Thermal transformations of pine wood components under pyrolysis/gas chromatography/mass spectrometry conditions

The analysis of thermal transformations of the main components of sound pine wood was performed through the application of Py/GC/MS. A gradient of sub-pyrolysis temperatures (200, 250, 300 and 350 degrees C) and a double-shot pyrolysis at 450 and 500 degrees C after a pre-pyrolysis step at 250 degrees C were performed. Then, a flash pyrolysis at 500 degrees C was also applied. The pyrograms obtained after applying a gradient of sub-pyrolysis temperatures showed the no detection of carbohydrate and lignin-derived compounds at 200 degrees C as well as a high relative abundance of trans-coniferaldehyde at 250 and 300 degrees C. An increase in the total released carbohydrates and the most selected methoxyphenols (guaicol, methylguaiacol, ethylguaiacol, vinylguaicol, and acetovanillone) was observed with the increase of sub-pyrolysis temperature up to 350 degrees C. The pyrograms corresponding to the double-shot pyrolysis showed a series of carbohydrate-derived compounds which were not detected at sub-pyrolysis temperatures. Moreover, at these conditions an increase in the total lignin peaks was observed except in the case of using 250 degrees C. In the pyrograms obtained after flash pyrolysis at 500 degrees C an increase in the total carbohydrates was detected compared with that obtained when the pyrolysis was applied after a pre-pyrolysis step. This result corroborates the higher release of carbohydrate-derived compounds at pre-pyrolysis conditions. Although at 250 degrees C the main biomarkers of lignin can be detected, higher temperatures are required to get a more complete information on lignin constituents of pine wood. (c) 2006 Elsevier B.V. All rights reserved.