Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
2001-10-23
2002-11-05
Padmanabhan, Sreeni (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C562S534000, C562S535000, C562S599000, C562S830000, C562S830000, C562S830000, C562S830000
Reexamination Certificate
active
06476259
ABSTRACT:
TECHNICAL FIELD TO WHICH THE INVENTION BELONGS
This invention relates to catalysts for methacrylic acid production and also to a process for producing methacrylic acid. More particularly the invention relates to improved catalysts for producing methacrylic acid at high yield stably over prolonged period, by vapor phase oxidation and/or vapor phase oxidative dehydrogenation of at least one compound selected from the group consisting of methacrolein, isobutylaldehyde and isobutyric acid; and to a process for producing methacrylic acid using the improved catalyst.
CONVENTIONAL TECHNOLOGY
Various improved catalysts have been proposed for high efficiency production of methacrylic acid by vapor phase catalytic oxidation and/or vapor phase oxidative dehydrogenation reaction of methacrolein, isobutylaldehyde or isobutyric acid. For example, JP Kokai Sho 55 (1980)-2619A1 has disclosed a catalyst which contains as the essential components Mo, V, P and at least one of K, Rb, Cs and Tl; JP Kokai Sho 60 (1985)-239439 Al has disclosed a catalyst which contains as the essential components Mo; V; P; at least one of K, Rb, Cs and Ti; at least one of Sc, Y, La, Ce, Pr, Nd, Pu and Sm; and at least one of Cu, As, Sb, Co, Zr, Bi, Ti, Te and Ag. Inferring from the methods of their preparation, those known catalysts whose chief components are molybdenum and phosphorus are basically considered to be phosphomolybdic acid or salts thereof (e.g., ammonium salts or alkali metal salts) and structurally they are mixtures of heteropolyacids or their analogues.
Those catalysts, however, are still open to further improvements in respect of methacrylic acid yield and their life. Because heteropolyacids have low heat resistance, those catalysts show decomposition of the heteropolyacid structure when used for prolonged period. Therefore, in order to obtain a catalyst for methacrylic acid production which exhibits stable performance over a prolonged period, it is necessary either to increase stability of heteropolyacid or to find a highly active heteropolyacid which is useful as the catalyst also at relatively low temperatures.
JP Kokai Sho 61 (1986)-5043 A1 has disclosed a catalyst whose essential components comprise; Mo; V; P; Ce; at least one of K, Rb, Cs and Tl; and at least one of Cu, As, Sb, Co, Zr, Bi, Ni, Cr, Mn and Zn. However, such a catalyst composed of conventional components to which cerium component is simply added is yet insufficient as to improvement in the catalyst life because cerium oxide aggregates with time.
On the other hand, various proposals have been also made as to complex oxides whose essential components are cerium and zirconium. Most of these complex oxides are known as additive components to waste gas-purging catalysts, but it is entirely unknown that such complex oxides whose essential components are cerium and zirconium exhibit effective catalytic activity in methacrylic acid-forming reaction comprising vapor phase oxidation and/or vapor phase oxidative dehydrogenation of methacrolein, isobutylaldehyde or isobutyric acid, when used in combination with heteropolyacid catalyst.
OBJECTS OF THE INVENTION
One of the objects of the present invention is to provide catalysts useful in production of methacrylic acid at high yield.
A further object of the present invention is to provide catalysts for methacrylic acid production, which have long catalyst life and enable stable operation over prolonged period.
Still another object of the present invention is to provide catalysts for methacrylic acid production which enable stable operation over prolonged period, even under heavy load operation aiming at high productivity.
An additional object of the present invention is to provide a process for producing methacrylic acid at high yield and stably over prolonged period, using the above catalysts.
MEANS TO SOLVE THE PROBLEMS
We have discovered that a composition in which a catalyst known as that for methacrylic acid production, containing molybdenum and phosphorus as the essential components, is combined with a complex oxide whose essential components are cerium and zirconium exhibits high activity in the intended reaction and excellent stability; and that the use of such a composition as a catalyst in said reaction accomplishes the above objects.
Thus, according to the invention, as a catalyst for producing methacrylic acid through oxidation and/or oxidative dehydrogenation of at least one compound selected from the group consisting of methacrolein, isobutylaldehyde and isobutyric acid with molecular oxygen or a molecular oxygen-containing gas at vapor phase, a complex oxide composition characterized by comprising
(A) a complex oxide containing as essential components molybdenum and phosphorus, which is known per se as a catalyst for said vapor phase catalytic oxidation and/or vapor phase oxidative dehydrogenation reaction, and
(B) a complex oxide containing cerium and zirconium as the essential components, is provided.
According to the present invention, there is also provided, as a catalyst for producing methacrylic acid through oxidation and/or oxidative dehydrogenation of at least one compound selected from the group consisting of methacrolein, isobutylaldehyde and isobutyric acid with molecular oxygen or a molecular oxygen-containing gas at vapor phase, a complex oxide composition which is characterized by having a composition expressed by the following general formula (3):
P
a
Mo
b
Ce
c
Zr
d
A
e
B
f
C
g
D
h
E
i
G
j
O
x
(3)
(wherein P is phosphorus; Mo is molybdenum; Ce is cerium; Zr is zirconium; A is at least an element selected from the group consisting of arsenic, antimony, germanium, bismuth and selenium; B is at least an element selected from the group consisting of copper, silver, iron, cobalt, nickel, lead, manganese, chromium, tin, zinc, palladium, rhodium and tellurium; C is at least an element selected from the group consisting of tungsten, vanadium and niobium; D is at least an element selected from the group consisting of alkali metals and alkaline earth metals; E is at least an element selected from the group consisting of titanium, silicon and aluminium; G is at least an element selected from the group consisting of lanthanoide series elements except cerium; yttrium and indium; and O is oxygen; a, b, c, d, e, f, g, h, i, j and x denote the atomic ratios of P, Mo, Ce, Zr, A, B, C, D, E, G and O, respectively; and where b is 12, a is 0.5-4, c is 0.01-12, d is 0.01-16, e is 0.01-3, f is 0.01-5, g is 0.01-5, h is 0.01-6, i is 0.01-10 and j is 0.001-2, and x is a numerical value determined by degree of oxidation of each of the elements)
and the cerium and zirconium therein forming a complex oxide.
According to the invention, furthermore, there is provided a process for producing methacrylic acid through vapor phase oxidation and/or oxidative dehydrogenation of at least one compound selected from the group consisting of methacrolein, isobutylaldehyde and isobutyric acid with molecular oxygen or a molecular oxygen-containing gas, in the presence of a catalyst, the process being characterized in that it uses the above-defined complex oxide composition as the catalyst.
EMBODIMENTS OF THE INVENTION
Catalyst (I) for methacrylic acid production according to the invention is a complex oxide composition which is characterized by comprising
(A) a complex oxide containing as essential components molybdenum and phosphorus, which is known per se as a catalyst for producing methacrylic acid through said vapor phase catalytic oxida- tion and/or vapor phase oxidative dehydrogenation reaction of methacrolein, isobutylaldehyde or isobutyric acid, and
(B) a complex oxide containing cerium and zirconium as the essential components.
Catalyst (II) for methacrylic acid production according to another embodiment of the present invention is a complex oxide composition which is characterized by having the composition as expressed by above general formula (3), in which cerium and zirconium form a complex oxide.
First, the Catalyst (I) shall be explained. The component (A) corresponds to a cat
Kase Yuichi
Onodera Hideo
Forohar Farhad
Nippon Shokubai Co. , Ltd.
Padmanabhan Sreeni
Sherman & Shalloway
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