Chemical and Biological Engineering MS Thesis Defense by Zeynep Sümer

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KOÇ UNIVERSITY

GRADUATE SCHOOL OF SCIENCES & ENGINEERING

CHEMICAL AND BIOLOGICAL ENGINEERING

MS THESIS DEFENSE BY ZEYNEP SÜMER

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Title: Efficient Ranking of Metal Organic Framework Adsorbents and Membranes Using Molecular Simulations

Speaker: Zeynep Sümer

Time: July 25, 2017, 15:00

Place: ENG-120

Koç University

Rumeli Feneri Yolu

Sariyer, Istanbul

Thesis Committee Members:

Assoc. Prof. Seda Keskin Avcı (Advisor, Koc University)

Asst. Prof. Alper Uzun (Koc University)

Asst. Prof. İlknur Eruçar Fındıkçı (Özyeğin University)

Abstract:

Efficient ranking methods for promising metal organic framework (MOF) adsorbents and membranes were defined using molecular simulations. First, MOF adsorbents that can efficiently separate CO₂ from natural gas (CO₂/CH₄), power plant flue gas (CO₂/N₂) and petroleum refineries (CO₂/H₂) were investigated. Several adsorbent evaluation metrics including selectivity, working capacity, adsorption figure of merit, sorbent selection parameter, per cent regenerability were computed for 100 different MOFs and for each gas separation. Results showed that regenerability is a very important metric to screen the materials at the first step of the adsorbent search and MOFs can be then ranked based on their selectivities. In the second part of thesis, gas permeability and selectivity of 700 new mixed matrix membranes (MMMs) composed of 70 different MOFs and 10 different polymers were calculated for CO₂/N₂ separations. This was the largest number of MOF-based MMMs for which computational screening was done to date. Selecting the appropriate MOFs as filler particles in polymers resulted in MMMs that have higher CO₂/N₂ selectivities and higher CO₂ permeabilities compared to pure polymer membranes. It was found that for polymers that have low CO₂ permeabilities but high CO₂ selectivities, the identity of the MOF used as filler is not important. The outcome of adsorbent evaluation and membrane evaluation results were then applied for nitrogen separation from methane (CH₄/N₂). Combined adsorption and diffusion data obtained from molecular simulations were used to predict both membrane selectivities and gas permeabilities of 102 MOFs for separation of CH₄/N₂ mixtures. The relations between easily computable structural properties such as pore sizes, surface areas and porosities of MOFs and performance evaluation metrics were also examined to provide structure-property relationships that can serve as a guide for experimental studies.