Efficient depolymerization of lignins to alkylphenols using phosphided NiMo catalysts

Abstract

Greening up the chemical industry by using waste biomass streams as feed is a topic of high relevance. Residual lignins from for example the pulp and paper industry and second-generation...

Solvent-Free Catalytic Hydrotreatment of Alcell Lignin Using Mono- and Bimetallic Ni(Mo) Catalysts Supported on Mesoporous Alumina

“…Such aromatic chemicals can be obtained by acid- and base-catalyzed depolymerization approaches, oxidation, and catalytic hydrotreatment . Such hydrotreatments are typically performed using a supported metal catalyst in combination with a hydrogen source (e.g., molecular hydrogen) in the presence (e.g., dodecane, dioxane, alcohols, and water) − and absence of solvents. − In the latter case, the lignin or products thereof act as the solvent and this is considered advantageous from a technoeconomic point of view. The lignin oils may either serve as a source for biobased chemicals like alkylphenols, or, after deep hydrotreatment, a biofuel with properties mimicking current hydrocarbon fuels.…”

“…In addition to noble metal catalysts, limonite ore, a low-cost Fe-containing catalyst, was used for the hydrotreatment of Alcell lignin, yielding 19.0 wt % monomers and 8.7 wt % alkylphenols based on lignin intake (450 °C, 100 bar initial H 2 pressure, and 4 h reaction time) . Recently, it was found that Ni catalysts also have potential and, for instance, it was shown that the use of a phosphided bimetallic NiMo catalyst (NiMoP/SiO 2 ) results in a lignin oil yield with 34.4 wt % monomers of which half were alkylphenols (400 °C, 100 bar initial H 2 pressure, and 2 h reaction time with 10 wt % catalyst loading) …”

Enhanced Catalytic Depolymerization of a Kraft Lignin by a Mechanochemical Approach

“…Catalytic hydrotreatment of unmilled and milled lignins was conducted in a batch reactor at 400 °C for 2 h and 100 bar initial H 2 pressure without an external solvent, using a NiMoP/SiO 2 catalyst (the detailed characterization of the NiMoP/SiO 2 catalyst is presented in the Supporting Information). Typically, the hydrotreatment led to the formation of gas-phase products and a liquid phase with suspended solids. The latter was separated by centrifugation followed by acetone extraction to obtain an organic product oil, an aqueous phase, and a solid residue (Scheme S1 of the Supporting Information).…”

“…Processes, such as oxidative, base/acid-catalyzed, and (catalytic) fast pyrolysis, have also been explored for lignin depolymerization . Additionally, aromatic bulk chemicals, such as phenols and aromatics, can be obtained from kraft lignin using reductive processes, like catalytic hydrotreatment. − In this communication, we show that a simple mechanochemical pretreatment (viz., ball milling) of kraft lignin before solvent-free hydrotreatment can lead to improved performance (i.e., 15% increase in the recovered oil yield, 15% more alkylphenols, and 33% reduction in solids) compared to unmilled kraft lignin.…”

“…Our group has reported high yields of such alkylphenols and aromatics from kraft lignin via this solvent-free catalytic hydrotreatment approach. , This approach was extended using multiple types of technical lignins and different lignin fractions obtained from solvent fractionation. , Extensive catalyst screening studies have been conducted using the solvent-free catalytic hydrotreatment approach. ,, The objective of all of these studies has been to enhance the yields of the liquid products and, particularly, the amounts of low-molecular-weight chemicals because these are deemed most valuable. A recent study shows that the use of a NiMoP/SiO 2 catalyst resulted in a lignin oil yield and monomer yield as high as 68.1 and 51.8 wt %, respectively …”