JPS61197608A - Polymerization of ethylene - Google Patents

Abstract

PURPOSE:To (co)polymerize ethylene without hydrogenation loss in such a manner that olefin monomers can be easily removed from the discharged gas because of the absence of nitrogen gas, etc., by conducting the vapor phase (co) polymerization of ethylene in the presence of a light saturated hydrocarbon. CONSTITUTION:In the vapor phase polymerization of ethylene or the vapor phase copolymerization of ethylene with an alpha-olefin in the presence of a polymerization catalyst, not an inert gas conventionally used, such as nitrogen, but a 1-3C saturated hydrocarbon gas (e.g., methane or ethane) is used as a gas for adjusting the pressure in the polymerization system. The gas discharged from the polymerization system contains no inert gas such as nitrogen, so that olefin monomers can be easily recovered from the discharged gas and the recovered olefins can be used as a fuel of a high heating value. In addition, the loss of olefin monomers due to hydrogenation in the case of (co) polymerization in the presence of hydrogen can be prevented or decreased.

Description

[Detailed description of the invention] The present invention relates to a method for gas phase (co)polymerization of ethylene.

Conventional technology In a method for producing an ethylene (co)polymer by homopolymerizing ethylene or copolymerizing ethylene and α-olefin in the gas phase, the concentration of ethylene or an olefin monomer consisting of ethylene and α-olefin in the gas phase is The partial pressure needs to be maintained constant, and in order to maintain it, an inert gas such as nitrogen or argon is generally supplied to the polymerization system to adjust the pressure of the polymerization system.

In this polymerization system, it is necessary to discharge a part of the gas containing the olefin monomer to the outside of the system because of the accumulation of by-product impurities in the polymerization system (brought into the system as raw materials).

However, although the gas discharged outside the system contains a considerable amount of useful olefin monomers,
Because the olefin monomer is a mixture with a large amount of inert gas, it is economically impractical to recover it by returning it to the olefin production equipment, etc., and when it is used as a fuel gas, it generates heat. Due to the low amount and nitrogen content, there are problems such as generation of large amounts of nitrogen oxides during combustion, and the reality is that it cannot be used effectively. Furthermore, in these 1 polymerization systems, 1. Hydrogen gas is often used, but because of this hydrogen gas, the raw material olefin mono! There is a problem that - is hydrogenated and lost in large part.

Problems to be Solved by the Invention The present invention solves the above-mentioned problems caused by inert gas such as nitrogen used to adjust the pressure of the polymerization system in the gas phase (co)polymerization method of ethylene. The purpose is to

The present inventors have discovered that the object of the present invention can be achieved by using a light saturated hydrocarbon gas such as methane or ethane in place of conventionally used nitrogen gas, etc.
We have arrived at the present invention.

Summary of the Invention That is, the present invention provides for the production of Ethyray or 1 in the presence of a polymerization catalyst.
The gist of the present invention is a method for polymerizing ethylene and α-olefin in a gas phase, which comprises performing the polymerization in the presence of a C1 to C3 saturated hydrocarbon.

Polymerization catalyst The polymerization catalyst used in the present invention is an ethylene gas phase (co-)
There are no particular restrictions on catalysts that can be used in polymerization, and any conventionally used chromium-based or titanium-based catalysts can be used. These polymerization catalysts used in gas phase polymerization must be solid, and it is effective to use catalyst components supported on a solid carrier.

As the chromium-based catalyst, for example, those in which the following catalyst components are supported on an inorganic carrier such as silica can be used, and methods for preparing these catalysts are disclosed in detail in the following documents.

Silylchromate (U.S. Pat. No. 3,324,095,
3,324,101), π-allyl chromium complex (Japanese Patent Publication No. 47-13002), π-arene chromium tricarbonyl (% Japanese Patent Publication No. 47-13048), bis(cyclopentadienyl)chromium ( compound (U.S. Pat. No. 3,709,853), a bis(cyclopentadienyl)chromium compound modified with a silanized compound (Japanese Patent Publication No. 49-21433)
, titanated chromium oxide (U.S. Pat. No. 3.622,5
Specification No. 21) etc.

Examples of titanium-based catalysts include magnesium compounds such as magnesium halides, titanium compounds such as titanium halides, and electron-donating alkyl esters of aliphatic and aromatic carboxylic acids, aliphatic ethers, cyclic ethers, and aliphatic ketones. A catalyst in which a contact substance of a chemical compound is supported on an inorganic oxide carrier such as silica or alumina (Japanese Patent Application Laid-Open No. 54-14
No. 2192, No. 54-148095, No. 56-106
No. 910, No. 57-131207, No. 58-2771
No. 0, No. 58-74705, etc.).

Polymerization method In the present invention, when ethylene is homopolymerized or ethylene and α-olefin are copolymerized in a gas phase, (co)polymerization is carried out in the presence of a C1 to C3 saturated hydrocarbon. These include methane, ethane and propane.

Examples of the α-olefin used include propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, etc. Two or more types of these α-olefins can be used, and they can be used at the same time. Alternatively, they may be used sequentially.

The saturated hydrocarbon to be present during the (co)polymerization may be any of the above, but it is preferable to use ethane, which can easily be obtained as a high-purity stream from the olefin production equipment and whose boiling point is close to that of the raw material ethylene. However, it is economically and operationally advantageous. The amount of the saturated hydrocarbon used is usually 0.5 to 3 times the volume of ethylene. Hydrogen is used to adjust the molecular weight of the resulting (co)polymer, but the amount is usually up to 5 mol per 1 mol of raw material ethylene. Further, the amount of α-olefin used in copolymerization is usually 0.1 to 10 moles per mole of ethylene.

The (co)polymerization is usually carried out at a temperature of 50 to 250C and under a pressure that maintains the olefin monomer in a sufficient gas phase at the polymerization temperature.

(Co)polymerization is carried out in the presence of a polymerization catalyst, but if necessary, an activator can be used in combination with the polymerization catalyst, and in that case, the activator can be supplied separately to the polymerization system. good. As the activator, organic compounds such as metals from Groups I to L of the periodic table, such as lithium, magnesium, zinc, and aluminum, can be used. Examples of the organic compound of the metal include alkyllithium, alkylmagnesium, arylmagnesium, alkylmagnesium halide,
Examples include arylmagnesium halides, alkylmagnesium hydrides, dialkylzincs, trialkylaluminums, dialkylaluminum halides, alkylaluminum cybarides, alkylaluminum sesquihalides, alkylaluminum hydrides, alkylaluminum alkoxides, alkyllithium aluminums, etc. The above are also in use.

The present invention can be applied to batch polymerization or is effective in continuous polymerization, particularly in continuous gas phase polymerization using a fluidized bed. In that case, a polymerization catalyst, an activator if necessary, and an oleinine monomer and a C1 to C3
saturated hydrocarbons are continuously fed to the polymerization system, and a fluidized bed is formed by the olefin monomers fed to the polymerization system, the saturated hydrocarbons, and/or their recycle gas. The polymerization catalyst is usually supplied to the polymerization system separately from the olefin monomer. Also, the olefin monomer and the saturated hydrocarbon can be fed to the polymerization system simultaneously or separately.

The gas utilized in the (co)N-polymerization is extracted from the polymerization system with or without the (co)polymer and is separated from the (co)polymer contained therein. Either it is recycled into the system, or it is not recycled, and the residue is taken out of the system and sent to an olefin production equipment, where the olefin monomers contained therein are separated and recovered, or it is directly used as fuel gas. used.

Effects of the Invention According to the method of the present invention, the gas discharged from the polymerization system is free of inactive gases such as nitrogen, so olefin polymers can be easily recovered in the olefin production equipment. Furthermore, it can be used as a fuel with a high calorific value, and can prevent or reduce the loss of olefin monomers due to hydrogenation when hydrogen is used during further K(co)polymerization.

Hereinafter, the present invention 8A will be explained in detail using examples.

Example A polymerization catalyst was prepared by vN based on the description in JP-A-54-148093. i.e. 12 with a stirrer! Into the flask, add S water MgC,12
41,8/i and tetrahydro7ran (THF) 2.54
Enter i, then 'rlcz427,7 j''ft
o, dripped over 5 hours. The mixture was heated at 6 oc for 0.5 hour to form a solution.

To this solution was added 50% of subelongated silica, dried at 800C and treated with 6% by weight triethylaluminum (TgAL).
09 was added and stirred for 15 minutes. This mixture was dried by blowing nitrogen gas into it for 4 hours to obtain silica powder adsorbing the following composition.

TlMg30''t, (THF)6.7 The silica powder obtained above and T g A L 'i AI!/T1
Suspended in isopentane so that the molar ratio is 4.5,
After mixing for 20 minutes at room temperature, blow in nitrogen gas.
A polymerization catalyst containing 14.5% of the above composition was prepared by drying with SC.

Inner diameter 33tM, height s, lower part of o s in, inner diameter 5
9cII, an upper part with a height of 1.83 m, the polymerization catalyst obtained above at a rate of t-25.611/h, and TEAlt-Titanium in the polymerization catalyst F) At/
The gas was supplied so that T1 (molar ratio) was 25, and a fluidized bed was formed in the polymerization tank by circulating gas (4410 ky/hour) from the upper part of the polymerization tank.

In this polymerization tank, ethylene (ethane in, containing 01 mol%) and 1-butene (butane in 3.0 mol% tfj) t-1
1-Butene/ethylene (molar ratio) was supplied at a ratio of 0.43, and ethane gas (ethylene in 0.4% by mole) was supplied to adjust the pressure of the polymerization system. Hydrogen gas, 5 parts water! /ethylene (mole ratio) Oj 1, and the polymerization temperature was 8.
8C1 ethylene and 1 under the conditions of polymerization pressure 20 kg/cm'
Butene copolymerization t-24 hours, density 0.918
11 fl/cm' of ethylene-1-butene copolymer
Obtained at the rate of kp/hour.

The gas at the upper outlet of the polymerization tank had the composition shown below, and its exothermic value was 250 Kcaj/ky.

Further, from calculation of the material balance within the polymerization system, the loss due to hydrogenation of ethylene was 0.11%/hour.

Hydrogen 4.1% by volume Butane 1.4% by volume Methane 1.0 #1-Butene 15.61 Ethane 41.51 Impentane 0.21 Ethylene 56.51
Nitrogen Trace Comparative Example Ethylene and nitrogen gas were used in the same manner as in Example 1, except that nitrogen gas was used in place of the ethane gas used in the Example.
-Copolymerization of butene, density 0.918. 10.9 kg of p/- ethylene-1-butene copolymer per hour]
obtained at a rate of The gas at the upper outlet of the polymerization tank has the following composition, and its heat generation is 7,890 Kcal! /k). Also, the loss due to hydrogenation of ethylene is 0.1
It was 9%/hour.

Claims (1)

[Claims] In a method of polymerizing ethylene or ethylene and α-olefin in the gas phase in the presence of a polymerization catalyst, the polymerization is carried out in c_1 to
A method for polymerizing ethylene, comprising carrying out the polymerization in the presence of a saturated hydrocarbon of c_3.