The sorption of furans on silica gels

Abstract

The adsorption of furan and tetrahydrofuran on a range of thermally modified silica gels has been studied at temperatures close to the boiling points of the two adsorbates. Adsorption–desorption isotherms have been measured along with isosteric and isothermal calorimetric heats of adsorption up to and including monolayer coverage. For furan adsorbed at 304 °K on gel heat treated at 240° the variation in calorimetric heat is from above 30 kcal. mole^–1 at θ= 0·01 to near 7 kcal. mole^–1 at θ= 1·00. On the same material at 338 °K, the variation for tetrahydrofuran is from 26·5 kcal. mole^–1(θ < 0·1) to 12·0 kcal. mole^–1(θ= 1·00). Data are included also for the adsorption of furan on γ-alumina, aluminium-impregnated and hydrothermally treated silica gels. The nature of the adsorbed complexes is believed to depend on the degree of surface coverage with adsorbed molecules and also on surface hydroxy-group concentrations.