Aluminium chloride supported

Such reactions have also been carried out successfully using aluminium chloride supported on MCM-41, prepared by the reaction of the support with AICI3. The activity of this Lewis acid is comparable to that of AICI3 itself, and its selectivity towards monoalkylation is better, because the reaction takes place within the narrow pore structure of the catalyst. 

The product distribution in the reaction of benzene with dodecene was determined for a number of catalysts (Table 5.1-4). As can be seen, the reaction with the zeolite H-Beta gave predominantly the 2-phenyldodecane, whereas the reaction in the pure ionic liquid gave a mixture of isomers, with selectivity similar to that of aluminium chloride. The two supported ionic liquid reactions (H-Beta / IL and T 350 / IL) again gave product distributions similar to aluminium(III) chloride (T350 is a silica support made by Degussa). 

Mixtures of ethylene and aluminium chloride, initially at 30-60 bar, rapidly heat and explode in presence of supported nickel catalysts, methyl chloride or... 

Bound reagents are an excellent alternative in cases where the reagent is used in excess and can be difficult to remove. Purification is now a simple process of filtration and evaporation. For example, silica-supported aluminium chloride is a Lewis acid and an effective catalyst for Friedel-Crafts alkylations (Figure 3.15). 

IMMOBILISED LEWIS ACIDS 3.1 Supported aluminium chloride... 

The procedure for preparing supported aluminium chloride relies on the small but significant solubility of aluminium chloride in aromatic hydrocarbons (typically toluene) and the slow reaction of the dissolved A1C13 with the surface hydroxyls of a commercial silica gel or acid-treated clay (Figure 1). One mole equivalent of HC1 is produced during the catalyst preparation consistent with the formation of mostly -OAlCl2 units on the surface and the use of hot solvent is essential so as to force the reaction and to ensure that the HC1 is driven from the system. 

In some cases the heterogeneous version of a catalyst can be prepared by direct reaction of that catalyst with a suitable support material. Thus reactive Lewis acids such as aluminium chloride will react with hydroxylated materials such as silica gel to give directly bonded surface species such as -OAICI2.20 Another single-step route to the supported catalyst is via sol-gel techniques, typically to produce an organically modified mesoporous silica. This is based on the co-polymerisation of a silica precursor and an organosilicate precursor (Figure 1.5). 

The activity of the catalyst shown in Figure 4.10 in the alkylation of benzene with alkenes is comparable to that of aluminium chloride, but it shows improved selectivity towards monoalkylation compared to A1C13 itself and is readily recoverable and reusable (unlike A1C13, which needs to be removed from the reaction after one use, typically by a water quench). The alkylation of alkylbenzenes, and to a lesser extent halobenzenes, can also be carried out using supported aluminum chloride (Table 4.11). 

More recently, it has been shown that it is possible to extend the methodology for supported aluminium chloride for liquid-phase applications to hexagonal mesporous silicas as supports (HMSs and including MCM materials).115,116 Activity in the alkene alkylation of alkylaromatics is again comparable to that of A1C13 itself, and the solid adds are also easily recovered and can be reused. Most significantly, the increase in selectivity towards monoalkylation through... 

Figure 4.10 Preparation of supported aluminium chloride for liquid-phase organic reactions...

Table 4.11 Activity of (optimised) supported aluminium chloride solid acids in the alkylation of aromatic substratesa...

A variety of catalysts have been examined, comprising protonated acids inciuding phosphoric acid on Fuller s earth, sulphuric acid on the same support, and cation exchange materials. Lewis acids such as aluminium chloride, boron trifiuoride and its etherates, zinc chioride, siiica/aiumina, toluene-4-sulphonic acid and montmorillonite clays have found some application in numerous studies although generally the phosphoric acid system appears to be most favoured. 

Boroujeni, K. P. and Parvanak, K. 2011. Efficient and solvent-free synthesis of bis-indolyl-methanes using silica gel-supported aluminium chloride as a reusable catalyst. Chin. Chem. Lett. 22(8) 939-942. 

Therefore triflic acid as a catalyst is efficient and effective in producing more yield of cumene from the by-products of isopropylation reactions at room temperature and atmospheric pressure. It is more superior than the other catalysts such as supported phosphoric acid aluminium chloride and zeolite, which are currently used in industries at higher pressures and temperatures. 

The methylsulfonylation of toluene by reaction with methylsulfonyl chloride in the presence of aluminium chloride catalyst affords methyl tolyl sulfone (52% yield) with an ortho meta para isomer ratio of 53 14 33. Attempts have been made to obtain greater selectivity in sulfonylations a supported Lewis acid catalyst has been recommended for selective sulfonylation, but it did not give good results in the methylsulfonylation of toluene. The best pura-selectivity... 

PS/AICI3 = Polystyrene-supported aluminium chloride DMAC = W,W-Dimethylacetamide... 

Mata1997 Mata, E.G., -Lactams on Solid Support Mild and Efficient Removal of Penicillin Derivatives from Merrifield Resin using Aluminium Chloride, Tetrahedron Lett., 38 (1997) 6336-6338. 

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