A method for the preparation of the finely granular carbides of vanadium, titanium, tantalum and niobium

摘要

A carbide of V, Ti, Ta or Nb having a sub-micronic grain size and containing as possible impurities only the oxide of the metal and/or free carbon is prepared by passing a mixture containing M2 and a hydrocarbon containing at most 3 carbon atoms per molecule over an oxide of the appropriate metal at a temperature between 650 DEG and 1050 DEG C. CH4 is the preferred hydrocarbon. The metal oxides may be prepared previously by pyrolysis, in an inert or reducing atmosphere, of a less stable compound of the metal e.g. a hydroxide, an ammonium or complex mineral salt or an organic compound. This atmosphere may also comprise H2 and CH4 and the pyrolysis temperature is not more than 500 DEG C. In one embodiment Me pyrolysis and carburization are carried out successively in a fixed or fluidized bed, the gases being recycled after the latter step. The carbides may be incorporated with metals, metal oxides and alloys in articles and may also be used as catalysts or catalyst supports and in catalytic mixtures.