DE1618951A1 - Process for the preparation of monochloropivalic acid - Google Patents

Description

DR. ELISABETH JUNG AND DR. VOLKER VOSSiUS

«MÖNCHEN2S. β I CQ ΕββΤΑΑββΕ 26. TeLEPON 84 · ββΤ · TELEG «AMM-ADRES $ Ei! NVENT / MONCHEN

I ö. 3EP. 1967

u.z.j F 1603 Bu / J / hh

Shell Internationale Research Maatsohappi;) N.V. The Hague, Netherlands

"Process for the preparation of MonochiorpivalinsSure" Priority! 22nd September 1966, the Netherlands, no 66 135

The invention relates to a process for the preparation of monochloropivalic acid, i.e. o £, oC-Dimethyl-ß-chloropropionic acid.

Monochloropivalic acid is, among other things, an important starting material for the production of the lactone of pivalic acid, di oC »oC dimethyl-Ö-propioleoton. They polymers of oi / ^ ß-propiolactone are very valuable products.

The invention now relates to a method for dividing up of monochloropivalic acid, which is characterized in that it contains chlorine gas with liquid pivalic acid or in the height of the boiling point of pivalic acid under the prevailing conditions or at least at a temperature not more than 30 ° C below the

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Boiling point is brought into contact with that from a reaction mixture is withdrawn from the chlorination zone,

there is at least 0.25 mol of unreacted pivalic acid contains per mole of Monoohlorplvalinsäure formed that this Gemisoh is subjected to rectification, in which the Monochiorpivalic acid obtained as bottom product continuously or is withdrawn discontinuously, while the pivalic acid is optionally in the chlorination zone is returned.

Surprisingly, it has been found that in the inventive Process monochloropivallic acid is obtained in good yield without undesired by-products develop.

According to the invention, the chlorination of the pivalic acid thus takes place in a chlorination zone. AneohlieSend is in a rectIfizlerungszone the unreacted pimelic acid is separated from the reaction product. It is essential that that the chlorination mixture subjected to rectification contains at least 0.25 mol of pimelic acid per mol of konoehlorpivalic acid and that the product leaving the rectification zone is continuous or at least discontinuous is withdrawn in order to report a thermal decomposition of the monoehlorpivalic acid formed as far as possible.

It is particularly important that the reaction mixture is already is then withdrawn from the chlorination zone, if only

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some of the pivalic acid has been converted into monoehlorpivalic acid. The molar ratio of pivalic acid ssO. Monochloropivalic acid in this mixture should then not be less than 0.25 Ho ¹ . It has been found "that too great a conversion of Pival ynoic to the formation of considerable amounts of undesirable products, especially hr ago chlorinated derivatives," he Dichlorpivalinsäure, AnIaB are. Favorable molar ratios of pivalic acid to monochxorpivalic acid are generally above 1 mol per haul, preferably between 1 mol and 10 mol and in particular between 3 and 6 mol per mol. The unreacted pivalic acid is then distilled off from the chlorination mixture in a rectification zone. You pivalic acid kens. Sann to be brought into contact with chlorine again in the chlorination zone.

In the process according to the invention, it is necessary that the bottom product obtained in the production of sparkling wine is withdrawn together with the monohydrate pivalic acid formed during the hectification, thereby avoiding excessively long heating in the evaporator. It has been found that otherwise a contaminated product is obtained with a considerably lower content of monohydro pivalic acid, which is presumably due to a decomposition. It is therefore necessary. that the monochloropivalic acid formed is withdrawn continuously or at least intermittently. It's particularly beneficial, too. apply this purpose min continuous process. The fcektifi cation can, if necessary, under

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be carried out under reduced pressure.

let recommended that Chlorierungsgemlsoh obtained by the erfindunpßgemäßen method at least O _t 25 koi pimelic acid per mole Bfonoehlorpivelinsäure contains subtract "continuously from the Chlorierungezone and in the Rektifizierungezone to transfer, beer the nioht unreacted pivalic acid is" leather recovered and preferably continuously recirculated in the Ohlorlerungszone , while the monochloropivalic acid is obtained as a bottom product. The rectification is generally carried out in a customary distillation column or in a column provided with packing elements. If necessary, the rectification can also be carried out in stages with different columns.

Very favorable results are obtained when the chlorination takes place at or near the boiling point »Depending on the composition of the mixture, the! temperature between, for example, 145 and 160 ° C at normal pressure If appropriate, the process can also be carried out under reduced pressure. Overpressure can can also be used «You can also use chlorination at lower temperatures, which can be up to 80 ° O below the boiling point, are carried out, however the reaction then usually proceeds more slowly if the process is not under the influence of catalysts or high-energy radiation is carried out. Surprisingly However, it was found that according to the invention Pivslinic acid process very easily and in

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high yields can be converted into monochloropirenic acid can without the need for catalysts and / or irradiation. Therefore a wide variety of chlorination equipment can be used be used. Ss let particularly cheap, then use the column described below if For example, irradiation with ultraviolet light on a technical scale is too expensive and also with constructive difficulties would be associated. The use of high-energy beams and / or catalysts eats not excluded, however.

The chlorination can, for example, in one with pivalic acid θ filled reactor can be carried out by chlorine gas is passed through the Slüssigkelt. Possibly can also be different, preferably backed-up Reactors are used. Sas chlorination mixture can then be subjected to rectification in a distillation column, in the case of Monochiorpivalinsäujfe is drawn off at the bottom, while the distilled off, supplemented with fresh pivalic acid β plvalic acid in recycled to the chlorination zone or zones can be.

According to a particularly two-year-old carcassing form of the inventive concept The process is chlorination in one Stage reactor, preferably carried out in one * column, to promote contact between liquid and gas, with full bodies, such as basal gringea, saddle bodies and

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such a thing, behave. You-the in the usual columns with fractional booths are provided. For example, an upward flow of chlorine fed in at the bottom of the column reacts with the liquid plvalic acid introduced at the top of the column and leaving the column at the bottom · Beaktionsgemisoh is transferred to a beectification column. Ss It is often advantageous to have chlorine gas at different points and at different heights of the column at the same time initiate, whereby ea is possible, each different to dose. You pivallic acid can also take part in different Places of the column are initiated.

The pivalic acid distilled off from the rectification column is usually returned to the chlorination zone together with the supplemented fresh pivalic acid

According to a particularly preferred embodiment of the invention a single column is used, the upper part of which consists of a chlorination zone and the lower part, i.e. the part that lies below the point where the chlorine flows in serves as a detection zone in this foil the pivalic acid recovered in the process of liquefaction distilled directly into the chlorination zone, during the Bottom of the column honochloropivalic acid which has no or contains almost no plvalic acid, is withdrawn.

It is generally recommended to use chlorination in the case of To carry out boiling point, the evaporating Piyalinaäure

to condense using a RüokfluSkuhlers and proven in the Chlorierungasone gurtteklaufen su lessen · Be net look as EthR Advantageously, the Bücklauf of pimelic bo 'n regulate that per McI initiated chlorine gas Bin »least 2 Get pivalic snrüeklaufen · door in the event that the Raaktlon product in a? is rectified in a separate column »this includes the same amount of pyrallic acid that is recovered in the rectification. A ratio of 3-8 Hol return ~ plvalic acid per Hol chlorine is predicted. In addition, as much plvalic acid has to be added in every case "as was consumed during the chlorination" just 0.9 mol to 1 mol of chlorine.

The product obtained in the manner described contains% n usually even small amounts Dioh1orpimelinsäure _# but can be vernaohläeeigt in ellgemeinen. This product can be used without further purification as a starting material for the production of C.eC-IDimethyl-ß-propiolaetone.

example

The production of Monochiorplvalineäure took place in one 3 m direct glass column with a surohm sea of 2.5 em, which was filled with saddles with a diameter of 6 mm, so that the volume of the cavities was about 60 t fraud. The column was covered with a second column jacket wrapped with a rope to protect against heat loss isolated. In this way, an air jacket was formed around the column, which easily reached the desired temperature could be sustained.

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The inlet for the introduction of the chlorine was about in the middle of the column. As a result, the column was in an upper part, in which the chlorination reaction takes place, and a lower! ceil, which is used as a beectification gone serves, shared. In addition, the column was provided with a cooler to prevent the pivalic acid evaporating overhead then over a calibrated measuring vessel and a continuous sea was returned to the column, eu condense, while the residual gases, mainly hydrogen chloride, were drained overhead · The evaporator on The bottom of the column consisted of a 200 ml flask which was kept at the desired temperature with the aid of a ffärmemantele was held and provided with a drain line was by which the reaction product was removed by pumping.

The reaction was started as follows. Pivalic acid was brought to boiling temperature in the evaporator and the heating at the bottom of the column regulated so that the desired Amount of pivalic acid evaporated, was condensed again with the condenser located at the top of the column and ran back. Next, the flow meter was set to the above-mentioned value, whereupon the desired amount Chlorine was continuously introduced into the column at a constant rate .. Then the column was preheated to 160 ° C freshly fed pivalic acid introduced at the top of the column at a rate which corresponds to an amount of about 1 mole per mole of chlorine corresponds. Hit progressive Reaction, the content of the soil product in mono-organ

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pivalinoaure and thus the boiling point. The Brhitaen at the bottom of the column, has now been adjusted so that the ! The temperature of the Bodenproäuktea was about 222 ° C The soil product then only contained traces of Plvallns mud. You have been supplying fresh pimelic acid ichlieSlloh bo regulated that the liquid level in the calibrated measuring vessel remained constant

A typical experiment was carried out under the following conditions: "Chlorine was introduced at a rate of τοη 107 β (1 | 51 mol) per hour and fresh pimelic acid at a rate of 141 g (1 * 36 KoI) per hour". The amount of pivalic acid condensed with the cooler and flowing in was 714 g (7 mol) per hour, the _I corresponds to 4.67 mol per MqI of chlorine gas introduced. 191 & - ^] Bottom product was removed per hour by pumping.

The product obtained was composed as follows: 95% by weight of monohydric acid, 6 % by weight of diohlorpivalic acid, 1% by weight of neutral products and 0.2% by weight of plralic acid. The conversion of the pivalic acid was therefore 99.7% by weight with a selectivity corresponding to the formation of monoohlorpivalic acid ron about 94 * 5 mol-? t. According to the analysis of the exhaust gas, 97 moles of chlorine have been converted.

Claims (9)

Claims 1. Process for the production of τοη monochiorpimelic acid, characterized in that gaseous chlorine with liquid pimelic acid at or near the boiling point of the Pimelic acid under the prevailing conditions or Brewed in contact at least at a temperature not more than 80 ° C below the boiling point is that a reaction mixture is withdrawn from the chlorination zone is that at least 0.25 mole not uaceeetst Contains PiTalinaic acid per mole of Konoohlorpimalic acid formed, that this oemieoh is subjected to the cultivation, in which the Honoohlorpimalln arising as a soil product « acid is withdrawn continuously or discontinuously, and that optionally the pimalic acid in the chlorination exon is returned. 2. The method according to claim 1, characterized in that de β the Oemisoh sucked out of the Chlorlerungssone 1 to 10 Hol Pimelic acid, in particular 3 to 6 Hol pimelic acid »per Hol Honoohlorpiralic Acid contains 3 · Method according to claim 1 to 2, characterized in that that the chlorination mixture continuously from the Chlorierungesone is transferred to the Bektification zone onqo «« WWW mW MnHHAftTa ι - η - · ■ 4. The method according to claim 1 to 3, characterized in that that the bottom product obtained in the frectification kontlrruierlioh is withdrawn from the evaporator. 5. The method according to claims 1 to 4, characterized by that the unconverted Hvaline acid, which in the BektlflBierung is being recovered, continually within you Chlorination zone Euruok is led. 6. The method according to Anepruoh 1 to 5 _t characterized in that the chlorination is carried out at or around the boiling point. 7. Procedure naoh Anepruoh 1 to 6, daduroh known without, that the chlorination is carried out in a column which is provided with packing or fractionation booths 8. The method according to claim 1 Ue 7, daduroh {rekenneeiohnet, that a column is used, the one above the inlet points for the part lying under chlorine, the chlorination zone is used, while the part lying below this point Part is used as a rectification zone 9. The method according to claim 1 to 8, daduroh gekennaelohnet, that the chlorination carried out under RüokfluQ and the The reflux of pimelic acid is regulated so that per mole introduced chlorine again at least 2 moles of fivalic acid run back, including that amount of pivalic acid -2-09816 / 1630
BATH ORIGINAL which are recovered by rectification in a separate colon is won. IQ. Method according to Claim 9, characterized in that per mole of chlorine. 5 - 8 Bring pivalic acid into the chlorination zone ssurüolcführung «earth. 209816/1630 BAD ORIGfNAL