Novel catalysts for eco-compatible anisole acylation

LUIS RENE PIZZIO; VANESA M. FUCHS,; MIRTA N. BLANCO

Dresden (Alemania)

Congreso; 1st International IUPAC Conference on Green-Sustainable Chemistry; 2006

Certain salts of Keggin heteropolyacids exhibit interesting characteristics as catalysts due to they can present Lewis and/or Brønsted acidity. In the present paper novel materials were prepared by immobilizing stoichiometric aluminium or copper salts of tungstosilicic acid in a polymeric matrix in order to avoid its solubilization in the reaction medium during reaction. The matrix was constituted by polyvinyl alcohol and polyethylene glycol and was prepared with spherical shape by the freeze-thawing method. It was observed by Fourier transform infrared spectroscopy that the salts retain the Keggin primary structure of the heteropolyanion during their synthesis and immobilization. By potentiometric titration with n-butylamine it was estimated that the immobilized salts present very strong acid sites, being the acid strength of the catalyst based on the aluminium salt higher than that of the copper salt. X-ray diffraction patterns of the solid samples did not present any line corresponding to crystalline structures of the bulk salts. This may be attributed to a high dispersion of the salts in the polymeric matrix.