Influence of the organic phase on the properties of CrO3-derived chromia aerogels

A series of chromia materials was prepared from CrO3 and C1–C4 alcohols. After high-temperature super- or subcritical drying, considerable organic residue was detected and identified mainly as carboxylates. The amount and the identity of organic species depended, respectively, on the drying temperature and on the alcohol used. When organic content was reduced under inert conditions the resulting materials had high surface areas and were amorphous and partly reduced. Formate species are completely decomposed at 400°C, while other C2–C4 carboxylates decompose at temperatures higher than 450°C. Properties of CrO3-derived chromia materials reflect the chemical behaviour of alcoholic precursors during oxidation. All C1–C4 primary alcohols form aerogels while secondary and tertiary alcohols form differently shaped materials with inferior characteristics. Primary alcohols directly form stable carboxylate species on chromia surface. This process seems to promote the formation of solid aerogel structures.