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

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 CH(3)Cl (nonemulsified media) are converted, producing hydrogenated porphyrins and/or free metal (Ni or V), by active permeated atomic hydrogen generated by applying -1.92 mA cm (2) at 25 degrees 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) CHCl(3)/H(2)O; (ii) CHCl(3)/1 x 10 (5) M HCl (pH = 5); (iii) CHCl(3)/1 x 10 (5) M HCl (pH = 5)+4 x 10 (4) M EDTA and (iv) CHCl(3)/4 x 10 (4) M 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. (C) 2011 Elsevier Ltd. All rights reserved.