Biodiesel production using heteropoly acid-derived solid acid catalyst H4PNbW11O40/WO3–Nb2O5 Original Research Article

A heteropoly acid-derived solid acid catalyst, H4PNbW11O40/WO3–Nb2O5 calcined at 773 K (HPNbW/W-Nb), showed a higher catalytic activity for transesterification between triolein and ethanol into ethyloleate compared to the activities of conventional solid acid catalysts. The HPNbW/W-Nb was insoluble to the reaction mixture, while such heteropoly acids as H4PNbW11O40 and H3PW12O40 showed high activities but were dissolved into the reaction mixture. The activity was sensitive to calcination temperature, and calcination around 773 K provided a highly active catalyst. The reaction rate showed the maximum at 10–30 of the ethanol/triolein molar ratio. The activity was observed in the co-presence of water and oleic acid. The reaction rate was high when methanol was used in place of ethanol. In a fixed-bed continuous-flow reaction, its potential as an insoluble catalyst is suggested by its stable activity during at least 4 days of the reaction.