Organic compounds -- part of the class 532-570 series – Organic compounds – Nitriles
Reexamination Certificate
2002-04-10
2003-11-04
McKane, Joseph K. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Nitriles
C502S205000
Reexamination Certificate
active
06642405
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a catalyst suitably used for the production of acrylonitrile by ammoxidation of propylene, a process for producing said catalyst and a process for producing acrylonitrile by using said catalyst.
BACKGROUND ART
With respect to a catalyst suitably used for the production of acrylonitrile by ammoxidation of propylene, various catalysts are disclosed. In JP-B-38-17967, there is disclosed an oxide catalyst containing molybdenum, bismuth and iron, and in JP-B-38-19111, there is disclosed an oxide catalyst containing iron and antimony. After that, studies have been extensively continued to improve these catalysts. For example, in JP-B-51-33888, JP-B-55-56839, JP-B-58-2232, JP-B-61-26419, JP-A-7-47272, JP-A-10-43595, JP-A-4-11805 and the like, there are disclosed one improvement comprising using another component in addition to molybdenum, bismuth and iron, and the other improvement comprising using another component in addition to iron and antimony.
Also with respect to a process for producing a fluidized bed catalyst, there are descriptions in JP-B-37-8568, JP-B-42-22476, JP-B-57-49253, JP Patent 2640356, JP Patent 2701065, JP Patent 2747920 and others.
Further, in using these catalysts for the ammoxidation reaction, it is proposed to carry out said reaction while supplying a molybdenum-containing material thereto, thereby maintaining the catalyst efficiency. For example, in JP-B-58-57422, there is disclosed a process, wherein a particle formed by supporting a molybdenum-containing material on silica is supplied to a fluidized bed catalyst containing molybdenum, bismuth, iron, cobalt and others, thereby restoring the catalyst efficiency. In DE 3, 311, 521 and WO 97/33863, there is disclosed a process, wherein molybdenum trioxide or a molybdenum compound capable of converting to said trioxide in a specific amount is supplied to a catalyst similar to that mentioned above.
These catalysts of the prior arts were effective to improve a yield of acrylonitrile to a certain extent. However, these catalysts have been N still insufficient in respect to repeatability in the production thereof and long-term stability of the yield) of desired products. It has been very important to solve these problems from an industrial point of view and further improvements of these catalysts have been requested.
In addition, also with respect to the process comprising supplying the molybdenum component to maintain the catalyst efficiency, it is difficult to say that it is always effective. Even if the molybdenum component is supplied, no effect can be observed in the case where a catalyst structure is markedly damaged. Further, even if loss of molybdenum is not so large, no effect can be exhibited in the case where lowering of the catalyst efficiency is mainly caused by change of the catalyst structure. It is finding that the catalyst to be applied it self-should be stable and should have no extreme damage on its structure.
It has been desired to find a catalyst, which is capable of further improving the acrylonitrile yield, satisfactory in the repeatability in the production thereof, stable when used for the ammoxidation reaction, and capable of maintaining its efficiency for a long period of time by the supply of molybdenum. The present invention is to solve these problems and to improve Japanese Patent No. 2640356, Japanese Patent Application No. 10-128098 and others particularly with the aim of improving a process for producing acrylonitrile by ammoxidation of propylene.
DISCLOSURE OF INVENTION
The present inventors have undertaken extensive studies to solve the above-mentioned problems. As a result, it has been found that the desired product can be obtained with a high yield and such an effect can be maintained for a long period of time, when a fluidized bed catalyst is used and the ammoxidation reaction is carried out while appropriately adding and supplying a molybdenum-containing material, which fluidized bed catalyst comprises molybdenum, bismuth, iron, nickel, chromium, an F component of a trivalent metal and potassium as essential components and has an Mo/Me of from 0.8 to 1, wherein the Mo/Me is a number obtained by dividing the product 20 of a valence number of molybdenum as molybdic acid and an atomic ratio of molybdenum by the sum of respective products of respective valence numbers and atomic ratios of bismuth, iron, nickel, chromium, potassium, an F component element, a G component element and a Y component element.
The fluidized bed catalyst is capable of giving a high acrylonitrile yield. Moreover, the catalyst is stable in its catalyst structure, and so resistant to use of a long-term reaction. When the Mo/Me exceeds the above-defined range, an excess molybdenum component may enter the interface of metal molybdate, which functions as a catalyst, and as a result, dysfunction may be caused. Whereas, when the Mo/Me is less than the above-defined range, the acrylonitrile yield decreases and at the same time variation with the lapse of time becomes large.
Still, in the case where the catalyst in accordance with the present invention, which is structurally stable, is used without interruption for the ammoxidation reaction, a decrease of the acrylonitrile yield due to escaping of the molybdenum component may be observed. Since the ammoxidation reaction using this kind of the molybdenum containing catalyst is carried out at a temperature exceeding 400° C., it seems that the escaping of the molybdenum component is inevitable during the reaction. In this regard, the acrylonitrile yield was able to be maintained at a high degree for a long period of time by continuing the reaction while adding the molybdenum-containing material.
According to the catalyst in accordance with the present invention, which is structurally stable, the yield of desired products can be more sufficiently maintained, improved or restored by appropriately adding the molybdenum-containing material at the time of the ammoxidation reaction. Moreover, since the addition of the molybdenum-containing material at the time of the ammoxidation reaction can be repeated, the catalyst in accordance with the present invention can be used for a much longer period of time by such a repeated addition of the molybdenum-containing material. The addition of the molybdenum-containing material may be carried out from an early stage of the reaction. In applying the catalyst to the ammoxidation reaction, a catalyst surface composition and a catalyst structure are optimized by means of a preparation composition, a preparation method or the like. However, it is difficult to say that the optimization can be always realized. As the case may be, the yield of the desired product increases by the addition of the molybdenum-containing material at an early stage of the reaction. This seems that optimization of the catalyst surface composition and the structure thereof can be realized also with the aid of the addition of the molybdenum-containing material.
With respect to a conventional catalyst, the acrylonitrile yield has been insufficient, and it has not been always easy to maintain its efficiency even when the reaction is carried out while adding the molybdenum-containing material. Moreover, it has been insufficient to restore its efficiency even if the molybdenum-containing material is added on the ground that the yield decreases owing to a long-term use of the catalyst. According to the present invention, there is provided a process capable of maintaining a high acrylonitrile yield for a long period of time.
That is, the present invention provides a process for producing acrylonitrile, which comprises using a fluidized bed catalyst of a composition represented by the following empirical formula in the production of acrylonitrile by ammoxidation of propylene. The present invention also provides a process for producing acrylonitrile according to said process, wherein the ammoxidation reaction is carried out while appropriately adding a molybdenum-containing material.
Mo10 Bia Feb Sbc Nid Cre Ff Gg Hh Kk Mm
Miyaki Kenichi
Mori Kunio
Sasaki Yutaka
Watanabe Hirokazu
McKane Joseph K.
Mitsubishi Rayon Co. Ltd.
Shiao Rei
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