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

Abstract

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.

Ultrasound-assisted low-temperature catalytic lignin-first depolymerization of pine wood biomass to selectively produce propyl guaiacol

“…A summary of the literature on the RCF of biomass, including the biomass source, catalysts, operating conditions, degree of delignification, selectivity to lignin monomers and carbohydrates retention is provided in Table 4. 4,15–17,29,54,55,57,58 The degree of delignification and carbohydrate retention are observed to be in the range of 70–95% and 85–95%, respectively. Recently, Liu et al 17 reported 95% delignification and ∼87% retention of the carbohydrate of the birch wood biomass using the N-doped Ru/ZnO/C catalyst at 240 °C and 30 bar initial H 2 partial pressure.…”

“…52 Therefore, carbon-based catalysts are widely used for RCF of different lignocellulosic biomasses owing to their neutral character. Typically, carbon-supported monometallic Pt, 53 Pd, 16,54 Ru 4,29 and Ni, 55 and bimetallic NiFe 56 catalysts have been evaluated. Zhai et al 56 studied the RCF of birch sawdust using a NiFe bimetallic catalyst.…”

“…2 Therefore, delignication of biomass without altering the holocellulose in it has gained signicant attention. 3,4 Devising smart strategies to utilise lignin, the most abundant source of aromatics, is vital for a sustainable biorenery. In conventional delignication processes such as kra, organosolv and steam explosion, the native lignin undergoes irreversible degradation yielding condensed lignin.…”

“…The use of commercial carbon supported Pd and Ru catalysts (with metal loading ∼5 wt%) demonstrated excellent RCF activity by achieving near theoretical yield of lignin monomers. 4,7,19,20 However, due to high metal loading, these catalysts would hardly meet industrial applicability. From this viewpoint, evaluation of low-metal containing highly dispersed catalysts for RCF is gaining attention.…”

Catalytic hydrogenolysis of lignin to phenolic monomers over Ru supported N,S-co-doped biochar: The importance of doping atmosphere

“…The chemical states of Ru, C, N, and S elements in the three catalysts were studied by XPS measurements. The XPS spectra of Ru 3p 3/2 can be deconvoluted into Ru 0 and Ru n+ species, in which the Ru 0 species had been recognized as the active sites for hydrogenolysis of lignin ( Wu et al, 2021 ; Ding et al, 2022 ). As shown in Figure 4A , the content of Ru 0 species slightly increased from 75.45% (Ru@C) to 78.14% (Ru@CNS-N 2 ), suggesting that the co-doping of nitrogen and sulfur could facilitate the formation of Ru 0 species.…”