Grand Canonical Monte Carlo simulations of hydrogen adsorption on aluminophosphate molecular sieves

The hydrogen adsorption simulations were carried for several model AlPOs (VPI-5, AlPO-5, AlPO-11 and AlPO-25) employing the Grand Canonical Monte Carlo (GCMC) simulations at 77 K to investigate the effect of pore size and the pore volume on the hydrogen uptake. The adsorption capacity showed no relationship with the pore size, surface area and micropore volume of AlPOs. However, the adsorption capacity per unit micropore volume increased as the pore size decreases. The heat of adsorption also increased as the pore size decreases. For all model AlPOs, the hydrogen exists homogeneously near the oxygen atoms in the framework.