The development of sustainable solvent systems for industrial chemical processes represents a critical advancement in green chemistry, aiming to reduce reliance on traditional organic solvents like dichloromethane, DMF, and hexane, which pose significant environmental and health risks. Among the most promising alternatives are bio-derived solvents such as 2-methyltetrahydrofuran (2-MeTHF), produced from renewable biomass like furfural, which offers comparable performance to THF in Grignard reactions and extractions while boasting lower toxicity and better recyclability. Similarly, Cyrene (dihydrolevoglucosenone), derived from cellulose, serves as an eco-friendly replacement for polar aprotic solvents like DMF and DMSO in applications ranging from polymer chemistry to peptide synthesis. Water-based systems have also gained traction, particularly superheated or subcritical water, which can be tuned by adjusting temperature and pressure to act as a green reaction medium for hydrolysis and oxidation reactions, eliminating the need for organic solvents altogether. Additionally, aqueous micellar catalysis, employing biodegradable surfactants such as TPGS-750-M, enables efficient organic transformations in water while minimizing waste. For more specialized applications, ionic liquids (ILs) and deep eutectic solvents (DESs) offer tunable, non-volatile alternatives, though challenges remain regarding their cost and biodegradability. Supercritical fluids like scCO₂ provide another versatile option, particularly in extraction processes where they replace hexane and other hydrocarbons, while switchable solvents, which change properties in response to stimuli like CO₂, allow for easy separation and reuse. Solvent-free approaches, including mechanochemistry and molten salt media, further push the boundaries of sustainability by entirely eliminating solvent use in certain reactions. Despite these advancements, widespread adoption requires careful consideration of factors such as scalability, cost-effectiveness, and process efficiency, necessitating lifecycle assessments to ensure true sustainability. Nevertheless, the growing industrial uptake of these alternatives—evidenced by Pfizer’s use of 2-MeTHF in API synthesis and BASF’s incorporation of limonene in pesticide formulations—highlights their potential to transform chemical manufacturing into a more sustainable enterprise. Future research should focus on optimizing these systems for broader applications while addressing remaining limitations to unlock their full potential in green chemistry.

There is no "green" solvent. It is ideal for all processes, but the most suitable system is chosen according to criteria such as: compatibility with the reaction, toxicity, recyclability, and economic sustainability. Water is an excellent solvent for sustainability and toxicity, but it is not compatible with many organic reactions that love fat. Supercritical carbon dioxide (scCO₂) is great for some reactions and extraction, but it requires expensive high-pressure equipment.

I suggest you take a look at NADES, natural deep eutectic solvents, they come in many forms, depending on the basic components you combine to make them and are non-toxic, degradable, cheap. There is already a substantial amount of scientific literature on the use of NADES. Please let me know if you are in need of specific references.

Green solvents are sought to replace existing dangerous traditional organic solvents. The key aim is to innovate sustainable solvent substitutes, hence minimising the industrial sector's carbon footprint and fostering a safer and healthier working environment. Due to their low vapor pressure and thermal stability, ionic liquids (ILs) are considered diminishingly volatile, which is advantageous over volatile organic substances. There is an increasing drive toward using ILs as a sustainable solvent because they have the ability to change a broad range of chemicals. Moreover, they can also catalyse chemical reactions, scale up namely efficient route (Welton, 2018).

Despite having less vapor temperature and thermal stability than traditional organic solvents, researchers are currently testing and developing deep eutectic solvents (DESs) and bio-based solvents as substantially less toxic alternatives. DES is naturally occurring and non-flammable, a blend of a hydrogen acceptor and a hydrogen donor, while bio-based solvents can be from plant materials or comparable biodegradable sources. In addition to the processes being optimized, these eco-friendly solutions currently entail less optimisation to function at their peak. Although these biodegradable solvent solutions must be developed further due to costing issues and the expensiveness of the systems required, their cost-effectiveness and better environmental footprint suggest an extremely lucrative potential (Clark et al., 2018). It is crucial to describe the significant aspects of ILs. For example, they are usually known as "green solvents," which are generally used for applications given their eco-friendliness. ILs display desirable characteristics such as non-flammability, recyclability and easy disposal.

Choosing the appropriate cation and anion combination for each process is significant for designing green solvents since they are specifically engineered to be functional solvents. Because of the high cost of production, the twisting of the ILs need the development and evaluation of numerous ionic compositions for a certain kinematic anima (Welton, 2018). For example, there is a lack of commercial IL blends because they are hard to develop and test due to the expense. In practice, as well as their separation, recycling and handling limitations, ILs must be handled with the same caution as common solvents. A factor to consider in the research and development of such is process (Clark et al., 2018). Although DESs are made up of naturally occurring chemicals, they must have products that are ready for commercialisation. Scientists and technologists may find it difficult to replicate DES characteristics in the laboratory when taking them from the lab.

In reality, based on the specific methods and materials employed, the understanding within the literature is results may vary on how feasible and economic use of ILs or DESs becomes. There is not a lot of industrial viability because ILs and DESs can create derivatives from natural compounds that are similarly obtainable commercially. Hoepfner and Braunschweig (2020) write that real solvents are not cheap with the prices of some ionic substances currently being as high as 99.5 percent pure cooking grade.

References:

Clark, J., Farmer, T. J., Herrero-Davila, L., Sherwood, J., and A. J. Hunt (2018). "Du Pont’s biobased sebonium process: Reproductive health in the plant-2-Ethylhexanoic Acid Century". Green Chemistry 20(5): 965-971.

Hoepfner, S., and Kalev Braunschweig. "Chemistry and cost exhaustiveness in small-scale farm-like systems." Sustainable Chemistry and Pharmacy 18 (2020): 100307.

Welton, T. (2018). Sustainable solvents: the concept, final report.

Please be aware. Joseph's post is very likely AI generated and certiaanly includes fictional references - AI Hallucinations. You will find none on Google Scholar or at the respective journal internet tables of contents..

Joseph has done this many others times.

For example, Hoepfner, S., and Kalev Braunschweig. "Chemistry and cost exhaustiveness in small-scale farm-like systems." Sustainable Chemistry and Pharmacy 18 (2020): 100307. - CAN NOT BE FOUND.

In Green Chemistry, one of the key principles is to design safer solvents and auxiliaries, since conventional organic solvents (toluene, dichloromethane, hexane, etc.) are often volatile, toxic, and environmentally persistent. Several sustainable solvent systems are being explored and increasingly used in industry:

🔹 1. Water as a Solvent

• Advantages: Non-toxic, abundant, inexpensive, nonflammable.
• Applications: Aqueous-phase catalysis, biocatalysis, micellar catalysis. Surfactant-assisted “micellar media” allow reactions of hydrophobic substrates in water.
• Challenges: Limited solubility of many organic compounds, sometimes requiring cosolvents or surfactants.

🔹 2. Supercritical Fluids

• Supercritical CO₂ (scCO₂): Non-toxic, non-flammable, recyclable. Widely used in extraction processes (e.g., decaffeination, essential oils) and as a medium for polymerizations. Easy separation of the product by depressurization.
• Supercritical water: Applied for oxidation of hazardous waste.
• Challenges: Equipment costs and high-pressure requirements.

🔹 3. Ionic Liquids (ILs)

• Description: Organic salts are liquid at
  2 votes 2 thanks

Nosrat O Mahmoodi

We can call them "green chemistry" but If water or ethanol were functional in a process, it would have already been in use long before the "green" stuff started.

Agree ssCO2 has applications - a little expensive (~500,000 for industrial capacity extractor + power)

Hi there,

Verbio SE will start ethenolysis of rapeseed oil methyl ester to gain following products:

1-Decene

9-Decenoic acid methyl ester (9-DAME)

9-DAME could repalce terpene, D-limonene or palm oil based methyl ester. The reaction is based on metathesis, the catalyst is a Schrock Type (tungsten based).