Structures of active sites for alkane transformations over the Pt/HZSM-5 and Pt/NaZSM-5 catalysts

The structure and reactivity of Pt-6 particles in the sodium and hydrogen forms of the ZSM-5 zeolite were investigated by the DFT method. Upon adsorption on the sodium form, the interaction energy is 15 kcal mol(-1) and a negative charge appears on the metal cluster. In channels of the hydrogen form, the adsorption energy of the metal particle increases to 45 kcal mol(-1) and the oxidized states of platinum are formed. The formation of an active site in the H-form of the zeolite involves the interaction of the platinum particle with the acid site resulting in the suppression of the acidity of the support. An alternative mechanism of alkane transformations avoiding acid site participation was proposed. A possibility to envisage the direction of the transformation of alkanes adsorbed on the metal particles was shown.