Abstract
Supported microporous organosilica membranes made from bridged silsesquioxane precursors by an acid-catalyzed sol–gel process have demonstrated a remarkable hydrothermal stability in pervaporation and gas separation processes, making them the first generation of ceramic molecular sieving membranes with sufficient performance under industrially relevant conditions. The commercial availability of various α,ω-bis(trialkoxysilyl)alkane and 1,4-bis(trialkoxysilyl)benzene precursors facilitates the tailoring of membrane properties like pore size and surface chemistry via the choice of precursor(s) and process variables. Here, we describe the engineering of sols for making supported microporous thin films, discuss the thermal and hydrothermal stability of microporous organosilicas and give a short overview of the developments and applications of these membranes in liquid and gas separation processes since their first report in 2008.
Highlights
Microporous ceramic membranes have been receiving considerable attention since the late 1980s because of their ability to separate gases and liquids on the molecular scale [1,2,3]
Supported microporous organosilica membranes made from bridged silsesquioxane precursors by an acid-catalyzed sol–gel process have demonstrated a remarkable hydrothermal stability in pervaporation and gas separation processes, making them the first generation of ceramic molecular sieving membranes with sufficient performance under industrially relevant conditions
Very high gas separation selectivities have been reported for acid-catalyzed sol–gel-derived silica membranes, which are typically based on the use of tetraethyl orthosilicate (TEOS) as precursor [4]
Summary
Microporous ceramic membranes have been receiving considerable attention since the late 1980s because of their ability to separate gases and liquids on the molecular scale [1,2,3]. The introduction of hydrolytically stable :Si–C2H4–Si: bonds in the network structure in 2008 resulted in a microporous silica-based membrane with good membrane separation properties for the removal of water from n-butanol, with long-term stability at the industrially relevant temperature of 150 °C [7], see Fig. 1. The development of this so-called hybrid silica or hybrid organosilica membrane has led to renewed interest in molecular separations of gases and liquids under harsh conditions.
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