Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Inorganic carbon containing
Reexamination Certificate
2002-06-18
2003-07-15
Wood, Elizabeth D. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Inorganic carbon containing
C502S200000
Reexamination Certificate
active
06593268
ABSTRACT:
FIELD OF THE INVENTION
The subject invention generally relates to methods of synthesizing a double metal cyanide (DMC) catalyst.
BACKGROUND OF THE INVENTION
Polyether polyols are integral intermediate components utilized to manufacture a wide array of products, including polyurethanes. As such, the production of polyether polyols is critical. It is known in the art that polyether polyols are produced from the polymerization of epoxides, such as propylene oxide (PO) and ethylene oxide (EO). It is also known in the art that double metal cyanide (DMC) catalysts are effective catalysts for the polymerization of the epoxides. DMC catalysts produce polyether polyols having narrow molecular weight distributions as well as relatively low unsaturation.
In conventional methods, DMC catalysts are prepared by combining an aqueous solution of a metal salt and an aqueous solution of a complex metal cyanide salt. As a specific example, an aqueous solution of ZnCl
2
(excess), as the metal salt, is combined with an aqueous solution of K
3
Co(CN)
6
, as the complex metal cyanide salt. This combination precipitates out the desired DMC catalyst, in this case specifically Zn
3
[Co(CN)
6
]
2
. Examples of such conventional methods are disclosed in U.S. Pat. Nos. 5,470,813 and 5,714,639. These conventional methods, in one form or another, utilize a complex metal cyanide salt. The complex metal cyanide salts are very expensive which limits the economic viability of utilizing DMC catalysts in the production of polyether polyols. One reason these complex metal cyanide salts are so expensive is that they are pre-purified. That is, any secondary products, such as KCl, which may have the potential of wholly or partially deactivating the DMC catalysts, are removed from the complex metal cyanide salt before the ZnCl
2
is combined with the complex metal cyanide salt.
Thus, it would be desirable to provide methods of synthesizing DMC catalysts that do not utilize expensive complex metal cyanide salts as intermediates thereby improving the economic viability of DMC catalysts utilized in the production of polyether polyols.
SUMMARY OF THE INVENTION
The present invention provides various methods of synthesizing a double metal cyanide (DMC) catalyst. As disclosed above, the methods of the subject invention do not utilize complex metal cyanide salts to synthesize the DMC catalyst.
The method of the subject invention, in a single step, combines an aqueous solution of a first metal salt of the general formula M(X)
n
wherein M is selected from the group consisting of aluminum, zinc, and the transition metals; X is an anion selected from the group consisting of halides, hydroxides, sulfates, acetates, carbonates, cyanides, oxalates, thiocyanates, isocyanates, isothiocyanates, carboxylates, and nitrates; and n is a value from 1 to 3 satisfying the valency state of M with an aqueous solution of a second metal salt of the general formula N(Y)
n
wherein N is selected from the group consisting of the transition metals and the lanthanides; Y is an anion selected from the group consisting of halides, hydroxides, sulfates, carbonates, cyanides, oxalates, thiocyanates, isocyanates, isothiocyanates, carboxylates, and nitrates; and n is a value from 1 to 3 satisfying the valency state of N; and with an aqueous solution of an alkali metal cyanide to form a suspension having a particle phase and a continuous phase. The particle phase comprises the DMC catalyst synthesized from the combination of the aqueous solutions of the first metal salt, the second metal salt, and the alkali metal cyanide. The continuous phase comprises a secondary product such as KCl. In this method, the DMC catalyst is produced independent of a complex metal cyanide salt.
In an alternative method of synthesizing the DMC catalyst, the aqueous solution of the first metal salt and the aqueous solution of the second metal salt are each independently fed into the aqueous solution of the alkali metal cyanide. In a further alternative method of synthesizing the DMC catalyst, the aqueous solution of the metal salt of the general formula N(Y)
n
, i.e., the second metal salt, is combined with the aqueous solution of the alkali metal cyanide of the general formula XCN to form an intermediate solution comprising a DMC catalyst precursor and the secondary product. In this method, the aqueous solution of the metal salt of the general formula M(X)
n
, i.e., the first metal salt, is next combined with the intermediate solution such that the DMC catalyst is synthesized upon reaction between the DMC catalyst precursor and the first metal salt. In either alternative method, the DMC catalyst is produced independent of a complex metal cyanide salt.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Various methods of synthesizing a double metal cyanide (DMC) catalyst are disclosed. More specifically, the methods of the subject invention synthesize the DMC catalyst by combining aqueous solutions of a first metal salt, a second metal salt, and an alkali metal cyanide in different manners.
An aqueous solution of the first metal salt is prepared. The strength of the aqueous solution of the first metal salt can range from 1 to 50 parts by weight of the first metal salt based on 100 parts by weight of the aqueous solution. Similarly, aqueous solutions of a second metal salt and an alkali metal cyanide are also prepared. The strengths of these aqueous solutions can also range from 1 to 50 parts by weight of the second metal salt and the alkali metal cyanide, respectively, based on 100 parts by weight of the aqueous solution. In any event, it is most preferred that the first metal salt is combined in molar excess relative to the second metal salt. In other words, the molar ratio of the first metal salt to the second metal salt is greater than 1. This molar ratio preferably ranges from 1.1:1 to 6:1, more preferably from 1.1:1 to 3:1.
Additionally, at least one of the aqueous solutions of the first metal salt, the second metal salt, and the alkali metal cyanide further comprise a water-soluble, organic activator. As understood by those skilled in the art, organic activators activate the surface of the DMC catalyst to improve the overall activity of the catalyst. If included, the water-soluble, organic activator preferably comprises at least one of ethanol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, and glyme. Other water-soluble, organic activators are known in the art. The most preferred organic activator for purposes of the subject invention is tert-butyl alcohol. If included, the water-soluble, organic activator is preferably introduced in a washing step as described below.
The first metal salt of the subject invention observes the general formula M(X)
n
. In this formula, it is to be understood that M is selected from the group consisting of aluminum, zinc, and the transition metals, X is an anion selected from the group consisting of halides, hydroxides, sulfates, acetates, carbonates, cyanides, oxalates, thiocyanates, isocyanates, isothiocyanates, carboxylates, and nitrates, and n is a value from 1 to 3 satisfying the valency state of M. In preferred embodiments of the subject invention, M is selected from the group consisting of Al(III) and Zn(II), X is selected from the group consisting of halides and acetates, and n is a value from 1 to 3 satisfying the valency state of M. The first metal salt of the subject invention may comprise at least one of zinc acetate and aluminum acetate. Most preferably, however, the first metal salt of the subject invention is ZnCl
2
.
The second metal salt of the subject invention observes the general formula N(Y)
n
. In this formula, it is to be understood that N is selected from the group consisting of the transition metals and the lanthanides, Y is an anion selected from the group consisting of halides, hydroxides, sulfates, carbonates, cyanides, oxalates, thiocyanates, isocyanates, isothiocyanates, carboxylates, and nitrates, and n is a value from 1 to 3 satisfying the valency state of N
Dexheimer Edward Michael
Grosch Georg Heinrich
BASF Corporation
Borrego Fernando A.
Wood Elizabeth D.
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