Characterization and Comparison of Fast Pyrolysis Bio-oils from Pinewood, Rapeseed Cake, and Wheat Straw Using ¹³C NMR and Comprehensive GC × GC

Abstract

Fast pyrolysis bio-oils are feasible energy carriers and a potential source of chemicals. Detailed characterization of bio-oils is essential to further develop its potential use. In this study, quantitative 13C nuclear magnetic resonance (13C NMR) combined with comprehensive two-dimensional gas chromatography (GC × GC) was used to characterize fast pyrolysis bio-oils originated from pinewood, wheat straw, and rapeseed cake. The combination of both techniques provided new information on the chemical composition of bio-oils for further upgrading. 13C NMR analysis indicated that pinewood-based bio-oil contained mostly methoxy/hydroxyl (≈30%) and carbohydrate (≈27%) carbons; wheat straw bio-oil showed to have high amount of alkyl (≈35%) and aromatic (≈30%) carbons, while rapeseed cake-based bio-oil had great portions of alkyl carbons (≈82%). More than 200 compounds were identified and quantified using GC × GC coupled to a flame ionization detector (FID) and a time of flight mass spectrometer (TOF-MS). Nonaromatics were the most abundant and comprised about 50% of the total mass of compounds identified and quantified via GC × GC. In addition, this analytical approach allowed the quantification of high value-added phenolic compounds, as well as of low molecular weight carboxylic acids and aldehydes, which exacerbate the unstable and corrosive character of the bio-oil.

Measuring biomass fast pyrolysis kinetics: State of the art

“…Groenewold et al reported 10.37 wt.% as the highest yield of LVG, 1.44 wt.% of acetic acid, 0.19 wt.% furfural, 0.13 wt.% of 5‐HMF (Groenewold et al, ). The results of furfural (0.24 %) and 5‐HMF (0.22 %) are comparable to those of Negahdar et al, while LVG and acetic acid were reported as 5.6% and 4.6%, respectively (Negahdar et al, ). Although this study does not provide an accurate quantification of all the biomass products, it sets a stage for utilization of comprehensive analytics to derive intrinsic kinetics.…”

“…A common problem in biomass pyrolysis is the complexity of product spectra. The two‐dimensional chromatographic techniques, such as GC × GC and LC × LC (LC: liquid chromatography), have improved chromatographic resolution when compared to their single‐dimensional counterparts (Bahng et al, ; Carpenter et al, ; Kanaujia et al, ; Michailof et al, ; Negahdar et al, ; Toraman et al, , Toraman, Franz, et al ). For example, a simple GC system can separate the bio‐oil components based on either their boiling point or polarity depending on the stationary phase of the column used.…”

“…At fast pyrolysis conditions (i.e., higher temperatures, heating rates and short residence times <1s), the formation of solid products is minimized and intermediate biomass molecules are converted into large amounts (65 wt% and higher) of liquid bio‐oil (Bahng et al, ; Bridgwater, ; Goyal et al, ). Bio‐oil consists of a significant amount of water, typically 10–25 wt%, oxygenates in the form of alcohols, aldehydes, ketones, carboxylic acids, esters, ethers, sugars, furans and phenols, and traces of sulfur and nitrogen compounds (Djokic, Dijkmans, Yildiz, Prins, & Van Geem, ; Negahdar et al, ; Toraman, Dijkmans, Djokic, Van Geem, & Marin, ; Venderbosch & Prins, ). Due to its high oxygen content, bio‐oil needs to be upgraded or stabilized to increase its heating value for its application in petroleum refineries (Demirbas, ; Meier et al, ).…”

Hybridization of ZSM‐5 with Spinel Oxides for Biomass Vapour Upgrading

“…Even though MgAl@ZSM5 product selectivity was similar to the combination of the individual active phases, the higher occurrence of aromatics and aliphatic C−C groups seems to indicate synergy between the active phases. Higher abundance in the aliphatic C−C region is of significant interest for fuel utilization, since this region accounts for the energy content of the bio‐oil . Thus, this data is in good agreement with the increasing trend of the H/C eff ratio and the calorific values of these bio‐oils (Table ).…”

The Chemical Conversion of Biomass-Derived Saccharides: an Overview

“…As it regards the production of aromatics, lignin is the most promising feedstock. 63 The chemical depolymerization of lignin can lead to a broad range of compounds containing phenolic compounds, 64 which can be further upgraded for the production of alkylphenols, 65 phenols, 65 arenes, 66 defunctionalized aromatics, 67,68 and, ultimately, the BTX compounds. [67][68][69][70] …”