DE2452568A1 - CARRIER STEAM DISTILLATION - Google Patents

Description

HAARMANN & R E I M E R GMBH

B / Hor

Carrier steam distillation

The present invention relates to a new process for the separation or purification of thermally sensitive products by distillation Carrier vapor connections.

The carrier steam distillation is a well-known process for Purification of thermally sensitive compounds by distillation. However, it is not applicable to a number of connections, because even with this gentle distillation process the thermal Stress is still too high, so that the compounds only in poor yields and / or an unsatisfactory degree of purity can be obtained.

A carrier steam distillation process has now been found where the thermal stress on the compounds to be distilled is so low that it can also be used to create thermally extremely sensitive compounds that are produced using the usual carrier vapor distillation process cannot be distilled or can only be distilled with decomposition. The inventive The method consists in that the superheated vapor of an organic solvent is used as the carrier vapor and that the superheated, laden with the compound to be distilled solvent vapor by treatment with condensed Cooling solvent in countercurrent while the amount of condensed solvent is measured so that one from the loaded superheated steam, a supersaturated solution of the compound which is approximately boiling point is obtained.

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609820 / 048B

An "about boiling point" solution is a Lo-. solution that is at boiling temperature or a few degrees C, e.g. 1 to 3 ⁰ C, below.

This type of evaporation condensation of the laden, superheated steam is carried out in a single process step 1.) a cooling of the steam to the boiling point of the solvent used and 2.) a concentration of the condensed vapor to a saturated solution of the distilled compound at the boiling point of the solvent achieved. Due to the inventive design of the carrier steam distillation an extremely short residence time of the compounds to be distilled at an elevated temperature is achieved. As a result of this short residence time, the thermal stress on the compounds to be distilled drops so much that no more decomposition occurs. The compounds are obtained in almost 100% yield and in high purity.

The embodiment of the carrier steam distillation according to the invention also has the technical advantage that all of the organic solvent used in the process is in high purity, too recovered from traces of distilled compound free form and therefore used again and again, d. H. in the cycle can be performed. Another technical advantage is that the purified compound is in the form of a homogeneous Solution accrues, which can be separated without difficulty leaves, and from which the compound crystallizes out on cooling.

Find as carrier vapor for the process according to the invention use of organic solvents which are inert towards the product to be cleaned, which, at least in the Heat, have good solvency for the compounds to be distilled and from which the compounds to be distilled crystallize, which is also thermally stable.,

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and are readily condensable. Its boiling point should be at normal conditions in the range of about 60 to 190 C, preferably 100 to 150 ⁰ C.

In principle, all organic compounds are suitable as organic solvents that are used as carrier vapor, which meet the aforementioned requirement. Examples include: aliphatic and alicyclic saturated Hydrocarbons such as hexane, heptane, octane, nonane, decane and cyclohexane and those substituted by lower alkyl radicals Derivatives of these compounds; furthermore benzene and benzene derivatives, which optionally with one or more lower alkyl radicals are substituted, e.g. B. toluene, ethylbenzene, n- and iso-propylbenzene, butylbenzene and trimethyl !benzene; furthermore halogenated, preferably chlorinated, Derivatives of the aforementioned hydrocarbons, such as chlorobenzene or o-, m- and p-dichlorobenzenes. Furthermore aliphatic Alcohols e.g. B. ethanol, or chain-like or cyclic aliphatic ethers, e.g. B. di-n-butyl ether, diisopropyl ether and 1,4-dioxane; Ketones e.g. B. methyl isobutyl ketone and dipropyl ketone, as well as phenol and phenolic ethers such as anisole and phenetole.

The carrier vapor for the process according to the invention has proven to be especially hexane, cyclohexane, benzene, toluene, ethylbenzene, chlorobenzene and anisole.

The distillation temperatures in the process according to the invention are in general]
between 140 and 190 ⁰ C.

Process in general between 110 and 220 ⁰ C, preferably

The inventive evaporation condensation of the superheat, laden vapor can both at normal pressure and at a 100th Torr, z. B. at 120, 150 or 360 Torr, lying negative pressure can be made.

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The method of the invention is advantageous in that way

carried out that one containing the compound to be distilled Mixture or crude product (1), or the solution of the mixture (crude product (I)) in the used as carrier vapor Solvent, treated in a conventional manner in countercurrent with superheated carrier vapor in an evaporator (2). Included any higher-boiling impurities already contained in the mixture or crude product feed (1) separate, Resins and inorganic compounds in the bottom (3) of the evaporator and can be drawn off there. The overheated, laden one Vapor (4) is then passed into a column (5), where it is condensed by the condensed solvent flowing towards it

(6) to a boiling point, but not more boiling solution saturated with distilled compound

(7) is cooled and concentrated at the same time.

Leaves the required amount of condensed solvent from the temperature difference to be overcome: temperature of the superheated, laden steam - boiling temperature of the Calculate the organic solvent used as the carrier vapor. However, it can also be determined empirically by that the feed of condensed solvent (6) is adjusted so that an approximately boiling temperature during the evaporation condensation having, but just no longer boiling, solution (7) saturated with distilled compound is obtained.

The same organic solvent is used to generate the carrier vapor and as the cooling liquid.

The carrier steam distillation process according to the invention is suitable suitable for the distillation of thermally sensitive, crystallizable and at least steam-distillable organic compounds. Examples of such compounds are:

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Oximes such as cyclohexanone oxime; Lactams, such as ξ, -caprolactam; aromatic nitro compounds such as nitrophenol ethers, ζ. Β. Nitroanisole, nitrodiphenylamines, and nitroanilines, e.g. B. 2,4-dinitroaniline; halogenated anilines, ζ. B. 2,4-dichloroaniline; Quinones such as o- and p-benzoquinone; aromatic bis-hydroxy compounds, such as catechol and hydroquinone; substituted aromatic aldehydes such as piperonal and anisaldehyde and phenols substituted by lower alkenyl radicals and lower alkoxy radicals, such as eugenol and isoeugenol.

The process according to the invention has proven to be particularly useful for the distillative separation or purification of _{4-hydroxybenzaldehydes which are optionally substituted by one or more C 1} -C 4 -alkoxy groups, such as 4-hydroxybenzaldehyde, 4-hydroxy-3-methoxy-benzaldehyde & (vanillin), 4-hydroxy-3-ethoxy-benzaldehyde (ethyl vanillin), 4-hydroxy-3-propoxybenzaldehyde and 4-hydroxy-3-isopropoxybenzaldehyde.

With the help of the method according to the invention it is possible for the first time to distill these thermally extremely sensitive compounds without decomposition and in this way, for. B. from Reaktiongsgemischen as in the preparation of the compounds apply (see. E.g., B. Organic Reactions (1957), Volume IX, page 37 u. _T f .; German Offenlegungsschrift 2,115,551) to separate.

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example 1

The carrier steam distillation according to the invention was carried out in the apparatus shown in FIG. Namely, the superheated steam carrier, 1.3 kg of toluene / h in the evaporator (9) evaporated to produce superheated of toluene vapor obtained "in the second evaporator (10) at 160 ⁰ C. The superheated toluene vapor (8) in the evaporator (2) (Falling film evaporator) in countercurrent with 3.3 kg / h of a solution (1) of 2.6% by weight of vanillin in toluene. The higher-boiling components and inorganic compounds in the feed (1), about 5 g / h, deposited in the sump (3) of the evaporator. The vapor (4) laden with vanillin was fed to the distillation column (5) (bubble-cap column) and there with condensed toluene (6), reflux from the condenser (11) , condensed in countercurrent so far (partially condensed) that in the bottom (7) of the column (5) 135 g / h of a boiling point saturated solution of vanillin in toluene were obtained, from which the vanallin crystallized on cooling. Accruing, vanillin-free toluene was after removal of the Return (6) divided into two streams, stream 12, which was discharged and the amount of which corresponded to the toluene content of feed (1) (' ^W 3.2 kg / h) and stream (13) (r ^ 1.3 kg / h ) which was fed back into the evaporator (9).

In this procedure, the vanillin was obtained in practically 100% yield in the form of white crystals.

Example 2

It was worked / only was as described in Example 1 instead of vanillin (3-methoxy-4-hydroxy-benzaldehyde) ethyl vanillin (3-ethoxy-4-hydroxy-benzaldehyde) is distilled.

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There was added 2.5 kg / h of toluene-carrier steam at 4.5 kg / h of a solution (1) from 3.3 wt -.% Äthylvanillin loaded in toluene. In the bottom of the column (5) about 250 g per hour of a saturated solution (7) of about boiling point of ethyl vanillin in toluene were withdrawn, from which the ethyl vanillin crystallized in the form of colorless crystals on cooling. The ethyl vanillin was obtained in practically quantitative yield.

A product of the same purity was also obtained in the same yield if ethylbenzene was used instead of toluene was used.

Example 3

The procedure was as described in Example 1, except that 2.5 kg / h of chlorobenzene were used as the carrier vapor instead of toluene (8) used. 2.5 kg of a solution (1) of 10% by weight vanillin in chlorobenzene were fed in. 3.5 g of higher-boiling compounds per hour fell in the bottom of the evaporator (2) at. In the bottom of the column (5), 400 g of a saturated solution (7) with approximately boiling temperature were per hour deducted from vanillin in chlorobenzene, from which the vanillin separated out in the form of colorless crystals on cooling. Yield: practically quantitative.

A product of the same purity was also obtained in the same yield if anisole was used instead of chlorobenzene was used.

Example 4

1.5 kg 18O ⁰ C superheated anisole were loaded within 1.5 hr. With a solution of 100 g vanillin in 200 g of anisole. The superheated laden steam (4) became:

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in experiment a)

in column 5 of the evaporator described in Example 1 subject to condensation. From the hot, saturated solution (7) withdrawn from the bottom of the column, the Cooling 97 g of vanillin in the form of colorless crystals.

in experiment b)

completely condensed in the usual way, and the resulting dilute solution of vanillin in anisole then through Concentrate in vacuo (<5 torr) until the solution is saturated of the aldehyde concentrated. When the concentrated solution cooled, 79 g of vanillin separated in the form of red-brown crystals away; in addition, 20 g of a resinous residue was obtained.

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Claims (4)

24525 (58 claims 1. Process for the distillative separation or purification of thermally sensitive compounds using carrier steam, characterized in that the superheated solvent vapor laden with the compound to be distilled is passed through Treating with condensed solvent in countercurrent cools and thereby the amount of condensed solvent so dimensioned that from the superheated, laden steam a saturated solution of the compound having approximately the boiling point arises. 2. The method according to claim 1, characterized in that the organic solvent hexane, cyclohexane, benzene, Toluene, ethylbenzene or anisole are used. 3. The method according to claim 1 and 2, characterized in that that one d: executes. that the distillation at temperatures of 110-220 ⁰ C. 4. The method according to claim 1 to 3, characterized in that it is used for the separation or purification of optionally substituted by one or more C-, - C λ-alkoxy groups Uses 4-hydroxybenzaldehydes. HR 58 - 9 - 609820 / D485 I ⁴⁰ -ι. Blank page