Sasha Neefe

Student: Sasha Neefe

Project: Reevaluating Green Solvent Metrics Using End-of-Life Considerations

View: Research Poster (PDF)

Institution: Lafayette College

Major: Chemical Engineering

Advisor: Lindsay Soh

Abstract

Virgin solvent production is energetically demanding, and along with solvent disposal often has adverse environmental effects. Efficiently processing solvent waste from chemical processes is crucial to minimizing energy use and environmental impacts. Two common options for end-of-life processing include 1) incineration, allowing for energetic solvent reuse but emitting toxins and requiring further solvent production,[1] and 2) solvent purification and recycling, which requires potentially energetically demanding separations but minimizes fresh solvent use.[1] Solvent selection guides provide environmental ratings for a wide range of solvents, but the only widely-used solvent recyclability metric is boiling temperature, implicating distillation heat-duty.[2] However, a full process design analysis determining the viability of solvent recycling is extensive.[3] The goal of this theoretical research is to determine a simple but robust metric utilizing thermophysical properties to better evaluate the end-of-life considerations for solvents, creating more sustainable chemical processes.

Water and isopropanol were chosen as polar and non-polar protic reference-solvents to compose binary mixtures with 100+ additional solvents. Solvent recovery via distillation was analyzed using King’s Equation and assumptions of ideality and constant relative volatility were evaluated using McCabe-Thiele analyses. The minimum pump energy to separate organic liquids via nanofiltration is estimated using dense-membrane solution diffusion correlations and investigating molecular size limitations. It was determined that distillation energy demands increase as boiling point differentials approach zero. Preferable solvent-mixture end-of-life pathways will be suggested utilizing minimum energy demands through comparing the production energy offset from a) incinerating or b) recycling via i) distillation or ii) organic solvent nanofiltration.

References:

1. Constable, David J. C. “Perspective on Solvent Use in the Pharma Industry.” Organic Process Research & Development 11 (2007): 133–37.
2. Alder, Catherine M. “Updating and Further Expanding GSK’s Solvent Sustainability Guide.” Green Chemistry, 2016. https://doi.org/10.1039/c6gc00611f.
3. Gani, Rafiqul. “A Systematic Approach to Green Solvent Selection, Design, and Verification.” In The Application of Green Solvents in Separation Processes. Elsevier Inc., 2017.