Green solvent
SCW is used as a reaction medium, especially in oxidation processes for the destruction of toxic substances such as those found in industrial aqueous effluents.
Temperatures above 31 °C and pressures above 7.38 MPa are sufficient to obtain supercriticality,[5] at which point it behaves as a good nonpolar solvent.
Ethyl lactate, made from lactic acid obtained from corn starch, is notably used as a mixture with other solvents in some paint strippers and cleaners.
Usually derived from natural gas or petroleum, the methanol used to produce FAMEs can also be obtained by other routes, including gasification of biomass and household hazardous waste.
[11] Solvents in a diverse class of natural substances called terpenes are obtained by extraction from certain parts of plants.
All terpenes are structurally presented as multiples of isoprene with the gross formula (C5H8)n. Turpentine, formerly used as a solvent in organic coatings, is now largely replaced by petroleum hydrocarbons.
The ecotoxicity and poor degradability of ionic liquids has been recognized in the past because the resources typically used for their production are non-renewable, as is the case for imidazole and halogenated alkanes (derived from petroleum).
Ionic liquids produced from renewable and biodegradable materials have recently emerged, but their availability is low because of high production costs.
[11] Bubbling CO2 into water or an organic solvent results in changes to certain properties of the liquid such as its polarity, ionic strength, and hydrophilicity.
This process is reversible, and was developed by Jessop et al. (2012) for potential uses in synthetic chemistry, extraction and separation of various substances.
2-Methyltetrahydrofuran, derived from lignocellulosic waste, would have the potential to replace tetrahydrofuran, toluene, DCM, and diethyl ether in some applications.
[22][23] Propylene carbonate and two DBEs are considered green in the manufacturer GlaxoSmithKline's (GSK) Solvent Sustainability Guide, which is used in the pharmaceutical industry.
[24] Propylene carbonate can be produced from renewable resources, but DBEs that have appeared on the market in recent years are obtained as by-products of the synthesis of polyamides, derived from petroleum.
Siloxanes are compounds known in industry in the form of polymers (silicones, R-SiO-R'), for their thermal stability and elastic and non-stick properties.
Soluble in water and readily biodegradable, liquid PEGs have the advantage of negligible volatility (< 0.01 mmHg or < 1.3 Pa at 20 °C).
The properties of switchable solvents[53][54] are caused by the strength of their conjugate acid's pKa and octanol-water partition coefficient ratio Kow.
The effectiveness of a green solvent is quantified by calculating the "E factor", which is a ratio of waste materials to desired product produced through a process.
Listed here is selected information from the safety data sheets of common green solvents:[65][66] Causes severe eye damage.
May cause skin allergy Very toxic to aquatic organisms, causes long-term adverse effects For ethanol, the American Conference of Governmental Industrial Hygienists, shortened ACGIH, advises a short-term exposure limit of 1000 ppm to avoid irritating the respiratory tract.
Since 1998, the ACGIH has suggested an 8-hour exposure limit value (ELV) of 20 ppm of butan-1-ol to prevent irritation of the upper respiratory tract and eyes.
The American Industrial Hygiene Association suggested an ELV of 2 ppm for THFA to prevent testicular degeneration in 1993 based on the No-observed-effect level of two subchronic investigations in rats and dogs DES components, according to Wazeer, Hayyan, and Hadj-Kali,[68] are typically non-toxic and biodegradable.
According to Hayyan et al.,[69] the DES they investigated were more harmful to the small crustacean artemia than each of their individual components, which could be attributed to synergy.
