Production of phenolic compounds from argan shell waste by reductive catalytic fractionation

For efficient utilization of lignocellulosic biomass components, reductive catalytic fractionation appears as a promising biorefinery strategy. In this work, this concept of biomass valorization was used to study the potential of an unexplored feedstock, argan shells. This material was processed in a non-catalytic route and over a Pd/C catalyst in two different reaction media. The effects of the treatment temperature (250, 275, and 300 °C), as well as the catalyst loading (catalyst/argan shells mass ratio of 0.05 and 0.1 g/g), were also studied. The main product (lignin-derived oil) was thoroughly characterized using GC/MS/FID, SEC, and NMR. The highest monomer yields of 48–49 wt% based on the lignin content were obtained for n-butanol/water reaction medium at 300 °C using a Pd/C catalyst load of 0.1 g/g and for methanol reaction medium at 275 °C and 0.05 g/g. Significantly lower monomeric phenol yields were obtained in the non-catalytic route (4–19 wt% for n-butanol/water and 9–16 wt% for methanol). The main phenolic monomers in the catalytic pathway were 4-n-propanolguaiacol, 4-n-propanolsyringol, and 4-alkyl guaiacols and syringols, with some differences in the selectivities from one solvent to another.