RU2715698C1 - Method of producing acetic acid and methyl ethyl ketone - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to a method of producing acetic acid and methyl ethyl ketone during reaction-rectification separation of mixtures of a complex composition obtained by liquid-phase oxidation of the n-butane fraction and containing acids C1-C4, alcohols C1-C4, esters C2-C6, carbonyl compounds C1-C4 and water. Disclosed is a method, characterized in that for removing formic acid, methanol, or a mixture of methanol with methyl acetate, is added to the rectification apparatus as a reagent, the formed methyl formate is removed as a component of the fraction with a boiling point of 31–53 °C, rectification is followed with separation of fractions containing methyl formate, methyl acetate and acetone, ethyl acetate with methyl ethyl ketone, methyl ethyl ketone with water, sec-butylacetate with n-butylacetate, water with acetic acid, acetic acid as main components, water-containing fractions can be dried by repeated azeotropic rectification with addition of any suitable separating additive – entrainer.

EFFECT: disclosed is a novel efficient method which enables to simplify production of acetic acid practically free of impurity of formic acid.

5 cl, 6 ex, 3 tbl

Description

The invention relates to methods for the separation of complex mixtures of products obtained by liquid-phase oxidation of the n-butane fraction, as well as other alkanes, with the separation of acetic acid (UK) and methyl ethyl ketone (MEK) as main products, as well as related products in the form of mixtures with the following the main components: "acetone - methyl acetate", "ethyl acetate - MEK" and " sec -butyl acetate - n-butyl acetate".

The separation of mixtures of products obtained by oxidation of the fraction of n-butane, as well as other alkanes, with the allocation as the main product of the criminal code, is a difficult task. One of the most difficult stages is the separation of the three reaction products MK, UK, H ₂ O. These compounds form not only the triple azeotrope "N ₂ O - UK - MK" (T boiling point = 107.1 ° C, 39% N ₂ O, 48 % MK and 13% MK), but also the double H ₂ O - UK azeotropes (76.6 ° C, 97% H ₂ O, 3% UK) and H ₂ O-MK (107.1 ° C, 22.5% H ₂ Oh, 77.5% MK). According to some literature data, CC does not produce azeotropes with water [Lange's Handbook of Chemistry, Ed. John A. Dean, 15th ed. McGraw-Hill, Inc. 1999; S.K. Ogorodnikov, T.M. Lesteva, V.B. Kogan, Azeotropic mixtures (reference, ed. By VB Kogan), Chemistry, L. 1971], according to other sources [Chemical Engineering Azeotrope Databank [Electronic resource]. URL: http://www.homepages.ed.ac.uk/jwp/Chemeng/azeotrope/ (accessed 11/14/2019)], including our experiments with distillation distillation of water from the UK, we cannot get rid of the presence of 1-2% acid in H ₂ O.

One of the effective industrial methods for separating water from organic compounds is azeotropic distillation. However, the selection of an effective separating agent (entrepreneur) in this case is not an easy task, since it must have a number of qualities: it is advisable not to give an azeotrope with either MK or CC, give a heterogeneous azeotrope with water with a boiling point of no higher than 90 ° C ( and better below 80 ° C), the water content in the azeotrope should be as high as possible, and the solubility of water in the entrepreneur as low as possible to avoid unnecessary energy losses.

The separation of water from individual carboxylic acids C2-C4 is not particularly difficult. A number of methods are described in the patent literature for separating water from individual carboxylic acids (for example, [DE 4426132, GB 312046, GB 331637, GB 348282, GB 356787, GB 371554, GB 383148, GB 455325, GB 467481, GB 467559, GB 506473, GB 513044, GB 623991, JP S 61176550, JP S 61176551, JP S 61176552, FR 622680, US 5492603, US 5409579, US 5662780,]. In addition, even in the case of a mixture of carboxylic acids C2-C4 with water (ie with the exception of MK) they are separated quite easily [GB 467481]. In the case where the concentration of carboxylic acids in the solutions is high, rectification methods are usually used, and in the case of low concentrations, extractive methods are preferred ktsii followed by distillation and extractive distillation (hydrocarbons, esters, ethers, alcohols, ketones, amines, organochlorine compounds, phosphine oxide, etc.).

There are a number of patents dedicated specifically to the separation of ternary mixtures MK - UK - H ₂ O. One of the main separation methods is azeotropic distillation. C5-C6 hydrocarbons, such as pentane, cyclopentane, hexane, cyclohexane, benzene, toluene, xylenes [GB 707153, GB 727078, DE 513024, JP 2542513, US 3258482] are used as entreners. Water, MK and hydrocarbon are removed from the top. the columns. This distillation is stratified, the upper layer containing predominantly hydrocarbon is returned for recycling, and the lower layer, mainly H ₂ O and MK, is sent for further processing. In the cube, there remains an AC with an admixture of hydrocarbon, which are subjected to repeated rectification. However, the use of aliphatic and aromatic hydrocarbons, traditionally used for azeotropic removal of water, has a significant drawback. Due to the fact that all hydrocarbons suitable for water removal form an azeotrope not only with H ₂ O, but also with MK, which is mainly concentrated in the water layer, this creates a problem of wastewater treatment.

In a number of patents, it is proposed to use chlorohydrocarbons, such as: chloroform, carbon tetrachloride, 1,2-dichloroethane, trichloroethane, 1-chlorobutane, [FR 1327752, DE 1204214, US 3024170, DE 513024] to be used in conjunction with MK from the criminal code for a number of patents to remove water . Typically, the process is carried out in the form of two consecutive azeotropic distillations. First, MK and water are distilled off together with chlorohydrocarbon, while CC remains in the cube. Then distillation of water and chlorohydrocarbon is carried out, while MK remains in the cube. A significant drawback of these methods is the use of organochlorine compounds that pose a high environmental hazard.

A number of methods are described for removing water from its mixtures with MK and AC by azeotropic distillation with the addition of ketones as methyl isopropyl ketone, methyl isobutyl ketone [GB 788931, GB 1112397, GB 1300886], aldehydes (furfural) [US 69557432], carbon carboxylic acids C3-C6, salicylic acid) [US 4692219, US 4909907]. Methylisopropyl ketone and methyl isobutyl ketone are quite expensive and have limited use. Aldehydes have low oxidation stability. The use of C3-C4 acids, due to the presence of triple azeotropes ("MK - H ₂ O - propanoic acid" 107.2 ° C and "MK - H ₂ O - butanoic acid" 107.6 ° C), will create the problem of subsequent cleaning of the separated aqueous layer from them.

A number of patents are presented for the separation of MK - UK - H ₂ O mixtures using esters (ethyl acetate, isopropyl formate, butyl formate, isopropyl acetate, butyl acetate, butyl benzoate) as GBs [GB788931, CN1342636, GB1112397, US4909907]. However, these methods have a number of significant drawbacks. So in the case of using C4-C5 esters, due to the high solubility of water in the ether and the low water content in the azeotrope, the process of water removal will be energetically disadvantageous. At the same time, due to the transesterification reaction, lighter boiling formates will form from the acetates, the azeotropes of which contain even less water and the solubility of water in which will be even higher. And formates will form heavier-boiling acetates, which have boiling points close to CC (sec-butyl acetate 112 ° C, n-butyl acetate 126 ° C), which will create a problem of their subsequent separation from CC.

In the patent [GB 735867] it is proposed to use the mixture "IEC - cyclohexane" as an entrepreneur. It is argued that in this case there is no acid impurity in the separated water, and the MEK is separated from the water in the form of an azeotrope during subsequent distillation. The disadvantage of this method is the significant solubility of MEK in water (~ 30%), which will lead to significant costs of MEK during rectification. The high solubility of water in the MEK (~ 10%), comparable with the water content in the MEK - N ₂ O azeotrope, will significantly complicate the regeneration of MEK from its aqueous solutions.

There are a number of patents describing the use of ethers for azeotropic and extractive distillation. The most popular is the use of diisopropyl ether (DIPE) and methyl tert-butyl ether (MTBE) [GB 771992, GB 788931, US 6695952, US 6793777, WO 02053524]. However, DIPE, according to our experimental data, creates a rather stable emulsion with water, which is very poorly stratified. So in the lower water layer after 1 h, 5.6 wt.% DIPE remains, and after 24 hours 3.2 wt.%. This will lead to the penetration of appreciable amounts of UK and MK into the water layer and will require subsequent treatment of water effluents not only from the entrepreneur, but also from acids. The use of MTBE to remove water is complicated by the fact that this ether has a high solubility in water, and such solutions pose a significant environmental hazard, which is why MTBE is banned for use in several countries (for example, the USA).

Despite the fact that MTBE and DIPE are declared as effective extractants, however, according to our data, the solubility of CC in water is much higher than in these ethers. With subsequent rectification, to remove water, they are also not very effective as entreners. This is due to the relatively low water content in the azeotrope (4 and 4.6 wt.%) And the relatively high solubility of water in it (1.0 and 0.6 wt.%), Which leads to the cost of about 3000 kcal of energy for the separation of 1 kg of water. The use of n-butyl ethyl and sec-butyl ethyl esters is much more efficient (estimated energy consumption of 2000 and 2400 kcal per 1 kg of water discharged) [Hunsmann, W., Simmrock, K. H. (1966). Trennung von Wasser, Ameisensäure und Essigsäure durch Azeotrop-Destillation. Chemie Ingenieur Technik - CIT, 38 (10), 1053-1059. (Germ.)]. However, the use of n-butyl ethyl and sec-butyl ethyl esters is complicated by the fact that they are not commercially available and their application will require the creation of a separate production.

After separation of water from the “UK - MK - N ₂ O” ternary system, formic and acetic acids no longer form an azeotrope and can theoretically be separated by ordinary distillation. However, due to the proximity of the volatility coefficients, they are often separated by azeotropic distillation. Hydrocarbons (heptane, benzene, toluene) or organochlorine compounds, for example, dichloroethane, chlorobutane, CHCl ₃ , CCl ₄ trichlorethylene [US 3555083, DE513024, DE 1204214, GB 771992] are used as the azeotropically forming agent. A number of Lloyd Berg patents are presented, which propose the use of a number of different entreners for the separation of MK and CC, such as carboxylic acids C3-C6 [US 5599979], isopropyl acetate and acetonitrile [US 5633402], nitrotoluene and nitropropane [US 5227029], cyclopentane and tetrachlorethylene [US 5264086]. In the patent [US 2016075629] a method is described for cleaning MC from impurities of MK by crystallization, which provides an impurity content of not more than 0.2%.

There are a number of chemical methods for cleaning MC from impurities of MK, such as: hydrogenation of MK by the action of H ₂ on heterogeneous catalysts [for example, GB 791044], decomposition of MK by the action of carboxylic acid anhydrides [GB 721301, GB 1434062], oxidation of MK by the action of potassium chromate [ CN 1523001], potassium permanganate [CN 103265424], chromium oxide (VI) [US 4061546] and H ₂ O ₂ [WO 9203403]. In addition, methods for the decomposition of MK in the gas phase by passing over a heterogeneous catalyst are described [GB 1089017, JP 4275270]. However, all these methods are applicable only in the case of low concentrations of MK and lead to irreversible destruction of MK.

A comprehensive method for the separation of complex mixtures having a composition similar to BF, with the allocation of MK and UK as separate products, are presented in the patent [GB 1112397]. The mixture obtained after the methanol carbonylation reaction and containing a number of aldehydes, ketones, and esters in addition to MK, CC, and water was subjected to rectification, using carbonyl compounds present as water entrainer, which partially returned to the column as reflux. In this case, the majority of MCs appeared in the water layer and then returned to recycling to the stage of synthesis of CCs.

The closest in technical essence and the achieved result to the proposed one is the following 4 ways to isolate UK from complex mixtures.

Distillers patent [GB 771992] describes the oxidation of C4-C8 hydrocarbons, followed by the release of carboxylic acids (primarily, carbon monoxide). Initially, fractional distillation is carried out, separating fractions boiling up to 99 ° C, and then water is separated by azeotropic distillation with DIPE to obtain a C1-C4 carboxylic acid mixture in the cube. Formic acid is then separated by azeotropic distillation with the addition of toluene as an entrepreneur, and, finally, rectification is carried out to obtain a fraction of CC.

In the patent [GB 707153], a fraction of low-boiling products giving an azeotrope with water is first distilled from the mixture obtained by alkane oxidation, and the remaining bottoms containing acids C1-C4 and water are subjected to azeotropic distillation with toluene or xylene. In the patent [US 3258482] of Knapsack AG, the mixture obtained after oxidation of alkanes is also subjected to fractionation to remove fractions boiling below 106 ° C. Higher-boiling fractions are distilled using benzene as an entrepreneur to obtain fractions of "N ₂ O - MK" and "anhydrous UK with small impurities MK". The latter is removed by a hydrogenation reaction on Pt and Ni-containing heterogeneous catalysts.

In Tekkosha Co. Patent Ltd. [US 3555083] the mixture after oxidation of hydrocarbons is subjected to flash distillation initially, then the target fraction is subjected to dehydration using low-boiling oxidation products (esters, alcohols and ketones from up to 82 ° C) as entreners, and to separate MK from UK and other acids use benzene or dichloroethane as antreners.

In addition to the above-mentioned drawbacks of existing methods, the removal of MK from its mixtures with CC and water is accompanied by the formation of concentrated MK solutions (above 20%), which have a high corrosivity. This requires the use of expensive equipment made of special metals and alloys, such as Hastelloy C4, titanium, zirconium, etc., which greatly reduces the economic efficiency of these methods due to the high capital costs.

The invention solves the problem of developing an effective process of reactive distillation separation of mixtures of complex composition resulting from liquid phase oxidation of the n-butane fraction and containing acids C1-C4, alcohols C1-C4, esters C2-C6, carbonyl compounds C1-C4 and water.

The problem is solved by the proposed method for producing acetic acid and methyl ethyl ketone in the process of reactive distillation separation of mixtures of complex composition obtained by liquid-phase oxidation of the n-butane fraction and containing acids C1-C4, alcohols C1-C4, esters C2-C6, carbonyl compounds C1-C4 and water, in which methanol is added as a reagent to remove formic acid in the distillation apparatus, or a mixture of methanol with methyl acetate, the resulting methyl formate is removed as a component of the fraction, boiling point 31 ÷ 53 ° C, as a result of rectification, fractions are isolated containing the main components methyl formate, methyl acetate with acetone, ethyl acetate with methyl ethyl ketone, methyl ethyl ketone with water, sec-butyl acetate with n-butyl acetate, water with acetic acid, acetic acid, and aqueous fractions can be dried by repeated azeotropic distillation with the addition of any suitable separating additive - entrepreneur.

At the stage of removing water from the aqueous fraction of acetic acid, ethers, preferably TAME tert-amylethyl ether, ETBE ethyl tert-butyl ether or di-n-propyl ether are used as an entrepreneur. For separation, a mixture of oxidation products of the n-butane fraction containing more than 20% methyl ethyl ketone and less than 15% water is used. For effective distillation separation of butyl acetates from acetic acid, water is additionally added to the initial mixture so that its amount is more than 15%. At the stage of water removal from the water-containing fraction of methyl ethyl ketone, ETBE ethyl tert-butyl ether or n-hexane is used as an entrepreneur.

Our proposed method is to add to the shared mixture of low molecular weight alcohol, preferably methanol and rectification. In the process of rectification, in the absence of a catalyst, alcohols react with MK formic acid and, in part, with AC acetic acid to form the corresponding esters. Due to the fact that the azeotropes of these esters with water have a lower boiling point than the starting alcohols and acids, they are removed from the mixture in the form of the corresponding fractions. The esterification reaction is reversible, however, in the conditions of rectification due to the removal of ethers, the equilibrium is almost completely shifted towards their formation. This makes it possible to apply this approach in the case of low concentrations of MK, for example, for its separation from the initial mixtures obtained by oxidation of the fraction of n-butane or other alkanes. Moreover, the concentration of MK at the first stage of rectification will not exceed its concentration in the initial mixture (less than 5%), and at all subsequent stages it will be close to zero, which will lead to a significant reduction in the negative corrosive effect on the equipment.

Methanol is an inexpensive reagent available that is highly reactive in the ester formation reaction. The main part of methanol is spent on the formation of methyl formate, and part on the formation of methyl acetate. Both esters can be isolated from the mixture by conventional distillation. Methyl acetate can be recycled and used together with methanol for reactive distillation removal of MK. Methyl formate can be isolated as a separate fraction and used as a commercial product or converted into MK using any known methods. The proposed method allows the purification of mixtures of the products of oxidation of the n-butane fraction from MK to obtain the fraction of CC containing not more than 0.02% MK.

The use of propanols and butanols as reagents for the separation of MK from mixtures of products of oxidation of the n-butane fraction is less preferred, and the use of ethanol is undesirable due to its negative effect on the isolation of the main products (IEC and CC). In this case, there is a problem of separation of ethanol from the IEC, requiring the use of extractive distillation methods (for example, [US 5876569, GB 795614]), and the complete separation of alcohol is not achieved. In addition, ethyl acetate formed during the reaction forms an azeorop with MEK, which will require the use of a complex of reactive distillation and extraction methods (for example, [SU1 45238), US 3404186, SU 250121] for their separation), which also do not ensure the completeness of their separation. In the case of the use of propanols and butanols, a number of problems also arise with the separation of both themselves and the esters formed from them from MEK or UK containing fractions. In addition, the cost of these alcohols is significantly higher compared to methanol.

During the separation of the mixture of n-butane oxidation products, the resulting water-containing fractions, in particular the MEK-H ₂ O and UK-H ₂ O fractions, can be dried using any suitable entreners.

Most preferred for the separation of water from the MEK-containing fraction are n-hexane and ethyl tert-butyl ether (ETBE). n-Hexane gives a triple azeotrope “n-hexane - MEK - Н ₂ О" (bp. 56-58 ° С), which is stratified into an upper layer containing mainly hexane with impurities of MEK (28%) and a lower layer, containing predominantly water with IEC impurities (8%). The upper layer is sent back to the column of the distillation apparatus in the form of reflux, and the lower is separated. The MEK is then removed from the lower water layer as an azeotrope (i.e., boiling water. 73.4 ° C, 12% H ₂ O), which is recycled for drying. Unlike n-hexane, ETBE does not produce an azeotrope with MEK and therefore is separated in the form of a double azeotrope ETBE - Н ₂ О (i.e., boiling point 65 ° С, 6% Н ₂ О). Excess ETBE can then be fairly easily separated from the IEC and recycled.

In the case of a water-containing fraction of CC, the most suitable entreners for the removal of H ₂ O are ethers. Most preferred are tert-amylethyl ether (TAME), ethyl tert-butyl ether (ETBE) and di-n-propyl ether. The aforementioned esters have the following advantages: they do not react with CC, do not give azeotropes with CC (unlike standard entreners for removing water - alkanes and C6-C7 arenes), form azeotropes with H ₂ O with suitable boiling points (i.e. . 65-75.4 ° C) and with a rather high water content (6-9%), which will help reduce energy costs, have low solubility in water (1-2%).

Technical result:

The proposed method for purification of the mixture makes it possible to significantly simplify the separation scheme of multicomponent mixtures obtained as a result of liquid-phase oxidation of the fraction of n-butane or other alkanes, removing two stages: distillation separation, MC from UK and MK from water and the entrepreneur. In addition, this method in some cases allows you to abandon the stage of the final purification of the fraction of the criminal code from the remaining impurities MK. With this method of separation of mixtures, MK concentrations at any stage of the process are low (<5%), which significantly reduces their corrosive effect on the equipment.

The invention is illustrated by the following examples.

Example 1

The mixture obtained as a result of liquid-phase oxidation of the n-butane fraction, under conditions favorable for obtaining CC, is subjected to preliminary debutanization at 25 ° C. To the resulting mixture of the oxidized fraction of n-butane (OFB-UK) weighing 700 g add 40 g of methanol (for reactive distillation removal of MK) and loaded into the distillation apparatus. The composition of the resulting mixture is shown in table 1.

The distillation apparatus is equipped with a packed column with a vacuum jacket 1 m long, with an inner diameter of 15 mm and a flask volume of 2 l. The temperature regime of the column was set by self-heating in pairs of the rectified mixture. Spiral-prismatic column nozzles with a diameter of 2 mm are made of AISI 304 stainless steel. The efficiency of the reaction apparatus is about 50 theoretical plates. Reflux numbers during rectification are from 4 to 12. Close fractions are combined in composition.

Table 1. Composition OFB-UK with the addition of 40 g of methanol

Component Amount, g Share% n-butane 1.3 0.2 Acetaldehyde 1.5 0.2 Ethanol 1.1 0.1 Ethyl formate 0.6 0.1 Acetone 8.5 1.1 Methyl acetate 8.2 1.1 Methanol 40.5 5.5 Ethyl acetate 9.5 1.3 IEC 24.4 3.3 Butanol-2 1.7 0.2 Sec-butyl formate 0.4 0.1 MK 19.6 2.6 UK 433 58.5 n-butanol 0.7 0.1 Sec-butyl acetate 5.4 0.7 Propanoic acid 7 0.9 n-butyl acetate 1.1 0.1 Butanoic acid 3.7 0.5 Other 3.1 0.4 H ₂ O 168.7 22.8 Amount 740 100.0

As a result of rectification, the following fractions are obtained.

Fraction 31 ÷ 56 ° C, 68 g, containing methyl acetate (42%), methyl formate (32%), acetone (12%), methanol (6%), ethyl formate (1%), acetaldehyde (2%), butane (1 %), water (0.5%), other products (3.5%).

Fraction 66 ÷ 72 ° C, 20 g, containing ethyl acetate (46%), MEK (18%), water (31%) ethyl formate (2%) other products (3%)

Fraction 72.4 ÷ 74.4 ° C, 22 g, containing MEK (75%), water (16%), ethyl acetate (3%), sec-butyl formate (2%), other products (4%).

Fraction 76.5 ÷ 95 ° C, 32 g, containing water (53%), sec-butyl acetate (23%), MEK (9%), n-butyl acetate (4%), butanol-1 (4%), butanol-2 (2%), other products (5%).

Fraction 96 ÷ 100 ° C, 148 g, containing water (94%), CC (4.0%), propanoic acid (0.5%), butanoic acid (0.2%), other products (1.3%).

Fraction 100 ÷ 117 ° C, 60 g, containing UK (62%), water (36%), other products (2%).

Fraction 117 ÷ 117.8 ° C, 351 g, containing AC (99.6%), water (0.3%), other products (0.1%).

Cube, 33 g, containing CC (75%), butanoic acid (10%), propanoic acid (18%), other products (4%).

The yield of UK in the fraction 117 ÷ 117.8 ° C is 81%, the content of MK does not exceed 0.02%. Such purity of the UK corresponds to the 1st grade according to GOST 19814-74. Under continuous rectification, taking into account the recycling of the Н ₂ О - УК fraction and methyl acetate, the yield of the УК will be noticeably higher (about 95%).

Example 2

The mixture obtained by liquid phase oxidation of the n-butane fraction under conditions conducive to the formation of MEK is subjected to preliminary debutanization at 25 ° C. To the resulting mixture of the oxidized fraction of n-butane (OFB-MEK) weighing 700 g, 50 ml of water (for azeotropic removal of esters of the composition C5 ÷ C6) and 40 g of methanol (for reactive distillation removal of MK) are added and loaded into a distillation apparatus. The composition of the resulting mixture is shown in table 2.

Table 2. Composition OFB-IEC with the addition of 50 g of water and 40 g of methanol

Component Amount, g Share% n-butane 1.4 0.2 Acetaldehyde 0.8 0.1 Methyl formate 3.2 0.4 Methanol 43 5.4 Ethanol 2.3 0.3 Ethyl formate 0.6 0.1 Acetone 8.8 1.1 Methyl acetate 7.6 1.0 Tert-butanol 4.3 0.5 Ethyl acetate 58.4 7.4 IEC 207.3 26.2 Butanol-2 8.3 1.1 MK 23.2 2.9 UK 275.7 34.9 Sec-butyl acetate 7 0.9 Propanoic acid 3.2 0.4 n-butyl acetate 0.6 0.1 Butanoic acid 3.2 0.4 Other 3.4 0.4 H ₂ O 127.8 16.2 Amount 790.1 100.0

As a result of rectification, the following fractions are obtained.

Fraction 31 ÷ 57 ° C, 93 g, containing methyl acetate (48%), methyl formate (28%), acetone (8%), methanol (9%), ethyl formate (4%), water (0.5%), other products ( 2.5%).

Fraction 66 ÷ 72 ° C, 91 g, containing ethyl acetate (58%), MEK (21%), water (14%) ethyl formate (3%) other products (4%)

Fraction 72.5 ÷ 74.5 ° C, 236 g, containing MEK (77%), water (16%), ethyl acetate (3.5%), other products (3.5%).

Fraction 76.5 ÷ 96 ° C, 53 g, containing water (51%), sec-butyl acetate (26%), MEK (11%), n-butyl acetate (4%) butanol-2 (3%), other products (5 %).

Fraction 97 ÷ 100 ° C, 48 g, containing water (89%), CC (3.5%), propanoic acid (1.5%), butanoic acid (1.5%), other products (4.5%).

Fraction 100 ÷ 117 ° C, 36 g, containing UK (48%), water (50%), other products (2%).

Fraction 117 ÷ 117.8 ° C, 197 g, containing UK (99.6%), water (0.3%), other products (0.1%).

Cube, 28 g, containing CC (80%), butanoic acid (8%), propanoic acid (8%), other products (4%).

The yield of UK in the fraction 117 ÷ 117.8 ° C is 71%, the content of MK does not exceed 0.02%. Such purity of the UK corresponds to the 1st grade according to GOST 19814-74

The yield of MEK in the fraction 72.5 ÷ 74.5 ° C is 85%.

Under the conditions of continuous rectification, taking into account recycles, the yields of UK and IEC will be significantly higher (about 90% for MEK and 95% for UK).

Example 3

To a mixture of OFB-MEK obtained by liquid-phase oxidation of the n-butane fraction, weighing 700 g, similar to that used in Example 2, 50 g of water was added and loaded into a distillation apparatus. The composition of the mixture is shown in table 3.

Table 3. The composition of the OFB with the addition of 50 g of water

Component Amount, g Share% n-butane 1.4 0.2 Acetaldehyde 0.8 0.1 Methyl formate 3.2 0.4 Methanol 3 0.4 Ethanol 2.3 0.3 Ethyl formate 0.6 0.1 Acetone 8.8 1.2 Methyl acetate 7.6 1.0 Tert-butanol 4.3 0.6 Ethyl acetate 58.4 7.8 IEC 207.3 27.6 Butanol-2 8.3 1.1 MK 23.2 3.1 UK 275.7 36.8 Sec-butyl acetate 7 0.9 Propanoic acid 3.2 0.4 n-butyl acetate 0.6 0.1 Butanoic acid 3.2 0.4 Other 3.4 0.5 H ₂ O 127.8 17.0

Amount 750 100

The following main fractions are obtained as a result of rectification.

Fraction 32 ÷ 56 ° C, 25.5 g, containing methyl acetate (30%), acetone (33%), methyl formate (16%), methanol (6%), acetaldehyde (2.5%), ethyl formate (5%), butane (2.5 %), water (1.5%), other products (3.5%).

Fraction 66 ÷ 72.2 ° C, 87 g, containing ethyl acetate (58%), MEK (22%), water (14%) ethyl formate (3%), ethanol (1%), other products (2%).

Fraction 72.8 ÷ 74.5 ° C, 221 g, containing MEK (78%), water (15%), ethyl acetate (2.5%), sec-butyl formate (1.5%), other products (3%).

Fraction 75 ÷ 99 ° C, 84 g, containing water (61%), sec-butyl acetate (13%), MEK (13%), sec-butyl formate (4%), n-butyl acetate (3%), butanol-2 (1 %), butanoic acid (1%), propanoic acid (1%), CC (0.5%), other products (2.5%).

Fraction 100 ÷ 117 ° C, 81 g, containing UK (39%), water (37%), MK (23%), other products (1%).

Fraction 117.1 ÷ 117.9 ° C, 216 g, containing UK (99.4%), water (0.3%), MK (0.2%), other products (0.1%).

Cube, 31 g, containing CC (72%), propanoic acid (7%), butanoic acid (7%), other products (4%).

The yield of UK in the fraction 117.1 ÷ 117.9 ° C is 78%. The content of MK is 0.2%, which exceeds the maximum permissible values for the synthetic acids of the 1st and 2nd according to GOST 19814-74 and requires the use of additional methods for its purification.

The yield of MEK in the fraction 72.8-74.5 ° C is 83%. Under the conditions of continuous rectification, taking into account recycles, the yields of UK and IEC will be significantly higher (about 90% for MEK and 95% for UK).

Example 4

In order to test the possibility of using the method of reactive distillation with the addition of lower alcohols to purify a fraction of 100-117 ° C from MK, we conducted a special experiment using a model mixture containing 39% CC, 37% water, 23% MK and 1% impurities. Ethanol is used as a reagent, since it has a higher boiling point, which helps to accelerate the esterification reaction. Its use is more appropriate, since in this case the task is not to isolate the MEK fraction, with which he and his ether form an azeotrope with CC. The mass of the loaded mixture is 500 g, the mass of ethanol is 190 g.

As a result of rectification, the following fractions are obtained.

Fraction 51.7 ÷ 54 ° C, 176 g, containing ethyl formate (95%), water (3.5%), ethanol (1.0%), other products (0.5%).

Fraction 54 ÷ 89 ° C, 161 g, containing ethyl acetate (61%), water (16%), ethanol (13.5%), ethyl formate (9%), other products (0.5%).

Fraction 90 ÷ 99 ° C, 226 g, containing water (94%), CC (5.5%), other products (0.5%).

Fraction 100 ÷ 117 ° С, 19 g, containing UK (77%), water (20%), MK (3.0%), other products (0%).

Fraction 117 ÷ 117.5 ° C, 76 g, containing UK (99.2%), water (0.3%), MK (0.4), other products (0.1%).

Cube 26 g, containing mainly UK (96%).

The yield of UK in the fraction 117 ÷ 117.5 ° C is about 40%. Under continuous rectification, taking into account the recycling of ethyl acetate, the yield of CC will be noticeably higher (about 95%).

It can be seen that in this case, even with an excess of alcohol, which leads to a significant decrease in the yield of CC, it is not possible to achieve the desired purity of the CC and completely get rid of MK. Thus, the optimal way to obtain CC of the required degree of purity from a mixture of RPB from MK is to add water and methanol to the initial mixture of RPB with subsequent rectification.

Example 5

In the rectification process according to example 1, a fraction of 100 ÷ 117 ° C is obtained, which contains mainly UK and water. To remove water from this fraction, azeotropic distillation was carried out with the addition of tertamyl methyl ether (TAME). 700 g of a mixture containing CC (58%) and water (40%) were charged into a distillation apparatus, and 70 g of TAME was added. Rectification is carried out using a Dean-Stark nozzle, where the water-TAME mixture delaminates. The lower layer containing predominantly water with small amounts of ether is separated, and the upper layer containing predominantly TAME is sent back to the column in the form of reflux.

As a result of rectification, the following fractions are obtained.

Fraction 73.5 ÷ 73.8 ° C (307 g) containing water (90%), TAME (8%) and other products (2%).

Fraction 84 ÷ 117 ° C (74 g), containing TAME (59%), CC (34%), water (3%) and other products (4%).

Fraction 117 ÷ 117.6 ° C (349 g) containing AC (99.6%), water (0.2%) and other products (0.2%).

Cube (34 g), containing predominantly UK (95%).

The yield of UK in the fraction 117 ÷ 117.6 ° C is 85%.

Example 6

A mixture having the same composition as the fraction 72.5 ÷ 74.5 ° C from Example 2 (77% MEK, 16% water, 3.5% ethyl acetate, 3.5% of the remaining products (sec-butyl formate, tert-butanol, etc.), in an amount 700 g is loaded into a distillation apparatus. 70 g of ETBE is added as an entrainer to remove water. The distillation is carried out using a Dean-Stark nozzle where the water-ETBE mixture exfoliates. The lower layer, which contains mainly water with small amounts of ETBE and tert-butyl alcohol separated, and the top layer, containing mainly ETBE, melt back into the column in the form of phlegmy.

As a result of rectification, the following fractions are obtained.

Fraction 65 ÷ 67 ° C (129 g) containing water (82%), ETBE (10%), ethyl acetate (3%) and other products (5%).

Fraction 67 ÷ 79.4 ° C (89 g) containing ETBE (61%), MEK (19.5%), ethyl acetate (14%) water (2.5%) and other products (3%).

Fraction 79.4 ÷ 79.6 ° C (501 g) containing MEK (96%), water (0.5%), ethyl acetate (1.5%) and other products (2%).

Cube (43 g), containing predominantly MEK (90%).

The yield of MEK in the fraction 79.4 ÷ 79.6 ° C is 89%. Under conditions of continuous rectification, taking into account recycling, the yield of MEC at the stage of water separation will be significantly higher (about 95%).

Claims (5)

1. A method of producing acetic acid and methyl ethyl ketone in the process of reactive distillation separation of mixtures of complex composition obtained by liquid-phase oxidation of the n-butane fraction and containing acids C1-C4, alcohols C1-C4, esters C2-C6, carbonyl compounds C1-C4 and water, characterized in that methanol is added as a reagent to remove formic acid in the distillation apparatus, or a mixture of methanol with methyl acetate, the resulting methyl formate is removed as a component of the fraction with a boiling point of 31 ÷ 53 ° C, As a result of rectification, fractions containing methyl formate, methyl acetate with acetone, ethyl acetate with methyl ethyl ketone, methyl ethyl ketone with water, sec-butyl acetate with n-butyl acetate, water with acetic acid, acetic acid, and water-containing fractions can be dried by repeated azeotropic rectification. the addition of any suitable separating additive - entrepreneur. 2. The method according to p. 1, characterized in that at the stage of removing water from the aqueous fraction of acetic acid, ethers, preferably TAME tert-amylethyl ether, ETBE ethyl tert-butyl ether or di-n-propyl ether are used as an entrepreneur. 3. The method according to p. 1, characterized in that for the separation using a mixture of oxidation products of the n-butane fraction containing more than 20% methyl ethyl ketone and less than 15% water. 4. The method according to p. 1, characterized in that for the efficient distillation separation of butyl acetates from acetic acid, water is additionally added to the initial mixture to make up more than 15%. 5. The method according to p. 1, characterized in that at the stage of removing water from the aqueous fraction of methyl ethyl ketone, ETBE ethyl tert-butyl ether or n-hexane is used as an entrepreneur.