Theoretical calculations within the framework of Density Functional Theory (DFT) are now widely used to investigate complex industrial supported catalysts [1]. This approach can give atomic scale insights into structural, thermodynamic and kinetic properties that are difficult to obtain from experimental techniques and, in particular, for amorphous materials. In this contribution we present relevant examples on how molecular dynamics DFT calculations (DFT-MD) help to describe the synthesis steps of γ-alumina supported catalysts, one of the most challenging, yet the most commonly used support in industrial heterogeneous catalysis. Our presentation will highlight the simulation of some key steps of the preparation of a heterogeneous catalyst, involving the (AlOOH) boehmite precursor and (Al2O3) γ-alumina itself. We will particularly focus on the atomic scale description of the interaction of organic surfactants and solvents with boehmite and γ-alumina using the DFT-MD approach. First we show calculated interfacial energies of boehmite in presence of water and organic solvents in order to quantify the evolution of boehmite particle sizes and morphologies as measured by XRD, SAXS and TEM techniques [2-4], which accounts for some of the textural properties of amorphous γ-alumina prepared in a subsequent calcination step. For γ-alumina, we show how DFT-MD reveals the reactivity of the hydroxyl groups in the presence of water which also depends on the nature of the exposed γ-alumina surfaces [5]. Finally, we will present theoretical calculations on the sorption of organic molecules and metal precursors on γ-alumina occurring in dried and wet environments during the preparation steps of supported heterogeneous catalysts [6-7]. Overall, this presentation will aim at illustrating how theoretical calculations can assist at finding descriptors capable to rationalize some of the complex phenomena taking place at the preparation steps of an amorphous heterogeneous catalyst.

Theoretical studies of the solid-liquid interface of γ-alumina supported catalysts: Impact on impregnation and dried state

253rd National Meeting (2017)

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