Green Chemistry      Jemma Vickery    jv2237@bris.ac.uk

  Introduction

    Biodiesel

    Green Solvents

    Ionic Liquids

    Degradable Plastics

    Famous Environmental Disasters

    Glossary

    References

What are Green Solvents?

Green solvents are environmentally friendly solvents or biosolvents, which are derived from the processing of agricultural crops. 

The use of petrochemical solvents are the key to the majority of chemical processes but not without severe implications on the environment.  The Montreal Protocol identified the need to re-evaluate chemical processes with regard to their use of volatile organic compounds of VOCs and the impact theses VOCs has on the environment.  Green solvents were developed as a more environmentally friendly alternative to petrochemical solvents.

Ethyl lactate, for example whose structure is shown below, is a green solvent derived from processing corn. 

Ethyl lactate is the ester of lactic acid.  Lactate esters solvents are commonly used solvents in the paints and coatings industry and have numerous attractive advantages including being 100% biodegradable,  easy to recycle, non-corrosive, non-carcinogenic and non-ozone depleting.

Ethyl lactate is a particularly attractive solvent for the coatings industry as a result of its high solvency power, high boiling point, low vapour pressure and low surface tension.  It is a desirable coating for wood, polystyrene and metals and also acts as a very effective paint stripper and graffiti remover.  Ethyl lactate has replaced solvents including NMP, toluene, acetone and xylene, which has resulted in the workplace being made a great deal safer.

Other applications of ethyl lactate include being an excellent cleaner for the polyurethane industry.  Ethyl lactate has a high solvency power which means it has the ability to dissolve a wide range of polyurethane resins.  The excellent cleaning power of ethyl lactate also means it can be used to clean a variety of metal surfaces, efficiently removing greases, oils, adhesives and solid fuels.  The use of ethyl lactate is highly variable as it has eliminated the use of chlorinated solvents.

The chart shows the synthetic route to products made from ethyl lactate:

Alternative promising areas of research in the replacement of the use of VOCs in industry include the application of supercritical carbon dioxide and ionic liquids as alternative solvents.  Both of which have proved to have valuable applications.

See references (6,7).