Diesel discoloration issue
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The hydrogenation refining unit uses the fractions obtained after the deasphalting of medium- and low-temperature coal tar as raw material; the products resulting from hydrogenation are naphtha fractions, diesel fractions, and residue fractions. Recently, the color of the diesel product has changed from white to brownish-red, and then gradually to light red. However, after the sample was left standing for some time, the light red color almost disappeared. I would like to ask the experts about the reasons for this color change and why the red color disappears after it is left undisturbed
It is best to conduct a comprehensive analysis of products at various stages in terms of color, including their components (the composition of various hydrocarbons), oxygen content, impurities, etc.
Does the discoloration of oil indicate heavier fractions or a poorer hydrogenation effect? The specific reason for the discoloration is unknown; it can be speculated that fading is related to H2S or S. These reducing groups bleach the chromophoric groups therein. I already returned my organic chemicals assignment to the teacher