THERMAL-DECOMPOSITION OF WOOD AND CELLULOSE IN THE PRESENCE OF SOLVENT VAPORS

The thermal decomposition of white birch wood and filter pulp was stud ied in water and methanol vapor at 2 MPa pressure in a flow-through re actor. The abundance of the volatile products was monitored by on-line GC/MS using repetitive sampling in combination with fast separation o n a short capillary column. The reactor was heated to 400 degrees C at 20 degrees C/min and the intensity profile of the product ions within the 30-200 amu range recorded. The system was capable of separating t he profiles of typical hemicellulose products evolved at lower tempera ture from the characteristic cellulose and lignin products detected fr om wood. Char yields in methanol were similar to those in an inert gas atmosphere; however, the presence of water markedly increased the amo unt of char produced. The product distribution of cellulose was strong ly affected by the solvents. In methanol, pyran derivatives dominate b esides levoglucosan and glycolaldehyde, whereas the relative abundance of 2-furaldehyde and 5-(hydroxymethyl)-2-furaldehyde increased in the presence of water. Water catalysis was also indicated by lowering the decomposition temperatures of cellulose. High-pressure (6.5 MPa) ther mogravimetric experiments in helium or hydrogen atmospheres were also found to lower the reaction temperature of wood. This observation can be explained by the catalytic effect of reaction water released during the thermal decomposition of wood.