Lignin Residue-Derived Carbon-Supported Nanoscale Iron Catalyst for the Selective Hydrogenation of Nitroarenes and Aromatic Aldehydes

Heterogeneous iron-based catalysts governing selectivity for the reduction of nitroarenes and aldehydes have received tremendous attention in the arena of catalysis, but relatively less success has been achieved. Herein, we report a green strategy for the facile synthesis of a lignin residue-derived carbon-supported magnetic iron (γ-Fe2O3/LRC-700) nanocatalyst. This active nanocatalyst exhibits excellent activity and selectivity for the hydrogenation of nitroarenes to anilines, including pharmaceuticals (e.g., flutamide and nimesulide). Challenging and reducible functionalities such as halogens (e.g., chloro, iodo, and fluoro) and ketone, ester, and amide groups were tolerated. Moreover, biomass-derived aldehyde (e.g., furfural) and other aromatic aldehydes were also effective for the hydrogenation process, often useful in biomedical sciences and other important areas. Before and after the reaction, the γ-Fe2O3/LRC-700 nanocatalyst was thoroughly characterized by X-ray diffraction (XRD), N2adsorption-desorption, X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HR-TEM), Raman spectroscopy, and thermogravimetric analysis (TGA). Additionally, the γ-Fe2O3/LRC-700 nanocatalyst is stable and easily separated using an external magnet and recycled up to five cycles with no substantial drop in the activity. Eventually, sustainable and green credentials for the hydrogenation reactions of 4-nitrobenzamide to 4-aminobenzamide and benzaldehyde to benzyl alcohol were assessed with the help of the CHEM21 green metrics toolkit. © 2022 American Chemical Society. All rights reserved

Hydrogenation of lignin-derived feedstocks and bio-oil using active and stable ruthenium catalyst

Value addition of lignin-derived phenols into high-value chemicals and fuels is highly desirable and beneficial for bio-refineries owing to their broad applications in chemical and polymer industries. Here we present selective hydrogenation of various lignin-derived phenols into cyclohexanol and its derivatives using SiO2-Al2O3 supported stable and reusable Ru nanoparticles (Ru-NC/SiO2-Al2O3) in a green and sustainable manner. The Ru-NC/SiO2-Al2O3 nanocatalyst is prepared by simple impregnation followed by the pyrolysis method. The Ru-NC/SiO2-Al2O3 nanocatalyst shows excellent activity for the hydrogenation of lignin-derived functional phenols, including o, p, m-cresols, catechol, 4-n-propylphenol, diphenyl ether, guaiacol, eugenol, and others. In addition, hemicelluloses-derived furfural and furfuryl alcohol were also transformed into their hydrogenated products. Further, this transformation is also used for the hydrogenation of alkali lignin bio-oil, which is selectively transformed into corresponding cyclohexanol derivatives. HR-TEM, XPS, powder-XRD, N2 adsorption-desorption, and NH3-TPD analyses were used to examine the physicochemical properties of both fresh and spent Ru-NC/SiO2-Al2O3 nanocatalysts. Furthermore, the Ru-NC/SiO2-Al2O3 nanocatalyst is recycled and reused four times with no loss of any catalytic activity. © 2022 Elsevier B.V