Preparation method of thymol

Abstract

The invention belongs to the technical field of organic synthesis, and particularly discloses a thymol preparation method which comprises the following steps: filling a reaction tube of a fixed bed reactor with a catalyst, and heating m-cresol and isopropanol as raw materials in a fixed bed for gas-solid heterogeneous reaction to obtain thymol, the catalyst is an H-M1-ZSM-5 molecular sieve catalyst, the metal M1 is selected from Sn, Fe or Zn, and the ratio of n (Si) / n (Al + M1) of the molecular sieve is 25-30. According to the H-M1-ZSM-5 molecular sieve catalyst adopted by the invention, Sn, Fe or Zn is introduced into an existing H-type ZSM-5 molecular sieve, and the catalyst prepared by the invention has the advantages of long catalysis life, mild reaction, capability of being carried out under normal pressure, few byproducts, good selectivity, easiness in realization of reaction conditions and good industrial application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic synthesis, and relates to synthesis of a perfume compound, in particular to a preparation method of thymol. BACKGROUND

[0002] Thymol (also known as thymol or thymol), chemical name 5-methyl-2-isopropyl phenol, is a white or translucent crystal at room temperature. Thymol is a widely used perfume with bactericidal, antiseptic and antioxidant functions. The substance is also a synthetic raw material for other chemicals. The most representative is that thymol is hydrogenated to prepare menthol.

[0003] There are two sources of thymol: one is extracted from natural products (thyme oil, oregano oil, basil oil). However, due to the limitation of natural resources and environmental pressure, the method is high in cost. The other is artificial synthesis of thymol.

[0004] At present, there are mainly four methods for artificial synthesis of thymol (1) α-pinene is used as raw material, and thymol is prepared by catalytic oxidation and then cleavage. The method has many steps, low yield and poor economy. (2) citronellol is used as raw material, and thymol is prepared by catalytic cyclization synthesis of isopulegol and then catalytic dehydrogenation. Although this method has a simple process and high yield, the raw material citronellol is relatively high in price, and the dehydrogenation catalyst is mostly noble metal, which has a short service life and high production cost. (3) m-cresol and isopropyl alcohol are used as raw materials, and thymol is prepared by sulfonation reaction and alkylation reaction with concentrated sulfuric acid as catalyst. The method has high corrosion resistance requirements for production equipment. Moreover, a large amount of waste acid wastewater is generated in the production process, and the environmental protection pressure is large. (4) m-cresol and substances that can provide isopropyl such as isopropyl alcohol, propylene or 2-chloropropane are used as raw materials, and thymol is prepared by one-step F-C alkylation reaction. The method has a simple process, and the key lies in the research of catalyst.

[0005] In the already published literature and patents, the alkylation reaction of m-cresol often needs high temperature reaction. Patent DE-OS 2528303 reports a kind of active alumina as catalyst, at 360-365 DEG C, 5 MPa or less reaction. This method is high temperature and high pressure, and the production safety requirement is higher. Chinese patent CN 101402551A discloses that 80-100 mesh of γ-Al2O3 treated with sulfuric acid is used as catalyst for the alkylation reaction of m-cresol and isopropanol, the temperature is 200-300 DEG C, the reaction time is 4-7 h, and inert gas is used as carrier gas. The reaction time is relatively long, and only the laboratory experiment of gram level is carried out, and the particle size of the filler is too small, so that the alkylation reaction has certain risk. Chinese patent CN 107398290 A discloses a microwave promoted m-cresol isopropanol alkylation reaction. The reaction uses Al-Cu / HAP as catalyst (HAP is carrier, hydroxyapatite), and the reaction is carried out at 100-200 DEG C, and the reaction time is only 0.1-60 min. Although the reaction has low temperature and fast reaction, it is limited by the reaction condition, and only the laboratory experiment of gram level is carried out, so that the industrial application has a long way to go. SUMMARY

[0006] In view of the deficiencies of the prior art, the purpose of the present application is to provide a preparation method of thymol. The present application uses a specially prepared catalyst, which not only has long catalytic life, but also makes the reaction mild, can be carried out at normal pressure, has less by-products, good selectivity, easy to realize reaction conditions, and good industrial application prospect.

[0007] The present application is realized by the following technical solutions: A preparation method of thymol, comprising the following steps: The catalyst is loaded in the reaction tube of the fixed bed reactor, m-cresol and isopropanol are used as raw materials, and the gas-solid heterogeneous reaction is carried out in the fixed bed by heating to obtain thymol; the catalyst is H-M1-ZSM-5 molecular sieve catalyst, wherein the metal M1 is selected from Sn, Fe or Zn, and the n(Si) / n(Al+M1) of the molecular sieve is 25-30.

[0008] Further improved schemes of the present application are: The molar ratio of m-cresol to isopropanol is 1-3:1, and the loading amount of the catalyst is 30-500 g.

[0009] Further, the temperature of the reaction is 200-300 DEG C, and the residence time of the raw materials in the reactor is 20-60 min.

[0010] Further, the H-M1-ZSM-5 molecular sieve catalyst is prepared by the following steps: dissolving a certain proportion of a silicon source, an aluminum source, a metal salt and a structure directing agent in water, adding sodium hydroxide to adjust pH, stirring uniformly, standing for aging at room temperature for a period of time, then transferring into a Teflon-lined high-pressure kettle for heating crystallization, naturally cooling after crystallization, filtering, washing and drying, ion exchange with NH4Cl solution, calcination, extrusion and re-calcination, so as to obtain the H-M1-ZSM-5 molecular sieve catalyst; and the metal is selected from Sn, Fe or Zn.

[0011] Further, in the preparation steps of the H-M1-ZSM-5 molecular sieve catalyst, the silicon source is low-sodium silica sol or tetraethyl orthosilicate (TEOS) or a mixture of both; Further, the aluminum source is pseudo-boehmite; Further, the structure directing agent is tetrapropylammonium hydroxide (TPAOH) or tetrapropylammonium bromide (TPABr) or a mixture of both; Further, the molar ratio of the silicon source, the aluminum source, the metal salt and the structure directing agent is 60:0.5-0.8:1-1.6:8-18.

[0012] Further, the aging time is 4-8 h; Further, the crystallization atmosphere is divided into two stages, the temperature of the first stage of crystallization is 95-105 DEG C, and the time is 10-14 h, the temperature of the second stage of crystallization is 110-130 DEG C, and the time is 20-25 h.

[0013] Further, the H-M1-ZSM-5 molecular sieve catalyst can also be prepared by the following steps: dispersing H-ZSM-5 molecular sieve in an aqueous solution of a metal nitrate, performing a sufficient ion exchange reaction, and then drying, calcining, extruding and re-calcining at high temperature, so as to obtain the H-M1-ZSM-5 molecular sieve catalyst; and the metal is selected from Sn, Fe or Zn.

[0014] Further, in the preparation process, the temperature of the ion exchange reaction is 70-90 DEG C, and the time is 20-25 h.

[0015] Compared with the prior art, the H-M1-ZSM-5 molecular sieve catalyst has the advantages of stable reaction, high selectivity and simple production process. The fixed bed Friedel-Crafts alkylation reaction has the advantages of stable reaction, high selectivity and simple production process.

[0016] The catalyst preparation process is simple and easy to operate; the selectivity of the target product and the conversion rate of the reactant can be improved; the reaction conditions are mild and can be carried out at normal pressure; and the catalyst has high catalytic activity, long service life and high reliability, and can be well applied to the production of thymol, so that the industrial application prospect is good. DETAILED DESCRIPTION

[0017] The present invention is described in detail below with reference to specific embodiments.

[0018] Example 1: Preparation of H-Fe-ZSM-5 catalyst To a 2 L beaker, 150 g of silica sol (40%, low sodium), 1.17 g of pseudoboehmite, 6.73 g of Fe(NO)₃·9H₂O, 67.8 g of TPAOH (40% aqueous solution), 4 g of anhydrous sodium hydroxide, and 1.5 g of deionized water were added in the following order, using a molar ratio of n(SiO₂):n(Al₂O₃):n(Fe₂O₃):n(TPAOH):n(NaOH):n(H₂O) = 120:1:1:16:12:900. The mixture was mechanically stirred at 300 rpm at room temperature for 3 h and aged naturally for 6 h. The gel was then transferred to a 250 mL polytetrafluoroethylene-lined crystallization reactor and crystallized at 100°C for 12 h, then at 120°C for 24 h. The reactor was cooled to room temperature, and the solid product was collected by filtration, washed with deionized water until the filtrate was neutral, and then air-dried at 120°C. The molecular sieve raw powder was immersed in 1000 mL of NH4Cl aqueous solution (2 mol / L), stirred at room temperature for 12 h, filtered, dried at 120 °C, and the operation was repeated three times. The ion exchange was performed and then calcined at 550 °C for 3 h (heating rate 2 °C / min) to obtain H-Fe-ZSM-5 molecular sieve powder.

[0019] Weigh 50 g of H-Fe-ZSM-5 raw powder and 15 g of pseudo-boehmite as a binder, stir and mix thoroughly. Add 25 mL of dilute nitric acid (5%) as an extrusion aid, stir and knead for several minutes, add an appropriate amount of deionized water to adjust the dryness and moisture content of the material, and extrude it using a screw extruder. Cut the extruded strips every 2-3 cm, with a diameter of 2-3 mm. Air-dry at room temperature for 24 hours, oven-dry at 120°C, and calcine at 500°C for 4 hours (heating rate 2°C / min) to obtain the H-Fe-ZSM-5 molecular sieve catalyst.

[0020] Example 2: Preparation of H-Sn-ZSM-5 catalyst The molar ratio of n(SiO2):n(Al2O3):n(SnO2):n(TPABr):n(NaOH):n(H2O) = 120:1:2:36:36:7200, according to sequentially adding 3.5 g pseudo-boehmite, 239.6 g TPABr (tetrapropylammonium bromide), 36 g anhydrous sodium hydroxide, 3235 g deionized water into a 10 L beaker; 17.53 g SnCl4·5H2O was dissolved in 50 mL anhydrous ethanol to form a uniform solution, which was also added to the reaction system, and finally 625.0 g TEOS was added dropwise while stirring for 3 h (300 rpm), and then the gel was naturally aged for 6 h. After that, the gel was transferred into a 2 L crystallization reactor with a polytetrafluoroethylene liner, and crystallized at 100℃ for 12 h, and then crystallized at 120℃ for 24 h. The reactor was naturally cooled to room temperature, and the solid product was collected by filtration, washed with deionized water until the filtrate was neutral, and dried at 120℃ with a blast dryer. The molecular sieve powder was immersed in 2.0 L of an NH4Cl aqueous solution (2 mol / L) at room temperature for 12 h, filtered, and dried at 120℃. The above operation was repeated three times for ion exchange, and then the H-Sn-ZSM-5 molecular sieve powder was obtained by calcining at 550℃ for 3 h (heating rate 2℃ / min).

[0021] 200 g of H-Sn-ZSM-5 powder was weighed, 60 g of pseudo-boehmite was weighed as a binder, and stirred and mixed uniformly. Then 100 mL of dilute nitric acid (5%) was added as a co-extrusion agent, and stirred and kneaded for 30 min. An appropriate amount of deionized water was added to adjust the dryness of the material, and a screw extruder was used for extrusion molding. The extruded strips were cut every 3 cm, and the extruded strip diameter was 2-3 mm. The strips were naturally air-dried at room temperature for 24 h, dried at 120℃, and calcined at 500℃ for 4 h (heating rate 2℃ / min) to obtain the molded H-Sn-ZSM-5 catalyst.

[0022] Example 3: Preparation of H-Zn-ZSM-5 catalyst Take 1.0 kg of commercial H-ZSM-5 molecular sieve powder (silicon aluminum ratio of about 30), disperse in 10 L of zinc nitrate aqueous solution (0.1 mol / L), 80℃ stirring ion exchange for 24 h, filter, wash with deionized water several times until the washing liquid is neutral, and dry at 120℃. The dried molecular sieve powder is dispersed in fresh zinc nitrate aqueous solution (0.1 mol / L) again, and the above operation is repeated for three times. To the dried powder, 300 g of pseudoboehmite is weighed as a binder, stirred and mixed uniformly, then 500 mL of dilute nitric acid (5%) is added as a co-extrusion agent, stirred and kneaded for 1 h, and then an appropriate amount of deionized water is added to adjust the dryness of the material. The screw extruder is used for extrusion molding, and the extruded strips are cut every 3 cm. The extruded strip diameter is 2-3 mm. After natural air drying at room temperature for 24 h, drying at 120℃, and calcination at 500℃ for 4 h (heating rate 2℃ / min), the molded H-Zn-ZSM-5 catalyst is obtained.

[0023] Example 4: Preparation of thymol A single-tube fixed-bed reactor is made by self, which is 50 cm high and the inner diameter of the reaction tube is 1.2 cm. 30 g of the catalyst described in Example 1 is loaded into the reaction tube, and the materials are stirred and mixed uniformly according to the molar ratio of isopropyl alcohol to m-cresol of 1:2. The feeding amount is 1.0 g / min, the reaction material is preheated at 80℃, and the reaction temperature is 240℃. Sampling is taken every 1 h. The reaction products are detected by gas chromatograph (Agilent 8860, INNOWAX, 130-0-10-220-30). Some data are shown in the following table Reaction time (h) m-Cresol conversion (%) Thymol selectivity (%) 1 32.2 84.76 4 32.6 84.32 8 33.3 84.64 12 33.8 85.01 16 34.1 85.23 24 34.5 85.49 Example 5: Preparation of thymol A single-tube fixed-bed reactor is made by self, which is 100 cm high and the inner diameter of the reaction tube is 1.6 cm. 120 g of the catalyst described in Example 2 is loaded into the reaction tube, and the materials are stirred and mixed uniformly according to the molar ratio of isopropyl alcohol to m-cresol of 1:2. The feeding amount is 5 g / min, the reaction material is preheated at 80℃, and the reaction temperature is 240℃. Sampling is taken every 1 h. The reaction products are detected by gas chromatograph (Agilent 8860, INNOWAX, 130-0-10-220-30). Some data are shown in the following table.

[0024] Reaction time (h) m-Cresol conversion (%) Thymol selectivity (%) 2 33.7 86.67 8 34.1 86.97 24 34.3 87.64 72 34.9 88.79 120 35.3 89.43 168 35.7 90.66 240 35.5 90.25 Example 6: Preparation of thymol Self-made fixed bed reactor with 200 cm high and 2.4 cm inner diameter, 500 g catalyst prepared in example 3 was charged into the reactor, the reactants were mixed at a molar ratio of isopropyl alcohol to m-cresol of 1:2, the single tube feeding amount was 20 g / min, the reactants were preheated at 80 ℃, and the reaction temperature was 240 ℃. The reaction products were detected by gas chromatograph (Agilent 8860, INNOWAX, 130-0-10-220-30).

[0025] Reaction time (h) m-Cresol conversion (%) Thymol selectivity (%) 1 33.7 84.36 5 34.1 85.72 10 34.3 87.54 24 34.9 87.71 60 35.3 88.63 120 35.7 89.88 240 35.5 91.12 600 36.1 91.05 1000 36.0 91.52 2000 35.7 91.35 The above description of the embodiments is only for the purpose of illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it. Those skilled in the art can obviously easily make various modifications to these embodiments, and apply the general principles described herein to other embodiments without having to go through creative labor, therefore, the above embodiments cannot be used to limit the protection scope of the present application. Any improvements and modifications made by those skilled in the art based on the disclosure of the present application without departing from the scope of the present application shall be covered within the protection scope of the present application.

Claims

1. A method for preparing thymol, characterized in that: The following steps are involved: The catalyst is loaded into a reaction tube of a fixed-bed reactor, and m-cresol and isopropanol are used as raw materials. The gas-solid heterogeneous reaction is carried out by heating in the fixed bed to obtain thymol. The catalyst is an H-M1-ZSM-5 molecular sieve catalyst, wherein the metal M1 is selected from Sn, Fe or Zn, and the molecular sieve has n(Si) / n(Al+M1)=25~30.

2. The method for preparing thymol according to claim 1, wherein: The molar ratio of m-cresol to isopropanol is 1-3:1, and the loading amount of the catalyst is 30-500 g.

3. The method for preparing thymol according to claim 1, wherein: The reaction temperature is 200-300° C., and the residence time of the raw materials in the reactor is 20-60 min.

4. The method for preparing thymol according to claim 1, wherein: The H-M1-ZSM-5 molecular sieve catalyst is prepared by the following steps: dissolving a certain proportion of a silicon source, an aluminum source, a metal salt, and a structure-directing agent in water, adding sodium hydroxide to adjust the pH, stirring evenly, standing and aging at room temperature for a period of time, transferring to a Teflon-lined autoclave for heating and crystallization, and naturally cooling after the crystallization, filtering, washing and drying, ion exchange with NH4Cl solution, roasting, extruding, and then roasting again to obtain the H-M1-ZSM-5 molecular sieve catalyst; the metal is selected from Sn, Fe, or Zn.

5. The method for preparing thymol according to claim 1, wherein: The H-M1-ZSM-5 molecular sieve catalyst is prepared by the following steps: dispersing the H-ZSM-5 molecular sieve in a metal nitrate aqueous solution, performing a sufficient ion exchange reaction, and then drying, calcining, extruding, and re-calcining to obtain the H-M1-ZSM-5 molecular sieve catalyst; the metal ions are selected from one or more of Sn, Fe or Zn.

6. The method for preparing thymol according to claim 4, wherein: The silicon source is low sodium silicate or ethyl orthosilicate or a mixture of the two; and / or, the aluminum source is pseudo-boehmite; and / or, the structure directing agent is tetrapropylammonium hydroxide or tetrapropylammonium bromide or a mixture of the two; And / or, the molar ratio of the silicon source, the aluminum source, the metal salt, and the structure directing agent is 60:0.5-0.8:1-1.6:8-18.

7. The method for preparing thymol according to claim 4, wherein: The aging time is 4 to 8 hours; And / or, the crystallization atmosphere has two stages, the temperature of the first stage is 95-105° C., the time is 10-14 hours, and the temperature of the second stage is 110-130° C., the time is 20-25 hours.

8. The method for preparing thymol according to claim 5, wherein: The temperature of the ion exchange reaction is 70-90° C., and the time is 20-25 hours.