The alumination of sepiolite led to a material with a moderate Lewis acidity, a high surface area, a microporous character, and a cation exchange capacity (CEC). The CEC increased to 45 meq/100 g and extraframework aluminum was formed. Alumination was accompanied by an increase in the sodium content of the sample and an improvement of the thermal stability, reflected in a microporosity more stable at 400 degrees C than in the starting material. The CEC resulting from alumination allowed for the dispersion of vanadyl cations without loss of crystallinity. Electron paramagnetic resonance spectra indicated an isolated, immobile octahedral environment compatible with charge balancing vanadyl cations and/or vanadyl species at the edges of the octahedral ribbons in the framework. Upon alumination, the activity for ethanol dehydration was increased threefold at 400 degrees C to 85% with a selectivity for ethylene of 50%. Upon dispersion of vanadyl cations, the reactivity for ethanol conversion was further increased. The possibility to apply successfully secondary isomorphic substitution techniques to natural minerals was clearly established and it was shown to alter their surface properties considerably, as shown here on sepiolite from both spectroscopic and reactivity studies.