SOLVAY

Gaspard P and Burghardt I (ed) 1997 XXth Solvay Conf on Chemistry Chemical Reactions and their Control on the Femtosecond Time Scale (Adv. Chem. Phys. 101) (New York Wiley)... 

International Solvay Institutes Universite Libre de Bruxelles Brussels, Belgium... 

Sodium hydroxide is manufactured by electrolysis of concentrated aqueous sodium chloride the other product of the electrolysis, chlorine, is equally important and hence separation of anode and cathode products is necessary. This is achieved either by a diaphragm (for example in the Hooker electrolytic cell) or by using a mercury cathode which takes up the sodium formed at the cathode as an amalgam (the Kellner-Solvay ceW). The amalgam, after removal from the electrolyte cell, is treated with water to give sodium hydroxide and mercury. The mercury cell is more costly to operate but gives a purer product. 

Mercury is extensively used in various pieces of scientific apparatus, such as thermometers, barometers, high vacuum pumps, mercury lamps, standard cells (for example the Weston cell), and so on. The metal is used as the cathode in the Kellner-Solvay cell (p. 130). 

Early demand for chlorine centered on textile bleaching, and chlorine generated through the electrolytic decomposition of salt (NaCl) sufficed. Sodium hydroxide was produced by the lime—soda reaction, using sodium carbonate readily available from the Solvay process. Increased demand for chlorine for PVC manufacture led to the production of chlorine and sodium hydroxide as coproducts. Solution mining of salt and the avadabiHty of asbestos resulted in the dominance of the diaphragm process in North America, whereas soHd salt and mercury avadabiHty led to the dominance of the mercury process in Europe. Japan imported its salt in soHd form and, until the development of the membrane process, also favored the mercury ceU for production. 

These disadvantages prompted Ernest Solvay (1838—1922) to develop and commercialize a procedure using ammonia to produce soda ash from salt and limestone. The first plant using the Solvay process was built in 1863 this process or variations are in use in much of the world in the 1990s. 

The basic Solvay process remains the dominant production route for soda ash. Its continued success is based on the raw matedals, salt and limestone, being more readily available than natural alkaU. AH soda ash processes are based on the manipulation of saline phase chemistry (6,7) an understanding of which is important both to improving current processes and to the economic development of new alkaU resources. 

The ammonium chloride process, developed by Asahi Glass, is a variation of the basic Solvay process (9—11). It requires the use of soHd sodium chloride but obtains higher sodium conversions (+90%) than does the Solvay process. This is especially important ia Japan, where salt is imported as a soHd. The major difference from the Solvay process is that here the ammonium chloride produced is crystallized by cooling and through the addition of soHd sodium chloride. The resulting mother Hquor is then recycled to dissolve additional sodium chloride. The ammonium chloride is removed for use as rice paddy fertilizer. Ammonia makeup is generally suppHed by an associated synthesis plant. 

Akzo Process. Akzo Zout Chemie has developed a route to vinyl chloride and soda ash from salt usiag an amine—solvent system catalyzed by a copper—iodide mixture (13). This procedure theoretically requires half the energy of the conventional Solvay processes. 

Alternatively, the ash can be converted to the monohydrate and calcined as practiced by the Solvay industry. 

Synthetic Processes. Traditional Solvay plants produce large volumes of aqueous, chloride-containing waste which must be discharged. This fact, in addition to a noncompetitive cost position, is largely responsible for the demise of U.S. synthetic plants. In countries other than the United States, waste is sent to the ocean, rivers, or deep underground wells. The AC and NA coproduct processes produce less aqueous waste than the traditional Solvay and NA mono processes. Related environmental concerns are added whenever a plant complex includes lime quarries and ammonia-producing equipment. 

Pulp-like olefin fibers are produced by a high pressure spurting process developed by Hercules Inc. and Solvay, Inc. Polypropylene or polyethylene is dissolved in volatile solvents at high temperature and pressure. After the solution is released, the solvent is volatilised, and the polymer expands into a highly fluffed, pulp-like product. Additives are included to modify the surface characteristics of the pulp. Uses include felted fabrics, substitution in whole or in part for wood pulp in papermaking, and replacement of asbestos in reinforcing appHcations (56). 

Solvay Fluor und Derivate, GmbH Haimover, Germany SFg, IF, perfluorinated hydrocarbons, CF p large... 

Economic Aspects. Halocarbon Products Corp. is the largest producer of trifluoroacetic acid. The commercial grade is of very high purity with the main impurity being ca 0.2% water. A grade, which has a low residue specification, intended for use in protein synthesis (Biograde) is available. Other producers include Rhc ne-Poulenc and Solvay. The 1992 price was ca 15/kg. 

Because of its excekent combination of properties, processibkity, and relatively low price compared to other fluoropolymers, PVDF has become the largest volume fluoropolymer after PTFE consumption in the United States has grown from zero in 1960 to about 6200 metric tons in 1991 (186). About 49% of the consumed volume is PVDF modified by copolymerization with 5—12-wt % HFP to enhance flexibkity. In 1992, Hst price for homopolymer powders was 15.32/kg, and for pekets 15.42/kg the reported market price was 14.09—14.22/kg (187). In the United States, almost ak PVDF is suppHed by Ausimont USA, Inc., Elf Atochem North America, Inc., and Solvay Polymers, Inc. Ausimont and Elf Atochem are producers Solvay is an importer of the resin. Smak amounts of resin are imported from Germany by Huls America, Inc, and from Japan by Kureha Chemical Industry Co., Ltd. PVDE producers and their trademarks are Hsted in Table 4. 

Brit. Pat. 1,004,172 (Sept. 8, 1965), Deutsche Solvay-Werke GmbH. 

SolefPMDF, Technical Brochure, Solvay Cie. SA, Bmssels, Belgium, 1987. 

Plastic materials represent less than 10% by weight of all packagiag materials. They have a value of over 7 biUion including composite flexible packagiag about half is for film and half for botties, jars, cups, tubs, and trays. The principal materials used are high density polyethylene (HDPE) for botties, low density polyethylene for film, polypropylene (PP) for film, and polyester for both botties and films. Plastic resias are manufactured by petrochemical companies, eg. Union Carbide and Mobil Chemical for low density polyethylene (LDPE), Solvay for high density polyethylene, Himont for polypropylene, and Shell and Eastman for polyester. 

Sodium bicarbonate may be prepared by the ammonia-salt (Solvay) process. Carbon dioxide is passed through a solution of sodium chloride in ammonia water. Sodium bicarbonate is precipitated and the ammonium chloride remains in solution. The ammonium chloride is heated with lime to regenerate ammonia (see Alkali AND CHLORINE PRODUCTS). 

The amount of soda ash, Na2C02, produced by the Solvay process has decreased, and most soda ash now comes from the Trona, Wyoming deposits (trona, Na2C02 NaHCO 2H20). Caustic soda, NaOH, solutions may be used ia wet batchiag processes as a source of soda (see Alkali and... 

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