Chloride process

Figure 10.4 The oxychlorination step of the vinyl chloride process. (From Smith and Petela, Chem. Eng., 513 24, 1991 reproduced by permission of the Institution of Chemical Engineers.)...

A fiowsheet for this part of the vinyl chloride process is shown in Fig. 10.5. The reactants, ethylene and chlorine, dissolve in circulating liquid dichloroethane and react in solution to form more dichloroethane. Temperature is maintained between 45 and 65°C, and a small amount of ferric chloride is present to catalyze the reaction. The reaction generates considerable heat. 

Figure 10.5 The direct chlorination step of the vinyl chloride process using a liquid phase reactor. (From McNaughton, Chem. Engg., December 12, 1983, pp. 54-58 reproduced by permission.)...

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. 

In the batch methylene chloride process, the sulfuric acid concentration can be as low as 1% and only limited desulfonation is required to reach a combined acetic acid content of 62.0%. With perchloric acid catalyst, the nearly theoretical value of 62.5% combined acetic acid is obtained. 

Economic Aspects. Malononitrile of minimum 99% purity was available as a soHdifted melt for ca 30/kg in 1993 for ton quantities. Malononitrile is produced by Lon2a Ltd. (Swit2edand) using the cyanogen chloride process. 

Chloride Process. The flow chart of the chloride process is presented in Figure 4. In the chloride process, finely ground mtile reacts with chlorine in the presence of calcined petroleum coke. At a temperature between 800 and 1200°C, the following reaction occurs ... 

Fig. 4. Flow chart for the chloride process for production of the pigment titanium dioxide.

Factors such as reaction temperature, excess of oxygen, water addition, addition of other minor reactants, eg, AlCl to promote the formation of mtile, mixing conditions inside the reactor, and many others influence the quaUty of Ti02 pigment. In general, titanium white pigments produced by the chloride process exhibit better lightness than those produced by the sulfate process. 

A.mmonium Sulfate—Sodium Chloride Process. Ammonium sulfate, a readily available by-product, has been much used to make ammonium chloride by a double decomposition reaction with sodium chloride. 

Ammonium Sulfite—Sodium Chloride Process. Ammonium chloride has been produced by the reaction of ammonium sulfite [10196-04-0] NH SO, and sodium chloride ia a large Canadian plant (14). Ammonium sulfite is never actually isolated, rather ammonia and sulfur dioxide react ia water with sodium chloride. 

Paints. Paints account for perhaps 3% of sulfur consumption (see Paint). The main sulfur use is for the production of titanium dioxide pigment by the sulfate process. Sulfuric acid reacts with ilmenite or titanium slag and the sulfur remains as a ferrous sulfate waste product. Difficulties with this process have led to the development of the chloride process (see Pigments, inorganic Titanium compounds). 

Chloride Process. In the chloride process (Fig. 3), a high grade titanium oxide ore is chlorinated in a fluidized-bed reactor in the presence of coke at 925-1010°C ... 

A high purity titanium dioxide of poorly defined crystal form (ca 80% anatase, 20% mtile) is made commercially by flame hydrolysis of titanium tetrachloride. This product is used extensively for academic photocatalytic studies (70). The gas-phase oxidation of titanium tetrachloride, the basis of the chloride process for the production of titanium dioxide pigments, can be used for the production of high purity titanium dioxide, but, as with flame hydrolysis, the product is of poorly defined crystalline form unless special dopants are added to the principal reactants (71). 

Two pigment production routes ate in commercial use. In the sulfate process, the ore is dissolved in sulfuric acid, the solution is hydrolyzed to precipitate a microcrystalline titanium dioxide, which in turn is grown by a process of calcination at temperatures of ca 900—1000°C. In the chloride process, titanium tetrachloride, formed by chlorinating the ore, is purified by distillation and is then oxidized at ca 1400—1600°C to form crystals of the required size. In both cases, the taw products are finished by coating with a layer of hydrous oxides, typically a mixture of siUca, alumina, etc. 

Although ilmenites and leucoxenes can be used in the chloride process, ores having higher Ti02 contents, eg, mineral mtile, which is not readily attacked by sulfuric acid, are preferred in order to minimise loss of chlorine in iron chloride by-product. 

The resultant slag, a complex mixture of titanates, may contain 70—85% Ti02- The slag route is particularly useful when ilmenite is closely associated with haematite, from which it cannot economically be separated mechanically. Because the iron content of the slag is low, its use reduces the quantity of iron sulfate in the Hquid effluent of sulfate process plants. Slag used as a feedstock for TiCl production must be low in magnesium and calcium. A variety of other ilmenite beneficiation or synthetic mtile processes have been pursued, primarily to provide alternative chloride process feedstocks. Low grade ilmenite... 

Chloride Process. A flow diagram for the chloride process is shown ia Eigure 1. The first stage ia the process, carbothermal chlorination of the ore to ... 

Fig. 1. Principal steps in a balanced vinyl chloride process.

The ethylene-based, balanced vinyl chloride process, which accounts for nearly all capacity worldwide, has been practiced by a variety of vinyl chloride producers since the mid-1950s. The technology is mature, so that the probabiUty of significant changes is low. New developments in production technology will likely be based on incremental improvements in raw material and energy efficiency, environmental impact, safety, and process reUabiUty. 

LiquidPha.se. The methyl chloride process with the widest use in the United States is the Hquid-phase methanol hydrochlorination process. SHicone producers use methyl chloride in its manufacture and produce an aqueous hydrochloric acid stream as a by-product. This by-product HCl is converted back to methyl chloride by hydrochlorination. In fact, it is possible to produce methyl chloride directiy from the chioromethylsilane hydrolysis step in the siHcone process (18,19) (see Silicon compounds, silicones). 

The palladium chloride process for oxidizing olefins to aldehydes in aqueous solution (Wacker process) apparendy involves an intermediate anionic complex such as dichloro(ethylene)hydroxopalladate(II) or else a neutral aqua complex PdCl2 (CH2=CH2)(H2 0). The coordinated PdCl2 is reduced to Pd during the olefin oxidation and is reoxidized by the cupric—cuprous chloride couple, which in turn is reoxidized by oxygen, and the net reaction for any olefin (RCH=CH2) is then... 

By copolymerising the vinylidene chloride with about 10-15% of vinyl chloride, processable polymers may be obtained which are used in the manufacture of filaments and films. These copolymers have been marketed by the Dow Company since 1940 under the trade name Saran. Vinylidene chloride-acrylonitrile copolymers for use as coatings of low moisture permeability are also marketed (Saran, Viclan). Vinylidene chloride-vinyl chloride copolymers in which the vinylidene chloride is the minor component (2-20%) were mentioned in Chapter 12. 

Chloride process. This process requires a high titanium feedstock. Rutile is reacted with hydrochloric acid to produce titanium tetrachloride, which can be hydrolyzed with steam or oxidized with air to render the dioxide. A rutile form of titanium dioxide is obtained. 

Case study Interception of chloroethanol In an ethyl chloride process... 

Case Study interception of Chloroethanol in an Ethyl Chloride Process... 

It is most economical when high-grade ores are used, becoming less economical with poorer feed materials containing iron, because of the production of chloride wastes from which the chlorine cannot be recovered. By contrast the sulfate process cannot make use of rutile which does not dissolve in sulfuric acid, but is able to operate on lower grade ores. However, the capital cost of plant for the sulfate process is higher, and disposal of waste has proved environmentally more difficult, so that most new plant is designed for the chloride process. 

Ironically, this episode proved beneficial to DuPont. DuPont became the dominant source of TEL after the niid-1920s because they perfected the chloride process and were far more experienced than Jersey Standard in producing and handling toxic substances. 

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