Hierarchical Porous Zeolite Structures for Pressure Swing Adsorption Applications

Abstract

Porous adsorbents with hierarchical structured macropores ranging from 1 to 100 μm are prepared using a combination of freeze casting and additional sacrificial templating of polyurethane foams, with a zeolite 13X powder serving as adsorbent. The pore system of the prepared monoliths features micropores assigned to the zeolite 13X particle framework, interparticular pores of ∼1-2 μm, lamellar pores derived from freeze casting of ∼10 μm, and an interconnected pore network obtained from the sacrificial templates ranging from around 100 to 200 μm with a total porosity of 71%. Gas permeation measurements show an increase in intrinsic permeability by a factor of 14 for monoliths prepared with an additional sacrificial templated foam compared to monoliths solely providing freeze casting pores. Cyclic CO2 adsorption and desorption tests where pressure swings between 8 and 140 kPa reveal constant working capacities over multiple cycles. Furthermore, the monoliths feature a high volumetric working capacity of ∼1.34 mmol/cm(3) which is competitive to packed beds made of commercially available zeolite 13X beads (∼1.28 mmol/cm(3)). Combined with the faster CO2 uptake showing an adsorption of 50% within 5-8 s (beads ∼10 s), the monoliths show great potential for pressure swing adsorption applications, where high volumetric working capacities, fast uptakes, and low pressure drops are needed for a high system performance.

Monoliths: A Review of the Basics, Preparation Methods and Their Relevance to Oxidation

“…Even so, there is limited literature on monoliths extruded with zeolites, although there has been renewed interest in the extrusion of monoliths with zeolites, particularly in the field of pressure-swing adsorption [178]. Pressure-swing adsorption offers an attractive alternative to the usual and expensive cryogenic separation of gases, for example, propane/propylene [179].…”

Straightforward Processing Route for the Fabrication of Robust Hierarchical Zeolite Structures

“…The additional amount of binder is always chosen depending on the amount of zeolite and presented in dry weight basis (dwb %). For the powdery binders, namely bentonite and kaolin, the processing route based on our previous study 9 is used, as schematically shown in Figure 1A. First, PEG serving as the dispersant and organic temporary binder is dissolved in deionized water.…”

“…In particular, to increase the efficiency of swing adsorption processes, zeolite powders are colloidal-processed to form monoliths with a hierarchical porosity. 3−9 Porous-structured monoliths feature superior heat-transfer properties for nonadiabatic processes and fast mass-transfer kinetics because diffusion on small scales is reduced to small path lengths. 10−13…”

Fabricating Mechanically Robust Binder‐Free Structured Zeolites by 3D Printing Coupled with Zeolite Soldering: A Superior Configuration for CO2 Capture

“…The detailed surface area and pore volume data are summarized in Table S2 in the Supporting Information. Table S4 in the Supporting Information summarizes the mechanical performance of reported structured zeolites manufactured by 3D printing (0.05-1.54 MPa) [32,33] or other shaping strategies, such as direct extrusion (2.58 MPa), [50] sacrificial templating (0.085 MPa), [16] pulsed current processing (1.6-2.2 MPa), [34] freeze casting (0.045-1.38 MPa), [15,51,52] and slip casting (0.21-0.75 MPa). The external surface area and mesopore volume of ZM-BF are 40 m 2 g −1 and 0.040 cm 3 g −1 , respectively, which are higher than the parental NaX powders (S ext = 32 m 2 g −1 and V mes = 0.017 cm 3 g −1 ), as a result of the mesoporous character of ZM-BF.…”

“…Table S4 in the Supporting Information summarizes the mechanical performance of reported structured zeolites manufactured by 3D printing (0.05–1.54 MPa) or other shaping strategies, such as direct extrusion (2.58 MPa), sacrificial templating (0.085 MPa), pulsed current processing (1.6–2.2 MPa), freeze casting (0.045–1.38 MPa), and slip casting (0.21–0.75 MPa) . It is clear that ZM‐BF exhibits a much higher mechanical strength than most of the reported structured zeolites, which is only lower than that of 3D‐printed polymer‐zeolite composite monoliths .…”