CN101475434B - Toluene disproportionation process for producing high-purity benzene - Google Patents
Toluene disproportionation process for producing high-purity benzene Download PDFInfo
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- CN101475434B CN101475434B CN2008102426681A CN200810242668A CN101475434B CN 101475434 B CN101475434 B CN 101475434B CN 2008102426681 A CN2008102426681 A CN 2008102426681A CN 200810242668 A CN200810242668 A CN 200810242668A CN 101475434 B CN101475434 B CN 101475434B
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Abstract
The invention relates to a toluene disproportionation process for producing high-purity benzene. The process comprises the following steps that: (1) a raw material containing more than 90 percent of toluene counted in percentage by weight enters a rectification system for removing impurities in order to improve the concentration of the toluene as the raw material (counted in percentage by weight)to more than 97 percent; and the water content is less than 300 ppm; and (2) the purified raw material passes through a reactor of a fixed bed and is contacted with a catalyst for reaction to obtain benzene and xylene under the condition of critical hydrogen; the reaction temperature is between 300 and 500 DEG C; the reaction pressure is between 0.5 and 5.0 MPa; the weight space velocity of the raw material is between 0.1 and 15.0 hours<-1>; and the molar ratio of hydrogen to toluene is 0.2-10.0:1. The process solves the technical problems that a benzene product has low purity; the disproportionation process strictly limits the combination of the reaction material and has instable reaction activity and more sub-reaction when the toluene is processed in the prior art.
Description
Technical field
The present invention relates to a kind of toluene disproportionation process of producing high-purity benzene.
Background technology
Toluene disproportionation (comprising methylbenzene shape selective disproportionation) is the significant element during aromatic hydrocarbons is produced, and is that the main method of producing benzene and YLENE is gone up in industry.Common toluene disproportionation process all adopts and contains the technology that methylbenzene raw material directly gets into reactor reaction.Raw material surge tank in the methylbenzene raw material advanced technologies and mixes with hydrogen after circulation toluene mixes again, after heating, contacts with catalyzer in the reactor drum and reacts; Reacted material separates gas phase and liquid phase after cooling off.Liquid phase is advanced follow-up distillation system, separates products such as non-virtue, benzene,toluene,xylene, and unreacted toluene loops back reaction.Gas phase is except that part discharge system, and major part loops back reaction.
Existing toluene disproportionation process technology all uses zeolite catalyst under hydro condition, to react.Because the impurity such as non-virtue that contain in the raw material are prone to take place scission reaction under hydro condition; Make the products benzene purity drop cause benzaldehyde product defective; The existence meeting of impurity such as the non-virtue in the raw material, indane simultaneously in activity of such catalysts in the heart carbon deposit activity of such catalysts is descended, cause the stability of catalyzer to reduce; Under the high-temperature and high-pressure conditions, the water in the raw material can make the molecular sieve generation framework dealumination in the catalyzer, causes catalyst active center's quantity minimizing, acidity of catalyst loss and micropore to stop up, and causes active decline, can cause catalyst deactivation in the time of seriously; Impurity such as the benzene in the raw material, YLENE can influence reaction once through yield and products distribution.Therefore must carry out strictness control to the foreign matter content in the reaction feed, require the non-fragrant content of charging usually below 0.5%.
Toluene level in the disproportionation reaction charging is high more, and the per pass conversion of toluene is high more, and therefore, the non-toluene composition that how effectively to reduce in the raw material is extremely important to whole technology operation.In US 6803463, handle the methylbenzene raw material that contains non-fragrant weight concentration 10-20% through the hydrocracking pre-reaction, will contain the non-aromatic hydrocarbons composition of C6～C7 raw material and be cracked into the non-virtue of small molecules through molecular sieve, leave away through the subsequent fine cut again and remove.But this method can't be removed other impurity except that above-mentioned non-virtue, need adopt multiple different catalyst simultaneously, and toluene conversion reduces greatly, and side reaction is violent, and the hydrogen consumption is high.
Existing toluene disproportionation process technology all has requirement for restriction to foreign matter content in the raw material, does not generally adopt the raw material that contains more impurity directly to be used for toluene disproportionation process, particularly toluene selective disproportionation reaction.
Summary of the invention
Technical problem to be solved by this invention is that low, the disproportionation processes of benzaldehyde product purity is formed the technical problem that restriction is strict, the toluene disproportionation process reactive behavior is unstable, side reaction is many to reaction mass when overcoming the processing treatment toluene that exists in the prior art, and a kind of toluene disproportionation process of new production high-purity benzene is provided.This technology has can use the high raw material of foreign matter content to carry out toluene disproportionation process, can obtain the high-purity benzene product characteristic.
For solving the problems of the technologies described above; The technical scheme that the present invention adopts is following: a kind of toluene disproportionation process of producing high-purity benzene; Comprise: a) contain by weight percentage raw material greater than 90% toluene and be introduced into distillation system and remove impurity; Raw material toluene concentration (by weight percentage) is brought up to more than 97%, and water-content is less than 300ppm; B) raw material after purifying is again through fixed-bed reactor, under hydro condition, contacts with catalyzer and reacts, and temperature of reaction is 300～500 ℃, and reaction pressure is 0.5～5.0MPa, and the raw material weight air speed is 0.1～15.0 hour
-1, hydrogen/toluene mole ratio is 0.2～10.0: 1, obtains benzene and YLENE.
In the technique scheme, the temperature of reaction preferable range is 320 ℃-470 ℃, and the reaction pressure preferable range is 0.5-3.5MPa, and raw material weight air speed preferable range is 1.0-7.0 hour
-1, hydrogen/hydrocarbon mol ratio preferable range is 0.3～6.0: 1.
In the technique scheme, the fresh reactant raw material can also contain at least a and water in non-virtue, benzene, ethylbenzene, YLENE, carbon nine and the above aromatic hydrocarbons thereof except that containing toluene; The fresh reactant raw material that will account for total raw material amount 10-100% earlier gets into distillation system, removes in the raw material behind the impurity toluene concentration (by weight percentage) and brings up to more than 98%, and water-content is less than 200ppm.
In the technique scheme, described catalyzer contains the ZSM-5 zeolite.
In the technique scheme, described reaction is toluene disproportionation and selective disproportionation of toluene.
Technique scheme is utilized the stalling characteristic of distillation system; Effectively improved the toluene concentration in the charging; Impurity such as non-virtue, indane have been removed; Controlled water-content, widened raw material range, suppress side reaction, keep toluene disproportionation process activity stabilized, improved benzaldehyde product quality and the effect that prolongs catalyst life thereby played.
Embodiment
[embodiment 1]
Form (by weight percentage) for containing toluene 90%, non-fragrant 2%, benzene 1.0%; YLENE 7%; The raw material of water-content 400ppm all gets into distillation system and removes impurity such as non-virtue, benzene, YLENE, and the raw material after the purification is formed (by weight percentage) for containing toluene 99%, non-fragrant 0.5%; YLENE 0.5%, water 150ppm.Raw material after the purification mixes with circulating hydrogen, through heating laggard reactor drum, contacts with the catalyzer that contains the ZSM-5 molecular sieve and carries out toluene disproportionation process.360 ℃ of temperature of reaction, pressure 3.2MPa, hydrogen/aromatic hydrocarbons mol ratio 2.8, air speed 5.0h
-1, the benzene,toluene,xylene weight concentration is respectively 20.5%, 50.0%, 26.8% in the product liquid that obtains, 5.46 ℃ of benzaldehyde product freezing points.React after 300 hours, the benzene,toluene,xylene weight concentration is respectively 20.2%, 50.5%, 26.6% in the product liquid, 5.46 ℃ of benzaldehyde product freezing points.
[Comparative Examples 1]
Raw material composition and reaction conditions are with embodiment 1, and methylbenzene raw material directly mixes with circulating hydrogen, through heating laggard reactor drum, contact with the catalyzer that contains the ZSM-5 molecular sieve and carry out toluene disproportionation process.The benzene,toluene,xylene weight concentration is respectively 18.0%, 55.0%, 22.5% in the product liquid that obtains, 5.35 ℃ of benzaldehyde product freezing points.React after 300 hours, the benzene,toluene,xylene weight concentration is respectively 16.0%, 60.0%, 19.2% in the product liquid, 5.35 ℃ of benzaldehyde product freezing points.
[embodiment 2]
Form (by weight percentage) for containing toluene 90.0%, non-fragrant 2.0%, YLENE 8.0%; Water-content 450ppm raw material is introduced into distillation system and removes impurity such as non-virtue, YLENE, and the raw material after the purification consists of and contains toluene 99.0%, and non-fragrant 0.5%; YLENE 0.5%, water 100ppm.Raw material after the purification and circulating hydrogen be through heating laggard reactor drum, contacts with the catalyzer that contains the ZSM-5 molecular sieve and carry out methylbenzene shape-selective disproportionation reaction.430 ℃ of temperature of reaction, pressure 1.6MPa, hydrogen/aromatic hydrocarbons mol ratio 2.0, air speed 4.2h
-1, the benzene,toluene,xylene weight concentration is respectively 13.0%, 68.9%, 15.6% in the product liquid that obtains, 5.46 ℃ of benzaldehyde product freezing points.
[embodiment 3]
Form (by weight percentage) for containing toluene 97.0%, non-fragrant 0.9%, benzene 0.7%; YLENE 1.4%, the raw material of water 400ppm gets into distillation system, removes impurity such as non-virtue, benzene, YLENE; Raw material after the purification consists of and contains toluene 98.5%; Non-fragrant 0.5%, YLENE 1.0%, water 150ppm.Raw material after the purification and circulating hydrogen be through heating laggard reactor drum, contacts with the catalyzer that contains the ZSM-5 molecular sieve and carry out methylbenzene shape-selective disproportionation reaction.450 ℃ of temperature of reaction, pressure 2.8MPa, hydrogen/aromatic hydrocarbons mol ratio 2.8, air speed 4.2h
-1, the product liquid that the differential responses time obtains is formed (by weight percentage) and is seen table 1, and the benzaldehyde product freezing point all is 5.46 ℃.
Table 1 methylbenzene shape-selective disproportionation reaction changes the composition table in time
[Comparative Examples 2]
Raw material form with reaction conditions with embodiment 3, raw material directly and circulating hydrogen through heating laggard reactor drum, contact with the catalyzer that contains the ZSM-5 molecular sieve and to carry out methylbenzene shape-selective disproportionation reaction.The benzene,toluene,xylene weight concentration is respectively 12.7%, 68.3%, 16.3% in the product liquid that obtains.The product liquid that the differential responses time obtains is formed (by weight percentage) and is seen table 2.
Table 2 methylbenzene shape-selective disproportionation reaction changes the composition table in time
[embodiment 4]
Form (by weight percentage) for containing toluene 97.0%, non-fragrant 0.9%, benzene 0.7%; YLENE 1.4%, the raw material of water 400ppm gets into distillation system, removes impurity such as non-virtue, benzene, YLENE; Raw material after the purification consists of and contains toluene 98.5%; Non-fragrant 0.5%, YLENE 1.0%, water 150ppm.Raw material after the purification and circulating hydrogen be through heating laggard reactor drum, contacts with the catalyzer that contains the ZSM-5 molecular sieve and carry out toluene disproportionation process.360 ℃ of temperature of reaction, pressure 3.2MPa, hydrogen/aromatic hydrocarbons mol ratio 2.8, air speed 3.0h
-1, the benzene,toluene,xylene weight concentration is respectively 20.5%, 50.0%, 26.8% in the product liquid that obtains, 5.47 ℃ of benzaldehyde product freezing points.Temperature of reaction of the present invention is at 360-450 ℃, and pressure 2.8-3.2MPa all is reaction conditionss preferably.
Claims (2)
1. toluene disproportionation process of producing high-purity benzene is characterized in that may further comprise the steps:
A) contain by weight percentage raw material greater than 90% toluene and be introduced into distillation system and remove impurity, raw material toluene by weight percentage concentration is brought up to more than 97%, water-content is less than 300ppm;
B) raw material after purifying is again through fixed-bed reactor, under hydro condition, contacts with catalyzer and reacts, and temperature of reaction is 300～500 ℃, and reaction pressure is 0.5～5.0MPa, and the raw material weight air speed is 0.1～15.0 hour
-1, hydrogen: toluene mole ratio is 0.2～10.0:1, obtains benzene and YLENE;
Fresh reaction raw materials except that containing toluene, also contain benzene, ethylbenzene, YLENE, carbon nine and more than at least a aromatic hydrocarbons and water; The raw material that gets into distillation system accounts for the 10-100% of total raw material amount; Temperature of reaction is 320 ℃-470 ℃, and reaction pressure is 0.5-3.5MPa, and the raw material weight air speed is 1.0-7.0 hour
-1, hydrogen: the mol ratio 0.3-6.0:1 of toluene; Described catalyzer is the catalyzer that contains the ZSM-5 zeolite.
2. the toluene disproportionation process of production high-purity benzene according to claim 1 is characterized in that removing in the raw material behind the impurity toluene by weight percentage concentration and brings up to more than 98%, and water-content is less than 200ppm.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6323381B1 (en) * | 1992-06-18 | 2001-11-27 | Chevron Corporation | Manufacture of high purity benzene and para-rich xylenes by combining aromatization and selective disproportionation of impure toluene |
| CN1340489A (en) * | 2000-08-29 | 2002-03-20 | 中国石油化工集团公司 | Process for preparing p-xylene |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6323381B1 (en) * | 1992-06-18 | 2001-11-27 | Chevron Corporation | Manufacture of high purity benzene and para-rich xylenes by combining aromatization and selective disproportionation of impure toluene |
| CN1340489A (en) * | 2000-08-29 | 2002-03-20 | 中国石油化工集团公司 | Process for preparing p-xylene |
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