Separation of C5-Hydrocarbons on Microporous Materials: Complementary Performance of MOFs and Zeolites

摘要

Abstract: This work studies the liquid-phase separation of the aliphatic C5-diolefins, mono-olefins, andnparaffins, a typical feed produced by a steam cracker, with a focus on the seldomly studied separation ofnthe C5-diolefin isomers isoprene, trans-piperylene, and cis-piperylene. Three adsorbents are compared:nthe metal organic framework MIL-96, which is an aluminum 1,3,5-benzenetricarboxylate, and two zeolitesnwith CHA and LTA topology. All three materials have spacious cages that are accessible via narrow cagenwindows with a diameter of less than 0.5 nm. The mechanisms determining adsorption selectivities on thenvarious materials are investigated. Within the diolefin fraction, MIL-96 and chabazite preferentially adsorbntrans-piperylene from a mixture containing all three C5-diolefin isomers with high separation factors and anhigher capacity compared to the reference zeolite 5A due to a more efficient packing of the trans isomernin the pores. Additionally, chabazite is able to separate cis-piperylene and isoprene based on size exclusionnof the branched isomer. This makes chabazite suitable for separating all three diolefin isomers. Its use innseparating linear from branched mono-olefins and paraffins is addressed as well. Furthermore, MIL-96 isnthe only material capable of separating all three diolefin isomers from C5-mono-olefins and paraffins. Finally,nthe MOF [Cu3(BTC)2] (BTC benzene-1,3,5-tricarboxylate) is shown to be able to separate C5-olefinsnfrom paraffins. On the basis of these observations, a flow scheme can be devised in which the C5-fractionncan be completely separated using a combination of MOFs and zeolites.