Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
2002-04-15
2003-11-25
Wilson, James O. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C568S772000, C568S814000, C568S862000, C585S250000, C585S260000
Reexamination Certificate
active
06653509
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a catalyst which consists of amorphous carbon with molecular planes that have curved surfaces and contain six-membered and non-six-membered carbon rings, optionally having at least one catalytically active, low-valency metal covalently bound thereto. The invention also relates to methods of producing the catalyst and applications thereof.
In many applications involving the use of catalytically active metals on a support system, it is of advantage if the latter is a carbon-based system. However, the use of graphitic material as support has the disadvantage that, due to the graphite's planar layering, there is only little interaction with the metals. As a result, the metal is apt to agglomerate, especially under reaction conditions and in particular at elevated temperatures. Agglomeration of the catalytically active metal means that the surface area thereof is reduced, which in turn causes a reduction in the catalytic activity of the system and thus, especially in the case of valuable metals, inadequate exploitation of the system's catalytic capacity.
In patent specification DE 43 24 693.1, the inventor has already suggested over-coming this disadvantage by using metal-fullerene intercalation compounds. These have the advantage of being defined compounds which are not only highly stable on account of their bonding strongly to the catalytically active metals, but can also be reproduced exactly. This is largely due to the fact that direct covalent bonds are formed between the carbon atoms of the fullerene molecule and a metal atom.
One disadvantage of using metal-fullerene intercalation compounds as catalysts is the fact that the supporting material is expensive. In addition, it would be beneficial if the catalytic efficacy—expressed in terms of the content of catalytically active metal or metal compound used in each case—could be enhanced further by making the metal more accessible for the components of the catalysed reaction. The object of this invention is thus to overcome the above-mentioned disadvantages of catalysts with a carbon-based support.
SUMMARY OF THE INVENTION
This object is achieved by means of a catalyst which consists of amorphous carbon with molecular planes that have curved surfaces and contain six-membered and non-six-membered carbon rings, optionally having at least one catalytically active, low-valency metal covalently bound thereto.
The invention is based on the surprising discovery that amorphous, carbon with molecular planes exhibiting curved surfaces and containing not only six-membered but also non-six-membered carbon rings are suitable as catalysts and/or as supporting material for catalytically active metals, and have especially desirable properties that result in superior catalysts. Without being bound by theory, it is assumed that this is due to the presence of curved sp
2
-hybridized carbon layers. The curvature of the layers is not due in this case to simple “rolling” or “bending” of otherwise intact graphite layers, but is due to the incorporation of non-six-membered rings in the sp
2
-hybridized carbon layers. The curvature produced thus in the carbon layers is associated with significant differences compared to the geometric and electronic structure of a planar, graphitic sp
2
-hybridized carbon layer. Besides a considerable stress-induced increase in potential energy, the &pgr; electrons are not completely delocalized within these curved areas, so that the curved carbon layers can be seen to a certain extent as conjugated double-bond systems.
Thus, the presence of non-six-membered rings in the carbon network not only introduces curvature into the surface of the materials described, but also a modulation of its electronic structure. The combined action of these two effects gives rise to the presence of anchoring sites for metal particles as well as of catalytically active sites.
When used as supporting materials for catalytically active low-valency metals, the carbon material used in the catalysts of the invention, like electron-deficient olefins, are able to form chemical bonds with transition metals in low formal oxidation states. These bonds are chemical bonds formed directly between the metal and the carbon support. They do not, as is the case with conventional carbon supports such as activated charcoal, anchor the metal atoms primarily by way of interactions with terminal heteroatom functionalities, predominantly oxygen.
The amorphous carbon contained in the catalysts of the invention consists of interlacing 6-C rings in which additional rings, mainly 5-C rings, are incorporated. The curved surfaces may be concave or convex. This structure, which is an essential feature of the amorphous carbon used in the catalyst of the invention, can be determined by physical methods, especially x-ray absorption spectroscopy (XAS), as is described by H. Werner et al., in Chem. Phys. Letters 194 (1992), 62-66. The curved areas can also be characterized by their special chemical reactivity; corresponding reaction products have been characterized by IR spectroscopy after partial oxidation of these carbon materials (M. Wohlers, A. Bauer, R. Schlögl, Microchim. Acta, submitted 1995, printing). An example of the materials suitable in the context of the invention is the product known as “Krätschmer soot”. This is a product which, during the production of fullerenes by the Krätschmer method, is left behind when the fullerenes are separated off. As described in more detail below, the amorphous carbon of the catalyst of the invention may also be obtained by methods other than the one described by Krätschmer.
REFERENCES:
patent: 4116996 (1978-09-01), Huang
patent: 4324695 (1982-04-01), Hinnenkamp
patent: 4569924 (1986-02-01), Ozin
patent: 5227038 (1993-07-01), Smalley et al.
patent: 43 24 693 (1995-02-01), None
patent: 2 217 701 (1989-11-01), None
patent: WO 95/10481 (1995-04-01), None
Harris,International Materials Review, 1997, vol. 42, No. 5, “Structure of Non-Graphitising Carbons”.
Tsang, et al., “Reduction of Nitric Oxide by Arc-Vaporized Carbon”,Applied Catalysis B., vol. 8, pp. 445-455, Jul. 1996.
Belz, et al., “Characterization of Fullerene Soots and . . . Electrode Deposits”,Synthetic Metals, vol. 77, pp. 223-226, 1996.
Belz Thilo
Braun Thomas
Schlögl Robert
Wohlers Michael
Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V.
Rothwell Figg Ernst & Manbeck P.C.
Wilson James O.
Witherspoon Sikarl A.
LandOfFree
Method for the liquid-phase hydrogenation of organic materials does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for the liquid-phase hydrogenation of organic materials, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for the liquid-phase hydrogenation of organic materials will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3131071