Low temperature reduction of metal oxides

A method for producing a powder of a reduced metal oxide, the method comprising:

• providing a reaction mixture comprising the metal oxide containing precursor and a magnesium reductant;
• heating the reaction mixture at atmospheric pressure in the presence of solid or gaseous aluminium chloride to a temperature at which reactions that result in the metal oxide being reduced are initiated, the amount of the aluminium chloride being between 1 wt% and 500 wt% of the weight of the metal oxide containing precursor;
• controlling reaction conditions whereby the reaction mixture is prevented from reaching a temperature at which thermal runaway can occur and whereby the formation of aluminium oxychloride as a by-product is favoured over aluminium oxide:
• and
• isolating reaction products in the form of a powder that include reduced metal oxide.

A method for reducing silicon oxide (SiO2) in a silicon oxide (SiO2) containing precursor, the method comprising:

• providing a reaction mixture comprising the silicon oxide (SiO2) containing precursor and an aluminium reductant;
• heating the reaction mixture in the presence of solid or gaseous aluminium chloride to a temperature of between about 400° C. and 600° C., whereby reactions that result in the SiO2 being reduced are initiated;
• controlling reaction conditions to maintain the temperature below about 650° C., whereby the reaction mixture is prevented from reaching a temperature at which thermal runaway can occur and
• isolating reaction products that include a powder of elemental silicon.

A method for producing a powder comprising silicon, the method comprising:

• providing a reaction mixture comprising a silicon oxide containing precursor and an aluminium reductant;
• heating the reaction mixture at atmospheric pressure in the presence of solid or gaseous aluminium chloride to a temperature of between about 300° C. and 600° C., whereby reactions that result in the silicon oxide being reduced are initiated, the amount of the aluminium chloride being between 1 wt% and 500 wt% of the weight of the silicon oxide containing precursor;
• controlling reaction conditions to maintain the temperature below about 650° C., whereby the reaction mixture is prevented from reaching a temperature at which thermal runaway can occur and whereby the formation of aluminium oxychloride as a by-product is favoured over aluminium oxide;
• and
• washing the reaction products in dilute acid to isolate the silicon powder.

A method for producing a powder comprising silicon, the method comprising:

• feeding a silicon oxide containing precursor and an aluminium reductant into a reaction vessel at atmospheric pressure and at a temperature of between 300° C. and 600° C., preferably between 450° C. and 600° C. and more preferably between 500° C. and 550° C., in the presence of solid or gaseous aluminium chloride,
• mixing the reactants together and in the presence of reaction products that form;
• controlling a feed rate of the silicon oxide containing precursor and the aluminium reductant into the reaction vessel such that the temperature in the reaction vessel does not exceed about 650° C.;
• and
• washing the reaction products in dilute acid to remove aluminium oxychloride by-product and isolate the silicon powder.