EP1373168A2

EP1373168A2 - Method for side chain alkylation or alkenylation

Info

Publication number: EP1373168A2
Application number: EP01980242A
Authority: EP
Inventors: Ulrich Steinbrenner; Ralf Böhling; Peter Zehner
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2000-08-17
Filing date: 2001-08-10
Publication date: 2004-01-02
Also published as: US20040106834A1; US6984766B2; DE10040184A1; JP2004529846A; CN1454193A; WO2002014241A3; WO2002014241A2

Abstract

The invention relates to a method for reducing the formation of polymers during the side chain alkylation or side chain alkenylation of alkylaromatic compounds by reacting olefins or diolefins in the presence of an alkali metal catalyst; and the ensuing distillation for preparing the alkylated or alkenylated compound. The alkali metal in the catalyst is situated on an inorganic carrier, and the catalyst is mechanically separated from the reaction mixture after the reaction and before distillation.

Description

Process for side chain alkylation or alkenylation

The invention relates to a process for reducing the formation of polymers in the case of side chain alkylation or side chain alkenylation of alkylaromatic compounds.

The side chain alkylation, in particular of aromatic compounds which carry an acidic proton in the α position of the side chain, in the presence of catalysts is known.

No. 2,448,641 describes a ner driving in particular for the side chain alkylation of toluene. 0.1 to 20% of an alkali metal, based on toluene, is used as the catalyst. It is described that the catalyst can be separated from the reaction product by filtration, whereupon the product is purified by fractional distillation. Sodium is used as the preferred catalyst.

No. 3,291,847 describes in particular the potassium-catalyzed alkylation of toluene with propene. Potassium, sodium or a sodium-potassium alloy together with graphite on sodium carbonate are used as the catalyst. The catalyst is formed in situ in particular in the reactor. It is described that the combination of the alkali metal with graphite and the support in the reactor does not form a brown tar-like polymer, which is the case without the use of a catalyst support. It is described that the catalyst can be removed from the reaction mixture after the reaction by filtration. The catalyst can also be inactivated or reacted with a polar compound such as an alcohol. Unreacted starting materials can be recovered and returned to the implementation. According to the examples, the catalyst in the reaction mixture is deactivated by quenching with an alcohol.

No. 4,914,250 relates to a process, in particular for the alkenylation of toluene with propene in the presence of a supported potassium or potassium alloy catalyst using sodium hydroxide or potassium hydroxide as co-catalyst. As suitable carrier materials are diatomaceous earth, activated carbon, carbon, silicon dioxide, aluminum oxide etc. After the reaction, the catalyst is deactivated by reaction with methanol.

It was found that when the catalyst in the reaction mixture is deactivated by protolysis, the subsequent distillation of the product mixture leads to the formation of tar-like polymers in the distillation bottoms. This severely complicates the separation or purification of the reaction product.

It is difficult to separate the catalyst from the reaction mixture, especially in the case of unsupported catalysts, so that catalyst residues can get into the distillation.

The object of the present invention is to provide a process for reducing the formation of polymers in the case of side chain alkylation or side chain alkenylation of alkylaromatic compounds.

The object is achieved according to the invention by a process for reducing the formation of polymers in the side chain alkylation or side chain alkenylation of alkylaromatic compounds by reaction with olefins or diolefins in the presence of an alkali metal catalyst and subsequent distillation to obtain the alkylated or alkenylated compound, the alkali metal in the catalyst is present on an inorganic support and the catalyst is mechanically separated from the reaction mixture after the reaction and before the distillation. This means that only the organic phase mechanically separated from the catalyst is fed to the distillation without the catalyst having been protolysed.

It has been found according to the invention that the distillative workup of the reaction mixture is considerably simplified if the catalyst is mechanically separated from the product mixture without protolysis. In this case, no tarry polymers are formed in the bottom of a downstream distillation column, which would pose major procedural problems.

In particular, (spent) mechanically separated catalyst can be protolysed, an organic phase formed during the protolysis not being returned to the distillation. It has also been found that the use of alkali metal carbonates, alkali metal halides or mixtures thereof as catalyst supports allows the alkali metal catalyst to be completely separated from the reaction mixture by simple filtration.

The mechanical separation of the catalyst is preferably carried out using a mixer-settler, settier, filter or cross-flow filter, depending on the particular design of the reaction apparatus.

The alkali metal catalyst can thus be completely removed from the reaction mixture before the reaction mixture is distilled. This largely, preferably completely, prevents the formation of tar-like polymers in the distillation apparatus.

The catalyst support is particularly preferably selected from K CO ₃ , K ₂ CO ₃ / KCl and K ₂ CO ₃ / NaCl. The alkali metal applied to the carrier is preferably sodium, potassium or a NaK alloy. Sodium is preferably used on the carrier.

The preparation of the supported catalyst is known and can be carried out, for example, as described in DE-A-197 15 203. The catalyst preferably has 0.5 to 20, in particular 1 to 15,% by weight of metallic sodium and / or potassium, based on the total catalyst.

In the overall process, the catalyst is prepared from alkali metal and support at temperatures above 100 ° C. before being used in the reaction. It can also be formed with hydrogen and / or alkyl aromatic compounds at temperatures above 100 ° C.

The reaction can be carried out batchwise or preferably continuously. Suitable apparatus are stirred tank reactors, stirred tank cascades, stirred columns, loop reactors, cascades of loop reactors or similar devices. The catalyst can be used as a suspension or moving bed (fluidized bed), preferably as a suspension. As described above, the catalyst is preferably retained by a mixer settler, a settier, a filter, a crossflow filter or a similar process engineering unit. Filter devices are particularly preferably used. The residence time of the catalyst in the reaction stage is significantly longer compared to the organic phase, that is, the catalyst is retained and used until loss of activity.

After the reaction has taken place and the catalyst has been separated off, the product mixture is separated by distillation. Unreacted starting materials can be returned to the reaction. The alkylated or alkenylated product can then be further purified by further processes, for example by fractional distillation, fractional crystallization, extraction, etc.

The reaction is preferably carried out continuously in the suspension mode, the catalyst being retained in the reactor. The reaction is preferably carried out with vigorous stirring.

The reaction is generally carried out at a temperature of -50 to 400 ° C., preferably at a temperature of -20 to 300 ° C., particularly preferably 80 to 250 ° C., in particular 100 to 200 ° C. and a pressure of preferably 0, 1 to 200, particularly preferably 1 to 150, in particular 1 to 100 bar, preferably in the liquid phase without a gas phase.

All suitable alkyl aromatics can be used as alkyl aromatic compounds. They can have, for example, a benzene or naphthalene nucleus as the aromatic nucleus. Alkylalicyclic compounds in which the cyclic nucleus can be a cyclic alkyl, alkenyl or alkynyl radical are also suitable. Residues in which several of the ring restrictions are linked can also be used. The link structures have an acidic hydrogen atom in the α-position of the side chain. They preferably have at least one alkyl radical which is bonded to the cyclic structure. The alkyl radicals can have any length and can be substituted by further substituents. Preferably, as alkylaromatic Verbindunden benzenes o- by 1 to 6, preferably 1 to 3, in particular 1 to 2 Cι- _2, preferably ₃ -Al Cι- yl radicals are substituted naphthalenes substituted by 1 to 10, preferably 1 to 5 , particularly preferably 1 to 2 Cι. ₂ o-, preferably Cι. ₃ alkyl radicals are substituted, and the alkylalicyclic compounds employed cyclopentenes or cyclohexenes by 1 to 5, preferably 1 or 2, or 1 to 6, preferably 1 to 3, especially 1 or 2 C ₁ - ₂₀ -, preferably Cι. ₃ alkyl radicals are substituted. The olefins preferably have 2 to 20, particularly preferably 2 to 10, in particular 2 to 5, carbon atoms. Ethene, propene, 1-butene, 2-butene, iosbutene, 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene and / or 3-methyl-1-butene are preferably used , Ethene and propene are particularly preferred. The diolefms preferably have 4 to 20, particularly preferably 4 to 10, in particular 4 to 6, carbon atoms. Butadiene and / or isoprene are particularly preferably used.

The reaction of toluene with ethene or propene to give propylbenzene or isobutylbenzene, the reaction of cumene with ethene to give tert-amylbenzene and the reaction of xylenes with butadiene to give 5-tolylpentenes are particularly preferred.

Used catalyst can be removed from the reactor, protolysed and then disposed of. The addition of salt to the alkali metal in conjunction with a filter can prevent alkali metal from escaping from the reactor into the work-up stage, where it would lead to major technical and safety-related problems.

The invention also relates to the use of alkali metal catalysts supported on an inorganic support in the side chain alkylation or side chain alkenylation of alkylaromatic compounds by reaction with olefins or diolefins and subsequent distillation to reduce the formation of polymers during distillation.

The invention is explained in more detail below with the aid of examples.

Examples

Preparation of the catalyst

35 g of KC1 and 35 g of K ₂ CO ₃ were mixed and dried overnight at 300 ° C. in a stream of argon. Then 10.8 g of Na were added and the metal was supported on the potassium salts at 300 ° C. in the course of 2 hours. The finished catalyst was then dispersed in 115 g of toluene and transferred to a stirred tank reactor with an internal volume of 270 ml.

Carrying out the experiment 0.117 mol h of dry liquid propene and 0.316 mol / h of dry toluene were continuously pumped into a reactor at 160.degree. C. for 160 h and then at 160.degree. C. for 80 h, and the reaction discharge was drawn off through a 4 μm filter. A magnetically coupled Stirrer with impeller turbine and 1000 to 1200 rpm kept the catalyst in suspension. After relaxing to ambient pressure, a discharge of 7.6 kg of the composition listed in Table 1 resulted. Na and K were neither visible nor detectable in the discharge (<10 ppm by weight).

75 ml of the reaction discharge obtained in this way (composition see table) were heated in a glass pressure autoclave at 250 ° C. for 72 h. The organic phase turned slightly yellow, there were no visible deposits.

75 ml of the reaction discharge were mixed with 15 ml of 30% aqueous NaOH and heated to 250 ° C. in a glass pressure autoclave with stirring for 72 h. The organic phase turned slightly yellow and there were no visible deposits either.

For comparison with the known procedure, EtOH / H ₂ O was added to the contents of the steel autoclave under argon and the organic phase (88 g, composition see table 1) was heated to 250 ° C. in a glass pressure autoclave with stirring for 72 h. The solution turned deep brown and black, sticky, tar-like deposits formed.

Table 1: Composition of the organic phases according to GC analysis

Comparative test (without added salt)

5.86 kg NaK ₂ and 45 g toluene were placed in a stirred tank reactor with an internal volume of 100 ml. The autoclave was then flooded with toluene and 0.044 mol / h of dry liquid propene and 0.119 mol / h of dry toluene were pumped continuously at 130 ° C. and the reaction discharge was drawn off through a 2 μm filter. On magnetically coupled stirrer with impeller turbine and 1200 rpm kept the catalyst in suspension. The experiment had to be stopped after a few hours because significant amounts (a few hundred milligrams) of liquid NaK _{2 had} escaped from the reactor.

Claims

claims

1. Process for reducing the formation of polymers in the side chain alkylation or side chain alkenylation of alkyl aromatic

Compounds by reaction with olefins or diolefins in the presence of an alkali metal catalyst and subsequent distillation to obtain the alkylated or alkenylated compound, characterized in that the alkali metal is present in the catalyst on an inorganic support and the catalyst after the reaction and before the distillation mechanically from

Reaction mixture is separated.

2. The method according to claim 1, characterized in that the mechanical separation of the catalyst is carried out with a mixer-settler, settier, filter or cross-flow filter.

3. The method according to claim 1 or 2, characterized in that alkali metal carbonates, alkali metal halides or mixtures thereof are used as inorganic carriers.

4. The method according to claim 3, characterized in that the carrier is selected from K ₂ CO ₃ , K ₂ CO ₃ / KCl and K ₂ CO ₃ / aCl.

5. The method according to any one of claims 1 to 4, characterized in that the reaction is carried out continuously in the suspension mode and the

Catalyst is retained in the reactor.

6. The method according to any one of claims 1 to 5, characterized in that toluene is reacted with propene.

7. The method according to any one of claims 1 to 6, characterized in that the reaction in the liquid phase is carried out at a temperature in the range from 100 to 200 ° C.

8. The method according to any one of claims 1 to 7, characterized in that spent mechanically separated catalyst is protolysed and an organic phase formed during the protolysis is not returned to the distillation. Use of alkali metal catalysts supported on an inorganic support in the side chain alkylation or side chain alkenylation of alkyl aromatic compounds by reaction with olefins or diolefins and subsequent distillation to reduce the formation of polymers in the

Distillation.