08 NovPhD DissertationSynthesis & Characterization of Quaternary Metal Chalcogenide Aerogels for Selective Gass Seperation & Volatile Hydrocarbons
Synthesis & Characterization of Quaternary Metal Chalcogenide Aerogels for Selective Gass Seperation & Volatile Hydrocarbons
  • Fatimah Edhaim
  • KAUST, PhD Student, Supervised by Prof. Alexander Rothernberger
  • Wednesday, November 08, 2017
  • 01:30 PM - 03:00 PM
  • Building 5, Level 5, Room 5209
2017-11-08T13:302017-11-08T15:00Asia/RiyadhSynthesis & Characterization of Quaternary Metal Chalcogenide Aerogels for Selective Gass Seperation & Volatile Hydrocarbons ChemS PhD DissertationBuilding 5, Level 5, Room 5209Linda J. Sapolu

Abstract: 

The separation of hydrocarbons with similar boiling points using conventional methods is a challenge. Due to the negative environmental impact of volatile organic compounds (VOCs), the development of alternative separation processes is currently being investigated. In this dissertation, the adsorption of volatile hydrocarbons using aerogels made from metal chalcogenides (chalcogels) was investigated. Such chalcogels are porous inorganic materials in which​ nanosized building blocks are interconnected to yield a polymeric network comprising high surface area, large pore size distribution, surface polarizability, and chemical selectivity.

In this context, three high BET surface area chalcogels AFe3Zn3S17 (A= K, Na, and Rb) were synthesized and the effect of the presence of different counter-ion within chalcogel frameworks on the adsorption capacity of the chalcogels was studied.

​Exploring a new chalcogel family containing the rare earth elements (Y, Gd, and Tb) and thiostannate building blocks {SnS4]-4 was a subject of interest. The incorporation of such elements results yields thermally stable, high surface area chalcogels. The notable adsorption capacity for toluene (NaYSnS4: 12.36 mmol/g), (NaGdSnS4: 9.76 mmol/g) and (NaTbSnS4: 6.90 mmol/g) and high selectivity for gases NaYSnS4 (CO2/H2: 172 and CO2/CH4: 50), NaGdSnS4 (CO2/H2: 155 and CO2/CH4: 37) and NaTbSnS4 (CO2/H2: 75 and CO2/CH4: 28) indicate potential future use of chalcogels in absorption-based gas or hydrocarbon separation processes. The resulting chalcogels have also been engaged in the absorption of different organic molecules, i.e., inert, electron acceptor or electron donor molecules. The results reveal the ability of the chalcogels to distinguish among these molecules based on their electronic structures; hence, they could be used for different applications such as optical devices or sensors. These materials demonstrate excellent adsorption selectivity for volatile hydrocarbons and gases.

The synthesis of metal chalcogenide aerogels Co0.5Sb0.33MoS4 and Co0.5Y0.33MoS4 by the sol-gel method was also reported. In this system, the building blocks [MoS4]2- chelated with Co2+ and (Sb3+) or (Y3+) salts in nonaqueous solvents forming amorphous networks with a gel property. The chalcogels obtained after supercritical drying have high BET surface areas, and showed higher adsorption capacity of toluene vapor (Co0.5Sb0.33MoS4: 4.2 mmol g-1) and (Co0.5Y0.33MoS4: 3.3 mmol g-1) over cyclohexane vapor and high selectivity of CO2 over CH4 or H2, Co0.5Sb0.33MoS4 (CO2/H2: 80 and CO2/CH4: 21), Co0.5Y0.33MoS4 (CO2/H2: 27 and CO2/CH4: 15). The uptake capacity and selectivity of toluene and CO2 adsorption of Co0.5Sb0.33MoS4 chalcogel were significantly enhanced by the post-synthetic modifications of various metal species like Ni2+, Li+, and Mg2+.

These results open up new prospects for the metal chalcogenide aerogels for effective use in hydrocarbon separation or purification and selective gas separations.​

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  • Linda J. Sapolu

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