Process and apparatus for performing endothermic catalytic reactions

In a process for reforming petroleum fractions by endothermic catalytic reactions, consisting of introducing the reaction stream into at least one elongated catalysis zone, constituted by at least one zone containing dilute catalyst and which can itself be preceded by a zone containing an inert catalyst-support, said dilute catalyst zone being followed by a conventional catalysis zone proper, each of said zones being also separable from neighbouring zones by intercalated zones containing no material, and of distributing along said zones heating means capable of providing variable amounts of heat to the reaction stream moving in each of said zones, the improvement consisting essentially of using at the most two zones of dilute catalyst arranged before the pure catalyst zone, if the direction of the reaction stream introduced is considered, and of carrying out the dilution of said dilute catalyst with a bulk material, different from said inert catalyst support and a better heat conductor than said inert catalyst support, which enables the temperature profile to be adapted along the reaction zone to the reaction speed in the latter.