Preparation and Activity of Ionic Liquid Catalysts Grafted on Hydrophobic Silica Gel

Abstract

An ionic liquid 1- (triethoxysilyl) propyl-3-methylimidazolium hydroxide ([Smim]OH) was grafted on three kinds of mesoporous hydrophobic silica gel by means of post-grafting under mild conditions. The catalysts were [Smim]OH/SiO2-MTES (methyltriethoxysilane), [Smim]OH/SiO2-TMCS (trimethylchlorosilane), [Smim]OH/SiO2-CPTEO (triethoxysilyl propyl chloride). Such grafted ionic liquids (GILs), which were characterized by means of FTIR and N2 adsorption-desorption could be used as effective heterogeneous catalysts toward propylene carbonate synthesis through cycloaddition of carbon dioxide with propylene oxide under solventless and mild conditions.

Superhydrophobic and breathable resorcinol-formaldehyde Xerogels

“…The porosity of all the samples ranges between 50-70% ( Regarding the surface chemistry of these materials, it is well established that the surface of the RF-xerogels is covered with some dangling phenolic groups (see Figure 3). 41 The passivating mechanism that would transform those hydrophilic sites into hydrophobic is also depicted in Figure 3. According to the methoxylation reaction shown in Figure 3, hydrophobic methyl ether groups will decorate the passivated surface of the treated RF xerogels.…”

“…[39,40] Hydrophilic silica gels, which also have surfaces rich on hydroxyl groups resembling that of RF xerogels, have been turned into hydrophobic materials by grafting methylsilane compounds on their surface. [30,41,42] However, the use of silane compounds to this aim has not been considered a suitable procedure due to the possible hydrolysis reactions that could likely take place at ambient conditions, which would limit the range of final applications of the resulting materials. A much more attractive alternative of surface passivation of surface hydroxyl groups has been described in a previous work, in which surface methoxylation was carried out using methanol vapor.…”