Effect of Light Gases in the Ethane/Ethylene Separation Using Zeolitic Imidazolate Frameworks

We use molecular simulations to study the adsorption of ethane and ethylene in zeolitic imidazolate frameworks. The separation of these two compounds is a crucial step in many industrial processes, most of them related to production of ethylene. Separation methods such as fractional cryogenic distillation require large energy consumption that increases the costs of ethylene production. Here, we analyze the suitability of zeolitic imidazolate frameworks for the separation of these gases on the basis of structural and chemical features. We pay special attention to the effect exerted by other gases on the adsorption and diffusion of ethane and ethylene in the structures. We found that nitrogen has an important role in the separation process and depending on the structure, it can enhance or hinder the adsorption selectivity for ethane. The presence of gases other than nitrogen also causes an effect on the ethane/ethylene separation. A mixture containing hydrogen, oxygen, methane, carbon monoxide, carbon dioxide, ethane, and ethylene in zeolitic imidazolate frameworks is also investigated. Our results identify ZIFs with rho, crg, and lta topologies as good candidates for the separation of ethane and ethylene.