Optimizing lattice oxygen mobility and acidity of heteropoly acid catalysts for oxidation of isobutane to methacrylic acid

Abstract

In this paper, a series of heteropoly acids, (Cs2.2Cu0.26V0.38)xPMo12O40 (x = 1.3, 1.1, 1.0, 0.88), are prepared, characterized and examined as the catalysts for the oxidation of isobutane to MAA. Under the employed reaction condition, Cs2.23Cu0.26V0.38PMo12O40 exhibits an isobutane conversion of 20% and a MAA selectivity of 51% at 335 °C, giving a MAA yield of 0.68 mmolMAA·h−1·gcatalyst−1. Lattice oxygen mobility and acidity of (Cs2.2Cu0.26V0.38)xPMo12O40 catalysts play key roles. A fast migration rate and a moderate release rate of lattice oxygen are beneficial to the selective oxidation of isobutane to MAA. Cs2.2Cu0.26V0.38PMo12O40 exhibits strong acid sites facilitating MAA desorption and surface sites strongly binding MAA, causing MAA polymerization which blocks the active sites and decreases the long-term catalytic activity. These results demonstrate that the optimization of lattice oxygen mobility and surface acidity is an effective strategy to fabricate efficient heteropoly acid catalysts for the oxidation of isobutane to MAA.