Abstract
Conversion of waste lignocellulosic (LC) biomass, a widely-available low-cost feedstock, into value-added biobased chemicals (and biofuels) has been gaining much attention recently. Therefore, the present lignin valorisation study was aimed at developing magnetically-separable highly-active catalysts for hydrodeoxygenation (HDO), also proposing surface chemical kinetics. Five carbonaceous substrate-deposited Ru were synthesised and tested for the HDO of monomer moiety eugenol. Their annealing temperatures differed, specifically between 300 and 750 °C, while one was not subjected to calcination. Experiments revealed the substantial influence of annealing temperature on the product distribution. Namely, fresh nonannealed nanocomposites were not active for hydrogenolysis. By further pretreatment increase, hydrogenation and, exclusively, the deoxygenation of saturated cyclic species, were enhanced, these being more promoted considering rates and yields than commercial carbon-supported ruthenium. Over 80 mol% of 4-propyl-cylohexanol and propyl-cyclohexane could be formed over the samples, treated at 500 and 600 °C, for 100 and 125 min, respectively, under 275 °C and 5 MPa of reactor hydrogen pressure. Interestingly, a notable 4-propyl-phenol amount was produced upon 750 °C pretreating. The intrinsic microkinetic model, developed previously, was applied to determine relevant turnover parameters. Calculated modelling results indicated a 47- and 10-fold greater demethoxylation and dehydroxylation mechanism ability upon the reheatingpreheating at 600 °C in comparison to industrial (heterogeneous) Ru/C.
Highlights
IntroductionLignocellulosic (LC) biomass is available in the form of agricultural residues, waste streams (pulp, paper, and food industry), wood, and energy crops
Lignocellulosic (LC) biomass is available in the form of agricultural residues, waste streams, wood, and energy crops
Somewhat higher acidity has been estimated for our catalysts relative to the Ru/C, which might be expected for Fe-containing catalyst being usually correlated to the grater HDO activity [33,34,35]
Summary
Lignocellulosic (LC) biomass is available in the form of agricultural residues, waste streams (pulp, paper, and food industry), wood, and energy crops. It is consisted of cellulose (40–50%), hemicellulose (15–30%), and lignin (15–30%) [1]. Lignin is a feedstock rich in aromatic functionality and represents a significant portion of the total carbon in biomass [5]. Valorisation of this abundant feedstock is required for improving the economic balance of any biorefinery [1]. Beside lignin’s transformation into chemicals (i.e., benzenes, cycloalkanes, phenols, and styrene) comprehensively reviewed by Isikgor and Becer [6], it can be converted into carbonaceous fibre nanocomposites, and other added value products [7,8,9]
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