Organic-functionalized molecular sieves. III. Shape selective catalysis

Abstract

Several organic-functionalized molecular sieves (OFMSs) are investigated for use as shape-selective catalysts. OFMSs with the ∗ BEA topology containing ethylcyclohexenyl, phenethyl and mercaptopropyl functional groups are synthesized and characterized by X-ray diffraction, FT-Raman spectroscopy, solid-state 13C NMR spectroscopy, thermogravimetric analysis, nitrogen physisorption, scanning electron microscopy, energy dispersive spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy. Acidic OFMSs derived from phenethyl and mercaptopropyl containing OFMSs are used in catalytic tests. Sulfonated phenethyl-containing OFMSs can exhibit poor shape selectivity in discriminating between cyclohexanone and 1-pyrenecarboxaldehyde reactions with ethylene glycol at low temperatures in the liquid phase. This poor selectivity is shown to be due to the introduction of silanol-bound sulfonic acid species on the external surface by sulfonation of extracted phenethyl-functionalized beta samples. Sulfonic acid containing OFMSs derived from the oxidation of mercaptopropyl groups are very selective for the conversion of cyclohexanone relative to 1-pyrenecarboxaldehyde, with an initial rate ratio ( R HEX/ R PYC) that can exceed 200. The rate of reaction over this shape-selective catalyst is significantly slower than over commercial zeolite beta, organic-functionalized mesoporous materials, and homogeneous acids.