Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Inorganic carbon containing
Reexamination Certificate
2000-05-19
2002-08-06
Sellers, Robert E. L. (Department: 1712)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Inorganic carbon containing
C502S169000, C528S412000, C528S414000
Reexamination Certificate
active
06429166
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to methods for making metal cyanide catalysts complexes and to methods for polymerizing alkylene oxides in the presence of a metal cyanide catalyst.
Polyethers are prepared in large commercial quantities through the polymerization of alkylene oxides such as propylene oxide and ethylene oxide. This polymerization reaction is usually conducted in the presence of an initiator compound and a catalyst. The initiator compound usually determines the functionality (number of hydroxyl groups per molecule of the polymer) and in some instances imparts some desired functionality. The catalyst is used to provide an economical rate of polymerization.
Metal cyanide complexes are becoming increasingly important alkylene oxide polymerization catalysts. These complexes are often referred to as “double metal cyanide” or “DMC” catalysts, and are the subject of a number of patents, including, for example, U.S. Pat. Nos. 3,278,457, 3,278,458, 3,278,459, 3,404,109, 3,427,256, 3,427,334, 3,427,335 and 5,470,813, among many others. In some instances, these complexes provide the benefit of fast polymerization rates and narrow polydispersities. Additionally, these catalysts are associated with the production of polyethers having very low levels of monofunctional unsaturated compounds.
Development efforts have focussed mainly on one specific metal cyanide catalyst complex, zinc hexacyanocobaltate, complexed with a specific complexing agent, t-butanol. The catalyst is typically prepared in a multistep process. First, separate solutions of zinc chloride and potassium hexacyanocobaltate are prepared. These solutions are then mixed together, followed immediately by adding a mixture of water and the complexing agent, t-butanol. A catalyst complex precipitates and is recovered and washed multiple times with mixtures of water and t-butanol. This washing process removes unwanted occluded ions, particular potassium and chlorine, and contributes the complexing agent to the structure of the catalyst complex. Often, a polyether polyol is included in one or more of these washings. Finally, the catalyst complex is dried and ground. It is then mixed with an initiator compound and an alkylene oxide to prepare the desired polyether.
The process just described is complex, requiring several washing steps. It also requires that excesses of water and t-butanol be used. The t-butanol complexing agent itself causes the complex to be difficult to handle. Often, a polyether polyol must be added to facilitate easy handling of the catalyst complex.
Thus, it would be desirable to provide a less expensive, more convenient method for preparing a metal cyanide catalyst complex and a simple method for using such catalyst complexes.
SUMMARY OF THE INVENTION
In one aspect, this invention is a method for preparing an active metal cyanide catalyst, comprising
(I) mixing;
a) a solution or dispersion of a metal cyanide compound in a first inert organic compound or mixture thereof, wherein the metal cyanide compound is represented by the general formula H
w
[M
1
(CN)
r
(X)
t
] wherein
M
1
is a transition metal ion;
each X represents a group other than cyanide that coordinates with the M
1
ion; r is from 4 to 6, t is from 0-2, and w represents the absolute value of the valence of the M
1
(CN)
r
(X)
t
group; and
b) a solution or dispersion of a metal salt in a second inert organic compound or mixture thereof, wherein the metal salt is represented by the general formula M
x
A
y
wherein M is a metal ion that forms an insoluble precipitate with the metal cyanide grouping M
1
(CN)
r
(X)
t
, A represents an anion, and x and y are integers that balance the charges in the metal salt, and said second inert organic compound is the same as or miscible with said first inert organic compound or mixture thereof, said mixing being performed under conditions such that a precipitate forms and is suspended in said first and second inert organic compounds;
(II) dispersing the resulting mixture in an initiator compound, and
(III) removing said first inert organic compound or mixture and said second inert organic compound or mixture from the resulting dispersion.
This method provides a convenient way to make metal cyanide catalysts as fine dispersions in an initiator compound. Preferably, no separate organic complexing agent compound is present in the preparation, so that the costs associated with the use of the complexing agent are eliminated. In this process, multiple process steps, particularly catalyst washings, are eliminated. Costs associated with drying the catalyst complex and handling solids are also reduced or eliminated.
In a second aspect, this invention is a method for preparing an active metal cyanide catalyst, comprising
(I) mixing;
a) a first solution or dispersion of a metal cyanide compound in an initiator compound or mixture thereof, wherein the metal cyanide compound is represented by the general formula H
w
[M
1
(CN)
r
(X)
t
] wherein
M
1
is a transition metal ion;
each X represents a group other than cyanide that coordinates with the M
1
ion; r is from 4 to 6, t is from 0-2, and w represents the absolute value of the valence of the M
1
(CN)
r
(X)
t
group; and
b) a second solution or dispersion of a metal salt in said initiator compound or mixture thereof, wherein the metal salt is represented by the general formula M
x
A
y
wherein M is a metal ion that forms an insoluble precipitate with the metal cyanide grouping M
1
(CN)
r
(X)
t
, A represents an anion, and x and y are integers that balance the charges in the metal salt,
said mixing being performed under conditions such that a precipitate forms and is suspended in said initiator compound or mixture thereof
In a third aspect, this invention is a process wherein a dispersion of the first or second aspect is mixed with an alkylene oxide and the resulting mixture subjected to conditions sufficient to polymerize the alkylene oxide to form a poly(alkylene oxide) based on said initiator compound.
DETAILED DESCRIPTION OF THE INVENTION
In the first aspect of the invention, a solution or dispersion of a metal compound in an organic compound is mixed with a solution or dispersion of a metal salt in an organic compound. The metal compound is represented by the general formula H
w
[M
1
(CN)
r
(X)
t
], in which M
1
, X, r, t and w are as described before.
M
1
is preferably Fe
+3
, Fe
30 2
, Co
+3
, Co
+2
, Cr
+2
, Cr
+3
, Mn
+2
, Mn
+3
, Ir
+3
, Ni
+2
, Rh
+3
, Ru
+2
, V
+4
and V
+5
. Among the foregoing, those in the plus-three oxidation state are more preferred. Co
+3
and Fe
+3
are even more preferred and Co
+3
is most preferred.
Preferred groups X include anions such as halide (especially chloride), hydroxide, sulfate, carbonate, oxalate, thiocyanate, isocyanate, isothiocyanate, C
1-4
carboxylate and nitrite (NO
2
—), and uncharged species such as CO, H
2
O and NO. Particularly preferred groups X are NO, NO
2
— and CO.
r is preferably 5 or 6, most preferably 6; t is preferably 0 or 1, most preferably 0. w is usually 2 or 3, and is most typically 3. In most cases, r+t will equal six.
Mixtures of two or more metal cyanide compounds can be used. In addition, the solution may also contain compounds that have the structure H
w
M
2
(X)
6
, wherein M
2
is a transition metal and X is as before. M
2
may be the same as or different from M
1
. The X groups in any M
2
(X)
6
do not have to be all the same.
The organic compound is one that meets several requirements. First, it is inert to the metal cyanide compound and any H
w
M
2
(X)
6
compounds that may be present. In addition, it is inert to the metal salt. It is not a solvent for the metal cyanide catalyst complex that is formed in the reaction of the metal salt and the metal cyanide compound. Preferably, the organic compound is a solvent for the metal cyanide compound and any H
w
M
2
(X)
6
compounds that may be used. In addition, the organic compound preferably is miscible
Dow Global Technologies Inc.
Sellers Robert E. L.
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