Cobalt-doped magnesium fluoride as a support for platinum catalysts: The correlation of surface acidity with hydrogenation activity

The binary Mg-Co fluorides have been employed for the first time as platinum catalyst supports and tested for o-chloronitrobenzene hydrogenation in batch, flow and aqueous-phase reforming conditions. Isomorphous substitution of Co2+ cations for Mg2+ ones in the tetragonal structure of MgF2 was verified by XRD analysis. The DFT calculations showed a decrease in the strength of surface Lewis acid centers with increasing cobalt content in the binary fluorides and were confirmed by NH3-TPD and Py-FTIR studies. The activity of Pt/MgCoF catalysts for o-chloronitrobenzene hydrogenation correlates with Lewis acidity and the amount of chemisorbed nitrobenzene. The latter forms on the catalyst surface adsorbed species not described in the literature yet. The mode of chloronitrobenzene adsorption on platinum support boundary centers via electron-deficient Mg2+ and electron-rich platinum centers has been proposed. It has been found that the application of in-situ generated hydrogen from APR of methanol makes it possible to obtain o-chloroaniline with 100% selectivity. (C) 2019 Elsevier Inc. All rights reserved.