Absorption selective

Ethylene Stripping. The acetylene absorber bottom product is routed to the ethylene stripper, which operates at low pressure. In the bottom part of this tower the loaded solvent is stripped by heat input according to the purity specifications of the acetylene product. A lean DMF fraction is routed to the top of the upper part for selective absorption of acetylene. This feature reduces the acetylene content in the recycle gas to its minimum (typically 1%). The overhead gas fraction is recycled to the cracked gas compression of the olefin plant for the recovery of the ethylene. 

Dyes, on the other hand, ate colored substances which ate soluble or go into solution during the appHcation process and impart color by selective absorption of light. In contrast to dyes, whose coloristic properties ate almost exclusively defined by their chemical stmcture, the properties of pigments also depend on the physical characteristics of its particles. 

Selective absorption of durene from heavy gasoline (bp 150—225°C) is possible using a version of UOP s Sorbex technology where the X zeoHte is made selective for durene by replacing the exchangeable sodium cations with lithium ions (16). 

Extensive work has been done on corrosion inhibitors (140), activated carbon use (141—144), multiple absorption zones and packed columns (145,146), and selective absorption and desorption of gas components (147,148). Alkan olamines can also be used for acid gas removal in ammonia plants (149). 

A number of analytical methods have been developed for the determination of chlorotoluene mixtures by gas chromatography. These are used for determinations in environments such as air near industry (62) and soil (63). Liquid crystal stationary columns are more effective in separating m- and chlorotoluene than conventional columns (64). Prepacked columns are commercially available. ZeoHtes have been examined extensively as a means to separate chlorotoluene mixtures (see Molecularsieves). For example, a Y-type 2eohte containing sodium and copper has been used to separate y -chlorotoluene from its isomers by selective absorption (65). The presence of ben2ylic impurities in chlorotoluenes is determined by standard methods for hydroly2able chlorine. Proton (66) and carbon-13 chemical shifts, characteristic in absorption bands, and principal mass spectral peaks are available along with sources of reference spectra (67). 

TABLE 23-7 Selected Absorption Coefficients for CO in Various Solvents in Towers Packed with Raschig Rings ... 

Physical absorption using a selective absorption solvent. 

Electrolysis with a mercury cathode or with controlled cathode potential. (g) Application of physical methods utilising selective absorption, chromatographic separations, and ion exchange separations. 

Take some crude cresol mixture (1 g) and dissolve it in cyclohexane (20 mL). Obtain the infrared spectrum for the mixture if necessary, dilute the solution further with cyclohexane to obtain absorbances which will lie on the calibration graphs. From the selected absorption peaks calculate the absorbances for the three individual isomers and use the calibration graphs to calculate the percentage composition of the cresol mixture. 

Fig. 5-3. The spectrum, recorded photographically, from a tungsten tube. The silver and bromine absorption edges due to the selective absorption by the chemicals in the film are clearly shown.

Room-temperature fluorescence (RTF) has been used to determine the emission characteristics of a wide variety of materials relative to the wavelengths of several Fraunhofer lines. Fraunhofer lines are bands of reduced intensity in the solar spectrum caused by the selective absorption of light by gaseous elements in the solar atmosphere. RTF studies have recently included the search for the causes of the luminescence of materials and a compilation of information that will lead to "luminescence signatures" for these materials. For this purpose, excitation-emission matrix (EEM) data are now being collected. 

Mixed solvents are generally unsatisfactory for use in the determination of polymer molecular weights owing to the likelihood of selective absorption of one of the solvent components by the polymer coil. The excess of polarizabilit f of the polymer particle (polymer plus occluded solvent) is not then equal to the difference between the polarizabilities of the polymer and the solvent mixture. For this reason the refractive increment dn/dc which would be required for calculation of K, or of i7, cannot be assumed to equal the observed change in refractive index of the medium as a whole when polymer is added to it, unless the refractive indexes of the solvent components happen to be the same. The size Vmay, however, be measured in a mixed solvent, since only the dissymmetry ratio is required for this purpose. 

They showed further that the limiting slope (RTA2) of the plot of the osmotic pressure-concentration ratio tz/c against the polymer concentration in a binary solvent mixture should be proportional to the value of the quantity on the left side of Eq. (17),f with V2 representing the volume fraction of solvent in the nonsolvent-solvent mixture which is in osmotic equilibrium with the solution. The composition of the liquid medium outside the polymer molecules in a dilute solution must likewise be given by V2. The composition of the solvent mixture within the domains of the polymer molecules may differ slightly from that outside owing to selective absorption of solvent in preference to the nonsolvent. This internal composition is not directly of concern here. If the solution is made sufficiently dilute, the external nonsolvent-solvent composition v2 = l—Vi) will be practically equal to the over-all solvent composition for the solution as a whole. Hence... 

These detectors are based on selective absorption of ultraviolet or visible light by the desired solute. A large number of single or multiple wavelength... 

The transfer of an automated analysis from the laboratory to the plant will often require special precautions for instance, while turbidities in a process stream can cause a loss of selective absorptivity in a spectrophotometric measurement, in potentiometric methods fouling of the electrodes, potential leakage in metal containers or tubing and loss of signal in remote control may occur (see later). 

Most dyes and pigments owe their colour to the selective absorption of incident light. In some compounds, colour can also be observed as a result of the emission of visible light of specific wavelengths. These compounds are referred to as luminescent. The most commonly encountered luminescent effects are fluorescence and phosphorescence. The transitions which can occur in a molecule exhibiting either fluorescence... 

Environmental applications Oxidation of volatile organic compounds (VOCs) [114] Decomposition of organic dyes [115] Removal of aqueous phenol [116] Superwetting nanowire membranes for selective absorption [117]... 

D-Glucosone (XII), prepared from D-glucose phenylosazone (XI) by the action of concentrated hydrochloric acid, is treated in aqueous solution with potassium cyanide. The imino-D-glucoascorbic acid (XIV) which readily separates shows many of the properties of ascorbic acid. Thus it shows a strong selective absorption band in the ultra-... 

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