MODELING OF THE KINETICS OF ALKALI FUSION

Alkali fusion is applied to substitute a sulfonic acid group with a hy droxyl group in a substituted aromatic ring. Beside the main reaction, also side reactions appear, because the substituents in the aromatic ring are eliminated and the aromatic rings are polymerized. A kinetic model for the main and the side reactions in alkali fusion of a substi tuted aminobenzenesulfonic acid was developed. The substitution reacti on of sulfonic acid with a hydroxyl group, the elimination of sulfonic acid and amino groups, the dealkylation reactions, and the polymeriza tion reactions were included in the kinetic model. The system consiste d of the main reaction and of 27 side reactions. The number of adjusta ble constants in the kinetic model was reduced by assuming that the re activity of any functional group in the aromatic ring is not affected by the other substituents. The reactions could then be described with eight kinetic parameters only. The kinetic data were obtained from iso thermal experiments carried out in a batchwise operating laboratory re actor at-the temperature range of 220-270 degrees C. The kinetic param eters were estimated from the experimental data using nonlinear regres sion analysis. The model agreed well with the experimental data, which implies that the proposed reaction scheme is suitable for the descrip tion of alkali fusion and that the assumption concerning the reactivit ies of the functional groups is reasonable.