THERMOGRAVIMETRY MASS-SPECTROMETRY STUDY OF 6 LIGNINS WITHIN THE SCOPE OF AN INTERNATIONAL ROUND-ROBIN TEST

Thermogravimetry/mass spectrometry was applied to characterize six lignins prepared for an international round robin test. The sample set includes a mildly isolated lignin, and technical lignins prepared by steam explosion, Alcell, Indulin and Sucrolin processes. The samples were thermally degraded in an argon atmosphere using a heating rate of 20 degrees C min(-1). The weight loss and the evolution profiles of the thermal decomposition products of low molecular mass were monitored. It was found that the intensity and the evolution profile of the products (especially water, formaldehyde, methane and methanol) reflect the severity of the isolation procedure and the origin of the lignin. Correlations have been observed between the abundance of volatile products and the type and amount of functional groups. The terminal CH2OH groups decompose by the release of both water and formaldehyde, as demonstrated by the relationship between the aliphatic hydroxyl group content and the formaldehyde as well as the water evolution. The dependence of the methane yield on the methoxyl group content provided evidence that the scission of methoxyl groups results in the formation of methane as well as methanol. The correlations found allow the assignments of the gaseous products to functional groups.