Ammonia synthesis over rhenium supported on mesoporous silica MCM-41
Ammonia synthesis over rhenium supported on mesoporous silica MCM-41
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DOI：
10.1016/j.micromeso.2011.03.035
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发表时间：
2011-12
影响因子：
5.2
通讯作者：
Fumitaka Hayashi;M. Iwamoto
中科院分区：
文献类型：
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作者：
Fumitaka Hayashi;M. Iwamoto
以介孔硅氮氧化物（MS（O）N）和介孔硅MCM-41（M41）为载体制备了N2/H2合成氨催化剂。Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zr、Nb、Rh、Ta、W、Ir或Pt负载的MS（O）N和MS（O）N本身在673- 773 K对合成反应是催化惰性的，而Re、Mo和Ru负载的MS（O）N是活性的。在后者的金属Re表现出最高的活性，因此催化活性的Re支持作为一个功能的支持，支持的Re量，Re前体用于制备，和添加剂进行了研究。M41是一个很好的支持。Re前体对活性的作用是有限的。在0- 30 wt.%范围内，Re/M41催化剂的活性随Re含量的增加而线性增加并且在30- 60重量%之间近似恒定Re.活性最高的Re/M41，30 wt.%在常压下，Re的活性与Ru/MgO和双促进铁催化剂相当。Cs、Ba、La、Ce等添加剂对Re/M41催化剂的活性没有明显的促进作用。在623- 693 K和常压下，Re/M41上各组分的反应活化能和反应级数分别为63.0kJmol− 1和PN20.95PH20.52PNH 3 - 1.22。氢上的有序度是正的，与其他Re催化剂上的有序度形成鲜明对比，这对于实际应用是非常重要的。
Mesoporous silicon (oxy)nitride (MS(O)N) and mesoporous silica MCM-41 (M41) were examined as supports of catalyst for ammonia synthesis from N2and H2. Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Rh, Ta, W, Ir, or Pt-loaded MS(O)N and MS(O)N itself were catalytically inert for the synthesis reaction at 673–773K, while Re, Mo, and Ru-loaded MS(O)N were active. Among the latter metals Re showed the highest activity and thus catalytic activity of Re supported was studied as a function of support, amount of Re supported, Re precursor used in the preparation, and additive. M41 was a good support. The role of Re precursor upon activity was limited. The activity of Re/M41 increased linearly with increasing Re content in the range 0–30wt.% and was approximately constant between 30–60wt.% Re. The most active Re/M41 with 30wt.% Re showed equivalent activity to those of Ru/MgO and doubly-promoted iron catalysts at an atmospheric pressure. Several additives such as Cs, Ba, La, and Ce did not increase the activity of Re/M41. Finally the activation energy and the reaction orders on the respective components on Re/M41 were determined to be 63.0kJmol−1and PN20.95PH20.52PNH3-1.22at 623–693K and an atmospheric pressure. The order on hydrogen was positive in sharp contrast to those reported on other Re catalysts and would be very important for the practical application.