Aniline and water

For conditions of forced convection, Frossling(5I) studied the evaporation of drops of nitrobenzene, aniline and water, and of spheres of naphthalene, into an air stream. The drops were mainly small and of the order of 1 mm diameter. Powell (44) measured the evaporation of water from the surfaces of wet spheres up to 150 mm diameter and from spheres of ice. 

In the manufacture of aniline from nitrobenzene the reactor products are condensed and separated into an aqueous and organic phases in a decanter. The organic phase is fed to a striping column to recover the aniline. Aniline and water form an azeotrope, composition 0.96 mol fraction aniline. For the feed composition given below, make a mass balance round the column and determine the stream compositions and flow-rates. Take as the basis for the balance 100 kg/h feed and a 99.9 percentage recovery of the aniline in the overhead product. Assume that the nitrobenzene leaves with the water stream from the base of the column. 

Partition of cyclo-hexylamine between aniline and water at 30°C ... 

Water was used as the catalyst phase for the palladiiun complex of TPPTS and toluene or an excess of the substrate anihne served as the non-polar product phase. To determine an appropriate solvent system cloud titrations were performed at 90 °C, 60 °C, 40 °C and 25 °C. A solution of 4-chloro-nitroben-zene in aniline and water were mixed in a weight ratio of 1 1 and semi-polar solvents were added as a mediator until a homogeneous solution was formed. As the mediator the following solvents were apphed methanol, ethanol, isopropyl alcohol, n-butanol, DMF, DMSO, ethylene glycol, N-methylpyrrohdone (NMP), 1.4-dioxane and acetonitrile. The cloud titrations were repeated whereby the substrate 4-chloro-nitrobenzene was replaced with the product 4-nitrodiphenylamine. In all cases more of the semi-polar mediator is required for the product mixture at 25 °C than for the reaction mixture at 60 °C to obtain a clear solution. 

In an extreme case the surface tension of diphenyl is almost double that of benzene at the same temperature and it would be expected that in a mixture of these substances the benzene would be preferentially adsorbed at the surface, and any attempt to find the mean molecular weight of the two would break down. Certain mixtures of aniline and water were found by Worley (J.G.S. ov. 260, 1914) to have positive temperature coefficients of surfiice tension as exemplified in the following data for a 3-3 °/o aniliiie... 

In a 3-I. round-bottom flask are placed 750 g. (8.1 moles) of aniline (Note 1) and 1 kg. (8.2 moles) of benzoic acid. When about two-thirds of the benzoic acid is in the flask the mixture is melted to make room for the rest. The flask is placed in a large oil bath and connected to a condenser for distillation. The temperature of the oil is raised quickly to 180-190°, at which point distillation starts. The bath is held at this temperature until practically no more aniline and water distil (about two hours), and then the temperature is slowly raised to 225° and maintained at this temperature until no further distillation takes place (one to two hours). The oil bath is now removed and the contents of the flask are allowed to cool below 180° and 550 g. (5.9 moles) of aniline is added. The distillations at 190° and 225° are repeated (about six hours). The hot mixture is poured into two 20-cm. evaporating dishes (hood) and is allowed to cool. The crude product weighs 1600-2000 g., depending on the amount of aniline retained. 

The mechanism of phenol amination on MgO can be formulated in an identical way since it is known that ammonia also dissociates heterolyti-cally on the most unsaturated Mg 0 pairs (264) located at edges, steps, and corners, with formation of surface NH2 and OH species (see Section IV.A.5). Since phenol (an acidic molecule) is adsorbed on all surface Mg2 O2 pairs, the most plausible adsorption interaction mechanism is that shown in Scheme 8. The densely packed negatively charged OH, phenoxide, and amino groups are then expected to readily react at the reaction temperature with elimination of aniline and water. 

At this point aniline can be isolated. You could reduce the solubility of aniline by dissolving in the steam distillate 0.2 g of sodium chloride per milliliter, extract the aniline with 2-3 portions of dichloromethane, dry the extract, distill the dichloromethane (bp 4rC), and then distill the aniline (bp 184°C). Or the aniline can be converted directly to acetanilide. The procedure calls for pure aniline, but note that the first step is to dissolve the aniline in water and hydrochloric acid. Your steam distillate is a mixture of aniline and water, both of which have been distilled. Are they not both water-white and presumably pure Hence, an attractive procedure would be to assume that the steam distillate contains the theoretical amount of aniline and to add to it, in turn, appropriate amounts of hydrochloric acid, acetic anhydride, and sodium acetate, calculated from the quantities given in Experiment 2. 

Octaphenyldi-iodosilicotetrane, Si4ph3lg, prepared from the hydrocarbon as stated above, is a colourless or pale-yellow product, which turns pink and then yellowish-brown on exposure to light and moisture. It crystallises from benzene or ether in lustrous, very acute, rhomboidal plates, which do not melt below 250° C. In cold ether it is only very sparingly soluble, moderately soluble in cold benzene, but these solutions soon turn brown on exposure to air. Hydrolysis of the compound by an ammoniacal solution of acetone yields octaphenyl-silicanetetrane oxide, Si4PhgO, and the rhomboidal oxide, Si PhgO. the former oxide is also obtained when the hydrolysis is carried out with aniline and water. 

A special situation may arise if reaction products considerably affect the hydrogen solubility, which then varies during the reaction. Such a phenomenon occurs most often in the hydrogenation of the substrate in bulk, without solvent, mainly where the chemical character of the hydrogenation product markedly differs from that of the initial compound [e.g., hydrogenation of nitrobenzene to aniline and water (72)]. In such a case the hydrogen concentration cannot be drawn into the constant, because its varying concentration in the liquid phase is reflected in the form of the kinetic equation. In many such cases the effect of reaction products is also reflected in the kinetic equation. 

Aniline is a colorless liquid. However, the aniline used in industry has a light yellow color. Aniline and water form two layers when mixed together. Aniline stays below the water because its density is higher (left tube). Aniline can react with HCI solution since it is a weak base (middle tube). If a sufficient amount of HCI is added, a colorless anilinium chloride (C6H5NH Ct) is formed (right tube). 

Carbolic Acid, also colled Phe tol Phenic acid, and hydrate of Phenyle, It consists of long, colorless prismatic crystals, which melt at about 90 Fahr. into an oily liquid resembling creosote. Tho crystals deliquesce in moist air, forming a sort of hydrate, which boils at 370 and has a specifle, gravity of 1.0G5. Heated with ammonia, it yields aniline and water and nitric acid converts it into picric acid. Commercial creosote... 

Aniline sulfate is first prepared in a cast-iron kettle equipped with a reflux condenser and 25-rpm propeller agitator. Sulfuric acid (3,520 lb 92 per cent acid—33.0 lb moles 100 per cent acid) is charged to the kettle. The aniline (3,030 lb—32.5 lb moles) is then added through an orifice with agitation as the temperature rises to 150°C, aniline and water being refluxed in the condenser. Two hours after addition of the aniline, the reaction is complete. 

As an example of the vapor-phase process, nitrobenzene vapor and hydrogen are mixed and passed through a fluidized bed of copper-on-sihca catalyst at 280—290°C and 500 kPa (5 atm). The reaction gas is filtered, cooled to condense aniline and water, and the excess hydrogen is recyded. The yidd reported is 99.5% (42). The catalyst bed is regenerated by passing hot air through the bed to bum off the carbonaceous deposits. The aniline and water condensate are separated, and the latter is sent to the wastewater column. The organic phase is dried and the product is distilled. 

D7. Aniline and water are partially miscible and form a heterogeneous azeotrope. At p = 778 mm Hg the azeotrope concentrations are The vapor is 0.0364 mole frac aniline, the liquid aqueous phase contains 0.0148 mole frac aniline, and the liquid organic phase contains 0.628 mole frac aniline. Estimate the relative volatility of water with respect to aniline in the organic phase. Note Be careful to use the mole fracs of the correct conponent. 

Saturated equilibrium solutions of aniline and water at 100°C. contain 0.0148 and 0.628 mole fraction aniline. From these data calculate the van Laar constants, and compare with the values used in Fig. 3.4c. Calculate the values of activity coefficients for the system using the constants so determined, and compare with the observed data, Fig. 3.4c. 

Inspired by He and Yu [163], Wolz and Hein [ 164] applied the Pickering approach in the synthesis of a porous electrode structure, in which the porosity is predefined by the oxide-polymer sphere size. Sb-doped SnOj (ATO) nanoparticles were used to stabilize a PANI core, while the size of these spheres and the stability of the emulsion could be tailored by the chosen synthesis conditions (pH value and solid content) between ATO, toluene/aniline, and water (A. Wolz and S. Hein, unpublished results). An optimized Pickering solution was stable for about 40 min without visible coalescence of the organic phase. 

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