Factors influencing chemisorption and ignition of wood chars

Abstract

Solid discs of cottonwood have been pyrolyzed under nitrogen to an appropriate temperature and then cooled under nitrogen to chemisorption temperature for study of oxygen chemisorption activity. The following variables were studied, with the effects indicated. Presorption of nitrogen slowed the initial rate of oxygen chemisorption but had no effect on long-term (4 hours) chemisorption. Variation of pyrolysis temperature led to a pronounced maximum chemisorption for 450–500°C chars. The causes of this effect are assumed to be chemical in origin and are being studied further. Removal of indigenous metal ions from the wood and replacement with individual metal ions resulted in small but significant changes in chemisorption in the chars. Ignition of the char samples prepared by prepared by pyrolysis in nitrogen has been studied without removal of the char from the thermal balance. Ignition was dramatically influenced by the nature of the cations present. The complete removal of cations was most effective in raising ignition temperature or preventing ignition. The physical form of the wood samples (i.e., fine and coarse powders and solid discs) also had considerable influence on ignition, either in oxygen or in air.