# Comparative Analysis of Kinetic Parameters of Sustainable Branched Esters Obtained from Lauric Acid

## TL;DR

This study compares the production of sustainable branched esters from lauric acid using different alcohols and a biocatalyst, finding optimal conditions and reaction rates.

## Contribution

The paper introduces a validated kinetic model for esterification reactions using branched alcohols and a biocatalyst, enabling process simulation and optimization.

## Key findings

- Esterification with 3,7-dimethyl-1-octanol achieved the highest average reaction rate.
- The kinetic model accurately predicted conversion values across different alcohol substrates.
- Internal diffusional limitations significantly impacted reaction rates, especially with longer-chain alcohols.

## Abstract

A comparison between four esterification reaction systems
to obtain
new sustainable branched esters using Novozym 435 as a biocatalyst,
the same acid (lauric acid), and four alcohols with different chain
lengths and side chains (2-hexyl-1-decanol, 2-ethyl-1-hexanol, 2-butyl-1-octanol,
and 3,7-dimethyl-1-octanol) has been carried out. The parameters of
the reaction have been optimized in 0.5 g of biocatalyst, temperature
of 70 °C, and the stoichiometric molar ratio (1:1). Under these
conditions, conversion values of >90% are obtained in the four
reactions.
Using a kinetic model developed by the authors and based on a Bisubstrate
Ping-Pong mechanism, where internal diffusional limitations are considered,
the kinetic parameters for each reaction system were determined and
the theoretical conversion values closely matched the experimental
results, validating the model for this wide range of substrates. Attending
at the conversion values obtained, where both the reaction rate and
transport rate are considered, the esterification with 3,7-dimethyl-1-octanol
leads to the highest average rate, followed by the reactions with
2-ethyl-1-hexanol, 2-butyl-1-octanol, and, finally, 2-hexyl-1-decanol.
In the first two systems, the ones with alcohols of shorter side chain
and chain length, respectively, the k
cat values are very high (49.526 and 90.13 Mh–1 g–1, respectively) and so is the reaction rate, leading
to a high average rate. However, when 3,7-dimethyl-1-octanol is used,
the conversion values decrease at long reaction times, due to the
high volatility of this alcohol. In the reaction system with 2-butyl-1-octanol,
there is mixed control of the reaction and transport stages with higher
values of the effectiveness factor (above 0.5 in most cases). Finally,
in the reaction with 2-hexyl-1-decanol, the alcohol with the longest
chain length and side chain, and the highest molecular weight and
viscosity, internal diffusional limitations are very high (with low
values of the effectiveness factors as expected, around 0.2 for all
conditions tested), and the reaction rate is quite low as well, which
explains the low average rates obtained. The obtained branched esters
are of interest in the biolubricant sector, and the kinetic parameters
calculated in this study can be useful to allow simulation, further
optimization, and scale up of the esterification process.