Method for preparing 3-methoxy-3-methyl-1-butanol

Abstract

The invention provides a method for improving the selectivity of a product 3-methoxy-3-methyl-1-butanol (MMB). According to the method, the content of the isopentene methyl ether in the raw material isoprenol is controlled to be 0.005-0.25 wt%, so that the selectivity of the MMB can be effectively improved, the generation of key byproducts of isoprenol methyl ether and isoprenol methyl ether is reduced, and the purity of the MMB is improved.

Description

Technical Field

[0001] The invention relates to the field of recycling of effective components in chemical industry, and in particular to a method for recovering effective components in a post-processing process of MMB production. Background Art

[0002] 3-Methoxy-3-methyl-1-butanol (MMB) is an important fine chemical raw material. Due to its good hydrophilicity, lipophilicity, low toxicity and biodegradability, it is widely used as a solvent for cosmetics, air fresheners, industrial and civilian detergents, pesticides and insecticides.

[0003] At present, the only MMB producer is Japan's Kuraray Company, and at this stage, my country's demand for MMB is entirely dependent on imports. Due to the tight domestic supply and strong demand growth, its production prospects are very broad. Japan's Kuraray Company uses 4,4-dimethyl-1,3-dioxane (DMD) alcoholysis and 3-methyl-1,3-butanediol (MBD) etherification to produce MMB. Among them, the MBD etherification method is aimed at the reuse of MBD generated in the DMD alcoholysis method; the DMD alcoholysis method has many by-products, the selectivity of the main product is low, and it does not meet the green atom economy. For example, patent literature: CN102206142B is known, 3-methyl-3-butene-1-ol, methanol and a catalyst are placed in a sealed reactor for reaction, and then the product is distilled and separated to obtain 3-methoxy-3-methyl-1-butanol.

[0004] At present, in the mixed material of the post-processing process of the MMB production process, methanol and isopentyl methyl ether are azeotropic, and the azeotropic composition under normal pressure is 42.57wt% methanol and 57.43wt% isopentyl methyl ether. In the past, the recycled light components obtained by conventional distillation contained a large amount of isopentyl methyl ether. Summary of the invention

[0005] An object of the present invention is to provide a method for preparing MMB to improve the selectivity of the product.

[0006] Another object of the present invention is to provide a method for recycling the mixed material in the post-processing process of the production process for preparing MMB, so as to realize the recycling of effective components.

[0007] It was found in the study that too low or too high content of isopentenyl methyl ether in the raw material (isoisopentenol) would affect the selectivity of the MMB preparation reaction, resulting in the generation of a large number of by-products, such as isopentenol methyl ether and isopentenol methyl ether, affecting the purity of the product.

[0008] Based on the above research, in order to achieve the above invention objectives, the present invention adopts the following technical solutions:

[0009] The first aspect of the present invention provides a method for preparing MMB.

[0010] A method for preparing MMB, wherein the MMB is obtained by reacting isopentenol with methanol under the action of a heterogeneous acid catalyst, wherein the content of isopentenyl methyl ether in the isopentenol is between 0.005 and 0.25 wt %;

[0011] The structure of the isopentyl methyl ether is shown below:

[0012]

[0013] In the preparation method, the heterogeneous acid catalyst can refer to CN102206142B, such as composite oxides, heteropoly acids, zeolite molecular sieves, and cation exchange resins;

[0014] The amount of the catalyst used accounts for 0.1 to 1 wt% of the total reaction liquid mass;

[0015] Among them, the composite oxides are, for example, SiO2-Al2O3, SiO2-TiO2, SiO2-SnO2, SiO2-ZrO2, SiO2-ZnO, SiO2-Y2O5, SiO2-La2O3, SiO2-MoO3, SiO2-WO3, Al2O3-ZnO, Al2O3-B2O3, Al2O3-TiO2, Al2O3-ZrO2, Al2O3-MoO3, Al2O3-Fe2O3, Al2O3-Co3O4, T iO2-ZnO, TiO2-CdO, TiO2-ZrO2, TiO2-SnO2, TiO2-MoO3, TiO2-WO3, TiO2-Fe2O3, TiO2-Co3O4, ZrO2-MoO3, ZrO 2-WO3, ZrO2-Fe2O3, ZrO2-Fe3O4, ZnO-Fe2O3, ZnO-Fe3O4 or MoO3-CoO-Al2O3; preferably MoO3-CoO-Al2O3, SiO2-Al2O3.

[0016] The heteropolyacids such as H3PW 12 O 40 / C, H3PW 12 O 40 / SiO2、H3PW 12 O 40 / ZrO2、H3PW 12 O 40 / SnO2、H3PW 12 O 40 / MCM-41、H3PW 12 O 40 / Si-SBA-15、H4SiW 12 O 40 / C, H4SiW 12 O 40 / SiO2, H4SiW 12 O 40 / ZrO2, H4SiW 12 O 40 / SnO2, H4SiW 12 O 40 / MCM - 41, H4SiW 12 O 40 / Si - SBA - 15, H3PMo 12 O 40 / C, H3PMo 12 O 40 / SiO2, H3PMo 12 O 40 / ZrO2, H3PMo 12 O 40 / SnO2, H3PMo 12 O 40 / MCM - 41, H3PMo 12 O 40 / Si - SBA - 15, H4SiMo 12 O 40 / C, H4SiMo 12 O 40 / SiO2, H4SiMo 12 O 40 / ZrO2, H4SiMo 12 O 40 / SnO2, H4SiMo 12 O 40 / MCM - 41, H4SiMo 12 O 40 / Si - SBA - 15, Cs 2.5 H 0.5 PW 12 O 40 、Cs 2.5 H 0.5 PMo 12 O 40 或Cs 2.5 H 0.5 PW 12 O 40 / SiO2; 优选H3PW 12 O 40 / SiO2, H3PW 12 O 40 / MCM - 41。

[0017] The zeolite molecular sieves are, for example, HZSM-5, HZSM-11, HY, HX, H-β, H-MCM-22, L-type zeolite, montmorillonite, mordenite, SAPO-34 or SAPO-11; preferably HZSM-11.

[0018] The cation exchange resins are for example NKC-9 or Nifon-H.

[0019] In the preparation method, the reaction temperature is 100-150° C., the reaction pressure is 0.5-1.5 MPa, and the reaction time is 1-5 h.

[0020] In the preparation method, the molar ratio of isopentenol to methanol is between 0.01 and 0.5.

[0021] The second aspect of the present invention provides a method for recycling mixed materials in the post-processing process of preparing MMB production, comprising the following steps:

[0022] (1) subjecting the mixed material in the post-processing process of MMB production to an azeotropic distillation with the entrainer n-hexane in an azeotropic distillation tower;

[0023] (2) collecting the light components of the azeotropic mixture at the top of the tower, extracting and separating the phases through water to obtain an organic phase containing a high-purity azeotropic agent;

[0024] (3) The aqueous phase containing light components obtained by extraction enters into an aqueous phase distillation tower for distillation, and light component methanol is obtained at the top of the tower. The high-purity water in the bottom of the tower can be used for extraction;

[0025] (4) The bottom liquid of the azeotropic distillation tower is subjected to vacuum distillation in an effective component recovery tower, and the effective component isopentyl methyl ether is recovered from the top of the tower.

[0026] In the recycling method, the mixed material in the post-processing process of MMB production contains: 0.01-0.05wt% of isopentanol, 96-98wt% of methanol, 0.3-0.6wt% of isopentanol methyl ether, 0.02-0.06wt% of isopentanol methyl ether, and 1.3-3.5wt% of isopentanol methyl ether.

[0027] In the recycling method, in step (1), the mass ratio of the entrainer n-hexane to the mixed material is 2.5:1-4.5:1, the absolute pressure of the azeotropic distillation system is 0.2-0.9 bar, the azeotropic distillation tower has 35-45 plates, the reflux ratio is 2:1-10:1, and the material is fed from the lower part of the tower. The tower bottom temperature is 50-60°C, and the tower top temperature is 30-38°C.

[0028] Methanol containing high-purity entrainer is obtained at the top of the tower, and a mixture containing a small amount of methanol is obtained at the bottom of the tower.

[0029] In the recycling method, in step (2), the mass ratio of water to azeotropic light components is 3.5:1 to 6.2:1, the extraction temperature is 10 to 15° C., and the operating pressure is 0.8 to 1 bar.

[0030] In the recycling method, in step (3), the water phase distillation tower has 35 to 42 plates, the reflux ratio is 1.5:1 to 11:1, the material is fed from the bottom of the tower, the operating pressure is 0.8 to 1.5 bar absolute pressure, the tower bottom temperature is 90 to 105°C, and the tower top temperature is 55 to 74°C.

[0031] In the recycling method, in step (4), the effective component recovery tower has 28 to 36 plates, a reflux ratio of 2:1 to 5:1, and feed is provided in the lower part of the tower. The operating pressure is 0.5 to 1 bar absolute pressure, the tower bottom temperature is 65 to 85°C, and the tower top temperature is 28 to 45°C.

[0032] In the recycling method, further, the isopentenyl methyl ether recovered in step (4) is mixed with fresh raw material isopentenyl alcohol to make the isopentenyl methyl ether content between 0.005 and 0.25 wt %, and MMB can be prepared according to the above method.

[0033] In the present invention, after the reaction for preparing MMB is completed, the reaction solution is subjected to light removal and heavy removal treatment to obtain 3-methoxy-3-methyl-1-butanol (MMB) with a purity of ≥99.5%.

[0034] The positive effects of the present invention are:

[0035] 1. The present invention can effectively improve the selectivity of the raw material and reduce the generation of key by-products such as prenol methyl ether and isopentenol methyl ether by controlling the content of isopentenyl methyl ether in the raw material isopentenol to be between 0.005 and 0.25 wt %, thereby improving the yield and purity of MMB.

[0036] 2. There are mixed materials in the post-processing process of MMB, and the organic components are complex, containing a large amount of azeotropic isopentyl methyl ether. If the effective components are reused by traditional methods, the content of the key component isopentyl methyl ether is too high, which affects the selectivity and yield of the product. A large amount of materials need to be discharged as waste liquid, but the cost of three wastes treatment is increased, and resources are wasted. Therefore, the method of the present invention is adopted to realize the recovery of effective substances through azeotropic distillation, extraction, vacuum distillation and other methods, and efficiently recover methanol and isopentyl methyl ether, effectively reducing production costs, reducing the amount of three wastes to be treated, and reducing pollution to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The present invention is a schematic diagram of a process for recovering effective components in the post-treatment process of MMB.

[0038] Among them, C001 is an azeotropic distillation tower, C002 is an aqueous phase distillation tower, C003 is an effective component recovery tower, D001 is a phase separation tank, D002 is a n-hexane recovery tank, D003 is a methanol recovery tank, and D004 is a water recovery tank. DETAILED DESCRIPTION

[0039] The following embodiments are not intended to limit the scope of implementation of the present invention. Any modification or equivalent substitution of the present invention without departing from the spirit and scope of the present invention shall be included in the protection scope of the claims of the present invention.

[0040] The azeotroping agent used was ≥ 95 wt% n-hexane from Merck.

[0041] The raw material ≥99wt% of isoprenol comes from Kuraray.

[0042] The recovery rates of methanol and isopentyl methyl ether were calculated by analyzing the liquid chromatograph equipped with a UV detector. The liquid chromatograph was Agilent's 1200 series, equipped with a C18 liquid chromatograph column, the column temperature was set at 40°C, acetonitrile and 0.05 mol / L NaH2PO4 solution were used as the mobile phase, the flow rate was 1.0 mL / min, the UV detector was used for detection at a wavelength of 360 nm, and the external standard method was used for quantification. Before the sample was injected, it was appropriately diluted with ultrapure water, and after adding an excess of dinitrofluorobenzene solution for full derivatization, it was injected and analyzed.

[0043] The selectivity and yield of 3-methoxy-3-methyl-1-butanol (MMB) were obtained by gas chromatograph: Agilent 7820A, chromatographic column HP-5 (30m×320μm×0.25μm), injection port temperature: 150℃; split ratio 50:1; carrier gas flow rate: 1.5ml / min; heating program: 40℃ for 1min, heating to 90℃ at 10℃ / min, holding for 0min, then heating to 160℃ at 5℃ / min, holding for 0min, then heating to 280℃ at 30℃ / min, holding for 6min. Detector temperature: 280℃, and analyzed and calculated.

[0044] Example 1

[0045] use Figure 1 The mixed material post-processing system in the MMB production process is shown.

[0046] 845 g of mixed material in MMB production was taken, which included 96.55 wt % of methanol, 0.03 wt % of isopentenol, 0.48 wt % of isopentenyl methyl ether, 0.04 wt % of isopentenyl methyl ether and 2.9 wt % of isopentenyl methyl ether.

[0047] The azeotropic distillation agent is 2535g of n-hexane, the azeotropic distillation tower has 40 theoretical plates, the feed plate is the 25th plate (counted from top to bottom), the operating pressure is 0.5bar, the pressure drop of the whole tower is 0.02bar, the reflux ratio is 5:1, the tower top temperature is 34.8℃, and the tower bottom temperature is 52.1℃.

[0048] 2650g of azeotrope at the top of the tower, 9275g of water was added to extract and separate at a temperature of 15°C and a pressure of 1 bar to obtain high-purity 99.8wt% n-hexane. The aqueous phase entered the aqueous phase distillation tower, which had 40 theoretical plates, the 35th feed plate, an operating pressure of 1 bar, a pressure drop of 0.02bar for the whole tower, a reflux ratio of 7:1 for the distillation tower, a top temperature of 64.08°C, and a bottom temperature of 100.1°C. 99.66wt% methanol was obtained at the top of the tower, with a yield of 99.71wt%, and 99.94wt% water was obtained in the bottom of the tower. The bottom liquid of the azeotropic distillation tower entered the effective component recovery tower, which had 35 theoretical plates, the 25th feed plate, an operating pressure of 0.6bar, and a pressure drop of 0.025bar for the whole tower. The reflux ratio of the distillation tower was 2.5:1, the top temperature was 31°C, and the bottom temperature was 68.3°C. The high-purity 98.7wt% isopentyl methyl ether extracted from the top of the effective component recovery tower has a yield of 98wt%.

[0049] Preparation of MMB:

[0050] The recovered isopentyl methyl ether is mixed with fresh isopentyl alcohol in a certain proportion, and the isopentyl methyl ether content in the isopentyl alcohol is 0.05wt%. Methanol is mixed with isopentyl methyl ether content in the isopentyl alcohol of 0.05wt%,

[0051] The molar ratio of isopentanol to methanol is 0.2; the above-mentioned mixed raw materials are introduced into a sealed reactor filled with MoO3-CoO-Al2O3 heterogeneous acid catalyst, the amount of the catalyst accounting for 0.5wt% of the total mass of the reaction liquid, and the reaction is carried out at a reaction temperature of 120°C and a reaction pressure of 0.75MPa for 3h.

[0052] The reaction liquid enters the light removal tower, which has 30 theoretical plates, the 10th feed plate, the operating pressure is 0.8 bar, and the pressure drop of the whole tower is 0.02 bar. The reflux ratio of the light removal tower is 2:1, the tower top temperature is 58.7°C, and the tower bottom temperature is 86.1°C. The bottom liquid of the light removal tower enters the heavy removal tower, which has 25 theoretical plates, the 20th feed plate, the operating pressure is 0.2 bar, and the pressure drop of the whole tower is 0.01 bar. The reflux ratio of the heavy removal tower is 3:1, the tower top temperature is 74.5°C, the tower bottom temperature is 95.6°C, and 3-methoxy-3-methyl-1-butanol (MMB) with a purity of 99.64wt% is obtained at the top of the heavy removal tower, and the total yield of MMB is 85wt%.

[0053] Comparative Example 1

[0054] MMB was prepared according to the same reaction conditions as in Example 1, except that the content of isopentenyl methyl ether in isopentenyl alcohol was 0.004 wt %. The MMB reaction solution was subjected to the same light and heavy removal as in Example 1 to obtain 3-methoxy-3-methyl-1-butanol (MMB) with a purity of 99.2 wt %. The total yield of MMB was 79.3 wt %.

[0055] Comparative Example 2

[0056] MMB was prepared according to the same reaction conditions as in Example 1, except that the content of isopentenyl methyl ether in isopentenyl alcohol was 0.32 wt %. The MMB reaction solution was subjected to the same light and heavy removal as in Example 1 to obtain 3-methoxy-3-methyl-1-butanol (MMB) with a purity of 98.9 wt %. The total yield of MMB was 78.85 wt %.

[0057] Example 2

[0058] 548 g of mixed material in MMB production was taken, which included 96.84 wt % of methanol, 0.025 wt % of isopentenol, 0.43 wt % of isopentenyl methyl ether, 0.035 wt % of isopentenol methyl ether and 2.67 wt % of isopentenol methyl ether.

[0059] The azeotropic distillation agent is 1562g of n-hexane, the azeotropic distillation tower has 42 theoretical plates, the feed plate is the 28th plate (counted from top to bottom), the operating pressure is 0.48bar, the pressure drop of the whole tower is 0.02bar, the reflux ratio is 4.5:1, the tower top temperature is 34.3℃, and the tower bottom temperature is 51.51℃.

[0060] 1580g of azeotrope at the top of the tower, 6636g of water was added to extract and separate at a temperature of 12°C and a pressure of 0.9bar to obtain high-purity 99.85wt% n-hexane. The aqueous phase entered the aqueous phase distillation tower, which had 42 theoretical plates, the 36th feed plate, an operating pressure of 0.9bar, and a pressure drop of 0.02bar throughout the tower. The reflux ratio of the distillation tower was 6.5:1, the top temperature was 63.2°C, and the bottom temperature was 98.5°C. 99.45wt% methanol was obtained at the top of the tower, with a yield of 99.05wt%, and 99.87wt% water was obtained at the bottom of the tower.

[0061] The bottom liquid of the azeotropic distillation tower enters the effective component recovery tower, which has 30 theoretical plates, the feed plate is the 28th, the operating pressure is 0.65 bar, and the pressure drop of the whole tower is 0.025 bar. The reflux ratio of the distillation tower is 3.2:1, the top temperature is 35°C, and the bottom temperature is 70.1°C. The high-purity 97.9wt% isopentyl methyl ether extracted from the top of the effective component recovery tower has a yield of 98.8wt%.

[0062] Preparation of MMB:

[0063] The recovered isopentyl methyl ether is mixed with fresh isopentyl alcohol in a certain proportion, and the isopentyl methyl ether content in the isopentyl alcohol is 0.15wt%. Methanol is mixed with isopentyl alcohol with an isopentyl methyl ether content of 0.15wt%, and the molar ratio of isopentyl alcohol to methanol is 0.31; the mixed raw materials are passed into a sieve filled with SiO 2- The AI2O3 heterogeneous acid catalyst was used in a sealed reactor with the catalyst amount accounting for 0.65wt% of the total reaction liquid mass. The reaction was carried out at a reaction temperature of 110°C and a reaction pressure of 0.8MPa for 3.5h.

[0064] The reaction liquid enters the light removal tower, which has 35 theoretical plates, the 12th feed plate, the operating pressure is 0.82 bar, and the pressure drop of the whole tower is 0.02 bar. The reflux ratio of the light removal tower is 2.5:1, the top temperature is 60.2°C, and the bottom temperature is 87.12°C. The bottom liquid of the light removal tower enters the heavy removal tower, which has 30 theoretical plates, the 21st feed plate, the operating pressure is 0.25 bar, and the pressure drop of the whole tower is 0.01 bar. The reflux ratio of the heavy removal tower is 2.2:1, the top temperature is 78.2°C, the bottom temperature is 97.42°C, and the top of the heavy removal tower obtains 3-methoxy-3-methyl-1-butanol (MMB) with a purity of 99.41wt%, and the total yield of MMB is 84.2wt%.

[0065] Example 3

[0066] 1058g of mixed material in MMB production was taken, which included 96.38wt% of methanol, 0.036wt% of isopentenol, 0.375wt% of isopentenyl methyl ether, 0.057wt% of isopentenyl methyl ether and 3.152wt% of isopentenyl methyl ether.

[0067] The azeotropic distillation agent is 2962.4g of n-hexane, the azeotropic distillation tower has 36 theoretical plates, the feed plate is the 20th plate (counted from top to bottom), the operating pressure is 0.6bar, the pressure drop of the whole tower is 0.015bar, the reflux ratio is 3:1, the tower top temperature is 35℃, and the tower bottom temperature is 53.5℃.

[0068] 2855g of azeotrope at the top of the tower, 11705.5g of water was added to extract and separate at 12℃ and 0.9bar pressure to obtain high-purity 99.53wt% n-hexane. The water phase entered the water phase distillation tower, which had 36 theoretical plates, the 32nd feed plate, the operating pressure was 0.9bar, and the pressure drop of the whole tower was 0.018bar. The reflux ratio of the distillation tower was 5:1, the top temperature was 56.3℃, and the bottom temperature was 91.7℃. 99.57wt% methanol was obtained at the top of the tower, with a yield of 98.32wt%, and 99.9wt% water was obtained at the bottom of the tower.

[0069] The bottom liquid of the azeotropic distillation tower enters the effective component recovery tower, which has 29 theoretical plates, the 18th feed plate, the operating pressure is 0.55 bar, and the pressure drop of the whole tower is 0.02 bar. The reflux ratio of the distillation tower is 2.5:1, the top temperature is 42.5℃, and the bottom temperature is 76.5℃. The high-purity 99.9wt% isopentyl methyl ether extracted from the top of the effective component recovery tower has a yield of 97.3wt%.

[0070] Preparation of MMB:

[0071] The recovered isopentyl methyl ether is mixed with fresh isopentyl alcohol in a certain proportion, and the isopentyl methyl ether content in the isopentyl alcohol is 0.21wt%. Methanol is mixed with isopentyl alcohol with an isopentyl methyl ether content of 0.21wt%, and the molar ratio of isopentyl alcohol to methanol is 0.23; the mixed raw materials are introduced into a sealed reactor filled with HZSM-11 heterogeneous acid catalyst, and the amount of the catalyst accounts for 0.38wt% of the total reaction liquid mass, and the reaction is carried out at a reaction temperature of 134° C. and a reaction pressure of 0.94MPa for 4.25h.

[0072] The reaction liquid enters the light removal tower, which has 28 theoretical plates, the 11th feed plate, the operating pressure is 0.75 bar, and the pressure drop of the whole tower is 0.018 bar. The reflux ratio of the light removal tower is 2.5:1, the top temperature is 55.2°C, and the bottom temperature is 84.5°C. The bottom liquid of the light removal tower enters the heavy removal tower, which has 28 theoretical plates, the 22nd feed plate, the operating pressure is 0.25 bar, and the pressure drop of the whole tower is 0.015 bar. The reflux ratio of the heavy removal tower is 2.8:1, the top temperature is 78°C, the bottom temperature is 100.5°C, and 3-methoxy-3-methyl-1-butanol (MMB) with a purity of 99.32wt% is obtained at the top of the heavy removal tower, and the total yield of MMB is 80.3wt%.

Claims

1. A method for preparing MMB, which is obtained by reacting isopentenol with methanol under the action of a heterogeneous acid catalyst, wherein: The content of isopentenyl methyl ether in isopentenyl alcohol is between 0.005 and 0.25 wt %.

2. The method according to claim 1, wherein: The molar ratio of isopentenol to methanol is 0.01 to 0.

5.

3. The method according to claim 1 or 2, wherein: The heterogeneous acid catalyst is selected from composite oxides, heteropoly acids, zeolite molecular sieves, and cation exchange resins; Preferably, the amount of the catalyst used accounts for 0.1 to 1 wt % of the total reaction solution.

4. The method according to any one of claims 1 to 3, wherein: The reaction temperature is 100-150°C, the reaction pressure is 0.5-1.5MPa, and the reaction time is 1-5h.

5. A method for recycling mixed materials in the post-processing process of preparing MMB production, comprising the following steps: (1) subjecting the mixed material in the post-processing process of MMB production to an azeotropic distillation with the entrainer n-hexane in an azeotropic distillation tower; (2) collecting the light components of the azeotropic mixture at the top of the tower, extracting and separating the phases through water to obtain an organic phase containing a high-purity azeotropic agent; (3) the aqueous phase containing light components obtained by extraction enters into an aqueous phase distillation tower for distillation, and light component methanol is obtained at the top of the tower; (4) The bottom liquid of the azeotropic distillation tower is subjected to vacuum distillation in an effective component recovery tower, and the effective component isopentyl methyl ether is recovered from the top of the tower.

6. The method according to claim 5, wherein: The mixed material in the post-processing process of MMB production comprises: 0.01-0.05 wt% of isopentanol, 96-98 wt% of methanol, 0.3-0.6 wt% of isopentanol methyl ether, 0.02-0.06 wt% of isopentanol methyl ether, and 1.3-3.5 wt% of isopentanol methyl ether; In step (1), the mass ratio of the entrainer n-hexane to the mixed material is 2.5:1-4.5:1, the absolute pressure of the azeotropic distillation system is 0.2-0.9 bar, the azeotropic distillation tower has 35-45 plates, the reflux ratio is 2:1-10:1, the material tower is fed in the middle and lower part, the bottom temperature is 50-60°C, and the top temperature is 30-38°C.

7. The method according to claim 5, wherein: In step (2), the mass ratio of water to azeotropic light components is 3.5:1 to 6.2:1, the extraction temperature is 10 to 15°C, and the operating pressure is 0.8 to 1 bar.

8. The method according to claim 5, wherein: In step (3), the water phase distillation tower has 35 to 42 plates, a reflux ratio of 1.5:1 to 11:1, material is fed from the lower part of the tower, the operating pressure is 0.8 to 1.5 bar absolute pressure, the bottom temperature is 90 to 105°C, and the top temperature is 55 to 74°C.

9. The method according to claim 5, wherein: In step (4), the effective component recovery tower has 28 to 36 plates, a reflux ratio of 2:1 to 5:1, feed is taken from the lower part of the tower, the operating pressure is 0.5 to 1 bar absolute pressure, the bottom temperature is 65 to 85°C, and the top temperature is 28 to 45°C.

10. The method according to any one of claims 5 to 9, wherein: The isopentenyl methyl ether recovered in step (4) is mixed with fresh raw material isopentenyl alcohol to make the isopentenyl methyl ether content between 0.005 and 0.25 wt %, and MMB is prepared according to the method according to any one of claims 1 to 3.

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