Non-catalytic Hydrothermal Liquefaction of Biomass: An Experimental Design Approach

A face centered central composite design was used for determining the effects of reaction temperature (180-260 °C), reaction time (0-2 h) and sawdust concentration (9.1-25 wt%) on conversion and recovered product yields during hydrothermal liquefaction of pine sawdust. The determined conversion and aqueous product (AP) yield were in the range 23.1-57.2% and 14.6-43.4%, respectively. The results showed that all linear model terms and some interaction terms were statistically significant for sawdust conversion and liquid product yields, whereas all quadratic terms were found statistically insignificant. In general, increasing reaction temperature increased sawdust conversion and AP formation, while increasing sawdust concentration led to a reduction in conversion and liquid product yields. The determined model revealed that the decomposition reactions of lignocellulosic constituents may have occurred competitively, thus resulting in a certain trend in recovered AP and heavy oil (HO) yields.