CBE Seminar - Jennifer Wilcox

Jennifer Wilcox

Assistant Professor
Department of Energy Resources Engineering
Stanford University

Tuesday, November 24th, 2015 11:30 AM
130 Koffolt Lab, CBEC 151 W. Woodruff Ave
Reception at 11:00 CBEC Lobby

Carbon Capture Using Adsorption and Membrane Processes

Abstract

The scale by which CO₂ must be mitigated worldwide dwarfs the existing chemical industry, making utilization of CO₂ as a chemical feedstock a minor component of the portfolio of mitigation options. Carbon capture and storage is one strategy that could potentially mitigate gigatons of CO₂ emissions per year, provided geological storage of CO₂ is feasible. The scale and energy requirements associated with CO₂ separation processes will be presented. Strategies based upon adsorption and catalytic membrane separation processes in particular, will be of focus. Regeneration of CO₂ is known to be a significant component of sorption-based separation processes and is absent when using membrane technologies. Nitrogen-selective membranes will be introduced. Kinetics of separation is also a challenge due to the scale of CO₂ emissions from a given power plant. Adsorbents will also be introduced with focus on mass-transfer kinetics.

Adsorption-based technologies for CO₂ capture have several advantages over traditional amine-based solvent absorption approaches. For instance, within an adsorption-based approach water is absent, which decreases the energy requirements associated with regeneration since heating a large amount of water is a significant energy expense. The heat of regeneration of a solvent-based separation process is CpΔT + ΔH, such that Cp is the heat capacity of the solvent and ΔH is the heat of reaction required for breaking the chemical bond between CO₂ and the chemical species (e.g., amine) responsible for capturing CO₂. The heat capacity of water is 4.18 J/gK, while that of sorbents is on the order of 1 J/gK. Another benefit of using solid sorbents is the ability to tune the structural parameters of the material, as well as perform chemical modifications to enhance CO₂ uptake.  In addition, materials such as carbon possess favorable heat conduction properties.

In addition to adsorption investigations, metallic membrane materials for selective N₂ separation for carbon capture will also be presented. This work involves the adsorption, dissociation, and sub-surface diffusion of N₂ in Group V-based metals, including vanadium, niobium, and their alloys with ruthenium. The electronic structure of the metal can be tuned based upon alloying, thereby enhancing N₂ permeability. Experimental N₂ flux measurements have been carried out to validate the theoretical predictions.

Bio

Jennifer Wilcox has been an Assistant Professor in the Department of Energy Resources Engineering at Stanford University since 2008. Her Ph.D. in Chemical Engineering in 2004 is from the University of Arizona, and her B.A. in Mathematics in 1998 is from Wellesley College. She received an ARO Young Investigator Award (Membrane Design for Optimal Hydrogen Separation), an ACS PRF Young Investigator Award (Heterogeneous Kinetics of Mercury in Combustion Flue Gas), and an NSF CAREER Award (Arsenic and Selenium Speciation in Combustion Flue Gas). Within her research group, she focuses on trace metal and CO₂ capture. Her research involves the coupling of theory to experiment to test newly designed materials for sorbent or catalytic potential. She has served on a number of committees including the National Academy of Sciences and the American Physical Society to assess CO₂ capture methods and impacts on climate. She is the author of the first textbook on Carbon Capture, published in March 2012.