Comparison among technical and milled wood lignins through principal component analysis of FTIR spectra

With the growth of biomass processing in biorefineries, there is an increasing need to develop rapid and simple methods for biomass characterization. One important component of biomass that is of signification interest in pyrolysis and liquefaction research is lignin, which is the world’s predominant source of renewable aromatic carbon. Due to its complex, heterogeneous nature and distinct variations among different biomass feedstocks, the characterization of lignins presents a unique challenge. In this study, we will show that clear divisions and comparisons can be made among a variety of lignins based on their FTIR spectra quantitatively assessed through principal component analysis (PCA). The eight lignins so far characterized are: two varieties of softwood kraft, one hardwood kraft, corn stover milled wood lignin (MWL), Douglas fir MWL, hybrid poplar MWL, wheat straw soda, and wheat straw organosolv. These samples were analyzed using a Bruker Alpha FTIR-ATR instrument (in addition to other characterization techniques). The spectra were baseline corrected and normalized, and the intensities of 15 peaks were recorded. The 15 spectral peaks were chosen based on previous work published by Li and McDonald (Industrial Crops and Products, 62, 2014, 67-76). PCA and data visualization was done using Python in the Jupyter Notebook environment. Fig. 1: Explained Variance of Each PC Principal component analysis revealed that among the eight lignins, they can be qualitatively grouped based on both their feedstock variety (e.g., hardwood, softwood) and isolation method (i.e., kraft, MWL, soda, organosolv). Quantification of the explained variances for each principal component (PC) suggests that three PC’s are necessary to capture over 90% of the variation among the samples (Figure 1). The principal component plots (Figure 2) show that softwood kraft lignins are clustered, corn stover and Douglas fir MWLs are clustered, and hardwood kraft and wheat straw soda are clustered. The two wheat straw and two hardwood samples tend to have positive values for PC1, while the softwoods and corn stover are negative. The MWLs are closely grouped along PC2, and the organosolv wheat straw is uniquely large along PC3. Depending on which of the three PC plots are assessed, other possible groupings can be reasonably drawn, suggesting that the FTIR spectral characteristics of lignins are distinctly affected by both their original biomass feedstock and isolation or extraction method. The analysis of FTIR spectra with PCA is a simple and efficient way to quickly assess the characteristics of an unknown or poorly-understood lignin sample, based on its comparison with other well-studied lignins. Previous work has shown that PCA is a robust technique for analyzing bio-oil MS data (Jia, et al., Energy & Fuels, 29, 2015, 7364-7374; Pattiya, et al., Fuel, 89(1), 2010, 244-253), and this work shows that such analysis can easily be extended to FTIR spectra of contrasting lignins. Continuing research will further assess the FTIR data for other important characteristics (both qualitative and quantitative), as well as to include additional technical lignins in the analyses. Please click Additional Files below to see the full abstract

Effect of pressure and gas velocity on biochar formation: hindered tar evaporation or tar cracking?

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Moroccan Two-phase olive mill wastes hydrothermal carbonization: effect of water phase recycling on hydrochar yields and properties

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Pyrolysis of plastics: highlighting the potential interest of a reflux to control liquid products

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Effects of mass transfers and heating rates during bark and wood hydrothermal treatment

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Multi-technique characterization of biochar formation

It is known that biomass forms an intermediate liquid before forming the solid “char” (figure 1) but the role of this intermediate liquid on the structure of char and on the mechanisms of pyrolysis is still poorly understood. In this talk we will present how in-situ rheology and 1H NMR analysis [2] are interesting technique to understand the mechanism of biochar formation through an intermediate “visco-elastic” material. These techniques allow assessing the physical-chemistry of biomass conversion to char at real-time and high temperature conditions. Please click on the file below for full content of the abstract

Characterization and catalytic performances of biochars synthesized from a hyperaccumulator plant: Alyssum murale

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Physico-chemical qualities and potentials for biochar agro- environmental valorization

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On-line Photoionisation Mass Spectrometry: an Interesting Technique to Study Biomass Pyrolysis

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Combination of electrospray ionization, atmospheric pressure photoionization and laser desorption ionization Fourier transform ion cyclotronic resonance mass spectrometry for the investigation of complex mixtures - Application to the petroleomic analysis of bio-oils

The comprehensive description of complex mixtures such as bio-oils is required to understand and improve the different processes involved during biological, environmental or industrial operation. In this context, we have to consider how different ionization sources can improve a non-targeted approach. Thus, the Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has been coupled to electrospray ionization (ESI), laser desorption ionization (LDI) and atmospheric pressure photoionization (APPI) to characterize an oak pyrolysis bio-oil. Close to 90% of the all 4500 compound formulae has been attributed to CHO with similar oxygen class compound distribution. Nevertheless, their relative abundance in respect with their double bound equivalent (DBE) value has evidenced significant differences depending on the ion source used. ESI has allowed compounds with low DBE but more oxygen atoms to be ionized. APPI has demonstrated the efficient ionization of less polar compounds (high DBE values and less oxygen atoms). The LDI behavior of bio-oils has been considered intermediate in terms of DBE and oxygen amounts but it has also been demonstrated that a significant part of the features are specifically detected by this ionization method. Thus, the complementarity of three different ionization sources has been successfully demonstrated for the exhaustive characterization by petroleomic approach of a complex mixture