THERMOCHEMICAL FRACTIONATION AND LIQUEFACTION OF LIGNOCELLULOSIC MATERIALS

Fractionation and liquefaction of cellulose, lignin and wood have been studied in the temperature range of 150-275{dollar}spcirc{dollar}C with the following independent variables: solvents, gas type and pressure in the presence of catalysts at different reaction times. The evaluation was based on the nature and proportion of acetone-solubles and insolubles (residue), glucose in residue and acid-condensibles. The molecular weight distribution and crystallinity were obtained for cellulose degradation. The temperature dependence of the final products was strongest above 200{dollar}spcirc{dollar}C with the residue exhibiting marked decreases at higher temperatures. The amount of acetone-solubles was catalyst and solvent dependent at 200{dollar}spcirc{dollar}C and above.; The liquefaction using a rocking furnace reactor at a high pressure (1000 psi) of reducing gases (CO:H{dollar}sb 2{dollar}) with 95% aqueous ethanol resulted in high acetone-solubles with the hydrogenation catalysts (PdCl{dollar}sb 2{dollar} and RhCl{dollar}sb 3{dollar}): 17.2% from cellulose, 42.5% from wood (200{dollar}spcirc{dollar}C) and 95.3% from kraft lignin (260{dollar}spcirc{dollar}C) with RhCl{dollar}sb 3{dollar}. The greatest amount of glucose preserved in the residue from wood and cellulose was with Co{dollar}sb 2{dollar}(CO){dollar}sb 8{dollar}: 96.8% from cellulose and 97.9% from wood (200{dollar}spcirc{dollar}C). Co{dollar}sb 2{dollar}(CO){dollar}sb 8{dollar} intensively catalyzed native wood lignin degradation, resulting in only 1.0% of residual lignin.; Acetic acid fractionation and liquefaction was studied (same reactor and pressure), the glucose preserved in the residue of cellulose and wood was greatest at 200{dollar}spcirc{dollar}C and 50% aqueous acetic acid concentrations. The high acid concentration (75 and 100%) degraded lignin to leave only a small amount: 2.3% from kraft lignin and 7.0% from wood (200{dollar}spcirc{dollar}C and 100% acetic acid concentration).; A fluidized bed heater was used to evaluate the reactions under more controlled time and temperature conditions. A combination of a hydrogenation catalyst (PdCl{dollar}sb 2{dollar}) in an acidic medium (pH = 3) resulted in maximum acetone-solubles under various gas pressures: 34.5-54.8% from cellulose compared to 0.6-2.6% from uncatalyzed runs (200{dollar}spcirc{dollar}C and 20 minutes). A high retention of glucose in the residue was obtained when Co{dollar}sb 2{dollar}(CO){dollar}sb 8{dollar} was used under different liquefaction conditions.; The effect of liquefaction conditions on cellulose degradation was monitored through the molecular weight changes. The maximum decrease of the weight average degree of polymerization of cellulose was obtained in an acidic medium (pH = 3): a DPw of 132 (200{dollar}spcirc{dollar}C, 20 minutes and 500 psi of CO:H{dollar}sb 2{dollar}) was obtained from an original DPw of 2950. The highest DPw was obtained using Co{dollar}sb 2{dollar}(CO){dollar}sb 8{dollar} to catalyze the reactions: a DPw of 2240 in 95% aqueous ethanol (atmospheric pressure, 200{dollar}spcirc{dollar}C and 20 minutes).