Degree Type
Dissertation
Date of Award
2017
Degree Name
Doctor of Philosophy
Department
Mechanical Engineering
Major
Biorenewable Resources and Technology
First Advisor
Robert C. Brown
Abstract
ABSTRACT
Technical lignin, the byproduct from cellulosic ethanol production, is a potential feedstock for producing coumaric and ferulic acids. These biorenewable aromatic hydroxycinnamic acids can be upgraded to high value chemicals for the manufacture of cosmetics, flavoring agents, and sunscreens. We hypothesize that during the fast pyrolysis of lignin, aromatic acid esters can be recovered from coumaric, ferulic and other hydroxycinnamic acids using a methylation agent. In this study, technical lignin from cellulosic ethanol production was pyrolyzed in a micropyrolyzer with a methylation agent to produce gas chromatography (GC) detectable aromatic acid esters. Corn stover lignins from enzymatic hydrolysis and the organosolv processing were combined with different methylation agents to produce, identify and quantify the hydroxycinnamic acid esters. High performance liquid chromatography (HPLC) with a diode array detector (DAD) was used to separate and quantify the extracted hydroxycinnamic acids from lignin for determination of yield recoveries.
To determine the actual total extractable yields of coumaric and ferulic acid in the lignin an alkaline extraction method was used. The yields on a mass basis of coumaric and ferulic acid in the enzymatic hydrolysis lignin was 5.6% and 1.9%, respectively. The yields on a mass basis of coumaric and ferulic acid in the organosolv lignin was 7.7% and 2.9%, respectively.
The recovery of hydroxycinnamic acids from enzymatic hydrolysis and organosolv lignin with different loading of methylation agent were compared using a micropyrolyzer at 500ÃÂðC and the pyrolysis cup method. Using tetramethylammonium hydroxide (TMAH) or tetra-methyl carbonate of pentaerythritol (PEMC) at concentrations of 1ÃÂõL – 10ÃÂõL produced high yields of coumaric and ferulic acid that can be recovered at concentrations up to 89% and 97%, respectively.
The recovery of hydroxycinnamic acids from enzymatic hydrolysis and organosolv lignin with different loading of methylation agent were compared using a micropyrolyzer at 500ÃÂðC and the micro reaction method. Using tetramethylammonium hydroxide (TMAH) or tetra-methyl carbonate of pentaerythritol (PEMC) at concentrations of 1ÃÂõL – 10ÃÂõL produced high yields of coumaric and ferulic acid that can be recovered at concentrations up to 97% and 90%, respectively.
Overall, both techniques and methylation agents produced a significantly high concentration of biorenewable chemical intermediates from the lignin byproduct of corn stover cellulosic ethanol production. The hydroxycinnamic acids that are produced can be further upgraded into high value chemical products. Utilizing lignin valorization could provide a substantial effect on the economics of cellulosic ethanol production via precursors or intermediates of high value commodity chemicals.
DOI
https://doi.org/10.31274/etd-180810-5161
Copyright Owner
Patrick Allan Johnston
Copyright Date
2017
Language
en
File Format
application/pdf
File Size
101 pages
Recommended Citation
Johnston, Patrick Allan, "Thermochemical methylation of lignin to produce high value aromatic compounds" (2017). Graduate Theses and Dissertations. 15544.
https://lib.dr.iastate.edu/etd/15544
