Comparative Study on the Alcohothermal Degradation of 2 Lignin Feedstocks in Sub-/Supercritical Ethanol

Huayan alcohol-soluble alkali lignin and TCI dealkali lignin as raw materials were converted into oils, chars and gas products at 180−300 ℃ with sub-/supercritical ethanol. The effects from reaction temperature, reaction time and inorganic additives on the product composition and the chemical structure of bio-oils and bio-chars were studied. The results showed that as the reaction temperature increased from 180 ℃ to 300 ℃, lignin feedstocks were cracked, reformed and dealkoxylated to produce bio-oils with increased concentration of saturated aliphatic composition and less aromatic compounds, while gas product mainly composed of H₂ and gaseous hydrocarbons was also detected. The yield of bio-oil was firstly decreased and then increased with temperature. The activity of ethanol taking part in the reaction was enhanced under supercritical condition, which contributed to the rapid increase in gas yield. When the reaction time at 260 ℃ was extended to longer than 5 h, the yield of oil and gas rose rapidly, which might be related to the catalytic effect of solid carbonaceous residue, but had little impact on the formation of biochar. The addition of H₂SO₄ and Na₂SiO₃ provided adverse effect on the production of oil and gas during alcohothermal reaction.