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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.

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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Reductive Depolymerization of Lignin to Aromatic Compounds over Promoted Nickel Catalysts in Sub– and Supercritical Methanol

The use of γ-Al 2 O 3 -supported Ni catalysts promoted with either Cu or Fe was investigated for the reductive catalytic fractionation (RCF) of hybrid poplar in methanol at 200 and 250 °C. The effectiveness of lignin depolymerization was quantified in terms of the lignin oil production, the quantity and distribution of identifiable monomers present in the lignin oil, and the yield of residual solids. All of the Ni-based catalysts tested provided improved yields of lignin oil and monomers, along with reduced char formation, relative to blank (sans catalyst) runs. The highest monomer yield of 51 % was obtained at 250 °C over a 20 wt.% Ni-5 wt.% Cu/Al 2 O 3 catalyst, the improved performance obtained through Cu promotion being attributed to the ability of Cu to facilitate NiO reduction, resulting in an increased amount of Ni 0 on the catalyst surface and, consequently, improved hydrogenation activity. Finally, the main monomers formed were propanol-, propyl- and propenyl-substituted guaiacol and syringol, the S/G ratio of the products corresponding closely to that in the native lignin.

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

Lignin-based carbon quantum dots with high fluorescence performance prepared by supercritical catalysis and solvothermal treatment for tumor-targeted labeling

The poor fluorescence performance of lignin-based carbon quantum dots (L-CQDs) prepared using the bottom-up method has hindered their development. Here, in this study, a two-step strategy was proposed to efficiently enhance the fluorescence properties of L-CQDs. Lignin was first cracked using an ethanol supercritical/noble metal catalyst; then, the L-CQDs were prepared with the cracked lignin fragments as carbon precursors without adding any modified reagents. Compared with the OL-CQDs prepared by the traditional one-pot hydrothermal method, the L-CQDs-1 prepared from CL-1 containing much low molecular weight compounds, and have photoluminescence (increased from 63 to 975) and excellent up-conversion photoluminescence (enhanced by 16.3 to 963), which significantly enhanced by about 15 times and 60 times, respectively. They can emit bright blue fluorescence under both ultraviolet and near-infrared light irradiation owing to a large amount of surface defects caused by the rich compound composition. When L-CQDs-1 were combined with, and quenched by folic acid (FA), the prepared FA@L-CQDs-1 show the ability to target and label tumor cells. This study opens new avenues for the preparation of L-CQDs with high fluorescence performance using lignocellulosic material without heteroatom additives.

59 BASIC BIOLOGICAL SCIENCES↗