Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
2002-06-10
2004-06-08
Silverman, Stanley S. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S310000
Reexamination Certificate
active
06746983
ABSTRACT:
The present invention relates to a catalyst for the oxidation of alkanes, or a mixture of alkanes and alkenes, to their corresponding unsaturated carboxylic acids by vapor phase catalytic oxidation; to a method for making the catalyst; and to a process for the vapor phase catalytic oxidation of alkanes, or a mixture of alkanes and alkenes, to their corresponding unsaturated carboxylic acids using the catalyst. The present invention also relates to a process for the vapor phase catalytic oxidation of alkanes, or a mixture of alkanes and alkenes, in the presence of ammonia, to their corresponding unsaturated nitrites using the catalyst.
Nitriles, such as acrylonitrile and methacrylonitrile, have been industrially produced as important intermediates for the preparation of fibers, synthetic resins, synthetic rubbers, and the like. The most popular method for producing such nitrites is to subject an olefin such as propene or isobutene to a gas phase catalytic reaction with ammonia and oxygen in the presence of a catalyst at a high temperature. Known catalysts for conducting this reaction include a Mo—Bi—P—O catalyst, a V—Sb—O catalyst, an Sb—U—V—Ni—O catalyst, a Sb—Sn—O catalyst, a V—Sb—W—P—O catalyst and a catalyst obtained by mechanically mixing a V—Sb—W—O oxide and a Bi—Ce—Mo—W—O oxide. However, in view of the price difference between propane and propene or between isobutane and isobutene, attention has been drawn to the development of a method for producing acrylonitrile or methacrylonitrile by an ammoxidation reaction wherein a lower alkane, such as propane or isobutane, is used as a starting material, and it is catalytically reacted with ammonia and oxygen in a gaseous phase in the presence of a catalyst.
In particular, U.S. Pat. No. 5,281,745 discloses a method for producing an unsaturated nitrile comprising subjecting an alkane and ammonia in the gaseous state to catalytic oxidation in the presence of a catalyst which satisfies the conditions:
(1) the mixed metal oxide catalyst is represented by the empirical formula
Mo
a
V
b
Te
c
X
x
O
n
wherein X is at least one element selected from the group consisting of niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, antimony, bismuth, boron and cerium and, when a=1, b=0.01 to 1.0, c=0.01 to 1.0, x=0.01 to 1.0 and n is a number such that the total valency of the metal elements is satisfied; and
(2) the catalyst has X-ray diffraction peaks at the following angles (±0.3°) of 2&thgr; in its X-ray diffraction pattern: 22.1°, 28.2°, 36.2°, 45.2°and 50.0°.
Unsaturated carboxylic acids such as acrylic acid and methacrylic acid are industrially important as starting materials for various synthetic resins, coating materials and plasticizers. Commercially, the current process for acrylic acid manufacture involves a two-step catalytic oxidation reaction starting with a propene feed. In the first stage, propene is converted to acrolein over a modified bismuth molybdate catalyst. In the second stage, acrolein product from the first stage is converted to acrylic acid using a catalyst composed of mainly molybdenum and vanadium oxides. In most cases, the catalyst formulations are proprietary to the catalyst supplier, but, the technology is well established. Moreover, there is an incentive to develop a single step process to prepare the unsaturated acid from its corresponding alkene. Therefore, the prior art describes cases where complex metal oxide catalysts are utilized for the preparation of unsaturated acid from a corresponding alkene in a single step.
Japanese Laid-Open Patent Application Publication No. 07-053448 discloses the manufacture of acrylic acid by the gas-phase catalytic oxidation of propene in the presence of mixed metal oxides containing Mo, V, Te, O and X wherein 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, Li, Na, K, Rb, Cs and Ce.
Commercial incentives also exist for producing acrylic acid using a lower cost propane feed. Therefore, the prior art describes cases wherein a mixed metal oxide catalyst is used to convert propane to acrylic acid in one step.
U.S. Pat. No. 5,380,933 discloses a method for producing an unsaturated carboxylic acid comprising subjecting an alkane to a vapor phase catalytic oxidation reaction in the presence of a catalyst containing a mixed metal oxide comprising, as essential components, Mo, V, Te, O and X, wherein X is at least one element selected from the group consisting of niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, antimony, bismuth, boron, indium and cerium; and wherein the proportions of the respective essential components, based on the total amount of the essential components, exclusive of oxygen, satisfy the following relationships: 0.25<r(Mo)<0.98, 0.003<r(V)<0.5, 0.003<r(Te) <0.5 and 0.003<r(X)<0.5, wherein r(Mo), r(V), r(Te) and r(X) are the molar fractions of Mo, V, Te and X, respectively, based on the total amount of the essential components exclusive of oxygen.
Nonetheless, the prior art continues to seek ways to improve the performance of such mixed metal oxide catalysts.
For example, Ueda, et al., “Hydrothermal Synthesis of Mo—V—M—O Complex Metal Oxide Catalysts Active For Partial Oxidation Of Ethane”, Chem. Commun., 1999, pp. 517-518, discloses Mo—V—M—O (M=Al, Fe, Cr or Ti) complex metal oxide catalysts prepared by hydrothermal synthesis, which exhibit activity for the partial oxidation of ethane to ethene and acetic acid.
Ueda, et al., “Selective Oxidation Of Light Alkanes Over Mo-Based Oxide Catalysts”, Res, Chem. Intermed., Vol. 26, No. 2, pp. 137-144 (2000) discloses that Anderson-type heteropoly compounds linked with vanadyl cations, VO
+2
, were synthesized by hydrothermal reaction and showed good catalytic activity for the oxidation of ethene to acetic acid.
Watanabe, et al., “New Synthesis Route For Mo—V—Nb—Te Mixed Metal Oxides For Propane Ammoxidation”, Applied Catalysis A: General, 194-195, pp. 479-485 (2000) discloses an examination of several methods for preparing Mo—V—Nb—Te mixed oxides. Hydrothermal treatment was shown to give a precursor of an ammoxidation catalyst which shows activity twice as high, after calcination, as the catalyst prepared by the known dry-up method. Mixed oxides prepared by a solid state reaction gave poor catalytic activity.
Ueda, et al., “Selective Oxidation of Light Alkanes Over Hydrothermally Synthesized Mo—V—M—O (M=Al, Ga, Bi, Sb and Te) Oxide Catalysts”, Applied Catalysis A: General, 200, pp. 135-143 (2000) discloses selective oxidations of ethane to ethene and acetic acid, and of propane to acrylic acid, carried out over hydrothermally synthesized Mo—V—M—O (M=Al, Ga, Bi, Sb and Te) complex metal oxide catalysts. The solids were classified into two groups, i.e. Mo—V—M—O (M=Al, possibly Ga and Bi) and Mo—V—M—O (M=Sb and Te). The former were moderately active for the partial oxidation of ethane to ethene and acetic acid. The latter were extremely active for the oxidative dehydrogenation and were also active for the partial oxidation of propane to acrylic acid. Grinding of the catalysts, after heat treatment at 600° C. in N
2
, increased the conversion of propane and enhanced the selectivity to acrylic acid.
Chen, et al., “Selective Oxidation Of Ethane Over Hydrothermally Synthesized Mo—V—Al—Ti Oxide Catalyst”, Catalysis Today, 64, pp. 121-128 (2001) discloses synthesis of a monophasic material, Mo
6
V
2
Al
1
O
x
, by the hydrothermal method, which shows activity for gas-phase oxidation of ethane to ethene and acetic acid. Addition of titanium to the Mo
6
V
2
Al
1
O
x
oxide catalyst resulted in a marked increase of the activity for the ethane selective oxidation.
It has now been found that certain novel mixed metal oxide catalysts, which may be prepared by a hydrothermal synthesis technique, may be utilized
Gaffney Anne Mae
Song Ruozhi
Bodner Marcella M.
Holler Alan
Johnson Edward M.
Rohm and Haas Company
Silverman Stanley S.
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