ABSTRACT
In this study a kinetic model was
developed to represent the kinetics of transesterificiation of waste vegetable
oil (frying oil) in a batch reactor at different isothermal conditions of 313
K, 323 K, 333 K and 338 K. The reaction occurs in series of 3 steps. Solution
to the model was derived using MATLAB the method for solving was done by
applying ode solver ode15s which makes use of backward differential formulas
known as Gear method was used to solve the equations derived and to simulate
kinetic data from literature. The effect of temperature on concentration profile
of species and the reaction rate constant was studied for the selected
isothermal conditions. Temperature had no effect on formation of triglyceride,
alcohol and Methyl ester because the concentration at 313 K, 323 K, 333 K and
338 K were close but temperature favoured the formation of Diglyceride and
Monoglyceride. High temperature did not favour formation of glycerol which is
the undesired product. The maximum yield of methyl ester for was obtained at
338 K which was 79.97%.and corresponds to what was obtain experimentally from
the work of Jisieke (2015).The molar ratio of methanol to oil was held constant
at 6:1.the rate constant obtained from the simulation were close to that which
is obtainable from the work of Nivea et al. (2008) .The value of the
rate constant k2 and k-2 increased as temperature increased.
CHAPTER ONE
1.0
INTRODUCTION
Transesterificiation is the general
term used to describe the important class of organic reactions where an ester
is transformed into another ester through interchange of the alcohol to
glycerol moiety. This is also described as chemical process by which biodiesel
is produced. It is primarily the displacement of alcohol from an ester by
another alcohol; the reaction reduces the high viscosity of triglycerides
usually present vegetable oil and animal fat. (Orificia et al., 2013).
The transesterificiation reaction is an equilibrium reaction and the
transformation occurs essentially by mixing the reactants. However, the
presence of a catalyst (strong acid, base or alkali metal) accelerates
considerably the adjustment of the equilibrium. In order to achieve a high
yield of the ester, the alcohol has to be used in excess.
Vegetable oils are oils from feedstock
and plants are usually found to contain long chain alkyl (methyl, propyl and
ethyl) esters. For this study used frying oil would be used as the oil of
interest for the transesterificiation reaction. Some vegetable oils may be in
form of a colorless liquid and could be a pale yellow liquid sometimes with distinct
taste and odor, their boiling point ranges from 313 0C to 350 and likewise the
density is from 800kg/m3.to 961kg/m3 they contain triglyceride in which most of
their fatty acids chains are ricinoleate. Oleate and linoleates and other
components vegetable oils can be used for domestic purposes and commercial
purposes like in the production of soaps, brake fluids and hydraulic, paints,
dyes, inks, coatings etc. (Leonor and Forero, 2012).
Vegetable oils are a good source of
ricinoleic and oleic acid, this acid is a mono unsaturated, 18-carbon fatty
acid ricinoleic acid has a unique characteristic in which its hydroxyl
functional group lies on the 12th carbon. This unique feature causes it to be
more bipolar than most fats (Leonor and Forero, 2012).
To carry out a transesterificiation
reaction, this is achievable with the use of a Batch reactor, continuous
stirred tank reactors (CSTR), tubular reactors, fixed bed catalytic reactors
etc. In this study, the research will be focused on modeling a Batch for the
transesterificiation of castor oil with methanol. The concept of batch reactors
is readily applied in chemical industries.
In a batch reactor some catalyst like
silica gel, sodium hydroxide could be used to aid certain reaction whilst
perfect mixing of the fluids is being carried out by the stirrer, this concept
is applied to different operations such as esterification, saponification,
transesterificiation, alcohol synthesis etc In all these applications size of
the reactor is usually estimated and design equations are usually obtained to
also estimate the pressure drop of fluids flowing in the reactor In a batch
reactor the catalyst placed inside in a position in such a way that reacting
fluids must make an appreciable contact with the catalyst. Energy balances
together with material balances are carried out on both the fluid in contact
with catalyst particles and the catalyst particles in the reactor (Levenspiel,
1999).
Generally in reactors the following
steps of a reaction usually takes place;
1. Reactants are continuously stirred
to ensure proper mixing.
2. Reactants are transported as well
as energy from bulk fluid to the catalyst external surface.
3. Reactants transported with energy
from external surface into the porous pellets,
4. Adsorption of reactants chemical
reactions and desorption of newly formed products at the active sites of
catalyst.
5. Products are transported from the
internal pores of catalyst to the external surface of the pellet.
6. Product is transported into the
bulk fluid.( Levenspiel,1999)
Chemical reactions in a reactor are
either exothermic or endothermic and require that energy may either be removed
or added to the reactor to maintain a constant temperature. The batch reactor
is normally run such that the temperature and concentration are the same
throughout the fluid. The batch reactor is generally modeled as having no
special variations in concentration and temperature or reaction rate throughout
the vessel. In the case of using a batch reactor for transesterificiation
reaction, the fluids are to be perfectly mixed and operated at isothermal or
non isothermal conditions and products to be withdrawn after a certain time
interval.
In theory, ideal batch reactors are
assumed to have a constant volume; therefore equal volume of reactor content is
expected to be withdrawn after a certain time interval. These contents are
usually accounted for by using lumped parameters of material and energy
balances with mathematical equations which is being described by a set of
ordinary differential equations (Hill, 2011).
In a batch reactor the reactants are
charged and reaction is allowed to take place for a given time. Batch reactors
are usually best used for liquid solid reactions and liquid phase reactions it
is majorly used in heterogeneous reactions with a catalyst. The major advantage
of using a batch reactor is that it facilitates good quality for the product
and reaction occurs faster within less resident time compared to CSTR through
provision of greater constancy in reaction conditions. (Hill, 2011).
1.1 Aim and Objectives of Study
The aim of this study is to obtain a
kinetic model for transesterificiation reaction of frying oil.
The objectives include the following
Apply model to fit that of a batch
reactor at isothermal conditions
Simulate the reaction using
computational software package MATLAB
Study the effects of temperature on
the kinetic rate constant and concentrations of components.
MATLAB is the application applied in
this study because it is can be applied to solve complex differential equations
It is most suitable for solving differential equations of any kind.
Using MATLAB and the derived model
equations can be solved and simulated to obtain results that can be compared to
existing results in literature. In obtaining a suitable model of a batch
reactor to carry out this reaction certain parameters such as different
temperature only at isothermal condition would be considered, therefore to
achieve this mass balance equations coupled with rate kinetic rate constants
for both the forward and backward reaction will be greatly employed in this
study.
TOPIC: MODELLING AND SIMULATION OF TRANESTERIFICATION OF WASTE VEGETABLE OIL (FRYING OIL) IN A BATCH REACTOR
Chapters: 1 - 5
Delivery: Email
Delivery: Email
Number of Pages: 55
Price: 3000 NGN
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