CN111871428B - A kind of rhodium catalyst for preparing d,l-menthol and the 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 d,l-menthol. The rhodium catalyst is prepared by the following method: 1) adding rhodium salt, nickel salt and zinc salt into water, Obtain a mixed saline solution; 2) immerse the carrier in the mixed saline solution, stir evenly, and then distill off the water under reduced pressure to obtain a powder; 3) Restore the powder in a hydrogen atmosphere, then wash and dry, that is A rhodium catalyst is obtained. The preparation method of d,l-menthol is: S1) rhodium catalyst and thymol are added in the hydrogenation kettle, and replace air with hydrogen; S2) heat up and feed hydrogen, carry out catalytic hydrogenation reaction, then carry out isomerization reaction . Compared with the prior art, the present invention utilizes a self-made rhodium catalyst to catalyze the hydrogenation of thymol to obtain various isomers mainly composed of d,l-menthol, and the conversion rate of thymol can reach 99.9%, generating d,l-menthol The selectivity of ‑menthol is high, 65.0‑70.0%; the selectivity of d,l‑isomenthol is low, 6.0‑8.0%.

Description

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

technical field

The invention belongs to the technical field of d,l-menthol preparation, and relates to a gamma-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 output 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 and planting areas, resulting in very large price fluctuations. The output of naturally extracted menthol can no longer meet the growing industrial needs. The output of synthetic menthol is stable and the price is relatively cheap, so chemically synthesized menthol is becoming more and more important.

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

EP0563611 discloses the method of using a fixed-bed catalyst to reduce thymol with hydrogen, the catalyzer contains palladium, ruthenium or rhodium or a mixture of these elements as an active component, an alkali metal hydroxide and/or a sulfate as a promoter, and is loaded on On a support doped with rare earth metals and manganese. The method is carried out at 180-191° C. and 240-270 bar pressure to obtain various isomers of menthol. It contains 52.3-56.8% d,l-menthol and 25.4-32.6% d,l-neomenthol, the content of d,l-isomenthol is not clear.

US20020019573 discloses the use of metal ruthenium catalysts with gamma-alumina as a carrier to make the various isomers of menthol (wherein d, l-menthol content 52.1-56.8%, d, l-isomenthol content 12.0-12.6%) %) isomerized at 30-170° C. and 0.05-300 bar pressure to obtain the isomers of menthol (wherein d, l-menthol content is 65.0-66.8%, d, l-isomenthol content is 8.2-10.3 %).

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

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

US20140066664 discloses the use of metallic rhodium supported on a gamma-alumina carrier as a catalyst, cyclohexane as a solvent, and 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, d,l-neomenthol (bp: 211.7°C), d,l-neoisomenthol (bp: 214.6°C), d,l-menthol (bp: 216.5°C) and d,l-neomenthol (bp: 216.5°C) were obtained by hydrogenation of thymol. l-Isomenthol (bp: 218.6°C) is four racemic menthol isomers, the structural formulas are as follows:

In order to improve the yield of d,l-menthol, in the synthetic process, the content of d,l-menthol should be improved as far as possible, and the content of d,l-isomenthol should be reduced as far as possible (reducing the content of d,l-isomenthol conducive to distillation). In the current prior art, it is mainly prepared by using high temperature and high pressure, or using a solvent and a two-step reaction method. Among them, high temperature and high pressure will produce some unfavorable hydrocarbons, and the use of solvents and two-step method is not conducive to production environmental protection and cost.

Contents of the invention

Purpose of the present invention is exactly in order to provide a kind of rhodium catalyst for preparing d, l-menthol and the preparation method of d, l-menthol, has improved raw material conversion rate and the selectivity of d, l-menthol, is suitable for industrial Production.

The purpose of the present invention can be achieved through the following technical solutions:

A kind of preparation method for preparing the rhodium catalyst of L-menthol, the method comprises the following steps:

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

2) immersing the carrier in a mixed saline solution, stirring evenly, and distilling off the water under reduced pressure to obtain a powder;

3) Reducing the powder in a hydrogen atmosphere, and then washing and drying 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 species, 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 100-150m ² , and the particle size is 30-50nm. In the rhodium catalyst, nickel and zinc are used as auxiliary active components, and γ-Al ₂ O ₃ is used as a carrier.

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

In step 3), the reduced product is completely washed 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 as the carrier.

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

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

S1) adding the rhodium catalyst and thymol into the hydrogenation kettle, and replacing the air with hydrogen;

S2) Heating up and feeding hydrogen to carry out catalytic hydrogenation reaction, and then carry out isomerization reaction.

Further, in step S1), the mass ratio of the rhodium catalyst to thymol is 1:(25-30), and the air is replaced with hydrogen for 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 hours, so that the gas phase analysis product does not contain thymol.

Further, in step S2), the time for the isomerization reaction is 4-6 hours, so that the equilibrium among isomers is reached. Afterwards, the isomer products mainly composed of d,l-menthol and the recovered catalyst were obtained by filtration.

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

1) Utilize the homemade rhodium catalyst to catalyze the hydrogenation of thymol to obtain isomers mainly composed of d,l-menthol, the conversion rate of thymol can reach 99.9%, and the selectivity of d,l-menthol is high , 65.0-70.0%; the selectivity of d,l-isomenthol is low, 6.0-8.0%.

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

Detailed ways

The present invention will be described in detail below in conjunction with specific embodiments. This embodiment is carried out on the premise of the technical solution of the present invention, and detailed implementation and specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

Example 1:

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

Example 2:

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

Example 3:

In a 250ml round bottom flask, add 25.58g rhodium trichloride trihydrate, 4.05g nickel dichloride hexahydrate and 2.08g zinc chloride, dissolve with 40ml distilled water, then add 88gγ-Al ₂ O ₃ ; fully stir, Distill the water 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 product 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 twice with hydrogen; turn on stirring to raise the temperature, feed hydrogen, control the internal pressure at 4.0-5.0MPa, and control the internal temperature at 80 -100°C, gas phase analysis, detection of no thymol in the reaction mixture, time 10-11h, continue the isomerization reaction, time 5-6h; after the reaction, cool, filter and recover the catalyst for the next batch reaction. Collect crude product 187.2g, composition analysis is as follows:

Example 5:

In a 250ml autoclave, add 6.5g of catalyst (from Example 2) and 180.0g of thymol, and replace it twice with hydrogen; stir 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, detection of no thymol in the reaction mixture, time 9-10h, continue the isomerization reaction, time 4-5h; after the reaction, cool, filter and recover the catalyst for the next batch reaction. Collect crude product 187.2g, composition analysis is as follows:

Embodiment 6:

In a 250ml autoclave, add 6.5g of catalyst (from Example 3) and 180.0g of thymol, and replace it twice with hydrogen; start stirring to raise the temperature, feed hydrogen, control the internal pressure at 4.0-5.0MPa, and control the internal temperature at 80 -100°C, gas phase analysis, detection of no thymol in the reaction mixture, time 8-9h, continue isomerization reaction, time 4-5h; after the reaction, cool, filter and recover the catalyst for the next batch reaction. Collect crude product 187.2g, composition analysis is as follows:

Embodiment 7:

In a 250ml autoclave, add 6.0g of catalyst (from Example 2) and 180.0g of thymol, and replace it twice with hydrogen; turn on stirring to raise the temperature, feed hydrogen, control the internal pressure at 4.0-5.0MPa, and control the internal temperature at 80 -100°C, gas phase analysis, detection of no thymol in the reaction mixture, time 8-9h, continue isomerization reaction, time 4-5h; after the reaction, cool, filter and recover the catalyst for the next batch reaction. Collect crude product 187.2g, composition analysis is as follows:

Embodiment 8:

In a 250ml autoclave, add 7.2g of catalyst (from Example 2) and 180.0g of thymol, and replace it twice with hydrogen; turn on stirring to raise the temperature, feed hydrogen, control the internal pressure at 4.0-5.0MPa, and control the internal temperature at 80 -100°C, gas phase analysis, detection of no thymol in the reaction mixture, time 8-9h, continue isomerization reaction, time 4-5h; after the reaction, cool, filter and recover the catalyst for the next batch reaction. Collect crude product 187.2g, composition analysis is as follows:

Embodiment 9:

In a 250ml autoclave, add 6.5g of catalyst (from Example 2, applied mechanically for the 15th time) and 180.0g of thymol, and replace it twice with hydrogen; start stirring to raise the temperature, feed hydrogen, and control the internal pressure at 4.0-5.0MPa, The internal temperature is controlled at 80-100°C, and gas phase analysis detects that there is no thymol in the reaction mixture. The time is 11-12 hours, and the isomerization reaction is continued for 5-6 hours. After the reaction, cool, filter and recover the catalyst for the next batch reaction. . Collect crude product 187.2g, composition analysis is as follows:

Example 10:

A kind of preparation method for preparing the rhodium catalyst of L-menthol, the method comprises the following steps:

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

2) immersing the carrier in a mixed saline solution, stirring evenly, and distilling off the water 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 100-150m ² , and the particle size is 30-50nm.

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 is carrier.

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

S1) adding the above-mentioned rhodium catalyst and thymol into the hydrogenation kettle, and replacing the air with hydrogen;

S2) Heating up and feeding hydrogen to carry out catalytic hydrogenation reaction, and then carry out isomerization reaction.

In step S1), the mass ratio of rhodium catalyst to thymol is 1:25, and the air is replaced with hydrogen for 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 time for the isomerization reaction is 6h.

Example 11:

A kind of preparation method for preparing the rhodium catalyst of L-menthol, the method comprises the following steps:

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

2) immersing the carrier in a mixed saline solution, stirring evenly, and distilling off the water 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 100-150m ² , and the particle size is 30-50nm.

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 is carrier.

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

S1) adding the above-mentioned rhodium catalyst and thymol into the hydrogenation kettle, and replacing the air with hydrogen;

S2) Heating up and feeding hydrogen to carry out catalytic hydrogenation reaction, and then carry out isomerization reaction.

In step S1), the mass ratio of 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 hours. The time for the isomerization reaction is 4h.

Example 12:

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

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

2) immersing the carrier in a mixed saline solution, stirring evenly, and distilling off the water 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 100-150m ² , and the particle size is 30-50nm.

In step 3), during 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 is carrier.

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

S1) adding the above-mentioned rhodium catalyst and thymol into the hydrogenation kettle, and replacing the air with hydrogen;

S2) Heating up and feeding hydrogen to carry out catalytic hydrogenation reaction, and then carry out isomerization reaction.

In step S1), the mass ratio of rhodium catalyst to 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 time for the isomerization reaction is 5h.

The above descriptions of the embodiments are for those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments, and apply the general principles described here to other embodiments without creative efforts. Therefore, the present invention is not limited to the above-mentioned embodiments. 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 fall within the protection scope of the present invention.

Claims (5)

1. a kind of d, the preparation method of l-menthol is characterized in that, the method comprises the following steps: S1) adding the rhodium catalyst and thymol into the hydrogenation kettle, and replacing the air with hydrogen; S2) Heating up and introducing hydrogen to carry out catalytic hydrogenation reaction, and then carry out isomerization reaction; Described rhodium catalyst is prepared by following method: 1) adding rhodium salt, nickel salt and zinc salt into water to obtain a mixed brine solution; 2) immersing the carrier in a mixed saline solution, stirring evenly, and distilling off the water under reduced pressure to obtain a powder; 3) reducing the powder in a hydrogen atmosphere, then washing and drying to obtain the rhodium catalyst; 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, so The zinc salt includes one or more of zinc acetate, zinc nitrate or zinc chloride; In step 2), the carrier is γ-Al ₂ O ₃ , the BET specific surface area of the γ-Al ₂ O ₃ is 100-150m ² , and the particle size is 30-50nm; 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 is carrier. 2. A method for preparing d,l-menthol according to claim 1, characterized in that, in step 3), during the reduction process, the temperature is 250-300°C and the time is 3-4h. 3. a kind of d according to claim 1, the preparation method of l-menthol is characterized in that, in step S1), the mass ratio of described rhodium catalyst and thymol is 1:(25-30), Replace the air with hydrogen 1-3 times. 4. A kind of d, the preparation method of l-menthol according to claim 1 is characterized in that, in step S2), in catalytic hydrogenation reaction process, reaction temperature is 80-100 ℃, reaction pressure is 4.0- 5.0MPa, the reaction time is 10-12h. 5. A kind of preparation method of d,l-menthol according to claim 1, is characterized in that, in step S2), the time of isomerization reaction is 4-6h.