CN111606776A - Clean production process for synthesizing methane chloride by liquid-phase catalyst-free synthesis - Google Patents

Clean production process for synthesizing methane chloride by liquid-phase catalyst-free synthesis Download PDF

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CN111606776A
CN111606776A CN201910140102.6A CN201910140102A CN111606776A CN 111606776 A CN111606776 A CN 111606776A CN 201910140102 A CN201910140102 A CN 201910140102A CN 111606776 A CN111606776 A CN 111606776A
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methanol
liquid
chloride
methane
hydrogen chloride
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韩向阳
罗秋生
温少桦
张长香
唐能敏
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Sichuan Chenguang Engineering Design Institute Co ltd
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    • C07ORGANIC CHEMISTRY
    • C07CACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C17/00Preparation of halogenated hydrocarbons
    • C07C17/093Preparation of halogenated hydrocarbons by replacement by halogens
    • C07C17/16Preparation of halogenated hydrocarbons by replacement by halogens of hydroxyl groups
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    • C07ORGANIC CHEMISTRY
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Abstract

The invention discloses a clean production process for synthesizing methane chloride by a liquid-phase catalyst-free method, which belongs to the field of preparation of methane chloride and is characterized by comprising the following steps of: a. introducing gaseous hydrogen chloride or hydrochloric acid mixed with 10-25% of the proportion and gaseous or liquid mixed methanol into a main reactor; b. mixing methyl chloride at the outlet of the main reactor, unreacted hydrogen chloride and excessive methanol mixed gas, and introducing into a post-reactor; c. the synthesized methane chloride mixed gas is collected into a product after non-water washing, freeze dehydration, dimethyl ether removal, pressurization and condensation. The invention adopts non-catalytic liquid phase hydrochlorination to synthesize the monochloro methane, the main reactor and the post reactor can ensure that the conversion rate of the hydrogen chloride is 99 percent, and the monochloro methane mixed gas is collected into a product after non-water washing, freeze dehydration, dimethyl ether removal, pressurization and condensation, does not produce a byproduct of hydrochloric acid, does not consume liquid alkali and a catalyst, has high yield of the monochloro methane, and has the characteristics of economy, cleanness and environmental protection.

Description

Clean production process for synthesizing methane chloride by liquid-phase catalyst-free synthesis
Technical Field
The invention belongs to the field of preparation of methane chloride, and particularly relates to a clean production process for synthesizing methane chloride by using a liquid phase catalyst-free method.
Background
The chloromethane is used for producing chemical products such as organic silicon, methane chloride, methyl cellulose, glufosinate and the like, the production technology is developed for nearly thirty years, the domestic mainstream development process is mainly a liquid phase catalysis method and a gas-solid phase catalysis method, the extensive development gradually turns into the refined development along with the deep development of the economy of China, and the process technology pursues energy conservation, economy, high efficiency and reliability. The mainstream process of hydrochlorination is: the liquid phase catalysis method is adopted by companies such as Dow Chemical, ATOCHEM in France and the like; there are companies such as Deshan, Japan, which use a gas phase catalytic method; only japan shin-Etsu chemical company adopts the liquid phase non-catalytic method. The reactor performance is shown in table 1.
TABLE 1 hydrochlorination Process technical comparison
Figure BDA0001978248560000011
TABLE 1
In the above process, both gas phase and liquid phase methods are used, and unreacted hydrogen chloride and dimethyl ether impurities are generated in the methanol hydrochlorination reaction, so that devices such as water washing, alkali washing, concentrated sulfuric acid drying dehydration and dimethyl ether removal are usually needed when mixed gas is treated, and a large amount of low-concentration hydrochloric acid, alkali-containing waste liquid and about 75-80% of dilute sulfuric acid containing organic impurities are needed to be generated and are difficult to treat.
Therefore, the traditional process for producing the monochloromethane has the problems of long process flow, numerous auxiliary materials, more byproducts or three wastes and the like, the progress of the methanol hydrochlorination technology aims to improve the conversion rate, reduce the impurity content, shorten the process flow, reduce the use of various auxiliary raw materials as far as possible, and reduce the generation of the three wastes, which is the general trend of the current technical development.
The world famous chloromethane producer says that chemical companies and Japanese transcievery chemical companies also report patent technologies, and both skillfully utilize the characteristic that hydrogen chloride, water and methanol can form binary or ternary azeotrope, discharge the moisture of a system through distillation without additionally using auxiliary chemicals such as sulfuric acid drying and the like, and adopt a non-catalytic method or utilize high-concentration 37% hydrochloric acid to inhibit the generation of dimethyl ether, so that the hydrochlorination process is simpler, more convenient and more scientific. (Songlixin, progress in chloromethane production technology, organosilicon materials 2000,14 (3): 7-10). The pressure of the raw material and the system is higher, the raw material and the product are strong corrosive articles, the material selection of equipment and pipelines is higher, the equipment and the pipelines need to adopt tantalum noble metal according to experience, and the equipment investment is huge. Meanwhile, the reactor adopts a combined tower structure, so that the processing and manufacturing difficulty of equipment is high; the control logic is complex; the hydrochloric acid discharged from the first rectifying tower still contains a small amount of methanol, and the generated wastewater contains a small amount of methanol; the methyl chloride coming out of the second absorption tower still contains a large amount of water and a trace amount of hydrogen chloride, and alkali washing is still required to be added in the process. So the industrialization case is not many.
Chinese patent publication No. CN 101429093a, published as 2009, 05, and 13, discloses an energy-saving production method for preparing monochloromethane by a liquid phase method, which comprises using a zinc chloride solution as a catalyst, and reacting hydrogen chloride and methanol in a reactor to generate monochloromethane, and is characterized in that: gas-phase hydrogen chloride or gas-phase hydrogen chloride and part of gas-phase methanol gasified by the methanol gasifier are mixed and enter a reactor, part or all of the methanol directly enters the reactor in a liquid-phase state to participate in the reaction, and the liquid-phase methanol is introduced into the reactor at the temperature of 150 ℃ to 160 ℃.
The energy-saving production method for preparing the methane chloride by the liquid phase method disclosed by the patent document has the advantages of simple process and energy consumption saving, but still needs to add a catalyst, and improves the production cost of enterprises.
Chinese patent documents with publication number CN 1347862 and publication date 2002 of 05 and 08 disclose a production method for synthesizing methane chloride by a gas-solid phase catalysis method, which is characterized in that: in the presence of a high-efficiency active catalyst, the molar ratio is 1: 1.02-1.1, reacting methanol and hydrogen chloride heated to more than 200 ℃ in a reactor at the temperature of 240-300 ℃ under the reaction pressure of 0-0.5 MpaG for 4-6 seconds to generate methane chloride and unconverted anhydrous hydrogen chloride, and washing with water, washing with alkali and drying with sulfuric acid to obtain the methane chloride.
Chinese patent publication No. CN 101134708, published as 2008, 03 and 05, discloses a method for producing high-purity monochloromethane, which comprises the following steps:
1) after being vaporized and heated, the methanol and the hydrogen chloride enter a reactor filled with an alumina catalyst and react in the reactor to generate a mixture of methane chloride, methane, ethyl chloride and dichloromethane; the mol ratio of the hydrogen chloride to the methanol is 1.1-1.2: 1;
2) the mixture generated in the step 1) enters a chiller, enters an acid washing tower, an alkali washing tower and a sulfuric acid drying system after being chilled and separated, and is compressed to prepare crude methane chloride;
3) the crude methane chloride enters a methane chloride refining tower, and heavy components are separated from the bottom of the tower; evaporating light components of methane and methane chloride to the top of the tower together, then cooling by water and deeply cooling, liquefying the methane chloride, and emptying unliquefied methane to an exhaust washing tower through a deep cooler so as to realize the separation of the methane chloride and the methane and obtain the high-purity methane chloride; the recombinant is chloroethane and dichloromethane.
Chinese patent literature with publication number CN 103351274A and publication date of 2013, 10 and 16 discloses a process for synthesizing methane chloride in a gas-liquid phase at low temperature and low pressure, which is characterized in that: the gaseous hydrogen chloride and the liquid methanol are sequentially subjected to synthesis reaction in at least four stages of reaction vessels connected in series to synthesize the methane chloride under the conditions of 60-85 ℃ and the pressure not greater than 0.1 MPa.
The process for synthesizing monochloromethane by low-temperature low-pressure gas-liquid phase disclosed in the patent document has low reaction temperature and pressure and the space-time yield is only 30-50kg/m3H, at least four stages of reaction containers are connected in series, the reaction pressure is low, the post-treatment process still adopts the processes of water washing, alkali washing, acid washing and the like, the process is complex, the yield is low, and the generation of waste acid, waste salt water and waste sulfuric acid is not reduced.
Chinese patent document with publication number CN 102234216A and publication date 2011, 11 and 09 discloses a gas-liquid non-catalytic process for producing methyl chloride, which is characterized in that: the reactor, the stripping tower, the left heat exchanger, the right heat exchanger, the condensing tower, the reflux tank, the condenser, the hydrogen chloride separation tower, the reboiler and the distillation tower are assembled into a whole through connecting pipelines according to the system functions.
The process for producing methyl chloride by the gas-liquid phase non-catalytic method disclosed by the patent document does not need a catalyst, has high methanol conversion rate and high raw material utilization rate, but has large reaction space requirement of reaction equipment and higher requirement on the reaction equipment; and the methanol and the hydrogen chloride after the single-pass reaction need to be separated and then introduced into the reaction equipment again for reaction, so that the process complexity is high.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a clean production process for synthesizing methane chloride by a liquid-phase catalyst-free method, the invention adopts a non-catalytic liquid-phase hydrochlorination method to synthesize the methane chloride, a main reactor and a post reactor are adopted to ensure that the conversion rate of hydrogen chloride is 99 percent, the methane chloride mixed gas is collected into a product after non-water washing, freeze dehydration, dimethyl ether removal, pressurization and condensation, hydrochloric acid byproducts are not produced, liquid alkali and a catalyst are not consumed, the yield of the methane chloride is high, and the method has the characteristics of economy, cleanness and environmental protection and is simple in process.
The invention is realized by the following technical scheme:
a clean production process for synthesizing methane chloride by a liquid-phase catalyst-free method is characterized by comprising the following steps:
a. introducing gaseous hydrogen chloride or hydrochloric acid mixed with 10-25% of the proportion and gaseous or liquid mixed methanol into a main reactor for synthesis reaction;
b. mixing methyl chloride at the outlet of the main reactor, unreacted hydrogen chloride and excessive methanol mixed gas, and introducing the mixture into a post reactor for synthesis reaction;
c. the synthesized methane chloride mixed gas is collected into a product after non-water washing, freeze dehydration, dimethyl ether removal, pressurization and condensation.
In the step a, the molar ratio of the hydrogen chloride to the methanol is 1.005-1.01:1.00, the reaction temperature is 60-140 ℃, the synthesis reaction is carried out under the pressure of 0.05-0.6MPaG, and the conversion rate of the hydrogen chloride is 90-95%.
In the step a, the gaseous hydrogen chloride is a byproduct of phosphorous acid production by hydrolyzing phosphorus trichloride, a byproduct of hydrolyzing methyl chlorosilane or a byproduct of hydrolyzing chlorosilane, and the concentration of hydrochloric acid is 15% -35%.
In the step b, the molar ratio of hydrogen chloride to methanol is 1.00: 1.50-3, the reaction temperature is 60-140 ℃, the synthesis reaction is carried out under the pressure of 0.05-0.6MPaG, and the conversion rate of the hydrogen chloride is 98-100%.
The main reactor and the post reactor are both provided with uniformly distributed gas flow distributors.
In the step c, the non-water washing refers to that the kettle liquid from the post reactor is used for primary washing, the methanol solution in the methanol tail gas absorption tower of the tail gas treatment process system is used for secondary washing, the washing liquid is methanol hydrochloric acid solution, the methanol gas is removed by using a methanol removing tower, and the methanol gas is sent to the reactor for recycling.
In the step c, the freeze dehydration means that the methane chloride mixed gas is washed by liquid methanol, then is subjected to freeze dealcoholization, is demisted by an alcohol foam demister, and is then sent to concentrated sulfuric acid for drying.
The freezing dealcoholization adopts one-stage or two-stage cooling, the refrigerant adopts methane chloride or circulating water for cooling, and the dehydration controls the content of the methanol and water in the methane chloride mixed gas to be 20-100ppm and the temperature to be controlled between minus 10 ℃ and minus 15 ℃.
In the step c, the dimethyl ether removal means that the dimethyl ether, the methanol and the trace water in the mixed gas after the freezing dehydration are removed by adopting concentrated sulfuric acid, the concentration of the concentrated sulfuric acid is 95-98%, and the dimethyl ether content of the mixed gas of methane chloride is controlled to be 5-20 ppm.
The synthesis reaction is a multi-stage reaction, a plurality of main reactors are connected in series or in parallel, and a plurality of post reactors are connected in series or in parallel.
The beneficial effects of the invention are mainly shown in the following aspects:
firstly, introducing gaseous hydrogen chloride or hydrochloric acid mixed with 10-25% of proportion and gaseous or liquid mixed methanol into a main reactor for synthesis reaction; b. mixing methyl chloride at the outlet of the main reactor, unreacted hydrogen chloride and excessive methanol mixed gas, and introducing the mixture into a post reactor for synthesis reaction; c. the synthetic methane chloride mixed gas is collected into a product after non-water washing, freeze dehydration, dimethyl ether removal, pressurization and condensation, the methane chloride is synthesized by adopting non-catalytic liquid phase hydrochlorination, the hydrogen chloride conversion rate can be ensured to be 99% by adopting a main reactor and a post reactor, the product is collected after the methane chloride mixed gas is subjected to non-water washing, freeze dehydration, dimethyl ether removal, pressurization and condensation, hydrochloric acid by-products are not generated, liquid alkali and a catalyst are not consumed, the yield of the methane chloride is high, and the method has the characteristics of economy, cleanness and environmental protection and is simple in process.
Secondly, in the invention, in the step a, the molar ratio of the hydrogen chloride to the methanol is 1.005-1.01:1.00, the reaction temperature is 60-140 ℃, the synthesis reaction is carried out under the pressure of 0.05-0.6MPaG, the conversion rate of the hydrogen chloride is 90-95%, and the conversion rate of the hydrogen chloride can be greatly improved by carrying out the synthesis reaction under the specific conditions, which is shown in Table 3 in the specific implementation mode.
Thirdly, in the invention, in the step b, the molar ratio of the hydrogen chloride to the methanol is 1.00: 1.50-3, the reaction temperature is 60-140 ℃, the synthesis reaction is carried out under the pressure of 0.05-0.6MPaG, the conversion rate of the hydrogen chloride is 98-100%, the synthesis reaction is carried out under the specific condition, and the conversion rate of the hydrogen chloride can be further improved, see Table 4 in the specific embodiment.
In the step c, non-water washing refers to that the kettle liquid from the post reactor is used for primary washing, the methanol solution in a methanol tail gas absorption tower of a tail gas treatment process system is used for secondary washing, the washing liquid is a methanol hydrochloric acid solution, a methanol removing tower is used for removing methanol gas, the methanol gas is sent to the reactor for recycling, and the industrial water or the regenerated waste water is not used for washing the synthesized methyl chloride mixed gas, so that the diluted hydrochloric acid of the conventional process is not generated.
In the step c, the freeze dehydration means that the methane chloride mixed gas is washed by liquid methanol, then is subjected to freeze dealcoholization, is demisted by an alcohol foam demister and then is sent to concentrated sulfuric acid for drying, and a small amount of water is dissolved with the methanol, so that the separation of a large amount of water is realized, and the water enters the methanol solution.
Sixthly, the freezing dealcoholization is cooled by one stage or two stages, a refrigerant is cooled by methane chloride or circulating water, and the dehydration is carried out to control the content of the methanol in the methane chloride mixed gas to be 20-100ppm, the temperature is-10 to-15 ℃, and the content of the methanol in the mixed gas is about 60 ppm; when the temperature is too low, the methanol content is further reduced, but the energy consumption is multiplied; at too high a temperature, the methanol content increases and a good balance can be achieved at this particular temperature condition, see table 5 in the detailed description.
Seventhly, in the invention, in the step c, the dimethyl ether removal means that the dimethyl ether, the methanol and the trace water in the mixture gas after the freeze dehydration are removed by adopting concentrated sulfuric acid, the concentration of the concentrated sulfuric acid is 95% -98%, the dimethyl ether content of the methane chloride mixture gas is controlled to be 5-20ppm, and the concentration of the concentrated sulfuric acid is specifically controlled to be 95% -98%, so that the dimethyl ether content of the methane chloride mixture gas can be effectively reduced, which is shown in table 6 in the specific implementation mode.
Detailed Description
Example 1
A clean production process for synthesizing methane chloride by a liquid-phase catalyst-free method comprises the following steps:
a. introducing gaseous hydrogen chloride or hydrochloric acid mixed with 10% of proportion and gaseous or liquid mixed methanol into a main reactor for synthesis reaction;
b. mixing methyl chloride at the outlet of the main reactor, unreacted hydrogen chloride and excessive methanol mixed gas, and introducing the mixture into a post reactor for synthesis reaction;
c. the synthesized methane chloride mixed gas is collected into a product after non-water washing, freeze dehydration, dimethyl ether removal, pressurization and condensation.
Introducing gaseous hydrogen chloride or hydrochloric acid mixed with 10% of proportion and gaseous or liquid mixed methanol into a main reactor for synthesis reaction; b. mixing methyl chloride at the outlet of the main reactor, unreacted hydrogen chloride and excessive methanol mixed gas, and introducing the mixture into a post reactor for synthesis reaction; c. the synthetic methane chloride mixed gas is collected into a product after non-water washing, freeze dehydration, dimethyl ether removal, pressurization and condensation, the methane chloride is synthesized by adopting non-catalytic liquid phase hydrochlorination, the hydrogen chloride conversion rate can be ensured to be 99% by adopting a main reactor and a post reactor, the product is collected after the methane chloride mixed gas is subjected to non-water washing, freeze dehydration, dimethyl ether removal, pressurization and condensation, hydrochloric acid by-products are not generated, liquid alkali and a catalyst are not consumed, the yield of the methane chloride is high, and the method has the characteristics of economy, cleanness and environmental protection and is simple in process.
Example 2
A clean production process for synthesizing methane chloride by a liquid-phase catalyst-free method comprises the following steps:
a. introducing gaseous hydrogen chloride or hydrochloric acid mixed with 12% of proportion and gaseous or liquid mixed methanol into a main reactor for synthesis reaction;
b. mixing methyl chloride at the outlet of the main reactor, unreacted hydrogen chloride and excessive methanol mixed gas, and introducing the mixture into a post reactor for synthesis reaction;
c. the synthesized methane chloride mixed gas is collected into a product after non-water washing, freeze dehydration, dimethyl ether removal, pressurization and condensation.
Further, in the step a, the molar ratio of hydrogen chloride to methanol is 1.005:1.00, the reaction temperature is 60 ℃, the synthesis reaction is carried out under the pressure of 0.05MPaG, and the conversion rate of the hydrogen chloride is 90%.
In the step a, gaseous hydrogen chloride is a byproduct in the production of phosphorous acid by hydrolyzing phosphorus trichloride, and the concentration of hydrochloric acid is 15%.
Furthermore, in the step b, the molar ratio of the hydrogen chloride to the methanol is 1.00: 1.50, the reaction temperature is 60 ℃, the synthesis reaction is carried out under the pressure of 0.05MPaG, and the conversion rate of the hydrogen chloride is 98 percent.
Example 3
A clean production process for synthesizing methane chloride by a liquid-phase catalyst-free method comprises the following steps:
a. introducing gaseous hydrogen chloride or hydrochloric acid mixed with 15% of proportion and gaseous or liquid mixed methanol into a main reactor for synthesis reaction;
b. mixing methyl chloride at the outlet of the main reactor, unreacted hydrogen chloride and excessive methanol mixed gas, and introducing the mixture into a post reactor for synthesis reaction;
c. the synthesized methane chloride mixed gas is collected into a product after non-water washing, freeze dehydration, dimethyl ether removal, pressurization and condensation.
Further, in the step a, the molar ratio of hydrogen chloride to methanol is 1.008:1.00, the reaction temperature is 80 ℃, the synthesis reaction is carried out under the pressure of 0.09MPaG, and the conversion rate of the hydrogen chloride is 92%.
In the step a, gaseous hydrogen chloride is a byproduct of methyl chlorosilane hydrolysis, and the concentration of hydrochloric acid is 18%.
Furthermore, in the step b, the molar ratio of the hydrogen chloride to the methanol is 1.00: 1.80 at a reaction temperature of 80 ℃ under a pressure of 0.09MPaG, and the conversion rate of hydrogen chloride is 99 percent.
Example 4
A clean production process for synthesizing methane chloride by a liquid-phase catalyst-free method comprises the following steps:
a. introducing gaseous hydrogen chloride or hydrochloric acid mixed with 18% of proportion and gaseous or liquid mixed methanol into a main reactor for synthesis reaction;
b. mixing methyl chloride at the outlet of the main reactor, unreacted hydrogen chloride and excessive methanol mixed gas, and introducing the mixture into a post reactor for synthesis reaction;
c. the synthesized methane chloride mixed gas is collected into a product after non-water washing, freeze dehydration, dimethyl ether removal, pressurization and condensation.
Further, in the step a, the molar ratio of hydrogen chloride to methanol is 1.01:1.00, the reaction temperature is 120 ℃, the synthesis reaction is carried out under the pressure of 0.2MPaG, and the conversion rate of the hydrogen chloride is 93%.
In the step a, gaseous hydrogen chloride is a byproduct of chlorosilane hydrolysis, and the concentration of hydrochloric acid is 25%.
Furthermore, in the step b, the molar ratio of the hydrogen chloride to the methanol is 1.00: 2, the reaction temperature is 100 ℃, the synthesis reaction is carried out under the pressure of 0.2MPaG, and the conversion rate of the hydrogen chloride is 100 percent.
Example 5
A clean production process for synthesizing methane chloride by a liquid-phase catalyst-free method comprises the following steps:
a. introducing gaseous hydrogen chloride or hydrochloric acid mixed with 25% of proportion and gaseous or liquid mixed methanol into a main reactor for synthesis reaction;
b. mixing methyl chloride at the outlet of the main reactor, unreacted hydrogen chloride and excessive methanol mixed gas, and introducing the mixture into a post reactor for synthesis reaction;
c. the synthesized methane chloride mixed gas is collected into a product after non-water washing, freeze dehydration, dimethyl ether removal, pressurization and condensation.
Further, in the step a, the molar ratio of hydrogen chloride to methanol is 1.01:1.00, the reaction temperature is 140 ℃, the synthesis reaction is carried out under the pressure of 0.6MPaG, and the conversion rate of the hydrogen chloride is 95%.
In the step a, gaseous hydrogen chloride is a byproduct of chlorosilane hydrolysis, and the concentration of hydrochloric acid is 35%.
Furthermore, in the step b, the molar ratio of the hydrogen chloride to the methanol is 1.00: 3, the reaction temperature is 140 ℃, the synthesis reaction is carried out under the pressure of 0.6MPaG, and the conversion rate of the hydrogen chloride is 100 percent.
Example 6
A clean production process for synthesizing methane chloride by a liquid-phase catalyst-free method comprises the following steps:
a. introducing gaseous hydrogen chloride or hydrochloric acid mixed with 25% of proportion and gaseous or liquid mixed methanol into a main reactor for synthesis reaction;
b. mixing methyl chloride at the outlet of the main reactor, unreacted hydrogen chloride and excessive methanol mixed gas, and introducing the mixture into a post reactor for synthesis reaction;
c. the synthesized methane chloride mixed gas is collected into a product after non-water washing, freeze dehydration, dimethyl ether removal, pressurization and condensation.
Further, in the step a, the molar ratio of hydrogen chloride to methanol is 1.01:1.00, the reaction temperature is 140 ℃, the synthesis reaction is carried out under the pressure of 0.6MPaG, and the conversion rate of the hydrogen chloride is 95%.
In the step a, gaseous hydrogen chloride is a byproduct of chlorosilane hydrolysis, and the concentration of hydrochloric acid is 35%.
Furthermore, in the step b, the molar ratio of the hydrogen chloride to the methanol is 1.00: 3, the reaction temperature is 140 ℃, the synthesis reaction is carried out under the pressure of 0.6MPaG, and the conversion rate of the hydrogen chloride is 100 percent.
The main reactor and the post reactor are both provided with uniformly distributed gas flow distributors.
In the step c, the non-water washing refers to that the kettle liquid from the post reactor is used for primary washing, the methanol solution in the methanol tail gas absorption tower of the tail gas treatment process system is used for secondary washing, the washing liquid is methanol hydrochloric acid solution, the methanol gas is removed by using a methanol removing tower, and the methanol gas is sent to the reactor for recycling.
In the step c, the freeze dehydration means that the methane chloride mixed gas is washed by liquid methanol, then is subjected to freeze dealcoholization, is demisted by an alcohol foam demister, and is then sent to concentrated sulfuric acid for drying.
The freezing dealcoholization adopts one-stage or two-stage cooling, the refrigerant adopts methane chloride or circulating water for cooling, and the dehydration controls the content of the methanol in the methane chloride mixed gas to be 20ppm and the temperature to be-10 ℃.
In the step c, the dimethyl ether removal means that the dimethyl ether, the methanol and the trace water in the mixed gas after the freezing dehydration are removed by adopting concentrated sulfuric acid, wherein the concentration of the concentrated sulfuric acid is 95 percent, and the dimethyl ether content of the mixed gas of methane chloride is controlled to be 5 ppm.
In the step c, the non-water washing refers to that the kettle liquid from the post reactor is used for carrying out primary washing, the methanol solution of a methanol tail gas absorption tower of a tail gas treatment process system is used for carrying out secondary washing, the washing liquid is methanol hydrochloric acid solution, then a methanol removing tower is used for removing methanol gas, the methanol gas is sent to the reactor for recycling, and as industrial water or regenerated waste water is not used for washing the synthesized methyl chloride mixed gas, the diluted hydrochloric acid of the conventional process is not generated.
Example 7
A clean production process for synthesizing methane chloride by a liquid-phase catalyst-free method comprises the following steps:
a. introducing gaseous hydrogen chloride or hydrochloric acid mixed with 25% of proportion and gaseous or liquid mixed methanol into a main reactor for synthesis reaction;
b. mixing methyl chloride at the outlet of the main reactor, unreacted hydrogen chloride and excessive methanol mixed gas, and introducing the mixture into a post reactor for synthesis reaction;
c. the synthesized methane chloride mixed gas is collected into a product after non-water washing, freeze dehydration, dimethyl ether removal, pressurization and condensation.
Further, in the step a, the molar ratio of hydrogen chloride to methanol is 1.01:1.00, the reaction temperature is 140 ℃, the synthesis reaction is carried out under the pressure of 0.6MPaG, and the conversion rate of the hydrogen chloride is 95%.
In the step a, gaseous hydrogen chloride is a byproduct of chlorosilane hydrolysis, and the concentration of hydrochloric acid is 35%.
Furthermore, in the step b, the molar ratio of the hydrogen chloride to the methanol is 1.00: 3, the reaction temperature is 140 ℃, the synthesis reaction is carried out under the pressure of 0.6MPaG, and the conversion rate of the hydrogen chloride is 100 percent.
The main reactor and the post reactor are both provided with uniformly distributed gas flow distributors.
In the step c, the non-water washing refers to that the kettle liquid from the post reactor is used for primary washing, the methanol solution in the methanol tail gas absorption tower of the tail gas treatment process system is used for secondary washing, the washing liquid is methanol hydrochloric acid solution, the methanol gas is removed by using a methanol removing tower, and the methanol gas is sent to the reactor for recycling.
In the step c, the freeze dehydration means that the methane chloride mixed gas is washed by liquid methanol, then is subjected to freeze dealcoholization, is demisted by an alcohol foam demister, and is then sent to concentrated sulfuric acid for drying.
The freezing dealcoholization adopts one-stage or two-stage cooling, the refrigerant adopts methane chloride or circulating water for cooling, and the dehydration controls the content of the methanol in the methane chloride mixed gas to be 80ppm and the temperature to be-13 ℃.
In the step c, the dimethyl ether removal means that the dimethyl ether, the methanol and the trace water in the mixed gas after the freeze dehydration are removed by adopting concentrated sulfuric acid, wherein the concentration of the concentrated sulfuric acid is 97 percent, and the dimethyl ether content of the mixed gas of methane chloride is controlled to be 15 ppm.
The synthesis reaction is a multi-stage reaction, a plurality of main reactors are connected in series, and a plurality of post reactors are connected in series.
Example 8
A clean production process for synthesizing methane chloride by a liquid-phase catalyst-free method comprises the following steps:
a. introducing gaseous hydrogen chloride or hydrochloric acid mixed with 25% of proportion and gaseous or liquid mixed methanol into a main reactor for synthesis reaction;
b. mixing methyl chloride at the outlet of the main reactor, unreacted hydrogen chloride and excessive methanol mixed gas, and introducing the mixture into a post reactor for synthesis reaction;
c. the synthesized methane chloride mixed gas is collected into a product after non-water washing, freeze dehydration, dimethyl ether removal, pressurization and condensation.
Further, in the step a, the molar ratio of hydrogen chloride to methanol is 1.01:1.00, the reaction temperature is 140 ℃, the synthesis reaction is carried out under the pressure of 0.6MPaG, and the conversion rate of the hydrogen chloride is 95%.
In the step a, gaseous hydrogen chloride is a byproduct of chlorosilane hydrolysis, and the concentration of hydrochloric acid is 35%.
Furthermore, in the step b, the molar ratio of the hydrogen chloride to the methanol is 1.00: 3, the reaction temperature is 140 ℃, the synthesis reaction is carried out under the pressure of 0.6MPaG, and the conversion rate of the hydrogen chloride is 100 percent.
The main reactor and the post reactor are both provided with uniformly distributed gas flow distributors.
In the step c, the non-water washing refers to that the kettle liquid from the post reactor is used for primary washing, the methanol solution in the methanol tail gas absorption tower of the tail gas treatment process system is used for secondary washing, the washing liquid is methanol hydrochloric acid solution, the methanol gas is removed by using a methanol removing tower, and the methanol gas is sent to the reactor for recycling.
In the step c, the freeze dehydration means that the methane chloride mixed gas is washed by liquid methanol, then is subjected to freeze dealcoholization, is demisted by an alcohol foam demister, and is then sent to concentrated sulfuric acid for drying.
The freezing dealcoholization adopts one-stage or two-stage cooling, the refrigerant adopts methane chloride or circulating water for cooling, the dehydration controls the content of the methanol in the methane chloride mixed gas to be 100ppm, and the temperature is controlled to be-15 ℃.
In the step c, the dimethyl ether removal means that the dimethyl ether, the methanol and the trace water in the mixed gas after the freezing dehydration are removed by adopting concentrated sulfuric acid, wherein the concentration of the concentrated sulfuric acid is 98 percent, and the dimethyl ether content of the mixed gas of methane chloride is controlled to be 20 ppm.
The synthesis reaction is a multi-stage reaction, a plurality of main reactors are connected in parallel, and a plurality of post reactors are connected in parallel.
In the step c, the freeze dehydration means that the methane chloride mixed gas is washed by liquid methanol, then is subjected to freeze dealcoholization, is demisted by an alcohol foam demister and then is sent to concentrated sulfuric acid for drying, and a small amount of water is dissolved with the methanol, so that the separation of a large amount of water is realized, and the water enters the methanol solution.
The specific process of the invention is as follows:
mixing gaseous hydrogen chloride and methanol from a dealcoholization tower and a methanol tail gas absorption tower in a mixer in proportion, then entering a main reactor, fully and uniformly contacting in a reaction container, and carrying out bubbling reaction to obtain gaseous methyl chloride and unreacted hydrogen chloride; the mixed gas and newly supplemented methanol are mixed in the mixer according to the proportion again and then enter the post-reactor, and unreacted gaseous hydrogen chloride carried in the gaseous methyl chloride is subjected to hydrochlorination reaction with the methanol again; removing the monochloro methane mixture of unreacted gaseous hydrogen chloride, water mist and methanol gas, circularly washing the reactor liquid in the post reactor, and ensuring the unreacted gaseous hydrogen chloride to be circulated back to the reaction kettle again: the mixed gas is washed by methanol from a MEVA tower, a small amount of hydrogen chloride is ensured to be dissolved in methanol water bath liquid, the methane chloride mixed gas containing a large amount of methanol and water is removed, freezing cooling dehydration (alcohol) is adopted, and an alcohol foam demister is used for removing alcohol mist or water mist, so that the mixed gas only contains methane chloride, a small amount of dimethyl alcohol and ultra-low-content water.
The mixed gas is contacted with concentrated sulfuric acid to remove dimethyl ether and ultra-low content water, and high-purity liquid methane chloride with the purity of more than or equal to 99.99 percent is obtained after compression and condensation.
Methanol is removed by a methanol removing tower in a methanol washing tower and a methanol hydrochloric acid solution generated by freeze dehydration, and methanol steam is directly recycled; 93-95% of dilute sulfuric acid discharged from the dimethyl ether drying tower is removed, trace organic matters are contained, the organic matters are stripped by a sulfuric acid stripping tower, the organic matters are rectified and recycled by an organic matter fractionating tower, and the wastewater is discharged; the sulfuric acid discharged from the sulfuric acid stripping tower is concentrated to 95-98% by a sulfuric acid concentrator for recycling.
The following table 2 shows the raw material consumption, the amount of three wastes and the steam power consumption of the synthesis of methane chloride according to the present invention.
Figure BDA0001978248560000101
Figure BDA0001978248560000111
TABLE 2
Further explanation can be found in table 2: the invention adopts equimolar feeding of hydrogen chloride and methanol, and the methanol system is used in a closed manner, so that the conversion rate of the hydrogen chloride can be effectively improved, the method of recycling the hydrogen chloride in the conventional process is eliminated, and the non-aqueous solution replaces industrial water washing, so that the liquid alkali, the sulfuric acid drying and other dehydration and the like are avoided, the auxiliary chemical consumption and the steam consumption of hydrochloric acid desorption are increased, and the hydrochlorination process is simpler, more convenient, more economic, more environment-friendly and cleaner. The process has much lower raw material consumption, three wastes, steam and other power consumption than other common gas-solid phase process or liquid phase catalytic method, and much lower dimethyl ether content than other processes, and has obvious technical advantages.
Table 3 below shows the effect of different temperature/molar concentrations of the first-order reaction on the invention, with the concentration of methyl chloride content excluding water vapor.
Figure BDA0001978248560000112
Figure BDA0001978248560000121
TABLE 3
Table 4 below shows the effect of different temperature/molar concentrations of the second order reaction on the invention, in which water vapor is excluded from the concentration of methyl chloride content.
Figure BDA0001978248560000122
TABLE 4
Table 5 below shows the effect of the freeze dealcoholation temperature on the water/alcohol content, the data below being measured at a pressure of 450 kPaG.
Temperature of Methanol content ppm in the gas phase Gas phase H2O content ppm
40℃ 3600 112
-15℃ 60 ≦30
-30℃ 0.883 ≦1
TABLE 5
Table 6 below shows the effect of concentrated sulfuric acid concentration on dimethyl ether, and the data below were measured while ensuring the same amount of concentrated sulfuric acid sprayed.
Figure BDA0001978248560000123
Figure BDA0001978248560000131
Table 6.

Claims (10)

1. A clean production process for synthesizing methane chloride by a liquid-phase catalyst-free method is characterized by comprising the following steps:
a. introducing gaseous hydrogen chloride or hydrochloric acid mixed with 10-25% of the proportion and gaseous or liquid mixed methanol into a main reactor for synthesis reaction;
b. mixing methyl chloride at the outlet of the main reactor, unreacted hydrogen chloride and excessive methanol mixed gas, and introducing the mixture into a post reactor for synthesis reaction;
c. the synthesized methane chloride mixed gas is collected into a product after non-water washing, freeze dehydration, dimethyl ether removal, pressurization and condensation.
2. The clean production process for liquid-phase catalyst-free synthesis of methane chloride according to claim 1, characterized in that: in the step a, the molar ratio of the hydrogen chloride to the methanol is 1.005-1.01:1.00, the reaction temperature is 60-140 ℃, the synthesis reaction is carried out under the pressure of 0.05-0.6MPaG, and the conversion rate of the hydrogen chloride is 90-95%.
3. The clean production process for liquid-phase catalyst-free synthesis of methane chloride according to claim 1, characterized in that: in the step a, the gaseous hydrogen chloride is a byproduct of phosphorous acid production by hydrolyzing phosphorus trichloride, a byproduct of hydrolyzing methyl chlorosilane or a byproduct of hydrolyzing chlorosilane, and the concentration of hydrochloric acid is 15% -35%.
4. The clean production process for liquid-phase catalyst-free synthesis of methane chloride according to claim 1, characterized in that: in the step b, the molar ratio of hydrogen chloride to methanol is 1.00: 1.50-3, the reaction temperature is 60-140 ℃, the synthesis reaction is carried out under the pressure of 0.05-0.6MPaG, and the conversion rate of the hydrogen chloride is 98-100%.
5. The clean production process for liquid-phase catalyst-free synthesis of methane chloride according to claim 1, characterized in that: the main reactor and the post reactor are both provided with uniformly distributed gas flow distributors.
6. The clean production process for liquid-phase catalyst-free synthesis of methane chloride according to claim 1, characterized in that: in the step c, the non-water washing refers to that the kettle liquid from the post reactor is used for primary washing, the methanol solution in the methanol tail gas absorption tower of the tail gas treatment process system is used for secondary washing, the washing liquid is methanol hydrochloric acid solution, the methanol gas is removed by using a methanol removing tower, and the methanol gas is sent to the reactor for recycling.
7. The clean production process for liquid-phase catalyst-free synthesis of methane chloride according to claim 1, characterized in that: in the step c, the freeze dehydration means that the methane chloride mixed gas is washed by liquid methanol, then is subjected to freeze dealcoholization, is demisted by an alcohol foam demister, and is then sent to concentrated sulfuric acid for drying.
8. The clean production process for liquid-phase catalyst-free synthesis of methane chloride according to claim 7, characterized in that: the freezing dealcoholization adopts one-stage or two-stage cooling, the refrigerant adopts methane chloride or circulating water for cooling, and the dehydration controls the content of the methanol and water in the methane chloride mixed gas to be 20-100ppm and the temperature to be controlled between minus 10 ℃ and minus 15 ℃.
9. The clean production process for liquid-phase catalyst-free synthesis of methane chloride according to claim 1, characterized in that: in the step c, the dimethyl ether removal means that the dimethyl ether, the methanol and the trace water in the mixed gas after the freezing dehydration are removed by adopting concentrated sulfuric acid, the concentration of the concentrated sulfuric acid is 95-98%, and the dimethyl ether content of the mixed gas of methane chloride is controlled to be 5-20 ppm.
10. The clean production process for liquid-phase catalyst-free synthesis of methane chloride according to claim 1, characterized in that: the synthesis reaction is a multi-stage reaction, a plurality of main reactors are connected in series or in parallel, and a plurality of post reactors are connected in series or in parallel.
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