CN111100105A - Method for preparing epsilon-caprolactone from solvent-free cyclohexanone - Google Patents
Method for preparing epsilon-caprolactone from solvent-free cyclohexanone Download PDFInfo
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- CN111100105A CN111100105A CN201911422480.XA CN201911422480A CN111100105A CN 111100105 A CN111100105 A CN 111100105A CN 201911422480 A CN201911422480 A CN 201911422480A CN 111100105 A CN111100105 A CN 111100105A
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Abstract
The invention discloses a method for preparing epsilon-caprolactone from non-solvation cyclohexanone. The method comprises the following steps: adding a nitrogen-doped carbon nanotube catalyst into a mixture of cyclohexanone and acrolein, and reacting at 30-100 ℃ by taking molecular oxygen as an oxidant to obtain epsilon-caprolactone; no solvent is added into the reaction system. The method adopts the nitrogen-doped carbon nano tube as the catalyst, realizes that the cyclohexanone is converted into the epsilon-caprolactone with high conversion rate and high selectivity under the condition of no solvent, simplifies the process of solvent separation in the industrial process, reduces the process energy consumption, more fully utilizes the space of a container, increases the volume utilization rate of a reactor, is easy to recover the catalyst, is environment-friendly for oxidant and has lower cost.
Description
Technical Field
The invention relates to the field of preparation of epsilon-caprolactone, in particular to a method for preparing epsilon-caprolactone from non-solvation cyclohexanone.
Background
The epsilon-caprolactone is an important organic synthesis intermediate and a novel polyester monomer, and has very excellent physical and chemical properties. The polycaprolactone prepared from the epsilon-caprolactone monomer has excellent thermoplastic property and processing and forming capability, can be prepared into a plastic product with better environmental affinity, and can also be prepared into a degradable medical material. A plurality of methods for synthesizing epsilon-caprolactone have been reported, wherein a method for synthesizing epsilon-caprolactone by oxidizing cyclohexanone Baeyer-Villiger (B-V) is a research hotspot.
The early oxidation method of cyclohexanone BV mainly adopts peroxy acid and hydrogen peroxide as oxidants, and has better activity. However, peroxy acids and hydrogen peroxide have serious safety problems in storage, transportation and use, and have potential explosion risks, so that the industry is prompted to find more reliable oxidation systems to replace. In recent years, development of a system using oxygen as an oxidizing agent and aldehydes as pro-oxidizing agents has attracted attention in the scientific research community and the industrial community. The system usually uses benzaldehyde, acrolein and the like as pro-oxidants, and can promote cyclohexanone to be converted into epsilon-caprolactone with high selectivity under mild conditions. For example, Yuta Nabae et al (ACCCATALYSis.2013, 3,230-236) use benzaldehyde as a co-oxidant to catalyze the cyclohexanone B-V reaction in an oxygen atmosphere, although the selectivity of epsilon-caprolactone can reach 99%. The carbon material developed by Yi Shuang Feng et al (CN102603446B) of Hunan university catalyzes and oxidizes cyclohexanone to prepare epsilon-caprolactone, and the selectivity of the epsilon-caprolactone can reach 100 percent. In the work at the early stage of this topic group (CN106397386B), we found that acrolein can also be used as a co-oxidant to catalyze cyclohexanone to produce epsilon-caprolactone with a selectivity of more than 80%. However, a large amount of solvent is needed in the system, the concentration of a reaction substrate is very low (cyclohexanone usually accounts for about 10 wt% of the total mass, aldehyde accounts for 5-20 wt%, and the remaining about 70 wt% is solvent), the production capacity of epsilon-caprolactone is severely limited, and meanwhile, the recovery cost is increased due to the large amount of solvent in the system, which is also an important limiting factor for the industrial application of the epsilon-caprolactone. The inventors also disclose in CN108558819A that fluorinated carbon nanotubes can have higher catalytic activity when used as a catalyst. However, the system still needs a large amount of solvent, and the cost cannot be further reduced.
The development of a solvent-free method is an important way for promoting the industrialization of synthesizing the epsilon-caprolactone by oxidizing cyclohexanone B-V by an oxidation method, and the method avoids the recovery of a large amount of solvent, so the method has the characteristics of higher safety and low cost. Sinhamapatra et al (Catal. Sci. Technol.,2012,2, 2375-2382) reported that zirconium phosphate was used as a catalyst and benzaldehyde was used as a co-oxidant under solvent-free and normal temperature conditions to catalyze the conversion of cyclohexanone to epsilon-caprolactone as early as 2012. However, zirconium used in the system is a rare metal, is expensive, and cannot be used in industrial production. In addition, the dosage of benzaldehyde in the system is too high, the generated benzoic acid is insoluble in cyclohexanone, and can be continuously precipitated in the reaction process, so that the system generates solid crystals, and the risk of pipeline blockage exists in industrial application. Based on the two points, the low-cost nonmetal catalyst is developed to efficiently catalyze cyclohexanone to synthesize epsilon-caprolactone without solvent, and has important significance for the safe production of epsilon-caprolactone without solvent.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a cyclohexanone B-V oxidation reaction O2A process for the solvation-free reaction of aldehyde systems. The method of the invention does not add solvent, reduces the energy consumption of the process of solvent separation in the industrial process, and leads the synthesis process of the epsilon-caprolactone to be more economical, green and reliable.
The above object of the present invention is achieved by the following technical solutions:
a method for preparing epsilon-caprolactone by cyclohexanone without solvation comprises the following steps:
adding a nitrogen-doped carbon nanotube catalyst into a mixture of cyclohexanone and acrolein, and reacting at 30-100 ℃ by taking molecular oxygen as an oxidant to obtain epsilon-caprolactone;
the nitrogen-doped carbon nanotube has a nitrogen content of 0.68 to 3.32 at%.
More preferably, the nitrogen-doped carbon nanotube has a nitrogen content of 2.28 at.%.
The inventors have surprisingly found that epsilon-caprolactone can be obtained with high conversion rate under the condition of no solvent by using the nitrogen-doped carbon nanotube as a catalyst. Although the inventor reports nitrogen-doped carbon nanotubes as a catalyst, the system is still a solvent system, and the conversion rate of acrolein is low. Also, the reaction process of the present invention generates a strong exotherm, so it is generally desirable to dilute the substrate concentration with a solvent to control the phenomenon of temperature runaway and the like.
The nitrogen-doped carbon nano tube is prepared by a CVD method and pyridine as a nitrogen source.
Specifically, the method can be performed according to the following steps:
uniformly spreading a certain amount of carbon tubes purified by HCl in a porcelain boat, placing in a constant temperature section of an energy-saving tube furnace, and introducing N2The tube furnace was heated to 760 ℃ with a gradient temperature rise. When the temperature is raised to 760 ℃, pyridine is injected into the quartz tube by using an injection pump, the pyridine is kept for a plurality of minutes after the injection, the energy-saving tube furnace stops heating, when the temperature is cooled to be below 100 ℃, a sample can be taken out, and then alcohol acetone is used for washing, drying and grinding, so that the obtained sample is the nitrogen-doped carbon nano tube.
The carbon tube may be a common commercially available carbon tube.
Preferably, the molar ratio of the acrolein to the cyclohexanone is 0.01 to 100.
Further, the molar ratio of the acrolein to the cyclohexanone is preferably 0.4 to 2. In the past system, in order to ensure that the selectivity of cyclohexanone reaches 80%, the molar ratio of aldehyde to ketone is required to be more than 4, and in the system, the inventors unexpectedly found that the high-efficiency conversion (> 80%) of cyclohexanone can be realized under the condition that the ratio of aldehyde to ketone is 0.4-2. Most preferably, the molar ratio of acrolein to cyclohexanone is 1.
Preferably, the mass ratio of the nitrogen-doped carbon nanotube catalyst to cyclohexanone is 0.01-0.1.
More preferably, the reaction temperature is 30-50 ℃.
Preferably, the pressure of the reaction is 0.1-1 MPa.
Preferably, the reaction time is 0.5-12 h.
Preferably, the reaction is carried out at a stirring speed of 100 to 1200 rpm.
Compared with the prior art, the invention has the following beneficial effects:
the invention adopts the nitrogen-doped carbon nano tube as the catalyst, realizes the conversion of cyclohexanone into epsilon-caprolactone with high conversion rate and high selectivity under the condition of no solvent, simplifies the process of solvent separation in the industrial process and reduces the energy consumption of the process. In addition, the solvent-free method can be carried out at the temperature of 30-50 ℃, and the reaction conditions are milder than those of the prior art.
Drawings
FIG. 1 is a gas chromatogram of a typical liquid sample after reaction.
Detailed Description
The invention is further described below with reference to examples and figures, but the scope of the invention is not limited to the examples.
In the following examples, the conversion (%) of cyclohexanone and the selectivity (%) of epsilon-caprolactone were measured by Gas Chromatography (GC) analysis after diluting the liquid after the reaction by 10 times with acetone at the end of the reaction. The GC detection adopts an internal standard method, o-dichlorobenzene is used as an internal standard substance, corresponding standard curves of the two substances are respectively drawn, and then the GC detection of the reaction solution is combined for calculation.
In the examples, the preparation method of the nitrogen-doped carbon nanotube is as follows: uniformly spreading a certain amount of carbon tubes purified by HCl in a porcelain boat, placing in a constant temperature section of an energy-saving tube furnace, and introducing N2(10L/min) at 10 ℃ min-1The rate of temperature increase of (a) heats the tube furnace to 760 ℃. When the temperature is raised to 760 ℃, pyridine is injected into a quartz tube at the flow rate of 2mL/min by using an injection pump, the injection time is 4 hours, the pyridine is kept for 10 minutes after injection, the energy-saving tube furnace stops heating, when the temperature is cooled to be below 100 ℃, a sample can be taken out, and then alcohol acetone is used for washing, drying and grinding, so that the obtained sample is the nitrogen-doped carbon nano tube. The nitrogen content was 2.28 at.%.
Examples 1 to 3
The method comprises the following steps: 1.306g of o-dichlorobenzene (internal standard), 0.4907g of cyclohexanone, 1.121g of acrolein and 100mg of nitrogen-doped carbon nanotubes were put into a high-pressure reaction vessel, and 17ml of the reaction solvent shown in Table 1 was added.
A solvent-free system: 1.306g of o-dichlorobenzene (internal standard), 10.45g of cyclohexanone, 6.216g of acrolein and 100mg of nitrogen-doped carbon nanotubes were added to the autoclave.
Both systems are heated to 50 ℃ at the rotating speed of 1000rpm, oxygen is introduced, timing is started, and the pressure is maintained to be 1MPa in the reaction process. After reacting for 2h, the reaction kettle is cooled to 15 ℃ in ice water, and the solid-phase mixture of the liquid and the solid is filtered to obtain the solid catalyst and the liquid-phase mixture containing unreacted reactants and reaction products. The GC assay results are shown in Table 1.
TABLE 1 Effect of solvent on the B-V Oxidation of Cyclohexanone
Example 4
1.306g of o-dichlorobenzene (internal standard substance), 10.45g of cyclohexanone, 6.216g of acrolein and 50mg of nitrogen-doped carbon nanotube are added into a high-pressure reaction kettle, mixed and heated to 50 ℃ at the stirring speed of 1000rpm, oxygen is introduced, timing is started, and the pressure is maintained to be 1MPa in the reaction process. After reacting for 2h, the reaction kettle is cooled to 15 ℃ in ice water, and the solid-phase mixture of the liquid and the solid is filtered to obtain the solid catalyst and the liquid-phase mixture containing unreacted reactants and reaction products. Product GC detection results: the conversion of cyclohexanone was 17.88%, and the selectivity and absolute amount of epsilon-caprolactone produced were 71 mol% and 13.46mol, respectively. The conversion of acrolein was 83.3% and the selectivity of acrylic acid was 97.6%.
Example 5
1.306g of o-dichlorobenzene (internal standard substance), 10.45g of cyclohexanone, 6.216g of acrolein and 100mg of nitrogen-doped carbon nano tube are added into a high-pressure reaction kettle, stirred and heated to 50 ℃ at the rotating speed of 1000rpm, oxygen with the pressure of 0.5MPa is introduced, timing is started, and the pressure is kept unchanged in the reaction process. After reacting for 2h, the reaction kettle is cooled to 15 ℃ in ice water, and the solid-phase mixture of the liquid and the solid is filtered to obtain the solid catalyst and the liquid-phase mixture containing unreacted reactants and reaction products. Product GC detection results: the conversion of cyclohexanone was 16.11%, and the selectivity and absolute amount of caprolactone produced were 76% and 12.88mmol, respectively. The conversion of acrolein was 87.4% and the selectivity of acrylic acid was 99.7%.
Example 6
1.306g of o-dichlorobenzene (internal standard substance), 100mg of nitrogen-doped carbon nano tube, 7.6g of cyclohexanone and 8.376g of acrolein mixture are sequentially added into a high-pressure reaction kettle, stirred and heated to 50 ℃ at 1000rpm, oxygen with the pressure of 1MPa is introduced, timing is started, and the pressure is kept unchanged in the reaction process. After reacting for 2h, the reaction kettle is cooled to 15 ℃ in ice water, and the solid-phase mixture of the liquid and the solid is filtered to obtain the solid catalyst and the liquid-phase mixture containing unreacted reactants and reaction products. The GC detection result of the product shows that the conversion rate of the cyclohexanone is 24.6 percent, and the selectivity and the absolute generation amount of the caprolactone are 94.36 percent and 17.97mmol respectively. The conversion of acrolein was 62% and the selectivity of acrylic acid was 91.1%.
Example 7
1.306g of o-dichlorobenzene (internal standard substance), 10.45g of cyclohexanone, 6.216g of acrolein and 100mg of nitrogen-doped carbon nanotubes are sequentially added into a high-pressure reaction kettle, stirred and heated to 50 ℃ at 1200rpm, oxygen with the pressure of 1MPa is introduced, timing is started, and the pressure is kept unchanged in the reaction process. After reacting for 2h, the reaction kettle is cooled to 15 ℃ in ice water, and the solid-phase mixture of the liquid and the solid is filtered to obtain the solid catalyst and the liquid-phase mixture containing unreacted reactants and reaction products. Product GC detection results: the conversion of cyclohexanone was 19.77%, and the selectivity and absolute amount of caprolactone produced were 85.1% and 17.91mmol, respectively. The conversion of acrolein was 92% and the selectivity of acrylic acid was 100%.
Example 8
1.306g of o-dichlorobenzene (internal standard substance), 10.45g of cyclohexanone, 6.216g of acrolein and 100mg of nitrogen-doped carbon nanotubes are sequentially added into a high-pressure reaction kettle, stirred and heated to 50 ℃ at 1000rpm, oxygen with the pressure of 1MPa is introduced, timing is started, and the pressure is kept unchanged in the reaction process. After 12 hours of reaction, the reaction kettle was cooled to 15 ℃ in ice water, and the liquid-solid mixture was filtered to obtain a solid catalyst and a liquid-phase mixture containing unreacted reactants and reaction products. Product GC detection results: the conversion of cyclohexanone was 22.32%, and the selectivity and absolute amount of caprolactone produced were 79.5% and 18.89mmol, respectively. The conversion of acrolein was 98.4% and the selectivity of acrylic acid was 89%.
Example 9
1.306g of o-dichlorobenzene (internal standard substance), 10.45g of cyclohexanone, 6.216g of acrolein and 100mg of nitrogen-doped carbon nanotubes are sequentially added into a high-pressure reaction kettle, stirred and heated to 35 ℃ at 1000rpm, oxygen with the pressure of 1MPa is introduced, timing is started, and the pressure is kept unchanged in the reaction process. After reacting for 2 hours, the reaction kettle is cooled to 15 ℃ in ice water, and the solid-phase mixture of the liquid and the solid is filtered to obtain the solid catalyst and the liquid-phase mixture containing unreacted reactants and reaction products. Product GC detection results: the conversion of cyclohexanone was 15.32%, and the selectivity and absolute amount of caprolactone produced were 84% and 13.64mmol, respectively. The conversion of acrolein was 79.5% and the selectivity of acrylic acid was 100%.
Examples 10 to 14
1.306g of o-dichlorobenzene (internal standard substance), 10.45g of cyclohexanone, 6.216g of acrolein and 50mg of nitrogen-doped carbon nanotubes are sequentially added into a high-pressure reaction kettle, stirred and heated to 50 ℃ at 1000rpm, oxygen with the pressure of 1MPa is introduced, timing is started, and the pressure is kept unchanged in the reaction process. After reacting for 2 hours, stopping timing, cooling the reaction kettle in ice water to 15 ℃, and filtering the liquid-solid phase mixture to obtain a solid catalyst and a liquid phase mixture containing unreacted reactants and reaction products. The above process was repeated 5 times with the nitrogen-doped carbon nanotubes recovered by filtration. The GC assay results are shown in Table 2.
TABLE 2 influence of catalyst cycle number on the B-V Oxidation of Cyclohexanone
Claims (9)
1. A method for preparing epsilon-caprolactone from non-solvation cyclohexanone is characterized by comprising the following steps:
adding a nitrogen-doped carbon nanotube catalyst into a mixture of cyclohexanone and acrolein, and reacting at 30-100 ℃ by taking molecular oxygen as an oxidant to obtain epsilon-caprolactone; no solvent is added into the reaction system, and the nitrogen content in the nitrogen-doped carbon nano tube is 0.68-3.32 at%.
2. The method of claim 1, wherein the nitrogen-doped carbon nanotube catalyst is prepared by a CVD method using pyridine as a nitrogen source.
3. A process according to claim 1, wherein the molar ratio of acrolein to cyclohexanone is from 0.01 to 100.
4. A process according to claim 2, wherein the molar ratio of acrolein to cyclohexanone is from 0.4 to 2.
5. The method according to claim 1, wherein the mass ratio of the nitrogen-doped carbon nanotube catalyst to cyclohexanone is 0.01-0.1.
6. The method according to claim 1, wherein the reaction temperature is 30 to 50 ℃.
7. The method according to claim 1, wherein the reaction time is 0.5-12 h.
8. The method according to claim 1, wherein the reaction is carried out at a stirring speed of 100 to 1200 rpm.
9. The method of claim 1, further comprising a separation step after the reaction is finished, wherein the separation step is to separate the catalyst from the system and recycle the catalyst for next catalysis.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115286611A (en) * | 2022-08-22 | 2022-11-04 | 华南理工大学 | Method for simultaneously preparing epsilon-caprolactone and propionic acid |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106397386A (en) * | 2016-09-13 | 2017-02-15 | 华南理工大学 | Method used for preparing epsilon-hexanolactone |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106397386A (en) * | 2016-09-13 | 2017-02-15 | 华南理工大学 | Method used for preparing epsilon-hexanolactone |
Non-Patent Citations (2)
| Title |
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| APURBA SINHAMAHAPATRA, ET AL.: "Room temperature Baeyer-Villiger oxidation using molecular oxygen over mesoporous zirconium phosphate", 《CATAL. SCI. TECHNOL.》 * |
| 侯萌萌: "掺氮碳纳米管催化丙烯醛氧化及环己酮Baeyer-Villiger氧化的性能研究", 《中国优秀硕士学位论文全文数据库工程科技I辑》 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115286611A (en) * | 2022-08-22 | 2022-11-04 | 华南理工大学 | Method for simultaneously preparing epsilon-caprolactone and propionic acid |
| CN115286611B (en) * | 2022-08-22 | 2023-08-22 | 华南理工大学 | Method for simultaneously preparing epsilon-caprolactone and propionic acid |
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