The conversion of pyridine (PY), quinoline (QUI) and meso-tetraphenylporphyrin (TPP) using active hydrogen passing through a Pd membrane under mild conditions (25 degrees C and ambient pressure) by applying -1.92 mA cm (2) is reported. Moreover, some results regarding VGO and diesel hydrotreating, under similar conditions, are shown. Relative kinetic conversion constants (k'), calculated for each tested molecules, support the following reactivity order: PY (k' = 87 x 10 (4) min (1)) > QUI (k' = 5 x 10 (4) min (1)) > TPP (k' = 1 x 10 (4) min (1)). Based on the reduction and increasing factors found for aromatic and saturated fractions respectively, it can be established that diesel is easier to transform than VGO. Nevertheless, hydrodenitrogenation seems to be more notable for VGO than for diesel. (C) 2010 Elsevier Ltd. All rights reserved.