Post-treatment method of catalyst in menthol production process

Abstract

The invention provides a post-treatment method of a catalyst in a menthol production process, which comprises the following steps: 1) after a catalytic reaction is finished, separating the catalyst from a reaction product; heating and aging the catalyst in the separation process or after the separation is finished; and 2) after heating and aging, immersing the catalyst in menthol, and stirring and aging. According to the method, the service life of the catalyst can be remarkably prolonged, the reaction selectivity of the catalyst can be remarkably improved, meanwhile, the stable quality of the product can be kept, and remarkable economic value and practical significance are achieved.

Description

Technical Field

[0001] This invention relates to a post-treatment method for catalysts in the production of menthol. Background Technology

[0002] Menthol, also known as peppermint, has the molecular formula C60. 10 H 20 O is a colorless and transparent liquid or solid with a very strong cooling sensation and minty flavor. It is a very important flavoring agent and is widely used in food, cigarettes, daily chemicals, medicine and other fields.

[0003] Because the menthol molecule has three chiral centers, there are eight chiral isomers: (±)menthol, (±)neomenthol, (±)isomenthol, and (±)neoisomenthol. As a flavoring product, even slight changes in the composition or content of impurities can significantly impact the quality of menthol. Therefore, maintaining stable reactions and product quality is a common challenge in the industry.

[0004] Patent CN101821221B discloses a method for preparing racemic or optically active menthol. The catalyst in the method is a catalyst containing metals such as nickel, zirconium, copper, and molybdenum. The method involves continuous production in a main reactor and a supplementary reactor. The L-menthol content in the product can reach 99.7%, but the method does not mention the post-treatment process of the catalyst.

[0005] Patent CN104211566A also mentions a method for producing menthol by hydrogenating isomenthol using a metal catalyst. It mentions that the menthol product is produced by distillation / rectification purification, but it also does not mention the post-treatment process of the catalyst, nor does it mention the stability of the catalyst or the quality stability of the product.

[0006] The present invention aims to provide a post-treatment method for catalysts in the production of menthol. The method described in the present invention can significantly improve the catalyst life and reaction selectivity, while helping to maintain the stability of product quality, and has significant economic value and practical significance. Summary of the Invention

[0007] This invention provides a post-treatment method for catalysts in the production of menthol. The method described in this invention can significantly improve the service life and reaction selectivity of the catalyst, while also helping to maintain the stability of product quality.

[0008] The technical solution adopted in this invention is as follows:

[0009] In a first aspect, the present invention provides a method for post-treatment of catalysts in the production of menthol, comprising:

[0010] 1) After the catalytic reaction is completed, the catalyst is separated from the reaction products; the catalyst is aged by heating during or after the separation process.

[0011] 2) After the heating aging is completed, the catalyst is immersed in menthol and stirred for aging.

[0012] In the method of the present invention, in step 1), the catalytic reaction refers to the reaction of preparing menthol by hydrogenation of isopreneol as a raw material under the action of a catalyst; preferably, the amount of catalyst used is 1-2 wt% of the amount of isopreneol; the conditions for hydrogenation reaction are a temperature of 45-70°C and a pressure of 0.1-2.0 MPaG.

[0013] The catalyst is one or more of Raney nickel, Raney cobalt, Pd / C, and Ru / C, preferably Raney nickel; preferably, the content of Pd or Ru in the Pd / C or Ru / C catalyst is 5-20 wt%.

[0014] In step 1), the heating aging temperature is 40-100℃, preferably 40-80℃, and the heating is carried out by hot air or hot nitrogen purging, preferably hot nitrogen, and the purging time is 10-60min, preferably 10-30min.

[0015] In the method of the present invention, in step 2), the menthol used for stirring and aging can also be the reaction product separated from this batch. The amount of menthol used is 3-15 times the mass of the catalyst, preferably 5-10 times, and the stirring and aging time is 10-120 min, preferably 10-60 min.

[0016] A method for recycling catalysts in the production of menthol includes: returning the catalyst treated by the aforementioned post-treatment method to the reactor for reaction.

[0017] On the other hand, the present invention provides a method for preparing menthol, comprising:

[0018] Menthol was obtained by hydrogenation of isomenthol as a raw material under the action of a catalyst.

[0019] In the method, the catalyst is a Raney nickel, Raney cobalt, Pd / C, or Ru / C catalyst that has been treated by the post-treatment method described in the first aspect.

[0020] Preferably, the amount of catalyst used is 1-2 wt% of the amount of isoprene;

[0021] Preferably, the conditions for the hydrogenation reaction are a temperature of 45-70°C and a pressure of 0.1-2.0 MPaG.

[0022] The beneficial effects of this invention are as follows:

[0023] 1) Research has found that water in the raw material isoprene selectively adsorbs onto the surface and pores of the catalyst during the catalytic reaction, resulting in significant poisoning of the catalyst. As the number of catalyst reuses increases, the degree of poisoning gradually deepens, specifically manifested in the increase of batch reaction time and the decrease of product selectivity. By heating and aging the catalyst, some of the adsorbed water can be removed, thereby activating the catalyst.

[0024] 2) After heat aging treatment, the active species on the catalyst surface are exposed due to the evaporation of moisture. The excessively high reactivity will cause a decrease in reaction selectivity and an increase in the impurity content in the reaction products, which will ultimately affect the product quality. By immersing the catalyst in the reaction products, the impurities in the reaction products (such as menthol) will be adsorbed on the catalyst surface, which will cover the exposed active centers and inhibit side reactions, thereby improving the selectivity of the reaction.

[0025] 3) By controlling the heating and stirring aging conditions, the catalyst activity can always be maintained at an ideal level, and the reaction products can meet the external sales standards without purification.

[0026] The catalyst obtained according to the present invention has better reaction stability and reaction selectivity, while helping to maintain the stability of product quality. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to the embodiments, but the scope of the present invention is not limited to these embodiments.

[0028] Main raw materials

[0029] L-Isomentheptyl, wherein the isomentheptyl content is 99.90% and the ee value is 99.86%, Aladdin reagent;

[0030] Raney nickel, Raney-6800, Grace Company;

[0031] Raney Cobalt, Raney-2724, Grace Company.

[0032] Analytical methods

[0033] Methods for detecting isomentheptyl alcohol content and menthol content:

[0034] The chromatographic column model is HP-INNOWAX (polyethylene glycol), the vaporization chamber temperature is 220℃, the detector temperature is 260℃, the split ratio is 50, and the column oven temperature program is as follows: initial temperature 50℃, hold for 2 min, then increase the temperature to 80℃ at 5℃ / min, then increase the temperature to 250℃ at 15℃ / min, and hold for 10 min.

[0035] Isopyramine EE value and menthol EE value detection methods:

[0036] The chromatographic column model is Alpha-DEX-120, the vaporization chamber temperature is 220℃, the detector temperature is 300℃, the split ratio is 100, and the column oven temperature program is as follows: initial temperature 85℃, hold for 55 min, then increase the temperature to 130℃ at 20℃ / min, and hold for 15 min.

[0037] Aroma Evaluation Methods

[0038] A team of 10 professional fragrance evaluators evaluated the samples based on two dimensions: fragrance purity and cooling sensation. The average score was taken, with each dimension having a maximum score of 10. A higher score indicates better performance in that category.

[0039] Implementation Methods

[0040] Example 1

[0041] Place 1g of Raney-6800 into a dry 500ml high-pressure reactor purged with nitrogen (the reactor's discharge pipe is equipped with a filter). Pressurize the reactor to 1MPaG using 99% pure hydrogen, then release the pressure to atmospheric pressure. Repeat this step three times to complete the gas purging. Use a horizontal pump to deliver 100g of L-isomenthol into the reactor, maintaining a temperature of 50℃ and a reactor pressure of 1MPaG. Start the stirrer, ensuring uniform mixing, and react for 8 hours. Then, send samples for analysis.

[0042] After the reaction is complete, the pressure inside the reactor is released to atmospheric pressure, and then pressurized to 1 MPaG using 99% pure nitrogen. The pressure is then released to atmospheric pressure, and this step is repeated 3 times. After that, nitrogen is purged to 1 MPaG to expel the reaction product. Then, the inlet valve and the pressure relief valve are opened, and nitrogen at 40°C is continuously introduced into the reactor. After purging at atmospheric pressure for 10 minutes, 10g of the reaction product that was just expelled is pumped into the reactor using a horizontal flow pump. After stirring for 120 minutes, the pressure relief valve is closed, nitrogen is purged to 1 MPaG, and the 10g of reaction product that was just pumped in is expelled.

[0043] The pressure was increased to 1 MPaG using 99% pure hydrogen, then released to atmospheric pressure. This step was repeated three times to complete the gas replacement. 100g of L-isomenthol was then pumped into the reactor using a horizontal flow pump to begin the reaction (referring to the hydrogenation reaction and catalyst post-treatment process).

[0044] The evaluation results are as follows (menthol / % refers to the menthol content in the reaction solution; the same applies below):

[0045] Initial reaction Apply 30 times Apply 60 times Menthol / % 99.91 99.90 99.68 ee value / % 99.85 99.84 99.77 Cooling sensation evaluation 9.3 9.0 8.8 Characteristic odor evaluation 9.1 9.0 8.6

[0046] Example 2

[0047] Place 1g of Raney-6800 into a dry 500ml high-pressure reactor purged with nitrogen (the reactor's discharge pipe is equipped with a filter). Pressurize the reactor to 1MPaG using 99% pure hydrogen, then release the pressure to atmospheric pressure. Repeat this step three times to complete the gas purging. Use a horizontal pump to deliver 100g of L-isomenthol into the reactor, maintaining a temperature of 50℃ and a reactor pressure of 1MPaG. Start the stirrer, ensuring uniform mixing, and react for 8 hours. Then, send samples for analysis.

[0048] After the reaction is complete, the pressure inside the reactor is released to atmospheric pressure, and then pressurized to 1 MPaG using 99% pure nitrogen. The pressure is then released to atmospheric pressure, and this step is repeated 3 times. After that, nitrogen is purged to 1 MPaG to expel the reaction product. Then, the inlet valve and the pressure relief valve are opened, and nitrogen at 60°C is continuously introduced into the reactor. After purging at atmospheric pressure for 30 minutes, 5g of the expelled reaction product is pumped into the reactor using a horizontal flow pump. After stirring for 40 minutes, the pressure relief valve is closed, nitrogen is purged to 1 MPaG, and the 5g of the injected reaction product is expelled.

[0049] The pressure was increased to 1 MPaG using 99% pure hydrogen, then released to atmospheric pressure. This step was repeated three times to complete the gas replacement. 100g of L-isomenthol was then pumped into the reactor using a horizontal flow pump to begin the reaction.

[0050] The evaluation results are as follows:

[0051] Initial reaction Apply 30 times Apply 60 times Menthol / % 99.91 99.91 99.89 ee value / % 99.86 99.86 99.85 Cooling sensation evaluation 9.4 9.2 9.1 Characteristic odor evaluation 9.2 9.1 9.1

[0052] Example 3

[0053] Place 1g of Raney-6800 into a dry 500ml high-pressure reactor purged with nitrogen (the reactor's discharge pipe is equipped with a filter). Pressurize the reactor to 1MPaG using 99% pure hydrogen, then depressurize to atmospheric pressure. Repeat this step three times to complete the gas purging. Use a horizontal pump to deliver 100g of L-isomenthol into the reactor, maintaining a temperature of 55℃ and a reactor pressure of 1MPaG. Start the stirrer, ensuring uniform mixing, and react for 8 hours. Then, send samples for analysis.

[0054] After the reaction is complete, the pressure inside the reactor is released to atmospheric pressure, and then pressurized to 1 MPaG using 99% pure nitrogen. The pressure is then released to atmospheric pressure, and this step is repeated 3 times. After that, nitrogen is purged to 1 MPaG to expel the reaction product. Then, the inlet valve and the pressure relief valve are opened, and nitrogen at 80°C is continuously introduced into the reactor. After purging at atmospheric pressure for 60 minutes, 3g of the reaction product that was just expelled is pumped into the reactor using a horizontal flow pump. After stirring for 60 minutes, the pressure relief valve is closed, and nitrogen is purged to 1 MPaG to expel the 3g of reaction product that was just injected.

[0055] The pressure was increased to 1 MPaG using 99% pure hydrogen, then released to atmospheric pressure. This step was repeated three times to complete the gas replacement. 100g of L-isomenthol was then pumped into the reactor using a horizontal flow pump to begin the reaction.

[0056] The evaluation results are as follows:

[0057] Initial reaction Apply 30 times Apply 60 times Menthol / % 99.89 99.89 99.70 ee value / % 99.85 99.84 99.77 Cooling sensation evaluation 9.3 9.0 9.1 Characteristic odor evaluation 9.1 9.1 8.4

[0058] Example 4

[0059] Place 1g of Raney-2724 into a dry 500ml high-pressure reactor purged with nitrogen (the reactor's discharge pipe is equipped with a filter). Pressurize the reactor to 1MPaG using 99% pure hydrogen, then release the pressure to atmospheric pressure. Repeat this step three times to complete the gas purging. Use a horizontal pump to deliver 100g of L-isomenthol into the reactor, maintaining the temperature at 55℃ and the reactor pressure at 0.5MPaG. Start the stirrer, ensuring uniform mixing, and react for 8 hours. Then, send samples for analysis.

[0060] After the reaction is complete, the pressure inside the reactor is released to atmospheric pressure, and then pressurized to 1 MPaG using 99% pure nitrogen. The pressure is then released to atmospheric pressure, and this step is repeated 3 times. After that, nitrogen is purged to 1 MPaG to expel the reaction product. Then, the inlet valve and the pressure relief valve are opened, and nitrogen at 100°C is continuously introduced into the reactor. After purging at atmospheric pressure for 30 minutes, 15g of the reaction product that was just expelled is pumped into the reactor using a horizontal flow pump. After stirring for 10 minutes, the pressure relief valve is closed, nitrogen is purged to 1 MPaG, and the 15g of reaction product that was just pumped in is expelled.

[0061] The pressure was increased to 1 MPaG using 99% pure hydrogen, then released to atmospheric pressure. This step was repeated three times to complete the gas replacement. 100g of L-isomenthol was then pumped into the reactor using a horizontal flow pump to begin the reaction.

[0062] The evaluation results are as follows:

[0063] Initial reaction Apply 30 times Apply 60 times Menthol / % 99.89 99.83 99.58 ee value / % 99.86 99.84 99.71 Cooling sensation evaluation 9.1 8.7 8.6 Characteristic odor evaluation 9.2 8.9 8.4

[0064] Example 5

[0065] Place 1g of Raney-2724 into a dry 500ml high-pressure reactor purged with nitrogen (the inlet discharge pipe is not equipped with a filter; it is connected to an external filter). Pressurize the reactor to 1MPaG with 99% pure hydrogen, then depressurize to atmospheric pressure. Repeat this step three times to complete the gas purging. Use a horizontal pump to deliver 100g of L-isomenthol into the reactor, maintaining the temperature at 60℃ and the reactor pressure at 0.2MPaG. Start stirring to ensure uniform mixing and react for 8 hours. Then, send samples for analysis.

[0066] After the reaction is complete, the pressure inside the reactor is released to atmospheric pressure, and then pressurized to 1 MPaG using 99% pure nitrogen. The pressure is then released to atmospheric pressure, and this step is repeated 3 times. After that, nitrogen is purged to 1 MPaG, and the reaction product is expelled into an external filter. After filtration, nitrogen at 70°C is continuously introduced into the filter through the discharge pipeline, and the filter is purged at atmospheric pressure for 30 minutes. Then, 10g of the expelled reaction product is injected into the filter, and after 30 minutes, the reaction product is emptied. The catalyst is then reused in the reactor.

[0067] The pressure was increased to 1 MPaG using 99% pure hydrogen, then released to atmospheric pressure. This step was repeated three times to complete the gas replacement. 100g of L-isomenthol was then pumped into the reactor using a horizontal flow pump to begin the reaction.

[0068] The evaluation results are as follows:

[0069] Initial reaction Apply 30 times Apply 60 times Menthol / % 99.88 99.85 99.52 ee value / % 99.85 99.81 99.66 Cooling sensation evaluation 9.1 8.5 8.4 Characteristic odor evaluation 9.1 8.5 8.0

[0070] Comparative Example 1

[0071] Place 1g of Raney-6800 into a dry 500ml high-pressure reactor purged with nitrogen (the reactor's discharge pipe is equipped with a filter). Pressurize the reactor to 1MPaG using 99% pure hydrogen, then release the pressure to atmospheric pressure. Repeat this step three times to complete the gas purging. Use a horizontal pump to deliver 100g of L-isomenthol into the reactor, maintaining a temperature of 50℃ and a reactor pressure of 1MPaG. Start the stirrer, ensuring uniform mixing, and react for 8 hours. Then, send samples for analysis.

[0072] After the reaction is complete, the pressure inside the reactor is released to atmospheric pressure, then pressurized to 1 MPaG using 99% pure nitrogen, and then released to atmospheric pressure. This step is repeated 3 times. After that, nitrogen is purged to 1 MPaG to expel the reaction product. Then, 99% pure hydrogen is purged to 1 MPaG, and then released to atmospheric pressure. This step is repeated 3 times to complete the gas replacement. 100g of L-isomenthol is then delivered into the reactor using a horizontal flow pump to start the reaction.

[0073] The evaluation results are as follows:

[0074] Initial reaction Apply 30 times Apply 60 times Menthol / % 99.90 99.82 98.67 ee value / % 99.86 99.34 99.12 Cooling sensation evaluation 9.1 8.0 6.1 Characteristic odor evaluation 9.3 7.9 5.5

[0075] Comparative Example 2

[0076] Place 1g of Raney-6800 into a dry 500ml high-pressure reactor purged with nitrogen (the reactor's discharge pipe is equipped with a filter). Pressurize the reactor to 1MPaG using 99% pure hydrogen, then release the pressure to atmospheric pressure. Repeat this step three times to complete the gas purging. Use a horizontal pump to deliver 100g of L-isomenthol into the reactor, maintaining a temperature of 50℃ and a reactor pressure of 1MPaG. Start the stirrer, ensuring uniform mixing, and react for 8 hours. Then, send samples for analysis.

[0077] After the reaction is complete, the pressure inside the reactor is released to atmospheric pressure, and then pressurized to 1 MPaG using 99% pure nitrogen. The pressure is then released to atmospheric pressure, and this step is repeated 3 times. After that, nitrogen is purged to 1 MPaG to expel the reaction product. Then, the inlet valve and the pressure relief valve are opened, and nitrogen at 150°C is continuously introduced into the reactor. After purging at atmospheric pressure for 120 minutes, 10g of the expelled reaction product is pumped into the reactor using a horizontal flow pump. After stirring for 60 minutes, the pressure relief valve is closed, nitrogen is purged to 1 MPaG, and the 10g of the injected reaction product is expelled.

[0078] The pressure was increased to 1 MPaG using 99% pure hydrogen, then released to atmospheric pressure. This step was repeated three times to complete the gas replacement. 100g of L-isomenthol was then pumped into the reactor using a horizontal flow pump to begin the reaction.

[0079] The evaluation results are as follows:

[0080] Initial reaction Apply 30 times Apply 60 times Menthol / % 99.90 99.80 99.07 ee value / % 99.86 99.54 99.40 Cooling sensation evaluation 9.2 8.1 6.5 Characteristic odor evaluation 9.1 8.0 6.6

[0081] Comparative Example 3

[0082] Place 1g of Raney-6800 into a dry 500ml high-pressure reactor purged with nitrogen (the reactor's discharge pipe is equipped with a filter). Pressurize the reactor to 1MPaG using 99% pure hydrogen, then release the pressure to atmospheric pressure. Repeat this step three times to complete the gas purging. Use a horizontal pump to deliver 100g of L-isomenthol into the reactor, maintaining a temperature of 50℃ and a reactor pressure of 1MPaG. Start the stirrer, ensuring uniform mixing, and react for 8 hours. Then, send samples for analysis.

[0083] After the reaction is complete, release the pressure inside the reactor to atmospheric pressure, pressurize it to 1 MPaG using 99% pure nitrogen, release the pressure to atmospheric pressure, and repeat this step 3 times. Then, pressurize the reactor to 1 MPaG with nitrogen to expel the reaction product. After that, pump 10g of the expelled reaction product into the reactor using a horizontal pump, stir for 10 minutes, close the pressure relief valve, pressurize the reactor to 1 MPaG with nitrogen, and expel the 10g of reaction product that was just pumped in.

[0084] The pressure was increased to 1 MPaG using 99% pure hydrogen, then released to atmospheric pressure. This step was repeated three times to complete the gas replacement. 100g of L-isomenthol was then pumped into the reactor using a horizontal flow pump to begin the reaction.

[0085] The evaluation results are as follows:

[0086]

[0087]

[0088] It is readily understood that the above embodiments are merely illustrative examples for clear explanation and do not imply that the invention is limited thereto. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for post-treatment of catalysts in the production of menthol, comprising: 1) after the catalytic reaction, separating the catalyst from the reaction product; heating and aging the catalyst during or after the separation; 2) after the heating and aging, stirring and aging the catalyst in menthol.

2. The method of claim 1, wherein, In step 1), the catalytic reaction refers to the reaction of preparing menthol by hydrogenation of isobornyl alcohol in the presence of a catalyst; preferably, the amount of the catalyst is 1-2 wt% of the amount of isobornyl alcohol; the hydrogenation reaction is carried out at a temperature of 45-70℃ and a pressure of 0.1-2.0 MPaG.

3. The method of claim 1 or 2, wherein, In step 1), the catalyst is one or more of Raney nickel, Raney cobalt, Pd / C and Ru / C, preferably Raney nickel; preferably, the content of Pd or Ru in the Pd / C or Ru / C catalyst is 5-20 wt%.

4. The method according to any one of claims 1 to 3, wherein, In step 1), the heating and aging is carried out at a temperature of 40-100℃, preferably 40-80℃, and the heating is carried out by blowing hot air or hot nitrogen, preferably hot nitrogen, for 10-60 min, preferably 10-30 min.

5. The method of claim 1, wherein, In step 2), the amount of menthol is 3-15 times, preferably 5-10 times, the amount of the catalyst, and the stirring and aging is carried out for 10-120 min, preferably 10-60 min.

6. A method for preparing menthol, comprising: hydrogenating isobornyl alcohol in the presence of a catalyst to obtain menthol; In the method, the catalyst is Raney nickel, Raney cobalt, Pd / C or Ru / C treated by the post-treatment method of any one of claims 1-5.

7. The method of claim 6, wherein, The amount of the catalyst is 1-2 wt% of the amount of isobornyl alcohol.

8. The method of claim 6 or 7, wherein, The hydrogenation reaction is carried out at a temperature of 45-70℃ and a pressure of 0.1-2.0 MPaG.

Images