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1.
The V-K catalysts were produced on porous α-alumina substrate by a solution impregnation route and the compositions and catalytic activities for soot oxidation were
studied by XRD, TG/DTG, DSC and TPR. According to the catalytic activity studies, the catalytic activity of the crystalline
phases is in the order: KNO3+KVO3>K3V5O14+KVO3. The appearance of excessive KHCO3 phase will lead to the deterioration of catalytic activity when the catalysts contain higher KNO3 content. It is also found that when the K:V molar ratio is higher than 1:1, the prepared catalysts show a strong CO2 absorption characteristic and this behavior will become gradually significant with the increasing of K:V molar ratio. Considerable
amount of absorbed CO2 are strongly bonded to the crystal lattice with onset desorption temperature of 200 °C. 相似文献
2.
采用KNO3、Ba(NO3)2、Sm(NO3)3.6H2O 3种化合物为原料,以多孔氧化铝为载体,运用涂抹法制备了用于催化柴油机尾气碳烟氧化的催化剂。用TPR对催化剂的活性进行了测量,并采用SEM和XRD对其结构进行了表征。实验结果表明,K-Ba-Sm催化剂的催化性能良好,最终能将陶瓷基片上的碳烟在低于450℃条件下完全催化氧化掉。其中以n(K)∶n(Ba)∶n(Sm)=1∶0.1∶0.1组成的催化剂效果最好,其起燃点为325℃。保持K、Ba的含量不变,随着Sm(NO3)3.6H2O物质的量的增大,其催化活性有些减弱,碳烟起燃温度升高。另外,K、Ba、Sm组成的催化剂有吸收空气中CO2的现象。 相似文献
3.
CO氧化催化剂研究进展 总被引:1,自引:0,他引:1
在 CO氧化过程中贵金属催化剂活性好、寿命长 ,但由于贵金属资源缺乏 ,人们又探讨用非贵金属或少量贵金属来替代贵金属催化剂。其中 ,稀土氧化物在 CO氧化催化剂中的作用越来越引起人们的重视。本文对 CO氧化催化剂的种类和发展现状作了综述 相似文献
4.
文章采用浸渍法、水热合成法和共沉淀法制备了3种不同类型的碳烟催化剂:CeFeCo、La-Mn-O和BiCeO。通过对3种样品扫描电镜(SEM)、X射线衍射(XRD)、X射线电子能谱(XPS)和氢气程序升温还原(TPR)等表征结果进行比较分析,发现:La-Mn-O样品中吸附氧的占比量最大;CeFeCo样品中的金属离子含量最多,且Ce3+含量大于BiCeO样品。在氢气程序升温还原中,可以观察到CeFeCo具有最低温的还原峰,在283℃左右。最后通过程序升温氧化反应系统对3个样品进行活性评估,在紧密接触情况下CeFeCo、La-Mn-O和BiCeO样品催化50%碳烟氧化所需的温度,即T50分别为329、355和374℃,与碳烟燃烧的空白组相比,T50分别降低了265、239和220℃。这表明3种催化剂均成功制备并且具有良好的催化碳烟燃烧性能,特别是CeFeCo催化剂表现出的低温催化燃烧性能最好。 相似文献
5.
采用低温燃烧合成法制备了纳米级不同K 取代量的La1 - x KxCoO3 催化剂,通过H2 -TPR,XRD,BET 和化学分析等多种方法对催化剂的组成和结构进行了表征,利用程序升温氧化反应( TPO) 评价了催化剂同时净化碳颗粒物和NOx 的催化活性,考察了K+ 掺杂后晶体结构和表面氧化性能的变化对催化剂性能的影响。结果表明,K+ 部分取代La3 + 会影响La1 - x KxCoO3的晶体结构和组成。当x ≤0. 3 时,La1 - x KxCoO3仍为单一的斜方晶型钙钛矿结构,晶格参数和晶粒度增大;当x ≥0. 4 后,出现不能进入晶格析出的Co3O4 晶体。La1 - x KxCoO3钙钛矿
型催化剂对碳烟和NOx 同时净化具有良好的催化活性,La0. 7 K0. 3CoO3 催化剂氧的非化学计量值λ最大为0. 017 6,表面氧空位量最多,催化活性最好,碳烟在催化剂上的起燃温度下降到290 ℃,NOx 的转化率为53 %。 相似文献
6.
Hairong Yin Chunxiang Zhang Liying Liu Guoping Chen Baojun Tang 《武汉理工大学学报(材料科学英文版)》2009,24(4):640-643
The glass-forming region of B2O3-Al2O3-SiO2 (BAS) glass heavily doped with rare earth oxides was investigated by an effective method, and the chemical stability was
investigated by powder method. Influences of rare earth oxides on the glass-forming ability and the chemical stability of
the BAS glass were also discussed. The experimental results show that the BAS glass-forming region expands firstly with the
increase of the Tb2O3 content up to 30mol% and then shrinks. The acid-resistant capacity of the BAS glass doped with rare earth oxides is the lowest,
the water-resistant capacity is secondary, and the alkali-resistant capacity is the best. Besides, the glass chemical stability
can be improved by doping appropriate amount of rare earth oxides. Moreover, the stronger the ionic polarization ability of
the rare earth ions is, the better the chemical stability of the BAS glass will be. 相似文献
7.
Two types of secondary emitter materials, the rare earth oxides (RE2O3) doped Mo cermet cathodes and the Y2O3-W matrix pressed cathode, are introduced in this paper. According to the calculation results, Y2O3 exhibits the best secondary emission property among Y2O3, La2O3, CeO2 and Lu2O3. The rare earth oxides co-doped Mo cathodes in which Y2O3 is the main active substance exhibit better secondary emission property than single RE2O3 doped Mo cathode. The results obtained by the Monte-Carlo calculation method show that the secondary electron emission property is strongly related to the grain size of the cathode. The decreasing of the grain size reduces the positive charge effect of the rare earth oxide due to the electrons supplement from the metal to the rare earth oxide, whereby the secondary electrons are easier to escape into the vacuum. Y2O3 is introduced into Ba-W cathode to fabricate a pressed Y2O3-W matrix dispenser cathode. The result indicates that the secondary emission yield of the Ba-W cathode increases from 2.13 to 3.51 by adding Y2O3, and the thermionic emission current density (J 0) could reach 4.18 A/cm2 at 1050 °Cb. 相似文献
8.
以Al(NO3)3(或Al2O3)和KNO3(或KOH)为原料,采用直接涂抹法,制取不同比例的Al/K碳烟催化剂。通过程序升温氧化(TPO)研究了焙烧温度、老化时间对催化剂催化活性的影响,同时用XRD对催化剂的成分进行分析。结果表明,Al/K摩尔比为3∶1、1∶1和3∶1的Al2O3/KNO3,Al(NO3)3/KNO3和Al2O3/KOH催化活性都较高。但是,高温焙烧或老化时,由于降低催化剂的比表面积导致催化剂催化活性明显降低;Al2O3/KOH经过焙烧形成K2Al2O4,故表现出较好的催化活性,但是吸水能力较强。 相似文献
9.
Granular CuO-CeO2-MnO
x
/γ-Al2O3 catalysts were synthesized by the sol-gel method. The performance of the CuO-CeO2-MnO
x
/γ-Al2O3 catalysts for the selective catalytic reduction (SCR) was studied in a fixed bed system. Preliminary tests were carried out
to analyze the behavior of NH3 and NO over catalyst in the presence of oxygen. The optimum temperature range for SCR over the CuO-CeO2-MnO
x
/γ-Al2O3 catalysts is 300–400 °C. The catalysts maintain nearly 100% NO conversion at 350 °C. The °C NH3 oxidation experiments show that both NO and N2O are produced gradually with the increase of temperature. The catalysts in this experiment have a stronger oxidation property
on NH3, which improves the denitrification activity at low temperature. The over-oxidation of NH3 at high temperature is the main cause leading to a decrease in the NO conversion. The NH3 and NO desorption experiments show that NH3 and NO can be adsorbed on CuO-CeO2-MnO
x
/γ-Al2O3 granular catalysts. The transient response of NH3 and NO indicates that the SCR reaction proceeds in accordance with the Eley-Rideal mechanism. The adsorbed NO has little
influence on the denitrification activity in SCR process.
Foundation item: Projects (50776037, 50721005) supported by the National Natural Science Foundation of China 相似文献
10.
The ignition-proof mechanism of ZM5 magnesium alloy added with 0.1% (mass fraction) rare earth (RE) was investigated. The oxide scales and substrates were characterized by scanning electronic microscope (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and tensile test. And an oxidation model of ZM5 alloy with RE was established. The results show that the ignition temperature of ZM5 alloy is particularly elevated from 654 to 823 ℃, the microstructure is refined, and the tensile strength i... 相似文献
11.
靳惠明 《武汉理工大学学报(材料科学英文版)》2010,25(5):734-737
Electroless Ni-P/nano-CeO2 composite coating was prepared in acidic condition, and its microstructure and corrosive property were compared with its
CeO2-free counterpart. Scanning electronic microscopy (SEM), transmission electronic microscopy (TEM) and differential scanning
calorimeter (DSC) were used to examine surface morphology and microstructure of the coating. Aqueous corrosion was done in
3%NaCl+5%H2SO4 solution and high temperature oxidation was done at 750 °C in air. The results showed that Ni-P coating had partial amorphous
structure mixed with nano-crystals, while the Ni-P/CeO2 coating had perfect amorphous structure. At high temperature, Ni3P precipitation and Ni crystallization took place in both
coatings at different temperatures. Aqueous corrosion property and high temperature oxidation property of the composite coating
were remarkably improved due to the coating’s microstructure change and the rare earth doping effect. During the co-deposition
process, some Ce
n+(n=3, 4) ions may be adsorbed to metal/solution interface and hinder nickel deposition. Ni-P/CeO2 coating’s perfect amorphous structure results from the hindered crystal- typed deposition of nickel and the promoted deposition
of phosphorous. 相似文献
12.
采用溶胶-凝胶法合成了K2 Ti4O9 , K2 Ti6O13 和K2 Ti2O5 钛酸钾型催化剂。利用X 射线衍射 (XRD)、智能重量分析仪(IGA)等手段进行了表征, 同时采用固定床对钛酸钾催化脱除柴油机尾气中碳烟颗粒的性能进行了测试, 并对钛酸钾催化氧化碳烟的动力学进行了研究。结果表明, 钛酸钾与传统催化剂相比具有更高的碳烟颗粒氧化性能, 在松散接触下依然能保持良好的活性, 且钾钛物质的量比为1 ∶1 的钛酸钾催化剂的脱除碳烟颗粒的效果最好。钛酸钾作用下碳烟的氧化为一级动力学反应, 且所建立的碳烟燃烧动力学方程与实验数据拟合较好。 相似文献
13.
采用溶胶-凝胶法合成了K2Ti4O9,K2Ti6O13和K2Ti2O5钛酸钾型催化剂。利用X射线衍射(XRD)、智能重量分析仪(IGA)等手段进行了表征,同时采用固定床对钛酸钾催化脱除柴油机尾气中碳烟颗粒的性能进行了测试,并对钛酸钾催化氧化碳烟的动力学进行了研究。结果表明,钛酸钾与传统催化剂相比具有更高的碳烟颗粒氧化性... 相似文献
14.
李媛媛 《武汉理工大学学报(材料科学英文版)》2016,31(4):823-826
Carbon nanoparticles (C-dots) were prepared by refluxing the combustion soots of candles and corn stalk in nitric acid. The synthesized C-dots were characterized. The results showed a sharp increase in oxygen content and a sharp decrease in carbon content after oxidation. The C-dots had -OH and -CO2H groups introduced which made them hydrophilic. However, their difference was also obvious. The C-dots from candle soot had a 10-45 nm broad particle size distribution, and those from corn stalk soot had a 6-18 nm relatively small and narrow size distribution. The C-dots were mainly of sp 2 and sp 3 carbon structure different from the C-dots of diamond-like structure from candle soot. Interestingly, two kinds of C-dots all exhibited unique photoluminescent properties. The obtained C-dots have potential applications in a broad range of areas. 相似文献
15.
颜学敏 《武汉理工大学学报(材料科学英文版)》2014,29(2):237-241
A series of mesoporous phosphotungstic acid/alumina composites (HPW/Al_2O_3) with various HPW contents were synthesized by evaporation-induced self-assembly method. These composites were characterized by nitrogen adsorption-desorption, TEM, FTIR, and UV-vis, and were tested as catalysts in oxidation desulfurization of model fuel composed of dibenzothiophene (DBT) and hydrocarbon, using H202 as the oxidant. These composites exhibited high activity in catalytic oxidation of DBT in model fuel and good reusing ability. The best performance was achieved by using the mesoporous HPW/Al_2O_3 with 15wt% HPW content, which resulted in a DBT conversion of 98% after 2 h reaction at 343 K, and it did not show significant activity degradation after 3 recycles. Characterization results showed that the mesoporous structure of alumina and the Keggin structure of HPW were preserved in the formed composite. These results suggested that HPW/ Al_2O_3 could be a promising catalyst in oxidative desulfurization process. 相似文献
16.
The selective catalytic reduction reaction belongs to the gas-solid multiphase reaction, and the adsorption of NH3 and NO on CuO/γ-Al2O3 catalysts plays an important role in the reaction. Performance of the CuO/γ-Al2O3 catalysts was explored in a fixed bed adsorption system. The catalysts maintain nearly 100% NO conversion efficiency at 350
°C. Comprehensive tests were carried out to study the adsorption behavior of NH3 and NO over the catalysts. The desorption experiments prove that NH3 and NO are adsorbed on CuO/γ-Al2O3 catalysts. The adsorption behaviors of NH3 and NO were also studied with the in-situ diffusion reflectance infrared Fourier transform spectroscopy methods. The results
show that NH3 could be strongly adsorbed on the catalysts, resulting in coordinated NH3 and NH4+ NO adsorption leads to the formation of bridging bidentate nitrate, chelating bidentate nitrate, and chelating nitro. The
interaction of NH3 and NO molecules with the Cu2+ present on the CuAl2O4 (100) surface was investigated by using a periodic density functional theory. The results show that the adsorption of all
the molecules on the Cu2+ site is energetically favorable, whereas NO bound is stronger than that of NH3 with the adsorption site, and key information about the structural and energetic properties was also addressed. 相似文献
17.
Photocatalytic reduction of CO2 was carried out on villiform spherical catalysts of Pd-TiO2 in isopropanol solution. The catalysts were synthesized by hydrothermal method, their structures, morphologies and optical absorption properties were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and UV-vis absorption spectroscopy (UV-vis). The photocatalytic activities with different loading amounts and morphologies were evaluated for determining the dominant effect and optimizing the catalyst preparation. Based on a villiform spherical TiO2 with the largest specific surface area in our experiments, we prepared a set of catalysts with various loading amounts of palladium and tested them by bubbling CO2 through the slurry of catalyst and isopropanol. The highest formation rate of isopropyl formate was 276.6 μmol/g·cat/h. Eventually we proposed the reaction mechanism. 相似文献
18.
阐述了近年来我国重油催化裂化催化剂的发展状况。近年来 ,重油的催化裂化发展很快 ,新型的重油催化裂化催化剂不断应用于工业中。我国重油催化裂化催化剂在性能上有很大突破 :其重油裂化能力高 ,抗重金属污染 ,并且干气和焦炭产率低。RFCC催化剂的新品种也在不断推出 ,我国的稀土Y型分子筛、超稳Y型分子筛和稀土 1氢Y分子筛催化裂化催化剂的品种在不断更新换代。工业应用结果表明 ,USY分子筛重油催化裂化催化剂具有高的水热稳定性 ,低的焦炭选择性 ,以及较好的抗重金属污染能力。我国研究开发抗重金属污染的催化裂化钝化剂已应用于工业中 ,而且效果令人满意。我国新开发的DCC ,MGG ,ARGG ,MIO ,HCC等几种典型重油催化裂化工艺所用的催化剂具有世界水平。此外 ,Orbit系列重油催化裂化催化剂的工业实践表明 ,该系列催化剂性能很好 ,可以满足不同装置的需要 相似文献
19.
Hu Guorong Liu Yexiang Yang Jianhong 《中南工业大学学报(英文版)》1999,6(1):13-15
Diamondtoolsaremadegeneralythroughthepowdermetalurgicalsinterproces.Itisobviousthattheinterfaceenergybetwenthediamondandord... 相似文献
20.
The soot surface growth plays significant role on the soot mass accumulation,which starts with H(hydrogen)atom abstraction forming activated soot surface sites,and is followed by the acetylene addition process.In this study,the effect of the mixture inhomogeneity and combustion temperature on the soot surface activity and soot formation was investigated by developing a new multi-step phenomenological(MSP)soot model of diesel engines.A new detailed soot surface growth mechanism was proposed by correlation analysis of combustion parameters with soot formation.The inhomogeneity coefficient of soot surface activityαCH and the specific rate of soot surface growth R CH were derived to highlight the effect of inhomogeneity of mixture and combustion temperature on soot formation.The predicted diesel engine-out soot agreed well with experimental findings in wide ranges of combustion conditions.In the case of lower engine load with single fuel injection and higher EGR(exhaust gas recirculation)rate,it had quiet homogeneous mixtures before ignition when the combustion temperature dominated the soot surface activity.At medium engine load with multi-pulse fuel injections,it got mixture slightly stratified before ignition and revealed that the mixture inhomogeneity became more dominated on soot surface activity than the combustion temperature.An increased soot surface activity led to increased soot emission.Under the full engine loads with single fuel injection but quite high boost pressure over 0.4 MPa,it led to the combustion conditions of higher mixture density and higher mixture heat capacity,which benefits the mixture homogeneity.The decay rate of soot surface activity became lower due to the decreased combustion temperature and the soot surface activity decreased due to improved mixture homogeneity.In addition,the lowered intake oxygen concentration due to usage of EGR played a role to lower the specific rate of soot surface growth R CH,but to increase the soot surface activityαCH. 相似文献