DE1443472C - Isomerization of 4-methylpentene-1 to 2 methylpentene-2 in the presence of a catalyst - Google Patents

Description

There are a variety of different isomerization processes for lower olefins. To describe z. B. British patent 865 738 and the French patent 1,265,661 process for converting internal to terminal olefins. On the other hand, Belgian patent application 604 445 deals with the conversion of olefins with terminal ends Double bonds to olefins with double bonds in the middle. It is z. B. at the Isomerization of a mixture of different hexenes, among other things, also on the formation of 2-methylpentene-2 from 4-methylpentene-1 pointed out.

In the process of the invention, however, using a new catalyst, 4-methylpentene-1 converted to ^ -Methylpentene in good yields.

The invention relates to a process for isomerizing 4-methylpentene-1 to 2-methylpentene-2 by passing 4-methylpentene-1 at temperatures in the range from 150 to 200 ^° C. over a catalyst which is characterized in that the Carries out isomerization in the presence of a catalyst which contains a Friedel-Crafts metal halide and an alkali metal halide on a support, the alkali metal halide is at least in equimolar amounts to the Friedel-Crafts metal halide and the total amount of metal halide between 1 to 50 percent by weight of the metal halide and the Carrier amounts.

You can work under reduced pressure, normal pressure or overpressure.

The Friedel-Crafts metal halide and the alkali metal halide can be a complex halide form. Preferably, chloride or bromide are used as halide components.

Aluminum chloride is preferred as the Friedel-Crafts metal halide. Very suitable as Friedel-Crafts metal halide is also ferric chloride. Other suitable Friedel-Crafts metal halides are aluminum bromide and stannous chloride.

The alkali metal halide is preferably an alkali chloride or bromide, in particular potassium chloride, used. Optionally, two or more alkali metal halides can be used, or the complex halide may contain three or more metal components.

The metal halides are used in essentially equimolecular proportions. However, you can In comparison to the Friedel-Crafts metal halide, higher proportions of an alkali metal halide are used thereby promoting the migration of the double bond.

The complex halide of the formula KAlCl ₄ can optionally be used.

Activated silica gel is suitable as a catalyst carrier, natural silicates, diatomaceous earths such as kieselguhr, corundum and silicon carbide. Preferred as The carrier is activated silica gel.

The catalyst of the process according to the invention is prepared by mixing a molten mixture of Friedel-Crafts and alkali metal halides. mixes with the catalyst support. Preferably the mixing takes place mechanically, for example with a stirrer, under an inert gas such as nitrogen.

Preparation of the catalyst A

11.9 g of potassium chloride was added to 22.4 g of resublimed Given aluminum chloride. The mixture was heated and carefully stirred in the absence of air, until a homogeneous melt formed, which was allowed to cool, during which time a solid formed.

60 g of silica gel (particle size 150 to 120 μm) were calcined by heating to 500 ° C. for 1 hour. 20 g of the calcined silica gel were heated again to 220 ° C. and stirred with 21.6 g of solidified KCl / AlCljj product under nitrogen for 30 minutes. A further 20 g of the calcined silica gel were placed in a ^{vertical fluidized bed tube kept at 220 to 230 °} C. and dry air was blown through it in an amount of 2.5 to 3.0 l / minute. The previously prepared KCl / AJCls-silica gel mixture was added and the whole thing was homogenized for 4 hours.

The catalyst obtained in this way was in the form of a pale yellow, free-flowing, coarse powder.

Preparation of the catalyst B

3.03 ground potassium chloride was added to 5.97 g anhydrous ferric chloride in ground form. The mixture was ^{heated to 250 °} C. to form a homogeneous melt. The mass melted at around 180 ° C.

20.6 g of calcined silica gel (particle size 150 to 210 μ) were stirred with 7.39 g of the melt at 250 ° C. under nitrogen. Another 20 g of the calcined gel were placed in a bath maintained at 220 to 230 ⁰ C fluidized bed tube and blow of dry air in an amount of 2.5 to 3.0 l / minute. The previously prepared KCl / FeCl ₃ -silicic acid gel mixture was added and the whole thing was homogenized for 4 hours. "

example

1.4 cm ^{3 of} the catalyst A prepared above was placed in a small standing reactor. While the catalyst was kept at 184 ° C, 4-methylpentene-1 was from top to bottom in the vapor phase at normal pressure and a space flow rate of 0.2 V / V / hour. (calculated as a liquid) passed through.

An analysis of a product sample taken after a running time of 7 hours showed the following weight composition:

• 49.0 ° / ₀
.12.5%

• 9.1% -

1 29.4 ° / ₀ (by difference)

2-methylpentene-2

2-methylpentene-l

cis / trans-

3-methylpentene-2

4-methylpentene-l

cis / trans-

4-methylpentene-2

Claims (1)

Claim: Process for the isomerization of 4-methylpentene-1 to 2-methylpentene-2 by passing 4-methylpentene-1 ^{over a catalyst at temperatures in the range from 150 to 200 0} C, characterized in that the isomerization is carried out in the presence of a catalyst, which contains a Friedel-Crafts metal halide and an alkali metal halide on a support, the alkali metal halide being present in at least equimolar amounts to the Friedel-Crafts metal halide and the total amount of the metal halide being between 1 and 50 percent by weight of the metal halide and the support.