Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Patent
1998-07-28
2000-02-22
Geist, Gary
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
562531, 562532, 562545, 568479, C07C20500, C07C 5116
Patent
active
060282207
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a method in which acrolein and acrylic acid are produced by carrying out vapor phase catalytic oxidation of propylene with molecular oxygen or a gas containing molecular oxygen using a fixed bed multitubular reactor.
PRIOR ART
A number of complex oxide catalysts containing molybdenum, bismuth and iron have already been proposed for use in the production of acrolein and acrylic acid by a method in which propylene is subjected to vapor phase catalytic oxidation, and some of them are now industrially used. Their typical examples include those which are disclosed in Japanese Patent Publication (KOKOKU) No. 47-27490 (1972), Japanese Patent Publication (KOKOI(U) No. 47-42241 (1972) and Japanese Patent Publication (KOKOKU) No. 48-1645 (1973).
However, industrial production of acrolein or acrylic acid using these catalysts causes various problems.
One of these problems is generation of a local abnormally high temperature part (hot spot) in the catalyst layer. Generation of the hot spot is caused by the exothermic reaction of said vapor phase catalytic reaction. In order to improve productivity in the industrial production of acrolein and acrylic acid, a means is generally employed in which the concentration of the starting material propylene is increased or the space velocity of the reaction gas is increased, but heat accumulation at the hot spot is increased under such high load reaction conditions. Increase in heat accumulation at the hot spot causes shortened catalyst life, increased formation of by-products due to over oxidation reaction and, in the worst case, runaway reaction.
If the activity of a part of the catalyst wherein the hot spot is generated is decreased, the activity of the whole catalyst is probably lowered due to migration of hot spots to other layers (parts) of the catalyst.
In order to avoid generation of such hot spot or excessive heat accumulation at the hot spot, one must unwillingly accept low productivity or must take a countermeasure for example by reducing the reaction tube diameter, which, however, are economically disadvantageous.
In consequence, various studies have been reported, in order to avoid the aforementioned danger in reaction operations caused by the hot spot to ensure economy in the aforementioned industrial production. For example, a method in which a catalyst wherein the hot spot could be generated is diluted with an inert substance (Japanese Patent Publication (KOKOKU) No. 53-30688 (1978)) and a method in which the catalyst to be used is made into a tubular shape (Japanese Patent Publication (KOKOKU) No. 62-36739 (1987)) have been proposed.
Also, reaction methods have been proposed in which two or more reaction zones are arranged in a reaction tube, and in which the reaction is carried out by packing a plurality of catalysts having different activities. Examples of such a type of methods so far reported include a method in which a plurality of catalysts whose activities are controlled by changing composition of catalytically active components (kind and/or quantity of an alkali metal in particular) are packed in a reaction tube along its axis in such a manner that catalysts having higher activities are arranged toward the outlet side from the inlet side of the material gas (Japanese Patent Publication (KOKOKU) No. 63-38331 (1988)) and a method in which a plurality of catalysts having different occupying volumes are packed in a plurality of reaction zones in such a manner that the occupying volume becomes small toward the outlet side from the inlet side of the reaction tube (Japanese Patent Application Kokai No. 4-217932 (1992)).
However, in the method in which a catalyst is diluted with an inert substance, an intensive effort is required in uniformly mixing the inert substance for dilution with the catalyst, but their uniform packing cannot always be effected by this method, thus not only causing frequent generation of hot spots but also entailing inconvenience in carrying out the reaction, because the position and tem
REFERENCES:
patent: 5276178 (1994-01-01), Onodera et al.
patent: 5719318 (1998-02-01), Kawajiri et al.
patent: 5892108 (1999-04-01), Shiotanai et al.
Iwamoto Akira
Nowatari Hiroyoshi
Sakai Fumio
Seo Yoshimasa
Shiraishi Kazuo
Deemie Robert W.
Geist Gary
Nippon Kayaku Kabushiki Kaisha
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