Mesoporous silica materials modified with aggregated transition metal species (Cr, Fe and Cr-Fe) in the role of catalysts for selective catalytic oxidation of ammonia to dinitrogen

Abstract

Mesoporous silica sieves (SBA-15 and HMS) modified with propylsulfonic groups were used as supports for deposition of trinuclear acetate oligocations (Cr, Fe and Cr-Fe) by ion-exchange method. The obtained samples were characterized with respect to: textural parameters (low-temperature N2 adsorption), ordering of their porous structure (XRD), efficiency of organic functional groups anchoring (DRIFT, TG-DTG and elemental analysis), form and aggregation of deposited transition metal species (UV–vis-DRS), surface acidity (NH3-TPD), transition metal loadings (EDS microanalysis) and reducibility of deposited transition metal species (H2-TPR). The obtained samples were tested as catalysts for selective catalytic oxidation of ammonia by oxygen (NH3-SCO). Mesoporous silica supports modified with chromium and iron species were found to be active and selective catalysts in this process. Moreover, it was shown that the samples doped with mixed-metal oligocations (Cr2Fe1 or Cr1Fe2) were characterized by better catalytic activity in comparison to the samples modified with monometallic species (Cr3 or Fe3).