CN1344240A - Method for extracting catalyst in solution form in the production of adipic acid - Google Patents

Abstract

The present invention relates to a process for extracting a metal catalyst in solution from a reaction mixture prepared by oxidizing cyclohexane to adipic acid in the presence of acetic acid and a metal catalyst. According to the invention, substantially all of the cyclohexane can be removed, as well as a major portion of the adipic acid. A major portion of the acetic acid may also be removed without precipitating the catalyst, thereby forming a solution concentrate. In a preferred embodiment of the invention, the concentrate enters a counter-current flow of counter-current water and cyclohexanone, resulting in an aqueous solution of metal catalyst as an extract and a concentrate solution phase dissolved in cyclohexanone as a raffinate. The two solutions may be further treated and/or recycled.

Description

Method for extracting catalyst in solution form in the production of adipic acid

technical field

The present invention relates to a process for the oxidation of cyclohexane to adipic acid, and more specifically, the present invention relates to how to continuously extract the catalyst in solution, preferably for recycling.

Background technique

There are numerous references (patents and articles) to the formation of acids, the most important being adipic acid formed by oxidation of hydrocarbons. Adipic acid is used in the production of nylon 66 fibers and resins, polyesters, polyurethanes, and various other compounds.

There are different methods of producing adipic acid. The usual method involves first oxidation of cyclohexane with oxygen to a mixture of cyclohexanone and cyclohexanol (KA mixture), followed by oxidation of the KA mixture with nitric acid to adipic acid. Other methods include the "hydroperoxide method," the "boronic acid method," and the "direct synthesis method," which involves the direct oxidation of cyclohexane to adipic acid with oxygen in the presence of solvents, catalysts, and cocatalysts.

Direct synthesis has been in the spotlight for a long time. However, there has been little commercial success to date. One reason for this is that, despite its apparent simplicity, it is actually extremely complex. Due to this complexity, one can find very contradictory results, statements and opinions in different references.

It is well known that after the reaction according to the direct synthesis method, a mixture of two liquid phases exists at room temperature, and a solid phase mainly composed of adipic acid. The two liquid phases are called "polar phase" and "non-polar phase". Yet little attention has been paid to the importance of these two phases, other than to separate the adipic acid from the "polar phase" and to recycle these phases back to the reactor in part or in whole, with or without further treatment middle.

It is also worth noting that most studies on direct syntheses were performed in a batch fashion, literally or purely for practical purposes.

As mentioned above, there is a great deal of literature on the oxidation of organic compounds such as adipic acid and/or intermediates such as cyclohexanone, cyclohexanol and cyclohexyl hydroperoxide to produce acids.

With regard to the preparation of dibasic acids and other intermediate oxidation products, the following references may be considered representative of oxidation processes.

US Patent 5463119 (Kollar); US Patent 5374767 (Drinkard et al); US Patent 5321157 (Kollar); US Patent 3987100 (Barnette et al); US Patent 3957876 (Rapoport et al); U.S. Patent 3,515,751 (Oberster et al.); U.S. Patent 3,361,806 (Lidov et al); U.S. Patent 3,234,271 (Barker, etc.); U.S. Patent 3,231,608 (Kollar); Hamblet et al); US Patent 2,439,513 (Hamblet et al); US Patent 2,223,494 (Loder et al); US Patent 2,223,493 (Loder et al).

German Patent DE 4426132 A1 (Kysela et al.) discloses a process for the dehydration of acetic acid from the liquid phase oxidation of cyclohexane with air by separating adipic acid after filtration in the presence of cobalt salts as catalysts Carried out afterwards, while preventing the precipitation of cobalt salts in the dehydration column, characterized in that, under the condition of distilling off water to a residual content of less than [sic] 0.3-0.7%, by using added cyclohexane, it is necessary to return to the process starting point The acetic acid phase at the starting point was subjected to azeotropic distillation.

PCT international application WO 96/03365 (Costantini etc.) and U.S. Patent 5,756,837 (Costantini etc.) disclose a kind of in the reaction that cyclohexane directly oxidizes to adipic acid, reclaim the method for cobalt-containing catalyst, it is characterized in that comprising A step wherein the reaction mixture resulting from oxidation to adipic acid is treated by extracting at least a portion of the glutaric and succinic acids formed during the reaction.

None of the above references, or any other references known to the present inventors, alone or in combination, disclose or suggest controlling oxidation reactions subject to the complex and critical controls and requirements of the present invention as described and claimed below.

Summary of the invention

As stated above, the present invention relates to a process for the oxidation of hydrocarbons, such as cyclohexane, to their respective intermediate oxidation products, such as adipic acid, and more particularly, the present invention relates to how to continuously extract the catalyst in solution, preferably for recycle. More specifically, the present invention relates to a method for extracting a metal catalyst in solution from a reaction mixture prepared by oxidation of cyclohexane to adipic acid in the presence of acetic acid and a metal catalyst, the method Include the following steps:

(a) removing substantially all of the cyclohexane;

(b) removing a substantial portion of adipic acid;

(c) removing a major portion (up to substantially 100%) of the acetic acid, but being careful not to remove the acetic acid beyond the point at which the catalyst begins to precipitate, thereby forming a solution concentrate;

(d) introducing said concentrate into the middle zone of a countercurrent stream, the countercurrent stream also having a bottom zone and an upper zone, the bottom zone having a bottom end and the upper zone having a top end;

(e) introducing cyclohexanone, which may contain a small amount of water, into the bottom region of said countercurrent stream;

(f) introducing water, which may contain a small amount of cyclohexanone, into the upper region of the countercurrent stream;

(g) withdrawing from the top of the upper zone a first liquid or raffinate containing a major fraction of concentrate other than catalyst; and

(h) removing a second liquid or extract from the bottom end of the bottom region, the second liquid containing a substantial portion of the metal catalyst.

Preferably the metal catalyst is a cobalt-containing compound. Metal catalysts are essentially the metal itself, preferably in ionic form, regardless of the compound or moiety with which it is associated. Thus, a metal may be associated with one moiety in step (a) and with a different moiety in step (h); for example, it may be predominantly cobalt acetate in step (a) and in In step (h) it may be primarily cobalt adipate, or cobalt glutarate or cobalt succinate, or any mixture thereof.

Cyclohexane may be removed before, during, or after adipic acid removal, or before and after adipic acid removal. Before or after refers to an earlier or later stage of the process, while in process refers to being at the same stage. For example, cyclohexane can be removed by lowering the temperature and allowing the formation of two distinct liquid phases, the non-polar phase containing a major portion of cyclohexane and the polar phase containing a major portion of acetic acid, adipic acid and other polar moieties , followed by removal of the non-polar phase by decantation and crystallization to remove adipic acid. Another alternative is to remove cyclohexane during the flash crystallization of adipic acid. Cyclohexane can also be removed by distillation.

It is particularly preferred that steps (d), (e), (f), (g) and (h) are carried out simultaneously. Furthermore, step (c) is preferably carried out by distillation. A small amount of water may be added continuously or intermittently in step (c).

It is also particularly preferred that substantially all of the acetic acid is removed in step (c) and substantially all of the metal catalyst is removed in step (h).

Where substantially complete removal of the catalyst is desired, it is absolutely important to maintain a sufficiently high temperature in the portion of the countercurrent stream, such as the head portion of the countercurrent stream where only a small amount of catalyst is present, in order to reduce or eliminate the tendency for emulsification.

The temperature of the top, middle and bottom sections may be substantially the same; the preferred temperature range is 50-80°C.

More preferably, however, the temperature of the top is higher than the temperature of the middle part, and the temperature of the middle part is higher than the temperature of the bottom. Still more preferably, the temperature range of the top is 50-90°C, the temperature range of the middle part is 30-50°C, and the temperature range of the bottom is 10-40°C.

The present invention also relates to a method for extracting a metal catalyst in solution from a reaction mixture prepared by oxidizing cyclohexane to adipic acid in the presence of acetic acid and a metal catalyst, the method comprising Follow the steps below:

(k) removing substantially all of the cyclohexane;

(l) removing a major portion of adipic acid;

(m) removing a substantial portion of the acetic acid without precipitating the catalyst, thereby forming a solution concentrate;

(n) introducing said concentrate into an intermediate stage of a countercurrent multistage apparatus comprising an intermediate mixing zone and an intermediate separation zone, said countercurrent multistage apparatus also comprising a front stage and a rear stage, The front stage includes a front mixing zone and a front separation zone, and the rear stage includes a rear mixing zone and a rear separation zone;

(p) introducing cyclohexanone, which may contain a small amount of water, into said front mixing zone;

(q) introducing water, which may contain a small amount of cyclohexanone, into the rear mixing zone;

(r) withdrawing a raffinate from the rear separation zone, the raffinate containing a major fraction of concentrate other than catalyst; and

(s) An extract is taken from the front separation zone, the extract containing a major part of the metal catalyst.

Preferably step (m) is carried out by distillation, in which case the process may further comprise the step of adding water in step (m).

At least in said rear separation zone, separation can be at least partly performed by a centrifugation step.

In one embodiment of the invention, the rear stage has a rear stage temperature, the middle stage has a middle stage temperature, and the front stage has a front stage temperature; the rear stage temperature, the middle stage temperature and the front stage temperature Basically the same. Preferably, the substantially identical temperature range is 50-80°C.

In a different embodiment, the temperature of the latter stage is higher than the temperature of the middle stage, and the temperature of the middle stage is higher than the temperature of the front stage. Preferably, the temperature range of the rear stage is 50-90°C, the temperature range of the middle stage is 30-50°C, and the temperature range of the front stage is 10-40°C.

According to the present invention, it is preferred that substantially all of the acetic acid is removed in step (m). It is also preferred that substantially all of the metal catalyst is removed in step (s).

As mentioned above, the metal catalyst is preferably a cobalt-containing compound. Metal catalysts are essentially the metal itself, preferably in ionic form, regardless of the compound or moiety with which it is associated. Thus, a metal may be associated with one moiety in step (k) and a different moiety in step (s); for example, it may be predominantly cobalt acetate in step (k) and in step (s) In step (s) it may be essentially cobalt adipate, or cobalt glutarate or cobalt succinate, or any mixture thereof.

Particular preference is given to carrying out steps (n), (p), (q), (r) and (s) simultaneously. Furthermore step (m) is preferably carried out by distillation. A small amount of water may be added continuously or intermittently in step (m) to maintain the solubility of the metal catalyst.

The method of the present invention may further comprise the step of reacting the prepared adipic acid in some way with a reactant selected from polyols, polyamines and polyamides to form polyesters, or polyamides, or (polyimide and/or polyamideimide) polymers that can be further spun into fibers or mixed with fillers and/or other additives to form composites.

"Majority" and a portion referring to a "substantial portion" means more than 50%, and up to substantially 100%, by weight of said portion.

"Minor amount" and moieties referring to "minor portion" means less than 50%, and down to 0%, by weight of said moiety.

By "upper phase" is meant a "relatively less polar cyclohexane phase containing a small amount of catalyst", while by "lower phase" is meant a "relatively more polar aqueous phase containing predominantly catalyst". For the sake of simplicity, this description applies not only to the case where the separator producing the upper cyclohexanone phase and the lower aqueous phase is a decanter, but also to the case where the separator is a centrifugal separator.

An "intermediate stage" is any stage other than the anterior stage and the posterior stage.

Description of drawings

Understanding of the present invention will be deepened by referring to the following detailed description and accompanying drawings, wherein:

Figure 1 is a block diagram of a preferred embodiment of the invention wherein catalyst extraction is performed in a countercurrent stream.

Figure 2 is a block diagram of another preferred embodiment of the present invention wherein catalyst extraction is performed in a multi-stage extraction unit.

BEST MODE FOR CARRYING OUT THE INVENTION

As stated above, the present invention relates to methods and apparatus for the oxidation of, for example, cyclohexane to adipic acid, and more particularly to how the catalyst can be extracted in solution after the reaction, preferably for recycling.

Proper handling of catalysts in oxidation reactions has been a concern in the field. According to the invention, the catalyst is separated in liquid form dissolved in the aqueous phase and is returned to the reaction chamber, preferably with and without further treatment.

The inventors have found that after oxidation of cyclohexane to adipic acid at the desired conversion, and after removal of the major part of the adipic acid, the remaining cyclohexane as well as water and at least the major acetic acid, the reaction mixture can Before and after addition of critical amounts of cyclohexanone and water, a single-phase liquid state free of solids is obtained or maintained. The catalyst can then be extracted with an additional amount of water, or by temperature reduction, and returned to the reaction chamber, preferably with and without further treatment.

According to the present invention, the catalyst separation process will be greatly improved by using the following process:

Referring now to FIG. 1, illustrated is a catalyst separation unit 10 comprising an evaporator or still 12 connected by a transfer line 16 to an intermediate region 19 of a complex countercurrent extraction column 14. . The complex countercurrent extraction column 14 includes a complex extraction zone 18 . In addition to the middle region 19 , the column 14 also has a bottom region 20 and an upper region 22 . The bottom region 20 has a bottom end 24 and the upper region 22 has a top end 26 . Water line 28 and cyclohexanone line 30 are connected to complex countercurrent extraction column 14 which in turn is connected to catalyst solution line or extract line 32 and concentrate solution line or raffinate line 34 .

Evaporator or still 12 is connected to vapor line 15 , while optional feed line 13 and treated reaction mixture line 11 are connected to evaporator 12 . A heater or heat exchanger 17 is part of the evaporator 12 .

The equipment preceding and following the catalyst separation unit 10 is not shown in Figure 1 as they are described in detail in our patents and applications which are hereby incorporated by reference.

In the operation of this embodiment, the treated reaction mixture from the oxidation of cyclohexane to adipic acid (as described in our patents and pending applications, which are hereby incorporated by reference) is passed through the line 11 into the evaporator or distiller 12. The treated mixture is the mixture remaining after removal of at least a substantial portion of adipic acid from a reaction mixture prepared by oxidation of cyclohexane to adipic acid in the presence of acetic acid and a metal catalyst, preferably a cobalt compound of. The worked up reaction mixture may contain major or minor amounts of unreacted cyclohexane. can be removed by separating the reaction mixture into (i) a polar phase containing a major portion of acetic acid, adipic acid, other polar moieties, and catalyst, and (ii) a non-polar phase containing a major portion of cyclohexane. Cyclohexane. In such a case, the non-polar phase can be recovered, while a major part of the adipic acid can be removed by crystallization from the polar phase. In this case, after removal of adipic acid, the residue constitutes the treated reaction mixture. In a different case, a major part or a small amount of cyclohexane can be removed by simultaneous flash crystallization of adipic acid. In this case, after removal of adipic acid, the residue constitutes the treated reaction mixture.

It is important to realize that removal of cyclohexane, although highly desirable, prior to the evaporator or still 12 of the treated reaction mixture is not necessary.

The treated reaction mixture entering evaporator 12 is concentrated to a desired degree by evaporating off a substantial portion of the acetic acid present. Obviously, due to its higher volatility, any cyclohexane present and most of the water will evaporate through line 15 even before the acetic acid evaporates. It is very important that the concentrate produced by evaporating a major part of the acetic acid will leave via line 16 as a liquid which, even if viscous, is still pumpable.

During the evaporation of acetic acid, a small amount of water can be added continuously or intermittently through the feed line 13. The addition of water is important to minimize the amount of acetic acid in the concentrate in order to maintain the concentrate in a solids-free form, depending on factors such as conversion and the relative amounts of compounds in the concentrate.

The concentrate enters the complex extraction zone 18 of the complex countercurrent extraction column 14, wherein a countercurrent stream 18' is present in zone 18.

The countercurrent stream 18' has an intermediate zone 19' which corresponds to the intermediate zone 19 of the column 14. Similarly, countercurrent stream 18' has a bottom region 20' (corresponding to bottom region 20 of column 14), and an upper region 22' (corresponding to upper region 22 of column 14). Furthermore, the bottom region 20' of the countercurrent stream 18' has a bottom end 24' (corresponding to the bottom end 24 of the bottom region 20 of the column 14). The upper region 22' of the countercurrent stream 18' has a top end 26' (corresponding to the top end 26 of the upper region 22 of the column 14).

As can be seen in FIG. 1 , countercurrent stream 18 ′ is produced by a plurality of secondary streams entering and exiting column 14 .

One of these second streams is the concentrate entering the intermediate zone 19' of the countercurrent stream 18'. Another second stream is a cyclohexanone stream which is introduced through cyclohexanone line 30 at bottom region 20' of countercurrent stream 18'. Yet another second stream is a stream of water which is introduced through water line 28 at the upper region 22' of countercurrent stream 18'.

Since cyclohexanone has a lower specific gravity than water, it moves downward in column 14 (in the direction from bottom region 20' to upper region 22' of countercurrent 18'), while water moves downward in column 14 ( in the direction from the upper zone 22' towards the bottom zone 20' of the countercurrent stream 18'). Since the two second streams move in opposite directions, the composition of the countercurrent stream 18' changes from place to place, eventually resulting in the formation of an aqueous phase containing at least a major portion of the metal catalyst near the bottom end 24', and at the top end 26'. ’ forms a cyclohexanone phase containing at least a major part of the concentrate in addition to the catalyst. The aqueous phase, which is the extract and contains the major part of the catalyst, is removed through the catalyst solution line or extract line 32 , while the cyclohexanone phase is removed through the concentrate solution line or raffinate line 34 .

Through this process, the dissolution of the concentrate is achieved and at the same time the metal catalyst is obtained in the form of a solution extracted by water. The concentrate solution or raffinate and catalyst solution or extract can be further treated and/or recycled as described in our above mentioned patents and patent applications.

Substantially all of the metal catalyst can be extracted and removed via catalyst solution line or extract line 32 by controlling the temperature and feed rate through lines 16 , 28 and 30 .

The water entering line 28 may contain small amounts of cyclohexanone, while the cyclohexanone entering via line 30 may contain small amounts of water. Similarly, the catalyst solution or extract in water withdrawn via line 32 contains a small amount of cyclohexanone, while the concentrate solution or raffinate withdrawn via line 34 contains a small amount of water.

In regions of countercurrent streams with low concentrations of catalyst, such as the upper portion 22' of countercurrent stream 18', emulsification of water and cyclohexanone with various products tends to occur, which allows a small amount of catalyst to be incorporated into the concentrate solution or raffinate Liquid line 34. To reduce or eliminate this tendency to a considerable extent, the temperature of the upper portion 22' must be above a certain critical temperature which can be easily found without undue experimentation. Thus, the entire countercurrent stream 18' can be maintained above this critical temperature, or at least only in its upper part 22'. A simple way to control the temperature of the bottom 20', middle part 19' and upper part 22' of the countercurrent stream 18' is to control the cyclohexanone stream through line 30, the concentrate stream through line 16 and the concentrate stream through line 28, respectively. temperature of the water stream.

In cases where it is desired to maintain the entire countercurrent stream at approximately the same temperature, the preferred temperature range is 50-80°C.

More preferably, however, the temperature of the upper portion 22' is maintained in the range of 50-90°C, the middle portion 19' is maintained in the range of 30-50°C, and the temperature of the bottom 20' is maintained in the range of 10-40°C. As stated above, a simple way of achieving this is to control the temperature of the cyclohexanone stream via line 30, the concentrate stream via line 16, and the water stream via line 28, respectively, however this It is not required, as external or internal heating or cooling, and/or other means of controlling temperature may be used for this purpose.

Referring now to FIG. 2, there is illustrated a catalyst separation unit 110 comprising an evaporator or still 112 connected by a transfer line 116 to an intermediate stage 119 of a multistage countercurrent extraction unit 114. The intermediate stage 119 includes an intermediate separator 118 and an intermediate mixer 118a. In addition to the intermediate stage 119, the multi-stage countercurrent extraction apparatus has a front stage 120 and a rear stage 122. Front stage 120 has a front separator 124 and a front mixer 124a. Similarly, rear stage 122 has a rear separator 126 and a rear mixer 126a. Water line 128 is connected to rear mixer 126a and cyclohexanone line 130 is connected to front mixer 124a. Extract line 132 is connected to front separator 124 and raffinate line 134 is connected to rear separator 126 .

Also shown in Figure 2 are intermediate stages 136 and 138, which include intermediate separators 140 and 142, respectively, and intermediate mixers 140a and 142a. However, the number of stages can be greater or lesser depending on the individual circumstances and the extent to which the extraction has been accomplished.

As clearly illustrated in Figure 2, the individual mixers and separators are interconnected by inlet and outlet lines. Some of the inlet lines are shown merged with each other to form a single inlet line leading to the mixer. However this is not required. The inlet line can lead separately and directly to the mixer. Such a direct connection is particularly preferred where there is a possibility of solid precipitation. For the sake of clarity, the pumps and other accessories in the pipelines that move the various streams from a given vessel to another are not shown, but they and their operation are well known in the art.

The separator may be a decanter, a centrifuge, or any other type of separator suitable for separating two mobile phases from each other.

Heating or cooling of the different stages or portions of stages, including mixers, separators, inlet and outlet lines, etc., can be done by any means known in the art. For simplicity, the heating/cooling device is not shown in Figure 1 .

Evaporator or still 112 is connected to vapor line 115 , while optional feed line 113 and treated reaction mixture line 111 are connected to evaporator 112 . A heater or heat exchanger 117 is part of the evaporator 112 .

Devices before or after the catalyst extraction unit 110 are not shown in Figure 2 as they have been described in detail in many of our patents and applications, which are hereby incorporated by reference.

In the operation of this embodiment, the treated reaction mixture from the oxidation of cyclohexane to adipic acid (as described in our patents and pending applications, which are hereby incorporated by reference) is passed through the line 111 into the evaporator or distiller 112. The treated mixture is the mixture remaining after removal of at least a substantial portion of adipic acid from a reaction mixture prepared by oxidation of cyclohexane to adipic acid in the presence of acetic acid and a metal catalyst, preferably a cobalt compound of. The worked up reaction mixture may contain major or minor amounts of unreacted cyclohexane. can be removed by separating the reaction mixture into (i) a polar phase containing a major portion of acetic acid, adipic acid, other polar moieties, and catalyst, and (ii) a non-polar phase containing a major portion of cyclohexane. Cyclohexane. In such a case, the non-polar phase can be recovered, while a major part of the adipic acid can be removed by crystallization from the polar phase. In this case, after removal of adipic acid, the residue constitutes the treated reaction mixture. In a different case, a major part or a small amount of cyclohexane can be removed by simultaneous flash crystallization of adipic acid. In this case, after removal of adipic acid, the residue constitutes the treated reaction mixture.

Of course, cyclohexane can be removed by evaporation or any other process.

It is important to realize that removal of cyclohexane, although highly desirable, prior to the evaporator or still 112 of the treated reaction mixture is not necessary.

The treated reaction mixture entering evaporator 112 is concentrated to a desired degree by evaporating off a substantial portion of the acetic acid present. Obviously, due to its higher volatility, any cyclohexane present and most of the water will evaporate through line 115 even before the acetic acid evaporates. It is very important that the concentrate produced by evaporating a major portion of the acetic acid will leave via line 116 as a liquid which, even though viscous, is still pumpable.

During the process of evaporating acetic acid, a small amount of water can be added continuously or intermittently through feed line 113. The addition of water is important to minimize the amount of acetic acid in the concentrate in order to maintain the concentrate in a solids-free form, depending on factors such as conversion and the relative amounts of compounds in the concentrate.

The concentrate enters the intermediate stage 119 of the multi-stage countercurrent unit 114 via line 116, and the stream in line 116 is combined with the stream in line 140' and then combined with the stream in line 142", terminating in intermediate mixer 118a. The three streams from lines 116, 140' and 142" are thoroughly mixed in mixer 18a, and the resulting mixture is sent through line 118a' to separator 118 where it is separated into an upper phase rich in cyclohexanone , and a water-rich lower phase. The lower phase is sent via line 118" to the preceding mixer (intermediate mixer 140a), while the upper phase is sent via line 118' to the following mixer (intermediate mixer 142a).

Cyclohexanone is added to front mixer 124a via line 130, where it is thoroughly mixed with the stream coming from the lower phase of intermediate separator 140 via line 140". The resulting mixture is fed to front separation via line 124a'. 124, where it is separated into a lower phase which is discharged from the apparatus via line 132, and an upper phase which is sent to intermediate mixer 140a via line 124'.

The lower phase discharged from unit 114 via line 132 is an extract containing a major part of the catalyst in aqueous solution. It also contains small amounts of cyclohexanone.

In the latter stage 122 of unit 114, water enters mixer 126a via line 128 where it is thoroughly mixed with the stream coming from the upper phase of intermediate separator 142 via line 142'. The resulting mixture is sent via line 126a' to separator 126 where it is separated into a lower phase and an upper phase. The lower phase is sent via line 126″ to intermediate mixer 142a, while the upper phase is discharged from unit 114 via line 134.

The upper phase withdrawn from unit 114 via line 134 is a raffinate of cyclohexanone solution containing a major part of the concentrate. There is also a small amount of water present.

As shown in Figure 2, the operation is based on several successive stages of extracting the catalyst to form the final aqueous catalyst extract, which is discharged from unit 114 via line 132, and leaving the concentrate in cyclohexanone for extraction. The raffinate is discharged from the device 114 through the pipeline 134.

As the extraction solvent (water) moves from the rear separator 126 to the forward separator 124, it is enriched in catalyst, leaving a continuously increasing raffinate from which the catalyst has been removed, which is eventually removed from unit 114 via line 134. Medium discharge.

By this process, separation of the concentrate entering the multi-stage countercurrent unit via line 116 is achieved, while the metal catalyst in solution is extracted by water. The raffinate and catalyst extract can be further treated and/or recycled as described in our aforementioned patents and applications.

Introducing the concentrate in the middle stage of a multi-stage countercurrent device or extractor (or in the middle section of a similar countercurrent column) is important to maximize the efficiency and effectiveness of catalyst extraction from the concentrate. Introducing the concentrate in the middle stage 119 of the multi-stage countercurrent device or extractor 114, rather than in the latter stage 122, ensures that a substantial amount of catalyst has been extracted before the final separator 126 for final extraction. Introducing the concentrate in the front stage 120 of the multi-stage countercurrent unit or extractor 114 will result in the incorporation of a substantial portion of the concentrate (non-catalyst) in the catalyst extract exiting via line 132 .

By controlling the temperature at the various stages, the feed rate via lines 128 and 130, and the number of stages, substantially all of the metal catalyst can be extracted and removed via extract line 132.

The water entering line 128 may contain small amounts of cyclohexanone, while the cyclohexanone entering via line 130 may contain small amounts of water. Similarly, the catalyst extract via line 132 contains a small amount of cyclohexanone and the raffinate via line 134 contains a small amount of water, as described above.

In the later stages of the countercurrent unit 114 near the rear stage 122, which has a relatively low catalyst concentration, emulsification of water and cyclohexanone with various products tends to occur, which allows a small amount of catalyst to be incorporated into the Line 134 exits the raffinate from the unit. In order to reduce or eliminate this tendency to a considerable extent, the temperature of the latter stages must be above a certain critical temperature, which can be easily found without undue experimentation. Thus, all stages can be kept above this critical temperature, or only in the later stages, or only in the latter stage 122 . A simple way of accomplishing this is to control the temperature of the individual streams in a manner known in the art, such as by means of heaters, coolers, heat exchangers and the like. Of course, it is also possible to heat or cool the separator or mixer by a similar process, for example using external or internal heating or cooling, and/or other means of temperature control.

In cases where it is desired to maintain approximately the same temperature throughout the multi-stage counterflow apparatus, the preferred temperature range is 50-80°C.

More preferably, however, the temperature of the rear stage 122 should be kept in the range of 50-90°C, the temperature of the middle stage 119 should be kept in the range of 30-50°C, and the temperature of the front stage 120 should be kept in the range of 10-40°C. scope. Where an intermediate stage is present, the temperature of the intermediate stage should preferably be maintained between the intermediate stage temperature and the temperature of each end stage (front or rear).

If unacceptable emulsification occurs in the latter stage 122 or in any other stage, a centrifugal separator such as separator 126 can be used in place of a simple decanter as shown in FIG. 1 . Keeping the temperature above the critical point of emulsification is less critical when using a centrifugal separator at least in the latter stage.

In accordance with the present invention it will be appreciated that any liquid or gas or off-gas may be recycled in whole or in part from any part back to any other part if so desired. Also any combination of some or all of the exemplified embodiments, or any equivalent arrangement or combination of equivalent arrangements may be used and remain within the scope of the invention.

While the various functions are preferably controlled by a computerized controller, any other type of controller may be used in accordance with the present invention, or even manual control and/or manual control of one or more functions. Preferred computer controls include artificial intelligence systems (expert systems, neural networks, and fuzzy logic systems, which are well known in the art). Among these three types of artificial intelligence systems, the neural network is a learning system that collects information (such as pressure, temperature, chemical or other analysis, etc.) reaction rate, reactivity, etc.) and programmed to use this information in the future, along with other available data, to make decisions about what happened in each situation. Expert systems are programmed based on experienced expert opinion. In addition to the laws of expertise, fuzzy logic systems are also based on laws of intuition.

The oxidation according to the invention is a non-destructive oxidation in which the oxidation product is other than carbon monoxide, carbon dioxide, and mixtures thereof, such as adipic acid. Of course, small amounts of these compounds may be formed along with oxidation products, which may be one product or a mixture of products.

As for adipic acid, the preparation of which is particularly suitable for the process of the invention, general information on it can be found in a number of US patents, among other references. These patents include but are not limited to:

美国专利2223493；2589648；2285914；3231608；3234271；3361806；3390174；3530185；3649685；3657334；3957876；3987100；4032569；4105856；4158739(戊二酸)；4263453；4331608；4606863；4902827；5221800和5321157。

According to techniques known in the art, dibasic acids (such as adipic acid, phthalic acid, isophthalic acid, and terephthalic acid, etc.) or other suitable compounds can be selected from polyols, polyamines, and polyamides. The third reactant reacts in some way to form a polyester, or polyamide, or (polyimide and/or polyamideimide) polymer, respectively. To prevent excessive crosslinking, it is preferred that the polyols, polyamines and polyamides are mainly diols, diamines and dibasic amides. The polymer resulting from this reaction can be further spun into fibers by techniques well known in the art. The polymers may also be mixed with fillers and/or other additives to form composites.

Examples illustrating the operation of the invention are given for illustrative purposes only and should not be construed as limiting the invention in any way. Furthermore, it should be emphasized that the preferred embodiments specified above, as well as any other embodiments included within the scope of the present invention, may be implemented in accordance with common knowledge and/or expert advice, individually or in any combination thereof. According to the invention, individual parts of each embodiment may also be implemented alone or in combination with other individual parts of each embodiment or the whole thereof. These combinations are also within the scope of the present invention. Moreover, any tentative interpretations in the specification are only speculative and are not intended to narrow the scope of the invention.

Claims (21)

1. A method for extracting metal catalyst in solution form from reaction mixture, said reaction mixture is to make adipic acid by cyclohexane oxidation in the presence of acetic acid and metal catalyst, the method may further comprise the steps: (a) removing substantially all of the cyclohexane; (b) removing a substantial portion of adipic acid; (c) removing a substantial portion of the acetic acid without precipitating the catalyst, thereby forming a solution concentrate; (d) introducing said concentrate into the middle zone of a countercurrent stream, the countercurrent stream also having a bottom zone and an upper zone, the bottom zone having a bottom end and the upper zone having a top end; (e) introducing cyclohexanone, which may contain a small amount of water, into the bottom region of said countercurrent stream; (f) introducing water, which may contain a small amount of cyclohexanone, into the upper region of the countercurrent stream; (g) withdrawing from the top of the upper zone a first liquid or raffinate containing a major fraction of concentrate other than catalyst; and (h) removing a second liquid or extract from the bottom end of the bottom region, the second liquid containing a substantial portion of the metal catalyst. 2. The method of claim 1, wherein steps (d), (e), (f), (g) and (h) are performed simultaneously. 3. The method of any one of claims 1-2, wherein step (c) is performed by distillation. 4. The method of any one of claims 1 to 3, further comprising the step of adding water in step (c). 5. The process of any one of claims 1 to 4, wherein substantially all of the acetic acid is removed in step (c). 6. The process of any one of claims 1 to 5, wherein substantially all of the metal catalyst is withdrawn in step (h). 7. The method according to any one of claims 1 to 6, wherein the upper part has an upper part temperature, the middle part has a middle part temperature, and the lower part has a lower part temperature, and the upper part temperature, the middle part temperature and the lower part temperature are substantially the same. 8. The method according to any one of claims 1 to 6, wherein the upper part has an upper part temperature, the middle part has a middle part temperature, the lower part has a lower part temperature, and the upper part has a higher temperature than the middle part. 9. The method of claim 8, wherein the temperature of the middle portion is higher than the temperature of the lower portion. 10. The method of any one of claims 1 to 9, further comprising the step of reacting adipic acid in some manner with a reactant selected from the group consisting of polyols, polyamines and polyamides to form polyesters, respectively, or Polyamide, or (polyimide and/or polyamideimide) polymers, the method may further include spinning these polymers into fibers, or mixing the polymers with fillers and/or other additives to form composites Material steps. 11. A method for extracting a metal catalyst in solution from a reaction mixture prepared by oxidation of cyclohexane to adipic acid in the presence of acetic acid and a metal catalyst, the method comprising the following step: (k) removing substantially all of the cyclohexane; (l) removing a major portion of adipic acid; (m) removing a substantial portion of the acetic acid without precipitating the catalyst, thereby forming a solution concentrate; (n) introducing said concentrate into an intermediate stage of a countercurrent multistage apparatus comprising an intermediate mixing zone and an intermediate separation zone, said countercurrent multistage apparatus also comprising a front stage and a rear stage, The front stage includes a front mixing zone and a front separation zone, and the rear stage includes a rear mixing zone and a rear separation zone; (p) introducing cyclohexanone, which may contain a small amount of water, into said front mixing zone; (q) introducing water, which may contain a small amount of cyclohexanone, into the rear mixing zone; (r) withdrawing a raffinate from the rear separation zone, the raffinate containing a major fraction of concentrate other than catalyst; and (s) An extract is taken from the front separation zone, the extract containing a major part of the metal catalyst. 12. The method of claim 11, wherein step (m) is performed by distillation. 13. The method of any one of claims 11 to 12, further comprising the step of adding water in step (m). 14. The method according to any one of claims 11 to 13, wherein at least in the latter separation zone the separation is performed at least partly by a centrifugation step. 15. The method of any one of claims 11 to 14, wherein the rear stage has a rear stage temperature, the middle stage has a middle stage temperature, and the front stage has a front stage temperature, and the rear stage temperature, the middle stage temperature and the front stage temperature The temperature of the sub-stages is basically the same. 16. The method of claim 15, wherein the substantially identical temperature is in the range of 50-80°C. 17. The method of any one of claims 1 to 14, wherein the rear stage has a rear stage temperature, the middle stage has an intermediate stage temperature, and the front stage has a front stage temperature, and the rear stage temperature is higher than the temperature of the middle stage , the temperature in the middle stage is higher than that in the front stage. 18. The method of claim 17, wherein the temperature range of the rear stage is 50-90°C, the temperature range of the middle stage is 30-50°C, and the temperature range of the front stage is 10-40°C. 19. The process of any one of claims 1 to 18, wherein substantially all of the acetic acid is removed in step (m). 20. The process of any one of claims 1 to 19, wherein substantially all of the metal catalyst is withdrawn in step (s). 21. The method of claims 11 to 20, further comprising the step of reacting adipic acid in some manner with a reactant selected from the group consisting of polyols, polyamines and polyamides to form polyesters, or polyamides, respectively or (polyimide and/or polyamideimide) polymers, the method may further include the step of spinning these polymers into fibers, or mixing the polymers with fillers and/or other additives to form composites .

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