DE1618467A1 - Process for the preparation of 4-methylpentene-1 - Google Patents

Description

Process for the preparation of 4-methylpentene-l

Qlanzstoff AO Wuppertal

4-Methylpentene-1 is known from the decomposition of propylene to manufacture. Among other things, a catalyst is suitable for this purpose, which by re-metallization of an organic lithium compound Li-R, where R is an alkyl radical with 2-18 carbon atoms, an aryl or cyoloalkyl radical, with another alkali metal, preferably Potassium, is manufactured (British Patent No. 979 * 877) This dimerization is carried out in an inert hydrocarbon and can be designed continuously and discontinuously. Because of the excellent selectivity of the lithium catalyst, the process gives high yields of 4-methylpentene-1

It has been shown, however, that during dimerization in the presence of solvents or diluents, the quantitative isolation of the resulting blemishes presents difficulties. For example, the solvent used for the Dimerlsierung of Propylene hoohsledendes diesel oil (Kp.- Löo - 220 ⁰ C), the hexenes from the solvent remaining in the NaOH the reaction to be carried out separation by distillation at a Destillationetemperatur of 125 ⁰ C for about 20 Oew.jf, at 150 ⁰ C. £ hexenes in the solvent always Nooh 10 0EW. A further increase in the distillation temperature is, however, prohibited because of a resulting reduction in the service life of the contact. As a result, when the process is carried out continuously, the inert hydrocarbon containing the catalyst still contains hexenes, including in particular 4-methylpentene-1, when it is returned to the reaction space. Since the density of dinerization decreases with increasing diner concentration, a decrease in conversion, that is, the amount of newly formed hexenes, is the consequence of this accumulation. Likewise, the recirculated 4-M-methylp-nttn-1 in the reaction aura suffers in some cases an undesired isomerization with 4-methylpentenes.

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Eb has now been found that the difficulties noted can be reported in a technically simple manner if, for the preparation of 4-methylpentene-1 by dimerization of propylene using metallic lithium as a catalyst, which is obtained by transmetallation of an organic lithium compound Li-R , wherein R is an alkyl radical with 2-18 carbon atoms, an aryl or cycloalkyl radical, is prepared with another alkali metal in an inert solvent, uses a process which is characterized in that the dimerization reaction after removal of the solvent over the solid lithium catalyst in the oas phase at temperatures of 100-175 ⁰ C and at a pressure of at least Io atü is carried out. A preferred embodiment provides for the use of reaction temperatures ranging between 12o 'and 150 ^0C.

In order to achieve a good implementation speed, it is necessary the solid contact the gaseous propylene in higher concentrations to feed. According to the invention there must be an above in the reaction vessel Io atü lying propylene pressure can be maintained. on the other hand you will usually print more than 600 atmospheres of effort because of avoid. The reaction pressure is preferably 150-500 atü. The known and are suitable for carrying out the process usual pressure vessel which either contain mixing devices or that can be shaken, rocked or rolled.

To prepare the catalyst to be used according to the invention, it is expedient to proceed in such a way that an alkali metal is preferably used, potassium is used, it is melted in an inert hydrocarbon and the metal dispersion is then allowed to cool with intensive mixing. In this way, the metal is precipitated in a very finely divided form. The solution of an organic lithium compound - for example lithiurabutyl - in the same hydrocarbon that was used as the dispersion medium is then added, whereupon the transmetallation reaction begins in a known manner. From the reaction mixture, the now lithium in finely divided form and the old by-product obtained organisohe alkali metal compound. Contains distributed in the inert solvent, the dispersant is then removed using a vacuum. This process can be carried out at room temperature. The catalyst is preferably used in this fora sum. It goes without saying that it is also possible in the form of re-cladding as a secondary product.

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NEN organic alkali metal compounds before removing the to separate inert solvent from metallic lithium.

4-Methylpentene-1 can be obtained with very good yields and excellent selectivity using the process according to the invention. The successful polymerisation of propylene in the oase phase is surprising, because an increased isomerisation of 4-methylpentene-1 or even the formation of fragments of propylene would have been expected, if only because if the reaction was carried out in the presence of liquid diluents this ease the Stoffrüoktransport of the reaction products from contact and counter lack these, überbasciiend was AUOH the particular effectiveness of the _# catalyst, because the Umsetzungsgesohwindigkeit when using the eri-l f Indungsgemäßen method readily accomplished those obtained from di- <merl8lerungsreaktlon in an inert hydrocarbon Sales. In addition, there is no need to separate off the inert reaction medium when working up the reaction products.

The process according to the invention can also be carried out continuously with excellent success. However, it is recommended here to use reaction ^{temperatures below 150 °} C., since a certain amount of contact fatigue can occur above these temperatures. To carry this out, propylene is passed into the reaction vessel which contains the solid catalyst and the dimerization is initiated under the pressure conditions indicated above and the recommended temperature range. After about 2-10 hours, when the hexene partial vapor pressure approaches the saturation value, the reaction mixture is continuously withdrawn, which practically consists only of hexene zeomers and propylene. Exceeding the saturated steam pressure specified in the following table for different temperatures should be avoided!

Tabel

Saturated steam pressure of a Hexengemlsohes with 95 <4-methylpentene-1 temperature (° C) 100 110 120 130 14O 150 pressure (atm) 3.9 4.9 6.0 7.3 Θ.Θ 10.8

The withdrawn reaction solution can be separated into propylene and dimerization product. The unreacted propylene is recycled to the reaction vessel, while "ioh which boils at 53.9 ⁰ C 4-methyl-i leiont by distillation from the higher boiling hexene isomers can be separated.

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example 1

20 g of K-metal are in a 1 1 flask in 500 ml of Cyolohexane under Ν «atmosphere melted at 80 ° C. While stirring vigorously with A high-speed stirrer turns the metal at 10-15,000 revolutions finely divided per minute within 2-5 minutes. Then will Heating and stirrer switched off, the batch is cooled to -5 ° C. At this temperature, a solution of> 3gLl-butyX in 165 ml of cyolohexane is added dropwise with slow stirring with a glass stirrer to * Then the stirring is continued for a further 2 hours to complete the transmetalation. The resulting catalyst insulation is pressed into a 5 l roller autoclave under Np. With the aid of a vacuum, the dispersant is completely removed from it.

1.5 kg of propylene are now introduced and the autoclave is heated to 145 ° C. The initial pressure is about JOO atm. The autoclave is now rolled for 10 hours. During this time, the pressure drops to around 190 atmospheres. The autoclave is now removed from the heatable roller device and placed in a row in a heating block. At a temperature of around 80 - 90 ° C, excess propylene is initially slowly depressurized via an intensive cooler. Then 3 kg of a Diraerengeraisohea with a 4-methyl-pentene-1 content of 91.2 % are distilled off.

After cooling the autoclave to room temperature and renewing it When filled with propylene, the catalyst remaining in the pressure vessel can be used again for the dimerization of propylene «

Example 2

According to the description of Example 1, five times the amount of catalyst suspension is prepared. The dispersant cyolohexane is withdrawn from the reaction flask with stirring in vacuo. The finely powdered catalyst that remains is removed from the reaction flask under vacuum gas into a vertical reaction tube of 3 η length and 100 mm clear width onto a metal interlayer on the floor

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brewed. A second plate is attached to the head of the pipe and the pipe is closed. Both pipe ends are connected to a circulation pump via a line. This urawilz line has one connection each for the supply of propylene and the discharge of the reaction product. After the reaction tube has been closed, the apparatus is rinsed several times with propylene Np-free and heated to 145.degree. In order to report condensation, the entire apparatus must be brought to the reaction temperature The gas stream passes the reaction tube from bottom to top. The course of the reaction is checked by gas chromatography. As soon as the hexene partial vapor pressure has reached 9 atm, 0 * 3 »of the circulating reaction product is withdrawn every hour. The product mixture is released to the side halfway up in a filling body (χ 50 mm. Return ratio Ui) to a pressure of 10 atm. Under this pressure, propylene distills off at the top of the tube at 20 ° G and is liquefied in a cooler filled with cooling water at 8 ° C the amount of propylene consumed by the Dlmerlslerung is supplemented and continuously pumped back into the reactor. The dimers formed are found in liquid form at a sump temperature of 150 ° C. in the distillation gases and can be drained off via a cooler. 320 g of reaction product are obtained per hour, 95 % of which consists of 4-methylpentene-1 and is processed by subsequent distillation to pure 4-methylpentene-1.

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109810/2181

Claims (4)

Claims 1. Process for the production of 4-methylpentene! by dimerization of propylene using metallic lithium as a catalyst, which is produced by transmetalation of an organic Lithium compound Li-R, where R is an alkyl radical with 2 to 18 carbon atoms, an aryl or Cyoloalkylrest, with a other alkali metal is prepared in an inert solvent, characterized in that the dimerization reaction after removal of the solvent over the solid lithium catalyst is carried out in the oasis phase at temperatures of 100 ° to 175 ° C and at a pressure of at least 10 attt. 2 «method according to claim 1, characterized in that the dimerization reaction is carried out at temperatures between 120 to 150 ⁰ C and at a pressure of 150 to 500 atmospheres. 3 · Process according to claims 1 and 2, because the dimerization reaction is carried out over a lithium catalyst which still contains the organic alkali compound formed as a by-product in the transmetalation. 4. Method naoh Anspruoh 3, characterized in that the im Lithium catalyst present as a by-product of the metalization Compound an * organic potassium compound 1st. BATH ORIGINAL 109810/2181