol-gel method and applied for the catalytic removal of 1,2-dichloroethane(DCE) as a model for chlorinated VOCs(CVOCs).The various characterization methods including X-ray diffraction(XRD),N_(2) adsorption-desorption,UV-Raman,NH_(3) temperature-programmed desorption(NH_(3)-TPD) and H_(2) temperature-programmed reduction(H_(2)-TPR) were utilized to investigate the physicochemical properties of the catalysts.The results show that doping Fe,Co,Ni or Mn can obviously promote the activity of CeO_(2)-TiO_(2) mixed oxides for DCE degradation,which is related to their improved texture properties,acid sites(especially for strong acidity) and low-temperature reducibility.Particularly,CeTi-Fe doped with moderate Fe exhibits excellent activity for 1,2-dichloroethane(DCE) degradation,giving a T_(90%) value as low as 250℃.More importantly,only trace chlorinated byproducts were produced during the low-temperature degradation of various CVOCs(dichloromethane(DCM),trichloroethylene(TCE) and chlorobenzene(CB)) over CeTi-Fe1/9 catalyst with high durability.展开更多
Series of Fe/Cu-SSZ-13 catalysts with different Fe loading content were synthesized by simple one-pot strategy.The obtained catalysts were subjected to selective catalytic reduction(SCR)of NO x with NH 3 and were char...Series of Fe/Cu-SSZ-13 catalysts with different Fe loading content were synthesized by simple one-pot strategy.The obtained catalysts were subjected to selective catalytic reduction(SCR)of NO x with NH 3 and were characterized by various techniques.The results show that Fe 0.63/Cu 1.50-SSZ-13 catalyst with proper Fe content exhibits excellent catalytic activity with widest operation temperature window from 160 to 580℃,excellent hydrothermal stability as well as good resistance to sulfur poisoning when compared with Cu-SSZ-13,signifying its great potential for practical applications.Further characterizations reveal that the synthesized Fe/Cu-SSZ-13 catalysts present typical chabazite(CHA)structure with good crystallinity,while isolated Cu^2+and monomeric Fe 3+are revealed as the predominant copper and iron species.At low temperatures,isolated Cu^2+species act as primary active sites for SCR reaction,while monomeric Fe^3+species provide sufficient active sites for sustain the SCR activity at high temperature.Moreover,Fe over doping would lead to the damage of zeolite structure,destruction of isolated Cu^2+site,as well as the formation of highly oxidizing Fe2O3,thus causing deterioration of catalytic performances.展开更多
The physicochemical properties of Pt-,Pd-and Rh-loaded(Ce,Zr,La)O_(2)(shorted for CZL)catalysts before/after aging treatment were systematically characterized by various techniques to illustrate the relationship of th...The physicochemical properties of Pt-,Pd-and Rh-loaded(Ce,Zr,La)O_(2)(shorted for CZL)catalysts before/after aging treatment were systematically characterized by various techniques to illustrate the relationship of the dynamic oxygen storage/release capacity and redox ability with their catalytic performances for HC,NO_(x)and CO conversions.Pt/CZL catalyst exhibits the optimum catalytic performance for HC and NO_(x)elimination,which mainly contribute to its excellent redox ability and dynamic oxygen storage/release capacity(DOSC)at lower temperature due to the stronger PM(precious metals)-support interaction.However,the worse stability of Pt-O-Ce species and volatile Pt oxides easily result in the dramatical decline in catalytic activity after aging.Pd/CZL shows higher catalytic activity for CO conversion by reason of more Olatt species as the active oxygen for CO oxidation reaction.Rh/CZL catalyst displays the widest dynamic operation window for NO_(x)elimination as a result of greater oxygen mobility at high temperature,and the ability to retain more Rh-O-Ce species after calcined at 1100℃effectively restrains sintering of active RhOx species,improving the thermal stability of Rh/CZL catalyst.展开更多
基金supported by a grant from the National Key Research and Development Program of China (2016YFC0204300)the National Nature Science Foundation of China (21477109)。
文摘A series of CeO_(2)-TiO_(2)mixed oxides supports with various Ce/Ti molar ratio were synthesized by modified coprecipitation method. The corresponding Pt loaded(0.5 wt% Pt) catalysts were prepared by electronless deposition method and evaluated for the deep oxidation of n-hexane as a model VOCs. The results show that the CeO_(2)and TiOxnanoparticles can highly disperse into each other and form Ce_(2)Ti_(2)O_(7)solid solution with appropriate Ce/Ti molar ratio, which significantly improves their redox ability by enhancing the interaction between CeO_(2)and TiO_(x). The dispersibility of Pt species can also be adjusted by altering the Ce/Ti molar ratio, and Pt/CeTi-2/1 catalyst with Ce/Ti molar ratio of 2:1 exhibits the best Pt dispersibility that Pt species mainly exist as Pt single atoms. The high dispersion of Pt species in the Pt/CeO_(2)-TiO_(2)catalysts would promote the catalytic activity of VOCs oxidation with low T90% values(1000 ppm, GHSV = 15,000 h^(-1)), such as for n-hexane degradation with T90% of 139℃. The characterizations reveal that the superior activity is mainly related to possessing the more Pt2+species,adsorbed oxygen species and higher low-temperature reducibility owing to the strong interaction between highly dispersed Pt species and CeO_(2)-TiO_(2)as well as the promoted migration of lattice oxygen by the formation of more Ce_(2)Ti_(2)O_(7)species. Furthermore, the Pt/CeTi-2/1 catalyst also exhibits excellent stability for chlorinated and other non-chlorinated VOCs oxidation, making it very promising for real application under various operating conditions.
基金supported by the National Key R&D Program of China(2016YFC0204300)the National Natural Science Foundation of China(21477109)~~
文摘A series of(Ce,Cr)xO2/Nb2O5 catalysts with different(Ce,Cr)xO2 to Nb2O5 mass ratios were synthesized by the deposition-precipitation method for use in deep catalytic oxidation of 1,2-dichloroethane(DCE), which is one of the typical chlorinated volatile organic compound pollutants. The textural properties were characterized by X-ray diffraction, N2 adsorption/desorption isotherms, UV-Raman spectroscopy, and scanning electron microscopy. The surface acidity and the redox properties were characterized by ammonia temperature-programmed desorption and H2 temperature-programmed reduction, respectively. The results show that the addition of a proper amount of(Ce,Cr)xO2 over Nb2O5 significantly improves the intrinsic catalytic activity towards the deep oxidation of DCE, and only a very small amount of C2H3Cl is detected as the byproduct of the oxidation process. Further study reveals the existence of an obvious synergistic effect between Nb2O5, with abundant strong acid sites, and(Ce,Cr)xO2, with strong oxidation sites, as the strong acid sites of Nb2O5 promote the adsorption and dehydrochlorination of DCE, while the strong oxidation sites of(Ce,Cr)xO2 contribute to the deep oxidation of the reactant, intermediates, and byproducts.
文摘Influence of three different preparation methods, i.e. impregnation, coprecipitation, and inverse coprecipitation, on the preferential oxidation of CO in excess hydrogen （PROX） over CuO-CeO2 catalysts has been investigated and CuO-CeO2 catalysts are characterized using BET, XPS, XRD, UV Raman, and TPR techniques. The results show that the catalysts prepared by coprecipitation have smaller particle sizes, well-dispersed CuOx species, more oxygen vacancies, and are more active in the PROX than those prepared by the other methods. However. the inverse coprecipitation depresses the catalytic performance of CuO-CeO2 catalysts and causes the growth of CuO-CeO2 because of different pH value in the precipitation process.
基金supported by the Ministry of Science and Technology of China (No.2004 CB 719504)
文摘High performance CuO-CeO2 catalysts for selective oxidation of CO in excess hydrogen were prepared by a hydrothermal method under different preparation conditions and evaluated for catalytic activities and selectivities. By changing the ^nCTAB/^nCe ratio and hydrothermal aging time, the catalytic activity of the CuO-CeO2 catalysts increased and the operating temperature window, in which the CO conversion was higher than 99%, was widened. XRD results showed no peaks of CuOx species and Cu-Ce-O solid solution were observed. On the other hand, Cu＋ species in the CuO-CeO2 catalysts, which was associated with a strong interaction between copper oxide clusters and cerium oxide and could be favorable for improving the selective oxidation performance of CO in excess H2, were detected by H2-TPR and XPS techniques.
基金supported by the Heavy Oil National Key Laboratory (No.2008-03)the Ministry of Science and Technology of China (No.2004 CB719504)the Starting Foundation of Hunan University
文摘CuO-CeO2 catalyst prepared with co-precipitation showed high catalytic performance for the preferential oxidation of CO in excess hydrogen（PROX）.Influence of pH values in the preparation of CuO-CeO2 on its catalytic performance was investigated in this work.The CuO-CeO2 catalyst prepared at pH = 13.03 had the smallest particle size（5.4 nm）,the largest surface areas（138m 2/g） and the highest activity with CO conversion of 99.6% at 130 ℃.The CuO-CeO2 catalyst was characterized using BET,XRD and TPR techniques.The results showed that when the pH value of the mixed solution containing Cu and Ce species was properly adjusted,both the adsorption layers and diffusion layers of the formed colloidal particles in hydroxide precursor of CuO-CeO2 were modified,resulting in the better catalytic performance for PROX on the final CuO-CeO2 catalyst
基金supported by the State Key Laboratory of Heavy Oil Processing (No. 200803)the Ministry of Science and Technology of China (No.2005CB221406)
文摘In the present study, we have investigated the reducibility of CuO species on CuO-CeO2 catalysts and the influence of CuO species on the catalytic performance for CO preferential oxidation （CO PROX） in excess hydrogen. It is revealed that the smaller the difference of reduction temperature （denoted as ？T） for two adjacent CuO species is, the higher the catalytic activity of CuO-CeO2 for the PROX in excess hydrogen may be obtained. It means that if the reduction energy of Cu0-Cu2＋ pairs matched better, the reduction-oxidation recycle of Cu0-Cu2＋ pairs would go on more easily, then the transferring energy of Cu0-Cu2＋ pairs would be lesser. Therefore, the CuO-CeO2 catalysts will be largely improved in their catalytic performance if the different CuO species on the catalysts have matched the reduction energy, which would allows them to cooperate effectively.
基金the National Basic Research Program of China (973 program, No. 2004 CB 7195040)
文摘Doping of different rare-earth metals （Pr, Nd, Y and La） had an evident influence on the catalytic performance of CuO-CeO2 for the preferential oxidation （PROX） of CO in excess hydrogen. As for Pr, the doping enhanced the catalytic activity of CuO-CeO2 for PROX. For example, the CO conversion over the above catalyst for PROX was higher than 99% at 120 °C. Especially, the doping of Pr widened the temperature window by 20 °C over CuO-CeO2 with 99% CO conversion. For Nd, Y, and La, the doping depressed the catalytic activity of CuO-CeO2 for PROX. However, the doping of transition metals markedly improved the selectivity of CuO-CeO2 for PROX.
基金the National Key Research and Development Program of China(2016YFC0204300)is gratefully acknowledged.
文摘Pt/Al_(2)O_(3) catalysts with smaller size of Pt nanoparticles were prepared by ethylene glycol reduction method in two different way and their oxidation activities for three typical VOCs(volatile organic compounds)were evaluated.The catalyst prepared by first adsorption and then reduction procedure is denoted as L-Pt/Al_(2)O_(3) while the catalyst prepared by first reduction and then loading procedure is defined as R-Pt/Al_(2)O_(3).The results show that L-Pt/Al_(2)O_(3) with the stronger interaction between Pt species and Al_(2)O_(3) exhibit smaller size of Pt nanoparticles and favorable thermal stability compared with R-Pt/Al_(2)O_(3).L-Pt/Al_(2)O_(3) is favor of the formation of more adsorbed oxygen species and more Pt^(2+)species,resulting in high catalytic activity for benzene and ethyl acetate oxidation.However,R-Pt/Al_(2)O_(3) catalysts with higher proportion of Pt^(0)/Pt^(2+)and bigger size of Pt particles exhibits higher catalytic activity for n-hexane oxidation.Pt particles in R-Pt/Al_(2)O_(3) were aggregated much more serious than that in L-Pt/Al_(2)O_(3) at the same calcination temperature.The Pt particles supported on Al_(2)O_(3) with~10 nm show the best catalytic activity for n-hexane oxidation.
基金Project supported by the National Key Research and Development Program of China (2022YFB3504200)。
文摘The catalytic behavior of a catalyst for chlorine-containing volatile organic compounds(CVOCs) oxidation largely depends on the synergistic interaction between the oxidizing and acidic sites.In the present work,two catalysts with different distributions of CeO_(2) on the inner and outer surfaces of 4.0Ce-USY-ex and 4.0Ce-USY-dp(USY zeolite) were prepared respectively by ion exchange and deposition methods,with a purpose of finding out how the location of the oxidation sites(CeO_(2)) influence its synergistic effect with the acidic sites of zeolite.The results show that 4.0Ce-USY-ex is much more active for catalytic degradation of 1,2-dichloroethane(DCE),while 4.0Ce-USY-dp catalyst exhibit higher catalytic degradation activity for other structured CVOCs(dichloromethane(DCM),trichloroethylene(TCE),chlorobenzene(CB)).CeO_(2) in 4.0Ce-USY-ex catalyst mainly disperses in the pore channels of USY zeolite,and there are many strong acid centers on the surface,which is conducive to the dechlorination conversion of CVOCs.However,CeO_(2) in 4.0Ce-USY-dp catalyst is mainly distributed on the outer surface of USY and has strong oxidation ability,which contributes to the deep oxidation of CVOCs.Moreover,the presence of a large number of strong acid centers on the catalyst surface of 4.0Ce-USY-ex catalysts leads to severe accumulation of surface carbon species and significantly decreases its stability towards DCE.However,a large number of active oxygen species on the surface of 4.0Ce-USY-dp and CeO_(2) catalysts are beneficial to the deep oxidation of DCE,reducing the formation of surface carbon and thus improving the stability of the catalyst.Thus,the influence of the location of the oxidation sites on its synergistic effect with the acidic sites was established in the present work,which could provide some new ideas for the rational design of CVOCs degradation catalyst with appropriate distribution of active sites.
基金supported by a grant from the National Key Research and Development Program of China (No. 2016YFC0204300)the Nature Science Foundation of China (No. 21477109)
文摘Different zeolites supported Pt catalystswithmicro-mesoporous structurewere prepared by organic base tetrapropylammonium hydroxide(TPAOH)treatment and their catalytic oxidation activity for various volatile organic compounds(VOCs)were evaluated.The results reveal that the synergistic effect between Pt nanoparticles and surface acid sites plays an important role in VOCs low-temperature removal.The small size and high dispersion of Pt nanoparticles on the surface of the zeolites would promote the catalytic oxidation of aromatics and alkanes over the Pt/zeolite catalysts,while strong acidity and abundant acid sites of catalysts are in favour of the oxidation of the VOCs containingNandOheteroatoms.In addition,it was found that Pt/ZSM-5 catalyst exhibits the highest oxidation activity for various VOCs low-temperature removal amongst all the catalysts due to the balance of both Pt dispersion and abundant acid sites in the catalyst.This comprehensive consideration should be very helpful when designing and preparing novel catalysts for the low-temperature removal of VOCs.
基金supported by the Key Program of Science Technology Department of Zhejiang Province (No.2018C03037)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (No.20KJB610005)+2 种基金the Natural Science Foundation of Jiangsu Province (Nos.BK20201037,BK20190705)Key Research and Development Program of Anhui Province (No.202104g01020006)the Scientific Research Fund of Nanjing Institute of Technology (Nos.YKJ2019111 and YKJ2019110)。
文摘Series of Cu-USY zeolite catalyst with different Cu loading content were synthesized through simple impregnation method.The obtained catalysts were subjected to selective catalytic reduction of NOxwith NH_(3)(NH_(3)-SCR) performance evaluation,structural/chemical characterizations such as X-ray diffraction (XRD),N2adsorption/desorption,H_(2)temperature-programmed reduction (H_(2)-TPR),NH_(3)temperature-programmed desorption (NH_(3)-TPD) as well as detailed in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments including CO adsorption,NH_(3)adsorption and NO+O_(2)in situ reactions.Results show that Cu-USY with proper Cu loading (in this work 5Cu-USY with5 wt.%Cu) could be promising candidates with highly efficient NH_(3)-SCR catalytic performance,relatively low byproduct formation and excellent hydrothermal stability,although its SO_(2)poisoning tolerability needs alleviation.Further characterizations reveal that such catalytic advantages can be attributed to both active cu species and surface acid centers evolution modulated by Cu loading.On one hand,Cu species in the super cages of zeolites increases with higher Cu content and being more conducive for NH_(3)-SCR reactivity.On the other hand,higher Cu loading leads to depletion of Br?nsted acid centers and simultaneous formation of abundant Lewis acid centers,which facilitates NH_(4)NO_(3)reduction via NH_(3)adsorbed on Lewis acid centers,thus improving SCR reactivity.However,Cu over-introduction leads to formation of surface highly dispersed CuOx,causing unfavorable NH_(3)oxidation and inferior N2selectivity.
基金Project supported by the Key Program of Science Technology Department of Zhejiang Province(2018C03037)the Natural Science Foundation of Jiangsu Province(BK20201037)+2 种基金Jiangsu Industry-University-Research Cooperation Project(BY2022101)the Scientific Research Fund of Nanjing Institute of Technology(YKJ2019111)Students'Science and Technology Innovation Fund of Nanjing Institute of Technology(TB202312034).
文摘A series of Pt-Pd bimetallic catalysts supported on CeO_(2)-ZrO_(2)-La_(2)O_(3) mixed oxides were synthesized through the conventional impregnation method.Three-way catalytic performance evaluations along with detailed physio-chemical characterizations were carried out to establish possible structure-activity correlations.Results show that on the one hand,different Pt/Pd ratios can strongly affect the TWC behaviors of Pt-Pd/CZL catalysts by modulating the synergistic effect between Pt and Pd.On the other hand,higher Pt/Pd ratio also favors better dispersion of precious metals.Such improved precious metals(PM)dispersion can promote the metal-support interaction and increase the surface oxygen vacancies concentration,thereby raising the dynamic oxygen storage/release capacity,improving the redox ability as well as enha ncing the thermal stability of the Pt-Pd/CZL catalyst.Moreover,the stro ng metal-support interaction can augment surface oxygen vacancy concentration,thereby benefiting low temperature CO and NO reaction via augmented NOxadsorption and nitrate conversion.
基金supported by the National Natural Science Foundation of China (21177110)
文摘A series of CrOx–CeO2/Ti-PILC(PILC is pillared interlayered clay)catalysts for n-butylamine oxidation were prepared using an impregnation method,and the structures,surface acidity distributions,and redox properties of the catalysts were characterized using X-ray diffraction,X-ray photoelectron spectroscopy,transmission electron microscopy,H2temperature-programmed reduction,and NH3temperature-programmed desorption.The results show that addition of an appropriate amount of CeO2enhances the interactions between Cr and Ce,and this increases the acid strength and mobility of active oxygen species on the catalyst.8CrCe(6:1)/Ti-PILC(12,20)exhibits the best catalytic performance and control of NOxin n-butylamine oxidation.
基金supported by a grant from the National Key Research and Development Program of China (No.2016YFC0204300)the Nature Science Foundation of China (No.21477109)。
文摘Micro-mesoporous ZSM-5 zeolites were obtained by the post-treatment of tetrahydroxy ammonium hydroxide(TPAOH) solution with different concentration.The hierarchical pore structure formed during the desilication process facilitates the dispersion of Pt nanoparticles and Pt/ZSM-5 catalysts exhibit rather high catalytic activity for the deep oxidation of various VOCs at low temperature.The catalyst treated with TPAOH of 0.1 mol/L(Pt/ZSM-5(0.1)) shows the lowest degradation temperature(T90%) of 128 and 142℃, respectively for benzene and n-hexane.Compared with the untreated Pt/ZSM-5 catalyst, the abundant mesopores, small Pt particle size and finely dispersed Pt contribute to the superior catalytic activity and stability of the Pt/ZSM-5 catalysts for VOCs removal.More importantly, the existence of H_(2)O in the feed gases hardly affected the activity of Pt/ZSM-5(0.1) catalyst at the low reaction temperature of 128℃, which is very important for VOCs low-temperature removal in the future practical applications.
基金Project supported by the Key Program of Science Technology Department of Zhejiang Province(2018C03037)
文摘Pd/Ce0.67Zr0.33O2 catalyst was pretreated in different atmosphere respectively, and characterized by CO chemical adsorption, XPS, HR-TEM, H2-TPR, Raman, OSC and in situ DRIFTS to investigate the effect of the structure properties of PdOx species on the catalytic performance for CO, HC and NOx elimination. The results show that Pd/CZ catalyst pretreated in air atmosphere has higher oxidation activity of HC due to having high Pd dispersion and strong interaction between PdOx and CZ support. Pd/CZ-H catalyst pretreated in reducing atmosphere exhibits better catalytic performance of NOx elimination because of having relatively big Pd particle size, more Pd species in metallic state and higher concentration of oxygen vacancies. While for the Pd/CZ-RG catalyst pretreated in reactant atmosphere, strong adsorption of HC species on the surface of catalysts would lead to a part of active sites being covered, which inhibits HC and NO conversions.
基金Project supported by the National Natural Science Foundation of China(21477109)National Key Research and Development Program of China(2016YFC0204300)。
文摘CeO2-TiO2 catalysts prepared by different methods were investigated for deep oxidation of 1,2-dichloroethane(DCE),as a typical representative of the chlorinated volatile organic compounds(CVOCs).Characterization analysis reveals that CeO2-TiO2 catalysts prepared by sol-gel and coprecipitation methods exhibit higher specific area,CeO2 and TiO2 particles are highly dispersed into each other and the reducibility and mobility of active oxygen species are obviously promoted due to the strong interaction between the two catalysts CeO2 and TiO2,resulting in higher catalytic activity for DCE oxidation to and less chlorinated byproduct.The high calcination temperature would lead to the formation of a new monoclinic phase Ce0.3Ti0.7O2 and sintering,which is the main reason for the catalytic activity for DCE oxidation markedly decreases.
基金Project supported by the National Key Research and Development Program of China(2016YFC0204300)the National Natural Science Foundation of China(21477109)。
文摘A series of transition metals(Fe,Co,Ni,Cu,Cr and Mn)-doped CeO_(2)-TiO_(2) catalysts were prepared by the sol-gel method and applied for the catalytic removal of 1,2-dichloroethane(DCE) as a model for chlorinated VOCs(CVOCs).The various characterization methods including X-ray diffraction(XRD),N_(2) adsorption-desorption,UV-Raman,NH_(3) temperature-programmed desorption(NH_(3)-TPD) and H_(2) temperature-programmed reduction(H_(2)-TPR) were utilized to investigate the physicochemical properties of the catalysts.The results show that doping Fe,Co,Ni or Mn can obviously promote the activity of CeO_(2)-TiO_(2) mixed oxides for DCE degradation,which is related to their improved texture properties,acid sites(especially for strong acidity) and low-temperature reducibility.Particularly,CeTi-Fe doped with moderate Fe exhibits excellent activity for 1,2-dichloroethane(DCE) degradation,giving a T_(90%) value as low as 250℃.More importantly,only trace chlorinated byproducts were produced during the low-temperature degradation of various CVOCs(dichloromethane(DCM),trichloroethylene(TCE) and chlorobenzene(CB)) over CeTi-Fe1/9 catalyst with high durability.
基金the Key Program of Science Technology Department of Zhejiang Province(No.2018C03037)the Scientific Research Fund of Nanjing Institute of Technology(No.YKJ2019111)。
文摘Series of Fe/Cu-SSZ-13 catalysts with different Fe loading content were synthesized by simple one-pot strategy.The obtained catalysts were subjected to selective catalytic reduction(SCR)of NO x with NH 3 and were characterized by various techniques.The results show that Fe 0.63/Cu 1.50-SSZ-13 catalyst with proper Fe content exhibits excellent catalytic activity with widest operation temperature window from 160 to 580℃,excellent hydrothermal stability as well as good resistance to sulfur poisoning when compared with Cu-SSZ-13,signifying its great potential for practical applications.Further characterizations reveal that the synthesized Fe/Cu-SSZ-13 catalysts present typical chabazite(CHA)structure with good crystallinity,while isolated Cu^2+and monomeric Fe 3+are revealed as the predominant copper and iron species.At low temperatures,isolated Cu^2+species act as primary active sites for SCR reaction,while monomeric Fe^3+species provide sufficient active sites for sustain the SCR activity at high temperature.Moreover,Fe over doping would lead to the damage of zeolite structure,destruction of isolated Cu^2+site,as well as the formation of highly oxidizing Fe2O3,thus causing deterioration of catalytic performances.
基金This work was supported by Key Program of Science Technology Department of Zhejiang Province(No.2018C03037).
文摘The physicochemical properties of Pt-,Pd-and Rh-loaded(Ce,Zr,La)O_(2)(shorted for CZL)catalysts before/after aging treatment were systematically characterized by various techniques to illustrate the relationship of the dynamic oxygen storage/release capacity and redox ability with their catalytic performances for HC,NO_(x)and CO conversions.Pt/CZL catalyst exhibits the optimum catalytic performance for HC and NO_(x)elimination,which mainly contribute to its excellent redox ability and dynamic oxygen storage/release capacity(DOSC)at lower temperature due to the stronger PM(precious metals)-support interaction.However,the worse stability of Pt-O-Ce species and volatile Pt oxides easily result in the dramatical decline in catalytic activity after aging.Pd/CZL shows higher catalytic activity for CO conversion by reason of more Olatt species as the active oxygen for CO oxidation reaction.Rh/CZL catalyst displays the widest dynamic operation window for NO_(x)elimination as a result of greater oxygen mobility at high temperature,and the ability to retain more Rh-O-Ce species after calcined at 1100℃effectively restrains sintering of active RhOx species,improving the thermal stability of Rh/CZL catalyst.
