Catalytic performance and mechanism of KF-loaded catalysts for biodiesel synthesis

A number of KF-loaded heterogeneous base catalysts were prepared by doping KF on mixed oxide or single oxide supports containing Mg, Cu, Zn, Co, Al, Cr, Ni or Fe. The catalysts were characterized and tested for the transesterification of vegetable oil with methanol to produce biodiesel, in order to elucidate the active phase(s). The experimental results showed that KF doping increased activity irrespective of the nature of the support (i.e. whether it was mixed oxide or single oxide). For all catalysts KOH, formed during the treatment of each support with KF, was demonstrated to be the active phase. The activity of KF doped catalysts is promoted by the surface F-species. On this basis, it is possible to rationalize the general effect that KF has in promoting base catalyzed activity and select suitable supports in the design of highly active KF-loaded catalysts.