Hydrogenolysis of lignin to phenolic monomers over Ru based catalysts with different metal-support interactions: Effect of partial hydrogenation of C(sp~2)-O/C

摘要

Catalytic hydrogenolysis of lignin to phenolic monomers has received a lot of attention, but it is still a challenge because the cleavage of the strong C(sp2)-O/C bonds between structural units is usually under harsh conditions, resulting in the presence of the competing reaction of hydrogenation. Herein, hydrogenolysis of an herbaceous lignin into phenolic monomers was performed over Ru supported on various (non)-functionalized graphitized carbon nanotubes (CNT, CNT-OH, CNT-COOH, and CNT-NH2), which were featured by different hydrogenation performances originally from the diverse metal-support interactions. Among the investigated supports, CNT-NH2 enables the formation of the finest Ru nanoparticles with an average size of 1.86 nm, leading to the highest yield of phenolic monomers from lignin hydrogenolysis. The best hydrogenolysis performance of Ru@CNT-NH2 was mainly from the partial hydrogenation of C(sp2)-O/C bonds to C(sp3)-O/C bonds in lignin, thus reducing their bond dissociation energy (BDE). The intimacy between hydrogenolysis and hydrogenation was further proved by depolymerization of a lignin beta-O-4 model compound.