DE1172687B - Process for purifying dioxolane - Google Patents

Description

Process for purifying dioxolane The manufacture of dioxolane with the help of etherifying catalysts made of ethylene glycol and formaldehyde known.

The crude product produced in this way contains varying amounts of water, unreacted free formaldehyde and small amounts of free acid, for example formic acid. For cleaning the crude dioxolane from the impurities mentioned several processes are already known. This can be used to remove the formaldehyde a treatment with sodium bisulfite can be done while the water is salted out can be separated with common salt. Then this is done with the acid with soda removed and the dioxolane, after drying with calcium chloride, by distillation isolated (U.S. Patent 2,095,320). A dioxolane is obtained here, which is contaminated with traces of sulfur dioxide despite the soda treatment. aside from that is the unreacted formaldehyde due to the bond to sodium bisulfite for a Recovery practically lost.

It is also known that dioxolane forms an azeotropic mixture with water which contains about 6.7% water (U.S. Patent 2,395,265). It is therefore Attempts have also been made to remove the water by azeotropic distillation. It has been shown, however, that the resulting distillates are free formyldehyde contain.

Finally, the free formaldehyde in crude dioxolane is also known to bind by reaction with ammonia as hexamethylenetetramine and the dioxolane to be separated from this mixture by distillation.

However, this procedure involves post treatment for removal of ammonia necessary, but always small but detectable amounts of ammonia remain in the dioxolane distillate. This way is therefore not very suitable for extraction of a pure dioxolane.

A method for purifying crude dioxolane has now been found which does not have the disadvantages of the known processes and which is very pure Dioxolane yields.

The method according to the invention for purifying crude dioxolane consists in that one crude dioxolane with a not miscible with this in any proportion inert organic liquid which cannot be split off under the process conditions Contains elements and also no compounds of such elements under the process conditions able to form, treated in such a volume ratio that a delamination occurs, separates the dioxolane-containing layer, this with aqueous alkali or Alkaline earth lye or with an alkali or alkaline earth oxide or with an alkali or alkaline earth metal treated, after separation of the dioxolane-containing liquid this is distilled and optionally the purified dioxolane obtained, an aftertreatment subjected to filtration through a molecular sieve.

Such inert organic liquids are used as extractants suitable against alkali and alkaline earth metals and their oxides or hydroxides too are stable at their boiling point and, moreover, are not stable under the process conditions and also contain removable elements such as halogens, nitrogen or sulfur no compounds, especially volatile compounds of such elements among the Ability to form process conditions. Such inert organic liquids are, for example, diethyl ether, decahydronaphthalene, tetrahydronaphthalene, paraffin oils.

Tetrahydronaphthalene is preferably used in the process according to the invention (Tetralin) is used.

The use of such organic liquids is advantageous have the lowest possible dissolving power for formaldehyde and / or water.

The volume ratio in which the organic liquid is used depends on the layer separation that occurs. Appropriately is the volume ratio selected so that a two-layer separation takes place. at the use of tetralin is the volume ratio of tetralin to crude dioxolane expediently 1: 1, and when using paraffin oil is expedient a volume ratio of 4: 1 is used.

Which consists essentially of the organic liquid and dioxolane The existing layer contains, for example, only 3.2% of that present in the raw product Water and only 3.9% of the originally present formaldehyde.

The treatment with the inert organic Liquid carried out in the presence of sodium chloride and / or calcium chloride.

The treatment of the resulting dioxolane-containing layer is with aqueous alkali or alkaline earth lye or with an alkali or alkaline earth oxide, which should expediently be free of peroxide, or the corresponding metals. If aqueous alkali or alkaline earth lye is used, it expediently contains it 500in of the hydroxide in question.

When using an alkali or alkaline earth metal dispersion, choose one advantageously such amounts of metal that on the one hand a stable as possible Dispersion is formed and, on the other hand, complete conversion is achieved. For example An approximately 330% dispersion of sodium in tetralin has proven particularly useful. The treatment with the substances mentioned removes the free formaldehyde removed a Cannizzaro reaction. At the same time there is another drainage instead of. After rapid delamination and separation of the lye and, if necessary Subsequent filtration is a formaldehyde-free solution of the dioxolane in the inert organic liquid. The separation of these components takes place on by distillation. The resulting dioxolane contains small amounts of water (less than 0.3 percent by weight) no further impurities. With a follow-up treatment the purified dioxolane by filtration through a molecular sieve becomes a completely anhydrous dioxolane obtained, in which there is no more water with the Fischer reagent can be proven.

The process according to the invention can advantageously also be carried out continuously be performed.

Example 1 In a mixing vessel, 0.5 l of crude dioxolane (534.1 g) of the composition 71.83 percent by weight dioxolane (383.6 g), 26.08 percent by weight Water, 1.58 percent by weight of free formaldehyde (= 8.41 g) with 0.5 l of tetralin (480.7 g) and 40 g of sodium chloride are added, and the mixture is stirred for a few minutes.

After stirring, the layers separate within one minute.

The upper dioxolane-tetralin layer is separated off. It will be 857.5 g of this layer obtained containing 0.53 percent by weight of water (determined by the Fischer method), 0.045 percent by weight formaldehyde (determined by the sodium sulfite method), 56.05 Weight percent tetralin, 43.38 weight percent dioxolane (determined by the digestion method) contain. The lower layer consisting of water-formaldehyde-dioxolane with a Weight of 190.4 g contains 4.17 percent by weight of formaldehyde = 7.94 g (= 94.4 0 / o from use).

The dioxolane-tetralin layer is then used for further drainage and cleaning of formaldehyde residues with 5.501.0 / sodium hydroxide solution (50 weight percent Sodium hydroxide solution). The one that settles quickly Lye layer is separated and the resulting solution is additionally filtered. After the filtration there is a formaldehyde-free, colorless solution with 0.11 percent by weight of water. Be dioxolane and tetralin separated by distillation by means of a Vigreux column (about 1 theoretical plate). At a maximum bubble temperature of 132.8 "C, between 73.0 and 76.8" C go to 304.2 g of pure dioxolane with the following composition: 0.25 percent by weight water, O percent by weight formaldehyde, 99.75 percent by weight dioxolane (from the difference).

This amount of the dioxolane obtained corresponds to 79.1% of the amount in use existing dioxolane.

In the bubble residue (506.5 g) there is a dioxolane residue of 9.92 percent by weight contain. This proportion corresponds to 13.1% of the dioxolane present in use. The residue is completely anhydrous (0 ° / 0 determined by the method of F i s c h e r) and colorless.

Without further treatment, it is used to extract more crude dioxolane.

The pure dioxolane obtained contains, in addition to a small amount of water no detectable other inorganic or organic foreign constituents.

An absolute dewatering of the pure dioxolane succeeds without the expenditure of energy an azeotropic distillation, by filtration through molecular sieves (Na or Ca aluminum silicates from Linde Air Corporation in the range of about 4 to 13 Å).

7842 g of the pure dioxolane obtained in the above manner with a content of 0.48 percent by weight of water are passed through a 374 g molecular sieve (Type> 4 A «, a Na-Al-silicate) filled glass column 150 cm high and 2.3 cm filtered. The apparatus is filled with calcium chloride via a Drying tower vented. The overflow speed is 11 per hour.

The flow is collected in partial fractions of 11 each.

A total throughput of 7737.9 g (98.66% of the amount used) is obtained Pure dioxolane) with a content of 1.64 g of water (= 0.021 percent by weight).

3.5 (2589.2 g) of the run-through obtained is completely anhydrous (durable Browning with 1 drop of Karl Fischer reagent). This amount corresponds to a share of 330/0 of the pure dioxolane used. During the regeneration of the molecular sieve With steam, a further 88.4 g of dioxolane are collected in cold traps, so that drying of the pure dioxolane with a water content of 0.48 percent by weight over the molecular sieve is practically quantitative. The overall yield is 99.8% of theory.

Of the dioxolane present in the water-containing layer (approx 5 to 10 percent by weight of the dioxolane used) can be the main amount by simple Distillation can be obtained in a known manner.

Example 2 In a mixing vessel, 0.4 l of crude dioxolane (427.7 g) of the composition 72.71 percent by weight dioxolane, 25.45 percent by weight water, 1.50 percent by weight of free formaldehyde, 0.26 percent by weight of formic acid with 1.6 1 high-boiling paraffin oil with a boiling point of at least 360 "C (1.389 kg) and 32 g of table salt offset and the substances are mixed together for about 15 minutes by vigorous stirring.

After the stirrer has been switched off, one occurs within an hour Delamination a.

The upper dioxolane-paraffin oil layer is separated off. It will 1358.2 g of this layer were obtained, which contained 0.061 percent by weight of water, 0.026 percent by weight free formaldehyde, 0.008 percent by weight formic acid and the remainder consisting of Contains dioxolane and paraffin oil.

The lower one, consisting of water-formaldehyde-dioxolane-sodium chloride Layer with a weight of 175.7 g contains: 3.61 percent by weight (= 98.8 0 / o of the free formaldehyde contained in the insert), 0.29 percent by weight formic acid.

The dioxolane-paraffin oil layer is then used for drainage and cleaning of formaldehyde residues with about 1 0 / o sodium hydroxide solution (17 g 50 weight percent sodium hydroxide solution) stirred. After filtering the mixture through a cotton wool filter and separating it the caustic layer is a formaldehyde-free, colorless dioxolane-paraffin oil solution obtain.

The dioxolane and paraffin oil are separated by distillation by means of a Vigreux column (about 1 theoretical plate). At a bulb temperature from a maximum of 1410 C between 76.2 and 78.6 "C 209.8 g of pure dioxolane (67.3% of the dioxolane present in use) of the following composition: 0.29 percent by weight H2O (determined according to the Fischer method), 0 percent by weight formaldehyde, 0 percent by weight Formic acid.

The water-white, clear bubble residue (1435.0 g) contains a dioxolane residue of 4.50 percent by weight (corresponding to 64.52 g of dioxolane or 20.7% of the amount in use existing dioxolane). The residue is used for further treatment without additional treatment Extraction of crude dioxolane.

The low residual water content of the pure dioxolane can according to example 1 can be removed with a molecular sieve.

Example 3 Using a mixing pump (Heintz pump), 0.33 1 Crude dioxolane (349.0 g) with a composition of 72.58 percent by weight dioxolane (determined according to the digestion method), 25.85 percent by weight water (determined according to the Fischer method), 1.49 percent by weight of formaldehyde (determined by the sodium sulfite method) with 0.39 1 back tetralin (385.8 g) mixed. The back tetralin used comes from a Series of cleaning batches according to Example 1 and contains 84 percent by weight of tetralin and 16 percent by weight dioxolane. The drain of the mixing pump is placed in a sedimentation vessel and separates there into two layers. The layers are then separated, wherein 606.4 g of an upper layer containing 55.20 percent by weight tetralin, 43.60 percent by weight of dioxolane (determined by the digestion method), 1.14 percent by weight Water (determined according to the Fischer method), 0.03 percent by weight formaldehyde (determined is obtained by the sodium sulfite method).

The lower water-formaldehyde-dioxolane layer with a weight of 121.2 g contains 3.63 percent by weight formaldehyde, corresponding to 4.4 g or 84.6 0 / o of the formaldehyde contained in the raw dioxolane feed.

The upper dioxolane-tetralin layer (606.4 g) is used for further fine cleaning and dehydration in a stirred vessel under a nitrogen atmosphere and with external cooling of the vessel with 35 cc of a 330/0 dispersion of metallic sodium in tetralin offset. The implementation of the formaldehyde residues contained in this layer and des Water with the finely dispersed sodium is finished within 20 minutes. the The temperature of the mixture rose to 44 ° C. during this. After cooling to room temperature the mixture is filtered under a nitrogen atmosphere, whereby 602.3 g of a clear Dioxolane-tetralin solution can be obtained. The dioxolane and tetralin are through Distillation through a Vigreux column (about 1 theoretical plate) from one another separated.

At a maximum heating bath temperature of 150 "C, between 76.0 up to 76.8 "C at normal pressure 215.5 g formaldehyde-free 99.77 percent by weight pure dioxolane, which only contains 0.23 percent by weight of water (determined according to the Fischer method), above. This pure dioxolane corresponds to 68.5% of that in use (349.0 g of crude dioxolane and 385.8 g of dioxolane-containing back tetralin) contained dioxolane. In the bubble residue ("Rücktetralin"), which is 380.8 g, is a dioxolane residue of 12.6 percent by weight (48.0 g of dioxolane, corresponding to 15.2% of the total dioxolane input). Of the The residue is completely anhydrous and colorless. He serves, without further treatment, for the extraction of further crude dioxolane.

The low residual water content of the pure dioxolane can according to example 1 can be removed with a molecular sieve.

Example 4 In a mixing vessel, 1.6 l of crude dioxolane (1727 g) of the composition 72.58 percent by weight dioxolane (determined by the digestion method), 26.08 percent by weight of water (determined by the Fischer method), 1.58 percent by weight Formaldehyde (determined by the sodium sulfite method) with 1.9 l of back tetralin previous cleaning batches (1846 g with a content of 15.69 percent by weight Dioxolane, corresponding to 289.6 g of dioxolane) added and the mixture is after Add 130g of sodium chloride and stir intensively for a few minutes. After parking of the stirrer, smooth delamination occurs within one minute. The layers are then separated to give 3081 g of a top layer, except the total amount of tetralin used and the main part of Dioxolane contains 0.57 percent by weight water and 0.066 percent by weight formaldehyde. The lower water-formaldehyde-dioxolane layer with a weight of 611 g contains 4.12 percent by weight formaldehyde (corresponding to 25.2 g = 92.4 01o des in use existing formaldehyde).

The dioxolane-tetralin layer is then used for further purification of the remaining small formaldehyde residue and for further dehydration with 60 g powdered sodium oxide treated in four servings within about 1 Added hour with stirring and external cooling of the reaction vessel to the mixture will. The temperature of the mixture rose to 43 to 44 ° C. 3130 g are obtained a pink-red solution with a pale yellowish sediment, which is covered over glass wool underneath Air exclusion is filtered off. The filtrate (3004.4 g) is removed using a Vigreux column (about 1 theoretical plate) separated by distillation. At 75.5 to 76.2 C (normal pressure), where the bath temperature is a maximum of 1500C, 1086.8 g of formaldehyde-free go 99.81 percent by weight of pure dioxolane containing 0.19 percent by weight of water (determined by the Fischer method) about. In the bladder residue ("back tetralin"), the 1904.5 g is 16.5 percent by weight of dioxolane [314.7 g, corresponding to 20.4% of the total dioxolane input (raw dioxolane and back tetralin input)].

The low residual water content of the pure dioxolane can according to example 1 can be removed with a molecular sieve. Claims: 1. Method for cleaning of crude dioxolane, characterized in that crude dioxolane with a not in any proportion with this miscible inert organic liquid that does not have any Contains elements which can be split off under the process conditions and also no compounds such elements under the process conditions is able to form in such a Volume ratio treated that delamination occurs, the dioxolane Layer separates, this with aqueous alkali or alkaline earth or with a Alkali or alkaline earth oxide or treated with an alkali or alkaline earth metal, after the dioxolane-containing liquid has been separated off, it is distilled and optionally the purified dioxolane obtained after treatment by filtration through a Subjected to molecular sieve.

Claims (1)

2. The method according to claim 1, characterized in that as inert organic liquid tetrahydronaphthalene in a volume ratio of 1 part by volume of tetralin: 1 part by volume of crude dioxolane used.