The effect of water vapor on sulfur-resistant shift reaction
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I want to know the impact of high or low moisture levels on the catalyst (operating under high or low moisture levels over a long period), and how high or low moisture levels affect the active gases in the conversion process
The level of water vapor directly affects the extent of the reaction between CO and H2O. If the reaction takes place in an environment with either too high or too low levels of water vapor for an extended period, it will result in either too high or too low temperatures in the catalyst layer, which in turn affects the catalyst’s durability and can lead to deactivation or reduced catalytic efficiency
A high gas-to-solid ratio can easily lead to the resulfidation of sulfur-tolerant shift catalysts. Catalyst resulfidation occurs when the peak temperature in the catalyst bed remains too high for an extended period, or when the gas-to-solid ratio is too high over time; this results in the H2S content in the process gas remaining below the required levels, thereby causing the catalyst to resulfidate and transforming some of its active components into oxide forms, which in turn reduces the catalyst’s activity. The decrease in activity caused by anti-sulfidation is reversible; re-sulfidation to restore its sulfide form can bring the activity back to nearly its original level. Water enters the catalyst bed due to leaks in the water heater, or from hot water pouring into the hot water tower, or as a result of incomplete separation of water droplets in the humidifier; this liquid water enters the catalyst bed and causes its temperature to drop rapidly. A large amount of incoming water can also carry away the active components in the catalyst, resulting in an irreversible decrease in its activity; this loss of activity is even greater at low temperatures.
Detailed analyses of the effects of low-activity catalysts at high water vapor concentrations are provided in all the super-editions on the third floor； Medium-temperature catalysts, especially those that have just been reduced, exhibit high activity. Operating them under long-term conditions of low water vapor concentrations can cause the catalyst to undergo Fischer-Tropsch reactions, leading to an acceleration of side reactions and a decline in the catalyst’s normal activity ； Operating for a long time under high water vapor concentrations, with the catalyst installed at a large height, can cause the temperature at the catalyst hot spots to rise rapidly, as well as overheating and other phenomena.