Dehydration of 4-methylpentan-2-ol over zirconia catalysts
Several zirconia catalysts, differing in their preparative procedures and/or in the addition of dopants, have been tested for the title reaction. The catalysts were characterized by means of calorimetric techniques. The heats of adsorption of the probe molecules, ammonia and carbon dioxide, were measured to obtain information on the acid–base properties of the samples. Both flow and pulse reactors were used to investigate the behaviour of the catalysts. 4-Methylpentan-2-ol undergoes dehydration to give 4-methylpent-1-ene, which is the desired product, and 4-methylpent-2-ene, in variable amounts; skeletal isomers of C6-alkenes can also form. Simultaneous dehydrogenation of the reactant to 4-methylpentan-2-one can also occur. The acid-base properties of the catalyst appear to play a key role in governing the reaction mechanism, a well balanced number of acid and base sites being needed to obtain a good selectivity to the alk-1-ene isomer.