Vapour phase alkylation of ortho-, meta- and para-cresols with isopropyl alcohol in the presence of sol–gel prepared alumina catalyst

Abstract

Nanosized γ-Al 2O 3 catalyst was prepared by the alkoxide sol–gel method and characterized by XRD and TEM. The porous nature of the catalyst was studied by nitrogen adsorption–desorption isotherms. Acidity of the synthesised material was analyzed by pyridine-adsorbed FT-IR spectroscopy. The gas phase alkylation of isomeric methylphenols (cresols) with isopropyl alcohol over sol–gel prepared alumina catalyst was studied. The reactions were carried out in a continuous process at the atmospheric pressure with dependence on temperature, starting at 210 °C up to the point when the amount of alkylated cresols dropped due to decomposition. Both, O- and C-alkylated products were obtained at lower temperatures, while at higher temperatures ortho-isopropylated derivatives of isomeric cresols were the main products. According to the present method isopropylated cresols can be efficiently obtained with selectivity higher than 90%.