Product‐oriented Direct Cleavage of Chemical Linkages in Lignin

Abstract

Lignin is one of the most important biomacromolecules in the plant biomass and the largest renewable source of aromatic building blocks in nature. Selectively producing value‐added chemicals from the catalytic transformation of renewable lignin is of strategic significance and meet sustainability targets owing to the excessive consumption of non‐renewable petroleum resource, but remains a long‐term challenge owing to the complexity of lignin structure. This Minireview provides a summary and perspective of the extensive research that provides insight into selectively catalytic transformations of lignin and its derived monomers via directed scissor of chemical linkages (C−O and C−C bonds) with product‐oriented targets. Furthermore, some challenges and opportunities of lignin catalytic transformation are provided based on existing problems in this field for readers to discuss future research directions.

Catalytic self-transfer hydrogenolysis of lignin with endogenous hydrogen: road to the carbon-neutral future

“…The heterogeneous Cu, Ni, Pt, and Pd have been reported to catalyze DHDC and hydrogenolysis of C-O bond in alcohols. 3 However, the DHDC products are not the major products using these monometallic catalysts. Introducing other metals could tune the electronic and structural properties of monometallic catalysts.…”

“…Recently, it has been reported that FeO x decorated Ru/Nb 2 O 5 heterogeneous catalytic systems can effectively catalyze the conversion of birch lignin oil with C g H 2 -OH groups into ethylbenzene by the DHDC and hydrodeoxygenation. 3 Systematic characterization studies revealed that the introduction of FeO x to the Ru/Nb 2 O 5 not only reduced the ratio of Ru 0 /Ru + , resulting in the restrained hydrogenolysis of C g H 2 -OH groups in lignin oil, but also arose the amounts of oxygen vacancy on the Nb 2 O 5 support, which accelerated the cleavage of C aryl -OH. In this strategy, the selectivity toward ethylbenzene from lignin oil using RuFe/Nb 2 O 5 can be up to 63.4%, much higher than that of 23.2% using Ru/Nb 2 O 5 .…”

“…Lignin is the only large-volume sustainable feedstock for aromatic chemicals in nature, accounting for 10-35% of woody biomass. 3 Therefore, the conversion of lignin into valueadded commodity chemicals is of extreme significance and worth being given considerable attention. However, the natural recalcitrance and complexity of the lignin structure make its valorisation a tremendous challenge.…”

Phosphoric acid-modified commercial kieselguhr supported palladium nanoparticles as efficient catalysts for low-temperature hydrodeoxygenation of lignin derivatives in water

“…However, because of the high oxygen content in lignin or lignin pyrolysis derivatives, the hydrodeoxygenation (HDO) process to remove partial oxygen from these feedstocks is regarded as an effective route to produce high value-added chemicals and energetic biofuels. [7][8][9][10][11][12] On the other hand, >10 wt% of water is co-pro-duced during the production of lignin derivatives by direct pyrolysis of lignin or lignocellulosic biomass and a certain amount of generated lignin derivatives is miscible with water. [13][14][15][16][17][18] Therefore, direct HDO of lignin derivatives in water to avoid the energy-consuming separation process is highly desired for the maximum utilization of renewable carbon resources.…”

Investigations of Hydrocarbon Species on Solid Catalysts by Inelastic Neutron Scattering

“…A sustainable future for our society relies on developing alternative carbon resources [6][7][8]. Coal, natural gas (87-98% methane) and biomass are abundant resources on Earth [9,10].…”