Adsorb large quantity of water

Colloidal silicon dioxide is hygroscopic but adsorbs large quantities of water without liquefying. When used in aqueous systems at a pH 0-7.5, colloidal silicon dioxide is effective in... 

The most common adsorption systems consist of silica gel or alumina adsorbents in association with an organic solvent system. The adsorbent can exert a considerable influence on the separation of compounds. Alumina and silica gel, for example, have significantly different properties and can result in quite different separations. Activation of the adsorbent also influences sample retention. The presence of water on the adsorbent decreases the adsorbent activity due to blockage of active sites. If large quantities of water are present, a partition system may be set up which may extensively change the retention times due to the different chromatographic principle involved. Table 2.1 compares results obtained for the separation of the insecticide carbaryl (Sevin) and its hydrolysis product 1-naphthol on alumina and silica gel. Comparisons between activation and deactivation are made. The results show that separation of the two components is reversed with the two adsorbents examined. In most cases, activation of the plates caused the/ f values to increase relative... 

The selectivity of modified hydrotalcite material for carbon dioxide with respect to water vapor (an important prerequisite for the water-gas shift reaction) was good, but it adsorbed large quantities of HCN, even though carbon dioxide is the more acidic component, making it wholly unsuitable for the direct HCN synthesis, especially as it subsequently proved impossible to recover the adsorbed HCN as such [21],... 

In a well baked-out system the composition of the gases found in an all glass and ceramic vacuum system depends largely upon the gases to which the system has recently been exposed after baking out. The glass parts of the system, at room temperature, may adsorb small quantities of water vapor, even if dried gases are used. The furnace tube if operated... 

Although some specific examples are given, several aspects of the sorption of water by crystalline substances deserve attention at this point. First, it is important to recognize that the large quantity of water that associates with these systems actually obscures small changes in moisture content that occur between hydrate transitions. It has been stated that lactose monohydrate, for example, contains 5 /o water of crystallization and approximately 0.1 /o adsorbed water ,indicating that adsorption takes place on the hydrate. 

The glass powder, which served as the adsorbent, was obtained from the Arthur S. Lapine Company in the form of spherical beads approximately 40 fL in diameter. The beads were washed with a large quantity of distilled water and dried in an oven at 120 °C. before use in the adsorption experiments. 

The polymer industry requires large quantities of 4,4 -diaminodiphenyl-methanes. These compounds are used in various applications as polymer additives. Currently they are manufactured by the acid-catalysed condensation of anilines with formaldehyde but like so many reactions of this type, the processes require the neutralisation of waste acid leading to large amounts of salt waste. Cleaner processes are required and solid acids offer a way forward. One potentially useful example of this is the aqueous reaction of aromatic anilines adsorbed on kaolinite with formaldehyde which cleanly give the desired products (Figure 3.5).36 In a typical experiment, the clay is stirred with water before aniline is added to the stirred solution. To this is slowly added formaldehyde solution. The precipitated 4,4 -diaminodiphenylmethane can be extracted in hot ethanol in a yield of 96%. Similarly, several substituted analogues have been prepared in yields of 70-99%. 

Contact of one cm of a 0.025 molar solution of dialkyl phosphite in tetradecane at 403 K (130 C) with one gram of iron powder which had been ball milled under pentane resulted in depletion of the phosphorus in solution, as shown in Fig. 11-9. Reaction as well as adsorption took place, for soluble iron was found in the solutions of di(2-ethyIhexy1), dilauryl and distearyl phosphites. Chromatography of the solutions after contact revealed large quantities of alcohol dibutyl phosphite and di(2-ethylhexyl) phosphite yielded 92-97% of the theoretical amount of alcohol after 24 hours. Hydrolysis of the phosphite esters was ascribed to water adsorbed on the walls of the reaction tube and on the iron powder. Forbes and Battersby [46] postulated that hydrolysis is an important aspect of the mechanism of the additive action of phosphite esters. Oxidation to phosphate by the oxygen of the ambient air is deemed minor maximum augmentation of the oxygen uptake by a 6.5% solution of dibutyl phosphite over that of the tetradecane carrier fluid in the presence of iron was 20%. The easy hydrolysis of phosphites is well known. Partial... 

The extraction of the adsorbed phenol presents problems. It is impractical to use steam to extract phenol, particularly when it is adsorbed from waste liquors. One difficulty is that a large quantity of adsorbed water must be evaporated before the carbon can reach a temperature at which phenol will be desorbed. Then too, the concentration of phenol in the recovered aqueous solution is very low unless superheated steam is used, and this introduces other difficulties. The high temperature involved in the use of superheated steam causes chemical changes in adsorbed phenol and in other substances adsorbed from the waste liquors. These changes lower the recovery of phenol and also render the carbon unfit for re-use. 

The use of adsorbents obtained on the basis of natural zeolites has a large practical and theoretical importance for different branches of a national economy. Presence of even small quantities of water and iron ions in liquid hydrocarbons of influences negatively upon the quality of the products produced under manufacture of synthetic detergent - sulfonol corrosion of the industrial and transport equipment takes place too. Usually synthetic adsorbents, which are deficient and expensive are used when drying liquid hydrocarbons. 

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