Product quality diaphragm cell caustic

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 applications and accounts for about 85% of the NaOH consumed in the United States. However, it cannot 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 quality and... 

A major differentiator among the various chlor-alkali cells is the quality of their product caustic solutions. Diaphragm cells produce a liquor containing about 11% NaOH and... 

The diaphragm may be replaced by a cation exchange membrane which is suitable for high concentrated hydrochloric acid like Nafion (DuPont, perfluorosulfonic acid polymer, PFSA, see entry Chlorine and Caustic Technology, Membrane Cell Process ). This membrane has almost no usual porosity and is nearly exclusively permeable for ions including a hydration shell of some water molecules. Thus, product quality is significantly increased, process operation can be simplified, and cell voltage is reduced by about 0.3 V [1, 6]. However, the mechanical durability... 

Production of caustic soda solution. In 1998, the worldwide production capacity was about 54 million tons per year. Ca. 96-98% of this amount is produced by chloralkali electrolysis [313). The three processes are described in detail in chapter 5 (Mercury Cell Process), chapter 6 (Diaphragm Process) and chapter 7 (Membrane process), a comparison of the relative qualities is given in chapter 9. 

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