JPH0790402A - Rhodium recovering method - Google Patents

Abstract

PURPOSE:To efficiently recover rhodium from ash obtd. by combusting a rhodium org. soln. containing a rhodium complex and an org. phosphorus compd. CONSTITUTION:First, an org. soln. containing an org. phosphorus compd. and a rhodium complex having at least one kind of org. phosphorus compd. as a ligand is combusted. The residual matter of combustion is cleaned with a cleaning liquid containing a reducing agent to remove impurities of soluble salts except for rhodium. By this method, the quality of rhodium after cleaning and the loss ratio of dissolved rhodium are significantly improved, so that extremely excellent effects can be obtd.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rhodium complex capable of recovering rhodium from an organic solution containing a rhodium complex having at least one organic phosphorus compound as a ligand and an organic phosphorus compound in a high quality and at a high yield. It concerns the method of collection.

[0002]

2. Description of the Related Art Recently, a method of using a soluble complex of rhodium and an organic phosphorus compound as a catalyst has been developed in a homogeneous catalytic reaction. This complex is effective for various reactions such as hydrogenation of olefins, carbonyl compounds and aromatic compounds, hydroformylation and hydrocarboxylation of olefins. Further, since the complex is chemically extremely stable, it is possible to separate the reaction product and the catalyst solution by distillation and to circulate the catalyst solution in the reaction system for reuse.

However, in the above reaction, various high-boiling-point by-products and deactivated catalyst accumulate due to the circulation of the catalyst liquid, and in order to avoid this, a part of the catalyst liquid separated by distillation is continuously treated. It is necessary to remove it from the reaction system either intermittently or intermittently. Since the removed catalyst liquid contains expensive rhodium, it is desired to recover rhodium efficiently.

As a method of recovering a noble metal such as rhodium, generally, a method of precipitating and recovering a noble metal such as rhodium as a noble metal sulfide, or a method of adding a reducing agent to reduce the noble metal to a metal state and recovering it There is also known a so-called wet recovery method, such as a method of recovering a precious metal by adsorbing an adsorbent such as activated carbon on the precious metal.

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

[0006]

However, in the case of the conventional wet recovery method as described above, the step of isolating the precious metal from the liquid resulting from the recovery step is complicated, and the purity of the recovered precious metal is considerably high. There was a problem that it became low.

Further, when the dry recovery method is used, there is a problem that the amount of ash (hereinafter referred to as ash) which is a recovered combustion residue is large and the quality of rhodium is deteriorated, and an efficient underwater combustion furnace is used. Even if used, a part of rhodium during combustion is scattered or volatilized, or a part of rhodium is dissolved and lost in the combustion liquid (phosphoric acid aqueous solution), so that the recovery rate is lowered. was there.

An object of the present invention is to provide a method capable of efficiently recovering rhodium from a rhodium organic solution containing a rhodium complex and an organic phosphorus compound by a combustion method.

[0009]

[Means for Solving the Problems] In order to solve the above-mentioned problems and achieve the above-mentioned object, the present inventors have earnestly studied a method for recovering rhodium by a combustion method, and as a result, obtained by burning an organic solution. We have found a cleaning method with low loss of rhodium that enables efficient recovery of high-grade rhodium by removing soluble impurities in the ash by cleaning the ash using a specific cleaning solution, and efficiently recovering high-quality rhodium. As a result, the present invention has been completed. That is, the present invention, after burning an organic solution containing a rhodium complex having at least one type of organic phosphorus compound as a ligand and an organic phosphorus compound, the combustion residue is washed with a washing liquid containing a reducing agent. ,
The present invention relates to a method for recovering rhodium that removes soluble salt impurities other than rhodium.

The rhodium complex having at least one kind of organophosphorus compound as a ligand in the present invention can be easily prepared from a rhodium compound and an organophosphorus compound by a known complex formation method, or in some cases, a rhodium compound. An organophosphorus compound may be supplied to the reaction system to form a catalyst complex.

The rhodium complex having at least one organic phosphorus compound as a ligand in the present invention can be prepared as described above. Examples of the rhodium compound include hydrogen compounds, halogen compounds and carboxylic acids. Examples thereof include salts, nitrates and sulfates, and specific examples include chloropentaamino rhodium chloride III, rhodium dicarbonyl chloride, rhodium nitrate, rhodium trichloride,
Examples thereof include rhodium compounds such as rhodium acetate and rhodium sulfate.

Specific examples of the organic phosphorus compound such as phosphine or phosphite used for preparing the complex include tributylphosphine, chlorodiethylphosphine, tris (aminoamyl) phosphine, tricyclohexylphosphine, triphenylphosphine, Tris (N, N-dimethylallyl) phosphine, tris (O-
Tolyl) phosphine, phenyldiisopropylphosphine, phenyldiamylphosphine, ethyldiphenylphosphine, chlordixylphosphine, tris (N, N
-Diethylaminomethyl) phosphine, ethylenebis (diphenyl) phosphine, trianilylphosphine,
Diphenyl (N, N-dimethylanilyl) phosphine,
Triphenylanilylethylenediphosphine, tris (3,5-diaminophenyl) phosphine, phosphines such as aminoethyltriisopropylhexamethylenediphosphine, trimethylphosphite, triphenylphosphite, chlorodiphenylphosphite, tricyclohexylphosphite, tetra Examples include organic phosphorus compounds such as phosphites such as phenylethylene diphosphite.

Since the ash recovered by burning the organic solution containing the rhodium complex and the organic phosphorus compound as described above contains a large amount of soluble impurities such as phosphoric acid or phosphate,
It is preferable to remove these impurities. In the present invention, by recovering the recovered ash while suppressing elution of rhodium, soluble impurities are dissolved, and ash containing rhodium is separated and recovered as an insoluble residue, whereby rhodium can be efficiently recovered. it can. Water is suitable as the cleaning liquid used at this time. The cleaning liquid can be used without heating, but warm water of 10 ° C. or higher is suitable for increasing the solubility of impurities and improving the removal rate. It is preferably warm water of 40 to 100 ° C., more preferably 50.
Use warm water at ~ 80 ° C.

The reducing agent used is a reducing agent such as formic acid, oxalic acid, hydrazine, sodium borohydride, etc., and sodium borohydride is particularly preferable. The addition amount varies depending on the presence or absence of addition of a basic compound at the time of combustion or the type of reducing agent, but addition of 0.001 mol / l or more has an effect of suppressing elution of rhodium, and is preferably 0.
Addition of 005 to 0.1 mol / l reducing agent is more effective. If it is less than 0.001 mol / l, the effect of the present invention is small, and if it is 0.5 mol / l or more, the elution rate of rhodium is leveled off and only the cost increases, which is not preferable. Further, the reducing agent is preferably added before cleaning the combustion residue, but may be added after adding the ash.

The addition of a coagulant has the effect of coagulating fine particles of insoluble residue containing rhodium of 0.1 μm or less to prevent ash leakage during solid-liquid separation after washing, especially in filtration operation. In addition to suppressing the loss of rhodium, it has the effect of increasing the filtration rate. The aggregating agent to be used is not particularly limited as long as it is effective for aggregating the fine particle residue, but a polymer aggregating agent having a large effect in a small amount is suitable, and particularly a cationic or anionic high-aggregating agent is used. The use of molecular flocculants is preferred. The amount of the polymer flocculant used may be, for example, an aqueous solution adjusted to a concentration of 0.01 to 0.05 wt% until flocs are formed. The preferable addition amount is 0.5 to 5 cc of the above-prepared solution per 1 liter of the washing solution.
The degree is good, and even if a large excess is added, flocs are formed, but the filtration rate is reduced, which is not preferable. The amount of cleaning liquid used is about 3 to 20 times the amount of ash to be added, but preferably 5 to 15 times.

Ash is added to the above cleaning solution to dissolve the soluble salt over 10 minutes. At this time, if stirring is performed, the dissolution rate is improved, which is effective in shortening the time. Then, the insoluble residue containing rhodium is collected by filtration by a conventional method. Although the effect can be obtained by performing the washing once, it may be repeatedly performed. When repeating, it can be washed by decantation without filtering. Further, the insoluble residue that has been filtered off is calcined at 600 to 800 ° C. for 3 to 5 hours to ash, and the above washing operation is further performed at least once to further enhance the washing effect.

In the present invention, the combustion for recovering rhodium from the organic solution comprises an evaporation process of the organic solution and an ashing process of the high boiling residue remaining after the evaporation of the organic solution. It is preferable to carry out under control.

In the combustion carried out to recover rhodium from the organic solution, the evaporation temperature of the organic solution is preferably 140 ° C. or higher and lower than 400 ° C.
It is preferable to control in the range of 350 ° C. That is,
Below 140 ℃, combustion becomes unstable, and 400 ℃
If it exceeds, the amount of rhodium that scatters or volatilizes increases, which is not preferable.

The temperature range for controlling the ashing temperature of the organic solution after evaporation is preferably 500 ° C. or higher and lower than 1000 ° C., more preferably 600 to 950 ° C. That is, if the temperature is lower than 500 ° C, ashing is difficult, and if the temperature is 1000 ° C or higher, the amount of rhodium that scatters or volatilizes increases and the recovery rate decreases, which is not preferable.

As a method for controlling the combustion temperature of the organic solution, when the amount of the organic solution supplied is constant, a method of controlling the amount of air used for combustion, a method of controlling by water cooling or air cooling, and a method of using water as an organic solvent And the like, a method of mixing and controlling a non-combustible substance such as nitrogen, a method of mixing a non-combustible gas such as nitrogen into the supplied air, or a method using these methods in combination. The evaporation temperature and ashing temperature of the solution can be controlled by any of these methods, but the method of controlling the amount of air used for combustion has a large effect and is economical, which is preferable.

In the present invention, the recovery rate of rhodium can be further increased by adding a basic compound to an organic solution and burning it.

Examples of the basic compound include Group Ia of the periodic table,
And oxides, peroxides, hydroxides of Group IIa elements,
Specifically, carbonates, caustic soda, potassium hydroxide,
Basic compounds such as sodium carbonate, potassium carbonate, sodium bicarbonate, magnesium oxide, magnesium hydroxide, calcium hydroxide, magnesium carbonate, calcium carbonate, or a sulfide of Group I a of the periodic table, or a hydride, For example, a basic compound such as sodium sulfide or sodium borohydride, or a salt formed by an alkali and an organic acid, for example, a basic compound such as sodium formate, sodium acetate, sodium oxalate, or sodium citrate. At least one selected from the group, preferably a hydroxide or carbonate of Group I a of the periodic table or a salt of an alkali and a carboxylic acid, specifically caustic soda or sodium formate, or ,
Mixtures of caustic soda and other basic compounds such as sodium formate are suitable.

These basic compounds are preferably added to the above-mentioned organic solution in the form of powder or granules, but they may be added in the form of solution or suspension. The amount of the basic compound used varies depending on the amount of the organic phosphorus compound contained in the organic solution, but is 0.1 equivalent or more, preferably 0.1 to 20 with respect to the phosphorus atom contained.
It is preferable to add an equivalent amount, more preferably 0.3 to 10 equivalent amounts.

If the amount is less than 0.1 equivalent, the effect is not sufficient, and even if added in a large excess to the reaction, the recovery of rhodium levels off and does not improve, and the amount of ash after combustion increases, which is not preferable. Because. Further, the basic compound is usually added to the organic solution before combustion, but it is also possible to add the basic compound during combustion and before cleaning after combustion. When the combustion is performed by spray combustion, the solution or suspension of the basic compound may be sprayed during spraying of the organic solution and spray-burned in a mixed state.

Thus, the present invention can be applied to recover rhodium from any organic solution containing a rhodium complex having at least one kind of organic phosphorus compound as a ligand and an organic phosphorus compound. However, in particular, the present invention relates to rhodium in a catalyst solution separated from a reaction product by distillation in a hydroformylation or hydrocarboxylation reaction using a homogeneous catalyst containing the rhodium complex and an organophosphorus compound. Can be effectively used when collecting. Further, by adding the basic compound as described above and burning the organic solution, it is possible to recover rhodium in a higher yield.

The ash recovered by burning an organic solution containing a rhodium complex having at least one organic phosphorus compound as a ligand and an organic phosphorus compound contains soluble impurities such as phosphoric acid or phosphate. Since it contains a large amount, it is necessary to remove these impurities. In the present invention, when washing the recovered ash, the elution of rhodium can be suppressed by adding a reducing agent, a basic compound, a coagulant, etc., and rhodium can be efficiently recovered in a high yield. It is a thing. Although the reason cannot be ascertained, it is considered that the additive changes the rhodium complex into a form that is difficult to elute in water.

[0027]

EXAMPLES Next, examples of the present invention will be described. Example 1 1000 g of waste catalyst organic solution containing rhodium-triphenylphosphine-based complex obtained from olefin hydroformylation reaction step, triphenylphosphine, triphenylphosphine oxide and high boiling by-product (475 mg rhodium, 35 phosphorus) 3.1 liters)
It was placed in a SUS304 container (diameter 20 cm, depth 10 cm) and burned with a burner for about 30 minutes. At this time, the evaporation temperature of the organic solution is 200 to 250 ° C., and the ashing temperature is 700 to 250 ° C.
The temperature was controlled to 800 ° C. Furthermore, the container is moved to an electric furnace and 650
The tar-like unburned material was calcined at 4 ° C. for 4 hours. The recovery rate of rhodium at this time was 94 to 95%. next,
Sodium borohydride (SB
H) 0.01, 0.05, 0.1 mol was added to each of the washing solutions, and the polymer flocculant Aron Floc (A-10
1) (trade name, manufactured by Toagosei Kagaku Co., Ltd.) 5 cc of 0.02 wt% aqueous solution was added to adjust each cleaning solution, and ash was added to each cleaning solution for cleaning for about 30 minutes while stirring,
The insoluble residue was filtered off, and then the whole filter paper was fired at 650 ° C. for 4 hours to be incinerated.

The ash before and after washing and rhodium in the washing filtrate were analyzed to determine the rhodium quality and the loss rate of rhodium elution to the washing filtrate. The results are shown in Table 1.

[0029]

[Table 1] Example 2 The reducing agent added to the washing solution was changed to hydrazine hydrate, and the addition amount was 0.01, 0.05, 0.1, 0.5 mol / l.
Rhodium was recovered in the same manner as in Example 1 except for the above, and the rhodium quality and the rhodium elution loss rate to the washing filtrate were obtained. The results are shown in Table 2.

[0030]

[Table 2] Comparative Example 1 Rhodium was recovered in the same manner as in Example 1 except that the reducing agent was not added and the washing was performed.
%), And the elution loss rate (%) to the washing filtrate. As a result, the rhodium quality was 0.60 wt% before cleaning, 8.84 wt% after cleaning, and the rhodium elution loss rate was 14.63.
%Met. Example 3 50 g (0.63 equivalent to P) of sodium formate was added and burned, and the amount of sodium borohydride (SBH) added was 0.001, 0.005, 0.
Rhodium was recovered in the same manner as in Example 1 except that the amounts were changed to 01, 0.05 and 0.1 mol / l.
The rhodium quality (wt%) and the rhodium elution loss rate (%) to the washing filtrate were determined. The results are shown in Table 3.

[0031]

[Table 3] Example 4 The reducing agent used in the ash washing operation was changed to hydrazine hydrate, and the addition amount was 0.005, 0.01, 0.05, 0.
Rhodium was recovered in the same manner as in Example 3 except that the concentration was changed to 0.5 mol / l.
%), And the loss rate (%) of elution of rhodium into the washing filtrate was determined. The results are shown in Table 4.

[0032]

[Table 4] Example 5 The amount of sodium borohydride added was 0.05 in the washing operation.
mol / l, and the cleaning solution was further added with caustic soda to 1.7.
Rhodium was recovered in the same manner as in Example 1 except that 3 mol was added, and the rhodium quality (wt%) and the rhodium elution loss rate (%) to the washing filtrate were determined. The results are shown in Table 5. Example 6 Rhodium was recovered by the same treatment as in Example 5 except that sodium borohydride was changed to hydrazine hydrate in the washing operation, rhodium grade (wt%), and rhodium elution to the washing filtrate. The loss rate (%) was calculated. The results are shown in Table 5.

[0033]

[Table 5] Example 7 An ash obtained by treating in the same manner as in Example 3 except that the amount of sodium borohydride (SBH) added was 0.001 mol / l in the washing operation was further added to sodium borohydride (SBH). A second washing filtration and calcination with a washing liquid prepared by adding 0.001 mol and 5 cc of 0.02 wt% of polymer coagulant Aron floc to 1.0 liter of hot water at 70 ° C. are treated in the same manner as in Example 3 to perform rhodium. Is collected,
The rhodium quality (wt%) and the rhodium elution loss rate (%) to the washing filtrate were determined. The results are shown in Table 6. Example 8 Sodium borohydride (SB
R) was recovered by performing the same treatment as in Example 7 except that the addition amount of H) was changed to 0.005 mol / l, the rhodium grade (wt%), and the rhodium elution loss rate to the washing filtrate. (%) Was calculated. The results are shown in Table 6.

[0034]

[Table 6] Comparative Example 2 Rhodium was recovered in the same manner as in Example 3 except that washing was performed without adding a reducing agent, and rhodium grade (wt
%), And the loss rate (%) of elution of rhodium into the washing filtrate was determined. As a result, the rhodium quality was 0.58 wt before cleaning.
%, After washing, 22.83 wt%, and the elution loss rate of rhodium was 4.21%. Comparative Example 3 Rhodium was recovered in the same manner as in Example 5 except that washing was performed without adding a reducing agent.
%), And the loss rate (%) of elution of rhodium into the washing filtrate was determined. As a result, the rhodium quality was 0.60 wt before cleaning.
%, 8.90 wt% after washing, and the rhodium elution loss rate was 6.45%.

[0035]

INDUSTRIAL APPLICABILITY The present invention uses a specific cleaning liquid in a method for recovering rhodium from an organic solution containing a rhodium complex having at least one organic phosphorus compound as a ligand and an organic phosphorus compound by a combustion method. As a result, it is possible to suppress the elution of rhodium into the washing filtrate and remove the soluble impurities of ash, and it is possible to recover rhodium with high quality and high yield. Is recognized.

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

Claims (6)

[Claims] 1. After burning an organic solution containing a rhodium complex having at least one organic phosphorus compound as a ligand and an organic phosphorus compound, the combustion residue is washed with a washing liquid containing a reducing agent, A method for recovering rhodium, which comprises removing soluble salt impurities other than rhodium. 2. A basic compound is added to an organic solution containing a rhodium complex having at least one kind of organic phosphorus compound as a ligand and an organic phosphorus compound, and the mixture is burned, and then the combustion residue is washed. Claim 1 characterized by the above.
The method for recovering rhodium described. 3. An organic solution containing a rhodium complex having at least one kind of organic phosphorus compound as a ligand and an organic solution containing the organic phosphorus compound are burned, and then a basic compound is added to wash the burning residue. The method for recovering rhodium according to claim 1, wherein 4. The method for recovering rhodium according to claim 1, wherein the cleaning liquid is water or warm water. 5. The method for recovering rhodium according to claim 1, wherein a flocculant is added to the cleaning liquid. 6. The method for recovering rhodium according to claim 1, wherein the washing or the washing and the firing are repeated twice or more.