What are the product specifications for Petroleum Benzene 545? A brief analysis of the reasons for low purity and unsatisfactory melting points of petroleum benzene?

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Specifications for petroleum benzene products: Color (Platinum-Cobalt scale) not deeper than 20; benzene purity not less than 99.72%； Toluene not more than 0.05% ； Crystal point 5.46 ； Sulfur content not exceeding 1 mg/kg ； The bromine index is not greater than 20 mg of bromine/100 g ； The color of the pickling colorimetric acid layer shall not be darker than that of the standard solution containing 0.10 g of potassium dichromate in 1000 mL of dilute acid. Reasons for low purity of petroleum benzene: the material supplied for extraction has a high non-aromatic content, and the amount of non-aromatics discharged from the top of the benzene tower is low ； Improper operation of the benzene tower results in a high content of toluene in the product ； Improper operation of Tower C-2501 caused non-aromatic compounds at the tower top to reach the bottom of the tower, resulting in an increase in the amount of non-aromatic compounds in the feed to the benzene tower ； It is also possible that the temperature rise during the disproportionation reaction is too low, resulting in insufficient effect; or the temperature rise is too high, leading to an increase in side reactions. The reason for the unsatisfactory crystallization point of petroleum benzene is the high proportion of non-aromatic compounds in the product, which causes the crystallization point to not meet the requirements ； The product has a high toluene content, resulting in unsatisfactory freezing points