CN102372583B - Fluidized catalytic method for preparing p-xylene by alkylating toluene - Google Patents
Fluidized catalytic method for preparing p-xylene by alkylating toluene Download PDFInfo
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- CN102372583B CN102372583B CN201010261512.5A CN201010261512A CN102372583B CN 102372583 B CN102372583 B CN 102372583B CN 201010261512 A CN201010261512 A CN 201010261512A CN 102372583 B CN102372583 B CN 102372583B
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Abstract
The invention relates to a fluidized catalytic method for preparing p-xylene by alkylating toluene. By the fluidized catalytic method, the problems of high temperature rise of a catalyst bed, multiple side reactions of an alkylating reagent and a low utilization rate in the prior art are mainly solved. In the fluidized catalytic method, methanol, dimethyl ether and toluene are subjected to mixed feeding, and the dimethyl ether partially replaces the methanol to be used as the alkylating reagent. Through the technical scheme, the problems are better solved. The fluidized catalytic method can be applied to industrial production of the p-xylene by performing alkylation reaction on the toluene serving as a raw material.
Description
Technical field
The present invention relates to the fluidized catalyzing method of a kind of alkylation of toluene p-Xylol processed.
Background technology
P-Xylol is a kind of important Organic Chemicals, main application is through being oxidized synthetic terephthalic acid, carry out polycondensation with ethylene glycol again and produce macromolecular material polyethylene terephthalate (being terylene), terylene is excellent property, the great polyester material of demand, is widely used in weaving and wrapping material field.
At present, industrial the most frequently used p-Xylol production method is toluene disproportionation and C9 aromatic transalkylation, owing to being subject to thermodynamics equilibrium limit, in the C8 aronmatic product that the method obtains conventionally only containing having an appointment 24% p-Xylol, and p-Xylol demand will account for more than 60% on dimethylbenzene market, so this concentration forms the demand that can not meet industrial polyester material produce.For obtaining high density p-Xylol and improving p-Xylol yield, mixed C 8 aromatics need pass through isomerization and fractionation by adsorption or Crystallization Separation combination technique and further process, and follow-up processing has brought the loss of raw material and the lifting of cost.In view of this, numerous investigators are devoted to develop new p-Xylol synthetic technology, be desirably in production link and just can cross the product that obtains high p-Xylol content, methylbenzene shape selective disproportionation, toluene and methanol shape selective alkylation are such technology, wherein industrialization has also been succeeded in developing and stepped into methylbenzene shape selective disproportionation technology, its feature is rich p-Xylol and the benzene of producing, toluene and methanol shape selective alkylation technique low yield benzene are not even produced benzene, therefore and improved the utilization ratio of methylbenzene raw material, adapt to especially the present situation of Present Domestic benzene glut the market.Yet because reaction system has been introduced methyl alcohol, methyl alcohol coking reaction very easily occurs under alkylation reaction condition and causes catalyst deactivation, this problem is a difficult problem for restriction alkylation of toluene methanol technical development always.
Fluidized-bed reaction technique is regeneration of deactivated catalyzer in real time, can very effectively solve the fast difficult problem of fixed bed catalyst inactivation.Existing about adopting the method for fluidisation catalysis to carry out the report of methylbenzene methanol methylation reaction at present, the fluid-bed aromatics alkylation method providing as patent CN1326430A, its technical characterstic is alkylating reagent from introducing fluidized bed reaction zone, a plurality of position, thereby make alkylated reaction occur in more equably each position of reactor, rather than concentrate on reactor inlet compared with zonule.By adopting this method, can high transform and highly selective carries out alkylation reaction of arene, and be specially adapted to the reaction that alkylation of toluene methanol is produced dimethylbenzene.Yet this method, obtaining methyl alcohol equally distributed while in reactor, inevitably causes alkylating reagent to mix with the inhomogeneous of aromatic hydrocarbons, has increased the possibility of alkylating reagent id reaction; And cannot improve the strong heat release of reaction and the higher temperatures liter of beds, thereby cannot effectively control the methyl utilization ratio of side reaction and raising alkylating reagent.
The fluidized catalyzing method of alkylation of toluene of the present invention p-Xylol processed, its separate part adopts existing mature technology, wherein the separation system of head product comprises lightness-removing column, benzene/methylbenzene recovery tower and benzenol hydrorefining, obtains the following light constituent of carbon six, benzene/methylbenzene, C8 aronmatic and carbon nine and above heavy aromatics product after this system separation.Further separated conversion of C8 aronmatic could be obtained to highly purified p-Xylol product, its operating process and operational condition are according to Chinese patent (application number: 200480035152.X), fractionation by adsorption step in this process can be replaced by Crystallization Separation step, and Crystallization Separation step can be with reference to Chinese patent (application number: 95197157.3) carry out; Also can be replaced by absorption-crystallization combination process, concrete scheme can be with reference to Chinese patent (application number: 92111073.1).
The catalyzer using in fluidized catalyzing method of the present invention is solid acid catalyst, there is acid solid material and all can obtain in the method application, as aluminum oxide, heteropolyacid, solid super-strong acid, molecular sieve etc., wherein the most frequently used is the molecular screen material of silicon-aluminum containing, applicable molecular screen material comprises ZSM-5, ZSM-11, ZSM-12, ZSM-23, EU-1, MCM-22, USY, Mordenite, Beta, SAPO-5, SAPO-11, SAPO-31, SAPO-34 etc., can on the basis of molecular screen material, carry out suitable modification, to improve the performance of catalyzer, common modifying method comprises (water) thermal treatment, oxide carried etc.
The specific performance index definition of toluene methylation reaction is as follows:
Beds temperature rise=fluidized-bed reactor temperature in-fluidized-bed reactor temperature out
Summary of the invention
To be solved by this invention is that in prior art, beds temperature rise is large, alkylating reagent side reaction is many and the low problem of utilization ratio, and a kind of fluidized catalyzing method of new alkylation of toluene p-Xylol processed is provided.The method has advantages of that exothermic heat of reaction is few, beds temperature rise is little, side reaction is controlled effectively and methyl utilization ratio is high.
For solving the problems of the technologies described above, the technical solution used in the present invention is as follows: the fluidized catalyzing method of a kind of alkylation of toluene p-Xylol processed, comprises the following steps:
A) methyl alcohol, dme and three strands of materials of toluene are mixed, obtain reaction mixture I;
B) reaction mixture I is vaporized, and be preheated to temperature of reaction, then passing into fluidized-bed reactor contacts with the alkylation catalyst of silicon-aluminum containing molecular sieve, reaction obtains being rich in oil phase reaction effluent II, gas-phase reaction effluent III and the water effluent IV of dimethylbenzene, and wherein gas-phase reaction effluent III and water effluent IV discharge after separated and environmental protection treatment;
C) oil phase reaction effluent II is isolated to unconverted toluene fraction, mixing carbon eight cuts and the above heavy arene cut of carbon nine that contains a small amount of benzene;
D) mix carbon eight cuts and enter absorption, crystallization or absorption/crystallization combination separation and isomerization system, obtain p-Xylol product, the unconverted toluene fraction that contains a small amount of benzene is refluxed, be merged into into fluidized-bed reactor and transform with reaction mixture I.
In technique scheme, methyl alcohol and dme mix as alkylating reagent, and wherein to account for the per-cent of the contained methyl total mole number of alkylating reagent be 0.1～99.9% to the contained methyl mole number of dme, is preferably 30.0～99.9%; In methyl alcohol and dme, the toluene feed molar ratio range of contained methyl total mole number and fluidized-bed reactor is 0.1～10: 1, is preferably 0.2～1: 1; Alkylation of toluene reaction conditions is as follows: 300～500 ℃ of temperature of reaction, reaction pressure 0.1～5.0MPa, hydrogen/toluene mole ratio 0～8, toluene by weight air speed 0.5～10.0h
-1.
In the fluidized catalyzing method of above-mentioned alkylation of toluene p-Xylol processed, select dme part instead of methanol to make alkylating reagent, can make exothermic heat of reaction greatly reduce, therefore fluidized-bed reactor temperature rise also declines.And temperature is the key factor that control reaction and side reaction are carried out, maintain suitable and stably temperature of reaction condition both can guarantee the normal operation of alkylation main reaction, can effectively control the side reaction of alkylating reagent again, Selectivity for paraxylene in methyl utilization ratio, dimethylbenzene selective and dimethylbenzene is significantly increased.Therefore, adopt above method, can solve preferably in prior art that beds temperature rise is large, alkylating reagent side reaction is many and the low problem of utilization ratio, obtained good technique effect.
Below by embodiment, the invention will be further described.
Embodiment
[comparative example]
Methyl alcohol is used alone as to alkylating reagent, mixes with toluene feed, obtain reaction mixture I; By reaction mixture I vaporization, and be preheated to temperature of reaction, then pass into fluidized-bed reactor and contact with the alkylation catalyst of silicon-aluminum containing molecular sieve, reaction conditions is: 2000 grams of catalyst loading amounts, and 400 ℃ of temperature of reaction, toluene by weight air speed is 4.0h
-1, methyl and toluene mole ratio are 0.5, do not face hydrogen, reaction pressure is 0.5MPa, the Al that alkylation catalyst used contains weight percent 20%
2o
3properties-correcting agent and 15% SiO
2properties-correcting agent, remaining is heavily Hydrogen ZSM-5 molecular sieve (silica alumina ratio SiO
2/ Al
2o
3=50), reaction obtains being rich in oil phase reaction effluent II, gas-phase reaction effluent III and the water effluent IV of dimethylbenzene, and wherein gas-phase reaction effluent III and water effluent IV discharge after separated and environmental protection treatment; Oil phase reaction effluent II is isolated to unconverted toluene fraction, mixing carbon eight cuts and the above heavy arene cut of carbon nine that contains a small amount of benzene; Mix carbon eight cuts and enter absorption, crystallization or absorption/crystallization combination separation and isomerization system, obtain p-Xylol product, the unconverted toluene fraction that contains a small amount of benzene is refluxed, be merged into into fluidized-bed reactor and transform with reaction mixture I.
Reaction evaluating the results are shown in table 1 and contrasts.
[embodiment 1～3]
According to step described in comparative example and condition, carry out alkylation of toluene and react, wherein alkylating reagent becomes the mixture of methyl alcohol and dme different ratios, and concrete ratio and reaction evaluating the results are shown in table 1 and contrast.
Table 1
Table 1 data show, use dme part instead of methanol to do after alkylating reagent, effectively controlled the heat release of alkylation process and the temperature rise of beds, dimethylbenzene selective, Selectivity for paraxylene are significantly improved, use ratio of methanol is also slightly improved, and aromatics conversion rate changes less.
[embodiment 4～6]
According to step described in embodiment 3 and condition, carry out alkylation of toluene and react, and change the ratio of the contained methyl of alkylating reagent and toluene, concrete reaction conditions and evaluation result are listed in table 2 and are contrasted.
Table 2
Table 2 data show that methyl/toluene ratio is higher, and methyl utilization ratio is lower, and bed temperature rise control, dimethylbenzene selective and Selectivity for paraxylene all have variation in various degree, and aromatics conversion rate has increase by a relatively large margin.
[embodiment 7～11]
According to step described in embodiment 3 and condition, carry out alkylation of toluene and react, and changed the conditions such as temperature of reaction wherein, pressure, toluene air speed, hydrogen/toluene ratio.Concrete reaction conditions and evaluation result are listed in table 3 and are contrasted.
Table 3
Table 3 data show that alkylation reaction condition is larger on products distribution impact, also has impact to beds temperature rise.By above-mentioned process optimization, can make that dimethylbenzene selective is the highest mentions 79.97%, Selectivity for paraxylene is up to 93.32%, and use ratio of methanol is up to 68.22%, and temperature rise is minimum is 18.3 ℃.
We find the data of contrast above-described embodiment, adopt the fluidized catalyzing method of alkylation of toluene of the present invention p-Xylol processed, can make fluidized-bed reactor temperature rise minimumly be down to 13.2 ℃ from 85.6 ℃, Selectivity for paraxylene is up to 93.32%, the methyl utilization ratio of alkylating reagent is up to 79.97%, in the control of exothermic heat of reaction, side reaction and methyl utilization ratio, all obtains good effect aspect improving.
Claims (1)
1. a fluidized catalyzing method for alkylation of toluene p-Xylol processed, step is:
Alkylating reagent is mixed with toluene feed, obtain reaction mixture I, wherein said alkylating reagent is the mixture being comprised of methyl alcohol and dme, and in dme, methyl mole number accounts for 90.0% of the total methyl mole number of alkylating reagent; By reaction mixture I vaporization, and be preheated to temperature of reaction, then pass into fluidized-bed reactor and contact with the alkylation catalyst of silicon-aluminum containing molecular sieve, reaction conditions is: 2000 grams of catalyst loading amounts, and 400 ℃ of temperature of reaction, toluene by weight air speed is 4.0h
-1, methyl and toluene mole ratio are 0.2, do not face hydrogen, reaction pressure is 0.5MPa, the Al that alkylation catalyst used contains weight percent 20%
2o
3properties-correcting agent and 15% SiO
2properties-correcting agent, remaining is heavily Hydrogen ZSM-5 molecular sieve, silica alumina ratio SiO in described Hydrogen ZSM-5 molecular sieve
2/ Al
2o
3=50, reaction obtains being rich in oil phase reaction effluent II, gas-phase reaction effluent III and the water effluent IV of dimethylbenzene, and wherein gas-phase reaction effluent III and water effluent IV discharge after separated and environmental protection treatment; Oil phase reaction effluent II is isolated to unconverted toluene fraction, mixing carbon eight cuts and the above heavy arene cut of carbon nine that contains a small amount of benzene; Mix carbon eight cuts and enter absorption, crystallization or absorption/crystallization combination separation and isomerization system, obtain p-Xylol product, the unconverted toluene fraction that contains a small amount of benzene is refluxed, be merged into into fluidized-bed reactor and transform with reaction mixture I; The result of alkylated reaction is:
Wherein:
Beds temperature rise=fluidized-bed reactor temperature in-fluidized-bed reactor temperature out.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101208409A (en) * | 2005-06-21 | 2008-06-25 | Sk能源株式会社 | Process for increasing production of benzene from hydrocarbon mixture |
| CN101456786A (en) * | 2007-12-12 | 2009-06-17 | 中国科学院大连化学物理研究所 | Method for preparing p-xylene and co-producing light olefins by toluene and methylating reagent |
| CN101602648A (en) * | 2009-07-24 | 2009-12-16 | 中国海洋石油总公司 | A kind of methyl alcohol/dimethyl ether conversion prepares the method for p-Xylol |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101208409A (en) * | 2005-06-21 | 2008-06-25 | Sk能源株式会社 | Process for increasing production of benzene from hydrocarbon mixture |
| CN101456786A (en) * | 2007-12-12 | 2009-06-17 | 中国科学院大连化学物理研究所 | Method for preparing p-xylene and co-producing light olefins by toluene and methylating reagent |
| CN101602648A (en) * | 2009-07-24 | 2009-12-16 | 中国海洋石油总公司 | A kind of methyl alcohol/dimethyl ether conversion prepares the method for p-Xylol |
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