CN101735000A - Combination method for producing p-xylene - Google Patents
Combination method for producing p-xylene Download PDFInfo
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- CN101735000A CN101735000A CN200810043975A CN200810043975A CN101735000A CN 101735000 A CN101735000 A CN 101735000A CN 200810043975 A CN200810043975 A CN 200810043975A CN 200810043975 A CN200810043975 A CN 200810043975A CN 101735000 A CN101735000 A CN 101735000A
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Abstract
The invention relates to a combination method for producing p-xylene, which mainly solves the problems of low concentration of p-xylene in mixed xylene, large circulating capacity of processing aromatics, rigorous requirements on reaction raw materials and high energy consumption during the production of the p-xylene in the prior art. In the combination method, a reaction technical scheme that the mixed xylene which contains high-concentration p-xylene and is produced by the selective disproportionation of the methylbenzene and aromatics with 9 and more carbon atoms are subjected to dealkylation reaction to produce combination of benzene, the methylbenzene and the mixed xylene which is in thermodynamic equilibrium, and a separation technical scheme that the high-concentration p-xylene adopts crystallization separation and low-concentration p-xylene adopts combination of adsorption-crystallization separation are adopted to solve the problems better, and the combination method can be used for industrial production of the p-xylene.
Description
Technical field
The present invention relates to a kind of combined method of producing p-Xylol.
Background technology
P-Xylol is one of main basic organic of petrochemical industry, in numerous chemical production field such as chemical fibre, synthetic resins, agricultural chemicals, medicine, plastics purposes is widely arranged.Typical p-Xylol production method is that the dimethylbenzene that contains ethylbenzene of the thermodynamic(al)equilibrium that generates from the petroleum naphtha catalytic reforming is to separate or molecular sieve simulated moving bed adsorption separation (abbreviation fractionation by adsorption) technology by multistage cryogenic crystallization the C8 aronmatic, and p-Xylol is separated from the close with it isomer mixture of boiling point.And, often take C for the processing of the dimethylbenzene of an ortho position and a position
8A (C8 aronmatic) isomerization (abbreviation isomerization) technology makes it isomery and turns to p-Xylol.In order to increase production p-Xylol, utilize toluene disproportionation or toluene and carbon nine and above aromatic disproportion thereof and transalkylation (being called for short toluene disproportionation and transalkylation) reaction to generate benzene and C
8A, thereby volume increase C
8A is the operational path that effectively increases production p-Xylol.
Up to now, in the world more typically, also the technology relevant with toluene disproportionation of comparative maturity has sixties Mo industrialized Tatoray tradition toluene disproportionation process, the MTDP of late nineteen eighties release and S-TDT technology and the TransPlus technology of releasing in recent years.Selective disproportionation of toluene is a new way of producing p-Xylol.Because toluene is at the C that can carry out selective disproportionation generation benzene and high p-Xylol concentration on the ZSM-5 of modification catalyzer
8Therefore A only needs can isolate most p-Xylol through simple once the step subzero fractionation.In recent years, along with improving constantly of catalyst performance, this technology has obtained considerable progress.Its typical process has industrialized MSTDP selective disproportionation of toluene technology and the pX-Plus technology released in recent years the late nineteen eighties.
Industrialized selective disproportionation of toluene technology-MSTDP is the catalyst treatment methylbenzene raw material with treated ZSM-5 type mesoporous molecular sieve, can obtain the C of high p-Xylol concentration (85～90%, weight percent, identical except that indicating below)
8The benzene of A and nitration grade.Do not see the PX-plus technology of industrial application report as yet, its main technique index is that the selectivity of pX reaches 90% in the dimethylbenzene under toluene conversion 30% condition, and the mol ratio of benzene and pX (p-Xylol) is 1.37.
Yet, in the technology of this class selective disproportionation of toluene, in the harshness of the simultaneous with high para-selectivity to material choice.This type of technology can only be raw material with toluene, and C
9 +A (carbon nine and above aromatic hydrocarbons thereof) does not have purposes in this technology, can not directly be utilized at least, causes the waste of aromatic hydrocarbon resource.In addition, this technology is a large amount of benzene of by-product also, causes the p-Xylol yield on the low side, and this is the fatal shortcoming of selective disproportionation technology.
The reactor feed of typical Tatoray technology is with toluene and C9 aromatic (C
9A) be reaction raw materials.The dimethylbenzene that is generated by Tatoray technology is to be in the isomer mixture that thermodynamic(al)equilibrium is formed, and has the p-Xylol content of industrial application value generally to have only about 24% most.For the xylol this point that selective disproportionation of toluene can obtain the p-Xylol concentration about 90%, Tatoray technology is in tangible inferior position undoubtedly, but Tatoray technology is exactly that Tatoray technology can be C with respect to one of selective disproportionation of toluene technology very big advantage
9A is converted into benzene and dimethylbenzene.Document based on Tatoray technology has USP4341914, Chinese patent 98110859.8, USP2795629, USP3551510, Chinese patent 97106719.8 etc.The technical process that representative USP4341914 proposes is for to carry out the aromatic hydrocarbons fractionation with reformate, toluene that obtains and C
9A enters the Tatoray technique unit and carries out disproportionation and transalkylation reaction, and resultant of reaction is toluene and C after separating
9A and part C10 aromartic (C
10A) circulation, benzene is as the product extraction, C8 aronmatic and the C8 aronmatic from isomerization unit enter the pX tripping device together and isolate highly purified p-Xylol product, and other C8 aronmatic isomer carries out the xylol that xylene isomerization reaction obtains being in thermodynamic(al)equilibrium again to isomerization unit.
Heavy aromatics takes off alkyl production C6～C8 aromatic hydrocarbons technology and caused people's attention gradually along with the rise of selective disproportionation of toluene technology in the last few years.USP5763721 and USP5847256 have proposed to be used for the catalyzer of heavy aromatics dealkylation respectively.Wherein, USP5847256 has announced a kind of mordenite catalyst of rhenium-containing, and this catalyzer is specially adapted to transform and contains the many raw materials of ethyl, can obtain products such as toluene, dimethylbenzene and benzene.
C
8The boiling point of each component of aromatic hydrocarbons is approaching: 136.2 ℃ in ethylbenzene, 138.4 ℃ of p-Xylol, 139.1 ℃ of m-xylenes, 144.4 ℃ of o-Xylols, the o-Xylol that its mid-boiling point is the highest can be separated by rectification method, need up to a hundred theoretical stages and bigger reflux ratio, the ethylbenzene that boiling point is minimum also can separate by rectification method, but much more difficult.C
8The fusing point of each component of aromatic hydrocarbons has bigger gap: 13.3 ℃ of p-Xylol, o-Xylol-25.2 ℃, m-xylene-47.9 ℃, ethylbenzene-94.95 ℃.Wherein the fusing point of p-Xylol is the highest, can adopt crystallization process that p-Xylol is wherein separated, and is not high as p-Xylol concentration in the raw material, for reaching the acceptable yield of industrial production, generally adopts two sections crystallizations.USP3177255, USP3467724 at first crystallize out most p-Xylol under-80～-60 ℃ low temperature and make productive rate reach theoretical maximum, this moment crystal purity between 65～85%, the crystallization second time is being carried out in the fusing back; Tc can obtain the p-Xylol of 99% above purity generally at-20～0 ℃ for the second time, and p-Xylol content is higher in the mother liquor, can return crystallized region recycle for the first time.
Utilize sorbent material to C
8Each component of aromatic hydrocarbons is difference optionally, can p-Xylol be separated by adsorption method of separation, after this method realizes industrialization in nineteen seventies for producing the main method of p-Xylol.USP2985589 has described the method for utilizing the simulation moving-bed separating paraxylene of adverse current; USP3686342, USP3734974, CN98810104.1 have described sorbent material that fractionation by adsorption uses X or the Y zeolite as barium type or barium potassium type; USP3558732, USP3686342 use toluene and the p-Diethylbenzene desorbing agent as fractionation by adsorption respectively.
Summary of the invention
Technical problem to be solved by this invention be in the conventional art when producing p-Xylol, exist owing to p-Xylol concentration in the xylol is low, cause dimethylbenzene separating unit and the isomerization unit internal circulating load is big, energy consumption is high problem, a kind of new p-Xylol production method is provided.This method is with benzene, toluene, C
8A and C
9 +A (carbon nine and above aromatic hydrocarbons thereof) produces p-Xylol for raw material, has the concentration that can improve p-Xylol in the xylol, reduce the scale of p-Xylol separating unit, isomerization unit and aromatic hydrocarbons fractionation unit greatly, thereby reduce the advantage of the energy consumption of whole device.
In order to solve the problems of the technologies described above, the technical solution used in the present invention is as follows: a kind of combined method of producing p-Xylol may further comprise the steps:
A. separate the mixing raw material that contains benzene, toluene, C8 aronmatic, carbon nine and above aromatic hydrocarbons and non-aromatics from reformer unit, isolate first strand of benzene, first strand of toluene, first burst of C8 aronmatic, carbon nine and above aromatic hydrocarbons and non-aromatics;
B.a) the isolated carbon nine of step and above aromatic hydrocarbons enters carbon nine and above aromatic hydrocarbons takes off the alkyl technique unit carries out dealkylation under hydro condition, generate second strand of benzene, second strand of toluene and second strand of C8 aronmatic;
C. first strand of toluene and second strand of toluene enter the selective disproportionation of toluene technique unit together, under hydro condition, carry out toluene selective disproportionation reaction, the reaction back generates C8 aronmatic and the benzene logistics that contains p-Xylol, after separating, obtain the 3rd strand of C8 aronmatic, the 3rd strand of toluene and the 3rd strand of benzene, wherein the 3rd strand of toluene turns back to the methylbenzene shape selective disproportionation technique unit;
D. first strand of C8 aronmatic, second strand of C8 aronmatic are sent into adsorption separation unit after mixing, and obtain the 5th strand of C8 aronmatic;
E. the 3rd strand of C8 aronmatic and the 5th strand of C8 aronmatic are sent into the Crystallization Separation unit, obtain the 4th strand of C8 aronmatic and pure p-Xylol, and wherein the 4th strand of C8 aronmatic turns back to adsorption separation unit.
In technique scheme, the used catalyzer in selective disproportionation of toluene unit is the type ZSM 5 molecular sieve catalyzer, type ZSM 5 molecular sieve contains at least a metal or its oxide compound that is selected from platinum, molybdenum or the magnesium, and its consumption is 0.005～5% by weight percentage; The operational condition of selective disproportionation of toluene technique unit is as follows: reaction pressure is 1～4MPa, and temperature of reaction is 300～480 ℃, and hydrogen/hydrocarbon mol ratio is 0.5～10: 1, and the liquid weight air speed is 0.8～8 hour
-1It is at least a molecular sieve that is selected among beta-zeolite, mordenite or the MCM-22 that carbon nine and above aromatic hydrocarbons thereof take off the used catalyzer of alkyl technique unit, and bismuthiferous metal or its oxide compound in the catalyzer, its consumption are 0.005～5% by weight percentage; The operational condition that carbon nine and above aromatic hydrocarbons thereof take off the alkyl technique unit is as follows: reaction pressure is 1～5MPa, and temperature of reaction is 250～480 ℃, and hydrogen/hydrocarbon mol ratio is 0.5～8: 1, and weight space velocity is 0.8～10 hour
-1The p-Xylol separating unit adopts absorption-Crystallization Separation combination process separating paraxylene, and Crystallization Separation adopts film-falling crystallization to separate or suspension crystallization separates; The isolating Tc of film-falling crystallization is-30～5 ℃; The isolating Tc of suspension crystallization is-30～5 ℃, and washings/crystallization weight ratio is 0.05～0.5: 1.
Among the present invention, take off the alkyl technique unit at carbon nine and above aromatic hydrocarbons thereof, under hydro condition, catalyzer has and carbon nine and above aromatic hydrocarbons thereof are taken off alkyl becomes benzene, toluene and C
8The function of A.The toluene that carbon nine and above aromatic hydrocarbons thereof take off the generation of alkyl technique unit enters the selective disproportionation of toluene unit; The benzene that reaction generates does not have the benzene of unnecessary extraction at this unit internal recycle, can reduce the generation of by-product benzene so as far as possible; The C that reaction generates
8A then enters fractionation by adsorption and isomerization unit is produced the xylol of p-Xylol concentration 80～95%.Toluene other toluene in Aromatic Hydrocarbon United Plant that carbon nine and above aromatic hydrocarbons thereof take off the generation of alkyl technique unit enters the selective disproportionation of toluene unit, under the effect of platiniferous ZSM-5 catalyzer, toluene selective disproportionation reaction takes place, generate benzene and the xylol that contains the high density p-Xylol, p-Xylol concentration can reach 80～95%, the Mixed XYLENE that this xylol and fractionation by adsorption obtain is sent to the Crystallization Separation unit and obtains pure p-Xylol, and the residue xylol also enters fractionation by adsorption and isomerization unit is produced pure p-Xylol.P-Xylol separates employing absorption-crystallization combination separation scheme among the present invention, fractionation by adsorption does not need to obtain pure p-Xylol, only need obtain the xylol of p-Xylol concentration 80～95%, thereby make that the sorbent material consumption reduces greatly in the adsorption separation unit, adsorption separation device is simplified greatly.As can be seen, such operational path can allow the concentration of producing p-Xylol in the xylol that obtains significantly improve, and has made full use of C again
9 +The A resource greatly reduces the treatment scale of isomerization unit and adsorption separation unit, has reduced energy consumption and facility investment scale effectively, and has reduced production cost, has obtained better technical effect.
Description of drawings
Fig. 1 is the technical process of traditional p-Xylol production equipment.
Fig. 2 produces the combination process flow process of p-Xylol for the present invention.
I is the reformer unit deheptanizer among Fig. 1 or Fig. 2; II is aromatic hydrocarbons extracting unit; III is the benzene toluene separating unit after the extracting; IV is the benzenol hydrorefining unit; V is toluene disproportionation and alkyl transfering process unit; VI is the selective disproportionation technique unit; VII is that heavy aromatics takes off the alkyl technique unit; VIII is the xylene isomerization process unit; IX is an adsorption separation unit; X is the aromatic hydrocarbons fractionation unit of selective disproportionation; XI is the Crystallization Separation unit.1 is the reformation de-pentane oil, and 2 is from deheptanizer cat head distilled C
7 -(comprising that benzene, toluene and carbon six carbon seven are non-aromatic), 3 is carbon eight and the above arene stream that deheptanizer tower still is extracted out, 4 for extracting benzene and the toluene logistics after non-aromatic, 5 is non-aromatic, 6 is the high purity product benzene that the benzene column overhead after the extracting is extracted, 7 is the toluene that the toluene tower cat head after the extracting is extracted, 8 C for the extraction of the toluene tower still after the extracting
8 +A (carbon eight and above aromatic hydrocarbons thereof), 9 is disproportionation and transalkylation product stream, 10 C for the extraction of heavy aromatics column overhead
9A and portion C
10A, 11 is the xylol of extracting out from the benzenol hydrorefining cat head, 12 is the C that heavy aromatics Tata still is extracted out
10A, 13 for heavy aromatics takes off the still liquid that alkyl unit benzene Tata still is extracted out, 14 small amount of toluene of separating for adsorption separation unit, 15 C that contain the high density p-Xylol that separate for adsorption separation unit
8 +A, 16 for fractionation by adsorption goes out xylol behind the PX, and 17 is the C that isomerization unit deheptanizer tower still is discharged
8 +The A logistics, 18 logistics that contain benzene and toluene of extracting for isomerization unit deheptanizer cat head, 19 is the benzene logistics of disproportionation and transalkylation extraction, the 20 nitrated benzene of extracting for the benzene column overhead of selective disproportionation, 21 toluene of extracting for the toluene tower cat head of selective disproportionation, 22 C that extract for the benzenol hydrorefining cat head of selective disproportionation
8 +A, 23 is the still liquid that the dimethylbenzene Tata still of selective disproportionation is extracted out, the 24 pure p-Xylol of separating for the Crystallization Separation unit, 25 go out xylol behind the PX for Crystallization Separation.
The technological process of tradition paraxylene production device as shown in Figure 1. Taking off pentane Tata still liquid 1 from reformation enters and takes off heptaner I, cat head is told carbon seven and following aromatic hydrocarbons non-aromatics logistics 2 thereof and is entered Aromatics Extractive Project unit II and carry out separating of aromatic hydrocarbons and non-aromatics, isolated non-aromatic 5 discharge, unit III is removed in benzene toluene logistics 4, the benzene column overhead of products benzene 6 after the extracting sent, and the toluene tower tower reactor of mixed xylenes 8 after the extracting extracted out and entered benzenol hydrorefining unit IV. In addition, take off heptaner tower reactor logistics 3 and also enter benzenol hydrorefining unit VI, mix carbon eight logistics 11 and distillate p-xylene separation unit IX from cat head, C9 aromatic 10 and from the raw material of the isolated toluene logistics 7 of toluene tower cat head as toluene disproportionation and transalkylation II, C10 +A logistics 12 is sent as byproduct; Disproportionation directly enters unit III with 9 of transalkylation product streams and separates; Adsorption separation unit IX isolates purpose product paraxylene 15, and a small amount of toluene 14 returns toluene disproportionation unit VI, and other mixed xylenes 16 enters xylene isomerization unit VIII and carries out the isomerization reaction, and isomerization unit takes off the C that the heptaner tower reactor is discharged8 +A logistics 17 is sent to benzenol hydrorefining unit IV, takes off the logistics that contains benzene and toluene 18 that the heptaner cat head extracts and is sent to the catalytic reforming unit.
Produce the combination technological process of paraxylene among the present invention as shown in Figure 2. Be that with the improvements of traditional handicraft technique of the present invention changes the toluene disproportionation process unit in the traditional handicraft into C9 aromatic and takes off the alkyl technique unit, in addition, increased by a cover selective disproportionation of toluene unit VI. The place that Fig. 2 is identical with Fig. 1 is no longer narrated, and the below only does in detail explanation with regard to difference. In the technique of the present invention former carbon nine and the above virtue thereof that is used as toluene disproportionation and transalkylation raw material taken off the raw material of alkyl unit through 10 as heavy aromatic hydrocarbons, the benzene that reaction generates circulates C in the unit7 +Toluene tower in the benzene toluene tower unit of A (carbon seven and above aromatic hydrocarbons thereof) logistics 13 after the extracting separates, all as the raw material of selective disproportionation unit, the mixed xylenes 11 of dimethylbenzene fractionation unit extraction enters adsorption separation unit and separates the C that obtains containing the high concentration paraxylene in toluene logistics 7 (comprise the toluene of bringing in the raw material and react the toluene that generates)8 +A15, selective disproportionation unit product logistics 9 enters the aromatic hydrocarbons fractionation unit X of selective disproportionation, from the nitrated benzene 20 of benzene column overhead extraction, toluene tower overhead extraction toluene 21 turns back to selective disproportionation unit VI, the still liquid 23 that the benzenol hydrorefining tower reactor is extracted out is sent into benzenol hydrorefining unit III, dimethylbenzene cat head extraction C8 +A logistics 22, Crystallization Separation unit XI is sent in logistics 22 and logistics 15, isolates pure paraxylene 24, and other mixed xylenes 25 is delivered to adsorption separation unit IX.
The present invention is further illustrated below by specific embodiment, and still, scope of the present invention has more than and is limited to the scope that embodiment covers.
Embodiment
[embodiment 1]
The mixing raw material that will contain benzene, toluene, C8 aronmatic, carbon nine and above aromatic hydrocarbons thereof and non-aromatics separates, obtain carbon nine and above aromatic hydrocarbons thereof, as raw material, under hydro condition, in fixed-bed reactor, carry out carbon nine and above aromatic hydrocarbons dealkylation performance thereof and investigate.Reactor inside diameter
Millimeter, 1000 millimeters of length, stainless steel.Beds is all fillings up and down
The millimeter granulated glass sphere plays air-flow and distributes and supporting role, and filling 20 gram bismuth-containings are 0.05% beta-zeolite catalyzer in the reactor.Aroamtic hydrocarbon raw material with after hydrogen mixes from top to bottom by beds, carry out C
9 +The dealkylation of A generates benzene, toluene and C
8A, temperature of reaction is 425 ℃, and pressure is 3.0MPa, and weight space velocity is 2.0 hours
-1, hydrogen/hydrocarbon mol ratio is 5.0: 1.
C in the raw material
9 +A derives from petrochemical complex Aromatic Hydrocarbon United Plant, H
2Be electrolysis hydrogen, through dehydrating processing, reaction result is listed in the table 1.
Table 1 C9 aromatic dealkylation raw material and product compositional analysis
| Component | ??NA | ??Ben | ??Tol | ??C 8A | ??C 9 +A | ??C 10 +A | ??∑ |
| Raw material, weight % | ??0.00 | ??0.00 | ??0.01 | ??0.82 | ??93.24 | ??5.93 | ??100.00 |
| Product, weight % | ??6.13 | ??1.92 | ??11.89 | ??19.22 | ??57.82 | ??3.02 | ??100.00 |
Wherein: NA is a non-aromatics, C
10 +A is carbon ten and above aromatic hydrocarbons thereof, and Ben is a benzene, and Tol is a toluene.
From embodiment 1 as can be seen: raw material C
9 +A has produced benzene, toluene and C after reacting
8A.
The mixing raw material that will contain benzene, toluene, C8 aronmatic, carbon nine and above aromatic hydrocarbons thereof and non-aromatics separates, and obtains toluene, is raw material with toluene, under hydro condition, carries out toluene selective disproportionation reaction on fixed-bed reactor.Reactor inside diameter
Millimeter, 1000 millimeters of length, stainless steel.Beds is all fillings up and down
The millimeter granulated glass sphere plays air-flow and distributes and supporting role, and filling 20 grams contain 0.05% platinum ZSM-5 molecular sieve catalyst in the reactor.Toluene with after hydrogen mixes from top to bottom by beds, carry out toluene selective disproportionation reaction, generate the C of benzene and high p-Xylol concentration
8A.
Raw material toluene derives from petrochemical complex Aromatic Hydrocarbon United Plant, H
2Be electrolysis hydrogen, through dehydrating processing, temperature of reaction is 420 ℃, and reaction pressure is 1.5MPa, and air speed is 4.0 hours
-1, hydrogen/hydrocarbon mol ratio is 3.0: 1.Reaction result is as shown in table 2.
Table 2 toluene selective disproportionation reaction result
| Component | ??NA | ??Ben | ??Tol | ??PX | ??C 8A * | ??C 9 +A | ??∑ |
| Form weight % | ??1.74 | ??14.05 | ??69.95 | ??11.62 | ??2.02 | ??0.62 | ??100.00 |
Annotate: C
8A
*Be meant other C8 aronmatic except that PX, as follows.
The aromatic hydrocarbons fractionation unit of toluene selective disproportionation reaction product through selective disproportionation separated, obtain xylol,, in falling-film crystallizer, carry out Crystallization Separation as raw material.The falling-film crystallizer internal diameter
Millimeter, external diameter
Millimeter, 500 millimeters of length, stainless steel.Raw material is walked tube side in the crystallizer.Raw material and cryogen countercurrent flow in crystallizer carries out Crystallization Separation, obtains mother liquor, sweating and pure p-Xylol.
In the Crystallization Separation process, be divided into three steps and carry out: material flow is 5 ml/min, and feeding temperature is 25 ℃, the cryogen flow is 50 ml/min, and refrigerant temperature is-20 ℃, and p-Xylol is in the crystallization of crystallizer tube wall, residue is mother liquor, and the raw material charging stopped charging after 2 hours; Refrigerant temperature is brought up to 20 ℃, plays heat effect, and purpose is melted the part crystal, melts liquid and is called sweating; Change product after 15 minutes into and collect, refrigerant temperature is brought up to 30 ℃, melts whole crystal, obtains pure p-Xylol.Film-falling crystallization is isolating to the results are shown in Table 3.
The isolating result of table 3 film-falling crystallization
| Component | Raw material, weight % | Sweating, weight % | Mother liquor, weight % | Product, weight % |
| ??PX | ??85.15 | ??96.73 | ??42.51 | ??99.84 |
| ??C 8A * | ??14.85 | ??3.27 | ??57.49 | ??0.16 |
[embodiment 2]
Reaction process such as embodiment 1.The aromatic hydrocarbons fractionation unit of toluene selective disproportionation reaction product through selective disproportionation separated, obtain xylol,, carry out suspension crystallization and separate as raw material.The volume of suspension crystallization device is 500 liters, has chuck and agitator, and stainless steel, the volume of washing tower are 40 liters, stainless steel.Raw material carries out suspension crystallization in crystallization, the slurry after the crystallization enters and carries out solid-liquid separation and purifying products in the washing tower.
The suspension crystallization sepn process comprises suspension crystallization and washing purge process, and the material flow of suspension crystallization is 200 liters/minute, and material temperature is 20 ℃, and Tc is-5 ℃, and the washings flow of washing purifying is 15 liters/minute, and wash temperature is 20 ℃.Suspension crystallization is isolating to the results are shown in Table 4.
The isolating result of table 4 suspension crystallization
| Component | Raw material, weight % | Mother liquor, weight % | Product, weight % |
| ??PX | ??85.15 | ??63.37 | ??99.84 |
| ??C 8A * | ??14.85 | ??36.63 | ??0.16 |
[embodiment 3]
With C in the typical reformation de-pentane oil
6A～C
10 +Each material of hydrocarbon consist of basic data, investigate the present invention produces p-Xylol and benzene according to the technical process shown in the accompanying drawing 2 ability and each unitary treatment scale situation.Typical reformer is sent the composition distribution of aromatic hydrocarbons and the flow rate of each component that present embodiment adopted sees Table 5.
Table 5 reformation de-pentane oil aromatic hydrocarbons is formed and flow rate
| Form | ??Ben | ??Tol | ??C 8A | ??C 9A | ??C 10 + | ??∑ |
| Form weight % | ??14.41 | ??26.79 | ??33.53 | ??24.02 | ??1.25 | ??100.00 |
| Flow, kilogram/hour | ??12673 | ??23560 | ??29482 | ??21122 | ??1095 | ??87932 |
C wherein
10 +Be carbon ten and above aromatic hydrocarbons thereof.
According to the aromatic hydrocarbons flow rate (fresh feed) in accompanying drawing 2 described technical process of the present invention and the table 5 and embodiment 1 carbon nine and above aromatic hydrocarbons dealkylation result, toluene selective disproportionation reaction result and film-falling crystallization separating resulting, selective disproportionation of toluene unit, heavy aromatics take off the material charging and the discharging data of alkyl unit and isomerization unit and list in table 6.Each unitary treatment scale of p-Xylol production equipment sees Table 7, and the output of product p-Xylol and benzene sees Table 8.
The result shows, utilization the technology of the present invention, and with the listed aroamtic hydrocarbon raw material of table 5, the ultimate production that technology of the present invention can be produced p-Xylol and benzene is 78328 kilograms/hour.The treatment scale of xylene isomerization unit and dimethylbenzene fractionation unit has descended 26% and 27% respectively, adsorption separation unit not only treatment scale descends to some extent, the more important thing is that the p-Xylol weight purity after the fractionation by adsorption drops to 90% by original 99.9%, this has obviously reduced the Design of device scale.Plant energy consumption is 18605 * 10
6Joule/ton (p-Xylol+benzene) is with respect to 26579 * 10 of comparative example 1
6Joule/ton (p-Xylol+benzene), energy consumption has reduced by 30%.Therefore, problems such as xylol concentration was low when patent of the present invention had overcome the production p-Xylol that exists in the conventional art, internal circulating load is big, energy consumption height, the method that provides a kind of brand-new more economical being used to produce p-Xylol.
Table 6 embodiment 3 process stream tables
Table 7 embodiment 3 each cell processing scale table
| The unit title | Heavy aromatics takes off alkyl unit | Isomerization unit | Adsorption separation unit | The Crystallization Separation unit | The dimethylbenzene fractionation unit |
| Scale, kilogram/hour | ??38750 | ??161209 | ??236427 | ??87031 | ??235861 |
Table 8 embodiment 3 product productions and purity table
| Product | P-Xylol | Benzene | Summation |
| Output, kilogram/hour | ??49258 | ??29066 | ??78328 |
| Product | P-Xylol | Benzene | Summation |
| Purity, % | ??99.84 | ??99.94 |
[embodiment 4]
Adopt reaction process flow process, reaction process condition, catalyzer and the suspension crystallization separation processes condition of embodiment 2, consist of benchmark with the raw material shown in the table 5, the xylol logistics of the unitary reaction product of selective disproportionation of toluene after the aromatic hydrocarbons fractionation unit separates enters the suspension crystallization separating unit and reclaims dimethylbenzene.Each unitary treatment scale of p-Xylol production equipment sees Table 9, and the output of product p-Xylol and benzene sees Table 10.
Table 9 embodiment 4 each cell processing scale table
| The unit title | Heavy aromatics takes off alkyl unit | Isomerization unit | Adsorption separation unit | The Crystallization Separation unit | The dimethylbenzene fractionation unit |
| Scale, kilogram/hour | ??38750 | ??161532 | ??26538 | ??87031 | ??245876 |
Table 10 embodiment 4 product productions and purity table
| Product | P-Xylol | Benzene | Summation |
| Output, kilogram/hour | ??49273 | ??29067 | ??78340 |
| Purity, weight % | ??99.84 | ??99.94 |
The result shows, utilization the technology of the present invention, and with the listed aroamtic hydrocarbon raw material of table 5, the ultimate production that technology of the present invention can be produced p-Xylol and benzene is 78340 kilograms/hour.The treatment scale of xylene isomerization unit and dimethylbenzene fractionation unit has descended 26% and 24% respectively, adsorption separation unit not only treatment scale descends to some extent, the more important thing is that the p-Xylol weight purity after the fractionation by adsorption drops to 90% by original 99.9%, has obviously reduced the Design of device scale.Plant energy consumption is 19402 * 10
6Joule/ton (p-Xylol+benzene) is with respect to 26579 * 10 of comparative example 1
6Joule/ton (p-Xylol+benzene), energy consumption has reduced by 27%.
[comparative example 1]
Still with typical reformation de-pentane oil C in the table 5
6A～C
10 +The flow rate of A logistics is a basic data, investigates traditional ability that contains toluene disproportionation and unitary Aromatic Hydrocarbon United Plant production p-Xylol of alkyl transfering process and benzene as shown in Figure 1.The material charging and the extraction situation of its disproportionation and transalkylation, isomerization unit see Table 11, and each unitary treatment scale sees Table 12, and the output of product p-Xylol and benzene sees Table 13.
Table 11 comparative example 1 process stream table
Table 12 comparative example 1 each cell processing scale table
| The unit title | Disproportionation and transalkylation | Isomerization unit | Adsorption separation unit | The dimethylbenzene fractionation unit |
| Scale, kilogram/hour | ??111988 | ??219438 | ??274572 | ??323269 |
Table 13 comparative example 1 product production and purity table
| Product | P-Xylol | Benzene | Summation |
| Output, kilogram/hour | ??54316 | ??22751 | ??77067 |
| Purity, % | ??99.80 | ??99.94 |
The result shows, traditional aromatic hydrocarbons production technique reaction aroamtic hydrocarbon raw material listed as table 5, and the total amount of having produced p-Xylol and benzene altogether is 77067 kilograms/hour, plant energy consumption is 26579 * 10
6Kilojoule/ton (p-Xylol+benzene).
Claims (7)
1. combined method of producing p-Xylol may further comprise the steps:
A. separate the mixing raw material that contains benzene, toluene, C8 aronmatic, carbon nine and above aromatic hydrocarbons and non-aromatics from reformer unit, isolate first strand of benzene, first strand of toluene, first burst of C8 aronmatic, carbon nine and above aromatic hydrocarbons and non-aromatics;
B.A) the isolated carbon nine of step and above aromatic hydrocarbons enters carbon nine and above aromatic hydrocarbons takes off the alkyl technique unit carries out dealkylation under hydro condition, generate second strand of benzene, second strand of toluene and second strand of C8 aronmatic;
C. first strand of toluene and second strand of toluene enter the selective disproportionation of toluene technique unit together, under hydro condition, carry out toluene selective disproportionation reaction, the reaction back generates C8 aronmatic and the benzene logistics that contains p-Xylol, after separating, obtain the 3rd strand of C8 aronmatic, the 3rd strand of toluene and the 3rd strand of benzene, wherein the 3rd strand of toluene turns back to the methylbenzene shape selective disproportionation technique unit;
D. send into adsorption separation unit after first strand of C8 aronmatic and second strand of C8 aronmatic mix, obtain the 5th strand of C8 aronmatic;
E. the 3rd strand of C8 aronmatic and the 5th strand of C8 aronmatic are sent into the Crystallization Separation unit, obtain the 4th strand of C8 aronmatic and pure p-Xylol, and wherein the 4th strand of C8 aronmatic turns back to adsorption separation unit.
2. according to the combined method of the described production p-Xylol of claim 1, it is characterized in that the used catalyzer in selective disproportionation of toluene unit is the type ZSM 5 molecular sieve catalyzer, type ZSM 5 molecular sieve contains at least a metal or its oxide compound that is selected from platinum, molybdenum or the magnesium, and its consumption is 0.005～5% by weight percentage.
3. according to the combined method of the described production p-Xylol of claim 1, the operational condition that it is characterized in that the selective disproportionation of toluene technique unit is as follows: reaction pressure is 1～4MPa, temperature of reaction is 300～480 ℃, and hydrogen/hydrocarbon mol ratio is 0.5～10: 1, and the liquid weight air speed is 0.8～8 hour
-1
4. according to the combined method of the described production p-Xylol of claim 1, it is characterized in that it is at least a molecular sieve that is selected among beta-zeolite, mordenite or the MCM-22 that carbon nine and above aromatic hydrocarbons thereof take off the used catalyzer of alkyl technique unit, bismuthiferous metal or its oxide compound in the catalyzer, its consumption are 0.005～5% by weight percentage.
5. according to the combined method of the described production p-Xylol of claim 1, it is as follows to it is characterized in that carbon nine and above aromatic hydrocarbons thereof take off the operational condition of alkyl technique unit: reaction pressure is 1～5MPa, temperature of reaction is 250～480 ℃, hydrogen/hydrocarbon mol ratio is 0.5～8: 1, and weight space velocity is 0.8～10 hour
-1
6. according to the combined method of the described production p-Xylol of claim 1, it is characterized in that the p-Xylol separating unit adopts absorption-Crystallization Separation combination process separating paraxylene, Crystallization Separation adopts film-falling crystallization to separate or suspension crystallization separates.
7. according to the combined method of the described production p-Xylol of claim 1, it is characterized in that the isolating Tc of film-falling crystallization is-30～5 ℃; The isolating Tc of suspension crystallization is-30～5 ℃, and washings/crystal weight ratio is 0.05～0.5: 1.
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