Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
2002-04-08
2003-11-11
McKane, Joseph K. (Department: 1626)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C558S318000, C558S319000
Reexamination Certificate
active
06645906
ABSTRACT:
The present invention relates to an improved process for the vapor phase catalytic oxidation of alkanes, or a mixture of alkanes and alkenes, to their corresponding unsaturated carboxylic acids.
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.
Moreover, the present invention relates to a process for producing an improved catalyst comprising a mixed metal oxide and the catalyst so-formed.
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°.
Similarly, Japanese Laid-Open Patent Application Publication No. 6-228073 discloses a method of nitrile preparation comprising reacting an alkane in a gas phase contact reaction with ammonia in the presence of a mixed metal oxide catalyst of the formula
W
a
V
b
Te
c
X
x
O
n
wherein X represents one or more elements selected from niobium, tantalum, titanium, aluminum, zirconium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, antimony, bismuth, indium 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 determined by the oxide form of the elements.
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.
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.
U.S. Pat. No. 5,994,580 discloses a process for producing acrylic acid from propane and oxygen gas through a vapor-phase catalytic oxidation reaction, the process comprising conducting the reaction using a metal oxide catalyst containing the elements Mo, V, Sb and A (wherein A is at least one element selected from the group consisting of Nb, Ta, Sn, W, Ti, Ni, Fe, Cr and Co).
Japanese Laid-Open Patent Application Publication No. 2000-037623 discloses a method for producing an unsaturated carboxylic acid comprising subjecting an alkane to a vapor phase catalytic oxidation in the presence of a catalyst having the empirical formula
MoV
a
Nb
b
X
c
Z
d
O
n
wherein X is at least one element selected from the group consisting of Te and Sb, Z is at least one element selected from the group consisting of W, Cr, Ta, Ti, Zr, Hf, Mn, Re, Fe, Ru, Co, Rh, Ni, Pd, Pt, Ag, Zn, B, Al, Ga, In, Ge, Sn, Pb, P, Bi, Y, rare earth elements and alkaline earth elements, 0.1≦a≦1.0, 0.01≦b≦1.0, 0.01≦c≦1.0, 0≦d≦1.0 and n is determined by the oxidation states of the other elements.
Despite the above-noted attempts to provide new and improved catalysts for the oxidation of alkanes to unsaturated carboxylic acids, one impediment to the provision of a commercially viable process for such catalytic oxidations is the identification of a catalyst providing adequate conversion and suitable selectivity, thereby providing sufficient yield of the unsaturated product.
By the present invention, there is provided a catalyst wherein the activity and/or selectivity is enhanced and, hence, the overall yield of the desired reaction product is also enhanced.
Thus, in a first embodiment, the present invention provides a process for producing an improved catalyst comprising a mixed metal oxide having the empirical formula
Mo
a
V
b
N
c
X
d
Z
e
O
f
wherein N is at least one element selected from the group consisting of Te and Sb,
wherein X is at least one element selected from the group consisting of Nb, Ta, Ti, W, Se, Al, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pt, Bi, B, In, As, Ge, Sn, Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Hf, Pb, P, Pm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu,
wherein Z is at least one element selected from the group consisting of Au, Ag, Re, Pr, Zn, Ga, Pd, Ir, Nd, Y, Sm, Tb, Br, Cu, Sc, Cl, F and I, and
wherein, when a=1, b=0.01 to 1.0, c=0.01 to 1.0, d=0.01 to 1.0, e=0 to 0.1 and f is dependent on the oxidation state of the other elements, comprising:
(a) admixing compounds of elements Mo, V, N, X and Z and at least one solvent at a temperature greater than or equal to 45° C. to form an admixture,
wherein Mo,
Bogan, Jr. Leonard Edward
Pak Alex
McKane Joseph K.
Rohm and Haas Company
Saeed Kamal
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