Kinetic study of the autoxidation of cellulose suspended in sodium hydroxide solution

An apparatus has been designed to measure small extents of gas absorption by a relatively large volume of liquid under conditions of vigorous agitation. With this apparatus a study has been made of the absorption of oxygen by finely divided cotton cellulose suspended in sodium hydroxide solution at 40°C. over a range of alkali concentration, cellulose content, and oxygen pressure. In one series of experiments cellulose depolymerization was also determined and in another experiment the alkaline autoxidation of β‐methyl cellobioside was followed. During the early stages the reaction is autocatalytic with alkali concentrations above 8N. In the absence of diffusion effects, that is with alkali concentrations below approximately 10N, the steady rate of oxygen absorption is given by the equation, where [Cell] refers to the weight of cellulose immersed in the solution, [O2] the partial pressure of oxygen, aNaOH the molal activity of the sodium hydroxide, θ[M] a function of the metal ion content and K and K′ are constants. The known characteristics of the autoxidation are consistent with a modified Gee‐Bolland mechanism. Thus a cellulose radical formed as a result of peroxide decomposition reacts with oxygen to form a radical of the type {article}{empty}{document}RO₂.{document} . The last named is likely to be unstable and split off the {article}{empty}{document}O₂.{document} radical ion which is comparatively unreactive but must nevertheless be capable of attacking an ionized cellulose molecule, thus completing one oxidation cycle. In principle a chain reaction could follow but the evidence indicates that a long chain mechanism is not involved, particularly at the stage of attainment of the steady rate.