Thermal Decomposition of Wood and Cellulose in the Presence of Solvent Vapors

The thermal decomposition of white birch wood and filter pulp was studied in water and methanol vapor at 2 MPa pressure in a flow-through reactor. The abundance of the volatile products was monitored by on-line GC/MS using repetitive sampling in combination with fast separation on a short capillary column. The reactor was heated to 400 °C at 20 °C/min and the intensity profile of the product ions within the 30−200 amu range recorded. The system was capable of separating the profiles of typical hemicellulose products evolved at lower temperature from the characteristic cellulose and lignin products detected from wood. Char yields in methanol were similar to those in an inert gas atmosphere; however, the presence of water markedly increased the amount of char produced. The product distribution of cellulose was strongly affected by the solvents. In methanol, pyran derivatives dominate besides 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) thermogravimetric 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.