Catalytic mineralization of formaldehyde catalysed by molybdovanado-phosphate polyanions supported on cellulose-silica hybrids

Polyoxometalates (POMs) of series [PMo 12-n V n O 40 ] (3+n)- (n = 1,2) supported on cellulose-silica hybrids (ca. 2 % w/w) exhibited high catalytic activity in gaseous aerobic oxidation of formaldehyde (CH 2 O) at room temperature. The oxidation of CH 2 O carried out in a packed-bed tubular reactor at a linear velocity of ca. 0.35 m/s and about 0.5 s residence time resulted in carbon dioxide and water as the main reaction products . The relative rate of CH 2 O oxidation at 294 K ranged from 1.5 × 10 − 2 to 2.7 × 10 − 2 mol CH2O /(mol cat s), i.e. ca. 0.35–0.49 g/(kg cat min) of catalytic material. The catalyst activity is determined by the reversible redox conversion V(V)↔V (IV) in POMs under aerobic conditions. The efficiency of POMs in the oxidation of CH 2 O and their re-oxidation with dioxygen is affected by its electrostatic interaction with a supporting material, as revealed by phosphorus solid-state nuclear magnetic resonance ( 31 P MAS NMR) and electron paramagnetic resonance (EPR) spectra. A mixed electron transfer/autoxidation mechanism has been proposed for the oxidation of CH 2 O in the aerobic catalytic system. Oxidation of CH 2 O by oxygen in the presence of POMs may include oxygen transfer via transient peroxomolybdate species, as elucidated by Raman spectroscopy. The catalysts maintained their activity after more than 300 turnovers thus allowing the continuous oxidation of CH 2 O in polluted air, at concentrations below 50 ppm. • Molybdovanadophosphates were supported on cellulose-silica hybrid material. • Aerobic oxidation of formaldehyde over catalyst carried out at room temperature. • The main oxidation products of formaldehyde were carbon dioxide and water. • A mixed electron transfer/autoxidation mechanism has been proposed. • The catalysts maintained their activity after more than 300 turnovers.