Quantitative analysis of pyrolysis bio-oils: A review

Abstract

Pyrolysis bio-oils are liquid products of lignocellulosic biomass pyrolysis. They have a highly promising potential to be widely used, after an appropriate upgrade, as advanced biofuels, or as a source of valuable oxygen-containing chemicals. The chemical composition of bio-oils is very complicated as they contain thousands of different, mostly oxygen-containing, compounds with a wide distribution of physical and chemical properties, and concentrations. Detailed knowledge of the bio-oil composition is crucial in order to optimize the pyrolysis processes and/or the subsequent bio-oil upgrading processes. The main challenge in bio-oil analytics is the identification and quantification of the individual compounds as well as the quantification of the total content of the compounds with the characteristic functional groups. In this review, we will discuss a state-of-the-art quantitative analysis of bio-oils and formulate strategies for obtaining in-depth information on the composition of the bio-oils and/or the products of their upgrading. Thermic, non-catalytic fast pyrolysis bio-oils and their hydrotreated analogues are of interest of this review. The emphasis will be placed on the quantification of the compounds with the key oxygen-containing functional groups present in the bio-oils including aldehydes, ketones, carboxylic acids, phenols, carbohydrates, etc. Also, methods for the quantification of the individual compounds will be presented. Hence, this overview and critical assessment of the quantitative methods can help the researchers to better understand the results obtained by these methods and formulate strategies and goals for further research. In addition, the knowledge presented in this review will serve as a reference to any scientist working with complex mixtures of oxygenates.