我国稀土汽车尾气净化器应用现状及发展趋势

本文介绍了2000年以来稀土在汽车尾气催化剂中的研究与应用现状,以及有关稀土汽车尾气净化器发展趋势。给出了一些关于机动车尾气排放污染控制的法规数据,提出了一些十五期间我国稀土汽车尾气净化器的发展思路,以及有关发展我国稀土汽车尾气净化器的政策和措施建议。     

Improvement of Gold to Reducibility of La-Ce-Mn Catalyst under Lean Combustion

The effect of Au on the reducibility of La-Ce-Mn catalyst was studied in the synthetic exhaust gas mixture containing 10% oxygen. The characteristics of samples were analyzed by BET, SEM, XRD and activity evaluation. The resuits show that, in lean combustion, the performance of perovskite-type catalysts is evidently enhanced through adding Au, and specially a satisfying reducibility for NOx is demonstrated between 300～500℃. The catalytic activity of samples increases with the loading amount of Au, and the maximum conversion rate for NOx decomposition reaches up to 47% in 360～400℃. Moreover, the dispersivity and uniformity of the surface distribution of perovskite with Au have an important influence on the catalytic activity.     

Synergistic effect between MnO and CeO2 in the physical mixture：Electronic interaction and NO oxidation activity

MnO and CeO2 powders were mechanically mixed by a spatula and by milling to obtain loose-contact and tight-contact mixed oxides,respectively.The monoxides and their physical mixtures were characterized by X-ray diffraction（XRD）,Brunauer-Emmett-Teller（BET）,X-ray photoelectron spectroscopy（XPS）,Raman,O2 temperature-programmed desorption（O2-TPD）,H2 temperature-programmed reduction（H2-TPR） and NO temperature-programmed oxidation（NO-TPO）.The MnOx-CeO2 solid solutions did not form without any calcination process.The oxidation state of manganese tended to increase while the ionic valence of cerium decreased in the mixed oxides,accompanied with the formation of oxygen vacancies.This long-ranged electronic interaction occured more significantly in the tight-contact mixture of MnO and CeO2.The formation of more Mn4＋and oxygen vacancies promoted the catalytic oxidation of NO in an oxygen-rich atmosphere.     

Oxygen Storage Capacity of Pt-, Pd-, Rh/CeO2-Based Oxide Catalyst

CZO （CeO2-ZrO2） and CZYO （CeO2-ZrO2-Y2O3） series of mixed oxides were prepared by coprecipitaion, and a part of these oxides were loaded with precious metals （PM）. XRD, BET, and oxygen storage capacity （OSC） investigations were performed on samples aged at 750, 900, and 1050 ℃. It was observed that BET surface area and OSC showed a marked decrease in CeO2 aged at high temperature, and the erystallite size showed an obvious increase. The CZO samples consist of cubic- and tetragonal crvstal phases, and their crystallite size increase rapidly when aged at high temperature. The CZYO samples consist of single crystal phase when the content of Y exceeds 0.15 mol, and their erystallite size increases slowly during high-temperature aging. It is concluded that additive Y can stabilize the performance of CZYO oxides. In the aged CZO and CZYO mixed-oxide systems, addition of a small amount of precious metals （Pt, Pd, Rh） increased the rate of reduction and led to an obvious improvement in OSC. OSC of CZO and CZYO with precious metals are related to their composition and the type of precious metal.     

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.     

Role of Surface Adsorption in Fast Oxygen Storage/Release of CeO2 -ZrO2 Mixed Oxides

Four kinds of CeO2-ZrO2 mixed oxides, i.e., a physical mixture of ceria and zirconia （CZP）, zirconia-coated ceria （ZCC）, ceria-coated zirconia （CCZ） and a chemical mixture of celia and zirconia （CZC）, were prepared. The oxygen storage capacity （OSC） measurements at 500℃ were performed under transient and stationary reaction conditions. All the curves of CO2 evolution during CO-O2 cycles presented a bimodal shape. The fast peak was primarily the result of the reaction of CO with the oxygen from the oxides, which was mainly determined by the nature of the material The sec- ond peak was mostly related to the CO2 adsorption behavior and was highly influenced by the surface area and the number of surface active sites. As a result, OSC activity of the samples followed in the order of CZC 〉 CCZ 〉 ZCC=CZP.     

稀土-锆复合氧化物在汽车尾气净化中的应用进展

稀土-锆复合氧化物在汽车尾气净化中有两种重要应用:氧传感器电解质和三效催化剂(TWC)助剂.本文简述了稀土-锆复合氧化物在这两种应用中的作用机理,介绍了氧传感器中ZrO2的稀土掺杂改性,以及CexZr1-xO2固溶体作为催化助剂的研究现状,并对稀土-锆复合氧化物在汽车尾气净化方面的应用进行了展望.     

光解水制氢的可见光催化材料的研究进展

利用可见光催化分解水制氢是利用太阳能的有效方法之一,从材料组成、结构、催化性能及改性等方面介绍了几类重要的可见光催化材料的研究进展,并展望了未来的发展方向.     

我国机动车排放污染控制与稀土催化剂的应用

本文从我国机动车排放污染的现状、机动车排放的法规与政策、国内外排放污染控制技术、稀土催化剂的研究与机动车净化催化剂中稀土的催化特性和机动车尾气净化催化剂研发中存在的问题等方面进行了综述与探讨 ,得到了一些有意义的结论 ,就机动车尾气净化稀土催化剂的研究与开发提出了一些设想和建议。     

我国水泥工业“生态化”的研究现状和发展趋势

分析探讨了中国水泥工业“生态化”的研究现状及发展趋势,为提高我国水泥工业发展的生态化水平,必须调整我国水泥工业的产业结构和产品结构,将高性能水泥熟料、高活性细掺料及低钙水泥系列熟料作为今后的研究重点,提高水泥中工业废弃物的利用效率,进行水泥产品生态化设计,以实现水泥生产的低消耗和低污染。