EP2804835A1

EP2804835A1 - Low-chloride lipf6

Info

Publication number: EP2804835A1
Application number: EP13700416.4A
Authority: EP
Inventors: Matthias Boll; Wolfgang Ebenbeck; Eberhard Kuckert
Original assignee: Lanxess Deutschland GmbH
Current assignee: Lanxess Deutschland GmbH
Priority date: 2012-01-19
Filing date: 2013-01-18
Publication date: 2014-11-26
Also published as: CN104093668A; JP5894299B2; CN104093668B; CA2861018A1; US20150044118A1; WO2013107877A1; JP2015504037A; KR20140114439A

Abstract

The invention relates to a method for producing low-chloride LiPF₆, in particular low-chloride LiPF₆ solutions, on the basis of the reactant PCl₃ via the intermediate product PCl₅ and to an apparatus to be used for this purpose.

Description

Low chloride LiPF ₆

The present invention relates to a process for the preparation of low-LiPFe LiPFe, in particular in the form of low-LiPF ₆ solutions, starting from the starting material PCI ₃ on the intermediate PC1 ₅ and an apparatus to be used for this purpose. Numerous processes for the preparation of LiPFe are described in the prior art. However, certain technical conditions require appropriate process variants. If PCI3 and HF are available, the following reaction path is available:

With the aim of a low PF ₃ content in the end product DE 197 12 988 A1 describes a batchwise operated process in an autoclave starting from PCI ₃ . In a dry test reactor made of stainless steel while 7.8 g of LiF were initially charged and heated at 150 ° C under argon in a laboratory autoclave PC1 _{3 was} charged and cooled to -52 ° C, then metered HF. After cooling to -58 ° C, the Cl ₂ dosage was carried out. The autoclave was then removed from the cooling bath and an HCl / PF ₅ gas mixture passed through the LiF in the experimental reactor After completion of the transfer of the gas mixture again 7.8 g of LiF were added to the resulting LiPF ₆ in the experimental reactor. An HCl / PF ₅ gas mixture was again generated analogously to the above preparation and passed over the LiPFe / LiF mixture in the experimental reactor. The resulting LiPFe was well crystalline and could be mortared without the development of visible vapors.

In addition to a batchwise process, DE 19722269 A1 also describes a process with continuous chlorine addition in an autoclave based on PCI ₃ . The starting materials were phosphorus trichloride: mass: 61.8 g = 0.45 mol of hydrogen fluoride (high purity): mass: 96.9 g = 3.84 mol, for the reaction with the PCI ₃ : excess of 1.59 mol = 70.7 % and chlorine / Ck: mass: 40.0 g = 0.56 mol used The vessels used were dried in a drying oven In the laboratory autoclave, the phosphorus trichloride was introduced and more than the equivalent amount of hydrogen fluoride (with N ₂ -polster) slowly metered ( the excess of HF served as solvent). The temperatures in the laboratory autoclave during the subsequent continuous open-system chlorine dosing (duration: 355 minutes) were between -65.7 ° C and -21.7 ° C. While The dosage of the chlorine was a gas mixture of PF ₅ and HCl, which was removed from the autoclave. The mixture was separated by customary separation methods, for example pressure distillation

In another example of the same prior art, the PCI _{3 was} metered into the autoclave, which was then sealed. After cooling the autoclave to -57.6 ° C, the hydrogen fluoride was metered in and cooled again to -59.3 ° C. Then the chlorine was added. The cooling was then removed, it came to a pressure build-up to 43 bar at 25.1 ° C. The resulting gas mixture of PF ₅ and HCl was drained from the autoclave and could be passed without further treatment in a reactor with LiF, in which then LiPF ₆ formed. In the gas mixture no PF ₃ could be detected.

Likewise starting from PCI ₃ and chlorine, CN 101723348 A describes a process for the preparation of LiPF ₆ in the liquid phase, wherein HF acts as the solvent and the reaction of the PCls / HF / HCl mixture with Cl ₂ at 35-70 ° C. and the reaction from PF ₅ with LiF at -30 to -10 ° C is performed. JP11171518 A2 likewise describes a process for the preparation of LiPFe starting from PCI ₃ and HF in order to produce PF ₃ and its conversion to PCI ₂ F ₃ by means of Cl ₂ , its reaction again with HF to PF ₅ and finally the reaction of PF ₅ with LiF to LiPF ₆ in an organic solvent. Diethyl ether and dimethyl carbonate are used as solvents Although JP 11171518 A2 points to the formation of toxic HCl gas, there are no indications in the prior art of a chloride content in LiPFe.

It has been shown that traces of chloride due to the by-produced HCl as well as traces of fluoride with moisture / water due to corrosion caused damage to electrochemical storage devices based on LiPFe.

Object of the present invention was therefore - starting from PCI ₃ - to develop a method using HF and Cl ₂ , which results in a solution of LiPFe in an organic solvent or a mixture of several organic solvents having a chloride content <100 ppm , preferably <50 ppm, more preferably <5 ppm, which can be further processed into an electrolyte suitable for electrochemical storage devices. Chloride contents below 100 ppm are referred to as "chloride-poor" in the context of the present invention

Solution to the problem and object of the present invention is a process for the preparation of LiPF ₆ solutions in an organic solvent or a mixture of several organic solvents starting from PCI ₃ , which is first reacted continuously in the gas phase with HF to a PF ₃ containing reaction mixture, which in turn continuously in the gas phase with Cl ₂ to a PCl ₂ F ₃ -containing reaction mixture and with additional HF to a PF _5- containing reaction mixture, characterized in that the reaction mixture containing PF ₅ finally in a fixed bed reactor or fluidized bed reactor of LiF moldings or with a LiF powder, for example ground or unground, and / or a LiFxHF adduct, for example ground or unground, is reacted and the reaction product is washed out of the fixed bed reactor or fluidized bed reactor with an organic solvent and isolated. A fluidized-bed reactor is also referred to in the present invention as a fluidized bed. According to the invention, a fixed-bed reactor is preferably used

The fact that the PF ₅ reacts in the fixed bed reactor or in the fluidized bed with LiF in solid form, surprisingly leads to dissolution of the reaction product in an organic solvent or a mixture of several organic solvents to a low-chloride LiPFE solution.

For clarification, it should be noted that the scope of the invention encompasses all the general and preferred definitions and parameters listed below in any combination.

In a further preferred embodiment, the PF ₅ -containing reaction mixture before entering the fixed bed reactor or in the fluidized bed to temperatures of -50 to +200 ° C, preferably from -20 to + 90 ° C, particularly preferably from -20 to +50 ° C, most preferably from -10 to 30 ° C tempered

In a further preferred embodiment, shaped bodies are used in the fixed bed reactor or in the fluidized bed which are prepared beforehand by extrusion from a mixture of LiF and water, the solids content being in the range from 20 to 95% by weight, preferably in the range from 60 to 90% by weight .-%, particularly preferably at about 70 wt .-% hedges and these moldings were dried after extrusion at temperatures of 50 to 200 ° C, preferably at temperatures of 80 to 150 ° C, more preferably at about 120 ° C. and they only have a water content of 0.05 to 5 wt .-%, preferably from 0.1 to 0.5 wt .-%, wherein the water content is determined by the method according to Karl Fischer, which is known in the art and, for example, in P.Bruttel, R. Schlink, "Water Determination by Karl Fischer Titration", Metrohm Monograph 8.026.5001, 2003-06, or G. Wieland, "Water Determination by Karl Fischer Titration", GIT Verlag Darmastadt , 1985, is described. In a preferred embodiment, the LiF is used in the form of shaped articles or in the form of fine particles having a particle size distribution in the range from 5 to 500 μm. The reaction can be carried out either in the form of a fixed bed, but also as a fluidized bed or stirred fluidized bed; all embodiments are known to those skilled In a preferred embodiment, the gas mixture leaving the fixed bed reactor or the fluidized bed in an aqueous solution of alkali metal hydroxide, preferably an aqueous solution of KOH, more preferably in a 5 to 30 wt .-%, most preferably in a 10 to 20 wt .-%, in particular preferably collected in a 15 wt .-% KOH solution in water. According to the reaction product from the fixed bed reactor or from the fluidized bed with an organic solvent or a mixture of several organic solvents is dissolved, and, if necessary, separated by solids separation preferably by filtration or by centrifugation of undissolved constituents Other possibilities for the separation of solids are the One skilled in the art Preferably, the dissolution and the optionally necessary separation of solids take place after the fixed bed reactor or the fluidized bed has been purged with inert gas and thus the reactive gas has been removed.

For dissolving the resulting LiPF ₆ , the reactor contents of the fixed bed reactor or of the fluidized bed are brought into contact with an organic solvent or a mixture of a plurality of organic solvents for a period of from 5 minutes to 24 hours, more preferably from 1 hour to 5 hours, preferably below Stirring or pumping, until the content of LiPF ₆ in the solvent or in the solvent mixture, applied against the contact time, remains constant

Organic solvents preferably to be used according to the invention are liquid, organic nitriles or liquid organic carbonates or mixtures thereof at room temperature. It is particularly preferred to use acetonitrile as the liquid organic nitrile

Dimethyl carbonate (DMC) or diethyl carbonate (DEC) or propylene carbonate (PC) or ethylene carbonate (EC) or a mixture of two or more of these solvents is particularly preferably used as liquid organic carbonate. Particular preference is given to using dimethyl carbonate The organic solvent to be used is preferably subjected to a drying process prior to its use, more preferably a drying process over a molecular sieve.

Molecular sieves preferably to be used according to the invention for drying consist of zeolites. Zeolites are crystalline aluminosilicates that can be found in many modifications in nature, but can also be produced synthetically. More than 150 different zeolites have been synthesized, 48 naturally occurring zeolites are known. The natural zeolites are summarized mineralogically under the term zeolite group

The composition of the substance group zeolites is:

The factor n is the charge of the cation M and is preferably 1 or 2.

M is preferably a cation of an alkali or alkaline earth metal. These cations are required for electrical charge balance of the negatively charged aluminum Tertraeder and are not incorporated into the main Gitte of the crystal, but remain in cavities of the lattice and are therefore also easily within the grid movable and also in the

Retrospectively interchangeable.

The factor z indicates how many water molecules were absorbed by the crystal.

Zeolites can absorb water and other low-molecular substances and release them again on heating without destroying their crystal structure.

The molar ratio of SiO ₂ to AIO ₂ or x / y in the molecular formula is called a module. It can not be less than 1 due to the Löwenstein rule.

Synthetic zeolites preferably to be used as molecular sieve according to the invention are:

The LiPFe-containing organic solvent usually still contains portions of unreacted LiF, which is separated as a solid from the organic solvent.

The separation preferably takes place by means of filtration, sedimentation, centrifugation or flotation, more preferably by filtration, particularly preferably by filtration through a filter having a mean pore size of 200 nm or smaller. The separated LiF can, after drying, in turn be recycled to the reaction with PF ₅ .

The reactors to be used in the gas phase for the continuous production process of the PF ₅ , preferably tubular reactors, and the fixed bed reactor or fluidized bed to be used for the synthesis of the LiPF _{6 are known} to the person skilled in the art and described, for example, in the Textbook of Technical Chemistry - Volume 1, Chemische Reaction Engineering, M. Baerns, H. Hofmann, A. Renken, Georg Thieme Verlag Stuttgart (1987), pp. 249-256.

The apparatus used in the present work is also the subject of the present invention. This will be described with reference to FIG. 1. In Fig. 1, 1 template means tempered, anhydrous HF with Massflow controller

2 template PCl ₃

3 template Cl ₂

4 pump

5 PCIs evaporators

6 stainless steel pipe

7 stainless steel pipe

8 heat exchangers 9 fixed bed reactor (alternatively fluidized bed reactor)

10 stir

11 scrubbers

12 disposal containers

Particularly essential to the invention is the combination of at least two series-connected tube reactors, preferably stainless steel tube 6 and stainless steel tube 7, for producing the PF ₅ in combination via at least one heat exchanger with at least one fixed bed reactor or fluidized bed reactor, in which case the reaction of the PF ₅ and finally of solid LiF to LiPF _The object of the present invention is therefore an apparatus for producing LiPF ₆ , preferably LiPF ₆ solutions and the intermediate product PF ₅ starting from PCI ₃ , characterized in that at least two tubular reactors, preferably two stainless steel tubes, are used to produce the PF ₅ . combined and for the production of LiPF ₆ these via at least one heat exchanger with at least one fixed bed reactor or a fluidized bed reactor, preferably a fixed bed reactor, combined

The reaction flow of the reactants taking place in the process according to the invention is described with reference to FIG. 1, here with two tubular reactors, a heat exchanger and a fixed bed reactor, as follows. By a heated stainless steel tube 6, preferably at temperatures of 20 ° C to 600 ° C, more preferably at 300 ° C to 500 ° C or alternatively at 100 ° C to 350 ° C, pre-tempered HF, preferably preheated to 30 ° C. to 350 ° C, alternatively 30 ° C to 100 ° C, gaseously dosed from a template 1 and reacted with gaseous PCI ₃ The gaseous PCI ₃ is previously liquid from template 2 by means of pump 4 in the evaporator 5, preferably at a temperature between 100 ° C. and 400 ° C, more preferably between 200 ° C and 350 ° C, most preferably between 200 ° C and 300 ° C and mixed therefrom with the HF in the stainless steel tube 6 and this heated, preferably to the above temperatures. The resulting reaction mixture is transferred into stainless steel tube 7 and mixed there with chlorine from template 3, preferably heated to 20 ° C to 400 ° C, more preferably to 200 ° C to 300 ° C, in an alternative embodiment preferably to -20 ° C to Tempered at 100 ° C, more preferably at 0 ° C to 50 ° C and reacted The resultant PF ₅ -containing reaction mixture is cooled by means of heat exchangers, preferably at -60 ° C to 80 ° C, particularly preferably -10 ° C. to 20 ° C, and with solid LiF or a LiFxHF adduct in the fixed bed reactor 9, preferably at temperatures of for example -60 ° C to 150 ° C, preferably between -60 ° C to 80 ° C, more preferably between -10 ° C and 20 ° C, or alternatively at 0 ° C to 90 ° C in contact brought, preferably by stirring by means of stirrer 10, or by turbulence or a combination of both. The reaction gas mixture emerging from the fixed bed reactor or fluidized bed reactor 9 is freed of acidic gases in the scrubber 11 and the resulting halide-containing solution is transferred to the disposal container 12. The solid Produldgemisch remains in the fixed bed reactor / fluidized bed reactor 9 and is there partially dissolved by Inkonlaktbringen with the organic solvent and the resulting suspension separated from the solid

However, the present invention also relates to the use of an apparatus from the combination of at least two tubular reactors, preferably at least two stainless steel tubes, for the production of PF ₅ in combination via at least one heat exchanger with at least one fixed bed reactor or fluidized bed reactor for the production of LiPF ₆ starting from PCI ₃ , preferably for the preparation of LiPF ₆ solutions. In a preferred embodiment, an apparatus of two tubular reactors, a heat exchanger and a fixed bed reactor or fluidized bed reactor is particularly preferably used an apparatus of two tubular reactors, a heat exchanger and a fixed bed reactor. However, the present invention also relates to a process for the preparation of PF ₅ starting from PCI ₃ , characterized in that one reacts in at least a first tubular reactor HF with gaseous PCI ₃ and the resulting reaction mixture in at least one second tubular reactor with addition of chlorine to PF ₅ react. In a preferred embodiment, the process is carried out with the combination of two tubular reactors

Examples

In the following, the term "%" always means% by weight.

With regard to the ion chromatography used in the present work, reference is made to the publication of the TU Bergakademie Freiberg, Faculty of Chemistry and Physics, Institute of Analytical Chemistry from March 2002 and the literature cited therein, and to Lydia Terborg, Sascha Nowak, Stefano Passerini, Martin Winter, Uwe Karst, Paul R. Hadad, Pavel N. Nesterenko, analytica Qiimica Acta 714 (2012) 121-126.

In the present work, the concentration of hexafluorophosphate and chloride was measured with an ion chromatograph with the following parameters:

Device type: Dionex ICS 2100

Column: IonPac® AS202 * 250-mm "Analytical Column with guard"

Sample volume: 1 μΐ

Eluent: KOH gradient: 0 min / 15 mM, 10 min / 15 mM, 13 min / 80 mM, 27 min / 100 mM, 27.1 min / 15 mM, 34 min / 15 mM

Eluent flow rate: 0.25 ml / min

Temperature: 30 ° C

Self-Regenerating Suppressor: ASRS® 300 (2-mm)

1. LiPF ₆ in DMC / EC mixture (according to the invention) A mixture of 23 l / h of HF (normal liter) and 0.48 g / min was heated through a heated stainless steel tube (ID 8 mm) heated to 450 ° C. for about 6 m PC1 ₃ (both gaseous) was passed into this reaction mixture 5.3 l / h of chlorine were introduced and passed through another, approximately 4 m long metal tube, which was heated to 250 ° C.

The gaseous reaction product was cooled to -10 to 0 ° C and then passed through a stainless steel tube (ID 8mm) with a diameter of about 18 mm, which was equipped with moldings of LiF (52.2 g). These moldings were previously prepared by extrusion from a mixture of LiF with water, wherein the solids content was about 70% and the moldings were dried for several days after the extrusion at 120 ° C.

The gas mixture leaving this LiF-filled reactor was collected in an aqueous 15% by weight KOH. After a total reaction time of 4 hours, the metered addition of the educts was replaced by the metered addition of an inert gas and the reactive gas was displaced from the system. Anschießend 446.3 g of a mixture of dimethyl carbonate and ethylene carbonate (1: 1 based on the weights used) over the, unreacted LiF and reaction product LiPFe containing reactor in the circulation about 20 hours pumped to 358.8 g of a reaction mixture obtained, from which a sample was filtered through a syringe filter with a 0.2 μιη filter and examined by means of ion chromatography. The filtered reaction mixture contained 9.15 wt .-% LiPFe, the chloride content was at the detection limit at <5 ppm.

2. LiPF ₆ in acetonitrile (according to the invention) A mixture of 23 l / h of HF and 0.48 g / l of PCl ₃ (both in gaseous form) was passed through a stainless steel tube (ID 8 mm) heated to 450 ° C. for about 6 m 5.3 l / h of chlorine were introduced into this reaction mixture and passed through another, approximately 4 m long, stainless steel tube (ID 8 mm), which was heated to 250 ° C.

The reaction product was cooled to -10 to 0 ° C and then passed through a fixed bed reactor with a diameter of about 18 mm, which was equipped with moldings of LiF (359 g). These moldings were previously prepared by extrusion from a mixture of LiF with water, wherein the solids content was about 70% and the moldings were dried for several days after the extrusion at 120 ° C.

The gas mixture leaving this LiF-filled reactor was collected in an aqueous 15% by weight KOH.

After a total of about 16 hours of reaction time, the dosage of the educts was replaced by the metering of an inert gas and displaced the reaction gas from the system. 1401 g of molecular sieve dried acetonitrile were then pumped through the reactor containing unreacted LiF and reaction product LiPF ₆ in the circulation for about 2 hours. 1436 g of a reaction mixture were obtained from which a sample was injected via a syringe filter with a 0.2 μm Filter was filtered and examined by means of ion chromatography. The filtered reaction mixture contained 16.17 wt .-% LiPFe, the chloride content was 67 ppm

3. LiPFe in DMC (according to the invention)

A mixture of 23 l / h HF and 0.48 g / min PC1 ₃ (both in gaseous form) was passed through a stainless steel tube (ID 8 mm) heated to 450 ° C. and about 6 m long. 5.3 l of this reaction mixture were added to this reaction mixture. H Chlorine introduced and passed through another, about 4 m long stainless steel tube (ID 8mm), which was heated to 250 ° C.

The reaction product was cooled to -10 to 0 ° C and then passed through a fixed bed reactor with a diameter of about 18 mm, which was equipped with moldings of LiF (384 g). These moldings were previously prepared by extrusion from a mixture of LiF with water, wherein the solids content was about 70% and the moldings were dried for several days after the extrusion at 120 ° C.

The gas mixture leaving this LiF-filled reactor was collected in an aqueous 15% by weight KOH. After a total reaction time of about 7 hours, the metered addition of the educts was replaced by the metered addition of an inert gas and the reactive gas was displaced from the system. Subsequently, 400 g of dimethyl carbonate were pumped through the reactor containing unreacted LiF and reaction product LIPF ₆ in the circulation for about 3 hours. 306.5 g of a reaction mixture were obtained from which a sample was passed through a syringe filter with a 0.2 μm diameter. Filter and using ion chromatography was investigated. The filtered reaction mixture contained 32.6 wt .-% LiPF ₆ , the chloride content was 11 ppm.

Claims

1. A process for the preparation of LiPF ₆ solutions in an organic solvent or a mixture of several organic solvents starting from PCI ₃ , which is first reacted continuously in the gas phase with HF to a PF ₃ containing reaction mixture, which in turn continuously in the gas phase is reacted with CI ₂ initially to a PCl ₂ F ₃ -containing reaction mixture and with additional HF to a PF ₅ - containing reaction mixture, characterized in that the PF ₅ containing reaction mixture finally in a fixed bed reactor or fluidized bed reactor of LiF moldings or with a LiF Powder and / or a LiFxHF adduct is reacted and the reaction product is washed out of the fixed bed reactor or fluidized bed reactor with an organic solvent and isolated.

2. The method according to claim 1, characterized in that the PF _5- containing reaction mixture is heated to temperatures of -50 to +200 ° C before entering the fixed bed reactor or fluidized bed reactor.

3. The method according to claims 1 or 2, characterized in that in the fixed bed reactor or fluidized bed reactor LiF moldings are used, which are previously prepared by extrusion from a mixture of LiF and water, wherein the solids content in the range of 20 to 95 wt. % Hegt and these moldings are dried after extrusion at temperatures of 50 to 200 ° C and they only have a water content of 0.05 to 5 wt .-%, wherein the water content is determined by the method according to Karl Fischer.

4. The method according to claim 3, characterized in that the LiF is used in the form of shaped articles or in the form of fine particles having a particle size distribution in the range of 5 to 500 microns.

5. The method according to claims 1 to 4, characterized in that the fixed bed reactor or the fluidized bed leaving gas mixture in an aqueous alkali solution, preferably in a solution of KOH, more preferably in a 5 to 30 wt .-% KOH solution in Water is caught.

6. The method according to claims 1 to 5, characterized in that the reaction product from the fixed bed reactor or from the fluidized bed with an organic solvent or a mixture of a plurality of organic solvents is dissolved and separated.

7. The method according to claim 6, characterized in that organic solvents used as organic solvents at room temperature, organic nitrites or liquid organic carbonates or mixtures thereof are used and as the liquid organic nitrile acetonitrile and as liquid organic carbonate dimethyl carbonate (DMC) or diethyl carbonate (DEC) or Propylene carbonate (PC) or ethylene carbonate (EC) or a mixture of two or more of these solvents is used.

8. The method according to claims 6 or 7, characterized in that the organic solvent to be used before a drying process, preferably a drying process over a molecular sieve is subjected.

9. Apparatus for the preparation of LiPFe solutions and the intermediate PF ₅ , starting from PCI _3, characterized in that one combines for the production of the PF ₅ at least two tubular reactors and for the production of LiPF ₆ solutions this via at least one heat exchanger with at least one fixed bed reactor or a fluidized bed reactor, preferably with a fixed bed reactor, combined. 10. Use of an apparatus comprising at least two tubular reactors, preferably at least two stainless steel tubes, for producing PF ₅ in combination via at least one heat exchanger with at least one fixed bed reactor or fluidized bed reactor for producing LiPF ₆ from PCI ₃ . 11. Use according to claim 10, characterized in that an apparatus of two tubular reactors, a heat exchanger and a fixed bed reactor or fluidized bed reactor, preferably a fixed bed reactor is used. 12. A process for the preparation of PF ₅ , characterized in that one reacts in at least a first tubular reactor HF with gaseous PCI ₃ and the resulting reaction mixture react in at least one second tubular reactor with metered addition of chlorine to the PF ₅ .