Method for preparing p-anisidine through catalytic hydrogenation by industrial-scale device

Abstract

The invention relates a method for preparing p-anisidine through catalytic hydrogenation by an industrial-scale device. The method comprises the following steps: adding a raw material namely p-nitroanisole in an industrial-scale hydrogenation kettle in each production cycle in a continuous mode or an intermittent mode, and monitoring the concentrations of the raw material and impurities in the hydrogenation kettle in a reaction process in real time so as to obtain p-anisidine with the purity of 99.5% or above and yield of 100%. The purity of the p-anisidine product obtained through the method reaches 99.5% or above, so that p-anisidine can be directly used and sold; p-anisidine can further be subjected to rectification treatment to obtain a high-quality p-anisidine product with the purity of 99.9% or above which can be used in special fields.

Description

technical field [0001] The invention relates to a method for preparing p-aminoanisole, in particular to a method for preparing p-aminoanisole with high selectivity (high purity) and high yield by carrying out 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 o-anisole, 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, claret-based GP, chromophore AS-SG, AS-RL, reduced scarlet, etc. In addition, p-aminoanisole can be used to synthesize 2-amino-4-acetamidoanisole, 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 violet 58, disperse navy blue S-2GL, etc. In the pharmaceutical industry, p-a...

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.