KR100470633B1 - Removal of Metal Compounds from Acid Solutions - Google Patents

Abstract

The present invention provides a method for removing an alkali metal compound from an acid solution that also includes a nickel and aluminum compound consisting of:

i) contacting the acid solution with a first ion exchange resin that removes nickel and aluminum from the acid solution,

ii) The obtained acid solution is contacted with a second ion exchange resin which removes the alkali metal compound from the acid solution.

Description

Method of removing metal compounds from acid solution

The present invention relates to a method for removing a metal compound from an acid solution. Specifically, the present invention relates to a method for removing an alkali metal compound from an acid solution that also contains nickel and aluminum compounds. More particularly, the present invention relates to a method for removing metal compounds from acid solutions used to remove alkali metal compounds from polymer cement.

Acids are often used to remove catalyst residues and alkali metal compounds from polymer cements. Strong acids, such as sulfuric acid and phosphoric acid, are particularly effective at washing hydrocatalyst residues (nickel and aluminum) and alkali metal compounds (lithium) from polymer cements. Acid recycling requires treatment by processes such as ion exchange to remove catalyst residues and alkali metal compounds. Basic lithium salts cause emulsification during washing, and one method of preventing emulsification has been found to use highly concentrated acids. However, most ion exchange resins have very low selectivity for lithium removal. As a result, it is very difficult to remove lithium from the acid solution by ion exchange in the presence of nickel and aluminum. It is more difficult if the washing step requires the use of concentrated acid.

An effective method has now been developed that enables improved removal of alkali metal compounds from acid solutions that also contain nickel and aluminum compounds.

The present invention thus provides a method for removing an alkali metal compound from an acid solution that also contains nickel and aluminum compounds, which consists of the following steps:

i) contacting the acid solution with a first ion exchange resin that removes nickel and aluminum compounds from the acid solution,

ii) contacting the obtained acid solution with a second ion exchange resin which removes the alkali metal compound from the acid solution.

In this method, the removal of the alkali metal compound (lithium) from the acid solution containing nickel and aluminum compounds is improved. Some ion exchange resins have been found to have a higher selectivity for lithium removal than others. Examples include AMBERLYST 35 and AMBERLYST 15 (trade name of Rohm and Haas for strong acid resins, H ⁺ form) and BAYER OC 1501 (miles trade name for strong acid resins, H ⁺ form). Nickel and aluminum were first removed on a resin such as AMBERLITE 200C (trade name of Rom and Haas for strong acid resins) and then lithium was removed on the second ion exchange resin with high selectivity to lithium. It has been found that lithium removal is improved. The second ion exchange resin is more selective for the removal of the alkali metal compound from the acid solution than the first ion exchange resin.

The acid solution according to the invention is preferably used for removing the alkali metal compound from the polymer cement. More preferably, the acid solution is used to remove the alkali metal compound from the low viscosity functionalized polymer cement.

Low viscosity functionalized polymers are well known (see, eg, US Pat. Nos. 4,039,503 and Re. 27,145, which are described herein by reference), for the anionic polymerization of conjugated diene hydrocarbons using lithium initiators. Can be prepared by Polymerization begins with a monolithium, dilithium or polylithium initiator that produces a living polymer backbone at each lithium position. Typical living polymer structures comprising polymerized conjugated diene hydrocarbons are as follows:

X-B-Li

X-A-B-Li

X-A-B-A-Li

Li-B-Y-B-Li

Li-A-B-Y-B-A-Li

In the above formula,

B represents a polymerized unit of one or more conjugated diene hydrocarbons such as butadiene or isoprene. A represents a polymerized unit of at least one vinyl aromatic compound, such as styrene. X is a residue of a monolithium initiator, such as tert-butyllithium, and Y is a residue of a dilithium initiator, such as an adduct of secondary-butyllithium and meta-diisopropenylbenzene. Some structures, including those belonging to polylithium initiators or random units of styrene and conjugated dienes, are known in the art but generally have limited utility.

Anionic polymerization of conjugated diene hydrocarbons is typically controlled by structural modifiers such as diethyl ether or figure (1,2-diethoxyethane) to obtain the desired amount of 1,4-addition. As described in Re 27,145, the level of 1,2-addition of butadiene polymers or copolymers greatly affects elastomeric properties after hydrogenation.

Dilithium initiation with adducts of secondary-butyllithium (s-BuLi) and meta-diisopropenylbenzene also requires the presence of an inert coordination agent such as diethyl ether, picture or triethyl amine, otherwise Monolithic initiation is obtained. Ethers are typically present during anionic polymerization, as discussed above, and the amount of ether required to obtain a particular polymer structure is typically sufficient to provide dilithium initiation.

Alternatively, anionic polymerization of the conjugated diene can be performed using a protected action initiator (PFI), as described, for example, in US Pat. Nos. 5,391,663 and 5,146,168, which are described herein by reference. have.

Anionic polymerization is sometimes terminated by the addition of water to remove lithium as lithium hydroxide (LiOH) or the addition of alcohol (ROH) to remove lithium as lithium alkoxide (LiOR). For polymers with terminal functional groups, the living polymer chains are preferably reacted with ethylene oxide, carbon dioxide, protected hydroxystyrene monomers, ethylene oxide and epichlorohydrin or amine compounds described in US Pat. No. 4,791,174, respectively. Terminated by hydroxyl, carboxyl, phenol, epoxy or amine groups.

Termination of living anionic polymers to form functional end groups are described, for example, in US Pat. Nos. 4,417,029, 4,518,753 and 4,753,991, which are described herein by reference. Of particular interest to the present invention are terminal hydroxyl, carboxyl, phenol, epoxy and amine groups. Such polymers having a number average molecular weight of 1000 to 20,000 as measured by gel permeation chromatography are low viscosity functionalized polymers.

Hydrogenation of at least 90%, preferably at least 95%, in low molecular butadiene polymers is described, for example, in US Pat. This is accomplished using the nickel catalysts described in 27,145 and 4,970,254 (the latter are also described herein by reference). Preferred catalysts are mixtures of nickel 2-ethylhexanoate and triethylaluminum.

Stir while sparging with polymeric cement and strong acid, eg aqueous solution of phosphoric acid (2-30% (volume)), sparging with oxygen mixture in nitrogen for 30-60 minutes at 50 ° C. in a ratio of 0.33-0.50 parts acid aqueous solution: 1 part polymer solution Therefore, it is preferable to extract the nickel catalyst after hydrogenation. Alternatively, an aqueous sulfuric acid solution will be sufficient to remove the hydrogenation catalyst. It should be understood that polymer cements are generally the resultant mixture of polymerization reactions that include components such as formed polymers, organic solvent (s), unconverted-monomers, polymerization initiators, catalyst residues, and the like.

The present invention relates to the removal of alkali metal compounds after hydrogenation. The polymerization reaction preferably uses a lithium initiator which is a protected functional initiator (PFI). PFI diols contain 1 mole of lithium per mole of polymer and the terminating step produces lithium salts. The magnitude of this effect is not fully known, but the presence of lithium salts affects the degree of hydrogenation performance. If the degree of hydrogenation is acceptable, the lithium salt may be removed after hydrogenation in the same steps used to remove the hydrogenation catalyst comprising nickel and aluminum.

As mentioned above, the removal of lithium salts from the polymer cement after hydrogenation can be accomplished by washing the cement with a strong acid such as phosphoric acid or sulfuric acid. This transfers the cation into the acid solution and must be treated to remove salts before recycling. Although only strong acid solutions have been mentioned above, it should be recognized that the concept also applies to weak acids such as, for example, citric acid and acetic acid. AMERLYST 35 resins are preferred and have greater selectivity for capacity and lithium than AMBERLITE 200C (AMBERLYST 35 and AMBERLITE 200C are trademarks of Rohm and Haas). The two-bed batch with the AMBERLYST 35 bed after the AMBERLITE 200C bed provides the best compromise between resin selectivity, capacity and regeneration in the fixed bed process. The process is preferably carried out in the range from 21 to 77 ° C, preferably 50 to 65 ° C. The acid is preferably at a concentration of 0.2 to 40% w, and the lithium salt is preferably 0.005 to 5% w. The process is preferably carried out at a rate of two bed volumes per hour.

When the alkali metal compound is used as a catalyst or initiator, other alkali metal compounds commonly found in polymer cement can be removed from the polymer cement. These include alkali metal hydrides, alkali metal alkoxides and alkali metal hydroxides.

The invention will be illustrated by the means of the following examples.

Example 1

To test the present invention, two column experiments were performed using 20% w phosphoric acid containing 280 ppm Li and 100 ppm Ni and Al, respectively. In the first experiment, a 20 cc bed of AMBERLITE 200C was used. In the second experiment, the bed consists of 10 cc of AMBERLITE 200C followed by 10 cc of AMBERLYST 35. All other parameters such as flow rate, temperature, bed L / D, etc. were the same in both experiments. The results obtained in this test show that the successive use of two resins increases the volume of acid treatment before lithium passage from two bed volumes to six bed volumes.

Example 2

The high lithium selectivity of AMBERLYST 35, AMBERLYST 15 and BAYER OC 1501 is confirmed in the isothermal test. In order to select the best resin, a screening experiment consists of a shake test to equilibrate the resin or adsorbent with a 2% w phosphoric acid solution containing 230 ppm lithium. In this experiment, the weight ratio of acid: adsorbent was 100: 1 and the temperature was 22 ° C. After equilibration, the residual lithium in the acid solution is determined by ion chromatography. From this result, the most effective substance for removing lithium is identified. Chelating resins, strong acid resins, weak acid resins, strong base resins with or without chelating agents, inorganic oxides, inorganic ion exchangers, activated zeolites impregnated with several zeolites, aluminas, acid-activated carbons and crown ethers do. The results confirmed AMBERLYST 35, BAYER OC 1501 and AMBERLYST 15 as the most effective materials for removing lithium. It is not clear why such resins are particularly effective. However, it is evident that they are strong acid resins in H ⁺ form. However, there seems to be some difference in the effects among H ⁺ type strong acid resins. This is suspected to be due to the difference in structure (eg pore size) and / or acid strength.

Claims (6)

i) contacting the acid solution with a first ion exchange resin that removes nickel and aluminum compounds from the acid solution; And ii) a method of removing an alkali metal compound from an acid solution containing nickel and aluminum compounds, comprising contacting the obtained acid solution with a second ion exchange resin which removes the alkali metal compound from the acid solution. The method of claim 1 wherein an acid solution is used to remove the alkali metal compound from the polymer cement. The method of claim 2 wherein the polymer cement is a low viscosity functionalized polymer cement. The method of claim 1 wherein the alkali metal is lithium. The method according to any one of claims 1 to 4, wherein the first ion exchange resin is a strong acid resin. The method according to any one of claims 1 to 4, wherein the second ion exchange resin is a strong acid resin.