Naphthalene extracted from coal tar is called tar naphthalene. In high-temperature coal tar, naphthalene accounts for about 8-12%. The naphthalene oil fraction with a temperature range of 210-230 ℃ is cut from the side line of the tar distillation tower. After cleaning and dephenolization, the light components are separated by distillation, and then the industrial naphthalene with a freezing point of 78 ℃ and purity of 96% can be obtained.
Industrial naphthalene contains residues of indene (1-3%), methyl naphthalene (1-2%), and small amounts of indene, tar base and tar acid. After advanced acid pickling and passivation and steam distillation, refined naphthalene with sulfur content less than 0.1% and freezing point of 79 ℃ can be obtained. If the sulfur content must be improved to be less than 0.05%, the hydrofining process should be selected.
The raw material of petroleum naphthalene comes from the heavy aromatic components in the whole process of catalytic reforming, catalytic cracking and nitrogen compound cracking. In the catalytic reforming oil, the water content of methylnaphthalene is about 55%. After purification and adsorption, various homologues of naphthalene were separated from the raw material fraction, and then the hydrodealkylation reaction was carried out using Cr2O3-Al2O3 as a metal catalyst, at 400-800 ℃ and 0.5-7 MPa. After the reaction material was cooled by liquid-phase chemical substances, the light components of benzene, xylene, xylene, etc. were removed by steam distillation, and finally the petroleum naphthalene products could be obtained by progressive distillation. The commodity is purified by organic solvent digestion and absorption and organic solvent cleaning, and the purity reaches 99.73%.
According to statistics, the butadiene equipment with an annual output of 300000 tons using light diesel oil as the cracking feedstock can produce 90000 tons of tar by side, of which the naphthalene and naphthalene potential are 40000 to 50000 tons.
Refined naphthalene for industrial production is the raw material of basic chemical plants, which is suitable for the production and manufacture of additives and external dispersants. It is also the raw material for the production and manufacture of resin materials, flame retardants, rubber antioxidants, surfactants, man-made fibers, dyes, pharmaceuticals and spices.
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