No abstract

Chemocatalysis of sugars to methyl lactate (MLA) exhibits great advantages over the conventional fermentation approach because of its higher productivity and cost-effective separation process. However, widely used supported metal oxide catalysts suffer from deactivation resulting from sintering during the reaction and removal of coke at high temperatures. Herein, we report ultrasmall cobalt oxide clusters (∼1.7 nm) stabilized within silicalite-1 crystals catalyst (CoO@silicalite-1), exhibiting superior catalytic activity and resistance to sintering for the conversion of fructose into methyl lactate. HAADF-STEM, EDS-mapping, and XRD experiments identify the existence of confined CoO clusters. XANES and Raman spectra demonstrated the covalent interaction between CoO and silicalite-1. Thanks to the ultrasmall CoO particle size (∼1.7 nm), the CoO@silicalite-1 affords nearly 100-fold higher Co-mass-based activity (mg MLA/mg Co) compared with CoO or Co3O4 particles outside the silicalite-1 framework. More importantly, this catalyst exhibits good reuse performance via the removal of coke with facile calcination.

As-synthesized Ni-based Lewis acidic catalysts, with tunable concentrations of β-Ni(OH) 2 and γ-NiOOH, were tested on the conversion of sugars to methyl lactate (MLA) in near-critical methanol solutions. The concentration of γ-NiOOH increased with an increase in the Ni(NO 3 ) 2 •6H 2 O/2-methylimidazole (Ni/2-Hmim) molar ratio. Compared to β-Ni(OH) 2 , the γ-NiOOH showed more mesopores in the catalyst, which facilitated the diffusion of reactant and products. Ni/2-Hmim-4 [Ni(NO 3 ) 2 • 6H 2 O/2-methylimidazole molar ratio = 4] exhibited the best catalytic activity. Under optimal conditions (180 °C for 12 h), the highest MLA yield was 41.9% on the conversion of glucose. Ni/2-Hmim-4 was employed to convert disaccharides to MLA. Notably, for sucrose, the reaction afforded a 38.7% MLA yield at 200 °C for 12 h. The catalyst was reusable for at least three cycles.

No abstract

Earth-abundant magnetic cobalt is highly efficient for CTH of oleic acid with isopropanol as a hydrogen donor, affording 100% conversion as well as 91.9% octadecanol yield at 200 °C, which can be ascribed to the synergistic effect between Coδ+ and Co0.