Infrared spectroscopic study of acrylonitrile adsorbed on mordenite zeolites. Part 2.—Surface interaction of CC double bond

Abstract

The adsorption of acrylonitrile on HM, BaM, HgM and CuM (M = mordenite), which were cation-exchanged in acid media, was studied by means of infrared spectroscopy and compared with its adsorption on NaM and CaM prepared by conventional ion-exchange in a sodium acetate–acetic acid buffer solution (pH 4.7).

In the presence of acidic protons, the CC double bond of acrylonitrile is activated with respect to interaction with the surface. Evidence shows that electrostatic attraction between the surface and the acrylonitrile molecule is a contributing factor to the bonding between the CN group and surface cations.

An absorption band near 2450 cm^–1 was observed ab initio in the mordenites (HgM, CuM, BaM) cation-exchanged in acid solution. The occurrence of this band appeared to be sensitive to the presence of Na⁺ ions, i.e. it occurred when H-mordenite was used for the cation exchange as the parent material but did not occur when Na mordenite was used as the parent material.

Tentative mechanisms are proposed by which the experimental results may be rationalized by means of the CC interaction with the surface.