Potentiometric Monitoring of the State of Homogeneous Oxidation Catalysts Based on Heteropoly Acids
Russian Journal of Applied Chemistry
, E-ISSN: 1608-3296
Boreskov Institute of Catalysis SB RAS
The redox potentials E and pH values of 0.2 M aqueous solutions of H3+nPVnMo12-nO40 (HPA-n, 2 less than or equal to n less than or equal to 4) and products of their reduction with hydrazine hydrate to (H3+n+mPmMo12-nO40)-Mo-IV (HmHPA-n, 0 less than or equal to m less than or equal to n) were measured. It is proposed to use the dependences E =f(m) and pH = phi(m) as calibration curves for monitoring the degree of reduction m (m = [V-IV]/[H(m)HPA-n]) in oxidation of alkylphenols (2,6-dimethyl-phenol, 2,6-di-tert-butylphenol, and 2-methyl-1-naphthol) with HPA-n solutions into the respective alkyl-1,4-quinones.