Phosphotungstic Acid by Extraction Process Preparation

Heteropoly acids with Keggin structure generally refer to inorganic compounds expressed in the following general chemical formulas. They are one of the most active catalysts used in acid catalytic reactions and redox reactions. It has good catalytic properties for the hydration and esterification of olefins, etherification of epoxides, alkylation of olefins and aldehydes, epoxidation of olefins and alkyl aromatization, etc. It has wide applications in petrochemical industry.

Over the years, scholars at home and abroad have devoted themselves to the study of how to reduce production costs, simplify process steps and achieve green and pollution-free preparation in the preparation of phosphotungstic acid. For example, some scholars have published papers that the extraction process can achieve high-efficiency extraction of phosphotungstic acid by adjusting the concentration of inorganic acid in phosphotungstic acid solution, and meet the environmental protection standards. The general contents of this process include:

Put scheelic acid in water, then add phosphoric acid and hydrochloric acid to form a mixed solution containing phosphotungstic acid, in which tungsten trioxide is 120 g/L, phosphorus is 5 g/L and hydrochloric acid is 3 mol/L. 15% n-octanol was used as extractant, diluent was sulfonated kerosene, and then four-stage countercurrent extraction was carried out, compared with O/A (oil/water phase) = 1:1; loading organic phase with water as stripping reagent, five-stage countercurrent extraction was carried out, compared with O/A (oil/water phase) = 5:1. The concentration of tungsten trioxide in stripping solution was 549.6g/L, and white phosphotungstic acid crystals were obtained by evaporation. The yield of tungsten trioxide is 91.6% by calculating the concentration of tungsten trioxide obtained from stripping solution.

Because the extractant used is alcohol extractant, only phosphotungstic acid molecule is extracted, impurity cations such as sodium ion, iron ion, impurity anions such as sulfate ion, phosphate ion, chloride ion and so on are not extracted, and because of the good phase separation effect, the entrainment of water solution will not be formed. Especially important is that the loaded organic phase can be stripped directly with distilled water, and the stripped organic phase can be reused directly without further treatment. The process is simple, the process is short, the preparation cost is low, the environment is not polluted, and it is easy for large-scale industrial production.

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