Barley straw was successfully converted to bio-crude by hydrothermal liquefaction at temperature of 280
e400 C using an alkali catalyst (K2CO3) in our previous work, and the maximum bio-crude yield was
obtained at 300 C. This paper extends previous work on studying liquefaction behavior of barley straw
without and with K2CO3 at 300 C. The effect of alkali catalyst on product distribution was investigated,
and a detailed analysis of characteristic properties of bio-crude and solid residue has been performed by
an elemental analyzer, FTIR (Fourier Transform infrared spectroscopy), TGA (thermogravimetric analysis)
and GC-MS. The addition of K2CO3 increased the bio-crude yield to 34.85 wt%, and inhibited solid residue
formation. Moreover, the bio-crude produced in the presence of a catalyst had better properties, in terms
of higher heating value and lower O/C. GC-MS analysis showed that the major compounds identified in
bio-crude were carboxylic acids, phenolic compounds and ketones, irrespective of whether the catalyst
was used. However, the distribution and relative content of these compounds were different. More
phenolic compounds and less carboxylic acids were observed in the catalytic run. In addition, the carbon
and energy recovery with the addition of K2CO3 were twice as high as that without catalyst, indicating an
improvement in energy efficiency.