Calculations of chemisorption and the elementary acts of catalytic reactions within the framework of a cluster model. III. Interaction of NH3 with silica gel and the H forms of zeolites

The energetics of the adsorption of ammonia molecules on the acid-base centers of silica gel and aluminosilicates were investigated within the framework of a cluster model and the CNDO/BW method. Calculations show that the most preferred form of adsorption is adsorption of the OH hydrogen atom-ammonia nitrogen atom type. The calculated interaction energies are in good agreement with the experimental data. Hypothetical structures corresponding to H-D heteroexchange of ammonia molecules with the OH groups of terminal and bridged types are examined