Preparation method of low-sodium low-ammonium high-purity molybdic acid

Abstract

The invention relates to a preparation method of high-purity molybdic acid in the catalyst industry, which comprises the following steps: (1) adding water into high-purity molybdenum trioxide to prepare slurry, then slowly adding solid sodium hydroxide, adjusting the pH value of the solution to 6-12, and filtering mother liquor to obtain clarified mother liquor which is a sodium molybdate solution; (2) slowly adding a nitric acid solution into the clarified mother liquor to adjust the pH acidity of the solution, and heating until molybdic acid crystals are separated out; and (3) carrying out solid-liquid separation on the mixed solution containing the crystallized molybdic acid, drying the solid at 60-95 DEG C, and screening to obtain the high-purity molybdic acid. The method is scientific and reasonable in design and excellent in application effect, the single molybdenum concentrate is selected as a raw material, through the two-stage purification process of ammonium tetramolybdate and high-purity molybdenum trioxide, the high-purity molybdenum trioxide is dissolved in specific sodium hydroxide, the solution is acidified through nitric acid to reach a certain pH value, crystals of molybdic acid are separated out from the solution, and solid-liquid separation, drying and screening are carried out to obtain a high-purity molybdic acid product.

Description

technical field [0001] The invention belongs to the field of chemical production and relates to catalyst production technology, in particular to a method for preparing low-sodium, low-ammonium and high-purity molybdic acid. Background technique [0002] Molybdic acid is an inorganic acid, an oxyacid of molybdenum, and has weak oxidizing properties. In the process of petroleum processing, it is the main active ingredient in the manufacture of high-end catalysts for residual oil hydrogenation, and plays a key role. The preparation method of ordinary molybdic acid mainly adopts the method of nitric acid acidifying the solution containing molybdate recovered from the discarded catalyst. Therefore, at present in my country's molybdenum industry market, only low-purity molybdenum acid products are used as raw materials for the production of low-quality ammonium tetramolybdate or sodium molybdate, which are supplied to molybdenum chemical companies. The finished product is not pu...

AI Technical Summary

Problems solved by technology

[0007] 1. Raw material: molybdate solution, the molybdate solution is ammonium molybdate, and the raw material source contains a large amount of ammonium, which brings great difficulties for subsequent impurity removal; 2. Ammonium removal: the invention uses all ammonium Add flaky sodium hydroxide and use it to evaporate free ammonium salts under high alkalinity conditions. After testing, it is found that the removal effect is poor, and the ammonium residues are serious, resulting in product caking; 3. The invention adds a large amount of Sheet-shaped sodium hydroxide is used to remove ammonium, but in the process of removing ammonium, a large amount of sodium ions are introduced, which brings new problems to the purification of subsequent molybdic acid; 4. Adopt 98% nitric acid acidification, the invention carries out Acidification treatment, the molybdate in the solution becomes precipitate after acidification, but it is found through practice that high-concentration nitric acid has high requirements in the storage and transportation process. It is very unfavorable to remove impurities, causing many impurities to be unable to get out. The product is viscous and precipitated at high temperature, and it will inevitably agglomerate after drying. Therefore, there is a subsequent crushing process in this invention. The above three points have caused downstream production enterprises Many inconveniences need to be resolved urgently