RU2119448C1 - Method and apparatus for producing fluorinated carbon - Google Patents

Abstract

FIELD: chemical engineering. SUBSTANCE: invention is appropriate to use in chemical power sources, lubricant additives, and insulator substratesТ production. Reactor 1 enclosing gas-impermeable accessory 2 filled with powdered amorphous or crystalline carbon is sealed and preheater 6 is switched on. Anode gas (12-21% fluorine content) of fluorine electrolyzer mixed with nitrogen is supplied through mixer 5, heat-chamber 7, and manifold valve 8. Operation temperature ranges from 320 to 500 C. Gases are continuously analyzed in mixer 5 and in reactor outlet pipe 4. Relation of reactor volume to geometric area of accessory 2 is 0.3-0.4. Product is fine white or grey fluorocarbon with fluorine content 59-63%, loose density 0.4-0.7 g/cu.cm (varies with kind of initial carbon material, particle size 10 to 10 mcm, and destruction temperature 630-660 C. EFFECT: enhanced process efficiency. 5 cl, 1 dwg, 2 tbl, 3 ex

Description

 The invention relates to the field of chemical technology, and specifically to the production of solid carbon fluorides (polycarbonofluorides), which are used as cathode material of lithium chemical current sources, additives and lubricants, as lubricants, in electronics - for the manufacture of dielectric substrates, etc.

Known methods for producing fluorinated carbon by treating a carbon material with a mixture of fluorine with an inert gas at a temperature of 200-600 ^o C (see J. of Fluorine Chem., 46 (1990), 461-477; Schmierungstechnir, Berlin, 1988, 19, N 4 114-117).

The methods allow to obtain, depending on the starting material and temperature, fluorocarbon from black to white with a fluorine content of from 11 to 66 wt.%, Bulk density of 0.1-1.0 g / cm ³ .

The main objective in the implementation of these methods is to prevent thermal degradation of the resulting fluorocarbon according to the equation
4 (CF) _n __ → nCF ₄ + 3nC ^* ,
Where
C ^* is active carbon.

 The process of thermal degradation proceeds with a large heat release and can lead to loss of the final product and to destruction of equipment.

 One typical way to prevent thermal degradation is to remove the heat of the exothermic reaction of fluorine with carbon by forcing the fluorinating mixture through the feed material loaded into the mesh cells (see IR Patent Application GB 2104884A, 1982). This method is mainly used for fluorination of graphite.

Another way to prevent thermal degradation (and, therefore, to prevent the loss of mass of the obtained fluorocarbon) is to add to the used fluorine hydrogen fluoride in an amount of not more than 5% vol. When processing carbon material in the temperature range 300-450 ^o C such fluorine fluorinated carbon loss is not observed. If hydrogen fluoride will contain more than 5% vol. , then there is a decrease in the mass of the finished product - fluorinated carbon with a ratio of C: F = 1: 1 (see the application of Germany N 2306737, 1978).

 The disadvantage of this method is the need to add hydrogen fluoride to fluorine, the possibility of thermal degradation of fluorinated carbon is not excluded.

 A variant of this method is a known method for producing fluorinated carbon, comprising treating the carbon material with a mixture of nitrogen and fluorine obtained by electrolysis of a melt of potassium acid fluorides, in particular KF • 2HF (application UK 2104883, class C 01 B 31/00, 1983). This method is a prototype of the invention.

 The disadvantage of the prototype method is the need to sieve the product obtained through a sieve to separate fluorinated graphite from unreacted carbon material (if the fluorination reaction is terminated before it is completed), there is no criterion for completing the process. The method does not allow to obtain fluorinated carbon with a given fluorine content, a product of uniform quality, and also does not exclude thermal degradation of fluorinated carbon.

 An object of the invention is to obtain fluorinated carbon with a given fluorine content therein, to obtain a fluorocarbon material of uniform quality, increasing productivity.

The technical problem is solved in that when the carbon material is treated with a mixture of an anode gas of a fluorine electrolyzer with an inert gas, in particular nitrogen, the fluorine content in the initial gas mixture is 12-21 vol.%, Processing is carried out at a temperature of 320-500 ^o C with continuous gas analysis at the entrance and exit of the reaction zone, and the process ends when the content of the components in the exhaust reaction gas reaches values corresponding to their content in the initial mixture of the anode gas of the fluorine electrolyzer with an inert gas.

 To implement the method, a device is proposed, the prototype of which is a device for producing fluorinated graphite, described in the application of the United Kingdom (N 2104884, 1993). The prototype device includes a reactor, a reactor heater, a fluorine and nitrogen mixer, a gas-permeable tooling for carbon material, a gas inlet to the reactor, and a gas outlet pipe from the reactor. Used to produce fluorinated graphite during the passage of a fluorinating mixture through carbon material loaded into mesh cells. This device does not exclude thermal degradation of the resulting fluorocarbon material.

Distinctive features of the proposed device are:
the ratio of the volume of the reactor (m ³ ) to the geometric surface of the tool (m ² ) for the carbon material is 0.3-0.4;
the reaction gas is fed into the reactor heated and additionally warmed up as it passes through a distribution comb mounted inside the reactor.

 These features provide stabilization of the process, eliminates the possibility of thermal degradation of fluorinated carbon.

The proposed device is presented in the drawing. The device includes a fluorination reactor 1, gas-permeable snap-in 2 for carbon material, a loading hatch 3, a source gas inlet unit, a gas outlet 4, a mixer 5 and a heater 6. The source of supply of the reaction gas is equipped with a heat chamber 7 in a distribution comb 8 located inside the reactor, the ratio of the reactor volume (m ³ ) to the geometric surface (m ² ) of gas-permeable tooling for the carbon material is made equal to 0.3-0.4.

Thus, the invention consists in processing a carbon material with a mixture of the anode gas of a fluorine electrolyzer and nitrogen with a fluorine concentration in the mixture of 12-21% vol. with continuous monitoring of the gas composition at the inlet and outlet of the reaction zone in the device with the ratio of the reactor volume (m ³ ) to the geometric surface of the tool (m ² ) for the carbon material equal to 0.3-0.4, with the heating of the initial gas mixture before feeding it into the reaction zone and in the distribution comb mounted inside the reactor, which allows to increase productivity, obtain fluorocarbon material with a given fluorine content, obtain a product of uniform quality at a lower temperature, use as the starting carbon material and any grade of crystallinity (carbon black, graphite, sibunite, coke) to exclude the possibility of thermal degradation of fluorinated carbon.

At a temperature of 320 ^o C and a fluorine content in the initial mixture of less than 12 vol.% Decreases productivity.

At a temperature above 500 ^o C and with a fluorine content in the initial mixture of more than 21 vol. % there is also a decrease in productivity due to the burning of carbon to volatile substances.

 If you finish the process when the content of the components in the exhaust gas is less than their content in the original reaction gas, then we get fluorinated carbon with a fluorine content below 59-61 wt.%. Upon reaching the content of components (fluorine, volatile fluorocarbons) in the exhaust gases to their values in the initial gas mixture supplied to fluorination, a uniform fluorinated carbon with a fluorine content in the range of 59-61 wt.% Is obtained.

 Providing the claimed device with a heat chamber for heating the initial reaction gas and a distribution comb located inside the reactor allows avoiding temperature differences in the reactor reaction zone and stabilizing the fluorination process.

The ratio of the reactor volume (m ³ ) to the geometric surface of the gas-permeable tooling (m ² ) actually determines the amount of fluorine in the gas phase per 1 m ^{2 of} carbon material, which is very important in the event of inevitable fluctuations in the parameters and conditions of the actual fluorination process, during which fluorine from the reaction mixture is continuously consumed by carbon material. Too small a volume of the reactor with respect to the surface of the carbon material ensures rapid absorption of fluorine from this volume by the carbon material (up to zero), which will inevitably lead to destruction, partial or complete, of fluorinated carbon. Too large a reactor volume relative to the surface of the carbon material, from this point of view, is not harmful to the process, but is not economically justified. We found the optimum ratio of 0.3-0.4 m ³ / m ² , providing a sufficient amount of fluorine in the gas phase over the carbon material under any fluctuations in the parameters and conditions of the process in normal mode.

The fluorination process is carried out as follows. Through the hatch 3, a gas-permeable tool 2, filled with the starting carbon material (carbon black, sibunite, graphite, etc.) with a layer of 5-10 mm, is loaded into the reactor 1. The reactor is sealed, the reactor heater 6 is turned on and the heat chamber 7 is heated, and nitrogen is supplied to the reactor through the mixer 5 and the inlet unit (heat chamber 7 and distribution comb 8) for the time required to bring the reactor to a predetermined temperature regime. The consumption of nitrogen is 1 m ³ / hour.

 During this period, moisture and volatile impurities are removed from the carbon material, and air is removed from the reactor volume.

Upon reaching the set temperature, a continuous analysis of the gases begins in the mixer 5 and at the outlet of the reactor (pipe 4), the anode gas of the fluorine electrolyzer (0.7-0.8 m ³ / h) is supplied to the mixer 5 so that the fluorine content in the mixture with nitrogen was equal to 12-21 vol.%, as a rule, the content of volatile carbon fluorides in the initial mixture is at the level of 0.01% vol. (mass spectrometric analysis). From the mixer 5, the reaction gas is supplied to the reactor through a heat chamber 7 heated to 300 ^° C. and through a distribution comb 8. The gas passing through the distribution comb is additionally heated to the temperature of the reaction zone and reacts with the carbon material. The surface fluorination of carbon begins - stage I of the process, which is evident from the composition of the gases leaving the reactor outlet 4 from the reactor: the fluorine content in the first 0.5 hours decreases to 5-10 vol.%, Increases to 1 vol.% And higher - the volatile content fluorocarbons. This stage lasts 10-20 hours. At the end, its fluorine content in the gases at the outlet of the reactor rises to the initial one, the content of volatile fluorocarbons decreases to 0.02-0.09 vol.%. At this stage, surface treatment of the carbon material occurs, the bulk of the volatile carbon impurities is burned by fluorine.

 Then comes the second stage of fluorination. It lasts 20-40 hours. In the initial period, the content of volatile impurities in the exhaust gases increases sharply to 0.8-0.9 vol. % and then gradually decreases to 0.02-0.03 vol.%, the fluorine content decreases to 5-6 vol.%. At this stage, fluorine is introduced into the interlayer space of carbon material, fluorine reacts with secondary and tertiary carbon atoms to form C-F bonds.

. Хотя общее количество концевых (первичных) атомов углерода относительно меньше, чем вторичных и третичных, но потребляют фтора они практически такое же количество. Содержание летучих фторуглеродов на этой стадии плавно снижается до уровня 0,02-0,03 об.%, содержание фтора достигает минимума 2-5 об.%. Эта стадия длится 20-40 часов.The next is stage III fluorination. Fluorine reacts with the least reactive carbon atoms - primary with the formation of bonds

. Although the total number of terminal (primary) carbon atoms is relatively less than secondary and tertiary, they consume almost the same amount of fluorine. The content of volatile fluorocarbons at this stage gradually decreases to the level of 0.02-0.03 vol.%, The fluorine content reaches a minimum of 2-5 vol.%. This stage lasts 20-40 hours.

 Then comes the final, IV stage of fluorination. The fluorine content in the exhaust gases gradually increases to the initial value (12-21 vol.%), And the content of volatile fluorocarbons decreases to the initial value - 0.01 vol.%. The duration of the stage is 10-20 hours, at the end of it the blocking of the carbon end groups by fluorine ends, which significantly increases the thermal stability of the formed solid fluorocarbon.

И здесь важную роль играет найденное нами эмпирическое соотношение объема реактора к геометрической поверхности оснастки для углеродного материала, равное 0,3-0,4. При меньшем соотношении более резко сказываются неизбежные флуктуации параметров и условий ведения процесса или нештатное их отклонение (нарушение герметичности оборудования, температура, соотношение: фтор - инертный газ).But at the same time, until the fluorine blocking of the end groups of the carbon material has ended, this stage is the most dangerous and unstable. It is at this stage that one should expect a landslide thermal decomposition of the obtained fluorocarbon, which can even lead to the destruction of equipment. Thermal degradation, for example, at stage III of fluorination is not so dangerous due to the low content of end groups in fluorocarbon

And here the important role is played by the empirical ratio of the reactor volume to the geometric surface of the tooling for the carbon material, which is 0.3-0.4. With a lower ratio, the inevitable fluctuations in the parameters and conditions of the process or their abnormal deviation (violation of equipment tightness, temperature, ratio: fluorine - inert gas) are more sharply affected.

It should be noted that the fluorination process can continue further (stage V), but it will be associated with the burnout of the carbon material according to the equation:
4 (CF) _n __ → nCF ₄ + 3nC ^*
There can be no collapse of thermal decomposition (subject to technological parameters), but, continuing the process, it is possible to transfer all of the carbon source material into volatile fluorides. The fluorine content in the exhaust gases decreases slightly, but sharply, up to 1 vol.% And higher, the content of volatile fluorocarbons in them increases.

At the end of the process, the anode gas supply to the mixer is stopped, only nitrogen (1 m ³ / h) is supplied to the reactor, and the heating of the heat chamber and reactor is turned off. When the temperature of the reactor decreases to room temperature, the nitrogen supply is stopped, the reactor is opened, and the resulting fluorinated carbon is recovered.

With the timely completion of the process (in stage IV), finely dispersed fluorocarbon of white or gray color is obtained with a fluorine content of 59-63%, bulk density of 0.6-0.7 g / cm ³ for fluorinated carbon black and 0.4-0.5 g / m ³ for fluorinated sibunit with a group ratio of CF ₂ : CF equal to 1: (15-42) for carbon black and 1: (94-15) for sibunit, with a particle size of 10 to 150 microns and a decomposition temperature in air of 630-660 ^o C (at a heating rate on a derivatograph of 10 ^o / min). The content of heavy metal impurities (Ni, Cu, Fe, Cr, Mn, Ti, Al) in total does not exceed 0.1% by weight (all parts of the device are made of nickel).

 However, the method also allows you to get fluorinated carbon with any given fluorine content below 61 wt.%, If you finish the fluorination process at stage I, II or III.

 Example 1

A 2.25 m ³ experimental nickel reactor was charged with gas-permeable nickel equipment (trays) filled with T-900 carbon black or sibunite, a layer 5-10 mm thick. The geometric surface of the snap is 6.8 m ² . The ratio V: S = 0.33. A mixture of anode gas (0.8 m ³ / h) of a medium temperature fluorine electrolyzer with nitrogen was fed into the reactor (see table 1).

 Example 2

In the experimental Nickel reactor with a volume of 0.5 m ³ loaded snap filled with carbon material with a layer thickness of 5-10 mm The geometric surface of the tool is 2.5 m ² . The ratio V: S = 0.20. A mixture of an anode gas of a fluorine electrolyzer (0.5 m ³ / h) and nitrogen was fed into the reactor (see table 2).

 In example 1, the ratio of volume to geometric surface snap 0.33. In each of the experiments, fluorocarbon is uniform in color (white) and fluorine content. In experiment 3, relatively less fluorocarbon was obtained due to the ongoing fluorination (burnout) in stage V.

 In example 2, the ratio of volume to geometric surface snap 0.2. In experiment 1, almost all of the carbon burned out, in experiment 2 there was a thermal degradation of fluorocarbon at the IV stage of fluorination, in experiment 3 fluorocarbon was obtained, and its output was much lower than in example 1.

 Example 3

A snap filled with powdered graphite (Botogolsky deposit) with a layer thickness of 5-10 mm was loaded into an experimental 0.1 m ³ nickel reactor. The geometric surface of the snap is 0.25 m ² . The ratio of V: S = 0.4. At a temperature of 480-500 ^o C the process was 38 hours. Fluorine consumption 39 l / h, nitrogen consumption 260 l / h (fluorine content in the mixture 13 vol.%). Loaded 700 g of graphite. 1,400 g of white fluorinated graphite with a fluorine content of 61.3 wt.% Were unloaded.

The fluorinated carbon obtained in Example 1 was tested as the cathode mass of lithium chemical current sources. When using an electrolyte - 1 M solution of ZiClO ₄ in polypropylene carbonate - the specific capacity of the chemical current source was 500 - 700 mA • hour • g ^-1 , specific energy 1500 - 1800 W • hour • kg ^-1 .

Claims (5)

1. The method of producing fluorinated carbon, which consists in treating the carbon material with fluorine and hydrogen fluoride obtained by electrolysis of acid potassium fluorides in a mixture with nitrogen, characterized in that the mixture contains 12 to 21 vol.% Fluorine and processing is carried out at 320 to 500 ^o C.  2. The method according to claim 1, characterized in that the process of fluorination of the carbon material is controlled by the content of fluorine and volatile fluorocarbons in the gases at the inlet and outlet of the reaction zone.  3. The method according to PP.1 and 2, characterized in that as the starting carbon material using powdered carbon of any structure - amorphous or crystalline. 4. A device for producing fluorinated carbon, including a reactor, a reactor heater, a fluorine and inert gas mixer, a gas-permeable tooling for carbon material, a gas inlet to the reactor and a gas outlet from the reactor, characterized in that the ratio of the volume (m ³ ) of the reactor to the geometric surface of the residue (m ² ) for the carbon material is made equal to 0.3 - 0.4.  5. The device according to claim 4, characterized in that the node for introducing gas into the reactor is equipped with a heat chamber and a distribution comb located inside the reactor.

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