Abstract
Nb2O5-supported bimetallic catalysts were prepared by the impregnation method applied for the in situ hydrogenation of guaiacol. Guaiacol can be effectively transformed into cyclohexanol over different bimetallic catalysts using alcohol as the hydrogen donor. Meanwhile, the effects of different hydrogen donors such as isopropanol, sec-pentanol, and ethylene glycol on in situ hydrogenation of guaiacol were investigated in detail, and the results showed that isopropanol is the best hydrogen supply solvent. Then, the dependence of Ni–Mn/Nb2O5 properties on metal loading, reaction time, reaction temperature, and reaction pressure was studied for the in situ hydrogenation of guaiacol by using isopropanol as the hydrogen donor. Guaiacol can be completely converted, and the yield of cyclohexanol reached 71.8% over Ni–Mn/Nb2O5 with isopropanol as the hydrogen donor at 200°C for 5 h. The structures and characteristics of better catalytic properties of the Ni–Mn/Nb2O5 catalyst were determined by BET, NH3-TPD, XRD, XPS, SEM, and TEM, and the results indicated the particle size of the metal was small (approximately 10 nm) and the metal particles are finely dispersed in the whole support. Therefore, a large number of medium acid sites were generated on the 10Ni-10Mn/Nb2O5 with a large specific surface area, which could increase the interface between the metal and the support and may be beneficial to the hydrodeoxygenation of guaiacol.
Highlights
Lignocellulosic biomass is the largest renewable resource in nature and an ideal substitute for fossil energy (Mushtaq et al, 2015)
The result showed that guaiacol can be efficiently converted into cyclohexanol under mild conditions (200°C, 1 MPa N2), and the yield of target product cyclohexanol was up to 71.8%, which suggested the catalyst has remarkable hydrogenation performance
The catalyst had the characteristics of high metal dispersibility and large pore size from Scanning electron microscope (SEM), transmission electron microscope (TEM), and BET, which may be helpful for the in situ hydrogen production of the hydrogen supply solvent and the hydrogenation process of phenolic chemicals
Summary
Lignocellulosic biomass is the largest renewable resource in nature and an ideal substitute for fossil energy (Mushtaq et al, 2015). Noble metal catalysts have excellent adsorption capacity for reactants and active hydrogen generated in the hydrogenation process, so they have better catalytic performance and high activity for deoxygenated products than other catalysts. Nonprecious metal catalysts represented by nickel-based catalysts have attracted much attention because of their high hydrogenation activity and low cost It can effectively convert hydrogen into active hydrogen and apply it to the hydrogenation of phenolic compounds. This study prepared a series of bimetallic catalysts (Ni–Mn/Nb2O5, Ni–Zr/Nb2O5, Ni–Cu/Nb2O5, Ni–Mo/Nb2O5, and Ni–Co/Nb2O5) with Nb2O5 as the support and studied the hydrogenation process of lignin-derivative phenolic compounds by using a low-carbon alcohol and water composite solvent to in situ produce active hydrogen. The oven temperature program was increased from 50°C (hold for 1 min) to 260°C (hold for 10 min) at a rate of 10°C/min
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