As. Bodke et Ld. Schmidt, On-line addition of catalyst in high-temperature reactors: high selectivity to olefins, CATAL LETT, 63(3-4), 1999, pp. 113-120
By adding solutions containing catalyst salts to hot monolith catalysts dur
ing partial oxidation processes, the salt decomposes instantly and is depos
ited selectively near the front face. We have used this technique to deposi
t extremely small amounts of Pt on alpha -Al2O3 monoliths during ethane oxi
dation to olefins. We find that on this catalyst with H-2 addition, the sel
ectivity to ethylene rises from similar to 65 to over 80% at an ethane conv
ersion of similar to 60% and at complete O-2 conversion. We also examine th
e addition of promoters including Sn, which gives improved performance comp
ared to the Pt catalyst alone. This appears to be a general effect that cou
ld be useful in preparing catalysts with different loadings and distributio
ns in high-temperature processes. It can also be used for rapid and accurat
e diagnosis of catalysts and additives and to modify catalysts on-line in s
ituations where deactivation or catalyst loss occurs.