Fluorination apparatus

The typical fluorination apparatus used in the LaMar process for these reactions is simple in design (Fig. 4) (33). It is essential that the materials of constmction are resistant to fluorine (34). The presence of even traces of oxygen or moisture can have a deleterious effect and, therefore, extreme precautions must be taken to eliminate these contaminants. 

The Aerosol Fluorination process [42] (Aerosol) is operated on the principle that the substrate is absorbed onto the surface of fine sodium fluoride particles in the fluorination apparatus in which the fluorine concentration and the temperature increases along the length of the reaction vessel. A U.V. photo-fluorination finishing stage completes the perfluorination process which has the advantage that it is a continuous flow method. 

Figure 2.1 Fluorination apparatus used by Bigelow and Fukuhara for perfluorination of a variety of organic substrates (courtesy of the American Chemical Society) [6].

Catalysts are prepared in a fluorination apparatus that is composed of an oven and a stainless-steel reactor where fluorination takes place. At the bottom of the reactor a vessel with distilled water absorbs excess HF. 

The fluorination apparatus consists of a Cu trap, cooled with liquid nitrogen to remove impurities in the Eg stream, and a long Cu reactor tube, about 2 cm. in diameter, screwed onto the trap. A cap, opening into a thin Cu tube 1 to 2 mm. in diameter, is screwed to the other end of the Cu tube. 

For many years fluorine has been deterrnined by the Willard-Winters method in which finely ground ore, after removal of organic matter, is distilled with 72% perchloric acid in glass apparatus. The distillate, a dilute solution of fluorosiUcic acid, is made alkaline to release fluoride ion, adjusted with monochloroacetic acid at pH 3.4, and titrated with thorium nitrate, using sodium a1i2arine sulfonate as indicator. 

We wish to thank Dr. G. H. Cady for lending us his apparatus, Professor Don M. Yost and Mr. A. Beerbower for preparing the fluorine nitrate used in this work, Mr. K. S. Palmer for assisting in the preparation of the electron diffraction photographs, and Dr. Sidney Weinbaum and Mrs. M. Lassettre for assisting in their interpretation. 

CVD, the other major deposition process, is used on a large scale. A typical low-E glass is obtained by depositing a thin film of silicon dioxide followed by another thin film of fluorine-doped tin oxide. The Si02 acts as a diffusion barrier and the Sn02 reduces the emissivity. A typical CVD apparatus is shown in Fig. 

For this reason, industrial fluorinations of aromatics are performed by other routes, mostly via the Schiemann or Halex reaction [54, 55]. As these processes are multi-step syntheses, they suffer from low total selectivity and waste production and demand high technical expenditure, i.e. a need for several pieces of apparatus. 

There have been several accidents with metalloids detonation with fluorine very violent reaction with boron at 700°C, and ignition with white phosphorus. In the last case, the dangerous character of the reaction of the preparation of hydrogen iodide by distillation of the phosphorus/moist iodide mixture was also mentioned. The formation of phosphonium iodide often causes the conduits of the apparatus to block, which causes the apparatus to detonate due to overpressure. Several accidents involve this factor, which is not due to a reaction that is intrinsically dangerous. 

Long, G., Apparatus for Disposal of Fluorine on a Laboratory Scale, Harwell, AERE, 1956... 

Stewart, J. W., Proc. 7th Int. Conf. Low Temp. Phys. (Toronto), 1960, 671 Dining the study of phase transitions of solidified gases at high pressures, solid fluorine reacted explosively with apparatus made from stainless steel. 

Fluorodec [Fluorine on demand by electrolysis] An electrolytic process and apparatus for generating fluorine. The electrolyte is molten KHF2, the fluorine is liberated at a nickel anode. Offered by Fluorogas, UK. 

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