INFRARED SPECTROSCOPIC STUDY OF THE OCCUPATION OF HYDROGEN-CYANIDE RECEPTOR-SITES OF METALLO-OXIDE PILLARED CLAYS BY HYDROCARBONS

The decrease in the numbers of receptor sites for hydrogen cyanide on metallo-oxide pillared clays detectable by infrared spectroscopy, whic h occur when there is an initial exposure of the pillared clays to the various hydrocarbons, has been interpreted to be Lewis acid sites on the oxidic pillar material and Bronsted acid sites on the clay sheet a long with a distinctive site resulting essentially from the pillar fix ation process and have been used to define the reactivity of these rec eptor sites toward the hydrocarbons. 1-Hexene is an effective competit or for all the hydrogen cyanide receptor sites. The distinctive sites associated with the pillaring process while not exhibiting any marked selectivity toward the hydrocarbons, n-hexane, cyclohexane, benzene an d toluene are most affected by the nature of the oxide pillar in the o rder Al > Cr > Ti > Zr > Fe. A measure of selectivity toward the hydro carbons is shown by zirconium oxide pillared hectorite whose distincti ve sites are more effectively tenanted by benzene or toluene than by n -hexane or cyclohexane.