CN101306382B

CN101306382B - Catalyst for alkyl aromatics isomerization

Info

Publication number: CN101306382B
Application number: CN200710040698XA
Authority: CN
Inventors: 谢在库; 钱斌; 杨为民; 贾银绢; 王仰东
Original assignee: China Petroleum and Chemical Corp; Sinopec Shanghai Research Institute of Petrochemical Technology
Current assignee: China Petroleum and Chemical Corp; Sinopec Shanghai Research Institute of Petrochemical Technology
Priority date: 2007-05-16
Filing date: 2007-05-16
Publication date: 2011-05-18
Anticipated expiration: 2027-05-16
Also published as: CN101306382A

Abstract

The invention relates to a catalyst used for the isomerization of alkyl aromatics, and mainly solves the problems of the ring cleavage secondary reaction of cyclane which can not be ignored and the crack which can accompany subsequently. The catalyst better solves the problems by adopting the technical proposal that the catalyst comprises 10 to 90 percent of UFI zeolite with silica alumina ratiomol ratio Si/Al being 50-100, 0.05 to 1 percent of Pt, 0 to 0.4 percent of Pd and surplus alumina bonding agent in balancing amount, and can be applied to the industrial production of the isomerization of alkyl aromatics.

Description

The catalyst that is used for Alleyl aromatics isomerizating

Technical field

The present invention relates to a kind of catalyst that is used for Alleyl aromatics isomerizating.

Background technology

C8 aromatic hydrocarbons is mainly derived from catalytic reformate, pyrolysis gasoline, in addition, also has toluene disproportionation or transalkylated product and coal tar wet goods.In the C8 aromatic hydrocarbons in above-mentioned source except that contain to,, the ortho-xylene, also contain ethylbenzene.Because the boiling point of ethylbenzene and dimethylbenzene is very approaching, if adopt highly efficient distilling or adsorbing separation directly to separate ethylbenzene, its processing charges height, uneconomical, be dimethylbenzene or benzene so general oil company adopts chemical reaction more with ethylbenzene conversion.The C8 aromatic hydrocarbons composition in above-mentioned source is in thermodynamic equilibrium state substantially, and paraxylene only accounts for 20% in the C8 aroamtic hydrocarbon raw material.And paraxylene is the raw material of synthetic fibers, polyester etc., and demand is big, added value is high, and therefore with regard to regard to numerous benefit and social benefit, the volume increase paraxylene is a far reaching job.

C8 aromatic hydrocarbons extracts paraxylene by separation method or to, ortho-xylene, its raffinate adopts Xylene isomerization process, the raffinate of non-equilibrium composition is converted into equilibrium composition, separate by raffinate circulation isomery, can with meta-xylene or, ortho-xylene all is converted into paraxylene or to, ortho-xylene.

When acidic catalyst was adopted in isomerization, disproportionation and dealkylation can take place in ethylbenzene under harsh operating condition, thereby generate benzene and heavy aromatics, simultaneously, transalkylation reaction also takes place in ethylbenzene and dimethylbenzene, and the reaction of this class will influence the yield of purpose product to, ortho-xylene.

When bifunctional catalyst was adopted in isomerization, ethylbenzene can be converted into dimethylbenzene in the presence of C8 cycloalkane, and ethylbenzene conversion is that the selectivity of dimethylbenzene can reach more than 50%.

Ethylbenzene isomerization becomes dimethylbenzene to need VIII family noble metal to exist, and is inclined to use modenite, ZSM series zeolite traditionally.Select the ZSM-5 zeolite for use as US4482773.EP458378 has described a kind of C8 arene isomerization catalyst, contains the platinum active component and a kind ofly contains 2～3% alkali-metal H type modenites, and select for use hibbsite or gama-alumina to make binding agent.This catalyst is converted into H type modenite by ion-exchange with modenite, mixes with binding agent then, perhaps earlier modenite is mixed with binding agent, and moulding then, and ion-exchange provide the H-modenite, at last with platinum dipping, roasting reduction again.

US6150292 has described a kind of isomerization catalyst of the C8 of being used for aromatic fraction, select modenite and a kind of binding agent between the silica alumina ratio 5-10 for use, contain at least a platinum and the palladium of taking from the periodic table group VIII element, contain at least a preferred indium of gallium, indium, thallium and at least a germanium, tin, the plumbous preferred tin of taking from periodic table IV family of taking from the periodic table III-th family simultaneously in the catalyst.But the side reaction that its existence can't be ignored.As the cycloalkane open loop, may follow cracking etc. subsequently.

Summary of the invention

Technical problem to be solved by this invention is the cycloalkane open loop side reaction that can't ignore that exists in the prior art, and the cracking problem that may follow subsequently, and a kind of new catalyst that is used for Alleyl aromatics isomerizating is provided.This catalyst is used for C8 aromatics isomerization when reaction, and the concentration of paraxylene in dimethylbenzene reaches or near thermodynamical equilibrium in the product, paraxylene yield height, and ethylbenzene can transform in a large number simultaneously, has avoided it to stop during the course.

For solving the problems of the technologies described above, the technical solution used in the present invention is as follows: a kind of catalyst that is used for Alleyl aromatics isomerizating comprises following component by weight percentage:

A) 10～90% silica alumina ratio Si/Al are 50～100 UFI zeolite;

b)0.05～1％Pt；

c)0～0.4％Pd；

D) alumina binder of surplus.

In the technique scheme, the consumption preferable range of UFI zeolite is 15～85% by weight percentage, and the consumption preferable range of aluminium oxide is 15～85%.The silica alumina ratio Si/Al preferable range of UFI zeolite is 50～60.

UFI prepare zeolite method among the present invention is with reference to Chinese patent CN1269734C, the reactant mixture that comprises the reactive sources material of R, Al, Si comprising formation, with reactant mixture is being comprised that temperature is 12 hours～2 weeks of reaction under 100～175 ℃ the reaction condition, the composition that reactant mixture had according to the mol ratio of oxide is:

aM _2/nO∶bR _2/pO∶(1-c)Al ₂O ₃∶cE ₂O ₃∶dSiO ₂∶eH ₂O

Wherein M is the alkali metal or the alkaline-earth metal of for example lithium and strontium, and R is the nitrogenous organic cation of tetramethyl-ammonium for example, and E is the framework element of for example gallium, a=0～2, b=1.5～30, c=0～0.5, d=5～30, e=30～6000.

UFI zeolite among the present invention is the nano-grade crystal, and crystallite dimension is less than 450 nanometers, and thickness is 10～100 nanometers, and length and width are about 100～600 nanometers, and its X diffracting spectrum is seen accompanying drawing 1, and diffraction data sees Table 1.The duct is short because UFI zeolite nano-sized crystal has, and external surface area is big, the characteristics of moderate acid strength, thereby zeolite is difficult for coking in course of reaction, the catalytic cracking side reaction is few, isomerization reaction efficient height.

Table 1

Extremely strong (the I/I of VS= ₀=75～100), the strong (I/I of S= ₀=50～74),

Medium (the I/I of M= ₀=25～49), the weak (I/I of W= ₀=0～24).

Preparation of catalysts method of the present invention is as follows: earlier with synthetic ammonia type or sodium type UFI zeolite and aluminium oxide mixing, with ammonium salt solution wherein sodium ion is exchanged again through overmulling is pinched, moulding, drying, roasting are made carrier, use the precious metal salt solution impregnated carrier at last, through super-dry, roasting, reduction, promptly get catalyst finished product of the present invention again.

The operating condition that the catalyst that the present invention relates to is used for the reaction of C8 aromatics isomerization is as follows:

Temperature is 250～600 ℃, and preferable range is 350～510 ℃; Pressure is 0.06MPa～10MPa, and preferable range is 0.3MPa～3MPa; Weight space velocity is 0.6～210 hour ^-1, preferable range is 3～110 hours ^-1Mol ratio (the H of hydrogen and aromatic hydrocarbons in the raw material ₂/ HC) be 0.6～15, preferable range is 2～7.

The performance of catalyst is evaluated by following computational methods:

Adopting the UFI structural zeolite is the bifunctional catalyst that main active component obtains, and is used for C8 cut aromatics isomerization, especially contains dimethylbenzene (adjacent,, contraposition), only includes dimethylbenzene, or the mixture of dimethylbenzene and ethylbenzene.Alleyl aromatics isomerizating, especially dimethylbenzene have quite high commercial significance.Generally speaking, paraxylene is most important isomers, because it is the intermediate of synthetic polyester fibers.And paraxylene can make by the meta-xylene isomerization, and meta-xylene can obtain by o-xylene isomerization.In addition, ethylbenzene is difficult to separate from xylene mixture by the method for distillation, because the boiling point of these compounds is very approaching, and often is present in again in the C8 aromatics isomerization raw material.Adopt bifunctional catalyst to help addressing the above problem.For the reaction characteristics of meta-xylene:, be difficult to diffuse into eight annulus ducts of UFI zeolite because the reactant volume is bigger in UFI zeolite acidity position.Therefore, meta-xylene carries out at the surface-active center of UFI zeolite basically in the reaction of acidic site.Product is carried out owing to be reflected at the outer surface of zeolite based on isomerization product, lacks valid density and carries out bimolecular reaction (transalkylation), thereby help monomolecular reaction (isomerization), therefore, side reactions such as transalkylation reaction takes place hardly, has obtained better technical effect.

The invention will be further elaborated below by embodiment.

Figure of description

Fig. 1 is the X-ray diffraction spectrum of the UFI zeolite among the present invention.

XRD composes obvious broadening among Fig. 1, and the UFI zeolite that shows preparation is a nano-sized crystal.

The specific embodiment

[embodiment 1]

With reference to the synthetic UFI zeolite of Chinese patent CN1269734C.

With Ludox (40 weight %) 15 gram, aluminium secondary butylate 3 grams, tetraethyl ammonium hydroxide (35 weight %) 21 grams, and distilled water 25 grams mix and stir, and under 100 ℃, aging 18 hours, behind aging the end, take out aging liquid; Tetramethyl ammonium chloride 0.95 gram is mixed with water and stir, mix, stir with the aging liquid that takes out, under 155 ℃, after the crystallization 48 hours, with the crystallizing kettle cool to room temperature, take out crystallization liquid, again through UFI zeolite crystallite centrifugal, that filter, wash with water the recovery generation, product was put into 120 ℃ of dryings of baking oven 8 hours, standby.

Synthetic UFI zeolite silica alumina ratio Si/Al=7, sodium content is 2% of its butt weight, pore volume is 0.21 centimetre ³, P/P ₀=0.3, the BET specific area is 530 meters ²/ gram.

[embodiment 2]

UFI zeolite, aluminium oxide that [embodiment 1] is synthetic mix, and mixed powder and rare nitric acid (concentration is 0.5 weight %) mix by the weight ratio of 100:60 and pinches, moulding, drying.550 ℃ of following roastings promptly got catalyst carrier of the present invention after 6 hours in air.

The catalyst carrier of making is with 0.4 molar concentration ammonium nitrate solution, and wherein sodium type UFI zeolite is carried out the exchange of 3 secondary ions, at every turn at 75 ℃, lasts 3 hours, handles the back sodium content less than 50ppm.

With the carrier after the exchange of above-mentioned ammonium in room temperature, with soluble chlorine platinic acid and/or the acid of chlorine palladium, flood 8 hours (noble metal loading amount 0.34 heavy %), filter then, drying, in air, activate 4 hours under 500 ℃ of temperature, under 400 ℃ of temperature, reduction is 4 hours in the nitrogen atmosphere then, and cool to room temperature promptly gets catalyst of the present invention.

[embodiment 3～7]

The preparation process of [embodiment 3～7] is identical with [embodiment 2] with method, just changes proportioning, the concentration of raw material and additive, and the temperature of moulding, activation, reduction, the time etc.The concrete preparation condition of catalyst sees Table 2 in [embodiment 3～7], and what it was used for the reaction of C8 aromatics isomerization the results are shown in Table 3

Table 2

Table 3 is near the selectivity treatment effeciency of balance

Claims

1. catalyst that is used for Alleyl aromatics isomerizating, composed of the following components by weight percentage: a) silica alumina ratio Si/Al is 7 UFI zeolite; B) 0.05%Pt; C) 0.2%Pd; D) alumina binder of surplus, wherein UFI/Al ₂O ₃Weight ratio is 0.18;

The Preparation of catalysts method is as follows: with Ludox 15 gram, aluminium secondary butylate 3 grams of 40 weight %, and 35 weight % tetraethyl ammonium hydroxides, 21 grams, and distilled water 25 grams mix and stir, and under 100 ℃, aging 18 hours, behind aging the end, take out aging liquid; Tetramethyl ammonium chloride 0.95 gram is mixed with water and stir, mix, stir with the aging liquid that takes out, under 155 ℃, crystallization is after 48 hours, with the crystallizing kettle cool to room temperature, take out crystallization liquid, through UFI zeolite crystallite centrifugal, that filter, wash with water the recovery generation, product was put into 120 ℃ of dryings of baking oven 8 hours, synthetic UFI zeolite silica alumina ratio Si/Al=7 again, sodium content is 2% of its butt weight, and pore volume is 0.21 centimetre ³, P/P ₀=0.3, the BET specific area is 530 meters ²/ gram;

Synthetic UFI zeolite, aluminium oxide are mixed, mixed powder and concentration be the rare nitric acid of 0.5 weight % mix by 100: 60 weight ratio pinch, moulding, drying; 550 ℃ of following roastings promptly got catalyst carrier after 6 hours in air; The catalyst carrier of making is with 0.4 molar concentration ammonium nitrate solution, and wherein sodium type UFI zeolite is carried out the exchange of 3 secondary ions, at every turn at 75 ℃, lasts 3 hours, handles the back sodium content less than 50ppm;

With the carrier after the exchange of above-mentioned ammonium in room temperature, with soluble chlorine platinic acid and the acid of chlorine palladium, flooded 8 hours, noble metal loading amount 0.34 heavy %, filtration, drying activate 4 hours under 500 ℃ of temperature, then under 400 ℃ of temperature in air then, reduction is 4 hours in the nitrogen atmosphere, and cool to room temperature promptly gets described catalyst.