A kinetic study of 2-propanol dehydration on carbon acid catalysts

Activated carbons with high surface acidity were obtained in a single step by chemical activation of hemp residues with H3PO4 and used as catalysts for the dehydration reaction of 2-propanol. Despite the washing process performed after the activation, the resulting carbons show a considerable amount of surface phosphorus as revealed by XPS. The surface acidity, predominantly of Bronsted type, was dependent on the amount of phosphorus retained on the carbon surfaces. Conversion of 2-propanol yielded only dehydration products, mostly propylene with a very low amount of di-isopropyl ether. The effect of a thermal treatment performed to carbon catalyst on the surface chemistry, acidity and dehydration activity was analyzed. A kinetic study of the catalytic dehydration of 2-propanol on the best carbon catalyst was carried out, where two different Langmuir-Hinshelwood mechanisms, via surface elimination reactions, E1 and E2, were analyzed. The rate expressions derived from both models fitted properly the experimental results and activation energy values of about 98 kJ/mol were obtained. The results indicate that the 2-propanol dehydration reaction takes place by an E2 elimination mechanism with strong E1 character. (C) 2010 Elsevier Inc. All rights reserved.