Synthesis and catalytic properties of M0.5(1 + x)Fe x Ti2 − x (PO4)3 (M = Co, Ni, Cu; 0 ≤ x ≤ 2) for methanol conversion reactions

Abstract

New phosphates with the general formula M 0.5(1 + x) Fe x Ti 2 -x (PO 4 ) 3 (M = Co, Ni, Cu; 0 ≤ x ≤ 2) have been synthesized by a sol-gel process. We have studied phase relations in these systems and determined the composition stability limits of NASICON type solid solutions. The catalytic properties of the phosphates for methanol dehydration and dehydrogenation reactions have been investigated in an inert atmosphere.

Highly Selective Solid Acid Catalyst H1−xTi2(PO4)3−x(SO4)x for Non-Oxidative Dehydrogenation of Methanol and Ethanol

“…Structural protons in the NASICON-channels were detected by magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. The strongly-polarizing nature of the sulfate ligand should increase the acidity of structural protons and, yet, the reducibility of Ti 4+ to Ti 3+ may play a role in non-oxidative dehydrogenation as indicated previously [22]. The current studies indicate that HTPS shows an excellent performance in methanol dehydrogenation to formaldehyde, and in the conversion of ethanol through non-oxidative dehydrogenation and dehydration.…”

“…Interestingly, although the selectivity was still low, the study found that at relatively low temperatures the residual solid acidity in the aluminosilicate framework was important in preventing the complete dehydrogenation of formaldehyde to carbon monoxide. More recently, the sodium (Na) super ionic conductor (NASICON)-type nickel titanium phosphate (Ni 0.5 Ti 2 (PO 4 ) 3 , showed a selectivity around 80% for formaldehyde and total conversion around 70% at relatively low temperatures (340-360 • C) but, unfortunately, the stability of the catalyst was not reported [22]. While good performance was attributed to redox activity, it is worth noting the expected acidity of the titanium phosphate framework structure.…”

A novel phosphate with CoII square planar coordination, BaCo0.5Fe(PO4)2: structural and magnetic features

“…These materials, composed of transition metal ions intimately linked to phosphorus groups, exhibit intriguing electronic, 1–3 magnetic, 4,5 optical, 6,7 and catalytic behaviors. 8–10 A thorough understanding of the crystal structures of transition metal phosphates is essential for unlocking their distinctive physical properties.…”