Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “lignin oligomer”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

43 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

From lignin to market: a technical and economic perspective of reductive depolymerization approaches

Lignin has grown into one of the main candidates to replace fossil-based resources as it is the largest renewable source of aromatic building blocks. The complex structure of polymeric lignin, however, requires depolymerization to simpler building blocks for the chemical industry. One of the most promising depolymerization approaches is reductive depolymerization of which two process configurations are currently studied in pilot scale installations for upscaling to industrial scale: (i) reductive catalytic fractionation (RCF), and (ii) reductive catalytic depolymerization (RCD). Both technical and techno-economic aspects will be covered within this review, discussing the advantages and challenges of both approaches regarding processing, production costs, product output, and applications. In this regard, RCF benefits from its decreased energy and solvent consumption linked with being a one-step process and delivers a product with a high monomer content (∼25–45 wt%). RCD, on the other hand, has the advantage of continuous processing and reduced catalyst fouling and delivers a product that mainly consists of oligomers (<10 wt% monomers). The complete overview of both processes presented here addresses their potential, and can guide future researchers, policy makers and companies to make thoughtful decisions on lignin valorization.

09 BIOMASS FUELS↗
DOE OSTI2023

Hydroxycinnamaldehyde-derived benzofuran components in lignins

Abstract Lignin is an abundant polymer in plant secondary cell walls. Prototypical lignins derive from the polymerization of monolignols (hydroxycinnamyl alcohols), mainly coniferyl and sinapyl alcohol, via combinatorial radical coupling reactions and primarily via the endwise coupling of a monomer with the phenolic end of the growing polymer. Hydroxycinnamaldehyde units have long been recognized as minor components of lignins. In plants deficient in cinnamyl alcohol dehydrogenase, the last enzyme in the monolignol biosynthesis pathway that reduces hydroxycinnamaldehydes to monolignols, chain-incorporated aldehyde unit levels are elevated. The nature and relative levels of aldehyde components in lignins can be determined from their distinct and dispersed correlations in 2D 1H–13C-correlated nuclear magnetic resonance (NMR) spectra. We recently became aware of aldehyde NMR peaks, well resolved from others, that had been overlooked. NMR of isolated low-molecular-weight oligomers from biomimetic radical coupling reactions involving coniferaldehyde revealed that the correlation peaks belonged to hydroxycinnamaldehyde-derived benzofuran moieties. Coniferaldehyde 8-5-coupling initially produces the expected phenylcoumaran structures, but the derived phenolic radicals undergo preferential disproportionation rather than radical coupling to extend the growing polymer. As a result, the hydroxycinnamaldehyde-derived phenylcoumaran units are difficult to detect in lignins, but the benzofurans are now readily observed by their distinct and dispersed correlations in the aldehyde region of NMR spectra from any lignin or monolignol dehydrogenation polymer. Hydroxycinnamaldehydes that are coupled to coniferaldehyde can be distinguished from those coupled with a generic guaiacyl end-unit. These benzofuran peaks may now be annotated and reported and their structural ramifications further studied.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Non-catalytic oxidative depolymerization of lignin in perfluorodecalin to produce phenolic monomers

We demonstrate for the first time non-catalytic, oxidative cracking with molecular oxygen (O 2 ) to depolymerize native lignin into oxygenated phenolic monomers. Maximum monomer yield of 10.5 wt% was achieved at 250 °C after only 10 min of reaction and included vanillin, syringaldehyde, vanillic acid, and syringic acid. High rates of oxidation are attributed to the use of perfluorodecalin as solvent. Perfluorodecalin is a perfluorocarbon (PFC), characterized by their chemical stability and exceptionally high solubility for O 2 . Monomer yields were typically five-fold higher in perfluorodecalin compared to solvents more commonly employed in lignin conversion, such as methanol, butanol, acetonitrile, and ethyl acetate. Phenolic monomer production in perfluorodecalin favors high temperatures and short reaction times to prevent further oxidation of the produced monomers. Lignin oil obtained under oxidative conditions in perfluorodecalin showed lower molecular weight and smaller polydispersity compared to other solvents. Increasing the reaction time further decreased the molecular weight, while increasing reaction time in an inert atmosphere increased the molecular weight of the lignin oil. High concentrations of O 2 in perfluorodecalin not only increased lignin depolymerization but suppressed undesirable condensation reactions. Depolymerization is likely initiated by thermally induced homolytic cleavage of ether linkages in lignin to form phenoxy and carbon-based radicals. These radicals bind with O 2 as a radical scavenger and further react to form phenolic monomeric products rather than repolymerizing to large oligomers. The PFC process was scaled from 5 mL to 250 mL without any loss of yield. Because most organic compounds are not soluble in perfluorodecalin, recycling is easily achieved via liquid–liquid separation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Dual-function lignin monomers enable high-performance graphene electrodes via interface confinement and proton transfer enhancement

Graphene oxide (GO)-based energy storage faces dual bottlenecks: unsustainable reduction methods and sluggish proton transfer kinetics. Here, we introduce a groundbreaking green strategy using lignin-derived vanillyl alcohol (VA) as a dual-function monomer to simultaneously address these challenges. By thermally annealing GO/VA films at mild temperatures (<100 °C), VA triggers an interface-confined reduction of GO while self-polymerizing into redox-active oligomers (P-VA) that intercalate between graphene layers. This dual role-reducing agent and proton highway enables a 3D conductive network with minimized graphene restacking, abundant redox sites, and rapid H + transport pathways. Density Functional Theory (DFT) reveals how P-VA optimizes proton dynamics, while the resulting rGO-P-VA4-T90 electrode achieves a record volumetric capacitance of 311.1F/cm 3 (777.8F/cm 2 ) and retains 87.8 % capacity after 10,000 cycles. Flexible solid-state supercapacitors deliver 94.2 μWh/cm 2 energy density at 63.8 μW/cm 2 , rivaling state-of-the-art devices. Furthermore, this work redefines sustainable graphene engineering, merging biomass valorization with high-performance energy storage in a scalable, eco-friendly paradigm.

Graphene oxide reduction↗
DOE OSTI2023

A Sustainable Multi-Dimensional Printable Material

Polymeric materials are usually tailored for specific functionality. A single polymer exhibiting multiple simultaneous functionalities often requires intricate molecular architecture, which is difficult to manufacture at scale because of its complex synthesis routes. In this work, a facile, partly renewable composition—prepared via reactive melt processing—that induces tunable functionalities such as 3D printability, shape recovery, and self-healing while exhibiting satisfactory mechanical properties is reported. The system with a hydrogen-bonded 3D network consists of thermally reversible nano-scale agglomerates of sustainable, rigid phenolic oligomers and crystallizable flexible polymer. Local molecular mobility and temperature-dependent relaxation and recovery of the non-equilibrium networked states enable exploiting these simultaneous functionalities. Transitions involving solidification and structure stabilization at ambient temperature spanning several hours after preheating only at 70 °C directly contrast typical thermoplastic or thermoplastic elastomer behaviors. Results from this study can inform the design of future rheology modifiers and materials for soft robotics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Comparison of the Chemical Composition of Liquids from the Pyrolysis and Hydrothermal Liquefaction of Lignocellulosic Materials

Major differences in thermal stability and hydrotreatment behavior of HTL and pyrolysis oils have been reported in the literature. However, little is known about the variations in the chemical composition of these oils that could explain such differences. Two commercial wood pyrolysis oils (Pyrovac and BTG), and their water-soluble (WS) and water-insoluble fractions (WIS) were analyzed and compared with the aqueous (WS WD-57 ) and oily (WIS WS-57 ) fractions obtained from hydrothermal liquefaction (HTL) of Douglas-fir. The samples were characterized by GC/MS, Karl Fischer titration, carbonyl content, total acid number, elemental composition, calorific value, proximate analysis, Fourier Transform Infrared Spectroscopy (FTIR), Folin-Ciocalteu (FC), and UV fluorescence. All the fractions were also analyzed by Fourier Transform Ion Cyclotron Resonance Mass Spectroscopy (FT-ICR-MS) and by Electrospray Ionization (EI). The most prevalent class of compounds in the water insoluble phases were phenols derived from lignin. Water-soluble phases contain mostly the oxygenated compounds derived from cellulose and hemicellulose and were richer in carbonyl functional groups. The water content of the resulting aqueous phases were between: 65 (WS BTG ) and 96 (WS Pyrovac ) wt. %. The bio-oil from BTG has higher water content and lower HHV, compared to Pyrovac oil. The GC/MS results of BTG oil show the presence of a more prominent acetic acid peak and higher TAN number than the Pyrovac oil. The GC/MS of Pyrovac oil showed more obvious mono-phenol peaks. The quantification of this family by Folin-Ciocalteu method confirmed higher content of monophenolic compounds compared with the BTG oil. The lower thermal stability of pyrolysis oils compared with HTL biocrudes can be partially explained by the fact that pyrolysis oils (BTG and Pyrovac) contain carbohydrates while HTL biocrude (WIS WD-57 ) doesn’t. Thus, we decided to further investigate the chemical differences between the phenolic rich fractions insoluble in water and the holocellulose derived compounds soluble in water. Even after water extraction, the acid content of the water insoluble fraction from BTG (WISBTG) was higher than the acid content of the water insoluble fraction obtained by HTL (WISWSD-57). Likewise, the acid content of the aqueous phases derived from pyrolysis oils (WS Pyrovac , WS BTG ) was also higher than for the aqueous phase obtained by HTL (WSWSD-57). This result is in part due to the use of bases in the HTL process that neutralizes the acid formed in that process. Moreover, the starting feedstock may also influence the differences between the oils. Although, the UV-Fluorescence spectra, ICR-MS and the EI analyses showed some minor differences in the molecular weight and chemical make-up of the oligomers soluble and insoluble in water from pyrolysis and HTL; the differences observed were not large enough to justify the differences in behavior between these oils reported in the literature. Our results suggest that the differences observed between HTL biocrudes and pyrolysis oils are likely partially due to the presence of holocellulose derived products in the pyrolysis oils and higher acid contents.

09 BIOMASS FUELS↗