Process For Preparing Polyether Alcohols Having A Low Metal Ion Content

Abstract

The invention relates to a process for preparing polyether alcohols by reacting one or more alkylene oxides having one or more H-functional starting substances in a continuous reactor that comprises flow channels, at a temperature of 180° C. to 250° C. and a pressure of 60 to 150 bar in the presence of a basic, metal-containing catalyst, wherein the concentration of the catalyst, based on the total amount of reaction mixture of alkylene oxide, H-functional starting substance and catalyst, is no more than 50 ppm by weight, and the residence time of the reaction mixture in the reactor is 15 to 120 minutes.

Claims

1. A process for producing a polyether alcohol by the steps of reacting one or more alkylene oxides with one or more H-functional starter substances in a continuously operated reactor, wherein the continuously operated reactor comprises flow channels at a temperature of 180° C. to 250° C. and a pressure of 60 to 150 bar in the presence of a basic, metal-containing catalyst, wherein the concentration of the catalyst reported as the metal content, based on the total amount of a reaction mixture composed of alkylene oxide, H-functional starter substance and catalyst, is not more than 50 ppm by weight, and the residence time of the reaction mixture in the reactor is from 15 to 120 minutes.

2. The process as claimed in claim 1, wherein hydroxides or alkoxides of alkali metals and/or alkaline earth earth metals, are used as the catalyst.

3. The process as claimed in claim 1, wherein the concentration of the catalyst reported as the metal content is 1 to 50 ppm.

4. The process as claimed in claim 1, wherein hydroxides or alkoxides of alkali metals selected from the group consisting of sodium or potassium are used as the catalyst, and wherein the sum of the concentrations of Na ions and K ions in the polyether alcohol is at most 30 ppm.

5. The process as claimed in claim 1, wherein the reactor contains a plurality of parallel, alternatingly superposed and microstructured layers of reaction channels and temperature-control channels.

6. The process as claimed in claim 1, wherein the pressure and temperature are chosen such that the reaction mixture remains liquid at all times.

7. The process as claimed in claim 1, wherein the residence time of the reaction mixture in the reactor is between 20 and 100 minutes.

8. The process as claimed in claim 1, wherein the flow axis of the reactor follows a temperature profile and the reactor comprises two or more heating or cooling zones having at least one distributing means and at least one collecting means per heating or cooling zone.

9. The process as claimed in claim 1, wherein the alkylene oxide is selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide, pentene oxide, glycidyl ether, hexene oxide and styrene oxide, preferably ethylene oxide, propylene oxide and mixtures thereof.

10. The process as claimed in claim 1, wherein the H-functional starter substance comprises an alcohol having a functionality of 1 to 8.

11. The process as claimed in claim 1, wherein the H-functional starter substance is an alkoxylate containing units of ethylene oxide and units of propylene oxide.

12. The process as claimed in claim 11, in which the units of ethylene oxide and units of propylene oxide are arranged blockwise.

13. The process as claimed in claim 1, wherein the H-functional starter substance comprises an alcohol having a functionality of 1 and conforming to the general formula R—OH, wherein R is an alkyl-, alkenyl-, aryl-, aralkyl or alkylaryl radical having 1 to 60 carbon atoms.

14. The process as claimed in claim 13, in which the H-functional starter substance is selected from methanol, butanol, hexanol, heptanol, octanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, butenol, hexenol, heptenol, octenol, nonenol, decenol, undecenol, vinyl alcohol, allyl alcohol, geraniol, linalool, citronellol, phenol, nonylphenol, and mixtures thereof.

15. The process as claimed in claim 1, wherein the H-functional starter substance comprises one or more alcohols having a functionality of 2 to 8.

16. The process as claimed in claim 1, wherein the H-functional starter substance is one or more alcohols selected from the group consisting of ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, glycerol, trimethylolpropane, pentaerythritol, sucrose, saccharose, glucose, fructose, mannose, sorbitol, hydroxyalkylated (meth)acrylic acid derivatives and alkoxylated derivatives of the abovementioned H-functional starter substances up to a molecular weight of 1500 D.

17. The process as claimed in claim 1, wherein a mixer is arranged upstream of the reactor.

18. The process as claimed in claim 17, in which the mixer is a microstructured mixer arranged outside the reactor.

19. The process as claimed in claim 1, wherein basic catalysts are used as the catalyst.

20. The process as claimed in claim 1, wherein the catalyst comprises an alkali or alkaline earth metal hydroxide and/or alkali metal alkoxide.

21. The process as claimed in claim 1, wherein the catalyst is selected from sodium hydroxide, potassium hydroxide and cesium hydroxide.

22. The process as claimed in claim 1, wherein the catalyst is present in a concentration of 5 to 30 ppm, based on the total weight of the reaction mixture.

Description

EXEMPLARY EMBODIMENTS

[0058] A continuously operated flow apparatus was constructed for the exemplary embodiments (FIG. 1). The test plant is configured for 100 bar (absolute pressure) to ensure that ethylene oxide remains liquid in the reactor even at temperatures up to 220° C. A simple flow tube reactor was used to study the reactions. The flow tube reactor consisted of a stainless steel tube having an external diameter of 3 mm and an internal diameter of 1.6 mm (Swagelok, 50 m in length, internal volume of 100 ml realizable).

[0059] The test plant has 2 pressure vessels (Büchi, design pressure 15 bar abs., see FIG. 1) of 500 ml in volume for the provision of EO and DEG. Both vessels may be pressurized with nitrogen from a nitrogen line (10 bar) to provide sufficient supply pressure for two HPLC pumps and to avoid outgassing of the EO due to the strokes of the pistons. In case of bubble formation in the pistons of the HPLC pump the pump may no longer convey liquid. To purge the EO pump the DEG pressure vessel may also be switched to this pump. Two further atmospheric pressure vessels, each of one liter in volume, are also available for purging the pumps.

[0060] Downstream of the pumps both material streams are mixed in an interdigital mixer (Ehrfeld Mikrotechnik) and then passed into the reactor. The product flow is cooled via a heat exchanger (Ehrfeld Mikrotechnik) downstream of the reactor. A pressure regulator (KPB series, Swagelok) makes it possible to adjust the plant pressure to 137 bar. Three pressure sensors (Keller, in modules from Ehrfeld Mikrotechnik) make it possible to capture and plot the pressure upstream of the reactor, upstream of the heat exchanger and upstream of the pressure regulator of the test plant.

[0061] For protection of the plant, respective pressure relief valves (Swagelok) adjusted to 120 bar abs are installed upstream of the reactor and upstream of the pressure controller. This ensures that in the event of a blockage in the reactor or in the region of the pressure regulator, even in the event of failure of the automatic shutdown of the HPLC pumps (max. pressure 120 bar) fails, a depressurization of the plant is possible.

[0062] The reactor is kept at the correct temperature via a heating bath under closed-loop control in which the reactor is immersed. To capture and plot the temperature of the product stream, respective Pt-100 thermocouple modules (Ehrfeld Mikrotechnik) are installed upstream and downstream of the heat exchanger.

EXAMPLE 1

[0063] Substrate: Diethylene glycol (DEG) [0064] Catalyst: sodium hydroxide, 50% aqueous solution [0065] Catalyst concentration: 0.0155 (% by wt. based on DEG) [0066] Metered addition rate of DEG+catalyst: 0.64 ml/min; metered addition rate of EO: 2.03 ml/min [0067] Reactor temperature: 210° C. [0068] Pressure: 95 bar abs [0069] Residence time: 45 min

EXAMPLE 2

[0070] Substrate: Diethylene glycol (DEG) [0071] Catalyst: sodium hydroxide, 50% aqueous solution [0072] Catalyst concentration: 0.0155 (% by wt. based on DEG) [0073] Metered addition rate of DEG+catalyst: 0.82 ml/min; metered addition rate of EO: 2.6 ml/min [0074] Reactor temperature: 220° C. [0075] Pressure: 95 bar abs [0076] Residence time: 35 min

EXAMPLE 3

[0077] Substrate: Diethylene glycol (DEG) [0078] Catalyst: sodium hydroxide, 50% aqueous solution [0079] Catalyst concentration: 0.0155 (% by wt. based on DEG) [0080] Metered addition rate of DEG+catalyst: 1.15 ml/min; metered addition rate of EO: 3.65 ml/min [0081] Reactor temperature: 230° C. [0082] Pressure: 95 bar abs [0083] Residence time: 25 min

EXAMPLE 4

[0084] Substrate: Diethylene glycol (DEG) [0085] Catalyst: sodium hydroxide, 50% aqueous solution [0086] Catalyst concentration: 0.0155 (% by wt. based on DEG) [0087] Metered addition rate of DEG+catalyst: 1.15 ml/min; metered addition rate of EO: 3.64 ml/min [0088] Reactor temperature: 220° C. [0089] Pressure: 95 bar abs [0090] Residence time: 25 min

EXAMPLE 5

[0091] Substrate: Diethylene glycol (DEG) [0092] Catalyst: sodium hydroxide, 50% aqueous solution [0093] Catalyst concentration: 0.0155 (% by wt. based on DEG) [0094] Metered addition rate of DEG+catalyst: 0.64 ml/min; metered addition rate of EO: 2.03 ml/min [0095] Reactor temperature: 220° C. [0096] Pressure: 95 bar abs [0097] Residence time: 45 min

EXAMPLE 6

[0098] Substrate: Diethylene glycol (DEG) [0099] Catalyst: sodium hydroxide, 50% aqueous solution [0100] Catalyst concentration: 0.0155 (% by wt. based on DEG) [0101] Metered addition rate of DEG+catalyst: 0.48 ml/min; metered addition rate of EO: 1.52 ml/min [0102] Reactor temperature: 220° C. [0103] Pressure: 95 bar abs [0104] Residence time: 45 min

EXAMPLE 7

[0105] Substrate: Diethylene glycol (DEG) [0106] Catalyst: sodium hydroxide, 50% aqueous solution [0107] Catalyst concentration: 0.155 (% by wt. based on DEG) [0108] Metered addition rate of DEG+catalyst: 1.15 ml/min; metered addition rate of EO: 3.64 ml/min [0109] Reactor temperature: 180° C. [0110] Pressure: 95 bar abs [0111] Residence time: 25 min

TABLE-US-00001 NaOH (50%) [% by wt. Sodium Ethylene Temper- Residence based Metal in oxide Ex- ature time on content product in product ample τ/° C. τ/min DEG] [ppm] [ppm] [ppm] 1 210 45 0.0155 44.6 13 1000 2 220 35 0.0155 44.6 21 23 3 230 25 0.0155 44.6 14 2000 4 220 25 0.0155 44.6 21 8000 5 220 45 0.0155 44.6 12 1 6 220 60 0.0155 44.6 12 <0.5 7 (C) 180 25 0.155 446 120 200

[0112] The EO content in the product indicates completeness of reaction. Preferably very little, if any, EO should remain after the reaction since it is toxic/explosive and may have to be removed at higher concentrations. Furthermore, complete conversion is desired to ensure the correct stoichiometry and to ensure that the low metal ion contents based on the mass of the end product are achieved.

[0113] Shorter residence times <600 s lead to incomplete reaction and would result in unreacted ethylene oxide being discharged from the reactor. This result was obtained experimentally. Ethylene oxide is a toxic/explosive gas. Such an experiment should not be carried out for safety reasons. Due to the incomplete reaction and the gaseous reactant ethylene oxide, no meaningful analytical evaluation of the experiment would be possible either.