Fabrication of lignin nanospheres by emulsification in a binary γ-valerolactone/glycerol system and their application as a bifunctional reducer and carrier for Pd nanoparticles with enhanced catalytic activity

• Published in: Green chemistry : an international journal and green chemistry resource : GC Vol. 22; no. 24; pp. 8594 - 863
• Main Authors: Wang, Guanhua, Pang, Tairan, Chen, Shilin, Sui, Wenjie, Si, Chuanling, Ni, Yonghao
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 21.12.2020
• Subjects: Biopolymers; Catalysis; Catalysts; Catalytic activity; Chromium; Dialysis; Emulsification; Fabrication; Formic acid; Glycerol; Green chemistry; Hydrogen evolution; Lignin; Nanoparticles; Nanospheres; Organic solvents; Palladium; Recyclability; Reducing agents; Room temperature; Size distribution; Solvents
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/d0gc02424d

Lignin nanosizing has received much interest as it offers new potential for value-added applications of the currently under-utilized lignin biopolymers. However, conventional lignin nanosizing technologies often rely on the use of large amounts of toxic organic solvents, and a time-consuming dialysis process that is required to remove the solvents. Herein, we present a novel and effective approach using a binary system consisting of green γ-valerolactone (GVL) and glycerol solvents to prepare lignin nanospheres (LNS) without lignin modification and additional dialysis processes. The rationale of LNS formation lies in the emulsification of uniform lignin-containing GVL droplets in glycerol by a process consisting of (1) heating to 80 °C, and (2) cooling to room temperature. Through this simple process, we obtained very high LNS yield (over 90%), with narrow size distribution (about 275 nm) by using maple kraft lignin as the raw material. This lignin nanosizing approach is universal when applied to different sources/types of lignins. The as-prepared LNS were further applied as a green reducing agent and carrier for the synthesis of Pd nanoparticles (NPs) in a facile in situ reduction process. Pd@LNS exhibited significantly enhanced catalytic capacity in the hydrogen evolution from formic acid and in the reduction of Cr( vi ) to Cr( iii ) compared with bare Pd NPs. The Pd@LNS catalyst demonstrated high recyclability owing to the good chemical stability of LNS and robust loading of Pd NPs on LNS. Consequently, this work offers a green, universal and effective approach for LNS fabrication and presents a promising application of LNS as metal NP carriers for catalysis purposes. Lignin nanosphere was prepared using green binary γ-valerolactone/glycerol system and then employed as a reducer and carrier for Pd nanoparticles.