Method for reactivation of a homogeneous oxidation catalyst

Abstract

The present invention relates to a method for the reactivation of homogeneous catalyst systems from organic reaction mixtures. The catalyst systems are suitable for the oxidation of organic compounds such as, for example, cyclododecene. The reactivation is carried out using an aqueous base.

Claims

1. A method for reactivating a catalyst system for epoxidizing an unsaturated organic compound in a reaction mixture, the method comprising: separating the catalyst system from an epoxidized organic compound in the reaction mixture prior to reactivating, and reactivating the catalyst system by adding at least one aqueous base at a pH≥4, wherein the reaction mixture comprises the catalyst system and at least one peroxide, the catalyst system is a homogeneous catalyst system for epoxidizing the unsaturated organic compound comprising at least one derivative of a metal in its highest oxidation state, wherein the derivative is at least one selected from the group consisting of H.sub.2WO.sub.4, H.sub.2MoO.sub.4, an alkali metal salt of H.sub.2WO.sub.4, an alkaline earth metal salt of H.sub.2WO.sub.4, an alkali metal salt of H.sub.2MoO.sub.4, an alkaline earth metal salt of H.sub.2MoO.sub.4, phosphoric acid, and a phosphoric acid salt.

2. The method according to claim 1, wherein the reaction mixture comprises an aqueous phase, an organic phase, and a phase transfer reagent.

3. The method according to claim 2, said reaction mixture is at a pH≤4.

4. The method according to claim 3, wherein the pH is ≤4, from at least one inorganic acid having a pKa (25° C.) of 2.5 or less.

5. The method according claim 2, wherein an organic phase is removed after the reactivating.

6. The method according to claim 1, wherein the pH of the catalyst system after the reactivating is adjusted to a value of <7.

7. The method according to claim 1, wherein the at least one peroxide is hydrogen peroxide.

8. The method according to claim 1, wherein the base is at least one selected from the group consisting of ammonia, alkali metal hydroxides, and any mixture thereof.

9. The method according to claim 8, wherein the base is at least one selected from the group consisting of sodium hydroxide and potassium hydroxide.

10. The method according to claim 1, wherein the organic compound is an unsaturated cyclic compound having six to twelve carbon atoms.

11. The method according to claim 1, wherein said reaction mixture does not contain an organic solvent.

12. A method for synthesizing a lactam, the method comprising: epoxidizing a cyclic unsaturated compound to an epoxide, rearranging the epoxide to a ketone, oximating the ketone to an oxime and rearranging the oxime to a lactam, wherein the cyclic unsaturated compound is epoxidized in the presence of a homogeneous oxidation catalyst system, and wherein a reactivation of the catalyst system is carried out according to claim 1.

13. A method for epoxidizing an unsaturated organic compound with a peroxide, the method comprising: epoxidizing the unsaturated organic compound with a homogeneous epoxidation catalyst system, which comprises at least one derivative of a metal in its highest oxidation state, in a reaction mixture, thereby obtaining an epoxidized organic compound, separating the catalyst system from the epoxidized organic compound, then reactivating the catalyst system by adding at least one aqueous base at a pH≥4, and recycling the catalyst system to the reaction mixture after reactivating, wherein the derivative is at least one selected from the group consisting of H.sub.2WO.sub.4, H.sub.2MoO.sub.4, an alkali metal salt of H.sub.2WO.sub.4, an alkaline earth metal salt of H.sub.2WO.sub.4, an alkali metal salt of H.sub.2MoO.sub.4, an alkaline earth metal salt of H.sub.2MoO.sub.4, phosphoric acid, and a phosphoric acid salt.

14. The method according to claim 13, wherein the catalyst system is reactivated by addition of at least one aqueous base at a pH≥4.5.

15. The method according to claim 14, wherein the catalyst system is reactivated by addition of at least one aqueous base at a pH≥7.

16. The method of claim 13, further comprising: maintaining a substantially constant concentration of the catalyst system in the reaction mixture.

Description

EXAMPLES

Example 1 (Non-Inventive)

(1) Continuous Procedure without Reactivation

(2) An epoxidation of cyclic unsaturated C12 compounds was carried out as a continuous operation in a 3 stage stirred tank cascade. The stirred tank cascade used comprised 2 reactors each having a 5 litre nominal capacity and, as a final stage, a stirred tank having a 25 litre nominal capacity. The three reactors comprised a jacket and were heated to a temperature of about 80° C. therewith.

(3) The first reactor of the cascade was supplied with 2 kg/h of a cyclic unsaturated C12 compound (91% by weight CDEN and 9% by weight CDAN), trioctylammoniummethyl sulfate (as phase transfer reagent), sodium tungstate and phosphoric acid and a 50% H.sub.2O.sub.2 solution. In addition, a further quantity of H.sub.2O.sub.2 was metered into the second reactor. In total a ratio of 1.05 mol H.sub.2O.sub.2 per mol of CDEN was added.

(4) The reaction mixture consisting of two liquid phases was passed from the cascade into a phase separation vessel from which the organic phase was supplied to a continuous membrane system using a pump.

(5) The organic phase was fed at 45° C. through the membranes at a trans-membrane pressure difference of 41.5 bar and a cross flow rate of ca. 300 L/h. The membrane used was a polymer membrane from Evonik MET Ltd. with a nominal membrane surface area of 0.6 m=. The separation-active layer of the membranes consists of silicone acrylate and the carrier layer consists of polyimide.

(6) 83% of the feed to the membrane system was obtained as permeate. The retentate (17% of the feed to the membrane system), which comprises the catalyst system, was recycled into the reaction.

(7) The aqueous phase from the phase separation vessel was likewise fed to a second continuous membrane system by means of a pump. The aqueous phase at 43° C. was fed through the membranes at a trans-membrane pressure difference of 40 bar and a cross flow rate of ca. 800 L/h. The membrane used was a thin layer composite polymer membrane Desal DK from GE Power & Water with a nominal membrane surface area of 0.7 m=. 55% of the feed to the membrane system was obtained as permeate. The retentate (45% of the feed to the membrane system), which comprises the catalyst system, was recycled into the first reactor of the cascade.

(8) In addition to the recycling of the catalyst system with the retentate from the membrane system, phase transfer reagent, sodium tungstate and phosphoric acid were added to the first reactor. The amounts added are presented in the table below based on the CDEN amount in the feed.

(9) TABLE-US-00001 Trialkylammoniummethyl Na.sub.2WO.sub.4 H.sub.3PO.sub.4 sulfate Amount based on 0.9 mg/g 3.4 mg/g 2.2 mg/g the amount of CDEN fed

(10) With these catalyst characteristics, a conversion of the CDEN portion of 97% resulted after an operating time of 105 hours and a concentration of tungsten in the first reactor of the cascade of 0.45 mol % tungsten was determined by ICP mass spectrometry, based on CDEN in the feed.

(11) After an operating time of the experimental system of 863 hours, a drop of the conversion of CDEN to 90% was observed. The concentration of tungsten in the first reactor of the cascade of 0.45 mol % tungsten was determined by ICP mass spectrometry, based on CDEN in the feed. Accordingly, a significantly poorer conversion resulted at the same tungsten concentration.

Example 2 (Non-Inventive)

(12) Continuous Procedure without Reactivation

(13) An epoxidation of cyclic unsaturated C12 compounds was carried out as a continuous operation in a 3 stage stirred tank cascade. The stirred tank cascade used comprised 2 reactors each having a 5 litre nominal capacity and, as a final stage, a stirred tank having a 25 litre nominal capacity. The three reactors comprised a jacket and were heated to a temperature of about 80° C. therewith.

(14) The first reactor of the cascade was supplied with 1.5 kg/h of a cyclic unsaturated C12 compound (81% by weight CDEN and 19.1% by weight CDAN), Alamine (trioctylamine as phase transfer reagent), sodium tungstate and phosphoric acid and a 50% H.sub.2O.sub.2 solution. In addition, a further quantity of H.sub.2O.sub.2 was metered into the second reactor. In total a ratio of 1.08 mol H.sub.2O.sub.2 per mol of CDEN was added.

(15) The reaction mixture consisting of two liquid phases was passed from the cascade into a phase separation vessel from which the organic phase was supplied to a continuous membrane system using a pump.

(16) The organic phase was fed at 45° C. through the membranes at a trans-membrane pressure difference of 41.5 bar and a cross flow rate of ca. 300 L/h. The membrane used was a polymer membrane from Evonik MET Ltd. with a nominal membrane surface area of 0.6 m.sup.2. The separation-active layer of the membranes consists of silicone acrylate and the carrier layer consists of polyimide.

(17) 79% of the feed to the membrane system was obtained as permeate. The retentate (21% of the feed to the membrane system), which comprises the catalyst system, was recycled into the reaction.

(18) The aqueous phase from the phase separation vessel was likewise fed to a second continuous membrane system by means of a pump. The aqueous phase at 43° C. was fed through the membranes at a trans-membrane pressure difference of 40 bar and a cross flow rate of ca. 800 L/h. The membrane used was a thin layer composite polymer membrane Desal DK from GE Power & Water with a nominal membrane surface area of 0.7 m.sup.2. 70% of the feed to the membrane system was obtained as permeate. The retentate (30% of the feed to the membrane system), which comprises the catalyst system, was recycled into the first reactor of the cascade.

(19) In addition to the recycling of the catalyst system with the retentate from the membrane system, Alamine, sodium tungstate and phosphoric acid were added to the first reactor. The amounts added are presented in the table below based on the CDEN amount in the feed.

(20) TABLE-US-00002 Na.sub.2WO.sub.4 H.sub.3PO.sub.4 Alamine Amount based on 2.39 mg/g 4.4 mg/g 4.6 mg/g the amount of CDEN fed

(21) With these catalyst characteristics, a total conversion for the CDEN portion of 94.5% resulted.

(22) After an operating time of the experimental system of 240 hours, a concentration of tungsten in the first reactor of the cascade of 1.08 mol % tungsten was determined by ICP mass spectrometry, based on CDEN in the feed. In addition, solid deposits were observed in the experimental system which led to blockage of the connecting lines between phase separation vessel and membrane system and further operation of the experimental system was no longer possible.

Example 3 (Inventive)

(23) Continuous Method with Reactivation

(24) In the inventive example, the experimental set-up of Example 2 was supplemented by an alkali treatment for the retentate and a subsequent acid addition (analogous to FIG. 2).

(25) The first reactor of the cascade was supplied with 2.3 kg/h of a cyclic unsaturated C12 compound (91% by weight CDEN and 9% by weight CDAN), Alamine (phase transfer reagent), sodium tungstate and phosphoric acid and a 50% H.sub.2O.sub.2 solution. In addition, a further quantity of H.sub.2O.sub.2 was metered into the second reactor. In total a ratio of 0.995 mol H.sub.2O.sub.2 per mol of CDEN was added.

(26) The reaction mixture consisting of two liquid phases was passed from the cascade into a phase separation vessel from which the organic phase was supplied to a continuous membrane system using a pump.

(27) The organic phase at 45° C. was fed through the membranes at a trans-membrane pressure difference of 41.5 bar and a cross flow rate of ca. 300 L/h. The membrane used was a polymer membrane from Evonik MET Ltd. with a nominal membrane surface area of 0.6 m.sup.2. The separation-active layer of the membranes consists of silicone acrylate and the carrier layer consists of polyimide.

(28) 79% of the feed to the membrane system was obtained as permeate. The retentate (21% of the feed to the membrane system), which comprises the catalyst system, was fed into a further stirred tank, in which a 0.5M aqueous sodium hydroxide solution was added. The mixture was adjusted to a pH of 11. Subsequently the mixture was passed into a further stirred tank and there treated with sulphuric acid and adjusted to a pH of 2. The resulting mixture was recycled to the first reactor of the cascade.

(29) The aqueous phase from the phase separation vessel was likewise fed to a second continuous membrane system by means of a pump. The aqueous phase at 43° C. was fed through the membranes at a trans-membrane pressure difference of 40 bar and a cross flow rate of ca. 800 L/h. The membrane used was a thin layer composite polymer membrane Desal DK from GE Power & Water with a nominal membrane surface area of 0.7 m=. 70% of the feed to the membrane system was obtained as permeate. The retentate (30% of the feed to the membrane system), which comprises the catalyst system, was recycled into the first reactor of the cascade.

(30) In addition to the recycling of the catalyst system, Alamine, sodium tungstate and phosphoric acid were added to the first reactor. The amounts added are presented in the table below based on the CDEN amount in the feed.

(31) TABLE-US-00003 Na.sub.2WO.sub.4 H.sub.3PO.sub.4 Alamine Amount based on 1.2 mg/g 2.0 mg/g 6 mg/g the amount of CDEN fed

(32) With these catalyst characteristics, a total conversion for the CDEN portion of 95% resulted.

(33) After an operating time of the experimental system of 840 hours, a concentration of tungsten in the first reactor of the cascade of 0.51 mol % tungsten was determined by ICP mass spectrometry, based on CDEN in the feed. No solid deposits were observed in the experimental system which would force a shutdown of the experimental system.

Example 4 (Inventive)

(34) Continuous Method with Reactivation

(35) In the inventive example, the experimental set-up of Example 3 was supplemented by a phase separation after the alkali treatment of the retentate (analogous to FIG. 4). The organic phase from the additional phase separation was recycled into the reactor cascade. The aqueous phase was discharged from the process.

(36) The first reactor of the cascade was supplied with 2.3 kg/h of a cyclic unsaturated C12 compound (91% by weight CDEN and 9% by weight CDAN), Alamine (phase transfer reagent), sodium tungstate and phosphoric acid and a 50% H.sub.2O.sub.2 solution. In addition, a further quantity of H.sub.2O.sub.2 was metered into the second reactor. In total a ratio of 0.979 mol H.sub.2O.sub.2 per mol of CDEN was added.

(37) The reaction mixture consisting of two liquid phases was passed from the cascade into a first phase separation vessel from which the organic phase was supplied to a continuous membrane system using a pump.

(38) The organic phase was fed at 45° C. through the membranes at a trans-membrane pressure difference of 41.5 bar and a cross flow rate of ca. 300 L/h. The membrane used was a polymer membrane from Evonik MET Ltd. with a nominal membrane surface area of 0.6 m.sup.2. The separation-active layer of the membranes consists of silicone acrylate and the carrier layer consists of polyimide.

(39) 84% of the feed to the membrane system was obtained as permeate. The retentate (16% of the feed to the membrane system), which comprises the catalyst system, was fed into a further stirred tank, in which a 0.5M aqueous sodium hydroxide solution was added. The mixture was adjusted to a pH of 11. Subsequently the mixture was passed into a further stirred tank and there treated with sulphuric acid and adjusted to a pH of 2. Subsequently the mixture was fed to an additional phase separation vessel. The aqueous phase was discharged from the process. The resulting organic phase was recycled to the first reactor of the cascade.

(40) The aqueous phase from the first phase separation vessel was likewise fed to a second continuous membrane system by means of a pump. The aqueous phase at 43° C. was fed through the membranes at a trans-membrane pressure difference of 40 bar and a cross flow rate of ca. 800 L/h. The membrane used was a thin layer composite polymer membrane Desal DK from GE Power & Water with a nominal membrane surface area of 0.7 m.sup.2. 83% of the feed to the membrane system was obtained as permeate. The retentate (17% of the feed to the membrane system), which comprises the catalyst system, was recycled into the first reactor of the cascade.

(41) In addition to the recycling of the catalyst system, Alamine, sodium tungstate and phosphoric acid were added to the first reactor. The amounts added are presented in the table below based on the CDEN amount in the feed.

(42) TABLE-US-00004 Na.sub.2WO.sub.4 H.sub.3PO.sub.4 Alamine Amount based on 1.2 mg/g 3.5 mg/g 4 mg/g the amount of CDEN fed

(43) With these catalyst characteristics, a total conversion for the CDEN portion of 91% resulted.

(44) After an operating time of the experimental system of 500 hours, a concentration of tungsten in the first reactor of the cascade of 0.42 mol % tungsten was determined by ICP mass spectrometry, based on CDEN in the feed. No solid deposits were observed in the experimental system which would force a shutdown of the experimental system.

Example 5 (Inventive)

(45) Continuous Method with Reactivation

(46) In the inventive example, the experimental set-up of Example 3 was used.

(47) The first reactor of the cascade was supplied with 2.0 kg/h of a cyclic unsaturated C12 compound (91% by weight CDEN and 9% by weight CDAN), trioctylammonium methyl sulphate (phase transfer reagent), sodium tungstate and phosphoric acid and a 50% H.sub.2O.sub.2 solution. In addition, a further quantity of H.sub.2O.sub.2 was metered into the second reactor. In total a ratio of 1 mol H.sub.2O.sub.2 per mol of CDEN was added.

(48) The reaction mixture consisting of two liquid phases was passed from the cascade into a phase separation vessel from which the organic phase was supplied to a continuous membrane system using a pump.

(49) The organic phase was fed at 45° C. through the membranes at a trans-membrane pressure difference of 41.5 bar and a cross flow rate of ca. 300 L/h. The membrane used was a polymer membrane from Evonik MET Ltd. with a nominal membrane surface area of 0.6 m.sup.2. The separation-active layer of the membranes consists of silicone acrylate and the carrier layer consists of polyimide.

(50) 84% of the feed to the membrane system was obtained as permeate. The retentate (16% of the feed to the membrane system), which comprises the catalyst system, was fed into a further stirred tank, in which a 0.5M aqueous sodium hydroxide solution was added. The mixture was adjusted to a pH of 11. Subsequently the mixture was passed into a further stirred tank and there treated with sulphuric acid and adjusted to a pH of 2. The resulting mixture was recycled to the first reactor of the cascade.

(51) The aqueous phase from the phase separation vessel was likewise fed to a second continuous membrane system by means of a pump. The aqueous phase at 43° C. was fed through the membranes at a trans-membrane pressure difference of 40 bar and a cross flow rate of ca. 800 L/h. The membrane used was a thin layer composite polymer membrane Desal DK from GE Power & Water with a nominal membrane surface area of 0.7 m.sup.2. 55% of the feed to the membrane system was obtained as permeate. The retentate (45% of the feed to the membrane system), which comprises the catalyst system, was recycled into the first reactor of the cascade.

(52) In addition to the recycling of the catalyst system, trioctylammonium methyl sulphate, sodium tungstate and phosphoric acid were added to the first reactor. The amounts added are presented in the table below based on the CDEN amount in the feed.

(53) TABLE-US-00005 Trioctylammonium Na.sub.2WO.sub.4 H.sub.3PO.sub.4 methyl sulphate Amount based on 0.6 mg/g 3.5 mg/g 1.6 mg/g the amount of CDEN fed

(54) With these catalyst characteristics, a total conversion for the CDEN portion of 95% resulted.

(55) After an operating time of the experimental system of 790 hours, a concentration of tungsten in the first reactor of the cascade of 0.52 mol % tungsten was determined by ICP mass spectrometry, based on CDEN in the feed. No solid deposits were observed in the experimental system which would force a shutdown of the experimental system.

Comparison of the Examples

(56) The examples 1-5 cited and the supplementary overview of the examples clarify the effectiveness of the invention.

(57) Example 1 shows a non-inventive oxidation of cyclododecene with hydrogen peroxide in which the tungsten concentration was kept constant over the entire experimental period. The conversion achieved over the course of the experiment decreased significantly from 97% after 105 hours to 90% after 863 hours.

(58) In example 5, in contrast, the catalyst was reactivated by adding aqueous sodium hydroxide solution to the retentate of the organophilic nanofiltration. After an operating time of 790 hours in example 5 with analogous operating conditions and analogous tungsten concentration, a significantly higher conversion of 95% could be observed.

(59) Comparison of examples 1 and 5 shows that, after around 800 operating hours, a higher conversion of CDEN can be achieved with less Na.sub.2WO.sub.4 and less phase transfer catalyst if the catalyst is reactivated. In example 2, in a non-inventive embodiment as a major difference to example 1, alamine was used instead of trialkylammoniummethyl sulfate as phase transfer reagent. Without catalyst reactivation in example 2, a lot of fresh catalyst had to be added in order to achieve good conversions. A very high tungsten concentration was observed. In addition, solid deposits hampered the operation of the experimental plant and the experiment had to be aborted.

(60) In example 3, in contrast to example 2, the catalyst was reactivated according to the invention by treating the retentate of the organophilic nanofiltration with aqueous sodium hydroxide solution. In contrast to example 2, with analogous phase transfer reagent, greater cydododecene throughput and longer experimental time, example 3 resulted in comparable conversions and thus a significantly higher space-time yield. At the same time, in example 3 less fresh catalyst was required and a very much lower tungsten concentration was found.

(61) Example 4 illustrates a further embodiment of the invention—see FIG. 4. In example 4, in contrast to example 3, the water phase, which results from reactivation of the catalyst in the retentate of the organophilic nanofiltration with aqueous sodium hydroxide solution and subsequent adjustment of the pH with sulfuric acid, is removed and discharged from the process.

(62) The comparison of examples 2 and 3 shows that more CDEN can be converted with less Na.sub.2WO.sub.4 if the catalyst is reactivated. The same applies to the comparison of examples 2 and 4. In addition, example 2 shows that the increased amount of catalyst which is needed to achieve the conversion without catalyst reactivation can lead to blockages and failure of the plant.

(63) TABLE-US-00006 Experimental result Set-up Cat tungsten Cat according to addition Operating concentration particular Example reactivation PTR FIG. in mg/g hours measured Conversion incidents 1* no TOAMS — 0.9 105 0.45% 97% 863 0.45% 90% 2* no alamine — 2.4 240 1.08% 94.5%.sup.  solid deposits 3 yes alamine 2 1.2 840 0.51% 95% 4 yes alamine 4 1.2 500 0.42% 91% 5 yes TOAMS 2 0.6 790 0.52% 95% *non-inventive cat = catalyst PTR = phase transfer reagent TOAMS = trioctylammoniummethyl sulfate