Since the year 2000, semicontinuous separation processes have been studied as a unique process intensification technique for the thermal separation of chemical mixtures. Typically, a single separation unit is used for multiple purposes with the aid of an auxiliary storage tank called a middle vessel. The system is operated cyclically but without startup or shutdown phases. As a result, multiple separation steps can be carried out with fewer capital expenses. In several cases, a significant profitability advantage over continuous or batch process alternatives has been shown, particularly for intermediate production capacities. The progress in semicontinuous systems is reviewed, including the development of semicontinuous ternary distillation, liquid-liquid extraction, azeotrope distillation, reactive distillation, and semicontinuous systems with integrated reaction and distillation or extraction. Control and operational strategies for semicontinuous systems are reviewed, as well as heuristics for modeling and simulation.