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Title: Kinetic Studies of Lignin Solvolysis and Reduction by Reductive Catalytic Fractionation Decoupled in Flow-Through Reactors

Reductive catalytic fractionation (RCF) is an effective active-stabilization strategy to selectively extract and depolymerize lignin into aromatic monomers. Here, the kinetics of RCF were investigated by using flow-through reactors to decouple the two limiting mechanistic steps, namely lignin solvolysis and reduction. When operating in a solvolysis-limited regime, apparent energy barriers of 63 ± 1 and 64 ± 2 kJ mol –1 were measured for the solvent mediated lignin extraction of poplar using particle diameters of 0.5 < d < 1 mm and 0.075 < d < 0.25 mm, respectively. In contrast, when using mechanically stirred batch reactors, apparent barriers of 32 ± 1 and 39 ± 3 kJ mol –1 were measured for particle diameters of 0.5 < d < 1 mm and 0.075 < d < 0.25 mm, respectively. The difference of activation barriers between flow and batch reactors indicated that lignin extraction under typical RCF conditions in a 100 mL batch reactor stirred at 700 rpm was mass-transfer limited. In the reduction-limited regime, cleavage of the β-O-4 bond in a model compound exhibited an apparent activation barrier of 168 ± 14 kJ mol –1. This study demonstrates RCF occurs by two limiting processes that can be independently controlled.more » Furthermore, both controlling which process limits RCF and verifying if transport limitations exist, are critical steps to develop a mechanistic understanding of RCF and to design improved catalysts.« less
Authors:
 [1] ;  [1] ; ORCiD logo [1] ; ORCiD logo [2] ; ORCiD logo [1]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Chemical Engineering
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Report Number(s):
NREL/JA-2A00-72048
Journal ID: ISSN 2168-0485
Grant/Contract Number:
AC36-08GO28308; 1454299; AC36?08GO28308
Type:
Published Article
Journal Name:
ACS Sustainable Chemistry & Engineering
Additional Journal Information:
Journal Volume: 6; Journal Issue: 6; Journal ID: ISSN 2168-0485
Publisher:
American Chemical Society (ACS)
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States); Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Bioenergy Technologies Office (EE-3B); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; biomass pretreatment; flow-through extraction; lignin conversion; lignin first; lignin kinetics; reductive catalysis; semicontinuous processing
OSTI Identifier:
1436364
Alternate Identifier(s):
OSTI ID: 1462319