Efficient selective Hydrodeoxygenation of Lignin-Derived Vanillin over Glucose-derived N-doped carbon-Encapsulated Cobalt Catalyst

Abstract

Catalytic transfer hydrodeoxygenation (CTHDO) has become an attractive method for upgrading lignin to fuels and valuable chemicals, and developing non-noble metal catalysts is the key step. Herein, the urchin-like N-doped carbon encapsulated Co nanoparticles catalysts (Co@NxCy-T) were successfully constructed using glucose as carbon source and structure-directing agent, and urea as nitrogen source through a hydrothermal method and carbothermal reduction processing, and applied for the CTHDO of vanillin to 2-methoxy-4-methylphenol (MMP). Co@N0.5C1.5-500 exhibited the best catalytic performance, achieving ~100% vanillin conversion with 92.1% yield of MMP under 160 ℃, 3 h, and atmospheric nitrogen pressure using isopropanol as H-donor. Based on the characterizations results, the addition of glucose led to the formation of N-doped carbon, which improved the dispersion and particle size of Co nanoparticles and brought the carbon defects and pyridinic-N Lewis base sites. Mechanistic studies indicated that metallic Co0 sites were responsible for the dehydrogenation of isopropanol and hydrogenation of C=O in vanillin, and the Lewis acid sites from cobalt oxides species were responsible for cleavage of C-OH bond to form MMP. Furthermore, the prepared catalyst had good stability, substrate applicability, and certain antioxidant capacity, which may pave the way for developing excellent non-noble catalysts for upgrading lignin in actual industrial production.