Nitrogen Analysis of Biocrude Oil Derived From Carbohydrates and Proteins

Abstract

Hydrothermal Liquefaction (HTL) has been the cornerstone of research in biofuels production with the recent advances utilising algae biomass as biofuels precursor. HTL technology offers a more cost-effective pathway in transforming algae into biofuel than other technology (such as pyrolysis and torrefaction), as it obviates the drying step. However, one of the main challenges in implementing algae-derived biocrude oils as transport fuels is the higher nitrogen content (5 – 7 wt%) than fossil fuels (~0.3 – 0.5 wt%). Nitrogen content in the biocrude oils is associated with the nitrogenous compounds (such as pyrazines) formed through carbohydrates and proteins reactions. To date, the chemistry understanding of nitrogenous species formation under HTL conditions is not well-established. The objective of this thesis is to study and analyse nitrogenous distribution in reaction products emerging from HTL involving carbohydrates and proteins. Arising from the foregoing, the research develops alternative reaction pathways to pyrazine formation to achieve an elevated understanding of the chemistry of nitrogenous species in biofuels. Included is a quantitative estimate of kinetic parameters, such as rate constants and activation energy. One key outcome of this research is the development of an analytical methodology for the quantitative estimation of pyrazines in a product mixture of HTL of carbohydrates and proteins. Scientific findings presented in this chapter provide a deep understanding of the nitrogenous species, including reaction pathways, nitrogen distribution, and kinetic parameters of sugars – alanine and sugar – ammonium interactions under HTL conditions. The impacts of these findings on biofuel industries are outlined and several recommendations for future research in sustainable biofuel development and production are proposed.