Chlor-alkali process hydrogen processing

The substitution of conventional hydrogen-evolving cathodes with oxygen-consuming gas-diffusion electrodes (GDE), often referred to as oxygen-depolarised cathodes (ODC), also allows a substantial reduction in the energy consumption of the chlor-alkali process. 

The products of the chlor-alkali process are all useful. Sodium hydroxide is used to make soaps and detergents. It is widely used as a base in many other industrial chemical reactions, as well. The hydrogen produced by the chlor-alkali process is used as a fuel. Chlorine has many uses besides water treatment. For example, chlorine is used as a bleach in the pulp and paper industry. Chlorine is also used in the manufacture of chlorinated organic compounds, such as the common plastic polyvinyl chloride (PVC). 

Would you predict the products of the chlor-alkali process to he hydrogen and chlorine Explain. 

Three useful products are obtained from this reaction chlorine gas (CI2), hydrogen gas (H2), and sodium hydroxide (NaOH). The chlor-alkali process is one of the most important industrial processes used today. 

The largest electrolysis process using an ion exchange membrane is the chlor-alkali process to produce caustic soda, chlorine gas and hydrogen gas. The production capacity of caustic soda in the world was about 56.4 million ton/year in 2001 (demand was about 45.1 million ton/year in 2001).117... 

Figure 11 Illustrates the basic principles of three chlor-alkali processes. In the mercury process, sodium ion forms a Na-amalgam, which is decomposed with water in a denuder to produce caustic soda and hydrogen. The diaphragm process uses an asbestos diaphragm to separate chlorine from hydrogen. Anolyte flows through the asbestos diaphragm...

Hydrogen evolution reaction (her) is one of the most frequently occurring cathodic reactions in industrial cell processes. Hydrogen is formed as a by-product in the chlor-alkali process and in the chlorate production, which are the major industrial electrochemical processes [1], but it is the desired reaction in water electrolysis. Traditional cathode materials for industrial applications have long been iron and mild steel. But, with the increasing cost of electrical power and especially... 

The chlor-alkali process produces chlorine and sodium hydroxide solution in fixed stoichiometric proportions. Experience has shown that there tends to be a surplus of either chlorine or sodium hydroxide. Chlorine may, however, be produced competitively without the byproduct sodium hydroxide by nonelectrolytic methods. The starting material is usually hydrogen chloride, which is catalytically oxidized to chlorine by oxygen, air, nitric acid, sulfur trioxide, or hydrogen peroxide. Other processes start from ammonium chloride or metal chlorides. 

The chlor-alkali process is an industrial process of using sodium chloride electrolysis to produce chlorine and sodium hydroxide (caustic soda). Besides the two main products, hydrogen is also produced through this process. 

Electrolytic Preparation of Chlorine and Caustic Soda. The preparation of chlorine [7782-50-5] and caustic soda [1310-73-2] is an important use for mercury metal. Since 1989, chlor—alkali production has been responsible for the largest use for mercury in the United States. In this process, mercury is used as a flowing cathode in an electrolytic cell into which a sodium chloride [7647-14-5] solution (brine) is introduced. This brine is then subjected to an electric current, and the aqueous solution of sodium chloride flows between the anode and the mercury, releasing chlorine gas at the anode. The sodium ions form an amalgam with the mercury cathode. Water is added to the amalgam to remove the sodium [7440-23-5] forming hydrogen [1333-74-0] and sodium hydroxide and relatively pure mercury metal, which is recycled into the cell (see Alkali and chlorine products). 

Conventionally, these five processes are grouped into three different plants. The chlor-alkali plant stands alone, as does the PVC polymerisation plant. The remaining three steps are often built as a single vinyl chloride plant , the so-called balanced mode producing VCM from the feedstocks of chlorine and ethylene, with all the EDC and hydrogen chloride recycled within the VCM plant to extinction. In this chapter, the discussion centres on an alternative way of thinking whereby the EDC unit is... 

HydroCopper A process for leaching copper from sulfide ores, using dilute aqueous cupric chloride. The copper is precipitated from the leach solution by sodium hydroxide, and the precipitated cuprous oxide is reduced to the metal by hydrogen. An intergrated chlor-alkali cell provides the sodium hydroxide and hydrogen. Planned for demonstration in Finland in 2003. 

Membrane electrolyzers for water decomposition use cation exchange membranes of the type used in the chlor-alkali membrane process, in this case made H+-ion conducting by different pretreatment. So, the ions generated at the anode (H2O -> 2H++ I/2O2 + 2e ) pass through the membrane and form at the cathode hydrogen (2H+ + 2e -> H2). 

The Farmers Cooperative ammonia plant has two sources of hydrogen available, 25 tonne/day via a chlor-alkali facility and a further 60 toime/day from operation of its own reforming and shift conversion processes. 

Oxygen evolution reaction (OER) can be considered as one of the most relevant processes in electrochemistry involved in, for instance, chlor-alkali and ozone productions. One of the challenges is seawater electrolysis in order to store pure hydrogen and oxygen gases and prevent CI2 formation. The overall OER,... 

The principal application of "Nafion" currently is as a membrane separator in chlor-alkali cells, shown schematically in Figure 1. In this process water is decomposed in the cathode compartment to produce caustic and hydrogen, while saturated brine is fed to the anode compartment where the chloride ion is reduced to chlorine gas. The role of the membrane is to separate the two compartments, allow the facile transport of sodium ions from the anode to cathode compartments, and to restrict the flux of hydroxyl ions across the membrane. In the classical picture of ion exchange membranes (14) where the ion exchange sites are... 

In recent years, a number of electrolytic processes have utilized membranes in producing both anodic and cathodic products. By far, however, the most important application of this technology has been in the chlor-alkali industry. Intense commercial and academic interest has been focused into this field during the past decade so that ion exchange theory as applied to membranes is in a more advanced state than any of the other ion exchange systems. The primary examples of industrial chlor-alkali electrochemistry are found in the production of chlorine, caustic soda and potash, hydrogen and hypochlorite (1) (4). 

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