Use of the Peroxide Method for Vanadium Activation to Obtain Mixed Keggin-Type Heteropoly Compounds

The possibility of preparing mixed Keggin-type heteropoly compounds by introducing catalytically active vanadium(V) atoms activated by the peroxide method into the framework of Mo- and W-containing heteropoly anions was demonstrated. The pretreatment of the required amount of vanadium(V) in the form of V₂O₅ with a concentrated H₂O₂ solution ensures a considerable decrease in the content of foreign ions in solutions of heteropoly compounds and in salts based on them. Incorporation of vanadium(V) atoms into the heteropoly anion framework with preservation of the structural integrity was proved by the example of acidic salts Cs_3.5H_0.5PMo₁₁VO₄₀, Cs_3.5H_0.5PW₁₁VO₄₀, and Cs_4.5H_0.5SiW₁₁VO₄₀. The textural characteristics of the target compounds were studied, their thermograms were recorded, and the phase composition was determined. High stability and low solubility of the Cs-containing salts in three cycles of hydrothermal treatment were demonstrated.