A QUANTUM CHEMICAL STUDY OF THE INTERACTION OF CARBONYLS WITH H-ZSM-5 ZEOLITE

摘要

The quantum cluster, ONIOM and embedded ONIOM models have been used to investigate adsorption properties of carbonyls in H-ZSM-5 zeolites. The active site has been modeled with realistic cluster sizes up to 46 tetrahedra. The predicted adsorption energies of ZSM-5/carbonyls complexes for the embedded ONIOM2(MP2/6-311G(d,p):UFF) scheme are -119.0 and -139.0 kJ/mol for acetaldehyde and acetone, respectively, the latter value compared well with the experimental estimated of 130 ± 4 kJ/mol, whereas the conventional quantum cluster yields an underestimate value of -68.2 kJ/mol. The results obtained in this study suggest that the new embedded ONIOM scheme provides a more accurate method of studying the interaction of carbonyls with zeolites.