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Ethylene is a major building block used in the chemical industry to produce a wide variety of important chemicals. The increasing availability of shale gas has boosted the ethylene industry as several ethylene production plants have been planned to be built in the United States [5]. The alternatives to produce ethylene include processes that use NGLs as feedstock, such as ethane cracking or propane dehydrogenation [25], and processes that transform methane to ethylene [26,27]. Among the processes that convert methane to ethylene, two important options are the oxidative coupling of methane (OCM) and the methanol to olefins (MTO) technology. OCM is a direct process in which methane and oxygen are fed to a catalytic reactor, with the products of the reaction being separated in a purification stage that consists of the removal of water and CO₂ and a cryogenic distillation train [26]. Although this process is known for the low yield achieved in the reactor, which render a process option with low profitability, the development of new catalyst structures has made possible the construction of demonstration facilities for this technology that offer better economic perspectives [28].

The other alternative for ethylene production is MTO, which is a more complex process as it involves several stages. First, the reforming of natural gas and the production of methanol take place. After the methanol synthesis, the crude methanol is sent to a catalytic reactor where low‐weight olefins are produced. In the reactor a variety of components are produced, such as ethylene and propylene, butylene, C₅s, hydrogen, low‐weight hydrocarbons, water, and CO₂. The effluent of the reactor is then sent to separation and purification units, which start with CO₂ removal and dehydration units. Then, the remaining stream is sent to a distillation train consisting of demethanizer, deethanizer, and depropanizer columns, as well as C₂ and C₃ splitters. A column to separate C₄s and C₅s is also needed. The overall process is very energy intensive, as it involves a reforming stage and a large distillation train.

Even when the MTO technology has been reported to be more profitable than the OCM option [26], the latter technology is less complex and avoids the need to transform the natural gas to intermediate products such as syngas. That provides an incentive to develop improvements to this technology in order to enhance its overall performance and profitability. Proposed ideas to achieve such improvements include the use of membranes in the CO₂ separation system and modifications to the ethylene fractionation column to reduce heating and condenser duties [29,30].