A novel adsorption-based method for revealing the Si distribution in SAPO molecular sieves: The case of SAPO-11

A novel adsorption-based method for quantitative estimation of the phosphorus atom replacement for a (Si, H+) pair in the SAPO-11 framework is suggested. The most probable configurations and regularities in the location of silicon atoms and protons in the SAPO-11 structure containing 1, 2, 3 and 5 Si atoms per unit cell were determined by computations. A new force field for adsorption simulation in the H2 – SAPO system was developed. The dependence of averaged Henry's constants for H2 adsorption at 77 K on the amount of substituted Si was calculated. The effect of model used for computation of the Si distribution probability in the SAPO-11 on the adsorption properties in the H2 – SAPO system was studied. Practical applications of the method for several SAPO-11 frameworks with different Si concentrations are demonstrated.