CN113816823A - Process for synthesizing chloroethylene by using mercury-free catalyst - Google Patents
Process for synthesizing chloroethylene by using mercury-free catalyst Download PDFInfo
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Abstract
The invention discloses a process for synthesizing chloroethylene by using a mercury-free catalyst, which belongs to the technical field of chemical synthesis and comprises the steps of raw material dehydration, hydrogen separation, conversion, gas-liquid separation and post-treatment; dehydrating the raw material, namely introducing the hydrogen chloride gas into a sulfuric acid drying tower to be washed, dried and dehydrated to obtain dehydrated dry hydrogen chloride gas; the hydrogen separation step is to introduce the dehydrated dry hydrogen chloride gas into a pressure swing adsorption device and separate redundant hydrogen and hydrogen chloride to obtain the dry hydrogen chloride after the hydrogen separation; the process of the invention can thoroughly realize mercury-free reaction, so that hydrogen chloride and excessive acetylene completely react, a traditional purification system of tail gas washing, alkali washing and the like is eliminated, a series of problems caused by high water content in the process of preparing chloroethylene by using an acetylene method are solved, the service life of the mercury-free catalyst is prolonged, and the yield and the purity of chloroethylene are improved.
Description
Technical Field
The invention relates to the technical field of chemical synthesis, in particular to a process for synthesizing chloroethylene by using a mercury-free catalyst.
Background
PVC is used as resin for five major general purposes in the world, and has a plurality of advantages of excellent flame retardance, wear resistance, corrosion resistance, easy processing and the like, so that the PVC has wide application in various industries. However, the energy structure characteristics of rich coal, poor oil and less gas in China determine that the calcium carbide acetylene method PVC production process occupies an absolute position in PVC production enterprises in China, and the energy structure characteristics reach more than 80%. With the promotion of the mercury-free process in the Water ensure convention, the calcium carbide acetylene process PVC industry meets the great test of reducing mercury consumption and pollution, and the industry faces the urgent need of replacing low-mercury catalyst with mercury-free catalyst.
Although there is no mercury-free catalyst capable of being applied in large-scale industrialization at present, research and development and tests of mercury-free catalysts have been carried out by various research and development units and chlor-alkali enterprises, and some research results have been obtained, the main research directions of the mercury-free catalysts are precious metal mercury-free catalysts and non-precious metal mercury-free catalysts, the precious metal mercury-free catalysts show excellent catalytic performance in the vinyl chloride synthesis reaction process, but the problems of poor stability, short service life, high cost, and possible other heavy metal pollution exist, and after the non-precious metal solid-phase mercury-free catalysts are applied to an industrial device, the following defects exist due to the limitation of traditional calcium carbide method PVC vinyl chloride synthesis process conditions:
1. the raw material gas HCl has high content of H2, and H2 has reducibility, so that the raw material gas HCl and a non-noble metal catalyst in a mercury-free catalyst can generate oxidation reduction reaction in a converter, effective catalytic components in the mercury-free catalyst can be continuously reduced along with the reaction, and the conversion efficiency is reduced.
2. The content of water in the raw material gas HCl is high, when the mixed gas of HCl and C2H2 is introduced into a mercury-free catalyst in a converter for reaction, excessive water can indirectly cause conversion side reaction to generate a large amount of metal complexes, and the metal complexes have large molecular diameters, so that the metal complexes are accumulated on the surface of activated carbon, and then the pores of the activated carbon are blocked greatly, the raw material gas is prevented from normally entering the mercury-free catalyst, so that the conversion reaction cannot be normally carried out, the catalytic activity is rapidly reduced, the service life of the mercury-free catalyst is influenced, and tests show that no continuous use condition exists after 2100 hours.
3. In the traditional process for synthesizing vinyl chloride by using mercury catalyst, the hydrogen chloride in the raw material gas is generally controlled to be kept in excess, and the ratio of C2H 2: the molar ratio of HCl is controlled to be 1:1.05-1.1, so that excessive hydrogen chloride contained in the crude monomer needs to be subjected to cleaning treatment by using a water washing tower and an alkali washing tower respectively, a large amount of by-product hydrochloric acid and high salt water are generated, waste is caused, and power and material consumption of a treatment system are additionally increased.
4. When the traditional mercury catalyst is used as a catalyst, the highest acetylene flux can reach 50 Nm/m for cultivating the catalyst, but at present, the highest flux of the non-noble metal mercury-free catalyst is controlled at 35 Nm/m for cultivating the catalyst, the reaction conversion rate is reduced due to the fact that the flux is continuously improved, the contents of acetylene and hydrogen chloride in the converted tail gas exceed the standard, waste is caused, the processing load of a subsequent system is increased, and the improvement of the conversion rate needs to be solved urgently.
Disclosure of Invention
The invention provides a process for synthesizing chloroethylene by using a mercury-free catalyst, which can thoroughly realize mercury-free reaction, completely react hydrogen chloride with excessive acetylene, remove the traditional purification systems of tail gas washing, alkali washing and the like, solve a series of problems caused by high water content in the process of preparing chloroethylene by using an acetylene method, prolong the service life of the mercury-free catalyst and simultaneously improve the yield and purity of chloroethylene.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a system for synthesizing vinyl chloride using a mercury-free catalyst, comprising: the system comprises a hydrogen chloride gas inlet pipe, an acetylene gas inlet pipe, a sulfuric acid drying tower, a pressure swing adsorption device, a mixer, an acetylene drying device, a preheater, a mercury-free front stage converter, a mercury-free rear stage converter, a corrosion-resistant compressor, a first condenser, a crude monomer storage tank, a rectification system, a dichloroethane purification and rectification system, a mercury-free three-section converter, a second condenser and a gas-liquid separator.
A process for synthesizing chloroethylene by mercury-free catalyst includes such steps as dewatering raw material, separating hydrogen, converting, gas-liquid separation and post-treating.
Dehydrating the raw material, namely introducing the hydrogen chloride gas into a sulfuric acid drying tower to be washed, dried and dehydrated to obtain dehydrated dry hydrogen chloride gas;
the water content of the raw material hydrogen chloride gas is more than or equal to 1000ppm before dehydration, and the water content after dehydration is less than or equal to 300 ppm.
The concentration of the sulfuric acid in the sulfuric acid drying tower is 98%.
And separating hydrogen, namely introducing the dehydrated dry hydrogen chloride gas into a pressure swing adsorption device, and separating redundant hydrogen and hydrogen chloride to obtain the dry hydrogen chloride after the hydrogen is separated.
The mass fraction of hydrogen chloride in the dehydrated dry hydrogen chloride gas is 94.3 percent, and the hydrogen content is 300 ppm; the mass fraction of hydrogen chloride in the dry hydrogen chloride after hydrogen separation is 94.5%, and the hydrogen content is less than 30 ppm.
The adsorbent of the pressure swing adsorption device is a 4A alumina molecular sieve with the grain diameter of 3-5 mm.
The system pressure of the pressure swing adsorption device is 35-50KPa, the pressure of the reverse discharge terminal is 50KPa, the evacuation pressure is 20KPa, and the temperature of the dehydrated dry hydrogen chloride gas is controlled to be more than or equal to 90 ℃.
And in the conversion step, the dry hydrogen chloride after the hydrogen gas is separated and the dry acetylene gas are mixed according to the molar ratio of 1: 1.03-1.05, introducing into a mixer, fully and uniformly mixing to obtain mixed gas, preheating the mixed gas to 90 ℃ by a preheater, and sequentially introducing into a mercury-free foreground converter and a mercury-free background converter to perform mercury-free catalyst catalytic conversion reaction to obtain the converted mixed gas.
The introduction speed of the mixed gas is 30-50m3/h。
The mercury-free catalyst comprises the following raw materials in percentage by mass: 54% of activated carbon, 16% of copper chloride, 12% of pyrrole acetamide, 11% of amino acid and 7% of phosphoric acid.
The preparation method of the mercury-free catalyst comprises the following steps: firstly, acid-washing activated carbon by using a hydrochloric acid solution to remove iron elements, then, cleaning by using ultrasonic waves, sequentially preparing a copper chloride solution with the mass fraction of 15-20%, a pyrrole acetamide solution with the mass fraction of 10%, an amino acid solution with the mass fraction of 7.5-9% and a phosphoric acid solution with the mass fraction of 3-5% in a range of 60-90 ℃ after impurities in pores of the activated carbon are thoroughly cleaned, and then, respectively putting the activated carbon into the solutions to be soaked for 24 hours, wherein after the activated carbon is soaked in the copper chloride solution, the content of copper-based chlorides in residual liquid after soaking is detected, and if the mass fraction of the copper chloride in the residual liquid is less than or equal to 5%, the adsorption is normal, and continuously putting the activated carbon into the pyrrole acetamide solution to be adsorbed; and (3) obtaining a mercury-free catalyst semi-finished product after the adsorption is completed, then drying the mercury-free catalyst semi-finished product in vacuum at the temperature of 120-150 ℃ under the protection of nitrogen, and obtaining the mercury-free catalyst finished product after drying for 20-24 h.
The mercury-free catalyst in the mercury-free foreground converter is the same as the mercury-free catalyst used in the mercury-free background converter, and the loading amount of the mercury-free catalyst in the mercury-free foreground converter and the mercury-free background converter is 5 tons.
The reaction temperature of the mixed gas in the mercury-free foreground converter and the mercury-free background converter is both 110-170 ℃, and the reaction time is both 5-10 min.
And gas-liquid separation, namely introducing the converted mixed gas into a corrosion-resistant compressor, compressing the mixed gas to the pressure of 0.5MPa, introducing the compressed mixed gas into a first condenser for condensation, performing gas-liquid separation, introducing the liquid-phase chloroethylene subjected to gas-liquid separation into a rectification system for purification, and introducing the gas-phase part into a mercury-free three-section converter for secondary catalytic reaction.
The mercury-free catalyst type, the mercury-free catalyst loading amount, the reaction temperature and the reaction time in the mercury-free three-section converter are the same as those in a mercury-free foreground converter and a mercury-free background converter.
The chloroethylene content in the liquid phase chloroethylene before purification is 99%, the chloroethylene content after purification is 99.99%, and the content of high-boiling-point substances is reduced to below 10 ppm.
And the post-treatment comprises the steps of cooling the gas after the re-catalytic reaction to room temperature, re-condensing and separating non-condensable gases such as liquid-phase chloroethylene, acetylene gas and the like, controlling the pressure stability of a pressurized reaction section through a throttle valve, directly introducing the liquid-phase chloroethylene into a rectification system for rectification, and preparing the finished product refined dichloroethane through a dichloroethane purification rectification system for the rectified high-boiling residue.
The purification process of the dichloroethane purification and rectification system comprises the following steps: introducing the high-boiling-point substances into a dichloroethane purification and rectification system, heating the bottom of the system to 150 ℃ by adopting heat conduction oil, arranging a condensation section at the top of the system, cooling by using chilled brine at the temperature of-35 ℃, and separating low-boiling-point components from the top of the system to obtain the residual high-boiling-point components, namely dichloroethane.
The purity of the chloroethylene in the crude monomer storage tank is detected, the purity can reach 90.5% -94%, and the yield of the chloroethylene can reach 95.2% -98.5%.
Compared with the prior art, the invention has the beneficial effects that:
(1) the process for synthesizing the chloroethylene by using the mercury-free catalyst can thoroughly realize mercury-free reaction and solve the industrial difficulty;
(2) according to the process for synthesizing chloroethylene by using the mercury-free catalyst, the hydrogen chloride and the excessive acetylene are completely reacted by using three-stage conversion and adopting an excessive acetylene proportioning mode, the traditional purification systems of tail gas washing, alkali washing and the like are removed, and a series of problems caused by high water content in the process of preparing chloroethylene by using an acetylene method are solved;
(3) according to the process for synthesizing chloroethylene by using the mercury-free catalyst, acetylene and hydrogen chloride are respectively dehydrated, so that the water content of the raw material gas is reduced, the generation of side reaction complexes is reduced, the conversion effect is improved, the pressure swing adsorption dehydrogenation gas device is independently added for hydrogen chloride, the hydrogen content in the raw material gas is greatly reduced, the reduction of mercury-free catalytic components by hydrogen is avoided, and the service life of the mercury-free catalyst is prolonged to more than 3000 hours;
(4) according to the process for synthesizing chloroethylene by using the mercury-free catalyst, the dichloroethane purification and rectification device is used for effectively recycling and producing high-boiling-point substances, byproducts in the reaction process are completely utilized, and the economic benefit is further improved;
(5) the process for synthesizing chloroethylene by using the mercury-free catalyst has the advantages that the yield of the prepared chloroethylene can reach 95.2-98.5%, and the purity of the prepared crude chloroethylene can reach 90.5-94%.
Drawings
FIG. 1 is a flow diagram of a process for the synthesis of vinyl chloride using a mercury-free catalyst.
In the figure, a 1-hydrogen chloride gas inlet pipe, a 2-acetylene gas inlet pipe, a 3-sulfuric acid drying tower, a 4-pressure swing adsorption device, a 5-mixer, a 6-acetylene drying device, a 7-preheater, an 8-mercury-free front stage converter, a 9-mercury-free back stage converter, a 10-corrosion-resistant compressor, an 11-first condenser, a 12-crude monomer storage tank, a 13-rectification system, a 14-dichloroethane purification and rectification system, a 15-mercury-free three-section converter, a 16-second condenser and a 17-gas-liquid separator.
Detailed Description
In order to more clearly understand the technical features, objects, and effects of the present invention, specific embodiments of the present invention will now be described.
Example 1
As shown in fig. 1, a system for synthesizing vinyl chloride using a mercury-free catalyst includes: the device comprises a hydrogen chloride gas inlet pipe 1, an acetylene gas inlet pipe 2, a sulfuric acid drying tower 3, a pressure swing adsorption device 4, a mixer 5, an acetylene drying device 6, a preheater 7, a mercury-free foreground converter 8, a mercury-free background converter 9, a corrosion-resistant compressor 10, a first condenser 11, a crude monomer storage tank 12, a rectification system 13, a dichloroethane purifying and rectifying system 14, a mercury-free three-section converter 15, a second condenser 16 and a gas-liquid separator 17.
A process for synthesizing chloroethylene by using a mercury-free catalyst comprises the following steps:
1. dehydrating raw materials: introducing a raw material hydrogen chloride gas into a sulfuric acid drying tower 3, washing, drying and dehydrating to obtain a dehydrated dry hydrogen chloride gas;
the water content of the raw material hydrogen chloride gas is more than or equal to 1000ppm before dehydration, and the water content after dehydration is less than or equal to 300 ppm.
The concentration of the sulfuric acid in the sulfuric acid drying tower 3 is 98%.
2. Hydrogen separation: and introducing the dehydrated dry hydrogen chloride gas into a pressure swing adsorption device 4, and separating redundant hydrogen gas from hydrogen chloride to obtain the dry hydrogen chloride after hydrogen separation.
The mass fraction of hydrogen chloride in the dehydrated dry hydrogen chloride gas is 94.3 percent, and the hydrogen content is 300 ppm; the mass fraction of hydrogen chloride in the dry hydrogen chloride after hydrogen separation is 94.5%, and the hydrogen content is less than 30 ppm.
The adsorbent of the pressure swing adsorption device 4 is a 4A alumina molecular sieve with the grain diameter of 3.2 mm.
The system pressure of the pressure swing adsorption device 4 is 36KPa, the pressure of the reverse release terminal is 50KPa, the evacuation pressure is 20KPa, and the temperature of the dehydrated dry hydrogen chloride gas is controlled to be 91 ℃.
3. And (3) transformation: and (3) mixing the dry hydrogen chloride after the hydrogen gas is separated with the dry acetylene gas according to the molar ratio of 1: 1.03 is introduced into a mixer 5, mixed gas is obtained after full mixing, the mixed gas is preheated to 90 ℃ by a preheater 7, and then a mercury-free fore-stage converter 8 and a mercury-free background converter 9 are sequentially introduced for mercury-free catalyst catalytic conversion reaction, so as to obtain the converted mixed gas.
The introduction speed of the mixed gas is 30m3/h。
The mercury-free catalyst comprises the following raw materials in percentage by mass: 54% of activated carbon, 16% of copper chloride, 12% of pyrrole acetamide, 11% of amino acid and 7% of phosphoric acid.
The preparation method of the mercury-free catalyst comprises the following steps: firstly, acid-washing activated carbon by using a hydrochloric acid solution to remove iron elements, then, cleaning by using ultrasonic waves, sequentially preparing a copper chloride solution with the mass fraction of 15.5%, a pyrrole acetamide solution with the mass fraction of 10%, an amino acid solution with the mass fraction of 7.6% and a phosphoric acid solution with the mass fraction of 3.05% -5% in a range of 60-90 ℃ after impurities in pores of the activated carbon are thoroughly cleaned, then, respectively putting the activated carbon into the above solutions to be soaked for 24 hours, wherein after the activated carbon is soaked in the copper chloride solution, the content of copper-based chlorides in residual liquid after soaking is detected, if the mass fraction of the copper chloride in the residual liquid is less than or equal to 5%, the adsorption is normal, and continuously putting the activated carbon into the pyrrole acetamide solution to be adsorbed; and (3) obtaining a mercury-free catalyst semi-finished product after complete adsorption, then drying the mercury-free catalyst semi-finished product in vacuum at the temperature of 125 ℃ under the protection of nitrogen, and obtaining the mercury-free catalyst finished product after drying for 20 hours.
The mercury-free catalyst in the mercury-free foreground converter 8 is the same as the mercury-free catalyst used in the mercury-free background converter 9, and the loading amount of the mercury-free catalyst in the mercury-free foreground converter 8 and the mercury-free background converter 9 is 5 tons.
The reaction temperature of the mixed gas in the mercury-free foreground converter 8 and the mercury-free background converter 9 is 115 ℃, and the reaction time is 5.2 min.
4. Gas-liquid separation: and introducing the converted mixed gas into a corrosion-resistant compressor 10, compressing the mixed gas to a pressure of 0.5MPa, introducing the compressed mixed gas into a first condenser 11, condensing the compressed mixed gas, performing gas-liquid separation, introducing the liquid-phase chloroethylene subjected to gas-liquid separation into a rectification system 13, purifying, and introducing the gas-phase part into a mercury-free three-section converter 15 for secondary catalytic reaction.
The kind of mercury-free catalyst, the loading amount of the mercury-free catalyst, the reaction temperature and the reaction time in the mercury-free three-section converter 15 are the same as those in the mercury-free foreground converter 8 and the mercury-free background converter 9.
The chloroethylene content in the liquid phase chloroethylene before purification is 99%, the chloroethylene content after purification is 99.99%, and the content of high-boiling-point substances is reduced to below 10 ppm.
5. And (3) post-treatment: and cooling the gas after the secondary catalytic reaction to room temperature, condensing again and separating non-condensable gases such as liquid-phase chloroethylene, acetylene gas and the like, controlling the pressure stability of the pressurized reaction section through a throttle valve, directly introducing the liquid-phase chloroethylene into a rectification system 13 for rectification, and preparing the finished product of refined dichloroethane through a dichloroethane purification and rectification system 14 for the rectified high-boiling-point substances.
The purification process of the dichloroethane purification and rectification system 14 is as follows: introducing the high-boiling-point substances into a dichloroethane purification and rectification system 14, heating the bottom of the system to 150 ℃ by adopting heat conduction oil, arranging a condensation section at the top of the system, cooling by using chilled brine with the temperature of-35 ℃, and separating low-boiling-point components from the top of the system to obtain the residual high-boiling-point components, namely dichloroethane.
The purity of the chloroethylene in the crude monomer storage tank 12 is detected, the purity can reach 90.5%, and the yield of the chloroethylene can reach 95.2%.
Example 2
A process for synthesizing chloroethylene by using a mercury-free catalyst comprises the following steps:
1. dehydrating raw materials: introducing a raw material hydrogen chloride gas into a sulfuric acid drying tower 3, washing, drying and dehydrating to obtain a dehydrated dry hydrogen chloride gas;
the water content of the raw material hydrogen chloride gas is more than or equal to 1000ppm before dehydration, and the water content after dehydration is less than or equal to 300 ppm.
The concentration of the sulfuric acid in the sulfuric acid drying tower 3 is 98%.
2. Hydrogen separation: and introducing the dehydrated dry hydrogen chloride gas into a pressure swing adsorption device 4, and separating redundant hydrogen gas from hydrogen chloride to obtain the dry hydrogen chloride after hydrogen separation.
The mass fraction of hydrogen chloride in the dehydrated dry hydrogen chloride gas is 94.3 percent, and the hydrogen content is 300 ppm; the mass fraction of hydrogen chloride in the dry hydrogen chloride after hydrogen separation is 94.5%, and the hydrogen content is less than 30 ppm.
The adsorbent of the pressure swing adsorption device 4 is a 4A alumina molecular sieve with the grain diameter of 4.8 mm.
The system pressure of the pressure swing adsorption device 4 is 49KPa, the pressure of the reverse release terminal is 50KPa, the evacuation pressure is 20KPa, and the temperature of the dehydrated dry hydrogen chloride gas is controlled to be 98 ℃.
3. And (3) transformation: introducing the dry hydrogen chloride and the dry acetylene gas into a mixer 5 according to a molar ratio of 1:1.05, fully and uniformly mixing to obtain a mixed gas, preheating the mixed gas to 90 ℃ by a preheater 7, and sequentially introducing the mixed gas into a mercury-free foreground converter 8 and a mercury-free background converter 9 for mercury-free catalyst catalytic conversion reaction to obtain the converted mixed gas.
The introduction speed of the mixed gas is 50m3/h。
The mercury-free catalyst comprises the following raw materials in percentage by mass: 54% of activated carbon, 16% of copper chloride, 12% of pyrrole acetamide, 11% of amino acid and 7% of phosphoric acid.
The preparation method of the mercury-free catalyst comprises the following steps: firstly, acid-washing activated carbon by using a hydrochloric acid solution to remove iron elements, then, cleaning by using ultrasonic waves, sequentially preparing a copper chloride solution with the mass fraction of 19.8%, a pyrrole acetamide solution with the mass fraction of 10%, an amino acid solution with the mass fraction of 8.9% and a phosphoric acid solution with the mass fraction of 4.96% in a range of 60-90 ℃ after impurities in pores of the activated carbon are thoroughly cleaned, then, respectively putting the activated carbon into the above solutions to be soaked for 24 hours, wherein after the activated carbon is soaked in the copper chloride solution, the content of copper-based chlorides in the residual liquid after soaking is detected, if the mass fraction of the copper chloride in the residual liquid is less than or equal to 5%, the adsorption is normal, and continuously putting the activated carbon into the pyrrole acetamide solution to be adsorbed; and (3) obtaining a mercury-free catalyst semi-finished product after complete adsorption, then drying the mercury-free catalyst semi-finished product in vacuum at the temperature of 148 ℃ under the protection of nitrogen, and obtaining the mercury-free catalyst finished product after drying for 24 hours.
The mercury-free catalyst in the mercury-free foreground converter 8 is the same as the mercury-free catalyst used in the mercury-free background converter 9, and the loading amount of the mercury-free catalyst in the mercury-free foreground converter 8 and the mercury-free background converter 9 is 5 tons.
The reaction temperature of the mixed gas in the mercury-free foreground converter 8 and the mercury-free background converter 9 is 168 ℃, and the reaction time is 9.8 min.
4. Gas-liquid separation: and introducing the converted mixed gas into a corrosion-resistant compressor 10, compressing the mixed gas to a pressure of 0.5MPa, introducing the compressed mixed gas into a first condenser 11, condensing the compressed mixed gas, performing gas-liquid separation, introducing the liquid-phase chloroethylene subjected to gas-liquid separation into a rectification system 13, purifying, and introducing the gas-phase part into a mercury-free three-section converter 15 for secondary catalytic reaction.
The kind of mercury-free catalyst, the loading amount of the mercury-free catalyst, the reaction temperature and the reaction time in the mercury-free three-section converter 15 are the same as those in the mercury-free foreground converter 8 and the mercury-free background converter 9.
The chloroethylene content in the liquid phase chloroethylene before purification is 99%, the chloroethylene content after purification is 99.99%, and the content of high-boiling-point substances is reduced to below 10 ppm.
5. And (3) post-treatment: and cooling the gas after the secondary catalytic reaction to room temperature, condensing again and separating non-condensable gases such as liquid-phase chloroethylene, acetylene gas and the like, controlling the pressure stability of the pressurized reaction section through a throttle valve, directly introducing the liquid-phase chloroethylene into a rectification system 13 for rectification, and preparing the finished product of refined dichloroethane through a dichloroethane purification and rectification system 14 for the rectified high-boiling-point substances.
The purification process of the dichloroethane purification and rectification system 14 is as follows: introducing the high-boiling-point substances into a dichloroethane purification and rectification system 14, heating the bottom of the system to 150 ℃ by adopting heat conduction oil, arranging a condensation section at the top of the system, cooling by using chilled brine with the temperature of-35 ℃, and separating low-boiling-point components from the top of the system to obtain the residual high-boiling-point components, namely dichloroethane.
The purity of the vinyl chloride in the crude monomer storage tank 12 is detected, and the purity can reach 94 percent, and the yield of the vinyl chloride can reach 98.5 percent.
All percentages used in the present invention are mass percentages unless otherwise indicated.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (6)
1. A process for synthesizing chloroethylene by using a mercury-free catalyst is characterized by comprising the steps of dehydrating raw materials, separating hydrogen, converting, carrying out gas-liquid separation and carrying out post-treatment;
and in the conversion step, the dry hydrogen chloride after the hydrogen gas is separated and the dry acetylene gas are mixed according to the molar ratio of 1: 1.03-1.05, introducing into a mixer (5), fully and uniformly mixing to obtain a mixed gas, preheating the mixed gas to 90 ℃ by a preheater (7), and sequentially introducing into a mercury-free foreground converter (8) and a mercury-free background converter (9) for mercury-free catalyst catalytic conversion reaction to obtain a converted mixed gas;
the introduction speed of the mixed gas is 30-50m3/h；
The mercury-free catalyst comprises the following raw materials in percentage by mass: 54% of activated carbon, 16% of copper chloride, 12% of pyrrole acetamide, 11% of amino acid and 7% of phosphoric acid;
the preparation method of the mercury-free catalyst comprises the following steps: firstly, acid-washing activated carbon by using a hydrochloric acid solution to remove iron elements, then, cleaning by using ultrasonic waves, sequentially preparing a copper chloride solution with the mass fraction of 15-20%, a pyrrole acetamide solution with the mass fraction of 10%, an amino acid solution with the mass fraction of 7.5-9% and a phosphoric acid solution with the mass fraction of 3-5% in a range of 60-90 ℃ after impurities in pores of the activated carbon are thoroughly cleaned, and then, respectively putting the activated carbon into the solutions to be soaked for 24 hours, wherein after the activated carbon is soaked in the copper chloride solution, the content of copper-based chlorides in residual liquid after soaking is detected, and if the mass fraction of the copper chloride in the residual liquid is less than or equal to 5%, the adsorption is normal, and continuously putting the activated carbon into the pyrrole acetamide solution to be adsorbed; after the adsorption is completed, obtaining a mercury-free catalyst semi-finished product, then under the protection of nitrogen, drying the mercury-free catalyst semi-finished product in vacuum at the temperature of 120-150 ℃, and obtaining a mercury-free catalyst finished product after drying for 20-24 h;
the gas-liquid separation is carried out, the converted mixed gas is introduced into a corrosion-resistant compressor (10), the mixed gas is compressed to the pressure of 0.5MPa and then introduced into a first condenser (11) for condensation, then gas-liquid separation is carried out, liquid-phase chloroethylene subjected to gas-liquid separation enters a rectification system (13) for purification, and a gas-phase part enters a mercury-free three-section converter (15) for carrying out catalytic reaction again;
the types of the mercury-free catalysts, the loading amount of the mercury-free catalysts, the reaction temperature and the reaction time in the mercury-free three-section converter (15) are the same as those in the mercury-free foreground converter (8) and the mercury-free background converter (9).
2. The process for synthesizing vinyl chloride by using the mercury-free catalyst as claimed in claim 1, wherein the raw material is dehydrated, and the raw material hydrogen chloride gas is introduced into a sulfuric acid drying tower (3) to be washed, dried and dehydrated to obtain dehydrated dry hydrogen chloride gas;
the water content of the raw material hydrogen chloride gas is more than or equal to 1000ppm before dehydration, and the water content after dehydration is less than or equal to 300 ppm;
the concentration of the sulfuric acid in the sulfuric acid drying tower (3) is 98%.
3. The process for synthesizing vinyl chloride by using the mercury-free catalyst as claimed in claim 1, wherein the hydrogen is separated, the dehydrated dry hydrogen chloride gas is introduced into a pressure swing adsorption device (4), and the redundant hydrogen and hydrogen chloride are separated to obtain the dry hydrogen chloride after the hydrogen is separated;
the mass fraction of hydrogen chloride in the dehydrated dry hydrogen chloride gas is 94.3 percent, and the hydrogen content is 300 ppm; the mass fraction of hydrogen chloride in the dry hydrogen chloride after hydrogen separation is 94.5%, and the hydrogen content is less than 30 ppm.
4. The process for synthesizing vinyl chloride using mercury-free catalyst as claimed in claim 3, wherein the adsorbent of the pressure swing adsorption device (4) is 4A alumina molecular sieve with a particle size of 3-5 mm;
the system pressure of the pressure swing adsorption device (4) is 35-50KPa, the pressure of the reverse terminal is 50KPa, the evacuation pressure is 20KPa, and the temperature of the dehydrated dry hydrogen chloride gas is controlled to be more than or equal to 90 ℃.
5. The process for synthesizing vinyl chloride using mercury-free catalyst as claimed in claim 1, wherein the reaction temperature of the mixed gas in the mercury-free front stage converter (8) and the mercury-free back stage converter (9) is 110 ℃ and 170 ℃, and the reaction time is 5-10 min.
6. The process for synthesizing vinyl chloride using the mercury-free catalyst as claimed in claim 1, wherein the post-treatment comprises cooling the gas after the re-catalytic reaction to room temperature, re-condensing and separating the noncondensable gas such as liquid-phase vinyl chloride and acetylene gas, controlling the pressure of the pressurized reaction section to be stable by a throttle valve, directly introducing the liquid-phase vinyl chloride into a rectification system (13) for rectification, and purifying the rectified high-boiling residue with dichloroethane by a dichloroethane purification and rectification system (14) to obtain the refined dichloroethane.
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| CN114682243A (en) * | 2022-04-12 | 2022-07-01 | 内蒙古圣龙大地科技有限公司 | Method for preparing mercury-free catalyst by adding dichloroethane |
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