Method for crystallization of β-ammonium tetramolybdate

Patent metadata

Field	Value
Publication number	US-11701600-B2
Application number	US-202217992949-A
Country	US
Kind code	B2
Filing date	Nov 23, 2022
Priority date	Nov 23, 2021
Publication date	Jul 18, 2023
Grant date	Jul 18, 2023

Abstract

A method for crystallization of β-ammonium tetramolybdate includes: performing a stepwise pH-adjusting treatment of an ammonium molybdate solution via zoning to obtain the β-ammonium tetramolybdate. When feeding the ammonium molybdate solution into a reaction system from a first zone and then into second to sixth zones successively, pH1 of a resultant solution in the first zone is 7.0-6.0; pH2 of a resultant solution in the second zone is less than 6 and greater than or equal to 4; pH3 of a resultant solution in the third zone is less than 4 and greater than or equal to 2.5; pH4 of a crystallized slurry in the fourth zone is less than 2.5 and greater than or equal to 1; pH5 of a crystallized slurry in the fifth zone is 2.5-4.0; and pH6 of a crystallized slurry in the sixth zone is less than 2.5 and greater than or equal to 2.0.

First claim

What is claimed is:

1. A method for a crystallization of β-ammonium tetramolybdate, comprising: performing a stepwise pH-adjusting treatment of an ammonium molybdate solution via zoning, wherein upon feeding the ammonium molybdate solution into a reaction system from a first zone, pH 1 of a resultant solution in the first zone is adjusted to 7.0-6.0, prior to discharge into a second zone; pH 2 of a resultant solution in the second zone is adjusted to be less than 6 and greater than or equal to 4, prior to discharge into a third zone; pH 3 of a resultant solution in the third zone is adjusted to be less than 4 and greater than or equal to 2.5, prior to discharge into a fourth zone; pH 4 of a crystallized slurry in the fourth zone is adjusted to be less than 2.5 and greater than or equal to 1, prior to discharge into a fifth zone; pH 5 of a crystallized slurry in the fifth zone is adjusted to 2.5-4.0, prior to discharge into a sixth zone; and pH 6 of a crystallized slurry in the sixth zone is adjusted to be less than 2.5 and greater than or equal to 2.0, prior to reflux of a portion of the crystallized slurry in the sixth zone to the third zone, with a remaining of the crystallized slurry in the sixth zone being fed into a product zone for a solid-liquid separation, to obtain the β-ammonium tetramolybdate.

2. The method for the crystallization of the β-ammonium tetramolybdate according to claim 1 , wherein pH 1 is 6-7;
pH 2 is 4.0-5.9;
pH 3 is 2.5-3.9;
pH 4 is 1.0-2.4;
pH 5 is 2.5-4.0; and
pH 6 is 2.0-2.4.

3. The method for the crystallization of the β-ammonium tetramolybdate according to claim 2 , wherein pH 3 is 3-3.9;
pH 4 is 1.5-2.4; and
pH 5 is 3.8-4.0.

4. The method for the crystallization of the β-ammonium tetramolybdate according to claim 1 , wherein a concentration of the ammonium molybdate solution is 50-200 g/L.

5. The method for the crystallization of the β-ammonium tetramolybdate according to claim 1 , wherein an acid used in a pH adjustment at each zone is at least one of an aqueous hydrochloric acid and an aqueous nitric acid.

6. The method for the crystallization of the β-ammonium tetramolybdate according to claim 5 , wherein a concentration of the acid used in the pH adjustment at each zone is 5-10 mol/L.

7. The method for the crystallization of the β-ammonium tetramolybdate according to claim 1 , wherein an alkali used in a pH adjustment is an aqueous ammonia.

8. The method for the crystallization of the β-ammonium tetramolybdate according to claim 1 , wherein a temperature of the resultant solution during a treatment at each of the first zone, the second zone, and the third zone is 60-90° C.

9. The method for the crystallization of the β-ammonium tetramolybdate according to claim 1 , wherein a total residence time of the ammonium molybdate solution is 2-6 h.

10. The method for the crystallization of the β-ammonium tetramolybdate according to claim 1 , wherein a reflux ratio is 5-20 v %.

11. The method for the crystallization of the β-ammonium tetramolybdate according to claim 1 , wherein the ammonium molybdate solution is continuously added to the first zone and is continuously subjected to the stepwise pH-adjusting treatment via zoning to continuously provide the β-ammonium tetramolybdate at the product zone.

12. The method for the crystallization of the β-ammonium tetramolybdate according to claim 2 , wherein the ammonium molybdate solution is continuously added to the first zone and is continuously subjected to the stepwise pH-adjusting treatment via zoning to continuously provide the β-ammonium tetramolybdate at the product zone.

13. The method for the crystallization of the β-ammonium tetramolybdate according to claim 3 , wherein the ammonium molybdate solution is continuously added to the first zone and is continuously subjected to the stepwise pH-adjusting treatment via zoning to continuously provide the β-ammonium tetramolybdate at the product zone.

14. The method for the crystallization of the β-ammonium tetramolybdate according to claim 4 , wherein the ammonium molybdate solution is continuously added to the first zone and is continuously subjected to the stepwise pH-adjusting treatment via zoning to continuously provide the β-ammonium tetramolybdate at the product zone.

15. The method for the crystallization of the β-ammonium tetramolybdate according to claim 5 , wherein the ammonium molybdate solution is continuously added to the first zone and is continuously subjected to the stepwise pH-adjusting treatment via zoning to continuously provide the β-ammonium tetramolybdate at the product zone.

16. The method for the crystallization of the β-ammonium tetramolybdate according to claim 6 , wherein the ammonium molybdate solution is continuously added to the first zone and is continuously subjected to the stepwise pH-adjusting treatment via zoning to continuously provide the β-ammonium tetramolybdate at the product zone.

17. The method for the crystallization of the β-ammonium tetramolybdate according to claim 7 , wherein the ammonium molybdate solution is continuously added to the first zone and is continuously subjected to the stepwise pH-adjusting treatment via zoning to continuously provide the β-ammonium tetramolybdate at the product zone.

18. The method for the crystallization of the β-ammonium tetramolybdate according to claim 8 , wherein the ammonium molybdate solution is continuously added to the first zone and is continuously subjected to the stepwise pH-adjusting treatment via zoning to continuously provide the β-ammonium tetramolybdate at the product zone.

19. The method for the crystallization of the β-ammonium tetramolybdate according to claim 9 , wherein the ammonium molybdate solution is continuously added to the first zone and is continuously subjected to the stepwise pH-adjusting treatment via zoning to continuously provide the β-ammonium tetramolybdate at the product zone.

20. The method for the crystallization of the β-ammonium tetramolybdate according to claim 10 , wherein the ammonium molybdate solution is continuously added to the first zone and is continuously subjected to the stepwise pH-adjusting treatment via zoning to continuously provide the β-ammonium tetramolybdate at the product zone.

Assignees

• Univ Central South

Inventors

• Li Jiangtao
• Zhao Zhongwei
• Li Zhichao
• Chen Xingyu
• Liu Xuheng
• He Lihua
• Sun Fenglong
• Luo Yongjin
• Cui Muye

Classifications

• B01D9/0063 Primary

  Control or regulation (control per se G05) · CPC title

• B01D9/005 Primary

  Selection of auxiliary, e.g. for control of crystallisation nuclei, of crystal growth, of adherence to walls; Arrangements for introduction thereof · CPC title

• C01G39/006

  Compounds containing molybdenum, with or without oxygen or hydrogen, and containing two or more other elements · CPC title

• B01D2009/0086

  Processes or apparatus therefor · CPC title

• C01P2002/72

  by d-values or two theta-values, e.g. as X-ray diagram · CPC title