Toluene azeotropic distillation

There is an alternate process for recovering toluene from the reformate stream called azeotropic distillation. It also can be used to split toluene from the other hydrocarbons that have boiling points near toluene. Azeotropic distillation is like solvent extraction with an extra twist. The process can be more efficient than extraction when the toluene concentration is high. 

N-(l,l,3,3-tetramethylbutyl)-formamide is prepared in 86-90% yield by refluxing 194 g. (1.5 moles) of 1,1,3,3-tetra-methylbutylamine with 138 g. (3.0 moles) of formic acid in 400 ml. of toluene. Azeotropic distillation using a Dean-Stark trap gradually removes all water and excess formie acid. The toluene is removed by distillation at atmospheric pressure, and the product is distilled at reduced pressure, b.p. 76-77° (1 mm.),... 

Diols that bear two hydroxyl groups m a 1 2 or 1 3 relationship to each other yield cyclic acetals on reaction with either aldehydes or ketones The five membered cyclic acetals derived from ethylene glycol (12 ethanediol) are the most commonly encoun tered examples Often the position of equilibrium is made more favorable by removing the water formed m the reaction by azeotropic distillation with benzene or toluene... 

Novolak Resins. In a conventional novolak process, molten phenol is placed into the reactor, foHowed by a precise amount of acid catalyst. The formaldehyde solution is added at a temperature near 90°C and a formaldehyde-to-phenol molar ratio of 0.75 1 to 0.85 1. For safety reasons, slow continuous or stepwise addition of formaldehyde is preferred over adding the entire charge at once. Reaction enthalpy has been reported to be above 80 kj /mol (19 kcal/mol) (29,30). The heat of reaction is removed by refluxing the water combined with the formaldehyde or by using a small amount of a volatile solvent such as toluene. Toluene and xylene are used for azeotropic distillation. FoHowing decantation, the toluene or xylene is returned to the reactor. 

The equihbrium shown in equation 3 normally ties far to the left. Usually the water formed is removed by azeotropic distillation with excess alcohol or a suitable azeotroping solvent such as benzene, toluene, or various petroleum distillate fractions. The procedure used depends on the specific ester desired. Preparation of methyl borate and ethyl borate is compHcated by the formation of low boiling azeotropes (Table 1) which are the lowest boiling constituents in these systems. Consequently, the ester—alcohol azeotrope must be prepared and then separated in another step. Some of the methods that have been used to separate methyl borate from the azeotrope are extraction with sulfuric acid and distillation of the enriched phase (18), treatment with calcium chloride or lithium chloride (19,20), washing with a hydrocarbon and distillation (21), fractional distillation at 709 kPa (7 atmospheres) (22), and addition of a third component that will form a low boiling methanol azeotrope (23). 

In order to shift the equilibrium, the water formed in that reaction is usually removed by azeotropic distillation with benzene or toluene. 

An alternative process from U.S. Patent 3,635,946 A vigorously stirred reaction mixture consisting of 32.B7 g (0.1 mol) of 5-fluorouracilmercury, 100 ml of dimethylformamide and 50 ml of toluene is dried by azeotropic distillation of toluene. It is then cooled to -40°C in a stream of dry nitrogen, and a solution of 21.3 g (0.2 mol) of 2-chlorofuranidin in 20 ml of dried dimethylformamide is gradually added to the stirred mixture, the temperature being maintained between -40°C and -30°C. After completion of the reaction (which is marked by complete dissolution of the starting 5-fluorouracilmercury) i.e. after about 3 to 4 hours, 60 to 80 ml of the solvent are distilled off in vacuo at a bath temperature not exceeding 35°C ... 

To remove water, the benzene was azeotroped and distilled over CaH2. The n-pentane was stored over LiAlH and distilled over CaH2. Toluene was distilled over CaH2. Toluene from Burdick Jackson, Muskegon, MI could also be used for dilute solution characterization without any adverse effects on polymer solubility. Tetrahydrofuran (THF) was dried over molecular sieves and doubly distilled over CaH2. The solvents were blanketed with nitrogen to maintain dryness. 

Enanthaldehyde, -METHYL-/3-OXO-, DIMETHYL ACETAL, 32, 79 Enanthic acid, e-oxo, 31, 3 Epichlorohydrin, 31, 1 Esterification, by azeotropic distillation with toluene, 30, 30, 31 of ethanol with phosphorus trichloride, 31, 111... 

The B-methyl catalysts were prepared by reacting the aminoalcohol with trimethyl-boroxine, followed by an azeotropic distillation with toluene. 

You might think the formation of azeotropes to be an unalloyed nuisance, but they can be useful. Toluene and water form a minimum-boiling azeotrope (20.2%water 85°C). If you needed very dry toluene for some reason, all you need to do is distill some of it. The water-toluene azeotrope comes off first,... 

In the first step, phenolic monomers were reacted with potassium hydroxide in DMSO solution to form the potassium arylate salts, which were then dried in situ by azeotropic distillation of the water with toluene. After removal of a portion... 

The water formed in the reaction is continuously removed from the reaction mixture by azeotropic distillation, in order to avoid reversible reaction between water and ester. The progress of reaction can be followed either by measuring the amount of water or by determining the amount of unreacted acid in aliquots withdrawn at regular intervals of time. The reaction can be carried out either in presence of a catalyst, i.e. a weak acid like p-toluene sulphonic acid (a strong acid can hydrolyse the polymer, formed) or in absence of the catalyst. 

To a vigorously stirred solution of 1,2-diaminoethane (60 g, 65 ml, 0.994 mol) in methanol (100 ml), at 0°C under nitrogen, was added a solution of (G = 0.5) dendri-PAMAM(C02Me)8 [3] (5 g, 0.004 mol) in methanol (20 ml). The addition was controlled such that the temperature did not rise above 40 °C. The mixture was stirred at room temperature for 96 h, after which time no ester groups were detectable by NMR spectroscopy. The methanol was removed by vacuum distillation at < 40 °C, and excess 1,2-diaminoethane was removed by azeotropic distillation using a mixture of toluene and methanol (9 1). The remaining toluene was removed by azeotropic distillation with methanol and... 

When azeotropic distillation is used for toluene, the solvent used is usually a mixture of methyl ethyl ketone (MEK) and water (10%). The solvent and the toluene are mixed, heated, and then charged to a distillation column... 

In a very similar way, hydroxy functionalized ATRP initiators such as 2,2,2-tribromoethanol can be used for the simultaneous polymerization of eCL and MMA (Scheme 25) [83]. Purposely, the ROP of eCL is promoted by Al(OfPr)3 added in catalytic amount so that the rapid alcohol-alkoxide exchange reaction (see Sect. 2.4) activates all the hydroxyl functions. In order to avoid initiation by the isopropoxy groups of Al(0/Pr)3. The in-situ formed zPrOH is removed by distillation of the zPrOH/toluene azeotrope. On the other hand, the ATRP of MMA is catalyzed by NiBr2(PPh3)3. The two aforementioned one-step methods provide block copolymers with controlled composition and molecular weights, but with a slightly broad MWD (PDI=1.5-2). 

When R2 substituent is flourocontaining alkyl group, the transformation 17 18 becomes hindered and its proceeding requires some special methods. For example, in [48] Biginelli-like cyclocondensations based on three-component treatment of 3-amino-l,2,4-triazole or 5-aminotetrazole with aldehydes and fluorinated 1,3-dicarbonyl compounds were investigated. It was shown that the reaction can directly lead to dihydroazolopyrimidines 20, but in the most cases intermediate tetrahydroderivatives 19 were obtained (Scheme 10). To carry out dehydration reaction, refluxing of tetrahydroderivatives 19 in toluene in the presence of p-TSA with removal of the liberated water by azeotropic distillation was used. The same situation was observed for the linear reaction proceeding via the formation of unsaturated esters 21. 

The reaction is carried out in dimethyl sulfoxide at 130-160 °C under an inert atmosphere. High purity of the starting materials is of prime importance in order to obtain high molecular weights. The water, which results from the neutralization of the bisphenols, can be removed via an azeotropic distillation with toluene. 

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