Methods and catalysts for the manufacture of carbon fibrils
View Patent ↗An improved catalyst for producing carbon fibrils is made by incorporating an effective yield-enhancing amount of a carboxylate into a fibril-forming catalyst. Alternatively, such a catalyst is made by coprecipitating a compound of a metal having fibril-forming catalytic properties and an aluminum and/or magnesium compound, optionally in the presence of carbon particles or carbon fibril aggregates. The catalyst may also be made by incorporating a compound of a fibril-forming metal onto magnesia particles in carbon particles or carbon fibril aggregates. The catalysts, methods of using them to form carbon fibrils and those carbon fibrils are also disclosed.
1. A method for the production of carbon fibrils comprising passing a fibril-forming feedstock under temperature and pressure conditions suitable for formation of fibrils over a supported fibril-forming catalyst made by a process comprising the steps of:
(a) forming an aqueous solution of an iron compound or iron and molybdenum compounds;
(b) forming a slurry of catalyst support particles comprising alumina and/or magnesia particles;
(c) precipitating an iron compound or iron and molybdenum compounds onto said alumina and/or magnesia particles in the presence of an effective yield-enhancing amount of a carboxylate; and
(d) separating the so-impregnated support material from said slurry and further processing it to produce a supported fibril-forming catalyst.
2. The method of claim 1 , wherein the precipitated catalyst is washed with a solution of a carboxylate prior to further processing to produce said fibril-forming catalyst.
3. The method of claim 1 , wherein said carboxylate is introduced into the slurry of support material prior to introduction of the solution containing said iron compound or said iron and molybdenum compounds.
4. The method of claim 1 , wherein the carboxylate comprises an anion of a carboxylic acid and the solution from which the iron compound or the iron and molybdenum compounds are precipitated onto said alumina and/or magnesia particles contains from about 0.04 to about 4 grams of the anion per gram of supported fibril-forming catalyst.
5. The method of claim 1 , wherein the said carboxylate is derived from formic acid or acetic acid.
6. The method of claim 1 , wherein the carboxylate comprises an anion of a carboxylic acid and the weight ratio of anion to iron or iron and molybdenum in the solution from which the iron compound or iron and molybdenum compounds is precipitated is in the range of 0.07 to 14.
7. The method of claim 1 , wherein the carboxylate is acetic acid, the fibril-forming metal compound includes an iron compound and the weight ratio of acetate to iron in the solution from which an iron compound is precipitated is in the range of 0.1 to 5.