KR20160036887A - Method for the recovery of catalytic metal from polyketone - Google Patents

Abstract

An object of the present invention is a method for recovering palladium catalyst in a polyketone slurry polymerization process, more specifically, a method for recovering palladium easily by precipitating palladium in a solid phase in a heavy end occurring during a fractional distillation purification process of a polymerization solvent MeOH.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a method for recovering a polyketone catalyst,

The present invention relates to a polyketone polymerization process and is a technique for increasing the recovery of palladium, which is a metal catalyst, in a by-product generated in a recovery apparatus for polyketone polymerization solvent MeOH

The polyketone having a structure in which repeating units derived from carbon monoxide and repeating units derived from an ethylenically unsaturated compound are substantially alternately linked has excellent mechanical and thermal properties and has high abrasion resistance, chemical resistance and gas barrier property, Expansion is expected. Specifically, polyketone is a useful material as high strength, high heat resistant resin, fiber, and film. Particularly, when a high molecular weight polyketone having an intrinsic viscosity of 2.5 dl / g or more is used as a raw material, a fiber or a film having a very high strength and an elastic modulus can be obtained. Such fibers and films are expected to be widely used for building materials such as belts, rubber reinforcements such as hoses and tire cords, concrete reinforcing materials, and industrial materials.

Polyketone mainly comprising a repeating unit composed of ethylene and carbon monoxide has a high melting point of 200 or more, but under long-term heating, thermal denaturation such as three-dimensional crosslinking occurs, molding workability due to disappearance of fluidity is lowered, There is a problem that the mechanical and heat resistance of the molded article deteriorates.

 Current polyketone polymerization techniques use MeOH or organic solvents as slurry polymerization techniques. In a pilot or commercial plant for mass production, re-use of the solvent through purification is essential, and most of the solvents are purified using fractional distillation. During refining through solvent fractionation, impurities and substances with a higher boiling point than the solvent to be refined are located at the heavy end of the refining tower, which is treated as waste after storage in a heavy end storage.

        The most economical polyketone polymerization solvent known to date is MeOH containing a small amount of water, and water has an effect of preventing the kettle of the polyketone polymer. The MeOH and water used in the polymerization are separated through the use of a fractional distillation column. MeOH is refined and reusable. However, water with a boiling point higher than that of MeOH can not be reused as a Heavy End reservoir together with various byproducts .

The polyketone polymerization catalyst is composed of palladium divalent and bidentate phosphine ligands and acids of pK 4 or less. After the polymerization reaction, about 50% of the palladium remains in the polyketone polymer, and the remaining 50% After passing through the MeOH purification distillation tower, it is discharged as a heavy end along with water, and as a result, the structure becomes inaccurate when cooled to room temperature.

        As a method for reducing the amount of palladium remaining in the polyketone polymer after polymerization, polyketone polymerized in an acetone solvent is subjected to extraction treatment with 2,4-pentanedione in Polymer, 42 (2001) 6283-6287 to obtain Pd And the content is reduced to 20 ppm or less to improve the heat resistance of the polyketone. This polyketone does not use alcohol as a polymerization solvent and therefore has very low polymerization activity under these conditions. Further, after complicated polymerization, complicated extraction of Pd is required, which can not be industrially employed from the viewpoints of productivity and cost.

 International Publication No. WO00 / 09611 discloses polyketones having a Pd content of 5 ppm. However, this polyketone is obtained by polymerizing Pd at 80 deg. C and 5 MPa and then removing Pd in the polymer by solvent extraction, which requires a long heat treatment.

  Therefore, it is not easy to remove palladium of about 50%, which is expected to remain in the polymerizate when considering economical process stability for production of polyketone polymer. Polyketone receives heat and generates chemical reaction such as formation of furan ring by Paal-Knorr reaction or formation of intramolecular and intermolecular crosslinking by aldol condensation, and deterioration by heat proceeds, and this chemical reaction remains in polyketone Although accelerated by the polymerization catalyst (palladium), when the residual amount of palladium in the polymer is lowered to the level of 5 to 10 ppm as a technique of improving the activity of the polymerization catalyst, the effect of palladium on deterioration is not a problem.

Therefore, it can be judged that the method of easily recovering the palladium used in the polyketone polymerization is a method of extracting palladium present in the heavy end, which is a by-product of the MeOH purification process in the polymerization process. As a technique for extracting palladium from a Heavy End solution obtained as a by-product in a MeOH distillation column, there is a palladium recovery technique using the ion exchange resin described in KR 1200807 B1. This is a method of pretreating the heavy end solution from the methanol distillation column with an appropriate pH, passing the ion exchange resin selectively to adsorb palladium, further separating the palladium through the desorption process, and reusing the ion exchange resin. This technique is effective in separating the selective palladium, but it has the burden of the additional facilities such as acid tank, titration tank and desorption solution for pH adjustment of the heavy end solution and the burden on expensive ion exchange resin.

Korean Patent No. 10-1200807 WO00 / 09611

It is an object of the present invention to provide a method of maximizing the amount of palladium precipitated by a simple base / reducing agent formulation in a heavy end solution in order to increase the recovery of palladium catalyst used in polyketone polymerization.

In order to accomplish the above object, the present invention provides a method for purifying a polyketone which comprises treating a clear solution containing about 2 to 4 ppm of palladium in a MeOH fractionation distillation and purification apparatus used as a polymerization solvent of a polyketone with a base and a reducing agent, To provide a technique for converting palladium to a precipitate phase.

The present invention provides a simple and unnecessary facility for maximizing the recovery of the palladium catalyst in the byproducts generated in the polyketone polymerization process of the present invention. The palladium catalyst is recovered by simple precipitation of palladium by cooling the Heavy End solution, which is a byproduct of the MeOH fractional distillation apparatus, at room temperature and a small amount of base / reducing agent.

In order to achieve the above object, the present invention provides a method for purifying a polyketone which comprises treating a clear solution containing about 2 to 4 ppm of palladium among the Heavy End by-products of a fractional distillation and purification apparatus using MeOH as a polymerization solvent, To provide a technique for converting palladium to a precipitate phase.

Palladium exists as a divalent to tetravalent cation in the state of catalytic activity and exists in a state of being dissolved in a solvent of polarity and weak polarity and exists as a black precipitate upon transformation into the form of palladium 0 (atom) It does not dissolve in solvents other than strong acids. Therefore, the palladium used as the polymerization catalyst is stored in the acetone and stored after the addition of the bidentate phosphine ligand and the acid below pK4 in order to stably maintain the divalent ion state. Approximately 50% of the palladium used in the polymerization is present in the polyketone powder, and the remaining 50% is discharged as MeOH, which is a polymerization solvent, and remains in the heavy end after the fractional distillation of MeOH. Although the mechanism of the palladium distribution is not known, the presence of palladium in the catalyst system using the palladium-phosphine ligand remains constant. Palladium divalent ions maintain a relatively stable morphology when the solution is acidic and produce black precipitates of palladium 0 over long periods of storage in the absence of acid.

In view of such palladium ion characteristics, the present invention aims to simplify the recovery process of palladium by converting the state of the heavy end solution into a basic state and adding an inexpensive reducing agent to prepare the palladium state in the solution to the maximum precipitation state. The Heavy End solution generated from the MeOH purification column is released into a clear solution of brown at about 60-70 ° C., but precipitates as it is cooled to room temperature, resulting in the structure shown in Table 1.

sample classification Occurrence rate Pd remaining ratio MeOH content (ppm) The solid (solid) 3.7% 82% N / A Liquid 96.3% 18% 12.29

Palladium can exist in a cationic state of 0, bivalent tetravalent, and 0-valent palladium maintains a black solid phase form that does not dissolve except for aqua regia / strong acid, and the divalent tetravalent cation exists in a polar organic solvent. In particular, palladium divalent cations are used as catalysts for polyketone polymerization catalysts or hydroformylation reactions as catalysts in a wide range of fields.

The polymerization process of the polyketone in the catalyst metal recovery method of the present invention is as follows. The polyketone is polymerized by the reaction of an ethylenically unsaturated compound that co-polymerizes with carbon monoxide with a metal catalyst polymer. Examples of the ethylenically unsaturated compound copolymerized with carbon monoxide include ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, -Olefins such as hexadecene and vinylcyclohexane; Alkenyl aromatic compounds such as styrene and? -Methylstyrene; But are not limited to, cyclopentene, norbornene, 5-methylnorbornene, 5-phenylnorbornene, tetracyclododecene, tricyclododecene, tricyclo undecene, pentacyclopentadecene, pentacyclohexadecene, Cyclic olefins such as cyclododecene; Vinyl halides such as vinyl chloride; Ethyl acrylate, and acrylates such as methyl acrylate. These ethylenically unsaturated compounds are used singly or as a mixture of plural kinds. Of these, preferred ethylenically unsaturated compounds are? -Olefins, more preferably? -Olefins having 2 to 4 carbon atoms, and most preferably ethylene.

The molar ratio of the carbon monoxide / ethylenically unsaturated compound to the ethylenically unsaturated compound in the reaction vessel is preferably 1/1 to 1 / 2.5 from the viewpoints of polymerization activity and recovery cost. The method of adding the carbon monoxide and the ethylenically unsaturated compound is not particularly limited and may be added after mixing them in advance, or they may be added in separate feed lines. In the present invention, a mixed gas having a molar ratio of carbon monoxide and an ethylenic unsaturated compound of 1 / 2.5 and 1/1 was mixed in advance, and then a certain amount of monomer was continuously added to increase the polymerization activity

In carrying out the present invention, the polymerization method includes a solution polymerization method using a liquid medium, a suspension polymerization method, a vapor phase polymerization method in which a small amount of a polymer is impregnated with a high concentration catalyst solution, and the like. The polymerization may be either batchwise or continuous. As the reactor used for the polymerization, known ones can be used as they are or by processing. The polymerization temperature is not particularly limited and is generally 40 to 180 占 폚, preferably 50 to 120 占 폚. The pressure at the time of polymerization is not particularly limited, but is generally from normal pressure to 20 MPa, preferably from 4 to 15 MPa.

Palladium as a polyketone polymerization catalyst is added in the form of palladium acetate. When an acid below pK 4 is added by bonding with a bidentate phosphine ligand, bivalent stable state is maintained and alternating copolymerization of an ethylenically unsaturated compound and carbon monoxide is achieved. After the polymerization process, it is reported that about 50% of the polyketone polymer remains and about 50% of the palladium is discharged in a bivalent form by the polymerization solvent MeOH.

This technique simplifies the palladium recovery process by adding only a simple filtration device to the already existing Heavy End storage tank, and by adding a certain amount of base / reducing agent, about 90% or more of the palladium present in the heavy end solution is dredged. The base used herein is any one selected from the group consisting of NaOH, KOH, LiOH, Mg (OH) 2 and NH3, and the reducing agent includes sodium thiosulfate, ferrocyanide, sodium borohydride, diborane, lithium aluminum hydride, But are not limited thereto. The base and the reducing agent may be used independently, and the base and the reducing agent may be used at the same time.

The content of the base is preferably 0.5 to 3 g / l, and the content of the reducing agent is preferably 0.5 to 2 g / l.

(1) The amount of the polyketone

Palladium and elements were measured using ICP-AES.

Comparative Example 1

Heavy - end solution, which is a by - product of MeOH fractionation distillation device operating in real - time during polyketone polymerization, is collected in real time and naturally cooled to room temperature (about 20 ° C). The temperature at the time of discharging the Heavy End solution was 65 ° C. It was a brownish turbid solution, and brown precipitates were formed upon cooling. A total of 15.77 kg of the solution was subjected to solid-liquid separation with a 10-μm glass filter, and 582 g of a precipitate was obtained. ICP-AES analysis of the solid / liquid phase revealed 507 ppm (82%) of palladium on the solid phase and 4.2 ppm (18%) on the liquid phase.

Examples 1-5

The Heavy End liquid phase obtained in Comparative Example 1 was sampled, NaOH and sodium thiosulfate were formulated as shown in Table 2, stirred for 6 hours, filtered, and the amount of palladium remaining in the solution phase was confirmed through ICP-AES analysis. The increase of NaOH addition in Heavy End Liquid was accompanied by increasing tendency of palladium precipitation in solid phase.

sample classification Amount of NaOH added (g / l) Amount of Na2S2O3 added
(g / l) Pd content
(ppm) Amount Generated (g) Pd remaining ratio (%) Comparative Example 1 Heavy End Solid - - 507 582 82 Heavy End liquid - - 4.2 15.190 18 Example 1 Heavy End Solid - - 507 582 83 Heavy End liquid 0.5 - 3.9 15.190 17 Example 2 Heavy End Solid - - 507 582 85 Heavy End liquid 1.0 - 3.5 15.190 15 Example 3 Heavy End Solid - - 507 582 89 Heavy End liquid 1.5 - 2.3 15.190 11 Example 4 Heavy End Solid - - 507 582 97 Heavy End liquid 2.0 - 1.4 15.190 7 Example 5 Heavy End Solid - - 507 582 94 Heavy End liquid 1.0 1.0 1.3 15.190 6

Claims (4)

In a method of recovering a palladium metal catalyst in a polyketone polymerization process, a palladium-bidentate phosphine ligand - a liquid polyketone slurry composed of an acid having a pK 4 or less fractionation, In the presence of a palladium catalyst.
The method according to claim 1,
Wherein a base and / or a reducing agent is used in the heavy end solution generated during the fractional distillation purification process.
3. The method of claim 2,
Wherein the base is any one selected from the group consisting of NaOH, KOH, LiOH, Mg (OH) 2 and NH3 and the reducing agent is selected from the group consisting of sodium thiosulfate, ferrocyanide, sodium borohydride, diborane, lithium aluminum hydride, Wherein the palladium metal catalyst is selected from the group consisting of palladium and palladium.
The method according to claim 2, wherein
Wherein the content of the base is 0.5 to 3 g / l, and the content of the reducing agent is 0.5 to 2 g / l.