Co-Hydrothermal Liquefaction of Lignocellulosic Biomass in Supercritical Water

Abstract

Hydrothermal liquefaction (HTL) is an effective technology for bio-crude production. To date, various co-liquefaction studies were performed with contrasted (different composition) biomasses in subcritical water. Therefore, the present study investigated co-hydrothermal liquefaction of similar kinds of lignocellulosic biomasses (wheat straw, eucalyptus, and pinewood) in supercritical water under equal ratios at 400 °C with catalytic medium (K2CO3). The lower bio-crude and higher solid yields were obtained in co-liquefaction experiments, as compared to liquefaction of individual feedstocks. On the other hand, higher carbon recovery and higher HHVs were noticed in co-liquefaction-derived bio-crudes. Gas chromatography with mass spectrometry (GC-MS) results showed that organic compounds were detected in all bio-crudes in the order of phenol derivatives > ketones/aldehydes > aromatics > carboxylic acids/esters. The aqueous phase from all samples contained higher TOC in the range of 19 to 33 g/L, with alkaline pH. In short, the co-liquefaction slightly improved the bio-crude quality with a significant reduction in bio-crude energy recovery. This reflects that co-liquefaction of lignocellulosic feedstock is not favorable for enhancing bio-crude yield and improving the overall process economics of HTL.

Keywords

• lignocellulosic biomass
• HTL
• co-liquefaction
• bio-crude