(544n) Kinetic of the Esterification of Fatty Acids with Methanol for Biodiesel Production

KINETIC OF THE ESTERIFICATION OF
FATTY ACIDS WITH METHANOL FOR BIODIESEL PRODUCTION

Abstract

Deodorization
process of crude palm oil (CPO) removes the free fatty acids (FFA) present in
the feed stream, usually around 3%, by high pressure steam stripping, up to values
as lower as 0.1%. FFA removing is required to avoid formation of soaps during
transesterification step in biodiesel production, avoiding separation problems
in decanters downstream the reaction system [1]. Production of methyl esters
from fatty acids has been widely studied, especially from palm oil, using
homogeneous and heterogeneous acid catalysts, as well as various types of
alcohols [2]. However, sulfuric acid and methanol are still attractive because of
the lower production cost and a higher reaction rate in compared to enzymes and
heterogeneous catalysts and other alcohols [3].

In this
study, a kinetic model (Figure 1) for the esterification reaction that occurs
between FFA and methanol using sulfuric acid as catalyst was proposed, fitting
its parameters from experimental data. Variables experimentally assessed were: concentration
of the catalyst (0.15wt%, 0.45wt% and 1.6 wt% based on the total mass loaded to
the reactor) and temperature (40 °C, 50 °C and 60 °C), keeping constant the mixing
rate (500 rpm) and the fatty acid to methanol mass ratio (1:1). The progress of
reaction was determined by measuring the acid value of the sample. Parameters
of the first order reversible kinetic model, were determined using a Modified-NonDominated
Sorting Particle Swarm Optimization algorithm (mNSPSO). The maximal difference
between experimental and predicted values was 8.12% (Figure 2), that better
fitting is achieved when reaction is close to the equilibrium.

Figure 1.  Kinetic model for esterification of FFA with
methanol

Figure 2.  Comparison
between experimental conversion data and calculated conversion data by the
kinetic model.