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Principles and techniques of hydrogenated benzene
The main raw materials in the production of benzene, toluene and xylene are petroleum catalytic reforming oil, petroleum cracking high temperature pryolysis gasoline and coking crude benzene. The ratio of the three materials in the total amount is: 70%, 27%, 3%. The aromatic hydrocarbon production processes using petroleum as raw material use hydrogenation process. The aromatic hydrocarbon production processes using coking crude benzene include pickling refining and hydrotreating methods.
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Table 1 Leto production benzene quality |
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|
Item |
Index |
Item |
Index |
|
Color (Pt - Co) |
≯No. 20 |
Density (20℃) , g/cm3 |
0.878~0.881 |
|
Crystallization point,℃ |
≮5.45 |
Pickling colorimeterK2Cr2O7, g/L |
≤0.05 |
|
Benzene, % |
≮99.9 |
Toluene , % |
≯0.05 |
|
Non-aromatics, % |
≯0.10 |
Total sulfur, mg/kg |
≯1 |
|
Thiophene, mg/kg |
≯1 |
Neutralisation test |
Neutral |
|
Water (20℃) (by visual) |
No |
|
|
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Table 2 Leto hydrotreating crude benzene energy consumption |
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Coke oven gas |
High-pressure steam |
Low pressure steam |
Electricity |
Recycled water |
Nitrogen |
Solvent |
|
m3/t crude benzene |
t / t crude benzene |
t / t crude benzene |
kWh/t crude benzene |
m3/t crude benzene |
m3/t crude benzene |
|
|
300.5 |
0.433 |
0.540 |
95.6 |
76.6 |
15.6 |
No need |
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Table 3 Extractive distillation low temperature hydrogenated benzene, toluene and xylene yield and total refining rate |
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Benzene, % |
Toluene, % |
Xylene, % |
Total refining rate, % |
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|
98.5 |
98.0 |
117 |
99.8 |
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Table 4 Extractive distillation low temperature hydrogenated benzene quality |
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Item |
Index |
Item |
Index |
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|
Color |
Colorless transparent |
Benzene content, % |
≮99.5 |
|||
|
Crystallization point,℃ |
≮5.5 |
Total sulfur, mg/kg |
≯0.5 |
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|
Cyclopentane content, mg/kg |
≯50 |
Hexane content, mg/kg |
≯50 |
|||
|
Methylcyclopentane content, mg/kg |
≯50 |
|
|
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Table 5 Extractive distillation low temperature hydrogenated toluene quality |
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|
Item |
Index |
Item |
Index |
|||
|
Appearance |
Transparent |
Density (20℃) ,g/cm3 |
0.865~0.870 |
|||
|
Toluene content, % |
≮99.0 |
Benzene content, % |
≯200 |
|||
|
Non-aromatic content, mg/kg |
≯9600 |
C8 aromatic content, mg/kg |
≯500 |
|||
|
Distillation range (including 110.6℃),℃ |
≯0.7 |
Total sulfur, mg/kg |
≯1 |
|||
|
Non-volatile substances,g/100mL |
≯0.002 |
Color (Pt - Co) |
≯No. 20 |
|||
|
Pickling colorimeter |
≯No. 2 |
|
|
|||
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Table 6 Extractive distillation low temperature hydrogenated xylene quality |
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|
Item |
Index |
Item |
Index |
|||
|
Density (20℃) ,g/cm3 |
0.862~0.872 |
Pickling colorimeter |
≯No.6 |
|||
|
Benzene, toluene content,, mg/kg |
≯5000 |
Non-aromatic content, % |
≯4 |
|||
|
Distillation range,℃ |
≯10 |
Color (Pt - Co) |
≯No. 20 |
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Table 7 Extractive distillation low temperature hydrogenation energy consumption (Ton crude benzene) |
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|
Circulating cooling water, m3 |
63.3 |
High-pressure steam,t |
0.739 |
|||
|
Electricity, kWh |
32.2 |
Coke oven gas, m3 |
31.6 |
|||
|
Soft water, m3 |
0.00528 |
Nitrogen, m3 |
10.56 |
|||
|
Instrument air, m3 |
21.1 |
Hydrogen, m3 |
36.9 |
|||
|
Medium pressure steam, t |
0.686 |
Solvent, kg |
0.0106 |
|||
|
Table 8 Solvent extraction low temperature hydrogenated benzene, toluene and xylene yield and total refining rate |
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|
Benzene, % |
Toluene, % |
Xylene, % |
Total refining rate, % |
|||
|
98 |
98 |
115 |
99.1 |
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Table 9 Solvent extraction low temperature hydrogenated benzene quality |
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|
Item |
Index |
Item |
Index |
|||
|
Appearance |
Colorless transparent |
Benzene content, % |
≮99.95 |
|||
|
Crystallization point,℃ |
≮5.5 |
Total sulfur, mg/kg |
≯0.5 |
|||
|
Table 10 Solvent extraction low temperature hydrogenated toluene quality |
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|
Item |
Index |
Item |
Index |
|||
|
Appearance |
Transparent |
Total sulfur, mg/kg |
≯1 |
|||
|
Toluene content, % |
≮99.99 |
|
|
|||
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Table 11 Solvent extraction low temperature hydrogenated xylene quality |
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|
Item |
Index |
Item |
Index |
|||
|
Distillation range,℃ |
≯5 |
Color (Pt - Co) |
≯No. 20 |
|||
|
Table 12 Solvent extraction low temperature hydrogenation energy consumption (Ton crude benzene) |
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|
Circulating cooling water, m3 |
101.9 |
High-pressure steam,t |
1.98 |
|||
|
Electricity, kWh |
30.5 |
Coke oven gas, m3 |
22.6 |
|||
|
Soft water, m3 |
0.167 |
|
|
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Conclusion
(1) In terms of product quality, yield, energy saving, environmental protection and other considerations, hydrogenation method is better than pickling method.
(2) In hydrogenation process, low temperature hydrogenation has lower hydrogenation temperature and pressure and good product quality. The low temperature hydrogenation process includes extractive distillation low temperature hydrogenated process and solvent extraction low temperature hydrogenation process. Both of them are relatively mature technologies and have been widely used in the hydrogenation production with petroleum reforming oil, high temperature pyrolysis gasoline, coking crude benzene as raw material. So it is better to use low temperature hydrogenation process in crude benzene refining.
