排序方式: 共有11条查询结果,搜索用时 31 毫秒
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采用两步共沉淀法制备了pH值7.0、沉淀温度分别为70℃、80℃、90℃及沉淀温度为70℃,pH值8.0的合成甲醇催化剂。考察了沉淀温度及pH值对催化剂性能的影响。采用X射线衍射、N_2吸附-脱附、同步热分析及H_2-程序升温还原对催化剂样品进行表征。结果表明,当沉淀pH值为7.0时,随着沉淀温度的降低,有利于前驱体中Zn~(2+)取代率增加,有利于第一步形成锌铝水滑石结构的前驱体,有利于提高催化活性;略低的沉淀pH值可以提高催化剂的高温稳定性。 相似文献
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采用共沉淀法制备以Ni为活性组分的Ni-Mg-Al-O高温甲烷化催化剂,考察焙烧温度对催化剂性能的影响。采用N2低温吸附、XRD、H_2-TPR和H_2-化学吸附对催化剂进行表征,并将催化剂用于合成气甲烷化反应。结果表明,焙烧温度高于700℃时,催化剂预还原后织构性能参数变化幅度小。随着焙烧温度的升高,Ni晶粒增大,活性组分与载体之间相互作用增强。焙烧温度700℃时,活性组分分散度最高,催化剂具有优异的低温活性和高温稳定性。 相似文献
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采用共沉淀法制备了一系列Nd2O3含量为0~13wt%的CeO2-ZrO2-A12O3(CZA)复合氧化物,并通过X射线衍射(XRD)、低温N2吸附–脱附、氧脉冲吸附(OSC)、H2–程序升温还原(H2-TPR)及扫描电子显微镜(SEM)等方法对所制备的材料进行了表征.研究结果表明,Nd2O3在CZA固溶体中的溶解限约为10wt%,过量Nd的添加会出现分相形成Nd0.5Ce0.5O1.75氧化物.掺杂适量Nd能有效抑制氧化物晶粒的长大,提高材料的热稳定性和氧化还原性能.Nd2O3的掺杂量为10wt%时,样品的织构稳定性最好,1000℃老化5 h后,比表面积和孔容分别达97.14 m2/g和0.44 mL/g.Nd2O3的掺杂量为7wt%时,样品有高的储氧量,经600℃和1000℃焙烧后储氧量分别为938.01μmol/g和821.72μmol/g;体相氧的移动能力最强,还原性能最佳,老化后还原峰温由465℃升高到483℃.SEM结果表明,所制备的材料均为球形颗粒,Nd2O3的添加可以有效阻止高温焙烧过程中粒子的团聚. 相似文献
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Ce-Zr-Al-Nd2O3 (CZAN) support materials were prepared by co-precipitation and impregnation methods, respectively. They were characterized by X-ray diffraction (XRD), low temperature nitrogen adsorption-desorption, oxygen pulsing technique, H2-temperature pro-grammed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The Pd-only three-way catalysts (Pd-TWC) supported on these materials were prepared by incipient wetness method and studied by activity tests. The results demonstrated that the CZAN supports obtained by the two methods showed better structural, textural and redox properties than the CZA without Nd2O3, and the addition of Nd2O3 improved the catalytic activity of TWC. Especially, the CZAN-i support prepared by impregnation method had better thermal stability and redox prop-erty. Meanwhile, the Pd/CZAN-i catalyst exhibited the best catalytic performance. XPS measurements indicated that the Nd-modified sam-ples possessed more Ce3+ and oxygen vacancies on the surface of samples, which led to a better redox property. The excellent redox property of support materials helped to improve the catalytic activity of TWC. 相似文献
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