Journal of Catalysis 227 (2004) 227–241 www.elsevier.com/locate/jcat Xylene isomerization and aromatic alkylation in zeolites NU-87, SSZ-33, β , and ZSM-5: molecular dynamics and catalytic studies Francisco J. Llopis a,b , German Sastre a , Avelino Corma a,∗ a Instituto deTecnologia Quimica, UPV-CSIC, Av/Naranjos s/n, 46022 Valencia, Spain b Departamento de Ingenieria Quimica, UVEG, Universitat de València, C/Dr. Moliner 50, 46100 Burjassot, Valencia, Spain Received 15 April 2004; revised 5 July 2004; accepted 9 July 2004 Abstract The unique pore topology of zeolite NU-87, with 10-membered ring (MR) channels intersected by perpendicular 12-MR cavities, can offer new opportunities for alkylaromatics isomerization, as well as for aromatics alkylation. The catalytic performance has been studied for meta-xylene isomerization and disproportionation, as well as toluene alkylation with methanol, ethanol, propanol, and isopropanol. Product distribution was interpreted on the basis of pore topology and compared to zeolites with 12-MR (β ), 10- and 12-MR (SSZ-33), and 10-MR (ZSM-5) zeolites. The presence of cavities allows more space for the location of bulky intermediates and/or products, and also traps the molecules, allowing consecutive reactions that lead to thermodynamic equilibrium. Channels, on the other hand, allow diffusion without trapping, if their free diameter is large enough. 10-MR channels in NU-87 are smaller than in ZSM-5 and this limits diffusivity. Furthermore, trimethylbenzenes formed will tend to equilibrate, but only the smaller isomer, i.e., 1,2,4-trimethylbenzene, fits in the NU-87 cavity and will have a small chance to diffuse. Catalytic experiments as well as atomistic molecular dynamics are used to interpret the behavior of NU-87 and to explain the results in comparison with other structures.  2004 Elsevier Inc. All rights reserved. Keywords: Reactivity NU-87 zeolite; Reactivity SSZ-33 zeolite; Aromatics alkylation with zeolites; Cumene production with zeolites; Xylene isomerization with 10 and 12MR zeolites; Diffusion of aromatics in zeolites 1. Introduction Zeolites with connected channels of 10 and 12 MR (mem- bered rings) offer an interesting pore arrangement for catal- ysis, since they may combine high conversion and shape- selectivity features [1,2]. Large channels of 12 MR allow large molecules to diffuse and react, while products formed may diffuse with different abilities in the two pore systems available [3]. Preferential diffusion paths may exist depend- ing on the relative size of the reactants and products. This was shown (by molecular dynamics simulations) to be the case for the diffusion of ortho and para-xylene in a CIT-1 structure with crossing channels of 10 and 12 MR, where relative para/ortho-xylene diffusivities of 3.2 and 2.3 were * Corresponding author. E-mail address: acorma@itq/upv.es (A. Corma). found at low and high loading, respectively [4]. A different situation appears in MCM-22 [5] with a sinusoidal 10-MR channel and a separated set of 12-MR cavities connected by 10-MR openings. In this case the two channel systems are independent and their relative contribution to the cat- alytic behavior for different reactions depends on the reac- tant size [6]. The relative contribution of the two-channel systems can also be tuned by delaminating a laminar precur- sor [7] of the MCM-22, thus increasing the external surface while preserving the 10-MR channels [8]. By doing this, the accessibility of larger molecules to the active centers is in- creased and the combined benefits of both pore systems was improved from the point of view of acidity and catalytic ac- tivity for particular reactions [9]. NU-87 contains 12-MR cages with four 10-MR entrances forming channels [10] as shown in Fig. 1. A number of patents have come out in the last few years that show poten- tial catalytic applications [11,12]. It is clear that the catalytic 0021-9517/$ – see front matter  2004 Elsevier Inc. All rights reserved. doi:10.1016/j.jcat.2004.07.014