Effects of hydrocarbonaceous deposits have been investigated in hydrogenation of 1,3-butadiene over Pd-Ag/Al2O3 catalysts. Studies on the effect of various treatments on self-poisoned samples revealed very different behavior of the surface deposits. Because of hydrogen's low surface fugacity, hydrogen treatment was not sufficient to remove surface species at T<373 K. Vacuum or O2 treatment increased the activity of the self-poisoned samples. The observation has been interpreted in terms of surface restructuring of the firmly held species. Deliberate poisoning - amount of deposits 1-20 mg/gcat - increased the selectivity of n-butane formation. Presence of deposits seems to decrease the effective surface concentration of butadiene. The results have been interpreted as slow diene transport allowing saturation of n-butenes on a certain fraction of sites.
ASJC Scopus subject areas
- Condensed Matter Physics
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry