DE1618076C - Process for the homodimerization of olefinic hydrocarbons. Eliminated from: 1418681 - Google Patents

Description

The invention relates to a method for homodimerization olefinic hydrocarbons mi? at least 3 carbon atoms in the molecule at increased Temperature and elevated pressure in the presence of an alkali metal catalyst applied to a carrier substance.

In British Patent 824,917 there is a process for the dimerization of propene in the presence an alkali metal catalyst at a temperature between 38 and 204 ° C and a pressure of 1 to 100 at. Suitable alkali metals are said to be lithium, sodium, potassium, rubidium and cesium include, pointing out the extraordinarily beneficial effects of potassium, rubidium and cesium will. This patent also states that the alkali metal can be used as a film on a inert carrier can be used, with the use of potassium on powdered potassium carbonate is set out in one embodiment.

It has now been found that the use of sodium on potassium, rubidium and cesium compounds, z. B. carbonates or silicates, as carrier substances, a catalyst for dimerization of propene, the potassium-potassium carbonate catalyst known from British patent specification 824,917 is superior in terms of its manufacturing costs, effectiveness and life span. It is surprising that a sodium based catalyst is used in the process of the invention Propene with great selectivity to 4-methylpentene-1 dimerized because it is from British patent specification 868 945 and from a publication in J. Amer.

Chem. Soc. 78, 5946-50 (1956), known that with Sodium catalysts in the dimerization of propene predominantly methyl pentenes with internal Double bonds are obtained. The advantageous properties of the ■ in the method of the invention The catalyst used is likely to take place in a chemical exchange reaction of the sodium with the special Support material should be established as it has been shown that other supports such as sodium carbonate, sodium sulfate

ίο or calcium carbonate a completely useless one Catalyst yield. So it does not become an inert carrier material like that of the British patent specification 824 917 used.

The invention is directed to a process for the homodimerization of olefinic hydrocarbons having at least 3 carbon atoms in the presence of an improved alkali metal catalyst. The process of the invention is characterized in that the homodimerization is carried out at a temperature of 100 to 200 ° C and a pressure between atmospheric and 280 kg / cm ² , optionally in the presence of hydrogen or a hydrogen-containing gas, in the presence of 1 to 20 percent by weight Performs sodium metal on an anhydrous potassium, rubidium or cesium compound containing catalyst by dispersing molten sodium metal at a temperature in the range 250 to 500 ° C on a stable at this temperature, finely divided, anhydrous compound of potassium, rubidium or cesium, preferably has been produced in an inert gas atmosphere.

The homodimerization is advantageously carried out in the presence of a dispersion of 4 to 6 percent by weight Sodium metal on anhydrous potassium carbonate as a catalyst.

Potassium compounds such as potassium hydroxide and potassium salts are particularly suitable as carriers of mineral acids such as silicates, phosphates and halides; potassium carbonate is preferred.

The catalyst can be prepared by mixing the molten sodium with an anhydrous potassium compound getting produced. Preferably the molten sodium is mixed with the potassium compound in ' vigorously stirred in a finely divided form. The potassium compound expediently has a particle size less than 152 microns. It is usually desirable to carry out the mixing under a protective gas, z. B. nitrogen to perform.

The temperature at which the sodium is brought onto the potassium compound is not critical. In general, it is necessary to stir vigorously for longer periods of time at temperatures closer to the melting point of sodium than when the elemental metal is applied at higher temperatures. It should be noted, however, that the potassium compound does not decompose and that it does not melt or sinter.
In general, the sodium metal is used in a

Uo temperature of at least 250 ° C, preferably 250 to 500 ° C, applied to the potassium compound, the potassium compound selected accordingly will.

The amount of elemental sodium used is generally between 1 and 20 percent by weight of the potassium compound, preferably between 2 and 7 percent by weight, with 4 to 6 percent by weight are particularly preferred.

The olefinic hydrocarbon is usually contacted with a preformed catalyst brought. However, the dimerization conditions can also be chosen so that the catalyst is formed in situ. In this case, elemental sodium and any of the above can be used Potassium compounds are brought into contact with the olefinic hydrocarbon.

Suitable starting materials are propene, isobutene, butadiene and isoprene. oc-olefins are the preferred starting materials. Temperatures from 100 to 200 ^° C. are used. Dienes may be dimerized at -10 to 5O ⁰ C. The choice of reaction temperature is determined by the ease with which the monomers can be dimerized.

Usually the reaction pressure is at least atmospheric pressure and can be up to 280 kg / cm ² gauge. The pressure is preferably between 70 and 176 kg / cm ² , in particular between 98 and 130 kg / cm ² .

The dimerization can also be carried out in the presence of hydrogen. In this case needs the catalyst to be regenerated less frequently. A mixture can also be used instead of hydrogen use, which advantageously contains 70 mole percent hydrogen, z. B. a mixture of 70 mole percent hydrogen and 30 mole percent methane. Other suitable gases are steam cracker off-gas from an off-gas catalytic crackers and exhaust gas resulting from the dehydrogenation of hydrocarbons.

The dimerization can be batch or continuous are executed. In the latter case, space velocities are between 0.5 and 10 V / V / h (Gas volume / catalyst volume / hour) preferred. The dimerization conditions used are according to the reactivity of the olefinic compound, the activity of the catalyst system and the nature of the product required.

If desired, the dimerization product can be recycled to recover unreacted monomers are distilled, which can be returned to the dimerization step.

If an increased yield of a certain isomer is desired, an isomerization can be carried out in a known manner using a catalyst customary in the isomerization of olefinic C "-hydrocarbons. Suitable catalysts include silica / alumina and natural clays, which are commonly used at 150 to 300 ⁰ C. Sodium or potassium on alumina, which are usually to greater than 15O ⁰ C, preferably at room temperature, used at -150, phosphoric acid catalysts on a support such. As phosphoric acid on pumice, which at 150 to 300 ° C and heteropolyacids, which are commonly used at 50 to 300 ⁰ C.

The process is particularly valuable in the dimerization of propene, the product containing a high proportion of 4-methylpentene-1. The dimerization is carried out at a temperature of 100 to 200 ⁰ C, preferably 130 to 18O ⁰ C is performed. Above 200 ^° C., higher polymers are formed, e.g. B. trimers and tetramers of propene can be obtained at temperatures between 200 and 300 ^{0 C.}

Commercially available propene sources often contain allene and methyl acetylene. These compounds are undesirable and can be removed by selective hydrogenation. The hydrogen-containing propene gas contained therein is a suitable starting product for the process of the invention.

The process of the invention can also be in the presence of a normally gaseous paraffinic Hydrocarbon, e.g. B. methane, ethane or propane, are carried out, the paraffin can be added to the olefin before or in the dimerization reactor. In the dimerization of

ίο Propene is a refined product particularly suitable in which the paraffin is already present, e.g. B. a propene-propane mixture. The ratio of olefin to paraffin can vary within wide limits. _{A C 3} fraction from a steam cracking plant is particularly suitable; such fractions usually contain about 65% propene.

The process of the invention can also be carried out in the presence of a normally liquid solvent, for example in liquid paraffins such as n-heptane.

The invention is explained in more detail with reference to the following examples.

example 1

A catalyst was prepared by drying 75 g of potassium carbonate with a particle size of less than 152 microns at 400 ^° C. and a pressure of 0.3 mm Hg and ^{adding 3.5 g of metallic sodium at 400 °} C. under a nitrogen blanket, the Mixture was stirred vigorously for 30 minutes.
71 g of the resulting catalyst, which contained 0.09 gram atoms of free alkali metal, were placed in an autoclave and propene was added up to a pressure of 129 kg / cm ² . The polymerization reaction was carried out for 24 hours at 160 ^° C. and the hexene fraction obtained was distilled off from the cooled products. 321 grams of hexenes were obtained, corresponding to about 95% conversion of propene. The gas chromatographic analysis showed the following composition:

Weight percent

4-methylpentene-l 74.8

4-methylpentene-2 17.7

2-methylpentene-1 4.1

2-methylpentene-2 1,2

n-hexenes 2.2

Example 2

A catalyst was prepared according to the process given in Example 1, potassium sulfate being used as the support material. 157.5 g of the catalyst, which contained 0.21 gram atoms of free alkali metal, were placed in an autoclave as in Example 1 and propene was added up to a pressure of 105 kg / cm ² overpressure. The polymerization reaction was carried out at 160 ° C for 18 hours to give 100 g of a hexene product having the following composition:

Weight percent

4-methylpentene-l 73.4

4-methylpentene-2 16.8

2-methylpentene-l 4.5

2-methylpentene-2 2.2

n-hexenes 3.1

Example 3

Catalysts which consisted of various amounts of metallic sodium on potassium carbonate were prepared according to the method given in Example 1. Each catalyst was then used in a continuous process for the polymerization of propene in which the space velocity of the propene was 1 V / V / h (gas volume / catalyst volume / hour), the pressure was 105 kg / cm ² and the temperature was 160 ° C. The table below shows the yields in grams of hexenes which were obtained per hour 1. per gram atom of free alkali metal on the potassium carbonate and 2. per liter of reactor space. The data show that the use of 2 to 7, preferably 4 to 6 percent by weight of sodium on potassium carbonate is particularly advantageous. Weight percent

4-methylpentene-l 86.5

4-methylpentene-2 4.7

2-methylpentene-1 6.1

2-methylpentene-2 0.5

n-hexenes 2.2

contained.
Example 6

There were added 100 g of potassium hydroxide dried for 2 hours in a 3-liter Autoklavbombe at 400 ⁰ C and 0.1 mm pressure; 15 percent by weight of water was given off. 5 percent by weight of sodium metal was added to the potassium hydroxide, the bomb was closed again and ^{heated with shaking at 400 °} C. for 4 hours. Propene was reacted in the presence of the catalyst thus formed at 16O ⁰ C and 107 kg / cm ² pressure. 45.6 g of hexene were obtained

Weight percent

0 / lfArf AiitoC Yield per hour Yield per hour per gram atom per liter !Sodium free alkali metal Reactor room 1 300 110 2 220 220 3 150 320 4V ₂ 130 340 6th 100 340 8th 90 310

Example 4

This example shows the use of a catalyst produced by dispersing metallic sodium on potassium carbonate is obtained in the polymerization of isobutylene.

The catalyst was prepared by dissolving 3.4 g of metallic sodium to 91 g of potassium carbonate, which had been dried in vacuum at 400 ⁰ C were distributed by thorough mixing at 400 ° C. The catalyst was placed in an autoclave and isobutene was added up to an overpressure of 105 kg / cm ² . The reaction was carried out at 175 ° C for 20 hours to give 145 g of a C _? Product whose analysis showed that it contained 82 percent by weight 2,4,4-trimethylpentene-1 and 13 percent by weight 2,4,4-trimethylpentene-2.

Example 5

4-methylpentene-l 76.9

4-methylpentene-2 10.8

2-methylpentene-l 6.7

2-methylpentene-2 1.1

n-hexenes 1.4

contained.

The following experiments show the superiority of the method of the invention over methods who work with other catalyst systems.

Attempt 1

This experiment shows that elemental sodium on different carrier materials than those in the process of Invention used catalyst systems results which show no activity.

The catalysts were prepared by drying 0.3 mm Hg, the support material at 400 ° C / and distributed thereon metallic sodium at 400 ⁰ C. The catalysts were placed in an autoclave; propene was added up to a pressure of 105 kg / cm ² . The reactor temperature was maintained at 16O ⁰ C. In no case had a reaction taken place after 18 hours. The catalysts had the following compositions:

a) 6.8 ° / _o strength distribution of metallic sodium to sodium carbonate,

b) 4,5 ° / ₀ owned distribution of metallic sodium on calcium carbonate,

c) 3% distribution of metallic sodium Sodium sulfate.

The following experiment shows the superiority of the Na / K ₂ CO ₃ catalyst system over K / K ₂ CO ₃ .

55

60

Sodium metal was distributed on anhydrous potassium silicate at 360 ^° C. so that 0.15 gram atoms of alkali metal came to 100 g of mixture. 112.5 h of the distribution were placed in a 1-liter autoclave and reacted propene in the presence of which at 16O ⁰ C and 105 kg / cm ² pressure. After 18 hours, 65.6 g of hexenes were obtained

Attempt 2

In parallel experiments propene at 160 ⁰ C and a pressure of 105 kg / cm ² was carried out using catalysts which consisted of a 3,46gewichtsprozentigen dispersion of sodium or potassium on anhydrous potassium carbonate, dimerized, the feed rate of propene 1 V / V / H

(Volume propylene / volume catalyst / hour). The following results were obtained:

catalyst

9.58

7.62

67 53 50 18th 82 87 8th 5 7th 6th 1 0.5 1.5 1

IO

Maximum activity (g hexene per hour per g dispersed

Metal)

% Conversion of Propylene

per run

Catalyst half-life (days) Analysis of the hexenes (after 4 days in electricity; percent by weight)

4-methylpentene-l

4-methylpentene-2

2-methylpentene-1 and

Witches-1

2-methylpentene-2

Hexen-2 and Hexen-3

The maximum activity of the potassium catalyst is only about 80% of that of the sodium catalyst, and its half-life, d. H. the time in which the catalyst activity is reduced to half of the maximum The value has dropped is considerably lower. Also the percentage conversion per pass is lower when the potassium catalyst is used. Both catalysts are selective for 4-methylpentene-1, where the potassium catalyst initially shows a slightly higher selectivity, but quickly to the same or lower selectivity of the sodium catalyst drops.

Na / K ₂ CO ₃

K / K ₂ CO ₃

However, this somewhat higher initial selectivity is technically insignificant with regard to the one obtained lower maximum activity and the very much reduced half-life.

The inferior activity of K / K ₂ CO ₃ and K / Na ₂ CO ₃ catalyst systems is also evident from Experiment 3 below.

Attempt 3

There have been a number of catalysts containing metallic potassium on potassium carbonate or sodium carbonate contained distributed, prepared in the manner indicated in Example 1 and during the polymerization of propene under the conditions given in Example 3 used. There were maximum yields obtained potassium free of 65 or 53 g hexenes per gram atom. These results were used in the Using an 8% distribution of metallic Potassium on potassium carbonate and an 8.5 weight percent distribution of potassium metal on sodium carbonate receive.

When compared with the results of the second column of the table in Example 3 it is found that a Catalyst made by distributing potassium metal on either potassium carbonate or sodium carbonate is obtained in the polymerization of propene under analogous reaction conditions much less is active as a catalyst obtained by dispersing metallic sodium on potassium carbonate will.

209582/335

Claims (2)

Patent claims: 1. A process for the homodimerization of olefinic hydrocarbons having at least 3 carbon atoms in the molecule at elevated temperature and pressure in the presence of an alkali metal catalyst applied to a carrier substance, characterized in that the homodimerization is carried out at a temperature of 100 to 200 ° C and a pressure between atmospheric and 280 kg / cm ² , optionally in the presence of hydrogen or a hydrogen-containing gas, in the presence of a 1 to 20 weight percent sodium metal on an anhydrous potassium, rubidium or cesium compound-containing catalyst carried out by dispersing molten sodium metal at a temperature in the range 250 to 500 ° C on a finely divided, anhydrous compound of potassium, rubidium or cesium that is stable at this temperature, preferably in an inert gas atmosphere. 2. The method according to claim 1, characterized in that the homodimerization in Presence of a dispersion of 4 to 6 weight percent sodium metal on anhydrous Performs potassium carbonate as a catalyst.