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

This work studies the liquid-phase separation of the aliphatic C-5-diolefins, mono-olefins, and paraffins, a typical feed produced by a steam cracker, with a focus on the seldomly studied separation of the C-5-diolefin isomers isoprene, trans-piperylene, and cis-piperylene Three adsorbents are compared the metal-organic framework MIL-96, which is an aluminum 1,3,5-benzenetricarboxylate, and two zeolites with CHA and LTA topology All three materials have spacious cages that are accessible via narrow cage windows with a diameter of less than 0 5 nm The mechanisms determining adsorption selectivities on the various materials are investigated. Within the diolefin fraction, MIL-96 and chabazite preferentially adsorb trans-piperylene from a mixture containing all three C-5-diolefin isomers with high separation factors and a higher capacity compared to the reference zeolite 5A due to a more efficient packing of the trans isomer in the pores Additionally, chabazite is able to separate cis-piperylene and isoprene based on size exclusion of the branched isomer This makes chabazite suitable for separating all three diolefin isomers Its use in separating linear from branched mono-olefins and paraffins is addressed as well Furthermore, MIL-96 is the only material capable of separating all three diolefin isomers from C-5-mono-olefins and paraffins Finally, the MOF [Cu-3(BTC)(2)] (BTC = benzene-1,3,5-tricarboxylate) is shown to be able to separate C-5-olefins from paraffins On the basis of these observations, a flow scheme can be devised in which the C-5-fraction can be completely separated using a combination of MOFs and zeolites