Infrared study of the adsorption of propionitrile on silica immersed in liquid hydrocarbons

Abstract

Infrared spectra have been recorded of silica which had been evacuated at 423 K and subsequently immersed in solutions of propionitrile in toluene, 2,2,4-trimethylpentane and toluene + 2,2,4-trimethylpentane mixtures. The adsorption process involved the formation of hydrogen bonds between surface hydroxyl groups and the cyano groups of propionitrile molecules. The adsorption of propionitrile on silica was impeded by strong lateral interactions between adjacent surface silanol groups. Only isolated hydroxyl groups and weakly interacting hydroxyl groups acted as adsorption sites. Increasing strength of interaction between the predominant (hydrocarbon) components of the liquid phase and surface silanol groups decreased the surface concentration of propionitrile molecules for a particular equilibrium concentration in solution.