Process for the preparation of polyglycerines.

The present invention relates to a process for the preparation of polyglycerines by reacting glycerines under heat.

From DE-OS 24 55 327 a method for preparing polyglycerols (optionally with small proportions of cyclic components) through acid-catalyzed reaction of glycerins in the heat is already known, wherein the glycerol in the presence of sulfuric acid and glycerol acetate of less than 20 mm Hg is condensed to give polyglycerol. A disadvantage is the formation of byproducts such as acrolein and sulfuric acid esters in this method. Another disadvantage is the necessary use of absolutely pure glycerin, otherwise there is a strong discoloration of the approaches by the hot sulfuric acid.

Aim and object of the present invention was to avoid these disadvantages and to provide a process which allows under little equipment and no further additions of auxiliaries producing Polglycerinen.

The present inventors have found that these aims and objects, a method for producing polyglycerols (optionally with small proportions of cyclic components) is accessible by reacting glycerols in the heat, with glycerol and / or diglycerol at temperatures from 340 K to 410 K with gaseous hydrogen chloride or converted to a mixture consisting essentially of α-monochlorohydrin of the glycerine or diglycerol and glycerol and / or diglycerol with concentrated hydrochloric acid and the resultant mixture or the separated from the mixture α-monochlorohydrin of the glycerine or diglycerine at temperatures of 320 K is added to 410 K to Alkaliglycerinolat and / or Alkalidiglycerinolat, after which the glycerol thus produced and / or diglycerol-polyglycerol mixture is separated from the resulting alkali metal chlorides as well as the glycerol and / or diglycerol of the polyglycerol.

The reaction of the glycerine and / or diglycerine with gaseous hydrogen chloride or with concentrated hydrochloric acid is carried out in the presence of a catalyst, preferably a liquid saturated C₁-C₃ carboxylic acid, in a concentration of catalyst (based on the total amount by weight of glycerine and / or diglycerine used of 0 5 to 3 wt .-%, preferably 0.5 to 2 wt.%.

According to a preferred embodiment of the method, the glycerol and / or diglycerol at temperatures of 340 K is converted to 410 K with gaseous hydrogen chloride or with concentrated hydrochloric acid in the presence of a catalyst and the resulting mixture or the separated from the mixture α-monochlorohydrin of glycerol or diglycerol at temperatures from 320 K to 410 K at a Alkaliglycerinolat and / or Alkalidiglycerinolat that an alkaline substance, preferably alkali hydroxide, containing added, after which the glycerol thus produced and / or diglycerol polyglycerol from the resulting alkali metal chlorides and the glycerol and / or diglycerol of the polyglycerol to be separated.

According to a preferred embodiment, the points with gaseous hydrogen chloride or with concentrated hydrochloric acid to be reacted glycerol and / or diglycerol one glycerol and / or diglycerol content of more than 80 wt .-%, preferably more than 90 wt .-%, on. The unreacted glycerol and optionally a part of diglycerol are preferably separated by fractional distillation of the polyglycerol.

The Alkaliglycerinolat and / or Alkalidiglycerinolat used has a Alkaliglycerinolat- Alkalidiglycerinolatgehalt or of more than 80 wt .-%, preferably more than 90 wt .-%, and preferably additionally comprises an alkaline-reacting component, preferably alkali hydroxide.

When hydrogen chloride gas is in the process of pure hydrogen chloride or a hydrogen chloride gas mixture, preferably a hydrogen chloride gas mixture, obtained during the production of vinyl chloride and / or Allylchloridherstellung used.

As concentrated hydrochloric acid, a hydrochloric acid is used which has a content of 10 to 40 wt .-%, preferably 30 to 35 wt .-%, HCl. According to a preferred embodiment of the inventions to the invention method, the α-monochlorohydrin of the glycerine and / or diglycerine is added into the initial charge Glycerinolat and / or Diglycerinolat with stirring, preferably by continuous addition.

According to an advantageous embodiment of the method the α-monochlorohydrin of glycerol and / or diglycerol is continuously introduced simultaneously with the Glycerinolat and / or Diglycerinolat in a preferably thermally stabilized flow reactor, thereby short response times can be achieved.

After completion of the reaction or after the formation of the polyglycerols is preferably a portion of the resulting alkali metal chloride by known per se physical methods, preferably by sedimentation and / or centrifugation as a solid and the other part after adding water via ion exchange in a conventional manner from the resulting polyglycerol , for example according to the process of DE-OS 34 10 520 separated.

Furthermore, an improved cleaning of the inventively obtained glycerol and / or diglycerol polyglycerol should be achieved.

According to the invention the purification of the glycerol and / or diglycerol-polyglycerol mixture is carried out by dilution with water to a 70 to 40 wt .-% solution, preferably 60 to 50 wt% solution, which, at temperatures of 30 to 80 ° C preferably 40 to 60 ° C is desalted through a combination of strongly acidic cation and subsequent weakly basic anion exchangers.

The regeneration of the cation exchange medium in the cation exchangers takes place preferably by means of a direct current or composite-direct current regeneration.

According to a preferred embodiment, the salts are washed after regeneration. Upon completion of Auswaschvorganges the polyglycerol, preferably diglycerol solution passed through the ion exchanger and the anion exchanger leaving polyglycerol, preferably diglycerol solution until a polyglycerol content, preferably diglycerol content of 20 wt .-%, preferably until a polyglycerol content, preferably diglycerol , of 15 wt .-%, and returned for the production of 70-40 wt .-% strength, preferably 60-50 wt .-% by weight, polyglycerol, preferably concomitantly diglycerol starting solution.

The passage of the polyglycerol-containing, preferably diglycerol solution carried by the ion exchanger preferably under a positive pressure.

The polyglycerol, preferably diglycerol solution while under a pressure of 1.1 - 10 bar, preferably 2 - 6 bar, passed through the ion exchanger, that is, by one or more cation exchangers and at least one anion exchange. For controlling and maintaining the pressure are mounted at one or more points in the line or to the ion exchange valves.

In this case is suitably the polyglycerol, preferably diglycerol solution at a flow rate of 0.5 m / h to 15 m / h, preferably passed 1 m / h to 5 m / h through the ion exchanger.

As Kationenaustauschermassen and anion exchange used are preferably those that up above 80 ° C, preferably to about 100 ° C, are temperature resistant.

The ion exchanger of the cation exchanger and / or anion exchanger is expediently of a screen plate, perforated plate or in the height direction of the ion exchanger slidably mounted, covering the exchanger mass and a uniform liquid passage permitting device and / or an inert molding compound and / or elastic plastic material covered.

The strongly acidic cation exchange medium and the weakly basic anion exchange material preferably have an internal surface area (measured by the BET method) of more than 25 m² / g, preferably 50 to 100 m² / g.

Embodiment 1

In a solution of 1.104 kg of 99.5% glycerol (12 mol) and 31.5 g of 35% acetic acid for 2.5 hours introduced hydrogen chloride at about 383 K, the weight increase was approximately 40%. 500 g of this solution were added with stirring over 1.25 h in a reactor, which is 92 g (1 mol) of glycerol, 269.4 g were 50% sodium hydroxide and 160 ml of distilled water at 393 K.

After another 5 h, the reaction mixture was diluted with distilled water, desalted on ion exchanger and subsequently evaporated in vacuo.

The product mixture had the following composition (in weight percent): Glycerin 29.1, cylisches diglycerol 1.2, diglycerol 31.7, cyclic triglycerol 1.7, triglycerol 17.1, cyclic tetraglycerol 0.9, tetraglycerol 9.1, cyclic pentaglycerol 0.1, pentaglycerol 4.9, hexaglycerol 2.8, 1.3 heptaglycerol.

Embodiment 2

111 g (1 mol) of α-monochlorohydrin were introduced with stirring into a reactor, which is 92 g (1 mol) of glycerol and 81 g of 50% sodium hydroxide (1.1 mol) at 343 - 358 K were. After 5 min, the reaction mixture was diluted with distilled water, desalted on ion exchanger and subsequently evaporated in vacuo. The product mixture had the following composition (in wt .-%): 35.0 glycerol, cyclic diglycerol 0.3, 33.5 diglycerol, triglycerol cyclic 0,2, triglycerol 18.0, cyclic tetraglycerol 0.1, tetraglycerol 8.4 , Penta glycerin 3.4, 1.2 hexaglycerol, heptaglycerol 0.1.

Embodiment 3

111 g (1 mol) of α-monochlorohydrin were introduced with stirring into a reactor, which is 166 g (1 mol) of diglycerol and 88 g 55% sodium hydroxide (1.1 mol) were at 343-358 K. After 5 min. the reaction mixture was diluted with distilled water, desalted on ion exchanger and subsequently evaporated in vacuo.

The product mixture had the following composition (in wt .-%): Glycerin 4.5, cyclic diglycerol 0.1, diglycerol 35.4 cyclic triglycerol 0.2, triglycerol 30.8, cyclic tetraglycerol 0.1, 17.5 of tetraglycerol, pentaglycerol 8.0, 3.0 hexaglycerol, heptaglycerol 0, . 4

Embodiment of the method using of ion-exchangers:

The polyglycerol and / or diglycerol produced by the inventive process is with water to a 55 wt.% Strength polyglycerin, preferably diglycerin, diluted.

The resulting solution is at a temperature between 40 to 60 ° C successively passed through a strongly acidic ion exchanger having an ion exchanger, which is arranged above a sieve or nozzle bottom.

The screen bottom to leaving polyglycerol, preferably diglycerol solution enters the downstream ion exchange container in which to the nozzle or perforated base a weakly basic ion exchanger is arranged, which is overlaid by an inert molding material. The air leaving the anion exchanger aqueous solution having a salt content of less than 0.5 wt .-% is transferred to the distillation apparatus and separated by fractional distillation.