Hydrogen chloride, adsorption

It is known that alumina is chlorinated exothermically at above 200° C by contact with halocarbon vapours, and hydrogen chloride, phosgene etc. are produced. It has now been found that a Co/Mo-alumina catalyst will generate a substantial exotherm in contact with vapour of carbon tetrachloride or 1,1,1-trichloroethane at ambient temperature in presence of air. In absence of air, the effect is less intense. Two successive phases appear to be involved first, adsorption raises the temperature of the alumina then reaction, presumably metal-catalysed, sets in with a further exotherm. 

A glass drying trap on a hydrochloric acid storage tank was filled with silica gel instead of the calcium sulfate specified. The glass trap fractured, probably owing to thermal shock from the much higher heat of adsorption of water and hydrogen chloride on silica gel. 

While initial aging did cause some loss in volume resistivity, it was no more severe in unstabilized than in stabilized compositions. The most startling effect was the marked increase in volume resistivity under severe aging conditions. This may be due to volatilization loss of DOP or cross-linking of polyvinyl chloride, both of which could reduce migration of ionic impurities, or it may involve adsorption of ionic impurities by the dark-colored, conjugated, polyene structure which forms by loss of hydrogen chloride. In any case it deserves further study. 

The reported rate equations for the hydrohalogenation of acetylene, ethylene, propene and vinyl chloride are summarised in Table 15. Of special interest is the last entry it is based on a model which assumes two types of active centres, the first one for the adsorption of acetylene, the second for the adsorption of hydrogen chloride and vinyl chloride. 

Adsorption studies revealed that both reactants can be adsorbed on active catalysts. For the reaction of acetylene with hydrogen chloride, the... 

When carried out on a larger scale the volume of hydrogen chloride gas which is evolved justifies the attachment of a gas adsorption trap (Fig. 2.61) to the outlet of the calcium chloride guard-tube. On the scale suggested in this experiment, the apparatus should be sited within an efficient fume cupboard and the vapours led via a tube to a drain to prevent corrosion of the stirrer motor. 

With these compounds the presence of the halogen will have been detected in the tests for elements. Most acid halides undergo ready hydrolysis with water to give an acidic solution and the halide ion produced may be detected and confirmed with silver nitrate solution. The characteristic carbonyl adsorption at about 1800 cm -1 in the infrared spectrum will be apparent. Acid chlorides may be converted into esters as a confirmatory test to 1 ml of absolute ethanol in a dry test tube add 1 ml of the acid chloride dropwise (use a dropper pipette keep the mixture cool and note whether any hydrogen chloride gas is evolved). Pour into 2 ml of saturated salt solution and observe the formation of an upper layer of ester note the odour of the ester. Acid chlorides are normally characterised by direct conversion into carboxylic acid derivatives (e.g. substituted amides) or into the carboxylic acid if the latter is a solid (see Section 9.6.16, p. 1265). 

Theoretical and experimental studies of the interactions between water molecules and hydrogen chloride are of fundamental importance for the understanding of the production of stratospheric chlorine molecules which, in turn, take part in the catalytic ozone depletion reactions. This mainly heterogeneous atmospheric reaction begins with the adsorption of the HCl molecules on the surface of water icicles is the source of the stratospheric chlorine atoms in the polar regions380 - 382. Chlorine molecules are photolysed by solar radiation and the resultant chlorine atoms take part in the destruction of the stratospheric ozone. The study of the (H20) HC1 clusters is an important step towards understanding of the behavior of the HCl molecule on the ice surface383- 386. 

Dinitrophenylhydrazones (DNPHs) were applied to the GC analysis of keto acids. As with carbonyl compounds, they are prepared by reaction with 2,4-dinitrophenylhydrazine and are also used mainly for the preliminary isolation of keto acids. They can be isolated from a dilute aqueous sample by adsorption on activated carbon and selective desorption [178] hydrazones of aldehydes with a methyl formate-dichloromethane mixture and hydrazones of keto acids with a pyridine-water azeotropic mixture. Hydrazones of acids are released from their pyridine salts with methanol containing hydrogen chloride. After... 

Description Oxygen can be used from air separation plant, as well as, from the cost-effective pressure swing adsorption (PSA) process. The Vinnolit oxychlorination process is also able to handle ethylene and/or anhydrous hydrogen chloride containing vent streams from direct chlorination, acetaldehyde, monochloro acetic acid and other processes. 

Methyl chloride is an important industrial product, having a global annual capacity of ca. 900 000 tons. Its primary use is for the manufacture of more highly chlorinated materials such as dichloromethane and chloroform and for the production of silicone fluids and elastomers. It is usually manufactured by the reaction of methanol with hydrogen chloride with a suitable acid catalyst, such as alumina. To develop a site-specific reaction mechanism and a kinetics model for the overall process, one first needs to identify all the reagents present at the catalyst surface and the nature of their interactions with the surface. The first step in the reaction is dissociative adsorption of methanol to give adsorbed methoxy species. Diffuse reflectance IR spectroscopy (29d) showed the expected methoxy C-H stretch and deformations, but an additional feature, with some substructure, at 2600 cm was... 

SAFETY PROFILE A highly corrosive irritant to the eyes, skin, and mucous membranes. Mildly toxic by inhalation, Explosive reaction with alcohols + hydrogen cyanide, potassium permanganate, sodium (with aqueous HCl), tetraselenium tetranitride. Ignition on contact with aluminum-titanium alloys (with HCl vapor), fluorine, hexa-lithium disilicide, metal acetylides or carbides (e.g., cesium acetylide, rubidium ace-tylide). Violent reaction with 1,1-difluoro-ethylene. Vigorous reaction with aluminum, chlorine + dinitroanilines (evolves gas). Potentially dangerous reaction with sulfuric acid releases HCl gas. Adsorption of the acid onto silicon dioxide is exothermic. See also HYDROGEN CHLORIDE (AEROSOL) and HYDROCHLORIC ACID. 

The reaction of various metal oxides with hydrogen chloride and the reverse reactions have been extensively smdied [47] the reaction behavior of hydrogen chloride with various bivalent and trivalent metal oxides has been reported. Sakata et al. reported the spontaneous degradation of municipal waste plastics at low temperature [48] and also the dechlorination of chlorine compounds from PVC mixed plastics-derived oil using solid sorbents [22], Courtemanche and Levendis [49] reported the control of HCl emission from the combustion of PVC by in-fumace injection of calcium-magnesium-based sorbents at gas temperatures of 850 and 1050°C. In the present study, the adsorption temperature 350°C was found to be optimum for the complete removal of hydrogen chloride at moderate concentrations (1820 ppm). 

For the pyrolysis of plastic waste with a high PVC content, it is probably better to first dehydrohalogenize it in a reactor with added sand. Tests have shown that hydrogen chloride gas can be produced from PVC at temperatures of between 350 and 400°C, which is up to 99 % pure and, after adsorption of the residual hydrocarbons, may be used to make very pure hydrochloric acid. After treating PVC for 20 minutes at a temperature of 350°C, more than 90 % of the bound chloride has split off. This time is reduced to less than 10 minutes if the temperature is increased to 400°C (13). ... 

The reaction of phosgene with hydrogen fluoride offers a potentially attractive route to the synthesis of carbonyl difluoride. However, the hydrogen chloride co-product of the reaction, represented in Equation (13.4) has a boiling temperature (-83.1 C) very close to that of COFj (-84.6 "C). In addition, azeotrope formation occurs, so that the two materials are only separated with great difficulty using normal distillation techniques. Separation of the two materials may be affected using aliphatic nitriles (such as ethanenitrile) or aromatic hydrocarbons (such as toluene) in which HCl is more readily absorbed relative to COF j [629,630]. Alternatively, the separation may be affected by adsorption of the HCl onto a metal fluoride, SO 3 or PjOj, which do not react at all readily with the COFj [2069]. 

Stabilization. For example, calcium stearate may play the role of an associate thermal stabilizer when used in a system with calcium salts of fatty acids. These stabilizers use combinations of two or more metals - one of which (e.g. zinc) produces metal chlorides which accelerate PVC degradation. The presence of large amount of calcium salts helps to convert this chloride to calcium chloride which does not increase the degradation rate of PVC. Also, calcium carbonate can react with hydrogen chloride which is produced as PVC degrades. On the other hand, inclusion of fillers which contain admixtures of metals such as iron, nickel, copper, etc. reduces PVC thermal stability. Fillers also affect UV stabilization by adsorption of HALS stabilizers which immobilizes them and prevents them from performing as radical scavengers. 

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