Chemical and Biological Engineering MS Thesis Defence by Muhammad Anas

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KOÇ UNIVERSITY

GRADUATE SCHOOL OF SCIENCES & ENGINEERING

CHEMICAL AND BIOLOGICAL ENGINEERING

MS THESIS DEFENSE BY MUHAMMAD ANAS

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Title: Investigation of the Thermodynamics of Carbon Dioxide and Methane Adsorption on Various Aerogels

Speaker: Muhammad Anas

Time: June 16, 2017, 10:00

Place: ENG-208

Koç University

Rumeli Feneri Yolu

Sariyer, Istanbul

Thesis Committee Members:

Prof. Can Erkey (Advisor, Koc University)

Assoc. Prof. Seda Keskin (Koc University)

Assoc. Prof. Ayşe Bayrakçeken Yurtcan (Ataturk University)

Abstract:

Thermodynamics of carbon dioxide and methane adsorption on various aerogels was investigated to evaluate their potential as adsorbents for carbon dioxide capture and methane storage. Excess CO₂ and CH₄ adsorption isotherms on aerogels such as silica, resorcinol-formaldehyde, carbon and wheat starch were measured using a volumetric method in the temperature range of 298-328 K and pressures up to 120 bar. Total or absolute adsorption isotherms were calculated from experimentally obtained excess adsorption isotherms using the pore volume of each adsorbent. It was determined that silica aerogel had maximum absolute CO₂ uptake of 14 mmol/g at 308 K and 35 bar and resorcinol-formaldehyde aerogel (RFA-17) had maximum absolute CH₄ uptake of 22 mmol/g at 298 K and 100 bar. CO₂ adsorption isotherms for silica, resorcinol-formaldehyde and wheat starch aerogels and CH₄ adsorption isotherms for silica aerogel were well represented with the Langmuir model. CO₂ isotherms for carbon aerogel and CH₄ isotherms for carbon and resorcinol-formaldehyde aerogels were fitted with the Freundlich model. It was also found that the excess CO₂ uptake correlated well with the mesopore surface area of each aerogel at various pressures while micropore surface area significantly influenced CH₄ uptake in aerogels. The isosteric heat of adorption for each aerogel was also determined from the variation of pressure with temperature at a constant excess uptake and was found to be dependent on the surface coverage. Among all aerogels, wheat starch aerogel had highest heats of CO₂ adsorption and resorcinol-formaldehyde aerogel had highest heats of CH₄ adsorption. Kinetics of volumetric adsorption process was also explored to understand the mechanism of adsorption. Adsorption capacities of aerogels determined in this study are found to be comparable with other classes of adsorbents and presents an opportunity for further investigation of aerogels as potential materials for applications in carbon dioxide capture and methane storage.