TETRAHYDROFURAN AND TETRAHYDROPYRAN FROM B INARY SOLUTION WITH METHANOL ON A13+ AND Cr3+-EXCHANGED MONTMORILLONITE

ABSTRACT: Surface excess isotherms were determined for the adsorption of 1,4-dioxan (DIOX), tetrahydropyran (THP) and tetrahydrofuran (THF) from binary solution with methanol (MeOH) on AI 3 § and Cr3 § montmorillonite containing different amounts of pre-adsorbed water. The isotherm type is dominated by the binary mixture whereas the amplitude, which follows the sequence DIOX> THP> THF, is further influenced by the exchange cation, AI 3 §> Cr 3+, and the water content of the clay. The sorption of DIOX and THP from MeOH exhibit a type IV isotherm in the Schay-Nagy classification on both cation-exchanged forms, whilst that of THF from MeOH is of type I and THF is the preferred adsorbate. The azeotropic point for the type IV isotherms i close to a 1: 1 mole ratio for the samples dried at 120 ~ but when the samples are rehydrated at 12 % r.h. following thermal pretreatment at 120 ~ the azeotropic point shifts in favour of the cyclic ethers DIOX and THP, making them the preferred component over a substantial portion of the composition range. As the number and diversity of reactions catalysed by trivalent cation-exchanged montmorillonites grows, so too does the realization that little information is available concerning both the dynamic and steady-state b haviour of these reaction systems. As in an