Optimization of the operative conditions for heteropolyacids synthesis through ion exchange

Abstract

Phospho-tungstic and phospho-molybdic Wells-Dawson heteropolyacids, H<SUB>6</SUB>P<SUB>2</SUB>W<SUB>18</SUB>O<SUB>62</SUB>.xH<SUB>2</SUB>O and H<SUB>6</SUB>P<SUB>2</SUB>Mo<SUB>18</SUB>O<SUB>62</SUB>.xH<SUB>2</SUB>O respectively, were synthesized through ion exchange with a higher yield (∼ 90%) than the conventional organic route (∼ 70%). Pure, non-degraded heteropolyacids are obtained when the corresponding ammonium salt [(NH<SUB>4</SUB>)<SUB> 6</SUB>P<SUB>2</SUB>W<SUB>18</SUB>O<SUB>62</SUB>.13H<SUB>2</SUB>O or (NH<SUB>4</SUB>)<SUB>6</SUB>P<SUB>2</SUB>Mo<SUB>18</SUB>O<SUB>62</SUB>.12H<SUB>2</SUB>O] is kept in contact with an acid resin [about (1:0.8) salt:resin weight ratio] up to three days. The use of an organic media instead of an aqueous media greatly favors the completeness of the exchange.