Surface-active ionic liquids methods

The chloroaluminate catalysts prepared according to method 2 show even higher activity in Friedel-Crafts reactions. This can be explained by the fact that here an ionic liquid is simulated on the surface of the support. The hydroxyl groups on the surface of the support, which would otherwise react with AICI3 are now used for the grafting of the organic cation. As shown in Figure 2, this is supported by NMR data t9,10l... 

Quaternary phosphonium salts are organophosphorous compounds used as Wittig olefination reagents, phase transfer catalysts, electrolytes, ionic liquids, and as surface active reagents. Their preparation involves the C-P bond formation in tertiary phosphines. We envisaged that addition of phosphines to unsaturated compounds should be preferable as compared to the conventional method using a substitution reaction of organohalogen compounds (Scheme 1). In this chapter, we describe our recent study on this subject. 

The immobilization of ionic liquids (ILs) is intimately connected with spectroscopy, with the goal to characterize the support, the IL film, or the catalyst. Besides the characterization by BET surface methods and catalytic activity, the most powerful tools are nuclear magnetic resonance (NMR) spectroscopy and infrared (IR) spectroscopy, which are discussed separately in the following. NMR spectroscopy is mostly performed in the solid state, where either the support itself or the IL film with the dissolved catalyst therein is characterized. For the latter case, some liquid-state NMR experiments are also applicable. Besides the characterization of the SILP system itself, solubility effects of the reactants using liquid-state NMR are well established to understand the kinetics. Those examinations are beyond the theme of this chapter and are therefore not discussed here. 

This modern method, commonly known supported ionic liquid phase catalysis, is based on the simple chemical attachment of ILs to the support surface or the simple deposition of the catalytically active speciesmain idea for the preparation of these alternative materials is to avoid or at least decrease the deactivation of the catalyst after reactions as well as to minimize the amount of IL used in each process. In addition, the SILP method provides some advantages compared to other catalytic systems. For example, SILP catalytic systems offer the elimination/reduction of mass transfer limitations and give access to more robust/recyclable catalysts with an easy separation after reactions. In other words,... 

These materials are prepared by the covalent attachment of ionic hquids to the support surface or by simple deposition of the ionic liquid phases containing catalytically active species on the surface of the support (usually silica-based or polymeric materials including membranes). In various cases, the procedure involves the simple dissolution of a sulfonated phosphine-modified rhodium catalyst into a supported ionic liquid, while the alkene constitutes the organic phase. This method reduces the amount of ionic liquid and allows for a facUe and efficient separation of products from catalyst. In comparison to traditional biphasic systems, higher catalytic activity and lower metal leaching can be obtained by appropriately tuning the experimental conditions [35—41]. 

The selectivity of activated carbons for adsorption and catalysis is dependent upon their surface chemistry, as well as upon their pore size distribution. Normally, the adsorptive surface of activated carbons is approximately neutral, such that polar and ionic species are less readily adsorbed than organic molecules. For many applications it would be advantageous to be able to tailor the surface chemistry of activated carbons in order to improve their effectiveness. The approaches that have been taken to modify the type and distribution of surface functional groups have mostly involved the posttreatment of activated carbons or modification of the precursor composition, although the synthesis route and conditions can also be employed to control the properties of the end product. Posttreatment methods include heating in a controlled atmosphere and chemical reaction in the liquid or vapor phase. It has been shown that through appropriate chemical reaction, the surface can be rendered more acidic, basic, polar, or completely neutral [11]. However, chemical treatment can add considerably to the product cost. The chemical composition of the precursor also influences the surface chemistry and offers a potentially lower cost method for adjusting the properties of activated... 

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