Boundary-Layer Effects on Carbon Dioxide Adsorption in 70% Polyethyleneimine-Loaded SBA-15 Under Ambient Concentrations

Author

• Madeline Fischer, Portland State UniversityFollow

Sponsor

Mechanical and Materials Engineering

First Advisor

Raul Bayoan Cal

Term of Graduation

Summer 2026

Date of Publication

8-13-2026

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Mechanical Engineering

Department

Mechanical and Materials Engineering

Language

English

Subjects

Boundary Layer, Carbon Dioxide Adsorption, Mass Transfer, Turbulence

Physical Description

1 online resource (xi, 106 pages)

Abstract

As carbon dioxide CO₂ emissions continue to increase due to fossil fuel combustion, the global mean temperature rises in tandem. Transitioning to renewable energy sources is one practical approach to reducing CO^₂ emissions. However, this strategy alone may not be sufficient to reduce atmospheric CO₂ levels and avoid catastrophic warming. Carbon capture, utilization, and storage (CCUS) and carbon dioxide removal (CDR) are useful strategies to use alongside energy decarbonization. Solid sorbents, specifically amine-based hybrid materials, are of particular interest because they can capture CO₂ from ultradilute gas streams. In this study, 70% polyethylenimine-loaded SBA-15 was recessed into an independently installed wind tunnel floor to allow for controlled boundary layer development. Near-surface CO₂ concentration was measured at four streamwise locations to assess the performance of the material at varying thicknesses and Reynolds numbers under ambient air conditions. Coupled ordinary differential equations that model diffusion and saturation behavior allow unknown material parameters to be estimated from experimental data. Particle image velocimetry (PIV) was performed on a statistically equivalent synthetic reconstruction of the material to characterize boundary-layer development under different flow conditions. The results of this study show that the bulk quantity of adsorbed CO₂ increases with material thickness. Additionally, the combined CO₂ and boundary layer analyses indicate that lower Reynolds stresses and a thicker viscous sublayer are associated with greater CO₂ adsorption. These findings provide a framework for linking the performance of a 70% polyethylenimine-loaded SBA-15 sorbent to flow conditions, which is necessary for predicting how the material may perform in practical direct air capture systems.

Rights

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Persistent Identifier

https://archives.pdx.edu/ds/psu/45120

Recommended Citation

Fischer, Madeline, "Boundary-Layer Effects on Carbon Dioxide Adsorption in 70% Polyethyleneimine-Loaded SBA-15 Under Ambient Concentrations" (2026). Dissertations and Theses. Paper 7191.