[en] Lignin isolated from Miscanthus x giganteus using acidic (FAL) and alkali (AL) conditions was thereafter subjected to the catalytic depolymerization under thermal or ultrasounds activation. The characterization of lignins was achieved by thermogravimetric analysis and FTIR. Three different classes of catalysts, containing nickel as active species, have been prepared in this scope: (i) nano-Ni by reduction of NiCl2 with NaBH4 under ultrasonication, (ii) Fe3O4-(NiMgAlO)x and (NiAlO)x by calcination of Mg(Ni)–Al hydrotalcite incorporated Fe3O4 followed by reduction with hydrogen, and (iii) NiO(111) nanosheets by reduction of Ni(NO3)2 with urea in benzyl alcohol. The catalysts were characterized by XRD and XPS techniques. Reduced mixed oxides displayed a moderate activity while a significant increase in conversion (up to 90%) was observed in the presence of nano-Ni(0). NiO(111) nanosheets catalysts performed very close to nano-Ni(0). The conversion and the mass distribution of the reaction products were strongly related to the procedure used for the extraction of ligning. In all the case AL led to a better depolymerization. The performances of the tested catalysts under ultrasound conditions were inferior to those tested under conventional heating conditions. The nature of the solvent was also found to be very important in this process. Thus, ionic liquid [BMIM]OAc led to the best results in autoclave conditions, and methanol under ultrasounds.
Région wallonne : Direction générale des Technologies, de la Recherche et de l'Energie - DGTRE
TECHNOSE. Bioraffinerie végétale. Chimie et technologie des structures osidiques
The authors kindly acknowledge the American Chemical Society (ACS) for the ACS GREET pilot program grant in 2011 awarded to Kenneth Finch to study at the Department of Organic Chemistry, Biochemistry and Catalysis of University of Bucharest, under host Professor Dr. Simona Coman. Part of the work was supported by the strategic grant POSDRU/89/1.5/S/58852, Project “Postdoctoral programme for training scientific researchers” co-financed by the European Social Foundation within the Sectorial Operational Program Human Resources Development 2007–2013. Aurore Richel is grateful to the “Région Wallonne” (Belgium) for its financial support (“Technose” Excellence Programme). The authors are also grateful for the support of COST (UBIOCHEM action) and the STSM of Dr. Marian Verziu.