Alkane sorption on siliceous and aluminophosphate molecular sieves. A comparative study

The sorption of alkanes on AlPO4-11 (AEL) and AlPO4-5 and its all-silica analogue SSZ-24 (AFI) was studied by means of combined gravimetry and calorimetry and compared to the sorption on silicalite and highly siliceous faujasite. The heats of adsorption of all the alkanes investigated are identical on the isostructural aluminophosphate and the all-silica samples of AFI, both showing some contribution of intermolecular interactions of the sorbate. This suggests that the sorption of alkanes is mainly governed by the microporous structure and that the chemical composition has only a minor impact. As with acidic samples the sorption enthalpy increases with decreasing pore diameter and with increasing framework density for all-silica and aluminophosphate-based molecular sieves.