Chemistry of hydrocarbon compounds – Unsaturated compound synthesis – By dehydrogenation
Reexamination Certificate
1999-05-18
2001-05-29
Dunn, Tom (Department: 1754)
Chemistry of hydrocarbon compounds
Unsaturated compound synthesis
By dehydrogenation
C585S661000, C585S662000, C585S663000, C562S521000, C562S522000, C562S545000, C562S546000, C562S547000
Reexamination Certificate
active
06239325
ABSTRACT:
TECHNICAL FIELD TO WHICH THE INVENTION BELONGS
This invention relates to lower alkane oxidative dehydrogenation catalysts and a production process of olefins using said catalysts. More specifically, the invention relates to the catalysts which are suitable for use in vapor phase oxidative dehydrogenation of C
2
-C
5
lower alkanes (hereinafter occasionally referred to simply as “lower alkanes”) in the presence of molecular oxygen to produce corresponding olefins, and a process for oxydizing and dehydrogenating lower alkanes with molecular oxygen to produce corresponding olefins at high yields, with the use of said catalysts.
The invention also relates to a process for producing, from the olefins which have been obtained through vapor phase oxidative dehydrogenation of C
2
-C
5
lower alkanes in the presence of molecular oxygen, the corresponding unsaturated aldehydes and/or unsaturated carboxylic acids.
PRIOR ART
As a production process for lower olefins, in particular, propylene and isobutene, simple dehydrogenation process of lower alkanes is recently reduced to industrial practice. However, this process is subject to an essential problem that it is difficult of giving high conversion due to the equilibrium limitation and furthermore requires high temperatures. Still in addition, deterioration of the catalyst within a short period is inavoidable in said process, which necessitates frequent regeneration of the catalyst using a switch converter or the like. In consequence, plant construction costs and utility costs for running the process are high and, depending on the conditions of location, it is unprofitable and its industrial application is restricted.
Whereas, attempts to produce lower olefins from lower alkanes through oxidative dehydrogenation which is free from the limitation by equlibrium have been-made since long, and various catalyst systems therefor have been proposed. Among those known, there are Co-Mo oxide catalyst (U.S. Pat. No. 4,131,631), V-Mg oxide catalyst (U.S. Pat. No. 4,777,319), Ni-Mo oxide catalyst (EP 379,433 Al) CeO
2
/CeF
3
catalyst (CN 1,073,893A), Mg-Mo catalyst [
Neftekhimiya
(1990), 30(2) 207-10], V
2
O
5
/Nb
2
O
5
catalyst [
J. Chem. Commun.
(1991) (8) 558-9], rare earth vanadates catalyst [
Catal. Lett.
(1996), 37, (3,4), 241-6] and B
2
O
3
/Al
2
O
3
catalyst [
ACS Symp. Ser.
(1996), 638 (Heterogeneous Hydrocarbon Oxidation) 155-169). Those known catalysts, however, invariably show very low level oxidative dehydrogenation performance, the property of the prime importance, and are far short of industrial practice.
Japanese Laid-open (KOKAI) Patent Application, KOKAI No. 245494/1996 furthermore contains a disclosure on a process for further oxidizing propylene, which was formed through dehydrogenation of propane, to produce acrylic acid. This process, however, necessitates removal of the hydrogen formed during the dehydrogenation of propane from the reaction gas. Japanese KOKAI Nos. 045643/1998, 118491/1998, 62041/1980 and 128247/1992, etc. disclose processes for forming unsaturated aldehydes and/or acids from lower alkanes, in particular, acrolein and/or acrylic acid from propane and methacrolein and/or methacrylic acid from isobutane. However, yield of these object products indicated in these publications are very low, and the processes need to be improved in various aspects including the catalyst to be used.
THE PROBLEM TO BE SOLVED BY THE INVENTION
An object of this invention is to provide novel oxidative dehydrogenation catalysts useful for vapor phase oxidative dehydrogenation of lower alkanes with molecular oxygen to produce corresponding lower olefins at high yield; and also to provide a process for producing from lower alkanes the corresponding olefins at high yield, by the use of said catalysts.
Another object of the invention is to provide a process for producing from lower alkanes corresponding unsaturated aldehydes and/or unsaturated carboxylic acids at high yield.
MEANS FOR SOLVING THE PROBLEM
We have made concentrative studies in search of the catalysts suitable for oxidizing and dehydrogenating lower alkanes with molecular oxygen to produce the corresponding lower olefins, to discover that a catalyst containing molybdenum and/or chromium, antimony and tungsten as the indispensable components, or a catalyst in which said catalytically active components are supported on a refractory inorganic carrier exhibit excellent oxidative dehydrogenation performance; and that lower olefins could be produced at high yield with the use of said catalyst. The present invention has been completed based on these discoveries.
Thus, the present invention provides catalysts for oxidative dehydrogenation of lower alkanes, said catalysts being suitable for use in vapor phase oxidative dehydrogenation of C
2
-C
5
lower alkanes in the presence of molecular oxygen to produce corresponding olefins and characterized by having a composition expressed by a general formula (1) below:
A
&agr;
Sb
&bgr;
W
&ggr;
D
&dgr;
Ox
(1)
(in which A is at least one metal selected from the group consisting of molybdenum and chromium; Sb is antimony; W is tungsten; O is oxygen; and D is at least one metal selected from the group consisting of V, Nb, Ta, Fe, Co, Ni, Cu, Ag, Zn, B, TI, Sn, Pb, Te, Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, La, Ce and Sm; &agr;, &bgr;, &ggr;, &dgr; and x denote atomic numbers of A, Sb, W, D and 0, respectively, where when &agr;=1, &bgr;=0.5−10, &ggr;=0.1−10 and &dgr;=0−3; and x is a numerical value determined by the state of oxidation of those elements other than oxygen).
The present invention furthermore provides a process for producing olefins which comprises vapor phase oxidative dehydrogenation of C
2
-C
5
lower alkanes in the presence of molecular oxygen to form corresponding olefins, characterized by the use of the above-described catalyst.
According to the present invention, furthermore, a process for producing, from lower alkane, unsaturated aldehyde and unsaturated acid at high yield is provided, in which an olefin obtained through vapor-phase oxidative dehydrogenation of C
2
-C
5
lower alkanes in the presence of molecular oxygen using the above-defined catalyst is further oxidized at vapor phase in the presence of oxygen to provide unsaturated aldehyde and unsaturated acid.
The invention moreover provides a process for producing unsaturated acid from lower alkane at high yield, in which the unsaturated aldehyde obtained as above is further oxidized at vapor phase in the presence of molecular oxygen to provide unsaturated acid.
EMBODIMENTS OF THE INVENTION
More specifically, C
2
-C
5
lower alkanes signify ethane, propane, n-butane, isobutane, n-pentane and isopentane. The catalysts of the present invention are used in oxidative dehydrogenation reactions of these lower alkanes to produce corresponding olefins, more specifically, ethylene from ethane, propylene from propane, n-butene from n-butane, isobutene from isobutane, n-pentene from n-pentane and isopentene from isopentane. These lower alkanes may be used either singly or as a mixture of more than one. The oxidative dehydrogenation catalysts of the present invention are useful for the production of, in particular, propylene and isobutene from propane and isobutane, respectively.
Referring to the general formula (1), the catalysts in which, when &agr;=1, &bgr;=1−5, &ggr;=0.2−5 and &dgr;=0−0.5 are preferred. Inter alia, those in which when &agr;=1, &bgr;=1−3, &dgr;=0.3−3 and &dgr;=0−0.3 exhibit most favorable performance.
Also the catalysts containing, as the component D referring to general formula (1), V, Nb, K, Mg, Sn, Fe, Co or Ni are preferred. In particular, the catalysts containing V exhibit most favorable performance.
Accordingly, oxidative dehydrogenation catalysts represented by the following general formula (2) are exemplified as one embodiment of the present invention:
A
&agr;
Sb
&bgr;
W
Kishimoto Nobuji
Matsunami Etsushige
Dunn Tom
Ildebrando Christina
Nippon Shokubai Co Ltd
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