We have a hydrotreater, where I would like to limit my aromatics saturation. Can some one suggest if it is possible and what are the critical parameters for it?
Answers
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12/11/2010
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Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
For deep desulfurization of diesel fuel, UOP describes in their publications the "preferred path" of mild hydrocracking reactions. That path features avoiding saturating the aromatics. The publications describe the operating conditions and catalyst type required.
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10/11/2010
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Virendra Kapoor, Petroleum Refining Consultants, vkkapoor9@yahoo.com
Limiting the aromatics saturation is specific to the type of the in hydrotreater. Various major factors responsible for it are:
1-Type of catalyst
2- Partial pressure of hydrogen
3- Operating temperature
4- Space velocity
5- feed stock and its characteristics and type of aromatics
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10/11/2010
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Prashant Parihar, BPCL, pariharprashant@bharatpetroleum.in
Aromatic saturation is equilibrium limited at higher temperatures, this results in incomplete saturation of aromatics towards the end of catalyst life as to counter activity decay CAT has been increased. Higher bed temperatures will limit aromatic saturation but will compromise catalyst life and may result in increased cracking reactions in hydrotreater.
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09/11/2010
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RENE AGA, SECOT, renelaga@telefonica.net
The first parameter is feedstock properties, if it’s straight run and from which crude type or if it comes from thermal or catalytic cracking. Also the boiling range, in particular the end point, because the type and concentration of poly aromatics will change with it.
Then the product specs, i.e. sulfur content and aromatics content required; if it is to obtain diesel oil or heating gasoil, etc. Normally when we speak of aromatics reduction in gasoil we understand poly aromatics. If you want to limit aromatics saturation, I understand that the product is not for diesel formulation.
Third the catalyst type. To saturate aromatics the catalyst must have hydrogenation properties. Ni-Mo catalysts have higher hydrogenation selectivity than CoMo catalysts, but with CoMo catalysts it is more difficult to obtain very low sulfur contents, especially if the feedstock contains difficult to treat sulfur compounds (hindered sulfur compounds). Also the hydrocracking properties of the catalyst play a role if the feedstock is refractory.
Further there are the operating conditions: space velocity, hydrogen partial pressure and temperature.
You see, there is no simple answer to the question, and normally pilot plant studies are required to determine the optimum catalyst combination and operating conditions.
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09/11/2010
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keith bowers, B and B Consulting, kebowers47@gmail.com
There are several good hydrotreating catalysts that minimize aromatics saturation. Contact your Catalyst Supplier and discuss the specific needs and conditions with their technical support .
Lower temperatures, lower hydrogen partial pressures, smaller catalyst pore structure, lower aromatic saturation activity all trend to the 'keep the aromatics' objectives you ask.
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