Effective hydrodeoxygenation of lignin-derived phenols using bimetallic RuRe catalysts: Effect of carbon supports

• Published in: Catalysis today 2018-04, Vol.303, p.191-199
• Main Authors: Jung, Kyung Bin, Lee, Jinho, Ha, Jeong-Myeong, Lee, Hyunjoo, Suh, Dong Jin, Jun, Chul-Ho, Jae, Jungho
• Format: Article
• Language: English
• Subjects: Bimetallic; Carbon; Hydrodeoxygenation; Lignin; RuRe
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/j.cattod.2017.07.027

[Display omitted] •Effect of carbon supports on HDO activity of RuRe bimetallic catalysts is investigated.•RuRe/MWCNT displays considerably higher activity for the HDO of phenols than RuRe/AC.•Ru and Re metals are mostly segregated on the surface of the low activity RuRe/AC.•High surface oxygen content of the AC support hinders the formation of bimetallic particles.•Ru and Re in close proximity are required for the efficient hydrogenolysis of phenols. We have previously shown that an activated carbon-supported ruthenium catalyst promoted with ReOx (RuRe/AC) is highly active for the hydrodeoxygenation (HDO) of lignin-derived phenols (e.g., guaiacol). In this work, we have investigated the effect of carbon supports on the structure and HDO activity of bimetallic RuRe particles using three different carbon supports, i.e., activated carbon (AC), carbon black (Vulcan carbon, VC), multi-walled carbon nanotube (MWCNT). The MWCNT- and VC-supported catalysts show remarkably enhanced activity and hydrocarbon selectivity for the HDO of a range of phenolic molecules (i.e., guaiacol, eugenol, benzyl phenyl ether) compared to RuRe/AC. STEM-EDS and XPS analyses reveal that bimetallic RuRe particles are more common than monometallic Ru or Re particles in the VC- and MWCNT-supported catalysts, and hexavalent rhenium species are more easily reduced to tetravalent rhenium during the HDO reactions in these catalysts, suggesting that Ru and Re in close proximity are required for the efficient hydrogenolysis of phenols. The formation of bimetallic particles on the AC surface is likely hindered by high microporosity and high surface oxygen functionalities, both of which restrict the mobility of Re and Ru for assembly.