Hydrofluoric acid quality

The quality hydrofluoric acid required Tor these reactions may be... 

Fluorite is highly valued as a flux in the manufacture of steel also as a raw material for hydrofluoric acid. When of optical quality, the mineral is used for lens and prisms in scientific instruments. 

Impurities such as diolefins and mercaptans in the feed to the reactor affect adversely the quality of the alkylate produced. This is considered to be more critical in sulfuric acid than in HF catalyst units. Also, certain sulfuric unit designs seem to tolerate more normal butane than others. Whereas the isobutane content of the recycle to a hydrofluoric acid unit can operate at purities of around 75% without affecting product qualities appreciably, the isobutane content of the recycle stream to most sulfuric acid units should be 90 % or better. 

In industrial practice, two liquid acids are employed as catalysts for isobutane/ butene alkylation, namely sulfuric acid and hydrofluoric acid [3, 19, 20]. Both processes deliver a high-quality gasoline component. The catalyst consumption in the H2S04 process is high, typically 70-100kg/t The spent sulfuric acid contains tarry hydrocarbons and water and has to be processed externally. On the other hand, corrosiveness and toxicity of HF are reasons of concern that require use of additives that lower the HF vapor pressure and minimize the amount of HF released in the case of an accident. However, in many industrialized countries, new HF alkylation processes are no longer approved by authorities. 

On a manufacturing scale, an aq. soln. of hydrofluoric acid is made by gently heating the best quality of powdered fluorspar, free from silica, to about 130 along with cone, sulphuric acid—containing 10 per cent, of water. The retort is a cast-iron pot with a cast-iron cover. The rim of the cover dips into an annular trough the joint is sealed with cone, sulphuric acid. The retorts are connected with a series of lead boxes as condensers. These contain water or dll. hydrofluoric acid to absorb the gas from the retorts. The Condensers are submerged in water to keep them cool, and the acid so obtained is collected in leaden bottles. 

The raw silicon carbide is processed by crushing in jaw crushers or hammer mills and subsequent fine grinding in ball mills. Very pure SiC qualities are obtained by ehemical treatment with sulfuric acid, sodium hydroxide or hydrofluoric acid. 

For determinations in glass, dissolution of the matrix by treatment with HF and subsequent analysis of the trace concentrate is certainly a feasable approach. In high-quality glasses used e.g. for the production of fibers, even very low concentrations of trace elements may be relevant, so hydrofluoric acid of very high purity has to be used for the sample decomposition. This can be obtained by sub-boiling procedures in plastic apparatus. 

Formation of the boron complex in acidic (H2SO4) solution is not very rapid after the addition of fluoride in excess it requires some time at room temperature. The sulphuric acid concentration can be 0.2-0.8 M, and concentrations of -0.4 M for fluoride and -210 Af for Methylene Blue are suitable. Under these conditions, BF4 is formed in -30 min. Before extraction of the ion-pair, the sample solution should be diluted to reduce the acidity. 1,2-Dichloroethane is the most recommended solvent for the extraction of the boron ion-pair a good quality solvent is important for good extraction. Polyethylene separating funnels must be used because of the hydrofluoric acid medium. 

Production and quality control of uranium fuel rods used in nuclear power plants are monitored by DC arc emission spectroscopy. Trace elements in high-purity metal powders are measured for quality control purposes. Tungsten powder used to make light bulb hlament can be analyzed for trace elements by arc/spark emission spectroscopy without the need to dissolve the tungsten this eliminates the use of expensive and hazardous hydrofluoric acid. 

The 69% nitric acid (HNO3) and 37% hydrochloric acid (HCl) used for sample dissolution in a high pressure asher (HPA-S, Anton Paar, Austria) were supra grade quality purchased from Roth (Karlsruhe, Germany). The 40 % hydrofluoric acid (HF) used to remove silicates was of suprapure grade from Merck (Darmstadt, Germany). 

Commercially available silica particles (Kromasil, 13 pm mean diameter, C4-phase, 0.7 ml/g pore volume, 195 A pore size) are from Eka Chemicals AB (Bohus, Sweden). ( )-Isoproterenol HCl and (—)-isoproterenol HCl are purchased from Sigma (St. Louis, USA). (—)-Isoproterenol, trifluoromethacrylic acid (TFMAA), metha-crylic acid (MA A) and divinylbenzene (DVB) are obtained from Aldrich (Steinheim, Germany). DVB is of technical grade (80%) and the inhibitor is removed using basic alumina (Merck, Darmstadt, Germany) prior to use. Solvents for polymer preparation are of anhydrous quality and are from Labscan (Dublin, Ireland). Hydrofluoric acid (HF), acetone (p.a.) and acetonitrile (MeCN)(HPLC quality) are obtained from Merck. 

Especially for hydrofluoric acid bums, the delay and the quality of management appear cmcial. 

Alkylate octane improvement, 147-148 upgrading effluent treating, 148 additives, 148 Alkylate quality reduction (hydrofluoric acid alkylation), 151 Alkylation depropanizer (dehydrating light-ends towers), 398-399 drying procedure, 399-400 Alkylation depropanizer (tray fouling), 395... 

Alkylation quality, 145-146 Alkylation, 136-155 process description, 136-140 acid carryover, 140-148 improving alkylate octane, 147-148 hydrofluoric acid alkylation, 148-155 troubleshooting problems, 154 sulfuric acid, 155... 

In some cases, used perfluorinated fluoropolymers (e.g., PTFE, PFA) are recycled by special cleaning processes and are ending up in the Repro-PTFE or micropowder-PTFE-market. Perfluorinated thermoplasts (e.g., PFA) are reused in applications where the quality requirements (e.g., lot traceability) are much lower. Overall, the lion s share of used fluoropolymers is, however, ending up in landfills, in incineration plants, or in blast furnaces. Communal waste incinerators can tolerate only very limited amounts of fluoropolymers due to the high corrosion due to hydrofluoric acid formed in the process. 

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