Cleavage of lignin C–O bonds over a heterogeneous rhenium catalyst through hydrogen transfer reactions

Abstract

ReOx/AC exhibits high catalytic activity and selectivity for the C–O bond cleavage of lignin via hydrogen transfer reactions in isopropanol.

One‐Pot Conversion of Lignin into Naphthenes Catalyzed by a Heterogeneous Rhenium Oxide‐Modified Iridium Compound

“…It is reported that homogeneous methyltrioxorhenium (MTO) and supported ReO x catalysts have the ability to remove two adjacent hydroxy groups of polyols to obtain alkenes by deoxydehydration (DODH). In the area of lignin conversion, Crestini and co‐workers, Kühn and co‐workers, and our group reported that Re‐based catalysts such as MTO, Re 2 O 7 , and particularly ReO x /AC (AC=activated carbon) can cleave lignin C−O bonds. However, the products are a mixture of aromatic monomers and oligomers, and the latter are the major component in reactions with real lignin, which makes the subsequent utilization challenging and increases the difficulty of energy‐intensive separation/purification processes.…”

Hydrogenolysis of Organosolv Lignin in Ethanol/Isopropanol Media without Added Transition-Metal Catalyst

“…To our knowledge, there are no previous reports of using EtOH/i-PrOH mixtures alone for lignin depolymerization and HTH, although there have been reports for using supercritical ethanol or iso-propanol as sources of hydrogen equivalents for metal catalyzed HTH. [50][51][52][53][54][55][56][57] It has also been shown potassium isopropoxide aids in transfer hydrogenation from iso-propanol to coal in the formation of acetone and the equivalent of H2 transfer to substrate. 58 In our work, the observation of acetone in the liquid phase after reaction with OPL (Figure S3) clearly indicates that i-PrOH is the major source of hydrogen reducing equivalents needed for HTH of OPL.…”

Advances in Versatile Nanoscale Catalyst for the Reductive Catalytic Fractionation of Lignin

“…[8i] Recently, ReO x /AC has also emerged as a new catalyst for lignin hydrogenolysis. [43,66] The ReO x /AC catalyst exhibited high selectivity toward CÀ O bonds without destroying the aromatic rings. Both of βÀ OÀ 4 and αÀ OÀ 4 linkages in lignin dimeric models could be cleaved using 5 wt % Re of ReO x /AC at 200°C in nhexane under 3 MPa H 2 , the latter affording the aromatic monomers up to 98 % yield (entry 7, Table 2).…”