Catalyst drying in hydrogenation unit
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For this step of catalyst drying, do people use N2 or hydrogen as the medium?
Nitrogen and hydrogen are difficult to control and can easily reduce the catalyst.
The temperature can be controlled. If nitrogen is used, is it necessary to replace nitrogen with hydrogen before the subsequent presulfurization? By that time the furnace is already running, and could fluctuations in the pressure of the gas used for replacement cause significant temperature fluctuations?
First, dry it with nitrogen or hydrogen – it entirely depends on the drying temperature you control. Secondly, if your drying temperature is kept below 200°C, it is completely fine to use hydrogen as the drying medium, because at this temperature, even without sulfur supplementation, the active metal components in their oxidized state will not be reduced to elemental metal, thereby avoiding permanent deactivation. Third, drying temperatures below 200°C can only remove the surface water molecules in the catalyst; to eliminate the crystalline water molecules as well, the bed temperature must be raised above 230°C. At this temperature, in an environment of high-purity hydrogen, the active metal components in the catalyst in their oxidized state will be reduced to elemental metal, resulting in permanent deactivation. In summary, if you want to completely remove the crystalline water molecules from the catalyst, it is difficult to achieve this using hydrogen as a drying medium. Of course, if the catalyst manufacturer provides on-site guidance and says it works, that’s also an option; but there’s nothing around here that uses hydrogen for drying – I only heard about it a long time ago. For drying and vulcanization, the manufacturers provide detailed instructions, so there is little need for the users to worry about these processes; they can simply follow the parameters specified by the manufacturers
Additional note: Some catalysts do not require drying