Microwave-assisted production of furfural from the hemicellulosic fraction of olive stones

Olive stone (OS) is a lignocellulosic material obtained as a coproduct in the olive oil production industry, mainly composed of hemicelluloses, with xylose accounting for 24.4 % by weight as the main sugar. In this study, an optimized process for obtaining furfural from OS was assessed. The process consists of two steps; the first one, aimed at maximizing the solubilization of xylose, was performed in an autoclave at 130 °C and 2.6 %w/v H2SO4, resulting in 83 % xylose recovery in the liquid fraction. The second step, using the optimized liquid produced previously, was carried out in a microwave reactor at 200 °C with the addition of 0.1 M FeCl3 from which a solution with 18 g/L furfural and 63.3 % yield was obtained, equivalent to almost 90 kg of furfural per tonne of processed OS. Taking into account these results along with additional advantages in comparison with other lignocellulosic materials (such as no need of a grinding stage and being already available in the olive mills), OS can be considered as a promising raw material for furfural production.