The paper presents the design of a hierarchical control system for a depropanizer column. The hierarchical system has two levels: conventional control level and optimal control level. At the second level, a two- dimensional objective function is proposed. The optimization problem solving, which involved determining the optimal variables which maximize the objective function, was done in MATLAB®. The hierarchical control system with two levels was simulated in SIMULINK®, and the results confirmed that the application of the optimal variables determined at the second hierarchical level leads to an improvement in separation, which is the main objective of the depropanizer column.