Organic compounds -- part of the class 532-570 series – Organic compounds – Nitriles
Reexamination Certificate
2002-01-04
2004-05-25
Nguyen, Cam N. (Department: 1754)
Organic compounds -- part of the class 532-570 series
Organic compounds
Nitriles
C558S323000, C502S110000, C502S113000, C502S248000, C502S249000, C502S255000, C502S305000, C502S306000, C502S307000, C502S308000, C502S309000, C502S310000, C502S311000, C502S312000, C502S313000, C502S314000, C502S315000, C502S316000, C502S317000, C502S318000, C502S321000, C502S322000, C502S323000, C502S407000, C502S439000
Reexamination Certificate
active
06740769
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process for producing a molybdenum-bismuth-iron-containing metal oxide fluidized bed catalyst. In more particular, it relates to a process for producing a particle diameter-controlled molybdenum-bismuth-iron-containing metal oxide fluidized bed catalyst having a desired particle diameter distribution.
Further, the present invention relates to a molybdenum-bismuth-iron-containing metal oxide fluidized bed catalyst obtained by the above-mentioned process, the use of the catalyst, and a process for producing acrylonitrile or methacrylonitrile which uses the catalyst.
BACKGROUND ART
The use of a molybdenum-bismuth-containing metal oxide fluidized bed catalyst in ammoxidation of propylene, isobutene and/or tertiary butanol is disclosed, for example, in JP-B-36-3563, JP-B-36-5870, JP-B-38-17967, JP-B-39-3670, JP-B-39-10111, JP-B-42-7774, JP-B-50-64191, JP-B-47-27490, JP-B-54-22795 and JP-B-60-36812.
With regard to a process for producing a fluidized bed catalyst having a controlled particle diameter distribution, proposals have been made in JP-A-52-140490 as to an iron-antimony type oxide fluidized bed catalyst and in JP-A-5-261301 as to a vanadium-phosphorus type oxide fluidized bed catalyst. However, no effective method has been proposed as to a process for producing a molybdenum-bismuth-iron-containing metal oxide fluidized bed catalyst.
DISCLOSURE OF THE INVENTION
It is well known that, in a fluidized bed reaction, in order to keep catalyst particles in a good fluidizing condition thereby to make the reaction proceed efficiently, it is very important that the physical property, particularly the particle diameter distribution, of the catalyst is appropriate.
In producing a fluidized bed catalyst, it is usually conducted for obtaining a catalyst having a desired particle diameter distribution to control the conditions of spray drying. By such a means alone, however, it is quite difficult to produce the intended catalyst, and catalyst particles having unnecessarily large or small diameters tend to be inevitably formed. When the amount of catalyst particles having small diameters is too large, in a fluidized bed reaction, such catalyst particles tend to fly away during the reaction to cause an increase in the amount of the catalyst to be replenished. In particular, catalyst particles with a diameter of 20 &mgr;m or less are apt to fly out of the system. When the amount of catalyst particles having a large diameter is too large, the fluidizing property of the catalyst tends to deteriorate to worsen the result of the reaction.
Furthermore, even when a catalyst having an appropriate particle diameter distribution is used in a fluidized bed reaction, the catalyst particles with small diameters gradually fly away during the reaction to shift the particle diameters toward larger ones. In such a case, measure is commonly taken in which a catalyst containing much of fine particles is replenished so that the catalyst in the reactor may keep an appropriate particle diameter distribution. In preparing the catalyst used for replenishing mentioned above, it is difficult to obtain a catalyst of the desired particle diameter distribution by mere control of the spray drying conditions. Therefore, it is economically advantageous to use a supplementary catalyst having controlled particle diameters produced by the combination of the control of spray drying conditions with the removal by classification of particles with a diameter of 20 &mgr;m or less, which are apt to fly away. Further, it is favorable if the fine particles removed by classification can be reused as the catalyst starting material.
However, no such methods have been disclosed with regard to a molybdenum-bismuth-iron-containing metal oxide fluidized bed catalyst. Moreover, even when such a known method is applied as such to the present catalyst system, satisfactory results cannot be obtained because the activity and physical property of the catalyst are adversely affected. It is estimated that, in a catalyst of the present system, when the catalyst particles removed by classification and having particle diameters outside the desired range are added to a slurry before spray drying, the solution composition-precipitation composition ratio becomes different from that in the initial catalyst slurry, which may exert a great influence on the performance characteristics of the catalyst. Under such situations, development of a process has been awaited which can produce a molybdenum-bismuth-iron-containing metal oxide fluidized bed catalyst having controlled particle diameters economically efficiently while keeping good catalytic characteristics.
After extensive study, the present inventors have found that, in a process for producing a metal oxide fluidized bed catalyst containing molybdenum, bismuth, iron and silica as the essential constituents of the catalyst component, by separating dried particulate products with particle diameters outside the desired particle diameter range from spherical particles obtained by spray drying operation, pulverizing the dried products to particle diameters of 10 &mgr;m or less, then mixing the pulverized products into the slurry at a stage prior to spray drying within the range of 50% by weight or less (based on the oxides of the completed catalyst), spray-drying the resulting mixture, and subjecting the spray-dried product to classificatio, catalyst particles having diameters outside the desired particle diameter range can be effectively utilized and, as a whole, a practically useful molybdenum-bismuth-containing metal oxide fluidized bed catalyst which has a high strength, particularly excellent abrasion resistance, and moreover sufficient activity can be produced in a reasonable way.
Thus, according to the present invention, there is provided a process for producing a molybdenum-bismuth-iron-containing metal oxide fluidized bed catalyst containing molybdenum, bismuth, iron and silica as essential components and having a controlled particle diameter, said process comprising the step of spray-drying a slurry containing catalyst components to effect granulation, which comprises the steps of
[I] spray-drying a slurry containing catalyst components,
[II] subjecting the dry particles obtained by the spray drying to classification to separate dry particles having a particle diameter outside a desired range, and feeding dry particles having a particle diameter within the desired range to the subsequent calcination step,
[III] pulverizing the dry particles having a particle diameter outside the desired range so as to have a particle diameter of 10 &mgr;m or less to obtain a pulverized product, and
[IV] mixing the pulverized product into the slurry containing catalyst components at any desired stage prior to the spray drying so as to be in the range of not more than 50% by weight in terms of oxides based on oxides of a completed catalyst obtained after the spray drying and the calcination.
The metal oxide fluidized bed catalyst produced by the process for producing a metal oxide fluidized bed catalyst of the present invention described above is preferably a catalyst having a composition represented by the formula
MoaBibFecQdReXfYgOh(SiO
2
)i
wherein Mo, Bi, Fe and O respectively represent molybdenum, bismuth, iron and oxygen, Q represents at least one element selected from the group consisting of nickel, cobalt, magnesium, chromium, manganese and zinc, R represents at least one element selected from the group consisting of beryllium, phosphorus, boron, arsenic, selenium, lithium, sodium, potassium, rubidium, cesium, thallium and tellurium, X represents at least one element selected from the group consisting of vanadium, tungsten, yttrium, lanthanum, zirconium, hafnium, niobium, tantalum, aluminum, calcium, strontium, barium, lead, copper, cadmium, gallium, indium, germanium, antimony, tin and cerium, Y represents at least one element selected from the group consisting of praseodymium, neodymium, samarium, europium, gadolinium,
Mizutani Kouichi
Mori Kunio
Nakamura Yoshimi
Sasaki Yutaka
Mitsubishi Rayon Co. Ltd.
Nguyen Cam N.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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