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Is limonene a sustainable solvent?
The document discusses the properties of limonene as a solvent. Limonene is a renewable solvent obtained from citrus fruits but has some drawbacks. It is toxic to aquatic environments, produces volatile organic compound emissions, and can degrade air quality when used indoors. No solvent is inherently sustainable and the correct one must be selected based on multiple criteria like toxicity, emissions, and performance for the specific application and context.
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Is limonene a sustainable solvent?
- 1. www.greenchemistry.net Limonene: A _______Solvent acid metal James.Sherwood@york.ac.uk d-limonene p-cymene {insert adjective here!}
- 2. www.greenchemistry.net Adhesives Solvent is themajor ingredient (the ‘wet’ bit if you were wondering) Solvent is needed in manufacturing & processing Solvent used for washing Market: 20 Million Tonnes /year
- 3. www.greenchemistry.net Reactants Auxiliaries Water Solvent Material use indrug manufacture Product Waste Actual reaction
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- 6. www.greenchemistry.net 2. Maximise incorporation of materials 7.Use renewables 3. Lower toxicity 4. Design safer chemicals 12. Accident prevention 11. Monitor and analyse 1. Waste prevention better than clean-up 5. Don’t use solvents! 9. Use catalysis 8. No protecting group chemistry 6. Minimise energy 10. Design for degradation http://www.acs.org/content/acs/en/greenchemistry/what-is-green-chemistry/principles/12-principles-of-green-chemistry.html
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- 8. www.greenchemistry.net Limonene: A _______Solvent acid metal d-limonene p-cymene (& p-cymene too!) {insert adjective here!}
- 9. www.greenchemistry.net Limonene: A SuperiorSolvent G. Paggiola, A. J. Hunt, C. R. McElroy, J. Sherwood and J. H. Clark, Green Chem., 2014, 16, 2107. > >
- 10. www.greenchemistry.net Limonene: A SuperiorSolvent J. H. Clark D. J. Macquarrie and J. Sherwood, Chem. Eur. J., 2013, 19, 5174. Product selectivity Solvent induced tautomerisation
- 11. www.greenchemistry.net Limonene: A RenewableSolvent Oxidationp-Cymene Hydrogen J. A. Dávila et al., Waste Biomass Valor., 2015, 6, 253; M. Lohrasbi et al., Bioresource Technol., 2010, 101, 7382.
- 12. www.greenchemistry.net Limonene: A GreenSolvent ? Limonene n-Hexane p-Cymene Toluene LD50 (mg/kg) 4,440 25,000 4,750 >5,500 Chronic toxicity Nope Neurotoxic Not known Organs Aquatic toxicity Very toxic Toxic Toxic Low-mod. Flash point 48 °C -26 °C 47 °C 4 °C Boiling point 176 °C 69 °C 177 °C 111 °C Food safety GRAS - - - Biodegradability (aerobic) slow readily readily
- 13. www.greenchemistry.net Limonene: A GreenSolvent Limonene n-Hexane p-Cymene Toluene LD50 (mg/kg) 4,440 25,000 4,750 >5,500 Chronic toxicity Nope Neurotoxic Not known Organs Aquatic toxicity Very toxic Toxic Toxic Low-mod. Flash point 48 °C -26 °C 47 °C 4 °C Boiling point 176 °C 69 °C 177 °C 111 °C Food safety GRAS - - - Biodegradability (aerobic) slow readily readily
- 14. www.greenchemistry.net Solvent Safety HealthEnvironment Conclusion Limonene 4 2 7 Problematic n-Hexane 8 7 7 Hazardous p-Cymene 4 5 5 Problematic Toluene 5 6 3 Problematic D. Prat et al., Green Chem., 2016, 18, 288. CHEM21 selection guide of classical- and less classical-solvents
- 15. www.greenchemistry.net Limonene: An ExpensiveSolvent Esters and surfactant solutions are now marketed as limonene replacements: http://goo.gl/9EKWXY http://goo.gl/68PE7m http://goo.gl/QLmu8A http://goo.gl/b0A8ta Reason: Price VOC content Smell Performance
- 16. www.greenchemistry.net Limonene: An AirQuality Reducing Solvent Upstream, orange groves emit large amounts of VOC chemicals http://www.rsc.org/chemistryworld/2013/08/undiscovered-volatile-organic- compounds-orange-groves-climate-air-pollution J. -H. Park et al., Science, 2013, 341, 643. • Limonene itself creates aerosols, resulting in air pollution • POCP of alkenes (like limonene) > alkane (like n-hexane) Richard G. Derwent, J. Air Waste Manage. Assoc., 2012, 60, 914. • Limonene decomposes in contact with ozone to produce formaldehyde • Using limonene cleaning products indoors can lead to sensory irritation N. Carslaw, Atmospheric Environment, 2013, 80, 507; P. Wolkoff, Int. J. Hyg. Environ. Health, 2013, 216, 371.
- 17. www.greenchemistry.net Limonene: A SustainableSolvent ? Renewable Citrus Products Association LCA* (cradle-to-gate) http://www.renewablecitrus.org/sites/renewablecitrus.org/files/LCA%201-6-13.pdf Global warming potential (left): Less good in ‘habitat alteration’ and ‘eutrophication’ indicators due to direct land use change and fertiliser/agrochemicals *I don’t do LCAs – too hard. Tapwater Limonene Orangeoil Naphtha Kerosene Xylenes Benzene Toluene Ethylbenzene Acetone DCM Perc (steam distillation) (vacuum distillation)
- 18. www.greenchemistry.net The inherent propertiesof limonene make it a renewable solvent but also unstable, toxic to the aquatic environment, and a source of VOC emissions. The context is all important. The correct solvent should be selected using multiple criteria, not just performance or price. No solvent is inherently sustainable. How it is made, used, and disposed of is crucial. James.Sherwood@york.ac.uk
Editor's Notes
- #14 Limonene “May be fatal if swallowed and enters airways.” Hence aspiration toxicity symbol – however “if it is a hydrocarbon and has a kinematic viscosity of 20,5 mm2/s or less, measured at 40 oC.” H304 applies. Cymene is not an irritant so no exclamation mark.