Electrochemically assisted demetallisation of model metalloporphyrins and crude oil porphyrinic extracts in emulsified media, by using active permeated atomic hydrogen

Abstract

Electrochemically assisted metalloporphyrins demetallisation can be performed employing a unique palladium membrane without surface deactivation; in other words, palladium foils can be used several times. Vanadyl tetraphenylporphyrin (VO-TPP) or nickel tetraphenylporphyrin (Ni-TPP) dissolved in CH3Cl (nonemulsified media) are converted, producing hydrogenated porphyrins and/or free metal (Ni or V), by active permeated atomic hydrogen generated by applying −1.92mAcm−2 at 25°C. VO-TPP and Ni-TPP conversions are dramatically increased when reactions are carried out in the following Oil/Water (O/W) emulsified media (about 30% in emulsified media vs. 5% in nonemulsified medium): (i) CHCl3/H2O; (ii) CHCl3/1×10−5M HCl (pH=5); (iii) CHCl3/1×10−5M HCl (pH=5)+4×10−4M EDTA and (iv) CHCl3/4×10−4M EDTA. Moreover, VO-TPP and Ni-TPP demetallisation percentages depend on the water phase nature, the highest demetallisation percentage (71%) is achieved using HCl+EDTA as water phase. Crude oil porphyrinic extracts seem to be less reactive than model metalloporphyrins.