Metal–Organic Framework Materials for the Separation and Purification of Light Hydrocarbons

Abstract

The separation and purification of light hydrocarbons (LHs) mixtures is one of the most significantly important but energy demanding processes in the petrochemical industry. As an alternative technology to energy intensive traditional separation methods, such as distillation, absorption, extraction, etc., adsorptive separation using selective solid adsorbents could potentially not only lower energy cost but also offer higher efficiency. The need to develop solid materials for the efficiently selective adsorption of LHs molecules, under mild conditions, is therefore of paramount importance and urgency. Metal–organic frameworks (MOFs), emerging as a relatively new class of porous organic–inorganic hybrid materials, have shown promise for addressing this challenging task due to their unparalleled features. Herein, recent advances of using MOFs as separating agents for the separation and purification of LHs, including the purification of CH4, and the separations of alkynes/alkenes, alkanes/alkenes, C5–C6–C7 normal/isoalkanes, and C8 alkylaromatics, are summarized. The relationships among the structural and compositional features of the newly synthesized MOF materials and their separation properties and mechanisms are highlighted. Finally, the existing challenges and possible research directions related to the further exploration of porous MOFs in this very active field are also discussed.

Light Hydrocarbon Separations Using Porous Organic Framework Materials

“…Thisv ariation is an advantage in cryogenic distillation, ap rocess in which the boilingp oint difference between target molecules needs to be as large as possible. In addition, the greater molecular weights and polarizability of alkanes can potentially enhancea dsorption onto adsorbent materials through stronger van der Waals interactions.H owever,t he landscape is very different for unsaturated C 2…”

“…Currently, the industrial separation of C 2 H 4 from C 2 H 6 is usually achieved through cryogenic distillation, but because this purification method is energy‐ and cost‐intensive, the development of a more efficient approach is highly desired, particularly within the petrochemical industry. Adsorptive separation is considered as a potential solution to the challenges of C 2 H 4 /C 2 H 6 and C 2 H 2 /C 2 H 4 separations, and porous materials such as zeolites and MOFs have been studied to this end . These materials are promising adsorbents for such separations due to their highly ordered structures, which facilitate the adsorption and transport of guest molecules, and their exposed metal centers that allow them to polarize or bind guest molecules.…”

“…Light hydrocarbons (C 1 –C 3 ) are vital to the global energy sector, particularly to the natural gas and petrochemical industries . The crude mixtures generated from raw materials generally contain saturated and unsaturated hydrocarbons of various lengths, and large amounts of energy are spent separating these components to yield the valuable single‐component products.…”

“…Due to intensifying environmental pollution and global energy demands, it is extremely desirable to develop more efficient and economical separation methods for light hydrocarbons. Adsorptive separation using solid adsorbents is a promising alternative to traditional separation methods and has received tremendous attention due to its lower energy cost and higher efficiency . The development of high‐performance solid adsorbents is crucial to the realization of this alternative approach.…”

“…Light hydrocarbons (C 1 -C 3 )a re vital to the globale nergy sector,p articularly to the natural gas and petrochemical industries. [1][2][3][4][5] The crude mixtures generated from raw materials generally contain saturated and unsaturated hydrocarbons of various lengths, and large amounts of energy are spent separating these components to yield the valuable single-component products.C urrently,t he upgrading and purification of light hydrocarbonsi sa chieved by cryogenic distillation, extraction, and partial hydrogenation, which are highly energy-and costintensive. [6][7][8][9] For example, the purification and separation of ethylene and propylene accounts for 0.3 %o ft otal worldwide energy consumption annually.…”