Application of MnCeOx supported on palygorskite and Al(OH)3 for HCHO oxidation: Catalytic performance and stability

Indoor formaldehyde (HCHO) is an important air pollutant, while it is very difficult to reduce HCHO to low-level (e.g. <0.08 mg/m³). Catalytic oxidation at ambient temperature has been increasingly recognized as one of the important methods to mitigate HCHO pollution due to its good effectiveness, stability, and recyclability. To further improve the activity of catalytic oxidation, this study develops the integrated MnCeO_x catalysts supported on palygorskite (Pal) and aluminium hydroxide (Al(OH)₃). Our results indicate that the synergistic interaction in MnCeO_x through the oxygen transfer mechanism from the oxygen reservoir CeO₂ to MnO_x significantly improves the activity. Pal, Al(OH)₃, etc. were applied as the supports with a focus on their dispersion, microstructure, strength, and relative role. MnCeO_x can be anchored on the surface of Al(OH)₃ with high dispersion. With the integrated catalyst, HCHO concentration decreases from 1.012 to 0.086 mg/m³ within 48 h. Higher oxidation activity of MnCeO_x powder may be ascribed to the amount of active components on the surface. The incorporation of ZSM–5 and activated carbon can improve the adsorption of HCHO, and all integrated catalysts exhibit stronger activities, with HCHO being degraded to the level lower than 0.08 mg/m³. Meantime, the samples exhibit good stability and strength (20.2 MPa) without obvious decrease over five consecutive stability experiments.     

Catalytic wet oxidation of N,N-dimethyl formamide over ruthenium supported on CeO2 and Ce0.7Zr0.3O2 catalysts

A series of Ru supported on CeO₂ and Ce_0.7Zr_0.3O₂(CeZrO) was prepared by incipient-wet impregnation method and investigated in the catalytic wet oxidation of N,N-dimethyl formamide (DMF) in batch reactor. The physicochemical property of the catalysts was characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), H₂ temperature-programmed reduction (H₂-TPR), X-ray photoelectron spectroscopy (XPS) and thermogravimetry (TG). Compared with 3%Ru/CeO₂, 3%Ru/Ce_0.7Zr_0.3O₂ catalyst exhibits much higher performance for DMF degradation due to the promotion of Ru dispersion and the transfer of active oxygen, and 99% DMF conversion and 97% COD elimination are obtained at 453 K, 2.5 MPa oxygen pressure after 5 h. The reaction mechanism of DMF degradation was suggested. The carbonaceous species deposition and oxidation of Ru can be responsible for catalyst deactivation. And the catalyst activity can be recovered by air calcination and H₂ reduction.     

Catalytic ozonation of NH4+-N in wastewater over composite metal oxide catalyst

Large amounts of water containing-ammonium nitrogen(NH₄⁺-N)have attracted increasing attention.Catalytic ozonation technology,involving the generation of hydroxyl radical(OH)with strong oxidation ability,was originally utilized to degrade organic-containing wastewater.In this paper,Ce/MnOx composite metal oxide catalysts prepared with different preparation conditions were used to degrade wastewater containing inorganic pollutant(NH₄⁺-N).The as-prepared catalyst features were characterized using X-ray diffraction(XRD),Brunauer-Emmett-Teller method(BET),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS),Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS)and H₂-temperature programmed reduction(H₂-TPR)techniques.The results show that the catalyst,prepared by conditions with precipitant Na₂CO₃ and Ce/Mn molar ratio 1:2 calcined at 400℃for 3 h in pH 11.0,displays the optimal performance,with the removal rate of NH₄⁺-N and selectivity to gaseous nitrogen,88.14 wt%and 53.67 wt%,respectively.The effects of several operating factors including solution pH,initial NH₄⁺-N concentrations and scavengers were evaluated.In addition,XRD patterns of catalyst with the best performance and the comparative study on decontamination of NH₄⁺-N by various processes(O₃,catalyst and catalyst/O₃)show that the primary metal oxides are CeO₂ and MnO₂ in Ce/MnOx composite metal oxide catalysts,which have a synergistic effect on the catalytic ozonation of NH₄⁺-N,and the new phase MnO₂ plays a great role.After 5 consecutive use cycles,the degradation efficiency is declined slightly,and can still achieve better than 70 wt%over 1 h reaction.Additionally,the application of catalytic ozonation for actual wastewater on the removal rate of NH₄⁺-N was investigated.Possible mechanism and degradation pathway of NH₄⁺-N were also proposed.In a word,the application of CeO₂-MnO₂ composite metal oxide catalysts in catalytic ozonation can be regarded as an effective,feasible and promising method for the treatment of NH₄⁺-N.     

Low temperature catalytic oxidation of NO over different-shaped CeO2

To investigate the effect of CeO₂ nanomaterial morphology on its performance for NO catalytic oxidation. Three kinds of CeO₂ nanomaterials including CeO₂ nanorods, nanospheres and nanoparticles were prepared by hydrothermal method and used for catalytic oxidation of NO at low temperature. The experimental results show that CeO₂ nanorods are of the best catalytic performance. Characterization techniques including TEM, XRD, H₂-TPR, NO-TPD and XPS were used to determine the relationship between the morphology of CeO₂ nanomaterial and its catalytic performance. TEM images show that CeO₂ nanorods predominantly exposed (110) and (1 0 0) planes, while CeO₂ nanospheres and CeO₂ nanoparticles predominantly exposed (1 1 1) plane. The excellent catalytic performance of CeO₂ nanorods could be ascribed to the low crystallinity, high reducibility, strong NO adsorption ability and the presence of more surface chemisorbed oxygen.     

Effect of CuO species and oxygen vacancies over CuO/CeO2 catalysts on low-temperature oxidation of ethyl acetate

The catalytic oxidation of ethyl acetate(EA) was studied over CuO/CeO₂ catalysts which were prepared by ball milling with different precursors(copper oxide,cerium acetate,cerium dioxide,copper acetate and cerium hydroxide).The CuO/CeO₂ catalyst(O-A) prepared with copper oxide and cerium acetate as precursors shows very high catalytic activity that 100% EA conversion is achieved at low temperature of 220℃.It is found that specific surface area(112.8 m²/g),particle...     

A mechanic insight into low-temperature catalytic combustion toward ethylene oxide over Pt-Ru/CuCeOx bimetallic catalyst

The catalytic oxidation performance toward ethylene oxide(EO) and the consequent mechanism were investigated on the Pt-Ru/CuCeO_x bimetallic catalyst,which was prepared by a distinct method combining stepwise adsorption and subsequent impregnation.The catalytic tests show that the introduction of Ru into the Pt catalyst,so as to form Pt-Ru bimetallic active sites,can greatly increase the oxidation activity of the catalyst,as evidenced by the extremely lower full oxidation temperature(1...     

Catalytic thermal decomposition of ammonium perchlorate by a series of lanthanide EMOFs

Given their unique and excellent properties,metal-organic frameworks(MOFs) materials have been used in many scientific fields.EMOFs use energetic materials as ligands,which can provide part of the energy for the system while catalyzing ammonium perchlorate.The energetic material 1.1’-dihydroxyazotetrazole(H₂AzTO),as a high-energy nitrogen-rich material,was selected as a ligand.Five kinds of La³⁺,Ce³⁺,Pr³⁺,Nd³⁺,and Sm³⁺ lanthanide ...     

Lanthanum-doped Cu-Mn composite oxide catalysts for catalytic oxidation of toluene

CuMn mixed oxides catalysts doped with La were prepared following a co-precipitation method and used for the catalytic oxidation of toluene. Catalysts properties of the catalysts were investigated by X-ray diffraction, N_2 adsorption/desorption,scanning electron microscopy, H_2-temperature-programmed reduction(H_2-TPR), O_2-temperature-programmed desorption(O_2-TPD) and X-ray photoelectron spectroscopy techniques. Characterization data reveal that the phase change and decrease in crystallinity of the La-doped catalysts increase the number of oxygen vacancies. Improvements in reducibility and an increase in the amount of chemisorbed oxygen of the La-doped catalysts were also verified by H_2-TPR and O_2-TPD. The activity of the CuMn mixed oxides catalysts is significantly improved by the addition of a nominal amount of La. The CuMn/La-4 mol% catalyst exhibits the best catalytic activity, with a 90%conversion temperature of 255 ℃,attributed to a high Mn~(3+)ratio, superficial chemisorbed oxygen,and high surface area. This study indicates La to be a promising dopant for Cu-Mn catalysts toward toluene oxidation.     

Effect of cerium oxide prepared under different hydrothermal time on electrocatalytic performance of Pt-based anode catalysts

In this paper,CeO_2 with a pore size of 2-4 nm was synthesized by hydrothermal method.The CeO_2 modified graphene-supported Pt catalyst was prepared by the microwave-assisted ethylene glycol reduction chloroplatinic acid method,and the effect of the addition of CeO_2 prepared by different hydrothermal reaction time on the catalytic performance of Pt-based catalysts was investigated.The microstructures of CeO_2 and catalysts were characterized by X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),specific surface area and pore size analyzer(BET),scanning electron microscopy(SEM) and electron spectroscopy(EDAX),transmission electron microscopy(TEM),and the catalysts electrochemical performance was tested by electrochemical workstation.The results show that the catalytic performance of the four catalysts with CeO_2 is better than that of the catalyst without CeO_2.Adding CeO_2 with a specific surface area of 120.15 m~2/g prepared by hydrothermal reaction time of 39 h to Pt/C synthesis catalyst,its electrocatalytic performance,stability and resistance to poisoning are the best.The electrochemical active surface area is 102.83 m~2/g,the peak current density of ethanol oxidation is 757.17 A/g and steady-state current density of 1100 s is 108.17 A/g which shows the lowest activation energy for ethanol oxidation reaction.When the cyclic voltammogram is scanned for 500 cycles,the oxidation peak current density retention rate is 87.74%.     

Rare earth oxide modified Cu-Mn compounds supported on TiO₂ catalysts for low temperature selective catalytic oxidation of ammonia and in lean oxygen

Selective catalytic oxidation(SCO) of ammonia was carried out over Cu-Mn compounds catalysts modified with trivalent rare earth oxide Ce2O3 and La2O3 respectively.TiO2 was used as support and different ratio of O2 were tested in order to find an appropriate O2 concentration(vol.%),and the results showed that 1%O2(vol.%) was propitious to SCO of ammonia.The effects of the two rare earth oxides modified catalysts Ce2O3-Cu-Mn/TiO2 and La2O3-Cu-Mn/TiO2 on the catalytic activity and selectivity of ammonia oxidation were investigated under the reaction condition of 500 ppm ammonia,1%O2(vol.%),at the temperature from 125 to 250 oC.The results revealed the beneficial role of Ce2O3 and La2O3 in catalytic activity at low temperature and lean oxygen concentration,while the modification with Ce2O3 and La2O3 led to the negative influence on N2 selectivity.For the catalysts modified with Ce showed lower NO and N2O selectivity than the catalysts modified with La,then the effects of different Ce loadings on catalytic activity and selectivity were also considered,in combination with catalysts preparation methods,which include incipient wet impregnation,sol-gel method and co-precipitation.Results revealed that the catalysts prepared by sol-gel method obtained preferable catalytic activity compared with the others,reaching 99% ammonia at 200 oC,whereas 96% NO was detected.It also indicated that different catalyst preparation method significantly determined production distribution.     

Low-temperature catalytic combustion of trichloroethylene over MnOx-CeO2 mixed oxide catalysts

The cerium-based catalysts were investigated for the catalytic co mbustion of trichlo roethylene(TCE) and exhibit a surprising catalytic activity.MnO_x was doped into CeO₂ by a citric acid(CA) sol-gel method,and the effect of Mn content on the physicochemical properties and catalytic activities of MnO_x-CeO₂ mixed oxides was investigated systemically.The introduction of MnO_x into CeO₂ can evidently improve the catalytic activity and...     

Genesis of nanocrystalline Ho2O3 via thermal decomposition of holmium acetate: Structure evolution and electrical conductivity properties

This study focuses on the preparation of nanostructured holmium oxide via the decomposition of holmium acetate precursor utilizing the non-isothermal strategy. Thermogravimetric analysis(TGA) was used to follow up the various thermal events involved in the decomposition process. Dehydration completes approximately at 150℃, which is followed by the decomposition of the anhydrous acetate leading to the formation of holmium oxide. Based on the TGA results the acetate precursor was heated non-isothermally at the temperature range of 150 e700℃. The obtained solids were characterized using powder X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), Fourier transform infrared spectroscopy(FT-IR), field-emission scanning electron microscopy(FE-SEM) and transmission electron microscopy(TEM). It is found that nanocrystalline Ho_2 O_3 starts to form at 500℃ and presents the only phase detected at the 500 e700℃ range. The electrical conductivity of the solids that form at the temperature range of 300 e700℃ was investigated. The obtained values were correlated with the observed structural modifications accompanying the heat treatment. The electrical conductivity of the Ho_2 O_3 samples prepared at 500, 600 and 700℃ reaches the values of 1.92 × 10~(-7), 1.61 × 10~(-7) and 8.33 × 10~(-8) Ω~(-1)cm~(-1) at a measuring temperature of 500℃, respectively. These values are potentially advantageous for high-resistivity devices.     

Acid modified carrier on catalytic oxidation of dichloromethane over CeO2/HZSM-5 catalysts

In this study, a series of Hydrogen-Zeolite Socony Mobil-5-X (HZSM-5-X) catalysts were prepared by acid modification, then Ce/HZSM-5-X (X = 0, 0.2, 0.4, 1.0, 2.0) catalysts were prepared by impregnation method. The catalytic performance of the catalysts on dichloromethane (DCM) oxidation was investigated. Through different characterizations, HZSM-5-X exhibit high specific surface area, good redox ability, rich acidity and much suitable acidic site distribution after acid treatment. Among them, Ce/HZSM-5-0.4 shows better catalytic activity with the lowest by-product and the best CO₂ yield. Its T₉₀ is 302 °C and the CO₂ yield of T₉₀ is more than 80 wt%, which demonstrates that the acid modification of carrier plays the positive effect on the catalytic capacity for DCM oxidation.     

Catalytic performance of Zr-doped CuO-CeO_2 oxides for CO selective oxidation in H_2-rich stream

Zr-doped CuO-CeO_2 catalysts for CO selective oxidation were designed and prepared by the hydrothermal method and coprecipitation. The experimental samples were characterized by means of N_2 adsorption-desorption isotherms, powder X-ray diffraction, temperature-programmed reduction and Xray photoelectron spectroscopy. It is observed that the catalyst prepared by hydrothermal method exhibits larger specific surface area, smaller crystalline size and higher dispersion of active components compared with those of the catalyst obtained by coprecipitation. Meanwhile, redox properties of copper oxide are improved significantly and highly dispersed copper species providing CO oxidation sites are present on the surface. Furthermore, adsorptive centers of CO and active oxygen species increase on the copper-ceria interfaces. The Zr-doped CuO-CeO_2 catalyst prepared by hydrothermal method possesses superior catalytic activity and selectivity for selective oxidation of CO at low temperature compared with those of the sample prepared by coprecipitation. The temperature corresponding to 50% CO conversion is only 73 ℃ and the temperature span of total CO conversion is expanded from 120 to 160 ℃.     

Ce-Fe-Mn ternary mixed-oxide catalysts for catalytic decomposition of ozone at ambient temperatures

Ce-modified Mn-Fe mixed-oxide catalysts were prepared by a citric acid sol-gel method and characterized by X-ray diffraction,Raman,N_2 adsorption-desorption,infrared spectra H_2 temperature-programmed reduction and thermogravimetric analyses.Their catalytic properties were investigated in ozone(O_3)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 O_3 decomposition.Among the prepared catalysts.the C_(0.04)(FM)_(0.96) mixed-oxide catalyst exhibits the highest catalytic activity and stability.The O_3 conversion over C_(0.04)(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 O_3 conversion over C_(0.04)(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 O_3 conversion over C_(0.04)(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 MnO_2.and partial Fe is separated to form Fe_2O_3.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 forO_3 decomposition.     

Catalytic conversion and DFT analysis of post DDBD-catalysis system for degradation of toluene,ethyl acetate and acetone with different metal-oxides catalysts

A series of multiphase metal-oxide catalysts(MnO_x/γ-Al₂O₃,CuO_x/γ-Al₂O₃,FeO_x/γ-Al₂O₃,CeO_x/γ-Al₂O₃and LaO_x/γ-Al₂O₃) were prepared for plasma-catalyst degradation of multicomponent volatile organic compounds(VOCs,such as toluene,acetone and ethyl acetate).The results reveal that the degradation efficiency(DE) of acetone,toluene and ethy...     

Effect of Rare Earth Additives on the Catalytic Property ofVanadium－Phosphorus Catalyst

ＥｆｆｅｃｔｏｆＲａｒｅＥａｒｔｈＡｄｄｉｔｉｖｅｓｏｎｔｈｅＣａｔａｌｙｔｉｃＰｒｏｐｅｒｔｙｏｆＶａｎａｄｉｕｍ－ＰｈｏｓｐｈｏｒｕｓＣａｔａｌｙｓｔＬｉＭｉｎｇｘｉｕ（李铭岫）；ＹａｎｇＳｈｕｔａｏ（杨述韬）；ＬｉｕＣｕｉｇｅ（刘翠格）（Ｄｅｐ...     

Catalytic Performance for Oxidative Coupling of Methane over Eu_2O_3 Catalysts Promoted by Alkaline Earth Flourides

ＣａｔａｌｙｔｉｃＰｅｒｆｏｒｍａｎｃｅｆｏｒＯｘｉｄａｔｉｖｅＣｏｕｐｌｉｎｇｏｆＭｅｔｈａｎｅｏｖｅｒＥｕ２Ｏ３ＣａｔａｌｙｓｔｓＰｒｏｍｏｔｅｄｂｙＡｌｋａｌｉｎｅＥａｒｔｈＦｌｏｕｒｉｄｅｓＬｏｎｇＲｕｉｑｉａｎｇ（龙瑞强），ＷａｎＨｕｉｌ...     

Catalytic combustion of VOCs on Pt/CuMnCe and Pt/CeY honeycomb monolithic catalysts

The metal oxides CuMnCe and CeY washcoats on cordierite were prepared using an impregnation method, and then used as support for the active Pt component to prepare the Pt/CuMnCe and Pt/CeY monolithic catalysts for the deep oxidation of VOCs. In comparison with the Pt/CeY, CuMnCe, and CeY monolithic catalysts, the Pt/CuMnCe monolithic catalyst shows an excellent performance for toluene,ethyl acetate,and n-hexane oxidation and the T_(90%) is low to 216, 200 and 260 ℃,respectively. The active components Pt/PtO and CuMnCe result in a better synergetic interaction, which promote the catalyst reducibility, increase the oxygen mobility, and enhance the adsorption and activation of organic molecules.     

Understanding the role of tungsten on Pt/CeO2 for vinyl chloride catalytic combustion

Spherical CeO₂ synthesized by the hydrothermal process was used as support to prepare Pt/WO₃/CeO₂,and the effects of tungsten(W) contents on activity,stability and polychlorinated by-products were investigated to understand the role of W for vinyl chloride(VC) catalytic oxidation.The introduction of12 wt% W to Pt/CeO₂(P12 WC) exhibits the highest catalytic activity with 90% conversion of VC at 250℃,meanwhile the stability improves and the polychlorinat...