from first principles PP-I-1

PP-III-67Study of Mechanism of Benzene Alkylation by Alkanes over Pt-ZeoliteCatalystsMassenova A.T., Zhumakanova A.S., Sassykova L.R., Rafikova Kh.D.V.Sokolskii Institute of Organic Catalysis&Electrochemistry, Almaty, Kazakhstanalmasenova@mail.ruMechanism of alkylation of benzene with hexane and heptane has been studied on syntheticzeolite ZSM-5 and Y modified by Pt. The catalysts are characterized by the methods of -BET, porosimetry, IR spectroscopy, electron microscopy, temperature-programmeddesorption of ammonia. By IR spectroscopy the adsorption of benzene and hexane on thesurface has been studied. On the base of results of these studies a likely mechanism ofalkylation of benzene by alkanes with formation of alkylbenzenes with the yield of 40-50%has been suggested.The main stages of this process are the activation of the alkane on the Pt centers(dehydrogenation with the formation of an alkene) and the alkylation of benzene by theclassical mechanism of carbocations. Alkanes react with the oxidized form of platinum on thezeolite Bronsted center, forming an intermediate product:C 6 H 14 OHPt…O [Pt]C 6 H 13+Benzene reacts with Bronsted acid centers (BAC) and the carbocation C 6 H 7 is formed (BBC -Bronsted base center):BAC + С 6 H 6 C 6 H 7 + + [BBC] -Then strong and movable carbocation C 6 H +7 protonated hydroxyl group:OH++[Pt] + C 6 H 7 [ Pt…] + C 6 H 5 -C 6 H 14 + Н 2 ОC 6 H 13Formed intermediate reacts with Bronsted center of the zeolite to form product –hexylbenzene:2 C 6 H 5 -C 6 H 14++ [BBC] - 2 C 6 H 5 -C 6 H 13 + H 2Reduced Pt (inactivated during the reaction) in the last stage of the reactions by interactingwith water is oxidized and the activity of the metal center is regenerated again.[Pt…] + H 2 O Pt…О] + H 2221