Aluminum chloride toluene alkylation catalyst

Quaternary Salts. Herbicides paraquat (20) and diquat (59) are the quaternary salts of 4,4 -bipyridine (19) and 2,2 -bipyridine with methyl chloride and 1,2-dibromoethane, respectively. Higher alkylpyridinium salts are used in the textile industry as dye ancillaries and spin bath additives. The higher alkylpyridinium salt, hexadecylpytidinium chloride [123-03-5] (67) (cetylpyridinium chloride) is a topical antiseptic. Amprolium (62), a quaternary salt of a-picohne (2), is a coccidiostat. Bisaryl salts of butylpyridinium bromide (or its lower 1-alkyl homologues) with aluminum chloride have been used as battery electrolytes (84), in aluminum electroplating baths (85), as Friedel-Crafts catalysts (86), and for the formylation of toluene by carbon monoxide (87) (see QuaternaryAA ONiUM compounds). 

Alkyl halides are common alkylating agents in this reaction. Benzene is converted to toluene at atmospheric pressure by methyl chloride in the presence of aluminum chloride. Nitroparaffins have been used as solvents for the aluminum chloride catalyst. An amalgamated aluminum Catalyst is more effective than aluminum chloride in certain alkylations by alkyl chlorides. Boron trifluoride must be accompanied by water, alcohol, or some other polar compound in order to be effective in similar alkylations. Hydrogen chloride, hydrogen fluoride, ferric chloride, and beryllium chloride also have been used as catalysts. 

Alkylation takes place in the vapor phase, in the presence of a gaseous dflnent (nitrogen or hydrogen) around 47S°C, at 0.7.10s Pa absolute, with excess toluene (5 1 to 10 1 moles) intended to prevent the formation of inethyldiethylbenzenes. Dehydrogenation takes ptoce in similar conditions to those applied to produce styrene, namely in adiabatic reactors, with catalyst, around 450 to 500°C, and in t he presence of steam. The blend of methylstyrenes currently commercialized by Vow results from the liquid phase alkylation of toluene with aluminum chloride. 

The catalyst can be recovered and reused. The reaction is completed in a few minutes at room temperature. Sonication does not change the regioselectivity, e.g., with toluene. Similarly, alkylation of benzene with cyclohexene in the presence of aluminum chloride on silica undergoes a sonochemical acceleration of ca. 10 times, essentially due to the improved mass transport induced by sonication.162 jhg formylation of polystyrene represents an interesting case of a triphasic system, constituted by the polymer, aluminum chloride, and dichloromethyl methylether. Sonication provides a significant improvement. 

Styrene is produced mainly by catalytic dehydrogenation of high-purity ethylbenzene in the vapor phase. A typical integrated process scheme for the manufacture of styrene and ethylbenzene is shown in Fig. 22.17, in the earlier section on ethylbenzene. The alkylation reaction, with excess benzene, takes place in a homogeneous system with an aluminum chloride catalyst. The ethylbenzene dehydrogenation also is catalytic, using a commercially available catalyst. The fractionation train separates high-purity styrene, unconverted ethylbenzene, and minor reaction by-products such as toluene. 

Triflates of aluminum, gallium and boron, which are readily available by the reaction of the corresponding chlorides with triflic acid, are effective Fnedel-Crafis catalysis for alkylation and acylation of aromatic compounds [119, 120] Thus alkylation of toluene with various alkyl halides m the presence of these catalysts proceeds rapidly at room temperature 111 methylene chloride or ni-tromethane Favorable properties of the triflates in comparison with the correspond mg fluorides or chlorides are considerably decreased volatility and higher catalytic activity [120]... 

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