Binderless Faujasite Beads with Hierarchical Porosity for Selective CO2 Adsorption for Biogas Upgrading

Abstract

Biomethane can be isolated from biogas through selective CO2 adsorption. Faujasite-type zeolites are promising adsorbents for CO2 separation due to their high CO2 adsorption capacity. While commonly inert binder materials are used to shape zeolite powders into the desired macroscopic format for application in an adsorption column, here we report the synthesis of Faujasite beads without the use of a binder and their application as CO2-adsorbents. Three types of binderless Faujasite beads (d = 0.4–0.8 mm) were synthesized using an anion-exchange resin hard template. All the prepared beads consisted mostly of small Faujasite crystals, as demonstrated by characterization with XRD and SEM, which are interconnected through a network of meso- and macropores (10–100 nm), yielding a hierarchically porous structure, as shown by N2 physisorption and SEM. The zeolitic beads showed high CO2 adsorption capacity (up to 4.3 mmol g−1 at 1 bar and 3.7 mmol g−1 at 0.4 bar) and CO2/CH4 selectivity (up to 19 at the partial pressures mimicking biogas, i.e., 0.4 bar CO2 and 0.6 bar CH4). Additionally, the synthesized beads have a stronger interaction with CO2 than the commercial zeolite powder (enthalpy of adsorption −45 kJ mol−1 compared to −37 kJ mol−1). Therefore, they are also suitable for CO2 adsorption from gas streams in which the CO2 concentration is relatively low, such as flue gas.

Zeolites as Selective Adsorbents for CO2 Separation

“…Binderless zeolite LTA beads have been synthesized using resin beads as a hard template. 160 The resin beads were added to the zeolite synthesis mixture and resin-zeolite composite beads were formed. The resin was then removed by calcination, yielding hierarchically porous binderless zeolite beads (0.5−1 mm).…”

Design and synthesis of core shells HZSM-5@MCM-41 with variable acidity and mesoporosity for lignin-catalyzed fast pyrolysis to prepare aromatics

“…, CTAB) to substrates that are hydrophobic or hydrophilic, resulting in an uneven shell coating. 25–28 At present, the design and synthesis of core–shell catalysts are mainly based on a single ZSM-5 core, while there are few studies on the growth of shells on ZSM-5 surfaces with different acidity. Therefore, there is an urgent need to develop a more controlled method to synthesize core–shell catalysts with a uniform shell structure on the core surface at different acidity levels.…”

A Multifunctional Technology Platform for Sorbent Construction Using Polyacrylonitrile Scaffolds

“…Production of engineered forms of particulate sorbents can be realized through different approaches, depending on the type of sorbent. These include mixing them with another binder-type material (e.g., clay, polymer) and extruding or using wet granulation to create a desired size fraction, , using hard templates, using cationic photopolymerization followed by calcination, pressing the material into pellets and grinding to a desired size fraction, or embedding the active material into a passive matrix and forming the composites through a freezing technique. − The process of embedding (or affixing) active getters into passive matrices using a freezing process − has high potential toward providing solutions for a wide range of applications.…”