PFI: AIR-TT: Ultrapure Lignins Recovered from Paper-Mill Black Liquors as Renewable Biopolymers

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This PFI: AIR Technology Translation project focuses on translating the invention of an environmentally friendly extraction process for producing ultrapure lignins to fill the need in society for inexpensive, renewable biopolymers. Lignin is one of the world's most abundant biopolymers (second only to cellulose), but is unique because of its aromatic nature, giving it special properties. With the invention of the Aqueous Lignin Purification with Hot Acids (ALPHA) process, lignins with very low levels of impurities and of controlled molecular weight (i.e., "ultra pure") can now be recovered from biomass by-product streams, such as the black liquor from paper mills. These ultrapure lignins have the potential to replace petroleum-derived, nonrenewable polymers in a wide variety of applications, including foams, coatings, and carbon fibers. Today, the so-called Kraft lignins available on the market have over 100 times the metals content of ultrapure lignins (i.e., 10,000 vs 100 ppm), with little or no control of molecular weight. In this project, ALPHA will be integrated with the Sequential Liquid-Lignin Recovery and Purification (SLRP) process of Lignin Enterprises to convert black liquor to Kraft lignin and then to ultrapure lignin. Both processes use renewable aqueous acetic acid (SLRP as an acidification reagent and ALPHA as an extractive solvent) and both are continuous processes, so overall costs will be minimized compared to the current batch technologies.This project addresses several technology gaps so as to translate ALPHA from discovery towards commercial application. First, the fundamentals of the conversion of the hydrated liquid-liquid phase formed in the SLRP process to raw Kraft lignin via aqueous acetic acid needs to be better understood, so that operating conditions can be optimized for integration with ALPHA. Second, the liquid-liquid extraction, mixing-and-settling setup for the ALPHA prototype needs to be designed and constructed so as to obtain the desired purities and molecular weights of ultrapure lignin in 2-3 stages. Third, the technical difficulties of integrating the ALPHA prototype with the existing prototype SLRP unit need to be addressed, the final objective for this project being the production of 10-20 kg/day of ultrapure lignin from a typical softwood or hardwood black liquor. Undergraduate, graduate and post-doc students will receive experience in both technology translation and the successful start-up of a small company through their interaction with Lignin Enterprises.