Promoted Production of Phenolic Monomers from Lignin-First Depolymerization of Lignocellulose over Ru Supported on Biochar by N,P-co-Doping

Co-doping of heteroatoms into the support of metal-supported catalysts is a prevalent method to improve the catalytic performance by adjusting metal–support interactions. This paper investigated the catalytic performances of Ru supported on biomass-derived char (Ru@Char), N-doped char (Ru@N-Char), and N,P-co-doped char (Ru@NP-Char) in the emerging lignin-first depolymerization for both poplar (hardwood) and pine (softwood) samples, with an emphasis on the production of phenolic monomers. Various characterizations of the prepared catalysts showed that the codoping of N,P not only facilitated the formation of micropores in the char but also introduced weak and moderate acid sites. Furthermore, the sizes of Ru nanoparticles on the codoped char became smaller, and the proportion of metallic Ru species was increased, resulting from electron transfer from Ru to the codoped char. The yields of the phenolic monomers from poplar and pine over Ru@NP-Char were as high as 57.98 and 17.53 wt % Klason lignin, respectively, which were improved by factors of 1.4–2.5 in comparison to Ru@Char and Ru@N-Char. Full delignification during the depolymerization of both poplar and pine was also achieved over Ru@NP-Char.