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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Adhesives
Solvent is the major
ingredient (the ‘wet’ bit if
you were wondering)
Solvent is needed in
manufacturing &
processing
Solvent used
for washing
Market: 20 Million
Tonnes /year
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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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Limonene: A Superior Solvent
J. H. Clark D. J. Macquarrie and J. Sherwood, Chem. Eur. J., 2013, 19, 5174.
Product selectivity
Solvent induced
tautomerisation
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Limonene: A Renewable Solvent
Oxidationp-Cymene Hydrogen
J. A. Dávila et al., Waste Biomass Valor., 2015, 6, 253; M. Lohrasbi et al., Bioresource Technol., 2010, 101, 7382.
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Limonene: A Green Solvent ?
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
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Limonene: A Green Solvent
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
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Solvent Safety Health Environment 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
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Limonene: An Expensive Solvent
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
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Limonene: An Air Quality 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.
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Limonene: A Sustainable Solvent ?
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)
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The inherent properties of 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
Hinweis der Redaktion
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.