Extraction and separation of valuable materials of plant origin

Edit Székely, Erika Vági

BME, Department of Chemical and Environmental Process Engineering

Environmentally benign chemical

processes (EBChemP)

Traditional extraction (solvent/water) or

supercritical CO2 extraction

Main component families in plants

Oils and

waxes(waxes, oils,

phospholipids,

fatty acids,

tocopherols,

fitosterols, linear

chain alkanes)

Pigments(carotenoids,

chlorophylls,

xanthophyll,

anthocyanids) Alkaloids(proto-, pseudo-

alkaloids)

Miscellaneous(Diterpenes,

triterpenoids,

flavonoids,

cumarins,

glycosides, peptides

etc)

Volatile oils(monoterpenes,

sesquiterpenes,

sulphur compounds

etc.)

Volatile aromas

Steam distillation

Medieval representation

Steam distillation (past)

Methods to obtain volatile oils

Water, water and steam or steam distillation

Hydrodiffusion/ percolation

Cold pressing

Solvent extraction

- Concrete

- Absolute

- Enfleurage

Boiling points of typical volatile oil

components

Monoterpene hydrocarbons: 160-180°C

Monoterpene alcohols: 200-230°C

Sesquiterpene hydrocarbons: 260-290°C

α-humulene

Theoretical background

PPP wateroil 00

P

Py oil

oil

0

P

Py water

water

0

0

0

oil

water

oil

water

p

p

n

n

oiloil

waterwater

oil

water

Mp

Mp

m

m

0

0

Calculated water requirement

Monoterpene hydrocarbons 0.6 kg/kg

Monoterpenes containing oxygen 8 kg/kg

Sesquiterpenes 18 kg/kg

In practice more is needed (min. 10 kg/kg):

– Non-equilibrium

– Volatile oil is dissolved in waxes

– Volatile oil is in the cells

Water, water and steam or steam

distillation

water

water

and plant

steam

Sieve plateSieve plate

water

water

and plant

Sieve plate

Perforated tubesteam

plant

to condenser to condenser

to condenser

condense H2Ocondense H2O

Steam

distillation –

industrial

size

Methods to obtain volatile oils

Water, water and steam or steam distillation

Hydrodiffusion/ percolation

Hydrodiffusion

Essential oil separation - Florentine

flask• The final step in the distillation of essential oils is the separation from the

water flowing from the condenser using a special flask called a Florentine.

• Most essential oils are lighter than water and float to the surface of the

Florentine.

• Some oils, however, are denser than water and sink to the bottom. For this

reason two types of Florentine are used.

Methods to obtain volatile oils

Water, water and steam or steam distillation

Hydrodiffusion/ percolation

Cold pressing

Rolling Mill

Rolling Mill

Flaking Mill

Flaking Mill

It is employed in the oilseed

processing industry for the flaking of

cracked soy beans and soft oil seeds

such as sunflower, canola and corn

germ.

Proper oilseed flaking is a critical

factor in the oil extraction process, as

the seed's microscopic oil cells are

ruptured, allowing the extraction media

to penetrate easier into the material.

Cold pressing of olive oil

Screw press

Screw press

Methods to obtain volatile oils

Water, water and steam or steam distillation

Hydrodiffusion/ percolation

Cold pressing

Solvent extraction

- Concrete (with apolar solvent)

- Absolute (with ethanol)

- Enfleurage (with fat)

Characterization of solvent

Polarity ~ solvent power ~ solubility parameter

().

= [(ΔHV – RT)/ V]^0.5

ΔHV – latent heat at T temperature (J/mole);

V – molar volume (m3)

Choosing a solvent

For apolaric compounds:

→ Oils, fatty acids;

→ Essential oils;

→ Sterols (phytosterols);

→ Triterpenes;

→ Carotenoids.

Petrol ether,

pentane,

hexane,

Cyclohexane,

scCO2

etc…..

=

14.9

16.2

For polaric compounds:

→ Glycosides (saponins);

→ Alkaloids;

→ Gallic- and ellagic tannins;

→ Acids, sugars;

→ Bitter compounds.

Water,

EtOH:water

mixture

= 30 - 48

Choosing a solvent

For semi-polaric compounds:

→ Alkaloids;

→ Terpene-lactones;

→ Gylcoside-aglycons

(flavons, antrakinons,

anthocyanids);

→ Flavonoids;

→ Catechins,

pro-anthocyanids.

ether,

Ethyl-acetate,

Ethyl-alcohol,

methanol

acetone,

etc….

=

18.2

26.1

29.7

Choosing a solvent

Main steps of solid-liquid extraction

Extraction of oily seeds 100-200 tonnes / day in continuous operations.

Solvent extraction

Clean solvent

Pre-treatment Extraction Solvent

recovery

Extracted

material

Solvent

separation

Raw material

Regenerated solvent

Raffinate

Solvent extraction plant

Solvent extraction plant

Solid-liquid extractor

De Smet extractor

Linear wall extractor

Lurgi extractor

Lurgi extractor

Crown extractor, model IIRaw material

Solvent

Extracted

residue

Extract

Crown extractor, model II

Crown extractor, model II

Karussel- (Rotocel-) extractor

Karussel- (Rotocel-) extractor

CONTEX-extractor

Recovery of solvent from miscella

Deodorization / Oil refining

Krupp-toaster

Paddle dryer

Paddle dryer

Hexane content

Substitution of hexane

• Reasons: environmental and health; but:

economical at large scales or producing high

value products (e.g. sesame oil, rosehip oil)

• Possible alternative processes:

– Supercritical fluid extraction

– Water based extraction after cell disruption by

enzymatic treatment

– Cell disruption by ultrasound

– Osmotic shock

Emission decrease

• Condensation and scrubbers

• Recycling the solvent within the plant

• Technological improvements (leakage detection,

maintenance)

• Management issues (e.g. following the route of the

solvent)

Acknowledgement for Prof. Edit Székely and Prof.

Béla Simándi for using these slides, photos.

Thank you for your attention!