Electrolytic process development

Phosphoric acid was sometimes used instead of sulfuric acid. The process was first operated in Berlin in 1873 by the Schering Company. In the United Kingdom it was first operated in 1888 by B. Laporte Company. It was progressively replaced by the electrolytic process developed between 1908 and 1932. Also in the United Kingdom, Laporte Chemicals abandoned the barium process in 1950. 

In Japan the need for new technology was answered by the development of an electrolytic route to sebacic acid(33). The Kolbe type electrolytic process developed by Asahi involves dimerization of adipic acid half methyl ester salt to give dimethyl sebacate(34). The dimerization proceeds in 92% yield with 90% selectivity based on the adipate half ester. The main drawbacks of this process are the cost of energy utilized by the electrolytic process and the cost of adipic acid. A Chem Systems report indicates a small advantage for the Asahi electrolytic process with ample room for new technology development(35). 

These reactions of lead metal and lead alloys with alkyl esters are conducted at elevated temperatures (usually above 80 °C) and at elevated pressure (autogenous pressure of RX), and in the presence of a suitable catalyst, such as ethers, amines, iodides, dependent on the particular system involved. Despite the large number of systems which have been investigated, none has been found to be as economical for the commercial production of tetramethyllead and tetraethyllead as the sodium-lead alloy reaction, with the possible exception of the electrolytic process developed by Nalco Chemical Company for tetramethyllead. Electrolytic processes are discussed in Section 6. 

Inorganic Methods. Before the development of electrolytic processes, hydrogen peroxide was manufactured solely from metal peroxides. Eady methods based on barium peroxide, obtained by air-roasting barium oxide, used dilute sulfuric or phosphoric acid to form hydrogen peroxide in 3—8% concentration and the corresponding insoluble barium salt. Mote recent patents propose acidification with carbon dioxide and calcination of the by-product barium carbonate to the oxide for recycle. 

Most commercial tellurium is recovered from electrolytic copper refinery slimes (8—16). The tellurium content of slimes can range from a trace up to 10% (see Seleniumand selenium compounds). Most of the original processes developed for the recovery of metals of value from slimes resulted in tellurium being the last and least important metal produced. In recent years, many refineries have changed their slimes treatment processes for faster recovery of precious metals (17,18). The new processes have in common the need to remove the copper in slimes by autoclave leaching to low levels (<1%). In addition, this autoclave pretreatment dissolves a large amount of the tellurium, and the separation of the tellurium and copper from the solution which then follows places tellurium recovery at the beginning of the slimes treatment process. 

An electrolytic process for purifying cmde vanadium has been developed at the U.S. Bureau of Mines (16). It involves the cathodic deposition of vanadium from an electrolyte consisting of a solution of VCI2 in a fused KCl—LiCl eutectic. The vanadium content of the mixture is 2—5 wt % and the operating temperature of the cell is 650—675°C. Metal crystals or flakes of up to 99.995% purity have been obtained by this method. 

The development of the autoxidation of alkyl anthraquinones led to a rapid iacrease ia the production of H2O2 but a sharp decline in the importance of the electrolytic process. In 1991 the total North American, Western European, and Japanese capacity for H2O2 production was more than 870,000 t (77). No H2O2 was produced by the electrolytic peroxydisulfate process. The last plant using this process closed in 1983. 

The development of electrical power made possible the electrochemical industry. Electrolysis of sodium chloride produces chlorine and either sodium hydroxide (from NaCl in solution) or metallic sodium (from NaCl fused). Sodium hydroxide has applications similar to sodium carbonate. The ad vantage of the electrolytic process is the production of chlorine which has many uses such as production of polyvinyl chloride. PVC, for plumbing, is produced in the largest quantity of any plastic. 

It also follows from what was said that a zeta potential will be displayed only in dilute electrolyte solutions. This potential is very small in concentrated solutions where the diffuse edl part has collapsed against the metal surface. This is the explanation why electrokinetic processes develop only in dilute electrolyte solutions. 

Dynamic techniques are those in which electrolytic processes occur at the electrodes and therefore a finite current is passed through the electrochemical cell. Thig discussion will be limited to controlled-potential techniques, namely voltammetry and ampero-metry. While other dynamic electrochemical techniques have been developed, these two are by far the most commonly used for bioelectroanalytical studies. 

The first production of aluminum was by the chemical reduction of aluminum chloride with sodium. The electrolytic process, based on the fused salt electrolysis of alumina dissolved in cryolite, was independently developed in 1886 by C. M. Hall in America and P. L. Heroult in France. Soon afterwards a chemical process for producing pure alumina from bauxite, the commercial source of aluminum, was developed by Bayer and this led to the commercial production of aluminum by a combination of the Bayer and the Hall-Heroult processes. At present this is the main method which supplies all the world s needs in primary aluminum. However, a few other processes also have been developed for the production of the metal. On account of problems still waiting to be solved none of these alternative methods has seen commercial exploitation. 

FIGURE 1.8 Electrolytic process. (From Wang, L.K. et al. Case Studies of Cleaner Production and Site Remediation, Training Manual DTT-5-4-95, United Nations Industrial Development Organization, Industrial Sectors and Environment Division, Vienna, Austria, April 1995.)... 

AIAG Neuhausen An electrolytic process for making aluminum from an all-fluoride melt. Developed by the Societe Suisse de F Aluminium Industrie at Neuhausen, Germany. 

Betts An electrolytic process for refining lead and recovering silver and gold from it. The electrolyte is a solution of lead fluosilicate and hydiofluosilicic acid. The other metals collect as a slime on the anode and are retained there. Developed by A.G. Betts in 1901, first operated at Trail, British Columbia, in 1903, and now widely used in locations having cheap electric power. 

De Nora An electrolytic process for making chlorine and sodium hydroxide solution from brine. The cell has a mercury cathode and graphite anodes. It was developed in the 1950s by the Italian company Oronzio De Nora, Impianti Elettrochimici, Milan, based on work by I. G. Farbenindustrie in Germany during World War II. In 1958 the Monsanto Chemical Company introduced it into the United States in its plant at Anniston, AL. See also Mercury cell. 

Deville (2) An early process for making sodium by reducing sodium carbonate with carbon at or above 1,100°C. Developed in 1886 and used until it was superseded by electrolytic processes. See Downs and Castner (4). 

Dow bromine An electrolytic process for extracting bromine from brines. Ferric bromide was an intermediate. Developed by H. H. Dow, founder of the Dow Chemical Company. 

ElectroSlurry An electrolytic process for extracting copper from sulfide ores, liberating elemental sulfur. Developed by the Envirotech Research Center, Salt Lake City, UT. 

Griesheim (1) An early process for producing chlorine by electrolysis, developed by Chemische Fabrik Griesheim-Elektron, in Germany, and commercialized in 1890. The electrolyte was saturated potassium chloride solution, heated to 80 to 90°C. The byproduct potassium hydroxide was recovered. The process was superseded in the United States by several similar electrolytic processes before being ousted by the mercury cell, invented by H. Y. Castner and K. Kellner in 1892. See Castner-Kellner. 

Hoopes An electrolytic process for refining aluminum metal. The electrolyte is a mixture of fluoride salts. The cell is constructed of graphite. The electrolyte in contact with the side-walls of the cell is frozen, thus preventing short-circuiting of electricity through the walls. Developed by W. Hoopes and others at Aluminum Company of America in the 1920s. 

Tekkosha An electrolytic process for obtaining sodium from the sodium amalgam formed in the chlor-alkali process. The electrolyte is a fused mixture of sodium hydroxide, sodium iodide, and sodium cyanide. The sodium deposits at the iron cathode. Developed by Tekkosha Company, Japan, in the 1960s and commercialized in 1971. 

The process was complicated by the formation of calcium manganite, CaMn206, known as Weldon mud. Invented by W. Weldon in 1866 and developed at St. Helens from 1868 to 1870. Operated in competition with the Deacon process until both were overtaken by the electrolytic process for making chlorine from brine. Weldon mud has been used as a catalyst for oxidizing the hydrogen sulfide in coal gas to elemental sulfur. 

Wunsche An electrolytic process for liberating bromine from a bromide solution. It uses carbon electrodes and a porous clay separator. Developed in Germany in 1902. See also Kossuth. 

Implementation of upd in material synthesis has also been explored. A particularly interesting effort has focused on the production of E-VI compounds by successive upd reactions performed in two different electrolytes. Importantly, process development has been tightly coupled with STM studies of both upd and overpotential deposition (opd) of the constituents [299,304,365-369]. Similarly, the influence of upd on catalytic activity towards certain reactions is well known [370]. An STM study of the inhibition of four-electron oxygen reduction on Pt(l 11) by upd Cu clearly demonstrates the importance of upd structure on reactivity [371]. 

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