An in situ13C-NMR study of the mechanism of cumene- n-propylbenzene isomerization over H-ZSM-11

Diffusion of Benzene and Propylene in MCM-22 Zeolite. A Molecular Dynamics Study

“…Apart from environmental advantages, the use of zeolites presents the additional merit of reducing the amount of less desired products such as diisopropylbenzenes but has the drawback of the formation of n -propylbenzene, a product that is not formed in significant amounts when using mineral acid catalysts. It has been recently shown that n -propylbenzene is not formed, as originally thought, via monomolecular isomerization of the isopropyl isomer but rather from the transalkylation between propylbenzene and benzene. , In the case of zeolites, the pore dimensions and consequently the diffusion of the reactants and products are of paramount importance, since the final product distribution will depend highly on the zeolite channel structure. For instance, the formation of n -propyltoluene has been observed with ZSM-5 but not with Mordenite, which suggests that the transalkylation reaction occurs in the 10-member ring (MR) channel intersections of ZSM-5, whereas the intersection of 12-MR and 8-MR channels in mordenite does not provide sufficient space for the bimolecular transalkylation process to occur.…”

Theoretical Model of the n-Propylbenzene Formation in the Benzene Isopropylation over Zeolites. An Anti-Markovnikov-Type Proton Addition Promoted by the Steric Effect of MFI and MEL Zeolite Channels

“…A monomolecular mechanism of the isomerization of iso- to n -propyltoluene was proposed by Fraenkel and Levy, whereas a bimolecular mechanism of n -propylbenzene formation in an excess of benzene was suggested by Beyer and Borbély . A 13 C magic angle spinning (MAS) NMR study , on the transalkylation reaction between labeled isopropylbenzene and benzene reactants has unambiguously evidenced the bimolecular mechanism. A kinetic study of the reaction between toluene and isopropylbenzene, yielding n -propyltoluene and benzene with isopropyltoluene and resulting in n -propylbenzene formation over MFI, provided further support for the bimolecular mechanism .…”

“…According to a theoretical approach mentioned under the name "molecular traffic control," 23 the molecules adsorbed at the channel intersections of the MFI structure are especially suitable targets for attacks by reactant molecules from the direction of the sinusoidal channels. The primary aim of our study is to describe the isomerization reaction [4][5][6] between benzene and isopropylbenzene leading to n-propylbenzene, so we took into consideration the main effect of the MFI and MEL channels (i.e., their perpendicularity, with geometrical constraints). Therefore, we assumed that the protonated isopropylbenzene molecule (represented by cation b) is adsorbed at the channel intersection in zeolites of MFI or MEL structural type and undergoes an attack by the reactant benzene molecule approaching through the sinusoidal channel.…”

n-Hexaneactivation over zeolites: aromatic alkylation to 1-phenylhexane

“…n-Propylbenzene was observed during the alkylation of benzene with propane over bifunctional catalysts, and its formation was explained by the isomerization 6,9 of cumene and by transalkylation by a bifunctional mechanism. [17][18][19] We alkylated benzene with n-hexane over ZSM-5 and observed a significant fraction of the terminal alkylated product, 1-phenylhexane. The alkylation reaction was performed at 205 1C under autogeneous pressure in a batch reactor at a benzene-to-hexane ratio of one.…”

“…To test the ring opening route, cyclohexyl benzene was reacted.z No 1-phenylhexane was detected in the product mixture. Transalkylation, by which n-propylbenzene forms from cumene and benzene, [17][18][19] is unlikely. We reacted a mixture of 2-and 3-phenylhexane with benzene and found that 1-phenylhexane did not form.…”