Process for Separating Acid-Containing Gas Mixtures
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(19) TZZ Z¥_T (11) EP 2 705 893 A1 (12) EUROPEAN PATENT APPLICATION (43) Date of publication: (51) Int Cl.: 12.03.2014 Bulletin 2014/11 B01D 53/14 (2006.01) C01B 25/10 (2006.01) C07C 17/38 (2006.01) C01B 7/07 (2006.01) (2006.01) (2006.01) (21) Application number: 12183037.6 C01B 7/09 C01B 7/19 (22) Date of filing: 05.09.2012 (84) Designated Contracting States: (72) Inventor: Fischer, Reiner AL AT BE BG CH CY CZ DE DK EE ES FI FR GB 38173 Dettum (DE) GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR (74) Representative: Mross, Stefan P.M. et al Designated Extension States: SOLVAY S.A. BA ME Intellectual Assets Management Rue de Ransbeek, 310 (71) Applicant: Solvay SA 1120 Brussels (BE) 1120 Bruxelles (BE) (54) Process for separating acid-containing gas mixtures (57) A process for reversibly removing at least one vided. The process comprises contacting the gas mixture acid from a gas mixture comprising at least one acid and with a solvent comprising a sulphone compound. at least one of a carbonyl dihalide, a phosphoryl trihalide, a phosphorous pentafluoride, and an acid halide is pro- EP 2 705 893 A1 Printed by Jouve, 75001 PARIS (FR) 1 EP 2 705 893 A1 2 Description a pesticide and as an etching agent for silicon related compounds, while CHF2C(O)F is an intermediate in the Technical field manufacture of finishes for textiles. Acid fluorides may contain HCl or HBr depending on the method used for [0001] The present disclosure relates to a process for 5 preparing the acid fluorides. Sometimes, acid fluorides reversibly removing at least one acid from a gas mixture may further comprise HF. comprising at least one acid and at least one of a carbonyl [0007] Gas mixtures comprising HF may be, for exam- dihalide, a phosphoryl trihalide, phosphorous pentafluo- ple, result of a fluorination reaction with hydrogen fluoride ride, and an acid halide, as well as to the use of a solvent or fluorine. For example, carboxylic acid fluorides can be for reversibly removing at least one acid from such a gas 10 prepared by the reaction of carboxylic acid chlorides and mixture. HF or by photochemical oxidation, as described in US patent US 6 489 510 B1. Such gas mixtures may further Background art comprise HCl. [0008] There is the need of separating gas mixtures [0002] Acids such as HCl, HF and HBr, either alone or 15 comprising HCl and a carboxylic acid fluoride, or HF and in combination, are involved in many chemical reactions, a carboxylic acid fluoride, or HF, HCl and a carboxylic beit as starting materials, as reactionproducts or as prod- acid fluoride, or HCl and PF 5, or HCl and C (O)F2, or HCl ucts of a side reaction, and may be removed from gas and POF3, respectively. It is also generally desirable to mixtures containing these acids by separating agents separate HF, HCl and HBr from gas mixtures comprising such as amines. However, amine-hydrohalide adducts 20 HF, HCl and/or HBr and other gas constituents such as are obtained which have to be dumped or burned. Some- carbonyl dihalides, phosphoryl trihalides, phosphorous times, other constituents of the gas mixture may be sen- pentafluoride, and acid halides, or to separate these gas sitive towards or reactive with bases. In some gas mix- mixtures so as to obtain gas mixtures or pure gases which tures, the boiling points of the gas constituents may be are depleted of HF, HCl and HBr, respectively, and in so close that distillation is unsuitable to remove HCl or 25 which the other constituent (s) is(are) thus concentrated. other acids. Further, it can be desirable to remove the acid from the [0003] Carbonyl fluoride is a gas which can be used gas mixtures mentioned above under water-free condi- as etching gas for manufacturing semiconductors and tions, for example, to prevent corrosion damages in an for cleaning CVD chambers. International patent appli- apparatus or to reduce the amount of contaminated cation WO 05/085129 A2 describes a photochemical30 washer water used for acid removal. process for the manufacture of C (O)F2 from CHClF 2. The [0009] International patent application WO process described therein provides for the preparation 2006/045518 A1 describes a process for the removal of of C(O)F2 by photo-oxidation of CHClF2 with oxygen. HCl, HF or HBr from mixtures with C(O)F2, PF5 or car- Light having a spectral range covering at least 50 nm, in boxylic acid fluorides by means of ionic liquids. Several the sense that the light having the shortest wavelength 35 ionic liquids are disclosed as suitable separating agents. and the light having the longest wavelength are at least [0010] US patent application US 2007/0293707 A1 de- 50 nm apart, is radiated in. scribes a process for separating HCl and COCl2 com- [0004] Phosphoryl fluoride is a gas which can be pre- prising bringing a mixture of HCl and COCl 2 into contact pared by fluorination of phosphoryl chloride with metallic with an ionic liquid. fluorides. As described in international patent application 40 [0011] International patent application WO WO2012/016924 A1, phosphoryl fluoride can be reacted 2007/125065 A1 describes gas mixtures comprising ac- with Li 3PO4 to form LiPO 2F2 which is useful as electrolyte ids such as HF, HCl or HBr and other constituents, in salt or electrolyte salt additive in Li ion batteries and other particular gas mixtures comprising or consisting of car- devices suitable for storing electric energy. boxylic acid fluorides, C(O)F2 or phosphorous pentaflu- [0005] Phosphorous pentafluoride is an intermediate 45 oride and HCl and optionally HF, which are separated by for preparing electrolyte salts for lithium ion batteries. For ionic liquids. The process is performed reversibly. example, phosphorous pentafluoride can be reacted with [0012] However, on the one side, the choice of ionic lithium fluoride to form lithium hexafluorophosphate. liquids is limited and, on the other side, ionic liquids may Phosphorous pentafluoride can be prepared from phos- be sensitive to or reactive with some acids, such as for phorous pentachloride or phosphorous trichloride and 50 example HCl, HF or HBr, and may not ensure the attain- chlorine and hydrogen fluoride. HCl is formed in this re- ment of the desired degree of purification of the gas mix- action and must be separated off from phosphorous pen- ture from the acids. Furthermore, ionic liquids are expen- tafluoride. sive. [0006] Organic gaseous acid fluorides such as CF3C 55 (O)F or CHF 2C(O)F are starting compounds for fluorinat- Summary of the disclosure ed organic compounds, for example for fluorovinyl ethers, which in turn are comonomers used in the pro- [0013] An object of the present disclosure is to provide duction of resins or elastomers. CH3C(O)F is useful as a process for reversibly removing at least one acid from 2 3 EP 2 705 893 A1 4 a gas mixture comprising at least one acid and at least the gas mixture may be higher. For example, the gas one of a carbonyl dihalide, a phosphoryl trihalide, a phos- mixture may originate from a chlorine- fluorine exchange phorous pentafluoride, and an acid halide, which is ef- reaction, and may comprise COF2, PF5, CF3C(O)F or fective, results in an enhanced degree of purification and CHF2C(O)F, HCl and 1 % to 70 % by weight of HF. has a wide operability range, in particular as to the choice 5 [0021] According to one embodiment, the at least one of the separating agent. acid may consist of HCl and of traces of HF. Such acids [0014] According to one aspect thereof, the present may be formed starting from reaction mixtures initially disclosure provides a process for reversibly removing at comprising, for example, only HCl and COF 2, PF5, CF3C least one acid from a gas mixture comprising at least one (O)F or CHF 2C(O)F. Since said fluorides are susceptible acid and at least one of a carbonyl dihalide, a phosphoryl 10 to hydrolysis, a trace amount of HF may be formed. The trihalide, a phosphorous pentafluoride, and an acid hal- term "trace amount" is used to indicate an HF content of, ide, the process comprising contacting the gas mixture for example, from 10 ppm to 5,000 ppm in the reaction with a solvent comprising a sulphone compound. The mixture. solvent acts as a separating agent. [0022] The carbonyl dihalide may comprise one or [0015] According to one embodiment, the at least one 15 more carbonyl dihalides. In an analogous manner, the acid comprises at least one of HCl, HF and HBr. The at phosphoryl trihalide may comprise one or more phos- least one acid may consist of at least one of HCl, HF and phoryl trihalides, and the acid halide may comprise one HBr. or more acid halides. [0016] The content of HCl, HF or HBr may vary de- [0023] The carbonyl dihalide may comprise or consist 20 pending on the source of the gas mixture and any pre- of C(O)F2. treatment steps, such as for example adsorption. Gen- [0024] The phosphoryl trihalide may comprise or con- erally, the amount of HCl, HF or HBr in the gas mixture sist of POF3. may be in the range from 100 ppm by weight or even less [0025] The acid halide may comprise or consist of one to 99 % by weight. or more carboxylic acid halides.