Effect of the rehydration on the acidity and catalytic activity of SAPO molecular sieves

The structural changes occurring in the template-free SAPO-5 and SAPO-34 upon the rehydration are reversible and do not affect their acidity and catalytic activity. The rehydrated SAPO-37 loses irreversibly a considerable part of its initial crystallinity, surface area, acidity and catalytic activity. Nevertheless the remaining acid centers are stable against dehydrationrehydration cycles.