title: Laminated adsorbents with very rapid CO2 uptake by freeze-casting of zeolites.
abstract: Structured zeolite 13X monoliths with a laminated structure and hierarchical macro-/microporosity were prepared by freeze-casting aqueous suspensions of zeolite 13X powder, bentonite, and polyethylene glycol. Colloidally stable suspensions with a low viscosity at both room temperature and near freezing could be prepared at alkaline conditions where both the zeolite 13X powder and bentonite carry a negative surface charge. Slow directional freezing of the suspensions led to the formation of well-defined and thin lamellar pores and pore walls while fast freezing resulted in more cylindrical pores. The wall thickness, which varied between 8 and 35 μm, increased with increasing solids loading of the suspension. Thermal treatment at 1053 K of the freeze-cast bodies containing between 9 and 17 wt % bentonite resulted in mechanically stable zeolite 13X monoliths. The monoliths displayed a carbon dioxide uptake capacity of 4-5 mmol/g and an uptake kinetics characterized by a very fast initial uptake where more than 50% of the maximum uptake was reached within 15 s. Freeze-cast laminated zeolite monoliths could be used to improve the volumetric efficiency and reduce the cycle time, of importance in, for example, biogas upgrading and CO2 separation from flue gas.
authors.affiliation: Department of Materials and Environmental Chemistry and Berzelii Center EXSELENT on Porous Materials, Stockholm University, Stockholm 10691, Sweden.
authors.forename: Arto
authors.initials: A
authors.lastname: Ojuva
authors.forename: Farid
authors.initials: F
authors.lastname: Akhtar
authors.forename: Antoni P
authors.initials: AP
authors.lastname: Tomsia
authors.forename: Lennart
authors.initials: L
authors.lastname: Bergström