A process for carrying out heterogeneously catalyzed hydrogenation reactions in a fixed-bed reactor includes providing at least one main reactor containing a first amount of catalyst; providing a first auxiliary reactor and a second auxiliary reactor, each containing a second amount of catalyst, wherein the first amount of catalyst is relatively larger than the second amount of catalyst; passing a starting product of a fatty compound through the first auxiliary reactor and reacting the starting product with hydrogen in the presence of the catalyst; continuing the reaction through the at least one main reactor; and continuing the reaction through the second auxiliary reactor, wherein the first auxiliary reactor is reactivated. Another process provided includes a first and second main reactor, and a first and second auxiliary reactor, where relatively pure and impure starting products of a fatty compound are processed substantially continuously by cyclic switching of the reactors.