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The fluorination on the γ-alumina surface was studied by multinuclear MAS NMR and BET measurements. The fluorine species on the fluorinated γ-alumina can be identified by 19F MAS NMR combined with 1H MAS NMR and 27Al MAS and CP/MAS NMR. As proven by 1H MAS NMR, fluorination of the alumina preferentially replaced the basic hydroxyl groups. Quantitative analysis showed that, at lower fluoride loadings, one alumina hydroxyl is substituted by one fluoride without breaking the bridging Al−O−Al bonds. At high fluoride content, more of the acidic hydroxyl groups are displaced by fluorine, and the number of added fluorine atoms exceeds the number of lost hydroxyl groups. Bridging Al−O−Al bonds are broken at high fluoride loading, and isolated Al x Fy·nH2O fractions appear as observed by 19F MAS and 27Al MAS NMR. Three types of fluorine species were detected in the 19F MAS NMR spectra of the fluorinated γ-alumina, which could be assigned to the fluorine species bound to one, two, and three octahedral aluminum atoms.

Detailed adsorption thermodynamic data of organosulfur and organonitrogen molecules on NiMoS hydrotreating catalyst active sites were studied by density-functional theory (DFT) calculations. Initially, the adsorption of the molecules on the NiMoS edge surface is studied, and the most stable configuration for each molecule is identified. The changes in electronic energy and zero point vibrational energy upon the adsorption of different molecules on the NiMoS surface are calculated. The contribution of adsorbed molecules, as well as gas phase molecules, to changes in entropy and C p values are obtained by calculating vibrational frequencies of adsorbed and free molecules. With these data, the changes in enthalpy, entropy, and free energy due to the adsorption on the NiMoS edge surface at different temperatures are determined. These data can be used to estimate the relative surface coverage of each type of species at different reaction conditions.

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Despite the widespread use of gamma-Al2O3, there is still considerable disagreement over the nature of its structure due to both its poor crystallinity and differing preparation techniques during experimentation. Using density-functional theory (DFT) calculations and Rietveld simulations and refinement, the structure of three spinel-related models and a recently proposed nonspinel model were studied in reference to synchrotron X-ray powder diffraction (SXPD) patterns. The spinel-based structural models represent the structural features of gamma-Al2O3 better than the nonspinel model. The major failure of the nonspinel model is that the model cannot reproduce the SXPD reflection originating from tetrahedral aluminum. The Rietveld-refined spinel model can accurately reproduce the lattice parameters and other structural features of gamma-Al2O3, and it can generate a consistent diffraction peak at 2theta which lies between the splitting peaks of the experimental pattern that are originated from the disordered tetrahedral aluminum cations.

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