A preparation process and device for improving the selectivity of methallyl chloride

Abstract

The invention discloses a preparation process for improving the selectivity of methallyl chloride, comprising the following steps: a) drying, preheating and pressure controlling isobutylene and chlorine in gaseous form respectively, feeding them to the front end of a bubbling reactor for premixing and then carrying out a chlorination reaction to obtain a crude methallyl chloride product; the product exits the reactor in a gaseous form and enters a first gas-liquid separation tank, the crude chloride is cooled to a liquid state and temporarily stored in a first product storage tank, and the gaseous component enters a tubular reactor; a part of the crude product is heat-exchanged by a heat exchanger and enters the bubbling reactor again from the bottom as a circulating coolant; b) the cooled crude product is subjected to gas-liquid separation, and the liquid phase flows into the first product storage tank for temporary storage; the gaseous phase component enters the tubular reactor, and chlorine is introduced into the tubular reactor at the same time; c) the product passing through the tubular reactor is subjected to gas-liquid separation to obtain a liquid crude product and tail gas, and the liquid crude product is introduced into a second product tank. By adjusting the temperature and flow rate of the circulating coolant, the temperature in the reactor is controlled at the boiling point of the material, and the liquid level is highly stable, which is conducive to reaction control and long-term operation.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and in particular relates to a reactor and a production process with high selectivity for methallyl chloride. Background Art

[0002] Methallyl chloride is a common chemical intermediate product, which can be widely used in many fields. In the pesticide industry, methallyl chloride can be used to synthesize insecticides and acaricides such as carbofuran and fenbutatin; in addition, it can also be used directly as a grain and seed fumigant; methallyl chloride can be hydrolyzed in an alkaline environment to obtain methallyl alcohol, and the final product can be made into a water reducer and used in the construction industry; methallyl chloride reacts with sodium sulfite to prepare methallyl sulfonate, which can greatly improve the dyeing properties of acrylonitrile fiber after copolymerization with acrylonitrile, and is called the "third monomer" of acrylic fiber; methallyl chloride can be epoxidized to obtain methyl epichlorohydrin, which can be further synthesized into epoxy resin; the dimer of methallyl chloride can be used as a purifier and a solvent for synthetic resins and natural resins; in addition, it can also be used to prepare methyl glycerol, iso-olealdehyde and other organic compounds.

[0003] At present, the production of methallyl chloride on the market is to react gaseous isobutylene and chlorine in a tubular reactor. Due to the high activity and high heat release of this reaction, it is difficult to control the temperature, so there are many by-products. For example, the common side reactions are as follows, including the formation of tert-butyl chloride, isobutylene chloride, 1,2-dichloroisobutane, and 3-chloro-2-chloromethyl-propylene.

[0004]

[0005] The ratio of isobutylene to chlorine during the reaction has an important influence on the selectivity of methallyl chloride products: the higher the isobutylene ratio, the more tert-butyl chloride is present in the reaction system, and the less polychlorinated by-products such as 1,2-dichloroisobutane and 3-chloro-2-chloromethyl-propylene are produced; the higher the chlorine ratio, the more 1,2-dichloroisobutane, 1,2-dichloroisobutane, and 3-chloro-2-chloromethyl-propylene are produced, and the less tert-butyl chloride is produced. Therefore, only when the ratio of isobutylene to chlorine in the raw material is maintained within a specific range can the high selectivity of the main product be ensured.

[0006] The existing technology mainly uses a tubular reactor to prepare methallyl chloride, but this chlorination reaction is a highly exothermic reaction, the tubular reactor has a small heat exchange area, the reaction temperature is difficult to control, and the by-product content is high, so the selectivity of the main product is low; the current production technology controls the molar ratio of isobutylene to chlorine at 1 to 1.05:1, the purpose of which is to make the isobutylene react completely and avoid the problem of difficulty in separating isobutylene and hydrogen chloride in the tail gas. However, under this raw material ratio condition, the selectivity of methallyl chloride is not the highest. For example, the reaction temperature of patents CN03131083.4, CN101182279 and CN110642667 is controlled at about 80°C, and the selectivity is 80-85%. The selectivity of methallyl chloride is low, and the product economy is poor. It is urgent to improve the selectivity of the main product methallyl chloride through research. Summary of the invention

[0007] In view of the existing problems of the above-mentioned technology, the present invention provides the following technical solutions:

[0008] According to one aspect of the present invention, the object of the present invention is to provide a preparation process for improving the selectivity of methallyl chloride, comprising the following steps:

[0009] a) drying, preheating and pressure controlling isobutylene and chlorine in gaseous form respectively, and then feeding them to the front end of a bubbling reactor at a molar ratio of 1.10 to 1.25:1 for premixing, bubbling into the reactor for chlorination reaction, and obtaining a crude methallyl chloride product; the product exits the reactor in gaseous form and enters a first gas-liquid separation tank, the crude chloride is cooled to a liquid state and temporarily stored in a first product storage tank, and the gaseous component enters a tubular reactor; the heat release of the isobutylene chlorination reaction is 108.9 kJ / mol, and the vaporization latent heat of methallyl chloride is 0.37 kJ / mol, which is higher than The heat capacity is 1.98 J / (g·℃). The heat released by the reaction and the heat brought by the volatilization of the circulating liquid are balanced by calculation. A portion of the crude product is cooled by the heat exchanger and then enters the bubbling reactor again from the bottom as the circulating coolant. The pump flow is adjusted to 100-150 g / min to absorb the circulating coolant into the heat exchanger. The circulating coolant is kept at a temperature of 0-15℃ and enters from the bottom of the bubbling reactor. Under the conditions of this temperature and flow, the heat released by the reaction and the heat absorbed by the vaporization of the circulating liquid can be kept balanced, the temperature inside the reactor can be controlled at the boiling point, and the height of the liquid level in the reactor can be kept stable.

[0010] Isobutylene enters the gas distributor at a gas flow rate of 25-35 g / min, and chlorine enters the gas distributor at a gas flow rate of 30-35 g / min; maintaining an excess of isobutylene is beneficial to reducing the formation of polychlorinated by-products and improving the selectivity of the main product.

[0011] b) The crude product after cooling is subjected to gas-liquid separation, and the liquid phase flows into the first product storage tank for temporary storage; the gas phase component enters the tubular reactor, and chlorine is introduced at the same time, and the amount of chlorine added is sufficient to meet the molar ratio of the total raw material isobutylene to chlorine entering the bubbling reactor and the tubular reactor at 1 to 1.05:1; the amount of chlorine added is 5 to 7 g / min to ensure that the isobutylene can react completely.

[0012] c) The product passing through the tubular reactor is subjected to gas-liquid separation to obtain a liquid crude product and tail gas (the main component of which is by-product HCl), and the liquid crude product is introduced into a second product tank.

[0013] Preferably, the reaction temperature of the bubbling reactor in step a) is 70-75° C., and the temperature of the circulating cooling water is adjusted to 0-5° C. The circulating cooling water is used to remove the heat of the circulating medium to ensure that the reaction is carried out at a relatively low temperature, which is beneficial to improving the selectivity of methallyl chloride;

[0014] Preferably, the liquid in the first product tank in step b) is further purified to obtain pure methallyl chloride; the crude liquid product separated in step c) can be mixed with the separated liquid obtained in step b) and purified together, or the two can be purified separately.

[0015] Preferably, in step a), anhydrous calcium chloride is used for drying, and the water content of the raw material after drying is controlled to be below 20 ppm; in step a), the temperature control interval of the preheating of the gas is 10-25° C.; in step a), the pressure of the raw material and isobutylene transported to the bubbling reactor is controlled to be 0.2-0.4 MPa; in step c), a tubular reactor is selected, and jacket circulating water is used for heat.

[0016] According to another aspect of the present invention, a second object of the present invention is to provide a device for improving the selectivity of methallyl chloride, comprising: a raw material drying tank, a preheating buffer tank, a circulating liquid temporary storage tank, a heat exchanger, a bubbling reactor, a tubular reactor, a first gas-liquid separation tank, a second gas-liquid separation tank, a first product tank, and a second product tank;

[0017] Among them, isobutylene and chlorine are respectively passed through their respective raw material drying tanks and preheating buffer tanks in gaseous form to dry and control the temperature of the gas;

[0018] The preheating buffer tank is connected to the bubbling reactor through a pipeline, and the raw materials are premixed outside the reactor and then introduced into the bubbling reactor for reaction; the bubbling reactor is connected to the first gas-liquid separation tank through a pipeline, and then connected to the first product storage tank; the circulating coolant in the bubbling reactor can overflow into the circulating liquid temporary storage tank, the circulating liquid temporary storage tank is connected to the heat exchanger through a pipeline, and then the circulating liquid is injected into the reactor from the bottom of the bubbling reactor by a pump;

[0019] The bubbling reactor is connected to the first gas-liquid separation tank through a pipeline, and the first gas-liquid separation tank is used to separate gas and liquid in the crude product;

[0020] The material that has been separated into gas and liquid by the first gas-liquid separation tank is input into the first product storage tank through a pipeline; the first product storage tank is used to store liquid products and input gas into the tubular reactor at the same time;

[0021] The first product storage tank is connected to the tubular reactor through a pipeline, and the material is input into the tubular reactor. At the same time, the tubular reactor is connected to a chlorine preheating buffer tank to receive the input chlorine, so that the remaining isobutylene in the material reacts with the chlorine to complete the reaction of the isobutylene;

[0022] After the reaction in the tubular reactor is completed, the material is input into the second gas-liquid separation tank through a pipeline, and then the liquid product and the gaseous HCl tail gas are transported to the second product storage tank through a pipeline. The second product storage tank is used to store the liquid product, and the gaseous HCl tail gas is introduced into the subsequent HCl refining system.

[0023] Preferably, the first gas-liquid separation tank and the second gas-liquid separation tank both contain condensers for condensing materials to achieve gas-liquid separation.

[0024] Preferably, pressure reducing valves, flow controllers, pressure gauges, temperature controllers, etc. can be installed on various pipelines of the preparation device for improving the selectivity of methallyl chloride as needed to monitor the operating status of the preparation device.

[0025] Beneficial Effects

[0026] 1. The present invention adopts a bubbling reactor, crude methallyl chloride is used as a circulating medium, and the reaction heat is removed by using external circulation refrigeration and latent heat of medium vaporization, which can effectively control the reaction temperature, make the reaction proceed at a lower temperature, reduce the generation of addition by-products, and improve the selectivity of methallyl chloride;

[0027] 2. The feed ratio of isobutylene to chlorine is 1.10-1.25:1, which effectively inhibits the generation of polychlorinated by-products and improves the selectivity of the main product; the reaction materials enter the gas-liquid separation after leaving the main reactor, the liquid component enters the product storage tank for temporary storage, and the gas component enters another tubular reactor, and the corresponding amount of chlorine is introduced to consume excess isobutylene, thereby solving the problem of tail gas HCl separation and making the overall selectivity of methallyl chloride reach more than 93%.

[0028] 3. By adjusting the temperature and flow rate of the circulating coolant, the temperature in the reactor is controlled at the boiling point of the material and the liquid level is highly stable, which is beneficial to reaction control and long-term operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 It is a schematic diagram of the preparation method according to the present invention. DETAILED DESCRIPTION

[0031] Hereinafter, the present invention will be described in detail. Before describing, it should be understood that the terms used in this specification and the appended claims should not be interpreted as being limited to the general meaning and dictionary meaning, but should be interpreted according to the meaning and concept corresponding to the technical aspects of the present invention on the basis of the principle that the inventor is allowed to appropriately define the terms for the best interpretation. Therefore, the descriptions presented here are only preferred examples for illustrative purposes and are not intended to limit the scope of the present invention, so that it should be understood that other equivalents or improvements can be obtained therefrom without departing from the spirit and scope of the present invention.

[0032] As used herein, the terms "include", "comprising", "having", "containing" or any other similar terms are open-ended transitional phrases, which are intended to cover non-exclusive inclusions. For example, a composition or article containing multiple elements is not limited to the elements listed herein, but may also include other elements that are not explicitly listed but are generally inherent to the composition or article. In addition, unless otherwise expressly stated, the term "or" refers to an inclusive "or" rather than an exclusive "or". For example, any of the following situations satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), and both A and B are true (or exist). In addition, as used herein, the terms "include", "comprising", "having", and "containing" should be interpreted as having been specifically disclosed and simultaneously covering closed or semi-closed transitional phrases such as "consisting of" and "consisting essentially of".

[0033] In this article, all features or conditions defined in the form of numerical ranges or percentage ranges are only for brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be deemed to have covered and specifically disclosed all possible secondary ranges and individual values ​​within the range, especially integer values. For example, the range description of "1 to 8" should be deemed to have specifically disclosed all secondary ranges such as 1 to 7, 2 to 8, 2 to 6, 3 to 6, 4 to 8, 3 to 8, etc., especially secondary ranges defined by all integer values, and should be deemed to have specifically disclosed individual values ​​such as 1, 2, 3, 4, 5, 6, 7, 8, etc. within the range. Unless otherwise specified, the above interpretation method applies to all contents of the entire present invention, regardless of whether the range is broad or not.

[0034] If the quantity or other numerical value or parameter is expressed as a range, a preferred range or a series of upper and lower limits, it should be understood that all ranges consisting of any upper limit or preferred value of the range and the lower limit or preferred value of the range have been specifically disclosed herein, regardless of whether these ranges are disclosed separately. In addition, if a numerical range is mentioned herein, unless otherwise specified, the range should include its endpoints and all integers and fractions within the range.

[0035] In this document, under the premise of achieving the purpose of the invention, numerical values ​​should be understood to have the accuracy of the number of significant digits of the numerical value. For example, the number 40.0 should be understood to cover the range from 39.50 to 40.49.

[0036] In order to clarify the present invention, parts irrelevant to the description are omitted in the drawings, and the same or similar components are denoted by the same reference numerals throughout the specification.

[0037] In addition, the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of explanation, and thus the present invention is not necessarily limited to those shown in the drawings.

[0038] Throughout the specification, when it is mentioned that a certain element is “connected” to another element, it includes not only “direct connection” but also “indirect connection” between other components. In addition, when it is mentioned that a certain element “includes” a certain component, it means that the element may further include other components rather than excluding other components, unless explicitly described to the contrary.

[0039] In the method for preparing highly selective methallyl chloride according to the present invention:

[0040] a) The desiccant in the raw material drying tank can be anhydrous calcium chloride, and the water content of the raw material after passing through the drying tank is controlled below 20ppm; it can effectively absorb trace water in the two raw materials, and protect the pipes and reactors in the back section. The preheating buffer tank controls the gas temperature at 10-25°C. b) The gas partial pressure of the raw material gas is 0.2-0.4MPa after passing through the pressure reducing valve. c) The reaction temperature in the bubbling reactor is controlled at about 70°C; in c), the feed molar ratio of isobutylene and chlorine is controlled at 1.10-1.25:1. When the feed molar ratio of isobutylene and chlorine is controlled at 1.10-1.25:1, the best chlorination effect can be achieved. If the feed molar ratio of isobutylene to chlorine is lower than 1.10, the output of high-boiling polychlorinated byproducts is too high, resulting in low selectivity; if the feed molar ratio of isobutylene to chlorine is higher than 1.25:1, the content of low-boiling tert-butyl chloride is too high, thereby reducing the selectivity of the product methallyl chloride. Therefore, in order to obtain high selectivity of methallyl chloride, the feed ratio needs to be regulated. d) The amount of chlorine added to the tubular reactor satisfies the molar ratio of the total raw material isobutylene and chlorine fed into the bubbling reactor and the tubular reactor to be 1 to 1.05:1. Since the purpose of adding chlorine in the tubular reaction is to make the unreacted raw material isobutylene react as completely as possible, the amount of chlorine added needs to be controlled. When the amount of chlorine added is controlled within the above range, the residual raw material isobutylene can be effectively reacted completely.

[0041] According to the design of the gas-liquid bubbling reactor used in the method of the present invention, the heat exchange of the external circulating medium and the latent heat of the crude product vaporization are utilized to greatly increase the heat, which is conducive to controlling the reaction temperature to be maintained at a relatively low level and can effectively reduce the generation of addition by-products; the excess ratio of isobutylene is increased to inhibit the generation of polychlorinated by-products, thereby improving the selectivity of methallyl chloride; by adding a reactor and adding a portion of chlorine to consume the excess isobutylene, the isobutylene is completely converted, thereby solving the problem of difficulty in separating isobutylene.

[0042] The reaction temperature of the bubbling reactor is controlled at 70-75° C., the temperature of the circulating cooling water is adjusted to 0-5° C., the circulating cooling water is used to take away the heat of the circulating medium, and the reaction is ensured to be carried out at a relatively low temperature, which is beneficial to improving the selectivity of methallyl chloride. In the bubbling reactor, the molar ratio of isobutylene to chlorine is 1.10-1.25:1, and the excess ratio of isobutylene is increased, which can inhibit the generation of polychlorinated by-products, thereby improving the selectivity of methallyl chloride.

[0043] After the reaction in the bubbling reactor is completed, the material is subjected to gas-liquid separation, a small amount of unreacted isobutylene is introduced into a tubular reactor together with other substances in other forms, and chlorine is added for further reaction to make the isobutylene react completely, thereby avoiding the final tail gas HCl gas from being doped with unreacted isobutylene, which is difficult to separate and has a very high cost. The crude chlorinated product after gas-liquid separation no longer contacts chlorine and will not be further chlorinated. The crude chlorinated product is then recovered to solve the problem of difficult separation.

[0044] In addition, unless otherwise stated, the chlorine gas disclosed below was purchased from Shandong Binhua Dongrui Chemical Co., Ltd., isobutylene was purchased from Heze Xiling Chemical Co., Ltd., and GC was tested using an Agilent 8860 gas chromatograph with a column model of DB-624. Selectivity was calculated using the GC internal standard method.

[0045] Example 1

[0046] A bubbling reactor with an inner diameter of φ50mm and a height of 1000mm was prepared. The height of the armored allyl chloride in the reactor was 500mm. Isobutylene entered the gas distributor at a gas flow rate of 27.06g / min and chlorine entered the gas distributor at a gas flow rate of 31.12g / min. The molar ratio of isobutylene to chlorine was 1.10:1.

[0047] The mixed raw materials are then bubbled into the reactor to undergo a chlorination reaction. The crude product is heat exchanged in the heat exchanger and then added to the reactor from the bottom at a rate of 100 g / min. The temperature of the circulating coolant is adjusted to 0-5°C. The temperatures of the three temperature measurement points inside the reactor are 65.9°C, 72.5°C, and 72.7°C from bottom to top.

[0048] The crude reaction product leaves the reactor in gaseous form and enters the gas-liquid separation. The liquid phase flows into the first product storage tank for temporary storage, and the gas phase component enters the tubular reactor. The chlorine gas flow rate is 5.50 g / min.

[0049] The gas phase components are separated by gas and liquid, and the liquid phase is temporarily stored in the second product storage tank, and the non-condensable gas enters the hydrogen chloride refining device. The products in the two storage tanks are taken out and mixed evenly before gas chromatography testing.

[0050] Example 2

[0051] Prepare a bubbling reactor with an inner diameter of φ50mm and a height of 1000mm. The height of the armored substituted allyl chloride in the reactor is 500mm. Isobutylene enters the gas distributor at a gas flow rate of 28.29g / min and chlorine at a gas flow rate of 31.12g / min. The molar ratio of isobutylene to chlorine is 1.15:1. The mixed raw materials enter the reactor in the form of bubbles to undergo a chlorination reaction. After the crude product is heat exchanged in the heat exchanger, it is added to the reactor from the bottom at a rate of 100g / min. The temperature of the circulating coolant is adjusted to 10-15℃. The temperatures of the three measuring points inside the reactor are 66.9℃, 72.8℃, and 72.3℃ from bottom to top. The crude reaction product exits the reactor in a gaseous form and enters the gas-liquid separation. The liquid phase flows into the first product storage tank for temporary storage. The gas phase component enters the tubular reactor, and the flow rate of additional chlorine is 5.75g / min. The gas phase components are separated by gas and liquid, and the liquid phase is temporarily stored in the second product storage tank, and the non-condensable gas enters the hydrogen chloride refining device. The products in the two storage tanks are taken out and mixed evenly before gas chromatography testing.

[0052] Example 3

[0053] Prepare a bubbling reactor with an inner diameter of φ50mm and a height of 1000mm. The height of the armored substituted allyl chloride in the reactor is 500mm. Isobutylene enters the gas distributor at a gas flow rate of 29.52g / min, and chlorine enters the gas distributor at a gas flow rate of 31.12g / min. The molar ratio of isobutylene to chlorine is 1.20:1. The mixed raw materials then enter the reactor in the form of bubbles to undergo a chlorination reaction. After the crude product is heat exchanged in the heat exchanger, it is added to the reactor from the bottom at a rate of 100g / min. The temperature of the circulating coolant is adjusted to 10-15℃. The temperatures of the three measuring points inside the reactor are 66.8℃, 72.7℃, and 72.4℃ from bottom to top. The crude reaction product exits the reactor in a gaseous form and enters the gas-liquid separation. The liquid phase flows into the first product storage tank for temporary storage. The gas phase component enters the tubular reactor, and the chlorine flow rate is 6.00g / min. The gas phase components are separated by gas and liquid, and the liquid phase is temporarily stored in the second product storage tank, and the non-condensable gas enters the hydrogen chloride refining device. The products in the two storage tanks are taken out and mixed evenly before gas chromatography testing.

[0054] Keep the process conditions unchanged and run stably for 72 hours. Take samples and test every 8 hours. The experimental data are recorded in Table 2.

[0055] Example 4

[0056] Prepare a bubbling reactor with an inner diameter of φ50mm and a height of 1000mm. The height of the armored substituted allyl chloride in the reactor is 500mm. Isobutylene enters the gas distributor at a gas flow rate of 30.75g / min, and chlorine enters the gas distributor at a gas flow rate of 31.12g / min. The molar ratio of isobutylene to chlorine is 1.25:1. The mixed raw materials then enter the reactor in the form of bubbles to undergo a chlorination reaction. After the crude product is heat exchanged in the heat exchanger, it is added to the reactor from the bottom at a rate of 100g / min. The temperature of the circulating coolant is adjusted to 10-15℃. The temperatures of the three measuring points inside the reactor are 66.7℃, 72.3℃, and 72.6℃ from bottom to top. The crude reaction product exits the reactor in a gaseous form and enters the gas-liquid separation. The liquid phase flows into the first product storage tank for temporary storage. The gas phase component enters the tubular reactor, and the additional chlorine flow rate is 6.25g / min. The gas phase components are separated by gas and liquid, and the liquid phase is temporarily stored in the second product storage tank, and the non-condensable gas enters the hydrogen chloride refining device. The products in the two storage tanks are taken out and mixed evenly before gas chromatography testing.

[0057] Table 1 Summary of gas chromatography data

[0058]

[0059] Table 2 Summary of long-term experimental data

[0060]

[0061] It can be seen from Examples 1 to 4 that as the excess ratio of isobutylene in the bubbling reactor increases, the content of tert-butyl chloride gradually increases, the content of polychlorinated byproducts gradually decreases, and the content of methallyl chloride gradually increases. When the ratio reaches 1.20:1, the selectivity of methallyl chloride is the highest. By optimizing the process conditions, the selectivity of methallyl chloride is increased from 88.67% to 93.14%.

[0062] Through long-term experiments, it can be seen that under this process condition, the reaction temperature is stable, there is no temperature runaway phenomenon; the quality of the crude product is stable, and the main product is maintained at a high selectivity level. This example proves that the device can operate stably under this process condition.

[0063] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A preparation process for improving the selectivity of methallyl chloride, characterized in that: The following steps are involved: a) drying, preheating and pressure controlling isobutylene and chlorine in gaseous form respectively, and then feeding them to the front end of a bubbling reactor at a molar ratio of 1.10 to 1.25:1 for premixing, bubbling into the reactor for chlorination reaction, and obtaining a crude methallyl chloride product; the product exits the reactor in gaseous form and enters a first gas-liquid separation tank, the crude chloride is cooled to a liquid state and temporarily stored in a first product storage tank, and the gaseous component enters a tubular reactor; the heat released by the reaction and the heat of the circulating liquid volatilization zone are balanced by calculation, and a part of the crude product is cooled by a heat exchanger and then enters the bubbling reactor again from the bottom as a circulating coolant, with an entry flow rate of 100 to 150 g / min; the temperature of the circulating coolant is 0 to 15° C.; Isobutylene enters the gas distributor at a gas flow rate of 25-35 g / min, and chlorine enters the gas distributor at a gas flow rate of 30-35 g / min; b) The crude product after cooling is subjected to gas-liquid separation, and the liquid phase flows into the first product storage tank for temporary storage; the gas phase component enters the tubular reactor, and chlorine is introduced into the tubular reactor at the same time, and the amount of chlorine added is such that the molar ratio of the total raw material isobutylene and chlorine entering the bubbling reactor and the tubular reactor is 1 to 1.05:1; the amount of chlorine added is 5 to 7 g / min to ensure that the isobutylene can react completely; c) subjecting the product of the tubular reactor to gas-liquid separation to obtain a liquid crude product and tail gas, and the liquid crude product is introduced into a second product tank.

2. A preparation process for improving the selectivity of methallyl chloride according to claim 1, characterized in that: The reaction temperature of the bubbling reactor in step a) is 70-75°C, and the temperature of the circulating cooling water is adjusted to 0-5°C.

3. A preparation process for improving the selectivity of methallyl chloride according to claim 1, characterized in that: The liquid in the first product tank in step b) is further purified to obtain pure methallyl chloride; the crude liquid product separated in step c) can be mixed with the separated liquid obtained in step b) and purified together, or the two can be purified separately.

4. A device for improving the selectivity of methallyl chloride, comprising: Raw material drying tank, preheating buffer tank, circulating liquid temporary storage tank, heat exchanger, bubbling reactor, tubular reactor, first gas-liquid separation tank, second gas-liquid separation tank, first product tank, second product tank; Among them, isobutylene and chlorine are respectively passed through their respective raw material drying tanks and preheating buffer tanks in gaseous form to dry and control the temperature of the gas; The preheating buffer tank is connected to the bubbling reactor through a pipeline, and the raw materials are passed into the bubbling reactor for reaction; the bubbling reactor is connected to the first gas-liquid separation tank through a pipeline, and then connected to the first product storage tank; the circulating coolant in the bubbling reactor can overflow into the circulating liquid temporary storage tank, the circulating liquid temporary storage tank is connected to the heat exchanger through a pipeline, and then the circulating liquid is injected into the reactor from the bottom of the bubbling reactor by a pump; The bubbling reactor is connected to the first gas-liquid separation tank through a pipeline, and the first gas-liquid separation tank is used to separate gas and liquid in the crude product; The material that has been separated into gas and liquid by the first gas-liquid separation tank is input into the first product storage tank through a pipeline; the first product storage tank is used to store liquid products and input gas into the tubular reactor at the same time; The first product storage tank is connected to the tubular reactor through a pipeline, and the material is input into the tubular reactor. At the same time, the tubular reactor is connected to a chlorine preheating buffer tank to receive the input chlorine, so that the remaining isobutylene in the material reacts with the chlorine to complete the reaction of the isobutylene; After the reaction in the tubular reactor is completed, the material is input into the second gas-liquid separation tank through a pipeline, and then the liquid product and the gaseous HCl tail gas are transported to the second product storage tank through a pipeline. The second product storage tank is used to store the liquid product, and the gaseous HCl tail gas is introduced into the subsequent HCl refining system.

5. A preparation process for improving the selectivity of methallyl chloride according to claim 1, characterized in that: The first gas-liquid separation tank and the second gas-liquid separation tank both contain condensers for condensing materials to achieve gas-liquid separation.

6. A preparation process for improving the selectivity of methallyl chloride according to claim 1, characterized in that: Pressure reducing valves, flow controllers, pressure gauges, temperature controllers and the like can be installed on various pipelines of the preparation device for improving the selectivity of methallyl chloride as needed to monitor the operating status of the preparation device.

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