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Continuous Biodiesel ProductionContinuous Biodiesel ProductionReactive Distillation Makes It HappenReactive Distillation Makes It Happen

UNIVERSITY OF AMSTERDAMvan ‘t Hoff Institute for Molecular SciencesNieuwe Achtergracht 166, 1018 WV AmsterdamTel.+31-20-525.6468, E-mail: [email protected]: staff.science.uva.nl/~ktony

Tony KISS, A.C. Dimian, G. Rothenberg, F. Omota

NWO/CW Project Nr. 700.54.653

[email protected] 2/24

Acknowledgement

Jurriaan Beckers

Marjo C. Mittelmeijer-Hazeleger

STW – Dutch Technology FoundationNWO/CW Project Nr. 700.54.653

Entrainer-Based Reactive Distillation for Synthesis of Fatty Acids Esters

Cognis, Oleon, Sulzer and Uniquema

Thankyou!

☺


Emission type B20 = 20% biodiesel B20 B100

Total unburned hydrocarbons –20% –67%Carbon monoxide (CO) –12% –48%Carbon dioxide (CO2) –16% –79%Particulate matter –12% –47%Nitrogen oxides (NOx) +2% +10%Sulphur oxides (SOx) –20% –100%Polycyclic Aromatic Hydrocarbons (PAH) –13% –80%Nitrated PAH's (nPAH) –50% –90%

Biodiesel = green energy

CO2 Light CO2

Biomass Biodiesel

Biodiesel = mono-alkyl esters of fatty acidsSafe, renewable, non-toxic, biodegradableRaw materials: vegetable oils, fat, recycled greasePositive life cycle energy balancePositive social impactLess emissions than regular petroleum diesel


Project goalsDevelopment of an active and selective solid acid catalyst for fatty acids esterification.

Continuous biodiesel production process based on catalytic reactive distillation.

Water-tolerantLong lifeInexpensive

Active, selective, stableEasy to useAvailable on industrial scale

Catalyst requirements


Applications

Why fatty esters?Food industryPharmaceuticalsCosmeticsPlasticizersBio-detergentsBio-diesel

Cosmetics

Pharmaceuticals

Food

Bio-stuff

CH3 O

O

CH3

CH3


Industrial key players

STEARINERIE-DUBOIS


Process comparison

Current processBatch esterificationHigh alcohol / acid ratiosHomogeneous catalysisDifficult separationCorrosive & toxic

Novel processContinuous esterificationReactive distillationHeterogeneous catalysisEasy separationEnvironmentally friendly

Reactive distillation

• Reduced investment costs• Reduced energy consumption• Increased process controllability• Enhanced overall rates

SteamWater

Fatty ester

Fatty acid

Alcohol

Make up

SteamWater

Fatty ester

Fatty acidFatty acid

AlcoholAlcohol

Make upMake up

The key to success is an active & selective solid acid catalyst.The key to success is an active & selective solid acid catalyst.


Fatty acids & alcohols

Saturated fatty acids: CH3-(CH2)n-COOHLauric acid (n=10)Myristic acid (n=12)Palmitic acid (n=14)Stearic acid (n=16)Arachidic acid (n=18)

Unsaturated fatty acidsPalmitoleic acid: CH3(CH2)5CH=CH(CH2)7COOHOleic acid: CH3(CH2)7CH=CH(CH2)7COOH

Aliphatic alcohols:MethanolEthanolPropanol…2-Ethyl hexanol


Reaction pathwaysREACTANTSREACTANTS

Main product Secondary products Main product Secondary products

AlcoholFatty Acid

WaterFatty Ester AlkeneEther

dehydrationetherification

esterification

Excess of alcohol Water removal by distillation


Reaction mechanism

OC

OHR

H+OH+

COHR

RCOOH + R’OH ↔ RCOOR’ + H2O

Secondary reactions:2 Alcohol Ether + H2OAlcohol Alkene + H2O2 Acid Anhydride + H2OOH+

COHR

HOR' OH

CR OH

O+HR'

R'HO+

OHC

R OH H2O

R'O

OHC

R OH2+

OH+

COR

R'OH+

COR

R'OC

ORR'

H+

Catalyst

Catalyst

Similar mechanism for hetero- and homogeneous catalysis.


Surface hydrophobicity

Influence of surface hydrophobicity on catalytic activity.

H+

OHC

O

hydrophobic surface with isolated acid site

H+OH

CO

H+OH

CO

H+OH

CO

hydrophobic surface with adjacent acid site

H+OHOH H+H+

H+ H+H+

H2O

H2OH2OH2O

H2OH2O

H2O

H2O

H2O

hydrophilic surface/ numerous acid sites

Water tolerant.Not enough acid sites.

Water sensitive.Easy deactivation.

Proper trade-off hydrophobicity-acidity.Good catalytic activity.


Solid acid catalysts

Zeolites and claysBeta, Y, MOR, ZSM-5

HeteropolyAcidsOxides, sulphatesComposite materials

AmberlystNafion

Carbon-based catalystsPolysulfonated aromatics

CH3-(CH2)10-COOH + C8H15OH

CH3-(CH2)10-COOC8H15 + H2O

Dodecanoic acidDodecanoic acid 2 Ethyl 2 Ethyl hexanolhexanol

Acid catalyst

2 Ethyl 2 Ethyl hexylhexyl dodecanoatedodecanoate

= Not tested yet …


Catalyst screening

0

20

40

60

80

100

0 30 60 90 120

Time / [min]

Con

vers

ion

/ [%

]

Alcohol:Acid = 1:1T=130°C

H2SO4 1%wt

Non-catalyzed

Amberlyst 5%wt

Zeolites

0

20

40

60

80

100

0 30 60 90 120

Time / [min]C

onve

rsio

n / [

%]

Alcohol:Acid = 1:1T=150°C, 3%wt catalyst

SZ

Nafion

Non-catalyzed

Amberlyst

Reaction profiles for esterification of dodecanoic acid with 2-ethylhexanol

Organic resins are not thermo-stable. Zeolites have low activity.


Zeolites – structure

MFI – ZSM-5, orthorhombic

MOR – Mordenite, orthorhombic

*BEA – Beta, tetragonal

O

O

CH3 CH3

CH3

12.82 Å 7.78 Å

3.06 Å 4.86 Å22--ethylhexyl ethylhexyl dodecanoatedodecanoate

Diffusion limitations ?!


Sulphated zirconia

0

20

40

60

80

100

0 20 40 60 80

Time / [min]

Con

vers

ion

/ [%

]

Alcohol:Acid = 1:12%wt SZ Catalyst

Non-catalyzed

SZ 2%w

160°C

180°C

160°C180°C

7.3% min-1

2.3% min-13.4% min-1

1.2% min-1

Initial rate

Non-

Cat

alyz

ed

Nafio

n SZ

Amberlyst

Non-

Cata

lyze

d Nafio

n SZ

Amberlyst

0

20

40

60

80

100

Con

vers

ion

/ [%

]

20 min 60 min

Reaction profiles for esterification of dodecanoic acid with 2-ethylhexanol

0

20

40

60

80

100

Con

vers

ion

/ [%

]

T=150°C T=160°C T=170°C

0% 1% 2% 3%

Similar activity for esterification with 1-propanol and methanol.

SZ


Experiments + SimulationsIntegration of experimental results with simulations of the reactive distillation (RD) setup, in AspenTech AspenPlus™

RD column sectionsa. Rectifying section (water)b. Recovery of alcoholc. Reaction zoned. Recovery of fatty acide. Stripping section (ester)

Fatty acid

Alcohol

Feeds

Recycle

Reflux

Distillate

Biodiesel

a

b

d

c

e


Thermodynamic analysis

MethanolTb=65 ºC

2-EthylhexanolTb=186 ºC

n-PropanolTb=97 ºC

Dodecanoic acid Tb=298 ºC

CH3 O

O

CH3

CH3

2-Ethylhexyl dodecanoate Tb=334 ºC

CH3 O

OCH3

n-Propyl dodecanoate Tb=302 ºC

CH3 O

OCH3

Methyl dodecanoate Tb=267 ºC

WaterTb=100 ºC


CPE analysis

Chemical reactionand

phase equilibrium

One liquid phase• low conversion• alcohol excess• T < 100ºC

LLE

• T < 100ºC• reactants molar ratio=1

VLLE

• T > 100ºC• closed system• P > 1 bar

VLE• T > 100ºC• open system• water removal


RD process – methanol

Evaporator

Dodecanoic acid

Feed ratio 1:1

Methanol

Water ≥ 99.9 %

Distillation column

Ester ≥ 99.9 %

RDC

0

0.2

0.4

0.6

0.8

1

0 0.2 0.4 0.6 0.8 1

X1 (water+acid)

X 2 (a

cid+

este

r)

Ester, 267ºC Acid, 298ºC

Alcohol, 65ºC Water, 100ºC0

0.2

0.4

0.6

0.8

1

0 0.2 0.4 0.6 0.8 1

X1 (water+acid)

X 2 (a

cid+

este

r)

Ester, 267ºC Acid, 298ºC

Alcohol, 65ºC Water, 100ºC

Feasible RD process.High purity products.


Effect of reflux ratio

Partial alcohol conversionHighest reaction rate

Total acid conversion

Fatty acid

Alcohol

Total alcohol conversion

Highestreaction rate

Total acid conversion

Fatty acid

Alcohol

Maximum reaction rate is located in the centre of RD column for an optimum reflux ratio


Entrainer-based RD flowsheet

98

99

100

100 150 200 250 300

Catalyst loading, kg/m3

Aci

d co

nver

sion

, %

No entrainer

With entrainer

Enhanced mass transfer and reduced catalyst loading when entrainer is used.

Steam

Water

Fatty acid

Alcohol

Make up

Steam

Water

Biodiesel

Fatty acidFatty acid

AlcoholAlcohol

Make upMake upEntrainer

Feasible process. High purity products >99.9%

Reactive distillation column

Evaporator

Stripper

Decanter


RDC profiles

350

400

450

500

0 5 10 15 20 25Stage

Tem

pera

ture

, K

Separation zone Reaction zone Separation Reaction

0

0.2

0.4

0.6

0.8

1

0 5 10 15 20 25 30Stage

Liqu

id m

ole

fract

ion

1-Propanol

Water

n-Propyl acetateLauric acid

n-Propyl laurate

Liquid composition and temperature profiles


Reactive distillation – advantages

• Break azeotropes• Handle difficult separations

• No external recycles• Reduced investment costs• Reduced energy consumption• Increased process controllability

• Equilibrium shifted to products• Enhanced overall rates• Improved selectivity

Reaction Separation


Conclusions

Surface hydrophobicity and acid sites density determines catalyst's activity & selectivity.

Catalysts with small pores (e.g. zeolites) are not suitable. Resins are active but not thermally-stable.

Sulphated zirconia is active, selective and stable.

Biodiesel production by reactive distillation is feasible.

GREEN ENERGY Biodiesel

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