A method for synthesizing 2-chlorobutane

Abstract

The application belongs to the technical field of organic synthesis, and particularly relates to a method for synthesizing 2-chlorobutane. The method uses sec-butyl alcohol and hydrogen chloride as raw materials, adopts a fly ash-based catalyst to continuously react in a fixed bed reactor to synthesize 2-chlorobutane, and achieves a purity of more than 99.5% and a yield of 98% of 2-chlorobutane through continuous synthesis. In addition, the method for continuously synthesizing 2-chlorobutane in the fixed bed reactor is coupled with a kettle reaction, which not only can effectively utilize waste hydrochloric acid generated in the continuous synthesis of 2-chlorobutane in the fixed bed reactor, but also can share a set of post-treatment system with the kettle reaction, so as to reduce the equipment investment of the construction project.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to a method for synthesizing 2-chlorobutane. Background Technology

[0002] 2-Chlorobutane can be used as an intermediate in organic synthesis, as a functional solvent in the chemical industry for the production of rubber, resins, plasticizers, and surfactants. In the pharmaceutical field, it is a key raw material in the synthesis of many drugs. In agriculture, it is used to prepare pesticides. Furthermore, it can be used to prepare other chemicals, such as sec-butyl sulfide, sec-butyllithium, and Grignard reagents. Therefore, 2-chlorobutane has wide applications in the medical, industrial, and agricultural fields and enjoys a promising market prospect.

[0003] Currently reported methods for preparing 2-chlorobutane mainly involve a chlorination reaction between hydrochloric acid and sec-butanol in a reactor. Chinese patent CN113501744A uses excess hydrochloric acid and sec-butanol in a batch reactor to prepare 2-chlorobutane. However, this method is a liquid-phase reaction, and the backmixing of the product and raw materials leads to a continuous decrease in reactant concentration, slow reaction rate, low instantaneous yield, long reaction time, and low production efficiency.

[0004] Furthermore, Chinese patents CN119841706A and CN118666633A both mention using a fixed-bed reactor to achieve a similar chlorination reaction. Although this preparation process avoids many defects of the liquid-phase method, with raw materials continuously fed into the reactor and products discharged simultaneously, the fluid flow is close to plug flow, resulting in a fast instantaneous reaction rate and stable reaction, this method generates a large amount of acidic wastewater compared to the liquid-phase method. Moreover, the hydrochloric acid solution is difficult to recover and reuse, and is usually only treated as waste liquid, which greatly restricts the promotion and application of this method. In order to reduce the generation of hydrochloric acid, the above methods use a relatively low hydrogen chloride feed ratio, but they fail to fundamentally solve the problem of generating hazardous hydrochloric acid waste. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the above-mentioned methods by providing a process for synthesizing 2-chlorobutane, wherein the method uses sec-butanol and hydrogen chloride as raw materials and utilizes a combination of a fixed-bed reactor and a batch reactor to achieve the synthesis of 2-chlorobutane.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for synthesizing 2-chlorobutane includes the following steps:

[0008] S1. After the preheated hydrogen chloride gas and the vaporized sec-butanol are mixed in a mixer, they are further mixed and preheated by the packing material at the top of the tubular fixed bed reactor, and then come into contact with the solid catalyst to start the reaction, producing a mixed gas containing 2-chlorobutane.

[0009] The molar ratio of sec-butanol to hydrogen chloride is 1:1.16-1.36, the reaction temperature is 160-220℃, and the reaction pressure is atmospheric pressure; the solid catalyst is a fly ash-based catalyst.

[0010] S2. Condensation and purification: The mixed gas obtained in step S1 is passed into a gas-liquid separator containing residual hydrochloric acid solution after the batch reaction for gas-liquid separation, and the liquid phase is the condensed material.

[0011] The gas-liquid separation can not only condense and separate materials, but also concentrate the residual hydrochloric acid solution after the batch reaction.

[0012] S3. Separation and return: After the condensed material is allowed to stand and separate into layers, the upper layer yields the crude product, and the lower layer yields the concentrated hydrochloric acid solution. The concentrated hydrochloric acid solution is reused as a raw material for the batch reaction.

[0013] S4. Purification: The crude product obtained in step S3 is subjected to alkaline washing, distillation and drying to produce 2-chlorobutane.

[0014] Preferably, the space velocity of the reaction in step S1 is 0.3~0.6 m / s. 3 ·h -1 .

[0015] In step S1, the preheated hydrogen chloride and the vaporized sec-butanol reach the reaction temperature.

[0016] Preferably, the reaction temperature in step S1 is 170-210℃.

[0017] Preferably, in step S1, the molar ratio of sec-butanol to hydrogen chloride is 1:1.18-1.34. This feed ratio can concentrate the residual hydrochloric acid solution after the batch reaction to a preset concentration (30-32% mass fraction) and further reduce the generation of side reactions to obtain a high reaction yield.

[0018] In step S2, the mass fraction concentration of the residual hydrochloric acid solution after the batch reaction is 25-27%, and the mass fraction concentration of the concentrated hydrochloric acid solution is 30-32%.

[0019] The batch reaction is as follows: sec-butanol and hydrochloric acid solution (30-32% mass fraction concentration) are added to the reactor at a hydrogen chloride:sec-butanol molar ratio of 5-8:1. The reaction temperature is 60-80℃, the reaction pressure is less than 0.4MPa, and the reaction time is greater than or equal to 20 hours. Then, the mixture is allowed to stand and separate into layers. The upper layer is the crude product, and the lower layer is the residual hydrochloric acid solution after the batch reaction.

[0020] Preferably, in step P1, the gas-liquid separator is made of 316L material, and all parts of the interior that come into contact with the material are lined with fluorine.

[0021] Preferably, the condensation temperature inside the gas-liquid separator is 0℃~5℃.

[0022] Preferably, the solid catalyst is a fly ash-based catalyst, wherein fly ash serves as a support for loading Fe2O3 and Al2O3 at loading amounts of 5-8 wt% and 6-10 wt%, respectively.

[0023] The fly ash-based catalyst achieves resource recycling in a graded manner and, under conditions of high hydrogen chloride feed ratio, high yield and high selectivity.

[0024] The fly ash-based catalyst is prepared by sequentially processing fly ash through main steps such as screening, acid washing, alkali washing, molding, loading, and calcination.

[0025] The fly ash is Class F fly ash.

[0026] The fly ash-based catalyst of the present invention can be prepared by the following steps:

[0027] 1) Grind the fly ash thoroughly using an agate mortar and pestle, then sieve it through a 140-180 mesh screen for later use; the preferred screen mesh size is 150-170 mesh.

[0028] 2) Soak the sieved fly ash from step 1) in a 22-25% hydrochloric acid solution and stir thoroughly for 2-4 hours to obtain mixture A;

[0029] The mass ratio of fly ash to hydrochloric acid solution is 1:1.1-1.6, and the preferred mass ratio is 1:1.2-1.4.

[0030] 3) Filter the acid-washed mixture A from step 2) and wash it with water until it is neutral to obtain filtrate M (including the filtrate after filtering mixture A and the rinsing liquid obtained from washing the filter cake), set aside. After drying the filter cake at 80-100℃ for 8-12 hours, filter cake N is obtained, set aside.

[0031] 4) Mix the dried filter cake N from step 3) with a sodium hydroxide solution of 10-30% by mass at a mass ratio of 1:1.12-1.18, and place the mixture in a microwave reactor. Microwave heat at a constant temperature of 140-170℃ for 1-2 hours to obtain mixture B. After the reactor temperature cools to room temperature, filter and wash the microwave-heated mixture B. The filtrate can be used as a raw material for preparing silicon-based molecular sieves. After washing, dry the filter cake at 100-120℃ for 10-12 hours to obtain filter cake K for later use.

[0032] The inner liner and outer lining of the microwave reactor are both made of high-temperature resistant polytetrafluoroethylene. The reactor is fixed in a rotating disk and heated evenly. After alkaline treatment, the specific surface area of ​​fly ash will further increase, which is beneficial to the subsequent steps and improves the performance of the catalyst.

[0033] 5) Mix and grind the dried filter cake K from step 4) with guar gum powder at a mass ratio of 1:0.06-0.12 to obtain mixture C;

[0034] 6) Mix the mixture C obtained in step 5) and a nitric acid solution with a mass fraction concentration of 6-10% thoroughly at a mass ratio of 1:0.4-1.2 to obtain mixture D;

[0035] 7) The mixture D from step 6) is extruded into shape using a twin-screw extruder, and then dried and calcined to obtain fly ash-based carriers of different shapes.

[0036] 8) Mix all the fly ash-based carrier from step 7) and all the filtrate M from step 3), and adjust the pH to 5-8 using a 1-5% sodium hydroxide solution to reduce the Fe content in the filtrate. 3+ Al 3+ All the precipitate was collected, resulting in mixture E.

[0037] During the addition of sodium hydroxide solution, the mixture was continuously stirred using a magnetic stirrer, and the pH was measured using a pH meter.

[0038] 9) Filter the mixture E from step 8), continuously wash the filter cake until it is neutral, and then process the filter cake through drying and calcination steps to obtain a fly ash-based catalyst. The drying temperature and calcination temperature are 90-110℃ and 400-800℃, respectively. The drying time is 8-12 hours and the calcination time is 6-12 hours. The preferred calcination temperature is 500-600℃ and the calcination time is 8-12 hours.

[0039] Preferably, the mass fraction of sodium hydroxide solution in step 4) is 15-30%.

[0040] Preferably, in step 5), the mass ratio of filter cake K to guar gum powder is 1:0.07-0.11.

[0041] Preferably, in step 6), the mass ratio of mixture C to nitric acid solution is 1:0.45-0.65.

[0042] The beneficial effects of this invention are as follows:

[0043] 1. This invention uses sec-butanol and hydrogen chloride as raw materials and employs a solid catalyst in a fixed-bed reactor to continuously synthesize 2-chlorobutane, which greatly improves production efficiency through continuous synthesis. Furthermore, by coupling the continuous synthesis of 2-chlorobutane in a fixed-bed reactor with a batch reactor, this invention not only effectively utilizes the waste hydrochloric acid generated during the continuous synthesis of 2-chlorobutane in the fixed-bed reactor, but also allows the two reactors to share a post-treatment system, thereby reducing equipment investment for the project.

[0044] 2. This invention uses a fly ash-based catalyst as a solid catalyst for continuous reaction, which not only enables the effective resource utilization of solid waste fly ash, but can also be applied to a reaction system for preparing 2-chlorobutane from a specific high molar ratio hydrogen chloride feed, achieving a purity of over 99.5% and a yield of 98% for 2-chlorobutane. Attached Figure Description

[0045] Figure 1 The image shows the gas chromatogram of 2-chlorobutane prepared in Example 1. Detailed Implementation

[0046] The present invention will be further described below with reference to the embodiments, comparative examples, and accompanying drawings. In the embodiments and comparative examples of the present invention, the fly ash was purchased from Zibo Jiazhou Heating Co., Ltd., and the type was Class F Grade III fly ash; unless otherwise specified, all other raw materials and reagents used were commercially available.

[0047] Example 1

[0048] A method for synthesizing 2-chlorobutane, the specific steps of which are as follows:

[0049] (1) Catalyst preparation

[0050] Grind 350 grams of fly ash thoroughly using an agate mortar and pestle, then pass it through a 160-mesh sieve for later use.

[0051] All the sieved fly ash was added to a beaker containing 438 grams of hydrochloric acid solution with a mass fraction of 22.5%, and stirred at 600 rpm for 2.5 hours to obtain mixture A;

[0052] Filter the mixture A, wash the filter cake until neutral to obtain filtrate M, and set aside; dry the filter cake at 90°C for 10 hours to obtain filter cake N;

[0053] All the dried filter cake N 320g was thoroughly mixed with 371g of 20% sodium hydroxide solution, and then transferred to a polytetrafluoroethylene reaction vessel. The mixture was microwave heated at a constant temperature of 160℃ for 1.5 hours to obtain mixture B.

[0054] After the kettle temperature has cooled to room temperature, the microwave-heated mixture B is filtered and washed. The filter cake is then dried at 110°C for 12 hours to obtain filter cake K, which is then set aside.

[0055] The dried filter cake K was then mixed with 24.4 g of guar gum powder and ground in a ball mill at 1000 rpm for 1 hour to obtain mixture C.

[0056] 165 g of nitric acid solution with a mass fraction concentration of 8% was thoroughly mixed with the ground mixture C to obtain mixture D. The mixture was then transferred to a kneader and kneaded for 40 minutes. Mixture D was then extruded into a butterfly shape using a twin-screw extruder, dried at 80°C for 12 hours, and calcined at 550°C for 6 hours. The mixture was then cut into fly ash-based carriers with a length of 8 mm and a cross-sectional diameter of 5 mm.

[0057] The cut fly ash-based carrier was completely immersed in filtrate M, and the pH was adjusted to 5.5 using 2% sodium hydroxide solution. The sodium hydroxide solution was added dropwise at a constant speed of 150 rpm to obtain mixture E.

[0058] The mixture E was filtered, the filter cake was washed until neutral, and then the filter cake was dried at 105°C for 12 hours and calcined at 600°C for 10 hours to obtain the fly ash-based catalyst.

[0059] (2) 1L (330g) of fly ash-based catalyst is loaded into a tubular fixed-bed reactor with a diameter of Φ38mm and a height of 2300mm, and placed in the second and third beds of the tubular fixed-bed reactor. The first and fourth beds of the tubular fixed-bed reactor are filled with inert packing (inert alumina balls).

[0060] (3) Hydrogen chloride and sec-butanol were preheated and vaporized to 180°C respectively. Then, the two materials were mixed in a mixer and fed into a tubular fixed-bed reactor to react, resulting in a mixed gas containing 2-chlorobutane. The feed molar ratio of hydrogen chloride to sec-butanol was 1.26:1, the bed temperature of the tubular fixed-bed reactor was 180°C, the reaction pressure was atmospheric pressure, and the reaction space velocity was 0.4 m. 3 ·h -1 .

[0061] (4) The mixed gas is introduced into a gas-liquid separator containing a 25-27% hydrochloric acid solution for gas-liquid separation (condensation temperature is 1℃). The liquid phase is the condensed material. After settling and stratification, the upper layer is the crude product, and the lower layer is the concentrated hydrochloric acid solution (30-32wt%). The concentrated hydrochloric acid solution is used as the raw material for the batch reaction. The upper crude product is successively subjected to alkali washing, distillation, and drying to obtain 2-chlorobutane product with a purity of over 99.5%, and its gas chromatogram is shown in the figure. Figure 1 As shown.

[0062] In step (4), the 25-27% hydrochloric acid solution is the residual hydrochloric acid solution after the batch reaction.

[0063] In step (4), the batch reaction is as follows: sec-butanol and hydrochloric acid solution (31% mass fraction concentration) are added to the reaction vessel at a hydrogen chloride:sec-butanol molar ratio of 6:1. The reaction temperature is 70°C, the reaction pressure is 0.35MPa, and the reaction time is 20 hours. Then, the mixture is allowed to stand and separate into layers. The upper layer is the crude product, and the lower layer is the residual hydrochloric acid solution after the batch reaction.

[0064] The distillation process involves controlling the steam in the distillation vessel at 0.15 MPa, maintaining the temperature inside the vessel at 78.5°C, feeding the material and heating for 7 hours to distill off the product components.

[0065] Example 2

[0066] The difference between this embodiment and embodiment 1 is that, in step (1), all the dried filter cake N 320g is thoroughly mixed with 371g of sodium hydroxide solution with a mass fraction of 15%, and then transferred to a polytetrafluoroethylene reactor. The other steps are the same as in embodiment 1.

[0067] Example 3

[0068] The difference between this embodiment and embodiment 1 is that, in step (1), all the dried filter cake N 320g is thoroughly mixed with 371g of sodium hydroxide solution with a mass fraction of 25%, and then transferred to a polytetrafluoroethylene reactor. The other steps are the same as in embodiment 1.

[0069] Example 4

[0070] The difference between this embodiment and embodiment 1 is that, in step (1), all the dried filter cake N 320g is thoroughly mixed with 371g of sodium hydroxide solution with a mass fraction of 30%, and then transferred to a polytetrafluoroethylene reactor. The other steps are the same as in embodiment 1.

[0071] Example 5

[0072] The difference between this embodiment and embodiment 1 is that, in step (1), all the dried filter cake N 320g is thoroughly mixed with 358g of sodium hydroxide solution with a mass fraction of 20%, and then transferred to a polytetrafluoroethylene reactor. The other steps are the same as in embodiment 1.

[0073] Example 6

[0074] The difference between this embodiment and embodiment 1 is that, in step (1), all the dried filter cake N 320g is thoroughly mixed with 365g of sodium hydroxide solution with a mass fraction of 20%, and then transferred to a polytetrafluoroethylene reactor. The other steps are the same as in embodiment 1.

[0075] Example 7

[0076] The difference between this embodiment and embodiment 1 is that, in step (1), all the dried filter cake N 320g is thoroughly mixed with 378g of sodium hydroxide solution with a mass fraction of 20%, and then transferred to a polytetrafluoroethylene reactor. The other steps are the same as in embodiment 1.

[0077] Example 8

[0078] The difference between this embodiment and embodiment 1 is that the microwave heating temperature in step (1) is 140°C, while the other steps are the same as in embodiment 1.

[0079] Example 9

[0080] The difference between this embodiment and embodiment 1 is that the microwave heating temperature in step (1) is 150°C, while the other steps are the same as in embodiment 1.

[0081] Example 10

[0082] The difference between this embodiment and embodiment 1 is that the microwave heating temperature in step (1) is 170°C, while the other steps are the same as in embodiment 1.

[0083] Example 11

[0084] The difference between this embodiment and embodiment 1 is that the molar ratio of hydrogen chloride to sec-butanol in step (3) is 1.18:1, while the other steps are the same as in embodiment 1.

[0085] Example 12

[0086] The difference between this embodiment and embodiment 1 is that the molar ratio of hydrogen chloride to sec-butanol in step (3) is 1.22:1, while the other steps are the same as in embodiment 1.

[0087] Example 13

[0088] The difference between this embodiment and embodiment 1 is that the molar ratio of hydrogen chloride to sec-butanol in step (3) is 1.3:1, while the other steps are the same as in embodiment 1.

[0089] Example 14

[0090] The difference between this embodiment and embodiment 1 is that the molar ratio of hydrogen chloride to sec-butanol in step (3) is 1.34:1, while the other steps are the same as in embodiment 1.

[0091] Example 15

[0092] The difference between this embodiment and embodiment 1 is that the bed temperature in step (3) is 170°C, while the other steps are the same as in embodiment 1.

[0093] Example 16

[0094] The difference between this embodiment and embodiment 1 is that the bed temperature in step (3) is 190°C, while the other steps are the same as in embodiment 1.

[0095] Example 17

[0096] The difference between this embodiment and embodiment 1 is that the bed temperature in step (3) is 200°C, while the other steps are the same as in embodiment 1.

[0097] Example 18

[0098] The difference between this embodiment and embodiment 1 is that the bed temperature in step (3) is 210°C, while the other steps are the same as in embodiment 1.

[0099] Comparative Example 1

[0100] The catalyst used in this comparative example is the catalyst prepared in Example 1 of patent CN119841706A, and other conditions are the same as in Example 1 of this invention.

[0101] Comparative Example 2

[0102] The catalyst used in this comparative example is the catalyst prepared in Example 1 of patent CN118666633A, and other conditions are the same as in Example 1 of this invention.

[0103] Comparative Example 3

[0104] The difference between this comparative example and Example 1 is that in step (1), all the dried filter cake N 320g was thoroughly mixed with 371g of sodium hydroxide solution with a mass fraction of 5%, and then transferred to a polytetrafluoroethylene reactor. The other steps are the same as in Example 1.

[0105] Comparative Example 4

[0106] The difference between this comparative example and Example 1 is that in step (1), all the dried filter cake N 320g was thoroughly mixed with 371g of sodium hydroxide solution with a mass fraction of 35%, and then transferred to a polytetrafluoroethylene reactor. The other steps are the same as in Example 1.

[0107] Comparative Example 5

[0108] The difference between this comparative example and Example 1 is that in step (1), all the dried filter cake N 320g was thoroughly mixed with 346g of sodium hydroxide solution with a mass fraction of 20% and then transferred to a polytetrafluoroethylene reactor. The other steps are the same as in Example 1.

[0109] Comparative Example 6

[0110] The difference between this comparative example and Example 1 is that in step (1), all the dried filter cake N 320g was thoroughly mixed with 390g of sodium hydroxide solution with a mass fraction of 20% and then transferred to a polytetrafluoroethylene reactor. The other steps are the same as in Example 1.

[0111] Comparative Example 7

[0112] The difference between this comparative example and Example 1 is that the microwave heating temperature in step (1) is 130°C, while the other steps are the same as in Example 1.

[0113] Comparative Example 8

[0114] The difference between this comparative example and Example 1 is that the microwave heating temperature in step (1) is 180°C, while the other steps are the same as in Example 1.

[0115] Comparative Example 9

[0116] The difference between this comparative example and Example 1 is that the molar ratio of hydrogen chloride to sec-butanol in step (3) is 1.12:1, while the other steps are the same as in Example 1.

[0117] Comparative Example 10

[0118] The difference between this comparative example and Example 1 is that the molar ratio of hydrogen chloride to sec-butanol in step (3) is 1.38:1, while the other steps are the same as in Example 1.

[0119] Comparative Example 11

[0120] The difference between this comparative example and Example 1 is that the bed temperature in step (3) is 150°C, while the other steps are the same as in Example 1.

[0121] Comparative Example 12

[0122] The difference between this comparative example and Example 1 is that the bed temperature in step (3) is 230°C, while the other steps are the same as in Example 1.

[0123] The yield of 2-chlorobutane was calculated, and the purity of the obtained product was tested. The experimental results after 1000 hours of testing for each catalyst are shown in Table 1.

[0124] As shown in Table 1, the catalyst of Example 1 still achieved a catalytic yield of 98.25% and a product purity of 99.679% after 1000 hours of continuous testing.

[0125] After adjusting the mass fraction of sodium hydroxide in Comparative Examples 3 and 4, their purity and yield both decreased significantly. This is because the sodium hydroxide concentration in Comparative Example 3 was too low, which prevented effective etching of the fly ash surface, resulting in a small specific surface area, a small and uneven loading of active components, and consequently, poor catalyst activity. In contrast, the sodium hydroxide solution concentration in Comparative Example 4 was too high, which led to severe etching of the fly ash surface, severe surface and internal damage, structural destruction, agglomeration of the loaded active components, and a decrease in catalytic efficiency.

[0126] After adjusting the mass ratio of filter cake N to sodium hydroxide in Comparative Examples 5 and 6, the yield and purity were much lower than those in Example 1. This is because the amount of sodium hydroxide used in Comparative Example 5 was too small to effectively treat the surface of fly ash; while the amount of sodium hydroxide used in Comparative Example 6 was too large, resulting in severe damage to the fly ash structure.

[0127] Compared with Example 1, Comparative Examples 1, 2, 9, and 10 showed a significant decrease in catalytic yield and product purity. This indicates that the catalyst prepared by the present invention can achieve high catalytic yield and catalytic selectivity under experimental conditions with a high hydrogen chloride feed rate. Increasing the hydrogen chloride feed rate can simultaneously improve product yield and selectivity within a certain range. However, once the range is exceeded, the product selectivity will decrease significantly, leading to an increase in the isomer 1-chlorobutane, which in turn leads to a direct decrease in product yield.

[0128] Table 1 Experimental Results

[0129]

[0130] This invention successfully prepared a catalyst suitable for high-proportion hydrogen chloride feed by rationally utilizing fly ash, a solid waste material, and controlling the concentration and amount of sodium hydroxide and the temperature of the microwave process. Simultaneously, through a clever combination of existing fixed-bed reactor and batch reactor processes, excess hydrogen chloride from the high-proportion hydrogen chloride feed in the fixed-bed reactor is used to concentrate the residual hydrochloric acid solution after the batch reactor reaction, which is then reused in the batch reactor process. This largely solves the problem of unprocessable waste hydrochloric acid after the fixed-bed reactor reaction, while simultaneously achieving the regeneration and utilization of the residual hydrochloric acid solution after the batch reactor reaction. Furthermore, both reactors can share a single post-treatment system. By rationally matching the capacity of the batch reactor and the fixed-bed reactor, it is possible to increase production capacity and work efficiency while saving a significant amount of equipment investment.

Claims

1. A method for synthesizing 2-chlorobutane, characterized in that, Includes the following steps: S1. After the preheated hydrogen chloride gas and the vaporized sec-butanol are mixed in a mixer, they are further mixed and preheated by the packing material at the top of the tubular fixed bed reactor, and then come into contact with the solid catalyst to start the reaction, producing a mixed gas containing 2-chlorobutane. The molar ratio of sec-butanol to hydrogen chloride is 1:1.16-1.36, the reaction temperature is 160-220℃, and the reaction pressure is atmospheric pressure; the solid catalyst is a fly ash-based catalyst. S2. Condensation and purification: The mixed gas obtained in step S1 is passed into a gas-liquid separator containing residual hydrochloric acid solution after the batch reaction for gas-liquid separation, and the liquid phase is the condensed material. S3. Separation and return: After the condensed material is allowed to stand and separate into layers, the upper layer yields the crude product, and the lower layer yields the concentrated hydrochloric acid solution. The concentrated hydrochloric acid solution is reused as a raw material for the batch reaction. S4. Purification: The crude product obtained in step S3 is subjected to alkaline washing, distillation and drying to produce 2-chlorobutane; The preparation method of the fly ash-based catalyst is as follows: 1) Grind the fly ash thoroughly using an agate mortar and pestle, then sieve it through a 140-180 mesh screen for later use; 2) Soak the sieved fly ash from step 1) in a 22-25% hydrochloric acid solution and stir thoroughly for 2-4 hours to obtain mixture A; The mass ratio of fly ash to hydrochloric acid solution is 1:1.1-1.6; 3) Filter the acid-washed mixture A from step 2), wash the filter cake with water until it is neutral to obtain filtrate M, set aside. After drying the filter cake at 80-100℃ for 8-12 hours, filter cake N is obtained, set aside. 4) Mix the dried filter cake N from step 3) with a sodium hydroxide solution of 10-30% by mass at a mass ratio of 1:1.12-1.18, put the mixture into a microwave reactor, and microwave heat it at a constant temperature of 140-170℃ for 1-2 hours to obtain a mixture B. After the reactor temperature cools to room temperature, filter and wash the microwave-heated mixture B. After washing, dry the filter cake at 100-120℃ for 10-12 hours to obtain filter cake K for later use. 5) Mix and grind the dried filter cake K from step 4) with guar gum powder at a mass ratio of 1:0.06-0.12 to obtain mixture C; 6) Mix the mixture C obtained in step 5) and a nitric acid solution with a mass fraction concentration of 6-10% thoroughly at a mass ratio of 1:0.4-1.2 to obtain mixture D; 7) The mixture D from step 6) is extruded into shape using a twin-screw extruder, and then dried and calcined to obtain fly ash-based carriers of different shapes. 8) mixing all fly ash based support of step 7) and all filtrate M of step 3) and adjusting pH to 5-8 using 1-5% sodium hydroxide solution so that Fe 3+ , Al 3+ is precipitated from the filtrate to obtain a mixture E; 9) Filter the mixture E from step 8), continuously wash the filter cake until it is neutral, and then process the filter cake through drying and calcination steps to obtain a fly ash-based catalyst. The drying temperature and calcination temperature are 90-110℃ and 400-800℃, respectively, the drying time is 8-12 hours, and the calcination time is 6-12 hours.

2. The method for synthesizing 2-chlorobutane according to claim 1, characterized in that, The space velocity of the reaction described in step S1 is 0.3~0.6 m / s. 3 ·h -1 .

3. The method for synthesizing 2-chlorobutane according to claim 1, characterized in that, In step S1, the preheated hydrogen chloride and the vaporized sec-butanol reach the reaction temperature.

4. The method for synthesizing 2-chlorobutane according to claim 1, characterized in that, In step S1, the molar ratio of sec-butanol to hydrogen chloride is 1:1.18-1.

34.

5. The method for synthesizing 2-chlorobutane according to claim 1, characterized in that, In step S2, the mass fraction concentration of the residual hydrochloric acid solution after the batch reaction is 25-27%, and the mass fraction concentration of the concentrated hydrochloric acid solution is 30-32%.

6. The method for synthesizing 2-chlorobutane according to claim 1, characterized in that, The batch reaction is as follows: sec-butanol and hydrochloric acid solution are added to the reaction vessel at a hydrogen chloride:sec-butanol molar ratio of 5-8:

1. The reaction temperature is 60-80℃, the reaction pressure is less than 0.4MPa, and the reaction time is greater than or equal to 20 hours. Then, the mixture is allowed to stand and separate into layers. The upper layer is the crude product, and the lower layer is the residual hydrochloric acid solution after the batch reaction.

7. The method for synthesizing 2-chlorobutane according to claim 1, characterized in that, The condensation temperature inside the gas-liquid separator is 0℃~5℃.

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