Kinetic analysis and reaction mechanism for anisole conversion over zirconia-supported molybdenum oxide

Innovative flow-through reaction system for the sustainable production of phenolic monomers from lignocellulose catalyzed by supported Mo2C

Molybdenum carbide supported on activated carbon (β-Mo2C/AC) has been tested as catalyst in the reductive catalytic fractionation (RCF) of lignocellulosic biomass both in batch and in Flow-Through (FT) reaction systems. High phenolic monomer yields (34 wt.%) and selectivity to monomers with reduced side alkyl chains (up to 80 wt.%) could be achieved in batch in the presence of hydrogen. FT-RCF were made with no hydrogen feed, thus via transfer hydrogenation from ethanol. Similar selectivity could be attained in FT-RCF using high catalyst/biomass ratios (0.6) and high molybdenum loading (35 wt.%) in the catalyst, although selectivity decreased with lower catalyst/biomass ratios or molybdenum contents. Regardless of these parameters, high delignification of the lignocellulosic biomass and similar monomer yields were observed in the FT mode (13-15 wt.%) while preserving the holocellulose fractions in the delignified pulp. FT-RCF system outperforms the batch reaction mode in the absence of hydrogen, both in terms of activity and selectivity to reduced monomers that is attributed to the two-step non-equilibrium processes and the removal of diffusional limitations that occur in the FT mode. Even though some molybdenum leaching was detected, the catalytic performance could be maintained with negligible loss of activity or selectivity for 15 consecutive runs.

Size effect of Ru particles on the self-reforming-driven hydrogenolysis of lignin model compound

Particle size always has a great influence on catalytic performance. In this work, we investigated the size effect of Ru colloids on the self-reforming-driven hydrogenolysis of lignin model compound by...

Vacancy Engineering in Transition Metal Sulfide and Oxide Catalysts for Hydrodeoxygenation of Lignin-Derived Oxygenates

The catalytic hydrodeoxygenation (HDO) of lignin has long been a hot research topic and vacancy engineering is a new means to develop more efficient catalysts for this process. Oxygen vacancies and sulfur vacancies are both widely used in HDO. Based on the current research status of vacancies in the field of lignin-derived oxygenates, this Minireview discusses in detail design methods for vacancy engineering, including surface activation, synergistic modification, and morphology control. Moreover, it is clarified that in the HDO reaction, vacancies can act as acidic sites, promote substrate adsorption, and regulate product distribution, whereas for the catalysts, vacancies can enhance stability and reducibility, improve metal dispersion, and improve redox capacity. Finally, the characterization of vacancies is summarized and strategies are proposed to address the current deficiencies in this field.

In situ electro-organic synthesis of hydroquinone using anisole on MWCNT/Nafion modified electrode surface and its heterogeneous electrocatalytic reduction of toxic Cr(vi) species

Owing to its electro-inactive character, anisole (phenylmethyl ether, PhOCH3) and its related derivatives have been used as electrolytes in electrochemistry. Herein, we report a simple one-step electro-organic conversion of PhOCH3 to hydroquinone (HQ) on a pristine-MWCNT-Nafion modified electrode glassy carbon electrode surface, GCE/Nf-MWCNT@HQ, in pH 2 KCl-HCl solution within 15 min of working time. The chemically modified electrode showed a highly redox-active and well-defined signal at an apparent standard electrode potential, E o' = 0.45 V vs. Ag/AgCl (A2/C2) with a surface excess value, Γ HQ = 2.1 × 10-9 mol cm-2. The formation of surface-confined HQ is confirmed by collective physicochemical and spectroscopic characterizations using TEM, UV-Vis, Raman, FTIR, NMR and GC-MS techniques and with several control experiments. Consent about the mechanism, the 2.1% of intrinsic iron present in the pristine-MWCNT is involved for specific complexation with oxygen donor organic molecule (PhOCH3) and hydroxylation in presence of H2O2 (nucleophilic attack) for HQ-product formation. The GCE/Nf-MWCNT@HQ showed an excellent heterogeneous-electrocatalytic reduction of Cr(vi) species in acidic solution with a linear calibration plot in a range, 5-500 ppm at an applied potential, 0.4 V vs. Ag/AgCl with a detection limit, 230 ppb (S/N = 3; amperometric i-t). As a proof of concept, selective detection of toxic Cr(vi) content in the tannery-waste water has been demonstrated with a recovery value ∼100%.

Highly selective demethylation of anisole to phenol over H4Nb2O7 modified MoS2 catalyst

H₄Nb₂O₇ modified MoS₂ catalyst enables the highly selective demethylation of anisole to phenol which opens a window for the hydrogenolysis of lignin to value-added chemicals.

Product-oriented Direct Cleavage of Chemical Linkages in Lignin

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.