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Principles and techniques of hydrogenated benzene

Author: Tianhe chemical sources: original date:2012-4-16

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.

Table 1 Leto production benzene quality
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

Table 2 Leto hydrotreating crude benzene energy consumption
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

Table 3 Extractive distillation low temperature hydrogenated benzene, toluene and xylene yield and total refining rate
Benzene, %	Toluene, %	Xylene, %	Total refining rate, %
98.5	98.0	117	99.8

Table 4 Extractive distillation low temperature hydrogenated benzene quality
Item	Index	Item	Index
Color	Colorless transparent	Benzene content, %	≮99.5
Crystallization point,℃	≮5.5	Total sulfur, mg/kg	≯0.5
Cyclopentane content, mg/kg	≯50	Hexane content, mg/kg	≯50
Methylcyclopentane content, mg/kg	≯50

Table 5 Extractive distillation low temperature hydrogenated toluene quality
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

Table 6 Extractive distillation low temperature hydrogenated xylene quality
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

Table 7 Extractive distillation low temperature hydrogenation energy consumption (Ton crude benzene)
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
Benzene, %	Toluene, %	Xylene, %	Total refining rate, %
98	98	115	99.1

Table 9 Solvent extraction low temperature hydrogenated benzene quality
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
Item	Index	Item	Index
Appearance	Transparent	Total sulfur, mg/kg	≯1
Toluene content, %	≮99.99

Table 11 Solvent extraction low temperature hydrogenated xylene quality
Item	Index	Item	Index
Distillation range,℃	≯5	Color (Pt - Co)	≯No. 20

Table 12 Solvent extraction low temperature hydrogenation energy consumption (Ton crude benzene)
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

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.

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