In situ synthesis of ammonium salt of 12-molybdophosphoric acid on iron phosphate and the ammoxidation functionality of the catalyst in the transformation of 2-methylpyrazine to 2-cyanopyrazine

Abstract

The ammonium salt of 12-molybdophosphoric acid (AMPA) on iron phosphate was synthesized via in situ interaction between the phosphate species of the support and the molybdenum component of ammonium heptamolybdate. The concentration of AMPA was varied such that the nominal MoO 3 content of the catalysts was in the range of 5–20 wt.%. The formation of AMPA, possessing the typical Keggin structure, was confirmed by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and FT-Raman spectroscopy. Thermo-gravimetric and differential thermal (TG/DT) analyses were used to establish the stability of these catalysts. Whereas the support, FePO 4, displayed low activity but maximum selectivity to 2-cyanopyrazine (CP), the in situ synthesized catalysts exhibited higher activity during the ammoxidation of 2-methylpyrazine (MP). At lower reaction temperatures and particularly, at lower AMPA loading, the in situ synthesized catalysts have shown higher activity and retained substantially high selectivity.