solventless

Solventless refers to processes conducted without a chemical solvent. In chemistry and manufacturing, solventless methods avoid dissolving reagents in a liquid medium; instead materials are combined in their neat form, or made to react under mechanical, thermal, or catalytic conditions that minimize or eliminate solvent use. This term is used in various fields, including organic synthesis, polymer processing, pharmaceutical manufacturing, and natural product extraction.

Common approaches include neat (solvent-free) reactions, often facilitated by increased temperatures or catalysts; mechanochemical methods such as ball milling or grinding that enable reactions under solid-state conditions; and melt processing techniques for polymers, such as extrusion, calendaring, or pressing, where materials are heated until they flow without solvent.

In solventless extraction, especially in cannabis and essential oils industries, mechanical methods like ice-water or rosin pressing extractives without hydrocarbon or polar solvents.

Advantages of solventless methods include reduced environmental impact, lower solvent exposure risk, simpler downstream processing, and potential cost savings. Limitations include poorer heat and mass transfer, handling challenges for neat mixtures with high viscosity, energy requirements for heating, and scale-up difficulties. Reaction control and selectivity can be more difficult without solvent as a medium for heat distribution and mixing.

Solventless techniques are aligned with green chemistry and process intensification goals and continue to develop with advances in mechanochemistry, melt processing, and equipment design.