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Single‐Site Molybdenum on Solid Support Materials for Catalytic Hydrogenation of N 2 ‐into‐NH 3
Author(s) -
Azofra Luis Miguel,
Morlanés Natalia,
Poater Albert,
Samantaray Manoja K.,
Vidjayacoumar Balamurugan,
Albahily Khalid,
Cavallo Luigi,
Basset JeanMarie
Publication year - 2018
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201810409
Subject(s) - molybdenum , catalysis , hydride , chemistry , yield (engineering) , inorganic chemistry , ammonia , alkali metal , caesium , cobalt , mesoporous material , reaction mechanism , materials science , metal , organic chemistry , metallurgy
Very stable in operando and low‐loaded atomic molybdenum on solid‐support materials have been prepared and tested to be catalytically active for N 2 ‐into‐NH 3 hydrogenation. Ammonia synthesis is reported at atmospheric pressure and 400 °C with NH 3 rates of approximately 1.3×10 3 μmol h −1 g Mo −1 using a well‐defined Mo‐hydride grafted on silica (SiO 2‐700 ). DFT modelling on the reaction mechanism suggests that N 2 spontaneously binds on monopodal [(≡Si−O‐)MoH 3 ]. Based on calculations, the fourth hydrogenation step involving the release of the first NH 3 molecule represents the rate‐limiting step of the whole reaction. The inclusion of cobalt co‐catalyst and an alkali caesium additive impregnated on a mesoporous SBA‐15 support increases the formation of NH 3 with rates of circa 3.5×10 3 μmol h −1 g Mo −1 under similar operating conditions and maximum yield of 29×10 3 μmol h −1 g Mo −1 when the pressure is increased to 30 atm.