Inorganic support compounds, catalyst

The first example of SILP-catalysis was the fixation of an acidic chloroaluminate ionic liquid on an inorganic support. The acidic anions of the ionic liquid, [AI2CI7] and [AI3CI10], react with free OH-groups of the surface to create an anionic solid surface with the ionic liquid cations attached [72]. The catalyst obtained was applied in the Friedel-Crafts acylation of aromatic compounds. Later, the immobilisation of acidic ionic liquids by covalent bonding of the ionic liquid cation to the surface was developed and applied again in Friedel-Crafts chemistry [73]. 

The proton sponge, l,8-bis(dimethylaminonaphthalene) (DMAN), has been anchored onto amorphous and pure silica MCM-41.[182] DMAN supported on MCM-41 is an excellent base catalyst for the Knoevenagel condensation between benzaldehyde and different active methylene compounds, as well as for the Claisen-Schmidt condensation of benzaldehyde and 2 -hydroxyacetophenone to produce chalcones and flavanones. It was found that the activity of the supported catalyst is directly related to the polarity of the inorganic support. Moreover, the support can also preactivate the reagents by interaction of the carbonyl groups with the weakly acidic silanol groups of MCM-41. This preactivation step enables DMAN, anchored onto MCM-41, to abstract protons with a higher pK than that of the DMAN. 

PE catalysts supported on inorganic magnesium compounds commercialized Unipol gas-phase LLDPE emerges as potential replacement for LDPE... 

Reaction of dialkylmagnesium compounds with selected chlorinated compounds produces finely divided MgCl that can be used as a support for polyethylene catalysts. Other reagents may be used to produce different inorganic magnesium compounds, also suitable as supports. Examples are shown in Figure 4.1. Treatment of these products with transition metal compounds results in a supported "precatalyst." Typically, the transition metal is subsequently reduced by reaction with an aluminum alkyl and the solid catalyst isolated. The solid catalyst and cocatalyst (usually TEAL) may then be introduced to the polymerization reactor. 

Figure 4.1 Reactions of dialkylmagnesium compounds to produce inorganic magnesium compounds useful as supports for Ziegler-Natta catalysts.

Anchoring of metal complexes through interaction with surface hydroxyl groups of inorganic supports continues to be of interest. Studies with catalysts prepared with allyl, carbonyl, chloride, and ethoxy ligands have been reported. Kuznetsov and co-workers conclude that the precursors of metathesis-active centres of surface metal complexes, prepared by anchoring allyl and ethoxy compounds of Mo, W, and Re to silica, are co-ordinatively unsaturated metal ions with oxidation number +4. Metathesis activity of the surface species depends on the ligand environment of the metal ion. 

A new method of synthesis of selective platinum catalysts for the hydrogenation of unsaturated carbonyl compounds is presented. Platinum was deposited on the supports tailored with the monolayer of transition metal oxide. Selectivity of these catalysts strongly depended on the type of inorganic support as well as on the type of transition metal in the monolayer. Catalysts were tested in the hydrogenation of furfural, crotonaldehyde and cinnamaldehyde. Selectivity of the synthesis of the appropriate unsaturated alcohols was enhanced when compared with the reactions performed over classical Pt-metal oxide catalysts. 

Clays are a very important group of inorganic compounds due to their many possible practical applications, such as supports for catalysts, as lubricants, and for thermal insulation. Many clays such as vermicuHte, montmorUlonite, and steatite exhibit a lamellar nanostructure, which make them suitable hosts for the preparation of intercalation compoimds. As recently [1] demonstrated for soapstone, a compact form of steatite (talcum powder), even very small variations in chemical composition can exert significant effects on physical and chemical properties. 

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