US 20110286911A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2011/0286911 A1 Hagiwara et al. (43) Pub. Date: Nov. 24, 2011 (54) HYDROGEN FLUORIDE PURIFICATION Publication Classification METHOD (51) Int. Cl. COIB 7/19 (2006.01) (75) Inventors: Rika Hagiwara, Kyoto (JP); Kazuhiko Matsumoto, Kyoto (JP) (52) U.S. Cl. ......................................... 423/484; 423/483 (57) ABSTRACT (73) Assignee: KYOTO UNIVERSITY, Kyoto-shi, Kyoto (JP) To provide a novel method for purifying hydrogen fluoride, capable of efficiently reducing the content of arsenic in (21) Appl. No.: 13/131,703 hydrogen fluoride. The step (a) of bringing a crude hydrogen fluoride containing (22) PCT Fled: Nov. 25, 2009 arsenic trifluoride into contact with an oxidizing agent of a metal fluoride in a liquid State is carried out, for example, in (86) PCT NO.: PCT/UP2009/069836 a reactor (11) to obtain a reaction mixture wherein arsenic pentafluoride is formed by oxidizing arsenic trifluoride with S371 (c)(1), the oxidizing agent of the metal fluoride through a liquid (2), (4) Date: Aug. 15, 2011 liquid reaction; and the step (b) of separating purified hydro gen fluoride from the reaction mixture is carried out, for (30) Foreign Application Priority Data example, by a separator (13), the thus obtained purified hydrogen fluoride having a lower content of arsenic than that Nov. 28, 2008 (JP) ................................. 2008-304711 of the crude hydrogen fluoride. Crude lf -> - 2^- 4. Pur ified HF 11 Patent Application Publication Nov. 24, 2011 Sheet 1 of 2 US 2011/0286911 A1 Fig. 2 Crude HF --- Pur fied HF Purified HF Patent Application Publication Nov. 24, 2011 Sheet 2 of 2 US 2011/0286911 A1 Fig. 4 Crude HF-> w Pir fed HF US 2011/02869 11 A1 Nov. 24, 2011 HYDROGEN FLUORIDE PURIFICATION of arsenic is used as a reaction raw material, while a low METHOD quality fluorite having a high content of arsenic is not used at present. TECHNICAL FIELD Citation List 0001. The present invention relates to a method for puri Patent Literature fying hydrogen fluoride, and more particularly to a method 0005 Patent Literature 1: JP 47-16407B for reducing the content of arsenic in hydrogen fluoride. The 0006 Patent Literature 2: JP 61-151002 A present invention also relates to a method for purifying hydro 0007 Patent Literature 3: JP 2-502277 A gen fluoride using Such a purification method. 0008 Patent Literature 4: JP 3-146401 A 0009 Patent Literature 5: JP 3-205304A BACKGROUND ART 0010 Patent Literature 6: JP 6-263406 A O011 Patent Literature 7: JP 7-504149A 0002 Hydrogen fluoride is industrially produced by react ing fluorite (containing CaF2 as a main component) with SUMMARY OF INVENTION sulfuric acid (HSO) under heating (CaF+HSO->2HF + Technical Problem CaSO4), and collecting the reaction mixture, which contains thus generated hydrogen fluoride (HF), in the form of a gas, 0012 However, a high-quality fluorite is unevenly distrib followed by distillation. uted, and almost all of the high-quality fluorites is produced in 0003. A rude ore of fluorite may contain, in addition to China, presently. Therefore, exhaustion of resource is con cerned. Further, due to export restraint of the Chinese Gov calcium fluoride (CaF2) as a main component, impurities ernment, the permitted export quantity of the high-quality Such as silicon dioxide (SiO2), calcium carbonate (CaCO) fluorite has decreased, which has caused an increase in its and arsenic (AS). Usually, a commercially available fluorite price. has already been purified, and those which are now used in the 0013 Under these circumstances, there has been an industrial production of hydrogen fluoride contain usually increase in demand for utilization of a low-quality fluorite in about 1% by mass of impurities such as silicon dioxide an industrial scale in place of the high-quality fluorite. In (SiO2), calcium carbonate (CaCO) and arsenic (As). When order to obtain a high-purity hydrogen fluoride having a low hydrogen fluoride is produced by using such fluorite, silicon content of arsenic by using the low-quality fluorite, it is pos dioxide reacts with hydrogen fluoride to form silicon fluoride sible to take either a measure in which the low-quality fluorite (SiF). Silicon fluoride can be removed comparatively easily is purified in advance thereby reducing the content of arsenic by distillation (silicon fluoride and hydrogen fluoride can be thereof and then hydrogen fluoride is obtained using the puri separated from each other by distillation, the former as a fied fluorite, or a measure in which a crude hydrogen fluoride gaseous Substance and the latter as a condensate). Calcium is obtained using the low-quality fluorite and then the crude carbonate reacts with sulfuric acid to form calcium sulfate hydrogen fluoride is purified thereby reducing the content of (CaSO), carbon dioxide (CO) and water (H2O). Calcium arsenic thereof. However, since a conventional purification Sulfate remains in a reacting furnace and is not mixed in method of fluorite has not sufficient arsenic removing ability, hydrogen fluoride collected in the form of a gaseous Sub it is difficult to take the former measure. Therefore, in order to stance, and water can be easily removed by simple distillation take the latter measure, it has been desired to develop a and also carbon dioxide can be removed comparatively easily method for purifying hydrogen fluoride capable of efficiently by distillation. Therefore, both of them are not mixed in reducing the content of arsenic in hydrogen fluoride. hydrogen fluoride. In contrast, arsenic, what kind of form 0014. There have been proposed, as the method for puri which takes in fluorite is not clearly understood, reacts with fying hydrogen fluoride capable of reducing the content of hydrogen fluoride to form arsenic trifluoride (ASF). Since a arsenic in hydrogen fluoride, a method in which hydrofluoric difference in a boiling point between arsenic trifluoride and acid is treated with potassium permanganate (KMnO) and/or potassium dichromate (KCr2O7) and then distillation is car hydrogen fluoride is small (a boiling point of HF is 19.5°C., ried out in the presence of an inorganic salt of a divalent iron a boiling point of ASF is 63°C.), it is difficult to completely (Patent Literature 1), a method in which a fluorine gas is remove arsenic trifluoride by distillation, and therefore added to hydrofluoric acid and then distillation is carried out arsenic trifluoride is mixed in hydrogen fluoride as a product. (Patent Literature 2), a method in which an anhydrous hydro 0004 Hydrogen fluoride is utilized as a starting substance gen fluoride is brought into contact with hydrogen peroxide in for chlorofluorocarbon gases and fluororesins, which are the presence of a catalyst and then distillation is carried out fluorine chemical products, and is also utilized as an etching (Patent Literature 3), methods in which an anhydrous hydro agent in the production of a semiconductor. When arsenic is gen fluoride is reacted with a Sulfur compound (for example, mixed in hydrogen fluoride, there are problems that in the HS) or an iodine compound (for example, HI) to form a production of a chlorofluorocarbon gas, a catalyst can be precipitate of arsenic sulfide or arsenic iodide (Patent Litera poisoned, and that in the production of a semiconductor, tures 4 and 5), methods in which hydrofluoric acid is sub arsenic can diffuse into a semiconductor device thereby exert jected to an electrolytic operation (Patent Literatures 6 and 7) ing an adverse influence on operation of the device. There and the like. However, these methods have problems that a fore, there is a demand for a high-purity hydrogen fluoride reaction requires a long time (Patent Literatures 1, 2 and 3), a which contains as little arsenic as possible. In the process of large amount of waste is generated (Patent Literature 1), it is producing a high-purity hydrogen fluoride in an industrial difficult to remove a fluorine gas (Patent Literature 2), it is scale, a high-quality fluorite having an originally low content impossible to sufficiently decrease the content of arsenic US 2011/02869 11 A1 Nov. 24, 2011 (Patent Literatures 2, 4 and 5), and an electrolytic membrane 0023. According to one aspect of the present invention, has insufficient durability (Patent Literatures 6 and 7). there is provided a method for purifying hydrogen fluoride, 0015. An object of the present invention is to provide a which comprises the steps of: novel method for purifying hydrogen fluoride, capable of at 0024 (a) bringing a crude hydrogen fluoride containing least partially alleviating the aforementioned problems in the arsenic trifluoride into contact with an oxidizing agent of a prior art, and efficiently reducing the content of arsenic in metal fluoride in a liquid State to obtain a reaction mixture hydrogen fluoride. wherein arsenic pentafluoride is formed by oxidizing arsenic trifluoride with the oxidizing agent of the metal fluoride Solution to Problem through a liquid-liquid reaction, and 0016 Since arsenic existing in hydrogen fluoride takes a 0025 (b) separating purified hydrogen fluoride from the form of arsenic trifluoride (ASE), the present inventors have reaction mixture, the thus obtained purified hydrogen fluoride organized and studied methods of separating arsenic trifluo having a lower content of arsenic than that of the crude hydro ride from hydrogen fluoride. gen fluoride. 0017. As described above, since a difference in a boiling 0026. According to the method for purifying hydrogen point between arsenic trifluoride and hydrogen fluoride is fluoride of the present invention, at least the aforementioned small (a boiling point of HF is 19.5°C., a boiling point of problems in the prior art can be partially alleviated and the AsF is 63°C.) and also it is difficult to form a complex salt content of arsenic in hydrogen fluoride can be efficiently together with HF (thus, it is difficult to undergo ionization in decreased.