CN111871428A - Rhodium catalyst for preparing d, l-menthol and preparation method of d, l-menthol - Google Patents

Abstract

The invention relates to a rhodium catalyst for preparing d, l-menthol and a preparation method of the d, l-menthol, wherein the rhodium catalyst is prepared by the following method: 1) adding rhodium salt, nickel salt and zinc salt into water to obtain mixed salt water solution; 2) soaking the carrier in a mixed saline solution, uniformly stirring, and performing reduced pressure distillation to remove water to obtain a powder; 3) reducing the powder in hydrogen atmosphere, washing and drying to obtain the rhodium catalyst. The preparation method of the d, l-menthol comprises the following steps: s1) adding a rhodium catalyst and thymol into a hydrogenation kettle, and replacing air with hydrogen; s2) heating and introducing hydrogen to carry out catalytic hydrogenation reaction, and then carrying out isomerization reaction. Compared with the prior art, the method utilizes the self-made rhodium catalyst to catalyze the hydrogenation of the thymol to obtain various isomers mainly comprising d, l-menthol, the conversion rate of the thymol can reach 99.9 percent, and the selectivity of the generated d, l-menthol is high and is 65.0-70.0 percent; the selectivity of d, l-isomenthol formation is low, 6.0-8.0%.

Description

A kind of rhodium catalyst for preparing d,1-menthol and the preparation of d,1-menthol method

technical field

The invention belongs to the technical field of d,l-menthol preparation, and relates to a γ-Al ₂ O ₃ supported heterogeneous rhodium catalyst for preparing d,l-menthol and a preparation method of d,l-menthol.

Background technique

d,l-menthol is mainly used to synthesize l-menthol, and l-menthol is mainly used in the fields of medicine, food additives and spices. Due to the rapid growth of the global economy, the demand for menthol is also increasing. In 2007, the global annual production has increased from 6,300 tons in 1992 to nearly 20,000 tons, of which synthetic menthol has also increased from 2,200 tons in 1992 to 6,300 tons. Natural menthol is extracted from plants, and the output is greatly affected by seasons, planting areas, etc., resulting in very large price fluctuations, and the output of natural menthol can no longer meet the growing industrial needs. The production of synthetic menthol is stable and the price is relatively cheap, so chemically synthesized menthol is becoming more and more important.

US2843636 discloses using copper chromite, cobalt and nickel as catalysts to convert menthol isomers into d,l-menthol in an autoclave at 260-280°C and 3.45-8.97MPa pressure alcohol process, the resulting product contains 60-64% d,l-menthol and 10-12% d,l-isomenthol, but about 5% non-reusable hydrocarbons are produced in this process.

EP0563611 discloses a method for the reduction of thymol with hydrogen using a fixed-bed catalyst. The catalyst uses palladium, ruthenium or rhodium or a mixture of these elements as active components, alkali metal hydroxides and/or sulfates as promoters, and is supported on on a carrier doped with rare earth metals and manganese. The process is carried out at 180-191°C and 240-270 bar pressure to obtain menthol isomers. It contains 52.3-56.8% d,l-menthol and 25.4-32.6% d,l-neomenthol, and the content of d,l-isomenthol is not clear.

US20020019573 discloses the use of a metal ruthenium catalyst supported by γ-alumina, so that each isomer of menthol (wherein the content of d,l-menthol is 52.1-56.8%, and the content of d,l-isomenthol is 12.0-12.6% %) isomerization at 30-170°C and 0.05-300bar pressure to obtain various isomers of menthol (wherein the content of d,l-menthol is 65.0-66.8%, and the content of d,l-isomenthol is 8.2-10.3 %).

DE19853562 discloses a method for the hydrogenation of thymol under low pressure using a fixed catalyst bed, the catalyst uses palladium as the active component and alkali metal hydroxide as the promoter, supported on a carrier doped with rare earth metals and manganese, under a pressure of 3 bar A menthol isomer mixture containing 64.4% d,l-menthol and 12.1% d,l-isomenthol was obtained. The equimolar mixture of three menthols of d,l-neomenthol, d,l-isomenthol and d,l-neoisomenthol was isomerized at 70 ° C and 1 kg of hydrogen pressure to obtain 65.3% d,l - Menthol isomer mixture of menthol and 12.1% d,l-isomenthol.

US20060167322 discloses using Raney nickel to add other metals (iron and/or chromium) as catalysts at 165-185°C and 5-25bar to hydrogenate thymol to obtain menthol isomers, which contain 57.6 -60.6% d,l-menthol and 11.3-11.7% d,l-isomenthol; using the same catalyst, menthol isomers based on d,l-neomenthol (content 81.9%) at 175°C , isomerization at 20 bar to obtain menthol isomers (wherein the content of d,l-menthol is 56.8% and the content of d,l-isomenthol is 10.8%).

US20140066664 discloses that metal rhodium is supported on a γ-alumina carrier as a catalyst, and cyclohexane is used as a solvent. Under the conditions of 120 ° C and 30 bar, thymol is hydrogenated to obtain d,l-neomenthol, followed by isomerization to obtain mint Alcohol isomers (d,l-menthol content 67-68% and d,l-isomenthol content 32-33%).

Among them, thymol was hydrogenated to obtain d,l-neomenthol (bp: 211.7°C), d,l-neoisomenthol (bp: 214.6°C), d,l-menthol (bp: 216.5°C) and d,l-menthol (bp: 216.5°C), Four racemic menthol isomers of l-isomenthol (bp: 218.6°C) have the following structural formulas:

In order to improve the yield of d,l-menthol, the content of d,l-menthol should be increased as much as possible in the synthesis process, and the content of d,l-isomenthol should be reduced as much as possible (reduce the content of d,l-isomenthol) good for distillation). In the current prior art, it is mainly prepared by using high temperature and high pressure, or by using a solvent and by a two-step reaction method. Among them, high temperature and high pressure will produce some hydrocarbons that can no longer be beneficial, and the use of solvents and two-step method is unfavorable for production environmental protection and cost.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a kind of rhodium catalyst for preparing d,1-menthol and the preparation method of d,1-menthol, improve the raw material conversion rate and d, the selectivity of 1-menthol, suitable for industrial Production.

The object of the present invention can be realized through the following technical solutions:

A preparation method for the rhodium catalyst for preparing d,1-menthol, the method comprises the following steps:

1) adding rhodium salt, nickel salt and zinc salt to water to obtain mixed brine solution;

2) The carrier is immersed in the mixed saline solution, and after stirring, the water is distilled off under reduced pressure to obtain a powder;

3) The powder is reduced in a hydrogen atmosphere, and then washed and dried to obtain the rhodium catalyst (Rh-Ni-Zn/γ-Al ₂ O ₃ ).

Further, in step 1), the rhodium salt includes one or both of rhodium nitrate or rhodium chloride, and the nickel salt includes one or more of nickel acetate, nickel nitrate or nickel chloride The zinc salt includes one or more of zinc acetate, zinc nitrate or zinc chloride.

Further, in step 2), the carrier is γ-Al ₂ O ₃ , the BET specific surface area of the γ-Al ₂ O ₃ is 100-150 m ² , and the particle size is 30-50 nm. In the rhodium catalyst, nickel and zinc are used as co-active components, and γ-Al ₂ O ₃ is used as a carrier.

Further, in step 3), in the reduction process, the temperature is 250-300° C. and the time is 3-4 h.

In step 3), the reduced matter is washed completely with distilled water to remove CH ₃ COO ⁻ , NO ₃ ⁻ , Cl ⁻ plasma, and then dried and vacuum dried.

Further, in the rhodium catalyst, the weight percentage of rhodium is 6%-10%, the weight percentage of nickel is 0.3%-1.0%, the weight percentage of zinc is 0.3%-1.0%, and the rest for the carrier.

A rhodium catalyst for preparing d,l-menthol, the rhodium catalyst is prepared by the method described.

A preparation method of d,l-menthol, the method comprises the following steps:

S1) described rhodium catalyst and thymol are added in the hydrogenation still, and replace air with hydrogen;

S2) heat up and feed hydrogen to carry out catalytic hydrogenation reaction, and then carry out isomerization reaction.

Further, in step S1), the mass ratio of described rhodium catalyst and thymol is 1:(25-30), and replaces air with hydrogen 1-3 times.

Further, in step S2), during the catalytic hydrogenation reaction, the reaction temperature is 80-100° C., the reaction pressure is 4.0-5.0 MPa, and the reaction time is 10-12 h, so that the gas-phase analysis product does not contain thymol.

Further, in step S2), the time of the isomerization reaction is 4-6h, so that it reaches the equilibrium between the isomers. Then filter to obtain d,l-menthol-based isomer products and recovered catalyst.

Compared with the prior art, the present invention has the following characteristics:

1) Utilize self-made rhodium catalyst to catalyze the hydrogenation of thymol to obtain each isomer mainly based on d,l-menthol, the thymol conversion rate can reach 99.9%, and the selectivity of generating d,l-menthol is high , is 65.0-70.0%; the selectivity to generate d,l-isomenthol is low, 6.0-8.0%.

2) The preparation process of the rhodium catalyst is simple, the use process conditions of the catalyst are mild, the stability is good, the rhodium catalyst can be reused many times, and is suitable for industrial production.

Detailed ways

The present invention will be described in detail below with reference to specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and provides a detailed implementation manner and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

Example 1:

In a 250ml round-bottomed flask, add 15.35g of rhodium trichloride trihydrate, 1.21g of nickel dichloride hexahydrate and 0.63g of zinc chloride, dissolve with 30ml of distilled water, and then add 93.4g of γ-Al ₂ O ₃ ; stir well , the water is distilled off under reduced pressure to obtain a powder; the powder is reduced in hydrogen at 250-300 ° C for 3-4 hours, and then the reduced material is washed with distilled water to completely remove ^Cl- , then dried and vacuum-dried, that is, get a catalyst.

Example 2:

In a 250ml round-bottomed flask, add 20.46g of rhodium trichloride trihydrate, 2.43g of nickel dichloride hexahydrate and 1.25g of zinc chloride, dissolve with 35ml of distilled water, and then add 90.8g of γ-Al ₂ O ₃ ; stir well , the water is distilled off under reduced pressure to obtain a powder; the powder is reduced in hydrogen at 250-300 ° C for 3-4 hours, and then the reduced material is washed with distilled water to completely remove ^Cl- , then dried and vacuum-dried, that is, get a catalyst.

Example 3:

In a 250ml round-bottomed flask, add 25.58g of rhodium trichloride trihydrate, 4.05g of nickel dichloride hexahydrate and 2.08g of zinc chloride, dissolve with 40ml of distilled water, and then add 88g of γ-Al ₂ O ₃ ; stir well, The water is distilled off under reduced pressure to obtain a powder; the powder is reduced in hydrogen at 250-300 ° C for 3-4 hours, and then the reduced material is washed with distilled water to completely remove ^Cl- , then dried and vacuum-dried to obtain catalyst.

Example 4:

In a 250ml autoclave, add 6.5g of catalyst (from Example 1) and 180.0g of thymol, and replace it with hydrogen twice; start stirring and heat up, feed hydrogen, control the internal pressure at 4.0-5.0MPa, and control the internal temperature at 80 -100°C, gas phase analysis to detect the absence of thymol in the reaction mixture, time 10-11h, continue the isomerization reaction, time 5-6h; after the reaction, cool and filter to recover the catalyst for use in the next batch of reactions. The crude product 187.2g was collected, and the component analysis was as follows:

Example 5:

In a 250ml autoclave, add 6.5g of catalyst (from Example 2) and 180.0g of thymol, and replace it with hydrogen twice; start stirring and heat up, feed hydrogen, control the internal pressure at 4.0-5.0MPa, and control the internal temperature at 80 -100°C, gas phase analysis, detect the absence of thymol in the reaction mixture, time 9-10h, continue isomerization reaction, time 4-5h; after the reaction, cool and filter to recover the catalyst for use in the next batch of reactions. The crude product 187.2g was collected, and the component analysis was as follows:

Example 6:

In a 250ml autoclave, add 6.5g of catalyst (from Example 3) and 180.0g of thymol, and replace it with hydrogen twice; start stirring and heat up, feed hydrogen, control the internal pressure at 4.0-5.0MPa, and control the internal temperature at 80 -100°C, gas phase analysis to detect the absence of thymol in the reaction mixture, time 8-9h, continue the isomerization reaction, time 4-5h; after the reaction, cool and filter to recover the catalyst for use in the next batch of reactions. The crude product 187.2g was collected, and the component analysis was as follows:

Example 7:

In a 250ml autoclave, add 6.0 g of catalyst (from Example 2) and 180.0 g of thymol, and replace it with hydrogen twice; start stirring to heat up, feed hydrogen, control the internal pressure at 4.0-5.0 MPa, and control the internal temperature at 80 -100°C, gas phase analysis to detect the absence of thymol in the reaction mixture, time 8-9h, continue the isomerization reaction, time 4-5h; after the reaction, cool and filter to recover the catalyst for use in the next batch of reactions. The crude product 187.2g was collected, and the component analysis was as follows:

Example 8:

In a 250ml autoclave, add 7.2g of catalyst (from Example 2) and 180.0g of thymol, and replace it with hydrogen twice; start stirring to heat up, feed hydrogen, control the internal pressure at 4.0-5.0MPa, and control the internal temperature at 80 -100°C, gas phase analysis to detect the absence of thymol in the reaction mixture, time 8-9h, continue the isomerization reaction, time 4-5h; after the reaction, cool and filter to recover the catalyst for use in the next batch of reactions. The crude product 187.2g was collected, and the component analysis was as follows:

Example 9:

In a 250ml autoclave, add 6.5g of catalyst (from Example 2, applied for the 15th time), 180.0g of thymol, and replace it with hydrogen twice; start stirring and heat up, feed hydrogen, and control the internal pressure at 4.0-5.0MPa, The internal temperature was controlled at 80-100°C, gas phase analysis was performed to detect the absence of thymol in the reaction mixture, the time was 11-12h, and the isomerization reaction was continued for 5-6h; after the reaction, the catalyst was cooled and filtered to recover the catalyst for use in the next batch of reactions . The crude product 187.2g was collected, and the component analysis was as follows:

Example 10:

A preparation method for the rhodium catalyst for preparing d,1-menthol, the method comprises the following steps:

1) adding rhodium salt, nickel salt and zinc salt to water to obtain mixed brine solution;

2) The carrier is immersed in the mixed saline solution, and after stirring, the water is distilled off under reduced pressure to obtain a powder;

3) The powder is reduced in a hydrogen atmosphere, and then washed and dried to obtain a rhodium catalyst.

In step 1), the rhodium salt is rhodium nitrate, the nickel salt is nickel acetate, and the zinc salt is zinc acetate.

In step 2), the carrier is γ-Al ₂ O ₃ , the BET specific surface area of γ-Al ₂ O ₃ is 100-150 m ² , and the particle size is 30-50 nm.

In step 3), during the reduction process, the temperature is 250°C and the time is 4h.

In the rhodium catalyst, the weight percentage of rhodium is 10%, the weight percentage of nickel is 0.3%, the weight percentage of zinc is 1.0%, and the rest are carriers.

A preparation method of d,l-menthol, the method comprises the following steps:

S1) above-mentioned rhodium catalyst and thymol are added in the hydrogenation still, and replace air with hydrogen;

S2) heat up and feed hydrogen to carry out catalytic hydrogenation reaction, and then carry out isomerization reaction.

In step S1), the mass ratio of rhodium catalyst and thymol is 1:25, and the air is replaced with hydrogen 3 times.

In step S2), during the catalytic hydrogenation reaction, the reaction temperature is 80° C., the reaction pressure is 5.0 MPa, and the reaction time is 10 h. The isomerization time was 6h.

Example 11:

A preparation method for the rhodium catalyst for preparing d,1-menthol, the method comprises the following steps:

1) adding rhodium salt, nickel salt and zinc salt to water to obtain mixed brine solution;

2) The carrier is immersed in the mixed saline solution, and after stirring, the water is distilled off under reduced pressure to obtain a powder;

3) The powder is reduced in a hydrogen atmosphere, and then washed and dried to obtain a rhodium catalyst.

In step 1), the rhodium salt is rhodium chloride, the nickel salt is nickel nitrate, and the zinc salt is zinc nitrate.

In step 2), the carrier is γ-Al ₂ O ₃ , the BET specific surface area of γ-Al ₂ O ₃ is 100-150 m ² , and the particle size is 30-50 nm.

In step 3), during the reduction process, the temperature is 300°C and the time is 3h.

In the rhodium catalyst, the weight percentage of rhodium is 6%, the weight percentage of nickel is 1.0%, the weight percentage of zinc is 0.3%, and the rest are carriers.

A preparation method of d,l-menthol, the method comprises the following steps:

S1) above-mentioned rhodium catalyst and thymol are added in the hydrogenation still, and replace air with hydrogen;

S2) heat up and feed hydrogen to carry out catalytic hydrogenation reaction, and then carry out isomerization reaction.

In step S1), the mass ratio of the rhodium catalyst to thymol is 1:30, and the air is replaced with hydrogen once.

In step S2), during the catalytic hydrogenation reaction, the reaction temperature is 100° C., the reaction pressure is 4.0 MPa, and the reaction time is 12 h. The isomerization time was 4h.

Example 12:

A preparation method for the rhodium catalyst for preparing d,1-menthol, the method comprises the following steps:

1) adding rhodium salt, nickel salt and zinc salt to water to obtain mixed brine solution;

2) The carrier is immersed in the mixed saline solution, and after stirring, the water is distilled off under reduced pressure to obtain a powder;

3) The powder is reduced in a hydrogen atmosphere, and then washed and dried to obtain a rhodium catalyst.

In step 1), the rhodium salt is rhodium chloride, the nickel salt is nickel chloride, and the zinc salt is zinc chloride.

In step 2), the carrier is γ-Al ₂ O ₃ , the BET specific surface area of γ-Al ₂ O ₃ is 100-150 m ² , and the particle size is 30-50 nm.

In step 3), in the reduction process, the temperature is 270°C and the time is 3.5h.

In the rhodium catalyst, the weight percentage of rhodium is 8%, the weight percentage of nickel is 0.7%, the weight percentage of zinc is 0.5%, and the rest are carriers.

A preparation method of d,l-menthol, the method comprises the following steps:

S1) above-mentioned rhodium catalyst and thymol are added in the hydrogenation still, and replace air with hydrogen;

S2) heat up and feed hydrogen to carry out catalytic hydrogenation reaction, and then carry out isomerization reaction.

In step S1), the mass ratio of rhodium catalyst and thymol is 1:28, and the air is replaced with hydrogen for 2 times.

In step S2), during the catalytic hydrogenation reaction, the reaction temperature is 90° C., the reaction pressure is 4.5 MPa, and the reaction time is 11 h. The isomerization time was 5h.

The foregoing description of the embodiments is provided to facilitate understanding and use of the invention by those of ordinary skill in the art. It will be apparent to those skilled in the art that various modifications to these embodiments can be readily made, and the generic principles described herein can be applied to other embodiments without inventive step. Therefore, the present invention is not limited to the above-mentioned embodiments, and improvements and modifications made by those skilled in the art according to the disclosure of the present invention without departing from the scope of the present invention should all fall within the protection scope of the present invention.

Claims (10)

1. A method of preparing a rhodium catalyst for use in the preparation of d, l-menthol, the method comprising the steps of:

1) adding rhodium salt, nickel salt and zinc salt into water to obtain mixed salt water solution;

2) soaking the carrier in a mixed saline solution, uniformly stirring, and performing reduced pressure distillation to remove water to obtain a powder;

3) reducing the powder in hydrogen atmosphere, washing and drying to obtain the rhodium catalyst.

2. The method of claim 1, wherein in step 1), the rhodium salt comprises one or both of rhodium nitrate and rhodium chloride, the nickel salt comprises one or more of nickel acetate, nickel nitrate and nickel chloride, and the zinc salt comprises one or more of zinc acetate, zinc nitrate and zinc chloride.

3. The method for preparing a rhodium catalyst for preparing d, l-menthol according to claim 1, wherein the carrier in step 2) is γ -Al₂O₃Said gamma-Al₂O₃BET specific surface area of 100-²The grain diameter is 30-50 nm.

4. The method as claimed in claim 1, wherein the temperature of the reduction step in step 3) is 250-300 ℃ and the time is 3-4 h.

5. The method for preparing the rhodium catalyst for preparing the d, l-menthol as claimed in claim 1, wherein the rhodium catalyst comprises 6-10 wt% of rhodium, 0.3-1.0 wt% of nickel, 0.3-1.0 wt% of zinc and the balance of carrier.

6. A rhodium catalyst for the preparation of d, l-menthol, characterized in that it is prepared by a process according to any one of claims 1 to 5.

7. A method for preparing d, l-menthol, comprising the steps of:

s1) adding the rhodium catalyst of claim 6 and thymol to a hydrogenation kettle and displacing air with hydrogen;

s2) heating and introducing hydrogen to carry out catalytic hydrogenation reaction, and then carrying out isomerization reaction.

8. The method for preparing d, l-menthol according to claim 7, wherein in step S1), the mass ratio of the rhodium catalyst to the thymol is 1 (25-30), and air is replaced with hydrogen gas 1-3 times.

9. The method for preparing d, l-menthol as claimed in claim 7, wherein in step S2), the reaction temperature is 80-100 ℃, the reaction pressure is 4.0-5.0MPa, and the reaction time is 10-12h during the catalytic hydrogenation reaction.

10. The method for preparing d, l-menthol as claimed in claim 7, wherein the isomerization reaction time in step S2) is 4-6 h.