Surface electronic structure–catalytic activity relationship of partially reduced WO3 bulk or deposited on TiO2

Catalytic reactions of n-pentane and 1-pentene were carried out as a function of the reduction process of WO₃ as bulk or supported on TiO₂. In situ characterization by XPS–UPS techniques of the different chemical species formed following the reduction processes was performed. At reduction temperatures up to 773 K, two distinct W⁵⁺ and W⁴⁺ states were obtained. The acid functions associated with W⁵⁺, mainly of Brönsted type, enabled to isomerize only 1-pentene to unsaturated products. Dual metal–acid functions (bifunctional) of the W⁴⁺ state perform the isomerization processes of 1-pentene and n-pentane to isopentane in similar way to highly dispersed platinum on alumina catalysts. A conversion of 56% of n-pentane and a selectivity of 87% to isopentane were obtained at 623 K reaction temperature.