Walter R. Knox

The oxidation and leaching of some chromia-alumina and chromia-silica-alumina preparations

Abstract The oxidation and leaching of some chromia-alumina and chromia-silica-alumina preparations have been studied. A correlation has been found between ionic potential of a number of ions used as promoters on a chromia-alumina, and the amount of equivalent CrO 3 leached from these preparations after oxidation at 500 °. The correlation is good for ions having inert gas electron configurations. Those ions having pseudo-inert gas configurations fit the correlation as well. A study of extended oxidation and leaching shows that a limit of oxidizability of chromia on alumina can be reached. However, this limit is closely approached while much of the clump chromia is still present. This is shown by electron spin resonance spectra. The presence of dispersed phase chromia is also shown. The loss of oxidizability is related to activity in dehydrocyclization of n -hexane and is explained in terms of accumulated surface acidity. The effect of potassium promotion on oxidizability and dehydrocyclization activity has also been studied.