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A molecular dynamics study of the diffusion of trimethylbenzene (TMB) and xylene molecules involved in toluene and TMB transalkylation reaction has been performed over 6 different pure-silica zeolites, containing 10- and 12-ring channels: BOG, MSE, IWR, SFS, SOF, and UWY. The shape selective properties of these six frameworks have been tested using two different loadings: one loading characteristic of the early stage and another of the late stage of the reaction. The collected data explains the diffusion behavior of these molecules in the zeolite frameworks and allows researchers to obtain trends and also rationalize their performance as candidates for the selective production of p-xylene during transalkylation of toluene and TMB. UWY appears a promising zeolite that allows the reaction of the TMBs in the 12-ring channels, is able to host the transition states, and favors the preferential diffusion of p-xylene in the 10-ring channels., We thank Ministerio de Economia y Competitividad (MINECO) of Spain for funding through Project CTQ2015-70126-R, and the excellence programme Severo Ochoa (SEV-2012-0267). J.T. thanks MINECO of Spain for the SVP-2013-067662 Ph.D. scholarship. We thank ASIC-UPV and Paco Rosich for computational facilities and computational support.

Water intrusion-extrusion in hydrophobic microporous AFI, IFR, MTW and TON pure silica zeolites (zeosils) has been investigated through molecular dynamics (MD) simulations. It was found that intruded water volumes correlate with the free volume of the zeosil unit cells. Calculated adsorption isotherms allowed us to estimate the amounts of water intruded, and deviations from experiments (lower experimental with respect to calculated intrusion pressures) have been;explained in terms of connectivity defects in the synthesized materials. Water phase transitions in defectless zeosils occur in a narrow range at high pressure. On the basis of a simple model, we derived a thermodynamic equation that allows one to estimate the intrusion pressure with few parameters, which are easy to obtain, such as fractional free volume of zeosil and the intrusion pressure of a reference system. The structural properties of water clusters inside the zeosil micropores have been interpreted from the analysis of the MD simulations. Compact "bulk-like" clusters form in large channels such as those in AFI and IFR zeosils. The smaller channels of MTW and TON Promote the formation of chain-like clusters, which, interestingly, are commensurate with the zeolite channel topology due to a coincidence between the distances of the crystallographic parameter, along the channel, and a maximum in the O-O radial distribution function of hulk water., Y.G.B. acknowledges Universitat de Valencia for a visiting professor fellowship through the program "'Atraccio de talent' VLC Campus". J.V.d.J.-O. and J.G. acknowledge the support from the Spanish Ministerio de Ciencia e Innovacion (project SAF2009-13059-C03-02). Y.G.B. and G.S. thank CPD-UPV for the use of their computational facilities.

We present results from molecular dynamics simulations describing structural and dynamical characteristics of equimolar mixtures of water and acetonitrile, confined between two silica walls separated at interplate distances of d = 0.6, 1, and 1.5 nm. Two different environments were investigated: a first one where wall-solvent dispersion forces prevail (hydrophobic confinement) and a second one in which the terminal O atoms at the silica surface are transformed into silanol groups (hydrophilic confinement). For the former case, we found that, at the shortest interplate distance examined, the confined region is devoid of water molecules. At an interplate distance of the order of 1 nm, water moves into the confined region, although, in all cases, there is a clear enhancement of the local concentration of acetonitrile in detriment of that of water. Within hydrophilic environments, we found clear distinctions between a layer of bound water lying in close contact with the silica substrates and a minority of confined water that occupies the inner liquid slab. The bound aqueous layer is fully coordinated to the silanol groups and exhibits minimal hydrogen bonding with the second solvation layer, which exclusively includes acetonitrile molecules. Dynamical characteristics of the solvent mixture are analyzed in terms of diffusive and rotational motions in both environments. Compared to bulk mixtures, we found significant retardations in all dynamical modes, with those ascribed to water molecules bound to the hydrophilic plates being the most dramatic. Fil: Rodriguez, Javier. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina Fil: Elola, Maria Dolores. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; Argentina Fil: Laria, Daniel Hector. Comisión Nacional de Energía Atómica; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina