Azeotropic distillation, and

Azeotropic and Extractive Distillations. Effective as they are for producing various Hquid fractions, distillation units generally do not produce specific fractions. In order to accommodate the demand for such products, refineries have incorporated azeotropic distillation and extractive distillation in their operations (see Distillation, azeotropic and extractive). 

Another process employs a pH maintained at 4—7 and a catalyst that combines a divalent metal cation and an acid. Water is removed continuously by azeotropic distillation and xylene is recycled. The low water content increases the reaction rate. The dibenzyl ether groups are decomposed by the acid the yield of 2,2 -methylene can be as high as 97% (34). 

As mentioned earlier the ease or difficulty of separating two products depends on the difference in their vapor pressures or volatilities. There are situations in the refining industry in which it is desirable to recover a single valuable compound in high purity from a mixture with other hydrocarbons which have boiling points so close to the more valuable product that separation by conventional distillation is a practical impossibility. Two techniques which may be applied to these situations are azeotropic distillation and extractive distillation. Both methods depend upon the addition to the system of a third component which increases the relative volatility of the constituents to be separated. 

Synge21 isolated the elusive hydroxyamino compound by azeotropic distillation and identified it as 2-aminoethanol. He proposed a structure of 6 L-tryptophane, 6 D-leucine,... 

Varner, S.L., Breder, C.V. and Fazio, T. (1983). Determination of styrene migration from food-contact polymers into margarine, using azeotropic distillation and headspace gas chromatography, J. Assoc. Ojf. Anal. Chem., 66, 5, 1067-1073. 

Acetic acid is an important intermediate organic tonnage chemical that may be produced by the petroleum industry and fermentation. The latter process requires the recovery of acetic acid from water solutions, and several techniques have been applied to this separation, including solvent extraction, azeotropic distillation, and extractive distillation. A comparison of economics between azeotropic distillation and solvent extraction combined with azeotropic distillation (Table 10.3) shows that the introduction of... 

Batch Stirred Tank H2S04/Oleum Aromatic Sulfonation Processes. Low molecular weight aromatic hydrocarbons, such as benzene, toluene, xylene, and cumene, are sulfonated using molar quantities of 98—100% H2S04 in stirred glass-lined reactors. A condenser and Dean-Stark-type separator trap are installed on the reactor to provide for the azeotropic distillation and condensation of aromatic and water from the reaction, for removal of water and for recycling aromatic. Sulfone by-product is removed from the neutralized sulfonate by extraction/washing with aromatic which is recycled. 

It is used for detg the DEtPh content by saponifiqation with KOH soln the alcohol liberated in the reaction is separated by azeotropic distillation and measured by means of iodometric analysis afte dichromate oxidation... 

Using 20% more KOH, increasing the reaction time, stripping the benzene solution to dryness after the azeotropic distillation, and removing any unreacted 1,2-C2B10H12 by sublimation at 40°C prior to H3PO4 treatment affords high yields (80-90%) of pure product. 

Separation of the aromatics from each other and from other hydrocarbons by distillation is not economical because of the limited boiling-point differences and the formation of azeotropic mixtures. Instead, extractive or azeotropic distillation and liquid-liquid extraction are applied.234,235 The latter process is by far the most often used technique. The three processes are applied according to the aromatic content of the gasoline source. p-Xylene, the most valuable of the isomeric xylenes, is isolated by freezing (crystallization) or solid adsorption. 

Allyl alcohol forms an azeotropic mixture with water, and the mixture is a homogeneous liquid. Therefore, to obtain dry allyl alcohol, ternary azeotropic distillation and dehydration are required. 

The impact of electron donor ligands in NdX3-systems has already been discussed in Sect. 2.1.1.1. ligands such as alcohols, trialkyl phosphates, alkyl sulfoxides, alkyl amides, THF, N-oxides, pyridine etc. are added in order to facilitate water removal from NdCl3 6H20 by azeotropic distillation and in order to increase solubility and activity of NdCl3-based catalyst systems in organic solvents. 

Diaryl Tellurium 3-Mercaptopropanoate3 To a solution of 0.05 mol of the diaryl tellurium oxide in 50 ml anhydrous toluene are added 0.05 mol 3-mercaptopropanoic acid. The stirred mixture is refluxed for 3 h. Water is removed by azeotropic distillation and collected in a Dean-Stark trap. The toluene is evaporated. The diphenyl derivative is purified by preparative thin-layer chromatography and column chromatography with toluene as mobile phase. The ethoxyphcnyl derivative is recrystallized from benzene and hexane. Compounds thus prepared include ... 

The stripped solvent is practically free from water. The water undergoes overhead azeotropic distillation and is produced as separate subphase in the reflux drum. This water is then fed to the solvent recovery stage of the extraction process. 

The most strongly nonideal systems are those that may exhibit two liquid phases. We have avoided detailed discussion of such systems in this section because special algorithms are needed for these cases see, however, the section on azeotropic distillation and, for example, chapter 8 of Doherty and Malone (op. cit.) for entry points to the literature. 

Azeotropic distillation and pressure-swinp distillation. Methods that cause or exploit azeotrope formation or behavior to alter the boiling characteristics and separability of the mixture. 

Extractive distillation has been extensively used for nearly three decades in laboratory, pilot plant, and commercial plant operations. Calculation or prediction of phase equilibria for such separations has often been discussed (I, 2, 3). Some have discussed the selection of solvents for extractive distillation (4, 5). Others have discussed its recent application to particular separations (6, 7, 8). A comparison of extractive distillation, as a separation method, with azeotropic distillation and with liquid-liquid extraction has recently been discussed briefly by Gerster (9). 

Van HV, Vanden AL, Buekenhoudt A, Dotremont C, and Ley sen R. Economic comparison between azeotropic distillation and different hybrid systems combining distillation with pervaporation for the dehydration of isopropanol. Sep. Purific. Tech. 2004 37(l) 33-49. 

S. J. Wang, C. J. Lee, S. S. Jang, S. S. Shien,2008, Plant-wide design and control of acetic acide dehydration system via heterogeneous azeotropic distillation and divided wall distillation, J. Process Control, vol. 18, p. 45... 

The ability to separate a mixture of two liquid phases is critical to the successful operatiou of mauy chemical aud petrochemical processes. Besides its obvious importauce to liquid-liquid extractiou aud washing operations, liquid-liquid phase separation can be a critical factor in other operations including two-liquid-phase reaction, azeotropic distillation, and industrial wastewater treatment. Sometimes the required phase separation can be accomplished within the main process equipment, such as in using an extraction column or a batch-wise, stirred-tank reactor but in many cases a stand-alone separator is used. These include many types of gravity decanters, filter-type coalescers, coalescers filled with granular media, centrifuges, and hydrocyclones. 

The two procedures are applicable to condensations of ketones with both ethanedithiol and -mercaptoethanol. Previous methods (see ref 3 for literature) include use of zinc chloride and sodium sulfate, hydrogen chloride in ether, p-toluenesulfonic acid in benzene with azeotropic distillation, and an exchange method. 

Moate et al. and Kupfermann et al. presented analytical methods involving SPE for the extraction of alkyl phosphates from urine. Moate et alf used SPE for sample cleanup followed by azeotrope distillation and then derivatization of the analytes. Determination of the analytes was achieved using GC-FPD. In contrast, Kupfermann et alf purified the derivatized extract of urine samples from a case of OP poisoning on silica SPE columns followed by quantitative analysis by GC-MS. The LODs ranged from 3 to biiginL. ... 

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