Confusions regarding hydrothermal deactivation and catalyst water vapor regeneration, as well as the preparation of catalysts by hydrothermal methods

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Hello, everyone. I have been conducting research on hydrogenation catalysts recently, and I have a few questions regarding the impact of water on these catalysts that I would like to ask you: (1) Hydrothermal deactivation of catalysts: Under the influence of high-temperature steam, the active metals on the surface of the catalysts tend to aggregate, the crystal structure changes, and both the specific surface area and porosity are affected as well. I would like to ask everyone: under what temperature and pressure conditions does hydrothermal deactivation generally occur? Is there an approximate minimum temperature range at which hydrothermal deactivation occurs? (2) Catalyst steam regeneration: While reading relevant literature, I came across information stating that in addition to using air to burn off the coking deposits on the catalyst surface, another common method of regeneration involves the use of steam. My understanding is that introducing water vapor can dissolve and remove water-soluble impurities, while the water-gas reaction C+H2O=CO+H2 is used to remove carbon deposits. I would like to ask everyone: is there anything wrong with my understanding? What is the principle behind regeneration by introducing water vapor? But given the issue of hydrothermal deactivation, wouldn’t water vapor have an adverse effect on the catalyst? Then why is there a method that uses water vapor to regenerate the catalyst? What are the advantages of this approach? (3) Preparation of catalysts by hydrothermal method: During the preparation of catalysts via the hydrothermal method, the reaction takes place under high temperature and pressure inside a hydrothermal reactor, resulting in the formation of a crystal structure. In addition, core-shell catalysts can also be prepared using this method, allowing for the formation of a more stable core-shell structure in the catalysts. But my question is, since water has an adverse effect on catalysts, how does the hydrothermal method for preparing catalysts avoid affecting their morphology? Generally speaking, in catalytic reactions, except for those processes that require the presence of water in the reaction system, it is advisable to avoid introducing water into the system as much as possible to prevent any adverse effects on the catalyst. Is this summary reasonable? Thank you all~~