DE2040556A1 - Process for the production of benzene, toluene and polymethylbenzenes by catalytic cracking of heavy aromatic hydrocarbons - Google Patents

Description

"Process for the production of benzene, toluene and polymethylbenzenes by catalytic cracking of heavy aromatic hydrocarbons "

Priority: August 14, 1969, Japan, No. 638552/69 August 25, 1969, Japan, No. 66502/69

In the known processes for the production of aromatic hydrocarbons, v / ie benzene, toluene and xylenes, are used as Aunganrjsumaterialien mainly from raw formats, i.e. by catalytic Reforming oils obtained from heavy gasoline produces new extracts and cracked gasoline, i.e. through thermal cracking Oils obtained from heavy benzine are used. One from a reformate or aromatic hydrocarbon oil extracted from a cracked gasoline generally contains besides benaol, toluene and Xylenes have a high proportion of heavy aromatic hydrocarbons. About those heavy aromatic hydrocarbons are aromatic compounds with at least 9 O atoms (hereinafter referred to as "Oq aromatics"). to

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these Cg ₊ aromatics include many compounds which are similar to one another in terms of boiling point and other properties. Of these compounds, some polymethylbenzene are very valuable. Specific examples of these polymethylbenzene are pseudocuraol (1,2,4-trimethylbenzene) and durol (1,2,4,5-tetramethylbenzene). These compounds are important starting materials for the preparation of trimellitic acid or pyromellitic acid. Numerous other components of the aforementioned hydrocarbon oils other than polymethylbenzoene, such as alkyl aromatics with at least 2 carbon atoms per alkyl radical, have only a low value. Specific examples of these less valuable components are n-propylbenzene, isopropylbenzene, 1-methyl-2-ethylbenzene, 1-methyl-3-ethylbenzene, 1-methyl-4-ethylbenzene, four isomeric butybenzenes, three isomeric cymene (methylisopropylbenzenes), three isomeric methyl-n-propylbenzenes, three isomeric diethylbenzenes and six isomeric dimethylethylbenzenes The separation of these components is also extremely difficult.

fc There is a known process for recycling the C.G. aromatics in their Ilydrodealkylierung to benzene, toluene and xylenes, Bei

will
this process / requires large amounts of hydrogen.

A process is also known in which toluene and the Cg ₊ aromatics are converted to xylenes with transalkylation. However, this process mainly consumes expensive trimethylbenzenes. For these reasons, the Cq aromatics, in particular the Cn ₊ ~ Arurantons other than polymethylbenzones, have not yet been fully utilized.

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The object of the invention is to provide a new process for the preparation of benzene, toluene and polyethy.yenzenes from _{aromatic mixtures containing worthless Cg +} aromatics, in which the "valuable polymethylbenzenes are not subjected to any conversion reaction. This object is achieved by the Invention solved «

The invention thus relates to a process for the production of benzene, toluene and polymethylbenzenes by catalytic cracking of heavy aromatic hydrocarbons, which is characterized in that a vaporous starting mixture containing at least one alkyl radical with at least 2 carbon atoms substituted by aromatic hydrocarbons with at least 9 Contains carbon atoms (Cg ₊ aromatics) at elevated temperatures on a catalyst consisting mainly of aluminum oxide with a carbon content of 0.01 to 10 percent by weight.

The components of the reaction product obtained in the process of the invention can easily be separated from one another by distillation. For example, a reformate contains a high Proportion of used as starting material for the production of trimesic acid usable mesitylene (1,3,5-trimethylbenzene). Until now it was not possible to separate only the mesitylene from the reformate directly, since the latter has a high proportion of 1-methyl-2-ethylbenzene whose boiling point differs from that of mesitylene by only 0.5 C differs, laughing at the method of the invention However, the mesitylene can easily be separated off and recycled, since the l-methyl-2-ethylbenzene is split and the Cq aromatics

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is separated. As in the process of the invention as by-products "Ethylene and propylene are also produced, this process guarantees an excellent one compared to the known processes Utilization of the Cq aromatics.

According to the process of the invention, the lower aromatic Hydrocarbons benzene, toluene and xylenes are enriched.

A specific example of the alkyl aromatics used in the invented P heavy aromatic hydrocarbon mixtures used according to the invention may be included is ethyltoluene.

The catalyst used in the process of the invention consists, as mentioned, mainly of aluminum oxide, which

contains about 0.01 to 10 percent by weight, preferably 0.1 to 5 percent by weight of fluorine.

The catalyst activity can be increased by adding other effective elements such as magnesium, zinc, silicon or boron. The proportion of these additional elements is generally from 0.01 to 10 percent by weight, preferably from 0.1 to 10 percent by weight, based in each case on the catalyst. The catalyst used according to the invention can be prepared by the most varied of methods. For this purpose, for example, activated aluminum oxide can be mixed with an aqueous solution of suitable water-soluble fluorine compounds such as HF, NH, F, HBF. ,, H ₉ SiFc, Mg (BF,) ,,, CaSiPg, * 4 ^ 0 4 <l

Treat MgSiFg, / NH ^ BF ,, (NH ^) ₂ SiFg or ZnSiFg ₁ . Instead of such an aqueous solution, HF, SiF ₁ ^ or BF- can also be used in the vapor phase. Another advantageous method for producing the catalyst is that one Alurainium-

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oxide sol or silicon dioxide-aluminum oxide sol by adding Fluorine-containing acidic compounds such as HF, HpSiPg or HBF ,, brings to gelling and then the gel obtained dries and calcined. The fluorine treated catalyst is very active and has a longer service life than an untreated catalyst.

In carrying out the process of the invention, the starting material is previously heated and evaporated before it is brought into contact with the catalyst bed in the vapor phase. The vaporous starting material can be diluted with another gas, such as hydrogen, nitrogen, water vapor, lower paraffinic hydrocarbons, e.g. methane, ethane or propane or a gas mixture consisting of the aforementioned compounds, to reduce the carbon deposits on the catalyst. Preferably, hydrogen or a gas mixture consisting mainly of hydrogen is used as a diluent. The attenuation of the output material is preferably more than double. and diluted up to about βθ times its volume.

In the method of the invention is preferably carried out at temperatures of 400 to 700 ⁰ C, in particular of 450 to 650 ⁰ O,. If too high a temperature is used, the catalyst can degrade. If the temperature is too low, the reaction takes place too slowly.

The optimal loading speed depends on each applied reaction conditions, the type of catalyst and the composition of the starting material. Xm general will the starting material; but with a liquidity room "-

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from 0.01 to 10 parts by volume / part by volume of catalyst. Hours. fed in.

The method of the invention can be used in a wide variety of devices, which are suitable for catalytic vapor phase reactions, be performed. Fixed bed, fluidized bed or fluidized bed devices, for example, can be used.

The process of the invention can be carried out at normal pressure or at elevated pressure Pressing. However, when the pressure increases

™ is high, the formation of olefins is suppressed

2 work relatively low pressures (below 30 kg / cm).

To regenerate the catalyst used according to the invention, a gas containing free oxygen, such as air, is passed through the Catalyst layer passed to free the deposited thereon To burn off carbon »

The examples illustrate the invention.

example 1

20 g of a commercially available active aluminum oxide, which consists of amorphous particles with a grain size of about 1.65 to about 2.36 mm, are immersed in 100 ml of 35 percent aqueous magnesium silicofluoride hexahydrate solution and left therein for 36 hours at room temperature. The aluminum oxide is then ^{dried at 95-10O 0} C and then calcined at 500 C for 3 hours. The catalyst obtained in this way (fluorine content »approx. 2 ^L / o) is introduced into a reactor of the fixed bed type. Ansohllessend a product obtained from a reformate mixture of Cg ₊ aromatics with a boiling range above 148 ⁰ C is at

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55C C and a pressure of 19 kg / cm with a liquid space velocity of 0.5 part by volume / part by volume of catalyst. hours

passed through the reactor together with hydrogen gas (10 mol H ₂ / mol mixture).

Table I shows the compositions of the mixture of Co ₊ aromatics used and the solution obtained. The starting material can be, for example, l-meth.yl-2-n-propylbenzene, l-methyl-3-n-propylbenzene, l-methyl-4-n-propylbenzene, 1,2-diethylbenzene, 1,3-diethylbenzene, 1,4-diethylbenzene, n-butylbenzene, 1,3-dimethyl-5-ethylbenzene, 1,4-dimethyl-2-ethylbenzene, 1,3-dimethyl-4-ethylbenzene, 1,2-dimethyl-3-ethylbenzene, 1 , 3-bimethyl-2-ethybenzene, 1,2-dimethyl-4-ethylbenzoJ ,, 1,2,4,5-tetramethylbenzene or 1,2,3,5-tetramethylbenzene.

Example 2

The experiment of Example 1 is repeated, however, 20 g of a commercially available active alumina in 100 ml 25gewichtsprozentige aqueous Zinksilikofluorid hexahydrate solution immersed _f and it is worked with a liquid space velocity of 0.25 Yolumteil / Yolumteil catalyst · hr.. The plus content of the catalytic converter / is about $ 1.5. The results are shown in Table I.

Example 3

The experiment of Example 1 is repeated, but the catalytic conversion is carried out at 60O ⁰ C and with a liquid space velocity of 1.0 part by volume / part by volume of catalyst. Hrs. ' The results are shown in Table I.

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Example 4

The experiment from Example 1 is repeated, but the catalytic conversion is carried out at 470.degree. The results can be seen from Table I.

Table I.

benzene
toluene
Xylenes (including
Lich ethylbenzene) Starting
material example 1 2 3 4th Proportions by weight
. percent, Propylbenzene
Ethyl toluene
Triethylbenzenes : 4.0
23.4
35.8 3.85
23.4
32.4 3.16
18.6
28.5 - 2.02
12.7
-20.3 C ^ ₀ aromatics 2.7
21.3
36.4 0
5.4.
23.6 0
4.18
27.3 0
6.38
21.9 0.5
11.2
26, c Yield,? £ of theory 39.6 9.9 6.6 21.9 28.6 ■ 72 ", 1 78.2 75.7 95.5

Example 5 to 7

20 g of alumina of Example 1 are immersed in 100 ml aqueous 35gewichtsprozentige Magnesiumsilikofluorid-hexahydratlösung and left therein for 36 hours at Hardly temperature, then the "treated alumina obtained at the water bath is dried and then for 3 hours at 500 ⁰ C.

(Fluorine content about 2.0Ji)

calcined. The catalyst obtained in this way / is introduced into a pest bed type reactor. A mixture of Cg ₊ aromatics obtained from a reformate, the composition of which can be seen from Table II ^{, is then fed into this reactor at 55O 0} C and an excess pressure of 19 kg / cm with a liquid space velocity

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rate of 0.5 part by volume / part by volume of catalyst. Hours fed. . .

In Example 5, the vaporous starting material is per mole with 10 Hol nitrogen gas and in Example 6 per mole with 60 moles Diluted hydrogen gas. The diluted, vaporous starting material is then fed into the reactor.

For comparison, the reaction in Example 7 is carried out under the same conditions as in Example 5, but it becomes a commercially available silica / alumina catalyst used. From Table XI, those after J5Q are minutes, 4 hours or 8 hours long implementation seen results achieved. borrowed '/.

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Table II

O (O CD

- ·

Composition of the liquid feed 5 • 4th at f spat 8th 1 Γ 1/2 * 31.2 J 4th speed (proportions. weight
percent) - 1/2 2.2 Time i 4.1 2.3 0.9 - 4; 4 14.0 1/2 3td. 22.1 15.1 7.5 benzene - 25.1 1.4 4.3 1.2 1.0 1.0 toluene - 0.8 14.1 23.8 17.2 10.3 7.5 Ethylbenzene 2.6 19.1 1.0 0.10 Xylenes 5.1 16.4 1.3 n-propyrbenzene 14.8 0.14 2.9 p-ithyltoluene 5.3 1.3 0.7 methyl toluene 7.3 2.8 5.3 o- * ethyl toluene 53.0 52.0 0.57 24.0 34.0 Heeitylen , 10.6 23.1. 5.3 10.8 Pseudocumene 21.3 23.8 . 8.7 Hemimellithol and indan 10.5 other (mainly 8.8 C ₊ aromatics

O I

K)

cn cn

Example 8 to 10 20 g of the aluminum oxide from Example 1 v / earth in 50 ml

3 weight percent aqueous hydrogen fluoride solution stored for 18 hours at room temperature. Subsequently, v / ith the alumina from a water bath dried and then calcined for 3 hours at 500 ⁰ G to remove the residual volatiles. 6.8 g of that obtained in this way. Catalyst (bulk volume "= 10 ml) are poured into a quartz glass tube with an internal diameter of 15 mm, - which represents a" reactor of the fixed bed type. A reformate containing 82 $ aromatic hydrocarbons and the remainder paraffinic hydrocarbons is added 45Q ⁰ G or 550 ⁰ Cf or 650 ⁰ C (Example 8 or 9 or 10) and at normal pressure with a liquid clearance rate of 0.2 part by volume / part by volume of catalyst. Std ”is fed into the reactor .. .Wasserstoff in a mixture with the vapor feed at a rate of 0.01 standard liters / min, introduced were en from Tabelle'III apparent proportions of the reaction products at the individual • hydrocarbon S hours after start of the reaction determined -.., Ί .-; ■;.: .. ■■■ - ■ -'-.

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ORIGINAL

Table III

Proportions of aromatic hydrocarbons, Ge · weight percent

Initial Example" 3example example Temperature, C 550 650 material 8th 10 450 6.6 6.5 3.3 28.8 30.4 1.8 17.8 4.3 1.2 benzene 12.0 4.8 7.3 8.1 toluene 4.6 4.0 18.2 21.5 Ethylbenzene 3.7 11.9 6.1 5.9 p-xylene 10.1 5.3 5.7 5.2 m-xylene 5.5 4.5 7.5 8.8 ■ o-xylene 4.1 8.0 2.7 3.0 Mesitylene 7.7 3.6 12.5 8.4 Pseudoumole 3.3 36.8 Hemimellithol 47.2 other Co ₊ aromatics

10 9 8 1 0/19 8 3

Claims (8)

Patent claims AlJ A process for the production of benzene, toluene and polymethylbenzenes by catalytic cracking of heavy aromatic hydrocarbons, characterized in that a vaporous starting mixture containing at least one alkyl radical with at least 2 carbon atoms substituted aromatic hydrocarbons with at least 9 carbon atoms (Cg ₊ - Aromatics), at elevated temperatures, a catalyst consisting mainly of aluminum oxide with a fluorine content of 0.01 to 10 percent by weight brings about conversion. 2. The method according to claim 1, characterized in that one almost. Starting mixture consisting exclusively of Cq aromatics is used. 3. The method according to claim 1, characterized in that a reformate is used directly as the starting mixture. 4. The method according to claim 1 to 3, characterized in that a catalyst is used which mainly consists of HF and / or BF, and / or SiF ^ and / or HBF. and / or H ₂ SiFg and / or NH ^ F and / or III LBF, and / ο the (NIL) ₂ SiFg treated aluminum oxide. ' 5. The method according to claim 1 to 3, characterized in that a catalyst is used which consists mainly of aluminum oxide treated with MgSiFg and / or ZnSiFg and / or CaSiFg. 109810/1813 6. The method according to .Anspruch 1 to 5 »characterized in that that a catalyst is used with a fluorine content of 0.1 to 5 percent by weight. 7. The method according to claim 1 to 6, characterized in that a catalyst is used which also has a proportion of 0.01 to 10 percent by weight, preferably 0 _t l to 10 percent by weight, each based on the catalyst, of others effective elements, preferably magnesium, zinc, silicon or boron. 8. The method according to claim 1 to 7, characterized in that that one at temperatures of 400 to 700 C, preferably '* ■ O 2 ■ bia 650 C, pressures from 1 to 30 kg / cm and with liquid space velocities from 0.1 to 10 parts by volume of starting material / vaporous Part by volume catalyst. Hours and that you have the / Auogangs mixed previously with more than double and up to about 60 -, * times the amount of an oasis, preferably hydrogen. 109810 / IS!