Extraction solvent control for reducing stable emulsions

Disclosed herein are methods for recovering diphosphite-containing compounds from mixtures comprising organic mononitriles and organic dinitriles, using liquid-liquid extraction. Also disclosed are pre-treatments to enhance extractability of the diphosphite-containing compounds.

FIELD OF THE INVENTION

The invention relates to recovery of catalyst and ligand from a hydrocyanation reaction product mixture comprising organic dinitriles using liquid-liquid extraction.

BACKGROUND OF THE INVENTION

It is well known in the art that complexes of nickel with phosphorous-containing ligands are useful as catalysts in hydrocyanation reactions. Such nickel complexes using monodentate phosphites are known to catalyze hydrocyanation of butadiene to produce a mixture of pentenenitriles. These catalysts are also useful in the subsequent hydrocyanation of pentenenitriles to produce adiponitrile, an important intermediate in the production of nylon. It is further known that bidentate phosphite and phosphinite ligands can be used to form nickel-based catalysts to perform such hydrocyanation reactions.

U.S. Pat. No. 3,773,809 describes a process for the recovery of Ni complexes of organic phosphites from a product fluid containing organic nitriles produced by hydrocyanating an ethylenically unsaturated organic mononitrile such as 3-pentenenitrile through extraction of the product fluid with a paraffin or cycloparaffin hydrocarbon solvent. Similarly, U.S. Pat. No. 6,936,171 to Jackson and McKinney discloses a process for recovering diphosphite-containing compounds from streams containing dinitriles.

U.S. Pat. No. 4,339,395 describes the formation of an interfacial rag layer during extended periods of continuous extraction of certain phosphite ligands. The '395 patent notes that the interfacial rag hinders, if not halts, the phase separation. Because the process is operated continuously, the rag must be removed continuously from the interface as it accumulates to avoid interrupting operation. To solve this problem for the disclosed components, the '395 patent discloses the addition of minor amounts of substantially water-free ammonia.

SUMMARY OF THE INVENTION

This process recovers diphosphite-containing compounds from a mixture comprising diphosphite-containing compounds, organic mononitriles and organic dinitriles.

Disclosed is a process for recovering diphosphite-containing compounds from a feed mixture comprising diphosphite-containing compounds, organic mononitriles, organic dinitriles and a Lewis acid in a multistage countercurrent liquid-liquid extractor with extraction solvent comprising aliphatic hydrocarbon, cycloaliphatic hydrocarbon or a mixture of aliphatic and cycloaliphatic hydrocarbon. The process comprises:

a) flowing the feed mixture to a mixing section of a mixer-settler in the first stage of the multistage countercurrent liquid-liquid extractor;

b) contacting the feed mixture with extraction solvent from the second stage of the multistage countercurrent liquid-liquid extractor in the mixing section of the mixer-settler of the first stage to form a mixed phase comprising a light phase and a heavy phase, wherein the light phase comprises extraction solvent and extracted diphosphite-containing compounds, and wherein the heavy phase comprises organic mononitriles and organic dinitriles;
c) passing the mixture from step (b) to a settling section in the mixer-settler of the first stage, wherein the mixed phase separates into the light phase and the heavy phase; and
d) introducing a Lewis base into the settling section of the first stage,

wherein a complex of Lewis acid and Lewis base is formed in the settling section in the mixer-settler of the first stage, wherein at least a portion of the light phase is withdrawn from the settling section and treated to recover diphosphite-containing compounds extracted into the light phase, wherein at least a portion of the heavy phase is passed to the second stage of the multistage countercurrent liquid-liquid extractor.

The mixing sections of the stages of the multistage counter current liquid-liquid extractor form an intimate mixture of unseparated light and heavy phase. This intimate mixture comprises an emulsion phase. The emulsion phase may or may not comprise particulate solid material. This emulsion phase separates into a light phase and a heavy phase in the settling sections of the stages, including the first stage. Accordingly, the settling sections of the stages will contain at least some emulsion phase located between the upper light phase and the lower heavy phase. This emulsion phase tends to reduce in size over time. However, in some instances settling takes longer than desired or the emulsion phase never fully separates into a light phase and a heavy phase. This separation problem may be particularly troublesome in the first stage of a multistage countercurrent liquid-liquid extractor.

Addition of Lewis base to the settling section of the first stage has been found to result in enhanced settling of the emulsion phase. For example, this addition may result in the reduction of the size of the emulsion phase in the settling section, wherein the size of the emulsion phase is based upon the size of the emulsion phase in the absence of addition of Lewis base. Enhanced settling in the settling section may also be measured as an increased rate of settling, based upon the rate of settling in the absence of addition of Lewis base.

Another problem, which may be solved by addition of Lewis base is formation of rag and build-up of a rag layer the settling section. Rag formation is discussed in U.S. Pat. No. 4,339,395 and U.S. Pat. No. 7,935,229. Rag comprises particulate solid material, and may be considered to be a form of an emulsion phase, which is particularly stable in the sense that it does not dissipate in a practical amount of time for conducting an extraction process. Rag may form in the mixing section or the settling section of an extraction stage, particularly the first stage of a multistage countercurrent liquid-liquid extractor. In the settling section, the rag forms a layer between the heavy phase and the light phase. The formation of a rag layer in the settling section inhibits proper settling of the heavy phase and the light phase. The formation of a rag layer may also inhibit the extraction of diphosphite-containing compounds from the heavy phase into the light phase. In a worst case scenario, rag can build up to extent of completely filling a separation section, necessitating shut down of the extraction process to clean out the settling section. It has been found that addition of Lewis base to the settling section may reduce or eliminate the size of a rag layer or reduce its rate of formation, based upon the size and rate of formation of the rag layer in the absence of addition of Lewis base.

Accordingly, addition of Lewis base to the settling section of the first stage of a multistage countercurrent extractor may achieve at least one of the following results: (a) a reduction in the size of an emulsion phase in the settling section, based upon the size of the emulsion phase in the absence of addition of Lewis base; (b) an increase in the rate of settling in the settling section, based upon the rate of settling in the absence of addition of Lewis base; (c) an increase in the amount of diphosphite-containing compounds in the light phase, based upon the upon the amount of diphosphite-containing compounds in the light phase in the absence of addition of Lewis base; (d) a partial or total reduction in the size of a rag layer in the settling section, based upon the size of a rag layer in the settling section in the absence of addition of Lewis base; and (e) reduction in the rate of formation of a rag layer in the settling section, based upon the rate of formation of a rag layer in the settling section in the absence of addition of Lewis base.

A particular example of a Lewis acid, which may be present in the feed to the extractor, is ZnCl2.

The extraction solvent feed from the second stage of the multistage countercurrent liquid-liquid extractor to the first stage of the multistage countercurrent liquid-liquid extractor may comprise at least 1000 ppm, for example, from 2000 to 5000 ppm, of diphosphite-containing compounds. The extraction solvent feed from the second stage may comprise at least 10 ppm, for example, from 20 to 200 ppm, of nickel.

The diphosphite-containing compound may be a diphosphite ligand selected from the group consisting of:

wherein in I, II and III, R1is phenyl, unsubstituted or substituted with one or more C1to C12alkyl or C1to C12alkoxy groups; or naphthyl, unsubstituted or substituted with one or more C1to C12alkyl or C1to C12alkoxy groups; and wherein Z and Z1are independently selected from the group consisting of structural formulae IV, V, VI, VII, and VIII:

and wherein

X is O, S, or CH(R10);

and wherein

R11and R12are independently selected from the group consisting of H, C1to C12alkyl, and C1to C12alkoxy and CO2R13,

Y is O, S, or CH(R14);

wherein

R15is selected from the group consisting of H, C1to C12alkyl, and C1to C12alkoxy and CO2R16,

and wherein

for structural formulae I through VIII, the C1to C12alkyl, and C1to C12alkoxy groups may be straight chain or branched.

At least a portion of the diphosphite ligand may be complexed with zero valent Ni.

At least one stage of the extraction may be carried out above 40° C.

The Lewis base may be a monodentate triarylphosphite, wherein the aryl groups are unsubstituted or substituted with alkyl groups having 1 to 12 carbon atoms, and wherein the aryl groups may be interconnected.

The Lewis base may optionally be selected from the group consisting of:

If the Lewis base is a polyamine, the polyamine may comprise at least one selected from hexamethylene diamine, and dimers and trimers of hexamethylene diamine, for example, bis-hexamethylene triamine.

The Lewis base may optionally comprise a basic ion exchange resin, for example, Amberlyst 21® resin.

One example of a suitable cyclic alkane extraction solvent is cyclohexane.

The feed mixture may be an effluent stream from a hydrocyanation process, for example, a process for hydrocyanating 3-pentenenitrile, a process for the single hydrocyanation of 1,3-butadiene to pentenenitriles or a process for the double hydrocyanation of 1,3-butadiene to adiponitrile.

DETAILED DESCRIPTION OF THE INVENTION

The processes of the present invention involve methods for recovering diphosphite-containing compounds from a mixture comprising diphosphite-containing compounds and organic dinitriles, using liquid-liquid extraction.

FIG. 1is a diagram of a multistage countercurrent liquid-liquid extractor. Lines inFIG. 1represent flow of materials, rather than any particular type of equipment, such as pipes. Similarly, squares in this diagram represent stages or sections for mixing and settling, rather than any particular type of equipment.

Three stages are depicted inFIG. 1. The first stage is depicted by mixing and settling section1. The second stage is depicted by mixing and settling section2. The final stage is depicted by mixing and settling section3. Gap30represents a space where additional stages may be inserted. For example, one or more, for example, from one to four, mixing and settling sections may be inserted in gap30between mixing and settling section2and mixing and settling section3.

InFIG. 1, a fresh extraction solvent feed, for example, cyclohexane, is introduced into the multistage countercurrent extractor via line10. The extraction solvent or light phase exiting from mixing settling section3passes through line12to the next stage of the multistage extractor. In a multistage countercurrent liquid-liquid extractor having three stages, extraction solvent in line12would pass directly into stage2via line14. Extraction solvent from stage2passes through line16to stage1. The extraction solvent comprising extracted diphosphite-containing compounds passes out of the stage1mixing and settling section through line18.

A feed comprising diphosphite-containing compounds is fed into the stage1mixer and settler via line20. The feed further comprises a mixture comprising organic mononitriles and dinitriles, which is immiscible with the extraction solvent. The feed further comprises a Lewis acid. In stage1, a portion of the diphosphite-containing compounds is extracted into the extraction solvent which exits stage1via line18. The immiscible dinitrile and mononitrile mixture or the heavy phase is removed from the stage1mixing and settling section by line22and is passed into the stage2mixing and settling section. A portion of the diphosphite-containing compounds is extracted into the light phase in the stage2mixing and settling section. The heavy phase exits the stage2mixing and settling section by line24. Similarly, if there are additional stages in gap30shown inFIG. 1, extraction of diphosphite-containing compounds will take place in such intermediate stages in a similar manner to that taking place in stage2.

After the heavy phase passes through the first stage and any intermediate stages, it passes through the final stage mixing and settling section3. In particular, the heavy phase is introduced into mixing and setting section3through line26. After passing through the final stage mixing and settling section3, the heavy phase exits via line28.

A two-stage multistage countercurrent liquid-liquid extractor is represented inFIG. 1by mixing and settling sections1and2; lines14,16and18showing the direction of extraction solvent flow; and lines20,22and24showing the direction of heavy phase flow. In a two-stage multistage counter current liquid-liquid extractor, mixing and settling section3; lines10,12,26and28; and gap30are omitted. In the two stage countercurrent liquid-liquid extractor, extraction solvent comprising extracted diphospite-containing compounds passes from the extractor through line18, and extracted heavy phase, i.e. raffinate, passes from the extractor through line24.

Thus, it can be seen that the multistage countercurrent liquid-liquid extractor comprises two or more stages with countercurrent flow of extraction solvent and heavy phase. In view of the direction of flow of light and heavy phase through the stages of extraction, it will be appreciated that the concentration of solute, e.g., diphosphite-containing compound, is highest in both the light and heavy phases of the first stage and lowest in the light and heavy phases of the final stage.

FIG. 2is a diagrammatic representation of one type of a mixing and settling section, also referred to herein as a mixer-settler. This type of mixer-settler may be used in any of the stages shown inFIG. 1. This mixer-settler comprises a mixing section40and a settling section50. The mixing section40and the settling section50are separate. All of the effluent from the mixing section40flows into the settling section50. Fluid from the mixing section40flows through the settling section50in a in a horizontal manner, although there is also no restriction of movement of fluids vertically throughout the settling section50.

An extraction solvent is introduced into the mixing section40by line42. A feed comprising diphosphite-containing compounds is introduced into the mixing section40by line44. Alternatively, the contents of lines42and44may be combined upstream of the mixing section40and introduced into mixing section40through a single inlet. These two feeds are mixed in the mixing section40to provide a mixed phase comprising an emulsion phase represented inFIG. 2by shaded area46.

Line48represents the flow of mixed phase46from the mixing section40into the settling section50. As depicted inFIG. 2, there are three phases in the settling section50, including a heavy phase52, a mixed phase54, and a light phase56. The heavy phase52is depleted in diphosphite-containing compounds, insofar as it has a lower concentration of diphosphite-containing compounds as compared with the concentration of diphosphite-containing compounds in feed44, due to the extraction of diphosphite-containing compounds into the light phase56. Correspondingly, the light phase56is enriched in diphosphite-containing compounds, insofar as it has a higher concentration of diphosphite-containing compounds as compared with the concentration of diphosphite-containing compounds in extraction solvent feed42, due to the extraction of diphosphite-containing compounds into the light phase56. At least a portion of the heavy phase52exits the settling section50via line60. At least a portion of the light phase56is removed from the settling section50via line58.

Although not shown inFIG. 2, which is diagrammatically shows the flow of fluids, it will be understood that each of the mixing section40and the settling section50may comprise one or more stages, subsections, compartments or chambers. For example, settling section50may include more than one chamber between the point of introduction of the mixed phase46through line48and the point of withdrawal of light phase and heavy phase through lines58and60. Horizontal extension between the point of introduction of the mixed phase46through line48and the point of withdrawal of light and heavy phases through lines58and60promotes settling of the light and heavy phases56and52. The size of the mixed phase54may become progressively smaller as fluids settle and flow through the chamber. For example, the final chamber from where fluids are removed may include little or no mixed phase54. It will further be understood that mixing section40may include one or more types of mixing apparatus, such as an impeller, not shown inFIG. 2.

FIG. 3provides a representation of a mixer-settler100having a multistage settling section. Mixer-settler100has a mixing section110and a settling section112. In mixer-settler100, the mixing section110is separate from the settling section112. The settling section has three compartments, represented inFIG. 3as sections114,116, and118. These sections are separated by coalescence plates120. The coalescence plates120may be designed to provide flow of separated light and heavy phases between chambers, while restricting the flow of emulsion phase between chambers. A feed comprising a diphosphite-containing compound is passed into the mixing section110via line130. The extraction solvent is introduced into mixing section110via line132. The mixing section110includes an impeller134mounted on shaft136to provide for mechanical mixing of fluids. Mixing of the feeds provides a mixed phase comprising an emulsion phase represented inFIG. 3by shading140.

The mixed phase140flows into the settling section112as an overflow from the mixing section110. This mixed phase140is prevented from flowing directly into the light phase144by baffle plate142. As settling occurs in settling section112, the volume of the mixed phase140decreases, the volume of the light phase144increases, and the volume of the heavy phase146increases. Heavy phase146is removed from settling section112, in particular from chamber118, via line152and light phase144is removed from settling section112, in particular, from chamber118, via line150.

It is desirable for both a mononitrile and a dinitrile to be present in the countercurrent contactor. For a discussion of the role of monodentate and bidentate ligand in extraction of hydrocyanation reactor effluent streams, see U.S. Pat. No. 3,773,809 to Walter and U.S. Pat. No. 6,936,171 to Jackson and McKinney.

For the process disclosed herein, suitable molar ratios of mononitrile to dinitrile components include 0.01 to 2.5, for example, 0.01 to 1.5, for example 0.65 to 1.5.

Maximum temperature is limited by the volatility of the hydrocarbon solvent utilized, but recovery generally improves as the temperature is increased. Examples of suitable operating ranges are 40° C. to 100° C. and 50° C. to 80° C.

The controlled addition of monophosphite ligands may enhance settling. Examples of monophosphite ligands that may be useful as additives include those disclosed in Drinkard et al U.S. Pat. No. 3,496,215, U.S. Pat. No. 3,496,217, U.S. Pat. No. 3,496,218, U.S. Pat. No. 5,543,536, and published PCT Application WO 01/36429 (BASF).

As disclosed herein, the addition of Lewis base compounds to a mixture comprising diphosphite-containing compounds, organic mononitriles and organic dinitriles enhances settling, especially when the mixture comprises a Lewis acid, such as ZnCl2. Examples of suitable weak Lewis base compounds include water and alcohols. Suitable stronger Lewis base compounds include hexamethylene diamine, dimers and trimers of hexamethylene diamine, ammonia, aryl- or alkyl amines, such as pyridine or triethylamine, or basic resins such as Amberlyst 21®, a commercially available basic resin made by Rohm and Haas. The addition of Lewis base may reduce or eliminate any inhibiting effect of Lewis acid on catalyst recovery.

The reaction product of Lewis acid with Lewis base may become entrailed in the raffinate phase as it moves through the multistage countercurrent liquid-liquid extractor. In particular, this product may form a precipitate in the raffinate phase in the form of a complex of Lewis acid with Lewis base. However, this precipitate may exist as a dispersion of fine particles distributed throughout the raffinate phase. This precipitate may be removed by conventional techniques, such as filtration, centrifugation or distillation accompanied by removal of bottoms containing the precipitate, after the raffinate is removed from the last stage of the multistage countercurrent liquid-liquid extractor.

The diphosphite-containing compounds extracted by the processes described herein comprise bidentate phosphorus-containing ligands. These extracted ligands comprise free ligands (e.g., those which are not complexed to a metal, such as nickel) and those which are complexed to a metal, such as nickel. Accordingly, it will be understood that extraction processes described herein are useful for recovering diphosphite-containing compounds which are metal/ligand complexes, such as a complex of zero valent nickel with at least one ligand comprising a bidentate-phosphorus containing ligand.

Suitable ligands for extraction are bidentate phosphorous-containing ligands selected from the group consisting of bidentate phosphites, and bidentate phosphinites. Preferred ligands are bidentate phosphite ligands.

Examples of bidentate phosphite ligands useful in the invention include those having the following structural formulae:

and
wherein in I, II and III, R1is phenyl, unsubstituted or substituted with one or more C1to C12alkyl or C1to C12alkoxy groups; or naphthyl, unsubstituted or substituted with one or more C1to C12alkyl or C1to C12alkoxy groups; and Z and Z1are independently selected from the group consisting of structural formulae IV, V, VI, VII, and VIII:

and wherein

X is O, S, or CH(R10);

and wherein

R11and R12are independently selected from the group consisting of H, C1to C12alkyl, and C1to C12alkoxy; and CO2R13,

Y is O, S, or CH(R14);

wherein

R15is selected from the group consisting of H, C1to C12alkyl, and C1to C12alkoxy and CO2R16;

In the structural formulae I through VIII, the C1to C12alkyl, and C1to C12alkoxy groups may be straight chain or branched.

Another example of a formula of a bidentate phosphite ligand that is useful in the present process is that having the Formula X, shown below

Further examples of bidentate phosphite ligands that are useful in the present process include those having the Formulae XI to XIV, shown below wherein for each formula, R17is selected from the group consisting of methyl, ethyl or isopropyl, and R18and R19are independently selected from H or methyl:

Additional examples of bidentate phosphite ligands that are useful in the present process include a ligand selected from a member of the group represented by Formulae XV and XVI, in which all like reference characters have the same meaning, except as further explicitly limited:

wherein

R41and R45are independently selected from the group consisting of C1to C5hydrocarbyl, and each of R42, R43, R44, R46, R47and R48is independently selected from the group consisting of H and C1to C4hydrocarbyl.

For example, the bidentate phosphite ligand can be selected from a member of the group represented by Formula XV and Formula XVI, wherein

R42is H or methyl;

R43is H or a C1to C4hydrocarbyl;

R44is H or methyl;

R46, R47and R48are independently selected from the group consisting of H and C1to C4hydrocarbyl.

As additional examples, the bidentate phosphite ligand can be selected from a member of the group represented by Formula XV, wherein

R44is H or methyl;

R46and R48are H or methyl; and

or the bidentate phosphite ligand can be selected from a member of the group represented by Formula XVI, wherein

R45is methyl or isopropyl; and

It will be recognized that Formulae X to XVI are two-dimensional representations of three-dimensional molecules and that rotation about chemical bonds can occur in the molecules to give configurations differing from those shown. For example, rotation about the carbon-carbon bond between the 2- and 2′-positions of the biphenyl, octahydrobinaphthyl, and or binaphthyl bridging groups of Formulae X to XVI, respectively, can bring the two phosphorus atoms of each Formula in closer proximity to one another and can allow the phosphite ligand to bind to nickel in a bidentate fashion. The term “bidentate” is well known in the art and means both phosphorus atoms of the ligand are bonded to a single nickel atom.

Further examples of bidentate phosphite ligands that are useful in the present process include those having the formulae XX to LIII, shown below wherein for each formula, R17is selected from the group consisting of methyl, ethyl or isopropyl, and R18and R19are independently selected from H or methyl:

Additional suitable bidentate phosphites are of the type disclosed in U.S. Pat. Nos. 5,512,695; 5,512,696; 5,663,369; 5,688,986; 5,723,641; 5,847,101; 5,959,135; 6,120,700; 6,171,996; 6,171,997; 6,399,534; the disclosures of which are incorporated herein by reference. Suitable bidentate phosphinites are of the type disclosed in U.S. Pat. Nos. 5,523,453 and 5,693,843, the disclosures of which are incorporated herein by reference.

Extraction Solvent

Suitable hydrocarbon extraction solvents include paraffins and cycloparaffins (aliphatic and alicyclic hydrocarbons) having a boiling point in the range of about 30° C. to about 135° C., including n-pentane, n-hexane, n-heptane and n-octane, as well as the corresponding branched chain paraffinic hydrocarbons having a boiling point within the range specified. Useful alicyclic hydrocarbons include cyclopentane, cyclohexane and cycloheptane, as well as alkyl substituted alicyclic hydrocarbons having a boiling point within the specified range. Mixtures of hydrocarbons may also be used, such as, for example, mixtures of the hydrocarbons noted above or commercial heptane which contains a number of hydrocarbons in addition to n-heptane. Cyclohexane is the preferred extraction solvent.

The lighter (hydrocarbon) phase recovered from the multistage countercurrent liquid-liquid extractor is directed to suitable equipment to recover catalyst, reactants, etc. for recycle to the hydrocyanation, while the heavier (lower) phase containing dinitriles recovered from the multistage countercurrent liquid-liquid extractor is directed to product recovery after removal of any solids, which may accumulate in the heavier phase. These solids may contain valuable components which may also be recovered, e.g., by the process set forth in U.S. Pat. No. 4,082,811.

EXAMPLES

In the following examples, values for extraction coefficient are the ratio of weight fraction of catalyst in the extract phase (hydrocarbon phase) versus the weight fraction of catalyst in the raffinate phase (organonitrile phase). An increase in extraction coefficient results in greater efficiency in recovering catalyst. As used herein, the terms, light phase, extract phase and hydrocarbon phase, are synonymous. Also, as used herein, the terms, heavy phase, organonitrile phase and raffinate phase, are synonymous.

Analysis of the extract and the raffinate streams of the catalyst extraction was conducted on an Agilent 1100 series HPLC and via ICP. The HPLC was used to determine the extraction efficiency of the process.

To a 50 mL, jacketed, glass laboratory extractor, equipped with a magnetic stirbar, digital stir-plate, and maintained at 65° C., was charged 10 grams of the product of a pentenenitrile-hydrocyanation reaction, and 10 grams of the extract from the second stage of a mixer-settler cascade, operated in counter-current flow. The extract from the second stage contained approximately 50 ppm nickel and 3100 ppm diphosphite ligand. No additives were present.

The reactor product was approximately:

85% by weight C6dinitriles

14% by weight C5mononitriles

1% by weight catalyst components

420 ppm by weight active nickel

566 ppm by weight zinc.

The laboratory reactor was then mixed at 1160 rotations-per-minute, for 20 minutes, and then allowed to settle for 15 minutes. After settling for 15 minutes, a stable emulsion was present throughout the extract phase. Samples were obtained of the extract and raffinate phases of the extractor and analyzed to determine the extent of catalyst extraction. The ratio of active nickel present in the extract phase vs. the raffinate phase was found to be 14. The concentration of zinc in the raffinate was 566 ppm.

Example 1 was repeated except that 500 ppm of polyethylenimine (PEI) was added to the system. The polyethylenimine (PEI) was end-capped with ethylenediamine and had an average Mn˜600.

Example 1 was repeated except that 1000 ppm of polyethylenimine (PEI) was added to the system. The polyethylenimine (PEI) was end-capped with ethylenediamine and had an average Mn˜600.

Example 1 was repeated except that 500 ppm of polyethylenimine, aqueous solution (PEI/H2O) was added to the system. The polyethylenimine, aqueous solution was a polyethylenimine solution in water having a PEI/H2O ratio of 1:1. The polyethyleneimine had an average Mn˜1200.

Example 1 was repeated except that 1000 ppm of polyethylenimine, aqueous solution (PEI/H2O) was added to the system. The polyethylenimine, aqueous solution was a polyethylenimine solution in water having a PEI/H2O ratio of 1:1. The polyethyleneimine had an average Mn˜1200.

Example 1 was repeated except that 1000 ppm of polyacrylate, sodium was added to the system. The polyacrylate, sodium was poly(acrylic acid) sodium salt with an average Mw˜2100.

Example 1 was repeated except that 3000 ppm of polyacrylate, sodium was added to the system. The polyacrylate, sodium was poly(acrylic acid) sodium salt with an average Mw˜2100.

Example 1 was repeated except that 500 ppm of a surfactant was added to the system. The surfactant was an aqueous solution of mixture of an alkyldimethylamide, an alkylethersulfate, and an alkylphosphateester.

Example 1 was repeated except that 1000 ppm of a surfactant was added to the system. The surfactant was an aqueous solution of mixture of an alkyldimethylamide, an alkylethersulfate, and an alkylphosphateester.

Example 1 was repeated except that 250 ppm of hexamethylene diamine (HMD) was added to the system.

Example 1 was repeated except that 500 ppm of 250 ppm of hexamethylene diamine (HMD) was added to the system.

Example 1 was repeated except that 1000 ppm of 250 ppm of hexamethylene diamine (HMD) was added to the system.

Results of Examples 1-12 are summarized in Table 1. The data summarized in Table 1 represent evaluations of a number of additives for prevention of formation of stable emulsions and rags during catalyst extraction. Example 1 is a control experiment, which shows that in the absence of any additive a stable emulsion is formed. Examples 2-3 show that PEI is ineffective for preventing formation of a stable emulsion under these conditions. Example 4 shows that 1:1 polyethylenimine in water is ineffective for preventing stable emulsion formation at 500 ppm. By way of contrast, Example 5 shows that PEI/H2O is effective at 1000 ppm for preventing stable emulsion formation. Examples 6-7 show that polyacrylate, sodium salt, is not effective at 1000 ppm, but is at 3000 ppm loading. Examples 8-9 show that the surfactant solution is not effective under any of the conditions evaluated for prevention of a stable emulsion. Examples 10-12 show that hexamethylene diamine is effective under these conditions for prevention of formation of a stable emulsion during catalyst extraction over the range of concentrations from 250-1000 ppm.

TABLE 1Effectiveness of additives for prevention of stable emulsionformation during catalyst extractionConcentrationStableExampleAdditive(ppm)emulsion1None0Yes2PEI500Yes3PEI1000Yes4PEI/H2O (1:1)500Yes5PEI/H2O (1:1)1000No6Polyacrylate, sodium1000Yes7Polyacrylate, sodium3000No8Surfactant500Yes9Surfactant1000Yes10HMD250No11HMD500No12HMD1000NoA “No” in the column labeled Stable emulsion indicates that the additive was effective under the conditions tested for preventing the formation of a stable emulsion.

These Examples 13-17 illustrate that effective catalyst recovery occurs for a mononitrile to dinitrile ratio greater than 0.65.

Five different mixtures comprised of a Ni diphosphite complex, with the diphosphite ligand shown in Structure XX (where R17is isopropyl, R18is H, and R19is methyl), ZnCl2(equimolar with Ni) and differing in the ratio of mononitrile to dinitrile, were separately liquid-liquid batch extracted with an equal weight of cyane (i.e. cyclohexane). The molar ratio of organic mononitrile to organic dinitrile and the resulting extraction coefficients are shown in the Table 2 below. A compound may be effectively recovered if it has an extraction coefficient of 1 or greater at solvent to feed ratios greater than 1 using a countercurrent multistage extractor.

TABLE 2Catalyst and ligand extraction coefficients for varying ratios ofmononitriles-to-dinitrilesCatalyst extractionLigand extractionExamplemononitrile/dinitrilecoefficientcoefficient132.331.284.09141.851.338.08151.192.0216.97160.912.6335.99170.574.8249.59

This Example demonstrates the effect of hold-up time on the extractability of the diphosphite ligand catalyst.

A mixture comprised predominantly of organic dinitriles and a Ni diphosphite complex, the structure of the diphosphite ligand being shown in Structure XX (where R17is isopropyl, R18is H, and R19is methyl) and ZnCl2(equimolar with Ni) was divided into two portions. Both portions are liquid-liquid extracted in a three-stage contactor at 40° C., with an equal weight of cyclohexane. Both portions were sampled with time and the progress of the catalyst recovery into the extract phase is shown in Table 3 as the percent of the final steady state value achieved at a given time.

TABLE 3Concentration of Diphosphite ligand with time inthe extracting solvent phase.Time,% of steady stateminutesconcentration at 40° C.212419834145230786010091100

This Example illustrates the effect of temperature on the extractability of catalyst with first-stage extraction solvent recycle.

A mixture comprised predominantly of organic dinitriles and a Ni diphosphite complex, the structure of the diphosphite ligand being shown in Structure XXIV (where R17is methyl, R18is methyl and R19is H) and ZnCl2(equimolar with Ni) was divided into three portions. The portions were batch liquid-liquid extracted at 50° C., 65° C. and 80° C., respectively, with an equal weight of n-octane and monitored with time. The results are shown in Table 4.

TABLE 4% of steady state% of steady state at% of steady state atTimeat 50° C.65° C.80° C.20.00.01.840.00.01.680.00.03.6140.00.04.3200.00.03.6300.00.07.6600.01.616.3900.74.048.6

This Example demonstrates the effect of adding water in three-stage extraction with cyclohexane recycle in the first stage.

Fifteen grams of a mixture comprised predominantly of organic dinitriles and a Ni diphosphite complex, the structure of the diphosphite ligand being shown in Structure XXIV (where R17is methyl, R18is methyl and R19is H) and ZnCl2(equimolar with Ni), was extracted in a three-stage continuous extractor at a temperature of 50° C. with an equal weight of cyclohexane for one hour resulting in an catalyst extraction coefficient of 4.3, as measured by the amount of catalyst in the extract of the first stage divided by the amount of catalyst in the feed of the reaction mixture fed to the last stage of the three-stage countercurrent extractor.

To this mixture, 100 microliters of water was added. After continuing to heat and agitate for another hour, the diphosphite Ni extraction coefficient was measured as 13.4—a threefold increase.

Examples 21 and 22

These Examples demonstrate the effect of adding hexamethylene diamine (HMD) to the extraction zone.

Example 1 was repeated except that hexamethylene diamine was added to the product of a pentene-hydrocyanation reaction. In Example 21, 250 ppm of HMD was added, and in Example 22, 500 ppm of HMD was added. To a 50 mL, jacketed, glass laboratory extractor, equipped with a magnetic stirbar, digital stir-plate, and maintained at 65° C., was charged 10 grams of the product of pentene-hydrocyanation reactor product, and 10 grams of the extract from the second stage of a mixer-settler cascade, operated in counter-current flow.

The reactor product was approximately:

85% by weight C6dinitriles

14% by weight C5mononitriles

1% by weight catalyst components

360 ppm by weight active nickel.

The laboratory reactor was then mixed at 1160 rotations-per-minute, for 20 minutes, and then allowed to settle for 15 minutes. A stable emulsion was present throughout the extract phase in the absence of the addition of HMD. After 15 minutes of settling, essentially no emulsion phase was present when HMD was added. Samples were obtained of the extract and raffinate phases of the extractor and analyzed to determine the extent of catalyst extraction.