Hydrotreatment of Kraft Lignin to Alkylphenolics and Aromatics Using Ni, Mo, and W Phosphides Supported on Activated Carbon

Abstract

The conversion of lignin to biofuels and biobased chemicals is currently attracting a lot of attention. We here report on the valorization of Kraft lignin by a catalytic hydrotreatment using Ni, Mo, and W phosphide catalysts supported on activated carbon in the absence of an external solvent. Experiments were carried out in a batch setup in the temperature range of 400–500 °C and 100 bar initial H2 pressure. The synthesized catalysts were characterized by X-ray diffraction, nitrogen physisorption, and transmission electron microscopy. The lignin oils were analyzed extensively by different techniques such as GPC, GC-MS-FID, 13C NMR, and elemental analysis. Two-dimensional gas chromatography (GC×GC-FID) was applied to identify and quantify distinct groups of compounds (aromatics, alkylphenolics, alkanes, etc.). Mo-based catalysts displayed higher activity compared to the W-containing catalysts. The reaction parameters such as the effect of reaction temperature, reaction time, and catalyst loading were studied for two catalysts (15MoP/AC and 20NiMoP/AC), and optimized reaction conditions regarding yields of monomeric components were identified (400 °C, 100 bar H2 at RT, 10 wt % catalyst loading on lignin intake). The highest monomer yield (45.7 wt % on lignin) was obtained for the 20NiMoP/AC (Ni 5.6 wt %, Mo 9.1 wt %, P 5.9 wt %) catalyst, which includes 25% alkylphenolics, 8.7% aromatics, and 9.9% alkanes. Our results clearly reveal that the phosphide catalysts are highly efficient catalyst to depolymerize the Kraft lignin to valuable biobased chemicals and outperform sulfided NiMo catalysts (monomer yield on lignin < 30 wt %).

Dynamics of carbon formation during the catalytic hydrodeoxygenation of raw bio-oil

“…[12][13][14][15] Nonetheless, hydrodeoxygenation (HDO) becomes the imperative hydroprocessing goal when dealing with heavily oxygenated feedstock like bio-oil and, in this context, metal phosphides present interesting possibilities. 16,17 The higher HDO activity of phosphided catalysts is related to the presence of P-OH groups which act as Brønsted sites, providing active hydrogen. 18 Unsupported FeMoP catalysts were reported by Rensel et al 19,20 as highly selective materials towards aromatic compounds, also with a high catalyst stability and recyclability.…”

Efficient depolymerization of lignins to alkylphenols using phosphided NiMo catalysts

“…The supported NiMoP catalysts were prepared by an incipient wetness impregnation method. 23,29,30 The AC supported catalyst was prepared as follows: Ni(NO3)2•6H2O (2.50 g) was dissolved in deionized water (3.0 ml), (NH4)6Mo7O24•4H2O (1.51 g) was dissolved in 8.6 ml deionized water, and NH4H2PO4 (1.97 g) was dissolved in 6.0 ml deionized water. The aqueous metal precursor solutions were mixed, followed by the addition of the NH4H2PO4 solution.…”

Hydrothermal liquefaction versus catalytic hydrodeoxygenation of a bioethanol production stillage residue to platform chemicals: A comparative study

“…The HTL1 oil (of a heavier and more oxygenated nature) was hydrotreated at 410-450 • C using both the Ru/C and Pd/C catalysts, while the HTL2 was processed at milder conditions (410 • C with the Pd/C catalyst and 375-410 • C using the Ru/C catalyst). These are typical hydrotreatment conditions based on literature data and our previous experience reported on hydrotreatment of biomass and bio-liquids [28,52,53]. HDO at 450 • C was not considered to avoid over hydrogenation of the produced organic fraction to alkanes.…”