Sorption of benzene on AlPO4-5 containing various heteroatoms and analytical description of the system

Sorption of benzene on nonsubstituted AlPO4-5 occurs on adsorption centers originating from surface heterogeneity and created by structure defects. Th e metallic heteroatoms present in the framework of substituted AFI-type mat erials form additional centers able to bind the benzene molecules. This is equal to an increase of heterogeneity in comparison to nonsubstituted AlPO4 -5. Sorption capacity of the MeAPO-5 materials depends on both the content of metal and its distribution throughout the crystals. The distribution par ameter plays an important role and may even dominate the effect of the numb er of metallic heterocenters. Some of the equations based on the Polanyi-Du binin potential theory can be accepted as suitable for characterizing the d istribution of the adsorption potential and adsorption energy of the AFI-ty pe molecular sieves. The dependence between the adsorption potential and th e metal content may likely be disturbed by inhomogeneous distribution of th e heteroatom centers.