Comparative structural and electrochemical properties of mixed P2/O′3-layered sodium nickel manganese oxide prepared by sol-gel and electrospinning methods:Effect of Na-excess content

The effect of Na-excess content in the precursor on the structural and electrochemical performances of sodium nickel manganese oxide(NNMO)prepared by sol-gel and electrospinning methods is investigated in this paper.X-ray diffraction results of the prepared NNMO without adding Na-excess content indicate sodium loss,while the mixed phase of P2/O′3-type layered NNMO presented after adding Na-excess content.Compared with the sol-gel method,the secondary phase of NiO is more suppressed by using the electrospinning method,which is further confirmed by field emission scanning electron microscope images.N_(2) adsorption-desorption isotherms show no remarkably difference in specific surface areas between different preparation methods and Na-excess contents.The analysis of X-ray absorption near edge structure indicates that the oxidation states of Ni and Mn are+2 and+4,respectively.For the electrochemical properties,superior electrochemical performance is observed in the NNMO electrode with a low Na-excess content of 5wt%.The highest specific capacitance is 36.07 F·g^(-1)at0.1 A·g^(-1)in the NNMO electrode prepared by using the sol-gel method.By contrast,the NNMO electrode prepared using the electrospinning method with decreased Na-excess content shows excellent cycling stability of 100%after charge-discharge measurements for 300 cycles.Therefore,controlling the Na excess in the precursor together with the preparation method is important for improving the electrochemical performance of Na-based electrode materials in supercapacitors.

CeO_2-ZrO_2-La_2O_3-Al_2O_3 composite oxide and its supported palladium catalyst for the treatment of exhaust of natural gas engined vehicles

Composite supports CeO2-ZrO2-Al2O3（CZA） and CeO2-ZrO2-Al2O3-La2O3（CZALa） were prepared by co-precipitation method. Palladium catalysts were prepared by impregnation and their purification ability for CH4, CO and NOx in the mixture gas simulated the exhaust from natural gas vehicles （NGVs） operated under stoichiometric condition was investigated. The effect of La2O3 on the physicochemical properties of supports and catalysts was characterized by various techniques. The characterizations with X-ray diffraction （XRD） and Raman spectroscopy revealed that the doping of La2O3 restrained effectively the sintering of crystallite particles, maintained the crystallite particles in nanoscale and stabilized the crystal phase after calcination at 1000 ℃. The results of N2-adsorption, H2-temperatnre-programmed reduction （H2-TPR） and oxygen storage capacity （OSC） measurements indicated that La2O3 improved the textural properties, reducibility and OSC of composite supports. Activity testing results showed that the catalysts exhibit excellent activities for the simultaneous removal of methane, CO and NOx in the simulated exhaust gas. The catalysts supported on CZALa showed remarkable thermal stability and catalytic activity for the three pollutants, especially for NOx. The prepared palladium catalysts have high ability to remove NOx, CH4 and CO, and they can be used as excellent catalysts for the purification of exhaust from NGVs operated under stoichiometric condition. The catalysts reported in this work also have significant potential in industrial application because of their high performance and low cost.

Simultaneous removal of ethanol, acetaldehyde and nitrogen oxides over V-Pd/γ-Al_2O_3-TiO_2 catalyst

V-Pd/γ-Al2O3-TiO2 catalysts with different vanadium contents were prepared by a combined sol-gel and impregnation method. X-ray diffraction （XRD）, N2 adsorption-desorption （BET）, X-ray photoelectron spectroscopy （XPS） and catalytic removal of ethanol, acetaldehyde and nitrogen oxides at low temperature （〈300 ？C） were used to assess the properties of the catalysts. The results showed that the sample with 1wt% vanadium exhibited an excellent catalytic performance for simultaneous removal of ethanol, acetaldehyde and nitrogen oxides. The conversions of ethanol, acetaldehyde and nitrogen oxides at 250 ？C were 100%, 74.4% and 98.7%, respectively. V-Pd/γ-Al2O3-TiO2 catalyst with 1 wt% vanadium showed the largest surface area and higher dispersion of vanadium oxide on the catalyst surface, and possessed a larger mole fraction of V4＋ species and unique PdO species on the surface, which can be attributed to the strong synergistic effect among palladium, vanadium and the carriers. The higher activity of V-Pd/γ-Al2O3-TiO2 catalyst is related to the V4＋ and Pd2＋ species on the surface, which might be favorable for the formation of active sites.

Catalytic Partial Oxidation of Methane over Ni/CeO_2-ZrO_2-Al_2O_3

Nickel catalysts supported on CeO2-ZrO2-CeO2,ZrO2-Al2O3 and Al2O3 were prepared and characterized by means of X-ray diffraction（XRD）,BET areas,H2 temperature-programmed reduction（H2-TPR）,and X-ray photoelectron spectroscopy（XPS）.Through the test of catalytic partial oxidation of methane（CPOM）,Ni/CeO2-ZrO2-Al2O3 displayed the highest activity,which resulted from its largest BET area and best NiO dispersion.Furthermore,Ni/CeO2-ZrO2-Al2O3 maintained a long-time stability in CPOM,which was attributed to its best coking resistance among all the prepared catalysts.

Dielectric barrier discharge plasma synthesis of Ag/γ-Al_(2)O_(3) catalysts for catalytic oxidation of CO

In this study,Ag/γ-Al_(2)O_(3)catalysts were synthesized by an Ar dielectric barrier discharge plasma using silver nitrate as the Ag source andγ-alumina(γ-Al_(2)O_(3))as the support.It is revealed that plasma can reduce silver ions to generate crystalline silver nanoparticles(Ag NPs)of good dispersion and uniformity on the alumina surface,leading to the formation of Ag/γ-Al_(2)O_(3)catalysts in a green manner without traditional chemical reductants.Ag/γ-Al_(2)O_(3)exhibited good catalytic activity and stability in CO oxidation reactions,and the activity increased with increase in the Ag content.For catalysts with more than 2 wt%Ag,100%CO conversion can be achieved at 300°C.The catalytic activity of the Ag/γ-Al_(2)O_(3)catalysts is also closely related to the size of theγ-alumina,where Ag/nano-γ-Al_(2)O_(3)catalysts demonstrate better performance than Ag/micro-γ-Al_(2)O_(3)catalysts with the same Ag content.In addition,the catalytic properties of plasma-generated Ag/nano-γ-Al_(2)O_(3)(Ag/γ-Al_(2)O_(3)-P)catalysts were compared with those of Ag/nano-γ-Al_(2)O_(3)catalysts prepared by the traditional calcination approach(Ag/γ-Al_(2)O_(3)-C),with the plasma-generated samples demonstrating better overall performance.This simple,rapid and green plasma process is considered to be applicable for the synthesis of diverse noble metal-based catalysts.

Preparation of SiC_p/Al_2O_3-Al Composites by Directed Metal Oxidation

SiCp/Al2O3-Al composites were synthesized by means of direct metal oxidation method. The composition and microstructures of the composites were investigated using X-ray diffraction （XRD）, scanning electron microscopy （SEM） and metallurgical microscope. The effects of technical parameters on the properties of the product were analyzed. The results indicate that the composite possesses a dense microstructure, composed of three interpenetrated phases. Of them, SiO2 layer prohibits the powdering of the composites; Mg promotes the wetting and infiltration of the system and Si restricts the interfacial reaction while improving the wetting ability between reinforcement and matrix.

Preparation and characterization of Fe_2O_3-CeO_2-TiO_2/γ-Al_2O_3 catalyst for degradation dye wastewater

In order to develop a catalyst with high activity for catalytic wet oxidation （CWO） process at room temperature and atmospheric pressure, Fe2O3-CeO2-TiO2/γ-Al2O3 catalyst was prepared by consecutive impregnation method and the prepared parameters were optimized. The structure of the catalyst was characterized by BET, XRF, SEM and XPS technologies, and the actual wastewater was used to investigate the catalytic activity of Fe2O3-CeO2-TiO2/γ-Al2O3 in CWO process. The experimental results showed that the prepared catalyst exhibited good catalytic activity when the doping amount of Ti was 1.0 wt% （the weight ratio of Ti to carriers）, and the middle product, Fe2O3-CeO2-TiO2/γ-Al2O3, was calcined in 450℃ for 2 h. The CWO experiment for treating actual dye wastewater indicated that the COD, color and TOC of actual wastewater were decreased by 62.23%, 50.12% and 41.26% in 3 h, respectively, and the ratio of BOD5/COD was increased from 0.19 to 0.30.

Effect of Al Addition on Properties of Al_2O_3-SiC-C Dry Ramming Mixes for BF Trough

Aluminium powders were introduced to Al2O3-SiC-C dry ramming mixes in order to improve sintering properties and oxidation resistance according to their service conditions and installation methods. Properties such as bulk density, porosity, modulus of rupture, crushing strength and hot modulus of rupture as a function of aluminium addition were investigated in the present work. The microstructure and thermodynamics for the heat treated specimens were also analyzed. The results show that as aluminium addition increasing, the bulk density of the specimen treated at 220℃ tends to decrease and the apparent porosity increases, the strength of the specimens treated at 1100℃ and 1450℃ increases markedly, the bulk density tends to increase, apparent porosity and linear shrinkage decrease. The HMOR at 1400℃ is enhanced from 1.0 MPa to 3.5 MPa with 3% aluminium. Aluminium is served as sintering agent and anti-oxidant and it will react with CO and CO2 forming Al2O3 , which is helpful to enhance the strength, densify the structure and improve the overall properties.

水热改性制备固体酸S_2O_8^(2-)/Fe_2O_3-SiO_2及其催化性能的初步探讨

采用共沉淀法制备Fe2O3-SiO2 混合氧化物前驱体 ,并对其进行水热改性处理 ,经浸渍(NH4)2S2O8 溶液后再焙烧得S2O82 -/Fe2O3-SiO2 固体酸催化剂。研究了制备条件对催化活性的影响 ,用乙酸/丁醇酯化反应评估该固体酸的催化性能。实验结果显示 ,最佳工艺条件为,n(Fe):n(Si)=1:4 ,150℃水压热处理1h ,在0.5mol·L-1 的(NH4)2S2O8 溶液中浸渍6h ,500℃焙烧3h ,在此条件下乙酸的转化率可达94.11 %。

Efficient oxidative degradation of 2-chlorophenol and 4-chlorophenol over supported CuO-based catalysts

A series of metal oxide catalysts for catalytic oxidative degradation of 2-chlorophenol （2-CP） and 4-chlorophenol （4-CP） were prepared, and the supported CuO catalysts were studied particularly. The supported CuO catalysts were characterized by XRD and NH3-TPD techniques, in which CuO/γ-Al2O3 exhibited high degradation activity. The addition of Na2O or K2O into CuO/γ-Al2O3 improved the oxidative degradation of CPs remarkably, in which Na2O was more efficient than K2O. Over CuO/γ-Al2O3-Na2O, CPs were completely converted and the liberation of the inorganic chloride from 2-CP or 4-CP reached 97% or 100% respectively at 30 ？C for 2 h. The supported CuO catalysts with good dispersion of CuO particles and less acid sites were favorable for the efficient oxidative degradation of CPs. In addition, the initial pH of the reaction solution was found to be an important factor which influenced the catalytic oxidative degradation of CPs and the initial pH of 11.2 and 9.8 was preferred for the oxidative degradation of 2-CP and 4-CP respectively over CuO/γ-Al2O3 catalyst.

Selective Oxidation of Toluene with Hydrogen Peroxide Catalyzed by V-Mo-based Catalyst

The selective catalytic oxidation of toluene with hydrogen peroxide over V-Mo-based catalysts under mild conditions was studied.The promotion effect of Mo on the catalysts was studied with V/Al2O3 and Mo/Al2O3 as reference samples.The catalysts were characterized by XRD,TPR,and XPS techniques.The results show that the addition of Mo to V/Al2O3 may change the distribution of V species on Al2O3 surface.Over V-Mo/Al2O3 catalyst,highly dispersed amorphous V species facilitates benzaldehyde formation,and crystalline V2O5 species increases the conversion of toluene but decreases the selectivity to benzaldehyde,while AlVMoO7 species favors both the conversion of toluene and the formation of cresols.The yield of benzaldehyde depends remarkably on the surface O/Al and Mo/V atomic ratios,and gets to a maximum value of 13.2% with a selectivity of 79.5% at an O/Al atomic ratio of 3.0 and Mo/V atomic ratio of 0.7.

Comparison of desulfurization kinetics of copper oxide sorbent

Desulfurization experiments of CuO, γ-Al2O3 and CuO/γ-Al2O3 were made in simulated flue gas by means of thermogravimetric analysis. It is found that reaction activities of CuO supported on γ-Al2O3 could be highly improved. Desulfurization kinetics of CuO/γ-Al2O3 was studied in the temperature range of 250 °C-400 °C and SO2 concentration of 0.1%-0.9%. The experimental data were tested and compared with kinetics models of volume reaction model(VRM), grain size model(GSM), random pore model(RPM) and pore-blocking model(PBM). Correlation analysis shows that VRM and RPM models do not fit experimental data well. GSM contradicts with the changes in the physical and chemical properties of Cu O/γ-Al2O3 as the desulfurization proceeds. It is found that PBM is consistent with the change of pore structure of CuO/γ-Al2O3 sorbent during desulfurization process and predicts the conversion-time curves of the sorbent well. Meanwhile, kinetics parameters are obtained and discussed.

Sulfur poisoning and regeneration of MnO_x-CeO_2-Al_2O_3 catalyst for soot oxidation

MnOx-CeO2-Al2O3 mixed oxides were prepared by impregnating manganese and cerium precursors on alumina powders via a sol- gel deposition method. The oxide catalyst exhibited a poor resistance to sulfur dioxide after the treatment in 100 ppm SO2/air at 350 °C for 50 h. The formation of manganese sulfate and especially cerium sulfate reduced the availability of surface active metal oxides, blocked the pore structure and decreased the surface area of the catalyst. These changes in chemical and structural and textural properties resulted in a severe loss in the activities of the sulfated catalyst for NO and soot oxidation. The decomposition of sulfates was almost complete during the calcina-tion in air at 800 °C for 30 min, which partially recovered the surface active sites and the catalyst surface area despite the significant sintering of metal oxides. Consequently, the NOx-assisted soot oxidation activity of the catalyst was regenerated to some extent by the oxidation treatment.

Novel Pd/TiO2-Al2O3 Catalysts for Methane Total Oxidation at Low Temperature and Their ^18O-Isotope Exchange Behavior

Pd supported on TiO2-Al2O3 binary oxides prepared by coprecipitation method has been investigated for the total oxidation of methane. All Pd/TiO2-Al2O3 catalysts show higher activity than Pd/Al2O3 and Pd/TiO2. Among them, Pd/2Ti-3Al with a Ti/Al ratio of 2 to 3 has a T90% of 395 ℃ at a gas hourly mass velocity of 33000 mL/（h＊g）, which is at least 50 ℃ lower than that of Pd supported on single metal oxide Al2O3 or TiO2. The results of TPR and ^180-isotope exchange experiments demonstrated that the excellent activity of Pd/2Ti-3Al was due to its high oxygen mobility and moderate reducibility, which is in accordance with our previous work, XPS results indicated that the dispersion of Pd was not the key factor to influence the catalytic activity.

Influence of Supports on Catalytic Performance and Carbon Deposition of Palladium Catalyst for Methane Partial Oxidation

The catalytic performance of methane partial oxidation was investigated on Pd/CeO2-ZrO2 and Pd/α-Al2O3 catalysts.The catalysts were characterized by XRD,Raman spectra,and TG-DTA techniques.The results show that CeO2-ZrO2 support is more advantageous for the catalytic activity and stability of catalysts compared to α-Al2O3.TG-DTA and Raman spectra results indicated that carbon deposited on the catalysts was in the form of graphite,which is the main reason for the deactivation of catalysts after a 24-hour reaction.Moreover,CeO2-ZrO2 had positive effect on inhibiting carbon deposition.

Complete oxidation of ethanol over vanadium based catalysts

V2O5/γ-Al2O3-TiO2 catalysts were prepared by the mixing sol-gel and co-impregnation method. The performance of the catalysts for complete oxidation of ethanol was evaluated in a conventional fixed-bed quartz reactor. And the effects of support, preparation methods and vanadium content have been investigated. The results showed that 5% V2O5 catalyst supported on γ-Al2O3-TiO2 possessed the best ethanol conversion under the considered temperature. This may be ascribed to the highly dispersible active component, mutual function between the active component and the carriers. The nature of the best performance for 5%V/γ-Al2O3-TiO2 catalyst may be related to the high V4＋ amounts on the surface. And the surface V4＋ species may play an important role in the formation of active site for the total ethanol oxidation.

Selective oxidation of methanol to dimethoxymethane over V_2O_5/Ti O_2–Al_2O_3 catalysts

This paper describes the effect of the prepara- tion method of binary oxide supports （TiO2-Al2O3） on catalytic performance of V2O5/TiO2-Al2O3 catalysts for methanol selective oxidation to dimethoxymethane （DMM）. The TiO2-A1203 supports are synthesized by a number of methods including mechanical mixing, ball milling, precipitation, co-precipitation, and sol-gel method, which is followed by incipient wetness impregnation to produce V2O5/TiO2-Al2O3 catalysts. Among these samples, the V2O5/TiO2-Al2O3 catalyst prepared by the sol-gel method has the best catalytic performance with a maximum methanol conversion of 48.9 % and a high DMM selectivity of 89.9 % at 393 K, showing superior performance than V2O5/TiO2 and V2O5/Al2O3. The excellent catalytic performance of V2O5/TiO2-Al2O3 is attributed to the effective interaction between the active component and the mixed support. Such interaction changes the chemical states of supported active V components, produces an increased amount of V^4＋ species, and facilitates the electron transfer between support and active component. Additionally, the incorporation of titanium cation into the alumina structure could also help produce an appropriate amount of acidic sites, which increases the DMM selectivity. The coordinated environment of the dispersed vanadia on TiO2-Al2O3 mixed support improves the catalytic efficiency on methanol oxidation to DMM.

A Review on Metal-support Interaction in Automotive Catalysts

TWC-equipped exhausts are widely used in gasoline-fueled vehicles to meet stringent emission regulations. The main components in TWCs are precious metals such as palladium (Pd), platinum (Pt), and rhodium (Rh) as the active component, and inorganic oxides such as γ-alumina (Al 2 O 3 ), ceria (CeO 2 ), zirconia (ZrO 2 ) and ceria-zirconia (CeO 2-ZrO 2 ) are used as the support. Interaction of precious metals and support plays an important role in the thermal stability and catalytic performance of TWCs. The support can improve the dispersion of precious metals and suppress the sintering of precious metals at high temperature. In the same, precious metals can also enhance the redox performance and oxygen storage capacity of support. This paper reviews the reaction phenomenon and mechanism of precious metals (Pt, Pd, Rh) and supports such as Al 2 O 3 , CeO 2-based composite oxides.

Hydrothermal synthesis and physicochemical characterization of CuO/ZnO/Al_2O_3 nanopowder.Part I:Effect of crystallization time

A hydrothermal method was successfully used for synthesis of CuO/ZnO/AI203 （CZA） nanopowder with atomic ratio of 6：3：1. The effect of crystallization time （3, 6, 9, and 12 h） on physicochemical properties of nanopowder was investigated. Nanopowders were characterized using XRD, FESEM, EDX, FTIR, TG, and BET techniques. The XRD patterns confirmed metal oxides formation and their good crystallinity with average crystallite size of 20nm as obtained by the Scherrer equation. Relative crystallinity was shown to increase with increasing crystallization time. In agreement with XRD results, FESEM images also illustrated nanosized particles. EDX mapping indicated homogenous dispersion of elements. BET specific surface area analysis showed acceptable surface area for CZA nanopowder, FTIR spectroscopy confirmed metal oxides formation during hydrothermal and calcination processing. TG results illustrated high thermal stability of the synthesized nanopowders. TG-DTG and FTIR analyses were used to propose a reaction mechanism for nanopowder formation during processing. Physicochemical characterization showed optimal crystallization time to be 6 h.