a shows the product distribution at different temperatures in the pyrolysis of wood biomass when sepiolite was used as catalyst, and also in non-catalytic tests. The distribution of pyrolysis products (gas, char and the whole liquid product before phase separation) was analysed in terms of their yield (wt.%, g of product/g of biomass fed). As it can be observed in Fig. 1a, temperature clearly affected to the three products obtained in non-catalytic tests. Liquid and gas products rose with temperature while solid decreased. Regarding liquid yield, the observed rise was almost negligible above 450 °C, when remained steady at a level of around 48 wt.%. A different behaviour was observed in sepiolite tests: although liquid yield increased and solid product diminished with temperature, gas yield seemed not to be affected. It should be noticed the remarkable yield to the solid fraction (37–46 wt.%) which was obtained in sepiolite tests. It can be assumed that the promotion of secondary reactions by this catalyst can lead to the formation of heavy organic compounds, which form carbonaceous deposits through retrogressive reactions [21] and [22], increasing the solid fraction yield. Subsequently, catalyst to biomass proportion should be optimised in order to avoid an over production of char when bio-oil is the target product.