Alternative Solvents

Department of Chemistry

Green Chemistry Centre of Excellence

Sustainable and Economical Alternatives to Conventional Organic Solvents

The “Alternative Solvents” technology platform promotes the use of new alternative solvents - supercritical/liquid CO2, bio-based solvents and solvents from food waste - as sustainable and economically attractive alternatives to conventional organic solvents.

Our goal is to develop, apply and promote the implementation of safer, greener and more sustainable solvents into industry. The platform focuses on the use of both supercritical and liquid CO2 and bio-based solvents in a wide range of applications (extraction, fractionation of waxes, chemical reaction, product cleaning, material development, impregnation etc.)

Some of the applications already developed using supercritical or liquid CO2 and bio-based solvents include:

• Extraction of waxes and botanicals (food, beverage, cosmetic, personal care products

• Recovery of liquid crystals from end-of-life electronics

• Synthesis of aroma molecules using biocatalysts in alternative solvents

• Use of modelling tools to predict the properties and behaviour of a solvent

• Use of bio-based solvents for conducting important organic reactions

• Chromatographyinsupercriticalfluids

ALTERNATIVE SOLVENTS

SUPERCRITICAL FLUID CHROMATOGRAPHY

Traditional heterogeneous catalysts and biocatalytic processes can be performed in supercritical CO2 and bio-based solvents because they offer a number of advantages over the use of conventional solvents including:

• Lower rates of catalyst poisoning

• Enhanced stability

• Better enantioselectivity

• Simple product and catalyst recovery

The Green Chemistry Centre of Excellence is a world leading research centre which aims to promote the development and implementation of sustainable chemistry and related technologies into new products and processes.

REACTIONS IN ALTERNATIVE SOLVENTS

The alternative solvent technology platform also operates a state of the art semi-preparative supercritical chromatography system. This system allows one to carry out extractions, reactions and analysis all in the supercritical phase.

Solvents from biomass and food waste are viewed as one of the most promising types of alternative solvents:

BIO-BASED SOLVENTS AND MODELLING

EXTRACTION USING LIQUID OR SUPERCRITICAL CO2

CO2 is a non-polar solvent that can be used in liquid or supercritical states. Liquid CO2 is significantlylesspolarthansupercriticalCO2 and is limited to the extraction of small non-polar molecules. Supercritical CO2 has several distinct advantages over traditional organic solvents in extractions including:

• Highly tuneable solvent• Selective• Low surface tension • Low viscosity• High mass transfer rates• Highlyefficientsolvent• Simple product recovery• Leaves no solvent residues

CO2 extractions have been successfully developed to extract:• Herbs and spices (food and beverage use)• Waxes (cosmetics, personal care products) • Oils (neutraceuticals)• Pharmaceutical molecules (fractionation) • Liquid crystals (end-of-life electronics)

A key feature of our work is the use of modelling tools to predict the properties and behaviour of a solvent. The use of such tools allows for the prediction of those solvents offering the most favourable performance for a target application.

Our software modelling toolsaidinfindingexistingalternative solvents but can also design new bio-based solvents that can then be prepared at lab-scale (within GCCE) or at demonstrator scale (at our BDC facilities).

The GCCE has developed the S4 (Sustainable Solvent Selection Service)concept as a tailor-made service to replace hazardous solvents and to promote benign equivalents:

Laboratory & pilot plant facilities are available to carry out extractions & fractionation in liquid or supercritical CO2.Supercriticalchromatographyandreactionssystemsarealsoavailable.Tofindoutmore about the use of these technologies in your business or research area contact the GCCE (see back page).

S4 - SUSTAINABLE SOLVENT SELECTION SERVICEFlexible solutions for your product development

Green Chemistry Centre of Excellence Department of Chemistry

University of YorkYork

YO10 5DD

Tel: 01904 322567

Email: greenchemistry@york.ac.uk

www.york.ac.uk/greenchemistry

CARBONATES AS ALTERNATIVE SOLVENTS

Recentestimatesbythepharmaceuticalandfinechemicalindustryhavesuggested solvents account for 80-90 % of the total waste produced in a typical batch process. For this reason there has been a large amount of interestinthefieldofalternativesolvents.Asitpresentstheopportunityforthemostsignificantgains,intermsofreducingenvironmentalimpact.

Many efforts have investigated the use of neoteric or “new” solvents and solvent technologies, common examples include ionic liquids (IL’s), supercritical CO2orfluoroussolvents.However,thesehaveoftenbeenlimitedto small scale industrial applications or high value products

There still exists substantial scope for the exchange of volatile organic compounds (VOC) for molecular solvents with favourable environmental, health and safety characteristics. In recent years, organic carbonates (both cyclic and acyclic) have been highlighted as highly promising alternatives to VOCs. Current projects within the GCCE are investigating the use of carbonates as alternative solvents in various synthetic transformations.

Structures of the acyclic carbonates: dimethyl carbonate (1), diethyl carbonate (2) and cyclic carbonates: ethylene carbonate (3) and propylene carbonate (4)