Electrochemical reduction of 2-ethyl-9,10-anthraquinone (EAQ) and mediatedformation of hydrogen peroxide in a two-phase medium - Part II: Productionof alkaline hydrogen peroxide by the intermediate electroreduction of EAQ in a flow-by porous electrode in two-phase liquid-liquid flow

Hydrogen peroxide production by the intermediate electroreduction of the 2- ethyl-9,10-anthraquinone (EAQ) was carried out in a flow-by cell and a two- phase electrolyte formed by a mixture of tributylphosphate (TBP) and diethy lbenzene (DEB) as the organic phase, and a solution of NaOH as the aqueous phase. The cathode used was a reticulated vitreous carbon (RVC) foam. We ha ve examined the following process variables: electrolysis current (0.3-3.1A ), catholyte flow rate (470-1630 ml min(-1)), EAQ concentration in the orga nic phase (0.21-0.42 M), organic/aqueous phase volume ratio (1/9-4/6) and g rade of porosity of the RVC (30-45 ppi). The electrolyses can be carried ou t in the presence or absence of oxygen gas. The first method is the so-call ed 'one-step electrolysis' and the second method is the 'two-step electroly sis'. In the second method, the disodium salt of the hydroquinone (EAQNa(2) ) is electrochemically formed in the absence of oxygen. The second step con sists of the chemical reaction of this salt with oxygen to form hydrogen pe roxide. We obtained a hydrogen peroxide concentration of 0.8 M after 10 A h with an electrolysis current of 1.55 A and a current efficiency of 70%.