Heteropolyacids with Keggin-structure as green catalysts

V. PALERMO, G. ROMANELLI, P. VÁZQUEZ

Venice, Italy

Otro; Tenth Summer School on Green Chemistry; 2008

INCA

Heteropolyacid (HPA) with Keggin-structure are well known as oxidation and acid catalysts in which the red-ox and acid-based properties can be tuned by variation of primary, secondary or tertiary structures, the central heteroatom and addenda or transition-metal-substituted atoms. It is very important to use fully characterized and more reliable catalyst precursors for catalytic reactions.  On the other hand, H2O2 is one of the oxidants frequently used in fine chemicals synthesis, as an option to the conventional ones, since its use leads to a cleaner technology because it is easy to handle and its reaction produces only H2O as by-product. The selective catalytic of sulfides to sulfoxides has been a challenge for many years, owing to the importance of sulfoxides and sulfones as intermediates in organic synthesis. This work has as main objective to synthesize different HPA for their use in the selective oxidation of sulfides to sulfoxides or sulfones. The key difference respect to previous research is that the HPA solution impregnate, by equilibrium impregnation, uses like solvent ethanol for the impregnating of pure silica (S) or silica functionalized with 3-amino-propyltriethoxysilane (FS), adds H2O2 or H2O to S or FS, following to the HPA impregnation.  The catalysts prepared with FS allowed the reuse in the sulfide oxidation, without lose the catalytic activity after three cycles. The HPA employed in the impregnate solution were following: H6PMo11YO40, H6PMo11BO40, H6PMo11BiO40 and H5PMo11Bi0.5V0.5O40. Among these, Y ones, showed the best performance in the sulfide oxidation.