Isobutanol to isobutene: Processes and catalysts

The present review aims at summarizing the scientific literature data and patents concerning the isobutanol, preferably from a fermentation process, selective dehydration reaction to produce isobutene (isobutylene). The benefits and drawbacks of the conditions used on the process design and catalyst performances are illustrated, analyzed and discussed with much objectivity. Thermodynamic equilibria of the various reactants and products are provided together with the limiting step rate. Isobutanol selective dehydration to isobutene can be done under low or high pressure conditions. This choice impacts not only the downstream recovery and purification of isobutene, but also the stability of the catalyst and the reactor volume. Due to the strong inhibition of the alumina catalysts by steam, the reaction under pressure requires longer contact times and catalyst volume. The alumina catalysts need to have a good hydrothermal stability to avoid a rapid deactivation. Isobutene purifi-cation is also addressed. The impact of the water partial pressure on the catalytic dehydration is described and shown to affect the side reactions. Mass transfer limitations and kinetics of the reaction are well documented. Relevant advices are provided to perform the reaction without undesired products.