Facile synthesis of seed crystals and gelless growth of pure silica DDR zeolite membrane on low cost silica support for high performance in CO2 separation

Micro and Nanoporous Membrane Platforms for Carbon Neutrality: Membrane Gas Separation Prospects

“…Owing to its microstructure, the pure silica DDR zeolite (Si-DDR) membrane (Figure 5A d) is ideal for separating CO 2 molecules in a gas mixture due to its kinetic diameter of 0.33 nm, which can easily pass CO 2 and prevent the passing of CH 4 molecules, with a kinetic diameter of 0.38 nm, even in humid conditions as shown in Figure 5B a-d. [30] Furthermore, silica nanoparticles functionalized with lowdensity polyethylene (LDPE), when incorporated into polyvinylidene fluoride (PVDF) matrix, can act as an anti-wetting protection layer to overcome membrane wetting, which is of great concern when using membranes for gas separation and absorption. [5] LDPE facilitates functionalized silica dispersion in the composite membrane by leading to stronger interactions between functionalized silica and the PVDF polymer chains in Figures 6 (a and b).…”

Zeolite-based catalytic membrane reactors for thermo-catalytic conversion of CO2

“…The orientation is also affected by the pH value. In the synthesis of DDR zeolite membrane, a high pH value of the mother liquor led to a crystal growth toward various directions while a neutral pH could maintain the orientation at the beginning of the preparation ( Nguyen et al., 2021 ). Besides the mother liquor, a careful addition of acids during the membrane post-treatment enables a better crystallization by removing the amorphous zeolite crystals without destroying the morphology.…”

“…Based on the above discussion, a medium alkaline condition (pH = 11-12) is mostly preferred for the synthesis of high-quality zeolite membranes ( Hazrati et al., 2018 ; Hayakawa and Himeno, 2020 ). In certain scenarios, however, nearly neutral (pH = 7–7.5) or strong basic (pH = 14) environment enables the formation of zeolite membrane layers, such as Si-CHA and Si-DDR ( Araki et al., 2021 ; Nguyen et al., 2021 ).…”

“…In addition to OSDA-free synthesis, a gel-free process is a promising alternative to the conventional method where the precursor gels have to be aged. Benefiting from the gel-free secondary growth, the membrane synthesis turns out to be safer, more environmentally friendly, less expensive, and simpler in operation ( Le et al., 2020 ; Tang et al., 2021a ; Nguyen et al., 2021 ). For instance, with kaolin as the substrate, the compositional elements were provided from the support, and the SAPO-34 and AIPO-18 zeolite membranes were formed in situ .…”

Process Intensification in Bio-Ethanol Production–Recent Developments in Membrane Separation

“…The ceramic support cost occupies a major part of the fabrication cost of zeolite and zeolite-like micro-porous inorganic membranes [70]. Therefore, various ideas, using, for example, less expensive hollow fiber supports [71], re-usable stainless-steel supports [72], and other materials [73,74] are proposed. Improving the membrane flux is another approach because higher flux requires less membrane area and will reduce the capital cost of the membrane unit.…”