JPH07222927A - Dimerization catalyst of lower alpha-olefin - Google Patents

Abstract

PURPOSE:To obtain a catalyst having good selectivity while keeping activity by using an arihydrous potassium compd. composed of a mixture of potassium fluoride and potassium carbonate as a carrier and setting the specific surface area of the carrier to a definite value or more. CONSTITUTION:A catalyst for producing a dimer or co-dimer of lower alpha-olefin is obtained by supporting an alkali metal on a compression molded granular carrier consisting of an anhydrous potassium compd. and carbon. As the anhydrous potassium compd., a mixture of potassium fluoride and potassium carbonate is used. The specific surface area of the compression molded granular carrier is set to 0.25m<2>/g or more. This catalyst is improved in the selectivity to an objective product while keeping activity and, when this catalyst is used in the production of 4-methylpentene-1 by the dimerization of propylene, the formation of 4-methylpentene-2 being an isomer hard to separate is reduced.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a catalyst for dimerizing or codimerizing lower α-olefins. More specifically, it relates to a dimerization catalyst for lower α-olefins, which has excellent activity, and in particular, has improved selectivity of a target product.

[0002]

2. Description of the Related Art As a catalyst for producing a dimer or a co-dimer of a lower α-olefin, many catalysts in which an alkali metal is supported on a support have been proposed. Among these catalysts, it is advantageous to use a compression-molded granular carrier as a support for carrying out on an industrial scale. However, most of such catalysts have low activity and low selectivity, or even high activity is selected. There are some drawbacks such as low rate, and few of them can be used effectively. In particular,
Since the selectivity of the target product is the most important item in industrial production, its improvement has been strongly desired.

As the compression-molded granular catalyst, a catalyst in which metallic sodium is supported on a compression-molded granular carrier composed of anhydrous potassium carbonate and carbon is disclosed in JP-B-59-40503 and JP-B-59-59.
-40504, JP-B-59-40506, JP-A-3-42043
It is disclosed in the publication. Further, Japanese Patent Publication No. 59-40505 discloses a catalyst in which a mixture of metallic sodium, potassium carbonate and carbon is carried on a compression molded granular carrier comprising anhydrous potassium carbonate and carbon. In the propylene dimerization reaction using these catalysts, the desired product, 4-
The selectivity of methylpentene-1 is relatively good at 90-93%, but it is not yet high enough. Japanese Unexamined Patent Publication No. 62-38240 discloses a catalyst obtained by oxidizing a pellet made of potassium carbonate and carbon and carrying metal potassium on the pellet.
No. 4727213 has potassium carbonate, calcium aluminate,
A catalyst in which metal potassium is supported on a pellet made of carbon,
U.S. Pat.No. 4,835,330 discloses potassium carbonate, a catalyst in which glass powder and metallic potassium are supported on carbon pellets, but the selectivity of 4-methylpentene-1 is low,
It had the disadvantage that it was only 90% at maximum.

As a by-product isomer other than 4-methylpentene-1, 4-methylpentene-2, 2-methylpentene-2,
There are hexenes, but among them, 4-methylpentene-2
Has a small boiling point difference with 4-methylpentene-1 and is difficult to separate in the distillation and purification step, so that there is a problem that the product purity of 4-methylpentene-1 is lowered, and particularly, 4-methylpentene-2 is not produced. There was a need for less catalyst. (Boiling point of each isomer of propylene dimer 4-methylpentene-1: 53.9 ℃, cis-
4-methylpentene-2: 56.3 ° C, trans-4-methylpentene
-2: 58.6 ° C, 2-methylpentene-1: 60.7 ° C, hexene-
1: 63.5 ° C, cis-hexene-3: 66.4 ° C, trans-hexene-
3: 67.1 ° C, 2-methylpentene-2: 67.3 ° C, trans-hexene-2: 67.9 ° C, cis-hexene-2: 68.8 ° C)

SUMMARY OF THE INVENTION An object of the present invention is to provide a catalyst capable of improving the selectivity to a target product while maintaining the activity in the dimerization or codimerization of lower α-olefin. It is to be. Another object of the present invention is to provide a catalyst which, when used in the production of 4-methylpentene-1 by dimerization of propylene, produces less isomer 4-methylpentene-2, which is difficult to separate.

[0005]

The present invention provides a catalyst comprising an alkali metal supported on a compression-molded granular carrier comprising an anhydrous potassium compound and carbon, wherein (a) the anhydrous potassium compound is potassium fluoride and carbonic acid. A mixture with potassium, (b) the specific surface area of the compression-molded granular carrier is 0.25 m ² / g
The present invention relates to a lower α-olefin dimerization catalyst characterized by the above.

In the present invention, a mixture of potassium fluoride and potassium carbonate is used as the anhydrous potassium compound. The mixing ratio of potassium fluoride and potassium carbonate is not particularly limited, but with respect to the total weight of the anhydrous potassium compound,
It is preferable that potassium fluoride is in the range of 10 to 80% by weight and potassium carbonate is in the range of 90 to 20% by weight. further,
Particularly, it is preferable that potassium fluoride is in the range of 20 to 70% by weight and potassium carbonate is in the range of 80 to 30% by weight. The catalyst having the above range is more excellent in the selectivity of the target product and the supportability of sodium metal. As the anhydrous potassium compound, in addition to potassium fluoride and potassium carbonate, a small amount of potassium halide such as potassium chloride, potassium bromide, potassium iodide, potassium sulfate, potassium nitrate, potassium silicate, potassium silicofluoride, etc. may be contained. Good.

The specific surface area of the compression-molded granular carrier of the present invention has an important meaning. It is known that, unlike alumina and silica, anhydrous potassium compound powders such as potassium carbonate and potassium fluoride have a small specific surface area, but the specific surface area of these compression-molded granular carriers is due to compaction due to compression. Becomes even smaller. The specific surface area of the compression-molded granular carrier of the present invention before supporting an alkali metal needs to be 0.25 m ² / g or more. If the specific surface area is less than 0.25 m ² / g, the selectivity of the target product will decrease. In addition, when the specific surface area is much lower than 0.25 m ² / g, the alkali metal is not sufficiently absorbed by the carrier and it becomes impossible to raise the amount of the alkali metal supported to a desired value. Alternatively, the unsupported alkali metal becomes sticky, or the catalysts stick to each other and cannot be used as a reaction catalyst. A particularly preferable range of the specific surface area is 0.3 to 30 m ² / g.

Specific examples of the alkali metal used in the present invention include sodium, potassium and a mixture thereof. In general, the reaction activity of sodium metal is considerably lower than that of potassium metal,
By contacting sodium metal with potassium fluoride or potassium carbonate under heating, sodium metal easily undergoes an exchange reaction to produce sodium fluoride or sodium carbonate and potassium metal. It is also possible to use sodium metal alone.
In particular, in the present invention, the catalyst using sodium as the alkali metal component before loading has a remarkable selectivity improving effect.

The amount of the alkali metal used is not particularly limited, but is preferably 1 to 10% by weight, based on the total weight of the catalyst.
1.5 to 6% by weight is preferred. Generally, increasing the amount of the alkali metal supported increases the production rate per unit weight of the catalyst, which is industrially advantageous, but it is difficult to remove heat even if the amount is excessively increased, or the selectivity decreases. It is not preferable.

The carbon used in the present invention is activated carbon,
Examples include graphite and carbon black. These carbons may be used alone or in a mixture of two or more. Particularly, graphite can be preferably used.

In the present invention, the amount of carbon used is not particularly limited, but is preferably 0.2 to 3.0% by weight based on the total weight of the catalyst.

In the present invention, carbon and an anhydrous potassium compound raw powder are thoroughly mixed, and the mixed raw powder is compressed into a tablet molding machine,
The carrier can be produced by compression molding with a compression molding machine, pelletizer, or the like.

The anhydrous potassium compound is used as a mixed raw powder before compression molding and has a loosely packed bulk density of 0.6 g / carbon-free state.
If it goes below ml, the flow will be poor and compression molding will not be possible. When it exceeds 1.2 g / ml, the molding is easy, but the obtained granular carrier has a small specific surface area and becomes dense. The potassium fluoride and potassium carbonate raw powders may be used as they are as they are, or they may be pulverized or granulated and then mixed. Alternatively, it may be pulverized after mixing.

The shape of the compression-molded granular carrier is not particularly limited, but is usually cylindrical, pelletized, spherical, etc., and the particle size is usually 0.5 mm or more, preferably 1-10.
The range is mm. The strength of the carrier is not particularly limited, but may be in the range of 1.5 to 20 kg (radial crushing strength).

The carrier must be dried before supporting the alkali metal. Dry under reduced pressure at 50-200 ℃ or 200-600 ℃
It is preferable to perform normal pressure firing. Only vacuum drying,
Only normal pressure firing or both may be performed.

The method for supporting the alkali metal on the carrier is, for example, by stirring and mixing the dried or calcined carrier at a temperature not lower than the melting point of the alkali metal, preferably at a temperature of 200 to 450 ° C. under an inert gas atmosphere. It can be carried out. When sodium metal is used as the alkali metal component before loading, the sodium metal causes an exchange reaction during the loading operation to produce potassium metal. The catalyst of the present invention is also treated by the above alkali metal supporting treatment.
No significant decrease in crush strength was observed, and it can be effectively used as a practical catalyst.

Lower α-used in the dimerization method of the present invention
Specific examples of the olefin include ethylene, propylene,
1-butene, isobutylene, 1-pentene, 1-hexene and the like can be mentioned. Among the dimerizations or codimerizations using these lower α-olefins, the production of 4-methylpentene-1 by the dimerization of propylene, the production of 1-pentene by the codimerization of propylene and ethylene, 1- It can be used for production of 3-methylpentene-1 by co-dimerization of butene and ethylene, production of 2-methylpentene-1 by co-dimerization of isobutylene and ethylene, and the like. In particular, it can be preferably used for the production of 4-methylpentene-1 by dimerization of propylene.

The dimerization or co-dimerization reaction using the catalyst of the present invention can be carried out by a gas phase method or a liquid phase method under heating, but a gas phase fixed bed system is particularly preferable. When carrying out the reaction by the gas phase method, the reaction temperature is usually 50 to 250.
C., preferably in the range of 80 to 200.degree. The reaction pressure is
It is in the range of 20 to 200 kg / cm ² G. The liquid hourly space velocity (LHSV) of α-olefin is usually 0.5 to 10 h ^-1 , preferably 1
The range is from ~ 7h ^-1 .

[0019]

INDUSTRIAL APPLICABILITY The catalyst of the present invention can improve the selectivity to a desired product while maintaining the activity in the dimerization or codimerization reaction of lower α-olefin. Furthermore, when it is used for the production of 4-methylpentene-1 by the dimerization of propylene, it is characterized in that the isomer 4-methylpentene-2, which is difficult to separate, is less produced.

[0020]

EXAMPLES Examples of the present invention will be described below.

Example 1 50 parts by weight of potassium fluoride powder having an average particle diameter of 270 μm, a loosely packed bulk density of 1.148 g / ml and a BET specific surface area of 0.09 m ² / g,
Average particle size 250μm, bulk density 0.953g / ml, specific surface area 0.84
After mixing with 50 parts by weight of m ² / g potassium carbonate powder, pulverization treatment was performed. The bulk density after pulverization was 0.908 g / ml. After adding 0.99% by weight of graphite powder to this pulverized raw powder and mixing them well, they were tablet-molded into a cylindrical carrier having a diameter of 3 mm and a height of 3 mm. The crush strength (radial direction) measured using a Kiya type hardness meter was 4.2 kg. The specific surface area after drying under reduced pressure at 100 ° C. for 22 hours was 0.54 m ² / g. 2.50% by weight of metallic sodium was added to the dried carrier under a nitrogen atmosphere, and the mixture was stored at 370 ° C for 4 hours.
The catalyst was prepared by stirring for hr. The catalyst was smooth because the carrier absorbed sodium well, and no stickiness was observed on the surface of the catalyst. 66.98 g of this catalyst was filled in a tubular reactor with a catalyst volume of 54 ml and an inner diameter of 21 mm, and the reaction pressure was 1
The continuous flow reaction was carried out by supplying propylene at a liquid hourly space velocity (LHSV) of 5.1 h ⁻¹ while maintaining the reaction temperature at 00 kg / cm ² G and the reaction temperature at 150 ° C. The conversion of propylene was 15.4% and the selectivity of 4-methylpentene-1 was 93.8%. The treatment conditions, physical properties and reaction results of the carrier and catalyst are summarized in Table 1, Table 2 and Table 3.

Example 2 50 parts by weight of potassium fluoride powder having an average particle size of 280 μm, bulk density of 1.198 g / ml and BET specific surface area of 0.07 m ² / g and 50 parts by weight of potassium carbonate powder used in Example 1 After being mixed, the mixture was pulverized. The bulk density after pulverization was 0.893 g / ml.
The carrier shown in Table 1 was tableted using this pulverized raw powder. This carrier was dried under the conditions shown in Table 1, and carried and reacted in the same manner as in Example 1. The weight of the catalyst that could be filled in the catalyst portion volume of 54 ml was 61.24 g. The treatment conditions, physical properties and reaction results of the carrier and catalyst are summarized in Table 1, Table 2 and Table 3.

Example 3 A potassium fluoride powder having an average particle size of 240 μm, a bulk density of 1.253 g / ml and a BET specific surface area of 0.11 m ² / g was pulverized. 50 parts by weight of this ground potassium fluoride was mixed with 50 parts by weight of the potassium carbonate powder used in Example 1. The bulk density of the mixed powder was 1.036 g / ml. The carriers shown in Table 1 were tableted using this mixed raw powder. The carrier was dried and calcined under the conditions shown in Table 1, and sodium loading and reaction were carried out in the same manner as in Example 1. The treatment conditions, physical properties and reaction results of the carrier and catalyst are summarized in Table 1, Table 2 and Table 3.

Example 4 A potassium fluoride fine powder having a bulk density of 0.401 g / ml and a BET specific surface area of 0.56 m ² / g was wet-granulated and dried under reduced pressure at 100 ° C. for 20 hours. 50 parts by weight of this granulated potassium fluoride powder and 50 parts by weight of the potassium carbonate powder used in Example 1 were mixed. The bulk density of the mixed powder was 0.961 g / ml. The carriers shown in Table 1 were tableted using this mixed raw powder. This carrier was dried under the conditions shown in Table 1, and carried and reacted in the same manner as in Example 1.

Prior to the reaction, catalyst analysis was performed by the following method.
Butyl cellosolve and then water were added to the catalyst under a nitrogen atmosphere, and the generated hydrogen gas was collected in a gas buret. The amount of generated gas was the same as the amount of hydrogen calculated from the amount of supported sodium. In the ²³ Na solid-state NMR spectrum (based on 3M NaCl aqueous solution) of this catalyst, no peak around 1133 ppm attributed to sodium metal was found at all, and a peak around 0 ppm was observed.
Only the peak attributed to Na ion was seen. The treatment conditions, physical properties and reaction results of the carrier and catalyst are summarized in Table 1, Table 2 and Table 3.

Example 5 20 parts by weight of the potassium fluoride fine powder used in Example 4 was mixed with 80 parts by weight of the potassium carbonate powder used in Example 1 without granulating. The bulk density of the mixed powder was 0.769 g / ml.
The carriers shown in Table 1 were tableted using this mixed raw powder. This carrier was calcined under the conditions shown in Table 1, and sodium loading and reaction were carried out in the same manner as in Example 1. The treatment conditions, physical properties and reaction results of the carrier and catalyst are summarized in Table 1, Table 2 and Table 3.

Example 6 A mixed powder was prepared in the same manner as in Example 3 except that the mixing ratio of potassium fluoride and potassium carbonate was 30:70 (% by weight). The bulk density of the mixed powder was 1.021 g / ml. The carriers shown in Table 1 were tableted using this mixed raw powder. This carrier was calcined under the conditions shown in Table 1, and sodium loading and reaction were carried out in the same manner as in Example 1. The treatment conditions and physical properties of the carrier and the catalyst and the reaction results are shown in Table 1, Table 2 and Table 3.
Are summarized in.

Example 7 A mixed powder was prepared in the same manner as in Example 3 except that the mixing ratio of potassium fluoride and potassium carbonate was 60:40 (% by weight). The bulk density of the mixed powder was 1.030 g / ml. The carriers shown in Table 1 were tableted using this mixed raw powder. This carrier was dried under the conditions shown in Table 1, and carried and reacted in the same manner as in Example 1. The treatment conditions and physical properties of the carrier and the catalyst and the reaction results are shown in Table 1, Table 2 and Table 3.
Are summarized in.

Comparative Examples 1 and 2 Tableting, firing and loading were carried out in the same manner as in Example 1 except that only the potassium carbonate powder used in Example 1 was used as the anhydrous potassium compound and used as it was without crushing. ,
The reaction was carried out.

In the same manner as in Example 4, Comparative Example 1 before the reaction
Was analyzed. The amount of generated gas was the same as the amount of hydrogen calculated from the amount of supported sodium. ²³ Na of this catalyst
In the solid-state NMR spectrum (based on 3M NaCl aqueous solution), no peak around 1133 ppm attributed to sodium metal was observed at all, and only a peak attributed to Na ion around 0 ppm was observed. The treatment conditions, physical properties and reaction results of the carrier and catalyst are summarized in Table 1, Table 2 and Table 3.

Comparative Examples 3 and 4 The procedure of Comparative Example 1 was repeated except that the amount of graphite added and the crush strength of the carrier were as shown in Table 1. The treatment conditions, physical properties and reaction results of the carrier and catalyst are summarized in Table 1, Table 2 and Table 3.

Comparative Example 5 Only the potassium fluoride powder used in Example 3 was used as an anhydrous potassium compound, and tableting and firing were carried out in the same manner as in Example 1 without pulverization. Table 1 shows the physical properties of the carrier and the firing conditions. The operation for supporting 2.5% by weight of sodium was carried out in the same manner as in Example 1, but the catalyst became sticky due to poor suction of sodium and could not be used as a reaction catalyst.

Comparative Example 6 A mixed powder was prepared in the same manner as in Example 3 except that the crushing degree of the potassium fluoride powder was changed. Bulk density is 1.011 g / ml
Met. Using this mixed raw powder, a catalyst was prepared in the same manner as in Example 3. The catalyst was slightly sticky, so only 49.89 g could be loaded. The treatment conditions, physical properties and reaction results of the carrier and catalyst are summarized in Table 1, Table 2 and Table 3.

Comparative Example 7 The procedure of Example 3 was repeated, except that the carrier of Example 3 was used and the firing conditions were changed. The treatment conditions, physical properties and reaction results of the carrier and catalyst are summarized in Table 1, Table 2 and Table 3.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

Claims (1)

[Claims] 1. A catalyst comprising an alkali metal supported on a compression-molded granular carrier comprising an anhydrous potassium compound and carbon, wherein (a) the anhydrous potassium compound is a mixture of potassium fluoride and potassium carbonate, b) A lower α-olefin dimerization catalyst, wherein the compression-molded granular carrier has a specific surface area of 0.25 m ² / g or more.