Alkaline peroxide electrosynthesis by oxygen reduction using an acid anolyte in a divided reactor with a three-dimensional rotating cylinder cathode and two-phase flow induced by centrifugal force

Abstract

BACKGROUND: This work analyses the performance of a batch electrochemical reactor with a three-dimensional rotating cylinder cathode for the synthesis of alkaline peroxide by reduction of O2 under 0.1 MPa (abs). The centrifugal force produces a radial co-current flow of the gas and liquid phases through the cathode achieving good mass-transfer conditions for the O2 reduction. RESULTS: Galvanostatic experiments carried out during 2h at 2 A (macrokinetic current density 398 A m-2), 30°C and 1000rpm with 1molL-1 H2SO4 as anolyte demonstrates that the cationic exchange membrane Nafion® 415 is an appropriate separator. However, a small decrease in the alkalinity of the cathodic compartment was observed. The use as anolyte of an equimolar solution of Na2SO4 and H2SO4 (1molL-1) maintains constant the total alkalinity of the cathodic solution. An experiment of 6h yielded 10.3gL-1 H2O2 concentration with 62.3% current efficiency and 10.6 kWh kg-1 specific energy consumption, using Na2SiO3 as addition agent. CONCLUSION: A divided electrochemical reactor using an acid anolyte and a three-dimensional rotating cylinder cathode with co-current oxygen and liquid flows represents a simple strategy for localized generation of peroxide solutions with low total alkalinity.