Abstract: High purity ammonium dimolybdate or molybdenum oxide is produced by the pressure oxidation of low grade molybdenite concentrates or molybdenum intermediates. The process entails nearly complete oxidation of the sulfide minerals while optimizing the process chemistry and autoclave conditions to solubilize as little of the molybdenum values as possible. The autoclave discharge 12 is then subjected to a leaching step, either an alkaline leach 50, 400 or ammonium leach 250 process, before or after a liquid/solid separation step 20, 220, 410. The solution is then subjected to (a) filtration 60, 410, solvent extraction 70, 440, crystallization 90,450, and calcination 120, 480 or (b) filtration 260, 280, crystallization 290, and calcination 320 to produce a product suitable for chemical-grade molybdenum oxide 125, 325, 485.

Abstract: High purity ammonium dimolybdate or molybdenum oxide is produced by the pressure oxidation of low grade molybdenite concentrates or molybdenum intermediates. The process entails nearly complete oxidation of the sulfide minerals while optimizing the process chemistry and autoclave conditions to solubilize as little of the molybdenum values as possible. The autoclave discharge 12 is then subjected to a leaching step, either an alkaline leach 50, 400 or ammonium leach 250 process, before or after a liquid/solid separation step 20, 220, 410. The solution is then subjected to (a) filtration 60, 410, solvent extraction 70, 440, crystallization 90,450, and calcination 120, 480 or (b) filtration 260, 280, crystallization 290, and calcination 320 to produce a product suitable for chemical-grade molybdenum oxide 125, 325, 485.

Abstract: Molybdenite is roasted under controlled conditions to provide a polymolybdenum oxide composition having an oxygen content in excess of the stoichiometric oxygen content for MoO.sub.2 and less than that for MoO.sub.3, such that the composition contains MoO.sub.3 equivalent in excess of 5% and ranging up to 15% by weight, preferably, from about 10% to 15% by weight. The polymolybdenum oxide composition can be used to introduce molybdenum into baths of molten steel and the like with high recovery of the molybdenum content in the bath and with quiet addition characteristics as compared to the use of MoO.sub.3 per se. Preferably, a Herreshoff type roaster is used and the production rate of the furnace producing the new product is substantially increased, with an exit gas richer in SO.sub.2, as compared to use of the same roaster in roasting molybdenite to form MoO.sub.3 per se.

Abstract: Molybdenum trioxide containing potassium is heated to a temperature sufficiently high (i.e. at least about 525.degree. C.) to render the potassium soluble in hot water, the heated trioxide is quenched to less than about 400.degree. C. at a rate of at least about 30.degree. C. per minute, the quenched trioxide is leached with hot water (between about 50.degree. C. and about 100.degree. C.) to leach the solubilized potassium and after liquid-solids separation the molybdenum trioxide is dissolved in ammonium hydroxide to form ammonium molybdates, which can be recovered from solution and then can be calcined to chemical grade molybdic oxide. The process is advantageously conducted in conjunction with the roasting of molybdenite.