Catalyst useful for oxidation reactions

Details Catalyst useful for oxidation reactions Catalyst useful for oxidation reactions

2003-09-02

2004-11-02

Richter, Johann (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

C568S476000, C568S477000, C568S478000, C562S512200, C562S518000, C562S522000

Reexamination Certificate

active

06812366

ABSTRACT:

This invention relates to a catalyst which is useful for oxidation reactions. In particular, the invention relates to a catalyst which is efficient in converting alkanes, alkenes, or alcohols to unsaturated aldehydes and acids, and a process for preparing unsaturated aldehydes and acids using the catalyst.
Unsaturated aldehydes and acids are important commercial chemicals. Of particular importance is (meth)acrylic acid. The highly reactive double bond and acid function of (meth)acrylic acid makes it especially suitable as a monomer which may be polymerized alone or with other monomers to produce commercially important polymers. These unsaturated acids are also useful as a starting material for esterification to produce commercially important (meth)acrylate esters. Materials derived from (meth)acrylic acid or esters of (meth)acrylic acids are useful as plastic sheets and parts, paints and other coatings, adhesives, caulks, sealants, plastic additives, and detergents as well as other applications.
The production of unsaturated acids by oxidation of an olefin is well known in the art. Acrylic acid, for instance, may be commercially manufactured by the gas phase oxidation of propylene. It is also known that unsaturated carboxylic acids may also be prepared by oxidation of alkanes. For instance, acrylic acid may be prepared by the oxidation of propane. Such a process is especially desirable because alkanes generally have a lower cost than olefins. For example, at the time of filing this application propylene costs approximately three times more than propane. A suitable economic process for the oxidation of alkanes, as well as from oxidation of starting materials, to unsaturated aldehydes which is commercially viable has yet to be achieved.
There is continuing research in the area of new catalysts and starting materials for the production of (meth)acrylic acid and (meth)acrolein. This research generally is directed at reducing the cost of raw materials or increasing the yield of the oxidation process.
One impediment for the production of a commercially viable process for the catalytic oxidation of an alkane to an unsaturated acid is the identification of a catalyst having adequate conversion and suitable selectivity, thereby providing sufficient yield of the unsaturated acid end-product. U.S. Pat. No. 5,380,933 discloses a method for preparing a catalyst useful in the gas phase oxidation of an alkane to an unsaturated carboxylic acid. In the disclosed method, a catalyst was prepared by combining ammonium metavanadate, telluric acid and ammonium paramolybdate to obtain a uniform aqueous solution. To this solution was added ammonium niobium oxalate to obtain a slurry. The water was removed from the slurry to obtain a solid catalyst precursor. The solid catalyst precursor was molded into a tablet, sieved to a desired particle size and then calcined at 600° C. under a nitrogen stream to obtain the desired catalyst.
Co-pending U.S. patent application Ser. No. 09/316,007 disclosed a process for preparing a catalyst for catalyzing an alkane into an unsaturated aldehyde or carboxylic acid wherein phase segregation was minimized and improvement in selectivity, conversion, and yield were achieved.
Despite the disclosure of the references, there is a continuing need for new catalysts and improved processes for the production of (meth)acrylic acid and/or (meth)acrolein.
In one aspect of the present invention, there is provided a catalyst having the formula:
A
a
M
m
N
n
X
x
O
o
wherein 0.25<a<0.98, 0.003<m<0.5, 0.003<n<0.5, 0.003<x<0.5, and o is dependent on the oxidation state of the other elements, and A is at least one of Mo, W, Fe, Nb, Ta, Zr, and Ru; M is at least one of V, Ce, and Cr; N is at least one of Te, Bi, Sb, and Se; and X is at least one of Nb, Ta, W, Ti, Al, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pd, Pt, Sb, Bi, B, In, and Ce; wherein the catalyst exhibits at least two crystal phases, one phase including major x-ray diffraction peaks at 22.1, 28.2, 36.2, 45.2, 50.5, 54.2, 55.4, and 58.5, and a second phase including major x-ray diffraction peaks at 22.1, 27.2, 35.3, 45.2, and 51.1.
In a second aspect of the present invention, there is provided a process for preparing unsaturated aldehydes and acids including subjecting an alkane to catalytic oxidation in the presence of a catalyst having the formula
A
a
M
m
N
n
X
x
O
o
wherein 0.25<a<0.98, 0.003<m<0.5, 0.003<n<0.5, 0.003<x<0.5, and o is dependent on the oxidation state of the other elements, and A is at least one of Mo, W, Fe, Nb, Ta, Zr, and Ru; M is at least one of V, Ce, and Cr; N is at least one of Te, Bi, Sb, and Se; and X is at least one of Nb, Ta, W, Ti, Al, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pd, Pt, Sb, Bi, B, In, and Ce; wherein the catalyst exhibits at least two crystal phases, one phase including major x-ray diffraction peaks at 22.1, 28.2, 36.2, 45.2, 50.5, 54.2, 55.4, and 58.5, and a second phase including major x-ray diffraction peaks at 22.1, 27.2, 35.3, 45.2, and 51.1.
In a third aspect, the present invention provides a process for preparing unsaturated aldehydes and acids including subjecting a compound selected from propylene, acrolein, and isopropanol to catalytic oxidation in the presence of a catalyst having the formula:
A
a
M
m
N
n
X
x
O
o
wherein 0.25<a<0.98, 0.003<m<0.5, 0.003<n<0.5, 0.003<x<0.5, and o is dependent on the oxidation state of the other elements, and A is at least one of Mo, W, Fe, Nb, Ta, Zr, and Ru; M is at least one of V, Ce, and Cr; N is at least one of Te, Bi, Sb, and Se; and X is at least one of Nb, Ta, W, Ti, Al, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pd, Pt, Sb, Bi, B, In, and Ce; wherein the catalyst exhibits at least two crystal phases, one phase including major x-ray diffraction peaks at 22.1, 28.2, 36.2, 45.2, 50.5, 54.2, 55.4, and 58.5, and a second phase including major x-ray diffraction peaks at 22.1, 27.2, 35.3, 45.2, and 51.1.
FIG. 1
depicts the x-ray diffraction (XRD) spectra of major XRD peaks for catalysts 1-7.
As used herein, the expression “(meth)acrylic acid” is intended to include both methacrylic acid and acrylic acid within its scope. In a like manner, the expression “(meth)acrylates” is intended to include both methacrylates and acrylates within its scope and the expression “(meth)acrolein” is intended to include both acrolein and methacrolein within its scope.
As used herein the terminology “(C
3
-C
8
) alkane” means a straight chain or branched chain alkane having from 3 to 8 carbon atoms per alkane molecule.
As used herein the term “mixture” is meant to include within its scope all forms of mixtures including, but not limited to, simple mixtures as well as blends, alloys, etc.
For purposes of this application “% conversion” is equal to (moles of consumed alkane/moles of supplied alkane)×100; “% selectivity” is equal to (moles of formed desired unsaturated carboxylic acid or aldehyde/moles of consumed alkane)×100; and “% yield” is equal to (moles of formed desired unsaturated carboxylic acid or aldehyde/moles of supplied alkane)×(carbon number of formed desired unsaturated carboxylic acid or aldehyde/carbon number of the supplied alkane)×100.
For purposes of this application by “solution” is meant that greater than 95 percent of metal solid added to a solvent is dissolved. It is to be understood that the greater the amount of metal solid not initially in solution, the poorer the performance of the catalyst derived therefrom will be.
As recited above, a catalyst having at least two specific crystal phases is disclosed. The two crystal phases may be obtained either through a specific method of preparation of the catalyst or through varying the composition of the catalyst.
In a first step of the method of preparation of the catalyst, a solution is formed by admixing metal compounds, at least one of which contains oxygen, and at least one solvent in appropriate amounts to form the solution. Generally, the metal compounds contain elements A, M, N, X, and O. In one embodiment, A is at le

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