(723c) In Situ Raman Analysis for the Production of Biofuel Using a Heterogeneous Layered Double Hydroxide Catalyst

Oral Presentation

In Situ Raman Analysis for the Production of Biofuel
Using a Heterogeneous Layered Double Hydroxide Catalyst

Obakore Agbroko , Keyvan Mollaeian, William E. Holmes, Tracy
J Benson

            As the world’s energy consumption is rapidly
increasing many efforts are being made to produce renewable and sustainable
fuel sources that provide independence, or at least displacement, from fossil
fuels.  Many of these renewable sources include sunlight, wind energy,
geothermal energy, and the conversion of plant based biomass into biofuels. 
The conversion of vegetable oils into biodiesel is a highly viable option for
supplementing fossil fuel energy.  Unfortunately, most biodiesel is produced
from oils stemming from row-crops, which take up viable land resources needed
for food crops.  One promising alternative is microbially-produced oils (MPOs)
where microorganisms feed on industrial and municipal wastewaters.  MPOs,
however, contain high concentrations of free fatty acids (FFAs), unlike most
row-crops.  Under conventional biodiesel processes, high concentrations of FFAs
in oil feedstocks significantly complicate conversion and separation of the
fuel produced.  However, if dimethyl carbonate (DMC) is used as a substitute
for methanol, the formation of an unwanted glycerol byproduct is avoided.  In
addition, the use of a heterogeneous catalyst, in our case triazabicyclodecene
bound to Mg/Al layered double hydroxide (TBD-LDH), process wash water is not
required for separation of fuel components from catalyst salts. 

            In this study, an in situ Raman analysis method
was developed to monitor the reaction conversion as well as kinetic parameters
for the transesterification of lipid oils to biofuel using DMC and TBD-LDH
catalyst.  This in situ method, using a fiber optic probe attached to the 785
nm Raman system, does not require sample handling and
workup as needed for GC analysis.  The height of the C=C stretching mode of
unsaturated fatty acids of the oil at a Raman shift of 1,655 cm-1 was measured
to determine the conversion of the oil.  A Gaussian distribution deconvolution
algorithm was used to optimize the spectra for quantitative analysis.  Refined
canola oil and crude corn oil (4.5 wt% FFA) were used to test the robustness of
this technique. A high-temperature GC-FID analysis was used to validate the
Raman method.