SU1220566A3 - Method of purifying hexahydrobenzoic acid - Google Patents

Description

This invention relates to a process for purifying hexahydrobenzoic acid, namely, a method for purifying said acid from neutral by-products in the production of caprolactam.

The aim of the invention is to increase the purity of the target product.

FIG. 1 and 2 shows the installation used in the process.

Example 1: Oxidation of toluene and subsequent hydrogenation to obtain hexahydrobenzoic acid.

A continuously operating unit (Fig. 1) containing a reactor 1, with a capacity of 1.5 liters, operating in continuous mode and equipped with a device for mechanical displacement, input of oxygen-containing gas, a liquid mixture that reacts, and a catalyst and several vent holes are used. . When the installation is already established, for example, after 50 hours of operation, 230 g / h of toluene are continuously fed from the measuring tank using a pump. The second pump continuously feeds toluene into the reactor at a rate of 780 g / h. With intermediate reaction products that are continuously withdrawn from column 2, the level in the tank is kept constant. From the measuring tank 3 using the pump separately serves 25 g / h of a 2% aqueous solution of cobalt acetate. The reactor is maintained at 160 ° C and 10 atm. When toluene is removed from it, the exhaust gas contains A% oxygen. The reaction product is continuously discharged at a rate of 1114 g / h while maintaining a constant level in the reactor, and the head fraction is fed from a distillate column 2 having 20 cap plates 50 mm in diameter and equipped with a boiler through a heater and heater k. The mass ratio of the reaction product discharged from the reactor to the total mass fed to the reactor, 1.1. The convective preheater is installed at the bottom of the column and is equipped with electrical preheating means, which allows the controllers to maintain the desired temperature on the plates, which are intended for o-water intermediates.

Distillate is taken from the head of the column, which contains

in addition to water, all unreacted luol and part of the intermediate reaction products, such as benzyl alcohol, as well as lower organic acids. The distillate is directed through a condenser 5 and settled in a settling tank 6.

An additional fraction of products containing benzaldehyde, diphenyl, diphenylzane, and diphenylmethane in an amount equal to 5% of the total feed to column 2 is taken from the intermediate plate of the column at 200 ° C, these products are then settled in the sump 6.

By separating the aqueous phase in a settling tank 6, unreacted toluene and said intermediate products are recycled to the tank after stripping acidic organic by-products, which are discharged into the aqueous phase due to the gravity of the settling tank 6. The amount of these intermediate products is 1.8% by weight filing in. column 2 and, therefore, equal to about 2% of the total feed to the reactor.

From the bottom of the column 2 heated to 255-260 ° C, the product is pumped to the evaporator 7, into which steam is injected at a rate of 10 g per 100 g of benzoic acid, and heavy products, including cobalt, are separated at the base of the specified evaporator. The vapor flow exiting the evaporator is directed to two series-connected condensers 8 and 9, held at 130 and 20 ° C, respectively. Benzoic acid having a purity of 99.66% is taken from the first condenser, acidic water is collected from the second condenser and re-injected with a pump at the base of the column 2. I

The hydrogenation unit contains (FIG. 2) a battery of three reactors 10-12, each of which is equipped with mixing devices 13-15, respectively. The reactors are connected to a battery by conduits 16 and 17, through which the streams of liquid material to be treated and hydrogen flow countercurrently. At the top along the reactor 10 serves at the point 18 hydrogen (412.5 l / h) 5 which is preheated to the desired temperature in the heat exchanger 19, and at the point 20 - 450 g / h of liquid benzoic acid containing 1.5 wt.% fell

Ladies catalyst (5% deposited on coal), also after preheating by means of a pump 21, which feeds material from vessel 22, in which liquefaction is achieved due to combined thermal and mechanical action.

Hydrogen and products flow countercurrently at point 23 from the downstream reactor 12 and pass into separation tank 24, preferably after passing through temperature controlling output heat exchanger 25, and in this tank whose temperature is controlled, hydrogen and product are separated, hydrogen is removed on line 26, and the product on line 27. Hydrogen consumption can be controlled by counter 28.

The hydrogenation reaction is carried out at 180 ° C and a pressure of 15 atm for 10 hours; a yield of 98.6% hexa-hydrobenzoic acid is obtained.

The amount of impurities 1.34 wt.%, Including:

Hexahydrobenzoyl-hexadrobenzonate 0.069 Benzoic acid 0.262 Methyldicyclohexyl 0.131 Dicyclohexylmethane 0.540 Dicyclohexyl 0.118 Ethylcyclohexyl 0.119 Other by-products 0,101

The apparatus for the production of caprolactam by the reaction of hexahydrobenzoic acid (HH), dissolved in oleum with nitrosylsulfuric acid NOH 30, consists of a reactor.the preliminary mixing of hexahydrobenzoic acid with oleum (blender), the reactor (lactamizer), where the mass of the agitator is mixed S04 hydrolyser, in which the reaction mass from the lactate emulsifier is diluted with water, the extractor, in which the excess GGB and the solvent used to control the temperature of lactamization are separated from the reaction mass, diluted ennyh water column for washing the gases lactamisation (COj), which are allocated according to the stoichiometric equation

soon

-l-l OHSO / g with about - g about-sog

five

0

from a temperature control solvent that is captured by carbon dioxide according to a stoichiometric equation, and a distillation column that separates the temperature control solvent and the GGB extraction from the GGB proper,

I A 2453 kg / h of contaminated hexahydrobenzoic acid containing 37 kg / h of 5 neutral (1.4%) by-products is loaded into the washing column. This hexahydrobenzoic acid is combined with a stream of hexahydrobenzoic acid and a solvent (hexane) for temperature control, which comes from

extraction of GGB from the acidic reaction mass.

In the distillation column, the reaction solvent is partially separated from the HGB and neutral by-products, the solvent is sent to the storage tank, and the HGB and neutral by-products are sent to the mixing unit, where they are mixed with 0 oleum (temperature 30 ° C) and then passed into the decanter. Decantation is carried out at 30 ° C. The solid phase from the decanter is sent to the lactate, and the light phase to the distillation column.

The composition of the light phase,%: Hexahydrobenzoic acid5

Neutral by-products of h-Hexane. The effluent stream is continuously withdrawn from the pipeline that transports the light phase of the de-cantator to the distillation column of the solvent, and this stream contains 2 kg / h of HGB and 14 kg / h of neutral by-products after distillation (ratio Neutral byproducts to hexahydrobenzoic acid 7.0: 1).

Purity of hexahydrobenzoic acid fed to lactamizer 97.8%, Acid flow rate to lac35 60

55

tamizator 5858 kg / h. I

Example 2. It is carried out analogously to example 1. A temperature of 20 ° C is maintained in a device for decanting.

and is used as a thermoregulation solvent (temperature control during the lactamization process) N-hexane. The temperature at the mixing stage is 20 C.

The light phase that leaves the decanting device and is sent to the distillation column has the following composition, h,:, GGB 197, SO, absent, HjS04 39, neutral by-products 545, H-hexane 593.

26 h / h is continuously extracted from this stream and discharged. The ratio of neutral by-products to hexahydrobenzoic acid is 2.77: 1

The purity of the hexahydrobenzoic acid is 97.5%. The flow rate of the acid into the lactamizer is 5860 kg / h.

Example 3. It is carried out analogously to Example 1, however, tsclohexane is used as a temperature regulating solvent, and the temperature is maintained at 40 ° C in a mixing device and in a device for decanting.

19 h / h of the light phase is discharged, the stream contains 2.6, 3.65 h of neutral by-products and 8.5 h of cyclohexane, the ratio of neutral by-products to hexahydro-bendeic acid is 1.4: 1,

The purity of hexahydrobenzoic acid is 97.8%. The acid flow rate into the lactator is 5759 kg / h.

nineteen

22

21

Compiled by I.Kovalev Editor I.Nikolaychuk Tehred N. Bonkalo Corrector A.Zimokosov

Order 1337/62 Circulation 379 Subscription VNIIPI USSR State Committee

for inventions and discoveries 1L3035, Moscow, Zh-35, Raushsk nab., d.4 / 5

Branch PPP Patent, Uzhgorod, Proektna St., 4

-15 g ,,. 26

FIG. g

Claims (1)

METHOD FOR CLEANING HEXAHYDROBENZENIC ACID, used in the production of caprolactam, from neutral products arising from the preparation of the indicated acid Out.f by the oxidation of toluene followed by hydrogenation of the resulting benzoic acid, which is characterized in that, in order to increase the purity of the target product, hexahydrobenzoic acid is mixed at 20-40 ° C with oleum in the presence of hexane or cyclohexane with the formation of two phases, followed by by decantation of the upper phase containing by-products at 20-40 ° C and the mass ratio in the upper phase of the neutral by-products and hexahydrobenzoic acid, 1.4-7.0: 1, respectively, and the lower phase, containing oleum and hexahydrobenzoic. slot fed to laktomizator for reaction with nitrosylsulfuric acid. SU .. ,, 1220566