Why does carbon deposition occur during hydrofining reactions using heavy metal catalysts in the presence of acidic water?

Catalyst~Metal centers and acidic centers? Effect?

Could the specific components of the carbon deposits be analyzed, so as to identify the underlying mechanism and then find a solution?

It is mainly the effect of water that causes a decrease in catalyst activity, and even its destruction, which in turn leads to catalyst coking

It is also possible that polymers are the main cause of coking; this coking leads to an increase in the pressure difference within the reactor, thereby damaging the catalyst

Acidity is caused by hydrogen sulfide generated during the hydrogenation reaction dissolving in water, thus forming acidic water; in fact, whether it is acidic or not doesn’t really matter much

Acidic water center? You can’t be serious; it’s the acidic centers that cause carbon buildup, right? It has nothing to do with water. First, determine whether what you say is correct. In heavy metal hydrogenation catalysts, carbon deposition occurs due to hydrogen evolution, condensation, polycondensation, etc. at the acidic sites; the stronger the acidity, the faster the rate of carbon deposition.

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Acidic water center? Are you joking? It should be an acidic center, with carbon deposits gradually forming on the surface of the catalyst. Carbon deposition reduces the catalyst’s activity, as carbon-forming compounds strongly adsorb onto the acidic sites, covering those active sites. Moreover, carbon deposition blocks the pores, preventing reactants from reaching the active sites for adsorption, which in turn reduces the utilization rate of the catalyst surface. In the early stage of the reaction, the amount of carbon deposit begins to increase rapidly, and the catalyst’s activity also declines quickly. As time goes on, the amount of carbon deposit stabilizes, and the catalyst’s activity reaches a stable level. In the later stages of the reaction, excessive carbon deposits block the pores of the catalyst, causing a significant drop in its activity; therefore, an increase in temperature is necessary to compensate for this