Controlled calcination of Texas montmorillonite provides a family of materials differing only in cation exchange capacity (cec). Introduction of alumina pillar precursor ions, followed by calcination at 500-degrees-C, then provides a family of pillar densities ranging from near zero to the maximum attainable (ca. 0.16 pillars per unit cell) all, however, having cec below 10 mequiv./100 g dry clay and catalytically inactive. Cec and activity are regenerated by exposure to cyclohexylamine. All members of the regenerated family have cec of 36 +/- 1 but the proton concentrations vary widely, with a maximum of about 45 mequiv./100 g. The reactivity with respect to pentan-1-ol dehydration to alkene or ether varies with pillar density in similar manner to the proton count and these parameters are essentially linearly related so that there is no correlation between reactivity and pillar density per se. The reactivity of the pillared variety is a maximum with that pre-calcined at ca. 200-degrees-C but is only about two-thirds that of the unpillared analogue. The pillared variety is highly selective towards alkene formation, whereas the unpillared analogue strongly favours ether formation. It is suggested that future emphasis be given to improving regeneration techniques, and that since unpillared montmorillonite predominantly catalyses addition of water to alkene to yield ethers, the pillared analogue may be more useful in alkanol production.