Reductive Catalytic Fractionation of Cotton Stalks: Catalytic Strategy for Tuning the Selectivity of Phenolic Monomers

Meenu Jindal, Priyanka Uniyal, Adarsh Kumar, Ayan Banerjee, Debashish Ghosh, Thallada Bhaskar

Research output: Contribution to journalArticlepeer-review

Abstract

Pretreatment of lignocellulosic biomass is a primary step to delink lignin from the lignin-carbohydrate complex for bioethanol production and other value-added products. Presently, these processes yield lignin (technical) with significant structural changes compared to native lignin and make it difficult to valorize. Reductive catalytic fractionation (RCF) is an advanced pretreatment process to valorize native lignin to selective phenolic monomers before capitalizing on carbohydrates. Herein, cotton stalks (CS) were pretreated with ethanol: water mixture catalyzed by bimetallic, Ru-Ni/HY (RNY) and Ru-Fe/HY (RFY), and trimetallic, Ru-Fe-Ni/HY (RFNY), catalysts using the endogenously produced H2. The favorable catalytic properties of the RFNY catalyst, including high reducibility, acidity, metal dispersion, the synergistic effect of all the metals, and appropriate pore and particle size resulted in the highest catalytic activity. Maximum 92% delignification efficiency was achieved with 91% holocellulose retention. The extracted lignin after depolymerization in the same step produced a 19 wt.% yield of phenolic monomers. Increasing the duration of the reaction from 2 to 6 h increased the selectivity to saturated alkyl chain phenolics (1 to 16 wt.%) at the expense of hemicellulose (50 to 9%). The fate of carbohydrates left behind after the RCF (CS-RCF) process was analyzed through enzymatic saccharification and compared with raw CS and acid-pretreated CS. CS-RCF yielded maximum glucose yield (45 g/L) within an incubation period of 72 h.
Original languageAmerican English
JournalBiomass Conversion and Biorefinery
DOIs
StatePublished - 2024

NREL Publication Number

  • NREL/JA-2800-91579

Keywords

  • catalysis
  • enzymatic saccharifcation
  • lignin-first
  • pretreatment
  • reductive catalytic fractionation

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