JPH0649554A - Method for recovering rhodium - Google Patents

Abstract

PURPOSE:To efficiently recover rhodium by adding water to a rhodium complex mixed with alkali and heat-treated to hydrolyze the complex and facilitating the successive reduction reaction. CONSTITUTION:An alkali (sodium hydroxide, potassium hydroxide) is added to an org. soln. contg. a rhodium complex having an org. phosphorus compd. as a ligand and an org. phosphorus compd. The org. soln. contg. the alkali is heat-treated, and water is added to the soln. to hydrolyze the complex.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rhodium complex having at least one organic phosphorus compound as a ligand and a method for recovering rhodium from an organic solution containing an organic phosphorus compound.

[0002]

2. Description of the Related Art Recently, in the homogeneous catalytic reaction, VII
Methods have been developed which utilize soluble complexes of Group I noble metals with organophosphorus compounds. This complex is effective for various reactions such as olefins, carbonyl compounds, aromatic hydrogenation, olefin hydroformylation and hydrocarboxylation. Further, since the above complex is chemically very stable, it is possible to separate the reaction product and the catalyst solution by distillation and circulate the catalyst solution in the reaction system for reuse.

However, in the above reaction, various high boiling by-products are produced and the catalyst is partially deactivated, so that the circulation of the catalyst solution accumulates the high boiling by-products and the deactivated catalyst in the reaction medium. Therefore, in order to avoid this, it is necessary to remove a part of the catalyst liquid separated by distillation from the reaction system continuously or intermittently. Since the removed catalyst liquid contains an expensive noble metal of Group VIII, it is desired to recover it efficiently.

As a method for recovering a noble metal, generally, a sulfide is added to an organic solution containing a noble metal complex such as rhodium, and the noble metal is precipitated and recovered as a noble metal sulfide, or a reducing agent is added, Known so-called wet recovery methods are known, such as a method of recovering the noble metal by reducing it to a metal, or a method of adding an adsorbent such as activated carbon to adsorb the noble metal on the noble metal and recovering it.

On the other hand, as a dry recovery method, a method is used in which an organic solution containing a noble metal complex is burned and ashed in a combustion furnace or an underwater combustion furnace to recover the noble metal metal in the ash.

[0006]

However, in the case of the conventional wet recovery method as described above, the complex of rhodium and the organophosphorus compound has a particularly strong chemical bond among the noble metal complexes and is stable. In addition, there is a problem that rhodium cannot be efficiently recovered because it does not easily react with a sulfide or a reducing agent and its adsorption amount by activated carbon is low. Also, when using the dry recovery method, some rhodium may scatter or volatilize during combustion even if an efficient underwater combustion furnace is used, or some rhodium may dissolve in the combustion liquid (phosphoric acid aqueous solution). There was a problem that the recovery rate would decrease because of loss.

The present invention solves the above problems in recovering noble metals, particularly rhodium, and efficiently and advantageously recovers rhodium from an organic solution of rhodium using a rhodium complex and an organophosphorus compound by a wet recovery method. The purpose is.

[0008]

Means for Solving the Problems As a result of intensive investigations by the present inventors in order to achieve the above object in the recovery of rhodium, a rhodium complex and an organic compound having at least one organic phosphorus compound as a ligand are obtained. When an organic solution containing a phosphorus compound is reduced with a reducing agent to produce rhodium metal, an alkali is added to the organic solution to perform heat treatment, and then water is added to hydrolyze the solution to obtain rhodium metal. It has been found that the reduction reaction to γ can be easily progressed and the recovery rate of rhodium can be improved, and the present invention has been completed.

That is, according to the present invention, an alkali is added to an organic solution containing a rhodium complex having at least one organic phosphorus compound as a ligand and an organic phosphorus compound, which is subjected to heat treatment and then water is added to the solution. It is a method for recovering rhodium, which comprises hydrolyzing the rhodium complex therein, and then adding a reducing agent and concentrating.

[0010]

Next, details of the present invention and its operation will be described in detail.

The present invention is applicable to the recovery of rhodium from any organic solution containing a rhodium complex having at least one organophosphorus compound as a ligand and an organophosphorus compound, and in particular, the present invention. Is effectively used for recovering rhodium in the catalyst liquid separated from the reaction product by distillation or the like in hydroformylation or hydrocarboxylation reaction using a homogeneous catalyst containing the rhodium complex and the organic phosphorus compound. .

The rhodium complex having at least one organic phosphorus compound as a ligand is a rhodium compound such as a hydride, a halide, a carboxylate, a nitrate or a sulfate and an organic phosphorus compound such as phosphine or phosphite. Can be easily prepared by a known complex formation method. In some cases, a rhodium compound and an organic phosphorus compound may be supplied to the reaction system to form a catalyst complex.

Specific examples of the rhodium compound used for preparing the complex include chloropentaamino rhodium chloride III, rhodium dicarbonyl chloride, rhodium nitrate, rhodium trichloride, rhodium acetate and rhodium sulfate. Can be mentioned.

The organophosphorus compound used for preparing the complex includes tributylphosphine, chlorodiethylphosphine, tris (aminoamyl) phosphine, tricyclohexylphosphine, triphenylphosphine, tris (O-tolyl) phosphine, phenyldiisopropylphosphine, phenyl. Diamylphosphine, ethyldiphenylphosphine, chlordixylphosphine, tris (N, N-diethylaminomethyl) phosphine, ethylenebis (diphenyl) phosphine, trianilylphosphine, diphenyl (N, N-dimethylanilyl) phosphine, triphenyl Phosphines such as anilylethylenediphosphine, tris (3,5-diaminophenyl) phosphine, aminoethyltriisopropylhexamethylenediphosphine, Methyl phosphite, triphenyl phosphite, chloro diphenyl phosphite, tri-cyclohexyl phosphite, organic phosphorus compounds phosphites such as tetraphenyl ethylene phosphite.

In the present invention, when recovering rhodium from a solution containing a rhodium complex having at least one organic phosphorus compound as a ligand and an organic phosphorus compound as described above, first, alkali is added to the solution to obtain 60 to 110.
5 to 60 minutes at ℃, preferably 15 to 80 ~ 100 ℃
After heat treatment for 30 minutes, it is important to add water to this to cause hydrolysis. The alkali to be used is necessary as a pretreatment agent for hydrolyzing the complex, and it is preferable that the alkali is soluble in water and the aqueous solution thereof shows strong alkalinity, and water of Li, Na, K of Group I a of the periodic table is used. Oxides, carbonates, or Mg, Ca of Group IIa of the periodic table
Which is at least one selected from the hydroxides and carbonates of, and is particularly preferably an alkali compound of Group I a of the Periodic Table, more preferably sodium hydroxide or potassium hydroxide, These compounds are used after being dissolved in water.

That is, the alkali is 1 to 10 w of the amount of the organic solution.
The amount of t% is 5 wt% or more, preferably 20 to 40 w
It is used as a t% aqueous solution and has a pH of 2-1 by hydrolysis.
2, preferably at pH 6-10. p
When H2 or less, the reduction reaction of rhodium is lost slowly, resulting in pH1.
When it is 2 or more, the amount of salt deposited increases in the subsequent solid-liquid separation step, which is not preferable.

Rhodium in an organic solution containing a rhodium complex having at least one organic phosphorus compound as a ligand and an organic phosphorus compound can be recovered even in the presence of an organic solvent. It is preferable to evaporate and separate the solvent in order to reduce the amount handled in the subsequent steps and to reuse the separated organic solvent. Hydrolysis is carried out by adding 0.5 to 4 times the amount of the organic solution, preferably 1 to 2 times the amount of water, and adding the water at 50 to 110 ° C. for 5 to 60 times.
It is desirable to perform heat treatment for 10 minutes, preferably 70 to 100 ° C. for 10 minutes.

Next, a reducing agent is added to reduce rhodium. As the reducing agent, sodium borohydride, hydrogen gas, and the like are used. Among them, sodium borohydride is particularly suitable, and 0.5% equivalent or more, preferably 1 to 2 times equivalent to the rhodium to be recovered is used. 50-110 ° C,
This is preferably added while maintaining it in the range of 70 to 100 ° C. When the temperature is 50 ° C. or lower, the reduction reaction is too slow, and when the temperature is 110 ° C. or higher, the autolysis reaction of the reducing agent itself is promoted, which is not preferable.

The reaction of the reducing agent immediately after addition is relatively vigorous, and the reduction reaction of rhodium is slower than that, so it is desirable to add the reducing agent gradually over time. It is desirable to perform sufficient stirring during the heating reaction to promote the reaction and prevent bumping.
The reduction reaction is further promoted by heating and concentrating at a temperature of 80 ° C., preferably 80 to 110 ° C.

By repeating the above-mentioned operations of hydrolysis, reduction and concentration one or more times, aggregation and precipitation of reduced rhodium are further promoted, so that separation is further facilitated. The rhodium thus aggregated and precipitated can be recovered in a high yield by adding water to heat and dissolve the precipitated salt and then performing filtration under heating at a temperature of 60 to 70 ° C.

[0021]

EXAMPLES The present invention will be described in more detail with reference to the following examples. Example 1 A waste catalyst solution containing a rhodium-trisphenylphosphine-based complex, triphenylphosphine, triphenylphosphine oxide, and a high-boiling-point by-product obtained from an olefin hydroformylation reaction step, wherein rhodium is 8 in terms of metal. .14 mg and 20.00 g of an organic solution containing 0.65 g of phosphorus were placed in a 100 cc beaker,
After adding 0.5 ml of 40 wt% caustic soda (NaOH) aqueous solution and heating at about 90 ° C. for 15 minutes, 20 ml of water was added and further heated for 15 minutes for hydrolysis. The pH at this time was 7.3.

Next, while maintaining the temperature of the solution to about 85 ℃, 1.2wt% SBH (NaBH 4) solution of 3
Four times every 0 minutes for a total of 2.0 ml (2.
(0 times equivalent) was added to cause a reduction reaction of rhodium metal, followed by heating and concentration at the same temperature for 2 hours. Next, these operations of hydrolysis, reduction and concentration are repeated 4 times to aggregate the reduced rhodium, and then 20 ml of water is added and heated at about 85 ° C. for 30 minutes to dissolve the precipitated salt, and about 70 ° C. The rhodium was separated by performing hot filtration at the temperature of.

Finally, the residue separated by filtration using an electric furnace was roasted together with the filter paper at 800 ° C. for 2 hours to ash, and rhodium in the ash was melted with potassium pyrosulfate and analyzed by absorptiometry. As a result, it was confirmed that 7.95 mg of rhodium was obtained. The recovery rate of rhodium was 97.7%. Example 2 Rhodium was recovered in the same procedure as in Example 1 except that the amount of the 40 wt% caustic soda aqueous solution added was 3.0 ml and the pH after hydrolysis was 9.4.
It was possible to obtain 3 mg of rhodium. The recovery rate of rhodium at this time was 98.6%. Example 3 Using 20.00 g of the same organic solution sample as in Example 1, heating at a temperature of 150 to 160 ° C. for about 3 hours and stirring to obtain 7 ml of a solvent.
Was removed by evaporation, and then caustic soda was added, heat treatment and hydrolysis were carried out in the same procedure as in Example 1 except that the temperature was lowered to about 95 ° C. and stirring was further performed.
After 2.0 ml of 2 wt% SBH (2.0 times equivalent to rhodium) was gradually added over 30 minutes to reduce rhodium, concentration operation was performed at the same temperature for about 1 hour. The operations of hydrolysis, reduction and concentration were repeated twice, and filtration was performed while hot to separate rhodium in the same manner as in Example 1. As a result, 8.03 mg of rhodium could be obtained. The recovery rate of rhodium at this time is 98.6.
%Met. Example 4 After adding an alkali and performing a heat treatment, hydrolysis,
Rhodium was recovered by the same procedure as in Example 1 except that the reducing and concentrating operations were not repeated but only once, and the concentrating operation was performed for 8 hours.
7.58 mg of rhodium could be obtained. The recovery rate of rhodium at this time was 93.1%. Comparative Example 1 Alkali was added to an organic solution sample in the same procedure as in Example 2 except that no reducing agent was added, and heat treatment, hydrolysis and concentration were performed, and further hydrolysis and concentration were performed. After repeating this operation repeatedly, filtration was carried out while hot in the same manner as in Example 1 to separate rhodium.
3 mg of rhodium was obtained. The recovery rate of rhodium at this time was 7.7%, which was an extremely low rate. Comparative Example 2 Rhodium was recovered by the same procedure as in Example 4 except that the operation of adding an alkali for heat treatment and then adding water for hydrolysis was not performed.
1.94 mg of rhodium was obtained. At this time, the recovery rate of rhodium was as low as 23.8%. Comparative Example 3 Using the same organic solution sample as in Example 1, sodium sulfide (N
aS · 9H ₂ O) 0.5 g three times every 30 minutes, and a total of 1.5 g (19.8 times equivalent to rhodium) is added to give 8
After heating at 5 ° C. for 8 hours, the precipitate was separated and incinerated in the same procedure as in Example 1, and rhodium in the ash was analyzed. As a result, 2.23 mg of rhodium was obtained. The recovery rate of rhodium at this time was as low as 27.4%.

As can be seen from the results of the above Examples and Comparative Examples, according to the method of the present invention shown in Examples 1 to 4, it is possible to recover rhodium at an extremely high yield of 90% or more. On the other hand, according to the method other than the present invention, rhodium can be recovered only at a low yield of about 20%.

Data showing the relationship between the amount of chemicals consumed and the heating conditions and the recovery rate of rhodium in Examples 1 to 4 and Comparative Examples 1 to 3 are collectively shown in Table 1.

[0026]

[Table 1]

As described above, according to the method for recovering rhodium of the present invention, an alkali such as sodium hydroxide is added to the rhodium complex for heat treatment, and then water is added for hydrolysis. Rhodium can be easily reduced using a reducing agent such as sodium hydride.
It has an excellent advantage that rhodium can be efficiently recovered at low cost.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tomoyuki Mori 3-10 Shiodori, Kurashiki-shi, Okayama Mitsubishi Kasei Co., Ltd. Mizushima Plant (72) Akio Tsuboi 3-10 10 Shiodori, Kurashiki, Okayama Mitsubishi Kasei Mizushima Factory Co., Ltd.

Claims (4)

[Claims] 1. An alkali solution is added to an organic solution containing a rhodium complex having at least one organophosphorus compound as a ligand and an organophosphorus compound, followed by heat treatment, and then water is added to hydrolyze the solution. A method for recovering rhodium, which comprises reducing the rhodium by adding a reducing agent to the solution and concentrating the solution. 2. The method for recovering rhodium according to claim 1, wherein the operations of hydrolysis, reduction and concentration are repeated at least once to reduce rhodium. 3. The method for recovering rhodium according to claim 1, wherein the alkali is sodium hydroxide or potassium hydroxide. 4. The method for recovering rhodium according to claim 1, wherein the reducing agent is sodium borohydride.