SU454208A1 - The method of obtaining caprolactam - Google Patents

Description

one

A method of producing caprolactam from cyclohexanone is known by oximating with an aqueous solution of hydroxylamine salts. The process is carried out at 85 ° C and pH 7, the desired acidity of the medium being created by the introduction of gaseous ammonia or its aqueous solution. The process is carried out in a circulation circuit including a pump and a heat exchanger, with a Reynolds number of the circulating tray of about 7000 °. The residence time of the reaction mass in the circulation loop is about 10 minutes. The product obtained is separated in a settling tank onto a layer of oxime and sulphate oxime oxides. Oxime containing more than 5% water is sent to the over-grouping stage. Ecstrum was extracted from sulphate liquors with cyclohexanone; OXIM was dissolved in them, then cyclohexanone was distilled off, and the remaining aqueous solution was sent to extract ammonium sulfate from it.

With this method, a high degree of conversion of cyclohexanone to OXIM is achieved (the content of cyclohexanone in oxime is about 0.3% by weight), however, the method has the following features. The content in water oxime requires an increased consumption of oleum at the cyclohexanone oxime rearrangement stage in catsrolactam. This becomes especially sensitive when using a solution of hydroxylamine sulfate, obtained by catalytic reduction of nitric oxide with hydrogen in a medium of sulfuric acid. In addition, when used as a neutralizing agent on

The stages of oximation of an aqueous solution of ammonia are obtained by diluting sulphate liquors and watering oxime, which also requires an increased consumption of oleum at the stage of the rearrangement of oxime into lactams.

In order to reduce consumption of oleum, a process for preparing caprolactam by oximation of cyclohexanone with aqueous hydroxylamine in the presence of Knight | ralizuyuschego agent and rearrangement resulting cyclohexanone oxime into caprolactam in the presence of oleum followed by isolation of the desired product by known methods, characterized in that the cyclohexanone oxime to rearrangement is treated with an aqueous sulfate solution ammonium with a concentration of 38-45 weight. % At the same time, part of the ammonium sulfate aqueous solution obtained after treatment with cyclohexanone oxime (after extracting cyclohexanone oxime from it and distilling traces of cyclohexanone) is sent to an evaporator, through the heat exchange chamber of which the reaction solution of the rearrangement stage circulates, and the evaporated ammonium sulfate solution

return cyclohexanone oxime for processing. Another part of the aqueous solution of ammonium sulfate obtained by treating cyclohexanone oxpma is fed to the preparation of a neutralizing solution for oxyming by dissolving ammonia gas in it.

The consumption of oleum according to P1 proposed method is 1.5-1.6 tons per 1 ton of caprolactam, and in the absence of a drying stage in the technological scheme of 2.65-2.85 tons per 1 ton of caprolactam.

Cyclohexaion, an aqueous solution of hydroxylamine sulfate and a neutralizing agent in the following amounts are introduced into the circulation loop containing the pump and the heat exchanger: cyclohexanoH 5800 wt. hours, hydroxylamine sulfate (per 100%) 4950 weight. hours, the neutralizing agent (based on 100% ammonia) 1080 weight. hours, the process temperature is 85 ° C, pH 4.5.

At the end of oxylation in the circulation circuit, delamination is carried out in the sump, on oxime and an aqueous solution of ammonium sulfate. The oxime layer from the settling tank is sent to extract water from it into a desiccant, where it is treated with a concentrated solution of ammonium sulfate. The concentration of ammonium sulfate at the inlet to the desiccant is 40%, at the outlet of it is about 39%.

The dried oxime from the drying agent is fed into the rearrangement reactor with the circulation of the reaction solution through the heat exchange chamber with a pump.

From the oxychloride sulphate liquor from the settling tank, as well as from the sulphate solution from the drying agent, the oxime containing cyclohexanone rectified in the extractor is extracted from the desiccant in an extractor, then the anne is distilled off in the column, after which part of the stream is fed to the evaporator, to part - IB neutralizing agent for oxyemia.

The evaporated solution from the evaporator is partially directed to the drying of the oxime, and partly removed to the plant for the preparation of crystalline ammonium sulfate.

Subject invention

The method of producing caprolactam by oximating cyclohexanone with an aqueous solution of hydroxylamine sulfate in the presence of a neutralizing agent and rearranging the obtained cyclohexanone oxime into canrolactam in the presence of oleum, followed by isolating the target product using known techniques, wherein in order to reduce the consumption of oleum cyclohexanone oxime, it is determined by the procedure ammonium sulfate with a concentration of 38-45 weight. %