Wood ash as a potential heterogeneous catalyst for biodiesel synthesis

Wood ash is a highly alkaline material comprises of inorganic constituents. A limited information on use of wood ash as catalyst is available in literature. The present study was undertaken to investigate the catalytic activity of wood ash for transesterification of Jatropha oil. The thermal treatment (calcination) of wood ash was carried out at temperature in the range of 500–1200 °C to produce calcined wood ash catalysts (CWC). The wood ash was also chemically activated with K2CO3 and CaCO3 by double carbonate solid state reaction to yield activated wood ash catalysts (AWC). The prepared catalysts were characterized by analytical techniques for surface morphology, crystalline phases, textural characteristics and alkalinity. Methyl ester conversion of Jatropha oil was achieved in the range of 97–99% with CWC and AWC catalysts. The synthesized Jatropha methyl esters using CWC and AWC catalysts have been found meeting the critical physico-chemical properties of ASTM D-6751 standards of biodiesel. The present study revealed the possibility of producing potential heterogeneous catalyst from wood ash for biodiesel synthesis, which can find a way to utilize abundant wood ash and reduce the overall cost of biodiesel production.

► Alkaline wood ash used as CWC (calcined wood ash catalyst) and AWC (activated wood ash catalyst) catalysts for biodiesel synthesis.
► Higher alkalinity, lower surface area and increased particle size were major parameters for catalyst's activity.
► CWC800 and AkWC0.5 were best catalysts with max. 97–99% ester conversion of jatropha curcas oil.
► Catalysts could be reused up to 5 cycles. Provide fast reaction and trouble free work-up of reaction mixture.