Caustic soda synthesis

Caustic soda synthesis via brine electrolysis was described in Eqn (15.3). The main alternate chloralkali manufacturing technologies are based on diaphragm, mercury, and membrane cells (Burney, 1993 Venkatesh Tilak, 1983). Of course, the NaCl and NaOH in Eqn (15.3) are fuUy dissociated in the aqueous solution, i.e., NaCl(aq) Na" - -Cl and NaOH(aq) Na - -OH , so that an alternate, and... 

Three forms of caustic soda are produced to meet customer needs purified diaphragm caustic (50% Rayon grade), 73% caustic, and anhydrous caustic. Regular 50% caustic from the diaphragm cell process is suitable for most appHcations and accounts for about 85% of the NaOH consumed in the United States. However, it caimot be used in operations such as the manufacture of rayon, the synthesis of alkyl aryl sulfonates, or the production of anhydrous caustic because of the presence of salt, sodium chlorate, and heavy metals. Membrane and mercury cell caustic, on the other hand, is of superior quaUty and... 

The route of synthesis of pantoprazole sodium, as described in US patent 4758579 (1988), is as follows. 2-chloromethyl-3,4 dimethoxypyridinium hydrochloride(I) is condensed with 5-difluoromethoxy-2-mercapto-benzimidazole(H) in ethanolic sodium hydroxide solution to yield 5-(difluoromethoxy)-2-(((3,4-dimethoxypyrolidine-2-yl) methyl) thio)-l/7-benzimidazole)(III). This compound is oxidized during reaction with m-chloroperbenzoic acid in methylene chloride, yielding pantoprazole base (IV). Further reaction with aqueous caustic soda solution gives pantoprazole sodium, which is then purified by crystallization from methanol. The various steps of this synthesis are illustrated in Scheme 1. 

Cesium-exchanged zeolite X was used as a solid base catalyst in the Knoevenagel condensation of benzaldehyde or benzyl acetone with ethyl cyanoacetate [121]. The latter reaction is a key step in the synthesis of the fragrance molecule, citronitrile (see Fig. 2.37). However, reactivities were substantially lower than those observed with the more strongly basic hydrotalcite (see earlier). Similarly, Na-Y and Na-Beta catalyzed a variety of Michael additions [122] and K-Y and Cs-X were effective catalysts for the methylation of aniline and phenylaceto-nitrile with dimethyl carbonate or methanol, respectively (Fig. 2.37) [123]. These procedures constitute interesting green alternatives to classical alkylations using methyl halides or dimethyl sulfate in the presence of stoichiometric quantities of conventional bases such as caustic soda. 

When liquid air distillation is used as the source of nitrogen, the hydrogen also required for ammonia synthesis is obtained from a variety of sources. Some is obtained as the coproduct from the electrolytic production of chlorine and caustic soda (Chap. 8), some from refinery sources as a by-product of cracking processes or olefin synthesis, some from the water-gas reaction, and some is produced specifically for the purpose by the electrolysis of alkaline water (e.g., by Cominco, Trail, Eq. 11.14). 

Some industrial organic synthesis reactions take place in the presence of aqueous caustic soda. A typical exanqile is the dehydrogenation of amino alcohols to amino carboxylic acid salts, which is typically conducted at 1.0 MPa and 393K-483K in a concentration of caustic up to 50wt%. Under such harsh conditions, most supported copper catalysts cannot be used due to dissolution of... 

A variety of polysaccharide ethers are produced industrially. They include methyl, ethyl, hydroxyethyl, hydroxypropyl, and carboxymethyl ethers. Combinations of these with other subslitulions are often seen. Because of the wide range of properties produced and low cost, etherifications are among the most common industrial modifications. The mechanism for etherification varies, depending on the desired subslitulion. Methylalion can be achieved with a simple Williamson synthesis where the hydroxyl is exposed by the addition of caustic soda [Figure 2] (4). 

Alcohols react more sluggishly than water in a decomposer, and the rate of reaction declines as the carbon number of the alcohol increases. Except for the question of proper sizing, the decomposer design is much the same as those used for production of NaOH and KOH. Propyl alcohol is not active enough to be of any interest. Ethyl alcohol is less active than methyl alcohol, and it was in the case of sodium methylate that this reaction had its commercial success. This compound, like any alcoholate, hydrolyzes readily to the alcohol and caustic soda, so strictly anhydrous conditions are necessary for synthesis, another reason for limited commercial production of sodium ethylate. 

Two current synthesis processes are commercialized, with the economically most successful one said to be the interface process, which involves the dissolution of bisphenol A in aqueous caustic soda and the introduction of phosgene in the presence of an inert solvent such as pyridine. An alternative method involves transesterification of bisphenol A with diphenyl carbonate at elevated temperatures. 

Depending on the backward integration of the individual zeolite production process, the alumina source may be aluminum hydroxide as well as sodium aluminate [20,103,114,116,117,123, 124,129,130,132-136,139,141,152,158,160-165]. Usually, the synthesis starts with the dissolution of aluminum hydroxide in caustic soda solution at temperatnres above 80°C and filtration (see Equation 22.4) [15,20,99,104,110,126,128,166],... 

Apart from its nse in the synthesis of the raw materials, caustic soda is an important ingredient in the zeolite prodnction process. During the crystallization step, it supplies the sodium ions and assists additionally in controlling the pH. It is commonly used as 50 wt% aqueous solution [15,99,116,126,139,166]. 

On the other hand, electrolytic synthesis of endergonic reactions via practiced on a large scale in industry (Scott, 1993 Sequeira Santos, 2009), e.g., the modem electrochemical synthesis of caustic soda via the chloraUcali process (Burney, 1993 Venkatesh Tilak, 1983). The electrode and overall reactions (OR) in this process are ... 

Industrial scale electrolyzers were developed early in the 20th century for the manufacture of chlorine and caustic soda from brine, and for the commercial production of hydrogen used in ammonia synthesis. Large water-electrolysis plants were constructed in Norway and Canada in the 1930 s, based on cheap hydroelectric power, and the hydrogen so produced was used in fertilizer manufacture. With the advent of natural gas and low cost petroleum, hydrogen production moved toward catalytic steam-reforming of hydrocarbons, and water electrolysis became less significant. 

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