Biomass to fuels: A water-free process for biodiesel production with phosphazene catalysts

Non-ionic triamino(imino)phosphoranes (phosphazenes) give excellent results as base catalysts for the water-free alcoholysis of vegetable fatty esters. Two phosphazene catalysts, with different intrinsic basicities, P1-t-Bu and P4-t-Bu, together with reaction parameters, such as temperature, alcohol/oil molar ratio, or catalyst concentration, have been studied. It was found that activity can be directly correlated to the basicity of the catalyst. Very high biodiesel yields (93–95%mol) were achieved under mild reaction conditions with methanol and ethanol. The catalyst can be recovered and recycled.