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TRANSESTERIFICATION FOR BIOFUEL.
(R.COO)3.C3H5 + 3MeOH → 3 RCOOMe +
C3H8OH
In presence of catalyst and lots of water.
Interesterification
Interesterification involves an exchange of acyl group among triglycerides.
Acyl groups may exchange positions within a triglyceride or among triglyceride molecules.
Interesterification
Catalysts
• High temperature catalysts: KOH and NaOH
• Low temperature catalysts: Sodium Methoxide (NaOCH 3)
1. The formation of enolate ion
2. The formation of Beta-Keto ester
3. Interesterification
Reaction Mechanisms
Catalyst Function in Interesterification
Initial removal of an -proton by the base catalyst leads to the charge delocalized enolate anion.
CH3 C CH3
OOH
-
CH3 C CH2-
O
CH3 C CH2
O
+
C CH2CH3
O -
-
H2O +
Mechanism for Intramolecular Ester-Ester Interchange
O
O
C
COCH2R2
CH
O
R1
O COCH2R3
O
O
C
C
O COCH2R3
CH2R2O
O
C R1H
O
O-
O
C
COCH2R3
C
O
C CH2R2
H
R1
O
I II III
__
O
O
O
C
COCH2R3
C
O
C
H
CH2R2
O
R1
O
O
O
C
COCH2R3
C
O
C CH2R2
O
R1
H
__
III IV V
O
O
O
COCH2R2
C
COCH2R3
C
O
R1
H
_
Beta-Keto ester formation
Intraesterification
Enolate ion formation
Random Esterification
Interesterification can be carried out to an equilibrium condition, at which point the fatty acids assume an almost random distribution among triglycerides.
Intraesterification, Interesterification and Equilibrium Mixture.
O
L
O
L
S
O
S
L
L
O
S
S
Catalyst
Continued reaction
L
O
L
O
L
L
L
L
L
S
O
S
S
S
L
S
OO
S
S
S
S
LL
S
L
S
O
S
O
L
S
L
SS
O
O
O
O
O
LO
O
O
L
UUUSSS (SUS SSU) (SUU USU)
Interesterification can be directed away from its usually random end-point if the fat is allowed to crystallize during reactions.
The trisaturated glycerides crystallize first.
Direct Interesterification
Intraesterification, Interesterification and Equilibrium Mixture
O
L
O
L
S
O
S
L
L
O
S
S
Catalyst
Continued reaction
L
O
L
O
L
L
L
L
L
S
O
S
S
S
L
S
OO
S
S
S
S
LL
S
L
S
O
S
O
L
S
L
SS
O
O
O
O
O
LO
O
O
L
UUUSSS (SUS SSU) (SUU USU)
Directed Interesterification
S
O
L
1. Stearic-Stearic-Stearic 33.3 mole % solid2. Oleic-Oleic-Oleic 8.3 mole % liquid3. Linoleic-Linoleic-Linoleic 8.3 mole % liquid4. Oleic-Oleic-Linoleic 24.9 mole % liquid5. Oleic-Linoleic-Linoleic 24.9 mole % liquid
Applications
Shortenings: The proportion of palmitic acid in the 2-position is reduced from about 64% to 24% on random interesterification.
Natural lardRandomized lard
Randomization of lard improves its plastic range and thus makes it a better shortening than natural lard.
Plasticity and Consistency
Plasticity is the changes in consistency as a function of temperature.
Consistency is the apparent hardness at a temperature
Margarines – High Stability Margarine Blends
1. 75 % (co-randomized 40 % coconut oil / 60 % palm oil),
2. 10 % (co-randomized 50% coconut oil / 50 %
hydrogenated canola oil) and
3. 15 % hydrogenated soybean oil
Good spreadability, high temperature stability, and good eating qualities.
Nutritional Margarine Blends
High polyunsaturated content and low-to-zero
trans-acid containing margarines are produced by
interesterifying a blend of liquid oil and a fully
hydrogenated oil.
Confectionary Fats
Hydrogenated palm kernel oil is a hard butter melting at 46C and produces a waxy feel in the mouth.
On randomization, its melting point is reduced to 35C. By blending hydrogenated palm kernel oil and its randomized product, a whole series of hard butters with highly desirable melting qualities (rapid melt in mouth) are obtained
BLOCK DIAGRAM FOR KRAFT PROCESS
KRAFT PROCESS
Slaking &
Causticizing
Settling &
Filtration
Digester
Blow Tank
Recovery
Furnace
Dissolving
Tank
Lime Kiln
Mu
ltip
le E
ffect
Evap
ora
tors
Lime
Recovered White Liquor
Pulp to further
processing
GasesOff Gas
Wood Chips
SteamWeak
Black Liquor
Steam
Strong Black Liquor
Condensate
Flue Gas
Smelt
Off Gas
Water
Green Liquor
Calcium Carbonat
e
Air
Gases
Gaseous Waste
Washers
Reference: El-Halwagi, M. M., Reference: El-Halwagi, M. M., Pollution Prevention through Process Integration: Systematic Design Tools. Academic Press, 1997.. Academic Press, 1997.
Tier III – Problem Statement
Energy in the Kraft pulping processEnergy in the Kraft pulping process
The Kraft pulping process is a very energy-intensive process: electricity end-uses The Kraft pulping process is a very energy-intensive process: electricity end-uses common to all pulp and paper mills include pumping, air-handling, and lighting. In common to all pulp and paper mills include pumping, air-handling, and lighting. In addition, steam needs and the large number of process streams makes this sector addition, steam needs and the large number of process streams makes this sector of the industry a good candidate for improved heat integration. Black liquor of the industry a good candidate for improved heat integration. Black liquor concentration is usually the biggest single steam using operation in a Kraft pulp mill. concentration is usually the biggest single steam using operation in a Kraft pulp mill. Evaporators installed in the 1960s and 1970s were built with four or five effects, Evaporators installed in the 1960s and 1970s were built with four or five effects, whereas most Kraft mills today use five or six effect evaporators, with a whereas most Kraft mills today use five or six effect evaporators, with a concentrator to further increase solids content. Firing the recovery boiler with the concentrator to further increase solids content. Firing the recovery boiler with the black liquor at higher solids content improves overall boiler performance and is a black liquor at higher solids content improves overall boiler performance and is a general trend in the industry.general trend in the industry.
To counter this energy consumption problem, a Kraft pulp mill uses biomass. In fact, To counter this energy consumption problem, a Kraft pulp mill uses biomass. In fact, in addition to being the feedstock for pulp and paper production, biomass is also a in addition to being the feedstock for pulp and paper production, biomass is also a major energy resource for the industry. The industry also has access to residues of major energy resource for the industry. The industry also has access to residues of pulpwood harvesting, some of which can be removed from the forest on a pulpwood harvesting, some of which can be removed from the forest on a sustainable basis. All black liquor and most mill residues are used at mill sites to sustainable basis. All black liquor and most mill residues are used at mill sites to fuel cogeneration systems, providing steam and electricity for on-site use. fuel cogeneration systems, providing steam and electricity for on-site use. Cogeneration also known as Combined Heat and Power (CHP) is the simultaneous Cogeneration also known as Combined Heat and Power (CHP) is the simultaneous production of electricity and useful heat from the same fuel or energy. A typical production of electricity and useful heat from the same fuel or energy. A typical cogeneration system consists of an engine, steam turbine, or combustion turbine cogeneration system consists of an engine, steam turbine, or combustion turbine that drives an electrical generator. A waste heat exchanger recovers waste heat that drives an electrical generator. A waste heat exchanger recovers waste heat from the engine and/or exhaust gas to produce hot water or steam. from the engine and/or exhaust gas to produce hot water or steam.