Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
1999-02-16
2001-02-27
Dentz, Bernard (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C502S209000
Reexamination Certificate
active
06194588
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for the production of maleic anhydride. More particularly, it relates to an improved method for the production of maleic anhydride by the catalytic gas phase oxidation of a raw material gas containing an aliphatic hydrocarbon of not less than 4 carbon atoms and molecular oxygen with a vanadium-phosphorus oxide catalyst. This invention further relates to a method for the activation of the vanadium-phosphorus oxide catalyst. More particularly, it relates to a method for the activation of a vanadium-phosphorus oxide catalyst suitable for the production of maleic anhydride by the catalytic gas phase oxidation of an aliphatic hydrocarbon of not less than 4 carbon atoms with a molecular oxygen-containing gas.
2. Description of the Related Art
It has been well known to produce maleic anhydride by subjecting an aliphatic hydrocarbon of not less than 4 carbon atoms such as, for example, n-butane, to gas phase oxidation in the presence of a vanadium-phosphorus oxide catalyst. Numerous patents have issued to inventions relating to vanadium-phosphorus oxide catalysts and reaction conditions to be used for the production.
As respects the oxidation reaction itself, the practice of selectively oxidizing n-butane, for example, into maleic anhydride by causing a raw material gas containing n-butane and molecular oxygen to contact a vanadium-phosphorus oxide catalyst has been prevailing (as disclosed in U.S. Pat. No. 3,864,280, JP-B-04-4,969, JP-A-05-115,783, U.S. Pat. No. 4,855,459, JP-A-09-3,053, JP-A-07-171,398, U.S. Pat. No. 5,530,144, and U.S. Pat. No. 5,070,060, for example).
This method, however, has been unable to produce the maleic anhydride with satisfactory conversion and selectivity.
Naturally an addition to the yield of the maleic anhydride as a target product brings such a commercial advantage as a reduction in cost. Thus, a further increase in the yield of maleic anhydride has been a constant study theme for researchers in this technical field.
An object of this invention, therefore, is to provide an improved method for the production of maleic anhydride.
Another object of this invention is to provide a method which, in the production of maleic anhydride by the gas phase oxidation of an aliphatic hydrocarbon of not less than 4 carbon atoms in the presence of a vanadium-phosphorus oxide catalyst, allows the maleic anhydride to be produced with a higher yield.
Still another object of this invention is to provide a method which allows effective utilization of an inert gas to be used in the reaction of oxidation.
Yet another object of this invention is to provide a method for the activation of a vanadium-phosphorus oxide catalyst which, in the production of maleic anhydride by the gas phase oxidation of an aliphatic hydrocarbon of not less than 4 carbon atoms in the presence of a vanadium-phosphorus oxide catalyst, allows the maleic anhydride to be produced with a higher yield.
SUMMARY OF THE INVENTION
The objects mentioned above are accomplished by the following items (1)-(11).
(1) A method for the production of maleic anhydride by the catalytic gas phase oxidation of a raw material gas containing an aliphatic hydrocarbon of not less than 4 carbon atoms and molecular oxygen with a vanadium-phosphorus oxide catalyst, characterized by the raw material gas allowing presence therein of nitrogen and an inert gas possessing a thermal conductivity of not less than 800 (10
−4
Wm
−1
K
−1
) at 700 K.
(2) A method for the production of maleic anhydride by the catalytic gas phase oxidation of a raw material gas containing an aliphatic hydrocarbon of not less than 4 carbon atoms and molecular oxygen with a vanadium-phosphorus oxide catalyst, which comprises allowing presence in the raw material gas of nitrogen and an inert gas possessing a thermal conductivity of not less than 800 (10
−4
Wm
−1
K
−1
) at 700 K thereby oxidizing the aliphatic hydrocarbon in the oxidizing reaction region, recovering maleic anhydride from the gas produced by the oxidation reaction, separating the produced maleic anhydride from a remained oxidation reaction gas after recovering the maleic anhydride, and circulating the separated inert gas to the reaction region.
(3) A method set forth in (1) or (2) above, wherein the total concentration of the nitrogen gas and the inert gas in the raw material gas is in the range of 60-94.5% by volume.
(4) A method set forth in any of (1) through (3) above, wherein the ratio of nitrogen gas to the inert gas (the molar ratio of nitrogen gas/inert gas) is in the range of 0.05/1-1/1.
(5) A method set forth in any of (1) through (4) above, wherein the inert gas is at least one species of inert gas selected from the group consisting of helium and neon.
(6) A method set forth in any of (1) through (5), wherein the inert gas is helium.
(7) A method set forth in any of (1) through (6), wherein the aliphatic hydrocarbon of not less than 4 carbon atoms is n-butane.
(8) A method for the activation of a vanadium-phosphorus oxide catalyst, characterized by activating the vanadium-phosphorus oxide catalyst with a gas composition containing an inert gas possessing a thermal conductivity of not less than 800 (10
−4
Wm
−1
K
−1
) at 700 K.
(9) A method set forth in (8) above, wherein the gas composition contains nitrogen gas and the inert gas.
(10) A method set forth in (8) or (9) above, wherein the gas composition further contains an aliphatic hydrocarbon of not less than 4 carbon atoms and molecular oxygen.
(11) A method set forth in any of (8) through (10), wherein the activating temperature is in the range of 300°-600° C.
According to this invention, maleic anhydride aimed at can be produced with a high yield by causing the raw material gas to allow the presence therein of nitrogen and an inert gas possessing a thermal conductivity of not less than 800 (10
−4
Wm
−1
K
−1
) at 700 K. Further, according to this invention, the maleic anhydride aimed at can be produced with a high yield by activating the vanadium-phosphorus oxide catalyst by the use of a gas composition resulting from the incorporation of nitrogen and an inert gas possessing a thermal conductivity of not less than 800 (10
−4
Wm
−1
K
−1
) at 700 K in the raw material gas. The method provided by this invention for the production of maleic anhydride by the gas phase oxidation of an aliphatic hydrocarbon of not less than 4 carbon atoms with a molecular oxygen-containing gas in the presence of a vanadium-phosphorus oxide catalyst requires the presence of nitrogen and an inert gas possessing a thermal conductivity of not less than 800 (10
−4
Wm
−1
K
−1
) at 700 K at the reaction site and, at the same time, utilizes the inert gas entrained by the waste gas remaining after the recovery of the maleic anhydride by separating the inert gas from the waste gas and circulating the separated inert gas to the site of the reaction of oxidation. Thus, the method contemplated by this invention permits the inert gas such as, for example, helium which is relatively expensive to be utilized inexpensively and efficiently and, at the same time, allows the maleic anhydride to be produced with a high yield and at a low cost.
REFERENCES:
patent: 3864280 (1975-02-01), Schneider
patent: 4231943 (1980-11-01), Paradis et al.
patent: 4392986 (1983-07-01), Yang et al.
patent: 4855459 (1989-08-01), Mummey
patent: 5070060 (1991-12-01), Barone
patent: 5430181 (1995-07-01), Arpentinier et al.
patent: 5530144 (1996-06-01), Tsurita et al.
patent: 5773382 (1998-06-01), Mitchell et al.
patent: 0029317 (1980-10-01), None
patent: 044969 (1982-03-01), None
patent: 59-132938 (1983-01-01), None
patent: 05115783 (1991-10-01), None
patent: 7171398 (1993-12-01), None
patent: 093053 (1995-04-01), None
Cataysis Today 28 (1996) pp. 139-145.
Journal of Catalysis 156, 28-36 (1995).
Journal of Catalysis, 140, 226-242 (1993).
Journal of Catalysis 145, pp. 256-266 (1994).
Hashiba Hideto
Nakajima Akiyoshi
Takayasu Osamu
Behr, Esq. Omri M.
Dentz Bernard
Nippon Shokubai Co. , Ltd.
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