Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
2000-11-03
2003-02-04
Silverman, Stanley S. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S306000, C502S307000, C502S308000, C502S309000, C502S310000, C502S311000, C502S312000, C502S313000, C502S314000, C502S315000, C502S316000, C502S317000, C502S319000, C502S320000, C502S321000, C502S322000, C502S323000, C558S319000
Reexamination Certificate
active
06514902
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing an oxide catalyst for use in producing acrylonitrile or methacrylonitrile from propane or isobutane. More particularly, the present invention is concerned with a process for producing an oxide catalyst for use in producing acrylonitrile or methacrylonitrile from propane or isobutane by ammoxidation in the gaseous phase, wherein the oxide catalyst comprises a compound oxide containing molybdenum (Mo), vanadium (V), antimony (Sb) and optionally an element X. The process comprises subjecting a solution or slurry, in water and/or an alcohol, of a raw material mixture comprising a Mo compound, a V compound, an Sb compound and optionally an X compound to a specific oxidation treatment using an oxidizing gas and/or an oxidizing liquid before subjecting the raw material mixture solution or slurry to drying and subsequent calcination. When the oxide catalyst produced by the process of the present invention is used in the production of acrylonitrile or methacrylonitrile, not only can the desired acrylonitrile or methacrylonitrile be produced in high yield and in high space time yield, but also the deterioration of the catalyst is suppressed, so that production of acrylonitrile or methacrylonitrile can be stably performed for a prolonged period of time.
2. Prior Art
Recently, attention has been attracted to a technique for producing acrylonitrile or methacrylonitrile by a gaseous-phase catalytic ammoxidation of propane or isobutane, as a substitute for a gaseous-phase catalytic ammoxidation of propylene or isobutylene, and a number of proposals have been made with respect to a catalyst for use in the ammoxidation of propane or isobutane.
For example, as a catalyst for use in the ammoxidation of propane or isobutane, a compound oxide catalyst containing molybdenum (Mo), vanadium (V), tellurium (Te) and niobium (Nb) is known. Such a compound oxide catalyst is disclosed in, for example, Unexamined Japanese Patent Application Laid-Open Specification Nos. 2-257 (corresponding to U.S. Pat. No. 5,049,692), 5-148212 (corresponding to U.S. Pat. No. 5,231,214), 5-208136 (corresponding to European Patent No. 529,853), 6-227819, 6-285372 (corresponding to U.S. Pat. No. 5,422,328), 7-144132, 7-232071, 8-57319 and 8-141401.
When the above-mentioned catalyst is used for the ammoxidation of propane or isobutane, the yield and space time yield of acrylonitrile or methacrylonitrile {hereinafter, frequently referred to as “(meth)acrylonitrile”)} become high. However, this catalyst has a problem in that during the production of the (meth)acrylonitrile, the tellurium is volatilized from the catalyst, thereby leading to a deterioration of the catalyst.
For this reason, as described below, oxide catalysts containing Mo, V and antimony (Sb) and oxide catalysts containing Mo, V, Sb and Nb, each of which contains antimony in place of tellurium which is likely to be volatilized from a catalyst, have been proposed.
For example, a compound oxide catalyst containing Mo, V, Sb and Nb (wherein Nb is an optional component) is disclosed in Unexamined Japanese Patent Application Laid-Open Specification Nos. 9-157241 (corresponding to U.S. Pat. No. 5,750,760) and 10-28862. This catalyst is produced using an aqueous solution containing a molybdenum compound, a vanadium compound, an antimony compound and optionally a niobium compound. The catalyst production process described in those documents comprises mixing a compound of pentavalent vanadium and a compound of trivalent antimony so as to reduce the vanadium, or mixing a compound of hexavalent molybdenum and a compound of trivalent antimony so as to reduce the molybdenum; mixing the resultant reaction mixture with compounds of other component elements to thereby obtain a mixture; and drying the obtained mixture, followed by calcination. Specifically, in these documents, the oxide catalyst is produced by a process comprising heat-aging an aqueous slurry containing a compound of pentavalent vanadium and a compound of trivalent antimony, followed by addition of a molybdenum compound and a niobium compound, thereby obtaining an aqueous mixture; optionally cooling the obtained aqueous mixture; and drying the aqueous mixture, followed by calcination.
When the catalyst produced by the above-mentioned process is used for the production of (meth)acrylonitrile, the desired (meth)acrylonitrile can be produced in a relatively high yield. However, the space time yield of (meth)acrylonitrile [molar amount of (meth)acrylonitrile formed (&mgr;mol)/time of contact (contact time) between the raw material and the catalyst (g·sec/ml)×catalyst weight (g)] is disadvantageously as low as 0.11 to 0.22 [(&mgr;mol/{(g·sec/ml)·g}]. Therefore, the productivity of (meth)acrylonitrile per reactor becomes low. Further, when it is attempted to improve the space time yield of (meth)acrylonitrile by employing a high reaction temperature, the selectivity for (meth)acrylonitrile is lowered, so that the yield of (meth)acrylonitrile also is lowered.
Unexamined Japanese Patent Application Laid-Open Specification No. 5-293374 (corresponding to U.S. Pat. No. 5,094,989) describes an oxide catalyst which contains V and Sb as major components, and also contains a small amount of Mo. However, when this catalyst is used in the production of (meth)acrylonitrile, not only is a high reaction temperature needed, but also the yield of (meth)acrylonitrile is low.
New Developments in Selective Oxidation pp. 515-525 (1990) reports the results of the ammoxidation of propane which was performed using a catalyst comprising alumina having supported thereon a compound oxide containing Mo, V and Sb in a molar ratio of 1/0.14/0.71. According to this document, the above-mentioned catalyst has a problem in that not only the selectivity for (meth)acrylonitrile but also the activity to perform the desired conversion are low.
U.S. Pat. No. 4,760,159 describes an oxide catalyst which contains bismuth, vanadium and antimony as major components, and also contains a small amount of molybdenum. However, when this catalyst is used in the production of (meth)acrylonitrile a problem arises not only in that a high reaction temperature is needed, but also in that the yield of (meth)acrylonitrile is low.
As is apparent from the above, with respect to the oxide catalyst comprising Mo—V—Sb or Mo—V—Sb—Nb, the deterioration thereof during the production of (meth)acrylonitrile is suppressed, but not only the conversion-selectivity-based yield (hereinafter referred to simply as “yield”) but also the space time yield of (meth)acrylonitrile is low.
Further, the oxide catalyst comprising Mo—V—Sb or Mo—V—Sb—Nb has the following problem. As described in
Applied Catalysis A General
, Vol. 157, 143-172 (1997), in the ammoxidation of propane, ammonia is converted to not only acrylonitrile (the desired compound of the ammoxidation) but also to various by-products, such as acetonitrile and hydrocyanic acid as well as nitrogen (an oxidative decomposition product). When the oxide catalyst comprising Mo—V—Sb or Mo—V—Sb—Nb is used for the ammoxidation, the decomposition of ammonia into nitrogen vigorously occurs (that is, the ratio of ammonia decomposed to form nitrogen is high), so that the loss of ammonia is large.
SUMMARY OF THE INVENTION
In this situation, the present inventors have made extensive and intensive studies to solve the above-mentioned problems accompanying the prior art. As a result, it has unexpectedly been found that, in the production of an oxide catalyst comprising a compound oxide containing at least molybdenum (Mo), vanadium (V) and antimony (Sb), when a solution or slurry, in water and/or an alcohol, of a raw material mixture comprising at least an Mo compound, a V compound and an Sb compound is subjected to a specific oxidation treatment, and the resultant oxidized raw material mixture solution or slurry is then dried to thereby obtain a dried catalyst precursor, followed by calcination
Inoue Tomoya
Ishida Hiroshi
Asahi Kasei Kogyo Kabushiki Kaisha
Nguyen Cam N.
Pennie & Edmonds LLP
Silverman Stanley S.
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