Mechanisms of char production from oxidized cellulose

Abstract

A multi-technique approach, incorporating nuclear magnetic resonance (NMR), elemental analysis, differential scanning calorimetry (DSC), thermogravimetric analysis and surface area determination, has been used to investigate the formation of chars by oxidized cellulose. It was found that oxidation of the cellulose tends to increase the surface area of the resulting char. NMR, elemental analysis and DSC show how cellulose oxidation tends to increase aromaticity and cross-linking. This, in turn, decreases diffusion rates of volatiles out of the oxidized cellulose during pyrolysis, giving denser carbons and higher BET surface areas

Effects of Porosity on Carbon Reactivity in NO and O2

“…Figure shows the variation of reactivity for O 2 and NO at 773 K as a function of surface area for the set of oxidized cellulose chars. As expected from the work of Norton et al, there is a good correlation ( R = 0.99) between the reactivity in O 2 and the BET surface areas of the chars. However, there is no correlation between reactivity in NO and the BET surface area ( R = 0.2).…”

“…The chars are labeled Ceo xy , where xy is the time of preoxidation in days. As previously noted by Norton et al the surface area of the chars increases with increasing time of cellulose preoxidation. The only exception is Ceo22, which has a lower surface area than Ceo18.…”

“…The present study used similar NO partial pressures to Illán-Goméz et al and is based on a series of carbons made from cellulose oxidized in air for different amounts of time. Norton et al have shown how this procedure can produce carbons with different surface areas. The cellulose-based carbons were chosen because the reactivity in O 2 varies linearly with surface area, which implies that all of the surface is accessed by O 2 .…”