Preparation method and device for improving selectivity of methallyl chloride

Abstract

The invention discloses a preparation method and device for improving selectivity of methallyl chloride, the device adopts two sections of reactors, the first section is a main reactor, and a chlorination reaction is mainly carried out in the first section of reactor; chlorine is quantitatively introduced into the second-section reactor so as to consume residual isobutene at the front end. According to the method disclosed by the invention, the chlorination reaction is carried out by utilizing the two-stage reactor, the ratio of isobutene to chlorine is reasonably controlled, and the generation of polychlorinated by-products is inhibited, so that the main product methyl allyl chloride keeps high selectivity, meanwhile, the complete conversion of isobutene is ensured, and the problem of separation of isobutene and hydrogen chloride in tail gas is avoided. According to the process disclosed by the invention, the selectivity of the methallyl chloride reaches 90%, and the economic benefit of the device is obviously improved.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and in particular relates to a preparation method and a device capable of improving the high selectivity of methallyl chloride. Background Art

[0002] Methallyl chloride (3-chloro-2-methylpropene) is an important organic synthesis intermediate, widely used in water reducers, flame retardants, pesticides, fragrances and other fields.

[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 large heat release of this reaction, there are many by-products. For example, the common side reactions are as follows, including the production 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 content in the reaction system, and the less polychlorinated byproducts such as 1,2-dichloroisobutane and 3-chloro-2-chloromethyl-propylene; the higher the chlorine ratio, the more 1,2-dichloroisobutane, 1,2-dichloroisobutane, and 3-chloro-2-chloromethyl-propylene byproducts, and the less tert-butyl chloride content, so only when the ratio of isobutylene to chlorine in the raw material is maintained within a specific range can the high selectivity of the product be ensured. In addition, if isobutylene cannot react completely in the reaction system during the production process, it will lead to the problem of difficulty in separating isobutylene from the by-product hydrogen chloride in the tail gas. The existing technology mainly reduces the isobutylene ratio so that the isobutylene and chlorine should be complete. For example, Chinese patents CN88104076.2 and CN03131083.4 maintain the ratio of isobutylene to chlorine at about 1.02:1, so that the isobutylene reaction is complete. Although the separation problem of isobutylene and by-product hydrogen chloride in the tail gas is avoided, under the raw material ratio condition, the content of polychlorinated by-products is high, and the selectivity of the target product methallyl chloride is not optimal, and the selectivity of the general product is about 85%. Chinese patent CN88104076.2 examines the injection of chlorine into the reactor in 3 to 5 equal parts on the same reactor section, the purpose is to cancel the introduction of oxygen or air, so that the chlorination reaction can still be carried out at a stable temperature, but it is still difficult to overcome the problem of too high proportion of by-products and insufficient selectivity of methallyl chloride. Summary of the invention

[0006] In view of the problems existing in the above-mentioned prior art, the present invention designs a two-stage reactor, wherein the first stage is a main reactor, and the chlorination reaction is mainly carried out in the first stage reactor; the second stage reactor is quantitatively introduced with chlorine gas, the purpose of which is to consume the remaining isobutylene at the front end. The present invention utilizes two-stage reactors to carry out the chlorination reaction, reasonably controls the ratio of isobutylene to chlorine gas, inhibits the generation of polychlorinated by-products, ensures that the main product methallyl chloride maintains high selectivity while ensuring complete conversion of isobutylene, and avoids the problem of separation of isobutylene and hydrogen chloride in tail gas. The selectivity of methallyl chloride reaches 90% through the process of the present invention, which significantly improves the economic benefits of the device.

[0007] According to one aspect of the present invention, an object of the present invention is to provide a preparation method for improving the selectivity of methallyl chloride. The method comprises the following steps:

[0008] a) drying, temperature- and pressure-controlled isobutylene and chlorine in gaseous form, respectively, and then feeding them into the first stage reactor at a molar ratio of 1.10 to 1.30:1 for chlorination reaction, with a material gas velocity of 5.0 to 6.4 m / s;

[0009] b) After the chlorination reaction in the first stage reactor is completed, the crude reaction product is subjected to gas-liquid separation, and the separated gas is introduced into the second stage reactor, and chlorine is introduced into the second stage reactor at the same time, and the amount of chlorine added is such that the molar ratio of isobutylene to the total amount of chlorine in the first stage reactor and the second stage reactor is 1 to 1.05:1, and the separated liquid is introduced into the first product tank;

[0010] c) The product after the second stage 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 the second product tank.

[0011] Preferably, the first stage reactor and the second stage reactor are double-layered tubular reactors or single-layered jacketed tubular reactors.

[0012] Preferably, in step a), the temperatures of the raw materials isobutylene and chlorine are respectively controlled at 10-25°C.

[0013] Preferably, in step a), the water content of the raw materials isobutylene and chlorine is controlled below 20 ppm after drying.

[0014] Preferably, the pressure of the raw material and isobutylene transported to the first-stage reactor in step a) is controlled to be 0.2-0.4 MPa.

[0015] Preferably, in step a), the reaction temperature is controlled to be no higher than 90° C., the reactant gas velocity is 5.0 to 6.4 m / s, and the reaction residence time is no higher than 0.2 s. Too high a reaction temperature will lead to an increase in the content of addition by-products; too long a residence time will lead to an increase in the content of tert-butyl chloride, both of which will reduce the selectivity of the main product methallyl chloride.

[0016] Preferably, the reaction temperature in step a) is controlled at 50-90°C, more preferably 70-90°C.

[0017] Preferably, the liquid in the first product tank in step b) is further purified to obtain pure methallyl chloride.

[0018] Preferably, 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.

[0019] According to another aspect of the present invention, the second object of the present invention is to provide a preparation device capable of improving the selectivity of methallyl chloride, comprising: a raw material drying tank, a preheating buffer tank, a first stage reactor, a second stage reactor, a first gas-liquid separation tank, a second gas-liquid separation tank, a first product tank, and a second product tank;

[0020] 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;

[0021] The preheating buffer tank is connected to the first stage reactor through a pipeline, and the raw materials are passed into the first stage reactor;

[0022] The first stage 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;

[0023] 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 second stage reactor at the same time;

[0024] The first product storage tank is connected to the second stage reactor through a pipeline, and the material is input into the second stage reactor. Meanwhile, the second stage 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;

[0025] After the reaction in the second stage reactor is completed, the material is introduced 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.

[0026] 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.

[0027] 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.

[0028] Beneficial Effects

[0029] 1. The present invention adopts a two-stage reactor. The purpose of the first stage reactor is to optimize the feed ratio of isobutylene and chlorine to maintain the optimal selectivity of the reaction; the purpose of the second stage reactor is to supplement chlorine to completely react the excess isobutylene in the first stage reactor, thereby solving the problem of difficulty in separating isobutylene and hydrogen chloride in tail gas. After process optimization, it can ensure that the isobutylene reaction is complete and the selectivity of methallyl chloride is as high as more than 90%;

[0030] 2. The two-stage reactor of the present invention adopts a double-layered tubular reactor design, with cooling water passing through the inner and outer layers, and the middle layer passing the reaction material. The heat exchange area is significantly increased compared with the ordinary single-tube reactor, and the heat removal efficiency of the reaction system is significantly improved, so that the reaction can be maintained at a lower temperature, thereby improving product selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] 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.

[0032] Figure 1 It is a schematic diagram of the preparation method according to the present invention. DETAILED DESCRIPTION

[0033] 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.

[0034] In this document, the terms "include", "including", "have", "contain" or any other similar terms are open conjunctions, which are intended to cover non-exclusive inclusions. For example, a composition or product 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 product. In addition, unless otherwise explicitly 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 A and B are both true (or exist). In addition, in this document, the interpretation of the terms "include", "including", "have", and "contain" should be considered to have been specifically disclosed and simultaneously cover closed or semi-closed conjunctions such as "consisting of" and "consisting essentially of".

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] In the method for preparing highly selective methallyl chloride according to the present invention:

[0042] a) The desiccant in the raw material drying tank can be anhydrous calcium chloride. 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, protect the pipes and reactors in the back section, and the preheating buffer tank controls the gas temperature at 10-25°C. b) The gas partial pressure of the raw material gas after passing through the pressure reducing valve is 0.2-0.4MPa. c) The reaction temperature in the first stage reactor is controlled below 90°C; in c), the feed molar ratio of isobutylene and chlorine is controlled at 1.10-1.30:1. When the feed molar ratio of isobutylene and chlorine is controlled at 1.10-1.30:1, 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 by-products is too high, resulting in low selectivity; if the feed molar ratio of isobutylene to chlorine is higher than 1.30:1, 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 controlled within the above range. d) The amount of chlorine added in the second stage reactor satisfies the molar ratio of the total raw material isobutylene and chlorine fed into the first stage reactor and the second stage reactor to be 1 to 1.05:1. Since the purpose of adding chlorine in the second stage 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.

[0043] In the method according to the present invention, a double-layer reactor design is used to increase the heat exchange area, and low-temperature circulating water is used to carry heat to control the reaction temperature; the excess ratio of isobutylene is increased to suppress the formation of polychlorinated by-products, thereby improving the selectivity of methallyl chloride; by adding a reactor, a part of chlorine is added to consume the excess isobutylene, so that the isobutylene is completely converted, thereby solving the problem of difficulty in separating isobutylene.

[0044] The reaction temperature of the first stage reactor is controlled at 70-90°C, preferably 70-80°C, and the temperature of the circulating cooling water is adjusted to 0-10°C. The circulating cooling water is used to carry heat. The reactor adopts a double-layer design to increase the heat exchange area and ensure that the reaction is carried out at a relatively low temperature, which is beneficial to improving the selectivity of methallyl chloride.

[0045] In the first stage reactor, the molar ratio of isobutylene to chlorine is 1.10:1 to 1.3:1. Increasing the excess ratio of isobutylene can inhibit the generation of polychlorinated by-products, thereby improving the selectivity of methallyl chloride.

[0046] After the reaction in the first stage reactor is completed, the material is separated from the gas and liquid, and a small amount of unreacted isobutylene is introduced into the second stage reactor together with other substances in other forms, and then chlorine is added for further reaction to make the isobutylene react completely, thereby avoiding the final tail gas HCl gas being mixed with unreacted isobutylene, which is difficult to separate and very costly. 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 separation difficulties.

[0047] 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. Selectivity was calculated using the GC internal standard method.

[0048] The following examples are only listed as examples of embodiments of the present invention and do not constitute any limitation to the present invention. It can be understood by those skilled in the art that modifications within the scope of the essence and concept of the present invention fall within the scope of protection of the present invention. Unless otherwise specified, the reagents and instruments used in the following examples are all commercially available products.

[0049] Example 1

[0050] Prepare outer diameter inner diameter A tubular reactor with a cooling jacket and an annular gap of 3 mm and a length of 800 mm was used as the first and second stage reactors. Gaseous isobutylene was introduced into the tubular reactor from the air inlet at a flow rate of 13.53 g / min, and chlorine was introduced into the air inlet at a flow rate of 15.56 g / min, with a molar ratio of 1.10:1. Gaseous isobutylene and chlorine were pretreated in a drying tank and a preheating buffer tank, respectively, with a water content of less than 20 ppm and a temperature of 10 to 25°C.

[0051] The product after the first stage reactor is separated into gas and liquid by the first gas-liquid separation tank, and the circulating coolant is 0-5°C, and then input into the first product storage tank, and the liquid material is retained in the first product storage tank. The liquid material is analyzed by gas chromatography, named 1, and the results are shown in Table 1 below. The gas is introduced into the second stage reactor through the pipeline, and chlorine is introduced into the second stage reactor at the same time, with a flow rate of 2.75g / min. The total molar ratio of isobutylene to chlorine in the two stage reactors is 1.05:1. The crude product flowing out of the outlet of the second stage reactor is also separated into gas and liquid, and the liquid phase flows into the second product storage tank for temporary storage, and the non-condensable gas enters the subsequent HCl refining system for conventional HCl refining treatment.

[0052] Example 2

[0053] Prepare outer diameter inner diameter A tubular reactor with a cooling jacket and an annular gap of 3 mm and a length of 800 mm was used as the first and second stage reactors. Gaseous isobutylene was introduced into the tubular reactor from the air inlet at a flow rate of 14.14 g / min, and chlorine was introduced into the air inlet at a flow rate of 15.56 g / min, with a molar ratio of 1.15:1. Gaseous isobutylene and chlorine were pretreated in a drying tank and a preheating buffer tank, respectively, with a water content of less than 20 ppm and a temperature of 10 to 25°C.

[0054] The product after the first stage reactor is separated into gas and liquid by the first gas-liquid separation tank, and the circulating coolant is 0-5°C, and then input into the first product storage tank, and the liquid material is retained in the first product storage tank. The liquid material is analyzed by gas chromatography, named 2, and the results are shown in Table 1 below. The gas is introduced into the second stage reactor through the pipeline, and chlorine is introduced into the second stage reactor at the same time, with a flow rate of 2.87g / min. The total molar ratio of isobutylene to chlorine in the two stage reactors is 1.05:1. The crude product flowing out of the outlet of the second stage reactor is also separated into gas and liquid, and the liquid phase flows into the second product storage tank for temporary storage, and the non-condensable gas enters the subsequent HCl refining system for conventional HCl refining treatment.

[0055] Example 3

[0056] Prepare outer diameter inner diameter A tubular reactor with a cooling jacket and an annular gap of 3 mm and a length of 800 mm was used as the first and second stage reactors. Gaseous isobutylene was introduced into the tubular reactor from the air inlet at a flow rate of 14.76 g / min, and chlorine was introduced into the air inlet at a flow rate of 15.56 g / min, with a molar ratio of 1.20:1. Gaseous isobutylene and chlorine were pretreated in a drying tank and a preheating buffer tank, respectively, with a water content of less than 20 ppm and a temperature of 10 to 25°C.

[0057] The product after the first stage reactor is separated into gas and liquid by the first gas-liquid separation tank, and the circulating coolant is 0-5°C, and then input into the first product storage tank, and the liquid material is retained in the first product storage tank. The liquid material is analyzed by gas chromatography, named 3, and the results are shown in Table 1 below. The gas is introduced into the second stage reactor through the pipeline, and chlorine is introduced into the second stage reactor at the same time, with a flow rate of 3.00g / min. The total molar ratio of isobutylene to chlorine in the two stage reactors is 1.05:1. The crude product flowing out of the outlet of the second stage reactor is also separated into gas and liquid, and the liquid phase flows into the second product storage tank for temporary storage, and the non-condensable gas enters the subsequent HCl refining system for conventional HCl refining treatment.

[0058] Example 4

[0059] Prepare outer diameter inner diameter A tubular reactor with a cooling jacket and an annular gap of 3 mm and a length of 800 mm was used as the first and second stage reactors. Gaseous isobutylene was introduced into the tubular reactor from the air inlet at a flow rate of 15.37 g / min, and chlorine was introduced into the air inlet at a flow rate of 15.56 g / min, with a molar ratio of 1.25:1. Gaseous isobutylene and chlorine were pretreated in a drying tank and a preheating buffer tank, respectively, with a water content of less than 20 ppm and a temperature of 10 to 25°C.

[0060] The product after the first stage reactor is separated into gas and liquid by the first gas-liquid separation tank, and the circulating coolant is 0-5°C, and then input into the first product storage tank, and the liquid material is retained in the first product storage tank. The liquid material is analyzed by gas chromatography, named 4, and the results are shown in Table 1 below. The gas is introduced into the second stage reactor through the pipeline, and chlorine is introduced into the second stage reactor at the same time, with a flow rate of 3.12g / min. The total molar ratio of isobutylene to chlorine in the two stage reactors is 1.05:1. The crude product flowing out of the outlet of the second stage reactor is also separated into gas and liquid, and the liquid phase flows into the second product storage tank for temporary storage, and the non-condensable gas enters the subsequent HCl refining system for conventional HCl refining treatment.

[0061] Example 5

[0062] Prepare outer diameter inner diameter A tubular reactor with a cooling jacket and an annular gap of 3 mm and a length of 800 mm was used as the first and second stage reactors. Gaseous isobutylene was introduced into the tubular reactor from the air inlet at a flow rate of 15.98 g / min, and chlorine was introduced into the air inlet at a flow rate of 15.56 g / min, with a molar ratio of 1.30:1. Gaseous isobutylene and chlorine were pretreated in a drying tank and a preheating buffer tank, respectively, with a water content of less than 20 ppm and a temperature of 10 to 25°C.

[0063] The product after the first stage reactor is separated into gas and liquid by the first gas-liquid separation tank, and the circulating coolant is 0-5°C, and then input into the first product storage tank, and the liquid material is retained in the first product storage tank. The liquid material is analyzed by gas chromatography, named 5, and the results are shown in Table 1 below. The gas is introduced into the second stage reactor through the pipeline, and chlorine is introduced into the second stage reactor at the same time, with a flow rate of 3.24g / min. The total molar ratio of isobutylene to chlorine in the two stage reactors is 1.05:1. The crude product flowing out of the outlet of the second stage reactor is also separated into gas and liquid, and the liquid phase flows into the second product storage tank for temporary storage, and the non-condensable gas enters the subsequent HCl refining system for conventional HCl refining treatment.

[0064] Example 6

[0065] Prepare outer diameter inner diameter A tubular reactor with a cooling jacket and an annular gap of 3 mm and a length of 800 mm was used as the first and second stage reactors. Gaseous isobutylene was introduced into the tubular reactor from the air inlet at a flow rate of 15.37 g / min, and chlorine was introduced into the air inlet at a flow rate of 15.56 g / min, with a molar ratio of 1.25:1. Gaseous isobutylene and chlorine were pretreated in a drying tank and a preheating buffer tank, respectively, with a water content of less than 20 ppm and a temperature of 10 to 25°C.

[0066] The product after the first stage reactor is separated from the gas and liquid by the first gas-liquid separation tank, and the circulating coolant is 0-5°C, and then input into the first product storage tank. The liquid material is retained in the first product storage tank, and the liquid material is analyzed by gas chromatography, named 6.1, and the results are shown in Table 1 below. The gas is introduced into the second stage reactor through a pipeline, and chlorine is introduced into the second stage reactor at the same time, with a flow rate of 3.12g / min. The total molar ratio of isobutylene to chlorine in the two stages of the reactor is 1.05:1. The crude product flowing out of the outlet of the second stage reactor is also separated from the gas and liquid, and the liquid phase flows into the second product storage tank for temporary storage, and the GC is sampled and tested, named 6.2. The non-condensable gas enters the subsequent HCl refining system for conventional HCl refining treatment. After stopping the reaction, the chlorinated crude products in the two product storage tanks are mixed evenly and then analyzed by gas chromatography, named 6.3.

[0067] Table 1 Summary of gas chromatography data

[0068]

[0069] It can be seen from Examples 1 to 5 that as the excess ratio of isobutylene increases, the content of tert-butyl chloride gradually increases, the content of polychlorinated byproducts gradually decreases, and the content of methallyl chloride gradually increases to a maximum when it reaches 1.25:1. The selectivity of methallyl chloride is increased from 87.24% to 90.09% by optimizing the process conditions.

[0070] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A preparation method for improving the selectivity of methallyl chloride, comprising the following steps: a) drying, temperature- and pressure-controlled isobutylene and chlorine in gaseous form, respectively, and then feeding them into the first stage reactor at a molar ratio of 1.10 to 1.30:1 for chlorination reaction, with a material gas velocity of 5.0 to 6.4 m / s; b) After the chlorination reaction in the first stage reactor is completed, the crude reaction product is subjected to gas-liquid separation, and the separated gas is introduced into the second stage reactor, and chlorine is introduced into the second stage reactor at the same time, and the amount of chlorine added is such that the molar ratio of isobutylene to the total amount of chlorine in the first stage reactor and the second stage reactor is 1 to 1.05:1, and the separated liquid is introduced into the first product tank; c) The product after the second stage 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 the second product tank.

2. The preparation method according to claim 1, characterized in that: The first stage reactor and the second stage reactor are double-layered tubular reactors and single-layered jacketed tubular reactors.

3. The preparation method according to claim 1, characterized in that: In step a), the temperatures of the raw materials isobutylene and chlorine are respectively controlled at 10-25° C.; Preferably, in step a), the water content of the raw materials isobutylene and chlorine is controlled below 20 ppm after drying; Preferably, the pressure of the raw material and isobutylene delivered to the first stage reactor in step a) is controlled to be 0.2-0.4 MPa; Preferably, in step a), the reaction temperature is controlled to be no higher than 90° C., the reactant gas velocity is 5.0 to 6.4 m / s, and the reaction residence time is no higher than 0.2 s; Preferably, the reaction temperature in step a) is controlled at 50-90°C, more preferably 70-90°C.

4. The preparation method 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.

5. The preparation method according to claim 1, characterized in that: The crude liquid product separated in step c) can be mixed with the separated liquid obtained in step b) and then purified together, or they can be purified separately.

6. A preparation device capable of improving the selectivity of methallyl chloride, comprising: Raw material drying tank, preheating buffer tank, first stage reactor, second stage 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 first stage reactor through a pipeline, and the raw materials are passed into the first stage reactor; The first stage 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 second stage reactor at the same time; The first product storage tank is connected to the second stage reactor through a pipeline, and the material is input into the second stage reactor. Meanwhile, the second stage 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 second stage reactor is completed, the material is introduced 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.

7. The preparation device according to claim 6, 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.

8. The preparation device according to claim 6, 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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