Supported Keggin type heteropolycompounds for ecofriendly reactions

L. R. PIZZIO; P. G. VÁZQUEZ; C. V. CÁCERES; M. N. BLANCO

Applied Catalysis, A: General

Elsevier

Lugar: Amsterdam; Año: 2003 vol. 256 p. 125 - 139

New supported Keggin heteropolyacid (HPA) catalysts were prepared in order to make a contribution to the field ofcatalyzed acid reactions by means of ecofriendly technologies. The esterification of isoamyl alcohol and acetic acid ingaseous phase was studied using tungstophosphoric acid (TPA) supported on different carriers, silica materials, carbon andalumina. These catalysts were characterized by FT-IR, DRS, TPR and their acidity was evaluated through the isopropanoldehydration test reaction. The higher acidic catalysts prepared with silica materials led to the greatest activities due to thehigher proton availability which, in turn, was related to the lower interaction and dispersion of the active species. In orderto perform this acid reaction in heterogeneous liquid phase and to avoid the tungstophosphoric or molybdophosphoric acid(MPA) solubilization during reaction, functionalized silica and SiMCM-41, and polyvinyl alcohol hydrogel?polyethylenglycol(PVA-PVG) beads were used as new supports. The physical?chemical characterization of the supported catalysts by FT-IR,XRD, 31P MAS NMR and TG-DTA showed mainly undegraded primary Keggin structure. The solids exhibited low ornegligible solubilization and their acidity, measured by potentiometric titration with n-butylamine, was high. The SiMCM-41and polymeric bead-supported catalysts lead to obtain attractive activity in the isoamyl acetate synthesis through esterificationreaction.