Chemistry of hydrocarbon compounds – Unsaturated compound synthesis – By dehydrogenation
Reexamination Certificate
2001-10-23
2003-10-21
Dang, Thuan D. (Department: 1764)
Chemistry of hydrocarbon compounds
Unsaturated compound synthesis
By dehydrogenation
C585S658000, C585S660000
Reexamination Certificate
active
06635794
ABSTRACT:
TECHNICAL FIELD TO WHICH INVENTION THE INVENTION BELONGS
This invention relates to catalysts for oxidative dehydrogenation of alkanes and a process for producing 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 oxidizing and dehydrogenating lower alkanes at vapor phase with molecular oxygen to produce corresponding olefins at high yields, with the use of said catalysts.
PRIOR ART
Lower olefins are starting materials of important industrial products: Le., ethylene, for ethylene oxide, acetaldehyde, acetic acid and the like; propylene, for acrolein, acrylic acid, propylene oxide, polypropylene and the like; and isobutene, for methacrolein, methacrylic acid, methyl tert.-butyl ether and the like. Demands for those products invariably increasing recently and their prices running higher, development of low cost production process of these lower olefins is desired.
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 incapable 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 factory location, it is unprofitable and its industrial application at the present time 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 A1) 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 and are far short of industrially practicable level.
We also have disclosed for the purpose catalyst containing Cr or Mo, Sb and W as the essential components (2000-037624A-JP) and those containing Mn as the essential component (2000-037625A-JP), but catalysts exhibiting still higher activity level are desirable for industrial use.
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 yields; and also to provide a process for producing from lower alkanes the corresponding olefins at high yields, by the use of said catalysts.
MEANS FOR SOLVING THE PROBLEM
The above object of the invention can be accomplished by the catalysts which are characterized in that they contain Mn as the essential component and a crystal phase which is identified by the peaks appearing in X-ray diffraction spectrum (per Cu—K&agr; cathode) when diffraction angle 2&thgr; (±0.3°) is at 32.9°, 55.2°, 23.1°, 38.2° and 65.8° (i.e., when the inherent crystal lattice spacing, d-values, are 2.72 Å, 1.66 Å, 3.84 Å, 2.35 Å and 1.42 Å), that is, the crystal phase corresponding to Mn
2
O
3
. Use of the catalysts in the occasions of vapor-phase oxidative dehydrogenation of C
2
-C
5
lower alkanes enables production of lower olefins at high yields.
EMBODIMENTS OF THE INVENTION
More specifically, in the invention said C
2
-C
5
lower alkanes signify ethane, propane, n-butane, isobutane, n-pentane and isopentane. These lower alkanes may be used either singly or as a mixture of more than one kind.
According to the invention, from these lower alkanes the corresponding olefins can be prepared at high yields, 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. The invention is particularly suitable for producing propylene from propane and isobutene from isobutane.
The catalysts according to the invention are characterized by containing Mn and a crystal phase identified by the peaks appearing in X-ray diffraction spectrum (per Cu—K&agr; cathode) when the diffraction angle 2&thgr; (±0.3°) is at 32.9°, 55.2°, 23.1°, 38.2° and 65.8°. In particular, those composed substantially of the elementary composition expressed by the following formula (1) are preferred:
Mn
a
X
b
Y
c
O
x
(1)
in which Mn stands for manganese,
X stands for at least one element selected from the group consisting of Sb, W and Cr,
Y stands for at least one element selected from Re, Fe, Co, Ni, Nb, Ta, Ce, Zn, Tl, Li, Na, K, Rb, Cs, Mg, Ca, Sr and Ba,
and O stands for oxygen.
Of the catalysts represented by above general formula (1), those containing as the X component at least two elements selected from Sb, W and Cr, or all of those three elements are preferred. Among the preferred catalyst, those containing as the Y component one to four elements selected from the group consisting of Ni, Co, Nb, Ta, Ce, Li, Na and K are particularly advantageous.
Referring to the above general formula (1), a, b, c and x stand for the atomic ratios of Mn, X, Y and oxygen, respectively, and where when a is 1, b is 0.01-2, c is 0-2 and x is a numerical value determined by the extents of oxidation of those elements other than oxygen. Particularly recommendable catalysts are those in which, where a is 1, b is 0.05-1 and c is 0-1.
The oxidative dehydrogenation catalysts of the present invention may further contain refractory inorganic substances for the purpose of improving their activity level and physical durability. Suitable content of the refractory inorganic substances is 10-90% by weight of the whole catalyst containing the catalytically active ingredients. As such refractory inorganic substances, those known can be used, examples of which including silica, alumina, titania, zirconia, silica-alumina, silica-titania and silica-zirconia. In particular, silica, silica-alumina and titania are preferred, because they give higher yield of the object products. As the silica-alumina, those in which the ratio of the silica is at least 10% by weight but less than 100% by weight are suitably used.
The process for preparing the catalysts of the invention are not subject to critical limitations, so long as the catalysts containing the specified crystal phase are ultimately obtained. Whereas, depending on the kind of manganese source used, for example, combination of the preparation steps may become subject to certain limitations such as a need to modify the heat treatment conditions in the subsequent steps. Individual steps, however, are subject to no specific limitation but known methods can be applied. For example, the catalysts according to the invention can be prepared by the following steps: add at least one of antimony trioxide powder, aqueous solution of ammonium metatungstate and aqueous solution of chromium nitrate, to a slurry containing manganese (III) oxide powder; if necessary also add an aqueous solution or an oxide powder of a compound of at least one element selected from the group consisting of Ni, Co, Li, Na, K, Re, Fe, Nb, Ta, Ce, Zn
Dang Thuan D.
Nippon Shokubai Co Ltd
Sherman & Shalloway
LandOfFree
Catalysts for oxidative dehydrogenation of alkanes and a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Catalysts for oxidative dehydrogenation of alkanes and a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Catalysts for oxidative dehydrogenation of alkanes and a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3120754