METHOD FOR PREPARING EPSILON-CAPROLACTONE

Abstract

The present invention discloses a method for preparing -caprolactone. The method comprises the steps of: adding cyclohexanone, a co-oxidant and a certain amount of catalyst into a certain amount of organic solvent, using molecular oxygen as an oxidant, implementing a reaction with stirring for 0.1 to 24 hours under a pressure of 0.1 to 2 MPa and at a temperature of 60 C. to 100 C., wherein the co-oxidant is acrolein, and the catalyst is a carbon material. The present invention has the advantages of high-efficiency co-oxidant, easily available and recovered catalyst, environmental-friendly oxidant, simple operation and low cost.

Claims

1. A preparation method of -caprolactone, comprising the following steps: adding cyclohexanone, a co-oxidant and a catalyst into an organic solvent, using molecular oxygen as an oxidant, performing a reaction with stirring for 0.1 to 24 hours under a pressure of 0.1 to 2 MPa and at a temperature of 60 C. to 100 C., and obtaining the -caprolactone; wherein the co-oxidant is an aldehyde, and the catalyst is a carbon material.

2. The preparation method according to claim 1, wherein the organic solvent is one or more than one of 1,2-dichloroethane, carbon tetrachloride, acetonitrile, dichloromethane and toluene.

3. The preparation method according to claim 1, wherein the co-oxidant is acrolein.

4. The preparation method according to claim 1, wherein the catalyst is one or more than one of a nitrogen-doped carbon nanotube, a carbon nanotube, a carboxylated carbon nanotube and activated carbon.

5. The preparation method according to claim 1, wherein a mass ratio of the organic solvent to the cyclohexanone is (6 to 799):1.

6. The preparation method according to claim 1, wherein a molar ratio of the co-oxidant to cyclohexanone is (0.25 to 100):1.

7. The preparation method according to claim 1, wherein a mass ratio of the catalyst to cyclohexanone is (0.01 to 2):1.

8. The preparation method according to claim 1, wherein the temperature of the reaction is 60 C. to 80 C., the pressure of the reaction is 0.1 to 1 MPa, and the reaction lasts for 0.1 to 4 hours.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 is a gas chromatogram of a reaction liquid after reaction in a third embodiment.

[0021] FIG. 2 is a transmission electron micrograph (TEM) of a nitrogen-doped carbon nanotube used in the present invention.

[0022] FIG. 3 is an XPS spectrum of the nitrogen-doped carbon nanotube used in the present invention.

DETAILED DESCRIPTION

[0023] The present invention is further described hereinafter with reference to the embodiments and the accompanied drawings, but the scope of protection of the present invention is not limited to the description of the embodiments.

[0024] A transmission electron micrograph (TEM) and an N.sub.1s XPS spectrum of a nitrogen-doped carbon nanotube used in the present invention are as shown in FIG. 2 and FIG. 3. The result shows that a content of N is 4.34 at %.

[0025] In the following embodiments, conversion (%) of cyclohexanone and acrolein, and selectivities (%) of -caprolactone and acrylic acid are analyzed and measured by a gas chromatography (GC). An internal standard method is used in GC detection and calculation, o-dichlorobenzene is used as an internal standard substrate, and standard curves corresponding to four substrates are plotted respectively, which are then combined with the GC detection and calculation of a reaction solution to obtain the results.

Embodiments 1 to 5

[0026] 25 ml of 1,2-dichloroethane, 2.6 g of o-dichlorobenzene (internal standard substance), 4.75 g of cyclohexanone, 2.69 g of acrolein and 100 mg of nitrogen-doped carbon nanotube (a content of N was 4.34 at %) were sequentially added into a high-pressure reactor, stirred and heated to a temperature shown in Table 1, and charged with oxygen; then, timing was started, and the pressure was maintained at 1 MPa during the reaction. After reaction for 4 hours, timing was stopped, the reactor was cooled to a room temperature, and a liquid-solid phase mixture was filtered to obtain a solid catalyst and a liquid-phase mixture containing unreacted reactants and products. The liquid-phase mixture was measured by gas chromatography (GC). After the reaction in the Embodiment 3, a gas chromatogram of the reaction solution was shown in FIG. 3. GC measurement results were shown in Table 1 (effects of the reaction temperature on the Baeyer-Villiger oxidation of cyclohexanone).

TABLE-US-00001 TABLE 1 Embodiment 1 2 3 4 5 Reaction temperature ( C.) 60 70 80 90 100 Conversion of 0.93 16 22 32 43 cyclohexanone (%) Selectivity of 100 78 74 66 65 -caprolactone (%) Conversion of acrolein (%) 7 16 37 61 86 Selectivity of acrylic 100 100 100 82 80 acid (%) Efficiency of acrolein 0.13 0.78 0.44 0.35 0.32

[0027] It can be seen from Table 1 that temperature increase is favorable for oxidation of cyclohexanone, but when the temperature reaches 90 C., the selectivities of -caprolactone and acrylic acid, especially the selectivity of acrylic acid, are greatly decreased while the conversion are increased. Therefore, the optimal temperature is 80 C. on the premise of ensuring the high yield of -caprolactone and 100% selectivity of acrylic acid.

Embodiments 6 to 12

[0028] 25 ml of 1,2-dichloroethane, 2.6 g of o-dichlorobenzene (internal standard substance), 4.75 g of cyclohexanone, 2.69 g of acrolein and 100 mg of nitrogen-doped carbon nanotube (a content of N was 4.34 at %) were sequentially added into a high-pressure reactor, stirred and heated to a temperature of 80 C., and charged with oxygen; then, timing was started, and the pressure was maintained at 1 MPa during the reaction. After reaction for a time shown in Table 2, timing was stopped, the reactor was cooled to a room temperature, and a liquid-solid phase mixture was filtered to obtain a solid catalyst and a liquid-phase mixture containing unreacted reactants and products. The liquid-phase mixture was measured by gas chromatography (GC). GC detection results were shown in Table 2 (effects of the reaction time on the Baeyer-Villiger oxidation of cyclohexanone).

TABLE-US-00002 TABLE 2 Embodiment 6 7 8 3 9 10 11 12 Reaction time (h) 0.1 2 3 4 6 8 12 24 Conversion of cyclohexanone (%) 2 13 19 22 27 33 40 45 Selectivity of -caprolactone (%) 91 81 78 74 71 62 63 60 Conversion of acrolein (%) 2 13 29 37 49 64 79 90 Selectivity of acrylic acid (%) 100 100 100 100 98 81 82 80 Efficiency of acrolein 0.91 0.81 0.51 0.44 0.39 0.32 0.31 0.30

[0029] Through analyzing the data in Table 2, it can be known that the conversion of cyclohexanone is increased with the extension of time, the efficiency of acrolein is decreased with the increase of the conversion of acrolein, and the selectivity of acrylic acid is obviously decreased after 4 hours. The optimal duration within the time range studied in Table 2 is 4 hours on the premise of ensuring the high yield of -caprolactone and 100% selectivity of acrylic acid.

Embodiments 13 to 16

[0030] 25 ml of 1,2-dichloroethane, 2.6 g of o-dichlorobenzene (internal standard substance), 4.75 g of cyclohexanone, 2.69 g of acrolein and 100 mg of nitrogen-doped carbon nanotube (a content of N was 4.34 at %) were sequentially added into a high-pressure reactor, stirred and heated to a temperature of 80 C., and charged with oxygen; then, timing was started, and the mixture was maintained at a pressure shown in Table 3 during the reaction. After reaction for 4 hours, timing was stopped, the reactor was cooled to a room temperature, and a liquid-solid phase mixture was filtered to obtain a solid catalyst and a liquid-phase mixture containing unreacted reactants and products. The liquid-phase mixture was measured by gas chromatography (GC). GC detection results were shown in Table 3 (effects of the reaction pressure on the Baeyer-Villiger oxidation of cyclohexanone).

TABLE-US-00003 TABLE 3 Embodiment 13 14 3 15 16 Reaction pressure (MPa) 0.1 0.5 1 1.5 2 Conversion of 13 19 22 24 27 cyclohexanone (%) Selectivity of 88 81 74 70 64 -caprolactone (%) Conversion of acrolein (%) 15 30 37 43 48 Selectivity of acrylic acid (%) 100 100 100 95 89 Efficiency of acrolein 0.76 0.51 0.44 0.39 0.36

[0031] Through analyzing the data in Table 3, it can be known that the conversion of cyclohexanone is not increased obviously with the increase of pressure, while the efficiency of acrolein is decreased with the increase of pressure, and the selectivity of acrylic acid is obviously decreased after the pressure is greater than 1 MPa. The optimal pressure within the pressure range in Table 3 is 1 MPa on the premise of ensuring the high yield of -caprolactone and 100% selectivity of acrylic acid.

Embodiments 17 to 20

[0032] 25 ml of 1,2-dichloroethane, 2.6 g of o-dichlorobenzene (internal standard substance), 4.75 g of cyclohexanone, 2.69 g of acrolein and 100 mg of catalyst as shown in FIG. 4 were sequentially added into a high-pressure reactor, stirred and heated to a temperature of 70 C., and charged with oxygen; then, timing was started, and the pressure was maintained at 1 MPa during the reaction. After reaction for 4 hours, timing was stopped, the reactor was cooled to a room temperature, and a liquid-solid phase mixture was filtered to obtain a solid catalyst and a liquid-phase mixture containing unreacted reactants and products. The liquid-phase mixture was measured by gas chromatography (GC). GC detection results were shown in Table 4 (effects of different carbon materials on the Baeyer-Villiger oxidation of cyclohexanone).

TABLE-US-00004 TABLE 4 Embodiment 17 18 19 20 Carbon material NCNT CNT HNO.sub.3 + Activated CNT carbon Conversion of cyclohexanone (%) 16 12 4 5 Selectivity of -caprolactone (%) 78 67 96 90 Conversion of acrolein (%) 16 65 11 11 Selectivity of acrylic acid (%) 100 48 76 100 Efficiency of acrolein 0.77 0.12 0.38 0.43

[0033] Through analyzing the data in Table 4, it can be known that the nitrogen-doped carbon nanotube (a content of N is 4.34 at %) has the optimal catalytic activity.

Embodiments 21 to 24

[0034] 25 ml of 1,2-dichloroethane, 2.6 g of o-dichlorobenzene (internal standard substance), 4.75 g of cyclohexanone, 2.69 g of acrolein and nitrogen-doped carbon nanotube (a content of N was 4.34 at %) with an amount as shown in FIG. 5 were sequentially added into a high-pressure reactor, stirred and heated to a temperature of 80 C., and charged with oxygen; then, timing was started, and the pressure was maintained at 1 MPa during the reaction. After reaction for 4 hours, timing was stopped, the reactor was cooled to a room temperature, and a liquid-solid phase mixture was filtered to obtain a solid catalyst and a liquid-phase mixture containing unreacted reactants and products. The liquid-phase mixture was measured by gas chromatography (GC). GC detection results were shown in Table 5 (effects of the nitrogen-doped carbon nanotube of different amounts on the Baeyer-Villiger oxidation of cyclohexanone).

TABLE-US-00005 TABLE 5 Embodiment 21 22 23 3 24 Amount of nitrogen-doped 0 60 80 100 120 carbon nanotube (mg) Conversion of cyclohexanone <1 17 19 22 21 (%) Selectivity of -caprolactone 81 76 74 73 (%) Conversion of acrolein (%) <1 32 34 37 41 Selectivity of acrylic acid (%) 100 100 100 99 Efficiency of acrolein 0.43 0.42 0.44 0.37

[0035] It can be known from Table 5 that when the amount of the catalyst is 100 mg, the yields of -caprolactone and acrylic acid are both the highest, and the efficiency of acrolein is also the largest while ensuring 100% selectivity of acrylic acid.

Embodiments 25 to 28

[0036] 25 ml of a solvent as shown in FIG. 6, 2.6 g of o-dichlorobenzene (internal standard substance), 4.75 g of cyclohexanone, 2.69 g of acrolein and 100 mg of nitrogen-doped carbon nanotube (a content of N was 4.34 at %) were sequentially added into a high-pressure reactor, stirred and heated to a temperature of 80 C., and charged with oxygen; then, timing was started, and the pressure was maintained at 1 MPa during the reaction. After reaction for 4 hours, timing was stopped, the reactor was cooled to a room temperature, and a liquid-solid phase mixture was filtered to obtain a solid catalyst and a liquid-phase mixture containing unreacted reactants and products. The liquid-phase mixture was measured by gas chromatography (GC). GC detection results were shown in Table 6 (effects of different solvents on the Baeyer-Villiger oxidation of cyclohexanone).

TABLE-US-00006 TABLE 6 Embodiment 3 25 26 27 28 Different solvents 1,2-dichloroethane Carbon Acetonitrile Dichloromethane Toluene tetrachloride Conversion of 22 22 14 18 15 cyclohexanone (%) Selectivity of 74 54 73 75 54 -caprolactone (%) Conversion of 37 50 34 35 25 acrolein (%) Selectivity of acrylic 100 79 100 96 100 acid (%) Efficiency of 0.44 0.24 0.30 0.39 0.32 acrolein

[0037] It can be known from Table 6 that when 1,2-dichloroethane is used as the solvent, the yields of -caprolactone and acrylic acid and the efficiency of acrolein are all the highest.

Embodiments 29 to 36

[0038] A certain volume of 1,2-dichloroethane (ensuring that a mass ratio of the solvent to cyclohexanone was 6 to 799), 2.6 g of o-dichlorobenzene (internal standard substance), acrolein and cyclohexanone of various molar ratios as shown in Table 7 (wherein the amounts of cyclohexanone in Embodiments 29 to 31 were all 48 mmol, and the amounts of acrolein in Embodiments 32 to 36 were all 48 mmol) and 100 mg of nitrogen-doped carbon nanotube (a content of N was 4.34 at %) were sequentially added into a high-pressure reactor, stirred and heated to a temperature of 80 C., and charged with oxygen; then, timing was started, and the pressure was maintained at 1 MPa during the reaction. After reaction for 4 hours, timing was stopped, the reactor was cooled to a room temperature, and a liquid-solid phase mixture was filtered to obtain a solid catalyst and a liquid-phase mixture containing unreacted reactants and products. The liquid-phase mixture was measured by gas chromatography (GC). GC detection results were shown in Table 7 (effects of different molar ratios of aldehydes to ketones on the Baeyer-Villiger oxidation of cyclohexanone).

TABLE-US-00007 TABLE 7 Ratio of Conversion of Selectivity of Conversion of Selectivity of aldehydes cyclohexanone -caprolactone acrolein acrylic acid Efficiency Embodiment to ketones (%) (%) (%) (%) of acrolein 29 0.25 5.78 59 27 100 0.13 30 0.5 11 69 27 100 0.28 3 1.00 22 74 37 100 0.44 31 1.25 30 73 49 96 0.45 32 2.00 30 82 33 100 0.75 33 4.00 46 82 38 100 1.00 34 8.00 66 83 54 78 1.00 35 16.00 74 77 57 71 1.00 36 100.00 100 62 62 68 1.00

[0039] Through analyzing the data in Table 7, it can be known that the conversion of cyclohexanone is increased with the increase of the ratio of aldehydes to ketones, and when the ratio of aldehydes to ketones is 100, cyclohexanone can even be completely converted. After the ratio of aldehydes to ketones is greater than 4, the efficiency of acrolein is maintained at 100%, and the optimal molar ratio of aldehydes to ketones is 4.00 on the premise of ensuring the high yield of the -caprolactone and 100% selectivity of acrylic acid.