Experimental and Computational Investigations of the Deactivation of H-ZSM-5 Zeolite by Coking in the Conversion of Ethanol into Hydrocarbons

The catalytic conversion of ethanol into hydrocarbons on a H-ZSM-5 zeolite with a molar Si/Al ratio of 12 was investigated under different reaction conditions (WHSV, carrier flow). During catalyst-deactivation, the selectivity changed towards C2 products. These results indicated that the deactivation neither correlated with the total amount of deposits nor with the structural damage of the zeolite. Under the assumption that a pore-blockage caused the change in selectivity, characterization of the catalyst sample (TPAD, IR spectroscopy), the formed deposits (TGA, DSC), and also the regeneration process were performed. The experimental results were discussed in terms of the nature of the deposits (i.e., aromatic compounds, substituted aromatic compounds, or olefins) and correlated with quantum chemical calculations at the ONIOM(B3LYP/6-31G(d):PM6) level of theory with a purely siliceous model to consider the effect of pore-blockage in an inert SiO2 MFI network.