Silica inactivation of SO_3 absorbing sites is mentioned in the literature as the chief mechanism behind SOx additive deactivation, and steaming of mixtures of FCC catalyst with SOx additives is recommended prior to evaluation. The pilot riser experiments have shown that deactivation is very fast compared to the actual FCC catalyst and may calculated from the SO_2 base line level alone. From these results it is clear that steaming techniques developed to speed the slow mechanism of FCC catalyst deactivation are unsuitable for SOx additives, as they accelerate the wrong deactivation process. Therefore, SOx additives should be tested with no previous treatment in order to correctly evaluate their performance.
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