Extraction versus Distillation OR A hybrid process

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Formation of Organic Acid Esters via Reactive
Distillation
Navinchandra Asthana, Aspi Kolah, Dung Vu Dennis
J. Miller and Carl T. Lira Department of
Chemical Engineering and Materials
Science Michigan State University (MSU) East
Lansing, MI 48824 millerd_at_egr.msu.edu (517)
353-3928
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Reactive Distillation

• Simultaneous reaction and separation in a single
  piece of process equiupment
• Applicable to equilibrium limited reactions where
  one product is the most volatile component
• Process intensification results in lower energy
  and capital costs
• Each reaction system requires a unique approach
  for successful design and operation

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A Classic Example Methyl Acetate
MeOAc

• High Purity of MeoAc
• Reduced capital cost to one fifth
• Consume only one-fifth energy

Eastman Chemical Co (Agreda etal, 1990)
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Organic acid estersAn opportunity for
biorenewables

• TRADITIONAL
• Petroleum esters
• formate benzoate
• acetate adipate
• acrylate phthalate
• carbonate maleate
• butyrate stearate

• FUTURE
• Bio-based esters
• lactate itaconate
• propionate succinate
• acetate citrate
• malate hydroxybutyrate
• amino acid esters

Applications as solvents, polymers, plasticizers,
cosmetics Market is 3 billion (3 million MT/yr)
for non-polymer use
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RD Strategy for Organic Acid Esters

• Demonstrate ester formation in pilot-scale RD
  column
• Collect necessary physical and chemical
  properties to simulate process
• Simulate pilot-scale RD column to develop column
  performance parameters
• Carry out simulation (design) and economics of
  commercial scale esterification plant

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Ethyl Lactate
Lactic acid Ethanol
Ethyl lactate Water (L1)
(Et) (L1E)

• Ethyl lactate properties
• Low volatility (low odor, little evaporative
  loss)
• Stable to gt150oC
• Excellent solvent performance (use less, dissolve
  more)
• Recoverable by distillation (b.p. 154oC)
• Nontoxic, biodegradable, blendable, green
• Minimal waste generation in production

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Reaction Network for Ethyl Lactate Formation
Equilibrium oligomer distribution
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HPLC analysis of lactic acid oligomers and
esters
L1E
L1
L2E
L2
L3
L3E
L4E
L4
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Ethyl lactate via reactive distillation
Lactic Acid Ethanol Ethyl
lactate Water
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TABLE III. Pilot-scale results of ethyl lactate
formation
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Effect of reflux ratio on performance
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Kinetic model for lactate esterification
Power law activity model for esterification /
hydrolysis rj kf,jaEtOHaj kraH2Oak
Infinite series equilibrium model for lactic
acid oligomerization K anaH2O/an-1aL1 0.23
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Equilibrium Lactic Acid Oligomerization
Comparison of Model with Experiment
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EtLa H20 at 60oC
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Simulation of pilot-scale column operation
FEED RATES L1 9.519 kmol/hr L2
Acid 2.005 kmol/hr L3 Acid 0.505
kmol/hr Water 9.847 kmol/hr EtOH
54.000 kmol/hr
Distillate
Wt Sim Exp LA
0.74 0.0 EtOH 75.49
79.8 EtLA 8.63 3.0 Water
14.74 16.2 L2ES 0.39
0.0 L3ES 0.00 0.0
2
4
Stages 10 Reflux ratio 0.01 Boilup
ratio 1.8 Liquid holdup/stage 7 Column
capacity 7 Stage 2, 3 include uncatalyzed
reaction Stage 4-8 include catalyzed reaction
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10

Simul Expt Acid Conv
93 95 EtLA/(EtLAL2ESL3ES)
74 73
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Simulation of Commercial Scale Ethyl Lactate
RD Column
Stream 3
Wt EtOH
82.93 EtLA 0.13 Water
16.94
FEEDS (88 LA EtOH) LA 9.519
kmol/hr L2 Acid 2.005 kmol/hr L3 Acid
0.505 kmol/hr Water 9.847
kmol/hr EtOH 54.000 kmol/hr
Stream 4
Wt LA
0.00 EtOH 0.30 EtLA
72.64 Water 0.13 L2ES 19.44
L3ES 6.11 L2 Acid 0.66
L3Acid 0.63
Lactic acid conversion () gt99 Column size 35
stages
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Transesterification of oligomer esters to
L1E(L2E EtOH 2 L1E)
Composition (mol) Initial Final L1 18.3
4.8 L2 5.9 0.4 L3L4 0.5
lt0.1 L1E 12.2 85.0 L2E 58.1 8.5 L3E 5.1 1.1
EthanolLactate ratio 2.6 Temperature
80oC
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Process Concept for Ethyl Lactate
Production
Ethanol recycle
Ethanol / Water
Ethanol purification
Water
Ethyl lactate synthesis
Lactic Acid
Ethyl lactate
Ethanol
Ethyl lactate recovery
Oligomer esters Oligomer acids
Trans- esterification
Ethanol
Ethyl Lactate ( oligomers)
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Integrated Ethyl Lactate / Ethanol Production
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Summary of process economics

• Basis 25 MM lb/yr ethyl lactate production
• Capital costs lt 10 million
• Ethyl lactate selling price (includes installed
  capital depreciation, taxes, ROI, labor, etc..)
  is heavily influenced by lactic acid feed cost
• Lactic acid cost Ethyl lactate sale price
• 0.25 /lb 0.54 /lb
• 0.50 0.74
• 0.80 0.98

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Conclusions

• Ethyl lactate can be produced in high yield in a
  simple reactive distillation process
• Pilot-scale experiments show that separation of
  ethyl lactate from water and ethanol is possible
• Accurate simulation of process requires
  rate-based simulation and experimental
  thermodynamic data incorporation
• Process economics appear competitive for solvent
  displacement
• Additional work with other acids on-going

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Acknowledgment

• National Corn Growers Association
• U.S. Department of Energy
• Postdocs Aspi Kolah
• Navin Asthana
• Grad student Dung Vu