Study On Photo-chlorination Of O-/P-chlorotoluene Mixture And M-chlorotoluene

Chlorobenzaldehydes can take place oxidation, reduction, carbonyl group addition, condensation and substitution etc. These are all important fine chemical materials and are used to systhesize medication, pesticide and dye. This article summarized the present conditions of preparation and research of chlorobenzaldehydes. It pointed out that p(o)- chlorobenzaldehyde was made from catalyzing chlorination of p(o)-chlorotoluene, respectively, but the p-chlorotoluene and o-chlorotoluene were made from catalytic chlorination of toluene simultaneously, because of the boiling point of o-chloromethyl benzene being close to the one of p-chloromethyl benzene, a great deal of energy was consumed by traditional distillation separation. If mixed chlorotoluenes were photo-chlorinated without separation ,then mixed chlorobenzaldehydes were separated by crystallization because of their melting point being greater, a great amount of energy would be saved. So it was of importance to study mixed chlorotoluenes photo-chlorination no distillation separation. M-chlorobenzaldehyde was made from m-nitro-toluene by catalytic hydrogen and Sandmcyer reaction, but the process is of higher cost than the chlorination hydrolysis process. Hence it was of significance to study m-chlorotoluene photo-chlorination to preparation of m-chlorobenzaldehyde. The kinetic study of m-chlorotoluene photo-chlorination has not been reported.Mixed chlorotoluenes photo-chlorination experiments in a loop reactor were made, the effects of chlorine flow, temperature and p-/o- chlorotoluene initial ratio on mixed chlorotoluenes photo-chlorination were researched. The relations between the concentration of each component and time under different conditions were measured. The rule and the suitable process parameters of the photochlorination of p(o)-chloromethyl benzene in the side chain were obtained. Similarly, the rule and the suitable process parameters of the photochlorination of m-chloromethyl benzene in the side chain were obtained.Through analyzing the mechanism of the photochlorination of m-chloromethyl benzene in the side chain, the kinetic models of the consecutive reaction were built. Through a series of identification of the models, the concept of "competition coefficient" was introduced. The quantification expression of "competition coefficient" was obtained. The experimental values and the calculated values were identical. Finally, the macro-kinetic equations were as follows:According to the experimental data at different temperature , apparent reaction rate constants were obtained. The apparent reaction activation energy of each reaction was obtained by the Arrhenius equation. In the temperature rang from 120 to 150℃, the relations between the apparent reaction rate constant and temperature of the photochlorination in the side chain of m-chloromethyl benzene were: min-1 min-1 min-1The apparent reaction activation energies are:Ea1=33.54,Ea2=32.45,Ea3=24.26kJ/mol。 ...