Dehydration of 2-butanol by a sulfated zirconia/γ-alumina mixed metal oxide catalyst inside a gas chromatograph injection port

Abstract

A sulfated zirconia/γ-alumina mixed metal oxide catalyst is prepared and utilized in the injection port of a gas chromatograph (GC) for the investigation of 2-butanol dehydration. A linear correlation ( R 2=0.996) is found between the areas of the chromatographed butene peaks and the concentration of 2-butanol in dichloromethane standard solutions ranging from 0.003 to 3 vol.%, the injector temperature maintained at 250 °C. The kinetics of the alcohol dehydration are studied by varying the injector temperature. The data is found to support a pseudo-first-order reaction mechanism, with two different apparent activation energies observed over two distinct temperature ranges: 15 kJ/mol for the higher temperature range (∼150–325 °C) and 46 kJ/mol for the lower temperature range (75 to ∼150 °C) studied. The lower apparent activation energy obtained at the higher injector temperatures is attributed to mass transport-limited kinetics, while the higher apparent activation energy barrier observed at the lower temperatures suggests that the surface alcohol dehydration reaction provides the rate-limiting step. Following exposure to stress conditions, the coke-deactivated catalyst surface is observed by scanning electron microscopy (SEM).