HYDROGENATION

1
HYDROGENATION
2
Vegetable oil

• Seventy five (75) of world edible oil is
  vegetable oil
• Shortening
• Margarine
• Mayonnaise
• Confectionary fat
• Less desirable for salad and frying oil, Why?

3
Hydrogenation
Definition To treat oil with H2 and catalyst to
decrease double bonds and increase saturated
bonds. Reaction Result Saturation of double
bonds Migration of double bonds Trans-fatty
acid formation Advantages of Hydrogenation Maki
ng fat suitable for manufacture of margarine,
shortening, coating fats, cooking oil and
salad dressing oil.
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Hydrogenation
Complete Hydrogenation
Partial hydrogenation
?
5
Hydrogenation Reaction Rate

• Nature of the substance to be hydrogenate
• (Oleic acid vs Linoleic acicd)
• The nature and concentration of the catalyst
• Pressure (reaction) the concentration of
  hydrogen
• The reaction temperature
• The degree of agitation

6
Hydrogenation Steps of Oils

• Transfer and/or diffusion
• Adsorption
• Hydrogenation/isomerization
• Desorption
• Transfer

7
Transfer and Diffusion
Transfer and adsorption steps are critical steps
in controlling the degree of isomerization and
selectivity of reactions. Transfer Transfer of
reactants and products to and from the bulk of
the liquid oil phase and outside surface of
the catalyst. Diffusion Diffusion of reactant
into the pores of the catalyst. Diffusion of
products out of the pores of catalyst.
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Schematic Diagram of Hydrogenation
H
H
H

2
Catalyst Surface

C
C
C

1
2
3

H H
H
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Schematic Diagram of Hydrogenation
H
C
C
3
1
H
C
2
H
H
C
1
H
C
C
H
2
3
H
H
H
C
C
C
1
2
3
H H H

H
H
C

C
C
1
2
3
H
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Schematic Diagram of Hydrogenation
Catalysis
Oil Catalyst
à
Oil-Catalyst Complex
Oil-Catalyst Complex H

à
Hydrogenated Oil Catalyst
2
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Formation of Double Bond Migration and
Transisomers during Hydrogenation
8 9 10 11
H
H
H
H
R
C
C
C
C
R
1
2
H
H
(A)
.
.
H
H
8 9 10 11
8 9 10 11
H
H
H
H
H
H
H
H
.
.
C
C
C
R
R
C
C
C
C
R
R
C
1
2
1
2
R
H
H
H
H
H
H
(B)
(C)
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Formation of Double Bond Migration and
Transisomers during Hydrogenation
R
8 9 10 11
8 9 10 11
.
.
- H
- H
.
.
- H
- H
8 9 10 11
8 9 10 11
H
H
H
H
H
H
C
C
R
C
C
R
1
2
R
C
C
C
C
R
8 9 10 11
1
2
H
H
H
H
H
H
H
H
H
H
(D)
(
E)
R
C
C
C
C
R
1
2
H
H
(F)
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Conjugated Fatty Acids Formation
9 10 11 12 13 14 15 16
C
C
C
C
C
C
C
C
9 11 15
C
C
C
C
C
C
C
C
OR
10 12 15
C
C
C
C
C
C
C
C
OR
9 12 14
C
C
C
C
C
C
C
C
OR
9 13 15
C
C
C
C
C
C
C
C
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Adsorption
Adsorption of the reactants on the catalyst
surface is important in controlling the
selectivity and isomerization during
hydrogenation.
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Fatty Acid Compositions of Partially
Hydrogenated Oleic Acid
__________________________________________________
________________
Double bond
Positional
Total unsaturated fatty acide ()
Trans unsaturated fatty acids ()
isomer


(Position)
trans
form
__________________________________________________
________________
11
. . . . . . . 7.0
4.7
67.2
10 . . . . . . . 15.7

9.8
62.5
9 . . . . . . . 54.5

13.4
24.6
8 . . .
. . . . 15.8
9.8
62.0
7 . . . . . . . 7.0

4.7
67.2

__________________________________________________
________________
The unsaturated trans fatty acids is 42 of
total unsaturated fatty acids
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Hydrogenation Scheme
Linoleic
acid Oleic acid
Linolenic
acid
Stearic acid
Isolinoleic
acid
Isooleic acid
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Selectivity

Preferential hydrogenation of more unsaturated
acids with minimum formation of completely
saturated fatty acids. Linoleic
acid Oleic acid Very selective hydrogenation
50 1 Non-selective hydrogenation
4 1 Selectivity can be expressed as
the ratio KLO/KO the relative rate of
hydrogenation of linoleate to that of oleate.
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Selectivity for Hydrogenation
Oleic acid
Linoleic Acid

?
Polar or nonpolar catalyst surface
The affinity of unsaturated fatty acids to
catalyst through hydrogen bond. Geometric
configuration and chemical and physical
characteristics of catalyst will determine the
selectivity of catalyst will determine the
selectivity ration of different fatty acids.
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Why does selectivity important in hydrogenation?
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How can we increase the linoleic acid selectivity
ratio?
Selectivity
When the affinities of oleic and linoleic acids
to catalyst are the same, what are the
selectivity ratios of both acids?
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Hydrogenation of Soybean Oil
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Catalysts

• Nickel Catalyst Nickel on various supports
• Copper Catalyst
• Copper-Chromium (CUO 50 Cr2O3 40 BaO 10)
• High selectivity for linolenic acid (KLn / KLO
  10)
• Almost infinite selectivity for linoleate

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Double-bond migration to form conjugated
trans-fatty acids.
9 10 11 12 13 14 15 16
C
C
C
C
C
C
C
C
9 11 15
From the hydrogenation of A 9, 15 and 11,
15 From the hydrogenation of B 10,15 and 12,
15 From the hydrogenation of C 9, 12 and 9,
14 From the hydrogenation of D 9, 13 and 9,
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C
C
C
C
C
C
C
C
(A)
OR
10 12 15
(B)
C
C
C
C
C
C
C
C
OR
9 12 14
(C)
C
C
C
C
C
C
C
C
OR
9 13 15
(D)
C
C
C
C
C
C
C
C
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Triglyceride Stereospecificity
Hydrogenation of fatty acids in triglyceride is
not a function of their location
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Catalyst Activity
Defined as iodine value decrease per unit of time
during a hydrogenation under a specific set of
conditions. American Oil Chemists Society
method Comparison of the time to
hydrogenate soybean oil to iodine value to
80 from 120 at 350F, 20 psig, 0.05 your
catalyst to the time used by standard
catalyst from AOCS The life of catalyst
how long a catalyst will remain active
and useful.
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Production of Simulated Olive Oil from Soybean
Oil by Chromium Carbonyl

Hydrogenated
Soybean Oil
Olive Oil
Iodine Value
95
77-94
Palmitate ()
10.3
7-16
Stearate ()
4.3
1-3
Other Saturates ()
0.0
0.1-2
Monoene ()
60.7
65-85
Diene ()
23.9
4-15
Triene ()
0.8
Trans
-Acids ()
6.8
__________________________________________________
___________
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Production of Simulated Cocoa Butter from
Hydrogenated Cottonseed Oil by Chromium Carbonyl
__________________________________________________
___________
Hydrogenated CSO
Cocoa
Butter
Palmitate ()
58.0
24.4
Stearate ()
1.0
35.4
Monoene ()
37.6
38.1
Diene ()
3.4
2.1
Trans
-Acids ()
7.2
-
Iodine Value
38.0
36.7

Melting Range
(
C)
30-40
24-35
__________________________________________________
___________
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FACTORS AFFECTING HYDROGENATION
Independent Variables Pressure Temperature Agitati
on Catalyst concentration
Dependent Variables Trans fatty acids Selectivity
ratio Hydrogenation rate
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Effects of Pressure and Temperature on
Trans-Unsaturation at 80 I.V. Soybean Oil
As pressure 3 Psi 35 Psi at 180C,
trans fatty acids decrease from 40 to 35
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Effects of Pressure and Temperature on
Trans-Unsaturation at 80 I.V. Soybean Oil
As temperature 210 235C at 30 Psi,
trans fatty acids increase from 40 to 45
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Effects of Pressure, Temperature, and Catalyst
on Selectivity Ratio
What does selectivity 40 mean? As pressure 14
34 Psi at 180C, 0.02 catalyst, selectivity
rate decrease from 40 to 20
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Effects of Pressure, Temperature, and Catalyst on
Selectivity Ratio
As temperature 130C 160Cat 0.08 and 25
Psi, Selectivity rate increases from 20 to 40
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Effects of Pressure, Temperature, and Catalyst on
Selectivity Ratio
As catalyst 0.02 0.08 at 25 Psi and
165 C, selectivity rate increases from 20 to 40
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Effects of Agitation and CatalystConcentration
on Selectivity Ratio
As catalyst 0.03 0.07 at 1330 RPM,
selectivity rate increases from 28 to 36.
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Effects of Agitation and Catalyst Concentration
on Selectivity Ratio
As agitation 1300 1700 RPM at 0.06 ,
selectivity rate decreases from 36 to 28.
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Effects of Pressure and Temperature on
Selectivity Rate
As pressure 20 35 Psi at 170C,
selectivity rate increases from 20 to 28
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Effects of Pressure and Temperature on SR
As temperature 140 190 at 20 Psi,
selectivity increases from 20 to 36
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Effects of Agitation and Catalyst Concentration
on Hydrogenation Rate
As agitation 800 1000ppm at 0.06 Ni,
hydrogenation rate increase from 2.5 to 3.2
IV/min.
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Effects of Agitation and Catalyst Concentration
on Hydrogenation Rate
As catalyst 0.06 0.10 at 1000rpm
hydrogenation rate increases from 3.3 to 3.8
IV/min.
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Factors Affecting Hydrogenation
The Relationship between Process Conditions and
their Effects on Selectivity Ratio,
Trans-Contents, and the Rates of Reaction
Trans
Selectivity
Content Reaction Rate
Ratio
Temperature
Pressure
Agitation
Catalyst