Production of butadiene by oxidative butane dehydrogenation with NO: effect of the oxidant species and lattice oxygen mobility in V2O5–WO3/TiO2 catalyst

Abstract

V₂O₅–WO₃, supported on a TiO₂ catalyst, was tested for n-butane oxidative dehydrogenation with NO/O₂. The effect of the physical oxygen mobility and nature in the V₂O₅–WO₃/TiO₂ catalyst on the applicative catalytic performance was investigated. The influence of the O₂/NO species on the chemical reaction products/Mars–van Krevelen (MvK) cycle was examined by performing online time studies with the removal of an oxidant (O₂/NO) in the feed. A high rate of selectivity towards butadiene was obtained when NO was used. No trace concentration of NO was observed at commonly higher temperatures. N₂O or NO₂ was not present in the effluent gas compounds, and the mechanism was analyzed. In the presence of both O₂/NO, a high synthesis yield of diene was determined at lower reactant conversions. The former increased up to 40% n-butane conversion, and decreased with a further increase in n-butane conversion. X-ray photoelectron spectroscopy (XPS) showed that the re-oxidation with NO restored the lattice oxygen (O²⁻) in the catalyst, along with the surface oxygen species. The catalyst reduced at 350 °C showed the presence of the superficial lattice oxygen species (O⁻/O²⁻) generated from the lattice defects, which also involved the interstitial oxygen species. The catalyst reduced at 450 °C showed the presence of the O²⁻ radical anion with the co-existence of O₂⁻. The product distribution showed that the butane dehydrogenation to butene and butadiene occurred, and that the insertion of oxygen into the catalyst lattice favored butadiene production.