The mixing method first dissolves solid ferrous sulfate in desalinated water (deionized water), and adds ammonium carbonate solution to neutralize under stirring to generate amorphous iron hydroxide, iron carbonate and basic iron carbonate precipitate. After hot boiling and aging, rinse, filter, and dry to obtain semi-finished iron oxide. This semi-finished product is mixed and crushed with chromic anhydride (CrO3), KOH, K2CO3, other additives, adhesives (such as bentonite), lubricants (graphite), etc., and then granulated, dried, pressed and formed, calcined to obtain the finished product.
The coprecipitation method dissolves ferrous sulfate and chromic anhydride together in desalinated water, adds other additives, and adds ammonia water under stirring to precipitate iron hydroxide and chromium hydroxide together. After hot cooking, washing, filtering, drying and roasting, then crushing, adding KOH, graphite and a proper amount of water, mixing evenly, pressing and forming, and then drying to obtain the finished product.
The mixed precipitation method first uses ammonium carbonate to neutralize ferrous sulfate solution to generate iron compound precipitation, rinse and make slurry, and add chromic anhydride solution. At about 90 ℃, the soluble CrO3 was reduced to Cr2O3 and precipitated by the reduction of Fe2 +. Then KOH, graphite and other additives are added, mixed evenly, dried, granulated, molded and roasted to obtain the finished product.
The impregnation method first uses any of the above three methods to prepare the iron-chromium catalyst, and then uses the impregnation method to add other components, such as impregnated ammonium molybdate solution, or rare earth compound solution, etc., after impregnation, drying and roasting to obtain the finished product. Ferrous sulfate is commercially available, and ferrous sulfate solution can also be prepared by dissolving metallic iron with sulfuric acid.