SU401660A1 - METHOD OF FORMALDEHYDE ALLOCATION - Google Patents

Description

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The invention relates to methods for the separation of formaldehyde from the reaction mixture.

There is a known method for isolating formaldehyde from an organic layer obtained in the production of 4,4-dimethyldioxane-1,3 by interconnecting formaldehyde with isobutyloyl by washing the organic layer with water. The disadvantages of this method are significant losses of the target product due to the partial solubility of 4,4-dimethyldioxane1, 3 in water, as well as the complexity of the process technology due to the need to clean large amounts of wastewater.

The aim of the invention is to reduce the amount of wastewater and simplify the process technology.

This goal is achieved by using the method of heteroazeotropic distillation in the presence of a separating agent, using the Ci-Ce hydrocarbons, such as isobutane-pzobutylene fraction, hexane or benzene, as a last resort, to isolate formaldehyde.

The proposed method is carried out in the following manner.

An organic layer containing 4,4-dimethyldio-ane, 3, pere-reacted formaldehyde, water and other impurities, mixed with the hydrocarbon composition, is fed into the distillation column} of continuous action. Epaulet

COLUMNS are found in a mixture of hydrocarbon, water, H formaldehyde, which is stratified into a hydrocarbon layer and a water LAYER containing formaldehyde. The hydrocarbon is then used again in the process, and 4,4-dimethyldnoxai-1,3-raw is taken from the COLUMN cube, containing less than 0.1% formaldehyde. Thus, the proposed method allows to achieve a high degree of formaldehyde recovery from the reaction mixture while significantly reducing the amount of wastewater.

An example. A plate of the distillation column COLONNY and a continuous operation serves under a pressure of 3-5 atm. The mixture of the following composition (in wt.%): 4,4-dimethyldioxan-1, 3, trimetnylviyl carbinol 7.3, high boiling point by-products 8.0, water 3, 0, formaldehyde 1.7, as well as isobutane-isobutylene fraction in an amount of 3 weight. h. on 1 weight. h. mixture. From the top of the column, at 50-55 ° C, a heteroazeotrope is taken, which stratifies the condensation pprn. The top layer is a practically pure isobutane and isobutylene fraction, and the bottom layer is an aqueous solution of formaldehyde, which can be used in the synthesis of isoprene. A crude target product containing 0.06% formaldehyde is taken from the COLUMN cube. Example 2. A mixture of the following composition (in weight%): 4,4-dimethyldioxane-1, 3 87, high-boiling noble products 10.0, water 2.0, formaldehyde 1.0, and hexane in the amount of 1 weight. hours 2 weight. h. mixture. From the top of the column, at 66-68 ° C, a heteroazeotron is taken, the upper layer of which is almost pure hexane, and the lower layer is an aqueous solution of formaldehyde. A product containing 0.02% formaldehyde is taken from the cube of the column. Example 3. The same mixture as in nrmsr 2, as well as benzene in the amount of 1 wt. h. on 1 weight. Part of the mixture. Nz cube columns select a product containing 0.09% formaldehyde. The subject of the invention. A method for separating formaldehyde from an organic layer, obtained in the production of 4,4-dimethyldioxane-1,3 by reacting formaldehyde with isobutylene, by heteroazeotronic rectification in the presence of a separating agent, characterized in that in order to reduce the amount of waste water and simplify The process technology uses Ci-Ce hydrocarbons as a separating agent, for example, isobutane-isobutylene fraction, hexane, benzene.