Coupling hydrothermal liquefaction and aqueous phase reforming for integrated production of biocrude and renewable H2

Lignin-rich stream from lignocellulosic ethanol production was converted into biocrude by continuous hydrothermal liquefaction (HTL) while hydrogen was produced by aqueous phase reforming (APR) of the HTL aqueous by-product. The effects of Na2CO3 and NaOH were investigated both in terms of processability of the feedstock as well as yield and composition of the obtained products. A maximum biocrude yield of 27 wt% was reached in the NaOH-catalyzed runs. A relevant amount of dissolved phenolics were detected in the co-produced aqueous phase (AP), and removed by liquid-liquid extraction using butyl acetate or diethyl ether, preserving the APR catalyst stability and reaching an hydrogen yield up to 146 mmol H-2 L-1 AP. Preliminary mass balances integrating HTL and APR showed that the hydrogen provided by APR may account for up to 46% of the hydrogen amount theoretically required for upgrading the HTL biocrude, thus significantly improving the process performance and sustainability.

Automated summary

This study converted lignin-rich stream from lignocellulosic ethanol production into biocrude through continuous hydrothermal liquefaction (HTL), and produced hydrogen through aqueous phase reforming (APR). The use of NaOH catalyst resulted in a maximum biocrude yield of 27 wt%, and the phenolics in the co-produced aqueous phase were effectively removed through liquid-liquid extraction, improving the hydrogen yield of APR. Preliminary mass balances showed that APR can provide up to 46% of the theoretical hydrogen required for upgrading the HTL biocrude, enhancing the process performance and sustainability.