CS258650B1 - A method of recovering methyl alcohol from waste liquors to produce 4-aminodiphenylamine from 4-nitrosodiphenylamine - Google Patents

Abstract

The solution concerns a method of regenerating methyl alcohol from wastewater in the production of 4-aminodiphenylamine from 4-nitrosodiphenylamine in three stages, whereby in the first stage, methyl alcohol with a content of at least 10% by weight of water is obtained from the wastewater by rectification, in the second stage, the distillate from the first stage is treated with an acidic cation exchanger operating in the H+ cycle and methyl alcohol from the second stage is dewatered in the third stage by rectification with an efficiency of at least 10 theoretical stages, whereby the bottom product from the third stage is returned to the feed to the first regeneration stage.

Description

25 86 5 0

The present invention relates to a process for recovering methanol from wastewater in the production of 4-aminodiphenylamine from 4-nitrosodiphenylamine. 4-aminodiphenylamine is an intermediate in the manufacture of N-phenyl-N‘-isopropyl-β-phenylenediamine used as antidegradant rubber. For example, 4-aminodiphenylamine is prepared industrially by catalytic reduction of a solution of 4-nitrosodiphenylamine sodium salt using a metal catalyst (CS184,062 j. The reaction mixture is separated into an aqueous and organic layer after filtering off the catalyst, after which the solvent is distilled off). the crude 4-amino-diphenylamine The aqueous phase of the hydrogenate contains up to 16% by weight of inorganic material (NaOH, NaGl), organic impurities up to 1% by weight, and further 14 to 20% by weight of methyl alcohol and a small amount (by weight). The ammonia produced by hydrogenolysis by hydrogenolysis of 4-aminodiphenylamine or other decomposition reactions, methyl alcohol is recovered from the aqueous solution by regeneration and, with respect to the favorable proportions in the binary system, methyl alcohol is usually a single stage.

However, this is a simple disadvantage at first sight in this particular case. Due to the further use of regenerated methyl alcohol in the production of 4-nitrosodiphenylamine sodium salt (CS18360, 184 930), strict water requirements are required (max. as well as the content of methyl alcohol in the boiling residue which is treated as wastewater by purification and its presence above 0.5% by weight. significant impact on water pollution.

Although these requirements can be implemented in one step, it has been found in practice that some deviations of the rectification node parameters (e.g., change in concentration and / or temperature of the sprayer, etc.) result in the non-compliance with the required qualitative parameters of the recovered methyl alcohol. it then requires further processing or the permissible content of methyl alcohol in the reboiler residue is exceeded, resulting in increased wastewater pollution in addition to the loss of methyl alcohol. A further disadvantage of the one-stage regeneration of methanol is that it does not allow effective separation of ammonia therefrom. The A-moniacal, which is contained in the aqueous phase of the hydrogenate, is converted into methyl alcohol at rectification. From the recovered methanol, a hydrogen chloride solution is prepared which is used to rearrange the N-nitrosodiphenylamine to 4-nitroso-diphenylamine. The rearrangement reaction containing 4-nitrosodiphenylamine hydrochloride is made alkaline with sodium hydroxide solution and the resulting aqueous-methanolic solution of 4-nitrosodiphenylamine sodium salt is converted to 4-aminodiphenylamine. It will be appreciated that ammonia is not removed from this cycle and its concentration in the regenerated methanol is still increasing, and although a relatively small amount of α-monohydrate is generated in the hydrogenation, its concentration in the methanol mixture reaches 0.1 to 0.2. % wt. The preparation of the hydrogen chloride solution in methyl alcohol forms insoluble ammonium chloride, which absorbs the absorbers, piping the route and dispensing the solution. Thus, it is necessary to maintain the ammonia concentration in the methanol to the permissible limit, which is to be rectified. However, this is a complicated and expensive process in which the loss of methyl alcohol occurs.

These drawbacks are overcome by the method of re-generation of methyl alcohol from the effluent from the production of 4-aminodiphenylamine from 4-nitro-zodiphenylamine according to the invention. The essence of the present invention is that in the first regeneration stage formed by rectification of the bulk or exclusive depletion function, the aqueous phase of the hydrogenate methyl alcohol is almost completely removed. The A-moniacal present in the aqueous phase of the hydrogenate also passes into the overhead product, which is methyl alcohol containing 10 to 25% by weight. water and containing from 0.05 to 0.3. wt. ammonia. In the second stage, the sana head product of the first stage is treated with an acidic cation exchanger in the H + cycle, thereby removing ammonia from the high-activity dilute methanol by bonding to the cation exchanger. For a full activity catex, it is important that the water content of the first stage dilute methanol does not fall below the limit, since in the anhydrous environment the capacity of the kaolin is significantly reduced and released in the cation-bound water. It is not possible to obtain anhydrous methyl alcohol by a one-step rectification, since the disadvantage of the reduced capacity of the kaolin is further impaired by the degradation of anhydrous methanol by the water released from the cation exchanger, since the regenerated swollen cation exchanger contains about 50 wt. water.

Ammonia-depleted dilute methanol from stage 2 is injected into stage 3, which consists of rectification with predominantly enrichment activity and a top product with a maximum water content of 0.2% by weight. % of the recovery step, comprising 25 to 40 wt. methanol, is recycled and added to the feed to the 1 st regeneration stage.

Such a method of regeneration, in comparison with the one-stage process, ensures very easy and stable regulation of the high purity of the linen - the regenerated methanol and the waste leaders. This is achieved by the fact that in each rectification stage a high purity of only one linen is required (the heel product in the first stage and the head product in the third regeneration stage), while the concentration of the second linen (the top product in 1st degree

Claims (1)

The 5 th product in the third regeneration stage can move in a relatively wide range without adversely affecting the recovered methanol and effluents. Despite the over-regulation disturbances in the rectification re-generation stages, there is no detriment to the leakage flow currents and the necessity of further processing (regenerated methyl alcohol) or to an increased leakage of methanol to the wastewater with a negative impact on the economy and ecology. Upon depletion of the cation exchanger capacity in the second regeneration stage (which can be identified, for example, by pH), the cation exchanger is regenerated by treating the diluted mineral acid, which can be used after the regeneration to neutralize the alkaline base product from the 1st regeneration stage. This method of separating ammonia from the dilute methyl alcohol works with high efficiency and virtually no methanol loss, since all the methanol-containing water (e.g., from the cation exchanger prior to re-generation) can be recycled to the first generation stage. The following examples illustrate, but do not limit the invention. EXAMPLE 1 (Comparative) " The aqueous phase of the hydrogenate from the production of 4-aminodiphenylamine containing 17.4% by weight of methanol was injected (6.1 m < 3 > h < -1 >) into a continuous column with 45 shi. Pre-heated spraying (t = 95 ° C) was sprayed onto the 13th floor from the bottom of the wheel. The water content of the distillate ranged from 0.30 to 0.55% by weight, the content of methanol in the boiling residue varied from 0.4 to 1.5% by weight. depending on the steady state of the column. The long-term average of the content of ethyl alcohol in the boiling residue was 0.92% by weight. The distillate further contained 0.2 to 0.3 wt. ammonia, which was removed by recrystallization on a batch column in a high reflux ratio operating mode. Removal of ammonia from methanol, incomplete, residual ammonia content in the regenerated methanol was 0.05 to 0.1% by weight. Methanol losses (distillates) were 5% of the set amount. EXAMPLE 2 An aqueous phase of the hydrogenate from the production of 4-aminodiphenylamine containing 17.6% by weight of methanol was injected (1.0 m < 3 > h-1) into a continuous packed column with a height of 10 m. at a height of 7.0 m from the bottom of the column. The bottoms product of the column (wastewater) contained 0.1 to 0.3 wt. methyl alcohol, with a long-term average of 0.25% by weight. The distillate contained 75 to 80% by weight of methanol and 0.1 to 0.2% by weight. ammonium and was collected in a reservoir. This distillate was injected into a column filled with cation exchanger in H + cycle with a linear velocity of about 10 m. h-1. Methanol output was less than 0.01% by weight. ammonium nitrate and was captured into the template. The average cation exchange capacity determined from its multiple cycles was 1.2 mol NH3. I ”1 cation exchanger. Methyl alcohol with a water content of 20 to 25 wt. ammonia-free was injected (350 1 h "1) into a packed column of 10 m height. Pre-heated feed was introduced 3 m from the bottom of the column. The distillate (regenerated methyl alcohol) contained 0.1-0.2 wt. water, the boiling residue contained 20 to 30 wt. methyl alcohol and fed into the reservoir before the 1st regeneration step. OBJECTIVE The process of recovering methanol from wastewater in the production of 4-aminodiphenylamine from 4-nitrosodiphenylamine, characterized in that the regeneration takes place in three stages, wherein at the first stage the wastewater rate is rectified to yield methanol with a minimum content of 10% w / w. In the second step, the distillate of the present invention is treated with an acidic cation exchanger working in the H + cycle and the second stage methanol is dewatered by recrystallization with a efficiency of at least 10 theoretical plates, with the heel product lost. the step is returned to the feed into the first regeneration stage.