The present invention relates to a catalytic system comprising at least two catalytic zones of which at least one zone exclusively contains one or more noble metals selected from the group consisting of Rhodium, Ruthenium, Iridium, Palladium and Platinum and at least another zone contains Nickel, said catalytic system characterized in that at least one zone exclusively containing noble metals selected from the group consisting of Rhodium, Ruthenium, Iridium, Palladium and Platinum is always distinct but in contact with at least one zone containing Nickel. One or more metals selected from the group consisting of Rhodium, Ruthenium, Iridium, Palladium and Platinum are possibly added to the catalytic zone or zones comprising Nickel.