In this paper, a mathematical formulation for the short-term scheduling of a sequential multipurpose batch plant is proposed. The scheduling problems of the multipurpose batch plants under a mixed product campaign (MPC) are addressed here. A mixed-integer linear programming (MILP) model is developed based on the time slot, which is used to determine the production sequence and the production path of each batch. In order to reduce the search space, we propose a heuristic method that relies on the use of preordering constraints. Application of the preordering constraints to the proposed MILP model reduced the computational time required by more than 40%. The proposed model is extended to sequential multipurpose batch plants with parallel units.