One‐Pot Conversion of Lignin into Naphthenes Catalyzed by a Heterogeneous Rhenium Oxide‐Modified Iridium Compound
Xinxin Li, Bo Zhang, Xiaoli Pan, Jianwei Ji, Yujing Ren, Hua Wang, Na Ji, Qiying Liu, Changzhi Li
Abstract
Abstract The direct transformation of lignin into fuels and chemicals remains a huge challenge because of the recalcitrant and complicated structure of lignin. In this study, rhenium oxide‐modified iridium supported on SiO 2 (Ir‐ReO x /SiO 2 ) is employed for the one‐pot conversion of various lignin model compounds and lignin feedstocks into naphthenes. Up to 100 % yield of cyclohexane from model compounds and 44.3 % yield of naphthenes from lignin feedstocks are achieved. 2 D HSQC NMR spectroscopy before and after the reaction confirms the activity of Ir‐ReO x /SiO 2 in the cleavage of the C−O bonds and hydrodeoxygenation of the depolymerized products. H 2 temperature‐programmed reduction, temperature‐programmed desorption of NH 3 , IR spectroscopy of pyridine adsorption, X‐ray photoelectron spectroscopy, X‐ray absorption fine structure analysis, and control experiments reveal that a synergistic effect between Ir and ReO x in Ir‐ReO x /SiO 2 plays a crucial role in the high performance; ReO x is mainly responsible for the cleavage of C−O bonds, whereas Ir is responsible for hydrodeoxygenation and saturation of the benzene rings. This methodology opens up an energy‐efficient route for the direct conversion of lignin into valuable naphthenes.