Hydrothermal Carbonization of Lignocellulosic biomass: Chemical and Structural Properties of the Carbonized Products

Hydrothermal carbonization (HTC) is a novel thermochemical conversion process to convert lignocellulosic biomass into value-added products. In this work, two different biomass materials: corn stalk and Tamarix ramosissima were used as feedstock. HTC processes were performed at the temperature of 250 °C for 4 h, using a batch reactor system. Chemical and structural characterization of the solid materials was carried out by elemental analysis, nitrogen adsorption, scanning electron microscopy, X-ray diffraction, and spectroscopic techniques including Fourier transform infrared, X-ray photoelectron, and Raman. The results indicated HTC treatment brought an increase of the higher heating value up to 29.2 and 28.4 MJ/Kg for corn stalk and T. ramosissima, respectively, corresponding to an increase of 66.8% and 58.3% as compared to the natural biomass. The surface area determined by Brunauer–Emmett–Teller analyses was 10.8 and 11.3 m 2 /g, which was 4.8 and 10.9 fold for the hyrochars of corn stalk and T. ramosissima, respectively. Additionally, liquid products extracted with ethyl acetate were analyzed by gas chromatography–mass spectrometry. The identified compounds were phenolic and furan derivatives, confirming the mechanisms of dehydration, decarboxylation, and demethanation reactions during the carbonization processes. Based on these results, HTC is considered to be a potential treatment in a lignocellulosic biomass refinery.