Synthesis of bulk vanadium oxide with a large surface area using organic acids and its low-temperature NH3-SCR activity

Abstract

Selective catalytic reduction using NH3 (NH3-SCR) is a chemical process that is used for the elimination of NOx (NO and NO2). Although current vanadia-based catalysts need a high reaction temperature, which leads to deactivation of the catalysts, bulk vanadium oxide showed the potential for NH3-SCR at a low temperature below 150 °C. We investigated a method for synthesis of vanadium oxide with a large surface area using an organic acid to enhance its NH3-SCR activity. Vanadium oxide catalysts were synthesized from ammonium metavanadate (NH4VO3) and organic acids (oxalic acid, succinic acid, malic acid and citric acid). When carboxylic acids (oxalic acid and succinic acid) were used as the organic acid source, the surface area of the catalysts increased up to 41 cm2 g−1, which was larger than that of vanadium oxide synthesized without an organic acid and with hydroxy acid. SEM and TEM measurements showed that vanadium oxide catalysts synthesized by the calcination of vanadyl oxalate at 300 °C (V2O5-OX_300) formed a pore structure that contributed to the increase in surface area. An increase in the number of acid sites and redox sites, which is important for NH3-SCR to proceed, was confirmed from NH3-TPD and H2-TPR measurements for V2O5-OX_300. The NO conversion of V2O5-OX_300 (47 % at 100 °C) was higher than that of the catalysts synthesized from only NH4VO3 (19 % at 100 °C), indicating that vanadium oxide catalysts synthesized using carboxylic acid have the low-temperature NH3-SCR activity due to the increase in their surface area.