The Mechanism of Potassium Promotion of Chromia-Alumina Dehydrogenation Catalysts

Vapour phase catalytic transformations of terpene hydrocarbons in the C10H16 series. III. Dehydrogenation of Δ3-carene over modified chromia and chromia–alumina catalysts

“…The decreased activity of chromia and chromia-alumina by a larger amount of potassium ions, above I%, may be due to reduction in the number of isomerising and dehydrogenating sites either by chemical combination or by physical blocking by potassium ions as suggested by MacIver and co-workers (2).…”

Vapor Phase Catalytic Transformations of Terpene Hydrocarbons in the C10H16 Series. II. Aromatization of α-Pinene over Chromia–Alumina

“…The high activity of chromia-alumina catalyst prepared from sodium doped alumina may be explained on the basis of the fact that alkali metal ions doped on chromia-alumina promote the dehydrogenation activity of the catalyst by neutralizing the strong acid sites of alumina and thus preventing the undesirable side reactions leading to the formation of alkyl cyclopentenes which act as poisons for del~ydrogenation sites (8). The high aromatization activity of chromia-alumina-HF catalyst can be explained as follows.…”

The Effect of Transition Alumina (γ‐, η‐, χ‐Al2O3) on the Activity and Stability of Chromia/Alumina Catalysts. Part I: Model Catalysts and Aging Conditions

“…It means that in the case of Cr/χ‐Al 2 O 3 (1000), the effect of sodium promotion is observed. But a decrease in the specific catalytic activity should be expected with an increase in some threshold surface concentration of Na + because an excess of alkaline ions decreases the specific surface area of Cr 2 O 3 in the catalyst due to intensified crystallization of α‐Cr 2 O 3 and/or blocking of the Cr 2 O 3 surface . From this point, sodium redistribution from the bulk toward the surface may in practice lead to catalyst deactivation.…”

“…It is known that some addition of alkaline ions into chromiaalumina catalyst lead to an increase in the catalytic activity. [39,40] When comparing the value of catalytic activity loss and the degree of decrease in the specific surface area of the χ-series catalysts, it is found that sintering at 1000 C is more pronounced than the decrease in activity, whereas the chromium surface concentration remains the same as before artificial aging. It means that in the case of Cr/χ-Al 2 O 3 (1000), the effect of sodium promotion is observed.…”