Hydrotreater catalyst

[mm1975]

What will be the effect on Light Naptha hydrotreater catalyst, if lighter oelifins( C4's) are present in feed.
How it will effect the unit performance.

Thanks & regards

 

[epoisses]

Olefins may polymerize if your H2 pp is insufficient, creating maldistribution and eventually a delta P spike.

Secondly, olefins, H2S and sulfur compounds engage in equilibrium reactions, i.e. at high olefins levels you form sulfur compounds, that decompose into H2S and olefins as the olefins concentration declines. As your cat deactivates, olefins hydrogenation is not completed and removal of sulfur compounds to a low level becomes difficult because of the equilibrium reactions.

 

[25362]

My 2 cents:

1. When desulfurizing cracked feedstocks, desulfurization is always accompanied by saturation of olefins, resulting in loss of octane number and increased hydrogen consumption.

2. Light olefins may reduce the hydrogen partial pressure.

3. When unsaturated feedstocks need to be desulfurized, it may be desirable to split the catalyst into one or more beds providing cooling by cold recycle gas into the so-called quench zones between beds to compensate for any excessive temperature rise.

4. Olefins combine with H₂S to form mercaptans.

5. Temperatures above 340^oC can be counter-productive resulting in the formation of olefins, which may recombine with H₂S to form mercaptans. Feedstocks for cat. reformers require sulfur levels of less than 1 ppm. On occasions, increasing temperatures, instead of reducing the S content to desired level, as might have been expected, it is increased to 2 ppm because of those reactions.