Reply To: Sulfiding procedure of hydrotreating catalysts

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Nasir Hussain

Catalyst Sulfding or pre-sulfiding meaning is the process of converting catalyst metal oxides into the metal sulfides by reacting with H2S (Hydrogen Sulfide) in the presence of hydrogen gas. The Sulfiding process is accomplished by injecting easily decomposable Sulfiding chemical, containing high content of Sulfur. Sulfiding is required for the fresh or regenerated catalyst.
Its brief steps are;
1. Catalyst dry out or purging: Firstly fresh catalyst is dried out to remove moisture and made oxygen-free by purging with Nitrogen.
2.Pre-Wetting Step: Catalyst is pre-wet or soaked with feed oil at nearly more than 100 C temperature.
3. First Phase Sulfiding: At 190~220 C, the Sulfiding agent is injected with controlling 1.2~2 % total sulfur content which includes both feed oil and agent sulfur. Continue injection until Sulfur breakthrough reached in recycle gas.
Second Phase Sulfiding: his step is performed at 315~345 oC while maintaining the injection rate i.e. 1.5~2.0 %.During this phase, H2S content is maintained in recycle gas approximate 2000 ppm, maximum. At this stage, the catalyst will stop to take in the H2S and will pass through the reactor without reaction and H2S content in the recycle gas will start to increase above 2000 ppm.
For further details please visit the blog Sulfiding and its troubleshooting;

Sulfiding of Hydrotreating Catalysts and its Troubleshooting