Silicon distribution in SAPO-11 molecular sieves: Simulation and experimental adsorption study

A method for investigation of the Si distribution in the SAPO-11 structure based on the aggregate of simulation and experimental adsorption methods is suggested. Twelve possible configurations of the silicon location in the SAPO-11 framework corresponding to substitution of one P atom for a (Si,H+) pair in the elementary cell were simulated. The probabilities of silicon localization in each studied configuration were calculated. Hydrogen adsorption at 77 K on AlPO/SAPO was simulated by GCMC method for a fragment of the AEL structure consisting of 2 × 2 × 3 elementary cells. A comparison of the experimental and calculated Henry constants made it possible to estimate the silicon concentrations in the bulk of the zeolite crystallites.