Ammonia synthesis over rhenium supported on mesoporous silica MCM-41

作者：Hayashi Fumitaka; Iwamoto Masakazu^*

来源：Microporous and Mesoporous Materials, 2011, 146(1-3): 184-189.

DOI：10.1016/j.micromeso.2011.03.035

• Rhenium
• Ammonia synthesis
• Mesoporous silica
• Mesoporous silicon (oxy)nitride

Mesoporous silicon (oxy)nitride (MS(O)N) and mesoporous silica MCM-41 (M41) were examined as supports of catalyst for ammonia synthesis from N(2) and H(2). Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Rh, Ta, W, It, or Pt-loaded MS(O)N and MS(O)N itself were catalytically inert for the synthesis reaction at 673-773 K, 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 0-30 wt.% and was approximately constant between 30-60 wt.% Re. The most active Re/M41 with 30 wt.% 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 63.0 kJ mol(-1) and P(N2)(0.95)P(H2)(0.52)P(NH3)(-1.22) at 623-693 K 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.

• 出版日期2011-12