A Heterogeneous Nickel Catalyst for the Hydrogenolysis of Aryl Ethers without Arene Hydrogenation

Abstract

A heterogeneous nickel catalyst for the selective hydrogenolysis of aryl ethers to arenes and alcohols generated without an added dative ligand is described. The catalyst is formed in situ from the welldefined soluble nickel precursor Ni(COD) 2 or Ni-(CH 2 TMS) 2 (TMEDA) in the presence of a base additive, such as t BuONa. The catalyst selectively cleaves C Ar −O bonds in aryl ether models of lignin without hydrogenation of aromatic rings, and it operates at loadings down to 0.25 mol % at 1 bar of H 2 pressure. The selectivity of this catalyst for electronically varied aryl ethers differs from that of the homogeneous catalyst reported previously, implying that the two catalysts are distinct from each other.

Heterogeneously catalyzed lignin depolymerization

“…Considering that lignin depolymerization can be performed successfully with homogeneous base catalysts, such as KOH and NaOH, with conversions reaching 95 % [55], [60], and that heterogeneous Ni catalysts are able to cleave C-O bonds [67], Sturgeon et al proposed a combination of these active components [19]. A 5 wt% Ni supported on a MgAl hydrotalcite (a solid base catalyst employed widely for lipid transesterification to biodiesel [68][69][70]) was shown to depolymerise a lignin model compound, 2-phenoxy-1-phenethanol, and ball-milled lignin extracted from corn stover, into low molecular weight alkyl aromatics; interestingly, nickel nanoparticles present on the (likely external) hydrotalcite surface required no activation with H 2 prior to their catalytic application, suggesting that the active species was a mixed valence nickel oxide.…”

Improving Heterogeneous Catalyst Stability for Liquid-phase Biomass Conversion and Reforming

“…[56][57][58] However, as for many base metals, the Ni particles suffer from sintering. Nanoconfinement of Ni particles by self-assembly of Ni atoms inside the nanoribbons of hydrotalcite-derived mixed oxide provided increased catalytic stability for methane steam reforming, compared to Ni supported on commercial support surface.…”

Upgrading Lignocellulosic Biomasses: Hydrogenolysis of Platform Derived Molecules Promoted by Heterogeneous Pd-Fe Catalysts

“…At present, industrial processes are limited to vanillin and "kraft lignin" (about 60 kt/year) manufacture but, the research on the sustainable production of chemicals from lignin has developed rapidly in the last years [48][49][50][51][52]. To this regard, one of the major challenges is the low cost-effective catalytic depolymerization of lignin preserving its aromatic nature [53][54][55][56][57][58][59][60][61][62][63][64][65].…”