Catalyst choice impacts aromatic monomer yields and selectivity in hydrogen-free reductive catalytic fractionation

Abstract

Hydrogen-free reductive catalytic fractionation (RCF) is a promising method to extract and depolymerize lignin from native biomass without the use of external hydrogen gas. Here, we show that Pt/C and...

Interdependence of Solvent and Catalyst Selection on Low Pressure Hydrogen-Free Reductive Catalytic Fractionation

“…Initial catalyst–solvent performance studies for hydrogen-free reactions were conducted with EG as the solvent (Figure A). With external H 2 , similar monomer yields were obtained for reactions with Ru/C, Pd/C, Pt/C, and Ni/C of ∼21%, which agree with previous reports that observe similar monomer yields with sufficient hydrogen pressure, regardless of catalyst choice. , In hydrogen-free reactions, similar monomer yields to reactions with external hydrogen were achieved with Pd/C and Pt/C, while reduced monomer yields were observed in Ru/C and Ni/C (14.1% ± 0.8% and 11.5% ± 0.3%). This follows trends for hydrogen-free reactions with MeOH from our previous work …”

“…which agree with previous reports that observe similar monomer yields with sufficient hydrogen pressure, regardless of catalyst choice. 14,19 In hydrogen-free reactions, similar monomer yields to reactions with external hydrogen were achieved with Pd/C and Pt/C, while reduced monomer yields were observed in Ru/C and Ni/C (14.1% ± 0.8% and 11.5% ± 0.3%). This follows trends for hydrogen-free reactions with MeOH from our previous work.…”

“…This follows trends for hydrogen-free reactions with MeOH from our previous work. 14 Product distributions on all four of these catalysts differed from reactions with external hydrogen to hydrogen-free. While total monomer yield was retained, reactions with Pd/C exhibited increased yields of propyl and ethyl-substituted monomers, while those of propanol-substituted monomers were reduced, which is also consistent with reactions in MeOH.…”

“…While total monomer yield was retained, reactions with Pd/C exhibited increased yields of propyl and ethyl-substituted monomers, while those of propanol-substituted monomers were reduced, which is also consistent with reactions in MeOH. 14 Reactions with the 3 other catalysts exhibited near complete disappearance of propanol-substituted monomers, while unsaturated isoeugenol and propenylsyringol products were formed, indicating low hydrogen transfer activity.…”

Recent advances in biomass pretreatment using biphasic solvent systems

“…In addition, the cooling-induced phase separation of butanol and water offers a facile way to separate the aromatic component (organic phase) from polyol products (aqueous phase). Currently, the Ru/C-catalyzed RCF process in butanol/water has been performed on different types of biomass, such as Eucalyptus 82 and poplar sawdust, 83 which is aimed to firstly degrade lignin into aromatic monomers and obtain a lignin-rare solid for further enzymatic hydrolysis. In addition, coupling sodium dithionite with a butanol/water biphasic system has been examined with birch sawdust, which also produces a cellulosic pulp for enzymatic hydrolysis with a yield of 91.4%.…”