Poisoning of cobalt catalyst used for Fischer–Tropsch synthesis

• Threshold sulfur concentration for catalyst poisoning.
• Reversible poisoning for low-level sulfur.
• Low-level sulfur promotion of catalytic activity.

Sulfur in the form of H2S has been added at various concentration levels during cobalt Fischer–Tropsch synthesis. A steady-state FTS conversion was established prior to adding H2S. At low levels (<500 ppb) H2S addition does not cause a detectable decrease in activity during 5–10 days of exposure to H2S. Above the threshold limit of about 500 ppb, the rate of decrease in CO conversion is linearly related to the H2S concentration in the gas feed. At H2S levels in the 500–1000 ppb range, it appears that the poisoning effect is reversible so that catalytic activity is recovered when the addition of H2S is terminated.

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