Synthesis process of hexamethylenediamine piperidine

Abstract

The invention relates to a synthesis process of hexamethylenediamine piperidine. The process comprises the steps of: carrying out heating dehydration reaction on 2, 2, 6, 6-tetramethyl-4-piperidone and 1, 6-hexamethylenediamine in a negative pressure environment until no water is removed from the system, and adding a water removing agent to separate the residual water from the liquid system so asto obtain an intermediate Schiff base; introducing hydrogen into the obtained Schiff base in the presence of a catalyst for hydrogenation reaction to obtain hydrogenation liquid; and filtering out thecatalyst from the hydrogenation liquid, rectifying the filtrate, and carrying out crystallization-desolvation to obtain the hexamethylenediamine piperidine finished product. According to the method,a small amount of residual water is removed by using the water removal agent, so that the Schiff base is prevented from being decomposed in the presence of trace water, the purity of the Schiff base is improved, the yield of hexamethylenediamine piperidine is increased, and few solid wastes are generated; according to the method, negative pressure reaction and crystallization treatment are innovatively adopted, so that the quality of hexamethylenediamine piperidine is high, the solvent can be continuously recycled and reused, and no organic waste liquid is generated.

Description

technical field [0001] The invention relates to a preparation process of a compound, in particular to a synthesis process of hexamethylenediamine piperidine, an intermediate of a hindered amine light stabilizer. Background technique [0002] N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine (CAS No.: 61260-55-7) is a light stable Hindered amine light stabilizers can improve the performance of plastics in strong light environments, and are mainly used in the automotive and construction industries, as well as agricultural films. In recent years, the market demand for this product has continued to grow. In the present invention, piperidine hexamethylenediamine refers to N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine. [0003] Sumitomo Chemical Industry Co., Ltd. discloses in JPS619486A that 2,2,6,6-tetramethyl-4-piperidone (triacetone amine) and hexamethylenediamine react in H under a hydrogenation catalyst (such as Pt). 2 A method for preparing ...

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Problems solved by technology

Obviously, the above-mentioned method has extremely high requirements on the pressure in the hydrogenation step, which makes the requirements for the safety of the reaction equipment also need to be improved, which directly leads to an increase in production cost and difficulty

[0006] In US5945536A, HUELSATIENGESELLSCHAFT tried to use a supported catalyst (such as palladium supported on alumina) to replace the commonly used catalyst before, and adopted a continuous method to produce and achieved a relatively satisfactory yield, but its requirement for hydrogen pressure was as high as 285bar. This is a great hidden danger to production safety.

[0007] Chen Ligong of Tianjin University and others published their research results in the Journal of Tianjin University in 1999, pointing out that the framework nickel is easy to cause the production of by-product piperidinol because of its lack of selective catalytic performance, while Pd / C can select It catalyzes the hydrogenation of C=N double bonds, but because it is easy to poison, it has higher requirements on the purity of reactants

In 2001, CN1346825A disclosed a three-step method for preparing hexamethylenediamine piperidine, but because its pressure range is 30 times to 120 times atmospheric pressure, and the reaction operation is relatively complicated and the reaction time is long, it is not suitable for industrial production

The reason is that the intermediate Schiff base is easily hydrolyzed into intermediate by-products, and the presence of a small amount of water can affect the quality of the Schiff base, resulting in the generation of by-products

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