Anisole is alkylated with 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, and 1,3-cyclohexadiene using K10 montmorillonites exchanged with different cations as catalysts in a batch reactor. Brønsted acidity catalyses diene polymerization and favours retro-alkylation. With calcined clays, higher conversions can be reached. Para-monoalkylation is the preferred reaction, whereas the regioselectivity in the diene is controlled by the attack on the least hindered position of the most stable carbenium ion. The catalysts are only partially deactivated under these reaction conditions, and the final yield can be improved to more than 50%, in the case of weak acids, by gradually adding small portions of diene.

Titanium-pillared inter-layered clays (TiPILCs) were prepared by intercalating polymeric cationic species in clay layers. The intercalation was obtained by hydrolysis of TiCl4 with HCl (TiPILCCl) and H2SO4 (TiPILCS). The influence of the determinant parameters viz. the H+/Ti and Ti/clay ratios, was considered and experimental conditions leading to high specific surface areas and well defined structures of the pillared montmorillonites were determined. The structural properties of the resulting pillars suggest a different nature of the polymeric cationic species obtained by varying the acid. Smaller specific areas and stronger Brönsted acidic sites are observed on TiPILCS. Similar sites as those described for SO−4TiO2 superacids are proposed. These results might contribute to the development of a new catalyst family.

Various typical acid-catalyzed reactions leading to carbonyl compounds were studied using zeolites taking into account their acidic and shape selective properties. Acylation of aromatic compounds by carboxylic acids over Y zeolites leads to quantitative conversion in acylated derivatives with very high para selectivity. On the other hand, the Fries rearrangement of phenylbenzoate gives mainly ortho hydroxybenzophenone. Zeolites are also efficient catalysts in hydration of various aromatic and aliphatic alkynes leading to the corresponding ketones. The epoxide rearrangement of styrene oxide yields phenylacetaldehyde with high conversion. In this latter case, the use of surface-modified zeolites shows that both external and internal acid sites of the zeolite are involved in liquid phase epoxide conversion.

The activity of various cation-exchanged Y-type zeolites is investigated in the acylation of toluene with octanoic acid for which the yield in acylated product is 75% and the selectivity in para isomer 94%. The most efficient catalysts are the rare earth-exchanged zeolites (70% exchange). The following order of activity is observed: Cr3+, Zr4+ < Mg2+, Cu2+, Co2+ ⪡ H+ ⪡ Pr3+, La3+, Gd3+, Yb3+, Ce3+.

Four examples of acid-catalyzed organic reactions are presented which emphasize the similarities that exist between zeolites and liquid acids. Using Hammett correlations, it is shown that similar mechanisms operate. Thus a positively charged entity is formed in the transition state for acetal hydrolysis and aromatic acylation, with a similar charge transfer in the homogeneous and heterogeneous media. The efficiency and strength of the acid centers increases up to a constant value when the aluminium content of the zeolite decreases, as is observed by dilution of proton in solution. As a consequence, the activity of mordenites for olefin hydration and for dichlorobenzene isomerization follows volcano shaped curves as a function of the Al/(Al+Si)ratio.

The Friedel-Crafts acylation of aromatic compounds (benzene, toluene, xylene) with carboxylic acids (CH3(CH2)n COOH, n = 0–14) was performed over cation-exchanged montmorillonites (H+, Al3+, Ni2+, Zr4+, Ce3+, Cu2+, La3+).

A ϱ - σ+ relationship for zeolite catalyzed acylation of aromatic compounds by car☐ylic acids was studied. The large negative value of ϱ indicates that the mechanism is an electrophilic substitution in which the transition state resembles the Wheland intermediate. Obedience to the Brown selectivity relationship is also reported.