Design Bases for Modulated Complexation by Electrochemistry

Abstract

The treatment of liquid organic phases to remove undesirable compounds is currently a priority in different industries. In oil refinery, it is necessary to reduce sulphur compounds, in gasolines, to below 50 ppm.The traditional form is catalytic hydrodesulphuration; however, this system is not effective for some compounds, e.g., alkyl substituted dibenzothiophenes. The processes for modulated complexation by electrochemistry are based on the capacity of a complexing agent, in a certain oxidation state, to form a bond with the molecule to be removed from a liquid phase. If the contaminant, the solute, is in an organic phase, the complexant must be soluble in aqueous phase. When the complexant is formed and in contact with both phases the contaminant is extracted. In a second stage, the complexing agent is oxidized (or reduced) to a state of less affinity to the contaminant, and the aqueous phase is placed in contact with a new organic phase where the contaminant will be discharged and concentrated. The complexant agent in aqueous phase is reduced (or oxidized) to its state of higher affinity for the contaminant and recirculated to the extraction stage. In this work, we present the conditions necessary for this process to be feasible, the criteria for the selection of the complexes, the methodology for matter balances, determination of energy consumption and thermodynamic calculations, and also three examples of an organic phase: dibenzotiophene, pyridine, and methyl thioether, using as complexing agent iron tetrakis-(p-sulphonatophenyl) porphyrin.