The active alumina in the Klaus catalyst undergoes a hydration reaction with water vapor
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What is the equation for the hydration reaction of active alumina in a Klaus catalyst with water vapor? What is the final product? What is the rate of this reaction at normal operating temperatures?
Thermal aging, hydrothermal aging, and sintering cause changes in the basic structure of the catalyst.
The main cause of catalyst deactivation is the sulfation of its active sites. The mechanism of sulfation involves the chemical adsorption of SO2 onto the active hydroxyl or oxide ion sites, followed by a chemical reaction with oxygen: Al2O3 + SO2 → Al2O3(SO2); Al2O3(SO2) + 2 SO2 + 3/2 O2 → Al2(SO4)3. A moderate amount of chemically adsorbed SO2 only leads to slight deactivation, while permanent deactivation occurs only after a chemical reaction with oxygen; therefore, it is necessary to ensure that the oxygen concentration in the main combustion furnace does not exceed 0.2%. A high temperature of 24–48 hours can be employed, with process gas rich in H2S (with a H2S/SO2 ratio of 2.5:1 to 3:1) passed through the catalyst bed to reduce sulfation, which helps promote the reverse sulfation reaction: 2 Al2(SO4)3 + 18 H2 = 2 Al2O3 + 18 H2O + 3/4 S8. Then, the H2S/SO2 ratio is restored to 2:1, and the inlet temperature of the catalyst bed is gradually brought back to normal operating conditions. An increase in the significant temperature difference across the catalyst bed at normal operating temperatures indicates an improvement in catalyst activity after the elemental sulfur trapped on the catalyst surface has been successfully removed