Overview of water evolution during the thermal degradation of cellulose

The evolution of water during the heating of cellulose is of great importance in understanding the degradation of cellulose because of the autoaccelerating role water plays in the degradation process. Water evolution from cellulose occurs both physically through desorption and chemically by elimination reactions. This paper discusses the mechanisms of water evolution from cellulose in three distinct temperature regimes: (i) loss of absorbed water at low temperatures (<220C), (ii) loss of chemical water at moderate-to-high temperatures (220-550 degreesC), and (iii) loss of chemical water at high temperatures (>550 degreesC). The evolution of water from both cellulose paper and Kraft insulating paper, heated under a linear temperature ramp in helium, was measured with an aluminium oxide-based moisture probe. It was found that water production peaked at two temperatures, namely similar to 110 degreesC and 300 degreesC due to loss of absorbed and chemically eliminated water respectively. The total amount of water evolved from cellulose paper heated linearly from 25 degreesC to 400 degreesC was measured to be 14.3% (w/w) while Kraft paper gave 6.1% (w/w). For both samples, approximately 10% of the total water evolved is physically desorbed at temperatures close to 110 degreesC while the remaining 90% of the water is evolved in the higher temperature step (i.e. at approximately at 300 degreesC). (C) 2001 Elsevier Science Ltd. All rights reserved.