Multi-Component Separation and Purification of Natural Gas

Over the past decade, several technical developments (such as hydraulic fracturing) have led to an exponential increase in discovering new domestic natural gas reserves. Raw natural gas composition can vary substantially from source to source. Typically, methane accounts for 75% to 95% of the total gas, with the rest of the gas containing ethane, propane, butane, other higher hydrocarbons, and impurities, with the most common including H2O, CO2, N2, and H2S. All natural gas requires some treatment, if only to remove H2O; however, the composition of natural gas delivered to the commercial pipeline grids is tightly controlled. Sub-quality natural gas reserves, which are defined as fields containing more than 2% CO2, 4% N2, or 4 ppm H2S, make up nearly half of the world’s natural gas volume. The development of sub-quality, remote, and unconventional fields (i.e. landfill gas) can present new challenges to gas separation and purification methods. Adsorbent technologies, such as the use of activated carbons, zeolites, or metal-organic frameworks (MOFs), may hold the key to more efficient and economically viable separation methods. This work proposes to prove the applicability of the multi-component potential theory of adsorption (MPTA) to a real world natural gas adsorbent system to properly characterize the adsorbent’s selectivity for an individual gas component using only the single component isotherms. Thus, the real-world gas separation/purification application of a specific adsorbent for a given gas stream can be obtained simply and effectively without the need for large experimental efforts or costly system modifications until after an initial computational screening of perspective materials has been completed. While the current research effort will use natural gas, which is the world’s largest industrial gas separations application, to validate the MPTA, the tools gained through this effort can be applied to other gas separation effort.