Silica-supported heteropolyacids as catalysts in alcohol dehydration reactions

Optimization of the operative conditions for heteropolyacids synthesis through ion exchange

“…. Additionally, the ammonium salt possesses the infrared signal of the NH 4 + species at 1403 cm -1 similarly to the phospho-tungstic salt. Again, the comparison of the infrared spectra of the materials obtained in aqueous and ethanol media indicate that the ion exchange is greatly favored in organic media.…”

“…The ammonium phospho-molybdic Wells-Dawson salt was synthesized with Na 2 MoO 4 , H 3 PO 4 and HCl according to a method published before 17 . Additionally, the phospho-tungstic Wells-Dawson acid H 6 P 2 W 18 O 62 was synthesized according to the "etherate method" from a α/β-K 6 P 2 W 18 O 62 isomer mixture.…”

“…The free acid form of the heteropoly-anions, i.e. Keggin H 3 4 . Therefore, many heteropolyacids are more active catalysts than conventional organic and inorganic acids in liquidphase reaction.…”

“…The insolubility of the heteropoly-acids in many organic substances allows an easy separation and reutilization of these catalysts. Moreover, several liquid-phase processes showed that the reaction mixture separates in two phases, one of those containing the heteropoly-compound 3,4 . Undoubtedly, the catalytic processes based on heteropolyacids are an outstanding contribution in the development of environmental benign technologies.…”

Synthesis and Characterization of Zirconia Supported Vanadium Incorporated Ammonium Salt of 12-molybdophosphoric Acid Catalyst for Aerobic Oxidation of Benzyl alcohol

“…This method was proposed initially by Cid and Pecchi [36], Blanco et al [37,38] used it to determine the acidity of the catalysts with n-butyl amine as the titrant. In all the communications, it was mentioned that the strength of acid sites is indicated by the initial electrode potential and the value at the plateau region of the curve (meq/g of the solid) as the total number of acid sites of the titrated solid.…”