Collect. Czech. Chem. Commun. 1996, 61, 1115-1130

The Effect of Acidity of Al and Fe Silicates with MFI Structure on Benzene and Toluene Alkylation with Isopropyl Alcohol

Jiří Čejka, Naděžda Žilková and Blanka Wichterlová

J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, 182 23 Prague 8, Czech Republic


Kinetic study of toluene and benzene alkylation with isopropyl alcohol on alumo- and ferrisilicates of MFI structure has shown that the alkylation activity does not follow the acidity (both the number and strength of bridging OH groups) of these molecular sieves. The rate of the overall reaction is controlled by the desorption/transport rate of bulky, strongly adsorbed cymenes and cumene. A higher concentration of n-propyltoluenes compared to n-propylbenzene, both undesired reaction products, formed via a bimolecular isomerization of isopropyl aromate with benzene or toluene, was due to the higher reactivity of isopropyltoluene with toluene in comparison with that of cumene with benzene. It is concluded that ferrisilicates of MFI structure possessing low strength acid sites appear to be promising catalysts for achieving both a high isopropyl- and para-selectivity in toluene alkylation to p-cymene.

Keywords: Acidity strength; Benzene; Toluene; Alkylation; Propylation; MFI structure; Isomorphous substitution.