Frontiers in Chemical Engineering
Upcycling of Plastic Waste into Lubricants
Abstract: In my previous talk, I discussed the upcycling of plastic waste into high-value, high-market-volume surfactants. In a parallel direction, lubricants represent another compelling target for waste-plastic valorization because they also combine high market volume with high product value. This talk will describe our ongoing work, developed over the past several months, to convert commodity plastic waste into polyalphaolefin (PAO) lubricants and, more broadly, to transform discarded polymers into performance materials.
A central theme is that different waste plastics can play complementary roles in building this platform. We first show that polyvinyl chloride (PVC) serves as an effective model system for demonstrating that plastic waste can be converted into high-performance PAO-like lubricants. Using Lewis acids at mild temperatures, PVC undergoes dechlorination, alkylation, and chain scission, producing chlorine-free vinyl-derived polyalphaolefins (vPAO). PVC serves as an effective template for alkylation of α-olefins of various chain lengths, producing vPAO with limited short branches in the backbone without the need for metallocene catalysts essential for high-performance PAO. We then build on that concept by turning to polyolefins as a low-cost source of the α-olefin intermediates needed for PAO synthesis. Using temperature-gradient thermolysis (TGT), polyethylene waste can be selectively deconstructed into lubricant-relevant α-olefins, which are subsequently upgraded into PAOs with promising properties. Together, these studies outline a modular pathway in which one waste stream helps define the product platform and another helps supply the molecular feedstocks needed to make it more practical and scalable. More broadly, this work illustrates how plastic waste can be reimagined not simply as an end-of-life problem, but as a versatile carbon resource for high-value chemical manufacturing.
Bio: Liu earned a bachelor's degree in chemical engineering from Zhejiang University (China) in 2005. After completing his doctorate in 2011, he conducted postdoctoral research at Northwestern University, where he was named an Outstanding Researcher in the International Institute for Nanotechnology. He joined the Department of Chemistry at Virginia Tech in Fall 2014. He is affiliated with the Department of Chemical Engineering and the Department of Materials Science and Engineering. Liu holds about twenty patents. Among them, over ten are licensed or assigned to companies, including Intel®, Western Digital®, Ford Motor Company, SABIC, and Waves Audio (Israel). Liu has been named an Inventor of the Month at Virginia Tech. Liu is a recipient of the VT Junior Faculty Award, NSF CAREER award, Air Force Young Investigator Program (YIP) Award, ACS PRF Doctoral New Investigator (DNI) award, ACS PMSE Young Investigator award, John C. Schug Research Award, and CAPA Distinguished Professor Award. He is also named Young Talent or Emerging Investigator of a number of journals, including Macromolecular Rapid Communications, Polymer Chemistry, Journal of Materials Chemistry, Molecular Systems Design & Engineering, and ACS Applied Polymer Materials. He chairs the Blackwood Jr. Faculty Fellow of the College of Science at Virginia Tech. He is inducted into the National Academy of Inventors as a Senior Elite Member.