WO2014096774A1

WO2014096774A1 - Process for the recovery of aniline

Info

Publication number: WO2014096774A1
Application number: PCT/GB2013/053194
Authority: WO
Inventors: Carlos Grande
Original assignee: Sinvent As; De Bresser, Sara
Priority date: 2012-12-17
Filing date: 2013-12-03
Publication date: 2014-06-26
Also published as: GB201222737D0

Abstract

The present invention provides a process for the recovery of aniline or an aniline derivative from a fluid said process comprising: (i) contacting a feed stream having an aniline or aniline derivative concentration of C₁, with an adsorbent material at temperature, T₁, such that aniline or aniline derivative is adsorbed by the adsorbent material; (ii) subjecting the adsorbent material to a temperature, T₂, which is higher than T₁, such that adsorbed aniline or aniline derivative is released to yield an aniline-rich or aniline derivative-rich exit stream having an aniline or aniline derivative concentration of C₂, where C₂ is greater than C₁; and (iii) retaining the aniline-rich or aniline derivative-rich exit stream for recycling or further processing.

Description

Process for the recovery of aniline

The present invention relates to processes and apparatus for the separation and/or recovery of aniline and/or aniline derivatives from fluids containing them. In particular, it relates to the recovery of aniline from aniline/water mixtures.

Aniline is one of the important monomers in the polymer industry. In 2009 its production was 4x10⁶ tons per year worldwide with a growing rate of 5-6% per year. Aniline is feedstock for the preparation of a wide range of chemicals, particularly methylene diphenylene isocyanate, which is employed in fabrication of

polyurethanes.

The most common route for the production of aniline is the hydrogenation of nitrobenzene, for which a variety of gas and liquid phase technologies are known. The hydrogenation of nitrobenzene achieves very high conversion, with essentially only aniline and water exiting the reactor (together with some unconverted hydrogen). In a typical industrial process, the aniline/water stream exiting the reactor enters a cooler that acts as a first decanter. This is known as a "dewatering step" because a water-rich phase is separated from the aniline/water stream. In fact, because the solubility of aniline is a function of temperature, and two phases are formed at ambient temperature, two phases are formed in the decanter. One is an aniline-rich phase where the content of water is about 5% (denser phase) and the other is a water-rich phase containing around 3.6% aniline (this being the upper solubility limit of aniline in water around ambient temperature).

The aniline-rich and water-rich phases are separated in the cooler/decanter and proceed to different distillation towers. Due to the stringent regulations existing regarding discharge of aniline, the level of aniline in the water-rich stream should be reduced from around 3.6% to the ppm level (e.g. 30-100 ppm depending on the relevant regulations). This removal of aniline from the water-rich phase is currently carried out by distillation, which involves evaporating the water (which constitutes 96.4% of the phase) and thus significantly increases the energy consumption of the aniline production process. There thus exists a need for alternative means for the removal of aniline from aqueous solutions, particularly methods which enable the recovered aniline to be retained for future use.

Adsorption technology has been mentioned in the literature as a way of removing aniline from waste-waters. In such waste-waters the concentration of aniline rarely exceeds the ppm level and never approaches the saturation limit (-3.6% aniline at ambient temperature expressed as %w/v). In such applications, most of the literature reports the use of activated carbon or other cheap adsorbents in order to avoid the necessity of any adsorbent regeneration. As the aim of these technologies is to produce purified water, the aniline which has been removed from the solution is often intentionally destroyed by heating.

The applicant has now surprisingly found that adsorption, more specifically temperature swing adsorption (TSA), can be used to remove and/or recover aniline or derivatives of aniline from aqueous solutions, even from feed streams approaching 3.6% (w/v) aniline at ambient temperature. The process of the invention can be used to produce purified water but its main aim is to concentrate and recover aniline (or an aniline derivative).

When a temperature swing adsorption process is employed for the separation of liquid mixtures, it is also known as thermal parametric pumping (TPP). Despite being developed several decades ago, TSA/TPP does not yet have an industrial application, mostly due to high costs associated with regeneration of the adsorbent. TSA involves adsorption of a target material onto an adsorbent at one temperature, followed by release of the target material from the adsorbent, and thus regeneration of the adsorbent, at a different temperature.

Viewed from a first aspect, the present invention provides a process for the separation and/or recovery of aniline or an aniline derivative from a fluid, said process comprising:

(i) contacting a feed stream comprising aniline or an aniline derivative with an adsorbent material at a temperature, T such that the aniline or aniline derivative is adsorbed by the adsorbent material; and (ii) subjecting the adsorbent material to a temperature, T₂, which is higher than T_u such that at least a part of the adsorbed aniline or aniline derivative is released to yield an exit stream containing the aniline or aniline derivative.

In a preferred embodiment, step (ii) of the process includes the further step of lowering the temperature of the adsorbent material to T_u e.g. to permit reuse of the adsorbent material.

Preferably the process is for the recovery and enrichment of aniline (or an aniline derivative) from the feed stream, in which case the exit stream is enriched in aniline or an aniline derivative, i.e. this has an aniline (or aniline derivative) concentration which is greater than that of the feed stream. In one embodiment, the process includes a step (iii) in which the exit stream is retained, e.g. for recycling or further processing.

The invention is described herein primarily in the context of the separation and/or recovery of aniline. As will be appreciated, however, it extends to aniline derivatives.

Thus, in one embodiment the present invention provides a process for the recovery of aniline from a fluid, e.g. the enrichment of aniline in an aqueous solution, said process comprising:

(i) contacting a feed stream having an aniline concentration of d , with an adsorbent material at temperature, T_u such that aniline is adsorbed by the adsorbent material,

(ii) subjecting the adsorbent material to a temperature, T₂, which is higher than T such that adsorbed aniline is released to yield an aniline-rich exit stream having an aniline concentration of C₂, where C₂ is greater than Ci , and

(iii) retaining the aniline-rich exit stream for recycling or further processing.

The feed stream and/or the exit stream is preferably a liquid, e.g. a mixture of one or more liquids with aniline, particularly preferably a solution comprising aniline.

Especially preferably both the feed stream and also the exit stream is an aqueous solution of aniline. As will be appreciated by the skilled person, the term "aqueous solution" in this regard is used to denote a mixture of aniline (or an aniline derivative) with water and optionally other components. It is known from thermodynamic solubility data that a mixture of aniline and water may exist as a single phase or as two phases depending on the concentration of these components and other conditions, e.g. temperature. Reference to the "concentration" of aniline (or aniline derivative) in the feed and/or exit stream is to be construed accordingly, i.e. to the total amount of aniline in the mixture, whether the mixture is a single phase or not. For example, the aniline-rich exit stream comprises the material released when the adsorbent is regenerated and any fluid used to flush this material from the adsorbent. This stream will not necessarily be monophasic.

Not all adsorbed aniline is necessarily released from the adsorbent material during the desorption step (ii). For example, only a portion of the adsorbed aniline may be released, e.g. 50 to 100%, preferably 70 to 90%, more especially around 80% of the adsorbed aniline is released in step (ii). Preferably, at least 60% of the adsorbed aniline is released in step (ii), more preferably at least 75%, especially at least 85%.

Typical concentrations, d , of aniline (expressed as a mass concentration of aniline) in the feed stream depend on the solubility limit, which is dependent on temperature, however typical values are 1 g/100ml to 20g/100ml (i.e. close to the saturation point of aniline in water at high temperatures such as 423 K), especially preferably

1 .5g/100 ml to 8.0g/100ml or 2.0 to 4.5g/100ml, particularly preferably 2.4g/100ml to 3.6g/100ml (e.g. at ambient temperature), e.g. around 3.4g/100ml (e.g. at ambient temperature).

Typical concentrations of aniline, C₂, in the exit stream are at least 1 .1 times greater than in the feed stream. Preferably the concentration of aniline, C₂, in the exit stream is at least 1 .5 times greater than in the feed stream, especially at least 2, 2.5, 3 or 4 times greater. C₂ is typically up to 10 times greater than Ci , e.g. up to 8, 6, 5 or 4 times greater than Ci . In one embodiment, C₂ is between 2 and 6 times greater than Ci , e.g. between 3 and 5 times greater, e.g. around 4 times greater. Thus, for example, the concentration of aniline, C₂, in the aniline-rich exit stream may be from 3.6g/100ml to 80g/100ml, preferably 4.0g/100 ml to 32g/ml or 6.0g/100ml to

18g/100ml, particularly preferably 12.0g/100ml to 14.4g/100ml, e.g. between

3.6g/100ml and 18g/100ml, preferably around 13.6g/100ml. Ti may be referred to as the "adsorption temperature" and T₂ as the "regeneration temperature" or "desorption temperature". Suitable temperatures may be based on adsorption equilibrium and kinetic data. However, T₂ is higher than T Typically, T₂ is at least about 1 0K higher than J e.g. at least about 20, 30, 40 or 45K higher than T Especially preferably, T₂ is between 10 and 100K higher than T e.g. between 20 and 60K higher or between 40 and 45K higher. Suitable temperatures depend on the nature of the adsorbent material, but are typically in the range of 273 to 378K for T preferably 298 to 323K; and 303K to 473K for T₂, preferably 323 to 373K. In a preferred aspect, the regeneration temperature of the adsorbent (i.e. T₂) is less than 100 °C (373 K). This reduces the energy consumption of the overall process, leading to cost benefits.

The adsorption of aniline into the adsorbent material typically takes place in a column (or other suitable means) containing the adsorbent material. Regeneration in this case takes place by the released aniline being flushed from the column.

During the adsorption step, aniline is selectively adsorbed from the feed stream by the adsorbent material. This leaves the feed stream depleted in aniline, in comparison to its original state. The thus aniline-depleted stream can be viewed as a purified stream (e.g. purified water, in the case of an aqueous aniline solution being originally treated). The aniline-depleted/purified water stream can be retained for further use. Depending on its aniline content, it may be discharged. If its aniline content prohibits discharge, or it is desired to purify the stream further, it may be further processed to separate the aniline and water, e.g. by subjecting it to a further adsorption step, either by recycling to the initial adsorption step of the process or by subjecting it to a further adsorption column. Part of the aniline-depleted stream may also conveniently be used in the regeneration/desorption step, e.g. to flush released aniline from the adsorbent. The aniline-depleted stream preferably has a

concentration of aniline of less than 0.1 g/1 00 ml, especially preferably less than 0.05g/100 ml, particularly preferably less than 0.02g/100ml, e.g. around 100 ppm.

The temperature change between the adsorption of aniline onto the adsorbent and the release of aniline from the adsorbent 0Ί to T₂) can be effected by any suitable means. For example, the temperature of the stream that is contacted with the adsorbent material (e.g. the feed stream which enters the column for the adsorption step) can be adjusted before or during contact with the adsorbent, or contact may occur at ambient temperature. Additionally or alternatively, the temperature of the adsorbent material (rather than that of the stream) may be adjusted.

In all aspects, temperature adjustment may be direct and/or indirect. The

temperature of the adsorbent can be adjusted by any suitable means, e.g. by using a stream of water which has either direct or indirect contact with the adsorbent, or by using solar energy, microwaves, electric current, etc. Particularly preferably the temperature of the adsorbent is adjusted, e.g. raised from to T₂ or lowered from T₂ to T_{1 5} by passing a stream of liquid, e.g. a polar liquid (preferably a low-boiling point polar liquid that can easily be separated from aniline) such as aliphatic amines, alkanols, ethers, water or mixtures thereof, preferably water, past the adsorbent. This may be effected in co-current or counter-current fashion, preferably counter- current to the direction of the feed stream flow. For efficiency and convenience, the stream used for this step can be taken from the purified stream, i.e. the aniline- depleted stream, that is formed after removal of aniline from the feed stream (due to the aniline being adsorbed on the adsorbent). In the case of the

desorption/regeneration step, use of a stream of liquid has the added advantage that the stream flushes the released aniline from the adsorbent material.

Although water is purified in the process of the invention, the main aim is to recover aniline. For this reason, and unlike most TSA applications, the temperature control (e.g. heating) of the adsorbent for the regeneration step is particularly preferably carried out by indirect heating or a combination of direct and indirect heating, thus reducing the volume of the streams coming from the regeneration steps and therefore increasing the concentration of aniline in the exit stream (in comparison to the exit stream obtained with direct heating, e.g. where liquid contacts the adsorbent and thus dilutes the aniline-rich stream).

The temperature of the adsorbent may therefore be set by passing a stream of water over the adsorbent (i.e. direct temperature control as described above), or, more preferably, by use of heat exchangers (e.g. integrated into the adsorption column) to control the temperature of the adsorbent (i.e. indirect temperature control). The liquids and other temperature-control means mentioned above may also be applied to this indirect heating. Thus, the temperature change from to T₂ and/or T₂ to may be effected by direct heating/cooling and/or indirect heating/cooling.

As previously mentioned, a widely recognised disadvantage of TSA is the high adsorbent-regeneration costs. However, when used in conjunction with a process such as the production of aniline, the process of the present invention can utilise heat from the aniline production process in the regeneration of the adsorbent. Aniline production processes typically involve an excess of low-grade heat (e.g. in the form of hot water), and thus use of TSA can reduce the energy cost of the separation (by using the hot water as a cheap and readily available heat source) and also avoid waste of the heat. The present invention therefore allows for the replacement of an energy intensive separation step (i.e. the distillation steps currently used industrially) with a low-cost alternative. Thus, in a preferred aspect, the process of the invention involves the use of heat (e.g. in the form of hot water) from the aniline production process in the regeneration of the adsorbent. As mentioned above, this heating may be direct or indirect.

After release of aniline from the adsorbent material, the adsorbent is preferably cooled such that it is suitable for a further adsorption step. This cooling can be carried out by merely stopping the heating process and allowing the adsorbent to cool to ambient temperature, but the cooling is preferably assisted using the temperature-control means described herein, e.g. by contact with water directly and/or with the use of a heat exchanger. Preferably, the cooling of the adsorbent is effected in a direct or indirect fashion by use of fluid from the aniline production or purification process that is at or around T especially by use of the aniline-depleted stream generated during the adsorption step (i).

The aniline that is released when the adsorbent is regenerated, e.g. the stream exiting the column after the adsorbent is heated, is typically present in an aniline-rich stream (i.e. a stream which is aniline-rich compared to the original feed stream). The overall concentration of aniline in this aniline-rich stream may be greater than the saturation point of aniline in water (e.g. 3.6g/100ml at ambient temperature). This stream can have two phases (i.e. an aniline-rich and water-rich phase respectively) and can be further processed to recover further aniline. The formation of phases depends on the temperature used for regeneration and on the amount of liquid employed to flush (purge) the aniline from the adsorbent. If necessary, the phases can be separated prior to further processing, e.g. by decanting or centrifugation, preferably decanting, to separate the water-rich and aniline-rich phases. The water- rich phase can then be subjected to further contact with the adsorbent (i.e. it is recycled to the feed stream) according to the process of the invention for recovery of the aniline. Alternatively, or additionally, it may be distilled. The aniline-rich phase may be processed in the conventional manner, e.g. by distillation to remove water. These steps for further processing of the exit stream form preferred aspects of the process of the invention.

The enrichment factor of the temperature swing adsorption processes of the invention is typically around 4. Thus, an aqueous feed stream at the upper solubility limit of aniline in water at ambient temperature (3.6g/100ml) may produce an exit stream with a concentration of 14.4g/100ml. Streams of this sort have been observed in the laboratory (with a small flowrate and fast cooling down) to separate into two phases immediately. In a large production plant with isolated tubes, only one phase may exit the process. This exit stream will typically be at higher temperature than laboratory conditions and can be recycled to a "dewatering step" where it is cooled down to ambient temperature and the two phases are separated. The water-rich stream exiting the dewatering step may be recycled to the feed of the TSA, e.g. as described above.

As noted above, the feed stream for the process of the invention is a fluid, typically a liquid, especially a mixture of one or more liquids with aniline, particularly preferably a solution comprising aniline, especially preferably an aqueous solution of aniline. Most preferably, the feed stream consists essentially of aniline and water.

In any of the above types of stream, other components in addition to aniline may be present in the fluid mixture. In particular, solvents (e.g. ethanol), reactants, contaminants (e.g. cyclohexylamine, cyclohexanol, cyclohexanone, toluidines, phenol, phenylcyclohexylamines, dicyclohexylamine etc.) and/or by-products may be present.

As previously noted, although the invention is primarily described with reference to aniline, it will be appreciated that this is equally applicable to derivatives of aniline. Such derivatives may be present in addition to aniline, or in place of aniline in any of the processes and apparatus herein described.

The aniline derivatives which may be recovered according to the invention can be described by the following formula:

in which R¹ , R² and R³ independently of each other represent hydrogen, C C₆ alkyl, C C₆ alkoxy, fluorine, chlorine or bromine. More preferably, R¹ , R² and R³ are independently selected from hydrogen and C C₃ alkyl, especially preferably hydrogen, methyl and ethyl.

Covered by the above formula are, for example, the following compounds: aniline, N- methylaniline, N-ethylaniline, N-isopropylaniline, N-n-propylaniline, N-n-butylaniline, N-sec-butylaniline, N-tert-butylaniline, N,N-dimethylaniline, Ν,Ν-diethylaniline, N,N-di- n-propylaniline, N,N-di-isopropylaniline, N,N-di-n-butylaniline, N,N-di-sec-butylaniline and also the corresponding ortho-, meta- or para-toluidine derivatives or the corresponding aniline derivatives which additionally have an ethyl, propyl or butyl group in ortho, meta or para position on the aromatic nucleus, the corresponding ortho-, meta- or para- chloro-, -bromo- or -fluoroaniline derivatives or o-, m-, p- methoxy-, ethoxy-aniline derivatives.

The adsorbent material used in the process of the invention is typically a porous solid with a high surface area. For the TSA processes described herein, the adsorption capacity of the adsorbent should decrease with increasing temperature. Its adsorption capacity should also ideally change with concentration (especially in the whole concentration range), e.g. increase with concentration, e.g. increase with concentration before the saturation plateau. Preferably, the adsorbent has a surface area of at least 50 m²/g, particularly preferably at least 300 m²/g, e.g. at least 450 m²/g especially preferably at least 500 m²/g, for example around 750 m²/g or above. Preferred pore volumes for the adsorbent range from 0.05 ml/ml to 1 ml/ml, preferably 0.1 to 0.9 or 0.2 to 0.8 ml/ml, e.g. around 0.5 ml/ml. Typical adsorbent materials for use in the invention include the following (as well as cation exchanged and surface modified versions thereof) : porous polymer resins (such as amberlites, e.g. Amberlite XAD-4); ion exchanged resins; polymeric, organic or inorganic adsorbents; thermally sensitive gels; alumina; silica gels; zeolites, e.g. Faujasite zeolites; activated carbons; mesoporous materials, e.g. MCM-41 and SBA- 15; metal-organic frameworks (MOFs), e.g. CPO-27 and UIO-66; and zeolite imidazoles (ZIFs). In one embodiment, the adsorbent is not activated carbon.

Preferred adsorbents are porous polymer resins, especially Amberlite XAD-4 (a polymeric adsorbent, highly cross-linked macroreticular polystyrene with a surface are of 750 m2/g and a pore volume of 0.50 ml/ml), obtainable from Dow Chemicals, USA.

The present invention involves TSA, i.e. the adsorption of aniline at one temperature (Ti) and desorption of aniline at a higher temperature (T₂). Preferably, temperature is the only means used to effect and control adsorption and desorption, however other methods may be used (in addition to, or less preferably as an alternative to, temperature control) to assist the adsorption and desorption processes. For example the use of agents ("adsorption promoters") to promote adsorption of aniline onto the adsorbent forms a further aspect of the invention. Suitable materials will depend on the nature of the adsorbent, but could include alkali metal hydroxides or alkaline earth metal hydroxides, e.g. lithium hydroxide, sodium hydroxide, potassium hydroxide, caesium hydroxide, calcium hydroxide. Similarly, materials ("desorption promoters") may be used to promote desorption, e.g. mineral acids such as sulphuric acid, nitric acid, phosphoric acid, hydrochloric acid. A further way of controlling adsorption and/or desorption is by adjusting the pH at certain stages of the process, e.g. adjusting the pH during the adsorption step to at least around 10.8, for example by using the above-mentioned adsorption promoters. The use of materials to promote adsorption and/or desorption and the use of pH adjustment to effect adsorption and/or desorption are less preferred aspects of the invention and are preferably not used in the process of the present invention.

Preferably, therefore, temperature control is the only method used to effect adsorption and desorption. This has the advantage of being relatively easy to control, requiring less or simpler monitoring (e.g. than the use of agents or pH control) and removing the need for adding additional materials to the composition to be separated.

The process of the invention is typically cyclic, e.g. it involves multiple rounds of adsorption and desorption. Cyclic processes may be performed batch-wise or continuously, preferably continuously. Continuous processes typically rely on multiple adsorbent beds, e.g. utilising multiple columns, which allow adsorption and desorption to take place simultaneously but in separate beds.

In a preferred aspect, the adsorbent and the feed stream are contacted in a column. The column may be jacketed depending on the size of the process (i.e. jacketing may not be necessary on an industrial scale). Typically, the adsorbent material is present in a packed or fixed bed. If more than one adsorption bed is used, they may be arranged in series or parallel, and/or many zones may be present in one column/bed. More than one adsorbent may be used in the process, in which case the different adsorbents may be present in the same or different beds, columns, or zones.

Furthermore, the or each adsorbent bed may have one or more heat exchange zones which may be adapted for direct and/or indirect heating (see e.g. Figure 6). To avoid overloading of the adsorbent (e.g. overloading of the column) and thus break-though of aniline into the purified water stream, the composition of the exit stream should preferably be monitored during the process, either continuously or at certain stages. This is typically carried out using UV- Visible spectrometry.

Alternatively, the conditions may be tuned to avoid overloading of the adsorbent (e.g. overloading of the column). This may be achieved by comparing the amount of aniline present in the feed stream with the adsorption capacity of the adsorbent at the relevant aniline concentration. In this case monitoring of the exit stream is not strictly necessary. A batch-wise process would typically use a single column and would involve an adsorption step stopping flow at break-through and then performing a

desorption/regeneration step before beginning another adsorption step (preferably after cooling of the adsorbent material). Batch-wise processes may be useful for targeted applications, e.g. in the pharmaceutical industry. A continuous process would typically use more than one column, at least one of which is adsorbing aniline whilst the other(s) are being purged and/or regenerated. Continuous processes are generally applicable, e.g. for purifying aniline in large-scale chemical processes. A number of possible configurations of single and multiple columns are possible and some of these are described in more detail below.

A typical process according to the invention is illustrated in Figure 4, which shows a three-step cycle. The first step is adsorption where aniline is selectively removed from the feed mixture at a low temperature 0Ί), e.g. by passing an aqueous solution of 3.6% aniline through a column containing an adsorbent material at a rate of, e.g. 1 litre per minute. Immediately before aniline break-through, the feed is interrupted and the column undergoes a heating step (step 2). If aniline break-through occurs after 100 minutes, then 100 litre of mixture has been processed and thus 3.6 litre of aniline are adsorbed by the adsorbent. Heating of the adsorbent to temperature T₂ is carried out with part of the purified water stream produced by the same or another column (i.e. that which has passed the adsorbent and thus has had aniline removed) so that hot "fresh" water is not required. Figure 4 shows the purified water stream from the column being heated by means of a heat-exchanger. If the above-mentioned 3.6 litres of aniline are desorbed with 21 litres of water, the average final aniline concentration of the exit stream from the desorption / regeneration step is 14.6%, i.e. ^ ^ ^'^2ΐ] ^ani'^{ine releasecl} when the adsorbent is heated is thus present in an aniline-enriched (in comparison to the feed) stream. After desorption of aniline, the adsorbent is cooled down (step 3) to restart a new cycle. Purified water from the process can also be used for this step.

The 24.6 litres of exit stream can enter a decanter where it is cooled down to form two phases; e.g. 3 litres of aniline-rich phase (with 94% aniline and 6% water) and 21 .6 litres of water-rich phase (3.6% aniline). The 21 .6 litre water-rich phase can be recycled to the TSA column for further processing. In such a process, 2.82 litres of aniline is removed from the 3.6 litres initially fed. The other 0.78 litres are recycled to the TSA.

Although the process is very compact and efficient for the purification of water (i.e. the production of purified water due to aniline being adsorbed in the column), the aniline obtained in the regeneration steps (i.e. the aniline-enriched stream) can be quite diluted if it is mixed with water used for heating and cooling the adsorbent. For this reason, a preferred step involves the utilization of indirect heating of the adsorbent inside the adsorption column as shown in Figure 5 which shows use of the purified stream for indirect heating. In this way, the hot water used for heating is not contaminated with aniline because a heat exchanger is integrated in the column so that the hot fluid is not in contact with the aniline. This small modification in the cycle can result in a much higher concentration of aniline, but requires the integration of a heat-exchanger device in all adsorption columns. Preferred features of the present invention are now described with reference to the cycles shown in figures 7 to 15. It should be noted that each figure does not show a process flowsheet as such, but instead shows the different operations that a single column is carrying out over time within the overall process. Arrangement 1 (Figures 7 and 8):

Step 1 : Adsorption (i.e. the feed step during which aniline is adsorbed onto the adsorbent). The column is adsorbing aniline from the feed stream that is fed at a given flowrate and has a temperature J (which is the lower temperature of the cycle) and a concentration C1 . This step starts at time t=0 (t₀) and the aniline is being adsorbed in the column progressively, i.e. at the aniline has been retained in the first layers of adsorbent, then at t₂ (>ti) this concentration front has moved further in the column. The step should ideally be stopped when t = t_feed, with t_feed being defined as the time just before aniline breaks through the adsorbent column into the purified water stream.

Step 2: Heating (i.e. desorption, where the adsorbent is heated to release aniline, thus providing a stream more concentrated in aniline than the initial feed). In order to desorb the aniline from the column, part of the water-purified stream produced in the adsorption step is heated and recycled (counter-currently in this case) to the column. The water transfers heat to the adsorbent reaching T₂, the higher temperature of the cycle. Desorption of aniline is favoured at this temperature, thus releasing the aniline that is obtained. The resulting stream is concentrated in aniline when compared to the feed stream, because less water is used to heat the adsorbent than was removed during the adsorption step. It is expected that the average concentration exiting this step, C₂ (average because its value will be changing with time) is higher than d . This step ends when t=t_hot, i.e. when the adsorbent reaches temperature T₂. Step 3: Cooling. Once most of the aniline has been desorbed, the adsorbent should be cooled again to start a new cycle. This may also be carried out with part of the water produced in the adsorption step that is recycled (counter-currently in this case) to the column. The stream exiting this step should have a lower concentration of aniline and is thus recycled to the feed stream. This step ends when

i-e. when the adsorbent reaches temperature T

In the above description of Arrangement 1 , the adsorption process uses one column and therefore is discontinuous. The total "cycle" time is t_cyci_e = t_feed + t_hot + t_COid- Since the aniline stream should ideally be treated continuously, the process can have more than one column such that feed is always going to one column. Figure 8 shows the case where two columns are carrying out the three steps described above, such that each produces purified water for the other's heating and cooling steps.

For operation with two columns, in order for it to be continuous t_feed≥ 1 /2 t_cyci_e, i.e. tfeed≥ thot + tcoid- ^{| n} the simplest case for continuous operation with two columns, t_feed = 1 /2 t_cycie, in which case, t_feed = thot + t_COid- For example, if a feed time takes 2 hours, then the heating time can be 1 hour and the cooling time can be 1 hour. This means that the cycle time is 4 hours and the TSA process has two columns. The water recycle for steps 2 and 3 in Column 2 is carried out with the water produced in the feed step of column 1 . This may readily be extended to three, or more, columns.

Thus, a preferred feature of the present invention is that the process is carried out continuously, preferably with more than one column operating simultaneously. In a preferred aspect, the various columns should be used such that each provides purified water for heating or cooling another column, e.g. as and when required.

Arrangement 2 (Figure 9) :

In Arrangement 1 , the cooling of the adsorbent is carried out counter-currently, in which case the entire column should be cold at the end of the cooling step. If, however, the cooling is effected co-currently, as shown in step 3 of Figure 9, only part of the adsorbent bed needs to be cooled down during the cooling step, while the rest can be cooled down at the beginning of the adsorption step with the cold (i.e. at Ti) water that is purified. Efficiency of the cooling step may therefore be improved if is done co-currently. In general, heating and/or cooling of the adsorbent in the process of the invention may be carried counter-currently or co-currently, preferably co-currently. Arrangement 3 (Figure 10):

Arrangement 3 in Figure 10 demonstrates indirect heating, i.e. a process in which the heating step is divided into heating (indirectly, i.e. without water contacting the adsorbent) and then flushing (with water contacting the adsorbent), rather than the combined heat and flush that direct heating involves (with hot water contacting the absorbent and thus heating it and flushing aniline out).

When water is used to heat the adsorbent and flush aniline therefrom (direct heating), the water will leave the column together with the desorbed aniline, thus diluting its concentration. For this reason, an "indirect heating" step may be introduced. This way of heating means that the adsorbent will be heated indirectly in step 2 and then the aniline will be recovered in step 3 (termed a "flushing" step). The flushing is followed by the cooling step. A preferred aspect of the presently claimed process is thus that the heating of the adsorbent is carried out indirectly, i.e. the adsorbent is heated without direct contact with water. This may be achieved by the column with adsorbent having heat exchange capabilities with a hot external fluid; e.g. the adsorbent may placed in the tubes of a tube-shell heat exchanger.

Arrangement 4 (Figure 1 1 ):

Figure 1 1 corresponds to Arrangement 3 but with co-current cooling. Arrangement 5 (Figure 12):

Step 1 of Arrangement 5 shows the adsorption step. In this cycle, the adsorption step is stopped some time before the concentration front reaches the end of the column. After adsorption, a recycle step (step 2) takes place. In this "recycle" step, water coming from the last step (partially hot and with some aniline) is recycled to the column, thus acting as a further aniline-recovery step and also a pre-heating step to save some energy. Step 3 is indirect heating, step 4 is flushing and step 5 is co- current cooling. Preferably in such an arrangement, more than one, preferably more than two, columns are used simultaneously.

Thus, in some aspects of the present invention, the adsorption step should be stopped some time before the concentration front reaches the end of the column. Additionally, or alternatively, the processes herein described may involve a recycling step, e.g. a step in which an aniline-containing stream is directed from one stage of the process to another, preferably from the cooling step to the adsorption step or from the cooling step to the desorption step.

Arrangement 6 (Fiqure 13):

This corresponds to Arrangement 5 in which the cooling step is counter-current. In that way, the stream exiting the cooling step is richer in aniline (i.e. more aniline is recycled) and is hotter. Preferably in such an arrangement, more than one, preferably more than two, columns may be used simultaneously.

Thus, in a preferred aspect of the invention, when a recycling step is used, it is preferable that the cooling step takes place counter-currently.

Arrangement 7 (Fiqure 14):

This Arrangement aims to concentrate more aniline and to make the process more energy efficient at the same time. A lead-trim cycle arrangement has been used similar to that described in US patent No. 52371 1 1 except that the heating step in Arrangement 7 is indirect.

Step 3 shows an adsorption (feed) step where purified water is produced after aniline adsorption. In this step, aniline is adsorbed in the column and the step is preferably stopped immediately before aniline breakthrough.

After adsorption, the trim step starts (step 4). This is similar to the adsorption step, but aniline is allowed to break through the column. The stream exiting the trim step therefore contains some aniline and is fed to the lead adsorption step (step 2) of a different column, where purified water is also produced. Lead adsorption is a way of putting two columns into contact and allows more aniline to be adsorbed in step 4. The duration of the trim (and lead) steps may be determined by the properties of the adsorbent material and the total number of columns employed in the TSA process.

After the trim step, the bed is saturated with aniline and step 5 takes place, i.e.

indirect heating where aniline is partially released from the adsorbent. The aniline is removed from the column in step 6 (flushing or also termed "purge" step) as in the previous Arrangements. Direct heating may be used in place of steps 5 and 6. A deposit tank is typically used to retain the exit stream. Step 7 is a recycle step. The stream leaving the recycle step is fed to the initial step (step 1 ) termed rectification, where purified water is also produced. Rectification aims to avoid losses of aniline and the mixing of excessive water with the product and it is thus a preferred aspect of the processes of the invention. The stream leaving the recycle step may also be fed into step 4, i.e. as a feed for the trim step.

Step 8 is the cooling step. Indirect cooling is shown, but direct cooling may also be used.

As trim adsorption leads to better utilisation of the adsorbent, the use of lead-trim steps as described above is a preferred aspect of the present invention.

Arrangement 8 (Figure 15):

This Arrangement corresponds to Arrangement 7 in which the order of steps 7 and 8 has been switched.

In general, where a recycling step takes place, this may be before or after the cooling step. In cases where a heat exchanger or additional cooling may be required, it is preferred to recycle a colder stream than to recycle a hot stream.

Thus, in a preferred embodiment, the invention provides a continuous process for the recovery of aniline (or an aniline derivative) from a fluid stream as herein defined, wherein the process comprises steps as described above in Arrangements 1 to 8. Especially preferably, the process comprises the following steps:

a) contacting the feed stream with adsorbent material at a temperature J in a first column such that aniline is adsorbed by the adsorbent material and an aniline- depleted stream having an aniline concentration C₀ is produced (this is preferably continued until immediately before aniline breakthrough, e.g. until C₀/C^ reaches a value of about 0.1 , 0.01 , 0.005, 0.003, 0.001 or 0.0001 , preferably about 0.003) and retaining the aniline-depleted stream;

b) continuing to contact the feed stream with the adsorbent material in the first column until breakthrough (e.g. until C₀/C reaches a value of about 0.1 , 0.5, 0.75,

0.9, 0.95, 0.98, 0.99 or 0.995) such that a second aniline-containing stream is produced and using said second aniline-containing stream as a feed stream to contact with adsorbent material in a second column;

c) heating the adsorbent material in the first column either directly or indirectly to temperature T₂;

d) subsequent to (or simultaneously with) step (c), flushing aniline from the first column using a purging fluid (preferably water at or around temperature T₂) to yield an aniline-rich exit stream;

e) cooling the adsorbent material in the first column either directly or indirectly to temperature T_{1 5}

wherein either before or after step (e), at least some of the aniline remaining in the first column is optionally recycled to the first column (rectification) and/or to another column with or as the feed in step (b). The processes described herein may be applied to any stream containing aniline or an aniline derivative, such as residue streams in the pharmaceutical industry (e.g. waste streams from production of 5-amino-salicylic acid), although they are particularly applicable to use in an aniline production process, e.g. to recover aniline from the water-rich stream produced as part of that process. As mentioned above, aniline production processes can involve the production of an aniline/water stream. This may be processed according to the present invention either directly, or with separation of the aniline-rich and water-rich phases beforehand, e.g. by decanting, such that only the water-rich phase is subjected to the process of the invention. Thus, viewed from a further aspect, the present invention provides a process for the production of aniline or a derivative thereof (preferably involving the hydrogenation of nitrobenzene) comprising a process for recovering aniline (or a derivative thereof) as described herein. Preferably, the invention provides a process for the production of aniline which involves formation of an aniline/water stream which, following the optional prior removal of an aniline-rich phase, forms a feed stream having an aniline concentration of d , said process comprising: (i) contacting said feed stream with an adsorbent material at temperature, T_{1 5} such that aniline is adsorbed by the adsorbent material;

(ii) subjecting the adsorbent material to a temperature, T₂ which is higher than T such that adsorbed aniline is released to yield an aniline-rich exit stream having an aniline concentration of C₂, where C₂ is greater than d ; and

The initial aniline/water stream formed by the aniline production process is preferably separated into an aniline-rich and a water-rich phase and it is preferably only the water-rich phase which is contacted with the absorbent of the present invention. The aniline-rich phase of the initial aniline/water stream may be processed in the conventional manner, e.g. by distillation to remove undesired water.

The use of adsorption to remove aniline from concentrated aniline solutions is novel and thus forms a further aspect of the present invention. Thus, viewed from a further aspect, the present invention provides a process for removing aniline from a fluid comprising aniline, e.g. an aqueous solution of aniline, said process comprising contacting said fluid with an adsorbent material such that aniline is adsorbed by the adsorbent, characterised in that the concentration of aniline in said fluid prior to contact with the adsorbent material is greater than 0.1 g/100ml, e.g. greater than 0.3 g/100ml, especially greater than 0.9 g/100ml, particularly preferably 1 to 12 g/100ml, especially 1 .5 to 8 g/100ml, e.g. 2 to 6 g/100ml.

Preferred features of the process are as described above. Preferably said process involves TSA as described above.

A further aspect of the invention provides mixtures comprising aniline which are produced by the processes described herein.

Apparatus adapted for carrying out the processes of the invention forms a further aspect of the invention. Thus, viewed from a further aspect, the present invention provides an apparatus adapted for use in the processes herein described (e.g. for the recovery of aniline from a fluid, e.g. the enrichment of aniline in an aqueous solution) said apparatus comprising:

(i) means for contacting a feed stream having an aniline concentration of d , with an adsorbent material at temperature, T_{1 5} such that aniline is adsorbed by the adsorbent material,

(ii) means for subjecting the adsorbent material to a temperature, T₂, which is higher than T such that adsorbed aniline is released to yield an aniline-rich exit stream having an aniline concentration of C₂, where C₂ is greater than Ci , and

(iii) a reservoir arranged to receive said aniline-rich exit stream and to discharge it for recycling or further processing.

Preferred features of the apparatus are described above in relation to the process. In particular, the means for contacting the feed stream with the adsorbent material is a column containing an adsorbent material through which the feed stream can flow and/or the means for subjecting the adsorbent material to temperature T₂ is a channel through which a heated liquid, e.g. water, can flow or a heat exchanger integrated into the column. The means for retaining the exit stream can be a storage tank or a decanter for separating the phases in the exit stream. Particularly preferably the apparatus further comprises means, e.g. a decanter, for separation of the exit stream into a water-rich phase and an aniline-rich phase and optionally further means for processing these phases, e.g. a distillation device for removing water from the aniline-rich phase and/or means for recycling the water-rich phase to the means for contacting a feed stream with an adsorbent (e.g. the above-mentioned column).

Preferably the apparatus forms part of an aniline production plant and an aniline production plant comprising the above apparatus forms a further part of the invention.

The present invention will now be further described by means of the following non- limiting examples and Figures in which:

Figure 1 shows adsorption equilibrium isotherms of aniline on XAD-4 polymeric resin obtained using aniline/water mixtures at different temperatures: 302, 323 and 342 K. Figure 2 shows adsorption curves: (a) breakthrough curve using a solution of 1 .5% (15000 ppm) aniline diluted with water at 302 K; (b) desorption curve using pure water as diluent.

Figure 3 shows a breakthrough curve using a solution of 3.4% (34000 ppm) aniline diluted with water at 298 K.

Figure 4 shows a three-step TPP cycle used for separation of aniline - water mixtures. Hot water used as utility to promote desorption. Steps are: (1 ) adsorption; (2) heating; (3) cooling.

Figure 5 shows a three-step TPP cycle used for separation of aniline - water mixtures using indirect heating (with hot water). Steps are: (1 ) adsorption; (2) indirect heating; (3) cooling.

Figure 6 shows an example of an adsorbent bed having three adsorbent/heat- exchange zones, the first of which is adapted for indirect heating.

Figure 7 shows TSA recovery of aniline in Arrangement 1 showing columns over time in the process. Steps (1 ) loading/adsorption phase showing the movement of the concentration front of aniline from t₀ to t_feed- Step (2) heating/desorption phase in which the aniline-rich exit stream is produced. Step (3) cooling phase in which the exit phase is recycled to the feed stream.

Figure 8 shows the connectivity of two columns during different stages of the process described in Arrangement 1 and Figure 7.

Figure 9 shows TSA recovery of aniline in Arrangement 2 showing columns over time in the process (co-current cooling in step 3).

Figure 10 shows TSA recovery of aniline in Arrangement 3 showing columns over time in the process (including indirect heating in step 2).

Figure 1 1 shows TSA recovery of aniline in Arrangement 4 showing columns over time in the process (indirect heating and co-current cooling).

Figure 12 shows TSA recovery of aniline in Arrangement 5 showing columns over time in the process (recycle in step 2).

Figure 13 shows TSA recovery of aniline in Arrangement 6 showing columns over time in the process (recycle and counter-current cooling).

Figure 14 shows TSA recovery of aniline in Arrangement 7 showing columns over time in the process. The table shows the process applied to three columns working in a continuous fashion where at least one column is always accepting a feed (steps 3 and 4).

Figure 15 shows TSA recovery of aniline in Arrangement 8 showing columns over time in the process. The table shows the process applied to three columns working in a continuous fashion where at least one column is always accepting a feed (steps 3 and 4).

Example 1

Adsorption equilibrium of aniline/water solutions

The adsorption equilibrium data of aniline dissolved in water was investigated in the entire miscibility range of aniline in water (i.e. up to 3.6% or 3.6g/100ml). The adsorption equilibrium isotherm was measured at three different temperatures (302, 322 and 343 K) on a polymeric resin adsorbent. Adsorption equilibriums of aniline/water solutions were measured using the batch technique. 10 ml aqueous solutions of aniline at different concentrations (500 ppm, 16000 ppm and 34000 ppm) were added to amber flasks. The solutions were made using deionized water and aniline with purity≥ 99.5% (ACS reagent, Sigma Aldrich). Varying amounts between 0.05 and 1 .8 grams of adsorbent, polymeric resin

Amberlite™ XAD-4 (Dow Chemicals, USA), was also added to the flasks. The flasks were closed and placed in a heater in order to achieve the desired temperature, i.e. 302, 323 or 342K. A total of 24 flasks containing various amounts of adsorbent and concentrations of solution were placed in an oven for each experiment. The temperature variation inside the oven was ±1 K.

Contact between the solution and the adsorbent lasted for at least 48 hours to ensure that adsorption equilibrium was reached. After that period, samples of each solution were taken and analysed using a UV-Vis spectrometer (Biotek Powerwave HT spectrophotometer, USA) at a wavelength of 271 nm^"1. Solutions with concentration higher than 500 ppm were diluted prior to analysis.

The amount adsorbed in each adsorbent was calculated from the difference in concentration between the initial number of moles introduced in each flask and the amount existing in solution after adsorption equilibrium was reached, taking into account the amount of aniline present in the pores of the adsorbent. Adsorption of aniline at low concentrations can be described by a Type I isotherm model.

However, when the concentration of aniline is close to the saturation limit, a multi- layer effect (or capillary condensation) is observed and a Type IV isotherm model may be employed.

The adsorption equilibrium isotherms of aniline in the polymeric resin XAD-4 are shown in Figure 1 . It can be observed that the isotherms of aniline are Type IV according to lUPAC classification. This is typical from the formation of an initial monolayer followed by adsorption in multiple layers leading to capillary condensation in the pores of the adsorbent. The data presented cover the entire solubility range of aniline in water and thus covers a much higher range than previous studies regarding aniline adsorption. The loading of aniline on the polymeric resin was found to be relatively high (up to 6 mol/kg). As aniline is quite reactive, the temperature of desorption was not significantly increased from the adsorption temperature in order to avoid polymerization on the adsorbent. This also allows the use of hot water for regeneration.

Example 2

Dynamic experiments - temperature swing adsorption

Dynamic experiments on the polymeric resin packed in a fixed bed were performed at 302 K and regeneration of the adsorbent was carried out by heating the column. Amberlite XAD-4 was loaded in a jacketed borosilicate fixed bed column (20 cm long and 2.5 cm diameter) and deionised water was passed through it for over 12 hours (1 ml/min) using a peristaltic pump to remove any ethanol present in the adsorbent. The temperature of the column was maintained at 302 K by passing water with controlled temperature using a heating bath. Before starting the experiment, the total water flow-rate was changed to 5 ml/min. At time t = 0 of the experiment, the inlet stream was switched to a mixture of 1 .5% aniline diluted in water. Sometime after aniline break-through was detected at the column exit, the feed was stopped and the temperature of the column was increased for 30 minutes to 343 K. When the desired temperature was reached, the feed stream was switched to deionized water with a total flow-rate of 6 ml/min and desorption of aniline was monitored. The analysis was carried out by continuous sampling at the exit of the column and analysing by UV-Vis in a similar manner as in Example 1 .

Breakthrough experiments were carried out in order to identify possible problems of aniline diffusion through the pores of the polymeric resin. A breakthrough curve using a feed concentration of 1 .5% of aniline in water was used for the first experiment. The result of the breakthrough and the desorption with pure water are shown in Figure 2.

For the first 125 minutes, pure water was obtained from the top of the column, After that time, aniline break-through was observed and the adsorbent was therefore regenerated. Regeneration at the same temperature showed the effects of nonlinear isotherm (long desorption) which was improved by heating the adsorbent.

It can be observed that a typical S-shape curve is obtained as a response to a step- input of concentration. The desorption curve is more dispersed than the adsorption curve as a result of the non-linearity of the isotherm, i.e. adsorption is favourable and thus desorption is unfavourable. It can be observed from the breakthrough curve that the length of unused bed (LUB) is quite small and that the concentration profile is not very dispersed. This experiment therefore shows low diffusion resistance and strong adsorption.

The second breakthrough experiment was carried out using a solution of 3.4% aniline in water, using a flow of 5.3 ml/min. Adsorption took place at 303 K and regeneration at 348 K. In order to reduce the amount of aniline used in the experiment, a smaller column was employed in this experiment. The adsorption took place for some time after aniline break-through, although complete load of the column was avoided in order to emulate the performance of a lead-trim TSA cycle. After adsorption, the flow was stopped and the column temperature was increased to 348 K for 30 minutes. Then a flow of 6 ml/min of water was used for desorption/regeneration. The liquid obtained was turbid and a two phase separation was observed after decanting. The results are shown in Figure 3. In this example, the response of a step-function is not the typical S-shape, but a double-S shape that result from the Type IV isotherm, confirming the findings measured by batch adsorption. Due to this double-S shape, a value close to 25% of the equilibrium capacity is not used if the feed is stopped immediately after the breakthrough of aniline.

The adsorption took place for some time after aniline break-through, although complete load of the column was avoided in order to emulate the performance of a lead-trim TSA cycle. Adsorption of aniline in Amberlite XAD-4 resin was proved to be very efficient and in fact this adsorbent can be regenerated using a higher temperature.

Claims

Claims:

1 . A process for the recovery of aniline or an aniline derivative from a fluid said process comprising:

(i) contacting a feed stream having an aniline or aniline derivative

concentration of Ci , with an adsorbent material at temperature, T_u such that aniline or aniline derivative is adsorbed by the adsorbent material;

(ii) subjecting the adsorbent material to a temperature, T₂, which is higher than T such that adsorbed aniline or aniline derivative is released to yield an aniline-rich or aniline derivative-rich exit stream having an aniline or aniline derivative concentration of C₂, where C₂ is greater than Ci ; and

(iii) retaining the aniline-rich or aniline derivative-rich exit stream for recycling or further processing.

2. The process of claim 1 , wherein said feed stream and/or said exit stream is an aqueous solution of aniline or aniline derivative.

3. The process of claim 1 or claim 2, wherein step (ii) includes the further step of lowering the temperature of the adsorbent material to T

4. The process of any one of claims 1 to 3, wherein the concentration of aniline or aniline derivative in the aniline-rich or aniline derivative-rich exit stream, C₂, is at least 1 .5 times greater than the concentration in the feed stream, d .

5. The process of any one of claims 1 to 4, wherein the concentration of aniline or aniline derivative in the feed stream (expressed as a mass concentration of aniline or aniline derivative), Ci , is from 1 .5g/100 ml to 8.0g/100ml.

6. The process of any one of claims 1 to 5, wherein the concentration of aniline or aniline derivative in the exit stream (expressed as a mass concentration of aniline), C₂, is from 3.6g/100 ml to 18g/100ml.

7. The process of any one of claims 1 to 6, wherein T₂ is between 10 and 100K higher than T^

8. The process of any one of claims 1 to 7, wherein the adsorbent material has a surface area of at least 50 m²/g.

9. The process of any one of claims 1 to 8, wherein the process is performed batch-wise, cyclically or continuously, preferably continuously.

10. The process of any one of claims 1 to 9 comprising the steps:

a) contacting the feed stream with adsorbent material at a temperature J in a first column such that aniline or aniline derivative is adsorbed by the adsorbent material and an aniline-depleted or aniline derivative-depleted stream having an aniline or aniline derivative concentration C₀ is produced (this is preferably continued until immediately before aniline or aniline derivative breakthrough, e.g. until C₀/Ci reaches a value of about 0.1 , 0.01 , 0.005, 0.003, 0.001 or 0.0001 ) and retaining the aniline-depleted or aniline derivative-depleted stream;

b) continuing to contact the feed stream with the adsorbent material in the first column until breakthrough (e.g. until C₀/Ci reaches a value about 0.1 , 0.5, 0.75, 0.9, 0.95, 0.98, 0.99 or 0.995) such that a second aniline-containing or aniline derivative- containing stream is produced and using said second aniline-containing or aniline derivative-containing stream as a feed stream to contact with adsorbent material in a second column;

d) subsequent to (or simultaneously with) step (c), flushing aniline or aniline derivative from the first column using a purging fluid (preferably water at or around temperature T₂) to yield an aniline-rich or aniline derivative-rich exit stream;

e) cooling the adsorbent material in the first column either directly or indirectly to temperature T

wherein either before or after step (e), at least some of the aniline or aniline derivative remaining in the first column is optionally recycled to the first column (rectification) and/or to another column with or as the feed in step (b).

1 1 . The process of any one of claims 1 to 10 for the recovery of aniline.

12. A process for the production of aniline (or aniline derivative) comprising a process for the recovery of aniline (or aniline derivative) from a fluid as claimed in any one of claims 1 to 1 1 , wherein said process for the production of aniline (or aniline derivative) involves formation of an aniline/water (or aniline derivative/water) stream which, following the optional prior removal of an aniline-rich (or aniline derivative-rich) phase, forms the feed stream having an aniline (or aniline derivative) concentration of d -

13. A process for removing aniline (or aniline derivative) from a fluid comprising aniline (or aniline derivative) said process comprising contacting said fluid with an adsorbent material such that aniline (or aniline derivative) is adsorbed by the adsorbent, characterised in that the concentration of aniline (or aniline derivative) in said fluid prior to contact with the adsorbent material is greater than 0.1 g/100ml.

14. Use of temperature swing adsorption in the removal and/or recovery of aniline (or aniline derivative) from an aniline-containing (or aniline derivative-containing) fluid, wherein the concentration of aniline (or aniline derivative) in said fluid is at least 0.1 g/100ml.

15. A composition comprising aniline (or aniline derivative) produced by a process as claimed in any one of claims 1 to 13.

16. An apparatus adapted for use in a process as claimed in any one of claims 1 to 13, said apparatus comprising:

(i) means for contacting a feed stream having an aniline (or aniline derivative) concentration of d , with an adsorbent material at temperature, T_{1 5} such that aniline (or aniline derivative) is adsorbed by the adsorbent material,

(ii) means for subjecting the adsorbent material to a temperature, T₂, which is higher than T such that adsorbed aniline (or aniline derivative) is released to yield an aniline-rich (or aniline derivative-rich) exit stream having an aniline (or aniline derivative) concentration of C₂, where C₂ is greater than d , and

(iii) a reservoir arranged to receive said aniline-rich (or aniline derivative-rich) exit stream and to discharge it for recycling or further processing.

17. An aniline (or aniline derivative) production plant comprising the apparatus of claim 16.