RU2640781C1 - Method for purifying exhaust gases of isopropyl benzene oxidization - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method for purifying exhaust gases of isopropyl benzene oxidation consists in recovering isopropyl benzene by a low-temperature condensation. To create low temperatures, the energy of the exhaust gases of the isopropyl benzene oxidation is used.

EFFECT: invention makes it possible to increase the recovery of isopropyl benzene from the exhaust gases.

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Description

The present invention relates to the petrochemical or refining industries and may find application in the preparation of phenol and acetone by the oxidation of isopropylbenzene. Phenol and acetone are widely used in petrochemistry, for example, to obtain polycarbonate plastics.

The first step in the production of phenol and acetone by the cumene method is the oxidation of isopropylbenzene with atmospheric oxygen to cumyl hydroperoxide. Currently, most industrially implemented processes for the oxidation of isopropylbenzene are carried out at an excess pressure of 3 ÷ 5 kg / cm ² . In this case, the energy of the exhaust gases is not used in any way. The oxidation exhaust gases contain up to 5 g / m ^{3 of} isopropylbenzene.

A known method of purification of gases from organic impurities by oxidation on the surface of the catalyst (Handbook of petrochemistry. - L .: Chemistry, 1986, S. 556). According to this method, isopropylbenzene contained in the exhaust gas is oxidized with oxygen to carbon dioxide and water in the presence of an aluminum-palladium catalyst.

The disadvantage of this method is the use of an expensive catalyst, the difficulty of maintaining the required temperature in the afterburner, as well as the irretrievable loss of a valuable product - isopropylbenzene.

A known method of adsorption purification of exhaust gases from the oxidation of isopropylbenzene (Patent RU 2142326). The cleaning process consists of the following stages: adsorption of isopropylbenzene from the exhaust gases at low temperature, desorption of isopropylbenzene from the adsorbent with steam at high temperature, drying the adsorbent, cooling the adsorbent to the adsorption temperature. Water vapor containing desorbed isopropylbenzene condenses, the resulting organic layer after appropriate treatment is returned to the oxidation stage.

The disadvantage of this method is the cyclical process, high energy consumption (up to 10 tons of water vapor per ton of isopropylbenzene released), low adsorbent life due to significant temperature differences.

A known method of absorption treatment of exhaust gases of oxidation of isopropylbenzene, protected by patent RU 2300412. The essence of the invention lies in the fact that the exhaust gases of oxidation are purified from isopropylbenzene by absorption of polyalkylbenzenes at temperatures below + 10 ° C.

The disadvantage of this method is the low degree of gas purification from isopropylbenzene, high energy consumption to maintain low process temperatures, the cost of extracting isopropylbenzene from a saturated absorbent.

When conducting a patent search, a close analogue of the proposed method was not found.

An object of the present invention is to provide a new, more efficient process for the isolation of isopropylbenzene from oxidation exhaust gases.

The technical result is to increase the efficiency of the process by increasing the degree of extraction of isopropylbenzene from oxidation exhaust gases at low temperatures, while the energy of the exhaust gases is used to create low temperatures.

The technical result is achieved in that the extraction of isopropylbenzene is carried out using low-temperature condensation, and to create low temperatures, the energy of the exhaust gases from the oxidation of isopropylbenzene is used. The above gases pass through a condensation system, where they are cooled by heat exchange with return exhaust gas, the condensed liquid is separated from the gas in the separators, the exhaust gas freed from impurities expands isentropically in the expander, after which it enters the condensation system as a refrigerant and is discharged from the installation. As heat exchangers in a condensation system, it is preferable to use plate-fin heat exchangers, the expander can be either volumetric type (preferably screw), or gas-dynamic type (preferably axial or radial-axial). The expander brake device may be selected of any type and is not limited to the present invention. Since a significant amount of methanol is contained in the exhaust gases from the oxidation of isopropylbenzene, it is not necessary to use desiccants to implement the proposed scheme.

The above and other aspects and advantages of the present invention are disclosed in the following detailed description given with reference to FIG. 1, which shows an installation for the purification of exhaust gases from the oxidation of isopropylbenzene.

The isopropylbenzene oxidation exhaust gas purification plant consists of heat exchangers, separators, as well as a volumetric or gas-dynamic type expander.

The waste gases of oxidation of isopropylbenzene stream (a) enter the preliminary heat exchanger 1, designed to condense the bulk of the water vapor, where it is cooled to a level of -5 ÷ -10 ° C. The resulting gas-liquid mixture by stream (b) enters the separator 2, where it is separated into a gas stream (c) and a liquid stream (d). The stream (g) enters the collector 6, the stream (c) enters the main heat exchanger 3, where it is cooled to a level of -40 ÷ -50 ° С. The resulting gas-liquid mixture stream (e) enters the separator 4, where it is separated into a gas stream (e) and a liquid stream (g). The stream (g) enters the collector 6, the stream (e) enters the expansion in the expander 5, where it is cooled to a level of -50 ÷ -60 ° C. The gas leaving the expander with a stream (h) enters as a coolant into the main heat exchanger 3, from where it flows into a preliminary heat exchanger 1 by a stream (s), and then is withdrawn from the installation by stream (k). The condensate collected in the collection 6 is sent to the oxidation stream (l) after appropriate preparation.

The following are specific examples illustrating the advantages of the present invention.

Example 1

The waste gas of oxidation of isopropylbenzene, arriving at a flow rate of 12,500 nm ³ / h, a pressure of 3 atm and a temperature of 15 ° C, has the following composition:

Nitrogen 93.67% vol. Oxygen 6% vol. Isopropylbenzene 4030 mg / m ³ Water 1528 mg / m ³ Methanol 131 mg / m ³ Other impurities 689 mg / m ³

Having passed the preliminary heat exchanger 1, gas with a temperature of -9 ° C enters the separator 2 to separate the condensate. The gas leaving the top of the separator 2 has the following composition:

Isopropylbenzene 723 mg / m ³ Water 243 mg / m ³ Methanol 85 mg / m ³

After the separator 2, the gas enters the main heat exchanger 3, where it is cooled to a temperature of -46 ° C and the separator 4. The gas leaving the top of the separator 4 has the following composition:

Isopropylbenzene 13 mg / m ³ Water 2 mg / m ³ Methanol 15 mg / m ³

After the separator 4, the gas enters the turboexpander 5, where it is cooled to a temperature of -60 ° C, after which refrigerators 3 and 1 pass successively as refrigerant and are discharged from the installation. A hydraulic brake is used as a brake device for a turboexpander. The condensate collected in separators 2 and 4 enters the collector 6, from where it enters the washing of recycled isopropylbenzene. The gas after purification contains isopropylbenzene in an amount of less than 50 mg / m ³ , the degree of extraction of isopropylbenzene is more than 99%.

Thus, a new, more efficient method for purifying exhaust gases from the oxidation of isopropylbenzene has been proposed.

The method allows to isolate isopropylbenzene with a good yield and low energy consumption.

Other specialists may be obvious to other embodiments of the invention, without changing its essence, as it is disclosed in the present description. Accordingly, the invention should be considered limited in scope only by the following claims.

Claims (1)

The method of purification of isopropylbenzene oxidation exhaust gas, characterized in that the extraction of isopropylbenzene is carried out using low-temperature condensation, and the isopropylbenzene oxidation exhaust gas energy is used to create low temperatures.

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