Biodiesel production by acid catalysis with heteropolyacids supported on activated carbon fibers

• Supported HPA on activated carbon fiber are suitable catalysts for esterification.
• Catalytic activity of HPA is closely related with the micropore size.
• Leaching and the porosity blockage cause a reduction of the catalytic activity.
• Porosity blockage occurs progressively, from the external part to inward the fiber.
• Washing step with ethanol and H2SO4 is need for the catalyst regeneration.

Different catalysts, based on heteropolyacids supported on activated carbon fibers, have been prepared for palmitic acid esterification reaction. The influence of the catalyst (heteropolyacid) and the support on the catalytic activity have been analyzed. The results prove that an adequate combination of both is required to achieve the most suitable catalysts. Regarding to the heteropolyacid, phosphomolybdic acid seems to be the most suitable appropriate taking into account its lowest leaching. About the support, it must show an optimum microporosity, which must be wide enough to allow the entrance and exit of the reagents and products but not too wide in order to avoid the leaching of the catalyst. In addition, both decreasing of the catalytic activity and its recovery over several cycles have been analyzed.

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