Mechanistic details of C O bond activation in and H-addition to guaiacol at water-Ru cluster interfaces

The Role of Protons and Hydrides in the Catalytic Hydrogenolysis of Guaiacol at the Ruthenium Nanoparticle–Water Interface

“…The removal of O, − N, , and S − from substituted arenes by their reaction with hydrogen is an ubiquitous reaction that occurs in hydrodeoxygenation (HDO), hydrodenitrogenation (HDN), and hydrodesulfurization (HDS) processes, respectively. These reactions share an identical kinetic hurdle that require the cleavage of a strong C­( sp 2 )–X (X = O, N, S) bond.…”

“…For example, water is known to shift the enol–keto isomerization equilibrium position and lower the isomerization barrier during phenol hydrogenation on Pt(111) and Ni(111) . While aqueous-phase HDO of phenolic compounds on transition metals has been studied extensively using H/D isotopic labeling, kinetic/isotopic measurements, ,, infrared spectroscopy, and DFT calculations, ,,,− the nature of the reactive intermediates, the chemical identity and involvement of the reactive hydrogen species at the metal–solvent interface and in solution, and the catalytic role of water are still largely unresolved and often controversial. Here, we provide answers to some of these mechanistic questions by interrogating the atomistic details during aqueous-phase guaiacol–H 2 reactions catalyzed by Ru nanoparticles with combined kinetic measurements, H/D isotopic labeling studies, 1 H and 13 C nuclear magnetic resonance (NMR) spectroscopic studies, ab initio molecular dynamic simulations, and DFT calculations.…”

Selective Deoxygenation of Lignin-Derived Phenols and Dimeric Ethers with Protic Ionic Liquids

“…However, for the substrates of guaiacol, benzofuran, and some dimeric ethers, the catalytic system shows low catalytic activity for their HDO reaction at 120 °C for 6 h. After increasing the reaction temperature from 120 to 150 °C, the conversion rate of substrates and the yield of the corresponding alkanes (main products) increased about 20.0% (Table S1, entries 5–6 and 9–12). This phenomenon could be attributed to the introduction of electron-rich groups (−CH 3 and −OCH 3 ) and higher bond dissociation energy of methoxy groups compared with phenolic hydroxyl groups. ,, As for the guaiacol, when the reaction is conducted at 120 °C for 6 h under a H 2 pressure of 4 MPa, the yield of cyclohexane is 83.7, and 6.6% of cyclohexanol and 7.2% of cyclohexanone are detected after the reaction (see Figure S5 in the Supporting Information). However, after increasing the reaction temperature to 150 °C, no cyclohexanol and cyclohexanone are detected after the reaction, and the yield of cyclohexane is up to 97.5%.…”

“…This phenomenon could be attributed to the introduction of electron-rich groups (−CH 3 and −OCH 3 ) and higher bond dissociation energy of methoxy groups compared with phenolic hydroxyl groups. 15,18,42 As for the guaiacol, when the reaction is conducted at 120 °C for 6 h under a H 2 pressure of 4 MPa, the yield of cyclohexane is 83.7, and 6.6% of cyclohexanol and 7.2% of cyclohexanone are detected after the reaction (see Figure S5 in the Supporting Information). However, after increasing the reaction temperature to 150 °C, no cyclohexanol and cyclohexanone are detected after the reaction, and the yield of cyclohexane is up to 97.5%.…”

“…The deoxygenation reaction during the lignin-derived compound HDO process has been widely studied . Various catalysts and catalytic systems have been reported in recent years, for example, metal catalysts with the co-catalysts of Lewis acid or Brønsted acid are one of the most popular catalytic systems. ,, However, there are still relatively fewer reports on the deoxygenation reaction using ionic liquids (ILs) as the catalyst for lignin-derived compounds .…”