Influence of inorganic additives on oxygen chemisorption on cellulosic chars

✍ Scribed by William F. DeGroot; Fred Shafizadeh

• Publisher: Elsevier Science
• Year: 1983
• Tongue: English
• Weight: 865 KB
• Volume: 21
• Category: Article
• ISSN: 0008-6223
• DOI: 10.1016/0008-6223(83)90157-4

✦ Synopsis

Chemisorption of oxygen on cellulosic chars is the initial step leading to gasification and is a significant factor in controlling chemical reactivity and heat release in smoldering and glowing combustion of cellulose. Oxygen chemisorption kinetics have been determined for chars (HTT SSO'C) prepared from cellulose and cellulose treated with inorganic additives. Elovich kinetic analysis indicates that combustion behavior can be correlated with chemisorption kinetics. Addition of the same inorganic additives by grinding with pure cellulose chars had little or no effect on chemisorption kinetics. These data indicate that the mode of action on inorganic additives in enhancing or inhibiting the solid phase combustion of cellulose chars involves their influence on char functionality developed during pyrolysis. Chemisorption of oxygen on chars results in a decrease in free radical concentration, and heat treatment at WC in flowing nitrogen restores the original concentration. However, free radical concentrations do not differ significantly between additive treatments over most of the temperature range studied. Therefore, combustion behavior cannot be exolained strictlv in terms of changes in free radical concentration and other functional groups must also play a sjgnificant role: