Calorimetric study of the acidity of a new family of mesoporous catalysts

Thermally stable mesoporous aluminophosphates (AlPO) and silicoaluminophosp hates (SAPO) were prepared at room temperature in the presence of a cationi c surfactant and an organic base. These materials possess high surface area s and regular mesopores of approximately 35 Angstrom diameter. By contrast to microporous crystalline aluminophosphate molecular sieves, mesoporous co mpounds are amorphous and characterized by AVP ratios greater than 1. These particularities are responsible for a strong Lewis acidity, as evidenced b y ammonia adsorption microcalorimetry. Mesoporous materials are more acidic than the microporous analogues and the amount of strong acid sites increas es with the silicon content.