CN115850017A - Preparation method and system of efficient chloromethane - Google Patents
Preparation method and system of efficient chloromethane Download PDFInfo
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- CN115850017A CN115850017A CN202211528679.2A CN202211528679A CN115850017A CN 115850017 A CN115850017 A CN 115850017A CN 202211528679 A CN202211528679 A CN 202211528679A CN 115850017 A CN115850017 A CN 115850017A
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Abstract
The invention provides a methyl chloride synthesis method, which comprises a step of mixing methanol and hydrogen chloride gas under the action of a catalyst to perform a first-stage reaction, a step of performing a second-stage reaction under the condition of introducing hydrochloric acid, a step of washing mixed gas obtained after the second-stage reaction, and a step of performing gas-liquid separation on the washed gas. The temperature of a medium of the circulating pump is reduced by introducing hydrochloric acid, and a good working condition is created for long-time running of the circulating pump; the two-stage reaction is arranged, so that the utilization efficiency of the hydrogen chloride is effectively improved, and the content of dimethyl ether is reduced; the reverse washing in the washing step reduces the content of hydrogen chloride in the chloromethane obtained after the second-stage reaction, and improves the utilization efficiency of the chlorine in the system; part of the alcoholic acid obtained in the separation step is sent back to the washing step, and part of the alcoholic acid is sent back to the separation step to be recycled, so that the loss of chloride ions is further reduced.
Description
Technical Field
The invention relates to a method for preparing chloromethane, in particular to a method for efficiently preparing chloromethane matched with an organic silicon industry.
Background
Methyl chloride is also called methyl chloride, is colorless and easy to liquefy, is an important chemical raw material, is mainly used for producing methyl chlorosilane, tetramethyl lead, methyl cellulose and the like, can also be used for producing quaternary ammonium compounds, pesticides and the like, and is used as a solvent in the production of isobutyl rubber.
The existing methods for producing chloromethane generally comprise a methane chlorination method, a methanol chlorination method, a photochlorination method, an oxychlorination method and the like; the methanol chlorination method is a method widely used at present, and comprises the steps of heating and vaporizing methanol by steam, introducing the vaporized methanol into a reaction kettle, and reacting the vaporized methanol with hydrogen chloride under the condition of taking zinc chloride as a catalyst to generate methyl chloride.
The main chemical reaction for synthesizing methyl chloride by the methanol liquid phase catalysis method comprises the following steps:
CH 3 OH+HCl＝CH 3 Cl+H 2 o (main reaction, with catalyst heated)
CH 3 OH+CH 3 OH＝CH 3 OCH 3 +H 2 O (side reaction)
The method has the advantages of simple process flow, but has the following problems:
1) In the reaction process, since the single-pass conversion rate of the hydrogen chloride is about 86%, most of the incompletely converted methanol and hydrogen chloride are absorbed in the water washing tower to form alcohol-containing acid (hereinafter referred to as alcohol-containing acid). The current practice for alkyd-containing materials is to recover the alcohol from the acid by distillation and then recycle the alcohol. The treatment energy consumption is large and difficult.
2) The content of dimethyl ether at the outlet of the reaction kettle is 6000 to 7000ppm, which causes large use amount of sulfuric acid for treating dimethyl ether in the drying tower and excessive loss of raw material methanol.
CN 109320395A provides a method for synthesizing methyl chloride in series-parallel connection, which improves the utilization rate of raw materials by two-stage or multi-stage series-connection reaction kettles and adjusting the ratio of methanol to hydrogen chloride; but the second-stage reaction efficiency is not high due to the mixing of methyl chloride in the first-stage reaction kettle in the second-stage reaction; and the secondary stage adopts excessive methanol, and the hydrogen chloride gas is expected to be utilized as much as possible, so that the production amount of dimethyl ether is large, and the material consumption of a subsequent methyl chloride purification device is high.
CN209010413U describes a series pressurized methyl chloride synthesis process, i.e. two-stage methyl chloride reaction, wherein crude methyl chloride is compressed between the first stage and the second stage to achieve the second stage reaction temperature and pressure, but in the actual production situation, because the first stage reaction temperature is 140 ℃ to 160 ℃, and a large amount of water vapor and hydrogen chloride gas are carried in the crude methyl chloride, the working condition of the compressor is extremely severe, and the model selection of the compressor is very difficult.
CN214361086U describes a device for improving the mixing efficiency of methanol and hydrogen chloride by using a venturi system to improve the single-pass conversion rate of hydrogen chloride; however, the synthesis of methyl chloride can cause the existence of gas-liquid two-phase flow, which causes the problems of pipeline vibration, cavitation erosion and the like, and the stability and the capacity of the system are influenced to a certain extent.
Disclosure of Invention
The invention relates to a chloromethane synthesis method and a chloromethane synthesis system, which can effectively improve the conversion rate of hydrogen chloride and methanol and reduce the generation amount of a byproduct dimethyl ether.
The invention relates to a chloromethane synthesis method, which comprises the following steps: methanol and hydrogen chloride gas are mixed, chloromethane synthesis reaction is carried out under the action of a catalyst, hydrochloric acid is added in the reaction, and the generated mixed gas is subjected to subsequent cooling and condensation treatment.
According to the present invention, the catalyst is a conventional catalyst used in the synthesis of methyl chloride by the reaction of methanol and hydrogen chloride gas, including but not limited to zinc chloride, ammonium chloride, organic amines and the like. In some embodiments of the invention, the catalyst is a zinc chloride solution, for example, a 45% to 75% zinc chloride solution. In one embodiment of the invention, the catalyst is a 65% zinc chloride solution.
According to the invention, the methanol may be in excess compared to the hydrogen chloride gas, or the hydrogen chloride gas may be in excess compared to the methanol. In some embodiments of the invention, it is preferred that the molar ratio of methanol to hydrogen chloride is from 2.
According to the invention, the hydrochloric acid can be fresh hydrochloric acid or low-concentration hydrochloric acid generated by a hydrolysis process of the organosilicon monomer. From the economic viewpoint, the low-concentration hydrochloric acid generated by the hydrolysis of the organic silicon monomer is preferred, so that the problem of processing the low-concentration hydrochloric acid generated by the hydrolysis of the organic silicon monomer can be solved, and the production efficiency of methanol and hydrogen chloride gas can be improved.
According to the present invention, the hydrochloric acid has a concentration of 0.1% to 31% (e.g., 1%, 5%, 10%, 15%, 20%, 25%, 26%, 27%, 28%, 29%, 30%, etc.), and a temperature of 0 ℃ to 60 ℃ (e.g., 1 ℃,5 ℃,6 ℃,7 ℃,8 ℃, 9 ℃, 10 ℃, 15 ℃, 20 ℃, 25 ℃, 30 ℃, 35 ℃,40 ℃, 41 ℃, 42 ℃, 43 ℃, 44 ℃, 45 ℃, 46 ℃, 47 ℃, 48 ℃, 49 ℃, 50 ℃, 55 ℃, 60 ℃, etc.), preferably, the hydrochloric acid has a concentration of 5% to 15%, and a temperature of 10 ℃ to 40 ℃.
In one embodiment of the invention, the hydrochloric acid is added as soon as the reaction of methanol with hydrogen chloride gas takes place.
In another embodiment of the present invention, the hydrochloric acid is added to the liquid formed by the reaction of methanol and hydrogen chloride gas, and the mixed solution of hydrochloric acid and the liquid is reacted with the mixed gas formed by the reaction of methanol and hydrogen chloride gas. Preferably, the volume ratio of the liquid to the hydrochloric acid is 10; for example, 9.
The methanol and the hydrogen chloride gas are mixed, and the hydrochloric acid is added in the methyl chloride synthesis reaction under the action of the catalyst, so that the reaction heat of the methanol and the hydrogen chloride gas can be fully utilized, the temperature balance and the water balance of the whole reaction are regulated and controlled by adding the hydrochloric acid, the methanol utilization rate and the hydrogen chloride conversion rate are improved, and the generation of dimethyl ether is reduced.
In a preferred embodiment of the present invention, the methyl chloride synthesis method comprises:
s1, methyl chloride first-stage reaction: mixing methanol and hydrogen chloride gas, carrying out a first-stage reaction under the action of a catalyst, and feeding mixed gas formed after the reaction into a second-stage reaction step;
s2, methyl chloride two-stage reaction: and (2) mixing the liquid formed after the reaction in the step (S1) with hydrochloric acid, allowing the obtained mixed liquid to enter a second-stage reaction step, washing the mixed gas formed after the reaction in the step (S1), performing a second-stage reaction, and allowing the mixed gas obtained in the second-stage reaction to enter subsequent cooling and condensation treatment.
According to the invention, the methanol in the S1 step is in excess with respect to the hydrogen chloride.
According to the invention, in step S1, the temperature of the first reaction is between 130 ℃ and 170 ℃ and the pressure is between 0.5barg and 2barg, preferably between 140 ℃ and 160 ℃ and the pressure is between 1.0barg and 1.5barg.
According to the invention, in the step S2, the concentration of the hydrochloric acid is 0.1-31%, the temperature is 0-60 ℃, preferably, the concentration of the hydrochloric acid is 5-15%, and the temperature is 10-40 ℃.
According to the invention, in the step S2, the volume ratio of the liquid formed after the reaction of S1 to hydrochloric acid is 10; preferably 3.
According to the invention, in the S2 step, the temperature of the second stage reaction is between 100 ℃ and 160 ℃ and the pressure is between 0.5barg and 2barg, preferably between 130 ℃ and 145 ℃ and the pressure is between 1.0barg and 1.5barg.
Preferably, the liquid formed after the reaction in the step S1 is mixed with hydrochloric acid to obtain a mixed liquid, which is heated, preferably to 140 to 170 ℃, preferably 145 to 155 ℃, and then the mixture is subjected to the second reaction step S2. In one embodiment of the invention, the heating uses a preheater. In one embodiment of the invention, the mixed liquor is heated using a preheater with an outlet temperature of 140 ℃ to 170 ℃, preferably 145 ℃ to 155 ℃.
In a more preferred embodiment of the present invention, the methyl chloride synthesis method includes a step S3 of washing the mixed gas obtained in the second-stage reaction after the step S2, and the washed gas is subjected to a cooling condensation treatment.
According to the invention, step S3 is carried out in a washing apparatus at a temperature of between 80 ℃ and 130 ℃ and at a pressure of between 0.5barg and 2barg, preferably at a temperature of between 105 ℃ and 120 ℃ and at a pressure of between 0.8barg and 1.3barg. In some embodiments of the invention, the temperature at the top of the washing apparatus is controlled between 100 and 120 ℃, preferably between 105 and 115 ℃.
According to the invention, the washing liquid used in the step S3 is preferably alcoholic acid separated by subsequent cooling and condensation treatment.
According to the present invention, it is preferable that the washing liquid used in the step S3 is returned to the reaction in the step S2 after washing the mixed gas generated in the step S2, or returned to the reaction in the step S2 and the reaction in the step S1, to further promote the use of hydrogen chloride in the returned washing liquid.
According to the invention, the temperature-reducing condensation treatment is to separate methyl chloride gas and alcohol acid. The temperature reduction condensation treatment is carried out at a temperature of 40 ℃ to 90 ℃ and a pressure of 0.5barg to 2barg, preferably at a temperature of 50 ℃ to 75 ℃ and a pressure of 0.6barg to 1.0barg. In a preferred embodiment of the invention, the temperature-reducing condensation treatment of the methyl chloride synthesis gas is carried out by using a falling film absorber and a condensation buffer device which are connected in sequence, wherein the feeding temperature of the condensation buffer device is controlled between 30 and 80 ℃, and preferably between 45 and 65 ℃.
According to the invention, the separated chloromethane gas enters a subsequent process.
In one embodiment of the present invention, a part or all of the separated alcoholic acid is returned to the step S3 and used as a washing liquid.
In one embodiment of the invention, part or all of the separated alcoholic acid is returned to the falling film absorber for use as absorbent. And (4) recycling hydrogen chloride in the mixed gas washed in the step (S3) again through the falling film absorber, further reducing the loss of the hydrogen chloride, cooling the mixed gas, and condensing and separating water and methanol in the mixed gas.
The invention also provides a chloromethane synthesis device for the chloromethane synthesis method, which comprises a chloromethane reaction kettle, a two-stage reaction tower, a reaction circulating pump and a cooling and condensing device.
The second-stage reaction tower is positioned on the upper part of the methyl chloride reaction kettle, the top of the second-stage reaction tower is provided with a gas outlet, and the gas outlet is connected with a cooling and condensing device through a pipeline. And the reaction circulating pump is connected with the bottom of the methyl chloride reaction kettle and the upper part of the second-stage reaction tower. The bottom of the chloromethane reaction kettle is connected with a connecting pipeline of the reaction circulating pump, and a hydrochloric acid conveying pipeline is connected in front of the reaction circulating pump.
According to the invention, the methyl chloride synthesis device also comprises a preheating device. The preheating device is positioned on a connecting pipeline of the reaction circulating pump and the second-stage reaction tower.
According to the invention, the methyl chloride synthesis plant also comprises a washing tower. And the washing tower is positioned on a connecting pipeline between the air outlet of the two-section reaction tower and the cooling and condensing device. The gas outlet of the second-stage reaction tower is connected with the bottom of the washing tower through a pipeline; and the top of the washing tower is provided with an air outlet, and the air outlet is connected with a cooling and condensing device through a pipeline.
According to the invention, the temperature-reducing condensing device comprises a falling film absorber and a condensation buffer tank which are connected in sequence. The feed port end of the falling film absorber is connected with the gas outlet of the second-stage reaction tower or the gas outlet of the washing tower, and the discharge port end of the falling film absorber is connected with the condensation buffer tank. And a gas outlet is arranged at the top of the condensation buffer tank and used for discharging the chloromethane gas.
According to the invention, the methyl chloride synthesis plant further comprises a condensate transfer pump. The condensate transfer pump is connected to the outlet of the condensation buffer tank through a pipeline. In one embodiment of the invention, three lines are connected from the outlet of the condensate transfer pump, one line is connected to the upper part of the washing column, one line is connected to the feed inlet end of the falling film evaporator, and one line is connected to the wastewater treatment system.
According to the present invention, the two-stage reaction column, the washing column may employ any type of column known in the art, such as a sieve plate column, a packed column, a float valve column, a bubble column, and the like. The preheater, falling film absorber and condensation buffer tank may be selected from any type of equipment known in the art with corresponding functions and functions.
Interpretation of terms:
barg: is called Bar gauge, g represents gauge.
Alcohol-containing acid: or alkyd-containing, alcoholic hydrochloric acid, is generally referred to herein as a methanol-containing hydrochloric acid solution.
Compared with the prior art, the invention has the following beneficial effects:
1. the hydrochloric acid is introduced to fully utilize the reaction heat of the reaction of the methanol and the hydrogen chloride, balance the water and the temperature of a reaction system, reduce the temperature of a medium of a circulating pump and create a good working condition for long-time running of the circulating pump;
2. the two-stage reaction is further arranged, so that the utilization efficiency of hydrogen chloride can be effectively improved, and the generation of dimethyl ether is reduced;
3. a washing step is further added, the content of hydrogen chloride in chloromethane obtained after the second-stage reaction is reduced through reverse washing in the washing step, and the utilization efficiency of system chlorine is improved; and the loss of the catalyst can be further reduced by returning the washing liquid to the second-stage reaction step;
4. further recycling the alcohol-containing acid obtained after condensation, sending part of the alcohol-containing acid back to the washing tower, and sending part of the alcohol-containing acid back to the falling film absorber, so that the concentration of chloride ions in the alcohol-containing acid is further reduced, and the loss of the chloride ions is reduced to the maximum extent.
Drawings
FIG. 1: a process flow diagram of a preferred embodiment of the invention, wherein:
1. a chloromethane reaction kettle, 2, a second-stage reaction tower, 3, a washing tower, 4, a preheater, 5, a falling film absorber, 6, a condensation buffer tank, 7, a reaction circulating pump and 8, a condensate transfer pump; a: methanol, B: hydrogen chloride gas, C: hydrochloric acid, D: methyl chloride, F: an alcohol-containing acid; e-1: an alcohol-containing acid; e-2: contains alcohol acid.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application are clearly and completely described below, and it is obvious that the described embodiments are a part of the embodiments of the present application, but not all of the embodiments. The embodiments based on the present application also belong to the protection scope of the present application.
And mixing the hydrogen chloride gas B with the methanol A, and feeding the mixture into a methyl chloride reaction kettle 1 to perform methyl chloride primary reaction in the step S1. The top of the methyl chloride reaction kettle 1 is connected with the second-stage reaction tower 2, and the mixed gas obtained by the reaction in the step S1 enters the second-stage reaction tower 2 through the top of the methyl chloride reaction kettle 1. The hydrochloric acid C is mixed with liquid discharged from the bottom of the methyl chloride reaction kettle 1, the mixed liquid is conveyed to a preheater 4 through a reaction circulating pump 7 to be heated, and then the heated mixed liquid enters a second-stage reaction tower 2, mixed gas which enters the second-stage reaction tower 2 and comes from the top of the methyl chloride reaction kettle 1 is subjected to reverse washing, and a second-stage reaction is simultaneously carried out, wherein the step is S2. And (3) the mixed gas obtained after the second-stage reaction enters a washing tower 3 through a gas outlet at the top of the second-stage reaction tower 2 to be washed again, wherein the washing is the S3 washing step. The chloromethane gas washed by the washing tower 3 enters a falling film absorber 5 for temperature reduction and condensation, and then enters a condensation buffer tank 6 for gas-liquid separation. The separated gaseous chloromethane D enters a subsequent process; discharging from the bottom of the condensation buffer tank 6 to obtain alcohol acid, and conveying the alcohol acid by a condensate conveying pump 8, wherein one stream of alcohol acid E-1 enters a falling film absorber 5 to be reused as absorption liquid; a strand of alcohol acid E-2 enters the washing tower 3 from the upper part of the washing tower 3 and is reused as washing liquid for washing chloromethane gas in the step S3; a stream containing alkyd F was discharged from the system.
Example 1 was carried out:
mixing hydrogen chloride gas B with methanol A at 2.4t/h at 2.6t/h, continuously adding the mixture into a methyl chloride reaction kettle 1 for reaction, controlling the temperature of the reaction kettle at 145-150 ℃, controlling the pressure at 1.2-1.4 barg, and controlling 15% liquid hydrochloric acid C1.0t/h at 40 ℃ to be mixed with solution 2.0t/h discharged from the kettle bottom of the methyl chloride reaction kettle 1, controlling the temperature at 82-87 ℃, conveying the mixture into a preheater 4 through a reaction circulating pump 7, heating the mixture to 150 ℃, then feeding the mixture into a second-stage reaction tower 2, reversely washing outlet gas from the kettle top of the methyl chloride reaction kettle 1 and entering the second-stage reaction tower 2, and controlling the temperature of the second-stage reaction tower at 135-140 ℃; the washed methyl chloride gas enters a washing tower 3 for washing again, the outlet temperature at the top of the washing tower 3 is controlled at 110-115 ℃, the pressure is 0.8-0.9 barg, the methyl chloride gas washed by the washing tower 3 enters a falling film absorber 5 for cooling to 55-60 ℃, the methyl chloride gas enters a condensation buffer tank 6 for gas-liquid separation, and the separated methyl chloride D enters a subsequent process; discharging from the bottom of the condensation buffer tank 6 to obtain alcohol acid, and conveying the alcohol acid by a condensate conveying pump 8, wherein one stream of alcohol acid E-1 enters a falling film absorber 5; a strand of alcohol acid-containing acid E-2 enters the washing tower 3 from the upper part of the washing tower 3 and is used as washing liquid for washing chloromethane gas; a stream of alkyd-containing F was discharged from the system at 2.15 t/h.
The content of dimethyl ether in the chloromethane at the outlet of the condensation buffer tank 6 is below 100ppm through detection and analysis, and hydrogen chloride is not detected; in the alcohol-containing acid F discharged from the bottom of the condensation buffer tank 6, the concentration of the acid is below 1%; the conversion rate of the methanol and the hydrogen chloride reaches more than 98 percent.
Example 2 was carried out:
mixing hydrogen chloride gas B with methanol A at 5.0t/h at 5.6t/h, continuously adding the mixture into a methyl chloride reaction kettle 1 for reaction, controlling the temperature of the reaction kettle at 145-150 ℃, controlling the pressure at 1.2-1.4 barg, mixing 15% liquid hydrochloric acid C at 0.8t/h at 40 ℃ with solution discharged from the bottom of the methyl chloride reaction kettle 1 at 1.6t/h, controlling the temperature at 82-87 ℃, conveying the mixture into a preheater 4 through a reaction circulating pump 7, heating the mixture to 150 ℃, then feeding the mixture into a second-stage reaction tower 2, controlling the temperature of the second-stage reaction tower at 135-140 ℃, and reversely washing outlet gas from the top of the methyl chloride reaction kettle 1, which enters the second-stage reaction tower 2; the washed methyl chloride gas enters a washing tower 3 for washing again, the outlet temperature at the top of the washing tower 3 is controlled at 110-115 ℃, the pressure is 0.8-0.9 barg, the methyl chloride gas washed by the washing tower 3 enters a falling film absorber 5 for cooling to 55-60 ℃, the methyl chloride gas enters a condensation buffer tank 6 for gas-liquid separation, and the separated methyl chloride D enters a subsequent process; and discharging the alcohol acid from the bottom of the condensation buffer tank 6, conveying the alcohol acid by a condensate conveying pump 8, wherein one stream of alcohol acid E-1 enters a falling film absorber 5, one stream of alcohol acid E-2 enters a washing tower 3, and the other stream of alcohol acid F is discharged from the system at the speed of 3.5 t/h.
The content of dimethyl ether in the chloromethane at the outlet of the condensation buffer tank 6 is below 100ppm through detection and analysis, and hydrogen chloride is not detected; the concentration of the acid in the alcoholic acid F discharged from the bottom of the condensation buffer tank 6 is below 1%; the conversion rate of the methanol and the hydrogen chloride reaches more than 98 percent.
Claims (10)
1. A methyl chloride synthesis method is characterized in that: mixing methanol and hydrogen chloride gas, carrying out methyl chloride synthesis reaction under the action of a catalyst, adding hydrochloric acid in the reaction, and carrying out subsequent cooling and condensation treatment on the generated mixed gas;
preferably, the methanol is in excess compared to the hydrogen chloride gas;
preferably, the concentration of the hydrochloric acid is 0.1-31%, the temperature is 0-60 ℃, and preferably, the concentration of the hydrochloric acid is 5-15%, and the temperature is 10-40 ℃.
2. The methyl chloride synthesis process according to claim 1, characterized in that: the hydrochloric acid is added when the methanol reacts with the hydrogen chloride gas;
or adding the hydrochloric acid into the liquid formed after the methanol and the hydrogen chloride gas react, and reacting the mixed liquid of the hydrochloric acid and the liquid with the mixed gas generated by the reaction of the methanol and the hydrogen chloride gas; preferably, the volume ratio of the liquid to the hydrochloric acid is 10; preferably 3.
3. The methyl chloride synthesis process according to claim 1 or 2, characterized by comprising:
s1, methyl chloride first-stage reaction: mixing methanol and hydrogen chloride gas, carrying out a first-stage reaction under the action of a catalyst, and feeding mixed gas formed after the reaction into a second-stage reaction step;
s2, a chloromethane two-stage reaction step: mixing the liquid formed after the reaction in the step S1 with hydrochloric acid, feeding the obtained mixed liquid into a second-stage reaction step, washing the mixed gas formed after the reaction in the step S1, simultaneously carrying out a second-stage reaction, and carrying out subsequent cooling and condensation treatment on the mixed gas obtained in the second-stage reaction;
preferably, the methanol in step S1 is in excess with respect to the hydrogen chloride;
preferably, in the step S1, the temperature of the first-stage reaction is 130-170 ℃, the pressure is 0.5-2 barg, preferably, the temperature is 140-160 ℃, and the pressure is 1.0-1.5 barg;
preferably, in the step S2, the concentration of the hydrochloric acid is 0.1-31%, the temperature is 0-60 ℃, and preferably, the concentration of the hydrochloric acid is 5-15%, and the temperature is 10-40 ℃;
preferably, in the step S2, the flow ratio of the liquid formed after the reaction of S1 to the hydrochloric acid is 10; preferably 3;
preferably, in the step S2, the temperature of the second-stage reaction is 100-160 ℃, the pressure is 0.5-2 barg, the preferred temperature is 130-145 ℃, and the pressure is 1.0-1.5 barg;
preferably, after the mixed liquid obtained by mixing the liquid formed after the reaction in the step S1 and hydrochloric acid is heated, the mixed liquid is preferably heated to 140-170 ℃, preferably 145-155 ℃, and then the mixed liquid enters the second-stage reaction step S2; preferably, the mixed liquor is heated by a preheater, the outlet temperature of which is 140 to 170 ℃, preferably 145 to 155 ℃.
4. The methyl chloride synthesis method according to claim 3, wherein after the step S2, the step S3 of washing the mixed gas obtained in the second-stage reaction is carried out, and the washed gas is subjected to cooling condensation treatment;
preferably, step S3 is carried out in a washing apparatus at a temperature of from 80 ℃ to 130 ℃ and a pressure of from 0.5barg to 2barg, preferably at a temperature of from 105 ℃ to 120 ℃ and a pressure of from 0.8barg to 1.3barg;
preferably, the washing liquid used in the step S3 is alcoholic acid obtained by subsequent cooling, condensation and separation;
preferably, the cleaning liquid used in the step S3 is returned to the reaction in the step S2 after the mixed gas generated in the step S2 is cleaned, or returned to the reaction in the step S2 and the reaction in the step S1, to further promote the use of hydrogen chloride in the cleaning liquid.
5. The methyl chloride synthesis process according to any one of claims 1 to 4, wherein the reduced-temperature condensation is a separation of methyl chloride gas and an alkyd-containing acid, the reduced-temperature condensation being carried out at a temperature of from 40 ℃ to 90 ℃ and at a pressure of from 0.5barg to 2barg, preferably at a temperature of from 50 ℃ to 75 ℃ and at a pressure of from 0.6barg to 1.0barg;
preferably, the falling film absorber and the condensation buffer device which are connected in sequence are adopted to finish the cooling and condensation treatment of the methyl chloride synthesis gas;
preferably, part or all of the separated alcoholic acid is returned to the step S3 and used as a washing solution;
preferably, part or all of the separated alcoholic acid is returned to the falling film absorber for use as an absorbent.
6. A methyl chloride synthesis apparatus for use in the methyl chloride synthesis method according to any one of claims 1 to 5, characterized by comprising a methyl chloride reaction vessel, a two-stage reaction tower, a reaction circulation pump and a temperature-lowering condensing device; the second-stage reaction tower is positioned at the upper part of the chloromethane reaction kettle, the top of the second-stage reaction tower is provided with an air outlet, and the air outlet is connected with a cooling and condensing device through a pipeline; the reaction circulating pump is connected with the bottom of the methyl chloride reaction kettle and the upper part of the second-stage reaction tower; the bottom of the chloromethane reaction kettle is connected with a connecting pipeline of the reaction circulating pump, and a hydrochloric acid conveying pipeline is connected in front of the reaction circulating pump.
7. The methyl chloride synthesis plant of claim 6, further comprising a preheating device located in the line connecting the reaction circulation pump and the second stage reaction tower.
8. The methyl chloride synthesis apparatus according to claim 7, further comprising a washing tower, wherein the washing tower is positioned on a connecting pipeline between the outlet of the second-stage reaction tower and the cooling and condensing device, and the outlet of the second-stage reaction tower is connected with the bottom of the washing tower through a pipeline; and the top of the washing tower is provided with an air outlet, and the air outlet is connected with a cooling and condensing device through a pipeline.
9. The methyl chloride synthesis device according to any one of claims 6 to 8, wherein the temperature reduction and condensation device comprises a falling film absorber and a condensation buffer tank which are connected in sequence, a feed port end of the falling film absorber is connected with a gas outlet of the two-stage reaction tower or a gas outlet of the washing tower, a discharge port end of the falling film absorber is connected with the condensation buffer tank, and a gas outlet is arranged at the top of the condensation buffer tank to discharge methyl chloride gas.
10. The methyl chloride synthesis unit of claim 9, further comprising a condensate transfer pump connected by a line to an outlet of the condensate buffer tank;
preferably, three pipelines are connected from the outlet of the condensate conveying pump, one pipeline is connected to the upper part of the washing tower, the other pipeline is connected to the feed port end of the falling film evaporator, and the other pipeline is connected with a wastewater treatment system.
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| CN202211528679.2A CN115850017A (en) | 2022-11-30 | 2022-11-30 | Preparation method and system of efficient chloromethane |
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| CN202211528679.2A CN115850017A (en) | 2022-11-30 | 2022-11-30 | Preparation method and system of efficient chloromethane |
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