A process for the preparation of pentanediamine

Abstract

The present application relates to a kind of preparation method of pentanediamine. Including the following steps: a) 1,3-dichloropropene is prepared by cyanation reaction 4-chloro-3-butenenitrile;B) the product of step a) is prepared by double bond isomerization 4-chloro-2-butenenitrile;C) the product of step b) is prepared by cyanation reaction again 2-vinyl-pentanedinitrile;D) the product of step c) is prepared by hydrogenation reaction pentanediamine. Compared with the traditional lysine as raw material, biological synthesis pentanediamine, the present application is cheap propylene thermal chlorination by-product 1,3-dichloropropene as raw material, by cyanation-isomerization-cyanation-hydrogenation 4 steps important chemical raw material pentanediamine, for pentanediamine preparation provides a new way, and the route condition is mild, process is simple, process cost is low, with environmental protection and economic advantage, suitable for pentanediamine large-scale production.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of chemical synthesis, and particularly relates to a method for preparing pentanediamine by chemical method. BACKGROUND

[0002] Nylon is an important polymer material, which has important applications in the fields of automobiles and high-end textiles. However, the raw monomer adipic acid for synthesizing nylon 66 has been monopolized by foreign countries for a long time. Pentanediamine, as a high-performance nylon polymer monomer, can be used to produce polyamides such as nylon 56 and nylon 510. Nylon 56 is expected to be used as a new type of nylon to replace or supplement nylon 66 due to its excellent performance. In addition, pentanediamine is also an important chemical raw material, which can be used to synthesize isocyanate and used in the fields of epoxy resin curing agent and organic crosslinking agent. Therefore, the research and development of pentanediamine is of great significance.

[0003] Currently, the main production process of pentanediamine is biological fermentation method: biomass is used as raw material to produce lysine by fermentation, then 1,5-pentanediamine is produced under the action of decarboxylase, and finally the separation and purification of pentanediamine product is carried out. Considering the economic benefits, the research mainly focuses on improving the fermentation efficiency and optimizing the separation process. Patent CN101981202A discloses obtaining pentanediamine solution by direct fermentation, and the concentration of pentanediamine is 72 g / L; Patent CN111763699A accelerates the transportation process of L-lysine into cells by increasing the content of L-lysine transporter LysP, improves the tolerance of the strain to high-concentration L-lysine, and promotes the production of L-lysine, thereby improving the yield of metabolic product 1,5-pentanediamine; Patent CN104762336B discloses a method for synthesizing 1,5-pentanediamine from lysine fermentation broth under the action of lysine decarboxylase, which is more economical and simple; Patent CN115611748A discloses a separation method of 1,5-pentanediamine, which is separated from the fermentation broth by extraction in a simple and efficient manner. At present, the use of biological fermentation method has problems such as low production efficiency and complex separation process. In order to ensure the activity of the strain, the concentration of 1,5-pentanediamine product in the fermentation mother liquor is generally not high, and the reaction efficiency is low. In addition, the fermentation broth contains a large amount of inorganic salts, sugars, proteins and other impurities, so the separation process needs to consider concentration, enrichment and purification at the same time. The separation process is complicated, and the post-treatment is difficult.

[0004] There are also some studies trying to synthesize 1,5-pentanediamine by chemical method. Patent US2409086 discloses a reaction of nitrile and aldehyde compounds, mainly fatty aldehyde and acrylonitrile, under the catalysis of sodium hydroxide or sodium cyanide to prepare the corresponding cyan-containing aldehyde compounds, but the reaction has many by-products and the yield of target product is low. Patent CN113698300B discloses a method for preparing pentanediamine by two-step reaction of acrylonitrile and acetaldehyde as raw materials and N,N-dihydroxyethyl-1,4-pentanediamine as catalyst. The method can inhibit the occurrence of acrylonitrile and acetaldehyde self-polymerization side reaction and improve the selectivity of target product.

[0005] In summary, the existing pentanediamine preparation method has problems of low efficiency, complex process, serious environmental pollution and high production cost. Therefore, it is urgent to develop a synthesis method which is simple in process, good in economy, small in environmental pollution and can realize the industrialized production of pentanediamine. 1,3-Dichloropropene is a high-boiling-point residue of 3-chloropropene produced by thermal chlorination of propylene, and it is difficult to handle. Direct utilization not only causes environmental pollution, but also causes poisoning to users, so it is of great significance to develop high-value utilization ways. SUMMARY

[0006] The purpose of the present application is to provide a method for preparing pentanediamine from 1,3-dichloropropene, which overcomes the shortcomings of the prior art. The present application uses inexpensive 1,3-dichloropropene as raw material to prepare important chemical raw material pentanediamine through cyanation-isomerization-cyanation-hydrogenation of 4 steps, which provides a new way for the preparation of pentanediamine. The route has mild conditions, simple process and low process cost, and turns waste into treasure. Not only the pollution problem of industrial waste is solved, but also the high-value utilization is realized, which has environmental and economic advantages and is suitable for large-scale production of pentanediamine. In order to achieve the above invention purpose and realize the above technical effect, the technical scheme of the present application is as follows:

[0007] A method for preparing pentanediamine, comprising the following steps:

[0008] a) 1,3-dichloropropene is subjected to cyanation reaction with alkali metal cyanide under the action of an alkaline catalyst to prepare 4-chloro-3-butenenitrile crude product, and then vacuum drying is performed to remove low-boiling substances, and then oil-water phase separation is performed to obtain 4-chloro-3-butenenitrile;

[0009] b) The product of step a) is subjected to double bond isomerization under the action of an acidic catalyst to prepare 4-chloro-2-butenenitrile;

[0010] c) The product of step b) is subjected to cyanation reaction with alkali metal cyanide under the action of an alkaline catalyst to prepare 2-alkenyl-pentanedinitrile crude product, and then vacuum drying is performed to remove low-boiling substances, and then oil-water phase separation is performed to obtain 2-alkenyl-pentanedinitrile;

[0011] d) hydrogenating the product of step c) to obtain crude pentanediamine, separating light components from the top of the vacuum rectification column, and obtaining heavy components from the bottom of the column, and obtaining pentanediamine from the side line.

[0012] The reaction steps of the present application are as follows:

[0013]

[0014] 1,3-dichloropropene contains propenyl chloride and allyl chloride, both of which are prone to hydrogenolysis dechlorination during hydrogenation, resulting in reduced selectivity. In order to improve the reaction efficiency and convert propenyl chloride into allyl chloride as much as possible, and to minimize the impact of hydrogenolysis, it is necessary to first replace the relatively active allyl chloride with a protective group, then hydrogenate, and finally remove the protective group. The allyl chloride in 1,3-dichloropropene is protected and the carbon chain is lengthened by-CN, and the higher active allyl chloride is obtained by isomerization. After cyanation, hydrogenation is performed, the atomic utilization rate is high, and the selectivity of the target product is good.

[0015] In the method of the present application, the molar ratio of 1,3-dichloropropene to sodium cyanide in step a) is 1:1-4, the catalyst dosage is 1%-10% (relative to the molar amount of 1,3-dichloropropene), the reaction temperature is 60-120°C, and the reaction time is 1-5h.

[0016] In the method of the present application, after the reaction in step a) is completed, 4-chloro-3-butenenitrile is separated by vacuum drying and phase separation, the vacuum drying pressure is 10-40kPaA, and the temperature is 40-90°C.

[0017] In the method of the present application, the acid catalyst in step b) is an acid resin, preferably a sulfonic acid resin and a carboxylic acid resin, such as A35, A45, A3120, and D401, the reaction temperature is 70-140°C, preferably 90-130°C, the reaction pressure is 1-5MPaG, and the reaction liquid space velocity is 1-10h -1 , preferably 2-5h -1 ; the acid catalyst is beneficial to reducing the energy barrier of the double bond isomerization reaction and promoting the isomerization reaction, and the reaction is a solid-liquid two-phase reaction, which is easy to separate.

[0018] In the method of the present application, the molar ratio of 4-chloro-2-butenenitrile to alkali metal cyanide in step c) is 1:1.2-3, the catalyst dosage is 1-5% (relative to the molar amount of 4-chloro-2-butenenitrile), the reaction temperature is 70-130°C, and the reaction time is 1-5h.

[0019] In the method, after the reaction of step c) is completed, the 2-alkenyl-valeronitrile crude product is separated by vacuum drying and phase separation, the vacuum drying pressure is 10-30 kPaA, and the temperature is 50-100 DEG C.

[0020] In the method, the basic catalyst used in the cyanation reaction of steps a) and c) is selected from alkali metal hydroxides or tertiary amines, preferably, the basic catalyst is selected from one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, trimethylamine, triethylamine, tripropylamine, and N,N-diisopropylethylamine.

[0021] In the method, the hydrogenation catalyst used in step d) is selected from metal catalysts or supported metal catalysts, the metal includes any one or a combination of two or more of platinum, palladium, ruthenium, rhodium, nickel, iron, cobalt, molybdenum, and zinc; the support of the supported metal catalyst includes any one or a combination of two or more of alumina, silica, zirconia, and titania activated carbon; preferably, the catalyst is Pd / gamma-Al2O3, Raney nickel, or non-shaped Fe-Mo-Ni, which can efficiently hydrogenate the carbon-carbon double bond and the carbon-nitrogen bond, thereby improving the reaction selectivity. The hydrogenation reaction crude product is separated into light components at the top of a vacuum rectifying column, heavy components are collected at the bottom of the column, and the pentamethylene diamine product is collected through a side line.

[0022] In the method, the reaction temperature of step d) is 60-150 DEG C, the pressure is 3-10 MPaG, the liquid hourly space velocity is 0.1-10 h-1, the pressure of the vacuum rectifying column is 1-10 kPaA, the column bottom temperature is 150-190 DEG C, the reflux ratio is 0.5-10, and the side line collection temperature is 70-120 DEG C. -1

[0023] In the method, the reactor used in step d) is a packed fixed bed reactor, a stirred tank reactor, a fluidized bed reactor, or a multi-tube fixed bed reactor, preferably a fixed bed reactor.

[0024] The method for preparing pentamethylene diamine from 1,3-dichloropropene can achieve a yield of pentamethylene diamine of greater than 80% under continuous and stable operating conditions, the process is stable and easy to operate, and the high value-added utilization of 1,3-dichloropropene can be achieved.

[0025] The positive effects of the present application are as follows:

[0026] (1) The raw materials of the present application are cheap and easy to obtain, the target product is an important chemical raw material pentamethylene diamine with high added value, the single-pass yield of pentamethylene diamine prepared from 1,3-dichloropropene through cyanation, isomerization, and hydrogenation is greater than 90%, the process has obvious economic advantages, provides a new route for preparing pentamethylene diamine from 1,3-dichloropropene, and is suitable for industrial production.

[0027] ​(2) The process changes waste into treasure, solves the pollution and corrosion problem of organic chlorinated compound 1,3-dichloropropene, and is environmentally friendly.

[0028] (3) The reaction process is simple and easy to realize large-scale production. DETAILED DESCRIPTION

[0029] The application will be further described in detail below in combination with examples, but the scope of the application is not limited to these examples.

[0030] Gas phase analysis conditions: Shimadzu gas chromatograph, RTX-WAX column, 50°C for 5 min; 10°C / min to 80°C, hold for 5 min; 10°C / min to 100°C, hold for 5 min; 10°C / min to 220°C, hold for 20 min.

[0031] The main raw material sources are as follows:

[0032]

[0033]

[0034] Example 1

[0035] (1) 1,3-dichloropropene cyanation reaction

[0036] 1,3-dichloropropene (0.1 mol), sodium cyanide (0.15 mol) and a solvent ethanol aqueous solution (50%, 100 mL) were added into a 250 mL three-necked flask, 0.005 mol trimethylamine was added dropwise into the trimethylamine aqueous solution (30 wt.%) at 90°C, and the reaction was continuously stirred for 2 h to obtain a cyanation reaction liquid, the conversion rate and selectivity were calculated by sampling analysis; the reaction liquid was vacuum dried at 10 kpaA and 40°C to remove the solvent ethanol, and the remaining reaction liquid was separated into phases, and the obtained oil phase was 4-chloro-3-butenenitrile, and the yield of this step was 96%.

[0037] (2) 4-chloro-3-butenenitrile isomerization reaction

[0038] The product of step (1) was subjected to isomerization reaction in a fixed bed reactor with sulfonic acid resin A35 as catalyst at 110°C, nitrogen atmosphere, pressure 1 MPaG, liquid hourly space velocity 3 h -1 , and the conversion rate and selectivity were calculated by sampling analysis of the reaction liquid, and the yield of this step was 90%.

[0039] (3) 4-chloro-2-butenenitrile cyanation reaction

[0040] The isomerization product 4-chloro-3-butenenitrile (0.1 mol) of step (2), sodium cyanide (0.12 mol), NaOH (0.005 mol) and solvent aqueous ethanol solution (50%, 150 mL) were added into a 250 mL three-necked flask, and the reaction was continuously stirred at 110°C for 5 h to obtain a cyanation reaction solution. The conversion rate and selectivity were calculated by sampling analysis. The reaction solution was vacuum dried at 30 kPa A and 100°C to remove the solvent ethanol, and the remaining reaction solution was separated into phases. The obtained oil phase was 2-alkenyl-valeronitrile, and the yield of this step was 95%.

[0041] (4) Hydrogenation reaction of 2-alkenyl-valeronitrile

[0042] Pd / γ-Al2O3 was used as the catalyst in a fixed bed reactor, the temperature was 120°C, the pressure was 5 MPa G, the liquid hourly space velocity was 5 h-1, and the hydrogenation reaction was carried out at 120°C for 5 h to obtain the target product pentamethylene diamine. -1 Then, the hydrogenation reaction was carried out to obtain the target product pentamethylene diamine crude product. The crude product was subjected to vacuum rectification under the conditions of a pressure of 2 kPa A, a column bottom temperature of 162°C, and a reflux ratio of 1. The temperature of the side line was 76°C, and the yield of this step was 92%.

[0043] Example 2

[0044] (1) Cyanation reaction of 1,3-dichloropropene

[0045] 1,3-dichloropropene (0.1 mol), sodium cyanide (0.2 mol) and solvent aqueous ethanol solution (50%, 100 mL) were added into a 250 mL three-necked flask, 0.002 mol of NaOH was added at 60°C, and the reaction was continuously stirred for 5 h to obtain a cyanation reaction solution. The conversion rate and selectivity were calculated by sampling analysis. The reaction solution was vacuum dried at 20 kPa A and 50°C to remove the solvent ethanol, and the remaining reaction solution was separated into phases. The obtained oil phase was 4-chloro-3-butenenitrile, and the yield of this step was 95%.

[0046] (2) Isomerization reaction of 4-chloro-3-butenenitrile

[0047] Sulfonic acid resin A45 was used as the catalyst in a fixed bed reactor, the product of step (1) was subjected to isomerization reaction at 70°C under a nitrogen atmosphere and a pressure of 5 MPa G, the liquid hourly space velocity was 2 h-1, and the isomerization reaction was carried out at 70°C for 5 h. -1 The conversion rate and selectivity were calculated by sampling analysis of the reaction solution, and the yield of this step was 91%.

[0048] (3) Cyanation reaction of 4-chloro-2-butenenitrile

[0049] The isomerization product 4-chloro-3-butenenitrile (0.1 mol) of step (2), potassium cyanide (0.2 mol) and an aqueous solution of ethanol (50%, 150 mL) containing 0.002 mol of trimethylamine were added to a 250 mL stainless steel reactor, and the reaction was continuously stirred at 120°C for 2 h to obtain a cyanation reaction solution. The conversion rate and selectivity were calculated by sampling and analyzing the reaction solution. The reaction solution was vacuum dried at 18 kPa A and 50°C to remove the solvent ethanol, and the remaining reaction solution was separated into phases. The obtained oil phase was 2-alkenyl-valeridinitrile, and the yield of this step was 96%.

[0050] (4) Hydrogenation reaction of 2-alkenyl-valeridinitrile

[0051] Raney nickel (Ni 85%, Mo 15%) was used as the catalyst in a fixed-bed reactor at a temperature of 110°C, a pressure of 3 MPa G, and a liquid hourly space velocity of 10 h -1 The hydrogenation reaction was then carried out to obtain the target product pentanediamine crude product. The crude product was subjected to vacuum rectification under the conditions of a pressure of 1 kPa A, a column bottom temperature of 150°C, and a reflux ratio of 10. The temperature at which the side line was taken out was 70°C, and the yield of this step was 90%.

[0052] Example 3

[0053] (1) Cyanation reaction of 1,3-dichloropropene

[0054] 1,3-dichloropropene (0.1 mol), sodium cyanide (0.1 mol) and an aqueous solution of ethanol (50%, 100 mL) were added to a 250 mL stainless steel reactor, and 0.01 mol of an aqueous solution of triethylamine (30%) was added by pump at 110°C, and the reaction was continuously stirred for 2 h to obtain a cyanation reaction solution. The conversion rate and selectivity were calculated by sampling and analyzing the reaction solution. The reaction solution was vacuum dried at 40 kPa A and 90°C to remove the solvent ethanol, and the remaining reaction solution was separated into phases. The obtained oil phase was 4-chloro-3-butenenitrile, and the yield of this step was 97%.

[0055] (2) Isomerization reaction of 4-chloro-3-butenenitrile

[0056] Carboxylic acid resin A3120 was used as the catalyst in a fixed-bed reactor. The product of step (1) was subjected to an isomerization reaction at 140°C under a nitrogen atmosphere, a pressure of 3 MPa G, and a liquid hourly space velocity of 1 h -1 The conversion rate and selectivity were calculated by sampling and analyzing the reaction solution, and the yield of this step was 92%.

[0057] (3) Cyanation reaction of 4-chloro-2-butenenitrile

[0058] The isomerization product 4-chloro-3-butenenitrile (0.1 mol) of step (2), sodium cyanide (0.12 mol), solvent aqueous ethanol solution (50%, 150 mL) and aqueous trimethylamine solution (30%) containing 0.005 mol of trimethylamine were added into a 250 mL stainless steel reactor, and the reaction was continuously stirred at 130°C for 1 h to obtain a cyanation reaction solution. The conversion rate and selectivity were calculated by sampling analysis. The reaction solution was vacuum dried at 10 kPa A and 50°C to remove the solvent ethanol, and the remaining reaction solution was separated into phases. The obtained oil phase was 2-alkenyl-valerondinitrile, and the yield of this step was 98%.

[0059] (4) Hydrogenation reaction of 2-alkenyl-valerondinitrile

[0060] The non-shaped Fe-Mo-Ni was used as the catalyst, and the reaction was carried out in a fixed bed reactor at a temperature of 150°C, a pressure of 10 MPa G, a liquid hourly space velocity of 0.1 h -1 Then, the hydrogenation reaction was carried out to obtain the target product pentanediamine crude product. The crude product was subjected to vacuum rectification under the conditions of a pressure of 10 kPa A, a column bottom temperature of 190°C and a reflux ratio of 0.5. The temperature of the side line was 120°C, and the yield of this step was 95%.

[0061] Example 4

[0062] (1) Cyanation reaction of 1,3-dichloropropene

[0063] 1,3-dichloropropene (0.1 mol), potassium cyanide (0.4 mol), solvent aqueous ethanol solution (50%, 100 mL) and 0.001 mol of KOH were added into a 250 mL stainless steel reactor, and the reaction was continuously stirred at 120°C for 1 h to obtain a cyanation reaction solution. The conversion rate and selectivity were calculated by sampling analysis. The reaction solution was vacuum dried at 20 kPa A and 50°C to remove the solvent ethanol, and the remaining reaction solution was separated into phases. The obtained oil phase was 4-chloro-3-butenenitrile, and the yield of this step was 93%.

[0064] (2) Isomerization reaction of 4-chloro-3-butenenitrile

[0065] The carboxylic acid resin D401 was used as the catalyst, and the product of step (1) was subjected to the isomerization reaction in a fixed bed reactor at a temperature of 90°C, under a nitrogen atmosphere, a pressure of 1 MPa G and a liquid hourly space velocity of 10 h -1 The conversion rate and selectivity were calculated by sampling analysis of the reaction solution, and the yield of this step was 90%.

[0066] (3) Cyanation reaction of 4-chloro-2-butenenitrile

[0067] The isomerization product 4-chloro-3-butene nitrile (0.1 mol) of step (2), sodium cyanide (0.3 mol), solvent aqueous ethanol solution (50%, 150 mL) and 0.001 mol of aqueous triethylamine solution (30%) were added into a 250 mL three-necked flask, and the reaction was continuously stirred at 70°C for 4 h to obtain a cyanation reaction solution. The conversion rate and selectivity were calculated by sampling analysis. The reaction solution was vacuum dried at 20 kPa A and 80°C to remove the solvent ethanol, and the remaining reaction solution was separated into phases. The obtained oil phase was 2-alkenyl-valeronitrile, and the yield of this step was 94%.

[0068] (4) Hydrogenation reaction of 2-alkenyl-valeronitrile

[0069] Pd / γ-Al2O3 was used as the catalyst, and the reaction was carried out in a fixed bed reactor at a temperature of 60°C, a pressure of 6 MPa G, and a liquid hourly space velocity of 3 h -1 The hydrogenation reaction was then carried out to obtain the target product pentanediamine crude product. The crude product was subjected to vacuum rectification under the conditions of a pressure of 5 kPa A, a column bottom temperature of 173°C, and a reflux ratio of 2. The temperature of the side line was 84°C, and the yield of this step was 93%.

Claims

1. A method for preparing pentamethylenediamine, comprising the following steps: a) 1,3-Dichloropropene reacts with alkali metal cyanide in the presence of an alkaline catalyst to produce crude 4-chloro-3-butenonitrile, which is then dried under vacuum to remove low-boiling-point substances, followed by oil-water phase separation to obtain 4-chloro-3-butenonitrile; the reaction temperature is 60-120℃ and the reaction time is 1-5h. b) The product of step a) was converted to 4-chloro-2-butenonitrile via double bond isomerization under the action of an acidic catalyst; the reaction temperature was 70-140℃ and the reaction pressure was 1-5 MPaG. c) The product of step b) is subjected to cyanidation reaction with alkali metal cyanide again under the action of alkaline catalyst to obtain crude 2-alkenyl-glutaronitrile. The crude product is then dried under vacuum to remove low-boiling substances, and then subjected to oil-water phase separation to obtain 2-alkenyl-glutaronitrile. The reaction temperature is 70-130℃ and the reaction time is 1-5h. d) The product of step c) is hydrogenated under the action of a hydrogenation catalyst to obtain crude pentanediamine. The light component is separated from the top of a vacuum distillation column, the heavy component is collected from the bottom of the column, and the pentanediamine product is collected from the side stream. The alkaline catalyst used in the cyanidation reaction described in steps a) and c) is selected from alkali metal hydroxides or tertiary amines, and the acidic catalyst described in step b) is an acidic resin.

2. The method as described in claim 1, characterized in that, The molar ratio of 1,3-dichloropropene to sodium cyanide in step a) is 1:1-4, and the amount of catalyst used is 1%-10% relative to the molar amount of 1,3-dichloropropene.

3. The method as described in claim 1, characterized in that, After step a) the reaction is completed, vacuum dry at a pressure of 10-40 kPaA and a temperature of 40-90℃.

4. The method according to any one of claims 1-3, characterized in that, Step b) The acidic resins mentioned herein are sulfonic acid resins and carboxylic acid resins; and / or, the reaction temperature is 90-130°C, and the reaction time space velocity is 1-10 h⁻¹. -1 .

5. The method as described in claim 4, characterized in that, The acidic resins mentioned are commercially available A35, A45, A3120, and D401; the reaction liquid hourly space velocity is 2-5 h⁻¹. -1 .

6. The method according to any one of claims 1-3, characterized in that, The molar ratio of 4-chloro-2-butenonitrile to alkali metal cyanide in step c) is 1:1.2-3, and the amount of catalyst is 1-5% relative to the molar amount of 4-chloro-2-butenonitrile.

7. The method according to any one of claims 1-3, characterized in that, After the reaction in step c) is completed, vacuum drying is performed at a pressure of 10-30 kPaA and a temperature of 50-100℃.

8. The method according to any one of claims 1-3, characterized in that, The alkaline catalyst used in the cyanation reaction described in steps a) and c) is selected from one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, trimethylamine, triethylamine, tripropylamine, and N,N-diisopropylethylamine.

9. The method according to any one of claims 1-3, characterized in that, The hydrogenation catalyst mentioned in step d) is selected from metal catalysts or supported metal catalysts. The metals include any one or a combination of two or more of platinum, palladium, ruthenium, rhodium, nickel, iron, cobalt, molybdenum, and zinc. The support in the supported metal catalyst includes any one or a combination of two or more of alumina, silica, zirconium dioxide, titanium dioxide, and activated carbon.

10. The method as described in claim 9, characterized in that, The hydrogenation catalyst is selected from Pd / γ-Al2O3 catalyst, Raney nickel catalyst, and amorphous Fe-Mo-Ni catalyst.

11. The method according to any one of claims 1-3, characterized in that, The reaction temperature in step d) is 60-150℃, the pressure is 3-10 MPaG, and the liquid hourly space velocity is 0.1-10 h⁻¹. -1 The pressure for vacuum distillation is 1-10 kPaA, the bottom temperature is 150-190℃, the reflux ratio is 0.5-10, and the side stream temperature is 70-120℃.

12. The method according to any one of claims 1-3, characterized in that, Step d) The reactor can be a packed fixed bed reactor, a stirred tank reactor, a fluidized bed reactor, or a multi-tube fixed bed reactor.

Images