Effect of chromium content on the properties of a microspherical alumina-chromium catalyst for isobutane dehydrogenation prepared with the use of a centrifugal thermal activation product of gibbsite

The states of chromium in both promoted and unpromoted alumina-chromium catalysts with various chromium contents prepared with the use of a centrifugal thermal activation product of gibbsite were studied in detail. The presence of five chromium species was found in the catalysts of this type: two Cr⁶⁺ and three Cr³⁺ species. The concentration of each particular chromium species depends on the total chromium content of the catalyst. Based on the experimental data, we hypothesized that highly disperse Cr³⁺ particles, the formation of which was completed at a chromium content of ∼7–9 wt %, are responsible for the catalytic activity of alumina-chromium samples in the reaction of isobutane dehydrogenation.