(552f) Analysis of Pyrolysis Oil Model Compounds Using in-Situ Raman

In recent decades, the world has seen an exponential increase in the demand for fossil-based energy sources. This increase in the demand is leading to an exhaustion of the petroleum reserves and increase in the environmental pollution. Therefore, attention is being given to alternative, carbon-neutral renewable energy sources like biofuels. The carbon-neutrality and lower production costs make the production of biofuel from lignocellulosic biomass an alluring alternative to conventional fossil fuels. Biofuels are generally produced from biomass via pyrolysis which yields pyrolysis oil that is high in oxygenated compound. The pyrolysis oil is then upgraded to biofuel through hydrodeoxygenation (HDO). Analysis of the HDO reactions for conversion and kinetic parameters often requires gas chromatography (GC) with time-consuming material preparation steps prior to the GC analysis. An alternate, fast analytical method would be beneficial to both researchers and producers alike.

Therefore, in this research, we propose the use of in-situ Raman Spectroscopy which can yield us time-resolved information about molecular structure, intermediates, mechanisms, and rate of reaction. The HDO reaction was simulated by analyzing multiple samples of varying concentrations of the reactants, and their corresponding HDO products. The obtained Raman spectra was then deconvoluted using Gaussian Deconvolution algorithm, in order to identify, and differentiate between different peaks. The height of their respective characteristic stretching modes were then measured to determine the conversion of the model compound. The carbonyl (ν_C=O) stretching mode in hydroxyacetone, for instance, was found at 1,721 cm^-1, (ν_COCOC) sym. stretching mode of the acetal group found in glycolaldehyde diethyl acetal was observed at 1,140 cm^-1 and the phenol (ν_C-O) stretching mode of 4-n-propylphenol was obtained at 1,204 cm^-1, respectively. A calibration curve was then obtained from the corresponding peak height versus concentration. Insofar, in-situ Raman could be used to measure the conversion of the hydrodeoxygenation of pyrolysis oil compounds.