Refined diesel fuel appears fluorescent green in color; seeking an explanation for this phenomenon
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Recently, the color of refined diesel has turned fluorescent green. I’m looking for an explanation – could anyone explain this from a fundamental perspective?
It is likely related to the excessively high reaction temperature, which causes dehydrogenation of naphthenes to produce aromatics.
Thank you. The polyaromatic hydrocarbon content in the diesel we delivered was 2.8%, which is not very high. Initially, we considered using a higher degree of hydrogenation, but we have a reforming bed here that allows for mild ring-opening cracking; the production process focuses on producing naphtha. Even after the temperature was reduced, the color remained fluorescent green, so we increased the temperature again – with little change as a result.
Does your unit perform modified hydrogenation? I think the degree of hydrogenation is not sufficient. For our reformated products, when the sulfur content is below 5 ppm, they have no color; whereas when the sulfur content is high, they take on a light blue-green color.
Our current sulfur content is very low, at 1-2 ppm; it’s a diesel upgrading unit. What do you feed in? Is the charcoal content high?
The dry content of the catalytic carbon is high; it’s roughly 40%. What is your cracking temperature?
Ours isn’t that high; the char content is around 30%. We’re already at the end of the reaction phase here, with a uniform temperature for modification of 360–365
Oh, it’s still due to the decreased catalyst activity. The temperature set for the end of the modification process is 390°C; based on your current temperature, it’s a bit low – you might try raising it.
We also encountered color issues for a while; steam was present in the diesel output, which might indicate a leak inside the steam vessel. We also encountered issues with the composition of the raw materials later on; mixing in a fuel accelerator improved the results. In any case, the product testing at that time showed no abnormalities
It is the color resulting from the saturation of polycyclic aromatic hydrocarbons