Kinetic Study of the Decomposition of 2-Butanol on Carbon-Based Acid Catalyst

The catalytic conversion of 2-butanol on a carbon-based acid catalyst prepared by chemical activation of olive stone with phosphoric acid was investigated. The carbon catalyst showed a considerable amount of surface phosphorus, presumably in form of phosphate groups, as revealed by XPS, despite a washing step carried out after the activation process. Conversion of 2-butanol yields mainly dehydration products, mostly cis-2-butene and trans-2-butene with lower amounts of 1-butene, and a very small amount of nick as dehydrogenation product. Kinetic interpretation of the experimental data was performed using two elimination mechanisms for the dehydration reaction; an El-mechanism (two-step mechanism) and an E2-mechanism (one-step mechanism). The rate expressions derived from both models fit properly the experimental results, suggesting that probably the two mechanisms occur simultaneously. This is supported by the similar rate constant obtained for the formation of the carbocation and the olefins in the El and E2 mechanisms, respectively. (C) 2009 American Institute of Chemical Engineers AIChE J, 56: 1557-1568, 2010