High-purity ethylene separation: “three steps” reduced to “one step””

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Separation of high-purity ethylene: from “three steps” to “one step” Author/Source: Sinochem News Network Date: October 22, 2019 Clicks: 43 On October 11, a team led by Professor Chen Kaijie from the School of Science at Northwestern Polytechnical University published a research paper in Science, stating that they have, for the first time in the world, used three metal-organic framework (MOF) materials in combination for adsorption, thereby enabling the one-step separation and production of high-purity ethylene from a mixture of four gases. The high-purity production of ethylene plays a crucial role in the manufacture of basic chemical raw materials. However, traditional methods for ethylene separation are complicated and energy-intensive; the purification process involves three steps: using an alkaline tank to separate carbon dioxide; converting acetylene into ethylene or ethane with the help of precious metal catalysts under high temperature and pressure; and purifying and separating ethylene and ethane gases through fractional distillation, which takes advantage of the different boiling points of these components to control their sequential exit from the separation tower and subsequent collection. Such separation processes involve numerous steps, are costly, and require high energy consumption. Ethylene, acetylene, ethane, and carbon dioxide – these four gases often appear together in production. To achieve one-step separation and production of ethylene, it is necessary for specific porous MOF materials to selectively capture the other three gases at the same time, with only ethylene not being adsorbed, thereby allowing it to be isolated separately. The principle is very simple, but putting it into practice is by no means easy. Research by Chen Kaijie’s team has shown that by stacking three types of MOF materials within a single adsorption column, acetylene, ethane, and carbon dioxide can be removed efficiently in sequence, enabling the one-step separation and collection of high-purity ethylene at the end of the adsorption column. The “porous material” they use is a porous crystalline material with a three-dimensional ordered arrangement of atoms, formed by the bonding of metal ions and organic small molecules through coordination bonds. This physical adsorption separation process can be carried out at room temperature, and it **can reduce the energy consumption in ethylene separation processes; it provides a new design approach for the development of green, low-energy processes in complex industrial separation systems.