Abstract
A fundamental understanding of the solution behavior of lignin under reaction conditions is required for the rational design of porous heterogeneous catalysts that minimize the mass-transfer limitations on lignin depolymerization kinetics. In situ and ex situ small-angle neutron scattering (SANS) methods were used to study the structural changes of lignin during non-catalytic solvolysis reactions in deuterated methanol (MeOH-d4) and catalytic reactions in the presence of copper-containing porous metal oxide (CuPMO) and MeOH-d4. The results indicate that at room temperature, lignin adopted a rigid and stretched conformation that becomes more spherical, flexible, and folded when heated to the reaction temperature of 250 °C. In the presence of CuPMO, the volume fraction of small lignin particles (<50 Å) in the reactor is higher than under solvolysis conditions, while the median radius of this fraction of lignin particles is smaller. The SANS data were analyzed using a population balance model and found that two reaction processes dominate: disassembly of large lignin aggregate particles (>50 Å) and condensation of small lignin particles (<50 Å). The study also suggests that the cooling and quenching step in the ex situ experiments alters the small lignin (<50 Å) particle size distribution.
| Original language | English |
|---|---|
| Pages (from-to) | 2241-2251 |
| Number of pages | 11 |
| Journal | ACS Sustainable Chemistry and Engineering |
| Volume | 12 |
| Issue number | 6 |
| DOIs | |
| State | Published - Feb 12 2024 |
Funding
We acknowledge the Herman Frasch Foundation for Chemical Research in Agricultural Chemistry (801-HF17) and the U.S. National Science Foundation (CBET-1604095). We would also like to acknowledge financial support from Washington University in St. Louis and the Chemical and Environmental Analysis at Washington University in Saint Louis for the use of instruments and staff assistance. This research was partially funded by the DOE Office of Science, Office of Biological and Environmental Research under the Genomic Sciences Program (FWP ERKP752). Neutron scattering research conducted using the Bio-SANS instrument, a DOE Office of Science, Office of Biological and Environmental Research resource (FWP ERKP291), used resources at the High-Flux Isotope Reactor, a DOE Office of Science, Scientific User Facility operated by the Oak Ridge National Laboratory. This manuscript has been coauthored by UT-Battelle, LLC, under contract no. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript or allow others to do so for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). We acknowledge the Herman Frasch Foundation for Chemical Research in Agricultural Chemistry (801-HF17) and the U.S. National Science Foundation (CBET-1604095). We would also like to acknowledge financial support from Washington University in St. Louis and the Chemical and Environmental Analysis at Washington University in Saint Louis for the use of instruments and staff assistance. This research was partially funded by the DOE Office of Science, Office of Biological and Environmental Research under the Genomic Sciences Program (FWP ERKP752). Neutron scattering research conducted using the Bio-SANS instrument, a DOE Office of Science, Office of Biological and Environmental Research resource (FWP ERKP291), used resources at the High-Flux Isotope Reactor, a DOE Office of Science, Scientific User Facility operated by the Oak Ridge National Laboratory. This manuscript has been coauthored by UT-Battelle, LLC, under contract no. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript or allow others to do so for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ).
Keywords
- catalyst
- ex situ
- in situ
- lignin
- lignin aggregate
- quench
- size distribution
- small-angle neutron scattering