DE1127339B - Process for the production of alcohol-free and water-free acetals by extractive distillation - Google Patents

Description

The use of an alcohol-free and anhydrous acetal is required for various reactions to avoid unwanted side reactions. However, technical acetals contain from manufacture still a few percent alcohol, which by simple distillation as a result of being too close together Boiling points or can no longer be separated as a result of azeotrope formation. The processing e.g. a Methylalansatzes from methanol and formaldehyde can therefore by distillation at best only up to Composition of the azeotropic mixture take place.

To remove z. B. the methanol from methanol-containing methylal has already been proposed that Shake out methylal with concentrated aqueous salt or alkali hydroxide solutions. Apart from that the fact that the methanol cannot be completely removed in this way is obtained in this treatment a water-containing methylal, from which the water only through a further azeotropic distillation or must be removed again by desiccant. This procedure is cumbersome and inconvenient tied together.

Another proposal is based on the methanol-methylal azeotrope to distill with the addition of water. In this way, a methanol-free methylal is obtained, but water is brought back into the end product, which is only in a second stage either by desiccant or by a further azeotropic distillation must be removed. There are basically the same disadvantages as with the above procedure.

It has also been proposed to dehydrate alcohol using glycol. In this case the alcohol is the crude product of the extractive distillation.

It has been found that pure alcohol-free and water-free acetals can be obtained from alcohol-containing and / or water-containing ones Acetals can be obtained if you mix the mixture in the presence of polyhydric alcohols, Process for the production of alcohol

and anhydrous acetals

by extractive distillation

Applicant;

Wacker-Chemie GmbH,
Munich 22, Prinzregentenstr. 22nd

Dr. Eduard Enk, Dr. Fritz Knörr

and Dr. Hellmuth Spes, Burghausen (Obb.),

have been named as inventors

bonds which can be used with advantage in the method according to the invention are, for example Polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, 1,2,3-triaminopropane, amino alcohols such as ethanolamine, diethanolamine, triethanolamine, polyols such as glycol, glycerine, 1,3-butylene glycol, Diethylene glycol, triethylene glycol, or polyols that are partially, but not entirely, etherified, such as alkyl ethylene glycols, alkyl diethylene glycols and alkyl triethylene glycols.

As the starting product for the production of the alcohol-free and water-free acetals, alcohol-based and water-based Acetal mixtures can be used. Such mixtures fall e.g. B. as a reaction product in the Production of acetals from alcohols and aldehydes. Leave with the method according to the invention work up these mixtures in a single step to form anhydrous and alcohol-free acetal. Of course Mixtures that contain only one of the two interfering components can also be used according to this

Glycol ethers, polyvalent amines or alcohol can be separated with advantage,
amines extractive distilled. In addition, the method can be advantageous in

Proven when a compound of the general formula RX »is used as the extractant, where R is a heteroatom-substituted or unsubstituted hydrocarbon radical whose straight or branched carbon chain can optionally also be interrupted by heteroatoms. X has the meaning of -OH, -OR'-, -NH ₂ -, - NHR or - NR _'2 -, wherein at least one of the groups - OH or-NH ₂ -is. In these groups, R 'denotes an alkyl radical. η denotes an integer that is greater than 1. Ver-alcohol-acetal mixtures are used whose alcohol is not identical to the alcohol component of the acetal and whose separation by simple distillation does not succeed due to boiling points that are too close together.

The amount of compound required to completely remove the alcohol and / or water RX «can easily be determined by a preliminary test.

The method can e.g. B. be carried out so that the acetal to be cleaned in the lower part

209 559/504

3. ·. '■■ 4

a fractionation column and the compound RX ₇₁ glycol fed in a volume ratio of 6: 1. With one in the upper part is added continuously. With an hourly addition of 508 g of mixture and 109.6 g of an ethylene glycol, which can easily be determined by a preliminary test, an average of 490 g hourly ratio of crude acetal to RX ^ can be obtained at the top of pure methylal at the top of the column and 125 g of the column, the pure acetal the bottom of the 5 bottom drain removed. The yields are in the prak column, the alcohol and / or water-containing tables are deducted almost quantitatively with complete separation, binding RX ». Work-up In the same way and with the same success as in

the bottom drainage into the components takes place through Examples 1 to 4 can be with ethylene glycol Stripping off the lower boiling components. Separate the following mixtures: 1,3-dioxolane-water,

According to the process according to the invention, 1,3-dioxolane-ethanol, 1,3-dioxolane-ethanol The pure acetal obtained can easily be used as reaction water, propionaldehyde dimethylacetal, propanol, serve partners for reactions in which the propionaldehyde diisopropyl acetal - 2 - ethylbutanol, Essence of alcohol or water excluded methoxyethoxymethane - methanol, butyraldehyde become must, such as in the reaction with ketene ethylene acetal - isoamyl alcohol, methyl ethyl ketone / 3-alkoxycarboxylic acid alkyl esters. 15 ethylene acetal — butanol, acetone ethylene acetal — buta-

nol, acetone ethylene acetal — water. example 1

Example 5 Tn one provided with a still.

Column, the flask of which has a continuous over- 20 · A mixture of 94.6% methylal and 5.4% methalauf owns, a mixture nol and diethylene glycol are in the column in the lower third from 76% methylal and 24% methanol with a volume ratio of 3: 1 as in Example 1. Temperature of 35 ° C and ethylene in the upper third with an hourly addition of 258 g of methyl alglycol introduced at a temperature of 62 ° C. Methanol mixture and 112 g of diethylene glycol The volume ratio of the liquids introduced is an average of 241 g of pure methylal per hour is 4: 1. With an hourly addition of 332.5 g of top of the column and 128 g of bottom effluent obtained. Mixture and 111g of ethylene glycol are in the through- The yields are almost 100%, cut 250 g of pure methylal per hour at the head of the

Column and 189 g of bottom effluent withdrawn from - Example 6

which obtained by distillation 78 g of methanol ³ °

will. The sump drain is practically free of a mixture of 94.6% methylal and 5.4%

Methylal. The yields are practically full methanol and triethylene glycol are the column constant separation almost quantitative. in a volume ratio of 2: 1 as in Example 1.

With an hourly addition of 344 g of methyl alcohol

Example 2 35 methanol mixture and 225 g of triethylene glycol

an average of 319 g of pure methylal am per hour

As in Example 1, a mixture of the top of the column and 278 g of bottom effluent is obtained from the column, from 94.6% methylal and 5.4% methanol and the yields are almost quantitative. Ethylene glycol supplied in a volume ratio of 6: 1.

With an hourly addition of 515 g of mixture and 40 - Example 7

111 g of ethylene glycol are an average of 485 g of pure methylal per hour at the top of the column and As in Example 1, a mixture of 544 g of bottom drain with 27 g of methanol is withdrawn from the column. from 94.6% methylal and 5.4% methanol and the yields are supplied in the case of practically complete 1,3-butylene glycol in a volume ratio of 4: 1. Separation almost quantitative. 45 With an hourly addition of 344 g of methylal-. . _T methanol mixture and 101 g of 1,3-butylene glycol are Example i the an average of 323 g of pure methylal per hour 534 g of a mixture prepared by reaction at the top of the column and 120 g of methanol with formaldehyde in the bottom outflow. With practically all of the water and a catalyst and consisting of 50 separation, the yields are almost 100%. 60% methylal, 20% methanol and 20% water,. hourly as in Example 1 in the lower example part of a fractionating column with a temperature The apparatus described in Example 1 are introduced from 30 to 35.degree. The ethylene glycol, a mixture of 94.6% methylal and 5.4% methanol, is added in the upper part of the column at a 55 with 33 ⁰ C and methyl diglycol with 25 ° C in a volume temperature of 60 to 63 ° C and is 111 g per 3: 1 ratio. With an hourly addition hour. The volume ratio of mixture — Ex— of 258 g of the methylal-methanol mixture and of the traction agent is 6: 1. At the top of the column, 101 g of methyl diglycol are taken off an average of 318 g of pure methanol borrowed per hour, 237 g of pure methylal at the top of the column and anhydrous methylal, while 120 g of bottom effluent is obtained from 60 which is distilled to the bottom of the column every hour 767 g of a methanol can be separated into its components. Drain the water-ethylene glycol mixture. The yields are almost quantitative, but the separation is practically complete
almost quantitative. Example 9

Example 4 ^ _Gcmisc ^ ^ ₅ 94 _; 6 <y _o methylal and 5.4%

As in Example 1, the column will be a mixture. Methanol as well as ethanolamine are the column

from 97% methylal and 3% water and ethylene in a volume ratio of 5: 1 as in Example 8

guided. With an hourly addition of 430 g of the methylal-methanol mixture and 98 g of ethanolamine 405 g of pure methylal per hour on average are obtained at the top of the column and 121 g of bottom effluent. The yields are almost quantitative.

Example 10

A mixture of 97% methylal and 3% water and triethanolamine are the column as in Example 8 supplied in a volume ratio of about 6: 1. With an hourly addition of 422 g des Methylal-water mixture and 80 g of triethanolamine are an average of 416 g of pure, anhydrous per hour Received methylal at the top of the column and 84 g of bottom effluent. The yield is close quantitatively.

Example 11

A mixture of 94.6% methylal and 5.4% methanol and triethylenetetramine are the Column as in Example 8 in a volume ratio of 4: 1. With an hourly addition of 344 g the methylal-methanol mixture and. 98 g of triethylenetetramine are an average of 322 g per hour pure methylal obtained at the top of the column and 118 g of bottom effluent. The yield is close quantitatively.

The compounds RXji mentioned in Examples 5 to 11 can also be used with the same success the following mixtures can be used:

1,3-dioxolane water,
1,3-dioxolane -ethanol,
1,3-dioxolane — ethanol — water, propionaldehyde dimethylacetal — propanol, propionaldehyde diisopropyl acetal — 2 -ethylbutanol, methoxyethoxymethane —methanol, butyraldehyde-ethylene acetal — isoamyl alcohol, methyl ethyl ketone-ethylene acetal — butanol, acetone -ethylene acetal — butanol, acetone-ethylene acetal.

35

40

Example 12

45

A mixture of 60% methylal, 20% methanol and 20% water and ethanolamine are used Column as in Example 8 in a volume ratio of 6: 1. With an hourly addition of 415 g of the mixture and 80 g of ethanolamine are an average of 330 g of pure methylal per hour Obtained head of the column and 161 g of bottom effluent. The yield is almost 100%.

55 Example 13

The apparatus described in Example 1 is a mixture of 75% acetaldehyde and dimethylacetal 25% methanol at 35 ° C and ethanolamine at 57 ° C in a volume ratio of about 2: 1. With an hourly addition of 180 g of the acetal-methanol mixture and 101 g of ethanolamine an average of 133 g per hour of pure acetaldehyde dimethylacetal at the top of the column and 145 g of bottom effluent obtained, which can be broken down into its components by distillation. The yields are almost quantitative.

Hydrous acetaldehyde dimethyl acetal can be purified in the same way. Furthermore can Ethanolamine by the compounds RX «used in Examples 4 to 8 or 10 and 11 be replaced with equal success.

Example 14

A mixture of 80% acetaldehyde diethylacetal and 20% n-propanol and diethylene glycol can be used the column with temperatures of 67 and 80 ° C as in Example 13 in a volume ratio of about 4: 1 fed. With an hourly addition of 374 g of the mixture and 90 g of diethylene glycol are im Average hourly 295 g of pure acetaldehyde diethyl acetal at the top of the column and 165 g of bottom effluent obtain. The yields are almost 100%

Hydrous acetaldehyde diethyl acetal can be purified in the same way. Furthermore, the diethylene glycol can be replaced with the same success _{by the compounds RX ra used in Examples 4 and 6 to 11.}

Example 15

The apparatus described in Example 1, but operating at 10 Torr, is a mixture of 80% Formaldehyde dibutyl acetal and 20% sec. Octanol at 50 ° C and triethylene glycol at 30 ° C by volume of about 3: 1 fed. With an hourly addition of 270 g of the acetal-alcohol mixture and 90 g of triethylene glycol give an hourly an average of 212 g of pure formaldehyde dibutyl acetal at the top of the column and 143 g of bottom effluent 'obtained by distillation into its components can be disassembled. The yields are almost quantitative.

Claims (2)

PATENT CLAIMS: 1. A method for obtaining pure, alcohol-free and anhydrous acetals from alcohol- and / or water-containing acetals by extractive distillation, characterized in that a polyhydric alcohol, a glycol ether, a polyhydric amine or an alcoholamine is used as the extractant. 2. The method according to claim 1, characterized in that a compound of the formula RX »is used as the extractant, in which R denotes a hydrocarbon radical substituted or unsubstituted by heteroatoms, the straight or branched carbon chain of which can optionally also be interrupted by heteroatoms, Xeine — OH- , - OR ', - NH ₂ -, --NHR' or --NR ' ₂ group, where at least one of the groups _{--OH or --NH 2} is, R' is an alkyl radical and η is an integer greater than 1 is. Documents considered: Swedish Patent No. 148 544. © 209 559/504 4.