Fabrication modulation of lignin-derived carbon nanosphere supported Pd nanoparticle via lignin fractionation for improved catalytic performance in vanillin hydrodeoxygenation.

Nano-lignin presents great potential in advanced carbon materials preparation since it integrates the advantages of nanomaterials as well the preferable properties of lignin (e.g. high carbon content and highly aromatic structure). Herein, lignin-derived carbon nanosphere supported Pd catalysts (Pd@LCNS) were prepared via a two-step carbonization of Pd2+ adsorbed lignin nanospheres (LNS) and applied in vanillin hydrodeoxygenation. The effect lignin heterogeneity on the synthesis of Pd@LCNS as well as its catalytic performance was further investigated through the synthesis of Pd@LCNS using three lignin fractions with different molecular weight. The results showed that the three Pd@LCNSs exhibited significant differences in the morphology of both carbon support and Pd nanoparticles. Pd@LCNS-3 prepared from high molecular weight lignin fraction (L-3) presented stable carbon nanosphere support with the smallest particle size (∼150 nm) and the highest Pd loading amount (3.78 %) with the smallest Pd NPs size (∼1.6 nm). Therefore, Pd@LCNS-3 displayed superior catalytic activity for vanillin hydrodeoxygenation (99.34 % of vanillin conversion and 99.47 % of 2-methoxy-4-methylphenol selectivity) at 90 °C without H2. Consequently, this work provides a sustainable strategy to prepare uniformly dispersed lignin-based carbon-supported Pd catalyst using high molecular weight lignin as the feedstock and further demonstrate its superior applicability in the selective transfer hydrogenation of vanillin.

Lignin-coordinated highly dispersed PdZn alloy nanocluster supported on N-doped nanolayer carbon and its application in hexavalent chromium detoxification.

As a renewable and low-cost biomacromolecule with high aromaticity and carbon content, lignin is a promising raw material for preparation of versatile carbon materials. Herein, we present a facile one-pot approach to prepare PdZn alloy nanocluster catalysts supported on N-doped lignin-derived nanolayer carbon through facile pyrolysis of melamine-mixed lignin-Pd-Zn complex. The dispersion of the PdZn alloy nanoclusters could be effectively modulated by varying the addition of melamine and the molar ratio of Pd and Zn salts. PdZn alloy nanocluster catalysts (Pd-Zn29@N10C) with ultra-small particle size (about 0.47 nm) were prepared when 10 times of melamine (relative to lignin weight) was added and the molar ratio of Pd and Zn salts was 1:29. Thereby, the catalyst presented superior catalytic activity for reduction of Cr(VI) to harmfulless Cr(III), significantly better than the two references Zn@N10C (without Pd addition) and Pd-Zn29@C (without N doping), as well as the commercial Pd/C. In addition, thanks to the strong anchoring of the PdZn alloy on the N-doped nanolayer support, the Pd-Zn29@N10C catalysts also exhibited good reusability. Consequently, the current study provides a straightforward and feasible method for producing highly dispersed PdZn alloy nanoclusters by lignin coordination, and further demonstrates its excellent applicability in hexavalent chromium reduction.