KR102218342B1 - Steam stripping inorganic process liquid discharged from hpo® extraction section and utilizing heat of condensation - Google Patents

Abstract

Passing the extracted aqueous phase comprising an organic solvent directly from the extraction zone to a water stripping zone; Evaporating at least 5% by weight of water present in the extracted aqueous phase; Passing the steam-containing stream through a heat exchanger; And heating the in-process liquid and condensing at least a portion of the steam-containing stream by transferring energy from the water vapor-containing stream to the in-process liquid, there is provided a continuous method for producing cyclohexanone oxime. .

Description

Steam stripping of inorganic process liquids discharged from the HPO extraction zone and use of condensation heat {STEAM STRIPPING INORGANIC PROCESS LIQUID DISCHARGED FROM HPO® EXTRACTION SECTION AND UTILIZING HEAT OF CONDENSATION}

The present invention relates to a method for producing a cyclohexanone oxime comprising the step of extracting the cyclohexanone oxime with an organic solvent in an extraction zone and passing the extracted aqueous phase through a combined stripping zone, wherein Water vapor, organic solvents, cyclohexanone and at least 5% by weight of the extracted aqueous phase are removed. The resulting steam containing stream is at least partially condensed and the energy released upon condensation is used to heat the liquid during the process.

The present invention also relates to a method for continuously producing caprolactam by Beckmann rearrangement of cyclohexanone oxime. The method of the present invention is not limited to any particular form of lactam. This lactam is preferably ε-caprolactam. This manufacturing method of caprolactam includes a method in which the intermediate is manufactured according to the so-called (modified) Raschig technology, the hydrogenation-based technology of nitric oxide, the ammoximation-based technology, and the HPO (registered trademark) technology. do.

However, for this, a source of cyclohexanone oxime is required. Several pathways exist for producing cyclohexanone oxime, including the reaction of cyclohexanone with a buffered hydroxylammonium phosphate solution in the presence of toluene (so-called HPO (registered trademark) technology), or cyclohexanone oxime is peroxidation. It is produced by the reaction of cyclohexanone and ammonia in the presence of hydrogen (so-called darkening technique).

An important use of the hydroxylammonium salt is the preparation of oxime from ketones or aldehydes, in particular the preparation of cyclohexanone oxime from cyclohexanone. For this oxime preparation method, a cyclic process is known in which an aqueous acid-buffered reaction medium is continuously circulated through the hydroxylammonium salt synthesis zone and the oxime synthesis zone. This reaction medium is acid-buffered, for example by phosphoric acid and/or sulfuric acid and buffer salts derived from these acids (eg alkali and/or ammonium salts). In the hydroxylammonium salt synthesis zone, nitrate ions or nitrogen oxides in the circulating inorganic liquid are converted to hydroxylamine together with hydrogen gas.

Fresh hydrogen is supplied to the hydroxylammonium salt synthesis zone and a small amount of gas is periodically purged from this system to maintain a constant hydrogen partial pressure. The purged gas includes an inert gas component that was present in the new hydrogen and nitrogen (N ₂ ) and nitrous oxide (N ₂ O), which are gas by-products generated.

The hydroxylamine reacts with the free buffering acid to produce the corresponding hydroxylammonium salt, which is subsequently transferred to the oxime synthesis zone, where it reacts with the ketone to produce the corresponding oxime, releasing the acid. After the oxime is separated from the reaction medium, the reaction medium is recycled to the hydroxylammonium salt synthesis zone, and fresh nitrate ions or nitric oxide are added to the reaction medium.

When the hydroxylammonium salt synthesis starts from a solution of phosphoric acid and nitrate, the chemical reaction described above is represented as follows:

Reaction 1) Preparation of hydroxylammonium in the hydroxylammonium salt synthesis zone:

_{2 H 3 PO 4 + NO 3} - + 3 H 2 → NH 3 OH + + 2 H 2 PO 4 - + 2 H 2 O

Reaction 2) Preparation of oxime in the oxime synthesis zone:

Reaction 3) HNO ₃ is supplied to compensate for the depletion of the nitrate ion source:

_{H 3 PO 4 + H 2 PO} 4 - + HNO 3 + 3 H 2 O → 2 H 3 PO 4 + NO 3 - + 3 H 2 O.

The first reaction is catalyzed heterogeneously. Preferably, the catalyst is present as a finely divided solid as the dispersed phase in the liquid reaction mixture.

The resulting mixture of the first reaction is an aqueous inorganic process liquid (IPL) comprising a suspension of solid catalyst particles in a hydroxylammonium salt solution.

As is evident from this reaction, the inorganic process liquid may contain neutral species, such as hydroxylamine or ammonia, which may also be protonated (eg, hydroxylammonium or ammonium). This means that, according to the invention, both hydroxylamine and hydroxylammonium can be read as hydroxylamine and/or hydroxylammonium, and ammonia and ammonium can be read as ammonia and/or ammonium.

Before the aqueous inorganic process liquid (IPL) is transferred to the oxime synthesis zone (reaction 2), the solid catalyst particles are preferably separated from the aqueous inorganic process liquid. After filtration, the inorganic process liquid is the hydroxylammonium salt solution filtrate.

Such a process includes the HPO (registered trademark) process of DSM (eg, HJ Damme, JT van Goolen and AH de Rooij, Cyclohexanone oxime made without by-product (NH ₄ ) ₂ SO ₄ , July 10, 1972, Chemical Engineering; pp 54/55 or see page 6/7 of the caprolactam chapter of Ullmann's Encyclopedia of Industrial Chemistry (2005)).

Although the production of hydroxylammonium has been known for decades, and methods of improving known manufacturing methods have been thoroughly studied for many years, the currently known industrial processes (which generally have continuous properties) still have drawbacks.

U.S. Patent No. 3,940,442 discloses a method for preparing a cyclohexanone oxime, wherein a hydroxylamine-rich solution from a hydroxylamine synthesis zone is supplied to a cyclohexanone oxime synthesis zone together with a cyclohexanone (in this case, The hydroxylamine and cyclohexanone react with each other to form a cyclohexanone oxime), the cyclohexanone oxime, and the unreacted cyclohexanone are separated from the solution and recycled to the hydroxylamine synthesis zone. Subsequently, the solution recycled from the cyclohexanone oxime synthesis zone to the hydroxylamine synthesis zone was removed from the cyclohexanone oxime produced in the cyclohexanone oxime synthesis zone, and then any remaining amounts of cyclohexanone and cyclones present in the solution. Stripping is performed for a time sufficient to allow the hexanone oxime to be substantially reduced to less than about 0.02% by weight. This prevents poisoning of the palladium catalyst by adding nitrate ions to the stripped solution recycled from the cyclohexanone oxime synthesis zone to the hydroxylamine synthesis zone after stripping of the recycled solution.

U.S. Patent No. 7,309,801 discloses that an aqueous medium containing a phosphate is passed from a hydroxylammonium synthesis zone to a cyclohexanone oxime synthesis zone, and cyclohexanone and cyclohexanone oxime are extracted from the aqueous medium, and then the aqueous medium is stripped. To the zone, from the cyclohexanone oxime synthesis zone to the stripping zone, and from the stripping zone back to the hydroxylammonium synthesis zone, passing the steam through the aqueous medium in the stripping zone, discharging the vapor stream from the stripping zone, and steam A process for preparing cyclohexanone oxime is disclosed, comprising condensing the stream to obtain a condensed aqueous fluid and washing the organic product with the condensed aqueous fluid.

U.S. Patent No. 7,408,081 discloses an aqueous medium containing phosphate from a hydroxylammonium synthesis zone to a cyclohexanone oxime synthesis zone, a cyclohexanone oxime synthesis zone to a stripping zone, and a stripping zone back to a hydroxylammonium synthesis zone. Passing through, and in the stripping zone, a method for producing a cyclohexanone oxime is disclosed, comprising stripping the aqueous medium with steam and performing such stripping at a pressure higher than 0.11 MPa. The resulting vapor stream can be withdrawn from the stripping zone and the heat of the vapor stream can be exchanged for a process liquid. This extraction can be carried out by contacting the aqueous medium with any suitable solvent.

In the method of U.S. Patent No. 7,408,081, after the aqueous medium containing the phosphate stream is discharged from the cyclohexanone oxime synthesis zone and after extraction of the cyclohexanone and cyclohexanone oxime from the aqueous medium with an organic solvent, a significant amount Was observed to contain an organic solvent. These organic solvents exist not only in dissolved form, but also as incorporated and finely dispersed organic droplets. From U.S. Patent No. 7,408,081, it is evident that the organic solvent is removed from the aqueous medium before the aqueous medium is fed into the stripping zone for removal of cyclohexanone and cyclohexanone oxime, but U.S. Patent No. 7,408,081 How the removal is performed is not described.

The prior art process is still not very economical due to the high investment cost required for all separation units and the very variable cost due to the additional energy consumption in the whole process.

It is also an object of the present invention to provide an improved method while maintaining a target hydroxylammonium production rate compared to a conventional method operated in the same production facility. This is a more environmentally friendly method and will have the advantage of being a cheaper method compared to conventional methods operated in the same production facility.

Surprisingly, since the process according to the invention requires less equipment and less energy, the removal of the solvent from the aqueous medium and the removal of cyclohexanone and cyclohexanone oxime from the aqueous medium in one single stripping zone It has been found that by combining, the cost can be reduced. The advantage is that the present invention does not require a separate liquid-liquid phase separation zone or organic solvent stripping zone.

1 shows a comparative embodiment derivable by the method of the prior art comprising an organic solvent stripper and a liquid-liquid phase separator.
Figure 2 shows an embodiment of the invention that does not require an organic solvent stripper or liquid-liquid phase separator.

Thus, according to the present invention, there is provided a method for the continuous production of cyclohexanone oxime comprising the following steps:

(I) preparing an aqueous hydroxylammonium solution by catalytically reducing nitrate or nitrogen oxide with hydrogen in the hydroxylammonium synthesis zone;

(II) in a cyclohexanone oxime synthesis zone, reacting the hydroxylammonium from step (I) with cyclohexanone to provide an aqueous phase and a first organic phase, thereby preparing a cyclohexanone oxime;

(III) passing the aqueous phase resulting from step (II), comprising water, salt, organic solvent, cyclohexanone oxime and cyclohexanone, through an extraction zone;

(IV) extracting cyclohexanone oxime and cyclohexanone with an organic solvent in the extraction zone to provide an extracted aqueous phase and a second organic phase;

(V) passing at least a portion of the second organic phase produced in step (IV) again through the cyclohexanone oxime synthesis zone of step (II);

(VI) passing the extracted aqueous phase produced in step (IV) through a water stripping zone;

(VII) evaporating at least 5% by weight of water present in the extracted aqueous phase in the water stripping zone to provide a stripped aqueous phase and a steam containing stream;

(VIII) passing the steam-containing stream produced in step (VII) through a heat exchanger;

(IX) in the heat exchanger, transferring the energy of the steam-containing stream to the in-process liquid to heat the in-process liquid; And

(X) recycling at least a portion of the stripped aqueous phase obtained in step (VII) to step (I).

The present invention also,

(I) in the hydroxylammonium synthesis zone, preparing an aqueous hydroxylammonium solution by catalytic reduction of nitrate or nitrogen oxide with hydrogen;

(II) in a cyclohexanone oxime synthesis zone, reacting the hydroxylammonium from step (I) with cyclohexanone to provide an aqueous phase and a first organic phase, thereby preparing a cyclohexanone oxime;

(III) passing the aqueous phase resulting from step (II), comprising water, salt, organic solvent, cyclohexanone oxime and cyclohexanone, through an extraction zone;

(IV) extracting cyclohexanone oxime and cyclohexanone with an organic solvent in the extraction zone to provide an extracted aqueous phase and a second organic phase;

(V) passing at least a portion of the second organic phase produced in step (IV) again through the cyclohexanone oxime synthesis zone of step (II);

(VI) passing the extracted aqueous phase produced in step (IV) through a water stripping zone;

(VII) evaporating at least 5% by weight of water present in the extracted aqueous phase in the water stripping zone to provide a stripped aqueous phase and a steam containing stream;

(VIII) passing the steam-containing stream produced in step (VII) through a heat exchanger;

(IX) in the heat exchanger, transferring the energy of the steam-containing stream to the in-process liquid to heat the in-process liquid; And

(X) recycling at least a portion of the stripped aqueous phase obtained in step (VII) to step (I).

Provides a continuous method for producing a cyclohexanone oxime comprising a, wherein

(a) the first organic phase produced in step (II) contains more than 25% by weight of cyclohexanone oxime;

(b) the extracted aqueous phase resulting from step (IV) also comprises an organic solvent;

(c) At least a portion of the steam containing stream is condensed during the energy transfer in step (IX) above.

"At least some" herein is defined as more than 50% by weight, more preferably more than 75% by weight, and most preferably more than 85% by weight.

Thus, the method of the present invention does not require a separate liquid-liquid phase separation zone.

Thus, the method of the invention does not require an organic solvent stripping zone between step (IV) and step (VI).

In the method of the present invention, any suitable organic solvent in which cyclohexanone and cyclohexanone oxime can be dissolved can be used. Preferably, the organic solvent is selected from the group consisting of benzene, toluene, xylene, methylcyclopentane, cyclohexane and mixtures thereof. Most preferably, the organic solvent is toluene.

For example, organic solvents are used in the oximation zone and extraction zone. The extraction zone may comprise one or more extraction devices, such as a (pulsed) packed column, a rotary disk column and/or a mixer-settler. The extraction zone preferably comprises a countercurrent operation type pulse packed extraction column in which cyclohexanone and cyclohexanone oxime are recovered from the inorganic process liquid.

The inorganic process liquid (the extracted aqueous phase from step (IV) above) discharged from the extraction zone may contain a small amount of cyclohexanone and cyclohexanone oxime, saturated with an organic solvent, and the mixed organic solvent droplets It may contain.

Preferably, the weight fraction of organic solvent in the water vapor containing stream may be at least three times greater than the weight fraction of organic solvent in the extracted aqueous phase.

Preferably, the weight fraction of cyclohexanone in the steam-containing stream ranges from 0.01° to 2% by weight.

Preferably, the content of the organic solvent in the extracted aqueous phase obtained in step (IV) is in the range of 100 to 2000 ppm by weight. This is surprising because it means that low levels of organic solvents can be present without harming the process of the invention.

Preferably, the extracted aqueous phase of step (IV) is preheated prior to passing through the water stripping zone. Preheating is carried out by transferring heat from the stripped aqueous phase obtained in step (VII), prior to reusing at least a portion of the aqueous phase stripped in step (I), or alternatively, preheating is carried out in the step (IX ) By transferring energy from the steam containing stream.

The inorganic process liquid is supplied as it is to the water stripping zone, where steam is used as a stripping agent. The stripping zone may contain more than one water stripper. Preferably, a single water stripper is used which provides a long residence time in the extracted aqueous phase.

The water stripper is equipped with a reboiler using externally supplied high-pressure steam as an energy source. This high-pressure steam heats the liquid inside the column in the reboiler to convert it into steam, and the steam rises through the column. This is known as steam stripping. Due to this heat input, a fraction of the extracted aqueous phase, at least 5% by weight, more preferably 7-20% by weight, will be evaporated as a steam containing stream, which will strip (nearly all) organic solvents and cyclohexanone. . Cyclohexanone oxime has a too high boiling point and will not be stripped. However, cyclohexanone oxime is not stable at these temperatures and will decompose into cyclohexanone (and hyam).

The energy required to evaporate more than 5% by weight of water in step (VII) may be introduced through an internal or external reboiler by using an external energy source. The external energy source may be a superatmospheric steam containing stream.

The energy content of the water vapor-containing stream (additionally comprising some organic components such as organic solvents and cyclohexanone) is at least partially recovered. Water vapor condenses at least partially after leaving the water stripper in the heat exchanger. In addition, the organic matter in the water vapor is also recovered and reused in the method of the present invention. Preferably, both the organic solvent and cyclohexanone present in the condensate obtained in step c) are at least partially reused in the cyclohexanone oxime preparation method.

The energy released upon condensation of the steam containing stream is used to heat the liquid in the process, for example through the use of heat exchangers.

The heat exchanger is a reboil of a distillation column (e.g., a distillation column in which cyclohexanone oxime is separated from an organic product containing cyclohexanone and an organic solvent), or a crystallizer (e.g., water from an ammonium sulfate solution). A heat exchanger of a crystallizer that evaporates to perform crystallization of ammonium sulfate crystals; And an organic fluid introduction extraction column.

Examples thereof include driving reboiling of an oxime distillation column; Transfer heat in the heat exchanger of the ammonium sulfate crystallizer; Transferring heat to drive the reboiler of the condenser of the aqueous ammonium sulfate solution; Heating the organic fluid introduced into the extraction column; Or the released energy used to transfer heat to heat a non-process liquid (eg, water) or to generate steam (low pressure).

The steam stream can also be used as a stripping agent in the wastewater stripper in the cyclohexanone oxime wash zone.

According to the invention, there is also provided a process for producing caprolactam, comprising the process of the invention. In another embodiment of the invention, caprolactam obtained from the process according to the invention is also provided.

Fig. 1

A comparative embodiment derivable from the process of the prior art comprising a continuous purification and condensation zone of an inorganic process liquid (IPL) is schematically shown in FIG. 1.

The aqueous fluid containing water, salt, organic solvent, cyclohexanone oxime and cyclohexanone, discharged from the oximation zone (not shown in Fig. 1), is fed to the top of the extraction zone [E] via line [1]. And the organic solvent is introduced to the bottom of the extraction zone [E] via line [4]. In the extraction zone [E], the cyclohexanone and cyclohexanone oxime (dissolved and/or incorporated) present in the aqueous phase are recovered with the organic solvent via extraction. The extracted aqueous fluid obtained is discharged through line [3]. The obtained second organic phase comprising the organic solvent, cyclohexanone oxime and cyclohexanone is discharged via line [2], and is preferably reused in the cyclohexanone oxime synthesis zone (not shown in Fig. 1). The extracted aqueous phase obtained from the bottom of the extraction zone [E] is fed to the liquid-liquid phase separator [P] via line [3]. The extracted aqueous phase so obtained contains some cyclohexanone oxime and cyclohexanone and at least 100 ppm of organic solvent (dissolved and/or incorporated). In separator [P] an aqueous phase and an organic phase are formed. This organic phase exits the liquid-liquid phase separator [P] via line [5]. The aqueous phase (with some dissolved organic phase) of the liquid-liquid separator [P] is fed via line [7] to the organic solvent stripper [T]. Stripping in the organic solvent stripper [T] is carried out by introducing water vapor into the lower section of the organic solvent stripper [T] via line [8]. The vapor produced in the organic solvent stripper [T] contains water and an organic solvent. This vapor is discharged from the top of the organic solvent stripper [T] via line [6], condensed and then directed to the liquid-liquid separator [P]. The aqueous bottom fluid of the obtained, organic solvent stripper [T] is (almost) free of organic solvent, is discharged through line [9], and is fed to the top of the water stripping zone [W]. In this water stripping zone [W], at least 5% by weight of water is removed through evaporation. In addition, cyclohexanone is removed through stripping, and cyclohexanone oxime is decomposed into cyclohexanone.

The thickening of the organic solvent stripped aqueous fluid in the water stripping zone [W] is by creating water vapor at the bottom of the water stripping zone [W] due to partial evaporation of the water (which exists in the liquid phase) and/or water. This is done by introducing water vapor into the lower section of the stripping zone [W] (line not shown in Fig. 1).

Steam production during this process is carried out by partially evaporating the contents of the water stripping zone in a reboil (not shown in FIG. 1) (internal or external) by using an external energy source. The water vapor produced in the water stripping zone [W] contains water, and the cyclohexanone is discharged from the top of the water stripping zone [W] via line [10]. After condensation of the vapor fluid, cyclohexanone is recovered (not shown in FIG. 1). The condensed aqueous fluid exits the water stripping zone [W] via line [11].

Figure 2

One embodiment of the present invention comprising an IPL continuous purification and condensation zone is schematically illustrated in FIG. 2.

An aqueous fluid containing water, salt, organic solvent, cyclohexanone oxime and cyclohexanone discharged from the cyclohexanone oxime synthesis zone (steps (I) and II)) (not shown in FIG. 2) is in line [1 ] To the top of the extraction zone [E] (step (III)), and the organic solvent is introduced to the bottom of the extraction zone [E] via line [4]. In the extraction zone [E], the cyclohexanone and cyclohexanone oxime (dissolved and/or incorporated) present in the aqueous phase are recovered via extraction with an organic solvent (step (IV)). The obtained second organic phase comprising the organic solvent, cyclohexanone oxime and cyclohexanone is discharged via line [2] and is at least partially reused in the cyclohexanone oxime synthesis zone (step (V)) (Fig. 2 Not shown). The obtained extracted aqueous phase is discharged from the bottom of the extraction zone [E] via line [3] and fed to the top of the water stripping zone [W] (step (VI)). The extracted aqueous phase so obtained contains some cyclohexanone oxime and cyclohexanone and at least 100 ppm of organic solvent (dissolved and/or incorporated). In this water stripping zone [W], at least 5% by weight of water is removed via evaporation (step (VII)). In addition, cyclohexanone is removed through stripping, and cyclohexanone oxime is decomposed into cyclohexanone.

The thickening of the aqueous fluid in the water stripping zone [W] is by creating water vapor at the bottom of the water stripping zone [W] due to partial evaporation of the water (which exists in the liquid phase), or by the water stripping zone [W] (the line is Not shown) by introducing water vapor into the lower zone.

Steam production during this process is carried out by partially evaporating the contents of the water stripping zone in a reboil (not shown in FIG. 2) (internal or external) by using an external energy source. The steam-containing stream produced in the water stripping zone [W] contains water and cyclohexanone and exits from the top of the water stripping zone [W] via line [10]. This steam-containing stream is fed to several heat exchangers (not shown in FIG. 2) to condense most of the vapor by heating the various in-process liquids (steps (VIII) and (IX)). After condensation of the vapor fluid, cyclohexanone and organic solvent are recovered (not shown in Fig. 2). The condensed aqueous fluid (nearly) free of organic solvent is discharged from the water stripping zone [W] via line [11] and can be recycled to step (I) (step (X)) (not shown in FIG. 2) .

As shown in Fig. 2, there is no need for a separate organic solvent stripper and/or liquid-liquid phase separator to exist between the extraction zone [E] and the water stripping zone [W]. This simplifies the process and reduces the investment required, without affecting the quality of the final product.

The present invention is further illustrated by the following examples, but is not limited to these examples.

Example

This example is carried out in a commercially available HPO (registered trademark) plant for the production of cyclohexanone oxime operated in continuous mode.

In this plant, the nitrate was catalytically hydrogenated with hydroxylammonium in the hydroxylammonium reactor [hydroxyammonium synthesis zone of step (I)].

The obtained aqueous hydroxylammonium solution was filtered and fed together with toluene and fresh cyclohexanone to an oximation reactor (cyclohexanone oxime synthesis zone), where cyclohexanone oxime was produced (step (II)). The first organic phase (which contains about 42% by weight of cyclohexanone oxime, the remainder being mainly toluene) from this oximation reactor was further separated and purified to nearly pure cyclohexanone oxime. This separation and purification included removal of toluene by two-stage distillation. The reboiling of the first stage of this distillation was driven using a steam containing stream originating from the top of the stripping column, whereby most of the water vapor was condensed.

The aqueous phase containing dissolved salts (including ammonium phosphate and ammonium nitrate), toluene, cyclohexanone and cyclohexanone oxime is discharged from the oxime reactor, and the extraction column operated in a countercurrent manner [Extraction zone of step (III) Was supplied to the upper section of the ]. In the lower section of this column, almost pure toluene was fed for extraction (step (IV)). From the upper section of this extraction column, a second organic phase comprising toluene, cyclohexanone and cyclohexanone oxime was discharged and fed to the oximetization reactor (step (V)).

From the lower section of the extraction column, an extracted aqueous phase comprising about 60% by weight of water, dissolved salts (e.g., ammonium phosphate and ammonium nitrate), about 1800 ppm by weight of toluene, as well as cyclohexanone and cyclohexanone oxime. Was discharged. The aqueous phase was heated in a heat exchanger by condensing some of the water vapor present at the top of the steam stripping column. The aqueous phase thus preheated was fed to the upper section of a steam stripper column [(water stripping zone of step (VI)]) In this steam stripper column, about 1/3 of the weight of water present in the aqueous feed was evaporated ( Step (VII)).

The energy required for evaporation was introduced by a steam-driven external reboiler. The steam supplied to the reboiler is supplied from a low pressure steam grid. As a result of steam stripping, a steam containing stream containing about 9000 ppm by weight of toluene and about 0.04% by weight of cyclohexanone was present at the top of the steam stripper column. This steam-containing stream was fed to several heat exchangers to heat the various in-process liquids (steps (VIII) and (IX)) to condense most of the vapors. The heated in-process liquid included an aqueous stream fed to a steam stripping column, and a cyclohexanone oxime containing phase in the first stage of cyclohexanone oxime distillation. The stripped aqueous phase exiting the lower section of the steam stripping column was recycled to the hydroxylammonium reactor (step (X)).

Claims (15)

As a continuous production method of cyclohexanone oxime,
(I) preparing an aqueous hydroxylammonium solution by catalytically reducing nitrate or nitrogen oxide with hydrogen in the hydroxylammonium synthesis zone;
(II) in a cyclohexanone oxime synthesis zone, reacting the hydroxylammonium from step (I) with cyclohexanone to provide an aqueous phase and a first organic phase, thereby preparing a cyclohexanone oxime;
(III) passing the aqueous phase resulting from step (II), comprising water, salt, organic solvent, cyclohexanone oxime and cyclohexanone, through an extraction zone;
(IV) extracting cyclohexanone oxime and cyclohexanone with an organic solvent in the extraction zone to provide an extracted aqueous phase and a second organic phase;
(V) passing at least a portion of the second organic phase produced in step (IV) again through the cyclohexanone oxime synthesis zone of step (II);
(VI) passing the extracted aqueous phase produced in step (IV) through a water stripping zone;
(VII) evaporating at least 5% by weight of water present in the extracted aqueous phase in the water stripping zone to provide a stripped aqueous phase and a steam containing stream;
(VIII) passing the steam-containing stream produced in step (VII) through a heat exchanger;
(IX) heating the in-process liquid by condensing at least a portion of the steam-containing stream by transferring energy of the steam-containing stream to an in-process liquid in the heat exchanger, Wherein both the organic solvent and the cyclohexanone present in the condensate are at least partially reused in the method for continuously preparing the cyclohexanone oxime; And
(X) recycling at least a portion of the stripped aqueous phase obtained in step (VII) to step (I).
Containing, method. The method of claim 1,
(a) the first organic phase produced in step (II) contains more than 25% by weight of cyclohexanone oxime;
(b) the extracted aqueous phase produced in step (IV) also comprises an organic solvent. The method of claim 1,
The method, wherein the weight fraction of organic solvent in the water vapor containing stream is at least three times greater than the weight fraction of organic solvent in the extracted aqueous phase. The method of claim 1,
The method, wherein the weight fraction of cyclohexanone in the steam-containing stream ranges from 0.01 to 2% by weight. The method of claim 1,
The method, wherein the content of the organic solvent in the extracted aqueous phase obtained in step (IV) is in the range of 100 to 2000 ppm by weight. The method according to any one of claims 1 to 5,
The method, wherein the organic solvent is selected from the group consisting of benzene, toluene, xylene, methylcyclopentane, cyclohexane and mixtures thereof. The method of claim 1,
Wherein the heat exchanger comprises a reboiler of a distillation column, an ammonium sulfate crystallizer and/or an organic fluid introduction extraction column. The method of claim 1,
The method, wherein the aqueous phase extracted in step (IV) is preheated prior to passing through the water stripping zone. The method of claim 8,
The method, wherein the preheating is carried out by transferring the heat from the stripped aqueous phase obtained in step (VII) prior to reuse in step (I). The method of claim 8,
The method, wherein the preheating is carried out in step (IX) by energy transfer from the steam containing stream. The method of claim 1,
The method, wherein the energy required to evaporate at least 5% by weight of water in step (VII) is introduced via internal or external reboiler by using an external energy source. The method of claim 11,
Wherein the external energy source is a stream containing superatmospheric water vapor. A method for producing caprolactam comprising the method according to claim 1. delete delete

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