New nanoporous materials with optimized pore structure in the olefin/paraffin separation by adsorption: Experimental and model-based Evaluation

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This project aims at investigating and evaluating promising nanoporous materials with respect to their applicability for the adsorptive separation of olefin/paraffin mixtures at industrial scale. The adsorbents considered have pore structures that lead to either kinetic, diffusion-controlled separation or to thermodynamic, adsorption-controlled separation of short-chain olefins and paraffins. Existing studies consider so far only materials that adsorb preferably the target product, which is the olefin. Unfortunately, this necessitates rather complex process concepts when attempting to produce olefins with high purity. Against this background, adsorbents with a reversed selectivity, like those developed in the earlier project phases, appear attractive. In the project, therefore, ZIFs are investigated (ZIF-3, -4, -6, -8), which not only were proven to preferably adsorb the paraffin, but for which also higher adsorption capacities were predicted than for standard materials like zeolite 13X. Another interesting option are materials with a kinetic selectivity for the olefin like, for example, the aluminophosphate SAPO-34 (CHA). While the olefin has a favorable diffusivity in this material, it is preferably adsorbed on polar and cationic porous material, which in turn reduces diffusivity. The paraffin exhibits stronger adsorptive interactions on nonpolar and cation-free materials. By a clever choice of adsorbent materials, these properties may allow new operating concepts for pressure swing adsorption (PSA) processes in which either the paraffin or the olefin is retained more strongly.The performance of industrial applications achievable by these materials is predicted using suitable mathematical models of PSA and VPSA (vacuum pressure swing adsorption) processes. The model parameters required are determined based upon a new multi-step methodology for efficient parameter estimation and scale-up. The approach combines fundamental sorption measurements with isothermal and adiabatic breakthrough experiments using single columns at different scales. Finally, PSA experiments both at laboratory as well as pilot scale will be performed in a proof-of-concept study.