A tubular reactor is described, for catalytic reactions involving thermal exchanges, in particular for etherification reactions between branched olefins and linear alcohol, for dimerization reactions of branched olefins or cracking reactions, essentially consisting of a vertical tube-bundle exchanger whose tubes contain catalyst, having inlet and outlet nozzles for each passage side of the reagents, catalyst and thermal exchange liquid, characterized in that it has one or more metallic supports situated outside the lower tube plate in the lower part of the reactor for sustaining the catalyst so that the same catalyst is contained not only in the tubes of the tube-bundle but also in said lower part outside the lower tube plate and also in the upper part outside the upper tube plate.