Q & A > Question Details
For VGO Hydrotreating units at the upstream of the FCC, we currently use COMO Catalyst. The unit is operated by maintaining constant Sulfur spec in the sweet VGO which goes to FCC. Typically VGO feed sulfur is ~22000wtPPM and Nitrogen is ~2200 wtPPM. After processing in hydrotreater, sweet VGO sulfur is ~1500wtPPM and Nitrogen is ~1000wtPPM. Now the question is that if I change the catalyst from COMO to NiMO catalyst and maintain remaining all operating parameters same, what would be the Nitrogen conversion if I operate the unit by maintaining Sulfur level 1500wtPPM which is same as earlier? Will the Nitrogen conversion increases because of NiMo catalyst or it remains same since we are constraining the unit severity by maintaining same sulfur level?
20/08/2015 A: keith bowers, B and B Consulting, kebowers47@gmail.com
NiMo generally has higher hydrogenation of nitrogenous and aromatic compounds and comparable or slightly lower HDS activity.
17/08/2015 A: Liv Hovgaard, Haldor Topsoe A/S, liho@topsoe.dk
The performance of CoMo and NiMo catalysts for the FCC pretreater depends not only on the feed properties, such as the sulfur content and nitrogen content, but also on the operating conditions and product requirements. Moreover, there are impacts of various secondary promoters, depending on the actual manufacturer, which can also impact the activities and the relative HDS and HDN differences.
When processing a high nitrogen feed as in your case and producing a product with a content of about 1000 ppm nitrogen, using the Topsoe CoMo catalysts will always provide a highest HDS activity, and the NiMo catalysts will always give the highest HDN activity.
Regarding the hydrogenation activity, the NiMo catalysts are preferred, but only under the right conditions. If the nitrogen conversion is very low, which is typical at lower hydrogen partial pressures, the hydrogenation activity of the two types of catalysts will be very similar.
07/08/2015 A: Saleh Daryabari, Senior Process Engineer of RCD and RFCC, Arak Refinery, daryabari@gmail.com
Generally CoMo catalyst has higher HDS and same HDN activity comparing to NiMo catalyst. It means for same sulfur in product you should operate reactor at a little bit higher temperature and therefor you will have higher HDN (only because of higher temperature not higher catalyst activity). However you should consider the catalyst activity is affected by catalyst preparation method.
For FCC/RFCC feed hydrotreating I prefer NiMo catalyst. Because in addition to higher Nitrogen conversion it has higher hydrogeneration activity (higher Hydrogen addition) and you will have better product quality with higher UOP K factor that cause higher conversion in FCC/RFCC unit.
31/07/2015 A: Vincent Huang, HC advanced technology, chehaitao@gmail.com
General speaking, comparing with CoMo catalyst, NiMo catalyst has higher hydrogenation activity, therefore higher Nitrogen conversion. So by switching to NiMo, you would expect to have higher Nitrogen conversion and Higher aromatics saturation, which is good for FCC conversion, but make sure you have good hydrogen availability, Otherwise, the catalyst deactivation rate will be high.