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1.
Highly acidic catalysts stronger than the SO4/ZrO2 superacid with an acid strength of Ho –16.04 were obtained by kneading Zr(OH)4 with ammonium sulfate together with chlorides of Ir, Pt, Rh, Ru, Os, and Pd followed by calcining in air at 600°C, the metal concentration being equivalent to Pt of 7.5 wt% based on the hydroxide. The catalysts with Ir and Pt materials were highest in activity for the skeletal isomerization of butane to isobutane. The present catalysts were not obtained by treating the crystallized oxide, ZrO2 calcined at 700°C, but the amorphous form followed by calcination to the crystallization.Superacids by metal oxides, VI. For previous publication in this series see ref. [1].  相似文献   

2.
Conclusions It has been established that in the compositions ZrO2Y2O3Fe2O3 and ZrO2Nd2O3Fe2O3 the processes of formation of rare earth ferrites and ZrO2 cubic solid solutions occur simultaneously. At temperatures of up to 1300°C the ferrite-formation process is fastest; with a further increase in the temperature the synthesis of ZrO2 cubic solid solutions is significantly intensified.In the mixture of CaO, ZrO2, and Fe2O3, the calcium oxide reacts only with ZrO2.The greatest stability in relation to the action of Fe2O3 is clearly found in the case of the zirconia-calcium oxide solid solutions.In the mixtures of cubic solid solutions of Nd2Zr2O7-ZrO2 or ZrO2-Y2O3 and Fe2O3, an interaction is only possible in the case where the synthesis of ferrites is not accompanied by the restructuring of the crystal lattice of ZrO2, i. e., by destabilization of the material.The presence of Fe2O3 prevents the decomposition of zirconia-calcium oxide and zirconia-neodymium oxide solid solutions under conditions of prolonged heating in air at 1300°C. The zirconia-yttria cubic solid solution is the most stable and does not decompose, regardless of the concentration of Fe2O3, after a dwell of 250 h at 1300°C.Translated from Ogneupory, No. 1, pp. 45–49, January, 1980.  相似文献   

3.
The recycling of waste lubricant oil from automobile industry was found to be best alternative to incineration. Silica (SiO2), alumina (Al2O3), silica-alumina (SiO2-Al2O3) supported iron oxide (10 wt% Fe) catalysts were prepared by wet impregnation method and used for the desulphurisation of waste lubricant oil into fuel oil. The extent of sulphur removal increases in the sequence of Fe/SiO2-Al2O3<Fe/Al2O3<Fe/SiO2 and this might be due to the presence of smaller crystalline size (7.4 nm) of Fe2O3 in Fe/SiO2 catalyst. X-ray diffraction results suggest the presence of iron sulphide in the used catalyst. Gas chromatography with thermal conductivity detector analysis confirms the presence of H2S in gaseous products. In addition, Fe/SiO2 catalyst facilitated the formation of lower hydrocarbons by cracking higher hydrocarbons (≈C40) present in waste lubricant oil.  相似文献   

4.
The sinterability of Bi2O3-doped hydroxyapatite (HA) has been studied and compared with the undoped HA. Varying amounts of Bi2O3 ranging from 0.05 wt% to 1.0 wt% were mixed with the HA. The study revealed that most sintered samples composed of the HA phase except for compacts containing 0.3, 0.5 and 1.0 wt% Bi2O3 and when sintered above 1100 °C, 1000 °C and 950 °C, respectively. In general, the addition of 0.5 wt% Bi2O3 was identified as the optimum amount to promote densification as well as to improve the mechanical properties of sintered HA at low temperature of 1000 °C. Throughout the sintering regime, the highest value of relative bulk density of 98.7% was obtained for 0.5 wt% Bi2O3-doped HA when sintered at 1000 °C. A maximum Young's modulus of 119.2 GPa was measured for 0.1 wt% Bi2O3-doped HA when sintered at 1150 °C. Additionally, the ceramic was able to achieve highest hardness of 6.08 GPa and fracture toughness of 1.21 MPa m1/2 at sintering temperature of 1000 °C.  相似文献   

5.
Nanocrystalline hydroxyapatite powder has been synthesized from a Ca(NO3)2·4H2O and (NH4)2HPO4 solution by the precipitation method. In the next step we prepared ZrO2–Al2O3 powder. After preparation, the powder was dried at 80 °C and calcined at 1200 °C for 1 h. Various amounts (HAP–15 wt% ZA, HAP–30 wt% ZA) of powder were mixed with the hydroxyapatite by ball milling. The powder mixtures were pressed and sintered at 1000 °C, 1100 °C and 1200 °C for 1 h. In order to study the structural evolution, X-ray diffraction (XRD) was used. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to estimate the particle size of the powder and observe fracture surfaces. Results show that the bending strength of pressed nanocrystalline HAP was improved significantly by the addition 15 wt% of ZrO2–Al2O3 powders at 1200 °C, but the fracture toughness was not changed, however when 30 wt% of ZA powders were added to nanocrystalline HAP, the bending strength and fracture toughness of the specimens decreased at all sintering temperature.  相似文献   

6.
R. Anton 《Carbon》2009,47(3):856-865
Ni, Fe and Ni-Fe alloy particles were vapour deposited on thin films of amorphous carbon (a-C) inside a specially equipped transmission electron microscope, and reactions with the substrate were observed at elevated temperatures. The influence of oxidation of the particles was also investigated. In contrast to Ni, which was found in earlier work to graphitise the carbon at above 600 °C without bulk carbide being involved, pure Fe reacted with the a-C support at about 500 °C to Fe3C, which graphitised the carbon similar to Ni, starting at about 600 °C. No carbide was formed from oxidised Fe particles. FeO decomposes above 500 °C, higher oxides (Fe3O4, Fe2O3) only above 750 °C. The remaining Fe particles graphitised the carbon support directly. Alloy particles with composition Ni80:Fe20 (permalloy) graphitised a-C in the same way as pure Ni, without any phase separation. Annealing of a mixed phase of finely dispersed Ni-Fe-oxide or deposition of Ni-Fe under oxygen at above 300 °C resulted in nucleation of three-dimensional crystallites of virtually pure Ni, which graphitised the carbon, while the remaining phase of small particles was converted to inactive Ni-ferrite, NiFe2O4.  相似文献   

7.
A series of zirconia-supported molybdenum oxide catalysts with different molybdenum loadings prepared using conditions reported to generate “superacidity” have been evaluated for their performance as catalysts for methane oxidation. A marked dependence of Mo content on activity has been observed, with the most active material being that with intermediate molybdenum content. 5 wt% MoO3/ZrO2 compares favourably with ZrxCe1-xO2 for methane combustion. The presence of MoO3 is observed to stabilise the tetragonal polymorph of ZrO2 and, as Mo content is increased, dispersed MoO3 crystallites are formed as evidenced by Raman spectroscopy. Temperature-programmed reduction studies evidence differences in the reduction behaviour of the materials as a function of loading. The results indicate that molybdenum oxide supported on monoclinic zirconia gives rise to the most active catalyst. It is tentatively suggested that the formation of a MoO3 monolayer during reaction may be of importance. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

8.
J.D.A. Bellido 《Fuel》2009,88(9):1673-1034
ZrO2, γ-Al2O3 and ZrO2/γ-Al2O3-supported copper catalysts have been prepared, each with three different copper loads (1, 2 and 5 wt%), by the impregnation method. The catalysts were characterized by nitrogen adsorption (BET), X-ray diffraction (XRD), temperature programmed reduction (TPR) with H2, Raman spectroscopy and electronic paramagnetic resonance (EPR). The reduction of NO by CO was studied in a fixed-bed reactor packed with these catalysts and fed with a mixture of 1% CO and 1% NO in helium. The catalyst with 5 wt% copper supported on the ZrO2/γ-Al2O3 matrix achieved 80% reduction of NO. Approximately the same rate of conversion was obtained on the catalyst with 2 wt% copper on ZrO2. Characterization of these catalysts indicated that the active copper species for the reduction of NO are those in direct contact with the oxygen vacancies found in ZrO2.  相似文献   

9.
The aim of this study is to develop a process for the removal of Hg0 using H2S over iron oxides sorbents, which will be located just before the wet desulfurization unit and catalytic COS converter of a coal gasification system. It is necessary to understand the reactions between the iron oxide sorbent and other components of the fuel gas such as H2S, CO, H2, H2O, etc. In this study, the sulfidation behavior and activity for COS formation during Hg0 removal from coal derived fuel gas over iron oxides prepared by precipitation and supported iron oxide (1 wt% Fe2O3/TiO2) prepared by conventional impregnation were investigated. The iron oxide samples were dried at 110 °C (designated as Fe2O3-110) and calcined at 300 and 550 °C (Fe2O3-300 and Fe2O3-550). The sulfidation behavior of iron oxide sorbents in coal derived fuel gas was investigated by thermo-gravimetric analysis (TGA). COS formation during Hg0 removal over iron oxide sorbents was also investigated using a laboratory-scale fixed-bed reactor. It was seen that the Hg0 removal activity of the sorbents increased with the decrease of calcinations temperature of iron oxide and extent of sulfidation of the sorbents also increased with the decrease of calcination temperature. The presence of CO suppressed the weight gain of iron oxide due to sulfidation. COS was formed during the Hg0 removal experiments over Fe2O3-110. However, in the cases of calcined iron oxides (Fe2O3-300, Fe2O3-550) and 1 wt% Fe2O3/TiO2, formation of COS was not observed but the Hg0 removal activity of 1 wt% Fe2O3/TiO2 was high. Both FeS and FeS2 were active for Hg0 removal in coal derived fuel gas without forming any COS.  相似文献   

10.
This work involved the investigation on the removal of organic sulfur compounds from the model liquid fuels by using adsorption desulfurization (ADS) method. For this purpose, removal of 4-methyl dibenzothiophene (4-MDBT) in model gasoline streams with raw bentonite, nanobentonite and nanobentonite modified by nanomagnetite, active carbon and Ni(NO3)2.9H2O was considered. Various factors influencing the desulfurization capability, including loading and baking temperature were investigated. Thermo-gravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX) showed that the ability of modified bentonite to adsorb 4-MDBT depends strongly on surface chemistry, particularly on the presence of basic oxygen-containing groups and acid content. The adsorbents tested for desulfurization capacity at breakthrough followed the order: 30wt% Fe3O4/30wt% Active carbon/40% Na -Nanobentonite?>?30wt% Fe3O4/30wt% Active carbon/40% Ca – Nanobentonite > 30wt % Fe3O4/70% Ca-Nanobentonite?>?15wt % Fe3O4/15wt% Ni/70% Ca– Nanobentonite. The results of preliminary tests for raw bentonite and nanobentonite were not significant in comparison with the modified nanobentonites: a, b, c, d samples, (about 40% lower than the four sample models). The optimum calcination temperature was 800°C. The multivariate methods were used for optimization of acceptance parameters. A Plackett–Burman design (PBD) was chosen as a screening method to estimate the relative influence of the factors that can be affected on the analytical response. Results show that surface area, pore size and pore volume of the bentonite can be increased several times using the impregnation method by 30wt% Fe3O4/30% active carbon. Also, the surface morphology of the bentonite is changed with this modification.  相似文献   

11.
Conclusions Interaction of zirconium dioxide with oxides of cerium, yttrium and lanthanum in solid phases occurs at 1400°C with the formation of solid solutions with the cubic structure.Sintering of the specimens may result at 1700–1750°C with a 3-h soak. At 1400°C and a 6-h soak the porosity of the specimens was 30–40%.Complete stabilization of the zirconia is attained by heating to 1700–1750°C with additions of 20 mol.% CeO2, 15% Y2O3 or 25% La2O3. An addition of ceria and yttria displaces the effects of polymorphic inversion of the zirconia to the lower temperature region.New highly refractory materials may be obtained from solid solutions of ZrO2-20% CeO2, ZrO2-80% CeO2, ZrO2-15% Y2O3, ZrO2-80% Y2O3 and ZrO2-25% La2O3 and firing to 1750°C. Some of them have a low coefficient of thermal expansion compared with ZrO2, stabilized with calcium oxide and magnesium oxide, and apparently better thermal-shock resistance. The advantage in regard to resistance during prolonged heating at 1200°C is possessed by the solution ZrO2-Y2O3. The region of the most effective use of goods made from solid solutions of ZrO2 with CeO2, Y2O3 and La2O3 as highly refractory materials should be determined by extra studies.The possibility of reducing CeO2 (fusing temperature about 2700°C) to Ce2O3 (fusing temperature about 1700°C) limits the use of cerium-containing materials as refractories in chiefly oxidizing conditions.  相似文献   

12.
Due to the increasing availability of substitute materials for electrical porcelain, research is needed to adapt formulations involving these materials to the current economic realities of the industry. This study assessed the effect of iron oxide concentration (0, 1, 2, 3, 5, and 8 wt%) on the dielectric properties of an aluminous porcelain composition commonly employed for electrical insulation based on different values of temperature and frequency. Samples with iron oxide contents of 0, 3, and 5 wt% were analyzed using dilatometry, X-ray diffraction, and scanning electron microscopy to evaluate the thermal, structural, and microstructural changes related to their Fe2O3 concentrations. Both the dielectric constant (εr) and the loss tangent (tan δ) were measured and evaluated in every sample. Results indicated that the presence of Fe2O3 increased the dielectric constant and loss tangent, which could result in an increase in heating by dielectric losses. Fe2O3 contents of up to 5 wt% had no significant effect on the performance of these insulators at room temperature (∼30 °C) and a high frequency (1 MHz), especially when the hematite phase was completely solubilized in the porcelain phases.  相似文献   

13.
J. Li  Y. Li  R. Ma  Y. Song  C. Kong  P. Song 《应用陶瓷进展》2014,113(2):102-107
Abstract

This paper described the thermodynamic analysis and experimental verification of interface reactions between iron aluminide intermetallic and tetragonal zirconia. Thermodynamic analysis confirmed that chemical reactions between Fe–Al intermetallic and ZrO2 (3 mol.–%Y2O3 stabilised zirconia) mainly depended on the Al content in Fe–Al intermetallic. For ZrO2(3Y)/Fe3Al composite, the interface reactions to form Al2O3 and ZrAl2 would take place when Al content was >40 at-% in Fe–Al intermetallic, while no interface reaction occurred when using Fe3Al as toughening phase. ZrO2(3Y)/Fe3Al composite was synthesised by hot press sintering to further verify the thermodynamic analysis of interface reactions between iron aluminide intermetallic and tetragonal zirconia. The phase composition, morphology and interface structure of ZrO2(3Y)/Fe3Al were investigated by X-ray diffraction, SEM and TEM. The results show that Fe3Al was thermodynamic stable in ZrO2(3Y) matrix, which was in good agreement with thermodynamically analysis.  相似文献   

14.
《Ceramics International》2021,47(20):28252-28259
Oxide ceramics are considered as promising high temperature solar absorber materials. The major aim of this work is the development of a new solar absorber material with promising characteristics, high efficiency and low-cost processing. Hence, this work provides a comparative and inclusive study of densification behavior, microstructure features, thermal emissivity and thermal conductivity values of the two new high temperature solar absorbers of ZrO2/Fe2O3 and Al2O3/CuO ceramics. Ceramic composites of ZrO2/(10–30 wt%) Fe2O3 and Al2O3/(10–30 wt%) CuO were prepared by pressureless sintering method at a temperature of 1700 °C/2hrs. Identification of the solar to thermal efficiency of the composites was evaluated in terms of their measured thermal emissivity. Thermal efficiency and heat transfer homogeneity were investigated in terms of thermal conductivity and diffusivity measurement. The results showed that both composites exhibited comparable densification behavior, homogenous and harmonious microstructure. However, Al2O3/10 wt% CuO composite showed higher thermal and solar to thermal efficiencies than ZrO2/Fe2O3 composites. It gave the lowest and the best thermal emissivity of 0.561 and the highest thermal conductivity of 15.4 W/m. K. These values proved to be the best amongst all those of the most known solar absorber materials made from the expensive SiC and AlN ceramics. Thus, Al2O3/CuO composites have succeeded in obtaining outstanding properties at a much lower price than its other competitive materials. These results may strongly identify Al2O3/CuO composites as promising high-temperature solar absorber materials instead of ZrO2 and the other carbide and nitride ceramics.  相似文献   

15.
The influence of “superacidic” modification has been shown to enhance the methane combustion activity of ZrO2 at 800 °C. Modification with SO4 2−, Fe/Mn/SO4 2− and MoO3 has been investigated, with the latter showing the most marked effect although this is a critical function of loading. Ceria–zirconia catalysts are also active, although the compositions studied are not as effective as 5 wt% MoO3/ZrO2 which shows a greater mass normalised activity than Fe2O3.  相似文献   

16.
The oxidative dehydrogenation of 4-vinylcyclohexene (VCH) into styrene was carried out in the presence of oxygen over a ZrO2 catalyst promoted with Fe2O3 and CaO. Intrinsically, ZrO2 showed high dehydrogenation activity, which resulted in 80% styrene selectivity with 45% conversion at 425 °C and LHSV 3 h−1. When the ZrO2 was further promoted with calcium and iron, CaO/Fe2O3/ZrO2, the highest styrene selectivity of 88.9% was obtained as well as the lowest deactivation. The deactivation of catalyst was prohibited properly through the introduction of oxygen in the reactant together with the modification of Fe2O3/ZrO2 with CaO. The CaO/Fe2O3/ZrO2 showed constant catalytic activity and selectivity for more than 50 h without deactivation. The selectivity of styrene was strongly influenced by the mole ratio of O2/VCH and 95% selectivity with 80% conversion was obtained at O2/VCH mole ratio of 6 over Fe2O3/ZrO2. It is thought that the oxidative dehydrogenation proceeds through the dehydrogenation (DH) of ring-hydrocarbon of VCH followed by selective combustion of hydrogen (SHC) and the high selectivity of styrene was achieved by the bi-functional role of ZrO2 for DH and SHC reactions. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

17.
不同制备方法对MgFe氧化物催化吸附SO2性能的影响   总被引:5,自引:0,他引:5       下载免费PDF全文
用不同的制备方式得到了 3种MgFe复合氧化物和混合物 ,即机械混合的Fe2O3 +MgO ;以MgO为载体 ,浸渍法制备的Fe2O3 /MgO ;以MgFe水滑石类为前驱体 ,经焙烧制得MgFeOx.分别测定了 3种材料对SO2 氧化吸附的速率和硫容量 ,发现MgFeOx 脱硫性能最好 ,硫容量达到 1.4gSO2/g吸附剂 .通过BET、XRD和IR的表征 ,分析了材料脱硫性能好的原因 .主要是高度分散状态的MgFeOx 中Mg和Fe的协同作用 ,Fe起到了催化氧化的作用 ,Mg是吸附中心 ,氧化和吸附的耦合加快了MgFeOx 对SO2 的吸附速率 ,增加了硫容量  相似文献   

18.
Red phosphorus was combined with metallic oxides Fe2O3 and MgO to improve the fire properties of recycled PET. Both Fe2O3 and MgO act as co‐synergist agents at a total loading of 5 wt%. The analysis by diffraction X of the char formed during combustion shows that transformation of Fe2O3 to Fe3O4 occurs. Fe2O3 favours the oxidation and improves the effectiveness of red phosphorus. It is suggested that MgO interacts with acidic end groups of PET and forms a thermal stable residue. The thermal decomposition of recycled PET containing red phosphorus combined with Fe and Mg oxides was studied by thermal analysis and leads to an increase in char formation. While the incorporation of Fe2O3 in this ternary blend maintains the mechanical properties of PET, the reactivity of MgO leads to a brittle material. The use of reinforcements (talc and glass fibres) to mechanically stabilize the char formed during combustion of ternary blend with Fe2O3 entails a further decrease in heat release rate, nevertheless impact resistance of the material decreases dramatically. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

19.
Mill scale scrap, which contains vast amounts of valuable metals, is a solid waste produced in the iron and steel industry. Conventional mill scale scrap treatment methods for metal extraction are characterized by high energy consumption and low value addition. In this study, co-treatment of mill scale scrap and manganese ore via the oxidization roasting-magnetic separation process was investigated for the synchronous preparation of higher-value materials and recovery of valuable metals. Thermodynamic and magnetism analyses indicated that a higher temperature (>1100 °C) and a MnO2/Fe2O3 molar ratio of 0.75–1 are essential for the preparation of manganese ferrite. The experimental validation revealed that soft magnetic manganese ferrite powders with a purity of 97.5 wt% were obtained when the test was conducted at 1300 °C for 120 min, followed by a two-stage grinding and magnetic separation process; the corresponding yield and the Mn and Fe recoveries were 78.99 wt%, 86.14 wt%, and 84.60 wt%, respectively. During the oxidization process, [Fe2+]O was initially oxidized to the anti-form spinel-type structure of [Fe3+][Fe2+Fe3+]O4, and thereafter, it reacted with the decomposition product of [Mn3+][Mn2+Mn3+]O4 to form a hybrid spinel-type structure [Me2+xMe3+l-x][Me2+1-xMe3+1+x]O4 (Me refers to Mn and Fe) via the Mn2+/Fe2+/Mn3+/Fe3+ ions exchange at the tetrahedral and octahedral sites. Moreover, the as-purified ferrite can be used as an ingredient for the preparation of high-performance MnZn ferrite.  相似文献   

20.
Conclusions A technology was developed for the production of zirconia refractories from ZrO2 stabilized with Nd2O3. The thermal strength of the product is adequate for long-term service at a large (200–300°C/mm) temperature gradient. Products based on a zirconia — neodymium solid solution can be used several times.It was established that no appreciable Nd2O3 vaporization and, consequently, no appreciable destabilization of the ZrO2 develops in a neutral medium at 2100–2500°C.The solid-phase processes developing at 2100–2500°C in products from a mixture of 70% cubic solid solution (88 mole % ZrO2+12 mole % Nd2O3) and 30% unstabilized ZrO2 fired at 1750°C consist of the redistribution of the Nd2O3 between the cubic solid solution Nd2Zr2O7-ZrO2 and the unstabilized ZrO2, and the diffusion of some of the Nd2O3 from the cooler to the working zone.Translated from Ogneupory, No. 3, pp. 52–55, March, 1976.  相似文献   

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