Selective Defect‐Patching of Zeolite Membranes Using Chemical Liquid Deposition at Organic/Aqueous Interfaces

The elimination of possible defects is indispensable in making zeolite membranes popular in process industries. A novel counter‐diffusion chemical liquid deposition (CLD) technique is proposed and developed for selective defect‐patching of zeolite membranes. Dodecyltrimethoxysilane (DMS) is employed as the silane coupling agent, forming a protective layer on the membrane surface so that intracrystalline pores can be kept intact in the subsequent reparation step. By using tetraethoxy orthosilicate (TEOS) and (3‐chloropropyl)triethoxysilane (3CP‐TES), co‐hydrolysis and co‐condensation at the organic/aqueous interface fabricate the silsesquioxane/silicate hybrid on macro‐, meso‐ and even microdefects. The silicalite‐1 membrane before and after reparation is characterized using contact‐angle measurements, Fourier transform IR spectroscopy, and electron probe microanalysis. Permporometry is conducted to study the pore‐size distribution of the membrane before and after reparation. It is found that the silsesquioxane/silicate hybrid is only deposited at the pore‐mouth of the defects, and the defects can be plugged to less than 1.3 nm pores after patching. After reparation, the separation factor of a 50/50 n/i‐butane‐gas mixture through the membrane can be increased to 35.8 from 4.4, and the separation factor of a CO₂/N₂ gas mixture through the membrane can be increased to around 15 from 1, while keeping the two‐thirds CO₂ permeation flux of the synthesized membrane.