A method for continuously synthesizing 2-chloropropane

Abstract

The present invention belongs to the technical field of organic synthesis, and particularly relates to a method for continuously synthesizing 2-chloropropane. After preheated hydrogen chloride gas and vaporized isopropanol are uniformly mixed through a mixer, they are introduced into a fixed-bed reactor filled with a solid catalyst, and the reaction starts upon contact with the catalyst to generate a mixed gas containing 2-chloropropane. The mixed gas containing 2-chloropropane is subjected to gas-liquid separation, and the liquid phase is allowed to stand and separate layers. The upper layer is the 2-chloropropane product. The present invention solves the problem of continuous synthesis of 2-chloropropane, greatly improves the production efficiency, and at the same time solves the problem that the reaction requires high-cost special material equipment, reducing the production cost. It solves the efficiency problems of high reaction temperature, low selectivity and low yield. The purity of the product of this reaction exceeds 99%, and the yield reaches more than 98.5%.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic synthesis, and particularly relates to a method for continuously synthesizing 2-chloropropane. Background Art

[0002] 2-chloropropane, also known as chloro-isopropane and isopropyl chloride, is an important organic chemical raw material and an important organic intermediate. Due to the relatively active chlorine atom in its structure, it can react with aromatic amines, aliphatic amines, etc. to form corresponding amines. 2-chloropropane can be used as an intermediate for synthesizing pharmaceuticals, pesticides, additives, etc., and can also be used as one of the raw materials for the catalyst component in the preparation of polypropylene. In addition, 2-chloropropane can be used as a diluent for paints, a scrubbing agent for metals, etc. In different fields, it can be transformed into various products and intermediates through a series of methods such as dehydrochlorination, ammoniation, chlorinolysis, pressurized hydrolysis, and laser conversion after fluorination, with very wide applications. Therefore, the research on the refined utilization of 2-chloropropane products has great potential market value.

[0003] The synthesis technologies of 2-chloropropane mainly include the method of propylene and hydrogen chloride, the method of hydrochloric acid and isopropyl alcohol, or the method of hydrogen chloride and isopropyl alcohol. The current mainstream technology is batch kettle reaction, which can only have high reaction yield and selectivity at reaction temperatures below 100°C. Moreover, the batch reaction efficiency is low, and the water vapor generated during the reaction at low temperatures is easily liquefied to form hydrochloric acid with hydrogen chloride, corroding the reactor, and expensive special materials equipment needs to be purchased.

[0004] Patent CN1596238A discloses a method for synthesizing 2-chloropropane. Under the conditions of a temperature of 40 - 60°C and an absolute pressure of 1 - 3 atmospheres, using iron or pre-halogenated alumina as a catalyst, 2-chloropropane is prepared by the reaction of propylene and hydrogen chloride, with a yield of 86% - 94%. Although this method has a high yield and can achieve continuous synthesis, under the reaction conditions of pressurization and low temperature, the requirement for the water content of the raw materials is extremely strict, and expensive anti-corrosion equipment needs to be used. In addition, the raw material propylene is extremely prone to explosion, bringing potential dangers to transportation, storage, and production.

[0005] Patent CN109053364A discloses a method for synthesizing 2-chloropropane using hydrogen chloride gas and isopropyl alcohol. The reaction is carried out in a reaction kettle, and the reaction rate can reach 92%. However, this method requires vacuum pumping first, and then an inert gas is filled to maintain the pressure. After that, alcohol and a catalyst need to be added under a pressurized working condition. The alcohol can be transported under pressure by a pump, but the catalyst is a solid particle and it is difficult to enter under pressure. In addition, during the reaction process after hydrogen chloride enters, the pressure is maintained by inputting or discharging inert gas. When the pressure overloads, the pressure relief material will also flow out, resulting in uncontrollable material quantity and potential safety hazards. This method has complex operations, difficult process control, and cannot be continuously produced.

[0006] In addition, isopropyl alcohol and hydrochloric acid can be used to produce 2-chloropropane intermittently through a reaction kettle. However, this method has a low yield, complex subsequent operations, and cannot be continuously produced. Summary of the Invention

[0007] The object of the present invention is to provide a method for continuously synthesizing 2-chloropropane in view of the defects existing in the above method. The method uses isopropyl alcohol and hydrogen chloride as raw materials and continuously produces 2-chloropropane in a fixed-bed reactor using a solid catalyst.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for continuously synthesizing 2-chloropropane, comprising the following steps:

[0010] (1) After preheating hydrogen chloride gas and vaporizing isopropyl alcohol and mixing them evenly through a mixer, they are introduced into a fixed-bed reactor filled with a solid catalyst and start to react upon contact with the catalyst, generating a mixed gas containing 2-chloropropane; the molar ratio of isopropyl alcohol to hydrogen chloride is 1:1 - 1.20, the reaction temperature is 120°C - 180°C, and the reaction pressure is atmospheric pressure; the solid catalyst is a kaolin catalyst;

[0011] (2) Separating the gas-liquid of the mixed gas containing 2-chloropropane, allowing the liquid phase to stand and separate layers, and the upper layer is the 2-chloropropane product.

[0012] Preferably, the space velocity of the reaction in step (1) is 0.2 - 0.4 m 3 ·h -1 . Before the reaction, the hydrogen chloride gas is preheated to the reaction temperature, and the isopropyl alcohol is vaporized to the reaction temperature.

[0013] Preferably, the reaction temperature in step (1) is 140 - 170°C, and more preferably 160 - 170°C.

[0014] Preferably, the molar ratio of isopropyl alcohol to hydrogen chloride in step (1) is 1:1.04 - 1.16, and more preferably 1:1.04 - 1.08. At this reactant molar ratio, the highest yield can be ensured, and the amount of waste hydrochloric acid generated can be effectively controlled.

[0015] Preferably, the mixed gas containing 2-chloropropane in step (2) enters the gas-liquid separation tank from the bottom of the fixed-bed reactor in a gaseous state for condensation. The liquid phase in the gas-liquid separation tank includes an aqueous phase and an organic phase. The aqueous phase is mainly hydrochloric acid and unreacted alcohol, and the organic phase is 2-chloropropane and a small amount of by-products such as olefins and ethers; a very small amount of olefins and hydrogen chloride enter the tail gas absorption device. Subsequently, all the liquid phase in the gas-liquid separation tank enters the buffer tank for standing and separating layers, and the upper main product is 2-chloropropane.

[0016] Preferably, the gas-liquid separation tank body is made of 316L material, and the inner part in contact with the material is lined with fluorine. Preferably, the condensation temperature in the gas-liquid separation tank is -30°C to -15°C.

[0017] Preferably, the kaolin catalyst is composed of kaolin, sesbania powder, and nitric acid, wherein the mass percentage of sesbania powder is 2.5 - 3.0 wt%, the mass percentage of nitric acid is 5 - 13 wt%, and the rest is kaolin. Further preferably, the mass percentage of sesbania powder is 2.6 - 2.65 wt%, and the mass percentage of nitric acid is 8 - 12 wt%.

[0018] Preferably, the silicon-aluminum molar ratio in the kaolin catalyst is 1 - 2.5:1, further preferably 1.25 - 2.5:1, and even more preferably 2 - 2.25:1.

[0019] Preferably, the kaolin catalyst is prepared by mixing sesbania powder, kaolin, and nitric acid solution and then processing and forming. Among them, the concentration of the nitric acid solution is 15 - 30 wt%, preferably 15 - 25 wt%. The mass ratio of sesbania powder to kaolin is 0.01 - 0.1:1, preferably 0.02 - 0.06:1, and further preferably 0.03:1; the mass ratio of the total mass of sesbania powder and kaolin to the mass of the nitric acid solution is 1:0.15 - 1.15, preferably 1:0.35 - 0.75.

[0020] The beneficial effects of the present invention are as follows:

[0021] The synthesis method of 2-chloropropane described in the present invention is a continuous method. Using isopropanol and hydrogen chloride as raw materials, a solid catalyst is used for continuous reaction in a fixed-bed reactor to synthesize 2-chloropropane. The present invention realizes high reaction yield and selectivity while ensuring a certain temperature and avoiding equipment corrosion.

[0022] The present invention solves the problem of continuous synthesis of 2-chloropropane, greatly improves the production efficiency, and at the same time solves the problem that the reaction requires high-cost special material equipment, reducing the production cost.

[0023] The present invention prepares a simple and efficient catalyst from cheap and easily available kaolin, solves the efficiency problems of high reaction temperature, low selectivity, and low yield. The purity of the product of this reaction exceeds 99%, and the yield reaches more than 98.5%. Description of the Drawings

[0024] Figure 1 It is the gas chromatogram of the product obtained in Example 1 of the present invention. Detailed Embodiments

[0025] The present invention will be further described below through specific embodiments in conjunction with the accompanying drawings. The raw materials used in the embodiments and comparative examples of the present invention can all be obtained by purchase.

[0026] In the present invention, the fixed-bed reactor is a jacketed tubular reactor with an inner cavity tube diameter of Φ38mm×2200mm. The material of the fixed-bed reactor is 316L. The loading amount of the solid catalyst in the fixed-bed reactor is 1L. The solid catalyst is evenly loaded into the fixed-bed reactor using a funnel, and a leather hammer is used to continuously strike the side wall of the reactor during the loading process to make the catalyst loading uniform and prevent the phenomenon of "bridging".

[0027] The kaolin catalyst of the present invention can be prepared through the following steps:

[0028] 1) Grind and mix the sesbania powder and kaolin in a mass ratio of 0.01 - 0.1:1 to obtain a mixed powder;

[0029] 2) Mix the mixed powder obtained in step 1) and a nitric acid solution with a concentration of 15 - 30 wt% evenly according to a material mass ratio of 1:0.15 - 1.15;

[0030] 3) After further kneading the uniformly mixed materials in step 2) using a kneader, process them into a shape using an extrusion machine, and obtain the kaolin catalyst through drying and calcination.

[0031] Preferably, in step 1), the mass ratio of sesbania powder to kaolin is 0.02 - 0.06:1, and more preferably 0.03:1. The grinding is carried out using a spherical grinder with a grinding speed of 500 - 1200 revolutions per minute and a grinding time of 20 - 50 minutes.

[0032] Preferably, in step 2), the concentration of the nitric acid solution is 15 - 25 wt%, and the material mass ratio is 1:0.35 - 0.75.

[0033] Preferably, in step 3), continuing to knead the mixture in step 2) using a kneader can increase the strength of the catalyst before forming. The kneader is a twin-screw kneader with a kneading time of 0.5 - 1.5 hours. The extrusion machine is a twin-screw extrusion machine. The extrusion machine extrudes the material into catalysts of different shapes and cuts them into appropriate lengths through a cutting machine at the front end of the extrusion machine.

[0034] Preferably, in step 3), the drying temperature is 80 - 140°C and the drying time is 8 - 24 hours; more preferably, the drying temperature is 95 - 115°C and the drying time is 10 - 16 hours. The calcination temperature is 300 - 700°C and the calcination time is 5 - 15 hours; more preferably, the calcination temperature is 400 - 600°C and the calcination time is 6 - 12 hours.

[0035] Example 1

[0036] A method for continuously synthesizing 2-chloropropane, the specific steps are as follows:

[0037] (1) Preparation of catalyst

[0038] Add 400 grams of kaolin with a silica-alumina molar ratio of 2.25:1 and 12 grams of sesbania powder to a ball mill and grind at 800 revolutions per minute for 45 minutes;

[0039] Then evenly spray 200 grams of nitric acid solution with a mass fraction concentration of 20% on the ground powder, and mix while spraying;

[0040] Transfer the mixed material to a kneader for further kneading for 1.2 hours, and then use a twin-screw extruder to process the material into a rod-shaped catalyst with a four-leaf clover cross-section, 5-6 mm in length and a maximum cross-sectional diameter of 4-5 mm;

[0041] After drying the shaped catalyst at 110°C for 12 hours, place it in a muffle furnace and calcine it at 500°C for 8 hours to obtain the finished catalyst.

[0042] (2) Load about 350 g of catalyst into a tubular reactor with a pipe diameter of Φ38 mm × 2200 mm, and add 120 grams of inert porcelain balls to the upper end of the tube to further fully mix and preheat the material.

[0043] (3) Hydrogen chloride and isopropanol are preheated and vaporized to 160°C through a preheater and a vaporizer respectively, mixed in a mixer and then enter a fixed-bed reactor for reaction. The feed molar ratio of hydrogen chloride to isopropanol is 1.04:1, the reactor bed temperature is 160°C, and the reaction pressure is atmospheric pressure. The reaction space velocity is 0.32 m 3 ·h -1 .

[0044] (4) The mixed gas after the reaction is discharged from the bottom of the reactor and enters a gas-liquid separation tank. After gas-liquid separation, the liquid phase enters a buffer tank for static stratification. The upper layer liquid is the product 2-chloropropane, and its gas chromatogram is shown in Figure 1 as shown.

[0045] Example 2

[0046] The difference from Example 1 is that in step (3), the molar ratio of isopropanol to hydrogen chloride is 1:1, and the other steps are the same as in Example 1.

[0047] Example 3

[0048] The difference from Example 1 is that in step (3), the molar ratio of isopropanol to hydrogen chloride is 1:1.08, and the other steps are the same as in Example 1.

[0049] Example 4

[0050] The difference from Example 1 is that in step (3), the molar ratio of isopropanol to hydrogen chloride is 1:1.12, and other steps are the same as those in Example 1.

[0051] Example 5

[0052] The difference from Example 1 is that in step (3), the molar ratio of isopropanol to hydrogen chloride is 1:1.16, and other steps are the same as those in Example 1.

[0053] Example 6

[0054] The difference from Example 1 is that in step (3), the molar ratio of isopropanol to hydrogen chloride is 1:1.2, and other steps are the same as those in Example 1.

[0055] Example 7

[0056] The difference from Example 1 is that in step (3), the bed temperature is 125 °C, and other steps are the same as those in Example 1.

[0057] Example 8

[0058] The difference from Example 1 is that in step (3), the bed temperature is 140 °C, and other steps are the same as those in Example 1.

[0059] Example 9

[0060] The difference from Example 1 is that in step (3), the bed temperature is 150 °C, and other steps are the same as those in Example 1.

[0061] Example 10

[0062] The difference from Example 1 is that in step (3), the bed temperature is 170 °C, and other steps are the same as those in Example 1.

[0063] Example 11

[0064] The difference from Example 1 is that in step (1), the silica-alumina ratio of the kaolin used is 1.25:1, and other steps are the same as those in Example 1.

[0065] Example 12

[0066] The difference from Example 1 is that in step (1), the silica-alumina ratio of the kaolin used is 1.5:1, and other steps are the same as those in Example 1.

[0067] Example 13

[0068] The difference from Example 1 is that in step (1), the silica-alumina ratio of the kaolin used is 1.75:1, and other steps are the same as those in Example 1.

[0069] Example 14

[0070] The difference from Example 1 is that the silica-alumina ratio of the kaolin used in step (1) is 2:1, and the other steps are the same as those in Example 1.

[0071] Example 15

[0072] The difference from Example 1 is that the silica-alumina ratio of the kaolin used in step (1) is 2.5:1, and the other steps are the same as those in Example 1.

[0073] Example 16

[0074] The difference from Example 1 is that the concentration of nitric acid used in step (1) is 15 wt%, and the other steps are the same as those in Example 1.

[0075] Example 17

[0076] The difference from Example 1 is that the concentration of nitric acid used in step (1) is 25 wt%, and the other steps are the same as those in Example 1.

[0077] Example 18

[0078] The difference from Example 1 is that the concentration of nitric acid used in step (1) is 30 wt%, and the other steps are the same as those in Example 1.

[0079] Comparative Example 1

[0080] The difference from Example 1 is that the molar ratio of isopropanol to hydrogen chloride in step (3) is 1:0.85, and the other steps are the same as those in Example 1.

[0081] Comparative Example 2

[0082] The difference from Example 1 is that the bed temperature in step (3) is 185 °C, and the other steps are the same as those in Example 1.

[0083] Comparative Example 3

[0084] The difference from Example 1 is that the silica-alumina ratio of the kaolin used is 3:1, and the other steps are the same as those in Example 1.

[0085] Comparative Example 4

[0086] The difference from Example 1 is that 800 g of a nitric acid solution with a mass concentration of 5 wt% is used, and the other steps are the same as those in Example 1.

[0087] Comparative Example 5

[0088] The difference from Example 1 is that 100 g of a nitric acid solution with a mass concentration of 40 wt% is used, and the other steps are the same as those in Example 1.

[0089] Comparative Example 6

[0090] The difference from Example 1 is that the catalyst used is a commercially available finished four-leaf clover-shaped pure silica molecular sieve SBA-15, and other steps are the same as those in Example 1.

[0091] Comparative Example 7

[0092] The difference from Example 1 is that the catalyst used is a commercially available finished four-leaf clover-shaped Y-type molecular sieve with a silica-alumina ratio of 2.25:1, and other steps are the same as those in Example 1.

[0093] Comparative Example 8

[0094] The difference from Example 1 is that the catalyst used is a commercially available finished four-leaf clover-shaped pure alumina catalyst, and other steps are the same as those in Example 1.

[0095] Comparative Example 9

[0096] The catalyst was prepared by referring to Example 1 of Patent CN 118666633 A, and other conditions were the same as those in Example 1 of the present invention.

[0097] The yield of 2-chloropropane was calculated, and the purity of the obtained product was detected. The reaction conditions and results of each product are shown in Table 1:

[0098] Table 1 Reaction Conditions and Results

[0099]

[0100] It can be seen from the experimental results in Table 1 that the yield of the catalyst in Example 1 can reach 98.91%, and the purity can reach 99.679%. By comparing with Comparative Examples 6, 7, and 8, it can be seen that the pure silica molecular sieve (Comparative Example 6) has weak catalytic activity for this reaction; although the silica-alumina ratio of the silica-aluminum-containing molecular sieve is the same as that of the kaolin catalyst, the catalyst compositions are different, and the catalyst activities are also different. At high temperatures, Comparative Example 7 and Comparative Example 8 are more likely to cause isopropanol to crack to produce propylene, resulting in a decrease in the yield and purity of 2-chloropropane, and their costs are much higher than the kaolin catalyst described in the present invention. The catalyst in Comparative Example 9 has good results when applied to a fixed-bed reactor for producing 1-chlorobutane, but has poor effects on the synthesis of 2-chloropropane. The reason is that this catalyst makes isopropanol easily crack into propylene, resulting in a decrease in the product yield and purity.

[0101] By controlling the composition of the kaolin catalyst, the content of silicon and aluminum, the concentration of nitric acid during the forming process, etc., the present invention realizes the control of the number and strength of acidic sites of the catalyst, and then prepares a kaolin catalyst suitable for preparing 2-chloropropane at a relatively high temperature. It overcomes the deficiencies of the existing pure silicon catalyst with weak acidity and poor catalytic performance, the catalyst of pure alumina with too strong acidity, and the troublesome acidity regulation of silicon-aluminum molecular sieve. Moreover, the cost of the kaolin catalyst of the present invention is lower than the above three. The present invention realizes the control of the catalyst, acid strength and acidic sites through simple, effective and inexpensive raw materials, and develops a catalyst suitable for use at a relatively high temperature.

[0102] In summary, the method for synthesizing 2-chloropropane developed by the present invention not only realizes the continuous synthesis of 2-chloropropane from isopropanol and hydrogen chloride in a fixed-bed reactor, but also solves the problems of low yield and low purity at high temperature and the need to replace expensive corrosion-resistant equipment due to equipment corrosion at low temperature. It provides a safe, economical and efficient method for synthesizing 2-chloropropane.

Claims

1. A method for continuously synthesizing 2-chloropropane, characterized in that: The following steps are involved: (1) Preheated hydrogen chloride gas and vaporized isopropanol are mixed uniformly in a mixer, and then introduced into a fixed bed reactor filled with a solid catalyst to start a reaction with the catalyst to generate a mixed gas containing 2-chloropropane; wherein the molar ratio of isopropanol to hydrogen chloride is 1:1-1.20, the reaction temperature is 120°C-180°C, and the reaction pressure is normal pressure; the solid catalyst is a kaolin catalyst; and the kaolin catalyst is prepared by the following steps: 1) Grinding and mixing sesbania powder and kaolin in a mass ratio of 0.01-0.1:1 to obtain a mixed powder; 2) uniformly mixing the mixed powder obtained in step 1) and a nitric acid solution having a concentration of 15-30 wt% at a material mass ratio of 1:0.15-1.15; 3) The materials uniformly mixed in step 2) are further kneaded using a kneader, and then processed and shaped using an extruder, and then dried and calcined to obtain a kaolin catalyst; (2) The mixed gas containing 2-chloropropane is separated into gas and liquid, and the liquid phase is allowed to stand and separate into layers. The upper layer is the 2-chloropropane product.

2. The method for continuously synthesizing 2-chloropropane according to claim 1, characterized in that: The space velocity of the reaction in step (1) is 0.2~0.4m 3 ·h -1 .

3. The method for continuously synthesizing 2-chloropropane according to claim 1, characterized in that: The reaction temperature in step (1) is 140-170°C.

4. The method for continuously synthesizing 2-chloropropane according to claim 1, characterized in that: The molar ratio of isopropanol to hydrogen chloride in step (1) is 1:1.04-1.

16.

5. The method for continuously synthesizing 2-chloropropane according to any one of claims 3 or 4, characterized in that: The reaction temperature in step (1) is 160-170° C., and the molar ratio of isopropanol to hydrogen chloride is 1:1.04-1.

08.

6. The method for continuous synthesis of 2-chloropropane according to claim 1, characterized in that: The kaolin catalyst consists of kaolin, sesbania powder and nitric acid, wherein the mass percentage of the sesbania powder is 2.5-3.0wt%, the mass percentage of the nitric acid is 5-13wt%, and the rest is kaolin.

7. The method for continuously synthesizing 2-chloropropane according to claim 1, characterized in that: The molar ratio of silicon to aluminum in the kaolin catalyst is 1-2.5:

1.

8. The method for continuously synthesizing 2-chloropropane according to claim 7, characterized in that: The molar ratio of silicon to aluminum in the kaolin catalyst is 1.25-2.5:1.

Images