Nanodyne Incorporated

N.v. Union Miniere S.a.

N.v. Union Miniere S.a. Et Al.

Purnesh Seegopaul

Lin Gao

Li Wu

Bernard H Kear

A molybdenum carbide compound is formed by reacting a molybdate with a mixture of hydrogen and carbon monoxide. By heating the molybdate powder from a temperature below 300&#xb0; C. to maximum temperature 850&#xb0; C., a controlled reaction can be conducted wherein molybdenum carbide is formed. A high surface area, nanograin, metastable molybdenum carbide can be formed when the reaction temperature is below 750&#xb0; C. The metastable molybdenum carbide is particularly suitable for use as a catalyst for the methane dry reforming reaction and the water gas shift reaction.

Method of using molybdenum carbide catalyst

Tungsten carbide is formed from a tungsten material which is preferably tungsten carbide scrap. If scrap material is used, this is oxidized and acid leached to remove impurities and any binder material. This is then dissolved in a solution of sodium hydroxide and spray dried to form a precursor compound. A carbon compound such as citric acid can be added to the solution prior to spray drying to provide a carbon source for the tungsten carbide. The powder formed from the spray dried solution is calcined and carburized to form tungsten carbide.

Method of forming nanograin tungsten carbide and recycling tungsten carbide

A molybdenum carbide compound is formed by reacting a molybdate with a mixture of hydrogen and carbon monoxide. By heating the molybdate powder from a temperature below 300&deg; C. to maximum temperature 850&deg; C., a controlled reaction can be conducted wherein molybdenum carbide is formed. A high surface area, nanograin, metastable molybdenum carbide can be formed when the reaction temperature is below 750&deg; C. The metastable molybdenum carbide is particularly suitable for use as a catalyst for the methane dry reforming reaction.

Method of forming molybdenum carbide catalyst

Nanograined tungsten carbide particles are formed by a controlled, simultaneous reduction carburization reaction wherein the kinetics of the carburization and reduction reactions are controlled to permit simultaneous reduction and carburization. The kinetics are controlled by reacting a reduction carburization gas mixture, preferably hydrogen and carbon monoxide by slowly increasing the reaction temperature by controlling the rate of temperature increase. Preferably, the reaction temperature will be increased less than 25.degree. C. per minute, preferably about 1-2 degrees per minute, which prevents the formation of stable, undesirable species such as W.sub.2 C, which in turn interferes with the reaction efficiency.

Method of forming tungsten carbide particles

Grain growth inhibitors including vanadium carbide, chromium carbide, tantalum carbide, and niobium carbide are incorporated into a cobalt/tungsten carbide matrix during the formation of the cobalt/tungsten carbide matrix. A precursor powder is formed by combining in solution a cobalt composition, a tungsten composition and a grain growth inhibiting metal composition, which is then spray dried. The precursor compound is then carburized in carbon monoxide and carbon dioxide to form cobalt/tungsten carbide matrix. This is then further carburized in a hydrocarbon hydrogen gas at an elevated temperature to cause the grain growth inhibiting metal present to form the carbide. The second carburizing step is conducted with a carburizing gas having a carbon activity greater than about 2 for a relatively short period of time at 900.degree. C. to 1000.degree. C.

Multi-step process to incorporate grain growth inhibitors in WC-Co

In order to eliminate the oxygen sensitivity of chromium carbide and vanadium carbide particles, vanadium carbide and chromium carbide particles are formed by carburizing a precursor compound at a elevated reaction temperature of about 950.degree. C. Initially, the precursor compound is heated in an inert nitrogen-containing gas to the reaction temperature. Once the reaction temperature is achieved, hydrogen and a carbon-containing gas such as methane or ethylene are used to conduct the carbonization. After the carbonization has been completed, the carbonizing gas is then replaced with an inert nitrogen-containing gas and the product allowed to cool down. The carbonization cycle is adjusted so that the oxygen level is kept to less than 0.35%, while the nitrogen level is kept at about 2%. Powders produced from this process show minimal or no oxygen pickup when exposed to ambient air.

Synthesis of phase stabilized vanadium and chromium carbides

Tungsten carbide cobalt and tungsten-containing materials are recycled using a single high-temperature oxidation with standard dilution chemistry. The scrap material is ground, oxidized, and subjected to an acid digestion, preferably in hydrochloric acid. This causes the cobalt to form cobalt chloride while the tungsten remains insoluble. The pH is then increased to about 7.0 which causes the cobalt chloride to form cobalt hydroxide which precipitates out of solution. The cobalt and tungsten are separated and dissolved in a high-pH ammonia solution which can then be spray dried to form a precursor powder for subsequent carburization to form tungsten carbide-cobalt powders.

Reclamation process for tungsten carbide/cobalt using acid digestion

Tungsten carbide and/or tungsten can be recycled by oxidizing the tungsten composition at a temperature greater than 700.degree. C. to form a water insoluble tungsten trioxide. This is then reduced to form tungsten dioxide. The tungsten dioxide is subjected to a low temperature oxidation which forms monoclinic tungsten trioxide. The monoclinic tungsten trioxide is then dissolved in ammonia to form ammonium tungstate. If present, the binder metal such as cobalt is converted into the soluble ammine complex. This can be spray dried and carburized to form tungsten carbide. If the form composition includes cobalt or other binder metal, the ratio of cobalt to tungsten can be adjusted by adding cobalt salts or ammonium metatungstate to the aqueous solution prior to spray drying to form a precursor composition. This is uniquely suitable for forming a cobalt tungsten carbide composition.

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Flemington, NJ, United States of America

Purnesh Seegopaul