Aqueous phase reforming of HTL aqueous phase over Ni/AC catalyst for hydrogen production

A significant amount of solid residue (SR) and aqueous phase (AP) by-products are typically generated during the hydrothermal liquefaction (HTL) of lignocellulosic biomass. AP often contains substantial quantities of harmful organic matter, which can cause environmental pollution if not adequately treated. Conversely, SR can be utilized as a low-grade solid fuel. Realizing the high-value utilization of this type of by-product not only contributes to mitigating environmental pollution but also improves the overall efficiency of biomass conversion and utilization. The objective of this paper is to valorize AP and SR to produce H 2 . SR obtained from the HTL of corn stalks was converted into activated biochar (AC) to prepare a Ni/AC catalyst for H 2 production from AP through aqueous phase reforming (APR). Through CO 2 activation, the specific surface area of AC reached 691 m 2 /g at an activation temperature of 900 °C and a residence time of 3 h. Using 6 wt% Ni/AC (1/60 g catalyst /mL AP ), H 2 yield reached 17.12 μmol/COD at 320 °C over 3 h, approximately 6-fold of the non-catalyzed reaction, while the COD removal reached approximately 38 %. In the gaseous product, the composition of H 2 , CO, CH 4 , CO 2 was 31.69, 1.51, 0.67 and 66.13 vol%, respectively. In view of the adverse effect of the high COD value of AP on APR, reducing ketones, acetylenes and esters may improve the hydrogen production efficiency of the reaction system. Valorization of SR and AP for H 2 production contributes to enhancing the overall energy conversion of biomass HTL.