Does catalytically refined gasoline turn yellow after refinement?
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The raw material for catalytic refined gasoline comes from gasoline hydrogenation; it is colorless. However, after catalytic refining, its color turns slightly yellowish. I would appreciate some advice from those who are more experienced in this area{:1_90:}
This post was last edited by longziyun on 2018-12-8 at 08:54. I’m not aware of the source of the hydrogenated gasoline mentioned by the original poster, but based on experience, most fuel-grade gasoline comes from catalytic cracking, a process that was heavily developed in our country as part of the “Five Golden Flowers” program. The characteristics of the products obtained through catalytic cracking vary depending on factors such as the properties of the crude oil, the properties of the catalyst itself, and the extent of the reaction; however, the composition of gasoline, with components ranging from C5 to C11 and a boiling range around 200, remains relatively constant. After hydrogenation, the total sulfur and olefin content in gasoline is significantly reduced. However, the gums that are present in gasoline and formed during the catalytic cracking process remain largely unchanged during subsequent anaerobic reactions. Yet, further refining requires oxidation and desulfurization of thiols; due to the oxygen-rich environment, while thiols are oxidized to disulfides, the gums are also oxidized, leading to the formation of large molecular aggregates. This results in significant light dispersion, giving color to what was originally colorless and transparent gasoline. Temporarily, the amount of oxidizing air can only be reduced appropriately or antioxidants can be added. But in fact, the root cause should be one of the many effects caused by the fluctuations in the catalytic cracking unit – the butterfly effect, you know. It would be best to address the root cause by adjusting the catalytic cracking operations so that they function properly; in that case, the color of the gasoline will naturally return to normal. Of course, this is merely my personal opinion, and it may not be correct.
Can an anti-adhesive agent prevent discoloration to yellow?
As active substances, antioxidants or anti-gelling agents can only react with oxygen first; they prevent large molecular gums from aggregating due to oxidation, thereby preventing the color of the oil from darkening further, but they cannot bleach the oil.
Is the amount of unfiltered air flow too high?
This post was last edited by Refiner on 2019-3-3 08:39. It is likely caused by the oxidation of gasoline due to an increased amount of air being introduced
Eventually, it was found that the alkali solution used for the pre-alkaline washing of gasoline had been drained and transferred to the fixed-bed reactor; the gasoline alkaline washing tank no longer contained any alkali solution, and the alkaline residue was sent to another location.
Furthermore, the thiol compounds in gasoline are relatively easy to oxidize; they can be considered as antioxidants inherent in the oil itself. This is one of the reasons why gasoline that has been refined and desulfurized tends to change color more easily. Therefore, it is advisable to add some antioxidants as well.