THERMOGRAVIMETRIC, INFRARED AND MASS SPECTROSCOPIC ANALYS IS OF THE DESORPT ION OF TETRAHYDROPYRAN, TETRAHYDROFURAN AND 1,4-D IOXAN FROM MONTMORILLONITE

from Na +-, Ca 2+-, AI 3+- and Cr3+-exchanged montmorillonite has been studied using variable temperature infrared spectroscopy and thermogravimetric analysis. The derivative thermograms for the desorption of each cyclic ether exhibited three maxima but there was little uniformity in the temperatures at which these maxima occurred. Nonetheless, the desorption of both THP and THF occurred at lower temperatures in the Cr3+-exchanged form than in the AP+-form. The desorption of DIOX showed little cationic dependence. Mass spectroscopic analysis of the thermally evolved vapours indicated that no transformation products were desorbed at temperatures ~<230~ It is now well documented (Adams, 1987; Ballan-tine, 1986) that tr ivalent cat ion-exchanged mont-mori l lonite is an effective catalyst for reactions in which a solid source of protons is required. The small highly-charged ions (such as AP +, Cr 3+ or Fe 3+) cause considerable polarization of water in the primary coordination sphere which results in the generat ion of an acidic proton. Adams et al