Natural Gas Purification Using Metal-Organic Frameworks (MOFs)
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Of all fossil energy sources, natural gas has exhibited the strongest worldwide growth. Global demand for the fuel has increased at a rate of 3% per year over the past thirty years, and is predicted to account for nearly 23% of the global energy supply by 2030. Consequently, the efficient and cost-effective purification of hydrocarbons in natural gas reserves is becoming increasingly important for the petroleum industry. About 40% of extraction fields possess appreciable levels of hydrogen sulfide (H2S): a toxic and corrosive acid gas that must be removed to preserve the environmental and economic viability of the fuel. Mixtures of H2S with well-head hydrocarbons are known as “sour gas”, and they must be remediated prior to downstream processing. Unfortunately, current purification schemes entail either gas flaring into the atmosphere or heavily energy intensive separation schemes. These activities subsequently carry both economical and environmental concerns. Engineering selective adsorption media to facilitate the removal of H2S from sour gas can be a promising alternative natural gas refinement operation. The selective adsorption of H2S over carbon dioxide, methane, and other common sour gas constitutients is pursued in this thesis work through the modular chemistry offered by a class of nanoporous materials known as metal-organic frameworks (MOFs). MOF synthesis allows for users to carefully construct these highly porous and stable frameworks to contain a myriad of chemical functional groups and reaction sites, such that specific separations can be targeted through careful selection of the two (1) organic and (2) metallic MOF precursors utilized. This “designer chemistry” at the nanoscale will be utilized to construct and test a variety of tailor-made MOFs for sour gas purification applications. Constructed adsorbents will be evaluated in a fixed-bed adsorption column, simulating sour gas mixtures that are representative of actual well-head compositions in the United States. By utilizing the atomic-level adsorbent control afforded through MOF construction, stable and highly effective H2S adsorbents are sought to be produced through this work, in an effort to help sustain ecological and cost-effective improvements in global energy.