Preparation of a double metal cyanide catalyst

Details Preparation of a double metal cyanide catalyst Preparation of a double metal cyanide catalyst

2003-06-10

2004-04-06

Wood, Elizabeth D. (Department: 1755)

Catalyst, solid sorbent, or support therefor: product or process

Catalyst or precursor therefor

Inorganic carbon containing

C502S200000, C528S403000, C528S405000, C528S408000, C528S409000, C528S410000, C528S411000, C528S412000, C528S413000, C528S414000, C528S415000, C568S616000, C568S618000, C568S619000, C568S620000, C560S001000

Reexamination Certificate

active

06716788

ABSTRACT:

The present invention relates to a process for the preparation of a double metal cyanide catalyst, to a double metal cyanide catalyst per se, and to a process for the polymerization of alkylene oxides with the help of a double metal cyanide catalyst.
BACKGROUND OF THE INVENTION
Double metal cyanide (DMC) compounds are well known catalysts for epoxide polymerization, i.e. for polymerizing alkylene oxides like propylene oxide and ethylene oxide to yield poly(alkylene oxide) polymers, also referred to as polyether polyols. The catalysts are highly active, and give polyether polyols that have low unsaturation compared with similar polyols made using strong basic catalysts like potassium hydroxide. In addition to the preparation of polyether polyols, the catalysts can be used to make a variety of polymer products, including polyester polyols and polyetherester polyols. The polyols can be used to prepare polyurethanes by reacting them with polyisocyanates under appropriate conditions. Polyurethane products that can be made include polyurethane coatings, elastomers, sealants, foams, and adhesives.
Although active catalysts can be prepared with the help of the prior art processes, there is interest in further increasing the activity further.
WO 98/40162 describes a process for making double metal cyanide catalysts by reacting an aqueous solution of potassium hexacyanocobaltate, tert-butyl alcohol and an aqueous solution of zinc chloride in which the alkalinity of the aqueous solution of zinc chloride is about 0.2 to 2.0% wt of zinc oxide based on the amount of zinc chloride in the solution, most preferably from about 0.4 to about 0.9% wt. An amount of zinc oxide of 1.13% wt (Example 7) is considered too high: the polyols obtained had increased unsaturation and increased viscosity. 1.13% wt of zinc oxide corresponds with 0.019 mole of zinc oxide per mole of metal salt.
SUMMARY OF THE INVENTION
Contrary to the teaching of WO 98/40162, it has now been found that more active catalysts can be prepared in the presence of higher amounts of alkaline metal.
Therefore, the present invention relates to a process for the preparation of a double metal cyanide (DMC) catalyst, which process comprises:
(a) combining an aqueous solution of a metal salt with an aqueous solution of a metal cyanide salt and reacting these solutions; and
(b) recovering the DMC catalyst from the reaction mixture, in which process the DMC catalyst is prepared in the presence of from 0.03 to 0.4 mole of alkaline metal compound, based on amount of metal salt.
It has been found that the catalysts obtained by the process according to the present invention have unique characteristics. In addition to an increased activity, it was found that the molar ratio of metal derived from the metal salt to metal derived from the metal cyanide salt was higher than observed in catalysts prepared according to known methods. Therefore, the present invention further relates to double metal cyanide catalyst obtainable by a process according to the present invention, and to double metal cyanide catalyst prepared from a metal salt and a metal cyanide salt in which the molar ratio of metal derived from the metal salt to metal derived from the metal cyanide salt is at least 2.25.
The high activity of the present catalyst makes it possible to operate at much lower catalyst concentration than was envisaged until now.
Therefore, the present invention further relates to a process for the polymerization of alkylene oxides, which process comprises reacting initiator with alkylene oxide in the presence of at most 15 ppm of DMC catalyst.
DETAILED DESCRIPTION OF THE INVENTION
The process according to the present invention comprises preparation of the DMC catalyst in the presence of from 0.03 to 0.4 mole of alkaline metal compound, based on amount of metal salt. This alkaline metal compound can be present in any part of the preparation. Suitable methods comprise adding the alkaline metal compound to the metal salt solution and/or to the metal cyanide salt solution. A further method comprises adding the alkaline metal compound to solution which contains the DMC catalyst while it is being formed. In the latter method, the addition of alkaline metal compound can be carried out at any time during preparation of the catalyst, such as shortly after the aqueous solutions have been added together, during formation of the complex or during the further treatment of the complex that has been formed. Furthermore, the alkaline metal compound can be added at several different stages of the catalyst preparation. Improved activity was observed even if the alkaline metal compound was added when the complex had already been formed.
Preferably, the alkaline metal compound is present during reaction of the aqueous solution of metal salt and aqueous solution of a metal cyanide salt.
Alkaline compounds are those that give a solution having a pH greater than 7.0 when added to pure water.
When calculating the amount of alkaline metal compound which is present, the amount of such compound present in starting compounds such as zinc chloride, should also be taken into account.
The amount of alkaline metal is at least 0.03 mole of alkaline metal compound, based on molar amount of metal salt. The molar amount of metal salt is considered to be the total molar amount of metal salts present including the alkaline metal compounds such as metal oxides and metal hydroxides. Preferably, the amount is at least 0.035, more preferably at least 0.04.
The amount of alkaline metal strongly depends on the kind of alkaline metal compound present. It will be appreciated that the amount will generally be lower if a metal oxide is used than if a metal hydroxide is used. Generally, the amount of alkaline metal compound will be less than 0.4 mole, more specifically less than 0.3 mole.
A large variety of alkaline metal compounds have been found to be suitable for use in the present invention. Additionally, the alkaline metal compound does not need to be added as such but can be formed in-situ as well.
Preferred alkaline metal compounds are the hydroxides and/or oxides of metals. Metals which are especially suitable for use are metals of group 1a, 2a, 2b and 8 of the Periodic Table of the Elements of the Handbook of Chemistry and Physics, 63
rd
Edition. More specifically, the alkaline metal compounds are preferably hydroxides and/or oxides of one or more metals chosen from the group consisting to group 1a, 2a and the metal present in the metal salt and/or the metal cyanide salt. Preferably, the alkaline metal compound is one or more compound chosen from the group consisting zinc oxide, sodium hydroxide, potassium hydroxide, calcium oxide and/or barium oxide.
In the process of the invention, an aqueous solution of a metal salt and an aqueous solution of a metal cyanide salt are combined and reacted. Generally, this will be done in the presence of an organic complexing agent.
The metal salt preferably is water soluble and generally has the general formula M(X)
n
. in which M is selected from the group consisting of Zn(II), Fe(II), Ni(II), Mn(II), Co(II), Sn(II), Pb(II), Fe(III), Mo(IV), Mo(VI), AI(III), V(V), V(IV), Sr(II), W(IV), W(VI), Cu(II), and Cr(III). More preferably, M is selected from the group consisting of the metals of group 2b and 8 of the Periodic Table of the Elements of the Handbook of Chemistry and Physics, 63rd Edition. Preferably, M is zinc, iron, cobalt and/or nickel. More specifically, M is selected from the group consisting of Zn(II), Fe(II), Co(II), and Ni(II). In the formula, X is preferably an anion selected from the group consisting of halide, hydroxide, sulfate, carbonate, cyanide, oxalate, thiocyanate, isocyanate, isothiocyanate, carboxylate, and nitrate. The value of n generally is from 1 to 3 and satisfies the valency state of M. Examples of suitable metal salts include, but are not limited to, zinc chloride, zinc bromide, zinc acetate, zinc acetonylacetate, zinc benzoate, zinc nitrate, iron(II) sulfate, iron(II) bromide, cobalt(II) chloride, cobalt(II) thiocyanate, nickel(II) for

Affiliated with

Also associated with

Rating

Preparation of a double metal cyanide catalyst does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Preparation of a double metal cyanide catalyst, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Preparation of a double metal cyanide catalyst will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3252328