In-depth issues of hydrogenated diesel
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As the requirements for diesel quality become stricter, the degree of hydrogenation of diesel also increases. However, a higher degree of hydrogenation can lead to reduced wear resistance and light stability. Our plant’s medium-pressure hydrogenation reforming unit has experienced the phenomenon of fluorescent green appearing in the diesel produced; such diesel has very poor light stability. I would like to ask my colleagues whether they have encountered this issue as well How to solve it? In my opinion, this issue will not be significant when producing Euro IV diesel, but it could become a problem once Euro V standard diesel is produced.
I haven’t encountered this problem yet. It seems that for Euro V standards, the sulfur content is less than 10 ppm; it isn’t processed to such a low level! The work experience is not sufficient!
I have also seen these issues mentioned by the original poster in some papers; excessive hydrogenation of diesel is not desirable. If Euro V diesel is to be produced, it is likely necessary to replace the catalyst, or add some additives after production, such as anti-wear agents.
Replace the catalyst or add some additives.
Actually, the issue raised by the original poster isn’t unfounded, but I think the most crucial aspect of hydrogenation is the catalyst. As long as an appropriate catalyst is used, this shouldn’t be a problem at all!
We have not encountered this situation, but in the case of excessive hydrogenation, it is sufficient to make slight adjustments to the reaction pressure and temperature; there is no need to replace the catalyst, otherwise it indicates that the design parameters were not properly specified.
Wear resistance: Polycyclic aromatic hydrocarbons in diesel act as effective anti-wear agents; they exert a wear-resistant effect when their concentration is above 1%. During deep hydroprocessing of diesel, these anti-wear agents are removed, thereby reducing the diesel’s inherent wear resistance. Adding a certain amount of anti-wear agent to deeply refined diesel can improve this situation. In terms of color: The substance that may produce a fluorescent green color is a type of polycyclic aromatic hydrocarbon; its formation is related to the operating conditions, specifically to the degree of hydrogenation. The greater the degree of hydrogenation, the more severe the operating conditions, and the more colored substances are generated, resulting in a worse color for the diesel. This represents a trade-off with regard to the quality of the diesel. Light stability: Natural oils contain various antioxidants, and during the hydrogenation process these natural antioxidants are removed. The greater the degree of hydrogenation, the more completely these natural antioxidants are removed, which results in lower light stability of diesel. Antioxidants can be added to improve it. These problems arise mainly because the hydrorefining technology is not yet perfect and requires further development.
What are the antioxidants? Can everyone tell me?