JPS6241653B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved process for dimerizing ethylene. Specifically, when dimerizing ethylene using a catalyst consisting of an orthotitanate and an organoaluminium compound, ethylene can be dimerized with extremely high activity per orthotitanate by subjecting the orthotitanate to a specific treatment in advance. This is the way to do it. Butene-1 can be used as a raw material for producing polybutene-1 or as a comonomer when producing polyethylene by low-pressure polymerization of ethylene, and also as a comonomer for producing polyethylene by low-pressure polymerization of ethylene.
-Olefins are important monomers, especially in copolymerization with propylene, and the consumption of butene-1 has recently increased due to the specialization of polyolefins. At present, the source of butene-1 is to separate butene-1 from a fraction with a carbon number of 4, which is a by-product when producing ethylene from naphtha. It is difficult to separate -1 partly because the difference in boiling point of each component is small, and the cost is high because a special method is used for separation. On the other hand, many studies have already been conducted on the method of producing butene-1 by dimerizing ethylene, and in Japanese Patent Publication No. 32-5067, trialkylaluminum and orthotitanate were used as catalysts. However, the yield of butene-1 per orthotitanate is extremely small. As a method for improving the catalyst consisting of orthotitanate and trialkylaluminium,
-1445 and Japanese Patent Publication No. 49-2084 disclose a method using a special orthotitanate ester or a method using a special additive;
No. 113903 states that the yield of butene-1 per orthotitanate ester can be greatly improved by treating orthotitanate ester and/or trialkyl aluminum with hydrogen in the presence of ethylene, but it is still insufficient. It is. As a result of various studies, the inventors of the present invention have found that an extremely large improvement can be achieved by subjecting the orthotitanate to a specific treatment in advance using a catalyst consisting basically of an orthotitanate and an organoaluminum compound. They discovered a method for selectively producing butene-1 at high temperatures and completed the present invention. An object of the present invention is to provide a method for producing butene-1 with high selectivity by dimerizing ethylene using a highly active catalyst. The orthotitanate ester used in the method of the present invention has the general formula Ti(OR ¹ ) ₄ (wherein; R ¹ has a carbon number of 1 to 10
Hydrocarbon residues), specifically, tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, tetrabutyl titanate, tetra(2-ethylhexyl) titanate, tetrapropenyl titanate, Examples include tetrabutenyl titanate. Examples of the organoaluminum compound include aluminum trialkyl, aluminum dialkyl hydride, and aluminum dialkyl halide, with aluminum trialkyl and aluminum dialkyl hydride being preferred, and aluminum trialkyl being more preferred.
What is aluminum trialkyl? General formula AlR ² ₃ (in the formula; R ² is an aliphatic hydrocarbon residue having 1 to 10 carbon atoms)
More specific examples include trimethylaluminum, triethylaluminum, tributylaluminum, tripentylaluminum, trihexylaluminum, triheptylaluminum, trioctylaluminum, trinonylaluminum, and tridecylaluminum. When producing butene-1 by the method of the present invention, at least one gas selected from hydrogen, nitrogen, oxygen, helium, neon, or argon is passed through the orthotitanate ester in advance; It is possible to dimerize ethylene and selectively produce butene-1 with extremely high activity per catalyst. There are no particular restrictions on the method of passing the at least one gas, but generally the gas may be blown directly into ethyl orthotitanate. For example, in the case of a solid such as methyl orthotitanate, it may be diluted with an inert hydrocarbon such as hexane or heptane, and then the above gas may be blown into the solution. Furthermore, since orthotitanate esters are generally very viscous, it is preferable to dilute them with an inert hydrocarbon before blowing the above gas into them. This aeration operation can be performed either before or after contacting the orthotitanate with the organoaluminum compound, but it is easier to perform it before the contact treatment with the organoaluminum compound. In particular, when oxygen is used, it is more preferable to carry out the reaction before contacting the organoaluminum compound in order to avoid a reaction between the organoaluminum compound and oxygen. Preferably, the gas to be vented is substantially moisture-free. There is no particular restriction on the temperature at which ventilation is performed, but it may be performed at around room temperature of 10 to 30°C. The blowing time varies depending on the shape of the device and cannot be specified, but it usually takes about 1 minute to 30 minutes. The usage ratio of the orthotitanate ester and the organoaluminum compound needs to be 1.5 to 20 moles of aluminum to 1 mole of titanium, and 1.5
If it is less than 20 molar, the activity will be insufficient, and if it is more than 20, a large amount of polymer will be produced as a by-product, which is not preferable. Particularly preferred is a range of 2 to 10 moles. The dimerization reaction of the present invention is generally carried out in an inert solvent, and examples of the inert solvent include aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons such as pentane, hexane, heptane, octane, cyclohexane, and toluene. is used. It is also possible to use butene-1 produced in this reaction. There is no particular restriction on this reaction temperature, but it is generally 30 to 100°C, particularly preferably 40 to 90°C, and 30%
Activity is low at lower temperatures, and at temperatures above 100℃,
The catalyst is undesirable because it deactivates quickly and the reaction pressure becomes high. It is more preferable to carry out this reaction under pressure of ethylene because the activity is high. The present invention will be explained in more detail with reference to Examples below. Example 1 Under a nitrogen atmosphere in a sufficiently dried and nitrogen-substituted electromagnetic stirring autoclave with an internal volume of 3,
Prepare one charged with n-heptane. On the other hand, prepare a 200 ml flask that has been thoroughly dried and purged with nitrogen. This flask was charged with 1 mmol of n-butyl orthotitanate (first-class reagent manufactured by Wako Pure Chemical Industries, Ltd.) and 50 ml of n-heptane that had been thoroughly degassed with nitrogen, and then passed through a glass capillary tube with an inner diameter of 1 mm.
After passing air with a moisture content of 500 Volppm or less for 1 minute, the air in the space was replaced with nitrogen. Thereafter, 5 mmol of triethylaluminum was charged under a nitrogen stream and mixed thoroughly, and then the above-mentioned mixed solution was charged into the autoclave. Next, the nitrogen in the autoclave was evacuated using a vacuum pump, and then ethylene was charged to make the autoclave 2 kg/cm ² -gauge. After heating the autoclave with hot water to bring the internal temperature to 70℃, the pressure was maintained at 9Kg/cm ² -gauge while charging ethylene.
The reaction continued for hours. After 2 hours of reaction, the internal temperature of the autoclave was brought to 40°C by cooling with cold water, and then the gas inside the system was released through a trap cooled with a dry ice-methanol system, and the internal temperature of the autoclave was further lowered to 60°C. The temperature was raised to 100%, and the relatively low boiling point portion was collected in a trap cooled with dry ice-methanol. The above operation is performed until the internal pressure of the autoclave is 0Kg/cm ² -
After continuing until the temperature reached the gauge, the internal temperature of the autoclave was lowered to 30°C, and the contents were taken out. The portion collected in the trap and the contents of the autoclave were analyzed by gas chromatography to analyze the portions with 4 carbon atoms and 6 carbon atoms, and the contents of the autoclave were distilled to remove the non-volatile components at 100℃. , the polymer was separated. As a result of the above analysis, the number of carbon atoms was 4, the number of carbon atoms was 6, and the total nonvolatile content almost corresponded to the amount of ethylene charged. These results are shown in the table. Comparative Example 1 Ethylene was reacted in the same manner as in Example 1 except that n-heptane was not charged with air after dissolving n-butyl orthotitanate. The results are shown in the table. The activity per n-butyl orthotitanate is extremely low. Comparative Example 2 The reaction was carried out in the same manner as in Example 1 except that the amount of triethylaluminum used was 0.5 mmol, but ethylene was not completely absorbed. Comparative Example 3 Ethylene dimerization reaction was carried out in the same manner as in Example 1 except that the amount of triethylaluminum used was 25 mmol. The results are shown in the table. Examples 2 to 6 After dissolving n-butyl orthotitanate in n-heptane, instead of air, nitrogen (Example 2), hydrogen (Example 3), helium (Example 4),
Ethylene reaction was carried out in the same manner as in Example 1 except that neon (Example 5) and argon (Example 6) were used. The results are shown in the table. Comparative Example 4 An n-hexane solution of n-butyl orthotitanate was charged into an autoclave without venting to air, and then a mixed gas of ethylene and hydrogen (1:1) was added, and the autoclave was heated to 2 kg/cm ² gauge. The pressure was applied for 10 minutes. On the other hand, 5 mmol of triethylaluminum was placed in a round-bottomed flask containing 100 ml of n-hexane, which had been sufficiently replaced with a mixed gas of ethylene and hydrogen (1:1), and the atmosphere remained in the mixed gas of ethylene and hydrogen for 10 The mixture was held for a minute and then charged into the autoclave. Thereafter, as in Example 1, ethylene and hydrogen in the autoclave were removed using a vacuum pump, and then ethylene was added and reacted. The amount of ethylene reacted per gram of titanium compound was as small as 1150 g, about one-third of that in Example 1. The results are shown in the table. Comparative Example 5 The same procedure as in Example 1 was carried out except that a mixed gas of hydrogen and ethylene (1:9) was used instead of air as the gas to be vented, and the amount of ethylene reacted per 1 g of titanium compound was 1680 g. Although it is better than Example 4, it is about half of Example 1, and the butene-
The selectivity of 1 (butene-1/total reaction amount) was 0.77, which was poor. The results are shown in the table. 【table】

Claims (1)

[Claims] 1. A catalyst consisting of an orthotitanate ester represented by the general formula Ti(OR ¹ ) ₄ (wherein R ¹ is a hydrocarbon residue having 1 to 10 carbon atoms) and an organoaluminum compound for ethylene. In the dimerization method using (1) orthotitanate, at least one gas selected from hydrogen, nitrogen, oxygen, helium, neon, or argon is passed through the orthotitanate, and (2) an organic A method for dimerizing ethylene, characterized in that the amount of aluminum compound used is 1.5 to 20 mol per 1 mol of orthotitanate. 2 The organoaluminum compound has the general formula Al(R ² ) ₃
The method for dimerizing ethylene according to claim 1, wherein ^R2 is an aluminum trialkyl represented by the following formula: (wherein R2 is an aliphatic hydrocarbon residue having 1 to 10 carbon atoms).