The entropy production of the reaction that produces methanol in a methanol reactor, has been minimized. The results show that the entropy production of the reaction can be reduced by more than 70%. The optimal path through the reactor is characterized by a driving force for the chemical reaction that is close to constant. The entropy production due to heat transfer across the reactor walls in this state is large, however. Variations of the reactor design show that it is possible to accomplish considerable reductions of the entropy production due to heat transfer in the reaction-optimal state.This paper was presented at ECOS'00, Enschede, July 5-7, 2000