Influence of Ionic Additives on the Pyrolysis Behavior of Paper

Pyrolysis is a thermochemical decomposition of organic material at elevated temperatures in the absence of oxygen (or any halogen). However, literature on the pyrolysis of finished paper products is rare.

In the course of this study, the influence of ionic additives (sodium, potassium, lithium, magnesium, and manganese as cations; acetate, lactate, malate, malonate, succinate, and citrate as anions) on the pattern of volatile pyrolysis products of finished paper was investigated. The pyrolysis of paper caused a cascade of reaction products. As expected, the most abundant pyrolysis product was levoglucosan, however, along with other volatile products, such as hydroxyl and carbonyl compounds, furan and pyran derivatives, phenols, and other anhydrosugars, respectively. These compounds could easily be separated and characterized online using analytical pyrolysis in combination with gas chromatography (GC) and mass spectrometry (MS) detection. Both the composition and total amount of volatile pyrolysis products were significantly altered when the paper samples contained metal salt ions and salts of organic acids, respectively. Principal Component Analysis (PCA) was employed for the multivariate analysis of the obtained pyrolysis products. This allowed for a qualitative interpretation on how the various ionic additives affected the formation of specific pyrolysis products. When organic acids were added onto the paper, the pyrolysis pattern mainly depended on the protic properties of the organic acids (mono/di/triprotic) and to a lesser extent on the type within a protic class (monoprotic acetate or lactate vs.diprotic malate or malonate or succinate vs. triprotic citrate).

In conclusion, the pyrolysis pattern of the paper samples was more markedly influenced by the type of metal ions rather than by the type of organic acid. These effects significantly depended on both the valence and the concentration of the specific metal salt. Further investigation of this topic will include a variation of the counter cations of various acids as well as a concentration series for anionic additives. In addition, other counter anions will have to be investigated in more detail in order to specifically attribute as many effects as possible.

Article by Karin Stadlmann, et al, from Austria.

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