Chlorine processing absorption

Liquid phase chlorination work in the former U.S.S.R. has been summarized by Vereshchinskii (1972). With tetradecane, the reaction is nearly or partially diffusion-controlled at a dose rate of 0.1-0.4 rad s-1. However, during the chlorination process, the liquid phase properties change continuously because of chlorine absorption accompanying the chemical reactions. Due to long chain reactions the chlorination G value is high and can reach 105 per 100 eV of energy absorption. At around 10-30°C the reaction rate is found to vary as the square root of the dose rate. A set of consecutive reactions has been reported in the liquid phase chlorination of 1,1,1,5-tetrachloropentane (Vereshchinskii, 1972). 

Thus -alkanes (C10-C14) separated from the kerosene fraction of petroleum (by urea complexation or absorption with molecular sieves) are now used as one source of the alkyl group. Chlorination takes place anywhere along the chain at any secondary carbon. Friedel-Crafts alkylation followed by sulfonation and caustic treatment gives a more linear alkylbenzenesulfonate (LAS) which is soft or biodegradable. The chlorination process is now the source of about 40% of the alkyl group used for the manufacture of LAS detergent. 

Direct chlorination of ethylene is usually conducted in liquid EDC in a bubble column reactor. Under typical process conditions, the reaction rate is controlled by mass transfer, with absorption of ethylene as the limiting factor. Feme chloride is a highly selective and efficient catalyst for llus reaction, and is widely used commercially. The direct chlorination process may be run with a slight excess of either ethylene or chlorine, depending on how effluent gases from the reactor are subsequently processed. Conversion of the limiting component is essentially 100%. and selectivity to EDC is greater than 99%. The direct chlorination reaction is exothermic (AH = — 180 kJ/mol foreq. 1) and requires heat removal for temperature control. 

The presence of noncondensable gases in the chlorine means that liquefaction is always incomplete. These gases leave the process and carry a certain amount of chlorine with them. This tail gas must be treated to remove the chlorine before it can be disposed of by venting it to the atmosphere. The chlorine value can be converted to a salable product such as bleach, HCl, or FeCls. It also can be recovered as elemental chlorine by absorption in a solvent followed by stripping. In some cases, it is simply absorbed in an alkaline medium and then treated for disposal. Section 9.1.9 covers the subject of tail gas handling. 

The catalyst transfers back and forth between the two reactors, as in Fig. 15.5, and effectively carries the chlorine value from the chlorinator to the oxidizer, where it can be released as chlorine gas. For this reason, the process was dubbed the Catalytic Carrier Process. Separation of the two stages allows each to operate at its own optimum conditions, and higher conversion of HCI to CI2 is the result. This process has operated on a pilot scale in Spain, but no commercial operation has been reported. A study of projected economics [19] based on the optimistic assumptions of quantitative conversion of HCI vapor to chlorine and the recovery of chlorine by absorption in the prohibited solvent CCI4 indicated that this process had advantages over certain other oxidation processes... 

A schematic diagram of the water-absorption process for recovering chlorine from caustic-chlorine process sniff gas developed by the Hooker Electrochemical Company (Anon., 1957) is. shown in Figure 6-21. In this process, chlorine-containing noncondensable gas from the liquefaction stage of chlorine manufacture is scrubbed countercurrently with water in a packed absorber. The resulting chlorine-free gas can be vented to the atmosphere, and the... 

Hydrochloric acid [7647-01-0], which is formed as by-product from unreacted chloroacetic acid, is fed into an absorption column. After the addition of acid and alcohol is complete, the mixture is heated at reflux for 6—8 h, whereby the intermediate malonic acid ester monoamide is hydroly2ed to a dialkyl malonate. The pure ester is obtained from the mixture of cmde esters by extraction with ben2ene [71-43-2], toluene [108-88-3], or xylene [1330-20-7]. The organic phase is washed with dilute sodium hydroxide [1310-73-2] to remove small amounts of the monoester. The diester is then separated from solvent by distillation at atmospheric pressure, and the malonic ester obtained by redistillation under vacuum as a colorless Hquid with a minimum assay of 99%. The aqueous phase contains considerable amounts of mineral acid and salts and must be treated before being fed to the waste treatment plant. The process is suitable for both the dimethyl and diethyl esters. The yield based on sodium chloroacetate is 75—85%. Various low molecular mass hydrocarbons, some of them partially chlorinated, are formed as by-products. Although a relatively simple plant is sufficient for the reaction itself, a si2eable investment is required for treatment of the wastewater and exhaust gas. 

An integrated process for producing chlorine dioxide that can consume chlorine (46) involves the use of hydrochloric acid as the reductant. The spent chlorine dioxide generator Hquor is used as feed for chlorate production, and hydrogen gas from chlorate production is burned with chlorine to produce hydrochloric acid. The principal disadvantage in the integrated hydrochloric acid-based processes is that the chlorine dioxide gas contains Y2 mole of chlorine for each mole of chlorine dioxide produced. A partial purification is achieved by absorption in chilled water in which the solubiHty of chlorine is less than chlorine dioxide however, this product stiU contains 10—15% chlorine on the basis of total chlorine and chlorine dioxide. 

Hydrochloric By-product of organic chlorination, salt process, and synthetic HCl HCl Absorption... 

Direct synthesis of HCl by the burning of hydrogen in chlorine is the favoured process when high-purity HCl is required. The reaction is highly exothermic ( 92kJ/mol HCl) and requires specially designed burners and absorption systems,... 

Dechlorination requires a much shorter contact time than organics removal (perhaps only 60 seconds at pH levels below 7.0 but 3 minutes at pH over 8.5). The process involves reaction with carbon as well as absorption, such that 1 lb of carbon typically reacts (and is used up) with between 3 and 6 lb of chlorine. 

The band spectrum of chlorine in the visible and near ultra-violet is well known from the work of Kuhn8 and others. Absorption from at least the first five vibrational levels of the normal molecule is observable. One can say from which particular vibrational levels the absorption of chlorine in the above regions at ordinary temperatures originates, and the energy of these levels is known. This is sufficient to determine the temperature coefficient of such absorption. Indeed it is partly by a process the reverse of this that the allocation of absorption to the various vibrational levels is accomplished. And so from the positions of the four... 

The great advantage of the absorption process over the synthesis of a by-product was its direct recovery of chlorine. Such a process or one that uses chlorine in another on-site process with steady demand is the ideal. More vigorous liquefaction is one approach to reducing the amount of chlorine value to be disposed of, and it has usually been chosen as the substitute for absorption. In this chapter, we discuss the use of gas-separation membranes as an alternative. 

Chlorine relieved through process venting of the plants, or released inside one of the buildings handling liquefied chlorine will be scrubbed, i.e. treated through absorption in a solution of sodium hydroxide to generate sodium hypochlorite. 

The water or moisture permeability and absorption are low and the hydrolysis resistance is generally good. PVC is naturally fire resistant and an appropriate formulation can improve its behaviour. However, the high chlorine level in PVC is released in the event of combustion and can involve corrosion during processing, and the thermal behaviour is limited. 

In 1976 he was appointed to Associate Professor for Technical Chemistry at the University Hannover. His research group experimentally investigated the interrelation of adsorption, transfer processes and chemical reaction in bubble columns by means of various model reactions a) the formation of tertiary-butanol from isobutene in the presence of sulphuric acid as a catalyst b) the absorption and interphase mass transfer of CO2 in the presence and absence of the enzyme carboanhydrase c) chlorination of toluene d) Fischer-Tropsch synthesis. Based on these data, the processes were mathematically modelled Fluid dynamic properties in Fischer-Tropsch Slurry Reactors were evaluated and mass transfer limitation of the process was proved. In addition, the solubiHties of oxygen and CO2 in various aqueous solutions and those of chlorine in benzene and toluene were determined. Within the framework of development of a process for reconditioning of nuclear fuel wastes the kinetics of the denitration of efQuents with formic acid was investigated. 

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