On-line addition of catalyst in high-temperature reactors : high selectivity to olefins

By adding solutions containing catalyst salts to hot monolith catalysts during partial oxidation processes, the salt decomposes instantly and is deposited selectively near the front face. We have used this technique to deposit extremely small amounts of Pt on α-Al2O3 monoliths during ethane oxidation to olefins. We find that on this catalyst with H2 addition, the selectivity to ethylene rises from ∼ to over 80% at an ethane conversion of ∼60% and at complete O2 conversion. We also examine the addition of promoters including Sn, which gives improved performance compared to the Pt catalyst alone. This appears to be a general effect that could be useful in preparing catalysts with different loadings and distributions in high‐temperature processes. It can also be used for rapid and accurate diagnosis of catalysts and additives and to modify catalysts on‐line in situations where deactivation or catalyst loss occurs.