Two-Dimensional Gas Chromatography Characterization of Pyrolysis Bio-oils: A Review

Raw pyrolysis bio-oils can be used as liquid biofuels for district heating or as raw materials for producing O-containing substances. Additionally, they can be upgraded using different processes to obtain products with promising potential to be used as advanced liquid transportation biofuels. The more widespread use of the raw and upgraded bio-oils is associated with the detailed knowledge of their chemical composition. The chemical characterization of both the raw and upgraded bio-oils is challenging as bio-oils contain thousands of different, mostly O-containing, chemicals. One of the most critical problems in bio-oil analytics is identifying currently unknown bio-oil compounds, which can be achieved using powerful techniques such as two-dimensional gas chromatography (2D-GC). 2D-GC allows one to analyze volatile and semivolatile bio-oil compounds and provides much more detailed analytical information due to its higher chromatographic resolution than conventional one-dimensional GC. This review aims to summarize and critically evaluate the studies devoted to the 2D-GC characterization of pyrolysis bio-oils. Thermal and catalytic raw pyrolysis bio-oils and hydrotreated bio-oils are of interest to this review. Additionally, the strategies and goals for further research are outlined.