Vanadium phosphorus oxides (VPOs) fabricated by employing poly ethylene glycol (PEG) additive were used as catalysts for efficient conversion of acetic acid (methyl acetate) and formaldehyde to acrylic acid (methyl acrylate). The highest formation rate (19.8 mu mol g(cat)(-1) min(-1)) of desired products (acrylic acid + methyl acrylate) was accomplished over a VPO catalyst comprising mainly vanadyl pyrophosphate ((VO)(2)P2O7) and vanadyl phosphate in 5 form (delta-VOPO4). This catalyst is nearly three times more active than the analogue reported in literature. The VP0 catalyst activated in 1.5% butane-air is superior to that activated in air or nitrogen. Different from the PEG-derived VPO catalysts for n-butane oxidation to maleic anhydride, a better VPO catalyst for the current reaction requires a higher fraction of delta-VOPO4 entity and contains the medium strong acid sites of high density. Through systematic catalyst characterizations and evaluations, an unambiguous correlation between catalyst structure/constitution and performance was established. (C) 2014 Elsevier Inc. All rights reserved.