Hydrothermal Liquefaction of Lignocellulosic Biomass Components: Effect of Alkaline Catalyst

Abstract

The fundamental studies to understand the role of individual biomass components (cellulose and lignin) on the production of valuable hydrocarbons during hydrothermal liquefaction (HTL) is presented. Thermal and catalytic HTL of cellulose and lignin was performed at 280 °C under biomass:H₂O ratio of 1:6 at 15 min residence time. The use of alkaline catalysts significantly increased both bio-oil yield and conversion for cellulose as well as lignin. Maximum bio-oil yield (28%) and conversion (90%) in case of cellulose was observed with KOH. Similarly in case of lignin maximum bio-oil yield (17 wt%) as well as conversion (72%) was observed with KOH. From the analysis of bio-oil and bio-residue, it was observed both cellulose and lignin have undergone hydrolytic cleavage during HTL to form low molecular weight liquid products. The FTIR and NMR (¹H and ¹³C) of the bio-oil obtained from lignin indicated the presence of phenols and aromatic ethers.

Appendix

$$ Converion(\% ) = \frac{{W_{feed} - W_{residue} }}{{W_{feed} }} \times 100 $$

(1)

$$ Bio - oil1\,Yeild(wt.\% ) = \frac{{W_{ether\,soluble} }}{{W_{feed} }} \times 100 $$

(2)

$$ Bio - oil2\,Yeild(wt.\% ) = \frac{{W_{acetone\,soluble} }}{{W_{feed} }} \times 100 $$

(3)

$$ Gas\,Yield(wt.\% ) = \frac{{w_{(vessel + feed + water) before \, HTU} - w_{(vessel + feed + water)after \, HTU} }}{Amount\,of\,feed\,taken \, (g) + Amount\,of\,water\,added \, (g)} \times 100 $$

(4)

$$ Solid\,residure\,Yield \, (wt.\% ) = \frac{{w_{solid\,residue} }}{{w_{feed} }} \times 100 $$

(5)

$$ Other\,Yield(wt.\% ) = 100 - (bio - oil1 + bio - oil2 + solid\,residue + gas)Yield $$

(6)

W _feed is the weight of feed; W _residue is the weight of bio-residue; W _{ether soluble} is the weight of ether soluble hydrocarbons (bio-oil1); W _{acetone soluble} is the weight of acetone soluble hydrocarbons (bio-oil2). Others correspond to the water soluble hydrocarbons and some loses.