A PROCESS FOR PREPARATION OF HIGHLY PURE 4-(n-BUTYL) ANILINE

CROSS-REFERENCE TO RELATED APPLICATION AND PRIORITY

The present application claims priority from Indian complete patent application no. 202221008109 filed on the 16 February 2022, the details of which are incorporated herein by a reference.

FIELD OF INVENTION

The present invention relates to a process for the preparation of 4-(n-Butyl) nitro benzene and 4-(n- Butyl) Aniline. More particularly the said process is related to preparation of 4-(n-Butyl) nitro benzene followed by preparation of highly pure 4-(n-Butyl) Aniline from n-Butyl Benzene.

BACKGROUND OF INVENTION

During manufacturing of iso-Butyl benzene (IBB) by toluene metalation process along with propylene, a normal-Butyl benzene (NBB) is obtained as the co-product. The co-product can be used in this invention to make 4-(n-Butyl) Aniline (hereinafter may be interchangeably referred to as ‘4-BAN’), which has commercial usage.

4-(n-Butyl) amine is a clear, colourless liquid with an ammonia-like odour and it is used as intermediate in manufacturing of active dyes, pigments and colorants, which is prepared from 4-n- Butyl nitrobenzene.

Industrially, a nitration reaction is treated as hazardous reaction in terms of heat evolved during nitration. Generally, nitration reactions are very exothermic in nature and can lead to run-away conditions if not handled properly. Hence, the management of heat and mass transfer is very important in commercial scale nitration equipment. Usually, the nitration of organic compounds is carried out with nitric acid or nitrating acid or mixed acid (Sulphuric acid and Nitric acid mixture).

A Nitrating acid is a colourless to light yellow or grey to reddish brown mixture of undefined stoichiometric composition of sulphuric acid and nitric acid that may generally contain some amount of dissolved nitrogen oxides. The nitration agent comprises at least one nitrogen compound which is able to release the electrophilic nitronium cation (NO2) ⁺ which is deemed to be the true nitration agent (Nitration, Methods and Mechanisms, Series: Organic Nitro Chemistry Series, Olah, G. A., Malhotra, R., Narang, S. C. , Verlag VCH Publishers, Weinheim 1989).

Selectivity is a primary challenge in nitration aromatic hydrocarbon because usually the nitrating agent is used in excess and hence more than one nitro-derivative of the respective substrate are obtained, which affect the process viability. The undesired products thus obtained act as contaminants which reduces the yield and purity of the desired ones. Accordingly, it is desirable to design process pathways that yields better selectivity of the desired isomer for example, by controlling the reaction conditions.

Aromatic and hetero aromatic compounds can be easily nitrated and often it is difficult to obtain selective introduction of only one nitro group. Hence this poses a great challenge in selective nitration of the benzene rings to yield desired isomer. Conventionally, the aromatic nitration is a prolonged reaction that is carried out at very low temperatures predominantly using nitrating mixture comprising of concentrated nitric acid and sulphuric acid, which generates dilute sulphuric acid containing small amount of unreacted nitric acid which makes it unsuitable for use of dilute sulphuric acid in other applications.

Also, such nitration process (with mixed sulfuric acid and nitric acid) used in nitration of few aromatics viz. n-Butyl benzene results in sulphonation (when aromatic compound is mixed with concentrated sulphuric acid) over nitration of n-Butyl benzene, the sulfonated n-Butyl benzene being soluble in organic phase poses difficulties in separation and gets mixed with spent acid causing higher COD values of mixed acid making it unsuitable for its use in any other suitable application and can cause disposal problem.

Such processes result in mixtures of both required and undesired isomers. From this aggregated pool the required isomers have to be isolated in pure form by employing separation methods, such as distillation, fractional crystallization; selective precipitation or converting into amino compounds followed by separation of amino compound or using chromatographic purifications techniques etc. that adds additional cost to manufacturing process.

Further, unsubstituted aromatic compounds like benzene and naphthalene show relatively less reactivity and hence slowly react with a nitration agent which results in low yields. The batch processes being used till now for nitration of aromatic compounds have certain limitations like long reaction time, energy, poor yields, undesired isomers, effluents, etc. which pose a constant need for improved process for nitration of aromatic compounds which have variety of applications. Continuous flow synthesis could be an option but presently, there is no known continuous flow liquid phase synthesis that is feasible for nitration of aromatic compounds.

Hence, the inventors have come up with a novel methodology for continuous flow liquid phase nitration which overcomes the limitations of prior art methods and provides an easy, facile, timesaving, energy efficient, environment friendly process to synthesize nitrated alkyl benzene compounds including n-Butyl benzene with good selectivity. 4-nitro-n-butyl benzene is known to have applications for making 4-n-Butyl aniline which is used in dyestuff industry / pigments, as colorant and as a specialty chemical.

OBJECTIVES OF THE INVENTION

The main object of the invention is to provide a process for batch and continuous flow liquid phase nitration of n-Butyl benzene using mixed acid method as described in scheme -I, wherein mixed acid is a mixture of Sulphuric acid and Nitric acid mixture.

Scheme-I n-butyl benzene n-butyl Nitrobenzene

Another object of the present invention is to provide a process of continuous flow liquid phase nitration of n-Butyl benzene using acetyl nitrate as nitrating agent with better control on the product profile and thereby avoiding waste acid generation as described in scheme -II.

Scheme-II

Acetic anhydride

Nitric acid with or without zeolite catalyst n-butyl benzene n-butyl Nitrobenzene Yet another object of the present invention is to provide a process of liquid phase nitration of n- Butyl benzene using acetyl nitrate as nitrating agent in presence of Zeolite catalyst for highest selectivity of nitration reaction and with better control on the product profile, also thereby avoiding waste acid generation.

Another object of the present invention is to provide a process of liquid phase nitration of n-Butyl benzene which provides zero effluent process, recovery and recycle of nitration catalyst, thus easily manageable and can be operated at almost ambient temperature thus conserving time and energy.

Yet another object of present invention is to hydrogenate catalytically mass of nitro n-Butyl benzene (mixture) to convert it into n-Butyl aniline mixture, recover and recycle of hydrogenation catalyst, thus leaving no effluent stream in the reaction, as described in scheme -II.

Scheme-Ill

Hydrogen gas

Solvent, catalyst, heat n-butyl aniline

Another main objective of present invention is to isolate 4-n-Butyl aniline by distillation process to highly pure 4-n-Butyl aniline suitable for end application.

SUMMARY OF THE INVENTION

Before the present system, processes, method, and products are described in the said proposed invention, it is to be understood that the disclosed invention is not limited to the specific process, methods, and products as described herein, as there can be multiple possible embodiments which are not expressly illustrated in the present invention but may still be practicable within the scope of the invention.

This summary is provided to introduce concepts related to a process for preparation of highly pure 4-(n-Butyl) Aniline selectively over other aniline isomers by performing nitration followed by hydrogenation of n- Butylbenzene by using an optimized nitrating agent. This summary is not intended to identify essential features of the claimed subject matter not it is intended for use in determining or limiting the scope of the claimed subject matter. The instant invention describes about a process for preparation of highly pure 4-(n-Butyl) Aniline.

In one embodiment of the present invention, a process for preparation of highly pure 4-(n-butyl) Aniline is disclosed. The process may comprise a step of adding 90 to 92% concentrated sulfuric acid and a n-butylbenzene to a tank reactor under stirring. The process may comprise a step of nitration of n-Butylbenzene by using a nitrating agent comprising nitric acid in a tank reactor at a predefined reaction temperature. A reaction time is maintained between 45 minutes to 4.5 hours to selectively obtain a crude 4-nitro-n-Butylbenzene. The process may comprise a step of nitration of n-Butylbenzene by using a nitrating agent comprising nitric acid, characterized in that a mole ratio of n-Butylbenzene: Nitric acid is maintained between 1.7- 1 :0.5- 1.5. The process may further comprise a step of hydrogenation of the crude nitro-n-Butylbenzene in hydrogenator to obtain crude 4-(n-Butyl) Aniline. The process may further comprise a step of fractionating and separating a highly pure 4-(n-Butyl) Aniline in a high vacuum distillation set-up.

BRIEF DESCRIPTION OF DRAWINGS

The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to refer like features and components.

Figure 1 depicts a process (100) flowchart for preparation of highly pure 4-(n-butyl) aniline, in accordance with an embodiment of the present invention.

Figure 2 depicts a setup of tank reactor (200) in a step of nitration of n-butyl benzene wherein the nitrating agent is a mixture of sulfuric acid and nitric acid, in accordance with an embodiment of the present invention.

Figure 3 depicts a setup of tank reactor (300) in a step of nitration of n-butyl benzene wherein the nitrating agent is a zeolite catalyst and acetyl nitrate, in accordance with an embodiment of the present invention.

Figure 4 depicts a setup of tank reactor (400) in a step of nitration of n-butyl benzene wherein the nitrating agent is an acetic anhydride with concentrated nitric acid, in accordance with an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

Some embodiments of this disclosure, illustrating all its features, may now be discussed in detail. The words "comprising "having," "containing," and "including," and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items or meant to be limited to only the listed item or items. It must also be noted that, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise, although any methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present invention, wherein the exemplary methods are described. The disclosed embodiments are merely exemplary of the disclosure of the present invention, which may be embodied in various forms.

It may be understood by all readers of this written description that the example embodiments described herein and claimed hereafter may be suitably practiced in the absence of any recited feature, element or step that is, or is not, specifically disclosed herein. For instance, references in this written description to "one embodiment," "an embodiment," "an exemplary embodiment," and the like, indicate that the embodiment described can include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. The disclosed embodiments are merely exemplary of various forms or combinations. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one of ordinary skill in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

No terminology in this application should be construed as indicating any non-claimed element as essential or critical. The use of any and all examples, or example language (e.g., "such as") provided herein, is intended merely to better illuminate example embodiments and does not pose a limitation on the scope of the claims appended hereto unless otherwise claimed.

Recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. Where a specific range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is included therein. All smaller sub-ranges are also included. The upper and lower limits of these smaller ranges are also included therein, subject to any specifically excluded limit in the stated range.

The main purpose of the disclosed invention is to provide a cost effective, reagent recyclable, and selective process of preparation of highly pure 4-(n-butyl) Aniline.

Accordingly, in a process of preparation of 4-(n-butyl) Aniline involves various steps to selectively obtain a high yield of aniline derivative i.e., 4-(n-butyl) Aniline as described herewith.

Referring to Figure 1, a process (100) for preparation of highly pure 4-(n-butyl) Aniline (hereinafter may be interchangeably referred to as “BAN) from n-butyl benzene as a by-product obtained from a process of manufacturing of Isobutyl benzene (IBB) is illustrated in accordance with an embodiment of the present subject matter.

In one embodiment, a process (100) for preparation of highly pure 4-(n-butyl) Aniline (4-BAN) comprises a step of adding (101) sulfuric acid and n-butylbenzene to a tank reactor under stirring conditions. In one embodiment, the step (101) of adding sulfuric acid may comprise addition of dilute sulfuric acid, or 90 to 92% sulfuric acid to avoid undesired reaction of sulfonation and thereby improving the selectivity of nitration.

The process (100) may further comprise a step of nitration (103) of n-Butylbenzene by using a nitrating agent comprising nitric acid in a tank reactor at a predefined reaction temperature, wherein a reaction time is maintained between 45 minutes to 4.5 hours to selectively obtain a crude 4-nitro- n-Butylbenzene. In a preferred embodiment, a mole ratio of n-Butylbenzene: Nitric acid in the step of nitration (103) may be maintained between 1.7- 1 :0.5- 1.5.

In one embodiment, the step of nitration (103) of n-butylbenzene is a batch type nitration process or a continuous flow liquid phase nitration. The process (100) may further comprise a step of hydrogenation (105) of the crude nitro-n-butylbenzene in a hydrogenator to obtain a crude 4-(n- Butyl) Aniline. In one embodiment, a high pressure hydrogenator is a batch type stirred high pressure catalytic hydrogenator. In one embodiment, the pressure hydrogenator may be configured for recycling the hydrogenation catalyst by a catalyst filtration washing technique in a catalyst recovery tank thereby making the process economical. The process (100) may further comprise a step of fractionating and separating (107) a highly pure 4- (n-butyl Aniline) in a high vacuum distillation set-up.

In one embodiment, the step of nitration (103) may comprise a nitrating agent as a mixture of sulphuric acid and nitric acid. To overcome the limitations of producing nitrated n-Butylbenzene, the current method step of nitration (103) discloses a methodology for batch nitration using mixed acid method.

In one embodiment, referring to Figure 2, a step of nitration (103) of the present invention may comprise a batch nitration of n-Butylbenzene using mixed acid viz. sulphuric acid and nitric acid in a stirred tank reactor. In one embodiment, wherein a mole ratio of n-Butylbenzene: Nitric acid may be maintained between 1.0: 0.8 to 1.5. The temperature of the reaction wherein the mixture of sulphuric acid and nitric acid are used as the nitrating agent may be maintained between a range of 0°C to 22° C, wherein the reaction time may be maintained between 45 minutes to 4.5 hours. In one embodiment, the tank reactor for the nitration of n-butylbenzene is a bath type stirred tank reactor with cooling arrangement.

Accordingly, again referring to Figure 2, the tank reactor setup (200) may involve a jacketed 5 L stirred reactor (201), where the chilled water is circulated through the reactor jacket (202). Further, a metering pump (205) may be configured for charging nitrogen, cone. H2SO4, and NBB to the tank reactor. Further, a metering pump (204) may be used for charging the nitrating agent form a dropping funnel (203) as a mixed sulfuric acid and nitric acid in a reaction mixture of n- Butylbenzene and 90 to 92% concentration sulphuric acid in the tank reactor, i.e., the stirred reactor (201). Further, a step of hydrogenation (105) of the crude nitro-n-butylbenzene may be carried out in 5-L capacity stirred high pressure catalytic hydrogenator to obtain a crude mixture of n-Butyl aniline. The crude mixture of n-butyl aniline may be further fractionally separated and distilled (107) under vacuum using 10-L capacity fractional distillation facility (206). In one embodiment, the fractional distillation facility (206) may comprise a packed column for catalytic hydrogenation (207), a magnetic reflux splitter (208) connected to the condenser assembly comprising a condenser (209) and a CaCh guard tower (210). The magnetic reflux splitter (208) may be further connected to a product cooler unit (211) and a product receiver/collector unit (212). In one embodiment, the packed column may comprise a 40*1500 structured packing. In another embodiment, referring to Figure 3, the step of nitration (103) may comprise a nitrating agent as Acetyl nitrate generated in situ by treating Acetic anhydride with Nitric acid in presence of H-P-Zeolite catalyst. The step of nitration (103) using acyl nitrate may be a batch type nitration to selectively obtain 4-Nitro-n-Butyl benzene. In one embodiment, wherein the nitration is carried out over H-P-Zeolite catalyst, resulted in getting 77 to 78% selectivity towards 4-Nitro-n-Butyl benzene. In an embodiment, the reaction temperature may be maintained between 15 and 25 ⁰ C, and nitration time maintained is 60 minutes. In this embodiment, the tank reactor used may be a batch type stirred tank reactor with cooling arrangement.

Accordingly, again referring to Figure 2 and 3, the step of nitration (103) may be carried out by reacting n-butylbenzene with the nitrating agent selected as Zeolite catalyst using Acetyl nitrate as nitrating agent, wherein the selectivity towards para nitro isomer of crude nitro-butyl benzene is highest also the recyclability of the Zeolite catalyst may also be implemented In one embodiment, the process (100) may comprise a step of recycling (106) of the H-P-Zeolite catalyst by a catalyst filtration washing in a catalyst recovery tank (301). A recycled use of zeolite catalyst greatly enhances process economics and reduces any effluent load. Referring to Figure 2 and 3, the tank reactor setup (300) where the nitrating agent is used as a Zeolite catalyst and Acetyl nitrate which may be added to jacketed 5-L stirred reactor (201), wherein the chilled water is circulated through the reactor jacket (202). In one embodiment, the metering pump (203) may be configured for charging nitrogen, cone. H2SO4, NBB and the Zeolite catalyst to the tank reactor. Further the metering pump (202) may be used for charging nitric acid (nitrating acid) into the reaction mixture containing n-Butylbenzene, Acetic anhydride and Zeolite catalyst. The process (100) may further involve a step of recycling (106) by a catalyst filtration unit (302), washing and recovery facility.

In yet another embodiment, referring to Figure 1, 2, and 4, the step of nitration (103) may comprise the addition of nitrating agent selected as acetic anhydride with concentrated nitric acid in a micromixer unit (401) without any catalyst to form in situ Acetyl nitrate and acetic acid as a coproduct. The concentrated nitric acid may a fuming nitric acid, 98% nitric acid, or 67 to 70% nitric acid which may be reacted to acetic anhydride in situ to form acetyl nitrate and acetic acid as a coproduct. The step of nitration (103), wherein the nitrating agent is acetic anhydride with concentrated nitric acid forming acetyl nitrate may be a continuous flow liquid phase nitration. In one embodiment, the predefined temperature may be maintained in a range of the of 15 to 40 ⁰ C for a period in the range of 1 min to 10 min at atmospheric pressure to obtain Nitro-n-Butylbenzene. In one embodiment, a mole ratio of Acetic anhydride: n-Butylbenzene: Nitric acid may be maintained between 1.5 to 1.0: 1.0 to 0.9: 0.9 to 0.95. In this embodiment, the tank reactor used to carry out nitration may be a micromixer or a set of tubular reactors. In one embodiment, the step of nitration (103), wherein the nitrating agent is selected as acetic anhydride with concentrated nitric acid is a homogeneous process and advantageous to be scaled-up easily without any waste stream. Therefore, the process may be considered as an environment friendly green process.

Accordingly, the step of nitration (103) of n-butyl benzene by using a nitrating agent comprising Acetyl nitrate generated in- situ to overcome the limitations of the prior art in producing nitrated alkyl benzene compounds. The step of nitration (103) may comprise a continuous flow liquid phase nitration of alkyl benzene compounds in micromixer (401) and tubular reactors (402, 403) with better control on the product profile comprising reacting alkyl benzene compounds with nitrating agent at a temperature range of 10 to 40 ⁰ C. Referring to Figure 4, the continuous flow liquid phase nitration of alkyl benzene compounds according to the invention that may advantageously be carried out in the tank reactor (201) selected as continuous reactor including metal reactors with high heat transfer co-efficient.

In an embodiment, the experimental setup according to the invention may comprise of a set of three metering pumps (404, 405) for pumping of Acetic anhydride, the 98% nitric acid and n- Butylbenzene to the micromixer (401) (1ml) comprising by a residence time unit. In one embodiment, the residence time unit (402, 403) is made of 2 parts connected using a 4-way port for withdrawing a sample for analysis to track the reaction progress at different conditions. In one embodiment, a constant temperature bath may be used to maintain appropriate temperature.

In one embodiment, referring to Figure 4, the typical experimental setup (400) used for continuous flow nitration according to the invention includes a set of one or more pumps (201, 404, 405) for the dosing of reactants, a micromixer (401) comprising the residence time unit for the rapid and efficient mixing of these reactants, and the residence time unit (402, 403), which may be either a microfluidic device with channels or a tube. In one embodiment, the residence time unit may be configured to be immersed in a constant temperature bath. In an alternate setup the residence time unit may be built-in cooling/heating systems to maintain a specific temperature and to obtain a higher yield of 4-(n-Butyl) Aniline in a product collector unit (406). In one embodiment, an effect of experimental parameters such as temperature between 0 to 40°C, residence time between 10 sec to 10 min, and nitric acid equivalents 0.8- 1.2 moles is investigated in the present invention. It is surprisingly found that depending upon the nitrating agent and its mole ratio with the substrate, the reaction mixture is seen to be homogeneous.

The instant invention is further described by the following examples:

Experimental Details:

Example A

Referring to Figure 2, the following examples 1 to 13 shows method followed for Nitration of n- Butylbenzene using mixed acid method in a batch mode, where the experiments were carried out in 5-L capacity stirred nitration reactor, and the coolant was circulated through the jacket.

A process of selective nitration of n-Butylbenzene followed in the Examples 1-13 is disclosed as below:

Referring to Figure 2, in a five-litre jacketed reactor, equipped with agitator, dropping funnel, thermo-well & cryostat, weighed quantities of 91% H2SO4 and desired quantity of n-Butylbenzene were taken. Stirring was started and the reaction mixture was cooled to the desired reaction temperature with the help of cryostat. When the temperature of the reaction mixture attained the desired temperature, the addition of weighed quantity of nitration mixture was started using dropping funnel. The reaction temperature was maintained at desired value in the range of +/- 1° C. The addition time of nitrating mixture was maintained as mentioned in the following table. After addition of nitration mixture was complete, the reaction temperature was raised to 15° C and stirred at this temperature for 1.5 to 2 hours.

Work-up

The reaction mixture was brought to the room temperature and the material was taken out of reactor. After weighing the reaction mass, it was transferred to a separating funnel & allowed separating organic layer and spent acid layer. The bottom layer i.e. spent acid layer was removed & organic layer i.e. product layer was neutralized to pH 7 by using sodium carbonate solution. Then organic layer was washed twice with water & sample was given for GC analysis. This organic layer was used for hydrogenation trials.

Table-1 shows Examples 1-13 with input and reaction conditions of nitrating mixture

Table 1

Table 2 shows % output and selective nitration analysis of an organic layer of the Examples 1-13 when a ratio of NBB: nitric acid is maintained between 1:0.8-1.5.

Table 2 Example B

Further a process of nitration of n-Butylbenzene by using acetyl nitrate as nitrating agent in a batch mode for Examples 14-16 is disclosed below in accordance with an embodiment of the present invention.

Referring to Figure 2, in a 5L jacketed reactor, equipped with agitator, dropping funnel, thermowell & cryostat, weighed quantities of acetic anhydride and desired quantity of n-Butylbenzene were taken. Stirring was started and the reaction mixture if required was cooled to the desired reaction temperature with the help of cryostat. When the temperature of the reaction mixture attained the desired temperature, the addition of weighed quantity of concentrated nitric acid (98%) was started using dropping funnel. The reaction temperature was maintained at desired value in the range of +/- 1° C. The addition time of nitrating mixture was maintained as mentioned in the following table. After addition of nitration mixture was complete, the reaction temperature was raised to 15° C and stirred at this temperature for 0.5 to 1 hour.

Work-up

The reaction mixture was brought to the room temperature and the material was taken out of reactor. After weighing the reaction mass, it was transferred to the 10-L capacity rotary evaporator, and it was subjected flash distillation under reduced pressure of 450 mm Hg absolute to 40 mm Hg absolute pressure. Slowly the heating bath temperature of rotary evaporator was increased from 60° C to 120° C, during distillation the acetic acid generated in the process and excess acetic anhydride and any other lower boiler were recovered. The crude nitro mass was subjected to analysis and hydrogenation process. Following Table shows the input and reaction conditions.

Table 3 shows input and reaction conditions for Example 14-16 in accordance with an embodiment of the present disclosure.

Table 3

Further Analysis of crude nitro-mass of the Examples 14-16 was carried out and represented in Table 4 when a ratio of AC2O: NBB: nitric acid is maintained between 1.5:1:0.9-0.95. Table 4

Example C

In Example C, a process followed by Examples 17-20 for nitration of n-butylbenzene using P- Zeolite and nitric acid as a nitrating agent along with recovery and recycle of catalyst in a batch mode is disclosed in accordance with an embodiment of the present disclosure.

The set-up used for this reaction was 500 mL capacity flask placed on magnetic stirrer, water bath and condenser and dropping funnel. The flask was charged initially with desired quantity of nBB, acetic anhydride, Zeolite catalyst. The required reaction temperature was attained with the help of water bath. Then to it nitric acid (67 to 70%) was charged with 2.5 to 3.0 hours and it was further stirred for additional 5 hours.

Work-up

The Work-up step was followed as explained under Examples 14-16 in Example B. The following

Table 5 shows input and reaction conditions maintained for Examples 17-20.

Table 5

(a) Fresh catalyst was used; (b) Catalyst from Example 18 was recycled; (c) Catalyst from Example

19 was recycled

The Table 6 below represents analysis of crude nitro-mass obtained in Examples 17-20 by implementing P-Zeolite and nitric acid as a nitrating agent, in accordance with an embodiment of the present invention.

Table 6

Example D

In this Example, a process followed for Examples 21-23 for continuous nitration of n-Butylbenzene using acetyl nitrate as nitrating agent in a continuous mode is disclosed in accordance with an embodiment of the present disclosure.

The experimental setup according to the invention consisted of reactor made of SS316; 1 mL capacity micromixer followed by 1.56 mm ID tube having volume of 20 mL in a coil form, then it was connected to another 1 mL capacity micromixer followed by 1.56 mm ID tube having volume of 60 mL in a coil form. The total set-up was immersed in a cryostat / constant temperature bath. The first micromixer was connected with two liquid metering pumps; one for pumping of acetic anhydride and the other for pumping of nitric acid (98%); whereas the second micromixer was connected with third metering pump for metering of n-Butylbenzene. The residence time unit was made of 2 parts connected using a 4-way port for withdrawing a sample for analysis to track the reaction progress at different conditions. A constant temperature bath was used to maintain reactor at appropriate temperature. Each time reaction was continued for 4 hours by feeding the raw materials at desired rate as per residence time. See the Figure-3 for set-up details. The following Table shows the feed rate, and reaction conditions followed in a continuous nitration.

Work-up

The Work-up step was followed as explained under Examples 14-16 in Example B. The following Table 7 shows input and reaction conditions maintained for Examples 21-23.

Table 7 The Table 8 below represents analysis of crude nitro-mass obtained in Examples 21-23 by implementing acetyl nitrate as nitrating agent, in accordance with an embodiment of the present invention.

Table 8

Example E

In this Example, a process followed for Examples 24-25 for commercial large scale nitration of n- Butylbenzene by using a nitrating mixture as nitrating agent is disclosed in accordance with an embodiment of the present disclosure.

The set-up used in nitration on commercial reactor consist of 2000-L capacity stirred tank reactor with limpet coil for cooling, the reactor was associated with falling film cooler, recycle pump circulating liquid from stirred tank to falling film cooler (See the Figure-2). The set-up was associated with n-Butylbenzene feed tank with n-Butylbenzene metering pump, and the set-up was associated with mixed acid (nitrating mixture) feed tank and mixed acid metering pump. The reactor was charged with sulphuric acid, and it was diluted by charging water into it while under stirring. Once the desired temperature of dilute acid was achieved; the dilute acid was kept circulating through the falling film cooler with the help of recycle pump; then the mixed acid (nitrating mixture) and n-Butylbenzene were charged into reactor through the falling film cooler; in a continuous mode at the desired temperature and time. After reaction was over the reaction mixture was digested for one hour and the organic layer and aqueous layers were allowed to separate. The results are as shown in following table.

The below table 9 discloses input reaction conditions of the Examples 24 and 25 where a nitrating mixture was implemented in a commercial scale nitration reactor

Table 9 Further, the Table 10 below represents analysis of crude nitro-mass obtained in Examples 24-25 by implementing nitrating mixture as a nitrating agent in a commercial nitration reactor, in accordance with an embodiment of the present invention.

Table 10

Example F

Control Examples 1-4

In the Example F, control examples 1-4 nitration process of n-butylbenzene in presence of concentrated sulfuric acid in accordance with an embodiment of the present disclosure are represented.

The set-up used in nitration on commercial reactor consist of 2000-L capacity stirred tank reactor with limpet coil for cooling, the reactor was associated with falling film cooler, recycle pump circulating liquid from stirred tank to falling film cooler (See the Figure-2). The set-up was associated with n-Butylbenzene feed tank and the set-up was associated with mixed acid (nitrating mixture) feed tank and mixed acid metering pump. The reactor was charged with concentrated sulphuric acid and then to it n-Butylbenzene was charged to concentrated Sulphuric acid under stirring. Once the desired temperature of concentrated Sulphuric acid and n-Butylbenzene mixture was achieved; the mixture was kept circulating through the falling film cooler with the help of recycle pump; then the mixed acid (nitrating mixture) and n-Butylbenzene were charged into reactor through the falling film cooler; in a continuous mode at the desired temperature and time. After reaction was over the reaction mixture was digested for one hour. The reaction mixture was held standstill; but the layer separation was not observed even for holding long hours. The reaction mixture was diluted with water; but the layer separation was not observed.

Control Examples (Table) as disclosed below shows input and reaction conditions followed in a commercial nitration reactor.

Table

Example G

In this Example G, a process followed for Examples 26-31 for hydrogenation of crude Nitro mass as prepared in Examples 1-25 (crude reaction mass containing isomeric Nitro-n-Butyl benzene mixture) using catalytic hydrogenation is disclosed in accordance with an embodiment of the present disclosure.

In a 5L high pressure reactor equipped with agitator, cooling coil, reaction mass and catalyst charging facility with auto-cooling facility was charged crude Nitro-n-Butyl benzene (Refer Table- 1; out of total 11905 gm of crude Nitro-n-Butyl benzene mass) was charged along with solvent and catalyst. The hydrogenation reactor was inertized several times with nitrogen. Then the reactor was closed and heating was started; as soon as reaction temperature reached to 70-75° C; reactor was pressurized with hydrogen gas as shown in following table, the reaction was allowed to happen, the reaction was maintained under hydrogen pressure till there was no consumption of hydrogen gas. At this point the reaction mass held under hydrogen pressure for additional 30 minutes, then the reaction mass was cooled and depressurized. The total crude nitro products were converted to 2-n- Butyl Aniline (2-BAN), 4-n-Butyl Aniline (4-BAN) etc.

Work-up

The reaction mass containing catalyst was filtered; catalyst was washed with methanol and the catalyst was collected and was reused in next hydrogenation batch. The filtrate containing crude n-

Butyl Aniline was taken for fractional distillation for purification. The results are shown in following Table 11.

Table 11

(a) Fresh catalyst was used; (b) Catalyst from Example 27 was recycled; Catalyst from Example 29 was recycled

Further, the Table 12 below represents analysis of crude hydrogenated mass obtained in Examples 26-31 by hydrogenation catalyst and recycled use of the hydrogenation catalyst, in accordance with an embodiment of the present invention.

Table 12

Example H In this Example H, a process followed for Examples 32-33 for hydrogenation of crude nitro-n-Butyl benzene on commercial scale using catalytic hydrogenation using catalytic hydrogenation is disclosed in accordance with an embodiment of the present disclosure.

The set-up used in catalytic hydrogenation on commercial reactor consist of 5000-L capacity stirred tank reactor with limpet coil for cooling, the reactor was associated gas loading (nitrogen and hydrogen gas) facility. The set-up was associated with crude nitro-n-Butylbenzene, solvent (methanol) charging facility and catalyst charging facility. The reactor was equipped with inline catalyst filter (cricket type filter), catalyst recycle facility etc. The reactor was charged with crude nitro-n-Butylbenzene, then catalyst was charged and finally reactor was charged with fresh or recovered solvent. The hydrogenation reactor was inertized for 5 to 7 times with nitrogen gas. Then the reactor was closed and heating was started; as soon as reaction temperature reached to 60-65° C; reactor was pressurized with hydrogen gas as shown in following table, the reaction was allowed to happen, the reaction was maintained under hydrogen pressure till the desired consumption of hydrogen gas took place. At this point the reaction mass held under hydrogen pressure for additional 60 minutes, then the reaction mass was cooled and depressurized. The total crude nitro products were converted to 2-n-Butyl Aniline (2-BAN), 4-n-Butyl Aniline (4-BAN) etc. The recycling of the H-P-Zeolite catalyst is carried out by a catalyst filtration washing in a catalyst recovery tank, thereby making the process more economical.

Work-up

The reaction mass containing catalyst was filtered; catalyst was washed with methanol and the catalyst was collected and was reused in next hydrogenation batch. The filtrate containing crude n-

Butyl Aniline was taken for fractional distillation for purification. The results are shown in following Table 13.

Table 13

(a) Fresh catalyst was used; (b) Catalyst from Example 32 was recycled

Further, Table- 14 Shows analysis hydrogenated mass of commercial hydrogenation reactor

Table 14

Example I

Purification of 2-n-Butyl Aniline and 4-n-Butyl Aniline The crude material of n-Butyl Aniline as explained under Example 22 and 23 was charged in continuous distillation train having distillation column packed with structured packing with large number of theoretical plates, distillation condenser, re-boiler, product receiver, vacuum pump. The distillation was done sequentially to recover methanol, to recover unreacted n-Butylbenzene, highly pure 2-n-Butyl Aniline and to recover highly pure 4-n-Butyl Aniline. The following Table shows the conditions like temperature and pressure observed during recovery of each component.

Table-15 Shows distillation conditions followed during purification of different components where

4 BAN is obtained 99.3%.

Table 15

In some embodiments of the present invention, the said process (100) preparation of highly pure 4- (n-Butyl) Aniline possesses following advantages but not limited to:

• An n-butylbenzene co-product obtained from a process of manufacturing of iso-Butyl benzene (IBB) by toluene metalation process along with propylene can be used for selective production of make 4-(n-Butyl) Aniline (4-BAN) forming lesser quantity of undesired aniline isomers.

• The process (100) having a better control on the product profile of 4-(n-Butyl) Aniline (4- BAN) and thereby avoiding waste acid generation.

• The process (100) involving liquid phase nitration of n-Butyl benzene which provides zero effluent process enabling recovery and recycle of nitration catalyst.

• The process (100) involving liquid phase nitration of n-Butyl benzene which provides zero effluent process enabling recovery and recycle of hydrogenation catalyst, and thus leaving no effluent stream in the reaction.

• The process (100) is easily manageable and can be operated at almost ambient temperature thus conserving time and energy. The embodiments, examples, and alternatives of the preceding paragraphs or the description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination thereof. Features described in connection with one embodiment apply to all embodiments, unless such features are incompatible. List of Abbreviations:

IBB - iso-Butyl benzene

NBB- n-Butyl Benzene 4-BAN-4-(n-Butyl) Aniline