Book excerpt: Optimization-based strategies to solve problems in production scheduling have been extensively used in the last decades due to their generality, flexibility and potential to find the best solutions in terms of costs, customer satisfaction, and efficiency. Traditionally, most efforts have been directed towards the development of mathematical models that are computationally tractable. However, the effective solution of large-scale scheduling models remains nontrivial. The main objective of this thesis is the development of solution methods for the different types of chemical plants. Our discussion is largely motivated by a new approach to the analysis of timing and inventory restrictions in scheduling problems. First, we propose a family of algorithms that are suitable for maximization problems in network environments. By preprocessing the original data we calculate parameters that are used to develop tightening constraints. We also introduce the concept of variable start and finish times and derive expressions to relate them and connect them with original decision variables. By means of computational experiments we show the effectiveness of these methods in improving the solution process of optimization-based models for scheduling. Second, we develop a new family of discrete-time models for sequential environments. Almost all the existing models in the literature use a continuous representation of time. We discuss the advantages of discrete-time models and propose different solution methods to improve their computational performance. A computational study is included to test the improvements and compare with existing approaches. Significant reduction in computational time and optimality gap is achieved. Third, we extend methods based on reformulations and tightening constraints from discrete-time to continuous time models in network environments. We use specific characteristics of the latter to improve computational performance, testing our methods on several benchmark instances. Finally we test the proposed methods on large-scale instances for which optimal solutions had not been found before or whose computational performances demanded long solution times. This way we show that our formulations and methods improve the tractability of industrial-scale instances. Optimal or near-optimal solutions are now accessible in reasonable time for many cases for which only suboptimal solutions from heuristics procedures or empirical methods were available.