470848 In Situ Raman Analysis for the Production of Biofuel Using a Heterogeneous Layered Double Hydroxide Catalyst
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 worlds 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.