Determination of Carbon, Hydrogen, Nitrogen, and Oxygen in Bio-Oils. Laboratory Analytical Procedure (LAP), Issue Date: October 7, 2021

The determination of total carbon, hydrogen, and nitrogen in bio-oils is important as these values can be used to track the carbon balance of production processes as well as calculate total oxygen content by difference. Oxygen content of bio-oils is a key metric for production and upgrading strategies as these are typically aimed at reducing oxygen. Oxygenates in bio-oils contribute to poor hydrocarbon miscibility, high acidity, high viscosity, and poor stability. Upgrading of bio-oils via deoxygenation produces hydrocarbons which can be used to generate feedstocks for renewable fuels and chemicals. In this Laboratory Analytical Procedure (LAP), combustion-based ultimate analysis is used to determine the weight percent (wt%) of C, H, and N in bio-oils and upgraded products. Ultimate analysis uses high temperatures and a pure oxygen environment to completely combust organic samples to carbon dioxide (CO2), water (H2O), and nitrogen oxides (NOx). In this procedure the amount of C and H in the sample are quantified by measuring resultant CO2 and H2O with Fourier-transform infrared spectroscopy (FTIR). For N, NOx is reduced to nitrogen (N2) which is measured with a thermal conductivity detector (TCD), providing total N content.