JPH0533242B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for regenerating a Ziegler-type polymerization refrigerant, and particularly to a technique for hydrogenating and rendering harmless polymerization inhibitors in a polymerization solvent at high speed under mild conditions. (Prior Art) Industrially, the solvent recovered after polymerizing olefin in the presence of a Ziegler type catalyst and a solvent is used again for polymerization as is or after distillation. However, although the cause is not clear, when a recovered solvent is used, the catalyst activity often decreases or the physical properties of the produced polymer deviate from the target, compared to using a fresh solvent. This is thought to be because the recovered solvent contains trace impurities such as raw materials used in polymerization, catalysts, decomposition products of solvents, etc., and polymerization by-products.
In order to remove these impurities, it is necessary to increase the reflux ratio of distillation and the cut rate of high and low boiling point components, which causes problems such as deterioration of steam and solvent consumption. Moreover, even if the above-mentioned distillation was carried out, a decrease in catalyst activity could not be avoided with repeated use. On the other hand, recently, as the activity of polymerization catalysts has increased and catalysts are used at low concentrations, they are more susceptible to the effects of the above-mentioned by-products, resulting in a decrease in catalyst activity and large fluctuations in the physical properties of the resulting polymer, which requires a solution. was.
Therefore, a method has been considered in which the distilled recovered solvent is hydrogenated by a known method to convert the polymerization inhibitor into a harmless substance. (Problems with conventional technology) However, for this purpose, 10m ³ /h ~
Because it is necessary to process a large amount of recovered solvent (200 m ³ /h), the conventional fluidized bed batch hydrogenation method requires large-scale equipment and also requires post-treatment operations such as separation and recovery of the hydrogenation catalyst. It became complicated and had low industrial utility value. In addition, even in the fixed bed continuous system, when the superficial velocity is 0.1 to 10 h ^-1 , which is the condition of normal liquid phase hydrogenation, the equipment is
There was a problem that the processing efficiency was low due to the large size of ^100m3 . Additionally, since hydrogenation is normally carried out in an upward flow in a fixed bed, if the superficial velocity is set to 30 to 100 h ^-1 to increase efficiency, the catalyst pellets will wear out and the supported metal will fall off within a few days. There was a problem. (Means for solving the problem) As a result of intensive studies in order to solve the above-mentioned drawbacks associated with solvent hydrogenation regeneration treatment, the inventors conducted a series of intensive studies to resolve the above-mentioned drawbacks associated with solvent hydrogenation regeneration treatment. By charging a highly efficient catalyst and introducing it into the fixed bed in cocurrent contact with hydrogen, under mild conditions (room temperature to 150°C, 0 to 20 kg/cm ² G),
The present invention was completed by discovering that impurities in the recovered solvent can be hydrogenated and rendered harmless very efficiently (at a superficial velocity of 10 to 200 h ^-1 ). In the present invention, in the co-current catalyst of the recovered solvent and hydrogen, a hydrogen dissolution tank may be provided in front of the fixed catalyst bed to dissolve hydrogen in the recovered solvent, and hydrogenation may be performed only with dissolved hydrogen. In this way, only the liquid phase is introduced into the fixed bed of catalyst, thereby preventing air bubbles and drifting between catalyst pellets and improving hydrogenation efficiency. Furthermore, since efficiency is increased, it is only necessary to dissolve hydrogen in the required amount or in a slightly excess amount, eliminating the need to remove unreacted hydrogen. There is no need to discard the reaction hydrogen. The hydrogen dissolution tank is a stirring type to improve hydrogen absorption efficiency.
A perforated plate type, a filling type, etc. can be adopted. The recovered solvent and hydrogen can be supplied to the catalyst bed in an upward flow or a downward flow. However, when the superficial velocity is particularly high, a downward flow is advantageous because it reduces deterioration due to catalyst wear, etc. It is. The reactor type may be of the tank type, tube type, tower type, extruder type, etc., which are commonly used in hydrogenation reactions, but the tower type fixed bed type is particularly preferred.
When adopting the downflow contact method, it is necessary to select a column diameter that does not cause wall effects, and a column height that does not cause uneven flow in the downward flow, or to be equipped with a distributor. Further, the reaction mode may be a liquid phase, a gas phase, or a gas-liquid mixed phase system. As the catalyst for hydrogenation treatment of the present invention, both a supported transition metal catalyst and a transition metal mixed molded catalyst can be used, and the transition metals include Fe, Fe,
Examples include Co, Ni, Ru, Rh, Pd, Ir, and Pt. Oxides of these metals and salts such as complexes can also be used as catalysts. Furthermore, activated carbon, graphite, silica, silica alumina, alumina, etc. can be used as a carrier for the transition metal supported catalyst, and diatomaceous earth etc. can be used as the molding material for the transition metal mixed molded catalyst. The supporting (mixing) ratio of the transition metal or its oxide or salt on the carrier or molding material may be within the range used in ordinary hydrogenation reactions. The catalyst may be in the form of a powder, but in consideration of pressure loss in a fixed bed, a pellet form is preferable, and the packing porosity is preferably 0.2 to 0.7. The hydrogenation reaction conditions of the present invention include reaction temperature;
150°C, preferably room temperature to 100°C, reaction pressure: normal pressure to 30Kgf/ ^cm2 , preferably 3 to 9Kgf/ ^cm2 , superficial velocity (LHSV): 5 to 200h ^-1 , preferably 10 to
100h ^-1 . The concentration of olefin in the recovered solvent to be hydrotreated in the present invention is usually about 200 to 4000, preferably about 200 to 2000, in terms of bromine index (mg-Br/100g-solvent). The amount is usually about 0 to 200 in terms of bromine index. The polymerization solvent to be hydrogenated in the method of the present invention is:
Hydrocarbons that are usually used to dissolve or disperse polymers or catalysts produced during the polymerization of olefins, such as paraffins having about 4 to 20 carbon atoms, cycloparaffins, benzene, toluene, xylene, and the like. A mixture of two or more types is mentioned. The olefin polymerization reaction carried out in the present invention is carried out in the presence of the above-mentioned hydrocarbons.
This is a so-called Ziegler type polymerization reaction which is carried out using a combination catalyst consisting of a Group 6 transition metal compound, an organometallic compound of Groups 1 to 3 metals, and, if necessary, an electron donor compound. As the above transition metal compound, titanium, vanadium, and zirconium compounds are used, such as titanium trichloride, titanium tetrachloride, tetraalkoxytitanium, vanadium tetrachloride, vanadium oxytrichloride, alkoxyoxyvanadium halide, zirconium trichloride, Examples include dialkyl zirconium halides. Furthermore, when using a highly active catalyst in which these transition metal compounds are supported on a carrier such as magnesium chloride, the effects of the present invention are remarkable. The highly active catalyst supported on the above carrier includes a carrier such as magnesium chloride or magnesium oxide, a transition metal compound such as titanium tetrachloride, tetraalkoxytitanium, or vanadium tetrachloride, and, if necessary, an organic acid ester, an organic silicon compound,
A component in which an electron-donating compound such as an alkyl halide is supported by a known method is used. The above-mentioned organometallic compounds include organoaluminum compounds such as trialkylaluminium, dialkylaluminum halide, alkylaluminum sesquihalide, and alkylaluminum dihalide; organomagnesium compounds such as dialkylmagnesium; for example, triethylaluminum, triisobutylaluminum, ethylaluminum sesquihalide; Examples include chloride, diethylmagnesium, etc., and a mixture of these may be used. In addition to the transition metal compounds and organometallic compounds mentioned above, esters, amines, ethers,
Electron donating compounds such as haloalkanes can also be added. In addition, the olefins used in the above polymerization reaction include ethylene, propylene, 1-butene, 1
-hexene, 1-octene, 1-dodecene, 4-
There are α-olefins such as methyl-1-pentene, and the present invention is also applicable to the copolymerization reaction of these and also to the copolymerization of these with dienes such as butadiene, isoprene, dicyclopentadiene, and ethylidene norbornene. There are no particular restrictions on the polymerization conditions such as temperature, pressure, time, and concentration of reaction raw materials for the polymerization reaction of the present invention, and the polymerization reaction can be carried out under known conditions. The present invention will be explained in more detail below using Examples. (Examples 1 to 15) (Small test scale gas-liquid mixed phase continuous hydrogenation treatment) Hydrogenation catalysts shown in Table 1 were heated at 110 °C under a nitrogen atmosphere.
After heating above ℃ to remove adsorbed moisture and oxygen, reduction treatment using hydrogen diluted with nitrogen (60 to 110℃ for 1 hour for Pt-Pd catalyst; 210℃ for 4 to 8 hours for Ni catalyst) did. After polymerization is carried out in exactly the same manner as described below, except that dicyclopentadiene is added as a comonomer to the isohexane solvent at a concentration of 1.0 g/ml, the resulting polymer is separated, and the isohexane solvent washed with water is added to the isohexane solvent using the Older Sho type 20.
Distilled using a stage distillation column at a reflux ratio of 2 to 62 to 68
The fraction distilled at ℃ was collected. Hexane obtained by dehydrating the recovered solvent that had undergone this operation one or more times by nitrogen bubbling was used as recovered hexane. Separate the polymer produced after polymerization using the method described below, and add the isohexane solvent washed with water to an older model 20.
Distilled at a reflux ratio of 2 using a stage distillation column and heated to 62-68℃.
Collected fractions. Hexane obtained by dehydrating the recovered solvent that had undergone this operation (polymerization and distillation) one or more times by nitrogen bubbling was used as recovered hexane. The recovered hexane was hydrogenated in a small test scale continuous hydrogenation apparatus having the configuration shown in FIG. That is, the recovered hexane a is pumped using a pressurizing diaphragm pump 4 into a fixed catalyst bed made of corrosion-resistant steel with a hot water jacket (inner diameter 27 mm, length 220 mm; catalyst amount 50 or 80 c.c.,
The upper and lower spaces were filled with glass wool) and were introduced using an upward flow method. Further, a predetermined amount of hydrogen b was metered through a flow meter and mixed in line with recovered hexane a immediately before the fixed bed inlet. Isohexane after the hydrogenation treatment and unreacted hydrogen were separated into a gas phase and a liquid phase in a glass autoclave 2, and after further cooling and depressurization, the isohexane was collected to obtain hydrogenated hexane c. In this test device, unreacted hydrogen gas was disposed of through the vent without being circulated. The degree of impurity removal from hydrogenated hexane was evaluated based on the polymerization activity of ethylene-propylene copolymerization reaction and the polymerization activity of propylene polymerization. That is, 480 c.c. of hydrogenated hexane from which moisture had been removed by nitrogen bubbling was placed in a flask equipped with a condenser and a stirring device, and 0.1 mmo of vanadium oxytrichloride was added to it under nitrogen bubbling, followed by stirring at a rotational speed of 2000 rpm. At the same time, the charging gas was changed from nitrogen to ethylene/propylene mixed gas (volume ratio = 40/60) at 100/h. Solution at 35℃
Monomer gas charging rate 400
1 mmo of ethylaluminum sesquichloride in 20 c.c. of hydrogenated hexane.
A solution prepared by making the solution into a solvent was quickly added dropwise. Next, monomer gas was sucked in at a rate of 100 to 400/h while being controlled to avoid insufficient supply, and copolymerization was carried out at a temperature of 35° C. for 10 minutes. 1 ml of methanol was added to stop the copolymerization reaction, and a large amount of methanol was added to precipitate the polymer, which was then dried under reduced pressure to obtain ethylene-propylene copolymers in the yields shown in Table 1. The physical properties of the copolymer obtained were the same as when fresh isohexane was used. In addition, a propylene polymerization reaction was also carried out as follows. [Ι] Preparation of highly active Ti catalyst component Using the stainless steel ball mill No. 1, 20 g of anhydrous magnesium chloride and 4.8 g of ethyl benzoate were charged under a nitrogen atmosphere and co-pulverized for 24 hours. 200
15 g of the above carrier was placed in a ml round bottom flask under a nitrogen atmosphere, and then 150 ml of titanium tetrachloride was added dropwise at room temperature.
The temperature was raised to 80°C, and after stirring for 2 hours, the supernatant liquid was removed by decantation. Then n-hexane
After adding 100 ml and stirring, the operation of removing the supernatant liquid by decantation was repeated 5 times. n of this component
- When hexane was evaporated and analyzed, it was found that 1.3wt
% of Ti was contained. [] Propylene polymerization Hydrogenated hexane in two autoclave made of corrosion-resistant steel
Ti component prepared in 750ml [based on Ti]
0.0225mmo, triethylaluminum (A
3.75mmo and methyl paratoluate
After charging 1.25 mmol in a nitrogen atmosphere, 400 ml of hydrogen (in terms of normal pressure) was charged, and then propylene was charged and polymerization was carried out at a total pressure of 7 Kg/cm ² G and 60° C. for 2 hours. Thereafter, after depressurizing, the solvent hexane was filtered off, and powdered polypropylene was obtained in the yield shown in Table 1. The physical properties of the propylene polymer were comparable to those using fresh isohexane. (Comparative example 1~
3) Using fresh isohexane or recovered hexane as a polymerization solvent instead of hydrogenated hexane, ethylene-propylene copolymerization and propylene homopolymerization reactions were carried out in the same manner as in Example 1, and Table 1 (comparative example)
The results shown are obtained.

[Table] *2 Percentage of polymer yield when using virgin isohexane.
(Examples 16 to 34) (Small test scale pure liquid phase continuous hydrogenation treatment) The hydrogenation catalyst shown in Table 2 was treated in the same manner as in Example 1, and using this catalyst, the same procedure as in Example 1 was carried out. The recovered hexane obtained in the above operation was hydrogenated. Hydrogenation method is method A (gas-liquid mixed phase hydrogenation)
In the case of Example 1, the procedure was exactly the same as in Example 1 except that the recovered hexane was introduced in a downward flow manner. In the case of method B (pure liquid phase hydrogenation), the process shown in FIG. 2 was used. In other words, a hydrogen dissolution tank (7; stirring type) using a glass autoclave,
It was installed before the fixed catalyst bed 1. Fixed catalyst bed 1
In order to introduce the recovered hexane a in which hydrogen was dissolved, the flow rate was adjusted using the flow rate control valve 8 using the differential pressure. The recovered hexane was introduced into the fixed catalyst bed 1 in a downflow manner. According to Methods A and B, a copolymerization reaction was carried out in the same manner as in Example 1 using hydrogenated hexane obtained by hydrogenating the recovered solvent under the conditions shown in Table 2, and copolymerization reactions were carried out in the same manner as in Example 1. A polymer was obtained. The physical properties of the copolymer obtained were the same as when fresh isohexane was used. (Comparative Examples 4 to 6) An ethylene-propylene copolymerization reaction was carried out in the same manner as in Example 1 using fresh isohexane or recovered hexane as a copolymerization catalyst instead of hydrogenated hexane, and the results are shown in Table 1 (Comparative Examples). I got it.

【table】

[Table] (Effects of the invention) By hydrogenating using the method of the present invention, it is possible to regenerate a large amount of solvent at high speed under mild conditions. can be supported by. In addition, since the present invention uses a fixed catalyst bed and adopts a reaction method with less wear on the hydrogenation reaction catalyst, the catalyst treated by the method of the present invention does not contain impurities such as hydrogenation catalyst, and remains as it is. It can be used in polymerization reactions without post-treatment.

[Brief explanation of the drawing]

Figure 1 shows a gas-liquid mixed phase continuous hydrogenation process [method A].
FIG. 2 is a process flow sheet of the pure liquid phase continuous hydrogenation process [Method B].

Claims (1)

[Claims] 1. After distilling the recovered solvent of Ziegler type polymerization if necessary, it is treated with hydrogen in a fixed catalyst bed continuous hydrogenation apparatus using a transition metal hydrogenation catalyst at a temperature of room temperature to 150°C, 0 to 20 kg. /cm ² G pressure, superficial velocity 10~
A method for regenerating a polymerization solvent by hydrogenation and regeneration at 200 h ^-1 . 2. The method according to claim 1, which uses a continuous hydrogenation apparatus provided with a hydrogen dissolution tank at the front part where hydrogen and recovered solvent are introduced into the catalyst bed. 3. The method of claim 1, wherein hydrogen and recovered solvent are fed downflow to the catalyst bed. 4. The method according to claim 1, wherein the transition metal-based hydrogenation catalyst is a pellet-shaped transition metal supported catalyst or a transition metal mixed molded catalyst.