PROCESS FOR PREPARING DOUBLE METAL CYANIDE CATALYSTS

Abstract

The present invention relates to a process for preparing a double metal cyanide (DMC) catalyst, comprising the reaction of an aqueous solution of a cyanide-free metal salt, an aqueous solution of an alkaline metal cyanide salt, an organic complex ligand and optionally a complex-forming component, wherein the metal cyanide salt is one or more compound(s) and is selected from the group consisting of potassium hexacyanocobaltat(III), potassium hexacyanoferrate(II), potassium hexacyanoferrate(III), calcium hexacyanocobaltate(III) and lithium hexacyanocobaltat(III), where the organic complex ligand is one or more compound(s) and is selected from the group consisting of dimethoxyethane, tert-butanol, 2-methyl-3-buten-2-ol, 2-methyl-3-butyn-2-ol, ethylene glycol mono-tert-butyl ether and 3-methyl-3-oxetanemethanol, and wherein the alkaline metal cyanide salt used has an alkalinity by the titration method disclosed in the Experimental of between 0.700% and 3.000% by weight of sodium hydroxide (NaOH) based on the total weight of the alkaline metal cyanide salt used. The invention further relates to double metal cyanide (DMC) catalysts obtainable by the process according to the invention and to the use of DMC catalysts for preparation of polyoxyalkylene polyols.

Claims

1. A process for preparing a double metal cyanide catalyst (DMC) comprising reacting an aqueous solution of a cyanide-free metal salt, an aqueous solution of an alkaline metal cyanide salt, an organic complex ligand and optionally a complex-forming component, wherein the metal cyanide salt comprises potassium hexacyanocobaltate(III), potassium hexacyanoferrate(II), potassium hexacyanoferrate(III), calcium hexacyanocobaltate(III), lithium hexacyanocobaltate(III) or a mixture thereof, wherein the organic complex ligand comprises dimethoxyethane, tert-butanol, 2-methyl-3-buten-2-ol, 2-methyl-3-butyn-2-ol, ethylene glycol mono-tert-butyl ether, 3-methyl-3-oxetanemethanol, or a mixture thereof, and wherein the alkaline metal cyanide salt has an alkalinity, determined at 25° C. on a 24% by weight aqueous solution by titration with 0.1 mol/liter of hydrochloric acid, of between 0.700% and 3.000% by weight sodium hydroxide, based on the total weight of the alkaline metal cyanide salt used.

2. The process as claimed in claim 1, wherein the alkalinity of the alkaline metal cyanide salt is between 0.700% and 2.000% by weight NaOH.

3. The process as claimed in claim 1, wherein the alkaline metal cyanide salt contains a metal hydroxide, a metal carbonate, a metal oxide, or a mixture of any two or more thereof.

4. The process as claimed in claim 3, wherein the alkaline metal cyanide salt is obtained by addition of the metal hydroxide, the metal carbonate, the metal oxide, or the mixture of any two or more thereof, during the preparation of the alkaline metal cyanide salt.

5. The process as claimed in claim 3, wherein the alkaline metal cyanide salt is obtained by reaction of a metal cyanide salt with the metal hydroxide, the metal carbonate, the metal oxide, or the mixture of any two or more thereof.

6. The process as claimed in claim 5, wherein the metal cyanide salt comprises potassium hexacyanocobaltate(III).

7. The process as claimed in claim 3, wherein one or more metals of the first or second main group of the periodic table of the elements are present in the alkaline metal cyanide salt.

8. The process as claimed in claim 3, wherein the metal hydroxide, metal oxide, metal carbonate, or mixture of any two or more thereof comprises sodium carbonate, sodium hydroxide, potassium hydroxide, potassium carbonate, calcium oxide, calcium hydroxide, barium hydroxide, barium oxide, or a mixture of any two or more thereof.

9. The process as claimed in claim 8, wherein the reaction in step i) is effected in the presence of the metal hydroxide, the metal carbonate, the metal oxide, or the mixture of any two or more thereof.

10. The process as claimed in claim 8, wherein, for the reaction in step i), 0.2 to 1.0 mol of base equivalents, based on 1 mol of the alkaline metal cyanide salt used for the catalyst synthesis, of metal hydroxide, metal carbonate, metal oxide, or mixture of any two or more thereof is used.

11. The process as claimed in claim 1, wherein the aqueous solution comprises the complex-forming component, wherein the complex-forming component comprises a polyether.

12. The process as claimed in claim 1, wherein the organic complex ligand comprises tert-butanol.

13. The process as claimed in claim 1, wherein the reaction in step i) is effected using a mixing nozzle.

14. A double metal cyanide catalyst (DMC) obtained by the process of claim 1.

15. A polyoxyalkylene polyol prepared using the double metal cyanide catalyst of claim 14.

16. The process as claimed in claim 2, wherein the alkalinity of the alkaline metal cyanide salt is between 0.800% and 1.500% by weight NaOH.

17. The process as claimed in claim 10, wherein, for the reaction in step i), 0.3 to 0.7 mol, of base equivalents, based on 1 mol of the alkaline metal cyanide salt used for the catalyst synthesis, of metal hydroxide, metal carbonate, metal oxide, or mixture of any two or more thereof is used.

18. The process as claimed in claim 11, wherein the complex-forming component comprises a polyether polyol.

19. The process as claimed in claim 13, wherein the mixing nozzle comprises a jet disperser.

20. The polyoxyalkylene polyol of claim 15, wherein the polyoxyalkylene polyol comprises a polyether polyol and/or polyethercarbonate polyol.

Description

EXAMPLES

[0133] OH numbers were determined in accordance with the procedure of DIN 53240. Viscosities were determined by rotary viscometer (Physica MCR 51, manufacturer: Anton Paar) in accordance with the procedure of DIN 53018.

[0134] The alkalinity (in % by weight sodium hydroxide (NaOH)) of the alkaline metal cyanide salt used was determined at 25° C. on a 24% by weight aqueous solution by titration with HCl (0.1 mol/l).

[0135] Preparation of the DMC Catalysts:

Example 1 (Comparative)

[0136] The catalyst was prepared using an apparatus as per FIG. 4 from WO 01/39883 A1.

[0137] In a loop reactor containing a jet disperser as per FIG. 2 from WO 01/39883 A1 having one bore (diameter 0.7 mm) was circulated in step i) a solution of 258 g of zinc chloride and 1.43 g of NaOH (0.46 mol(NaOH)/1 mol(Khex)) in 937 g of distilled water and 135 g of tert-butanol at 50° C. (determined in the vessel D2 in FIG. 4 of WO 01/39883 A1). To this was metered in a solution of 26 g of potassium hexacyanocobaltate (Khex) having an alkalinity content of 0.400% by weight NaOH in 332 g of distilled water. The pressure drop in the jet disperser was 2.9 bar. Subsequently, the dispersion formed was circulated for 60 min at 50° C. with a pressure drop in the jet disperser of 2.9 bar. Thereafter, a mixture of 5.7 g of tert-butanol, 159 g of distilled water and 27.6 g of polypropylene glycol 1000 (PPG-1000) was metered in and the dispersion was then circulated for 80 min at 50° C. with a pressure drop in the jet disperser of 2.9 bar.

[0138] 230 g of the dispersion obtained were filtered in a pressure suction filter with filter area 20 cm.sup.3 (step ii)), and then washed with a mixture of 82 g of tert-butanol, 42.3 g of distilled water and 1.7 g of polypropylene glycol 1000 (step iii)). The washed filtercake was squeezed mechanically between two strips of filter paper and finally dried at 60° C. under high vacuum at about 0.05 bar (absolute) for 2 h (step iv)). The theoretical total alkalinity of the DMC catalyst is 1.534 g (NaOH), as the sum of the masses of the alkalinity of the potassium hexacyanocobaltate (Khex) used of 0.104 g (NaOH) and of the mass of the sodium hydroxide used in step i) of 1.43 g.

Example 2 (Comparative)

[0139] In a loop reactor containing a jet disperser as per FIG. 2 from WO 01/39883 A1 having one bore (diameter 0.7 mm) was circulated in step i) a solution of 258 g of zinc chloride and 1.36 g of NaOH (0.43 mol(NaOH)/1 mol(Khex)) in 937 g of distilled water and 135 g of tert-butanol at 50° C. (determined in the vessel D2 in FIG. 4 of WO 01/39883 A1). To this was metered in a solution of 26 g of potassium hexacyanocobaltate having an alkalinity content of 0.660% by weight NaOH in 332 g of distilled water. The pressure drop in the jet disperser was 2.9 bar. Subsequently, the dispersion formed was circulated for 60 min at 50° C. with a pressure drop in the jet disperser of 2.9 bar. Thereafter, a mixture of 5.7 g of tert-butanol, 159 g of distilled water and 27.6 g of polypropylene glycol 1000 (PPG-1000) was metered in and the dispersion was then circulated for 80 min at 50° C. with a pressure drop in the jet disperser of 2.9 bar.

[0140] 230 g of the dispersion obtained were filtered in a pressure suction filter with filter area 20 cm.sup.3 (step ii)), and then washed with a mixture of 82 g of tert-butanol, 42.3 g of distilled water and 1.7 g of polypropylene glycol 1000 (step iii)). The washed filtercake was squeezed mechanically between two strips of filter paper and finally dried at 60° C. under high vacuum at about 0.05 bar (absolute) for 2 h (step iv)). The theoretical total alkalinity of the DMC catalyst is 1.532 g (NaOH), as the sum of the masses of the alkalinity of the potassium hexacyanocobaltate (Khex) used of 0.172 g (NaOH) and of the mass of the sodium hydroxide used in step i) of 1.36 g.

Example 3

[0141] In a loop reactor containing a jet disperser as per FIG. 2 from WO 01/39883 A1 having one bore (diameter 0.7 mm) was circulated in step i) a solution of 258 g of zinc chloride and 1.31 g of NaOH (0.42 mol(NaOH)/1 mol(Khex)) in 937 g of distilled water and 135 g of tert-butanol at 50° C. (determined in the vessel D2 in FIG. 4 of WO 01/39883 A1). To this was metered in a solution of 26 g of potassium hexacyanocobaltate having an alkalinity content of 0.855% by weight NaOH in 332 g of distilled water. The pressure drop in the jet disperser was 2.9 bar. Subsequently, the dispersion formed was circulated for 60 min at 50° C. with a pressure drop in the jet disperser of 2.9 bar. Thereafter, a mixture of 5.7 g of tert-butanol, 159 g of distilled water and 27.6 g of polypropylene glycol 1000 (PPG-1000) was metered in and the dispersion was then circulated for 80 min at 50° C. with a pressure drop in the jet disperser of 2.9 bar.

[0142] 230 g of the dispersion obtained were filtered in a pressure suction filter with filter area 20 cm.sup.3 (step ii)), and then washed with a mixture of 82 g of tert-butanol, 42.3 g of distilled water and 1.7 g of polypropylene glycol 1000 (step iii)). The washed filtercake was squeezed mechanically between two strips of filter paper and finally dried at 60° C. under high vacuum at about 0.05 bar (absolute) for 2 h (step iv)). The theoretical total alkalinity of the DMC catalyst is 1.532 g (NaOH), as the sum of the masses of the alkalinity of the potassium hexacyanocobaltate (Khex) used of 0.222 g (NaOH) and of the mass of the sodium hydroxide used in step i) of 1.31 g.

Example 4

[0143] In a loop reactor containing a jet disperser as per FIG. 2 from WO 01/39883 A1 having one bore (diameter 0.7 mm) was circulated in step i) a solution of 258 g of zinc chloride and 1.26 g of NaOH (0.40 mol(NaOH)/1 mol(Khex)) in 937 g of distilled water and 135 g of tert-butanol at 50° C. (determined in the vessel D2 in FIG. 4 of WO 01/39883 A1). To this was metered in a solution of 26 g of potassium hexacyanocobaltate having an alkalinity content of 1.067% by weight NaOH in 332 g of distilled water. The pressure drop in the jet disperser was 2.9 bar. Subsequently, the dispersion formed was circulated for 60 min at 50° C. with a pressure drop in the jet disperser of 2.9 bar. Thereafter, a mixture of 5.7 g of tert-butanol, 159 g of distilled water and 27.6 g of polypropylene glycol 1000 (PPG-1000) was metered in and the dispersion was then circulated for 80 min at 50° C. with a pressure drop in the jet disperser of 2.9 bar.

[0144] 230 g of the dispersion obtained were filtered in a pressure suction filter with filter area 20 cm.sup.3 (step ii)), and then washed with a mixture of 82 g of tert-butanol, 42.3 g of distilled water and 1.7 g of polypropylene glycol 1000 (step iii)). The washed filtercake was squeezed mechanically between two strips of filter paper and finally dried at 60° C. under high vacuum at about 0.05 bar (absolute) for 2 h (step iv)). The theoretical total alkalinity of the DMC catalyst is 1.537 g (NaOH), as the sum of the masses of the alkalinity of the potassium hexacyanocobaltate (Khex) used of 0.277 g (NaOH) and of the mass of the sodium hydroxide used in step i) of 1.26 g.

Example 5

[0145] In a loop reactor containing a jet disperser as per FIG. 2 from WO 01/39883 A1 having one bore (diameter 0.7 mm) was circulated in step i) a solution of 258 g of zinc chloride and 1.20 g of NaOH (0.38 mol(NaOH)/1 mol(Khex)) in 937 g of distilled water and 135 g of tert-butanol at 50° C. (determined in the vessel D2 in FIG. 4 of WO 01/39883 A1). To this was metered in a solution of 26 g of potassium hexacyanocobaltate having an alkalinity content of 1.279% by weight NaOH in 332 g of distilled water. The pressure drop in the jet disperser was 2.9 bar. Subsequently, the dispersion formed was circulated for 60 min at 50° C. with a pressure drop in the jet disperser of 2.9 bar. Thereafter, a mixture of 5.7 g of tert-butanol, 159 g of distilled water and 27.6 g of polypropylene glycol 1000 (PPG-1000) was metered in and the dispersion was then circulated for 80 min at 50° C. with a pressure drop in the jet disperser of 2.9 bar.

[0146] 230 g of the dispersion obtained were filtered in a pressure suction filter with filter area 20 cm.sup.3 (step ii)), and then washed with a mixture of 82 g of tert-butanol, 42.3 g of distilled water and 1.7 g of polypropylene glycol 1000 (step iii)). The washed filtercake was squeezed mechanically between two strips of filter paper and finally dried at 60° C. under high vacuum at about 0.05 bar (absolute) for 2 h (step iv)). The theoretical total alkalinity of the DMC catalyst is 1.533 g (NaOH), as the sum of the masses of the alkalinity of the potassium hexacyanocobaltate (Khex) used of 0.333 g (NaOH) and of the mass of the sodium hydroxide used in step i) of 1.20 g.

Example 6

[0147] In a loop reactor containing a jet disperser as per FIG. 2 from WO 01/39883 A1 having one bore (diameter 0.7 mm) was circulated in step i) a solution of 258 g of zinc chloride and 1.10 g of NaOH (0.35 mol(NaOH)/1 mol(Khex)) in 937 g of distilled water and 135 g of tert-butanol at 50° C. (determined in the vessel D2 in FIG. 4 of WO 01/39883 A1). To this was metered in a solution of 26 g of potassium hexacyanocobaltate having an alkalinity content of 1.690% by weight NaOH in 332 g of distilled water. The pressure drop in the jet disperser was 2.9 bar. Subsequently, the dispersion formed was circulated for 60 min at 50° C. with a pressure drop in the jet disperser of 2.9 bar. Thereafter, a mixture of 5.7 g of tert-butanol, 159 g of distilled water and 27.6 g of polypropylene glycol 1000 (PPG-1000) was metered in and the dispersion was then circulated for 80 min at 50° C. with a pressure drop in the jet disperser of 2.9 bar.

[0148] 230 g of the dispersion obtained were filtered in a pressure suction filter with filter area 20 cm.sup.3 (step ii)), and then washed with a mixture of 82 g of tert-butanol, 42.3 g of distilled water and 1.7 g of polypropylene glycol 1000 (step iii)). The washed filtercake was squeezed mechanically between two strips of filter paper and finally dried at 60° C. under high vacuum at about 0.05 bar (absolute) for 2 h (step iv)). The theoretical total alkalinity of the DMC catalyst is 1.539 g (NaOH), as the sum of the masses of the alkalinity of the potassium hexacyanocobaltate (Khex) used of 0.439 g (NaOH) and of the mass of the sodium hydroxide used in step i) of 1.10 g.

[0149] Catalyst Test (“8K Diol Stressed Test”):

[0150] The DMC catalysts were tested in the so-called “8K diol stressed test”. Here, a polypropylene glycol having a calculated OH number=14 mg KOH/g, that is to say molecular weight=8000 g/mol (“8K diol”) was prepared proceeding from a bifunctional polypropylene glycol starter having an OH number=147 mg KOH/g (“Arcol Polyol 725” from Covestro) with a short propylene oxide metering time (30 minutes). The decisive evaluation criterion for the catalyst quality/activity in this test is the viscosity of the polyol obtained, with a DMC catalyst of increased quality/activity leading to a lower 8K diol viscosity.

[0151] General Implementation:

[0152] A 1 liter stainless steel reactor was initially charged with 75 g of a bifunctional polypropylene glycol starter (OH number=147 mg KOH/g) and 30.7 mg of DMC catalyst. After 5 cycles of nitrogen/vacuum exchange between 0.1 and 3.0 bar (absolute), the reactor contents were heated to 130° C. with stirring (800 rpm). The mixture was then stripped with nitrogen for 30 min at 130° C. and 100 mbar (absolute). 7.5 g of propylene oxide were then added at 130° C. and 100 mbar (absolute) to activate the catalyst. The catalyst activation manifested in an accelerated pressure drop in the reactor. After the catalyst had been activated, the remaining propylene oxide (685.7 g) was metered in within 30 min at 130° C. with stirring (800 rpm). After a post-reaction time of 30 min at 130° C., volatile constituents were distilled off under reduced pressure (<10 mbar) at 90° C. for 30 min. The product was then cooled down to room temperature and removed from the reactor.

[0153] The OH number and viscosity (25° C.) of the product obtained were measured. In the event of a deviation of the measured OH number from the calculated OH number (14 mg KOH/g), a “corrected viscosity” was determined from the measured viscosity using the following formula:

corrected viscosity (25° C.)=measured viscosity (25° C.)+659*(OHN−14)

[0154] The results of the catalyst tests in the “8K diol stressed test” are summarized in table 1.

TABLE-US-00001 TABLE 1 Khex alkalinity OH [% by weight n(NaOH number Viscosity Viscosity Catalyst DMC NaOH]/ step Theoretical [mg 25° C./ 25° C./ test/ catalyst/ [mol(NaOH)/mol i)/n(Khex) total alkalinity KOH/g] measured corrected Example Example (Khex)] [mobmol].sup.a) [g(NaOH)].sup.b) [mPas] [mPas]  7 (comp.) 1 (comp.) 0.400/0.033 0.46 1.534 14.0 5765 5765  8 (comp.) 2 (comp.) 0.660/0.055 0.43 1.532 13.7 5820 5622  9 3 0.855/0.072 0.42 1.532 13.9 5100 5034 10 4 1.067/0.090 0.40 1.537 14.3 4745 4943 11 5 1.279/0.108 0.38 1.533 14.0 4940 4940 12 6 1.690/0.143 0.35 1.539 14.0 5095 5095 .sup.a)Sodium hydroxide (NaOH) added in step i) as base equivalent based on 1 mol of the alkaline potassium hexacyanocobaltate (Khex) used for the catalyst synthesis as alkaline metal cyanide salt .sup.b)Theoretical total alkalinity of the DMC catalyst in [g NaOH], this mass being the sum of the mass of the alkalinity of the potassium hexacyanocobaltate (Khex) used [g (NaOH)] and the mass of the sodium hydroxide used in step i).

[0155] The results show that DMC catalysts prepared using alkaline potassium hexacyanocobaltate (Khex) with an alkalinity of between 0.700% and 3.000% by weight NaOH, for the same theoretical total alkalinity of the DMC catalyst, lead to lower viscosity values of the polyols in the “8K diol stressed test”.