Determination of the accessible metal fraction and the metal particle size on coked Pt/Al2O3 Cl catalysts

GARETTO, TF; APESTEGUIA C.R.

APPLIED CATALYSIS A-GENERAL

Elsvier

Año: 1986 vol. 20 p. 133 - 143

0926-860X

The chemisorption of H2, O2 and CO, and the H2-O 2 t i t r a t i o n method were used for determining the accessible metal fraction of coked Pt/AI2O3 reforming catalysts Several Pt/AI2O3 catalysts with different metal loading and metal particle size were employed. A high pressure run using naphtha as feed was performed to coke the samples. Gas uptakes were compared with the catalytic activity of benzene hydrogenation. It was found that the irreversible CO adsorption may be taken as a measure of the accessible metal fraction of coked Pt/AI2O3 catalysts; both oxygen and hydrogen uptakes led to wrong results. On the other hand, when the metal dispersion will be determined, it is necessary to eliminate the coke on the metal by O2 treatment at high temperature which can sinter the metal. The appropriate conditions to eliminate coke with no modification of the metal fraction were investigated by CO chemisorption and electron microscopy The coke burning by air treatment at 703 K was found to be adequate to eliminate the coke on the metal, with no measurable modification on the metal dispersion