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Anhydrous hydrogen fluoride (AHF), a critical raw material for industries such as aluminum, pharmaceuticals, and petroleum, has traditionally been sourced from fluorite--a non-renewable mineral. The unsustainable reliance on fluorite has catalyzed the search for alternative AHF production methods. A promising substitute is fluorosilicic acid (FSA), a byproduct of the phosphate fertilizer industry previously deemed waste. Transforming fluorosilicic acid into AHF not only yields a valuable resource but also addresses the environmental and economic challenges associated with waste management. The innovative practice of producing AHF from fluorosilicic acid signals a shift towards sustainable chemical production by capitalizing on waste, potentially diminishing reliance on fluorite and reducing the industry's environmental impact. This review thoroughly dissects the AHF synthesis process from fluorosilicic acid. Despite the acknowledged importance of fluorinated compounds in numerous industrial applications, research on their synthesis from fluorosilicic acid is limited and fragmented. This review seeks to amalgamate this scattered information by closely scrutinizing diverse industrial processing methods. Additionally, it explores the current and future landscape, economic feasibility, and strategies to navigate the obstacles inherent in synthesizing AHF from fluorosilicic acid. It also assesses the environmental impact of these methods, thereby contributing to the dialogue in this emerging field. The primary aim of this manuscript is to foster further research and promote the industrial uptake of this sustainable process. Highlighting the challenges and proposing potential improvements, the review supports the responsible reuse of waste and advocates for advancements in industrial practices. [ABSTRACT FROM AUTHOR]

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Anhydrous hydrogen fluoride (AHF), a critical raw material for industries such as aluminum, pharmaceuticals, and petroleum, has traditionally been sourced from fluorite-a non-renewable mineral. The unsustainable reliance on fluorite has catalyzed the search for alternative AHF production methods. A promising substitute is fluorosilicic acid (FSA), a byproduct of the phosphate fertilizer industry previously deemed waste. Transforming fluorosilicic acid into AHF not only yields a valuable resource but also addresses the environmental and economic challenges associated with waste management. The innovative practice of producing AHF from fluorosilicic acid signals a shift towards sustainable chemical production by capitalizing on waste, potentially diminishing reliance on fluorite and reducing the industry's environmental impact. This review thoroughly dissects the AHF synthesis process from fluorosilicic acid. Despite the acknowledged importance of fluorinated compounds in numerous industrial applications, research on their synthesis from fluorosilicic acid is limited and fragmented. This review seeks to amalgamate this scattered information by closely scrutinizing diverse industrial processing methods. Additionally, it explores the current and future landscape, economic feasibility, and strategies to navigate the obstacles inherent in synthesizing AHF from fluorosilicic acid. It also assesses the environmental impact of these methods, thereby contributing to the dialogue in this emerging field. The primary aim of this manuscript is to foster further research and promote the industrial uptake of this sustainable process. Highlighting the challenges and proposing potential improvements, the review supports the responsible reuse of waste and advocates for advancements in industrial practices., Competing Interests: Authors HuY, SL, HeY, HL, and XC were employed by Do-Fluoride New Materials Co., Ltd. The remaining author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Yang, Li, Yu, Liu, Sun and Chen.)

A process for the laboratory-scale production of fluorine gas using CaF2 as precursor was designed and commissioned. The first step uses a batch reactor in which anhydrous hydrogen fluoride (AHF) is produced by the reaction of CaF2 with sulphuric acid. The AHF is stored, then transferred to a Pauling-type cell, preloaded with KF·HF. The electrolyte, KF·2HF, which is a liquid at the working temperature, is formed in situ. AHF by itself is a weak acid and is is not sufficiently electrically conductive for direct electrolysis. This problem is bypassed by using KF·2HF. Above its melting point, KF·2HF dissociates to form K+ en F2H- in HF, and is sufficiently conductive for electrolysis. The HF batch reactor showed provideda yield of 70 %. The fluorine cell afforded an observable overpotential of 2.7 V, and its voltametric curve displayed the expected behaviour. [ABSTRACT FROM AUTHOR]

Hydroxylammonium tetrafluoridooxidovanadate(V) has been prepared by reaction of (NH3OH)Cl and VOF3 in anhydrous HF solvent and characterised in the solid state by single-crystal X-ray diffraction and Raman spectroscopy. Colourless (NH3OH)[VOF4] crystallises in the monoclinic P21/n space group with a = 7.2349(2) Å, b = 5.0351(2) Å, c = 12.8322(4) Å, b = 94.843(3)°, V = 465.79(3) Å3 and Z = 4 at 150 K. The crystal structure of the title compound is comprised of polymeric chain anions, [VOF4]nn−, interconnected by hydrogen bonds with hydroxylammonium cations, (NH3OH)+.

In the complex cation of the binuclear solvated title salt, [Pt2F(SbF6)2(C8H12)2]SbF6·0.75HF, an F atom bridges the two platinum(II) atoms with a bond angle of 123.3 (2)°. The corresponding Pt—F bond lengths are in the range of other fluorine-bridged binuclear platinum(II) complexes. Two of the three SbF6− anions each coordinate with one F atom to one platinum(II) atom. Including the η4-bound cyclooctadiene (COD) ligands, the overall coordination sphere of each platinum(II) atom is square-planar. The third SbF6− anion is not bound to the complex. Hydrogen fluoride is present in the crystal structure as a solvent disordered over three positions, each with an occupancy of 0.25. F...F distances of 2.5512 (7), 2.6076 (8) and 3.2215 (10) Å to surrounding SbF6− anions are indicative of F—H...F hydrogen-bonding interactions although no H atoms could be localized for the disordered solvent molecules. The resulting hydrogen-bonded network is three-dimensional.

Femtosecond laser irradiation followed by chemical etching (FLICE) with hydrogen fluoride (HF) is an emerging technique for the fabrication of directly buried, three-dimensional microfluidic channels in silica. The procedure, as described in literature, consists of irradiating a silica slab followed by chemical etching using hydrogen fluoride. With aqueous HF the etching process is diffusion-limited and is self-terminating, leading to maximum microchannel lengths of about 1.5 mm, while the use of low-pressure gaseous HF etchant can quickly produce 3 mm long channels with an aspect ratio (Length/Diameter) higher than 25. By utilizing this methodology the aspect ratio is not constant, but depends on the length of the channel. When the microchannel is short the aspect ratio increases quickly until it reaches a maximum length at around 1400 µm. Thereafter the aspect ratio starts to decrease slowly. In this paper we present a variation of the low-pressure gaseous HF etching method, which is based on the dynamic displacement of the etchant. This method results in a 13% increase in the aspect ratio (L/D = 29) at the expense of a low etching speed (4 µm/min).

We have synthesized NOUF6 by direct reaction of NO with UF6 in anhydrous HF (aHF). Based on the unit cell volume and powder diffraction data, the compound was previously reported to be isotypic to O2PtF6, however, detailed structural data, such as the atom positions and all information that can be derived from those, were unavailable. We have therefore investigated the compound by using single-crystal and powder X-ray diffraction, IR, Raman, NMR, EPR, and photoluminescence spectroscopy, magnetic measurements, as well as chemical analysis, density determination, and quantum chemical calculations. [ABSTRACT FROM AUTHOR]

During the reaction of phosphate ore and sulphuric acid, silicon tetrafluoride (SiF 4 ) and HF are formed as byproducts. These gases are usually scrubbed with water, forming fluorosilicic acid, H 2 SiF 6 (FSA) as a waste stream. Until recent years, FSA was mostly used for drinking water fluorination and for the production of Aluminium Fluoride (AlF 3 ) or, in most cases, was neutralised or disposed to sea or ponds. Research and pilot work for the industrialization of a process to produce hydrofluoric acid (HF) and anhydrous hydrofluoric acid (AHF) from FSA has been conducted for nearly six decades without having developed a process that was found suitable to be built on industrial scale. Buss ChemTech has scaled the process from pilot scale (800 t/a) in one step to full scale industrial plant. Since 2008, three plants with capacities of 12,000 and 20,000 tons (two plants) of AHF per year were erected and are in operation. [ABSTRACT FROM AUTHOR]

In the complex cation of the binuclear solvated title salt, [Pt2F(SbF6)2(C8H12)2]SbF6⋅0.75HF, an F atom bridges the two platinum(II) atoms with a bond angle of 123.3 (2)°. The corresponding Pt--F bond lengths are in the range of other fluorine-bridged binuclear platinum(II) complexes. Two of the three SbF6- anions each coordinate with one F atom to one platinum(II) atom. Including the η4-bound cyclooctadiene (COD) ligands, the overall coordination sphere of each platinum(II) atom is square-planar. The third SbF6- anion is not bound to the complex. Hydrogen fluoride is present in the crystal structure as a solvent disordered over three positions, each with an occupancy of 0.25. F⋯F distances of 2.5512 (7), 2.6076 (8) and 3.2215 (10) Å to surrounding SbF6- anions are indicative of F--H⋯F hydrogen-bonding interactions although no H atoms could be localized for the disordered solvent molecules. The resulting hydrogen-bonded network is three-dimensional. [ABSTRACT FROM AUTHOR]

Hydroxylammonium tetrafluoridooxidovanadate(V) has been prepared by reaction of (NH3OH)Cl and VOF3 in anhydrous HF solvent and characterised in the solid state by single-crystal X-ray diffraction and Raman spectroscopy. Colourless (NH3OH)[VOF4] crystallises in the monoclinic space group P21/n with a = 7.2349(2) Å, b = 5.0351(2) Å, c = 12.8322(4) Å, β = 94.843(3)°, V = 465.793 Å3 and Z = 4 at 150 K. The crystal structure of the title compound is comprised of polymeric chain anions, [VOF4]n n-, interconnected by hydrogen bonds with hydroxylammonium cations, (NH3OH)+. [ABSTRACT FROM AUTHOR]

Silver(I) tetrafluoridooxidovanadate(V) which contains the polymeric chain anion, [VOF4]nn-, has been prepared in reaction between AgNO3 and VOF3 in anhydrous HF solvent and characterised in the solid state by single-crystal X-ray diffraction and Raman spectroscopy. Pale yellow crystals of Ag[VOF4] crystallise in a monoclinic P21/c space group with α = 5.5452(4) Å,b = 5.0071(3) Å, c = 13.6511(11) Å, β = 100.543(3)°, and V= 372.63(5) ų at 200 K with Z= 4. The most intense feature in the Raman spectrum is the V=O stretching band of the anion at 1008 cm-1. Solid-state conformational isomerism exists between [VOF4]- anions in crystal structures of Ag[VOF4] and previously reported and structurally characterised K[VOF4] and Cs[VOF4] salts. [ABSTRACT FROM AUTHOR]

Abstract: The results of a thermogravimetric study into the dry fluorination of molybdenum disilicide, MoSi2, using hydrogen fluoride and dilute fluorine gas as fluorinating agents are reported. The reaction between molybdenum disilicide and fluorine follows the thermodynamically preferred route, viz. the formation of the volatile molybdenum hexafluoride along with gaseous silicon tetrafluoride, with the reaction starting just below 200°C. The reaction with hydrogen fluoride yields solid molybdenum metal and gaseous silicon tetrafluoride, similarly thermodynamically predicted, above 250°C. No reaction is observed at low temperatures where solid molybdenum trifluoride is expected to form. The results of a kinetic analysis of the data for the reaction with hydrogen fluoride are reported. In the range 250–450°C the kinetics are chemical reaction controlled. Above this, up to 700°C, the rate is controlled by diffusion through the stagnant gas films surrounding the solid particles. Evidence for a third, un-quantified, high-temperature mechanism is given. [Copyright &y& Elsevier]

Femtosecond laser irradiation followed by chemical etching (FLICE) with hydrogen fluoride (HF) is an emerging technique for the fabrication of directly buried, three-dimensional microfluidic channels in silica. The procedure, as described in literature, consists of irradiating a silica slab followed by chemical etching using hydrogen fluoride. With aqueous HF the etching process is diffusion-limited and is self-terminating, leading to maximum microchannel lengths of about 1.5 mm, while the use of low-pressure gaseous HF etchant can quickly produce 3 mm long channels with an aspect ratio (Length/Diameter) higher than 25. By utilizing this methodology the aspect ratio is not constant, but depends on the length of the channel. When the microchannel is short the aspect ratio increases quickly until it reaches a maximum length at around 1400 µm. Thereafter the aspect ratio starts to decrease slowly. In this paper we present a variation of the low-pressure gaseous HF etching method, which is based on the dynamic displacement of the etchant. This method results in a 13% increase in the aspect ratio (L/D = 29) at the expense of a low etching speed (4 µm/min). [ABSTRACT FROM AUTHOR]

The lead fluoridooxidovanadates(V), Pb(V2O2F8) and Pb(VOF5), were synthesized from PbF2 and VOF3 in anhydrous HF. Their crystal structures were determined and Raman spectra recorded. Compound Pb3F(V4O3F18) with a novel mixed valent vanadium(IV, V) fluoridooxido anion, V4O3F185-, obtained as a by-product, was also structurally characterized. [ABSTRACT FROM AUTHOR]

The lead fluoridooxidovanadates(V), Pb(V2O2F8) and Pb(VOF5), were synthesized from PbF2 and VOF3 in anhydrous HF. Their crystal structures were determined and Raman spectra recorded. Compound Pb3F(V4O3F18) with a novel mixed valent vanadium(IV, V) fluoridooxido anion, V4O3F185-, obtained as a by-product, was also structurally characterized. [ABSTRACT FROM AUTHOR]

Abstract: The thermogravimetric results of a study into the dry fluorination of tungsten disilicide, WSi2, using hydrogen fluoride and dilute fluorine gas as fluorinating agents, are reported. The reaction between tungsten disilicide and fluorine follows the thermodynamically preferred route, viz. the formation of the volatile tungsten hexafluoride along with gaseous silicon tetrafluoride, with the reaction starting just below 200°C. The reaction with hydrogen fluoride yields solid tungsten metal and gaseous silicon tetrafluoride, similarly thermodynamically predicted, above 250°C. No reaction is observed at low temperatures where solid tungsten tetrafluoride is expected to form. The results of a kinetic analysis of the data for the reaction with hydrogen fluoride are reported. At temperatures below 450°C, the kinetics cannot be reliably determined. In the higher temperature region, mass transport of the reactive hydrogen fluoride through the stagnant gas film surrounding the particle, and penetrating the pitted areas, controls the mass loss rate. [Copyright &y& Elsevier]

The electrochemical fluorination of alkanedisulfonyl fluorides, alkanesulfonyl amides and alkanedisulfonyl amides is described. Detailed analysis of the products and the electrolyte and new information on higher nickel fluorides have led to a new insight into the mechanism of electrochemical fluorination. [ABSTRACT FROM AUTHOR]

We have synthesized NOUF6 by direct reaction of NO with UF6 in anhydrous HF (aHF). Based on the unit cell volume and powder diffraction data, the compound was previously reported to be isotypic to O2 PtF6 , however, detailed structural data, such as the atom positions and all information that can be derived from those, were unavailable. We have therefore investigated the compound by using single-crystal and powder X-ray diffraction, IR, Raman, NMR, EPR, and photoluminescence spectroscopy, magnetic measurements, as well as chemical analysis, density determination, and quantum chemical calculations., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)