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钯、铜、锰、铈三效催化剂性能研究 总被引:6,自引:0,他引:6
应用脉冲-火焰反应装置、XRD、TPR和氢氧滴定技术来研究Pd-Cu-Mn-Ce-O三效催化剂的性能。实验结果表明,不同的制备Pd-Cu-Mn-Ce-O催化剂的方法,则催化活性各不相同。在分层制备的催化剂中,催化性能主要以外层组分性能为主;以混合浸渍法制备的样品中,CuMn_2O_4相消失,Cu-Mn-Ce-O表面氧环境发生变化;表面活性剂的添加改变了Pd的分布,使催化剂表面易于还原;这些改变均对催化剂的三效性能发生影响。催化剂表面的有效贮氧量与三效活性没有明显的关系。 相似文献
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汽车尾气净化剂的发展,现状及前景 总被引:4,自引:0,他引:4
催化净化是控制汽车尾气污染的主要手段。文章介绍了汽车尾气催化剂的发展过程:描了了当今普遍使用的三效转化催化剂“提出了未来尾气净化催化剂的发展趋势及需要解决的问题,TWC催化剂是以贵金属Pt,Pd和Rh为适性组元,引入Ce,La,Ba和Zr等为助剂,担载在高比表面物质上制备面成一的类性能优虹的催化剂,它能对尾气中的3种主要有害物质NOx,CO和HC同时进行转化。 相似文献
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PrO/γAl2O3等稀土氧化物催化还原SO2的研究 总被引:7,自引:0,他引:7
进行了负载于氧化铝上的镨,钕,锌,镧,钐等稀土氧化物上,CO,CH3及H2催化还原SO2反应的研究。实验着重考察了Pr-O/γ-Al2O3上CO2催化还在SO2的反应,测定了不同反应温度,不同反应物配比及不同空速下的活性,同时对Pr-o/γ-Al2O3催化剂进行了TPD,TG,XRD,XPS表征。结果表明,稀土氧化物具有非常高的CO催化还原SO2反应的活性,在500℃,CO:SO2=2:1,空速比 相似文献
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Activity and stability of 1%Pd-0.2%Pt/Al2O3 and 1%Pd-0.2%Pt/0.6%Ce/Al2O3 catalysts prepared by impregnation method for catalytic combustion of methane in air were investigated. The catalysts before and after reaction were characterized by BET, CO chemisorption, XRD and XPS techniques. Results showed that the presence of Ce significantly increased the activity and thermal stability of the Pd-Pt/Al2O3 catalyst towards methane combustion, which could be attributed to more highly-dispersed active PdO particles over the Pd-Pt/Ce/Al2O3 catalyst surface as well as the retarded sintering of PdO and the maintained oxidized state of surface Pd during the combustion process in the presence of Ce. 相似文献
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Mo-modified Pd/Al2O3catalysts were prepared by an impregnation method and tested for the catalytic combustion of benzene. The catalysts were characterized by N2 isothermal adsorption, X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), temperatureprogrammed desorption of NH3(NH3-TPD), H2temperature-programmed reduction(H2-TPR), and high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM). The results showed that the addition of Mo effectively improved the activity and stability of the Pd/Al2O3catalyst by increasing the dispersion of Pd active components, changing the partial oxidation state of palladium and increasing the oxygen species concentration on the surface of catalyst. In the case of the Pd-Mo/Al2O3catalyst,benzene conversion of 90% was obtained at temperatures as low as 190°C, which was 45°C lower than that for similar performance with the Pd/Al2O3catalyst. Moreover, the 1.0% Pd-5% Mo/Al2O3catalyst was more active than the 2.0% Pd/Al2O3catalyst. It was concluded that Pd and Mo have a synergistic effect in benzene catalytic combustion. 相似文献
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The effect of pretreatment on Pd/Al2O3 catalysts for the catalytic oxidation of o-xylene at low temperature was studied by changing the pretreatment and testing conditions. The fresh and pretreated Pd/Al2O3 catalysts were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The results showed that the pretreatment dramatically changed the Pd/PdO ratio and then significantly affected the Pd/Al2O3 activity; while the pretreatment had not much influence on Pd particle size. The Pd/Al2O3 pre-reduced at 300℃/400℃, which has fully reduced Pd species, showed the highest activity; while the fresh Pd/Al2O3, which has fully oxidized Pd species, presented the worst performance, indicating the Pd chemical state plays an important role in the catalytic activity for the o-xylene oxidation. It is concluded that metallic Pd is the active species on the Pd/Al2O3 catalyst for the catalytic oxidation of o-xylene at low temperature. 相似文献
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以共浸渍法制得的氧化铝负载铈锆固溶体为载体,并浸渍贵金属Pd得到了Pd/CZ/Al2O3催化剂.实验结果表明,该催化剂在老化前后都表现出良好的三效催化活性,新鲜样品Pd/CZ/Al2O3活性与Pd/CZ相当,老化后样品前者优于后者.结合XRD,BET,TPR等表征手段,讨论了Pd/CZ/Al2O3的催化活性特别是高温老化后活性与其组成结构之间的内在关系,揭示了其老化后仍具有较高活性的主要原因在于保持了Pd与CZ/Al2O3复合载体之间的强相互作用(SMSI). 相似文献
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Yunrui ZHOU Wanpeng ZHU Xun CHEN 《Frontiers of Environmental Science & Engineering in China》2008,2(3):354-357
In this paper, factors influencing the mineralization of dimethyl phthalate (DMP) during catalytic ozonation with a cerium-doped
Ru/Al2O3 catalyst were studied. The catalytic contribution was calculated through the results of a comparison experiment. It showed
that doping cerium significantly enhanced catalytic activity. The total organic carbon (TOC) removal over the doped catalyst
at 100 min reached 75.1%, 61.3% using Ru/Al2O3 catalyst and only 14.0% using ozone alone. Catalytic activity reached the maximum when 0.2% of ruthenium and 1.0% of cerium
were simultaneously loaded onto Al2O3 support. Results of experiments on oxidation by ozone alone, adsorption of the catalyst, Ce ion’s and heterogeneous catalytic
ozonation confirmed that the contribution of heterogeneous catalytic ozonation was about 50%, which showed the obvious effect
of Ru-Ce/Al2O3 on catalytic activity.
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Translated from China Environmental Science, 2006, 26(4): 445–448 [译自: 中国环境科学] 相似文献
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《环境科学学报(英文版)》2023,35(4):333-347
Pd/Al2O3 catalysts supported on Al2O3 of different particle sizes were synthesized and applied in methane combustion. These catalysts were systematically characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), high resolution-transmission electron microscopy (HR-TEM), high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM), H2-temperature-programmed reduction (H2-TPR), O2-temperature-programmed oxidation (O2-TPO), X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine structure (XAFS). The characterization results indicated that nano-sized Al2O3 enabled the uniform dispersion of palladium nanoparticles, thus contributing to the excellent catalytic performance of these nano-sized Pd/Al2O3 catalysts. Among them, Pd/Al2O3-nano-10 (Pd/Al2O3 supported by alumina with an average particle size of 10 nm) showed superior catalytic activity and stability for methane oxidation under harsh practical conditions. It maintained excellent catalytic performance for methane oxidation for 50 hr and remained stable even after harsh hydrothermal aging in 10 vol.% steam at 800°C for 16 hr. Characterization results revealed that the strong metal-support interactions and physical barriers provided by Al2O3-nano-10 suppressed the coalescence ripening of palladium species, and thus contributed to the superior sintering resistance of the Pd/Al2O3-nano-10 catalyst. 相似文献
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Kai Cheng Jian Liu Tao Zhang Jianmei Li Zhen Zhao Yuechang Wei Guiyuan Jiang Aijun Duan 《环境科学学报(英文版)》2014,26(10):2106-2113
CeO2–TiO2composite supports with different Ce/Ti molar ratios were prepared by a homogeneous precipitation method, and V2O5–WO3/CeO2–TiO2catalysts for the selective catalytic reduction(SCR) of NOx with NH3 were prepared by an incipient-wetness impregnation method. These catalysts were characterized by means of BET, XRD, UV–Vis,Raman and XPS techniques. The results showed that the catalytic activity of V2O5–WO3/TiO2 was greatly enhanced by Ce doping(molar ratio of Ce/Ti = 1/10) in the TiO2 support.The catalysts that were predominantly anatase TiO2 showed better catalytic performance than the catalysts that were predominantly fluorite CeO2. The Ce additive could enhance the surface adsorbed oxygen and accelerate the SCR reaction. The effects of O2 concentration, ratio of NH3/NO, space velocity and SO2 on the catalytic activity were also investigated. The presence of oxygen played an important role in NO reduction. The optimal ratio of NH3/NO was 1/1 and the catalyst had good resistance to SO2 poisoning. 相似文献
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The present article studies the effect of CeO2 and Al2O3 on the activity of Pd/Co3O4/cordierite catalyst in conversion of NO, CO, CnHm. The catalysts were characterized by temperature programmed reduction with hydrogen, X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. It is shown that the effect of CeO2 on the properties of Pd/Co3O4/cordierite catalyst depends on preparation method. The catalyst obtained by co-deposition of cerium and cobalt oxides has higher activity in CO oxidation (CO + O2 and CO + NO) and total hexane oxidation (C6H14 + O2). Such phenomenon is probably caused by more than stoichiometric amount of formed oxygen vacancies, an increase in both mobility of surface oxygen and dispersity of components in the catalytic composition. It is demonstrated that CeO2 addition promotes the SO2 resistance of Pd/Co3O4/cordierite. The second support decreases the activity of Pd/Co3O4/cordierite catalyst in the reactions of CO and C6H14 with oxygen because of CoAl2O4 formation. 相似文献
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《Journal of Cleaner Production》2006,14(8):708-712
Industrial production of hydrogen peroxide by anthraquinone (AO) process in China was briefly introduced. The pathways for cleaner production of hydrogen peroxide were discussed in detail from the viewpoint of process development and design, these included the replacement of Raney-Ni catalyst by highly active and highly selective Pd/Al2O3 catalyst, the reduction of raw materials, steam and power consumption, the usage of high boiling point, low water-soluble and low toxic solvents, the regeneration of degradations, the proper treatment of waste gas, water and solids. Because of these innovations and improvements, the AO process with Pd/Al2O3 catalyst for producing hydrogen peroxide was certified as a cleaner production technology by the Chinese government. 相似文献
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为解决传统铁基芬顿催化剂在水体通常酸碱(pH6)条件下活性低的问题,采用简单共沉淀法制备了Cu掺杂的Al_2O_3类芬顿催化剂.通过X射线衍射(XRD)、X射线光电子能谱(XPS)和紫外可见(UV-vis)吸收光谱分析表明,Cu-Al_2O_3中铜掺杂的质量分数低于4.77%时,催化剂中铜主要以Cu~(2+)和Cu~+的形式共存于Al_2O_3的骨架结构中,形成Al—O—Cu键;过量的铜掺杂会导致外骨架铜物种如铜氧化物团簇的存在.以难降解有机污染物2-氯苯酚(2-chlorophenol,2-CP)和染料罗丹明B(Rhodamine B,Rh B)为目标污染物,对Cu-Al_2O_3的类芬顿催化性能进行了详细地研究.结果表明,骨架铜物种在中性温和条件下对2-CP和Rh B显示出很高的催化去除效率和稳定性,反应2 h,Cu-Al_2O_3(Cu质量分数4.77%)对2-CP的去除率达到54%,相应的TOC去除率达到49%,而铜离子溶出浓度仅为0.025 5 mg·L-1,而Cu-Al_2O_3(Cu质量分数7.58%)由于外骨架铜的存在导致催化活性增加缓慢和稳定性下降.ESR测试结果表明,·OH和HO_2~-/O_2~-·是反应中主要的活性物种. 相似文献