Grafting of palladium nanoparticles onto mesoporous molecular sieve MCM-41: Heterogeneous catalysts for the formation of an N-substituted pyrrol

Palladium nanoparticles, obtained by thermochemical reduction of palladium(II) acetate in propylene carbonate or in tetrahydrofuran with added tetrabutylammonium acetate (Bu4NOAc), were deposited onto mesoporous molecular sieve MCM-41 (spontaneously or after solvent change) to give novel supported metal catalysts, which were characterized by chemical analysis, powder X-ray diffraction, nitrogen adsorption-desorption isotherms and high-resolution transmission electron microscopy (HR TEM). The materials, together with 10% Pd/C reference were utilized as catalysts in the condensation reaction of 2-aminoethanol with cis-butene-1,4-diol to afford N-(2-hydroxyethyl)pyrrol. Both supported catalysts showed significantly higher conversions that Pd/C, the one prepared in the presence of Bu4NOAc being the most active. Catalysts isolated after the reaction and used repeatedly showed lower activity than fresh ones. This apparently reflects partial metal leaching from the solid support and aggregation of the metal particles that were demonstrated by catalytic tests and HR TEM measurements, respectively.

Graphical abstractMCM-41 supported palladium nanoparticles were shown to promote condensation reaction of 2-ethanolamine with cis-butene-1,4-diol to give N-(2-hydroxyethyl)pyrrol with a good selectivity and yields. The properties of the supported catalysts were studied chemically and by N2-adsorption isotherms, X-ray diffraction and HR TEM. Figure optionsDownload full-size imageDownload as PowerPoint slide