Purification of Stock and Alkaline Lignin
Author: Collin Larsen | Major: Chemical Engineering | Semester: Fall 2022
Over the 2022 fall grant term, I worked alongside my honors research mentor, Dr. Keisha Walters of the Department of Chemical Engineering, and graduate research mentor, David Chem, on modifying Lignin structures to be more suitable for copolymerization. The overall goal of this research project is to examine the use of lignin as a copolymer component to form a green (bio-based and biodegradable) plastic to serve as a commercially viable alternative to commonly used petroleum-based, non-degradable plastics, such as those used for single-use packaging films. Lignin, which has little to no value, is a waste product generated from agricultural processes. Lignin will be utilized in conjunction with recycled plastics to form a new biodegradable copolymer—reducing the amount of waste and virgin feedstock and producing a method for reducing environmental contamination from plastics. Not only are there massive potential environmental advantages to this research but it can reinforce the economic strength of plastic upcycling and agricultural processes that produce lignin, economically incentivizing environmentally friendly practices.
I chose my topic because, if successful, the research could lead to a new generation of plastics that are safer for the environment and improve the financial motivation to participate in green practices. My main goal is to become a material engineer that creates novel materials (with an additional focus on polymers) that increase our overall sustainability. I am also heavily interested in nanotechnology — specifically material analysis and nanoparticles, making my project a perfect fit. My mentor’s research lab, Polymer and Nanomaterial Engineering Lab (or PolyNEL), perfectly merges these two passions and I’ve gotten to learn a lot about material science from this opportunity. I found my mentor while searching for research projects that also fell into my nanotechnology minor. After meeting with Dr. Leftwich from material science, He pointed me in the direction of Dr. Walters because of my interests in chemical engineering and nanotechnology.
In the first phase of the project, we investigated purifying and functionalizing Lignin from multiple sources. Along the way, I’ve learned how to perform multiple reactions to functionalize Lignin such as amination and esterification. David Chem was instrumental in teaching me the necessary laboratory techniques to succeed. One of the challenges of working with lignin is the differences between the sources of the Lignin, the alkali lignin exhibits a much more basic pH than the organosolv and typically creates a much darker solution than the organosolv.
In the second phase of the project, we used Purified Alkaline Lignin for use as a macroinitiator for copolymerization with styrene to create a Lignin-Styrene copolymer. Even though the grant is ending, we plan to continue experimenting by testing various modified lignin-olefin copolymers. The mechanical, chemical, and thermal properties of the resultant material will then be analyzed with Differential Mechanical Analysis (DMA), Fourier transform infrared spectroscopy (FTIR), and Differential Scanning Calorimetry (DSC). The modification of the Lignin-Olefin copolymer will be focused on creating a linear structure.
Through our research, we have successfully performed several functional group modifications of lignin, such as esterification and amination. One issue we ran into is that our purposed synthesis method of lignin grafted to polyethylene and polypropylene, common plastic film materials, requires more precautions to be safe. Currently, we are working on reviewing procedures and developing alternative methods to overcome this. In the meantime, we have successfully synthesized a copolymer of lignin-grafted-polystyrene (L-g-PS). Next, we plan to synthesize these polymers with the modified lignin and compare their properties.
In the future, I also plan to begin work on a related project using A.I. to predict lignin-based copolymer properties. This has reignited my interest in computer science as the experimental computer science and computational chemistry path offer the ability to combine all my passions. After I graduate, I intend to go into material science as a researcher and developer or go to graduate school for computer science to enhance my computational chemistry ability.