Apparatus and experimental procedure



In order to intensify the process of catalytic synthesis of m-xylenediamine from isophthalonitrile, studies were first carried out in the presence of various Nickel Renea based alloy catalysts "M", "H", "C", which showed high activity and selectivity in hydrogenation reactions of other organic compounds [9, 10].

The catalytic hydrogenation of benzonitrile  was carried out in the liquid phase in the isobaric-isothermal regime at a high-pressure kinetic unit (HPKU) (figures 1 and 2), which makes it possible to control the hydrogen flow per unit time.. Reactor is a catalytic " duck" from stainless steel. The volume of the reaction vessel is 0.15 liters, the number of unilateral swings is 600-700 per min. The hydrogenation is carried out until the absorption of hydrogen from the gas phase ceases.

 

 

1 – high-pressure apparatus «duck»; 2 – container for  substance to be hydrated ; 3 –charging hole; 4– thermostat; 5 –device for shaking of reactor; 6 –standard manometer; 7 – burette; 8 – equalizing vessel; 9 – fire-retardant; 10 – buffer capacity; 11–15 - ventilating adjustment.

 

Figure1 –High pressure kinetic unit (HPKU)

 

 

 

Figure 2 – Image of the installation of the HPKU

 

Hydrogenation of the nitrile was carried out under isobaric-isothermal conditions at a high-pressure kinetic unit (HPKU). The high-pressure kinetic unit is shown in Figure 1. The installation was developed under the guidance of Professor A.S. Chegolia. Its unique feature is the possibility of studying the kinetics of hydrogenation of organic compounds at constant pressure with a change in the hydrogen flow per unit time, the potential and electrical conductivity of the catalyst.

The reaction vessel is a catalytic "duck" - a metal reactor of stainless steel with a cylindrical shape with a conical bottom and a lid. "Duck" is equipped with a metal casing for temperature control. The required temperature was maintained by means of a thermostat, the speed of one-sided shaking of the "duck" was 700 ± 50 shakes per minute.

To introduce the hydratable substance in the "duck" design, a sampler is provided for sampling at any given time, without changing the pressure in the system. Burette for measuring the amount of hydrogen going to hydrogenation (accuracy ± 0,1 cm3) is a thick-walled tube made of an organic glass, placed in a metal sleeve made of steel and having side slits. The burette is hermetically connected to a reactor, an equalizing vessel and a buffer tank with a volume of 10 cm3. The measurement of hydrogen consumption is made by changing the height of the column of liquid filled in the burette. The catalyst is loaded into the "duck" under a layer of solvent. A sample of the hydrogenated substance is introduced into the special container, then the entire gas system and the "duck" are blown with hydrogen, the system is checked for leaks, and the necessary hydrogen pressure and temperature are created. When the set temperature is reached, an electric motor driving the "duck" swing mechanism is activated and the catalyst is saturated with hydrogen from the gas phase. After this, the calculated amount of the hydratable substance in the container is introduced through a special device into the "duck", without violating the condition of the experiment and the tightness of the system. Hydrogenation is conducted until the absorption of hydrogen from the gas phase ceases.

With the optimal nitrile-catalyst ratio, the promotion of skeletal nickel, the selection of a suitable solvent and the amount of ammonia, the use of hydrogen pressure can increase the catalyst activity 3-4 times and increase the yield of the desired product. However, all these factors do not always allow to achieve such a state of the reaction system that the rate of hydrogen consumption during hydrogenation of the nitrile exceeds the rate of its activation on the surface of the catalyst, therefore, the reaction proceeds at a decreasing rate during the experiment.

The increase in the catalytic properties of skeletal nickel promoted by titanium and niobium is also associated with the formation of the corresponding oxides. Oxides in turn increase the proportion of strongly bound hydrogen in the catalyst. They are also localized at the mouths of the pores and on the boundaries between the catalyst grains, preventing its recrystallization.

Owing to the use of a complex of modern physical and physicochemical methods of investigation, the presence of NiAl-Ti alloys in addition to the intermetallic compounds NiAl3, Ni2Al3, and TiAl3, NiAl3, Ni3Ti compounds has been confirmed. The results of studies of the structure and phase composition of the surfaces of nickel skeleton catalysts by the methods of electron and x-ray photoelectron spectroscopy have shown [46] that additions of transition d-metals introduced into the alloys that persist in the composition and on the surface of catalysts are more often produced by solid interstitial solutions. Consequently, the defectiveness of the lattice increases, and the probability of formation of cluster-like surface regions increases. The acid-base properties of the surface, due to the presence of sections of oxides, hydroxides, the corresponding d-metals, and partially hydrated alumina, vary. This leads to a change in the binding energy between metal atoms and their coordination numbers, to a decrease in the growth of nickel microcrystals, as well as to facilitating the formation of hydride and complex polyatomic loosely bound complexes.

The reaction products were analyzed by GLC, potentiometric titration and IRS (Specord-75 IR and UR-20).

Chromatographic analysis was carried out on a chromatograph LXM-72. The stationary phase for benzonitrile is PEG on celite, and for benzylamine-E-30 (5%) on a N-AW chromatograph, the grain is 0.16-0.20 mm. For both substances, the mode of operation of the chromatograph is the same: t columns - 200 ° C, detector - 260 ° C, bridge current - 100 mÅ, column length - 2.5 m, diameter - 4 mm.

To isolate the desired product (ethylamine), the reaction mixture is first passed through a filter where it separates from the catalyst, then the solvent is distilled off from the filtrate by distillation. The hydrogenated is subjected to vacuum distillation under a stream of nitrogen and a fraction of ethylamine.

Acetonitrile (methyl cyanide, ethanenitrile, acrylate nitrile) -CH3-CN for chemical properties is a typical nitrile. Colorless toxic liquid. Has a slight but unpleasant etheric smell. The molecular mass is 41.05 g / mol; the temperature of the boiling is 81.6 ° C; d204-0.7857; n20D-1.3441. Mixing with water (solubility 7.3%) and organic solvents (ethanol, acetone, ether, CCl4, etc.) The maximum permissible concentration (MPC) in working and other premises is 10 mg / m3. In water, 0.7 mg / m3.

In industry, acetonitrile is obtained by ammonolysis of acetic acid at 300-450 ° C (catalyst Al2O3, SiO2 etc.) using a small excess of NH3. Yield 90-95%. A significant amount of acetonitrile is obtained as a by-product in the production of acrylonitrile by the oxidative ammonolysis of propylene. Acetonitrile can also be obtained by ammonolysis of aliphatic hydrocarbons in the presence of oxides of Co, Mo, etc

Ethylamine or aminoethane CH3-CH2-NH2 - refers to the primary amines. Ethylamine is a clear liquid boiling at 16.6-18.7 ° C. Molecular weight-45.09 g / mol; d204-0.6828; n20D-1,3663.Ethylamine has a strong ammonia odor. Unlimitedly mixed with water, readily soluble in ethanol and other organic solvents. It mixes with water in all proportions with the release of heat and gives a strongly alkaline solution (for litmus and phenolphthalein); The aqueous solution is not very strong and can be completely removed from the solution by boiling [57].

Analyzes of ethylamines by GLC methods and acid titration of ethylamine solutions in water or in organic solvents.

Ethylamine - a strong base, have the properties of amines. Etilamines have a harmful effect on human organisms. The maximum permissible concentration (MPC) in workers and other premises is 10 mg / m3.

In the industry, a mixture of ethylamines is prepared by vapor-phase mamination of ethanol in the presence of Al2O3, SiO2, or mixtures of these at 350-450 ° C, 2-20 MPa, NH3: C2H5OH molar ratio (2: 6) or in the presence of Ni, Co, Cu, Re, etc. and H2 at 150-230 ° C, a pressure of 1.7-3.5 MPa, a molar ratio of C2H5OH: NH3: H2-1: (l, 5-6): (2-5). The yield in the first case is 75-80%, in the second 90-95% with the ethanol conversion of 95-100%. The composition of the ethylamine mixture is controlled by the amount of NH3, the process temperature and the recycle of one or two ethyl amines. A mixture of ethylamines (mono-, di- and triethylamines) is formed.

In the laboratory, ethylamines are synthesized by methods common to the preparation of aliphatic amines by hydrogenation of acetonitrile and nitroethane.

Ethylamines are used in the production of pesticides, corrosion inhibitors, medicinal substances (for example, novocaine, cardiamine, etc.), catalysts for the synthesis of polyurethanes. Monoethylamine is also used to produce plasticizers, flotation agents, textile auxiliaries, vulcanization accelerators; diethylamine - to obtain additives for motor fuels and oils, curing agents for epoxy resins; triethylamine - for the production of liquid rocket fuels, antiseptics for wood, oligomers.

 

 


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