DE19625234A1 - Process for the selective heterogeneous-catalytic synthesis of 4-methyl- and 4,4'-dimethylbiphenyl - Google Patents

Abstract

The invention relates to a process for selective preparation of 4-substituted or 4,4'-disubstituted alkylated derivatives of biphenyl or a biphenyl derivative. According to said process, biphenyl or a biphenyl derivative are brought into contact with an alkylated benzol in the presence of a catalyst. The invention is characterised in that a zeolite with a large micropore diameter is used as the catalyst.

Description

Processes for the preparation of 4-methyl- and 4,4'-dimethylbiphenyl are known from the Literature known.

So is the production of 4,4'-dimethylbiphenyl by homogeneous catalytic Coupling of toluene in the presence of a palladium-II compound, preferably Palladium acetate or Palladiumacetonylacetonat, and in the presence of Sauer have already been described in the literature (J. Org. Chem. Vol. 38, No.1, 76- 79, 1972; Bull. Chem. Soc. Jap., Vol. 46, 1973, 2490-2492). The attainable Yields vary, depending on the catalyst used 0.4 to 13%, with selectivities of 11.9% for 4,4'-dimethylbiphenyl (4,4'- DMBP).

The disadvantage of this process is the long reaction times (Up to 23 h) and in the poor separability of the expensive catalyst from Educt / product mixture.

US-A-5,177,286 describes the preparation of 4,4'-alkylmethylbiphenyl, starting from biphenyl or 4-methylbiphenyl or mixtures thereof Compounds using a special Lewis acid catalyst, e.g. B. AlCl₃, and in the presence of a methylating agent at temperatures from -40 to 80 ° C. The yields for 4,4'-dimethylbiphenyl are around 2% with selectivities of 9.6%.

Here, too, the catalyst can only be separated with a very high separation effort, if any, separate from the reaction mixture.

EP-B-0 202 752 describes a process for the preparation of 4-substituted or 4,4'-substituted alkylated derivatives of biphenyl or a biphenyl derivative in the presence of a catalyst containing a crystalline zeolite average pore diameter or a crystalline zeolitic substance with lerem pore diameter, the biphenyl or biphenyl derivative with is brought into contact with an alkylated benzene.

The reaction temperature is preferably in the range from 200 to 600 ° C. Of the  The disadvantage of this process is the large number of products can be obtained under the specified reaction conditions and in some cases only difficult to separate from each other. So are those with this Process achievable yields and selectivities, especially for 4,4'- Dimethylbiphenyl (yield: 1.1%, selectivity: 10.4%), unsatisfactory.

All methods known in the prior art have the disadvantage that the Production of 4-methylbiphenyl and 4,4'-dimethylbiphenyl, despite a long time Trial times and low conversion rates, only in low yields and low selectivity.

The task is therefore to provide a method which it allows 4-methylbiphenyl and 4,4'-dimethylbiphenyl with good yields and sufficiently high selectivity within relatively short reaction times supply.

The present invention solves this problem and relates to a method for selek tive preparation of 4-substituted or 4,4'-disubstituted alkylated, especially methylated and ethylated derivatives of biphenyl or a Biphenyl derivative in which biphenyl or a biphenyl derivative in the presence of a Catalyst is brought into contact with an alkylated benzene.

It has surprisingly been found that particularly good selectivities and Yields can be achieved if a zeolite with a large micropo diameter, in particular <7 Å, is used. Preferably, the used catalyst so-called super-cages with a diameter of at least 12 Å.

Faujasite catalysts with a molar SiO₂ / Al₂O₃ ratio are preferred nis in the range from <5 to 30, in particular 11 to 26, used. Examples for this are ®US-HY-11 (Grace GmbH) or ®US-HY-26 (DEGUSSA).

In the case of commercially available zeolite catalysts, pores are formed according to the invention knife, pore structure and acidity of the catalyst by treatment with phosphorus-containing compounds, preferably tributyl phosphite and ortho- Phosphoric acid, or by treating the catalyst with hydrochloric acid or  Modified water.

In the treatment with phosphorus compounds, the catalyst is mixed with aqueous Solutions of the corresponding phosphorus compounds impregnated and then ßend in nitrogen flow or air flow at temperatures in the range of 400 to 800 ° C, especially 500 to 700 ° C, calcined.

Modification of zeolite properties with tributyl phosphite on mordenite Medium pore diameter catalysts are known from the literature (Res. Chem. Intermed., 1993, Vol. 19, 319-332; Appl. Catal. A., General 131, 1995, 215-224).

In the treatment with hydrochloric acid, the catalyst is washed with aqueous hydrochloric acid Solutions added and 1 to 6 hours, preferably 2 to 4 hours, under Reflux cooked. Then the catalyst in the air flow Temperatures in the range from 400 to 800 ° C, in particular 500 to 700 ° C, calcined.

In the modification of the catalyst with water, the catalyst is before Use at temperatures from 400 to 800 ° C, especially 500 to 700 ° C, in Calcined nitrogen stream and then one for 24 to 72 hours exposed to saturated water vapor atmosphere.

In the process according to the invention, the alkylation agent is in particular Pentamethylbenzene used. The advantage of using the, in comparison to hexamethylbenzene, inexpensive pentamethylbenzene is among others included in it see that the di-, tri- and Tetramethylbenzenes, can easily be separated from the product mixture (e.g. by distillation) and dealuminized with methanol in a second reaction stage Mordenite catalysts, preferably on mordenite catalysts with a SiO₂ / Al₂O₃ ratio in the range of 5 to 25, again to the required Pentamethylbenzene be implemented. As a result, the yields of Pentamethylbenzene to <25%, especially 25 to 35%, which is one Selectivity of <30% corresponds to be increased.

In this way it is possible to implement unreacted di-, tri- or Tetramethylbenzene, which was regenerated to pentamethylbenzene, the  Recycle circuit supply and again for alkylation use.

For the preparation of 4-methylbiphenyl and / or 4,4'-dimethylbiphenyl after The inventive method is biphenyl or a biphenyl derivative in one Solvent dissolved or suspended and with the addition of polymethylbenzenes, e.g. B. tri-, tetra- and / or pentamethylbenzene, especially pentamethylbenzene, in a discontinuous stirred tank reactor made of stainless steel on a large pore Zeolite catalyst implemented.

The process can be either in the gas phase or the liquid phase or in a mixed phase (liquid / gas).

As a solvent or suspending agent for biphenyl or biphenyl derivatives in particular C₅ to C ₁₄ alkanes, preferably heptane, used. Further Solvents which can be used according to the invention are cyclic alkanes, such as, for. B. Cyclo-hexane or decalin. The ratio of biphenyl: solvent is especially in the range of 1:10 to 1:40.

The ratio of pentamethylbenzene: biphenyl is 5: 1 to 1: 5, preferably 4: 1 to 1: 4. The temperature in the reactor is that of the invention Processes above 200 ° C, in particular in the range from 220 to 270 ° C, at pressures from 20 to 60 bar, in particular 25 to 35 bar.

The reaction times are in the range from 1 to 10 hours, in particular 1.5 to 6 hours.

With the method according to the invention, conversion rates for biphenyl or Biphenyl derivatives in the range of 60 to 100% can be achieved.

With the help of the present method it is possible to obtain the yield for 4- Methylbiphenyl to 20 to 28% and the yield for 4,4'-dimethylbiphenyl 7 to 10%, with selectivities of 25 to 60% (for 4-methylbiphenyl) or 7 to 15% (for 4,4′-DMBP) to increase.

The catalysts modified according to the invention are particularly noteworthy due to good stability, high activities and low deactivations  as well as easy regenerability.

According to the opinion represented in the state of the art, it is in particular Surprisingly, the yields and selectivities for 4-methylbiphenyl and 4,4'-DMBP using large-pore zeolites considerably have it improved.

The compounds obtained by the method described above are coveted raw materials for the production of high-temperature Heat transfer media, thermotrophic liquid crystals and temperature resistant Plastics.

The invention is illustrated by the following examples.

Examples 1. Catalyst preparation

All specified preparation instructions were based on a protonated ultra stable faujasite with SiO₂ / Al₂O₃ ratio of 26 (US-HY-26) carried out.

1.1. example Calcination

The calcination of the zeolites is carried out in a quartz glass tube Oven performed. A volume flow is used on a rotameter for calcination 0.4 l nitrogen per minute. About 6 g of the zeolite will be filled in a graphite crucible and overnight at a temperature of 450 ° C exposed.

1.2. example Introduction of phosphorus in the zeolite a.) Treatment with phosphoric acid

i. The US-HY-26 to be modified is initially 2 hours at Calcined at 450 ° C. Then it is refluxed for 2 hours two molar phosphoric acid cooked at 140 ° C. By one under the suspension is attached to the piston touched. Then the phosphorus-containing faujasite is filtered off with Washed water, dried at 120 ° C for one hour and finally calcined at 450 ° C for 2 hours.

ii. Regulation 1.2a) i is modified in such a way that the US-HY-26 refluxed in one molar phosphoric acid for one hour becomes.

b.) Treatment with tributyl phosphite (TBP)

i. 15 g of the catalyst (US-HY-26) become 75 ml more aqueous Given 10% TBP solution. This suspension is used for 2.5 Cooked under reflux at 140 ° C for hours. After that, the zeolite filtered off and washed with water. The modified faujasite is then dried at 120 ° C for one hour and then at Calcined at 450 ° C for 2 hours.  

ii. The procedure is analogous to 1.2b) i. The difference is there in that you work with 20% TBP solution.

iii. The preparation instructions given for 1.2b) i are repeated twice carried out; Drying and calcination only take place once, at the end of the catalyst preparation.

iv. Compared to 1.2b) iii, the catalyst is a second time, ie a total of three times, with 10% TBP solution under reflux cooked.

v. The modified catalyst is made with acetone instead of water washed. This is said to cause excess tributyl phosphite, which is not has reacted with the catalyst, can be removed better. Otherwise is carried out analogously to 1.2b).

vi. First, the preparation instructions given for 1.2b) carried out completely. Then the TBP-modified US HY-26 for one hour with single molar phosphoric acid under reflux and stirring heated. After filtering off with water washed, dried for one hour at 120 ° C and then calcined at 450 ° C for two hours.

1.3. example Treatment of the catalyst with water

The catalyst to be prepared (US-HY-26) is placed in a porcelain bowl filled. From the desiccator, the agent used for drying, e.g. B. Silica gel, removed and the desiccator approx. 3 cm high with distilled water filled. The porcelain bowl is placed in the desiccator and this closed. A standing time of approx. 10 hours ensures that an atmosphere saturated with water vapor forms in the desiccator. A Part of the water vapor is absorbed by the zeolite. Just before In the experiment, the catalyst is removed from the desiccator and without further pretreatment of the reaction mixture was added.

1.4. Treatment of the catalyst with hydrochloric acid

a) 15 g of the catalyst are dissolved in 0.5 molar hydrochloric acid (225 ml)  slurried and heated under reflux for 2 h. After that, the zeolite filtered and first with cold, then with warm distilled water (approx. 300-400 ml) washed. The catalyst is in 1 h Drying cabinet dried at 100 ° C, then for 12 to 14 h at 450 ° C calcined in the calciner under synthetic air.

b) Procedure analogous to 1.4a), but a 1 M hydrochloric acid used.

c) Procedure analogous to 1.4a), but a 1 M hydrochloric acid used and the treatment was carried out for 4 h.

1.5. example Reactivation of catalysts already in use

After a single use, the coke becomes brownish Filter the catalyst from the product solution and overnight in a drying cabinet dried at 80 ° C. Then it is filled into graphite crucibles, which are placed in a Tube furnace are introduced. It becomes a volume flow of synthetic air of about 0.4 l / min, set at a temperature of 300 ° C, which makes it the The coke comes out of the pore structure to the surface. By briefly opening the heating jacket can be observed that the Zeolite gets much darker. After three hours, the temperature for increased to 450 ° C for a further 5 hours. The coke burns at this temperature from. This can be recognized optically by the fact that the zeolite becomes lighter again and finally returns to its original light color.

After the regeneration has ended, the catalytic converter can be switched over by Gas supply of synthetic air calcined on nitrogen in the same furnace will. During the regeneration, the zeolite becomes relatively moderate temperatures exposed to a maximum of 450 ° C. Through this gentle approach hydrothermal effects, such as dealumination, are avoided in order to Test results when using the regenerated catalysts do not distort.

All catalysts modified in the manner described above are characterized by good stability, high activities and low Deactivations and easy regenerability from (see Table 2).  

2. Catalyst screening experiments 2.1. Apparatus

Experimental plant: discontinuous stirred tank reactor made of stainless steel.
ϑ = 600 ml

Test conditions: liquid phase, suspension of catalyst in heptane

Table 1

Test conditions

Procedure for carrying out the experiment

• - The reactor was pressurized with sufficient N₂ that Solvents just not under the chosen test conditions boils.
• - Heating up the reactor to the operating point
• - If the temperature is constant, fill up to the final pressure and start the experiment

Analytics

• - The liquid product mixture was gas chromatographed using FID analyzed  
• - Dodecane was used as an internal standard
• - Separation column DB-1 glass capillary column, temperature program 70 to 200 ° C
• - Identification of the different dimethylbiphenyl isomers using GC-MS

2.2. Test results a) General reaction scheme (3n 6)

H₅C₆-C₆H₅ + (CH₃) _n C₆H _(6-n) → H₃C-H₄C₆-C₆H₅ + (CH₃) _(n-1 ) C₆H _(7-n1) (1)

H₃C-H₄C₆-C₆H₅ + (CH₃) _n C₆H _(6-n) → H₃C-H₄C₆-C₆H₄-C₃ + (CH₃) _(n-1) C₆H _(7-n) (2)

b) Reaction-technical assessment variables

Reaction characteristics (sales degrees X, Y yield and selectivity S) were used to assess the Screening attempts used. N stands for the molar amount, t for time and ν for the stoichiometric coefficient of chemical species i or k.

c) Results of the catalyst screening

The results obtained taking into account points 2.1 and 2.2b are listed in Table 2. The highest occurring in the course of the reaction Most values of the yield of the target products (while specifying Degree of conversion and selectivity) are at the corresponding test times listed. From this summary overview you can do the following Conclusions are derived:

• - Optimal alkylation agent / catalyst combination: pentamethyl benzene and US-HY-26.
• - All modifications described under points 1.2 and 1.3 methods result in a clear yield and Selectivity improvement for 4-methyl- and 4,4'-dimethylbiphenyl compared to the unmodified catalysts (point 1.1) same alkylation agent.
• - The modified catalysts are easy to regenerate.

Claims (10)

1. A process for the selective preparation of 4-substituted or 4,4'-di substituted alkylated derivatives of biphenyl or a biphenyl derivative in which biphenyl or a biphenyl derivative is brought into contact with an alkylated benzene in the presence of a catalyst, characterized in that the catalyst a large micropore diameter zeolite is used. 2. The method according to claim 1, characterized in that the catalyst a faujasite catalyst with a molar SiO₂ / Al₂O₃ ratio in Range is <5 to 30. 3. The method according to at least one of claims 1 to 2, characterized records that pentamethylbenzene is used as the alkylating agent. 4. The method according to at least one of claims 1 to 3, characterized records that the turnover rate for biphenyl or the biphenyl derivative in Range is from 60 to 100%. 5. The method according to at least one of claims 1 to 4, characterized characterized in that the reaction time in the range of 1 to 10 hours lies. 6. The method according to at least one of claims 1 to 5, characterized characterized in that the reaction temperature is <200 ° C. 7. The method according to at least one of claims 1 to 6, characterized characterized in that the catalyst prior to its use by Treatment with phosphorus compounds was modified. 8. The method according to at least one of claims 1 to 6, characterized characterized in that the catalyst prior to its use by Treatment with hydrochloric acid or water has been modified. 9. The method according to at least one of claims 1 to 8, characterized  characterized in that the selectivity for the formation of 4,4'- Dimethylbiphenyl is in the range of 7 to 15%. 10. The method according to at least one of claims 1 to 9, characterized characterized in that the selectivity for the formation of 4-methylbiphenyl is in the range of 25 to 60%.