Method for purifying hydrogen chloride in fluorine-containing hydrogen chloride tail gas

Abstract

The invention provides a method for purifying hydrogen chloride in fluorine-containing hydrogen chloride tail gas. The method comprises the following steps: enabling tail gas containing trace phosphorus pentafluoride, hydrogen fluoride and hydrogen chloride to pass through an adsorption column, and carrying out in-situ reaction on water generated after the hydrogen fluoride is chemically adsorbed by an adsorption column filling material and phosphorus pentafluoride to generate phosphorus oxyfluoride; gas at an outlet of the adsorption column passes through a microporous gas distributor, the gas reacts with a metal organic reagent, and then high-purity hydrogen chloride gas is obtained after hydrogen fluoride is separated through rectification. According to the method, high-purity hydrogen chloride can be prepared, and emission of pollutant-containing gas is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to a method for purifying hydrogen chloride from fluorine-containing hydrogen chloride tail gas. Background Art

[0002] Lithium hexafluorophosphate is the main electrolyte in lithium-ion battery electrolyte. The common industrial production method of solid lithium hexafluorophosphate is to add lithium fluoride powder to hydrogen fluoride solution to form a hydrogen fluoride solution of lithium fluoride, and then introduce phosphorus pentafluoride into the solution at a certain rate to react to obtain a hydrogen fluoride solution of lithium hexafluorophosphate. The obtained lithium hexafluorophosphate hydrogen fluoride solution is crystallized by intermittent cooling, dried, crushed and sieved to obtain lithium hexafluorophosphate crystals or powder.

[0003] Phosphorus pentafluoride is produced by fluorination of phosphorus pentachloride and hydrogen fluoride. This reaction process will produce five times the equivalent of hydrogen chloride. Hydrogen chloride mixed in phosphorus pentafluoride is used in the downstream synthesis device of lithium hexafluorophosphate. The tail gas of synthetic lithium hexafluorophosphate will contain a large amount of hydrogen chloride, phosphorus pentafluoride and hydrogen fluoride waste gas. All three gases have high recycling value. The boiling points of phosphorus pentafluoride and hydrogen chloride are very close, both at around -85°C, and cannot be separated by distillation process. Even if phosphorus pentafluoride or hydrogen chloride separated by pressurized distillation, impurities of the two are inevitable. In the industry, this fluorine-containing hydrogen chloride tail gas is usually absorbed with water as fluorine-containing waste hydrochloric acid. The amount of three wastes generated is large, difficult to handle, and seriously affects the environment. Therefore, it is necessary to develop a method to remove phosphorus pentafluoride from hydrogen chloride so as to recycle high-purity hydrogen chloride. Summary of the invention

[0004] One of the purposes of the present invention is to provide a method for purifying hydrogen chloride from fluorine-containing hydrogen chloride tail gas, which can prepare high-purity hydrogen chloride and reduce the emission of pollutant-containing gas.

[0005] There are a large amount of hydrogen chloride, hydrogen fluoride and trace phosphorus pentafluoride in the tail gas of lithium hexafluorophosphate synthesis. Because the boiling points of phosphorus pentafluoride and hydrogen chloride are very close, they can only be separated by the critical point temperature, but the energy consumption is very large and it is not easy to realize industrialization. In the industry, this mixed gas is made into fluorine-containing waste hydrochloric acid by water absorption, which is very difficult to handle and causes serious pollution to the environment. The present invention converts phosphorus pentafluoride in hydrogen chloride into phosphorus oxytrifluoride by adsorption and then converts it into fluorine-containing organic phosphate after organic reaction. The hydrogen fluoride in the system is separated from hydrogen chloride by distillation to obtain high-purity hydrogen chloride and hydrogen fluoride. The separated hydrogen fluoride can continue to be used for phosphorus pentafluoride or lithium hexafluorophosphate synthesis, and hydrogen chloride can be oxidized into chlorine by hydrogen chloride to produce phosphorus trichloride or phosphorus pentachloride, thereby reducing costs. The separated high-purity hydrogen chloride finally obtains PF5<5ppm, HF<10ppm high-purity hydrogen chloride gas.

[0006] To achieve the above-mentioned invention object, the present invention adopts the following technical solutions:

[0007] A method for purifying hydrogen chloride from hydrogen chloride tail gas containing fluorine, the method comprising the following steps:

[0008] S1: The tail gas containing trace amounts of phosphorus pentafluoride, hydrogen fluoride and hydrogen chloride is first passed through an adsorption column. The water generated after the chemical adsorption of hydrogen fluoride by the filling material in the adsorption column reacts in-situ with phosphorus pentafluoride to generate phosphorus oxyfluoride;

[0009] S2: The gas at the outlet of the adsorption column passes through a microporous gas distributor. The gas reacts with the metal organic reagent, and after rectifying and separating hydrogen fluoride, high-purity hydrogen chloride gas is obtained.

[0010] The reaction formula involved in the present invention is:

[0011]

[0012] In one embodiment of the present invention, the content of phosphorus pentafluoride in the mixed gas in S1 is 0.1 wt% - 2 wt%, and the content of hydrogen fluoride is 1 wt% - 10 wt%. Preferably, the phosphorus pentafluoride is 0.1 wt% - 1.5 wt%, and the hydrogen fluoride is 3 wt% - 8 wt%.

[0013] In one embodiment of the present invention, the filling material in S1 is a transition metal oxide filler doped with Al 2 O 3 ; Preferably, the selected transition metal oxides include divalent to hexavalent metal oxides, preferably ZnO, Pb 3 O 4 , PbO 2 , Ag 2 O, Fe 3 O 4 , Cu 2 O, MnO 2 , V 2 O 4 , CrO 3 , WO 3 , BeO, MgO, MnO 3 , Mn 2 O 7 , HgO, CuO, TiO 2 One or more of; Preferably, the ratio of Al 2 O 3 to the transition metal oxide is 3:1 to 1:2.

[0014] In one embodiment of the present invention, the gas source pressure in S1 is 0.5 - 3 MpaG, and preferably the gas source pressure is 1 - 2 MpaG.

[0015] In one embodiment of the present invention, the pore diameter of the microporous gas distributor in S2 is 1 mm - 50 mm, preferably 8 - 25 mm.

[0016] In one embodiment of the present invention, the metal-organic reagent in S2 includes one or more of Grignard reagents, organozinc reagents, organotin reagents, organolithium reagents, and alkynyl copper reagents, preferably methylmagnesium bromide, ethylmagnesium bromide, vinylmagnesium bromide, cyclopropylmagnesium bromide, cyclopentylmagnesium bromide, cyclohexylmagnesium bromide, benzylmagnesium bromide, isobutylzinc bromide, 4-chlorobutylzinc bromide, 4-cyanobutylzinc bromide, 3-methylbutylzinc bromide, n-pentylzinc bromide, hexylzinc bromide, cyclopropylzinc bromide, cyclopentylhexylzinc bromide, vinylzinc bromide, triethyltin chloride, tributyltin chloride, allyldibutyltin chloride, 1-azabicyclo[3.3.3]undecyltin chloride, tricyclohexyltin chloride, methyllithium, ethyllithium, n-butyllithium, tert-butyllithium, cyclopropyllithium, copper acetylide, butylpropargyl copper, phenylacetylene copper, ethynylmagnesium bromide, propargylzinc bromide, etc.

[0017] In one embodiment of the present invention, the mass ratio of the metal-organic reagent to the gas in S2 is 5:1 to 1:2.

[0018] In one embodiment of the present invention, the temperature of the reaction between the gas and the metal-organic reagent in S2 is controlled according to the stability of the metal-organic reagent and the different saturated vapor pressures of the gas; preferably, the temperature of the reaction between the gas and the metal-organic reagent is -40 - 10 °C, more preferably -30 - 0 °C.

[0019] In one embodiment of the present invention, the temperature of the rectification separation in S2 is -40 - 10 °C, the pressure is 0.5 - 30 MPaG, and the reflux ratio is (3 - 6):1; preferably, the temperature is -30 - 0 °C, the pressure is 1 - 10 MPaG, and the reflux ratio is (4 - 6):1.

[0020] Another object of the present invention is to provide a high-purity hydrogen chloride gas.

[0021] A high-purity hydrogen chloride gas, which is prepared by the above method, and the hydrogen chloride gas is prepared from fluorine-containing hydrogen chloride tail gas. The PF in the high-purity hydrogen chloride gas 5 < 5 ppm, HF < 10 ppm.

[0022] Another object of the present invention is to provide a use of the high-purity hydrogen chloride gas.

[0023] A use of a high-purity hydrogen chloride gas, the hydrogen chloride gas is prepared by the above method, or is the above hydrogen chloride gas, and the hydrogen chloride gas is used for high-purity hydrogen chloride in the electronics or battery industry.

[0024] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0025] (1) High-purity hydrogen chloride gas with PF 5 <5 ppm and HF < 10 ppm is obtained;

[0026] (2) Chlorine and fluorine elements are recycled, and the discharge of pollutants is reduced. Description of the Drawings

[0027] Figure 1 It is the F-NMR spectrum of the mixed gas in Example 1 of the present invention after reacting with the metal organic reagent 19 F-NMR spectrum. Specific Embodiments

[0028] In order to better understand the technical solution of the present invention, the content of the present invention will be further elaborated below in conjunction with embodiments. However, the content of the present invention is not limited to the following embodiments.

[0029] The source information of the main raw materials used in the embodiments of the present invention. All packing materials and organometallic reagents are purchased from Beijing InnoChem Technology Co., Ltd. If the reagent has a high water content, it is dehydrated through a molecular sieve. The reaction kettle, microporous distributor and feed pipeline are all made of 316L material. The adsorption column is made of DN10 (length 55 cm) and 316L material. The tail gas of lithium hexafluorophosphate comes from the lithium hexafluorophosphate device of Wanhua Chemical.

[0030] For the experimental operations involved in the following examples or comparative examples, if not otherwise specified, they are all conventional experimental methods in the art. Among them, Bruker AVANCNEO 500 MHz nuclear magnetic resonance, Agilent 5800 ICP-OES inductively coupled plasma technology, Mettler BION1881 fluoride ion electrode and Jianzhi RS2000 on-line Raman spectroscopy are used to qualitatively and quantitatively analyze fluorine and phosphorus substances in the mixed gas.

[0031] Example 1

[0032] Charge the tail gas of synthesized lithium hexafluorophosphate into a 3L gas tank. At this time, the content of phosphorus pentafluoride in the gas source is 1.3%, the content of hydrogen fluoride is 7%, and the remaining gas is hydrogen chloride. The gas source pressure is 2.0 MpaA.

[0033] Under a nitrogen environment, load Al 2 O 3 Spheres and ZnO mixed packing (mass ratio 2:1) into the adsorption column. Add 50 g each of vinylmagnesium bromide and cyclohexylmagnesium bromide mixed organometallic reagents to a 500 mL reaction kettle made of 316L material with an outer jacket and select a 15 mm microporous gas distributor.

[0034] Turn on the external circulation cold bath to maintain the temperature of the organometallic reagent at -20°C. Connect the gas distributor to the outlet of the adsorption column and the gas source to the inlet of the adsorption column through pipeline connections. The stirring speed is 500 rpm / min. After the system stabilizes, open the intake valve. After the pressure in the reaction kettle balances with the pressure of the gas source, let the reaction stay for 8 minutes, and then the reaction ends. Connect the non-condensable gas generated in the upper layer of the reaction kettle to the downstream distillation device and purify it through a distillation column (-5°C, 20 barG, reflux ratio 5:1). Hydrogen fluoride is drawn from the bottom of the column, and hydrogen chloride is drawn from the top of the column, and then high-purity hydrogen chloride is separated, where phosphorus pentafluoride < 5 ppm and hydrogen fluoride residue in hydrogen chloride < 10 ppm.

[0035] To verify the adsorption, reaction, and separation effects, take the gas at the outlet of the adsorption column and analyze the residual amount of phosphorus pentafluoride using on-line Raman spectroscopy. Absorb a part of the non-condensable gas in the reaction kettle with an alkaline solution for ICP detection of phosphorus elements to judge the removal effect of phosphorus pentafluoride. At the same time, absorb the high-purity hydrogen chloride after distillation with an alkaline solution for fluoride ion electrode detection of fluoride ions to judge the separation effect of hydrogen chloride and hydrogen fluoride. The results are shown in Table 1.

[0036] Table 1

[0037]

[0038] Example 2

[0039] Charge the tail gas of lithium hexafluorophosphate synthesis into a 3L gas tank. The content of phosphorus pentafluoride in this gas source is 1%, the content of hydrogen fluoride is 5%, and the remaining gas is hydrogen chloride. The gas source pressure is 1.5 MpaA.

[0040] Under a nitrogen environment, load Al 2 O 3 balls and WO 3 mixed packing (mass ratio 1:2) into the adsorption column. Add 100 g of ethynyl copper to a 500 mL reaction kettle with an outer jacket made of 316L material and equipped with an 8 mm microporous gas distributor.

[0041] Turn on the external circulation cold bath to maintain the temperature of the metal organic reagent at -30°C. Connect the gas distributor to the outlet of the adsorption column and the gas source to the inlet of the adsorption column through pipeline connections. The stirring speed is 800 rpm / min. After the system stabilizes, open the intake valve. After the pressure in the reaction kettle balances with the pressure of the gas source, let the reaction stay for 15 minutes, and then the absorption of phosphorus pentafluoride ends. Connect the non-condensable gas generated in the upper layer of the reaction kettle to the downstream distillation device and purify it through a distillation column (-10°C, 15 barG, reflux ratio 4:1). Hydrogen fluoride is drawn from the bottom of the column, and hydrogen chloride is drawn from the top of the column, and then high-purity hydrogen chloride is separated, where phosphorus pentafluoride < 5 ppm and hydrogen fluoride residue < 10 ppm. The results are shown in Table 2.

[0042] Table 2

[0043]

[0044] Example 3

[0045] The tail gas of synthetic lithium hexafluorophosphate is charged into a 3L gas cylinder. The content of phosphorus pentafluoride in this gas source is 0.2%, the content of hydrogen fluoride is 3%, and the remaining gas is hydrogen chloride. The gas source pressure is 1.0 MpaA.

[0046] Under a nitrogen environment, Al 2 O 3 balls, CrO 3 and PbO 2 mixed packing (mass ratio 1:1:1) are loaded into the adsorption column. 100 g of ethynyl copper is added to a 500 mL reactor with an external jacket made of 316L material and a circulation system, and an 8 mm microporous gas distributor is selected. 50 g of allyldibutyltin chloride and 50 g of tert-butyllithium are added to a 500 mL reactor with an external jacket made of 316L material and a circulation system, and a 5 mm microporous gas distributor is selected.

[0047] The temperature of the absorbent is maintained at -10°C by turning on the external circulation cold bath. The gas distributors and the adsorption column outlet are connected through pipelines, and the gas source is connected to the adsorption column inlet. The stirring speed is 400 rpm / min. After the system is stable, the inlet valve is opened. After the pressure in the reactor is balanced with the gas source pressure, the reaction stays for 12 minutes, and the absorption of phosphorus pentafluoride is completed. The non-condensable gas generated from the upper layer of the reactor is connected to the downstream distillation device. Hydrogen fluoride is extracted from the bottom of the distillation column (-15°C, 12 barG, reflux ratio 6:1), and hydrogen chloride is extracted from the top, and then high-purity hydrogen chloride is separated, in which the content of phosphorus pentafluoride is <5 ppm and the residual content of hydrogen fluoride is <10 ppm. The results are shown in Table 3.

[0048] Table 3

[0049]

[0050] Comparative Example 1

[0051] Referring to the method of Example 1, the only difference is that the filling material of the adsorption column is replaced with non-transition metal oxide CaO, and other operating parameters remain unchanged. The residual content of phosphorus pentafluoride in the separated hydrogen chloride is 107 ppm, and the content of hydrogen fluoride is 88 ppm.

[0052] Comparative Example 2

[0053] Referring to the method of Example 1, the only difference is that the metal organic reagent is replaced with other nucleophilic reagent ethanol, and other operating parameters remain unchanged. The residual content of phosphorus pentafluoride in the separated hydrogen chloride is 56 ppm, and the content of hydrogen fluoride is 43 ppm.

[0054] Comparative Example 3

[0055] Referring to the method of Example 1, the only difference is that the adsorbent column packing material is changed to non-transition metal oxide MgO, the metal organic reagent is changed to other nucleophilic reagents phenol, and other operating parameters remain unchanged. After separation, the residual phosphorus pentafluoride in hydrogen chloride is 211 ppm and hydrogen fluoride is 124 ppm.

[0056] Comparative Example 4

[0057] Referring to Example 1 of CN111410182A: The mixed gas with a mass ratio of HF, HCl and PF 5 of 0.552:0.384:0.064 is absorbed in an absorption tower with o-xylene as the absorbent, and the absorption efficiency of phosphorus pentafluoride is only 53.1%, while the absorption efficiency in Example 1 can reach over 99%.

Claims

1. A method for purifying hydrogen chloride from tail gas containing hydrogen fluoride and hydrogen chloride, characterized in that, the method comprises the following steps: S1: Pass the tail gas containing trace amounts of phosphorus pentafluoride, hydrogen fluoride and hydrogen chloride through an adsorption column first. The water generated after the chemical adsorption of hydrogen fluoride by the filling material of the adsorption column reacts in-situ with phosphorus pentafluoride to generate phosphorus oxyfluoride; S2: The gas at the outlet of the adsorption column passes through a microporous gas distributor. The gas reacts with a metal-organic reagent, and then after rectifying and separating hydrogen fluoride, high-purity hydrogen chloride gas is obtained.

2. The method according to claim 1, characterized in that, the content of phosphorus pentafluoride in the mixed gas in S1 is 0.1 wt% - 2 wt%, the content of hydrogen fluoride is 1 wt% - 10 wt%, preferably phosphorus pentafluoride is 0.1 wt% - 1.5 wt%, hydrogen fluoride is 3 wt% - 8 wt%, and the remaining gas is hydrogen chloride; And / or, the filling material described in S1 is a transition metal oxide filler doped with Al 2 O 3 ; Preferably, the selected transition metal oxide includes metal oxides with valence states from +2 to +6, preferably ZnO, Pb 3 O 4 , PbO 2 , Ag 2 O, Fe 3 O 4 , Cu 2 O, MnO 2 , V 2 O 4 , CrO 3 , WO 3 , BeO, MgO, MnO 3 , Mn 2 O 7 , HgO, CuO, TiO 2 or more of them; Preferably, the ratio of the Al 2 O 3 to the transition metal oxide is 3:1 to 1:2; and / or, the gas source pressure in S1 is 0.5 - 3 MpaA, preferably the gas source pressure is 1 - 2 MpaA.

3. The method according to claim 1 or 2, characterized in that, the pore diameter of the microporous gas distributor in S2 is 1 mm - 50 mm, preferably the pore diameter is 8 - 25 mm; and / or, the metal-organic reagent in S2 comprises one or more of Grignard reagents, organozinc reagents, organotin reagents, organolithium reagents and alkynyl copper reagents, preferably methylmagnesium bromide, ethylmagnesium bromide, vinylmagnesium bromide, cyclopropylmagnesium bromide, cyclopentylmagnesium bromide, cyclohexylmagnesium bromide, benzylmagnesium bromide, isobutylzinc bromide, 4-chlorobutylzinc bromide, 4-cyanobutylzinc bromide, 3-methylbutylzinc bromide, n-pentylzinc bromide, hexylzinc bromide, cyclopropylzinc bromide, cyclopentylhexylzinc bromide, vinylzinc bromide, triethyltin chloride, tributyltin chloride, allyldibutyltin chloride, 1-aza-bicyclo [3.3.3] undecyltin chloride, tricyclohexyltin chloride, methyllithium, ethyllithium, n-butyllithium, tert-butyllithium, cyclopropyllithium, copper acetylide, butyl propynyl copper, phenylacetylene copper, ethynylmagnesium bromide, propynylzinc bromide; and / or, the mass ratio of the metal-organic reagent to the gas in S2 is 5:1 to 1:2; preferably, the temperature for the reaction of the gas with the metal-organic reagent is -40 - 10 °C, preferably -30 - 0 °C; and / or, the temperature for rectifying and separating in S2 is -40 - 10 °C, the pressure is 0.5 - 30 MPaG, and the reflux ratio is (3 - 6):1, preferably the temperature is -30 - 0 °C, the pressure is 1 - 10 MPaG, and the reflux ratio is (4 - 6):

1.

4. A high-purity hydrogen chloride gas, which is prepared by the method described in any one of claims 1 - 3, characterized in that, The hydrogen chloride gas is prepared from the fluorine-containing hydrogen chloride tail gas, and PF 5 in the high-purity hydrogen chloride gas is <5 ppm, and HF is <10 ppm.

5. A use of a high-purity hydrogen chloride gas, the hydrogen chloride gas is prepared by the method described in any one of claims 1 - 3, or is the hydrogen chloride gas described in claim 4, characterized in that, the hydrogen chloride gas is used for high-purity hydrogen chloride in the electronics or battery industry.

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