Boron electrolytic reduction

It is easy to reduce anhydrous rare-earth hatides to the metal by reaction of mote electropositive metals such as calcium, lithium, sodium, potassium, and aluminum. Electrolytic reduction is an alternative in the production of the light lanthanide metals, including didymium, a Nd—Pt mixture. The rare-earth metals have a great affinity for oxygen, sulfur, nitrogen, carbon, silicon, boron, phosphoms, and hydrogen at elevated temperature and remove these elements from most other metals. 

Electrolytic reduction, apparatus, 52, 23 Enol acetates, acylation of, 52,1 Enol esters, preparation, 52, 39 Epichlorohydrin, with boron trifluoride diethyl therate and dimethyl ether to give trimethyloxonium tetra-fluoroborate, 51,142 ESTERIFICATION OF HINDERED ALCOHOLS f-BUTYL p-TOLUATE,... 

Boron may be prepared by several methods, such as chemical reduction of boron compounds, electrolytic reduction in nonaqueous phase, or by thermal decomposition. Many boron compounds including boron oxides, borates, boron halides, borohydrides, and fluoroborates can be reduced to boron by a reactive metal or hydrogen at high temperatures ... 

Electrolytic reduction and thermal decomposition have not yet been apphed in large scale commercial methods. Electrolysis of alkali or alkaline earth borates produces boron in low purity. Electrolytic reduction of fused melts of boron trioxide or potassium tetrafluroborate in potassium chloride yield boron in high purity. Also, boron tribromide or boron hydrides may be thermally dissociated hy heating at elevated temperatures. 

Other methods have also been used to produce high-purity boron, including the electrolytic reduction of KBF4 in molten KC1—KF mixtures. 

A review on the preparation of diborane (2) covers the literature to the year 1956. Some further information appears in articles and treatises dealing with the boranes as a whole (3, 155, 201, 250), but such a wide variety of methods for preparing diborane is now known that a separate critical treatment is badly needed. It is convenient here to classify the methods into six main types. All except the first two types involve either reducing agents or some kind of electrolytic reduction, and these four Ccin be further subdivided according to the chemical form in which the boron is introduced. Whereas some methods involve... 

Other Metals. AH the sodium metal produced comes from electrolysis of sodium chloride melts in Downs ceUs. The ceU consists of a cylindrical steel cathode separated from the graphite anode by a perforated steel diaphragm. Lithium is also produced by electrolysis of the chloride in a process similar to that used for sodium. The other alkaH and alkaHne-earth metals can be electrowon from molten chlorides, but thermochemical reduction is preferred commercially. The rare earths can also be electrowon but only the mixture known as mischmetal is prepared in tonnage quantity by electrochemical means. In addition, beryIHum and boron are produced by electrolysis on a commercial scale in the order of a few hundred t/yr. Processes have been developed for electrowinning titanium, tantalum, and niobium from molten salts. These metals, however, are obtained as a powdery deposit which is not easily separated from the electrolyte so that further purification is required. 

Electroless Electrolytic Plating. In electroless or autocatalytic plating, no external voltage/current source is required (21). The voltage/current is suppHed by the chemical reduction of an agent at the deposit surface. The reduction reaction must be catalyzed, and often boron or phosphoms is used as the catalyst. Materials that are commonly deposited by electroless plating (qv) are Ni, Cu, Au, Pd, Pt, Ag, Co, and Ni—Fe (permalloy). In order to initiate the electroless deposition process, a catalyst must be present on the surface. A common catalyst for electroless nickel is tin. Often an accelerator is needed to remove the protective coat on the catalysis and start the reaction. 

When the Abbe Hauy pointed out the close similarity and probable identity of beryl and the emerald, Vauquelin analyzed them carefully, and found in 1798 that they are indeed identical, and that they contain a new earth, which he named glucina, but which is now known as beryllia The metal was isolated thirty years later by Wohler and Bussy independently. Boron was isolated in 1808 by Gay-Lussac and Thenard in France and by Davy in England by reduction of boric acid with potassium. Although amorphous silicon was prepared by Berzelius in 1824, the crystalline form of it was not obtained until about thirty years later, when Henri Sainte-Clarie DeviUe prepared it by an electrolytic method Aluminum was isolated in 1825 by the Danish physicist, Oersted, and two years later Wohler prepared it by a better method. Successful commercial processes for the manufacture of this important metal were perfected by Henri Sainte-Claiie Deville, by Charles Martin Hall, and by Dr. Paul L. T. Heroult. 

Stability. Another major facet in the overall performance of electrochromic materials is the stability of the system. Many potential issues, such as degradation of the active redox couple due to irreversible oxidation or reduction at extreme potentials, iR loss of the electrode or the electrolyte, detrimental side reactions due to the presence of water or oxygen in the cell or heat release due to the resistive parts in the system, can result in the eventual loss of electrochromic contrast and function [7]. One effective approach towards the improvement of electrochemical cycling stability is the use of boron fluoride ethyl ether (REEF.) during the electrochemical synthesis of some heterocyclic compounds (including thiophene and bithiophene) [20]. For example, Camurlu et al. have shown reasonable stability and a switching speed of less than 1.5 s for the homopolymer of hexanedioic acid bis (2-thiophen-3-ylethyl) ester (HABTE) [21],... 

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