71. Kumar, Sandeep; Gupta, Ram B.. Biocrude Production from Switchgrass Using Subcritical Water. Energy & Fuels (2009), 23(10), 5151-5159.
Subcrit. water is an environmentally attractive solvent for org. matters and can be used to liquefy biomass to biocrude, which is a mixt. of oxygenated hydrocarbons of varying mol. wts. Liquefaction of switchgrass in subcrit. water is studied using a semicontinuous reactor in the temp. range of 235-260C. Subcrit. water is pumped through a tubular reactor packed with switchgrass particles of 40-60 mesh size. The effects of reaction temp. and catalysis by K2CO3 are examd. Potassium carbonate significantly enhances the hydrolysis of macromoleculer components of switchgrass into water-sol. products. More than 50 wt % of the org. carbon available in switchgrass was converted to biocrude after 20 min of steady operation at 235C in the presence of 0.15 wt % of K2CO3. At the high temp. (260C), dehydration of biomass was favored over hydrolysis reactions. On the basis of chromatog. and mass spectrometry analyses, biocrude contains lignin derived products, sugars, and its decompn. products. On the basis of the IR spectroscopy and electron microscopy of residue solid, the subcrit. water treatment causes complete breakdown of lignocellulosic structure of switchgrass. In fact, the residue solid mainly contained lignin fractions.