Flow-through mechanochemical synthesis by reactive extrusion

Chemical reactions are conventionally carried out in solution, wherein solvents assume a pivotal role in facilitating the dissolution of reagents and thereby enabling molecular interactions. However, this conventional approach is associated with substantial solvent consumption, waste production, and environmental and safety concerns, while also necessitating protracted reaction times. In recent years, there has been an increase in the study of various mechanochemical methods, with the flow-through mechanochemical approach via reactive extrusion (REX) emerging as one of the most promising alternatives. This process employs screws (single, twin or multiple) to generate mechanical energy (shear, compression and friction) to drive chemical reactions, offering precise control over temperature, mixing and residence time. Typically, REX is performed with minimal or no solvents, which significantly reduces its environmental impact. Furthermore, it ensures shorter reaction times and higher yields. In this review, a comprehensive analysis is conducted on the role of screw configuration, temperature control, and residence time in optimising the outcomes of various reaction types.