1966 Volume 39 Issue 10 Pages 2211-2215
The rate of the cobalt-catalyzed autoxidation of p-xylene by adding sodium bromide reaches the steady state within several minutes and increases remarkably at high cobalt concentrations. Although p-tolualdehyde as well as water, the main oxidation products of p-xylene at the initial stage, strongly affect the rate of oxidation, the apparent rate is kept constant over a long period. When cobalt dibromide is used, a pronounced induction period can be observed at high cobalt concentrations, and the rate of oxidation starts to decrease after a short while. The effect of the ratio of sodium bromide to cobalt has shown that cobalt monobromide is an effective catalyst for the propagation step. The rate of the oxidation of p-xylene is found to be of the order of from 1.5 to 2.0 with respect to cobalt at concentrations from 10−3 to 5×10−2mol./l. and at temperatures from 65 to 95°C, and to be first-order with respect to the p-xylene concentration; these findings show excellent agreement with the theory. When cobalt is partly replaced by manganese, a strong synergistic effect can be observed.
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