Process for carrying out heat exchange reactions comprising introducing a reactant stream into a bed of catalytic material placed outside at least one double walled heat transfer tube in a heat exchange reactor contacting the reactant stream with the catalytic material in indirect heat exchange with a heat transfer medium present in the annular volume of the at least one double walled heat transfer tube, the annular volume comprising one or more spacer elements creating a helical flow path of the heat transfer medium around the inner heat transfer tube of the at least one double walled heat transfer tube. The invention also includes a heat exchange reactor for carrying out the above reaction.