Rare earth containing catalysts for selective catalytic reduction of NO_x with ammonia:A Review

Increasingly stringent regulations in many countries require effective reduction and control of NOx emissions. To meet these limits, various methods have been exploited, among which the selective catalytic reduction of NOx using ammonia as the reductant(NH3-SCR) is the most favored technology. High catalytic activity, N2 selectivity and resistance to deactivation by sulfur, alkaline metals and hydrothermal conditions are the optimal properties of a successful SCR catalyst. Rare earth oxides, particularly CeO2, have been increasingly used to improve the catalytic activity and resistance to deactivation of deNOx catalysts, both modifying traditional vanadium catalysts, and also developing novel catalysts, especially for low temperature applications. This review summarized the open literature concerning recent research and development progresses in the application of rare earths for NH3-SCR of NOx. Additionally, the roles of rare earths in enhancing the performance of NH3-SCR catalyst were reviewed.     

Structure and oxygen storage capacity of Pd/Pr/CeO_2-ZrO_2 catalyst:effects of impregnated praseodymia

Praseodymium(Pr) was impregnated to CeO2-ZrO2 solid solution by an impregnation method.The as-obtained Pr modified CeO2-ZrO2 was impregnated with 1 wt.% Pd to prepare the catalysts.The structure and reducibility of the fresh and hydrothermally aged catalysts were characterized by X-ray diffraction(XRD),Raman,X-ray photoelectron spectroscopy(XPS),CO chemisorption and H2 temperature-programmed reduction(H2-TPR).The oxygen storage capacity(OSC) was evaluated with CO serving as probe gas.Effects of impregnated Pr on the structure and oxygen storage capacity of catalysts were investigated.The results showed that the aged Pr-impregnated samples had much higher OSC and better reducibility than the unmodified ones.The scheme of structural evolutions of the catalysts with and without Pr was also established.Partial of the impregnated Pr diffused into the bulk of CeO2-ZrO2 during ageing,which inhibited the sintering,and increased the amount of oxygen vacancies in CeO2-ZrO2 support.Furthermore,those impregnated Pr species which covered on the surface of the support obstructed the strong metal-support interaction between Pd and Ce so as to reduce the encapsulation of Pd as well as the back spill-over of the oxygen during the catalytic process.     

PVC塑钢中稀土热稳定剂的研究进展及产业分析

“绿色、科技、人文”是2008年奥运会的三大主题。随着奥运场馆建设的开工以及承办奥运所需投入的其他建设项目的启动，建筑业和建材工业将面对一个巨大的革新，“绿色”建筑塑料已成为21世纪建材工业的发展方向。热稳定剂是PVC加工中的重要助剂，发展“绿色”建筑塑料的要求也势必导致未来热稳定剂行业的主要发展趋势是高效、低毒、复合型、无污染，无铅类稳定剂逐渐成为发展的重点。     

稀土钙钛矿催化剂制备方法的研究进展

稀土钙钛矿超微粉体的常规制备方法主要有机械混合法、化学共沉淀法、溶胶-凝胶法以及微乳液法等等。本文总结了以上各种方法的制备过程、特点以及在工艺优化方面国内外所取得的研究进展,并从机理上探讨了上述工艺对稀土钙钛矿催化剂相关性能的影响。     

钇掺杂对Ce0.33Zr0.67O2储氧性能的影响

采用柠檬酸溶胶凝胶法制备了一系列钇掺杂的富锆铈锆复合氧化物Ce0.33YxZr0.67-xO2,并通过XRD,BET,OSC,XPS,in-situ CO-FTIR等测试,系统研究了钇掺杂后铈锆复合氧化物储放氧性能的变化规律及其影响因素。结果表明,钇离子能够进入铈锆晶格形成固溶体,并提高铈锆体系的结构热稳定性。对于新鲜样,钇掺杂可大幅提升Ce0.33Zr0.67O2材料的比表面积,提高单位质量铈锆材料的储氧能力;但老化后,钇掺杂样品的储氧性能随着掺杂量的增加而减小。通过XPS及原位红外吸附性能测试证实,钇在Ce0.33Zr0.67O2材料表面主要取代锆离子,其掺杂会降低样品的表面吸附能力,抑制铈的氧化还原反应,从而导致该体系储氧性能的下降。     

Structure and oxygen storage capacity of Pd/Pr/CeOe-ZrO2 catalyst： effects of impregnated praseodymia

Praseodymium （Pr） was impregnated to CeO2-ZrO2 solid solution by an impregnation method. The as-obtained Pr modi- fied CeO2-ZrO2 was impregnated with 1 wt.% Pd to prepare the catalysts. The structure and reducibility of the fresh and hydrother- really aged catalysts were characterized by X-ray diffraction （XRD）, Raman, X-ray photoelectron spectroscopy （XPS）, CO chemi- sorption and H2 temperature-programmed reduction （H2-TPR）. The oxygen storage capacity （OSC） was evaluated with CO serving as probe gas. Effects of impregnated Pr on the structure and oxygen storage capacity of catalysts were investigated. The results showed that the aged Pr-impregnated samples had much higher OSC and better reducibility than the unmodified ones. The scheme of structural evolutions of the catalysts with and without Pr was also established. Partial of the impregnated Pr diffused into the bulk of CeO2-ZrO2 during ageing, which inhibited the sintering, and increased the amount of oxygen vacancies in CeO2-ZrO2 support. Furthermore, those impregnated Pr species which covered on the surface of the support obstructed the strong metal-support interaction between Pd and Ce so as to reduce the encapsulation of Pd as well as the back spill-over of the oxygen during the catalytic process.     

山区35kV补偿电网消弧线圈投切运行的暂态分析(英文)

Based on a lot of measurement and analysis,this paper find that the unbalanced nature of 35 kV grids due to unsymmetrical capacitance values gives difficulty in neutral point operation in mountainous area.Improving compensation of Petersen coil can rectify imbalance of voltage but bring up new problem that Petersen coil can not extinguish grounding arc effectively in fault.To put down contradiction mentioned above,this paper proposes a combination operation for neutral point of 35 kV grids as neutral point insulated in routine operation and grounding through Petersen coil in fault,then EMTP simulation is carried out.Simulation indicates that new neutral operation method can improve lightning withstand level and decrease trip-out rate of grids.     

采用数学形态学的弧光接地过电压识别方法

配电网单相接地故障中危害较大的间歇性弧光接地占绝大多数。与目前广泛采用的发生接地故障后不区分故障性质直接补偿故障电流的经消弧线圈接地方式相比,依据过电压在线监测系统获取的故障过电压波形对故障类型进行快速准确的识别并进行相应的处理,抑制措施更加准确,可进一步提高系统和电气设备的安全运行水平。为此,通过对中性点不接地系统大量实测过电压波形进行分析,利用故障期间间歇性弧光接地存在多次暂态过程而金属性接地只存在1次暂态过程的特点,采用COOCG形态滤波算子提取线路零序电压标么值的奇异信号作为特征量,对间歇性弧光接地过电压进行识别,从而实现对系统单相接地类型的判别功能。经大量仿真和实测波形证明,该方法在不同故障条件下均有较好的准确性和有效性。     

Structure and oxygen storage capacity of Pr-doped Ce_（0.26）Zr_（0.74）O_2 mixed oxides

Binary Ce-Zr(CZ),Pr-Zr(PZ) and ternary Ce-Zr-Pr(CZP) mixed oxides were prepared by an ammonia-aided co-precipitation method,and were aged in a steam/air flow at 1050 °C.X-ray diffraction(XRD),Raman spectra,X-photon spectra(XPS) and CO temperature programmed reduction(TPR) were carried out to characterize the micro-structure and reducibility of catalysts.The oxygen storage capacity(OSC) was evaluated with CO serving as probe gas.The results showed that a pseudo cubic structure was formed for the Zr-rich ceria-zirconia mixed oxides with Pr doping.The insertion of Pr prevented the phase segregation of the mixed oxides during the hydrothermal ageing.The Pr doped samples showed better redox performances in comparison with CZ,and the sample doped with 5 wt.% Pr showed the most remarkably promoted dynamic oxygen storage capacity.This phenomenon was closely related to both the reducibility and oxygen mobility of the mixed oxides.The introduction of praseodymium into ceria-zirconia could accelerate the oxygen migration by increasing the amount of oxygen vacancies,although it was difficult for Pr3+ ions themselves to participate in the oxygen exchange process.     

PVC塑钢中无铅热稳定剂的研究进展及产业分析

“绿色、科技、人文”是2008年奥运会的三大主题。随着奥运场馆建设的开工以及承办奥运所需投入的其他建设项目的启动,建筑业和建材工业将面对一个巨大的革新“,绿色”建筑塑料已成为21世纪建材工业的发展方向。热稳定剂是P V C加工中的重要助剂,发展“绿色”建筑塑料的要求也势必导致未来热稳定剂行业的主要发展趋势是高效、低毒、复合型、无污染,无铅类稳定剂逐渐成为发展的重点。根据我国国情和行业需求状况,发展具有我国自主知识产权的低成本、高效、优质P V C无铅稳定剂品种,完全替代有毒的重金属类热稳定剂和部分替代价格昂贵的有…