Method for preparing p-aminoanisole by catalytic hydrogenation of an industrial scale device

Abstract

The invention relates to a method for preparing p-aminoanisole by catalytic hydrogenation of an industrial-scale device, which is to add raw materials to p-aminoanisole continuously or intermittently during each production cycle in an industrial-scale hydrogenation kettle. Nitroanisole, and real-time monitoring of the concentration of raw materials and impurities in the hydrogenation tank during the reaction to obtain p-aminoanisole with a purity of more than 99.5% and a yield of 100%. The p-aminoanisole product obtained by the present invention has a purity of more than 99.5%, and can be used and sold directly; it can also be further rectified to obtain a p-aminoanisole product with a purity of more than 99.9%, which can be used in special fields.

Description

technical field [0001] The invention relates to a preparation method of p-aminoanisole, in particular to a method for preparing p-aminoanisole with high selectivity (high purity) and high yield by catalytic hydrogenation with an industrial scale device. Background technique [0002] p-aminoanisole, also known as p-methoxyaniline, is an important intermediate for dyes, medicines and fragrances. Compared with anthranil, p-aminoanisole is more widely used in the dye industry widely. For example, in the dye industry, p-aminoanisole is used to synthesize blue salt VB, bay red base GP, naphthol AS-SG, AS-RL, reddish red, etc. In addition, 2-amino-4-acetamidoanisole can be synthesized by using p-aminoanisole, which is an important raw material for disperse dyes and can be used to further synthesize a series of disperse dyes, such as C.I. Disperse Blue 79, 139, 226 , 265, 301, disperse purple 58, disperse navy blue S-2GL, etc. In the pharmaceutical industry, p-aminoanisole is mai...

AI Technical Summary

Problems solved by technology

However, when it is scaled up to industrial production, only a crude product with a purity of 96% can be obtained, and after purification by vacuum distillation, the yield drops to 95%.

That is to say, this method that can be implemented in the laboratory can't obtain high selectivity (high purity), the p-aminoanisole of high yield on industrial scale at all, and, the utilization rate of raw material is lower, still can't really Realize clean and friendly production

[0016] In summary, prior art preparations still have the following problems in industrial scale production: (1) product yield is low

However, as far as the current situation is concerned, the preparation of p-aminoanisole by catalytic hydrogenation can only achieve a yield of 98% or 99%, and there is still room for further improvement.

(2) Applications where product purity cannot meet higher requirements

The purity of the product has always been the factor restricting the scope of application of the product, and the current process is difficult to meet the requirements at the end of the reaction, usually through complex processes and equipment such as vacuum distillation, rectification or recrystallization post-treatment. It will inevitably complicate the process and equipment, expand the investment, increase a large amount of operating costs in terms of energy consumption, manpower and material resources, etc., and ultimately increase the production cost significantly; at the same time, a considerable amount of waste residue will be generated, resulting in waste of resources and secondary pollution.

(3) Difficult to industrial scale production

The main reasons for this result may be: (1) the difference between the industrial scale and the laboratory scale in the equipment, which makes the industrial equipment unable to realize or meet the technical requirements of the micro-reactor (laboratory scale); (2) the industrial scale The purity of raw materials is often different from that of laboratory scale. Due to cost reasons, industrial products are used in industrialization, rather than chemically pure or even analytically pure raw materials on a laboratory scale, which will inevitably affect the yield of the reaction and the purity of the product; (3) Due to the complexity of the chemical reaction, the laboratory research work cannot really fully grasp and predict the influencing factors of the reaction process on an industrial scale

Due to the above reasons, the production process on an industrial scale tends to produce more by-products. Therefore, if the above-mentioned existing processes are adopted, the only way to obtain high-yield and high-purity p-aminoanisole is to increase in the post-treatment step. Equipment for further rectification or recrystallization, etc.

[0018] This may also be the reason why the relevant industrial examples of preparing p-aminoanisole by catalytic hydrogenation are not disclosed in the existing reports at home and abroad.