Of dehydrated

A knock out vessel may on the other hand be followed by a variety of dehydrating systems depending upon the space available and the characteristics of the mixture. On land a continuous dehydration tank such as a wash tank may be employed. In this type of vessel crude oil enters the tank via an inlet spreader and water droplets fall out of the oil as it rises to the top of the tank. Such devices can reduce the water content to less than 2%. 

Dehydration can be performed by a number of methods cooling, absorption and adsorption. Water removal by cooling is simply a condensation process at lower temperatures the gas can hold less water vapour. This method of dehydration is often used when gas has to be cooled to recover heavy hydrocarbons. Inhibitors such as glycol may have to be injected upstream of the chillers to prevent hydrate formation. 

Extremely dry (or super-dry ) ethyl alcohol. The yields in several organic preparations e.g., malonic ester syntheses, reduction with sodium and ethyl alcohol, veronal synthesis) are considerably improved by the use of alcohol of 99-8 per cent, purity or higher. This very high grade ethyl alcohol may be prepared in several ways from commercial absolute alcohol or from the product of dehydration of rectified spirit with quicklime (see under 4). 

Polymerisation may occur as a result of dehydration of these compounds to methylene and dimethylene urea or more probably by a stepwise loss of water between the molecules of methylol and dimethylol-urea. 

METHOD 3 This is not really a method. It is more of an idea Strike and others have been toying with. Eleusis had been supporting the idea that one could make use of the common 48% aq HBr if one employed the technique of dehydration . We remember that the water was competing with the Br in the normal 48% solution. But the literature demonstrates that in conditions such as this, a competing acid can strip away the water (dehydrate) from the beta carbon allowing the Br a second chance to pop in. 

Fig. 5.16 Surface concentration of hydroxyl groups of silica, as a function of the temperature of dehydration. Data are +, from Fripiat and Uytterhoeven A, from Kiselev and Zhuralev O, from Taylor (cf.

M. R. Olsen and R. K. Major, Comparative Study of Dehydrating Processes in the Manufacture of Nitrocellulose, United Technology Chemical Systems Division, Suimyvale, Calif., 1975. 

After the washing, the fiber is dried, and then is heat-drawn in the same manner as in the case of dehydration—coagulation with salt but to a much higher draw ratio. As a result the finished fiber has high strength and modulus and is, without acetalization, sufficientiy resistant to boiling water. Figure 3 shows schematic fiber stmctures (17). 

Dehydration or Chemical Theory. In the dehydration or chemical theory, catalytic dehydration of ceUulose occurs. The decomposition path of ceUulose is altered so that flammable tars and gases are reduced and the amount of char is increased ie, upon combustion, ceUulose produces mainly carbon and water, rather than carbon dioxide and water. Because of catalytic dehydration, most fire-resistant cottons decompose at lower temperatures than do untreated cottons, eg, flame-resistant cottons decompose at 275—325°C compared with about 375°C for untreated cotton. Phosphoric acid and sulfuric acid [8014-95-7] are good examples of dehydrating agents that can act as efficient flame retardants (15—17). 

Other processes recently reported in the Hterature are the gas-phase reaction of lactonitnle [78-97-7] with ammonia and oxygen in the presence of molybdenum catalyst (86), or the vapor-phase reaction of dimethyl malonate with ammonia in the presence of dehydration catalyst (87). 

This method, however, is not industrially practical because a large amount of dehydrating agent, such as ethyl orthoformate, is required to remove water formed in the reaction. Because water is an inhibitor of the reaction, the reaction system has to be kept under substantially anhydrous conditions. 

Amination. Isopropyl alcohol can be aminated by either ammonolysis ia the presence of dehydration catalysts or reductive ammonolysis usiag hydrogeaatioa catalysts. Either method produces two amines isopropylamine [75-31-0] and diisopropylamine [108-18-9]. Virtually no trisubstituted amine, ie, triisopropyl amine [122-20-3], is produced. The ratio of mono- to diisopropylamine produced depends on the molar ratio of isopropyl alcohol and ammonia [7664-41-7] employed. Molar ratios of ammonia and hydrogen to alcohol range from 2 1—5 1 (35,36). 

Pyrrohdines also can be obtained by reaction of 1,4-dihydroxyaLkanes with amines in the presence of dehydrating agents at elevated temperatures or by reaction of primary amines with 1,4-dihaloaLkanes. The dry distillation of 1,4-butanediamine dihydrochloride also generates pyrrohdine. Pyrroles can also be catalyticahy hydrogenated to pyrrohdines. 

Trinidad asphalt has a relatively uniform composition of 29% water and gas, 39% bitumen soluble in carbon disulfide, 27% mineral matter on ignition, and 5% bitumen that remains adsorbed on the mineral matter. Refining is essentially a process of dehydration by heating the cmde asphalt to ca 165°C. The refined product averages 36% mineral ash with a penetration at 25°C of about 2 (0.2 mm), a softening point (ring and ball method) of 99°C, a flash point (Cleveland open cup) of 254°C, a sulfur content of 3.3%, and a saponification value of 45 mg KOH/g. The mineral matter typically contains... 

Heats of dehydration per mole of water vapor are (74) decahydrate to pentahydrate, 54.149 kj (12.942 kcal), and decahydrate to tetrahydrate, 54,074 kj (12.924 kcal). Borax stored over a saturated sucrose-sodium sucrose—sodium chloride solution maintains exacdy 10 moles of water and can thus be used as an analytical standard. Commercial borax tends to lose water of crystallisation if stored at high temperature or ia dry air. 

Pentahydrate is reversibly converted to an amorphous dihydrate, at 88°C and 0.26 kPa (2 mm Hg) or by boiling with xylene (73,75). The heat of dehydration for the pentahydrate to tetrahydrate has been calculated to be 53.697 kj (12.834 kcal) per mole of water (74). Thermogravimetric analyses show that 2.75 moles of water are lost on heating to 140°C. Like borax, pentahydrate puffs when heated rapidly to give a product having a bulk density of 0.042 g/mL (79). 

The dihydrate loses water slowly at room temperature. Its heat of dehydration to NaB02 0.5H2O has been calculated as 58.1 kJ/mol (13.9 kcal/mol) of H2O (88). Sodium metaborate dihydrate reacts with atmospheric CO2 to produce sodium carbonate and borax. The melting point is 90—95°C, compared to 54°C for the tetrahydrate. Some crystallographic work has been done (91). 

Phase relationships ia the system K O—B2O2—H2O have been described and a portion of the phase diagram is given ia Figure 8. The tetrahydrate, which can be dried at 65°C without loss of water of crystallisation, begias to dehydrate between 85 and 111°C, depending on the partial pressure of water vapor ia the atmosphere. This conversion is reversible and has a heat of dehydration of 86.6 kj/mol (20.7 kcal/mol) of H2O. Thermogravimetric curves iadicate that two moles of water are lost between 112 and 140°C, one more between 200 and 230°C and the last between 250 and 290°C (121). 

The tetrahydrate is stable under normal conditions of storage. Its heat of dehydration has been calculated as 110.8 kJ/mol (26.5 kcal/mol) between 106.5 and 134°C (121). Its thermal stabiUty is highly dependent on the partial pressure of atmospheric water. It is stable when heated ia a vaccum up to 105°C ia an atmosphere saturated with water at 90°C, it is stable up to 170°C. 

The butanols undergo the typical reactions of the simple lower chain aUphatic alcohols. For example, passing the alcohols over various dehydration catalysts at elevated temperatures yields the corresponding butenes. The ease of dehydration increases from primary to tertiary alcohol /-butyl alcohol undergoes dehydration with dilute sulfuric acid at low temperatures in the Hquid phase whereas the other butanols require substantially more stringent conditions. 

The chemistry of ethyl alcohol is largely that of the hydroxyl group, namely, reactions of dehydration, dehydrogenation, oxidation, and esterification. The hydrogen atom of the hydroxyl group can be replaced by an active metal, such as sodium, potassium, and calcium, to form a metal ethoxide (ethylate) with the evolution of hydrogen gas (see Alkoxides, metal). 

Activated alumina and phosphoric acid on a suitable support have become the choices for an iadustrial process. Ziac oxide with alumina has also been claimed to be a good catalyst. The actual mechanism of dehydration is not known. In iadustrial production, the ethylene yield is 94 to 99% of the theoretical value depending on the processiag scheme. Traces of aldehyde, acids, higher hydrocarbons, and carbon oxides, as well as water, have to be removed. Fixed-bed processes developed at the beginning of this century have been commercialized in many countries, and small-scale industries are still in operation in Brazil and India. New fluid-bed processes have been developed to reduce the plant investment and operating costs (102,103). Commercially available processes include the Lummus processes (fixed and fluidized-bed processes), Halcon/Scientific Design process, NIKK/JGC process, and the Petrobras process. In all these processes, typical ethylene yield is between 94 and 99%. 

The use of dehydrating agents such as sulfuric or phosphoric acid on (555 X = OH) was also successful, and these closures may proceed via mixed anhydrides 67AHC(8)277, 75MIP41600). Carbonyldiimidazole effected the conversion of hydroxamic acid (557) into a 3-hydroxy-1,2-benzisoxazole derivative (79JHC1277). The mixed anhydride (558) where... 

It was shown by adsorption of eationie dye Rodamine 6G that in water VO, is negatively eharged. It is known that the surfaee of dehydrated films is positively eharged. 

The formation of oximes, hydrazones, and related imine derivatives is usually catalyzed by both general acids and general bases. General base catalysis of dehydration of the tetrahedral intermediate involves nitrogen deprotonation concerted with elimination of hydroxide ion. ... 

Glass or disposable plastic culture dishes are used. If glass petri dishes are employed, a humid environment must be maintained during incubation. This prevents losses of media by evaporation (the dishes have loose-fitting covers). Disposable plastic dishes have tight-fitting lids which minimize the problem of dehydration. 

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