Analysis of product distribution and characteristics in hydrothermal liquefaction of barley straw in subcritical and supercritical water

In this study, hydrothermal liquefaction of barley straw in subcritical and supercritical water with potassium carbonate catalyst was performed in the temperatures range of 280-400°C. The influence of final reaction temperature on products yield was investigated and some physicochemical properties of products were analyzed. It was found that products yield was significantly influenced by final reaction temperature under slow heating rate. The biocrude yield increased first and then declined as the temperature increased while the yield of solid residues showed the opposite trend. The highest biocrude yield (35.24 wt %) as well as the maximum energy recovery of 55.33% were obtained at 300°C. The products obtained were characterized in terms of CHNS elemental composition, higher heating values (HHVs), Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometer (GC-MS). Biocrude with more than 74% of C and H contents was produced under tested conditions with HHVs of 26.75-35.48 MJ/kg. The biocrude mainly consisted of carboxylic acids, phenolic compounds, and ketones, as well as some aldehydes and alcohols