Two optimization strategies for methanol synthesis were proposed to deal with the decreasing activity of the catalysts and were compared by simulation using a plug-flow model.In both strategies the methanol productivity remained constant in the early months by minimizing the operating pressure and was maximized for the remaining months.In the first strategy

the coolant temperature and space velocity were adjusted simultaneously with time on stream to the optimal values.In the second strategy

space velocity was kept constant all the time

while operating pressure was increased until it reached the upper bound and then coolant temperature was optimized.The results showed that the second strategy yielded a slightly smaller methanol productivity.However

since pressure and coolant temperature were adjusted independently

this simpler strategy was more acceptable by the industry.