Abstract: A process for producing the precursor of a precipitated catalyst for the sub.3 synthesis, based on Fe, Al, Co and K oxides, which comprises the steps of:(A) preparing an aqueous solution of water-soluble compounds of Fe, Al and Co--adding iron as a water-soluble ferrous salt of an organic acid--and causing, by addition of an alkaline precipitating solution, the co-precipitation of the corresponding (Fe, Al and Co) hydroxides, which still contain iron in the ferrous form;(B) oxidizing the hydroxide suspension prepared according to point (A) until divalent iron and trivalent iron are in a ratio to each other which ranges from 0.20 to 0.50;(C) operating an alkaline doping with a potassium compound and heating in an inert atmosphere up to above 850.degree. C.

Abstract: A process for preparing iron-based catalysts for the synthesis of ammonia by melting of magnetite along with metal oxides as promoters, subsequent cooling of the molten mass and reduction thereof to the desired size, wherein the abovesaid cooling occurs at a rate higher than 25.degree. C./min., preferably ranging from 100.degree. C. to 1600.degree. C./min., at a temperature ranging from 1700.degree. C. to 700.degree. C.The present invention relates to a process for preparing iron-based catalysts having a high activity in the ammonia synthesis, and to the catalyst so obtained.

Abstract: A process is disclosed for the preparation of black and brown thermostable pigments consisting essentially of mixed phases of iron and manganese oxides, characterized in that:(a). pyrolusite, in the form of particles having a mean diameter not exceeding 20 microns, is mixed and maintained in contact together with heptahydrated ferrous sulphate at a temperature between room temperature and 95.degree. C.; and(b). the mass thereby obtained is dried, crushed and screened, and then calcined in the presence of air in a fluidized bed reactor at a temperature between 800.degree. and 900.degree. C.The starting pyrolusite/heptahydrated ferrous sulphate mixture may be additioned with one or more compounds selected from the group consisting of FeCl.sub.2, SiO.sub.2, FeCl.sub.3, Na.sub.2 SiO.sub.3, Fe.sub.3 O.sub.4, NaAlO.sub.2, KAl(SO.sub.4).sub.2 and NaBO.sub.2. The total quantity of additives is between 0.5% and 5% by weight based on the final product.

Abstract: A process is disclosed for preparing .alpha.-Fe.sub.2 O.sub.3 in the form of acicular particles substantially free from occluded boils or cavities, and containing from 0.2 to 2% by weight of SiO.sub.2, and having a mean axial ratio between 6 and 8, and an intrinsic coercive force of 320 - 370 Oe. An aqueous solution of FeSO.sub.4. 7H.sub.2 O is treated with alkali, in the presence of air, thus forming acicular .alpha.-FeOOH, which is then dehydrated, reduced at Fe.sub.3 O.sub.4 under fluidizing conditions, and oxidized to .gamma.-Fe.sub.2 O.sub.3 at 200.degree.-350.degree. C under fluidizing conditions. The formation of the acicular .alpha.-FeOOH is carried out at a yield of 0.5-2.5 kg of ferric Fe per hour per m.sup.3 of reactor; the reaction product is filtered and washed and the .alpha.-FeOOH particles are coated with 0.2-2% by weight of SiO.sub.2, from an aqueous suspension of .alpha.-FeOOH brought to a temperature ranging from 50.degree. to 90.degree. C, adding Na.sub.2 SiO.sub.