3D-printed structured adsorbents for molecular separation
March 5-10, 2017
Most adsorbents are produced as porous, micron-sized powder materials and are thus not suitable to be directly used in adsorption processes. In order to avoid excessive pressure drop during flow of gas or liquid streams through a packed bed of adsorbent, these powders are shaped into larger particles or structured adsorbents. Extrudates, beads or pellets with a size of several millimeters are widely used in industrial processes. The most important disadvantages of such particles include the relatively large pressure drop they generate at high flow rates and the presence of mass transfer limitations as a result of slow diffusion of molecules to the core of the particles. A trade-off between these two effects limits the possibilities to optimize packed bed adsorptive separation processes; e.g. decreasing pellet size allows to reduce mass transfer limitations but this in turn leads to larger pressure drops. In practice, bed geometry (length/width of the packed bed) is adapted to limit pressure drop. Nevertheless, classical packed beds are not ideal for processes in which very short cycle times or very high gas or liquid velocities are required.
Other types of adsorbent formulation that allow eliminating the limitations mentioned above are thus of large interest. Monolithic adsorbents are superior to classical packed bed adsorbents in terms of pressure drop and mass transfer kinetics. The honeycomb structure, mostly known from catalytic exhaust treatment in the automotive industry, is a well-known example, but monolithic structures are also used in liquid chromatography and heterogeneous catalysis. Nevertheless, the production of monoliths is complicated; classical extrusion processes only offer a very limited flexibility in the geometric properties of the monolith while polymerization processes are not suited for the production of materials for high temperature applications.
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Sarah Couck, Jasper Lefevere, Steven Mullens, and Joeri F.M. Denayer, "3D-printed structured adsorbents for molecular separation" in "Separations Technology IX: New Frontiers in Media, Techniques, and Technologies", Kamalesh K. Sirkar, New Jersey Institute of Technology, USA Steven M. Crame, Rensselaer Polytechnic Institute, USA João G. Crespo, LAQV-Requimte, FCT-Universidade Nova de Lisboa, Caparica, Portugal Marco Mazzotti, ETH Zurich, Switzerland Eds, ECI Symposium Series, (2017). http://dc.engconfintl.org/separations_technology_ix/57