(19) TZZ_58Z5B_T (11) EP 1 585 705 B1 (12) EUROPEAN PATENT SPECIFICATION (45) Date of publication and mention (51) Int Cl.: of the grant of the patent: C01F 7/50 (2006.01) C01F 5/28 (2006.01) 10.04.2013 Bulletin 2013/15 C01B 9/08 (2006.01) (21) Application number: 04700458.5 (86) International application number: PCT/EP2004/000049 (22) Date of filing: 07.01.2004 (87) International publication number: WO 2004/060806 (22.07.2004 Gazette 2004/30) (54) METHOD FOR THE PREPARATION OF HIGH SURFACE AREA METAL FLUORIDES VERFAHREN ZUR HERSTELLUNG VON METALLFLUORIDEN MIT GROSSEROBERFLÄCHE PROCEDE DE PREPARATION DE FLUORURES METALLIQUES A SURFACE ACTIVE ELEVEE (84) Designated Contracting States: (74) Representative: Schulz Junghans AT BE BG CH CY CZ DE DK EE ES FI FR GB GR Chausseestraße 5 HU IE IT LI LU MC NL PT RO SE SI SK TR 10115 Berlin (DE) (30) Priority: 07.01.2003 EP 03000221 (56) References cited: 07.01.2003 US 438308 P FR-A- 1 383 927 GB-A- 995 186 25.03.2003 EP 03006656 US-A- 2 959 557 (43) Date of publication of application: • DELATTRE J.L. ET AL.: "Plasma-Fluorination 19.10.2005 Bulletin 2005/42 Synthesis of High Surface Area Aluminum Trifluoride from a Zeolite Precursor" JOURNAL (73) Proprietor: Nanofluor GmbH OF THE AMERICAN CHEMICAL SOCIETY, vol. 12489 Berlin (DE) 123, 2001, pages 5364-5365, XP002254993 cited in the application (72) Inventors: • KEMNITZ, Erhard Remarks: 10405 Berlin (DE) Thefile contains technical information submitted after • GROSS, Udo the application was filed and not included in this 12683 Berlin (DE) specification • RÜDIGER, Stephan 15834 Rangsdorf (DE) Note: Within nine months of the publication of the mention of the grant of the European patent in the European Patent Bulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with the Implementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). EP 1 585 705 B1 Printed by Jouve, 75001 PARIS (FR) EP 1 585 705 B1 Description [0001] The present invention is related to a method for preparing an amorphous metal fluoride, and a method for preparing a catalyst comprising an amorphous metal fluoride. 5 [0002] Metal oxides and metal fluorides are of great importance to the chemical, pharmaceutical and, e. g., ceramics industry. In particular, inorganic materials having high surface areas are of great interest for, e. g., heterogeneous catalysis where the activity of a catalyst depends largely on its surface. Metal oxides with very high surface areas can be prepared via sol-gel routes, by freeze-drying or under supercritical conditions as xerogels (c. f. Advanced Catalysts and Nanostructured Materials, editor W.R.Moser: Chapter 2 - The Role of Prehydrolysis in the Preparation of SiZr- 10 Aerogels by J.B.Miller and E.I.Ko, Academic Press, San Diego, 1996) or aerogels. The manufacture of metal fluorides used as thin film coating prepared on a quartz base material is described in Choi, J.-B. et al., J. Korean Ind. Eng. Chem., Vol. 11, No. 8, November 2000, 969-973. In the process of manufacturing said metal fluorides, more particularly mag- nesium fluoride, a mixture of magnesium methoxide is admixed with a water containing solution of hydrogen fluoride and methanol. 15 [0003] A particularly preferred metal catalyst is aluminium trifluoride which is used as a Lewis acidic catalyst for industrial fluorination. The synthesis, characteristics and uses of such aluminium fluorides are described in E. Kemnitz and D.-H. Menz, Prog. Solid St. Chem. 26 (1998), p. 97-153. [0004] Aluminium fluoride based catalysts such as AlF3 exhibit an octahedral arrangement of fluorine atoms, the aluminium atoms of which are thus saturated in a coordinative manner. Because of this arrangement these AlF 3 species 20 exhibit a comparatively low Lewis acidity. In addition, the crystalline structure goes along with a limited specific surface of, e. g., 0.5 to 30 m2/g which is disadvantageous as the activity of a solid phase or heterogeneous catalyst strongly depends on its specific surface area. Aluminium fluorides can be produced using wet- chemical synthesis and subsequent controlled dehydration. Alternatively, non- wet-chemical synthesis routes are reported. Ziegler, K. and Köster, R., Liebigs Ann. Chem. 608 (1957) 1-7 describe the synthesis of aluminium trifluoride using aluminium trialkyl and boron trifluoride 25 as starting materials. DE 4041771 describes the fluorination of aluminium chloride using anhydrous hydrogen fluoride. US 5,157,171 discloses the fluorination of AlCl3 using chlorofluorocarbons. Both methods result in an AlClxF3-x which still contains chlorine. This residual chlorine is responsible for both the observed high acidity and the high hygroscopicity. The product resulting from both methods is also referred to as aluminium chlorofluoride, ACF. Because of its hygro- scopicity ACF is extremely difficult to be used in technical applications. Also, ACF is rapidly deactivated upon, e. g., 30 contacting H containing organic solvents such as ethers, alcohols and the like. In addition, the particular fluorination process cannot be transferred to other metal chlorides as only the particular reaction provides the gain in energy required for the conversion of AlCl3 into AlF3. [0005] The basic considerations in relation to and the limitations of metal fluoride catalysts as described above, also apply for doped metal fluoride catalysts. Doped metal fluoride catalysts can be particularly advantageous as it is known 35 that in metal oxide as well as metal fluoride based catalysts a partial replacement of host metal atoms by doping metal atoms has a strong influence on the activity and/or selectivity of the respective catalyst. The manufacture of this kind of doped catalyst starts either from the solid host compound which is subsequently impregnated with the desired amount of a solution of the doping compound and subsequently dried and calcined at elevated temperatures. Alternatively, a solution is used in which both compounds, i. e. the host compound as well as the guest compound, are present at the 40 desired ratio whereupon both compounds are co-precipitated, dried and subsequently calcined. The resulting catalyst product has always an activity limiting small surface area. [0006] A further method for the manufacture of aluminium trifluoride is described by Delattre, J.L. et al., J. Am. Chem. Soc. 2001, 123, p. 5364-5, where a zeolite is fluorinated by an NF 3-plasma whereupon silicon concomitantly is removed from the solid alumo- zeolite. The thus obtained aluminium fluoride has a specific surface area of up to 190 m 2/g. However, 45 the particular etching technology is not applicable to a large scale, i. e. industrial, catalyst production line. [0007] In FR 1 383 927 A, an amorphous aluminium fluoride catalyst is described, which can be prepared by reacting aluminium chloride with anhydrous hydrogen fluoride. [0008] A method for the manufacture of transition metal fluorides, such as fluorides of titan, vanadium or iron, is described in GB 995 186 A, wherein a transition metal bromide, chloride or mixed halide reacts with ethylidene fluoride 50 or boron fluoride in presence of a chlorine containing solvent. [0009] The problem underlying the present invention is thus to provide a method for preparing an amorphous metal fluoride having a high active surface and preferably being catalytically active. It is a further problem underlying the present invention to provide a metal fluoride based catalyst which has a high specific surface and is moisture resistant, i. e. it may be handled in open air without becoming irreversibly deactivated. 55 [0010] According to the present invention the problem is solved in a first aspect by a method for preparing an amorphous x+ metal fluoride of the formula M Fx-δ comprising the steps of x+ a) providing a precursor, whereby the precursor comprises a structure having a formula of M F(x-δ)-yBy; and 2 EP 1 585 705 B1 b) reacting the precursor with a fluorinating agent generating the amorphous metal fluoride having a formula of x+ M Fx-δ, whereby 5 M is selected from the group comprising metals of the second, third and fourth main group and any subgroup of the periodic table, B is a coordinately bound group; x is any integer of 2 or 3; 10 y is any integer between 1 and 3; δ is 0 to 0.1; and x-δ > y. [0011] In an embodiment of the method B is selected from the group comprising alkoxides, enolates and salts of 15 carboxylic acid. Preferably, the alkoxides, enolates or the carboxylic acid has a length of 1 to 5 C atoms. [0012] In a further embodiment of the method B is an alkoxide having a formula of -O-CcH2c+1 20 wherein c is any integer from 1 to 6. In a preferred embodiment c is any integer from 1 to 3. [0013] In a still further embodiment of the method the precursor, any of the starting material for the precursor or the fluorinating agent is present in or introduced into an anhydrous organic solvent, whereby the anhydrous organic solvent is preferably selected from the group comprising alcohols, ethers, ketones, alkanes, formic acid, acetic acid and propionic acid. 25 [0014] In another embodiment of the method the precursor contains or is made from a compound of the formula x+ M F(x-δ)ByLd whereby 30 M, F, x, y, δ and B are as defmed herein; L is a solvent, preferably an anhydrous organic solvent as specified above; and d is ≤ 1. 35 [0015] In a preferred embodiment of the method step b is carried out at a temperature below the crystallisation point of the amorphous metal fluoride.