Improved Reductive\nCatalytic Fractionation of Lignocellulosic\nBiomass through the Application of a Recyclable Magnetic Catalyst

The reductive catalytic fractionation (RCF) of second\ngeneration\nlignocellulosic biomass is an elegant one-pot process to obtain a\nhighly delignified cellulose pulp, sugar-derived polyols, and depolymerized\nand stabilized lignin oils. However, the need of noble metal catalysts\nto prompt the reactions may impact the economic sustainability of\nthe overall “lignin-first” biorefinery if the catalyst\nrecovery and recyclability are not guaranteed. Herein, the use of\na novel catalyst based on supported ruthenium over maghemite for the\nRCF of poplar sawdust is reported for the first time. This material\nallows us to obtain a pure cellulose pulp with a quantitative magnetic\nrecovery efficiency after the first cycle. The obtained lignin oil\nis composed by a 12% yield in phenolic monomers (i.e., benzyl alcohol,\n4-<i>n</i>-propylguaiacol, and 4-<i>n</i>-propylsyringol),\ntogether with dimers and trimers as confirmed by GPC analyses. The\ncatalytic material was found to be stable and recyclable for three\nreaction cycles with only minor loss of RCF efficiency. On the other\nhand, the straightforward, lab-scale, magnetic recovery procedure\nneeds to be further improved in the future to ensure quantitative\nrecovery of the catalyst also after several RCF cycles.