ZnO/NiO/ZnAl2O4 mixed-metal oxides were successfully synthesized through a hydrotalcite-like precursor route, in which appropriate amounts of metal salts solutions were mixed to obtain a new series of ZnNiAl layered d...ZnO/NiO/ZnAl2O4 mixed-metal oxides were successfully synthesized through a hydrotalcite-like precursor route, in which appropriate amounts of metal salts solutions were mixed to obtain a new series of ZnNiAl layered double hydroxides（LDHs） as precursors, followed by calcination under different temperatures. The as-obtained samples were characterized by SEM, HRTEM, TEM, XRD, BET, TG-DTA, and UV-Vis spectra techniques. The photocatalytic activities of the samples were evaluated by degradation of methyl orange（MO） under the simulated sunlight irradiation. The effects of Zn/Ni/Al mole ratio and calcination temperature on the composition, morphology and photocatalytic activity of the samples were investigated in detail. The results indicated that compared with ZnNiAl-LDHs, the mixed-metal oxide showed superior photocatalytic performance for the degradation of MO. A maximum of 97.3% photocatalytic decoloration rate within 60 min was achieved from the LDH with the Zn/Ni/Al mole ratio of 2：1：1 and the calcination temperature of 500 ℃, which much exceeded that of Degussa P25 under the same conditions. The possible mechanism of photocatalytic degradation over ZnO/NiO/ZnAl2O4 was discussed.展开更多
The structure and catalytic desulfurization characteristics of CeO2-TiO2 mixed oxides were investigated by means ofX-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS） and catalytic activity tests. Acco...The structure and catalytic desulfurization characteristics of CeO2-TiO2 mixed oxides were investigated by means ofX-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS） and catalytic activity tests. According to the results, a CeO2-TiO2solid solution is formed when the mole ratio of cerium to titanium n（Ce）：n（Ti） is 5：5 or greater, and the most suitable n（Ce）：n（Ti） isdetermined as 7：3, over which the conversion rate of SO2 and the yield of sulfur at 500℃ reach 93% and 99%, respectively.According to the activity testing curve, Ce0.7Ti0.3O2 （n（Ce）：n（Ti）=7：3） without any pretreatment can be gradually activated by reagentgas after about 10 min, and reaches a steady activation status 60 min later. The XPS results of Ce0.7Ti0.3O2 after different time ofSO2＋CO reaction show that CeO2 is the active component that offers the redox couple Ce4＋/Ce3＋ and the labile oxygen vacancies, andTiO2 only functions as a catalyst structure stabilizer during the catalytic reaction process. After 48 h of catalytic reaction at 500℃,Ce0.7Ti0.3O2 still maintains a stable structure without being vulcanized, demonstrating its good anti-sulfur poisoning performance.展开更多
A series of Mn-Cu mixed oxide catalysts were prepared by precipitation method. The catalysts were characterized by N2 adsorp- tion-desorption, H2-TPR and XPS. When the loading ratio of manganese oxides to copper oxide...A series of Mn-Cu mixed oxide catalysts were prepared by precipitation method. The catalysts were characterized by N2 adsorp- tion-desorption, H2-TPR and XPS. When the loading ratio of manganese oxides to copper oxides was 8：2 or 7：3, the catalysts possessed better catalytic activity, and benzene was converted completely at 558 K. Results of H2-TPR showed that the loading of a small amount of copper oxides decreased the reduction temperature of catalysts. Results of XPS showed that the loading of a small amount of copper oxides increased the proportion of manganese and defective oxygen on the surface of catalysts, and stabilized manganese at higher oxidation state. And the catalyst with the loading ratio 7：3 was a little worse than 8：2, since the interaction between manganese oxides and copper oxides is too strong, copper oxides migrate to the surface of catalysts and manganese oxides in excess are immerged.展开更多
Samples of cerium-manganese oxides supported on modified glass-fiber with different Ce/Mn molar ratios （Ce-Mn/GF） were prepared by an impregnation method and tested for low-temperature （80 180 ℃） selective cataly...Samples of cerium-manganese oxides supported on modified glass-fiber with different Ce/Mn molar ratios （Ce-Mn/GF） were prepared by an impregnation method and tested for low-temperature （80 180 ℃） selective catalytic reduction （SCR） of NO with ammonia. This brand-new technology could remove NO and particles matter from coal-fired flue gas. The surface properties of the catalysts were examined by means of Bmnauer-Emmett-Teller （BET）, X-ray photoelectron spectroscopy （XPS）, X-ray diffraction （XRD）, and scanning electron microscopy （SEM）. The experimental results showed that the catalyst with a Ce/Mn molar ratio of 0.2 obtained high activity of 87.4% NO conversion at 150 ℃ under a high space velocity of 50000 h1. Deactivation poisoned by SO2 still occurred, but the Ce-Mn/GF（0.2） catalyst performed desirable tolerance to SO2 with decreasing 50% in 40 min and then maintaining at about 30% NO conversion. Characterization results indicated that the excellent low-temperature catalytic activity was related to the high specific surface area, pore structure, and amorphous phase.展开更多
CeO2-ZeO2 solid solutions are extensively used as oxygen storage promoters in the current automotive three-way catalysts. High thermal stability of the textural properties is one of the most important requirements for...CeO2-ZeO2 solid solutions are extensively used as oxygen storage promoters in the current automotive three-way catalysts. High thermal stability of the textural properties is one of the most important requirements for practical application since temperatures up to 1273 K are easily experienced by these materials under real working conditions. In the present paper, we investigated how hydrothermal treatments applied to cakes of doped and undoped ZrO2-rich CeO2-ZrO2 precursors might improve the thermal stability of the final CeO2-ZrO2 solid solution. A rationale was developed that allowed to correlate the morphology of the hydrothermaUy treated cake with the thermal stability at 1273 K of the final product, which did not depend on the composition of the mixed oxides.展开更多
The Ce-Fe-O mixed oxide with a ratio of Ce/Fe=7:3, which was prepared by coprecipitation method and employed as oxygen carrier, for direct partial oxidation of methane to syngas in the absence of gaseous oxygen was ex...The Ce-Fe-O mixed oxide with a ratio of Ce/Fe=7:3, which was prepared by coprecipitation method and employed as oxygen carrier, for direct partial oxidation of methane to syngas in the absence of gaseous oxygen was explored. The mixed oxide was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), and the catalytic performances were studied in a fixed-bed quartz reactor and a thermogravimetric reactor, respectively. Approximately 99.4% H2 se...展开更多
A series of supported Mn-Ce mixed oxide catalysts were prepared by the impregnation method and used for the oxidation of methane. The catalysts were characterized by N2 adsorption （BET）, X-ray diffraction （XRD）, l...A series of supported Mn-Ce mixed oxide catalysts were prepared by the impregnation method and used for the oxidation of methane. The catalysts were characterized by N2 adsorption （BET）, X-ray diffraction （XRD）, laser Raman spectrum （LRS）, and temperature programmed reduction （TPR） techniques. The XRD and LRS results confirmed the high dispersion of active components or formation of solid solution between manganese and cerium oxides in the bulk and on the surface of mixed oxide catalysts. The reducibility was remarkably promoted by the stronger synergistic interaction between the two oxides from H2-TPR measurements. As expected, all the experimental mixed oxide catalysts showed excellent activity for methane combustion at low temperature. Especially, for the catalyst with Mn-Ce ratio 3：7, methane conversion reached 92% at a temperature as low as 470 ℃.展开更多
A series of cerium zirconium mixed oxides were prepared by two co-precipitation methods using magnesium hydrogen carbonate （MHC） and mixed ammonia-ammonia hydrogen carbonate （AAHC） as precipitant respectively. The...A series of cerium zirconium mixed oxides were prepared by two co-precipitation methods using magnesium hydrogen carbonate （MHC） and mixed ammonia-ammonia hydrogen carbonate （AAHC） as precipitant respectively. The crystal structure, BET surface area and morphology of the produced cerium zirconium mixed oxides were characterized by X-ray diffraction （XRD）, Bru- mauer-Emmett-Teller （BET） and scanning electron microscopy （SEM） techniques. The reduction-oxidation behavior and oxygen storage capacity （OSC） performance were also studied by temperature programmed reduction （TPR） and oxygen pulse chemical adsorption methods. The XRD results demonstrated that the cerium zirconium mixed oxides obtained by both methods possessed struc ture of cubic solid solution phase. The fresh surface area calcinated at 600 ℃, aged surface area after 1000 ℃and OSC at 500 ℃ of cerium zirconium mixed oxides were determined to be 89.337, 34.784 ma/g, and 567 pmol O2/g for MHC method and 122.010, 46.307 m2/g, and 665 pmol O2/g for AAHC method, respectively.展开更多
Ce-modified Mn-Fe mixed-oxide catalysts were prepared by a citric acid sol-gel method and characterized by X-ray diffraction,Raman,N2 adsorption-desorption,infrared spectra H2 temperature-programmed reduction and ther...Ce-modified Mn-Fe mixed-oxide catalysts were prepared by a citric acid sol-gel method and characterized by X-ray diffraction,Raman,N2 adsorption-desorption,infrared spectra H2 temperature-programmed reduction and thermogravimetric analyses.Their catalytic properties were investigated in ozone(O3)decomposition reaction.Results show that the small amount of rare earth metal Ce added during Mn-Fe(FM) mixed-oxide synthesis greatly improves the catalytic performance in O3 decomposition.Among the prepared catalysts.the C0.04(FM)0.96 mixed-oxide catalyst exhibits the highest catalytic activity and stability.The O3 conversion over C0.04(FM)0.96 is 98% after 24 h reaction at 25℃ under dry condition,and that over FM decreases to 90% after 16 h reaction.At 0℃,the O3 conversion over C0.04(FM)0.96 is 95% after 7 h reaction under dry condition.and that over FM slows down to 70%.Under humid condition(RH 65%),the O3 conversion over C0.04(FM)0.96 is 63% after 6.5 h reaction at 25℃.while that over FM decreases to 55%.When Ce is doped into Mn-Fe mixed oxides,the small amount of Ce enters the crystal lattice of MnO2.and partial Fe is separated to form Fe2O3.This changes cause lattice distortion and increase defects and enable the as-synthesized Ce-Fe-Mn ternary mixed-oxide catalysts to acquire additional oxygen vacancies and increase their specific surface area,thereby increasing the number of reaction sites and enhancing the catalytic performance of the catalysts for O3 decomposition.展开更多
CeO2-ZrO2-MnOx mixed oxide series were prepared by sol-gel method. CO pulse and CO-O2 cycle measurements were carried out to examine the oxygen storage complete capacity （OSCC） and dynamic oxygen storage capacity （...CeO2-ZrO2-MnOx mixed oxide series were prepared by sol-gel method. CO pulse and CO-O2 cycle measurements were carried out to examine the oxygen storage complete capacity （OSCC） and dynamic oxygen storage capacity （OSC） of the samples. The doping method brought about strong interactions between manganese oxide and ceria, both in the bulk and on the surface. Only a small part of Mn cations are incorporated into the ceria lattice to form solid solutions and the remaining are left on the surface as finely dispersed Mn3O4. The OSC behaviors of the materials are influenced by the doping amount of Mn and the solubility of Mn in the CeO2 lattice. The OSC is more easily affected by available contents of oxygen storage components when the measurement frequency is low. Comparatively, the concentration of lattice defects, which affects the mobility of bulk oxygen, is the determining factor under high frequency.展开更多
Catalytic oxidation is regarded as one of the most promising strategies for volatile organic compounds(VOCs)purification.Mixed metal oxides(MMOs),after topological transformation using layered double hydroxides(LDHs)a...Catalytic oxidation is regarded as one of the most promising strategies for volatile organic compounds(VOCs)purification.Mixed metal oxides(MMOs),after topological transformation using layered double hydroxides(LDHs)as precursors,are extensively used as catalysts for VOCs oxidation due to their uniformity advantage.This review summarizes the developments in the LDH-derived VOCs heterogeneous catalytic oxidation over the last 10 years.Particularly,it addresses the VOCs abatement performance over MMO,noble metal/MMO,core-shell structured MMO,and integral MMO film catalysts originating from LDHs.Moreover,it highlights the water vapor effect and oxidation mechanism.This review indicates that LDH-based catalysts are a category of important VOCs oxidation materials.展开更多
A series of Ceo.sFeo.30Zr0.20O2 catalysts were prepared by different methods （co-precipitations method, citric acid sol-gel method, impregnation method, physical mixed method, and hydrotherrnal method） and character...A series of Ceo.sFeo.30Zr0.20O2 catalysts were prepared by different methods （co-precipitations method, citric acid sol-gel method, impregnation method, physical mixed method, and hydrotherrnal method） and characterized by X-ray diffraction （XRD）, Raman spectroscopy, Brunauer-Emmett-Teller （BET） and H2-TPR measurements. Potential of the catalysts in the soot oxidation was evaluated in a temperature-programmed oxidation （TPO） apparatus. The results showed that all the Fe3＋ and Zr4＋ were incor- porated into ceria lattice to form a pure Ce-Fe-Zr-O solid solution for the co-precipitation sample, but two kinds of Fe phases ex- isted in the Ce-Fe-Zr-O catalysts prepared by other methods： Fe3＋ incorporated into CeO2 lattice and dispersed Fe2O3 clusters. The free Fe2O3 clusters could improve the activity of catalysts for soot oxidation comparing with the pure Ce-Fe-Zr-O solid solution owing to the synergetic effect between free Fe2O3 and surface oxygen vacancies. In addition, the activity of catalysts strongly relied on the surface reducibility of free Fe2O3 particles. Holding both abundant free Fe2O3 particles and high oxygen vacancy concentration, the hydrothermal Ce0.5Fe0.3Zr0.202 catalyst presented the lowest Ti （251℃, ignition temperature of soot oxidation） and Tm （310 ℃, maximum oxidation rate temperature） for soot combustion （with tight-contact between soot and catalysts） among the five samples. Even after aging at 800 ℃ for 10 h, the Ti and Tm were still relatively low, at 273 and 361 ℃, respectively, indicating high catalytic stability.展开更多
Oriented attachment and Ostwald ripening are two aging mechanisms of precipitation particles which may result in differ- ent crystallization mechanism of precipitates during the aging process. In this work, the effect...Oriented attachment and Ostwald ripening are two aging mechanisms of precipitation particles which may result in differ- ent crystallization mechanism of precipitates during the aging process. In this work, the effects of different aging process on the structure and properties of cerium zirconium mixed oxides were investigated. The results indicated that the mixed structure of 11.48% CeO2 phase and 88.52% Ce0.26Zr0.62（LaPr）0.1202 solid solution phase were obtained under oriented attachment aging process. The rod-like CeO2 phase coexisted with spherical Ce0.26Zr0.62（LaPr）0.1202 solid solution phase, which improved the surface area （64 m2/g） and pore volume （0.32 mL/g） of cerium zirconium mixed oxides after 1000 ℃ 4 h thermal treatment. However, through controlling the aging process, the Ce0.35Zr0.55（LaPr）0.1002 solid solution with homogenous phase structure was generated by Ostwald ripening ag- ing process, exhibiting higher oxygen storage capacity （501 μmol O2/g） and H2 consumption per gram （1378.3 μmol H2/g）.展开更多
We rationally designed a high performance denitration(De-NOx) catalyst based on a micrometer-sized spherical Mn–Ce–Fe–Ti(CP-SD)catalyst for selective catalytic reduction(SCR). This was prepared by a co-precipitatio...We rationally designed a high performance denitration(De-NOx) catalyst based on a micrometer-sized spherical Mn–Ce–Fe–Ti(CP-SD)catalyst for selective catalytic reduction(SCR). This was prepared by a co-precipitation and spray drying(CP-SD) method. The catalyst was systematically characterized, and its morphological structure and surface properties were identified. Compare with conventional Mn–Ce–Fe–Ti(CP) catalysts, the Mn–Ce–Fe–Ti(CP-SD) catalyst had superior surface-adsorbed oxygen leading to enhanced 'fast NH3-SCR' reaction. The asobtained Mn–Ce–Fe–Ti(CP-SD) catalyst offered excellent NO conversion and N2 selectivity of 100.0% and 84.8% at 250℃, respectively, with a gas hourly space velocity(GHSV) of 40,000 h-1. The porous micro-spherical structure provides a larger surface area and more active sites to adsorb and activate the reaction gases. In addition, the uniform distribution and strong interaction of manganese, iron, cerium, and titanium oxide species improved H2O and SO2 resistance. The results showed that the Mn–Ce–Fe–Ti(CP-SD) catalyst could be used prospectively as a denitration(De-NOx) catalyst.展开更多
High electroactivity and good mechanical robustness of electrode materials are essential to deliver excellent elec-trochemical energy storage performance.Herein,metal–organic frameworks(MOF)derived mixed metal oxides...High electroactivity and good mechanical robustness of electrode materials are essential to deliver excellent elec-trochemical energy storage performance.Herein,metal–organic frameworks(MOF)derived mixed metal oxides(MMO,ZnO@NiO and Co_(3)O_(4)@NiO)are prepared by a two-step annealing process in air.Zinc-based MOF(ZIF-8)and cobalt-based MOF(ZIF-67)were employed,respec-tively,as hard templates for the chemical encapsulation of Ni(OH)_(2)nanostructures by hydrothermal synthesis.展开更多
MgAl and MgMAl oxides（M = Co,Ni and Cu） with a Mg：M：Al molar ratio = 4：1：1 were synthesized from the calcination of their corresponding layered double hydroxide（LDHs） precursors.Their catalytic activities were...MgAl and MgMAl oxides（M = Co,Ni and Cu） with a Mg：M：Al molar ratio = 4：1：1 were synthesized from the calcination of their corresponding layered double hydroxide（LDHs） precursors.Their catalytic activities were examined for the oxidation of ethylbenzene using tert-butylhydroperoxide（TBHP） as an oxidant.The oxidized product was mainly acetophenone.The catalytic activities were in the order of MgCuAlMgNiAl～NiAl～MgCoAl～CoAlCuAlMgAl oxides.Reusability studies show that the catalysts are stable under the reaction conditions.展开更多
CeO_2-ZrO_2 mixed oxides are widely used in the three-way catalysts due to their unique reversible oxygen storage and release capacity. Large surface area, high oxygen storage capacity and good thermal stability of ce...CeO_2-ZrO_2 mixed oxides are widely used in the three-way catalysts due to their unique reversible oxygen storage and release capacity. Large surface area, high oxygen storage capacity and good thermal stability of cerium zirconium mixed oxides are the key properties for the automotive catalysts so as to meet the strict emission regulations. In this work, alumina modified CeZrLaNd mixed oxides were prepared by a co-precipitation method. The effects of moisture in precursor and inert N2 atmosphere during calcinations on the structure and properties were investigated by Brunauer-Emmett-Teller(BET) surface area measurements, X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), hydrogen temperature-programmed reduction(H_2-TPR), oxygen storage capacity(OSC), Raman spectroscopy, and X-ray photoelectron spectroscopy(XPS). The results show that the moisture in precursor during calcinations increases the crystal grain size of the cerium zirconium mixed oxides, improving the thermal stability. And the aged surface area of sample after being calcined at1000 ℃ for 4 h reaches 68.8 m^2/g(5.7% increase compared with the common sample). The inert N2 atmosphere endows a great pore-enlarging effect, which leads to high fresh surface area of 148.9 m2/g(13.5% increase compared with the common sample) and big pore volume of 0.5705 mL/g. The redox and oxygen storage capacity are also improved by inert N2 atmosphere with high OSC value of 241.06μmolO_2/g(41.3% increase compared with the common calcination), due to the abundant formation of the crystal defects and oxygen vacancies.展开更多
Cu-Mn, Cu-Mn-Ce, and Cu-Ce mixed-oxide catalysts were prepared by a citric acid sol-gel method and then characterized by XRD, BET, H_2-TPR and XPS analyses. Their catalytic properties were investigated in the toluene ...Cu-Mn, Cu-Mn-Ce, and Cu-Ce mixed-oxide catalysts were prepared by a citric acid sol-gel method and then characterized by XRD, BET, H_2-TPR and XPS analyses. Their catalytic properties were investigated in the toluene combustion reaction. Results showed that the Cu-Mn-Ce ternary mixed-oxide catalyst with 1：2：4 mole ratios had the highest catalytic activity, and 99% toluene conversion was achieved at temperatures below 220°C. In the Cu-Mn-Ce catalyst, a portion of Cu and Mn species entered into the Ce O2 fluorite lattice, which led to the formation of a ceria-based solid solution. Excess Cu and Mn oxides existed on the surface of the ceria-based solid solution. The coexistence of Cu-Mn mixed oxides and the ceria-based solid solution resulted in a better synergetic interaction than the Cu-Mn and Cu-Ce catalysts, which promoted catalyst reducibility, increased oxygen mobility, and enhanced the formation of abundant active oxygen species.展开更多
A series of TiO 2-XSiO 2[X denotes the molar fraction(%) of silica in the mixed oxides] with different \{n(Ti)\}/n(Si) ratios was prepared with ammonia water as a hydrolysis catalyst. The photocatalysts prepared wer...A series of TiO 2-XSiO 2[X denotes the molar fraction(%) of silica in the mixed oxides] with different \{n(Ti)\}/n(Si) ratios was prepared with ammonia water as a hydrolysis catalyst. The photocatalysts prepared were characterized by XRD, thermal analysis, FTIR, UV-Vis and SPS. The characterization results of FTIR and UV-Vis spectra show that Ti atoms were gradually changed from octahedral coordination to tetrahedral coordination with the addition of silica, which is not beneficial for obtaining strong Brnsted acidity and higher photocatalytic activity. The photocatalytic activity experiments, which were conducted by using heptane(or SO 2) as the model reactant, showed that TiO 2-SiO 2 containing a suitable amount of silica can exhibit much higher photocatalytic activity than pure TiO 2. The enhanced photocatalytic activity can be attributed to three following factors: (1) smaller crystalline size; (2) higher thermal stability; (3) the new strong Brnsted acidity.展开更多
We employed modified substrates as outer heterogeneous catalysts to reduce the soot originating from the incomplete diesel combustion.Here,we proposed that ceria(CeO2)-based catalysts could lower the temperature at wh...We employed modified substrates as outer heterogeneous catalysts to reduce the soot originating from the incomplete diesel combustion.Here,we proposed that ceria(CeO2)-based catalysts could lower the temperature at which soot combustion occurred from 610 oC to values included in the operation range of diesel exhausts(270–400 oC).Here,we used the sol-gel method to synthesize catalysts based on mixed oxides(ZnO:CeO2)deposited on cordierite substrates,and modified by ruthenium nanoparticles.The presence of ZnO in these mixed oxides produced defects associated with oxygen vacancies,improving thermal stability,redox potential,sulfur resistance,and oxygen storage.We evaluated the morphological and structural properties of the material by X-ray diffraction(XRD),Brumauer-emmett-teller method(BET),temperature programmed reduction(H2-TPR),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).We investigated how the addition of Ru(0.5 wt.%)affected the catalytic activity of ZnO:CeO2 in terms of soot combustion.Thermogravimetric analysis(TG/DTA)revealed that presence of the catalyst decreased the soot combustion temperature by 250 oC,indicating that the oxygen species arose at low temperatures,which was the main reason for the high reactivity of the oxidation reactions.Comparative analysis of soot emission by diffuse reflectance spectroscopy(DRS)showed that the catalyst containing Ru on the mixed oxide-impregnated cordierite samples efficiently oxidized soot in a diesel stationary motor:soot emission decreased 80%.展开更多
基金Project(21306041)supported by the National Natural Science Young Foundation of ChinaProject(21271071)supported by the National Natural Science Foundation of ChinaProject(15A076)supported by the Scientific Research Foundation of Hunan Provincial Education Department of China
文摘ZnO/NiO/ZnAl2O4 mixed-metal oxides were successfully synthesized through a hydrotalcite-like precursor route, in which appropriate amounts of metal salts solutions were mixed to obtain a new series of ZnNiAl layered double hydroxides（LDHs） as precursors, followed by calcination under different temperatures. The as-obtained samples were characterized by SEM, HRTEM, TEM, XRD, BET, TG-DTA, and UV-Vis spectra techniques. The photocatalytic activities of the samples were evaluated by degradation of methyl orange（MO） under the simulated sunlight irradiation. The effects of Zn/Ni/Al mole ratio and calcination temperature on the composition, morphology and photocatalytic activity of the samples were investigated in detail. The results indicated that compared with ZnNiAl-LDHs, the mixed-metal oxide showed superior photocatalytic performance for the degradation of MO. A maximum of 97.3% photocatalytic decoloration rate within 60 min was achieved from the LDH with the Zn/Ni/Al mole ratio of 2：1：1 and the calcination temperature of 500 ℃, which much exceeded that of Degussa P25 under the same conditions. The possible mechanism of photocatalytic degradation over ZnO/NiO/ZnAl2O4 was discussed.
文摘The structure and catalytic desulfurization characteristics of CeO2-TiO2 mixed oxides were investigated by means ofX-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS） and catalytic activity tests. According to the results, a CeO2-TiO2solid solution is formed when the mole ratio of cerium to titanium n（Ce）：n（Ti） is 5：5 or greater, and the most suitable n（Ce）：n（Ti） isdetermined as 7：3, over which the conversion rate of SO2 and the yield of sulfur at 500℃ reach 93% and 99%, respectively.According to the activity testing curve, Ce0.7Ti0.3O2 （n（Ce）：n（Ti）=7：3） without any pretreatment can be gradually activated by reagentgas after about 10 min, and reaches a steady activation status 60 min later. The XPS results of Ce0.7Ti0.3O2 after different time ofSO2＋CO reaction show that CeO2 is the active component that offers the redox couple Ce4＋/Ce3＋ and the labile oxygen vacancies, andTiO2 only functions as a catalyst structure stabilizer during the catalytic reaction process. After 48 h of catalytic reaction at 500℃,Ce0.7Ti0.3O2 still maintains a stable structure without being vulcanized, demonstrating its good anti-sulfur poisoning performance.
基金Project supported by National Natural Science Foundation of China (20773090)the National High Technology Research and Development Program of China (863 Program, 2006AA06Z347)the Youth Fund of Sichuan University (2008119)
文摘A series of Mn-Cu mixed oxide catalysts were prepared by precipitation method. The catalysts were characterized by N2 adsorp- tion-desorption, H2-TPR and XPS. When the loading ratio of manganese oxides to copper oxides was 8：2 or 7：3, the catalysts possessed better catalytic activity, and benzene was converted completely at 558 K. Results of H2-TPR showed that the loading of a small amount of copper oxides decreased the reduction temperature of catalysts. Results of XPS showed that the loading of a small amount of copper oxides increased the proportion of manganese and defective oxygen on the surface of catalysts, and stabilized manganese at higher oxidation state. And the catalyst with the loading ratio 7：3 was a little worse than 8：2, since the interaction between manganese oxides and copper oxides is too strong, copper oxides migrate to the surface of catalysts and manganese oxides in excess are immerged.
基金Project supported by the National High Technology Research and Development Program of China(863 Program)(2008AA05Z305)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry(201109)+2 种基金the Master Dissertation Innovation Funded Projects(EG2013015)the Fundamental Research Funds for the Central Universities Special Fund Project(11D11315)Program of Shanghai Subject Chief Scientist(14XD1424700)
文摘Samples of cerium-manganese oxides supported on modified glass-fiber with different Ce/Mn molar ratios （Ce-Mn/GF） were prepared by an impregnation method and tested for low-temperature （80 180 ℃） selective catalytic reduction （SCR） of NO with ammonia. This brand-new technology could remove NO and particles matter from coal-fired flue gas. The surface properties of the catalysts were examined by means of Bmnauer-Emmett-Teller （BET）, X-ray photoelectron spectroscopy （XPS）, X-ray diffraction （XRD）, and scanning electron microscopy （SEM）. The experimental results showed that the catalyst with a Ce/Mn molar ratio of 0.2 obtained high activity of 87.4% NO conversion at 150 ℃ under a high space velocity of 50000 h1. Deactivation poisoned by SO2 still occurred, but the Ce-Mn/GF（0.2） catalyst performed desirable tolerance to SO2 with decreasing 50% in 40 min and then maintaining at about 30% NO conversion. Characterization results indicated that the excellent low-temperature catalytic activity was related to the high specific surface area, pore structure, and amorphous phase.
基金PRIN 2006, "Caratterizzazione spettroscopica e morfologica di Me-POSS eterogeneizzati", MEL Chemicals
文摘CeO2-ZeO2 solid solutions are extensively used as oxygen storage promoters in the current automotive three-way catalysts. High thermal stability of the textural properties is one of the most important requirements for practical application since temperatures up to 1273 K are easily experienced by these materials under real working conditions. In the present paper, we investigated how hydrothermal treatments applied to cakes of doped and undoped ZrO2-rich CeO2-ZrO2 precursors might improve the thermal stability of the final CeO2-ZrO2 solid solution. A rationale was developed that allowed to correlate the morphology of the hydrothermaUy treated cake with the thermal stability at 1273 K of the final product, which did not depend on the composition of the mixed oxides.
基金Project supported by the National Natural Science Foundation of China (50574046, 50774038)the Research Fund for the Doctoral Program of Higher Education of China (20095314120005)+1 种基金the Natural Science Foundation of Yunnan Province (2008E030M) the Foundation of Kun-ming University of Science and Technology (KKZ3200927010)
文摘The Ce-Fe-O mixed oxide with a ratio of Ce/Fe=7:3, which was prepared by coprecipitation method and employed as oxygen carrier, for direct partial oxidation of methane to syngas in the absence of gaseous oxygen was explored. The mixed oxide was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), and the catalytic performances were studied in a fixed-bed quartz reactor and a thermogravimetric reactor, respectively. Approximately 99.4% H2 se...
基金supported by the New Century Excellent Talent Project of China (NCET-05-0783)
文摘A series of supported Mn-Ce mixed oxide catalysts were prepared by the impregnation method and used for the oxidation of methane. The catalysts were characterized by N2 adsorption （BET）, X-ray diffraction （XRD）, laser Raman spectrum （LRS）, and temperature programmed reduction （TPR） techniques. The XRD and LRS results confirmed the high dispersion of active components or formation of solid solution between manganese and cerium oxides in the bulk and on the surface of mixed oxide catalysts. The reducibility was remarkably promoted by the stronger synergistic interaction between the two oxides from H2-TPR measurements. As expected, all the experimental mixed oxide catalysts showed excellent activity for methane combustion at low temperature. Especially, for the catalyst with Mn-Ce ratio 3：7, methane conversion reached 92% at a temperature as low as 470 ℃.
基金Project supported by Twelfth Five-Year National Science and Technology Pillar Program (2012BAE01B02)Eleventh Five-Year National 863 Program (2010AA03A405)
文摘A series of cerium zirconium mixed oxides were prepared by two co-precipitation methods using magnesium hydrogen carbonate （MHC） and mixed ammonia-ammonia hydrogen carbonate （AAHC） as precipitant respectively. The crystal structure, BET surface area and morphology of the produced cerium zirconium mixed oxides were characterized by X-ray diffraction （XRD）, Bru- mauer-Emmett-Teller （BET） and scanning electron microscopy （SEM） techniques. The reduction-oxidation behavior and oxygen storage capacity （OSC） performance were also studied by temperature programmed reduction （TPR） and oxygen pulse chemical adsorption methods. The XRD results demonstrated that the cerium zirconium mixed oxides obtained by both methods possessed struc ture of cubic solid solution phase. The fresh surface area calcinated at 600 ℃, aged surface area after 1000 ℃and OSC at 500 ℃ of cerium zirconium mixed oxides were determined to be 89.337, 34.784 ma/g, and 567 pmol O2/g for MHC method and 122.010, 46.307 m2/g, and 665 pmol O2/g for AAHC method, respectively.
基金supported by the National Natural Science Foundation of China(21506194,21676255)the Natural Science Foundation of Zhejiang Province(Y16B070011)the Commission of Science and Technology of Zhejiang province(2017C03007,2017C33106).
文摘Ce-modified Mn-Fe mixed-oxide catalysts were prepared by a citric acid sol-gel method and characterized by X-ray diffraction,Raman,N2 adsorption-desorption,infrared spectra H2 temperature-programmed reduction and thermogravimetric analyses.Their catalytic properties were investigated in ozone(O3)decomposition reaction.Results show that the small amount of rare earth metal Ce added during Mn-Fe(FM) mixed-oxide synthesis greatly improves the catalytic performance in O3 decomposition.Among the prepared catalysts.the C0.04(FM)0.96 mixed-oxide catalyst exhibits the highest catalytic activity and stability.The O3 conversion over C0.04(FM)0.96 is 98% after 24 h reaction at 25℃ under dry condition,and that over FM decreases to 90% after 16 h reaction.At 0℃,the O3 conversion over C0.04(FM)0.96 is 95% after 7 h reaction under dry condition.and that over FM slows down to 70%.Under humid condition(RH 65%),the O3 conversion over C0.04(FM)0.96 is 63% after 6.5 h reaction at 25℃.while that over FM decreases to 55%.When Ce is doped into Mn-Fe mixed oxides,the small amount of Ce enters the crystal lattice of MnO2.and partial Fe is separated to form Fe2O3.This changes cause lattice distortion and increase defects and enable the as-synthesized Ce-Fe-Mn ternary mixed-oxide catalysts to acquire additional oxygen vacancies and increase their specific surface area,thereby increasing the number of reaction sites and enhancing the catalytic performance of the catalysts for O3 decomposition.
基金Project supported by the National "973"Project (2004CB719503)Project supported by the National Natural ScienceFoundation of China (50502023)
文摘CeO2-ZrO2-MnOx mixed oxide series were prepared by sol-gel method. CO pulse and CO-O2 cycle measurements were carried out to examine the oxygen storage complete capacity （OSCC） and dynamic oxygen storage capacity （OSC） of the samples. The doping method brought about strong interactions between manganese oxide and ceria, both in the bulk and on the surface. Only a small part of Mn cations are incorporated into the ceria lattice to form solid solutions and the remaining are left on the surface as finely dispersed Mn3O4. The OSC behaviors of the materials are influenced by the doping amount of Mn and the solubility of Mn in the CeO2 lattice. The OSC is more easily affected by available contents of oxygen storage components when the measurement frequency is low. Comparatively, the concentration of lattice defects, which affects the mobility of bulk oxygen, is the determining factor under high frequency.
基金supported by the National Key R&D Program of China(2017YFC0211503,2016YFC0207100)the Strategic Priority Research Program(A)of the Chinese Academy of Sciences(XDA23030300)+2 种基金the National Natural Science Foundation of China(21401200,51672273)the Open Research Fund of State Key Laboratory of Multi-phase Complex Systems(MPCS-2017-D-06)the Young Talent Project of the Center for Excellence in Regional Atmospheric Environment,CAS(CERAE201805)~~
文摘Catalytic oxidation is regarded as one of the most promising strategies for volatile organic compounds(VOCs)purification.Mixed metal oxides(MMOs),after topological transformation using layered double hydroxides(LDHs)as precursors,are extensively used as catalysts for VOCs oxidation due to their uniformity advantage.This review summarizes the developments in the LDH-derived VOCs heterogeneous catalytic oxidation over the last 10 years.Particularly,it addresses the VOCs abatement performance over MMO,noble metal/MMO,core-shell structured MMO,and integral MMO film catalysts originating from LDHs.Moreover,it highlights the water vapor effect and oxidation mechanism.This review indicates that LDH-based catalysts are a category of important VOCs oxidation materials.
基金Project supported by National Natural Science Foundation of China(51374004,51204083,51174105,51104074)Natural Science Foundation of Yunnan Province(2010ZC018)
文摘A series of Ceo.sFeo.30Zr0.20O2 catalysts were prepared by different methods （co-precipitations method, citric acid sol-gel method, impregnation method, physical mixed method, and hydrotherrnal method） and characterized by X-ray diffraction （XRD）, Raman spectroscopy, Brunauer-Emmett-Teller （BET） and H2-TPR measurements. Potential of the catalysts in the soot oxidation was evaluated in a temperature-programmed oxidation （TPO） apparatus. The results showed that all the Fe3＋ and Zr4＋ were incor- porated into ceria lattice to form a pure Ce-Fe-Zr-O solid solution for the co-precipitation sample, but two kinds of Fe phases ex- isted in the Ce-Fe-Zr-O catalysts prepared by other methods： Fe3＋ incorporated into CeO2 lattice and dispersed Fe2O3 clusters. The free Fe2O3 clusters could improve the activity of catalysts for soot oxidation comparing with the pure Ce-Fe-Zr-O solid solution owing to the synergetic effect between free Fe2O3 and surface oxygen vacancies. In addition, the activity of catalysts strongly relied on the surface reducibility of free Fe2O3 particles. Holding both abundant free Fe2O3 particles and high oxygen vacancy concentration, the hydrothermal Ce0.5Fe0.3Zr0.202 catalyst presented the lowest Ti （251℃, ignition temperature of soot oxidation） and Tm （310 ℃, maximum oxidation rate temperature） for soot combustion （with tight-contact between soot and catalysts） among the five samples. Even after aging at 800 ℃ for 10 h, the Ti and Tm were still relatively low, at 273 and 361 ℃, respectively, indicating high catalytic stability.
基金Project supported by the Twelfth Five-Year National Science and Technology Pillar Program(2012BAE01B02,2012BAB10B11)
文摘Oriented attachment and Ostwald ripening are two aging mechanisms of precipitation particles which may result in differ- ent crystallization mechanism of precipitates during the aging process. In this work, the effects of different aging process on the structure and properties of cerium zirconium mixed oxides were investigated. The results indicated that the mixed structure of 11.48% CeO2 phase and 88.52% Ce0.26Zr0.62（LaPr）0.1202 solid solution phase were obtained under oriented attachment aging process. The rod-like CeO2 phase coexisted with spherical Ce0.26Zr0.62（LaPr）0.1202 solid solution phase, which improved the surface area （64 m2/g） and pore volume （0.32 mL/g） of cerium zirconium mixed oxides after 1000 ℃ 4 h thermal treatment. However, through controlling the aging process, the Ce0.35Zr0.55（LaPr）0.1002 solid solution with homogenous phase structure was generated by Ostwald ripening ag- ing process, exhibiting higher oxygen storage capacity （501 μmol O2/g） and H2 consumption per gram （1378.3 μmol H2/g）.
基金supported by Major Scientific and Technological Project of Bingtuan (No.2018AA002)the Program for Changjiang Scholars and Innovative Research Team in University (No. IRT_15R46)
文摘We rationally designed a high performance denitration(De-NOx) catalyst based on a micrometer-sized spherical Mn–Ce–Fe–Ti(CP-SD)catalyst for selective catalytic reduction(SCR). This was prepared by a co-precipitation and spray drying(CP-SD) method. The catalyst was systematically characterized, and its morphological structure and surface properties were identified. Compare with conventional Mn–Ce–Fe–Ti(CP) catalysts, the Mn–Ce–Fe–Ti(CP-SD) catalyst had superior surface-adsorbed oxygen leading to enhanced 'fast NH3-SCR' reaction. The asobtained Mn–Ce–Fe–Ti(CP-SD) catalyst offered excellent NO conversion and N2 selectivity of 100.0% and 84.8% at 250℃, respectively, with a gas hourly space velocity(GHSV) of 40,000 h-1. The porous micro-spherical structure provides a larger surface area and more active sites to adsorb and activate the reaction gases. In addition, the uniform distribution and strong interaction of manganese, iron, cerium, and titanium oxide species improved H2O and SO2 resistance. The results showed that the Mn–Ce–Fe–Ti(CP-SD) catalyst could be used prospectively as a denitration(De-NOx) catalyst.
基金financially supported by the Start-Up Grant of Central South University (No. 202045001)the Innovation-Driven Project of Central South University (No. 2019CX028)Huxiang Assembly Program for High-level Talents (No. 2018RS3018)。
文摘High electroactivity and good mechanical robustness of electrode materials are essential to deliver excellent elec-trochemical energy storage performance.Herein,metal–organic frameworks(MOF)derived mixed metal oxides(MMO,ZnO@NiO and Co_(3)O_(4)@NiO)are prepared by a two-step annealing process in air.Zinc-based MOF(ZIF-8)and cobalt-based MOF(ZIF-67)were employed,respec-tively,as hard templates for the chemical encapsulation of Ni(OH)_(2)nanostructures by hydrothermal synthesis.
基金support from the research grant"The 90th Anniversary of Chulalongkorn University Fund" from the Graduate School,Chulalongkorn University
文摘MgAl and MgMAl oxides（M = Co,Ni and Cu） with a Mg：M：Al molar ratio = 4：1：1 were synthesized from the calcination of their corresponding layered double hydroxide（LDHs） precursors.Their catalytic activities were examined for the oxidation of ethylbenzene using tert-butylhydroperoxide（TBHP） as an oxidant.The oxidized product was mainly acetophenone.The catalytic activities were in the order of MgCuAlMgNiAl～NiAl～MgCoAl～CoAlCuAlMgAl oxides.Reusability studies show that the catalysts are stable under the reaction conditions.
基金Project supported by the China National Key Research and Development Program(2017YFC0211002)
文摘CeO_2-ZrO_2 mixed oxides are widely used in the three-way catalysts due to their unique reversible oxygen storage and release capacity. Large surface area, high oxygen storage capacity and good thermal stability of cerium zirconium mixed oxides are the key properties for the automotive catalysts so as to meet the strict emission regulations. In this work, alumina modified CeZrLaNd mixed oxides were prepared by a co-precipitation method. The effects of moisture in precursor and inert N2 atmosphere during calcinations on the structure and properties were investigated by Brunauer-Emmett-Teller(BET) surface area measurements, X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), hydrogen temperature-programmed reduction(H_2-TPR), oxygen storage capacity(OSC), Raman spectroscopy, and X-ray photoelectron spectroscopy(XPS). The results show that the moisture in precursor during calcinations increases the crystal grain size of the cerium zirconium mixed oxides, improving the thermal stability. And the aged surface area of sample after being calcined at1000 ℃ for 4 h reaches 68.8 m^2/g(5.7% increase compared with the common sample). The inert N2 atmosphere endows a great pore-enlarging effect, which leads to high fresh surface area of 148.9 m2/g(13.5% increase compared with the common sample) and big pore volume of 0.5705 mL/g. The redox and oxygen storage capacity are also improved by inert N2 atmosphere with high OSC value of 241.06μmolO_2/g(41.3% increase compared with the common calcination), due to the abundant formation of the crystal defects and oxygen vacancies.
基金the financial support from the Natural Science Foundation of China (No. 21107096)Zhejiang Provincial Natural Science Foundation of China (No. Y14E080008)+1 种基金the Commission of Science and Technology of Zhejiang province (No. 2013C03021)the Specialized Research Fund for the Doctoral Program of Higher Education (No. 20133317110004)
文摘Cu-Mn, Cu-Mn-Ce, and Cu-Ce mixed-oxide catalysts were prepared by a citric acid sol-gel method and then characterized by XRD, BET, H_2-TPR and XPS analyses. Their catalytic properties were investigated in the toluene combustion reaction. Results showed that the Cu-Mn-Ce ternary mixed-oxide catalyst with 1：2：4 mole ratios had the highest catalytic activity, and 99% toluene conversion was achieved at temperatures below 220°C. In the Cu-Mn-Ce catalyst, a portion of Cu and Mn species entered into the Ce O2 fluorite lattice, which led to the formation of a ceria-based solid solution. Excess Cu and Mn oxides existed on the surface of the ceria-based solid solution. The coexistence of Cu-Mn mixed oxides and the ceria-based solid solution resulted in a better synergetic interaction than the Cu-Mn and Cu-Ce catalysts, which promoted catalyst reducibility, increased oxygen mobility, and enhanced the formation of abundant active oxygen species.
基金Supported by the National Natural Science Foundation of China(No.2 0 2 770 15 )
文摘A series of TiO 2-XSiO 2[X denotes the molar fraction(%) of silica in the mixed oxides] with different \{n(Ti)\}/n(Si) ratios was prepared with ammonia water as a hydrolysis catalyst. The photocatalysts prepared were characterized by XRD, thermal analysis, FTIR, UV-Vis and SPS. The characterization results of FTIR and UV-Vis spectra show that Ti atoms were gradually changed from octahedral coordination to tetrahedral coordination with the addition of silica, which is not beneficial for obtaining strong Brnsted acidity and higher photocatalytic activity. The photocatalytic activity experiments, which were conducted by using heptane(or SO 2) as the model reactant, showed that TiO 2-SiO 2 containing a suitable amount of silica can exhibit much higher photocatalytic activity than pure TiO 2. The enhanced photocatalytic activity can be attributed to three following factors: (1) smaller crystalline size; (2) higher thermal stability; (3) the new strong Brnsted acidity.
基金Project supported by the National Council for Scientific and Technological Development(CNPq)(105477/2012-5)
文摘We employed modified substrates as outer heterogeneous catalysts to reduce the soot originating from the incomplete diesel combustion.Here,we proposed that ceria(CeO2)-based catalysts could lower the temperature at which soot combustion occurred from 610 oC to values included in the operation range of diesel exhausts(270–400 oC).Here,we used the sol-gel method to synthesize catalysts based on mixed oxides(ZnO:CeO2)deposited on cordierite substrates,and modified by ruthenium nanoparticles.The presence of ZnO in these mixed oxides produced defects associated with oxygen vacancies,improving thermal stability,redox potential,sulfur resistance,and oxygen storage.We evaluated the morphological and structural properties of the material by X-ray diffraction(XRD),Brumauer-emmett-teller method(BET),temperature programmed reduction(H2-TPR),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).We investigated how the addition of Ru(0.5 wt.%)affected the catalytic activity of ZnO:CeO2 in terms of soot combustion.Thermogravimetric analysis(TG/DTA)revealed that presence of the catalyst decreased the soot combustion temperature by 250 oC,indicating that the oxygen species arose at low temperatures,which was the main reason for the high reactivity of the oxidation reactions.Comparative analysis of soot emission by diffuse reflectance spectroscopy(DRS)showed that the catalyst containing Ru on the mixed oxide-impregnated cordierite samples efficiently oxidized soot in a diesel stationary motor:soot emission decreased 80%.
