Chlorine reaction + silica

An extension of the reduction-chlorination technique described so far, wherein reduction and chlorination occur simultaneously, is a process in which the oxide is first reduced and then chlorinated. This technique is particularly useful for chlorinating minerals which contain silica. The chlorination of silica (Si02) by chlorine, in the presence of carbon, occurs above about 1200 °C. However, the silica present in the silicate minerals readily undergoes chlorination at 800 °C. This reaction is undesirable because large amounts of chlorine are wasted to remove silica as silicon tetrachloride. Silica is, therefore, removed by other methods, as described below, before chlorination. Zircon, a typical silicate mineral, is heated with carbon in an electric furnace to form crude zirconium carbide or carbonitride. During this treatment, the silicon in the mineral escapes as the volatile oxide, silicon monoxide. This vapor, on contact with air, oxidizes to silica, which collects as a fine powder in the furnace off-gas handling system ... 

The authors showed (table 11.3) that the relative contribution of the chlorination reaction (S) increases with increasing reaction temperature. The silica was previously degassed at 973 K. In all cases, the silanols have reacted completely. 

Methane, chlorine, and recycled chloromethanes are fed to a tubular reactor at a reactor temperature of 490—530°C to yield all four chlorinated methane derivatives (14). Similarly, chlorination of ethane produces ethyl chloride and higher chlorinated ethanes. The process is employed commercially to produce l,l,l-trichloroethane. l,l,l-Trichloroethane is also produced via chlorination of 1,1-dichloroethane with l,l,2-trichloroethane as a coproduct (15). Hexachlorocyclopentadiene is formed by a complex series of chlorination, cyclization, and dechlorination reactions. First, substitutive chlorination of pentanes is carried out by either photochemical or thermal methods to give a product with 6—7 atoms of chlorine per mole of pentane. The polychloropentane product mixed with excess chlorine is then passed through a porous bed of Fuller s earth or silica at 350—500°C to give hexachlorocyclopentadiene. Cyclopentadiene is another possible feedstock for the production of hexachlorocyclopentadiene. 

It is known that not all reactions proceed in the same manner on all adsorbent layers because the material in the layer may promote or retard the reaction. Thus, Ganshirt [209] was able to show that caffeine and codeine phosphate could be detected on aluminium oxide by chlorination and treatment with benzidine, but that there was no reaction with the same reagent on silica gel. Again the detection of amino acids and peptides by ninhydrin is more sensitive on pure cellulose than it is on layers containing fluorescence indicators [210]. The NBP reagent (. v.) cannot be employed on Nano-Sil-Ci8-100-UV2S4 plates because the whole of the plate background becomes colored. 

To prepare pure silicon, silica is first converted to SiClq. A redox reaction between coke and chlorine gas is coupled with a metathesis reaction to give SiClq, which liquefies on cooling ... 

Titanium tetrachloride is produced on an industrial scale by the chlorination of titanium dioxide-carbon mixtures in reactors lined with silica. During the reactor operation, the lining comes into contact not only with chlorine but also with titanium tetrachloride. There appears to be no attack on silica by either of these as the lining remains intact. However, the use of such a reactor for chlorinating beryllium oxide by the carbon-chlorine reduction chlorination procedure is not possible because the silica lining is attacked in this case. This corrosion of silica can be traced to the attack of beryllium chloride on silica. The interaction of beryllium chloride with silica results in the formation of silicon tetrachloride in accordance with the reaction... 

It follows that titanium tetrachloride can not chlorinate silica because at all temperatures the free energy change for that reaction has a large positive value. In general, in the interaction between the oxide (MO) of one metal (M) and the chloride (M C12) of a different metal (M ) ... 

Undoubtedly, the best method for the production of pure anhydrous lanthanide trihalides involves direct reaction of the elements. However, suitable reaction vessels, of molybdenum, tungsten, or tantalum, have to be employed silica containers result in oxohalides (27). Trichlorides have been produced by reacting metal with chlorine (28), methyl chloride (28), or hydrogen chloride (28-31). Of the tribromides, only that of scandium has been prepared by direct reaction with bromine (32). The triiodides have been prepared by reacting the metal with iodine (27, 29, 31, 33-41) or with ammonium iodide (42). 

The chemistry of silicone halides was recently reviewed by Collins.13 The primary use for SiCU is in the manufacturing of fumed silica, but it is also used in the manufacture of polycrystalline silicon for the semiconductor industry. It is also commonly used in the synthesis of silicate esters. T richlorosilane (another important product of the reaction of silicon or silicon alloys with chlorine) is primarily used in the manufacture of semiconductor-grade silicon, and in the synthesis of organotrichlorosilane by the hydrosilylation reactions. The silicon halohydrides are particularly useful intermediate chemicals because of their ability to add to alkenes, allowing the production of a broad range of alkyl- and functional alkyltrihalosilanes. These alkylsilanes have important commercial value as monomers, and are also used in the production of silicon fluids and resins. On the other hand, trichlorosilane is a basic precursor to the synthesis of functional silsesquioxanes and other highly branched siloxane structures. 

Modification Using a Halogenated Silica Surface. Silica gel is heated in 2 m HC1, filtered off, and washed with water the dried silica gel is then reacted with pure thionyl chloride. After removal of the excess of thionyl chloride and byproducts (S02 and HC1) under vacuum, chlorinated silica gel (=SiCl) is obtained. This is unstable in water and alcohol. The chlorinated silica gel can then be alkylated by one of a number of different reactions ... 

The compositions of biomass among fuel types are considerably varied, especially with respect to inorganic constituents important to the critical problems of fouling and slagging. Alkali and alkaline earth metals, in combination with other fuel elements such as silica and sulfur, and facilitated by the presence of chlorine, are responsible for many imdesirable reactions in combustion furnaces and power boilers. 

When benzo[a]pyrene adsorbed from the vapor phase onto coal fly ash, silica, and alumina was exposed to nitrogen dioxide, no reaction occurred. However, in the presence of nitric acid, nitrated compounds were produced (Yokley et al, 1985). Chlorination of benzo [a] pyrene in polluted humus poor lake water gave ll,12-dichlorobenzo[a]pyrene and 1,11,12-, 3,11,12- or 3,6,11-... 

It is seen that the trichlorosilane reacts with the silanol groups to form siloxane bridges. Subsequently the residual chlorines are hydrolyzed. Under carefiiUy controlled reaction conditions it is possible to obtain a product in which the hydrocarbonaceous layer at the surface is similar to that in a corresponding monomeric bonded phase. However, the hydrolysis of chlorines that did not react with surface silanbis may result in a silanol concentration at the surface that is higher than that in the silica gel proper used as the starting material for the reaction with alkyltri-chlorosilanes. 

Fig. 5.11. Vacuum reactor for chlorination of metals. A Reaction vessel (100 ml) B beryllia crucible containing titanium metal C silica cradle D crucible support also serving as evacuation duct, and finally sealed off at the top at E F capillary tube G duct for breaker H appendix containing liquid chlorine J fragile capillary tip K weighted glass breaker L glass-coated magnetic retainer.

Fused silica capillary tubes were variously coated for capillary electrophoresis. The chemical process involving a Grignard reaction is shown in equation 30. The silanol groups on the silica surface are treated with alkali, dried, convert to chlorosUanes with thionyl chloride and vinylmagnesium bromide replaces the chlorine atoms with vinyl... 

This procedure is general for the conversion of epoxides to dichlorides with inversion of configuration at each of the two carbons and, in effect, provides a method for the cis-addition of chlorine to a double bond.2 ci.v-1,2-Dichlorocyclohcxane has also been prepared from 1,2-epoxycyclohexane and sulfuryl chloride,3 but the stereospecificity of the reaction appears to be extremely sensitive to reaction conditions, and the yield is lower than that obtained by the method described here. Other methods give cis-1,2-dichlorocyclohexane contaminated with considerable amounts of the trans -isomer. This method has been used to convert cis- and trans-4,5-epoxyoctanes to meso- and d/-4,5-dichlorooctanes, respectively, and trans-7,8-epoxyoctadecane to fhreo-7,8-dichloro-octadecane. These conversions were carried out on smaller amounts of material, and the products were purified by column chromatography on silica gel. Yields were 51-63%. 

G. S. Serullas treated potassium chlorate with an excess of hydrofluosilicic acid the clear liquid was decanted from the sparingly soluble potassium fluosilicate, the soln. evaporated below 30°, and filtered through glass powder J. J. Berzelius evaporated the acid liquid mixed with finely divided silica below 30° in air, or over cone, sulphuric acid and potassium hydroxide in vacuo. The excess of hydrofluoric acid was volatilized as silicon fluoride, and the clear liquid was then filtered from the excess of silica. R. Bottger treated sodium chlorate with oxalic acid whereby sparingly soluble sodium oxalate was formed J. L. Wheeler, and T. B. Munroe treated sodium chlorate with hydrofluosilicic acid and M. Brandau treated potassium chlorate with aluminium sulphate and sulphuric acid and precipitated the alum so formed with alcohol. Chloric acid is formed in many reactions with hypochlorous and chlorous acid for example, it is formed when an aq. soln. of chlorine or hypochlorous or chlorous acid decomposes in light. It is also formed when an aq. soln. of chlorine dioxide stands in darkness or in light. A mixture of alkali chlorate and chlorite is formed when an aq. soln. of an alkali hydroxide is treated with chlorine dioxide. 

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