アクロレインの液相酸化における速度論的研究
1972 年 21 巻 4 号 p. 189-196
詳細
1972 年 21 巻 4 号 p. 189-196
Liquid-phase oxidation of acrolein was carried out in benzene or acetic acid under cobaltous ion catalyst, using two reaction apparatus of heterogeneous gas-liquid system (I) and homogeneous liquid system (II). The reaction mechanism was discussed mainly from the kinetic results.
In case I of fairly high reaction rate, in spite of well agitation of the liquid-phase, the oxygen in the gas-phase did not equilibrate with the oxygen in the liquid-phase, which concentration decreased with increase of the reaction rate. The reaction rate depended on first order of oxygen concentration and this means that the rate constant thus obtained contains contribution to diffusion of oxygen in the liquid-phase. On the other hand, in case of fairly low reaction rate in I or in case of II, the reaction rate depended on 0, 0-1 or 1 order of oxygen concentration which corresponds to high, medium or low concentration of oxygen, respectively. The rate constant does not contain the diffusion of oxygen. The difference of oxygen dependencies can be explained by the change of rate-determining step of which (1) is in high oxygen concentration and (2) is in low oxygen concentration, as follows :
CH2=CHCO3·+CH2=CHCHO → CH2=CHCO·+CH2=CHCO3H (1)
CH2=CHCO·+O2 → CH2=CHCO3· (2)
In the present study, the reaction began by the addition of the catalyst after 30 minutes' saturation of oxygen into the solution of acrolein. The initiation reaction is assumed to be derived from the decomposition of peracid and peroxide by the cobalt ion. In benzene, one cobalt ion reacts with one peracid and one acrolein. On the other hand, in acetic acid, two cobalt ions react with one peracid.
The experimental orders of the reaction factors which will influence the oxygen consumption rate are as follows :
