Chlorine decomposition

Because the decomposition rates are relatively insensitive to temperature, Eq. (18.3) is operated at 130°C to 150°C and 3.0 MPa132 to speed up the ratedetermining step. Excess ammonia, at a ratio of 40 1, is used to minimize the hydrazine-chlorine decomposition. Synthesis efficiency favors a dilute system although the increase in operating cost due to the low concentration may ultimately become inhibiting. The Raschig process is shown in Figure 18.1132. 

Derivatives of 3(2if)-pyridazinone are stable to acids, but those of 4,5-dihydro-3(2.ff)-pyridazinones, readily accessible from 1,4-keto-acids and hydrazines, are labile to acids, alkalis, and chlorine. Decomposition results in the formation of substituted butyric acids 123,129,136,146,146,162 lability of 5-substitutcd 3-methyl... 

By exposure to the light from a mercury vapour lamp in presence of oxygen and chlorine, decomposition takes place, and as an intermediate product, a compound of the formula COCl is formed. By exposure to ultra-violet light chlorine and carbon monoxide are formed. ... 

Notice that acid, represented here by C02 and water, is consumed and that sodium and bicarbonate ions are produced as albite alters to kaolinite. The material entering the lake as the stratification developed appears to have had two characteristic properties—easily hydrolyzed sodium and a limited content of halogens, particularly chlorine. Decomposition of organic matter furnished carbon dioxide. Concentration of sodium carbonates and other dissolved salts in solution in water of the stratified lake s lower layer built up, raising the water density. The evolution from normal lacustrine sediments to oil shale in the northwestern part of the Piceance Creek Basin is continuous... 

HAZARD RISK Non-combustible solid moderate fire hazard in the form of powder moderate fire hazard when exposed to flame or by spontaneous chemical reaction incompatible with halocarbons reacts incandescently with fluorine or chlorine decomposition emits toxic fumes of beryllium oxide reacts with strong acids and strong bases forming combustible gas forms shock sensitive mixtures with some chlorinated solvents including carbon tetrachloride and trichloroethylene NFPA code H3 FI RO. 

HAZARD RISK Combustible when exposed to heat or flame can react with oxidizing materials violent reaction with chlorine decomposition emits acrid smoke and fumes NFPA code H0 F1 R0. 

EXPLOSION and FIRE CONCERNS noncombustible solid or liquid exposure to heat or flame will enhance combustibility NFPA rating Health 2, Flammability 1, Reactivity 1 contact with strong oxidizers (such as bromine, chlorine, and fluorine) will result in violent reactions hydrochloric acid fumes and other chlorinated decomposition products may be released in a fire use dry chemical, carbon dioxide, water spray, fog, or foam for firefighting purposes. 

Nitrogen trichloride decomposes to nitrogen and chlorine. Decomposition may be represented by the following equation [9] ... 

The reaction between hydrogen and chlorine is probably also of this type and many organic free radical reactions (e.g. the decomposition of ethanal) proceed via chain mechanisms. 

Tellurium trioxide, TeOa, is an orange yellow powder made by thermal decomposition of telluric(VI) acid Te(OH)g. It is a strong oxidising agent which will, like H2Se04, oxidise hydrogen chloride to chlorine. It dissolves in hot water to give telluric(VI) acid. This is a weak acid and quite different from sulphuric and selenic acids. Two series of salts are known. 

Azobisnittiles are efficient sources of free radicals for vinyl polymerizations and chain reactions, eg, chlorinations (see Initiators). These compounds decompose in a variety of solvents at nearly first-order rates to give free radicals with no evidence of induced chain decomposition. They can be used in bulk, solution, and suspension polymerizations, and because no oxygenated residues are produced, they are suitable for use in pigmented or dyed systems that may be susceptible to oxidative degradation. 

Other acetyl chloride preparations include the reaction of acetic acid and chlorinated ethylenes in the presence of ferric chloride [7705-08-0] (29) a combination of ben2yl chloride [100-44-7] and acetic acid at 85% yield (30) conversion of ethyUdene dichloride, in 91% yield (31) and decomposition of ethyl acetate [141-78-6] by the action of phosgene [75-44-5] producing also ethyl chloride [75-00-3] (32). The expense of raw material and capital cost of plant probably make this last route prohibitive. Chlorination of acetic acid to monochloroacetic acid [79-11-8] also generates acetyl chloride as a by-product (33). Because acetyl chloride is cosdy to recover, it is usually recycled to be converted into monochloroacetic acid. A salvage method in which the mixture of HCl and acetyl chloride is scmbbed with H2SO4 to form acetyl sulfate has been patented (33). 

Early demand for chlorine centered on textile bleaching, and chlorine generated through the electrolytic decomposition of salt (NaCl) sufficed. Sodium hydroxide was produced by the lime—soda reaction, using sodium carbonate readily available from the Solvay process. Increased demand for chlorine for PVC manufacture led to the production of chlorine and sodium hydroxide as coproducts. Solution mining of salt and the avadabiHty of asbestos resulted in the dominance of the diaphragm process in North America, whereas soHd salt and mercury avadabiHty led to the dominance of the mercury process in Europe. Japan imported its salt in soHd form and, until the development of the membrane process, also favored the mercury ceU for production. 

Fig. 7. Mercury cathode electroly2er and decomposer (11) 1, brine level 2, metal anodes 3, mercury cathode, flowing along baseplate 4, mercury pump 5, vertical decomposer 6, water feed to decomposer 7, graphite packing, promoting decomposition of sodium amalgam 8, caustic Hquor exit 9, denuded mercury 10, brine feed 11, brine exit 12, hydrogen exit from decomposer 13, chlorine gas space 14, chlorine exit 15, wash water.

Molybdenum trioxide is a condensed-phase flame retardant (26). Its decomposition products ate nonvolatile and tend to increase chat yields. Two parts of molybdic oxide added to flexible poly(vinyl chloride) that contains 30 parts of plasticizer have been shown to increase the chat yield from 9.9 to 23.5%. Ninety percent of the molybdenum was recovered from the chat after the sample was burned. A reaction between the flame retardant and the chlorine to form M0O2 012 H20, a nonvolatile compound, was assumed. This compound was assumed to promote chat formation (26,27). 

Most chlorofluorocarbons are hydrolytically stable, CCI2F2 being considerably more stable than either CCl F or CHCI2F. Chlorofluoromethanes and ethanes disproportionate in the presence of aluminum chloride. For example, CCl F and CCI2F2 give CCIF and CCl CHCIF2 disproportionates to CHF and CHCl. The carbon—chlorine bond in most chlorofluorocarbons can be homolyticaHy cleaved under photolytic conditions (185—225 nm) to give chlorine radicals. This photochemical decomposition is the basis of the prediction that chlorofluorocarbons that reach the upper atmosphere deplete the earth s ozone shield. 

Basic oxides of metals such as Co, Mn, Fe, and Cu catalyze the decomposition of chlorate by lowering the decomposition temperature. Consequendy, less fuel is needed and the reaction continues at a lower temperature. Cobalt metal, which forms the basic oxide in situ, lowers the decomposition of pure sodium chlorate from 478 to 280°C while serving as fuel (6,7). Composition of a cobalt-fueled system, compared with an iron-fueled system, is 90 wt % NaClO, 4 wt % Co, and 6 wt % glass fiber vs 86% NaClO, 4% Fe, 6% glass fiber, and 4% BaO. Initiation of the former is at 270°C, compared to 370°C for the iron-fueled candle. Cobalt hydroxide produces a more pronounced lowering of the decomposition temperature than the metal alone, although the water produced by decomposition of the hydroxide to form the oxide is thought to increase chlorine contaminate levels. Alkaline earths and transition-metal ferrates also have catalytic activity and improve chlorine retention (8). 

The iodine compound is more stable and separates as so-called nitrogen trHodide monoammoniate [14014-86-9], NI NH, an insoluble brownish-black soHd, which decomposes when exposed to light in the presence of ammonia. In reactions of the halogens with the respective ammonium salts, however, the action is different. Chlorine replaces hydrogen and nitrogen chloride [10025-85-1], NCl, separates as oily, yeUow droplets capable of spontaneous explosive decomposition. 

Several commercial grades are available fine crystals of 99 to 100% purity, large crystals, pressed lumps, rods, and granular material. Double-Decomposition Methods. Double-decomposition processes all iavolve the reaction of sodium chloride, the cheapest chlorine source, with an ammonium salt. The latter may be suppHed directiy, or generated in situ by the reaction of ammonia and a supplementary iagredient. Ammonium chloride and a sodium salt are formed. The sodium salt is typically less soluble and is separated at higher temperatures ammonium chloride is recovered from the filtrate by cooling. 

Pyrotechnic mixtures may also contain additional components that are added to modify the bum rate, enhance the pyrotechnic effect, or serve as a binder to maintain the homogeneity of the blended mixture and provide mechanical strength when the composition is pressed or consoHdated into a tube or other container. These additional components may also function as oxidizers or fuels in the composition, and it can be anticipated that the heat output, bum rate, and ignition sensitivity may all be affected by the addition of another component to a pyrotechnic composition. An example of an additional component is the use of a catalyst, such as iron oxide, to enhance the decomposition rate of ammonium perchlorate. Diatomaceous earth or coarse sawdust may be used to slow up the bum rate of a composition, or magnesium carbonate (an acid neutralizer) may be added to help stabilize mixtures that contain an acid-sensitive component such as potassium chlorate. Binders include such materials as dextrin (partially hydrolyzed starch), various gums, and assorted polymers such as poly(vinyl alcohol), epoxies, and polyesters. Polybutadiene mbber binders are widely used as fuels and binders in the soHd propellant industry. The production of colored flames is enhanced by the presence of chlorine atoms in the pyrotechnic flame, so chlorine donors such as poly(vinyl chloride) or chlorinated mbber are often added to color-producing compositions, where they also serve as fuels. 

Rhenium Halides and Halide Complexes. Rhenium reacts with chlorine at ca 600°C to produce rheniumpentachloride [39368-69-9], Re2Cl2Q, a volatile species that is dimeric via bridging hahde groups. Rhenium reacts with elemental bromine in a similar fashion, but the metal is unreactive toward iodine. The compounds ReCl, ReBr [36753-03-4], and Rel [59301-47-2] can be prepared by careful evaporation of a solution of HReO and HX. Substantiation in a modem laboratory would be desirable. Lower oxidation state hahdes (Re X ) are also prepared from the pentavalent or tetravalent compounds by thermal decomposition or chemical reduction. 

G. S. Sayler, Microbial Decomposition of Chlorinated Aromatic Compounds, USEPA 600/2-86/090, Washington, D.C., 1986. 

Chemical Properties. The chemistry of the sulfur chlorides has been reviewed (141,142). Sulfur monochloride is stable at ambient temperature but undergoes exchange with dissolved sulfur at 100°C, indicating reversible dissociation. When distilled at its atmospheric boiling point, it undergoes some decomposition to the dichloride, but decomposition is avoided with distillation at ca 6.7 kPa (50 mm Hg). At above 300°C, substantial dissociation to S2 and CI2 occurs. Sulfur monochloride is noncombustible at ambient temperature, but at elevated temperatures it decomposes to chlorine and sulfur (137). The sulfur then is capable of burning to sulfur dioxide and a small proportion of sulfur trioxide. 

Physical Properties. Thionyl chloride [7719-09-7], SOCI2, is a colorless fuming Hquid with a choking odor. Selected physical and thermodynamic properties are Hsted in Table 6. Thionyl chloride is miscible with many organic solvents including chlorinated hydrocarbons and aromatic hydrocarbons. It reacts quickly with water to form HCl and SO2. Thionyl chloride is stable at room temperature however, slight decomposition occurs just... 

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