Synergetic hydrothermal co-liquefaction of crude glycerol and aspen wood

Crude glycerol-assisted hydrothermal co-liquefaction of aspen wood was studied in batch micro-reactors. An experimental matrix of 14 experiments was defined to investigate the effects of three different process parameters on the yields of biocrude and char, and on biocrude quality. Co-processing aspen wood and neat glycerol led to a significant reduction in the char yield, and glycerol is hypothesized to act as a radical scavenger, alleviating re-polymerization of especially lignin-derived fragments. In the temperature range of 380–420 °C, it was found that biocrude and char yield, and biocrude quality were all invariant to the reaction temperature. By increasing the crude glycerol to aspen wood mass ratio from 0:1 to 3:1, char yield was decreased from 18.3% (only aspen wood) to 3.4%. Furthermore, the biocrude quality in terms of the effective hydrogen-to-carbon ratio (H/C_eff) was significantly affected by the crude glycerol to aspen wood ratio. At a crude glycerol to aspen wood ratio of 3:1 the H/C_eff was 1.6 compared to 0.96 in the case of only aspen wood. The chemical composition of the biocrude was observed to be directly influenced by the two main feedstock constituents, which allows straightforward composition prediction of the biocrude, and hence enables controllability of the biocrude properties by feedstock mixing.