Organosilica-Based Membranes in Gas and Liquid-Phase Separation

Abstract

Organosilica membranes are a type of novel materials derived from organoalkoxysilane precursors. These membranes have tunable networks, functional properties and excellent hydrothermal stability that allow them to maintain high levels of separation performance for extend periods of time in either a gas-phase with steam or a liquid-phase under high temperature. These attributes make them outperform pure silica membranes. In this review, types of precursors, preparation method, and synthesis factors for the construction of organosilica membranes are covered. The effects that these factors exert on characteristics and performance of these membranes are also discussed. The incorporation of metals, alkoxysilanes, or other functional materials into organosilica membranes is an effective and simple way to improve their hydrothermal stability and achieve preferable chemical properties. These hybrid organosilica membranes have demonstrated effective performance in gas and liquid-phase separation.

Keywords: gas separation; hybrid membrane; hydrothermal stability; liquid separation; organosilica.

Figure 1

Most of the organoalkoxysilane materials along with their chemical structures. (Et: ethyl; Me: methyl; Letters in brackets are their abbreviation name.).

Figure 2

The represented bridge-type and pendant-type precursors and their organosilica structures formed (R: organic groups).

Figure 3

A cross-sectional SEM image on the constructions of BTESE membranes including intermediate and support layer. Reproduced from [16].

Figure 4

The colloidal and polymeric route in sol-gel process. Reproduced from [10].

Figure 5

(a) Dynamic light scattering for pH-swing sol and acid sols. (b) Time course of BTESE-derived sols in acid, acid-alkali and acid-alkali-acid. Reproduced from [39].

Figure 6

The permeance ratios of (a) H₂/N₂ and (b) H₂/CH₄ at 200 °C; (c) pore size prediction based on a NKP method as a function of the number of carbon linking units. Reproduced from [15] in context and supporting information.

Figure 7

(a) Bonding structure model, (b) H₂/N₂ permeance ratio at 200 °C and (c) water permeability versus salt rejection (25 °C, 1.15 MPa, and 2000 ppm of NaCl) for BTESE, BTESEthy, and BTESA membranes. Reproduced from [19,80].

Figure 8

H₂ separation performance of Metal-doped organosilica membranes and compared with organosilica membranes at 200 °C. Square data from Ref. [27,81,82,83,92,93], cycle data from Ref. [16,27,35,94].

Figure 9

CO₂ permeance of organosilica membranes as a function of water vapor activity at 40 °C (Feed side: 500 mL/min, permeate side: 1000 mL/min). Reproduced from [104].

Figure 10

A porosity-tailored network via the co-condensation of a dual flexible−rigid network of BTPP and rigid network of TEOS and BTESE. Reproduced from [109].