Application Research On A Catalyst Of Preparation 4-chloro-2, 5-dimethoxy Aniline

This article established the preparation methods, application conditions and the industrialized process parameters of a catalyst system, which is applicable for reduction of nitrobenzene derivatives, especially for 4-nitro-2,5-dimethoxy chlorobenzene, to prepare4-chloro-2,5-dimethoxyaniline with N₂H₄?H₂O as reductant. First, Fe??? defected catalyst with?-FeOOH as main composition was prepared. Then, suitable cocatalyst promoter which can improve the stabilization of reduction reaction, was optimized. This catalyst system is used for N₂H₄?H₂O reduction process of substituted nitrobenzene, and discusses the reduction of process parameters. Through a series of experiments and testing analysis, the results are obtained as followsAs the Fe??? plays a catalytic role on process of Fe?OH?₃ phase transformation; and FeOOH would be a intermediate on the process of Fe?OH? 3 phase transformation, which is influenced by the PH value of the reaction medium, when p H < 9, it shows ?-FeOOH; When the pH > 9.5, it shows ?-FeOOH. Therefore, this article introduces the prepare method of catalyst system A,though further drying dehydration Fe?OH? 3 cement which is prepared by acid and alkali neutralization titration under the condition of Fe???existence, which is used in the catalytic reduction of 4-nitro-2,5-dimethoxy chlorobenzene for 4-chloro-2,5-dimethoxyaniline preparation.And a suitable cocatalyst B is filtrated through a large number of experiments for the reduction reaction medium stabilization.According to a lot of experiments, catalyst A32 has showed a higher catalytic efficiency in preparation of 4-chloro-2,5-dimethoxyaniline, which can reduce defect rate of the target product to about 0.3%. The main parameters in the preparation of catalyst A32 presented as follows?a? the molar ratio of FeCl3.6H₂ O and FeSO4.7H₂ O is 73;?b? the amount of activated carbon carrier is10% of the total mass of FeCl3.6H₂ O and FeSO4.7H₂O;?c? drying temperature is 85-95 ?.In addition, a series of experiments using catalyst A32 mixed with cocatalyst B type indicate that the mixed catalyst of A32 and B type cocatalyst in quality ratio 31 would make the reduction reaction processing more steadily and quickly. Meanwhile, the final4-chloro-2,5-dimethoxyaniline products would be purer, and the yield can reach higher than 95%with the defective rate less than 0.1%.With the optimal catalyst system, a 4-chloro-2,5-dimethoxyaniline production enterprises inLuoyang has carried out the production test, which can reach a safe, clean, stable, continuous and efficient effect. Compared with the present domestic 4-chloro-2,5-dimethoxyaniline process using iron powder as reductant, the process has less "three wastes" emissions, high yield and high quality. What`s more important, catalyst A32 can be reused for 2-3 times, and the deactivated catalyst A32 can be recycled after recovery treatment.