EP1866084A2

EP1866084A2 - Method for producing an dmc catalyst

Info

Publication number: EP1866084A2
Application number: EP06708667A
Authority: EP
Inventors: Edward Bohres; Michael Triller; Raimund Ruppel
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2005-03-10
Filing date: 2006-03-07
Publication date: 2007-12-19
Also published as: US20080167502A1; CN101300074B; JP5329217B2; WO2006094979A3; CN101300074A; JP2008533227A; WO2006094979A2; DE102005011581A1; US7811958B2; KR20070116249A

Abstract

The invention relates to a method for producing DMC catalysts by reacting cyanometallate compounds, preferably cyanometallate salts, in particular, alkali or alkaline earth salts, with metal salts, wherein the inventive method is characterised in that it is carried out in the presence of a Bronsted acid.

Description

Process for the preparation of DMC catalysts

The invention relates to a process for the preparation of multimetal cyanide compounds, also referred to as DMC catalysts.

DMC catalysts are used in the preparation of polyether alcohols by addition of alkylene oxides to H-functional starter substances, especially alcohols. When using DMC catalysts, the space-time yield in the production can be increased. The polyether alcohols produced by this process are characterized by a reduced content of unsaturated constituents.

The preparation of DMC catalysts is usually carried out by reacting a hexacyanometallate compound, preferably hexacyanocobaltate or hexacyanocobaltic acid, with a metal salt. The use of hexacyanometallic acids in the reaction mixture is described, for example, in EP 862 997, WO 03/080239, WO 03/080240 and WO 03/080241.

The hexacyanometallic acids are usually prepared by means of ion exchangers, as described in EP 862 997.

In WO 03/080239, WO 03/080240 and WO 03/080241, the DMC preparation is carried out in a different way.

In this case, a Hexacyanometallatsalz is dissolved in water and acidified with sulfuric acid. To this solution, an organic solvent, for example methanol, is added, which leads to the precipitation of potassium sulfate. This is filtered off and the thus obtained solution of Hexacyanometallatsäure by combining with an aqueous solution of the metal salt component to the D MC catalyst reacted. In this reaction, ligands and / or organic additives may be present or added.

This process, also referred to below as "salt metathesis", represents an alternative to the recovery of hexacyanometallic acid by ion exchange. Removal of potassium sulfate by filtration, like ion exchange, is an additional process step, in this case even involving the handling of a solid In addition, an organic solvent must be used for precipitation, which leads to additional costs and it can not be ruled out that at least some of the salt formed remains in the catalyst. WO 99/56874 describes a catalyst which is treated with a protic acid. The addition of the acid occurs during or after the catalyst synthesis, but in any case only after the precipitation of the metal salt DMC compound and cyanometalate component. Polyetherols having a reduced high molecular weight fraction can be prepared with these catalysts.

US Pat. No. 4,477,489 describes DMC catalysts which contain a mineral acid, in particular a hydrohalic acid. For this purpose, the precipitated DMC compounds are treated with a mineral acid which is incorporated into the catalyst. By incorporating the acid, the viscosity of the suspension of the DMC catalyst should be improved. In addition, it is intended to react the hydroxyl groups which may be present in the catalyst after the precipitation.

The processes described require an additional process step of treating the precipitated DMC compound with a mineral acid. If the acid remains in the DMC catalyst as described in US Pat. No. 4,477,589, corrosion problems may arise, for example with hydrochloric acid, which is described as being preferred in US Pat. No. 4,477,589. So you have to design the reactors for polyol production corrosion resistant, which leads to higher costs. Furthermore, it can not be ruled out that the acid which has only been adsorbed on the DMC catalyst and thus becomes more volatile passes into the product prepared by means of DMC catalyst. For chlorine-containing acids, this could be problematic due to the possible formation of organochlorine compounds. For example, it can not be ruled out that the hydrochloric acid catalyzes an ether cleavage and thus an undesired reaction, in which organochlorine compounds in turn could also be formed.

The object of the present invention was to find a simplified process for the preparation of DMC catalysts, which leads to DMC catalysts having a high catalytic activity.

Surprisingly, it has been found that DMC catalysts having a high catalytic activity can be obtained when the reaction of the cyanometallate compound with the metal salt takes place in the presence of a Bronsted acid.

The invention thus provides a process for preparing DMC catalysts by reacting cyanometalate compounds, preferably cyanometalate salts, in particular alkali metal or alkaline earth metal salts, with metal salts, characterized in that the reaction is carried out in the presence of a Bronsted acid.

The invention furthermore relates to the DMC catalysts prepared by the process according to the invention. The metal salt and the cyanometallate compound are reacted with each other in the form of their solutions, in particular as aqueous solutions.

The invention furthermore relates to a process for preparing polyether alcohols by adding alkylene oxides to H-functional starter substances using the DMC catalysts prepared by the novel process.

In principle, all water-soluble and room temperature stable mineral and carboxylic acids can be used as Bronsted acids. Among the carboxylic acids which may contain one or more carboxyl groups and up to 20 carbon atoms are carboxylic acids substituted with electronegative elements, for example chloroacetic acids, fluoroacetic acids or halogenated benzoic acids. In particular, however, mineral acids are used. These are preferably selected from the group containing sulfuric acid, hydrochloric acid, sulfurous acid _, alkyl, aryl and halosulfonic acids HSO ₃ X, where X is halogen, alkyl having an alkyl group of 1 to 20 carbon atoms, aryl, preferably phenyl or naphthyl _, di Sulfuric acid, hydrochloric acid, chloric acid, perchloric acid, hydrobromic acid, hydrazoic acid, hydrofluoric acid, hydrosilicic acid, phosphoric acid, phosphorous acid, hypophosphorous acid, tetrafluoroboric acid, hexafluorophosphoric acid, nitric acid, nitrous acid. Particularly preferred are sulfuric acid, alkyl, aryl and halosulfonic, hydrochloric, perchloric, hydrobromic, hydroiodic, hydrofluoric, phosphoric, nitric, most preferably sulfuric and hydrochloric.

The acid is preferably added in an amount such that the pH after DMC precipitation is between 3 and 6, preferably between 4 and 6.

The acid can be added to at least one of the starting compounds or both or fed to the reaction vessel as a separate stream. Preferably, the acid is added to the hexacyanometallate compound. It is essential that the acid must already be present at the beginning of the reaction, that is to say when the solution of the metal salt is combined with the solution of the cyanometalate compound.

The preparation of the multimetal according to the invention takes place in the usual manner, wherein, as stated, the reaction takes place in the presence of a Brönsted acid.

For this purpose, an aqueous solution of a Cyanometallatverbindung, in particular a Cyanometallat salt, combined with the aqueous solution of a metal salt. in this connection is usually worked with a stoichiometric excess of the metal salt. Preferably, the molar ratio of the metal ion to the cyanometalate component is from 1.1 to 7.0, preferably from 1.2 to 5.0 and particularly preferably from 1.3 to 3.0. It is advantageous to provide the Cyanometallatlösung together with the Brönsted acid and add the metal salt solution, but it can also be reversed procedure. During and after the combination of the educt solutions, thorough mixing, for example by stirring, is necessary.

The content of the cyanometallate compound in the aqueous solution, based on the mass of aqueous solution, is from 0.1 to 30% by weight, preferably from 0.1 to 20% by weight, in particular from 0.2 to 10% by weight. The content of the metal salt component in the metal salt solution, based on the mass of metal salt solution, is 0.1 to 50 wt .-%, preferably 0.2 to 40 wt .-%, in particular 0.5 to 30 wt .-%.

In one embodiment of the process according to the invention, at least one of the aqueous solutions of the starting materials contains a ligand containing heteroatoms, as denoted and explained as L in the general formula (I). The ligands containing heteroatoms can also be added to the resulting suspension only after the two starting materials have been combined, and good mixing must also be ensured here.

The content of the ligands containing heteroatoms, if such compounds are used, in the suspension formed after the precipitation should be 1 to

60 wt .-%, preferably 5 to 40 wt .-%, in particular 10 to 30 wt .-% amount.

In order to adjust the morphology of the multimetal cyanide compounds, it has proven useful to carry out the preparation of these compounds in the presence of surface-active substances. The surface-active substances are generally already introduced into at least one of the two solutions or preferably added during and / or directly after the precipitation. The content of surface-active substances in the precipitation solution, based on the total mass of the precipitation suspension, is preferably between 0.01 and 40% by weight, in particular between 0.05 and 30% by weight. A further preferred embodiment provides that the surface-active substances are distributed proportionally to the two educt solutions.

In a further preferred embodiment of the preparation of the multimetal cyanide compounds described in WO 01/64772, the reaction of the metal salt with the cyanometalate compound takes place in two stages. In this case, a catalytically inactive, in particular cubic, phase of the multimetal cyanide compound is first prepared and subsequently converted by recrystallization into a catalytically active phase of the multimetal cyanide compound. The recrystallization can be carried out by various measures. This makes it possible to reduce the post-implementation pension add further educt solutions, in particular the solution of the metal salt. Another possibility is to change the temperature of Fätlsuspension after completion of precipitation, in particular to heat the suspension. Another possibility is to add further heteroatoms-containing ligands and / or surface-active substances to the precipitation suspension after completion of the precipitation.

In a particularly preferred embodiment of the process according to the invention, a particularly crystalline multimetal cyanide compound is first prepared, as described, for example, in WO 99/16775. This can then be converted into the multimetal cyanide compound according to the invention in a further step, for example by a temperature treatment, preferably in the presence of an inert gas.

To carry out the temperature treatment, the multimetal cyanide compound can be separated from the precipitation suspension and dried. In one embodiment of the process, the multimetal cyanide compound may also be subjected to the temperature treatment in the precipitation suspension. In a further embodiment of the process, the multimetal cyanide compound prepared by conventional methods can be added to the starting substance used for the preparation of the polyether alcohols and the mixture subjected to a temperature treatment, optionally under vacuum and / or by passing an inert gas, the temperature treatment.

The temperature treatment is preferably carried out at a temperature in the range between 90 and 200 ^° C., in particular between 100 and 160 ^° C.

After precipitation, the precipitated multimetal cyanide compound is separated from the precipitation suspension. This can be done by centrifugation or preferably by filtration. The separated precipitate is washed once or several times, preferably with water. It is also possible to add organic ligand and / or a surface-active compound to the wash water.

The multimetal cyanide catalysts prepared by the process according to the invention have the general formula:

M ¹ _a [M ² (CN) _b (A) _c ] _d -fM ¹ _g X _n -h (H ₂ O) eL-kP (I)

in which

M ^{1 is} a metal ion selected from the group consisting of Zn ²⁺ , Fe ²⁺ , Fe ³⁺ , Co ²⁺ , Co ³⁺ , Ni ²⁺ , Mn ²⁺ , Sn ²⁺ , Sn ⁴⁺ , Pb ²⁺ , Mo ⁴⁺ , Mo ⁶⁺ , Al ³⁺ , V ⁴⁺ , V ⁵⁺ , Sr ²⁺ , W ⁴⁺ , W ⁶⁺ , Cr ²⁺ , Cr ³⁺ , Cd ²⁺ , Cu ²⁺ , La ³⁺ , Ce ³⁺ , Ce ⁴⁺ , Eu ³⁺ , Mg ²⁺ , Ti ³⁺ , Ti ⁴⁺ , Ag ⁺ , Rh ²⁺ , Ru ²⁺ , Ru ³⁺ , Pd ²⁺ , preferably Zn ²⁺ , Fe ²⁺ , Fe ³⁺ , Co ²⁺ , Co ³⁺ , M ^{2 is} a metal ion selected from the group consisting of Fe ²⁺ , Fe ³⁺ , Co ²⁺ , Co ³⁺ , Mn ²⁺ , Mn ³⁺ , Ni ²⁺ V ⁴⁺ , V ⁵⁺ , Cr ²⁺ , Cr ³⁺ , Rh ³⁺ , Ru ²⁺ , Ir ³⁺ , preferably Fe ²⁺ , Fe ³⁺ , Co ²⁺ , Co ³⁺ and Ir ³⁺

mean and M ¹ and M ^{2 are} different,

A is an anion selected from the group comprising halide, hydroxide, sulfate, hydrogensulfate, carbonate, bicarbonate, cyanide, thiocyanate, isocyanate, cyanate, carboxylate, oxalate, nitrate, nitrosyl, phosphate, hydrogen phosphate or dihydrogen phosphate

X is an anion selected from the group comprising halide, hydroxide, sulfate, hydrogensulfate, carbonate, bicarbonate, cyanide, thiocyanate, isocyanate, cyanate, carboxylate, oxalate, nitrate or nitrite (NO ₂ ^' ),

L is a water-miscible ligand selected from the group comprising alcohols, aldehydes, ketones, ethers, polyethers, esters, polyesters, polycarbonate, ureas, amides, nitriles, sulfides or mixtures thereof,

P is an organic additive selected from the group comprising polyethers, polyesters, polycarbonates, polyalkylene glycol sorbitan esters, polyalkylene glycol glycidyl ethers, polyacrylamide, poly (acrylamide-co-acrylic acid), polyacrylic acid, poly (acrylamide-co-maleic acid), polyacrylonitrile, polyalkyl acrylates, polyalkyl methacrylates , Polyvinyl methyl ether, polyvinyl ethyl ether, polyvinyl acetate, polyvinyl alcohol, poly-N-vinylpyrrolidone, polyCN-vinylpyrrolidone-co-acrylic acid), polyvinyl methyl ketone, poly (4-vinylphenol), poly (acrylic acid-co-styrene), oxazoline polymers, polyalkyleneimines, Maleic acid and maleic anhydride copolymer, hydroxyethyl cellulose, polyacetates, ionic surfaces and surface-active compounds, bile acid or its salts, esters or amides, carboxylic esters of polyhydric alcohols and glycosides.

such as

a, b, d, g and n are integers or fractions greater than zero, c, f, e, h and k are integers or fractions greater than or equal to zero,

in which

a, b, c and d, and g and n are selected so that the electroneutrality is ensured.

The DMC catalysts are, as described, preferably by reaction of metal salts of the general formula M ¹ _a X _n with Cyanometallatverbindungen the general my formula M ³ _a [M ² (CN) _b (A) _c ] _d , wherein M ^{3 is} alkali or alkaline earth metals and the other symbols have the meaning described above, prepared.

The catalysts prepared by the process according to the invention may be crystalline or amorphous. In the case where k is zero, crystalline double metal cyanide compounds are preferred. In the case where k is greater than zero, both crystalline, partially crystalline, and substantially amorphous catalysts are preferred.

Of the DMC catalysts produced by the process according to the invention, there are various preferred embodiments.

A preferred embodiment is catalysts of the formula (I) in which k is greater than zero.

The preferred catalyst then contains: a) at least one multimetal cyanide compound b) at least one organic ligand c) at least one organic additive P.

In another preferred embodiment, k is zero, optionally e is also zero, and X is exclusively carboxylate, preferably formate, acetate and propionate. Such DMC catalysts are described, for example, in WO 99/16775. In this embodiment, crystalline double metal cyanide catalysts are preferred.

In another preferred embodiment of the catalysts, f, e and k are equal to zero. These are DMC catalysts containing a water-miscible organic ligand, usually in amounts of from 0.5 to 30% by weight, and an organic additive usually in amounts of from 5 to 80% by weight, as in WO 98/06312 described. The catalysts can be prepared with stirring, as described in US Pat. No. 5,158,922, preferably with vigorous stirring, for example 24,000 rpm with a Turrax.

Also suitable catalysts are described in the application WO 01/03830. Such DMC catalysts are prepared with organic sulfones of the general form RS (O) ₂ -R or sulfoxides of the general form RS (O) -R as an organic complexing agent. Advantages of the catalyst include short induction times and moderate exothermicity in the addition of the alkylene oxides. In WO 01/03831 a further variant of the catalyst synthesis is described. In this case, DMC catalysts are synthesized by an "Incipient Wetness Method." These catalysts can likewise be prepared by the process according to the invention. The preparation of polyether alcohols using the DMC catalysts prepared by the process according to the invention is carried out, as stated, by adding alkylene oxides using the catalysts described to H-functional starter substances.

As alkylene oxides, it is possible to use all known alkylene oxides, for example ethylene oxide, propylene oxide, butylene oxide, styrene oxide. In particular, the alkylene oxides used are ethylene oxide, propylene oxide and mixtures of the compounds mentioned.

As starting substances H-functional compounds are used. In particular, alcohols having a functionality of 1 to 8, preferably 2 to 8, are used. Alcohols having a functionality of 2 to 6, in particular 2 and 3, are used as starting substances for the preparation of polyether alcohols which are used for flexible polyurethane foams. Examples are ethylene glycol, propylene glycol, glycerol, trimethylolpropane, pentaerythritol, sorbitol. In the addition of the alkylene oxides by means of DMC catalysts, it is advantageous to use together with or in place of the alcohols mentioned their reaction products with alkylene oxides, in particular propylene oxide. Such compounds preferably have a molecular weight of up to 1000 g / mol. The addition of the alkylene oxides in the preparation of these reaction products can be carried out with any catalysts, for example with basic catalysts. The polyether alcohols for the production of flexible polyurethane foams usually have a hydroxyl number in the range between 20 and 100 mg KOH / g.

In general, the entire starting substance is initially charged and after activation the alkylene oxide is added.

In a particular embodiment of the preparation of polyether alcohols, only part of the starting substance is initially introduced and the reaction started by the addition of alkylene oxide. Thereafter, at least during part of the reaction further starting substance and alkylene oxide is added. This procedure is described, for example, in EP 879,259. By this embodiment of the method, the formation of very high molecular weight fractions in the polyether alcohol can be suppressed.

For the preparation of surface-active compounds, especially difunctional alcohols are used as starter substances. For the preparation of carrier oils are used as starting substances monofunctional alcohols having 5 to 20 carbon atoms in the main chain.

The addition of the alkylene oxides in the preparation of the polyether used for the process according to the invention can be carried out according to the known methods. It is thus possible that the polyether alcohols contain only one alkylene oxide. When using a plurality of alkylene oxides, a so-called block-wise addition in which the alkylene oxides are added one after the other in succession, or a so-called statistical addition, in which the alkylene oxides are added together, possible. It is also possible to incorporate blockwise as well as random sections into the polyether chain in the preparation of the polyether alcohols. For the preparation of surface-active compounds and carrier oils, the addition of the alkylene oxides takes place mostly in blocks.

Preferably, for the production of polyurethane slab foams

Polyether alcohols having a high content of secondary hydroxyl groups and a content of ethylene oxide units in the polyether chain of not more than 30 wt .-%, based on the weight of the polyether alcohol used. Preferably, these polyether alcohols have a propylene oxide block at the chain end. Polyurethane alcohols having a high content of primary hydroxyl groups and an ethylene oxide end block in an amount of <20% by weight, based on the weight of the polyether alcohol, are used in particular for the production of flexible polyurethane foams. For polyetherols for flexible foams produced exclusively by means of DMC catalysis, it is also possible to use the preparation processes for alkoxylation described in WO 01/44347 and the polyetherols resulting therefrom.

The addition of the alkylene oxides is carried out under the usual conditions, at temperatures in the range of 60 to 180 ⁰ C, preferably between 90 to 140 ⁰ C, in particular between 100 to 130 ° C and pressures in the range of 0 to 20 bar, preferably in the range of 0 to 10 bar and in particular in the range of 0 to 5 bar. The mixture of starting substance and DMC catalyst can be pretreated by stripping before starting the alkoxylation according to the teaching of WO 98/52689.

After completion of the addition of the alkylene oxides of the polyether alcohol is worked up by conventional methods by the unreacted alkylene oxides and volatile constituents are removed, usually by distillation, steam or gas stripping and other methods of deodorization. If necessary, filtration can also be carried out.

The polyether alcohols thus prepared can be used, for example, for the preparation of polyurethanes, as surfactants or as carrier oils.

By using the DMC catalysts according to the invention, surprisingly, polyether alcohols can be prepared which have very good properties. The narrow molecular weight distribution results in a low product viscosity and a low content of high molecular weight components. Furthermore, the induction time at the start of the reaction of the alkoxylation is significantly reduced, and the reaction on runs at lower total pressures and lower concentrations of free alkylene oxide.

Compared with the process described in the prior art for the preparation of DMC catalysts, in which a hexacyanometallic acid is first prepared in a separate step, a process step is thus saved. The catalytic activity is comparable to or better than DMC catalysts, hereinafter called conventional DMC catalysts, obtained from the reaction of H ₃ [Co (CN) ₆ ] prepared by ion exchange or salt metathesis with metal salt. The DMC catalysts prepared by the process according to the invention lead in the reaction of starter alcohols with alkylene oxides polyether alcohols of excellent quality, such as low viscosity, narrow molecular weight distribution, and a low content of high molecular weight fractions that are comparable or better than polyols ole, with conventional DMC Catalysts were synthesized. The new, improved DMC catalysts do not contain any acid as an ingredient.

The invention will be described in more detail in the following examples.

catalyst Preparation

example 1

In a 2L stirred tank 1000 g of an aqueous K3 [Co (CN) 6] solution

(0.9 wt .-% Co). The temperature was adjusted to 25 ⁰ C. With 5M sulfuric acid, a pH of 1, 1 was set. At a stirring power of 1 W / L, 580 g of zinc acetate solution (2.6% by weight of Zn) were metered in over the course of 45 minutes. The stirrer power was reduced to 0.4 W / L. 100g Pluronic ^® PE 6200 from BASF AG were added and the solution at 55 ⁰ C heated. Within 10 minutes, 200 g of zinc acetate solution (2.6% Zn) were added. The pH after dosing was 4.8. The post-reaction time was chosen so that the total test duration is 200 minutes. The catalyst was filtered off and then resuspended 2x in 1 L of water. After final filtration, the drying was carried out at 60 ° for 16 hours.

Example 2

The procedure was as used in Example 1, except that instead of 100 g of Pluronic ^® PE 6200, 40 g of Pluronic ^® PE 6200

Example 3 The procedure was as in Example 1, except that instead of 100g Pluronic ^® PE 6200 were 40 g Lutensol ^® AP20 BASF AG used Example 4

The procedure was as in Example 1, except that instead of 100g Pluronic ^® PE 6200 were 40 g Lutensol ^® APδ BASF AG used

Examination of the catalyst activity

In a 250 mL stirred autoclave 64 g of a glycerol propoxylate molecular weight about 900 g / mol (hereinafter called VP900) with the appropriate amount of DMC catalyst by means of an Ultraturrax device for 5 minutes finely dispersed. Subsequently, the reactor was sealed and evacuated at a temperature of 100 ⁰ C for two hours at 3 mbar. Subsequently, at 130 ^° C., 36 g of propylene oxide were metered in within 2 minutes and the course of the pressure and temperature was recorded. After complete reaction of the propylene oxide, recognizable by the drop in pressure to a constant level, the reaction product was discharged from the autoclave at 100 ^° C. after inerting with nitrogen and degassing at 10 mbar, and the yield was determined. From the recorded curves, the time to the occurrence of the maximum determined was taken as a measure of the activity.

Catalyst concentration light-off time max. Temp. Max. Pressure yield

From example [ppm] [min] [ ⁰ C] [bar] [g]

4 100 1 231 9,4 97

4 50 1 239 9,5 97

4 25 2 194 8,5 96

3 50 2 237 9,5 97

3 25 8 156 7.7 96

2 50 2 246 10.4 96

2 25 2 206 9,6 97

1 50 2 243 10.4 97

1 25 3 185 8,6 96

Example of the polyol synthesis

In a 20 L stirred autoclave 2.5 kg of the above VP900 were charged and with the calculated amount of DMC catalyst (TK085) (100 ppm, based on the final polyether alcohol), dispersed in VP900 added. After a dehydration phase under reduced pressure at 130 ^° C., 1.67 kg of a mixture of glycerol and DEG and 15.84 kg of propylene oxide were added in parallel so that the pressure did not exceed a value of 5 bar. The intermediate thus obtained had an OHN of 151.5 mg KOH / g. From this intermediate 6.34 kg were reacted in the same reactor without further catalyst addition at 120 ⁰ C with a total of 13.67 kg of a mixture of propylene and ethylene oxide.

After a short post-reaction phase of about 15 minutes, volatiles were removed from the reaction mixture by distillation and the product was discharged from the reactor after cooling. The colorless, clear liquid obtained had the following characteristics: OHN 49.0 mg KOH / g, acid number 0.034 mg KOH / g, viscosity (25 ° C.) 577 mPas, iodine value 0.04 g 12/100 g.

Claims

claims:

1. A process for preparing DMC catalysts by reacting cyano metal tetallate compounds, preferably cyanometalate salts, in particular alkali metal or alkaline earth metal salts, with metal salts, characterized in that the reaction is carried out in the presence of a Bronsted acid.

2. The method according to claim 1, characterized in that are used as Brönstedt acids all water-soluble and stable at room temperature mineral and / or carboxylic acids.

3. The method according to claim 1, characterized in that the carboxylic acids contain one or more carboxyl groups and up to 20 carbon atoms in the molecule.

4. The method according to claim 1, characterized in that the carboxylic acids are substituted electronegative elements.

5. The method according to claim 1, characterized in that the mineral acids are selected from the group comprising sulfuric acid, hydrochloric acid, sulfurous acid, alkyl, aryl and halosulfonic HSO ₃ X, where X is halogen, alkyl having an alkyl radical of 1 to 20 Carbon atoms, aryl, preferably phenyl or naphthyl, disulphuric acid, hydrochloric acid, chloric acid, perchloric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid, hydrobromic acid, phosphoric acid, phosphorous acid, hypophosphorous acid,

Tetrafluoroboric acid, hexafluorophosphoric acid, nitric acid, nitrous acid.

6. The method according to claim 1, characterized in that the mineral acids are selected from the group comprising sulfuric acid, alkyl, aryl and halogeno-lonsulfonic acids, hydrochloric acid, perchloric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid, phosphoric acid, nitric acid.

7. The method according to claim 1, characterized in that the mineral acids are selected from the group comprising sulfuric acid and hydrochloric acid.

8. The method according to claim 1, characterized in that the Brönstedt acids are used in such an amount that the pH after precipitation is in the range between 3 and 6.

9. DMC catalysts, preparable according to one of claims 1 to 8.

10. A process for the preparation of polyether alcohols by catalytic addition of alkylene oxides to H-functional starter substances, characterized in that are used as catalysts DMC catalysts according to claim 9.