金属元素改性的超高温氨分解催化剂Ni/Mg-Al的结构及性能

以MgO、Al2O3和ZrO粉末为载体，金属Ni为活性组分，金属元素Co、La等为助剂，制备超高温氨分解催化剂；采用X射线衍射（XRD）、BET比表面积测试（BET）、H2程序升温还原（H2-TPR）、透射电子显微镜（TEM）对其结构进行表征，并在催化剂评价装置上对其氨分解活性进行评价，考察不同金属元素对催化剂结构和性能的影响。XRD结果表明：制备的几种催化剂中均存在NiAl2O4尖晶石相；金属元素可以促使生成的NiAl2O4尖晶石的晶型更加完整；La对晶型的贡献大于Co和Zr。H2-TPR结果表明：加入金属元素La后，催化剂中形成了更多的晶相NiAl2O4，而加入金属元素Co后，生成了与载体具有强相互作用的类尖晶石结构的固溶体。BET及TEM结果表明：金属元素La有助于提高Ni物种在催化剂表面的分散度和浓度，形成更小的表面Ni粒子，从而提高Ni的活性位分布。在反应温度1 200 ℃、体积空速1 228 h-1的条件下，相比于Ni/Mg-Al和CoNi/ZrMg-Al催化剂，LaNi/ZrMg-Al催化剂表现出更好的高温耐磨损性能、抗烧结性能和热稳定性能。

STRUCTURE AND PROPERTIES OF Ni/Mg-Al CATALYST MODIFIED BY DIFFERENT METAL ELEMENTS

Using MgO, Al2O3 and ZrO powder as carriers, nickel as active component and cobalt and lanthanum as auxiliary agents, ultra-high temperature ammonia decomposition catalysts were prepared. The structure of which was characterized by XRD, BET, TPR and TEM.To investigate the influence of different metal elements on the structure and performance of catalyst, catalyst evaluation device was used. XRD results show that NiAl2O4 spinel phase exists in all the catalysts; metal elements can promote the crystalline form of NiAl2O4 spinel; compared with Co and Zr, La contributes more to the crystalline form. TPR results show that more crystalline phase of NiAl2O4could be formedafter adding of La, and a stronger interaction with carrier is formed after adding Co. BET and TEM experiment show that La is helpful to improve the dispersion and concentration of Ni species on the catalyst surface, and to form smaller surface nickel particles, so as to improve the active site distribution of nickel. Compared with Ni/Mg-Al and CoNi/ZrMg-Al catalysts, LaNi/ZrMg-Al catalyst shows better high temperature wear resistance, sintering resistance and thermal stability under experimental condition of reaction temperature 1200 ℃, volume space velocity 1228 h-1.