β‐Zeolite‐Assisted Lignin‐First Fractionation in a Flow‐Through Reactor**

Abstract

The valorization of lignin, one of the main constituents of lignocellulosic biomass, is essential for an economically feasible biorefinery. In the present work, a hydrogen-free one step catalytic fractionation of woody biomass using commercial -zeolite as catalyst in a flow-through reactor was carried out, leading to a maximum aromatic monomer yield of 20.5 wt.%. Birch, spruce and walnut shells were compared as lignocellulosic feedstocks. -zeolite acts as a bifunctional catalyst, which prevents lignin repolymerization due to its size-selective properties and also cleaves -O-4 lignin intralinkage.Crucial to optimizing system operation, a rate limiting step analysis using different reactor configurations revealed a mixed regime where the rates of both solvolytic delignification and zeolite-catalyzed depolymerization/dehydration affect the net rate of aromatic monomer production. Oxalic acid co-feeding was found to enhance monomer production at moderate concentrations by improving solvolysis, while it caused structural changes to the zeolite and led to lower monomer yields at higher concentrations. Zeolite stability was assessed through catalyst recycling and characterization using NH3-TPD, XRD, N2 physisorption and TGA. Main catalyst deactivation mechanisms were found to be coking and leaching, leading to widening of the pores and decrease of zeolite acidity, respectively.

Feedstock-agnostic reductive catalytic fractionation in alcohol and alcohol–water mixtures

“…This setup enables physical separation and recovery of the catalyst and carbohydrate-rich pulp, which is a challenge for batch RCF operation. 19,22,23,25,[55][56][57] To evaluate the fractionation efficiency and monomer yields through RCF with different types of feedstocks, we conducted FT-RCF reactions with methanol and 50 : 50 w/w methanol/water. Subsequently, the produced lignin oil and solid pulp residue were analyzed.…”

Intergrowth Zeolites, Synthesis, Characterization, and Catalysis

“…So far, Beta zeolites with various metal active sites have been impressed with assisting in the preferential fractionation of biomass and facilitating catalytic conversion to platform chemicals. , Catalytic conversion reactions on Beta involve hydrotreating, isomerization, dehydration, alkylation as well as catalytic cracking and pyrolysis, etc. − Each reaction is not discussed exhaustively in this review and can be easily found in other literature. − Many notoriously highly reactive reactions can be carried out by functionalized Beta, such as sugar isomerization or epimerization, , and production of lactates from carbohydrates, ,, as well as in more domino cascade reactions like conversion of 5-hydroxymethylfurfural from glucose, and production of γ-valerolactone from furfural . This is not possible with other catalysts.…”

Structure elucidation of prot, alkali and dealkaline lignin(s) by NMR, FT-IR and Py-GC/MS: effect of solid acid and base catalysts

“…Kramarenko and his co-workers suggested that bzeolite effectively cleaved the ether linkage, e.g., b-O-4 of lignin, and also helped to control the repolymerization of the active radical intermediates. 12 Deepa et al observed the production of aromatic monomers predominantly from the pyrolysis of dealkaline lignin using zeolites (H-USY, H-ZSM-5, H-BEA and H-MOR). 13 As per a study, Shen and his co-workers suggested that specic Si/Al ratios of zeolites signicantly affected the production of aromatic hydrocarbons.…”