Hydrothermally Robust Molecular Sieve Silica for Wet Gas Separation

Abstract

A major challenge in silica membranes for gas separation is to maintain a robust pore structure in the presence of steam. In this work, use of a carbonized template is proposed to reduce damage to the pore structure by inhibiting silica migration along the membrane pore surface. This departs from the conventional wisdom of creating hydrophobic surfaces to achieve hydrostability. The carbonized‐template molecular sieve silica (CTMSS) membranes can then be applied to clean‐energy systems such as hydrogen separation and carbon dioxide sequestration, and membrane reactors where steam is present.

Hydrothermal stability of silica, hybrid silica and Zr-doped hybrid silica membranes

“…This phenomenon is also described by other researchers [3,13,14] In Fig. 2B the gas permeances are displayed for a BTESE derived membrane before and after a hydrothermal treatment at 100°C (B and B100, resp.).…”

“…The good hydrothermal stability of BTESE-hybrid silica membranes is also reported in many other papers [3,10,11] but the origins of this hydrothermal stability is still unclear. In literature several features are mentioned [15] for the increased hydrothermal stability.…”

“…In several publications the hydrothermal stability of pure and metal doped silica as well as hybrid silica membranes are investigated [3,[9][10][11]. Unfortunately, a comparison is very difficult to make between these results, as different experimental conditions as well as membrane substrates and intermediate layers are used.…”

“…BTESE and Zr-doped BTESE sols were produced by the method as described in detail in [8]. BTESE was synthesized at 60°C for 90 min with a BTESE: EtOH:HNO 3 Porous a-alumina supports (pore diameter 80 nm, porosity 35%) with a diameter of 39 mm and a thickness of 2 mm (Pervatech B.V. the Netherlands) were coated twice under cleanroom conditions with a boehmite sol and calcined at 650°C at a heating rate of 1°C/min and a dwell of 3 h, resulting in a c-alumina intermediate layer with a thickness of 3 lm and a pore diameter of 5 nm, as reported by Uhlhorn et al [12]. TEOS, BTESE and Zr-BTESE layers were coated in one step under cleanroom conditions onto the supported c-alumina membranes using an automatic dip-coating machine, with an angular dipping rate of 0.06 rad s…”

“…However, these membranes are known to be unstable under hydrothermal conditions due to the reactivity of the formed silanol groups. [2,3] The last decade a lot of research was done on hydrothermally stabilizing these silica membranes.…”