CN113353893B - Sulfur tetrafluoride synthesis method and reaction system - Google Patents
Sulfur tetrafluoride synthesis method and reaction system Download PDFInfo
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Abstract
The invention provides a method for synthesizing sulfur tetrafluoride and a reaction system, and relates to the technical field of chemical industry. The method for synthesizing sulfur tetrafluoride provided by the invention comprises the following steps: the fluorine gas and the liquid sulfur are subjected to gas-liquid reaction to generate sulfur tetrafluoride, the reaction pressure is 90-120KPa, and the distance from the outlet of the fluorine gas to the liquid sulfur surface during the reaction is 3-10 mm. The invention has the advantages that the sulfur tetrafluoride has high quality, stability and high yield by controlling the reaction temperature, the reaction pressure and the gas-liquid distance, and the benefit is maximized.
Description
Technical Field
The invention relates to the technical field of chemical industry, in particular to a method for synthesizing sulfur tetrafluoride and a reaction system.
Background
Sulfur tetrafluoride is an indispensable selective fluorinating agent in organofluorine chemistry, and is dominant in the important field of deoxofluorination, which is the chemistry in which carbonyl, hydroxyl and carboxyl groups in organics are converted to-CF, -CF 2 、-CF 3 Has high selectivity and can deoxidize and fluorinate acyl fluoride-COF group in organic matters into trifluoromethyl, thereby laying a special position in the high-end manufacturing fields of modern pharmacy, electronic chemicals and the like.
The sulfur tetrafluoride synthesis method has at least more than five technological routes, and the most representative technological route is arranged according to the current industrialization scale;
1. a method for continuously producing sulfur tetrafluoride (patent number ZL 200410100441.5), which adopts iodine pentafluoride and liquid sulfur to generate sulfur tetrafluoride with high selectivity under the conditions of more than 200 ℃ and medium pressure, and the iodine is replaced for recycling, and has the following reaction formula:
4IF 5 +5S＝5SF 4 +2I 2
the product of the reaction has few impurities in gas phase at normal temperature and normal pressure, the purity of the product can be more than 98 percent through simple gas-solid-liquid separation, the urgent requirement of research and development of new drugs in the current medical industry can be met, the equipment is relatively simple, iodine can be replaced for recycling, and the cost is controllable, so that the technology has the capacity of more than 50 tons/year, and plays a key role in promoting research and development of sulfur tetrafluoride downstream products, setting up the confidence of industrial cultivation scale industry in the industry and expanding market demand.
2. Us patent 3399036 (AIR product AND CHEMICALS, INC.1968) is the same technical route as patent SU 823976 (1981). The process route is that fluorine gas is on the surface of the sulfur in the separated liquidChemical reaction is carried out at 1 inch, the temperature is controlled to be about 330 ℃, the product yield is 90-94%, and the main impurity S is 2 F 2 /SF 6 The main reaction formula is as follows:
2F 2 +S＝SF 4
two side reactions occur simultaneously:
3F 2 +S＝SF 6 (when the temperature is<330℃)
F 2 +2S＝S 2 F 2 (when the temperature is>330℃)
The technology realizes the capacity of more than 20 tons per year in the United states, lays a solid foundation for the development of modern fluorine-containing medicines by more than twenty years before 2015 for the continuous exclusive supply market for the development of new products of global fluorine-containing medicines.
3. U.S. patent 2992073 (1961 patent from dupont) discloses sulfur tetrafluoride obtained by reacting an alkali metal sulfide, chlorine gas and an alkali metal fluoride, wherein the byproduct is an alkali metal chloride, and the reaction formula is as follows:
M' 2 S+3Cl 2 +M"F→SF 4 +2M'Cl+4M"Cl
wherein M 'and M' may be the same or different alkali metals. The method is not reported in industrialization.
4. Japanese ASAHI GLASS CO., LTD.1982, see U.S. Pat. No. 4372938 for details. The method uses Am.nHF and SCl 2 Reaction to prepare SF 4 . Am.nHF is a complex of hydrogen fluoride and an organic amine, am is usually pyridine or triethylamine, n=1-4, and SF after the reaction 4 Is distilled off under vacuum, by-product S 2 Cl 2 The chlorine is re-introduced into the reactor to become SCl 2 The Am.HCl is treated by HF to Am.3HF for recycling. The main reaction is as follows:
SCl 2 +Am.nHF→ → SF 4 +Am.nHCl+S 2 Cl 2
the method has the advantages of more byproducts, complicated steps, difficult continuous and efficient production and no commodity market.
U.S. patent 3950498, 1974 issued to Rolf Appel reacted with Am.nHF in an organic solvent such as acetonitrile with sulfur tetrachloride (or a mixture of sulfur dichloride and chlorine) to give sulfur tetrafluoride, the reaction mechanism and fluorinating agent Am.nHF used are substantially the same as those of the above-mentioned 4 th Japanese company ASAHI GLASS CO., LTD. The reaction principle of the issued U.S. patent 4372938.
5. Us patent 5639435 to american jorger Miller, issued 1997, mentions the use of metal fluorides (AgF, cuF 2 、HgF 2 ) Synthesizing sulfur tetrafluoride with sulfur and then reacting with oxygen at high temperature to produce sulfur hexafluoride, wherein the sulfur tetrafluoride is only used as an intermediate product. The steps and the reaction modes described in the process route are complex, and a large amount of byproducts are difficult to treat, so that no report on realizing industrial production is seen.
At present, the device for producing sulfur tetrafluoride by the surface reaction method of fluorine gas and liquid sulfur in the United states AIr Products & Chemicals, inc. the commercial sulfur tetrafluoride product is replaced by the iodine pentafluoride method in China because the product quality and the price are inferior. However, the explosive development of new medical products and electronic information industry in the last five years causes the rapid increase of the sulfur tetrafluoride market demand scale, so that the product is not supplied and is high in price, and the further development of the downstream industrial chain of sulfur tetrafluoride is hindered. The iodine pentafluoride method for producing sulfur tetrafluoride has the advantages that the reaction efficiency is required to be improved when iodine is recycled, the bottleneck of capacity expansion is formed, and large-scale industrial production cannot be realized, so that a new route for synthesizing sulfur tetrafluoride with high efficiency and low cost is necessary, and a sufficient material foundation is provided for increasingly developed modern medicine and electronic industry.
Disclosure of Invention
The invention aims to provide a method for synthesizing sulfur tetrafluoride, which can ensure high-quality, stable and high-yield sulfur tetrafluoride and realize the maximization of benefits by controlling the reaction temperature, the reaction pressure and the gas-liquid distance.
Another object of the present invention is to provide a reaction system of the above-mentioned synthesis method of sulfur tetrafluoride, wherein the horizontal tubular device is configured as a reaction chamber and a charging chamber, and liquid sulfur is utilized to prevent gas phase reactants from entering the sulfur charging chamber, so that stable and high yield of high-purity sulfur tetrafluoride can be realized by combining the above-mentioned synthesis method.
The invention solves the technical problems by adopting the following technical scheme.
In one aspect, an embodiment of the present application provides a method for synthesizing sulfur tetrafluoride, including the steps of: the fluorine gas and the liquid sulfur are subjected to gas-liquid reaction to generate sulfur tetrafluoride, the reaction pressure is 90-120KPa, and the distance from the outlet of the fluorine gas to the liquid sulfur surface during the reaction is 3-10 mm.
On the other hand, the embodiment of the application provides a reaction system of the synthesis method of sulfur tetrafluoride, which comprises a device body and a reactor, wherein the reactor is a horizontal tubular device with a heating element, and the horizontal tubular device is divided into a reaction chamber and a sulfur charging chamber which are connected with a fluorine gas inlet pipe by a vertical partition plate; the bottom of the partition plate is provided with a channel for enabling molten sulfur to enter the reaction chamber, and liquid sulfur is used as a liquid seal to prevent gas-phase reactants from entering the sulfur feeding chamber.
Compared with the prior art, the embodiment of the invention has at least the following advantages or beneficial effects:
the effect is that in the prior art, the fluorine gas is higher (25.4 mm) from the surface of the liquid sulfur, the reaction relies on the gas-phase sulfur evaporated at high temperature to react with the fluorine gas above the surface of the liquid sulfur, and because a large amount of heat is required to be released during the reaction of the fluorine gas and the liquid sulfur, the temperature in the reaction zone is far higher than the proper reaction temperature of 280-300 ℃, so that the yield of the sulfur tetrafluoride in the prior art is not high, and the impurity content is high. In the reaction, the heat capacity of the gas phase space is too small, so that the heat conduction efficiency is low, the difficulty of heat dissipation and cooling is high, and a large amount of heat generated by the reaction of fluorine gas and sulfur cannot be dissipated in time, so that the reaction rate is low. SF (sulfur hexafluoride) 4 The specific heat capacity of the gas is 0.708KJ/Kg.K, the specific heat capacity of the liquid sulfur is 0.85KJ/Kg.K, and SF is about 300 DEG C 4 Density of less than 0.0045g/cm 3 But at this temperature the liquid sulfur has a density of greater than 1.6g/cm 3 The heat capacity of the two materials is more than 300 times different under the same volume. Because the fluorine gas carries out gas phase reaction on the surface of the liquid sulfur, the heat dissipation mainly depends on the gas substances (SF 4 Predominantly) toThe metal shell of the reactor, the liquid sulfur, is limited to its thermal conductivity (0.269W/(m.k)), does not dissipate heat well. Thus of equal volume SF 4 The present inventors adopted a great contrast in thermal conductivity (8 times difference) and heat capacity (300 times difference) of the gaseous phase and the sulfur liquid phase to accelerate the growth of the present inventors to reduce the fluorine gas concentration from 25mm to about 5mm at the fluorine gas outlet from the sulfur liquid surface and from 100% to about 35%, and the previous gas-gas reaction was adjusted to the gas-liquid reaction, thereby producing sulfur tetrafluoride. The synthesis method of sulfur tetrafluoride provided by the invention can obviously improve the heat conduction of a reaction zone, is very beneficial to the control of reaction temperature, thereby controlling the component stability of reaction products, improving the yield of target products, reducing the corrosion of a reactor metal material caused by local overhigh temperature and fluorine gas concentration, prolonging the service life of production equipment, realizing the purpose of high and stable production of sulfur tetrafluoride produced by the surface reaction of fluorine gas on liquid sulfur, and meeting the requirements of rapid increase of the current market; meanwhile, the cost is reduced, the application field of the special organic fluorinating agent is widened to the fields of pesticides, fine chemical engineering, special gases, green refrigeration and new materials, and a strong material foundation is provided for developing modern pharmaceutical chemical engineering, electronic industry, new materials in the future and other emerging industries.
In order to realize the production process of continuous high-efficiency reaction, the invention adopts a double-separation horizontal tubular reactor structure, namely the structure is divided into a charging area and a reaction area, which are separated by a metal plate, a channel is reserved between the baffle plate and the bottom of the tubular reactor so that molten sulfur in the charging area is continuously replenished to the reaction area to enable the reaction to be continuously carried out, 2-4 horizontal heating sleeves are arranged at the bottom so as to start the reaction when the sulfur is preheated to more than 240 ℃, the constant reaction temperature interval of 250-350 ℃ of the reaction area is maintained through a temperature controller and fluorine flux, namely the fluorine flux is reduced when the temperature is too high, the electric heating is started to replenish heat when the temperature is too low and the fluorine flux is limited, and the temperature maintenance stability is the key of realizing high-quality stable and high-yield of the reaction.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 shows a synthesis system used in the method for synthesizing sulfur tetrafluoride provided by the invention.
Icon: 1-fluorine gas mixture inlet valve; 2-a charging valve; 3-thermometer; 4-an air outlet valve; 5-a vacuum valve; 6-a vacuum pressure gauge; 7-a gas cylinder valve; 8-cold trap; 9-a reactor large flange; 10-a submerged air inlet pipe; 11-sulfur liquid level; 12-liquid level detector.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
It should be noted that, in the case of no conflict, the embodiments and features in the embodiments may be combined with each other. The present invention will be described in detail with reference to specific examples.
In one aspect, an embodiment of the present application provides a method for synthesizing sulfur tetrafluoride, including the steps of: the fluorine gas and the liquid sulfur are subjected to gas-liquid reaction to generate sulfur tetrafluoride, the reaction pressure is 90-120KPa, and the distance from the outlet of the fluorine gas to the liquid sulfur surface during the reaction is 3-10 mm.
In some embodiments of the invention, the above-mentioned sulfur tetrafluoride synthesis method, the distance from the liquid sulfur level at the outlet of fluorine gas during reaction is 3-5 mm, and the working pressure is 99-105KPa.
In some embodiments of the invention, the above-described method for producing sulfur tetrafluoride has a reaction temperature of 270-320 ℃.
In some embodiments of the present invention, the reaction temperature is 280-300 ℃.
In some embodiments of the present invention, the concentration of fluorine gas in the above-mentioned method for synthesizing sulfur tetrafluoride is 30-45% by volume.
In some embodiments of the present invention, in the above method for synthesizing sulfur tetrafluoride, the volume concentration of fluorine gas is 30-35%.
In some embodiments of the invention, the fluorine gas flow is 130-170 g/h.
In some embodiments of the present invention, the above-mentioned method for synthesizing sulfur tetrafluoride, wherein the fluorine gas is a mixed gas of fluorine gas and a diluent gas, and the diluent gas is one or more of hydrogen fluoride, nitrogen gas, argon gas, sulfur hexafluoride, perfluorocarbon, hexafluoroethane, perfluorobutane and perfluoroether.
The reaction system of the synthesis method of sulfur tetrafluoride comprises a device body and a reactor, wherein the reactor is a horizontal tubular device with a heating element, and the horizontal tubular device is divided into a reaction chamber and a sulfur charging chamber which are connected with a fluorine gas inlet pipe by a vertical partition plate; the bottom of the partition plate is provided with a channel for enabling molten sulfur to enter the reaction chamber, and liquid sulfur is used as a liquid seal to prevent gas-phase reactants from entering the sulfur feeding chamber.
In some embodiments of the invention, the system gas driving force is from the negative pressure formed by a post-reaction product cryogenic liquefaction plant.
The features and capabilities of the present invention are described in further detail below in connection with the examples.
Example 1
The aim of the embodiment is to provide a method for synthesizing sulfur tetrafluoride, which comprises the following steps:
the outlet of fluorine gas is 5mm away from the liquid surface of sulfur, the temperature of liquid sulfur is 290 ℃, the flux of fluorine gas is 150 g/h, the fluorine gas is diluted to 30% volume concentration by hydrogen fluoride, the pressure of a reactor is 99KPa, and the reactor is cooled in a cold trap of-85 ℃ (alcohol and liquid nitrogen)8 is trapped in a 10 liter nickel-aluminum alloy plating gas cylinder and reacts for 6 hours, and 2384 g of liquefied crude product is obtained. Heating the crude gas bottle to 40 ℃ and fully adsorbing hydrogen fluoride by spherical sodium fluoride to obtain 1280 g of purified product, and detecting SF by gas chromatography 4 86% of content, SF 6 8%, S 2 F 2 4%, SOF 2 0.6% and the balance of air and a trace of CF 4 。
Example 2
The aim of the embodiment is to provide a method for synthesizing sulfur tetrafluoride, which comprises the following steps:
the outlet of fluorine gas is 5mm away from the liquid surface of sulfur, the temperature of liquid sulfur is 300 ℃, the flow rate of fluorine gas is 140 g/h, the fluorine gas is diluted to 30% by volume concentration by hydrogen fluoride, the pressure of a reactor is 110KPa, the fluorine gas is trapped in a 10 liter nickel-aluminum alloy plating gas cylinder in a cold trap 8 of-80 ℃ (alcohol+liquid nitrogen), and the fluorine gas is reacted for 6 hours, so as to obtain 2225 g of liquefied crude product. Heating the crude gas cylinder to 40 ℃ and fully adsorbing hydrogen fluoride by spherical sodium fluoride, then re-putting the crude gas cylinder in a cold trap 8 to obtain 1187 g of purified product, and detecting SF by gas chromatography 4 Content 83%, SF 6 6%, S 2 F 2 10% SOF 2 0.7%, the balance being air and a trace of CF 4 。
Example 3
The aim of the embodiment is to provide a method for synthesizing sulfur tetrafluoride, which comprises the following steps: the outlet of fluorine gas is 5mm away from the liquid surface of sulfur, the temperature of liquid sulfur is 320 ℃, the flow rate of fluorine gas is 130 g/h, the fluorine gas is diluted to 30% by volume concentration by hydrogen fluoride, the pressure of a reactor is 105KPa, the fluorine gas is trapped in a 10 liter nickel-aluminum alloy plating gas cylinder in a cold trap 8 of-80 ℃ (alcohol+liquid nitrogen), and the mixture is reacted for 6 hours to obtain 2052 g of liquefied crude product. Heating the crude gas bottle to 40 ℃ and fully adsorbing hydrogen fluoride by spherical sodium fluoride to obtain 1100 g of purified product, and detecting SF by gas chromatography 4 Content 81%, SF 6 Is 3%, S 2 F 2 15%, SOF 2 0.8%, the balance being air and a trace of CF 4 。
Example 4
The aim of the embodiment is to provide a method for synthesizing sulfur tetrafluoride, which comprises the following steps:
the outlet of fluorine gas is 10mm away from the liquid surface of sulfur, the temperature of liquid sulfur is 300 ℃, the flow rate of fluorine gas is 168 g/h, the fluorine gas is diluted to 45% of volume concentration by hydrogen fluoride, the pressure of a reactor is 95KPa, the fluorine gas is trapped in a 10 liter nickel-aluminum alloy plated gas cylinder in a cold trap 8 of-80 ℃ (alcohol+liquid nitrogen), and the mixture is reacted for 5 hours, thus 1710 g of liquefied crude product is obtained. Heating the crude gas bottle to 40deg.C, fully adsorbing hydrogen fluoride with spherical sodium fluoride, recovering 1197 g of purified product, and detecting SF by gas chromatography 4 Content 89%, SF 6 5%, S 2 F 2 5%, SOF 2 0.5%, the balance being air and a trace of CF 4 。
Example 5
The aim of the embodiment is to provide a method for synthesizing sulfur tetrafluoride, which comprises the following steps:
the outlet of fluorine gas is 10mm away from the liquid surface of sulfur, the temperature of liquid sulfur is 270 ℃, the flow rate of fluorine gas is 140 g/h, the fluorine gas is diluted to 45% of volume concentration by hydrogen fluoride, the pressure of a reactor is 100KPa, the fluorine gas is trapped in a 10 liter nickel-aluminum alloy plating gas cylinder in a-90 DEG (alcohol+liquid nitrogen) C cold trap 8, and the fluorine gas is reacted for 6 hours, so 1715 g of liquefied crude product is obtained. Heating the crude gas bottle to 40 ℃ and fully adsorbing hydrogen fluoride by spherical sodium fluoride to obtain 1174 g of purified product, and detecting SF by gas chromatography 4 Content of 75%, SF 6 23%, S 2 F 2 1% SOF 2 0.5%, the balance being air and a trace of CF 4 。
Example 6
The aim of the embodiment is to provide a method for synthesizing sulfur tetrafluoride, which comprises the following steps:
the outlet of fluorine gas is 3mm away from the liquid surface of sulfur, the temperature of liquid sulfur is 270 ℃, the flow rate of fluorine gas is 160 g/h, the fluorine gas is diluted to 35% of volume concentration by carbon tetrafluoride, the pressure of a reactor is 102KPa, liquid nitrogen is taken as a refrigerant, the liquid nitrogen is trapped in a 10 liter nickel-aluminum alloy plated gas cylinder in a cold trap 8 at the temperature of minus 196 ℃, and the mixture is reacted for 6 hours, so that 5441 g of liquefied crude product mixture is obtained. Steaming out carbon tetrafluoride as diluent gas with boiling point of-128.1 ℃ in a cold trap 8 of-100 ℃ (alcohol+liquid nitrogen) to obtain 1301 g of purified product; detection by gas chromatography, the result is SF 4 Content 73%, SF 6 21%, S 2 F 2 3%, SOF 2 0.6%, CF 4 3% and the balance air.
Example 7
The aim of the embodiment is to provide a method for synthesizing sulfur tetrafluoride, which comprises the following steps:
the outlet of fluorine gas is 8mm away from the liquid surface of sulfur, the temperature of liquid sulfur is 300 ℃, the flow rate of fluorine gas is 160 g/h, the fluorine gas is diluted to 35% of volume concentration by carbon tetrafluoride, the pressure of a reactor is 101KPa, liquid nitrogen is taken as a refrigerant, the liquid nitrogen is trapped in a 10 liter nickel-aluminum alloy plated gas cylinder in a cold trap 8 at the temperature of minus 196 ℃, and the mixture is reacted for 6 hours, so as to obtain 5521 g of liquefied crude product mixture. Distilling out carbon tetrafluoride which is a diluent gas with the boiling point of-128.1 ℃ in a cold trap 8 of-100 ℃ (alcohol and liquid nitrogen), and obtaining 1341 g of purified substance; detection by gas chromatography, the result is SF 4 Content 84%, SF 6 8%, S 2 F 2 4%, SOF 2 0.5%, CF 4 3% and the balance air.
Example 8
The aim of the embodiment is to provide a method for synthesizing sulfur tetrafluoride, which comprises the following steps:
the outlet of fluorine gas is 3mm away from the liquid surface of sulfur, the temperature of liquid sulfur is 300 ℃, the flow rate of fluorine gas is 160 g/h, the fluorine gas is diluted to 35% of volume concentration by carbon tetrafluoride, the pressure of a reactor is 101KPa, liquid nitrogen is taken as a refrigerant, the liquid nitrogen is trapped in a 10 liter nickel-aluminum alloy plated gas cylinder in a cold trap 8 at the temperature of minus 196 ℃, and the mixture is reacted for 6 hours, so that 5441 g of liquefied crude product mixture is obtained. Steaming out dilute gas carbon tetrafluoride with the boiling point of-128.1 ℃ in a cold trap 8 of-100 ℃ (alcohol+liquid nitrogen), so as to obtain 1361 g of purified substance; detection by gas chromatography, the result is SF 4 Content 92%, SF 6 Is 3%, S 2 F 2 2%, SOF 2 0.6%, CF 4 2% and the balance air.
Example 9
The aim of the embodiment is to provide a method for synthesizing sulfur tetrafluoride, which comprises the following steps:
the outlet of fluorine gas is 5mm away from the liquid surface of sulfur, the temperature of liquid sulfur is 280 ℃, the flux of fluorine gas is 150 g/h, the fluorine gas is diluted to 30% of volume concentration by hydrogen fluoride, the pressure of a reactor is 99KPa, and the temperature of the liquid sulfur is 280 DEG CThe mixture was trapped in a cold trap 8 of-85℃and alcohol+liquid nitrogen in a cylinder of 10 liters of nickel-plated aluminum alloy, and reacted for 6 hours to obtain 2384 g of liquefied crude product. Heating the crude gas bottle to 40deg.C, fully adsorbing hydrogen fluoride with spherical sodium fluoride, recovering 1190 g of purified product, and detecting SF by gas chromatography 4 Content 82%, SF 6 12%, S 2 F 2 4%, SOF 2 0.5%, the balance being air and a trace of CF 4 。
Example 10
The object of this example is to provide a reaction system for a method of synthesizing sulfur tetrafluoride.
The reaction system comprises a device body and a reactor.
The reactor is a horizontal tubular device with a heating part, and the horizontal tubular device is divided into a reaction chamber and a sulfur charging chamber which are connected with a fluorine gas inlet pipe by a vertical partition plate; the bottom of the partition plate is provided with a channel for enabling molten sulfur to enter the reaction chamber, liquid sulfur is used as a liquid seal to prevent gas-phase reactants from entering the sulfur feeding chamber, and system gas driving force is from negative pressure formed by a post-reaction product cryogenic liquefying device.
The method for synthesizing sulfur tetrafluoride provided by the invention has the following advantages:
in the prior art, the U.S. patent 3399036, wherein fluorine gas is 1 inch (about 25.4 mm) away from the surface of liquid sulfur for gas phase reaction, the concentration of fluorine gas is close to 100% during the reaction, and heat is violently released, and in the reaction, the heat dissipation and cooling difficulty is high due to the fact that the heat capacity of a gas phase space is too small and the heat conduction efficiency is low, so that the reaction rate is low, and large-scale production is difficult to form; and the system temperature is unstable, and S in the product is caused by temperature fluctuation 2 F 2 And SF (sulfur hexafluoride) 6 The content is increased greatly, which affects the yield and quality of the product; meanwhile, the high-temperature harsh working environment of the reaction zone and the strong oxidizing property and corrosiveness of fluorine gas and hydrogen fluoride in the air flow also cause the materials in the high-temperature zone to be corroded quickly, so that the reactor is frequently replaced to influence the yield, and the frequent disassembly of equipment also causes the deterioration of the sanitary condition of a workshop and brings great pressure to the production safety.
As is well known, gasesIs much less efficient than liquids. SF (sulfur hexafluoride) 4 The thermal conductivity of the gas is 0.0354W/(m.K), and the liquid sulfur is 0.269W/(m.K) under the same condition, which is 8 times different; furthermore, because the fluorine gas carries out gas phase reaction on the surface of the liquid sulfur, the heat dissipation mainly depends on the gas substances (SF 4 Mainly) is conducted to the metal shell of the reactor, the liquid sulfur is limited in its thermal conductivity and cannot fully exert its excellent heat dissipation function. Moreover SF 4 The specific heat capacity of the gas is 0.708KJ/Kg.K, the specific heat capacity of the liquid sulfur is 0.85KJ/Kg.K, and SF is about 300 DEG C 4 Density of less than 0.0045g/cm 3 But at this temperature the liquid sulfur has a density of greater than 1.6g/cm 3 The heat capacity of the two is 300 times or more different under the same volume, so that the SF of the same volume 4 The present inventors adopted a great contrast in thermal conductivity (8 times difference) and heat capacity (300 times difference) of the gaseous phase and the sulfur liquid phase to accelerate the reaction closer to the surface of the liquid sulfur, the fluorine gas outlet was reduced from 25mm to about 5mm from the sulfur liquid level, and the fluorine gas concentration was reduced from 100% to about 35%, thereby producing sulfur tetrafluoride. The synthesis method of sulfur tetrafluoride provided by the invention can obviously improve the heat conduction of a reaction zone, is very beneficial to the control of reaction temperature, thereby controlling the component stability of reaction products, improving the yield of target products, reducing the corrosion of a reactor metal material caused by local overhigh temperature and fluorine gas concentration, prolonging the service life of production equipment, realizing the purpose of high and stable production of sulfur tetrafluoride produced by the surface reaction of fluorine gas on liquid sulfur, and meeting the requirements of rapid increase of the current market; meanwhile, the cost is reduced, the application field of the special organic fluorinating agent is widened to the fields of pesticides, fine chemical engineering, special gases, green refrigeration and new materials, and a strong material foundation is provided for developing modern pharmaceutical chemical engineering, electronic industry, new materials in the future and other emerging industries.
In order to realize the production process of continuous high-efficiency reaction, the invention adopts a double-separation horizontal tubular reactor structure, namely the structure is divided into a charging area and a reaction area, which are separated by a metal plate, a channel is reserved between the baffle plate and the bottom of the tubular reactor so that molten sulfur in the charging area is continuously replenished to the reaction area to enable the reaction to be continuously carried out, 2-4 horizontal heating sleeves are arranged at the bottom so as to start the reaction when the sulfur is preheated to more than 240 ℃, the constant reaction temperature interval of 250-350 ℃ of the reaction area is maintained through a temperature controller and fluorine flux, namely the fluorine flux is reduced when the temperature is too high, the electric heating is started to replenish heat when the temperature is too low and the fluorine flux is limited, and the temperature maintenance stability is the key of realizing high-quality stable and high-yield of the reaction.
The synthesis method of sulfur tetrafluoride provided by the invention has the following principle:
fluorine gas from the electrolytic tank enters a dilution buffer tank after three processes of dust removal, deep cooling to-80 ℃ and spherical sodium fluoride adsorption and pre-removal of hydrogen fluoride, and the diluted fluorine gas enters a reactor to react with liquid sulfur to generate sulfur tetrafluoride SF 4 Mainly, sulfur hexafluoride SF 6 And thiothionyl difluoride S 2 F 2 A mixed gas stream that is a byproduct; because the sulfur sublimates and evaporates under the conditions of high temperature, low pressure and the like, part of free sulfur carried in the mixed gas flow enters a buffer tank at the back and is condensed and settled, and then enters a cryogenic catcher for liquefaction through filtration and bottling to obtain a crude product. The diluted gas hydrogen fluoride is removed from the crude product by means of adsorption, low-temperature distillation and the like, and the mixed gas of the target product is obtained by cryogenic liquefaction again.
The embodiments described above are some, but not all embodiments of the invention. The detailed description of the embodiments of the invention is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Claims (9)
1. The synthesis method of sulfur tetrafluoride is characterized by comprising the following steps: the fluorine gas and the liquid sulfur are subjected to gas-liquid reaction to generate sulfur tetrafluoride, the reaction pressure is 90-120kPa, and the distance from the outlet of the fluorine gas to the liquid sulfur level during the reaction is 3-10 mm; the volume concentration of the fluorine gas is 30-45%.
2. The method for synthesizing sulfur tetrafluoride according to claim 1, wherein the distance from the liquid level of the liquid sulfur at the outlet of the fluorine gas during the reaction is 3-5 mm, and the working pressure is 99-105kPa.
3. The method for synthesizing sulfur tetrafluoride according to claim 2, wherein the reaction temperature is 270-320 ℃.
4. A method of synthesizing sulfur tetrafluoride according to claim 3, wherein the reaction temperature is 280 to 300 ℃.
5. The method for synthesizing sulfur tetrafluoride according to claim 1, wherein the volume concentration of the fluorine gas is 30 to 35%.
6. The method for synthesizing sulfur tetrafluoride according to claim 1, wherein the flow rate of fluorine gas is 130 to 170g/h.
7. The method for synthesizing sulfur tetrafluoride according to claim 1, wherein the fluorine gas is a mixed gas of fluorine gas and a diluent gas, and the diluent gas is one or more of hydrogen fluoride, nitrogen gas, argon gas, sulfur hexafluoride, perfluorocarbon, hexafluoroethane, perfluorobutane and perfluoroether.
8. A reaction system for a method of synthesizing sulfur tetrafluoride according to any one of claims 1 to 7, comprising a device body and a reactor, wherein the reactor is a horizontal tubular device with a heating element, and the horizontal tubular device is divided into a reaction chamber and a sulfur charging chamber connected with a fluorine gas inlet pipe by a vertical partition plate; the bottom of the partition plate is provided with a channel for enabling molten sulfur to enter the reaction chamber, and liquid sulfur is used as a liquid seal to prevent gas-phase reactants from entering the sulfur feeding chamber.
9. The reaction system of claim 8 wherein the system gas impetus is from a negative pressure created by a post-reaction product cryogenic liquefaction plant.
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