Green solvents

The omnipresence of solvents (organic and aqueous) in specialty chemicals generates a considerable amount of waste and requires the development of extraction, recycling and reprocessing processes that are often costly and time-consuming. In addition, the introduction of increasingly restrictive regulations is leading industry and academia to rethink the "solvent problem". This situation offers the experts in the field an opportunity to open up and evolve towards a more sustainable and environmentally-friendly chemistry, through the search for alternative processes or solvents.

While solvent-free approaches are now being considered and proposed, in most cases solvent substitution is essential. To this end, decision-making tools (Hansen-HSP method, COSMO-RS-type in silico approaches, not detailed in this article) have been developed, but the experimenter's expertise often remains a prerequisite.

Many alternatives are available on the market today, or are currently being developed. However, given the cost involved in changing a process, the choice of "THE" replacement solution is often crucial and difficult. Nevertheless, this notion of cost must be analyzed with discernment, and in particular compared with the real (and future) costs linked to the reprocessing and/or destruction of solvents (environmental impact) in current processes.

To help users make the right choices, we present an overview of the main alternative solutions, and discuss the relevance of each in both environmental and economic terms. The advantages and disadvantages of each approach are discussed.

A glossary of terms is provided at the end of the article.