Title
Crystal structure change of cellulose due to gaseous ammonia treatment
Authors
HERWIG HACKENBERG, MARTINA BREMER, MARIO ZAUER, STEFFEN FISCHER and ANDRÉ WAGENFÜHR

Received August 8, 2024
Published Volume 58 Issue 7-8 July-August
Keywords gaseous ammonia, cellulose III, XRD, Raman spectroscopy

Abstract
Dissolving pulp was treated with ammonia gas at 20 °C at different pressure levels. The modified pulp was analysed with regard to the change in crystal structure from cellulose I to III. X-ray diffraction and Raman spectroscopy were used as analytical methods. It was found that the transformation of cellulose from cellulose I to III takes place above a defined pressure level, which could be recorded continuously as a function of pressure. Below the characteristic pressure level, the cellulose is still present as cellulose I after treatment. This pressure level is lowered by the presence of water. The ammonia gas is therefore able to swell the crystalline areas of the cellulose starting from a defined process intensity, causing the cellulose to recrystallize in a different structure. Finally, the cellulose III obtained was partially converted back into cellulose I by water boiling.