Caustic chlorides

Corrosion Probiems in Service. The wide variety of corrosive factors that are present in refining and petrochemical processing (e.g., acids, caustics, chlorides, sulfides, sulfates) give rise to a wide variety of corrosive attacks, some of which act ... 

Additional forms of concentration cell corrosion include those involving sodium hydroxide (caustic), chlorides, and sulfates thus, some control over corrosion may be obtained by limiting salinity in the boiler. 

One of the outstanding attributes of alloy 25-6Mo is its resistance to environments containing chlorides or other halides. It is especially suited for applications in high-chloride environments such as brackish water, seawater, caustic chlorides, and pulp mill bleach systems. 

Molecular. sieves are the most expen.sive, but provide the lowest dew point. They are normally used to dehydrate natural gas feed streams for cryogenic hydrocarbon recovery units. Type 4A is the type most commonly employed, but 3A is gaining favor because it is less active catalytically and can be regenerated at a lower temperature than 4A. A disadvantage of molecular sieves for gas dehydration is that they can be fouled by impurities in the gas, such as amine, caustic, chlorides, glycol, and liquid hydrocarbons. However, fouling problems can be minimized by the installation of a buffer layer of one foot or more of activated alumina (for amine, caustic, and chlorides) or activated carbon (for glycol or hydrocarbon liquids) on top of the molecular sieve bed (Veldman, 1991). 

In early designs, the reaction heat typically was removed by cooling water. Crude dichloroethane was withdrawn from the reactor as a liquid, acid-washed to remove ferric chloride, then neutralized with dilute caustic, and purified by distillation. The material used for separation of the ferric chloride can be recycled up to a point, but a purge must be done. This creates waste streams contaminated with chlorinated hydrocarbons which must be treated prior to disposal. 

Most of the ethylene dichloride produced is utilized for the manufacture of vinyl chloride, which may be obtained from it by pyrolysis or the action of caustic soda. Large quantities are also used in anti-knock additives for gasoline. As a solvent It has been displaced by trichloroethylene and tetrachloroelhyJene. U.S. production 1978 4-75 megatonnes. 

Hydrolysis of Potassium Ethyl Sulphate. Dissolve about i g. of the crystals in about 4 ml. of cold distilled water, and divide the solution into two portions, a) To one portion, add barium chloride solution. If pure potassium ethyl sulphate were used, no precipitate should now form, as barium ethyl sulphate is soluble in water. Actually however, almost all samples of potassium ethyl sulphate contain traces of potassium hydrogen sulphate formed by slight hydrolysis of the ethyl compound during the evaporation of its solution, and barium chloride almost invariably gives a faint precipitate of barium sulphate. b) To the second portion, add 2-3 drops of concentrated hydrochloric acid, and boil the mixture gently for about one minute. Cool, add distilled water if necessary until the solution has its former volume, and then add barium chloride as before. A markedly heavier precipitate of barium sulphate separates. The hydrolysis of the potassium ethyl sulphate is hastened considerably by the presence of the free acid Caustic alkalis have a similar, but not quite so rapid an effect. 

P Keto esters (t.g., ethyl ocetoacetate) are soluble in solutions of caustic alkalis but not in sodium carbonate solution. They give colours with freshly prepared ferric chloride solution a little alcohol should be added to bring the ester into solution. Sodium ethoxide solution reacts to yield sodio compounds, which usually crystallise out in the cold. Phenylhydrazine yields pyrazolones. They are hydrolysed by boiling sulphuric acid to the Corresponding ketones, which can be identified as usual (Section 111,74). 

The benzoyl compounds frequently occlude traces of unchanged benzoyl chloride, which thus escape hydrolysis by the caustic alkali it is therefore advisable, wherever possible, to recrystaUise the benzoyl derivatives from methyl, or ethyl alcohol or methylated spirit, since these solvents will esterify the unchanged chloride and so remove the latter from the recrystalKsed material. Sometimes the benzoyl compound does not crystallise well this difficulty may frequently be overcome by the use of p-nitrobenzoyl chloride or 3 5-dinitro-benzoyl chloride, which usually give highly crystalline derivatives of high melting point (see Section IV,114j. 

Most aromatic acid chlorides impart a strongly acid reaction when shaken with water (compare Section 111,88). All are completely hydrolysed by boiling with solutions of caustic alkalis and yield no product volatile from the alkaline solution (compare Eaters, Sections 111,106 and IV, 183). They may be distinguished from acids by their facile reactions with alcohols (compare Section 111,27), phenols (compare Section IV,114), and amines (compare Sections 111,123 and IV.lOO). 

Phenol condenses with phthahc anhydride in the presence of concentrated sulphuric acid or anhydrous zinc chloride to yield the colourless phenolphthalein as the main product. When dilute caustic alkah is added to an alcoholic solution of phenolphthalein, an intense red colouration is produced. The alkali opens the lactone ring in phenolphthalein and forms a salt at one phenolic group. The reaction may be represented in steps, with the formation of a h3q)othetical unstable Intermediate that changes to a coloured ion. The colour is probably due to resonance which places the negative charge on either of the two equivalent oxygen atoms. With excess of concentrated caustic alkali, the first red colour disappears this is due to the production of the carbinol and attendant salt formation, rendering resonance impossible. The various reactions may be represented as follows ... 

Bemoyl chloride may replace acetyl chloride as a class reagent it possesses the advantage that it is only very slowly decomposed by cold water and consequently may be employed for detecting alcohols even in aqueous solution. The reaction is usually carried out in aqueous solution containing sufficient caustic alkali to decompose any excess of benzoyl chloride into the water-soluble alkali benzoate (Schotten - Baumann reaction compare Section IV,52). The benzoyl esters formed are insoluble in water ... 

Chlorine and caustic soda are coproducts of electrolysis of aqueous solutions of sodium chloride [7647-14-5] NaCl, (commonly called brine) following the overall chemical reaction... 

The reactor effluent, containing 1—2% hydrazine, ammonia, sodium chloride, and water, is preheated and sent to the ammonia recovery system, which consists of two columns. In the first column, ammonia goes overhead under pressure and recycles to the anhydrous ammonia storage tank. In the second column, some water and final traces of ammonia are removed overhead. The bottoms from this column, consisting of water, sodium chloride, and hydrazine, are sent to an evaporating crystallizer where sodium chloride (and the slight excess of sodium hydroxide) is removed from the system as a soHd. Vapors from the crystallizer flow to the hydrate column where water is removed overhead. The bottom stream from this column is close to the hydrazine—water azeotrope composition. Standard materials of constmction may be used for handling chlorine, caustic, and sodium hypochlorite. For all surfaces in contact with hydrazine, however, the preferred material of constmction is 304 L stainless steel. 

Comparison to the Raschig Process. The economics of this peroxide process in comparison to the Raschig or hypochlorite—ketazine processes depend on the relative costs of chlorine, caustic, and hydrogen peroxide. An inexpensive source of peroxide would make this process attractive. Its energy consumption could be somewhat less, because the ketazine in the peroxide process is recovered by decantation rather than by distillation as in the hypcochlorite process. A big advantage of the peroxide process is the elimination of sodium chloride as a by-product this is important where salt discharge is an environmental concern. In addition to Elf Atochem, Mitsubishi Gas (Japan) uses a peroxide 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). 

In the manufacture of 2-naphthalenol, 2-naphthalenesulfonic acid must be converted to its sodium salt this can be done by adding sodium chloride to the acid, and by neutralizing with aqueous sodium hydroxide or neutralizing with the sodium sulfite by-product obtained in the caustic fusion of the sulfonate. The cmde sulfonation product, without isolation or purification of 2-naphthalenesulfonic acid, is used to make 1,6-, 2,6-, and 2,7-naphthalenedisulfonic acids and 1,3,6-naphthalenetrisulfonic acid by further sulfonation. By nitration, 5- and 8-nitro-2-naphthalenesulfonic acids, [89-69-1] and [117-41-9] respectively, are obtained, which are intermediates for Cleve s acid. All are dye intermediates. The cmde sulfonation product can be condensed with formaldehyde or alcohols or olefins to make valuable wetting, dispersing, and tanning agents. 

On dehydration, nitro alcohols yield nitro-olefins. The ester of the nitro alcohol is treated with caustic or is refluxed with a reagent, eg, phthaUc anhydride or phosphoms pentoxide. A mil der method involves the use of methane sulfonyl chloride to transform the hydroxyl into a better leaving group. Yields up to 80% after a reaction time of 15 min at 0°C have been reported (5). In aqueous solution, nitro alcohols decompose at pH 7.0 with the formation of formaldehyde. One mole of formaldehyde is released per mole of monohydric nitro alcohol, and two moles of formaldehyde are released by the nitrodiols. However, 2-hydroxymethyl-2-nitro-l,3-propanediol gives only two moles of formaldehyde instead of the expected three moles. The rate of release of formaldehyde increases with the pH or the temperature or both. 

Benzene Chlorination. In this process, benzene is chlorinated at 38—60°C in the presence of ferric chloride catalyst. The chlorobenzene is hydrolyzed with caustic soda at 400°C and 2.56 kPa (260 atm) to form sodium phenate. The impure sodium phenate reacts with hydrochloric acid to release the phenol from the sodium salt. The yield of phenol is about 82 mol % to that of the theoretical value based on benzene. Plants employing this technology have been shut down for environmental and economic reasons. 

Aluminum flufenamate, tris-[2-(3-trifluoromethylphenyl)aminoben2oate]aluminum, is a safer and more effective analgesic than aspirin (94). The dihydroxyalurninum flufenamate is made by reaction of flufenamic acid with aqueous caustic, followed by addition of aluminum chloride with stirring at 42°C for 15 min to give 99% yield (95). Both forms are less irritating and less toxic than the parent acid or aspirin (94,95). 

Spills should be picked up before flushing thoroughly with water and neutralizing with soda ash or lime. The introduction of aluminum chloride into any drainage system results in the reduction of effluent pH, which can be adjusted using caustic soda or lime (11). 

This type of centrifuge is also used on borax and boric acid, -xylene, sodium bicarbonate, and sodium chloride from glycerol or electrolytic caustic. 

It was an adaptation of the Castner cell to sodium chloride for fused caustic electrolysis. A mixture of sodium chloride and other chlorides, molten at 620°C, was electroly2ed ia rectangular or oval cells heated only by the current. Several cells have been patented for the electrolysis of fused salt ia cells with molten lead cathodes (65). However, it is difficult to separate the lead from the sodium (see Electrochemical processing). 

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