DE1543175C - Process for the production and extraction of acetic acid - Google Patents

Description

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The invention relates to a method for producing propylene glycol and glycol monoesters containing-

and recovery of acetic acid. the components of an ester concentration

The technology already knows a large number of column feeds whose vapors together with Processes by which acetic acid is produced. the acetic acid from the bottom stream of the vinegar die most known methods have one or 5. acid refining column and the bottom stream several disadvantages that consist in that Oxyda- the azeotropic distillation in the presence of a tion catalysts, initiators, critical feed catalysts, preferably toluenesulfonic acid, quantities of the reactants, expensive or fully acylated polyoxyalkanes esterified or Hazardous raw materials, excessively high transesterified and these the oxidation process Reaction temperatures or difficult to carry out ίο ", supplies again. Separation procedures are required. The invention therefore aims to provide a process for The solvents used according to the invention The manufacture and extraction of acetic acid by are very resistant to attack by free ones non-catalytic, direct oxidation of propene with radicals generated in the oxidation process molecular oxygen in a liquid phase turning 15; they also mitigate the disturbing effects, contains fully esterified polyacyl esters of polyols. those of acidic components, especially the

Another purpose of the invention is formic acid and, to a lesser extent, vinegar production and recovery of acetic acid in an acidic, on commercially valuable, non-acidic Mitpro process, in which mechanical solvent losses, e.g. propylene oxide, are exerted, can be replaced by products of oxidation. 20 formed by the oxidation of olefins.

In addition, the process of the invention is simple, fully esterified polyacyl-

economical and expedient and does not require any esters of polyoxyalkanes, polyoxycycloalkanes,

expensive, dangerous and difficult to obtain polyglycols and mixtures thereof. The inventive

gang materials. according to the applicable polyacyl esters generally contain

The invention therefore relates to a process 25 common in each acyl group 1 to 18 carbon

for the production of acetic acid by oxidation of material atoms and in any alkylene or cycloalkylene

Propene and distillative production of acetic acid grouping 2 to 18 carbon atoms. The best

from the reaction product, characterized in that results are achieved when the acyl

that one ■ grouping contains 1 to 6 carbon atoms and the

30 alkylene and cycloalkylene groups 2 to 6 each

a) Propene with oxygen in the liquid phase contained in carbon atoms. These esters can without the presence of at least 25 percent by weight, further prepared by known processes, based on the liquid reaction mixture, one of the. For example, the United States patent fully acylated polyoxyalkane, Polyoxycyclo-1534 752 describes a process in which the corresponding glycol diacetate-containing solvent is produced in glycol ester by reaction of alkane or polyglycol, preferably propylene glycol, with carboxylic acids. Instead of the acids, a temperature range from 160 to 25O ⁰ C, you can also use acid anhydrides, preferably 180 to 230 ⁰ C, and a pressure. For example, the ethylene glycol, hexylene-200 at, converts 4 ° glycol or octadecylene glycol. Glycols with branched

b) and the reaction product using a ter chain, for example the iso-, primary, sec-fast Evaporator and a stripper into a dary and tertiary isomer of the above The acetic acid and low-boiling straight-chain glycols are also suitable for containing Gas phase and the main amount, for example, isobutylene glycol, the primary, secondary Solvent, high-boiling products and 45 dear and tertiary amylene glycol or 2,3-diden Liquid phase containing residue decomposed, methyl-2,3-dodecanediol. To the polyalkylene glycols

c) the liquid phase via an adsorber into the (polyols) include the diethylene glycol or di-oxidation zone returns in compliance with hexylene glycol. .

a residue concentration of less than 60 ■ Except for glycols with straight and branched chain

weight percent in the reaction mixture, ⁵ ° ^{you can also use} acyclic glycols,

d) The gas phase is subjected to the condensation T ^ ZiZtf ^ ^ * by cooling, the non- ^{condensed vapors via 1} ^ S ^ J £ gä _e hydroxy compounds are returned to the adsorber and _oxidation zone, polyoxyalkylene, for example glycerine, erythritol from the condensate propene and Propane ab- , J _v ^} . does

distilled and the propene and the en of a ⁵⁵ ° ΙΤ ^ ££ ™ carboxylic acids include the fatty sidestream acetaldehyde obtained in the _säu example, formic acid, acetic acid, oxidation zone and the remain- zuruckle.tet _P ^P _{ionsäure or} stearic acid, the naphthenic acids Bende condensate my distillation _residue, for _{example, the} cyclopentanecarboxylic acid, as well as

ün.ln ^ n ^ S " ¹ ". "Τ ^{86 EsSlgSaure ent} - 60 aromatic acids, for example benzoic acid,

holding distillate disassembled, _{to the suitable} p £ iy _acy lesters include poly-

e) from that first of all the low-boiling constituents acyl esters of Polyoxyalkanen, for example abdestilhert Triacylteile, the acetic acid by azeotropic _{esters of} glycerol, Tetraacylester of erythritol and distillation with benzene of water and pentaerythritol and of Polyacylester Polyalkylengly-Amciscnsäure freed by distillation and then _{$ 6 ko} i _ei1i, for example, diethylene glycol diacetate. This tion cleanses _a | _s solvent usable are Polyacylester

f) and the distillation residue of the condensate compatible with one another, so that. they aHein or im can be used together with the distilled, low-boiling mixture with one another. At-

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For example, you can use a mixture of different conditions up to 75 percent by weight of the liquid

Make up proportions of a diacyl ester of an oxyalkane, e.g. reaction medium,

of the propylene glycol diacetate, with a polyacyl ester in the practice of these less preferred

of a polyglycol, for example the dipropylene embodiment, the amount of in the liquid

use glycol diacetate. In the present Ver 5 reaction medium contained polyacyl ester solution

drive, which in the following execution means at least 25 percent by weight of this

Examples is explained, can be used as a solution medium, so that the above

medium also a mixture of a polyacyl ester can be achieved for these advantages. Olefin

Polyglycol, for example of the dibutylene glycol oxidizing solvent, are characteristic,

dibutyrate, with a polyacyl ester of a polyoxy- ίο In-further embodiments of the invention

alkane, for example the glycerol trivalerate or according to the method, the polyacyl ester

use the pentaerythritol tetrapropionate. Solvent suitable in combination with

Of particular interest in the thinners of the invention or auxiliary solvents used, According to processes, the vicinal diacyl esters are the high ones with respect to volatile reaction products of alkylene glycols, for example the diformates, have 15 boiling points and, under the reaction conditions, diacetates, Distearates of the abovementioned conditions are chemically relatively indifferent and relatively indifferent to them Alkylene and polyalkylene glycols ,. and their nature is resistant to oxidative and thermal attack mix. Of particular interest are the diacetates. In this case too, the polyacyl ester des Ethylene glycol and propylene glycol. These solvents in an amount of at least 25 can mixed alone or in any proportions weight percent of the liquid reaction medium be used. . be turned. The liquid reaction

Polyacyl esters with mixed acyl groups are medium that proportion of the total content of the

also suitable, for example called ethylene glycol, which is in the liquid

formate butyrate, tetraethylene glycol butyrate caprylate, phase.

Erythritol diacetatdipropionat, Pentaerythritdibutyrat- 25 Among the suitable diluents, which in the

divaleriate or cyclohexanediol acetate valerate. Framework of the invention together with the polyacyl

Monoacyl esters of polyoxylalkanes and polyglyester solvents can be used, kolen are heard for use as a reaction medium, for example, hydrocarbon solvents unsuitable in the present process. The same as xylenes, kerosene, biphenyl and the like, halogenated applies to other oxo compounds or hydroxylated benzenes such as chlorobenzene, dicarboxylic acid esters, such as Compounds, for example glycerol, glycols, dialkyl phthalates, sebazates, aromatic ethers, such as Polyglycols and oxycarboxylic acids. This is diphenyl ether on it; halogenated aryl ethers, e.g. B. the due to the fact that a large amount of reactive 4,4'-dichlorodiphenyl ether, also diarylsulfoxides, capable hydroxyl groups are present, such as diphenyl sulfoxide; Dialkyl and diarylsulfones, are subject to auto-oxidative attack, so that oxidative 35 z. B. the dimethyl sulfone and the dixylyl sulfone, and Side reactions occur which the. desired nitroalkanes, e.g. B. nitrohexane. The foregoing condemnations Affect oxidation of the olefin. bonds are examples of diluents

In the preferred embodiment, those specified form the within the scope of the invention with the Polyacyl ester are used over all other constituents polyacyl ester solvents; of the reaction mixture, including those contained therein, however, this list is not exhaustive. the solved reactants, oxidation products and with the help of these polyacyl esters achievable advantages By-products, most of the reaction, can also be practical when combined with mixed. This means that the weight of the solvent determines each chemically inert diluent is always higher than the total weight of everyone will hold.

other components. In a less preferred 45 As stated above, need at

Embodiment of the invention, however, the present oxidation process cannot be cata-

work that the total weight of all but the lysers to be added. As a result of the versatile

Polyac ^ esters present in the liquid phase usability of the above-described solvents

Components is higher than the weight of the poly-solvent used in the oxidation of propene

acyl esters of existing solvents. For example 5 ° but the usual oxidation catalysts are tolerated

can be used as a hydrocarbon feedstock, although they do not produce significant benefits

in refinery quality or a raw hydrocarbon lead. For example, catalysts can be used

material starting material, which is e.g. 50% by weight metal basis, such as platinum, selenium, vanadium, iron, nickel,

percent of the olefin to be oxidized and cobalt, cerium, chromium, manganese, silver, cadmium,

50 percent by weight of saturated hydrocarbons 55 mercury and its compounds, preferably in

substances, e.g. an alkane, such as propane, divided into oxidic form, etc., on a carrier

in an amount of up to 50 percent by weight, on or without a carrier, or as finely divided suspensions

on the solvent. According to the presence of oxy.

The oxidation of propene according to the invention cannot do this with this starting material converted olefin, the alkane "and the oxygen together rapidly after a short introduction period with oxidation products including the equip, are also no initiators or auxiliary acetic acid, Low-boiling compounds, such as acetal catalysts, are required, but these can do so dehyde, propylene oxide, acetone, and methyl acetate, and used to make the short introductory period high-boiling substances (components whose boiling point should be shortened or eliminated. After this period Point above that of the polyacyl ester solvent 65 do not need initiators or auxiliary catalysts is) that were formed during the reaction and / or more to be added.

recycled to the reaction vessel. Suitable initiators include organic ones

be, depending on the reaction or circulatory. Peroxides, for example benzoyl peroxide, also other

organic peroxides, for example hydrogen and sodium peroxide, as well as peracids such as peracetic acid and perbenzoic acid, ketones, e.g. B. acetone; Ether, e.g. B. diethyl ether, and aldehydes, e.g. B. that Acetaldehyde, propionaldehyde and isobutyraldehyde. When carrying out the method according to the invention the reaction mixture can be prepared in various ways. For example, you can the propene and the oxygen with the solution

The pressure can range from 0.5 to 350 at lie. The oxidation reaction is, however, facilitated by higher temperatures and pressures, so that the pressure is preferably in the range from 5 to 200 at, in particular in the range from 25 to 75 at. The pressure and temperature must of course be chosen so that the liquid phase is maintained will.

The oxidation of propene takes place autocatalytically

Mix medium and add the mixture to the reaction * o and proceed after a short introductory period insert a vessel. One can also use propene (expediently away very quickly. A typical oxidation of propene moderately in an amount up to 50 percent by weight, in a batch process preferably in an amount of 5 to 30 weight- about 0.1 to 20 minutes.

percent, based on the solvent) with the The reaction vessel can be made from the various

Premix the solvent. Preferably the 15 most keen materials will be made up. For example are P i d il d d li i l ki

Propene premixed with the solvent and the oxygen-containing gas in partial quantities or continuously introduced into the propene-solvent mixture. One can also use propene and the oxygen-containing one Introduce gas simultaneously through separate or common feed lines into a body of the solvent, which is in a suitable solvent, which is described below. In a Embodiment is a mixture of propene and i i

The amounts fed in can be from 0.014 to 42 m ³ per hour or more and are primarily dependent on the size of the reaction vessel. The oxygen supply is adjusted so that an acidic

Aluminum, silver, nickel, almost all ceramic materials, porcelain, glass, silica and various stainless steels suitable.

The oxidation products are preferably removed from the reaction vessel in the form of a Mixture of a liquid and a gas. According to the invention, the liquid reaction mixture containing the oxidation products is introduced into a processing plant that has a separating device

an oxygen-containing gas in which in a con »5 has a high-speed evaporator and a continuously stirred reaction vessel combined under the scraper. are. This arrangement in The temperature and pressure combination given below with the previous propene conditions initiated solvents. oxidation reaction and downstream separation suitable Volume ratios between propene and steps represents a new, safe, simple, Oxygen range from 1: 5 to 15: 1. 3 ° economical and expedient procedure for

large-scale production and extraction of acetic acid.

Significant advantages of using the separation device with the high-speed evaporator and

Substance excess (over 1%) in the exhaust gas or above the scraper consists in the fact that, firstly, the one-half of the reaction mixture is prevented because the heat of the oxidation reaction leads to an otherwise dangerous concentration of explosive separation between the gaseous and the liquid Gases is present. In supplying a large gene products is used, and secondly, the amount of oxygen (or air) is also of transitioning solvent stripped propene total amount to from the mixture, so that the concen- is reduced 40 _s in minimum so that the Lösungstration of propene in the liquid phase, the oxy-medium load of the downstream distillation rate of the propene and the circulating columns become smaller. This reduction in the rate of change can be reduced. Solvent pollution has the advantage that for

An intimate contact of the reaction partner, ie separation of the products, smaller columns of required propene and the molecular oxygen in which there are 45 ij _c h. Thirdly, the amount of acidic components, is determined by the various known solvents. Measures brought about. especially formic acid, in which the

AIs starting materials pure propylene guided solvents can be reduced to traces and mixtures of propylene with other olefins, fourthly, the mass examples of the non-condensable gases game as ethylene or olefinic materials, the overall 50 _an d very volatile components removed so that sattigte compounds, for example propane , in the pressure of preventing an excessive

high product loss is required in the downstream work-up stages, is reduced. A special feature of the separating device ⁵⁵ with the high-speed evaporator and stripper is that in the high-speed evaporator about a third of the acids formed during the reaction are separated off and transferred. The treatment of the reactant oxygen leaving the bottom of the cutting evaporator results in considerable decomposition; the polymerisation mixture in a stripping column results in the remaining reaction and excessively strong side reactions in the circulating solvent. In general, temperature acids are used essentially completely, with the exception of about doors in the range from about 160 to 250 ° C. In the course of 0.05 to 0.2 percent by weight of the circulation. To ensure safe operation, the temperature should be removed from the solvent. This extensive temperature should be so high that dangerous peroxides cannot accumulate in considerable amounts. Corrosive formic acid, of which a temperature in the range from 180 to running solvent is preferred, has the advantage that 23 (FC, in particular in the range from 190 to 210 ° C. All devices for processing the bottom stream

an amount of 50% or more can be used. This can be done by cracking Hydrocarbon oils, paraffin wax or other petroleum fractions are produced.

For the reaction temperature and the reaction pressure, only those limits are to be complied with, at which Exceeding when carried out in the liquid phase Oxidation of propene with molecular

of the scraper can now be made from low-cost carbon steel, while previously very expensive, corrosion-resistant, stainless steels were required.

The separation device according to the invention with a high-speed evaporator and a scraper is For various reasons, consider cleaning devices that use multiple high-speed evaporators exhibit. First, a combination ensures

contains functional groups including carboxyl, carbonyl, alkoxy and oxy groups.

When this residue is returned to the reactor, it is there that it is oxidized first 5 Line to acetic acid instead of carbon oxides and water, if the reaction conditions are correct are chosen. However, this residue material can only be used within certain concentration limits returned to the reaction zone and in this

of a flash evaporator with a scraper an io for the production of acetic acid can be evaluated, better control and higher adaptability. The upper limit is critical. The exceeding method, since it is much easier for a stripper to change this upper limit leads to several effects, than to change the separation conditions. The one with a fast vaporizer. This is the first of these effects is a viscosity effect. Line achieved by controlling the heat given off by a reboiler to the scraper as a result of excessively high viscosity of the bottom flow. Since'ein the reaction vessel the scraper in the high-speed evaporator is only clogged and has an overweight condition, one scraper increases so that the amount of the solvent constantly returned to the reactor according to the number and efficiency of its solvent returned to the reactor is clogged The degree ao achieved with high-speed vaporizers decreases. Along with the decrease in the product separation cycle. A further advantage of the run-out solvent decreases the acetic acid arrangement according to the invention of a rapid evaporator, because together with the solvent in the circuit and a stripper compared to the use, smaller amounts of the multiple high-speed evaporators are that in the case of a residue that can be oxidized to acetic acid is, into the use of a separator, e.g. B. be returned with two »5 reaction vessels. Since the amount of high-speed evaporator an undesirably large amount of the solution propylene oxide returned to the reaction vessel (about 7 to 8 · / · the amount produced) decreases by means of and residue, the concentration decreases as a result of the decreasing dilution returned to the reactor Overall yield is reduced. At ctes not converted propene. As a result, use of the resulting combination erflndungsgemäßen 30 the oxidation of propene to produce yet gröeines flash evaporator with a scraper is ßerer residue levels -'- "· - ·""\ n ^;. *> N the other hand, the propylene oxide almost completely by
separated from the recycled solvent. Another benefit of using a
Wiper instead of a second rapid evaporator 35
It also consists in the fact that the acids are formed
of the circulating solvent to
to a small residue that is about 0.05 to
Is 0.2 percent by weight of the total recycle stream. When using a range of 25 to 50 percent by weight, be quick evaporators, on the other hand, about 1 to 2 percent by weight of acids are retained in the circulating solvent. ... concentrations up to about 75% carried out

The bottom stream of the scraper contains the mass, but with residue concentrations of the solvent and the residues, ie the 45 over 60%, the load on the downstream components, which boil higher than the solution processing equipment, decreases due to the viscosity of the medium. This bottoms stream will progressively towards the top of the reaction mixture.
fed to an absorber. Non-condensed gases In the present process, the concentration

in the vapor of the flash evaporator and the removal of the residue in the reactor as a result the lower area of the absorber 50 controls the amount of oxidized residue fed and flow in this against the soil and the amount of that formed during the oxidation electricity. Residue within the above specified

An important feature of the present ver limits are coordinated. This driving consists in the controlled oxidation of controlling the residue concentration in the reactor Residue material that is formed in the reactor is caused by a combination of factors. Through this oxidation the yield becomes particular to the temperature, the movement, the spoilage acetic acid generated in the process increased. residence time and the proportion of the reaction

The Oxyda partner carried out in the liquid phase. When a steady state condition of hydrocarbons is reached, the residue concentration in the solvent returned in the cycle of a complete mixture of oxidation products is determined. If th. For example, in the present case the residue concentration is too high, leading to the oxidation of propene in the liquid phase with problems discussed above, it can be exposed to more than forty individual molecules by enhancing the agitation compounds. In addition to these individual additions and / or reductions in (1) the reaction temperature, a polymeric residue is also generated (2) the residence time in the reactor and (3) the ratio material, which is a complex combination between the propene and propene supplied Settlement has and has not yet been fully described O ₂ quantities. When applying the measures (1), (2) has been. It is known, however, that there are different or (3) the other two factors must be so

109 615/252

which further increase the viscosity, so that the normal oxygen distribution even more disturbed and the complete oxidation of the residue to acetic acid is prevented.

In the absence of excess residue in the reactor, these phenomena result in the Procedure soon impracticable.

The residue concentration in the reactor should therefore be below 60 percent by weight, preferably in

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be made to achieve optimal results. Drawn steam contains all amounts of acid, entire

If, however, it turns out that the residue water and all low-boiling components and

concentration for maximum acetic acid production is fed to a low-boiling separating column,

If the supply is too low, the residue concentration can be that of the low boilers and a small amount of water tion in the reaction vessel can be withdrawn as vapor by reversing the figure 5. These low boilers

above for the reduction of the residue can be divided into fractions that are

concentration indicated increases various uses suitable as a solvent

will. are. These low boilers can also be divided into individual components

When difficult-to-melt components are divided in the process as mentioned above Forming residues that do not oxidize and that have become in io, with the help of various

As they accumulate in the system, they can be easily removed using methods such as selective adsorption and extraction

by removing part of the desorption, solvent extraction,

recycled solvent through a small extractive distillation or azeotropic distillation

Distillation column leads, for example with the tion, using a suitable extractant bottom stream of the stripper described here,
is fed. The bottom stream of the acid-low boiler separating

The vapor phase of the flash evaporator and column contains acetic acid, formic acid and

streifers is fed to coolers. That of these water and becomes an azeotrope distillation column

released non-condensable material containing benzene is supplied. In this column agrees and fed to a primary product separator, ao forms azeotropic mixtures with water and benzene

from the unreacted propene and propane than with formic acid. These mixtures go over and

Steam is drawn to a separator for these components- are fed to a cooler, which is filled with cooling water

leads to be. From this propene is cooled as steam. After condensing, these will be

withdrawn and returned to the reaction vessel - water and formic acid in a separator guided. One can also cleanly separate and collect all the vapor of the as from the benzene. from

Primary product separator in an absorber and this separator is the benzene in the circuit to the

Work up desorber, as described below, recycled azeotropic distillation column while

will. Water and formic acid as the bottom stream of the

Can be withdrawn from an upper area of a primary product separator. The bottom current of the Scheiders, a secondary stream is drawn off, which mainly contains 30 azeotrope distillation column

contains all low boilers, d. H. Products containing an acetic acid and an acetic acid refining

have a lower boiling point than acetic acid, supplied by the column, in which purified acetic acid is

For example, propylene oxide, methyl formate, acetal goes and is obtained as an end product,
dehyde, acetone, methyl acetate and methanol. This The treatment and use of the soil

Side stream is an acetaldehyde separation column 35. Stream of the solvent-acid separator is a

supplied, withdrawn from the acetaldehyde as vapor, an important feature of the present process. It

and recycled to the reactor, it has been found that various components

will. The remaining products are used as the bottom stream of this mixed stream, for example the propylene

deducted. The recycled acetal glycol and various of its monoesters, in particular

dehydration increases the acetic acid yield, based on 40 of their propylene glycol monoacetate and monoformate,

disturb the propene consumption by oxidation with additional course of the reaction in the reactor. This

oxygen to acetic acid. disturbing effects are mainly due to

The acetic acid produced and other valuable pro-

Products of the present oxidation process are oxidized to undesired oxidation products

from the bottom stream of the aforementioned 45.

Primary product separator won. This ground- The disadvantage that in the presence of the upstream contains the total amount of the solvent, listed, harmful components in the which consists of the cleaning device with the high-speed solvent returned in the circuit, Evaporator and stripper as steam is withdrawn by the present process in one was, furthermore, the acid, the water, which was not transformed with great advantage. This is done with the help of a the secondary stream of the primary product separator is achieved by solvent treatment, which follows remote, low-boiling components, including to the solvent-acid separation column Methanol, methyl acetate, acetone, isopropanol, will lead. The bottom stream of this column consists Allyl alcohol, biacetyl and others, as well as some predominantly, at about 88 to 92 percent by weight higher boiling components, including 55 the solvent that is in the primary reactor Propylene glycol and various formed in situ is used, e.g. B. from propylene glycol diacetate, too high-boiling Esters of propylene glycol, for example together with about 8 to 12 percent by weight propylene glycol monoacetate, propylene glycol pylene glycol, d. H. a polymeric material that has a monoformate and propylene glycol acetate formate. has a higher boiling point than the solvent. This

The soil stream containing the substances mentioned is fed to an ester concentration device.

stream of the primary product separator is led to a Lö-, which consists of a distillation column,

Solvent-acid separator supplied, of which all of which the propylene glycol and the glycol ester

higher boiling components including that in the form of a vapor with a high content of

Solvent, the propylene glycol and the pro these components are stripped off while

pylene glycol esters are withdrawn as a bottom stream. 65 the bottom stream, the remaining residue and

Treat and use this soil- containing most of the solvent, first

Stroms is discussed below. to the absorber and then to the reaction vessel

Which is returned from the solvent-acid separator.

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The discharged from the ester concentration device are operated, the reaction draws Steam is fed with the acetic acid from the mixture of these reactors into the bottom stream below the acetic acid refining column and the described separation device are introduced, the column for removing water and that from a flash evaporator and a waste formic acid united. This combined stream will consist of 5 more closely.

fed to a reaction vessel in which the pro- The reaction product is partly gaseous, part pylene glycol and the glycol ester in the presence of a wise liquid and is continuously a rapid acid catalyst, for. B. of toluenesulfonic acid, supplied to the evaporator, in which a pressure of 16 at esters and are unesterified to a certain extent. and at the bottom a temperature of 190 ⁰ C and the stream from the Veresteningsgefäß is maintained with pro io a temperature of 170 ° C pylene glycol diacetate, which were in this process for. From this quick it evaporates. the solvent preferred for oxidation, greatly increasing the majority of all low boilers, including the whole, was enriched and, with regard to the above-mentioned unreacted propene, CO ₂ and at least harmful components, the half was negligible, in this example about 60%, the other depleted. 15 low boilers together with about a quarter of the. By treating the solvent, acids, e.g. B. formic and acetic acid, all dissolved therefore certain harmful products of the primary gases and about 6 to 8% of the solvent removed as an oxidation reaction in an excellent solvent vapor. The bottom stream of the rapid agent can be converted for oxidation. Furthermore, the steam was fed to a stripping column, in which a pressure of about 1.74 at and a solvent loss at the bottom, which was maintained in the process instead of a temperature of 200 ° C., can be compensated for, due to mechanical causes, while at the same time which contained six distillation trays. The rest of the efficiency and controllability of the Oxyda low boilers, generally between 40 and 50% of the eruption reaction, can be increased. amount produced, in the present example about The ester mixture is a stripping column to- as 33%, furthermore essentially the total amount of the in which the excess acetic acid and other acids and lighter components and small amounts of water, formic acid and other 10 to 15 % of the solvent was removed as vapor products of the esterification and / or transesterification. The bottom stream of the stripper contained the bulk of the solvent and the vapor from the solvent and was fed to a medium-acid separator for further treatment. That are cleaned up by the scraper. The bottom stream of the stripping column drawn solvent contained about 55 weight consists predominantly of propylene glycol diester, percent residue, ie reaction products .. with which the in the present process preferably a higher boiling point than the solvent,
th solvent, and a small amount of that from the flash evaporator and the off of propylene glycol and its monoesters. This steam withdrawn in small quantities became the partial condensate bottom stream and is fed to the ester concentration device in each case to a cooler, which was returned with cooling water and operated there again as above. In the cooler that deals with the described. In the following exemplary embodiment, the direct non-condensable substances, including the non-oxidation of propene in continuous working 4 ° condensable gases, most of the COj, are described wisely. Furthermore, a novel process is described for about 7% of the total amount of low boilers, for example for separating and purifying acetic acid, 74% of the unconverted propene and propane, which was produced by the reaction. von.den condensable substances separated and expedient modifications of the work-up countercurrent to the bottom flow from the dismantling are also indicated. 45 he grazes. withdrawn solvent to the absorber. . fed. The removed from the cooler, which is not connected to the example below, was an autoclave with a condensable substance containing CO _?> Propane and a capacity of 1 1 as a reaction vessel in propene and is either disposed of or can be continuously working system used. 50 also compressed in a compressor and the solvent, propene and oxygen were fed to the absorber so that the propene is recovered through a floor passage directly into the room. A turbine stirrer was introduced into the absorber under pressure, which circulated at 900 rpm of 10.5 atmospheres, a temperature of about 75 ° C. at the top. The reaction vessel was heated electrically. and below a temperature of 95 ° C.-The temperature regulation was carried out by control 55 received. He had 25 floors. The non-condensing water flow in internal cooling coils. The free gases O ₂ , H _{1, N 2} , CH ₄ , CO and CO ₂ , the reaction temperature, were drawn off on a measuring strip from the upper end of the absorber. Propane recorded continuously. Propene and other soluble components are in operation, the reactants, consisting of the solvent, which is returned in the circuit to the reaction vessel of 92% propene and 99% oxygen, or for purification with propylene glycol acetate, a preferred one The propene is processed further, as in the case of solvent, fed to a reactor in which an upright is described.

Pressure of 60 atü and a temperature of 210 ° C The condensate from the cooler, which was kept down. The molar ratio between the stripe he downstream was with the condensate the supplied amounts of C ₃ H ₈ and O ₂ was 0.8. 65 from the condenser, the one after the flash evaporator. The total residence time was 8 minutes. One can be switched, united. This combined stream also provide two or more reactors, which held 95% of the low boilers produced, most of them are connected in parallel and under identical conditions the acids and about 20% of the solvent and

13 14

was fed to a primary product separator. and other valuable oxidized by-products. This consists of a distillation column treated with products. The bottom stream of the above 40 floors, in which a pressure of 2.8 at, a primary product separator described above contains the temperature of about -16 ° C and below a total amount of the solvent that is maintained from the temperature of 145 ° C and which was operated with the flash evaporator and the scraper in a reflux ratio of 6.0. The unconverted propene and propane were drawn off as vapor, furthermore acid, water, in the secondary stream of the primary product separator as steam, the primary product separator not removed and the boiling components, including methanol, fed to a separator for these components. From this, propane is drawn off as bottom stream ίο methyl acetate, acetone, isopropanol, allyl alcohol, bi- and propene as vapor. The propene is recycled to the reaction vessel, acetyl and other various high boiling components. components, including Acetonylacetat, Pro-Der Propen-Propan _T Scheider has 75 floors. In pylene glycol and various esters of the same, a pressure of 21 atm is maintained, and for example propylene glycol monoacetate, propylene glycol is heated above to 50 ° C and below to 55 ° C 15 kolmonoformiat and propylene glycol acetate formate, and operated with a reflux ratio of 11.7 as well a small amount of residue. Practice this stream. If the temperature at the lower end is fed to a solvent-acid separator, the separator is increased, and some propane can also go over- This column had 10 trays, at the upper end. 'a temperature of about 105 ° C and at the bottom in another process for the separation of ao end a temperature of 192 ° C and was under propane from the circulated propene is a pressure of 1.05 at and with a reflux of the steam the primary product separator operated with a ratio of 3. The total amount of steam mixed from the coolers to the desolvent and high-boiling components sorber. As mentioned above, the bottom stream was withdrawn as the bottom stream and the solvent, propene and propane degassing system fed to a discharge system, the sustainable bottom stream from the absorber being described directly. The vapor returned from the solvent to the reactor or withdrawn to clean the acid separator contains the Ge-propene, ie for the separation of the propene, further all of the acid, the water and the deeply processed. When the propane concentration of boiling components and a distillation in the reaction vessel rises to a value at which the propene oxidation is disturbed for the separation of acids and low boilers, a reboiler is fed from which the low boilers, a small supply of additional or excess amount Water and traces of high boilers as propane in the reactor were prevented by the fact that the steam was withdrawn.

Bottom stream of the absorber wholly or partially in The bottom stream of this column contained about

one for example by means of an adjustable control 35 74% acetic acid, about 8.5% formic acid, about

divisor from the bottom stream of the absorber 6.5% water and traces of other components and

branched - side stream into a not shown was fed to an azeotropic distillation column.

Desorber is performed, in which a pressure of 21 at This possessed about 70 floors and had a tem-

and above a temperature of 50 ° C and below a temperature of about 77 ° C and below a temperature

Temperature of 100 ° C was maintained. Here 40 from 125 ° C and was under a pressure of

solvent is drawn off as a bottom stream and operated at 1.05 atm. For the formation of the azeotropic

returned to the reactor. Propane and propene mixture was used in the benzene in the column

are withdrawn as vapor and a CjH ₈ -C ₃ H ₈ - was introduced at a point that was fed above the separator, in which a pressure of 21 atm was on the uppermost bottom. The amount of benzene corresponded

right and the above to about 50 ° C and below 45 9 parts by weight of benzene per part of as vapor of

is heated to 55 ° C. Propane is withdrawn as the bottom stream of the column. In this

deducted. Propene essentially in the same supply system, the benzene forms two different

composition as the starting material is dene azeotropic mixtures, one with water and one

Circulation in the flow of the reaction vessel with formic acid, instead of 'a ternary azeotropic

led propene starting material initiated. 50 mixture of these three components. Operational

From the primary product separator, an azeotropic mixture of benzene, water and

the fifth tray, from the top of the column an azeotropic mixture of benzene and formic acid as

calculated from a side stream withdrawn, the one withdrawn steam and a water circulation cooler

Acetaldehyde separation column is fed. Fed by. After the condensation, a ge

acetaldehyde was drawn off as vapor and benzene, water and formic acid were mixed together

recycled to the main reactor. Collector supplied, in which the mixture is in a

The other low boilers were removed as the bottom stream - the upper benzene phase and a lower phase that separated

drawn. This can expediently in fractions of about 42% water, 55% formic acid and about

which contained as 3% acetic acid for various purposes. These components were Solvents are usable or optionally 60 removed from the bottom of the collector. The benzene of the

The upper phase, which was also further separated into individual components, was supplemented with further benzene the can. In the acetaldehyde separation column and in the circuit to the azeotropic distillation column

was a temperature of about 22 ° C and recycled above. ,

Maintain a temperature of 6O ⁰ C below. The bottom stream of this column consisted of

She had 70 floors and was made with a pressure of 65 largest part (more than 86 weight percent) 1.05 at and a reflux ratio of 6.0 be acetic acid and also contained small amounts of

drove. higher boiling components. It was fed to a vinegar-now is the extraction of the acetic acid produced acid affination column, which loads 40 floors

sat, had a temperature of about 118 ° C above, a temperature of 130 ° C below and below one Pressure of 1.05 at and with a reflux ratio of 5.0 was operated. When steam was cleaned, Acetic acid stripped off. S.

. The bottom stream of the solvent-acid separator contained about 90 vol. Propylene glycol diester, mainly the diacetate (about 88%) and a small amount of acetate formate. (about 2%), the remainder mainly propylene glycol and its monoesters, propylene glycol monoacetate and monoformate, as well as a small amount of acetonylacetate and residue. This stream was fed to a distillation column for Esterkonzentration which had 50 trays, the top having a temperature of 186 ° C and below a temperature of 195 ⁰ C and was operated at a reflux ratio of 7.0. The bottom stream of this column consisted of more than 97% of the propylene glycol diesters, which can be used as solvents for the oxidation reaction, the remainder being essentially residue. This stream was combined with the stream from the stripper and fed to the absorber, the stream of which was returned to the main reactor This absorber stream contained about 50 percent by weight of residue on entry into the reaction vessel are that the residue concentration in the reaction vessel is kept relatively constant.

The vapor withdrawn from the ester concentration column, which is about 20 percent by weight of the opposite an oxidation attack of volatile propylene glycol, its monoesters and acetonylacetate was fed to an esterification vessel in which, with the help of an acid catalyst (e.g. toluene sulfonic acid) the components mentioned have been esterified and transesterified to form useful propylene glycol diesters. Before entering the esterification vessel the vapor flow was combined with the flow, which was a mixture of the bottom flow the acetic acid refining column and a stream branched off from the bottom stream of the water-formic acid separation column was thus at an excess of acetic acid was ensured for the esterification reaction. This combined stream contained now about 61% propylene glycol ester, about 17% of the volatile components mentioned above and residue, about 21% acetic acid, the remainder unmarked high boilers. This stream became the esterification vessel fed, in which a temperature of 170 ° C and a pressure of 1.05 at are maintained would. After completion of the reaction, the esterification product contained about 70% useful propylene glycol diesters (about 14 weight percent more than in the reactor feed stream), about 6% acetonylacetate, propylene glycol and its monoesters (about 62 percent by weight less than in the feed stream of the reactor), about 18% acetic acid, the remainder esterification by-products and persistent High boilers.

The ester mixture of the esterifier was fed to a solvent stripping column which had 20 plates, a temperature of 150 ° C. above, below had a temperature of 200 ° C and under a pressure of 1.76 at and with a reflux ratio operated from 7.0. The steam withdrawn from this scraper contained over 77% acetic acid, about 6% water and small amounts of formic acid, lower and higher boiling components and was fed to the acid intermediate boiler column for further treatment. The bottom stream of the stripper was about 92% enriched in the solvent usable diesters, the remainder inconsistent Components, and was recycled to the ester concentrator so that the volatile components have been converted into persistent solvent esters. These useful, Resistant solvent esters were recycled to the absorber and ultimately to the reaction vessel.

In a typical oxidation process according to this embodiment, the main reaction vessel the starting materials are supplied in approximately the following quantities per hour: 575 g propene, 700g oxygen, 4600g solvent (e.g. propylene glycol diacetate). In the steady state (residence time in the reaction vessel about 8.0 minutes) the propene conversion was about 50% and the oxygen conversion 99.95%. Acetic acid is obtained in a yield of about .40 mol percent as well as smaller ones Quantities of other oxidation products.

Claims (1)

Claim: Process for the production of acetic acid by oxidation of propene and distillative Obtaining acetic acid from the reaction product, characterized in that man a) propene with oxygen in the liquid phase in the presence of at least 25 percent by weight, based on the liquid reaction mixture, a fully acylated polyoxyalkane, Polyoxycycloalkane or polyglycol, preferably propylene glycol diacetate, contain- ... the solvent in a temperature range from 160 to 250 ° C, preferably 180 to 230 ° C, and a pressure range of 0.5 to 350 at, preferably 5 to 200 at, implements b) -and the reaction product using a flash evaporator and a stripper in a gas phase containing the acetic acid and low-boiling products and a gas phase Most of the solvent, high-boiling products and the residue containing it Liquid phase decomposed, c) the liquid phase is returned to the oxidation zone via an adsorber, while adhering to a residue concentration below 60 percent by weight in the reaction mixture, d) the gas phase is subjected to condensation by cooling, the non-condensed Returns vapors to the oxidation zone via the adsorber, from the condensate Propene and propane are distilled off and the propene and the acetaldehyde obtained from a secondary stream are returned to the oxidation zone and the remaining con 109 615/252 densate in a distillation residue and in one containing the total amount of acetic acid Distilled distillate, e) the low-boiling components are first distilled off from this, the acetic acid through azeotropic distillation with benzene freed from water and formic acid and then purified by distillation f) and the distillation residue of the condensate together with the distilled, deep- boiling, propylene glycol and glycol monoester containing constituents of a concentration column Esier, whose Vapors together with the acetic acid from the bottom stream of the acetic acid refining column and the bottom stream of the azeotropic distillation in the presence of a catalyst, preferably toluenesulfonic acid, to be fully acylated Esterified or transesterified polyoxyalkanes and fed them back to the oxidation process.