Dana Procházková

Acylation Reactions over Zeolites and Mesoporous Catalysts

Molecular sieves are highly active and selective catalysts with industrial potential for acylation reactions. Zeolites are the catalysts of choice when shape selectivity influences the preferential formation of some products, while high conversions are achieved over mesoporous catalysts with enhanced diffusion rates of reactants and products. In this Minireview, we focus on the understanding of the relationship among the structure of molecular sieve, type and concentration of acid sites and activity/selectivity in various acylations of aromatic and olefinic hydrocarbons. The products of these acylation reactions are important compounds for the pharmaceutical industry, fragrance and flavor materials, dyes, polymers, agrochemicals, and other applications.

Selective monoacylation of ferrocene with bulky acylating agents over mesoporous sieve AlKIT-5.

Ferrocene acylation with bulky acylating agents (1-adamantoyl, benzoyl, 2-chlorobenzoyl, and cinnamoyl chlorides; and benzoic anhydride) catalyzed by AlKIT-5 mesoporous catalysts was investigated. AlKIT-5 catalysts with varying ratios of Si/Al were synthesized using tetraethoxysilane and aluminum isopropoxide as the structural building blocks and Pluronic F127 as a template under acidic conditions and were characterized in detail by X-ray powder diffraction, magic-angle spinning (MAS) NMR spectroscopy, sorption of nitrogen, energy-dispersive X-ray spectroscopy (EDS), SEM, TEM, and FTIR with pyridine as a probe molecule. The catalytic activity of the prepared AlKIT-5 catalysts in ferrocene acylation was shown to depend on the type of the acylating agent, thus likely reflecting the strength of interactions between the acyl source, the product, and the solid catalysts when the acylation reaction was carried out at 100 degrees C. In all reactions, the AlKIT-5 catalysts afforded exclusively the monoacylated products (100% selectivity) most likely due to deactivation of the second cyclopentadiene ring by attachment of the first acyl group, steric reasons, and some competitive interactions of the monoacylferrocenes with the catalysts. The prepared AlKIT-5 catalysts could be regenerated without any significant loss of the ferrocene conversion.