Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
2002-12-11
2004-02-03
Wood, Elizabeth D. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S305000, C502S306000, C502S307000, C502S313000, C502S318000, C502S319000, C502S329000, C502S330000, C502S331000, C502S332000, C502S335000, C502S336000, C502S337000, C502S338000
Reexamination Certificate
active
06686311
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is related to a catalyst system for preparing carbon fibrils. More specifically, the invention is related to carbon fibrils and new catalysts which have been found useful for the synthesis of carbon fibrils.
Carbon fibrils, also known as carbon nanotubes, are microscopic fibers of carbon which are either tubes or dense fibers (i.e. not hollow) with a typical diameter in a range between about 1 nanometer and about 500 nanometers. In particular, it is often preferable to synthesize carbon fibrils with a diameter in a range between about 10 nanometers and about 50 nanometers. The aspect ratio of length of the carbon fibril to the diameter of the carbon fibril is typically greater than about 100.
Production of carbon fibrils is a well known synthetic process. They are typically synthesized using a catalytic vapor decomposition process, in which an organic vapor is flushed over dispersed metal catalysts at temperatures ranging from 400° C. to 1300° C. to form carbon fibrils. The chemical nature of the metal catalysts influences the yield and morphology of the synthesized carbon fibrils.
Mandeville et al. and Moy et al., U.S. Pat. Nos. 5,500,200 and 5,726,116 respectively, discuss the reaction of a source of carbon over a catalyst in a reaction system to produce carbon fibrils. However, Mandeville et al. and Moy et al. are ostensibly limited to iron catalysts and their binary alloys. In addition, these patents are not concerned with tertiary or quaternary combinations of catalysts which may have a synergistic effect compared to singular or binary combinations.
Due to the increasing interest in carbon fibrils, alternate catalysts that will result in the synthesis of carbon fibrils at high yield and high efficiency are constantly being sought.
BRIEF SUMMARY OF THE INVENTION
In one embodiment, the present invention provides a catalyst system for making carbon fibrils, the system comprising a catalytic amount of an inorganic catalyst comprising nickel and one of the following substances selected from the group consisting of:
chromium;
chromium and iron;
chromium and molybdenum;
chromium, molybdenum, and iron;
aluminum;
yttrium and iron;
yttrium, iron and aluminum;
zinc;
copper;
yttrium;
yttrium and chromium; and
yttrium, chromium and zinc.
A further aspect of the invention provides a catalyst system for making carbon fibrils, the system comprising a catalytic amount of an inorganic catalyst comprising cobalt and one of the following substances selected from the group consisting of:
chromium;
aluminum;
zinc;
copper;
copper and zinc;
copper, zinc, and chromium;
copper and iron;
copper, iron, and aluminum;
copper and nickel; and
yttrium, nickel and copper.
Yet another aspect of the present invention is a method for making carbon fibrils wherein the method comprises reacting a carbon source and a catalyst system. The catalyst system comprises an inorganic catalyst comprising nickel and one of the following substances selected from the group consisting of:
chromium;
chromium and iron;
chromium and molybdenum;
chromium, molybdenum, and iron;
aluminum;
yttrium and iron;
yttrium, iron and aluminum;
zinc;
copper;
yttrium;
yttrium and chromium; and
yttrium, chromium and zinc.
Yet a further aspect of the present invention is a method for making carbon fibrils wherein the method comprises reacting a carbon source and a catalyst system. The catalyst system comprises an inorganic catalyst comprising cobalt and one of the following substances selected from the group consisting of: chromium;
aluminum;
zinc;
copper;
copper and zinc;
copper, zinc, and chromium;
copper and iron;
copper, iron, and aluminum;
copper and nickel; and
yttrium, nickel and copper.
DETAILED DESCRIPTION OF THE INVENTION
One aspect of the present invention is directed to new catalysts which successfully synthesize carbon fibrils have been discovered. The synthesis of carbon fibrils typically involves the reaction of a carbon source in the presence of an inorganic catalyst. In one embodiment of the present invention, the carbon fibrils are synthesized with a catalytic amount of a catalyst which includes nickel and at least one other substance. The catalyst may be substantially free of iron. “Substantially free” of iron as used herein refers to iron present in an amount less than 1% by weight of the total catalyst. In a second embodiment of the present invention, the carbon fibrils are synthesized with a catalytic amount of a catalyst which includes cobalt and at least one other substance. A “substance” as used herein refers to at least one metal, metal alloy, or combinations thereof with cobalt or nickel. “Catalytic amount” as used herein refers to an amount of catalyst sufficient to form carbon fibrils.
When the catalyst system is binary, the ratio of the metals, metal alloys, or mixtures thereof are typically in a range between about 10:1 and about 1:1. When the catalyst system is tertiary, the ratio of the metals, metal alloys, or mixtures thereof are typically in a range between about 10:10:1 and about 1:1:1. When the catalyst system is quaternary, the ratio of the metals, metal alloys or mixtures thereof are typically in a range between about 10:10:10:1 and about 1:1:1:1.
The catalyst, catalyst precursors or mixtures thereof are placed on a substrate. “Substrate” as used herein refers to any material which supports a collection of solid state materials (i.e. catalysts, catalyst precursors, or mixtures thereof). There is typically minimum interaction between the supported solid state materials and substrate material during chemical reaction or synthesis. However, certain substrates which have been found to be catalytic substances may have a synergistic effect on the production of carbon fibrils. Typical substrates include ceramics, for example, alumina; glass; metals, for example, aluminum, stainless steel, copper, silver, gold, platinum, and brass; and single crystals, for example, quartz, magnesium oxide, silicon, sapphire, and lanthanum aluminate.
The amount of catalysts placed on the substrate is typically in a range between nanograms and a few tens of milligrams. Typical total catalyst loading on the substrate is in a range between micrograms and a few grams, although with larger reactor size, the amount of catalysts loaded in a reactor may commonly be as much as a few pounds.
The catalysts may be deposited on the substrate sequentially or preferably, simultaneously. Catalysts may be deposited on a substrate using a gun sputtering deposition system. A gun sputtering deposition system contains elemental metal sources, metal alloy sources, or mixtures thereof placed in the gun cavity. An electrical discharge can be created at each source by applying radio frequency (RF) or direct current (DC) power in a range between about 10 Watts and about 1,000 Watts through the sputter gun, which heats the metal, metal alloy, or mixture thereof to form a metal plasma vapor. The metal vapor from the sputter gun is deposited onto a counter-facing substrate. The thickness of the material deposited is dependent upon several factors, including fixed power input. The amount of material deposited can be altered by changing the amount of time the sputter gun is pulsed.
Once the metal vapors have been deposited on the substrate, the catalysts are typically thermally annealed. The catalysts are heated to a temperature in a range between about 200° C. and about 1100° C., and preferably, to a temperature in a range between about 600° C. and about 800° C. During annealing, the catalysts are also typically in an environment to prevent the oxidation of the elemental metals or metal alloys. Examples of typical gases include argon, helium, nitrogen, hydrogen and mixtures thereof. Although the invention is not dependent upon theory, the temperature and atmospheric conditions may promote the interdiffusion and mixing of the combined metals to form catalysts.
An alternative manner for depositing a catalyst on a substrate is through the use of a liquid dispensing system. Each liquid dispenser is individually c
Levinson Lionel Monty
Singh Navjot
Sun Xiao-Dong
Caruso Andrew J.
General Electric Company
Patnode Patrick K.
Wood Elizabeth D.
LandOfFree
Catalyst system for producing carbon fibrils does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Catalyst system for producing carbon fibrils, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Catalyst system for producing carbon fibrils will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3312464