The role and stability of Li2O2 phase in supported LiCl catalyst in oxidative dehydrogenation of n-butane

This study was aimed at defining the role of active phases in supported LiC l and LiCl-DyCl3 catalysts in the catalytic oxidative dehydrogenation (ODH) of n-butane. LiCl supported on silica displayed the highest activity and s electivity in n-butane ODH compared with other alkali metal halides. Additi on of DYCl3 increased the activity. TPO, XRD and Raman light scattering (RL S) data showed that LiCl and DyCl3 formed during the preparation stage were converted to Li2O2 and DyOCl phases, respectively, by calcination in air a t > 400 degreesC. The results of separate TPR experiments (O-2-oxidation-bu tane reduction) along with XRD, RLS and X-ray photoelectron spectroscopy (X PS) data proved that butane reacts mainly with oxygen species of Li2O2 phas e at ODH conditions, probably attributed to [Li+O-] pairs. The proposed fun ctions of chlorine and dynamic oxygen in the ODH of butane are consistent w ith the activity, selectivity and stability of silica and magnesia-supporte d catalysts. High thermal stability of Li2O2 in oxidized LiCl catalyst was attributed to the formation of protective Li2O-LiCl surface layer. Deactiva tion of LiCl/SiO2 catalyst in n-butane,ODH is caused by the formation of Li -silicates at reaction conditions while LiCl/MgO display a stable performan ce. (C) 2001 Elsevier Science B.V.. All rights reserved.