Understanding Catalyst Properties and the Formation of Deactivating Surface Species During the Cracking of Lignin Monomers

Thumbnail Image
Files
STELLATO-DISSERTATION-2021.pdf (3.19 MB)
Author(s)
Stellato, Michael John
Advisor(s)
Editor(s)
Associated Organization(s)
Organizational Unit
School of Chemical and Biomolecular Engineering
School established in 1901 as the School of Chemical Engineering; in 2003, renamed School of Chemical and Biomolecular Engineering
Organizational Unit
Series
Series
Collections
Theses and Dissertations
Supplementary to:
Permanent Link
http://hdl.handle.net/1853/66486
Abstract
Recent research has proven that 30-40% of aromatic rings in lignin are accessible by catalytic fractionation. The resulting lignols can be further upgraded into drop-in replacement chemicals for many petroleum-based aromatics by cracking off the three-carbon sidechain over solid acids. The aim of this thesis is to fully explore the acid properties of potential catalysts and to understand the types of surface species that form during the cracking reaction that cause deactivation. Using FTIR spectroscopy, the molar extinction coefficient of pyridine bound to more than 40 solid acid catalysts is calculated. Significant differences in the extinction coefficient between materials are observed and this value is heavily influenced by the presence of surface ions. For example, sodium exchanged zeolites showed an order of magnitude difference in the extinction coefficient of pyridine bound on both Bronsted and Lewis acid sites. It has been reported in literature that water significantly reduces catalyst deactivation during the cracking of 4-propylphenol over a ZSM5 zeolite. Post reaction characterization of the ZSM5 showed that traditional causes for deactivation, such as polyaromatic coke formation, are not to blame. Investigations using NMR, FTIR, and Raman spectroscopy indicated that the catalyst surface is primarily occupied by substituted aromatic rings bound through the phenolic oxygen. These species form roadblocks in the channels of the zeolite and cause fast deactivation of the catalyst. The activity of this reaction is then tested on a novel delaminated MCM22 zeolite to improve accessibility and limit the influence of roadblocks. Traditionally, MCM22 is delaminated using complex synthesis techniques which are expensive and destroy active sites. By instead treating the laminate structure in a ball mill, acid site concentrations are preserved while partially delaminating the structure. These ball-milled zeolites showed slower deactivation than the untreated zeolites and higher activity than the fully delaminated structure. This shows that some pore confinement is necessary for the cracking reaction, while also proving the viability of delaminating zeolites in a ball mill.
Sponsor
Date
2021-05-01
Extent
Resource Type
Text
Resource Subtype
Dissertation
Rights Statement
Rights URI