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

摘要

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 CH3C1 (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 °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_2O; (ii) CHCl_3/1 × 10~(-5)M HC1 (pH-5); (iii) CHCl_3/1× 10~(-5)M HC1 (pH = 5)+4 × 10~(-4)M EDTA and (iv) CHCl_3/4 × 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 HC1 + EDTA as water phase. Crude oil porphyrinic extracts seem to be less reactive than model metalloporphyrins.