Applications of FT-ICR MS for the elucidation of oligomeric structures from thermochemical conversion of lignocellulosic biomass

Authors: Terrell, Evan; DENSON, MELBA - Washington State University; MANRIQUE, RAIZA - Washington State University; DUFOUR, ANTHONY - University Of Lorraine; GARCIA-PEREZ, MANUEL - Washington State University

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/6/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Introduction: Thermochemical conversion of lignocellulosic biomass produces complex mixtures of low, medium, and high molecular weight products. Relevant technologies include pyrolysis, hydrothermal liquefaction, and upgrading methods, including aqueous-phase reforming and hydrotreatment. In contrast to petroleum and other fossil resource-derived resources, biomass conversion products contain a significant quantity of oxygenates, adding additional challenges for analyses and valorization. In this work, the analysis of thermochemical biomass conversion products with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) is presented. Results are given across a range of disparate processing methods to which FT-ICR MS is applied. Further, emphasis is given to how mass spectrometry-based results can be extend to inform subsequent computational analyses (like DFT) on biomass conversion and (heavy) structure/property estimation. Methods: Thermochemical biomass conversion products from several technologies are analyzed. These include fast pyrolysis of lignin, fast pyrolysis and hydrothermal liquefaction (HTL) of whole woody biomass, wet oxidation of HTL aqueous effluents, and co-hydrotreatment of pyrolytic lignins and vegetable oils. Bio-oils/liquid phase analysis was conducted with FT ICR-MS (9.4 T) instruments using matrix assisted laser desorption ionization (MALDI) and electrospray ionization (ESI) depending on the given application. In parallel with FT ICR-MS analyses, computational approaches are also used to estimate potential structures of heavy oligomeric products. These include combinatoric modification of lignin and holocellulosic structures (based on pyrolysis chemistry) and density functional theory analyses (Gaussian 16) to probe potential reaction mechanisms and chemistry. Preliminary data: Applications of FT-ICR MS for lignin and whole biomass conversion products reveal oligomeric compositional fractions containing (approximately) 25 to 45 carbons and 10 to 20 oxygens. Double bond equivalents for these formulas range from approximately 15 to 25. Based on fragmentation modeling approaches applied to starting biomass structures (i.e., lignin and cellulosics), it is possible to conjecture feasible biomass-derived structures that match MS-detected formulas. The comparison between fast pyrolysis-derived and HTL-derived bio-crude products shows that their differences may be attributed, at least in part, to higher carbohydrate and acid contents in pyrolysis oils. Analyzing wet oxidation of aqueous fractions mirrors this result, showing greater complexity in water soluble fractions from fast pyrolysis (when compared to HTL). Ongoing work with DFT (M06-2X level of theory) is being used to further explore reaction mechanisms potentially responsible for formation of heavy thermochemical biomass conversion products. Oligomeric sugars are (computationally) subjected to several dehydration mechanisms and other fragmentation reactions yielding C2 and C3 products. Lignin oligomer demethylation reactions are also being studied. Results from DFT analyses are taken in parallel with structure estimation from FT-ICR MS analyses. Through this coupled approach relying on computational and analytical chemistry, there is greater confidence in estimated structures determined from formulas measured during mass spectrometry. Finally, ongoing work will extend applications for bio-oil MS characterization by utilizing quantitative structure-property relationships to estimate parameters (e.g., boiling point, heat of vaporization, solubility) with engineering relevance for alternative energy, fuels, and chemicals. Novel aspect: Coupling analytical chemistry through FT-ICR MS with independent computational chemistry analyses (like DFT) provides greater rigor in understanding biomass conversion.