Partial Hydrogenation of Vegetable Oil using Membrane Reactor Technology

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Partial Hydrogenation of Vegetable Oil using
Membrane Reactor Technology
Devinder Singh, Brent Dringenberg, Dr. Peter
Pfromm, Dr. Mary Rezac Department of Chemical
Engineering Kansas State University Manhattan,
Kansas
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Trans-Fatty Acids

• "..there is a direct, proven relationship between
  diets high in trans fat content and LDL (bad)
  cholesterol levels and, therefore, an increased
  risk of coronary heart disease..." from FDA web
  site 10-3-2005, FDA fact sheet dated July 9,
  2003
• By January, 2006 trans fat content will be shown
  on the Nutrition Facts Panel.Note lt0.5 g trans
  fat/14 g serving label "zero"

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Trans-Fatty Acids
USDA/CFSAN http//www.cfsan.fda.gov/ dms/transfat
.html 10-4-05

• ChE Freshmen class (9-2005) the vast majority
  knew trans fats were "bad" for you.
• Switch to butter?

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Origin of trans-fatty acids
oleic acid MP 16C
elaidic acid MP 52C
stearic acid MP 70C
cis (C181 9c)
trans (C181 9t)
(C180)

• Except for some animal fats (beef, mutton),
  natural oils/fats are cis.
• Trans-fatty acids by partial hydrogenation (in
  the rumen vaccenic acid or in technical
  hydrogenation of plant oils elaidic acid C181
  9t )
• Why technical partial hydrogenation optimize
  physical parameters (melting point), improve
  stability, reduce peroxidation

5
Strategies to avoid/minimize trans-fatty acid
intake

• Use trans fatty acid free fats and oils
• Avoid partial hydrogenation by changing the
  composition (Example "Crisco 0 trans fat"
  sunflower andsoybean oilwaxy fully hydrogenated
  cotton seed oil)
• Minimize/avoid formation of trans fatty acids
  during hydrogenation

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Standard hydrogenation process

• 1809 Sir Humphrey Davy coins the term
  "hydrogenation" W. Normann, 1902
  liquid/solid/gas for fat hardening
• Generally batch, 5-20 tons of oil. Parameters
  pressure, temperature, agitation, catalyst,
  catalyst/oil ratio. 15 MM tons/year world wide.

catalyst Ni 0.05-0.1 wt Ni on oil supported
catalyst
120-190C 1-6 atm
steam
"selective" conditions hydrogenate most
highly unsaturated fatty acids first (160-205C,
low H2 pressure, more catalyst, less agitation)
50 more trans
H2
http//www.thesoydailyclub.com/SFC/MSPproducts501.
asp Soyfoods Center, from unpublished manuscript
by Shurtleff, W., Aoyagi, A.,
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Alleviating mass transfer limitations of
hydrogenation
Conventional
Here Membrane based
H2 starved catalyst
Defect-free integral-asymmetric polymeric
membrane with metal sputtered surface
boundary layer
?P
?pH2
Oil
Catalyst
Membrane
H2
H2(dissolved) solubility is low in oils
H2 supplied by diffusion
H2 flux can be adjusted self-controlled H2
transport boundary layers can be controlled shear
can be introduced at the membrane
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Approach supply hydrogenwhere catalysis takes
place
Pt layer
H
H
H
H
H-H
H
H
H
"skin" (defect-free polymer layer)
H
H-H
H-H
H-H
metal layer defects
Pt Layer
Oil
(10-20 nm)
integral skin 100-500 nm
200-300 µm
porous substructure (polymeric)
hydrogen
Baker, R. W., Louie, J., Pfromm, P. H., Wijmans,
J. G., "Ultrathin Metal Composite Membranes for
Gas Separation", U.S. Patent 4,857,080,
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Integral-Asymmetric Polyetherimide membrane
QA/QC casting after US Patent 4,673,418,
Peinemann et. al., 1987
Gas Flux (GPU), RT 10-6 cm3 (STP)cm-2 s-1 (cm Hg)-1 Selectivity (H2/N2)
Before Pt Coating Before Pt Coating Before Pt Coating
Hydrogen 11.7 66
Nitrogen 0.18 66
After Pt Coating, before hydrogenation After Pt Coating, before hydrogenation After Pt Coating, before hydrogenation
Hydrogen 8 46
Nitrogen 0.18 46
After hydrogenation and washing in hexane After hydrogenation and washing in hexane After hydrogenation and washing in hexane
Hydrogen 0.5 12
Nitrogen 0.04 12
Peinemann et. al., 1987 Peinemann et. al., 1987 Peinemann et. al., 1987
Hydrogen 68 49
Nitrogen 1.4 49
base membrane OK (flux could be optimized)
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Integral-asymmetric membranes bridging the gap
from nanomaterials to the macroscopic world

• The selective polymer layer
• 100-500 nanometers thick
• absolutely defect-free
• made on a scale of
• square centimeters to square meters
• The porous support
• enables usefulness of thenanomaterial

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If membrane-based hydrogenation shows benefits,
can it be done on a technical scale? When?

• H2 pressure will be low while maintaining high H2
  availability existing H2 equipment is perhaps
  OK.
• Sputtering of technical membranes is relatively
  simple (flat sheet, hollow fiber)
• Technical scale gas permeation membranes are
  available (Air Liquide/Medal and others)

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Iodine value, IV

• Measure of the degree of unsaturation of a fat
  (one I2/DB, "g Iodine reacting with double
  bonds/100 g of fat")
• High IV less stable to oxidative attack
• Soybean Oil IV130, margerine stock soybean oil
  IV65 (40TFA), shortening stock IV80 (32TFA)
• If the fat composition is resolved
  chromatographically, IV can be calculated

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Analytical preparation of Fatty Acid Methyl
Ester (FAME) AOCS method Ce 2-66
centrifuge
add 2 ml hexane
add 0.1 mL methanolic KOH
shake
FAME, hexane
(30 sec.)
0.2 g Oil
FAME, potassium salt of glycerol , water
potassium salt of glycerol, water
add 2 drops FAME/hexane to 2 ml hexane
Inject 1µl
50 min
GC w/FID CP Sill88, 100m x0.25 mm) 170C
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Gas Chromatogram of Unhydrogenated Soybean Oil
(Iodine Value 126) (oil supplied by MP
Biomedicals, LLC, Irvine, CA analysis FAME, AOCS
method Ce 2-66
MeE
C182 9c12c
MeE
Methyl linoleate
MeE
C181 9c
MeE
MeE
Methyl Oleate
MeE
MeE
FID Response pA
MeE
Methyl stearate
MeE
C180
C183 9c12c15c
Methyl linoleneate
C183t
C181 11c
C200
C201
C182 t
Time min
15
Reactor system
Nitrogen
1/8 SS
1/8 SS
Oil
Data Acquisition
60-62 psig
Parr reactor (160 ml)
TC
Oil, 70 C
Membrane Reactor
(Membrane area 12.6 cm2)
50-52 psig
Oil
1/8 SS
1/8 SS
Hydrogen
1/4 SS
13 ml/min
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Membrane-facilitated hydrogenation
Trans Fatty Acid wt
Membrane Reactor 70C, pH23.4 atm Pt/polyimide
membrane
Iodine Value IV g iodine/100 g oil
Karabulut, I. Kayahan, M.Yaprak, S. ,
Determination of changes in some physical and
chemical properties of soybean oil during
hydrogenation , Food Chemistry, 81, 453, 2003.
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Non-hydrogenated vs. Partially Hydrogenated
Soybean Oil
C180
C181 9c
C182 9c12c
FID Response pA
C181 t
C181 11c
C182 t
C183 9c12c15c
C181 12c
C183 t
C201
C200
Time min
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Compare H2 consumed vs. supply through the
membrane
mol H2
Time h
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Conclusions

• Hydrogenation was observed with platinum-coated
  integral-asymmetric gas permeation membranes
• The membranes appeared physically stable over 120
  hours
• Formation of trans fatty acids was observed, but
  perhaps can be further reduced

Acknowledgements

• United States Department of Agriculture

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Iodine Value (IV) calculation based on gas
chromatographic resolution of oil
IV 0.8598(weight C181)1.7315(weight
C182)2.6152(weight C183)
0.8173(weight C201) Note weight is
relative to combined detected analytes
Discussion
From GC we obtain the relative amount of Fatty
Acid in the mixture of their methyl esters. For
free fatty acids the factors for IV can be
calculated as IVfree (Mol. Wt. of Iodine/Mol.
Wt. of Fatty acid)n where nno. unsaturated
bonds In oil we have to take into account the
extra molecular weight due to glycerol and we
find IVoil(Mol Wt. of Iodine/Mol. Wt. of Fatty
Acid12.68 )n where 12.68 takes into account the
additional molecular weight. So for example for
C181 (253.8/(282.4712.68)) 0.8598 (see above)