Supported oxides catalysts for the dehydration of isobutanol into butenes: Relationships between acidic and catalytic properties.

[Display omitted] • H 4 SiW 12 O 40 , WO 3 , TiO 2 and SnO 2 /SiO 2 catalysts were tested in the dehydration of isobutanol. • The catalytic activity was related to the Brønsted acidity and not the Lewis one. • Selectivity to butenes close to 100% was obtained for weak and moderate Brønsted type catalysts. • Linear butenes were mostly obtained through the equilibrium between carbocations. H 4 SiW 12 O 40 heteropolyanions, WO 3 , TiO 2 and SnO 2 were supported over SiO 2 at high loading by wet impregnation or grafting methods and evaluated in the dehydration of isobutanol to butenes. Their structural and textural properties were determined by different techniques such as XRD, TEM, IR, XPS and N 2 liquid physisorption respectively. Most of the prepared compounds contained amorphous oxide clusters of few nanometers lying over SiO 2 and were mesoporous. Their acidic properties (nature, density and strength) were investigated by pyridine and CO adsorption followed by FTIR. H 4 SiW 12 O 40 /SiO 2 contained strong Brønsted acid sites while mostly moderate Lewis acid sites were present on TiO 2 /SiO 2 and SnO 2 /SiO 2. WO 3 /SiO 2 had a mixed character with both moderate Brønsted and Lewis acid sites. The catalytic activity was related to the Brønsted acidity and the best selectivity to butenes close to 100% were obtained for the catalysts containing moderate and weak sites (WO 3 /SiO 2 and TiO 2 /SiO 2). Except for SnO 2 /SiO 2 catalysts, which were unstable and unselective to dehydration products, a significant selectivity to linear butenes (ca 30%) was obtained with all the catalysts. It is proposed that this isomerisation activity is mainly related to the equilibrium between carbocations formed after E 1 elimination of water. Its slight increase for H 4 SiW 12 O 40 /SiO 2 (and to a lesser extent WO 3 /SiO 2) was attributed to strong Brønsted acid sites able to catalyse the isomerization of isobutene to linear butenes. [ABSTRACT FROM AUTHOR]