Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
2000-04-28
2003-03-11
Killos, Paul J. (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C562S547000, C562S548000, C585S541000, C585S627000, C585S624000, C585S655000, C585S662000, C585S663000
Reexamination Certificate
active
06531631
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to new catalysts for the production of alkenes by selective, partial oxidation of the corresponding alkane and to methods of producing such catalysts and methods of using the same. More particularly, this invention relates to tungsten or manganese-based catalysts for the selective, partial oxidation of alkanes to the corresponding value added product, such as ethylene and acetic acid, with high selectivity, depending on the type of the metal oxide catalyst used in the process.
2. Description of the Related Art
Several publications are referenced in this application. These references describe the state of the art to which this invention pertains, and are incorporated herein by reference.
Many catalysts have been proposed for the activation of light alkane hydrocarbons in oxidation and oxidative dehydrogenation reactions. Some of these catalytic systems make use of one or more catalysts in order to maximize the yield of value added product, e.g., acetic acid via oxidative dehydrogenation of ethane. E. M. Thorsteinson, T. P. Wilson and F. G. Young,
Journal of Catalysis,
2:116-132 (1970) were the first to report the use of a molybdenum and vanadium-based mixed metal oxide catalyst for the production of ethane to ethylene. Several other publications have described the use of different catalytic systems for such reactions, including U.S. Pat. Nos. 5,162,578, 4,524,236, 4,568,790, 4,250,346, 5,153,162, 5,907,566, 4,849,003, 4,596,787, 4,339,355, and 4,148,759; European patent application nos. 0294845, 0480594, 0407091, 0518548, and 0627401; WO 9913980; WO 9805620; and U.S. application Ser. Nos. 09/107,115, 09/219,702, 08/997,913, 09/107,046, and 09/085,347.
Due to the great industrial importance of oxygenated hydrocarbons and dehydrogenated products, even a slight improvement in the redox behavior of the metal oxide catalyst, responsible for the activation and product selectivity, can impact tremendously on the catalyst's performance and strength. Ultimately, such improvements can have a remarkable commercial and economic impact on the process. Therefore, it would be desirable to produce a metal oxide catalyst having improved or modified redox properties which can achieve the goals of high product selectivity or activity.
SUMMARY OF THE INVENTION
The present invention provides a method for the selective oxidation of lower alkanes, e.g., ethane, with molecular oxygen to yield the corresponding carboxylic acid and/or olefin, e.g., acetic acid and ethylene, at relatively high selectivity and productivity. The process is carried out at temperatures of 150° C. to 450° C. and pressures of 1-50 bar. The method is achieved using catalyst compositions containing mixed metal oxides.
The catalyst compositions of the present invention include compositions of the formula:
Mo
a
V
b
Al
c
X
d
Y
e
O
z
wherein:
X is at least one element selected from the group consisting of W and Mn;
Y is at least one element selected from the group consisting of Pd, Sb, Ca, P, Ga, Ge, Si, Mg, Nb, and K;
a is 1;
b is 0.01 to 0.9;
c is >0 to 0.2;
d is >0 to 0.5;
e is >0 to 0.5; and
z is an integer representing the number of oxygen atoms required to satisfy the valency of Mo, V, Al, X, and Y. The catalysts are preferably produced using the methods disclosed herein.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
One aspect of the invention relates to a catalyst for the production of olefins and carboxylic acids from lower alkanes via a selective, partial oxidation. In a preferred embodiment, the method of the present invention provides a means for the selective partial oxidation of ethane to yield acetic acid and ethylene.
The catalyst compositions of the present invention comprise compositions of the formula:
Mo
a
V
b
Al
c
X
d
Y
e
O
z
wherein:
X is at least one element selected from the group consisting of W and Mn;
Y is at least one element selected from the group consisting of Pd, Sb, Ca, P, Ga, Ge, Si, Mg, Nb, and K;
a is 1;
b is 0.01 to 0.9;
c is >0 to 0.2;
d is >0 to 0.5;
e is >0 to 0.5; and
z is an integer representing the number of oxygen atoms required to satisfy the valence of Mo, V, Al, X, and Y. The catalysts of the present invention can be used with or without a support. The choice of the individual elements contained in the catalyst composition as well as the specific procedures followed in preparing the catalyst can have a significant impact on the performance of a catalyst.
Preferably, the catalyst is prepared from a solution of soluble compounds (salts, complexes, or other compounds) of each of the metals. The solution is preferably an aqueous system having a pH of 1 to 10, and more preferably a pH of 1 to 7, and it is maintained at a temperature of about 30° C. to about 100° C. After the elements are combined in solution, water is removed by filtration, and the catalyst is dried, e.g., in an oven at a temperature from 100° C. to 130° C. The dried catalyst is calcined by heating to a temperature of about 250° C. to about 600° C., preferably about 250° C. to about 450° C., in air or oxygen for about one hour to about 16 hours to yield the desired catalyst composition.
Suitable supports for the catalyst include alumina, silica, titania, zirconia, zeolites, silicon carbide, molybdenum carbide, molecular sieves and other microporous
onporous materials, and mixtures thereof. Support materials can be pretreated with acids, such as HCl, HNO
3
, H
2
SO
4
, per acids or heteropoly acids, and alkali bases. When used with a support, the composition usually comprises from about 5% to 50% by weight catalyst, with the remainder being the support material.
Preferably, molybdenum is introduced into the solution in the form of an ammonium salt, such as ammonium paramolybdate, or as an organic acid salt of molybdenum, such as an acetate, oxalate, mandelate, or glycolate. Some other partially water soluble molybdenum compounds which may be used to prepare the catalyst compositions of the present invention include molybdenum oxides, molybdic acid, and chlorides of molybdenum. Preferably, vanadium, aluminum, gallium, silicon, germanium, antimony, phosphorous, niobium, potassium, magnesium, palladium, tungsten, and manganese are introduced into the catalyst slurry as salts or acids, including but not limited to oxides, hydrate oxides, acetates, chlorides, nitrate acetates, oxalates, oxides, and tartrates.
The present method may be used to oxidize lower alkanes, e.g., C
2
-C
8
alkanes, preferably ethane, propane, and n-butane, as well as alpha-beta unsaturated aliphatic aldehydes. In a preferred embodiment, the starting material is ethane. The starting material(s) may be in the fluid or gas phase. If the starting material(s) is in the fluid phase, the catalyst may convert the reactant(s) to one or more fluid products. The starting material(s) may also be supplied in a gas stream, which contains at least five volume percent of ethane or a mixture of ethane and ethylene. The gas stream can also contain minor amounts of C
3
-C
4
alkanes and alkenes, with the proviso that the gas stream contain less than five volume percent of each. The gas stream can also contain major amounts, i.e., more than five volume percent, of nitrogen, carbon dioxide, and steam.
The reaction mixture used in carrying out the process is generally a gaseous mixture of 0.1 to 99 mol % ethane, 0.1 to 99 mol % molecular oxygen, either as pure oxygen or air, and zero to 50 mol % steam. In a preferred embodiment, the feed mixture contains 0.1-50% by volume molecular oxygen. Further, water may be added as a reaction diluent and as a heat moderator for the reaction. Water added as a co-feed in this way can also act as a desorption accelerator of the reaction product in the vapor phase oxidation reaction or to mask the sites responsible for total oxidation resulting in an increased yield of acetic acid. The amount of oxygen present may be equal to or less than a stoichiometric amount of oxygen in relation to the amount of hydrocarbons in the feed.
The gase
Al-Hazmi Mohammad H.
Karim Khalid
Khan Asad Ahmad
Zaheer Syed Irshad
Killos Paul J.
Kramer Levin Naftalis & Frankel
Saudi Basic Industries Corporation
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