DESC:FORM 2
THE PATENT ACT 1970
(39 of 1970)
&
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)

“A PROCESS FOR PREPARATION OF AROMATIC AMINES”

SRF LIMITED, AN INDIAN COMPANY,
SECTOR 45, BLOCK-C, UNICREST BUILDING,
GURGAON – 122003,
HARYANA (INDIA)

The following specification particular describe the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
The present invention provides a process for preparation of aromatic amine.

BACKGROUND OF THE INVENTION
Aromatic amines are useful intermediate in agriculture and pharmaceutical industries.
Chinese Patent No. 109053461A discloses a process for preparation of 2-chloro-4-aminotoluene by catalytic hydrogenation of 2-chloro-4-nitrotoluene using Raney Ni in methanol.
Chinese Patent No. 102786424 discloses a process for preparing 3-chloro-4-methylaniline from 3-chloro-4-methylnitrobenzene via catalytic hydrogenation using Pd-Fe/C as catalyst in an alcoholic solvent.
Chinese Patent No. 102285891 discloses a method for hydrogenation of aromatic nitro compound to prepare aromatic amine by catalytic hydrogenation in the presence catalyst and inhibitor ammonium compounds.
Gongye Cuihua (2016), 24(3), 79-81 discloses a process for catalytic hydrogenation of 3-chloro-4-methylnitrobenzene to 3-chloro-4-methylaniline over Pt/C catalyst.
Chinese Patent No. 104370747A discloses a process for hydrogenation for preparation of 3-chloro-4-methylaniline using carbon carried palladium catalyst.
Chemistry Select (2020), 5(23), 7086-7092 discloses a process for hydrogenation of 2-Iodo-1-methyl-4-nitrobenzene to form 3-Iodo-4-methylaniline using nanoporous palladium.
Green Chemistry (2018), 20(1), 130-135 discloses a process for hydrogenation of 2-bromo-1-methyl-4-nitrobenzene to form 3-bromo-4-methylaniline using Nickel (supported on iron nanoparticles with < 0.2% Pd), and Palladium (supported on iron nanoparticles with < 0.2 % Ni).
All the process known in the art use metal which are either expensive or pyrophoric hence pose challenges in recycling and disposal at the commercial scale. Therefore, a need was felt to develop a commercially viable and environment friendly process for preparation of aromatic amines.

OBJECT OF THE INVENTION
The present invention provides a commercially viable and environment friendly process for preparation of aromatic amine.

SUMMARY OF THE INVENTION
The present invention provides a process for preparation of an aromatic amine, comprising a step of reducing a nitro substituted aromatic compound using hydrogen in presence of encapsulated metal catalyst.

DETAILED DESCRIPTION OF THE INVENTION
As defined herein, C1-C3 alkyl refers to methyl, ethyl or propyl groups optionally substituted by one or more fluorine or chlorine.
The present invention provides a process for preparation of an aromatic amine, comprising a step of reducing a nitro substituted aromatic compound using hydrogen in presence of encapsulated metal catalyst.
In embodiment of the present invention, the encapsulated metal catalyst selected from Palladium and Nickel including 4% encapsulated Palladium, Graphene encapsulated Pd @ C, Graphene encapsulated Ni @ C, Ni Encat and Ni Encat TM PRO+, Pd Encat 30 NP, Pd Encat 30 and Pd Encat 40 or the like. The encapsulated palladium and nickel catalyst are non-pyrophoric and are safer to handle and dispose of compared to Pd/C. The “encapsulated” refers to a catalyst which is contained within a permeable polymer matrix. The polymer capsule matrix is permeable to the extent that the reaction medium being catalysed can contact the encapsulated catalyst.
In another embodiment of the present invention, the encapsulated metal catalyst is either spherical, cylindrical and granules or the like.
In another embodiment of the present invention, the catalyst is recovered in the process and reused. The recovery of palladium is >98%.
In another embodiment of the present invention, the step of reduction is carried out in a solvent selected from a group consisting of methanol, ethanol, propanol, 2-propanol, butanol, and 2-methyl-2-propanol or the like.
In another embodiment of the present invention, the step of reduction is carried out at a temperature of 50 to 70oC, preferably 65oC.
In another embodiment of the present invention, the step of reduction is carried out at a pressure of 10 to 20 bars, preferably 16 bars.
In another embodiment of the present invention, the aromatic amine is a compound of formula I,

Formula I
wherein X is one or more independently selected from a group consisting of hydrogen, chlorine, bromine, fluorine and C1-C3 alkyl.
In another embodiment of the present invention, the nitro substituted aromatic compound is a compound of formula II,

Formula II
wherein X is as defined above.
In another embodiment of the present invention, the aromatic amine is aniline or pyridine, optionally substituted by methyl, trifluoromethyl, ethyl, chloro, fluoro, and bromo group and is selected from a group consisting of 2-chloroaniline; 3-chloroaniline; 4-chloroaniline; 2-chloro-3-methylaniline; 2-chloro-4-methylaniline; 2-chloro-5-methylaniline; 2-chloro-6-methylaniline; 3-chloro-2-methylaniline; 3-chloro-4-methylaniline; 3-chloro-5-methylaniline; 3-chloro-6-methylaniline; 4-chloro-2-methylaniline; 2-methylaniline; m-methylaniline; p-methylaniline; o-ethylaniline; m-ethylaniline; p-ethylaniline; 2,3-dimethylaniline; 2,4-dimethylaniline; 2,5-dimethylaniline; 2,6-dimethylaniline; 3,4-dimethylaniline; 3,5-dimethylaniline; 2,3,4-trimethylaniline; 2,3,5-trimethylaniline; 2,3,6-trimethylaniline; 2,4,5-trimethylaniline; 2,4,6-trimethylaniline; 3,4,5-trimethylaniline; 2,3,4,5-tetramethylaniline; 2,3,5,6-tetramethylaniline; 2,3,4,6-tetramethylaniline; 2-chloro-3-(trifluoromethyl)aniline; 2-chloro-4-(trifluoromethyl)aniline; 2-chloro-5-(trifluoromethyl)aniline; 2-chloro-6-(trifluoromethyl)aniline; 3-chloro-2-(trifluoromethyl)aniline; 3-chloro-4-(trifluoromethyl)aniline; 3-chloro-5-(trifluoromethyl)aniline; 3-chloro-6-(trifluoromethyl)aniline; 4-chloro-2-(trifluoromethyl)aniline; 2-(trifluoromethyl)aniline; m-(trifluoromethyl)aniline and p-(trifluoromethyl)anilinepentamethylaniline or the like.
Unless stated to the contrary, any of the words “comprising”, “comprises” and includes mean “including without limitation” and shall not be construed to limit any general statement that it follows to the specific or similar items or matters immediately following it.
Embodiments of the invention are not mutually exclusive but may be implemented in various combinations. The described embodiments of the invention and the disclosed examples are given for the purpose of illustration rather than limitation of the invention as set forth in the appended claims.
The following example is given by way of illustration and therefore should not be construed to limit the scope of the present invention.
EXAMPLES
Example 1: Preparation of 3-chloro-4-methylaniline
2-Chloro-4-nitrotoluene (50 g, 0.29 moles) was taken with methanol (480g, 15mol) and added catalytic quantity (0.83 g, 0.00015 moles) of 4% Pd (0) Encat 30 NP. Charged the above solution into 1000 mL parr reactor (SS). Reaction mass was heated to 65°C and raised the reaction pressure to 16 bar by introduced hydrogen gas. Reaction was performed by continuous feeding of hydrogen gas (1.74g, 0.87moles). Progress of the reaction was monitored by gas chromatography technique. After getting the desired conversion, terminate the hydrogen feeding, cool and unload the reaction mass. Performed atmospheric distillation to separate the solute, followed by negative pressure distillation to get pure product (37.8g, Purity: 98.00%, Yield: 90%).
Example 2: Preparation of 3-trifluoromethylaniline
3-Trifluoromethylnitrobenzene (50g, 0.26moles) was taken with methanol (480g, 15mol) and added catalytic quantity (0.83 g, 0.00015 moles) of 4% Pd (0) Encat 30 NP. Charged the above solution into 1000 mL parr reactor (SS). Reaction mass was heated to 65 °C and raised the reaction pressure to 16 bar by introducing hydrogen gas. Reaction was performed by continuous feeding of hydrogen gas (1.56g, 0.78moles). Progress of the reaction was monitored by gas chromatography technique. After getting the desired conversion, terminate the hydrogen feeding, cool and unload the reaction mass. Performed atmospheric distillation to separate the solute, followed by negative pressure distillation to get pure product (38.2g, Purity: 98.90 a%, Yield: 92%).
Example 3: Preparation of 2,6-dimethylaniline
2,6-Dimethylnitrobenzene (50g, 0.33moles) was taken with methanol (480g, 15moles) and added catalytic quantity (0.83 g, 0.00015 moles) of 4% Pd (0) Encat 30. Charged the above solution into 1000 mL parr reactor (SS). Reaction mass was heated to 65 °C and raised the reaction pressure to 16 bar by introducing hydrogen gas. Reaction was performed by continuous feeding of hydrogen gas (1.98g, 0.99moles). Progress of the reaction was monitored by gas chromatography technique. After getting the desired conversion, terminate the hydrogen feeding, cool and unload the reaction mass. Performed atmospheric distillation to separate the solute, followed by negative pressure distillation to get pure product (36.37g, Purity: 98.80 a%, Yield: 89%).
Example 4: Preparation of 2-chloroaniline
2-Chloro-nitrobenzene (50g, 0.32moles) was taken with methanol (480g, 15moles) and added catalytic quantity (0.83g, 0.00015moles) of 4% Pd (0) Encat 30 NP. Charged the above solution into 1000 mL parr reactor (SS). Reaction mass was heated to 65 °C and raised the reaction pressure to 16 bar by introducing hydrogen gas. Reaction was performed by continuous feeding of hydrogen gas (1.92g, 0.96moles). Progress of the reaction was monitored by gas chromatography technique. After getting the desired conversion, terminate the hydrogen feeding, cool and unload the reaction mass. Performed atmospheric distillation to separate the solute, followed by negative pressure distillation to get pure product (37.14g, Purity: 99.10 a%, Yield: 90%).
EXAMPLE 5: Preparation of 2-chloro-3-trifluoromethylaniline
2-Chloro-3-trifluoromethylnitrobenzene (50g, 0.22moles) was taken with methanol (480g, 15mol) and added catalytic quantity (0.83g, 0.00015moles) of 4% Pd (0) Encat 30 NP. Charged the above solution into 1000 mL parr reactor (SS). Reaction mass was heated to 65 °C and raised the reaction pressure to 16 bar by introducing hydrogen gas. Reaction was performed by continuous feeding of hydrogen gas (1.34g, 0.66moles). Progress of the reaction was monitored by gas chromatography technique. After getting the desired conversion, terminate the hydrogen feeding, cool and unload the reaction mass. Performed atmospheric distillation to separate the solute, followed by negative pressure distillation to get pure product (39.35g, Purity: 99.30 a%, Yield: 89%).

EXAMPLE 6: Preparation of 3-chloro-4-methylaniline
2-Chloro-4-nitrotoluene (50 g, 0.29 moles) was taken with methanol (480g, 15mol) and added catalytic quantity (0.038g, 0.00015 moles) of Ni Encat TM PRO (50%, Ni content 22-25%) Charged the above solution into 1000 mL parr reactor (SS). Reaction mass was heated to 65 °C and raised the reaction pressure to 16 bar by introducing hydrogen gas. Reaction was performed by continuous feeding of hydrogen gas (1.9g, 0.9moles). Progress of the reaction was monitored by gas chromatography technique. After getting the desired conversion, terminate the hydrogen feeding, cool and unload the reaction mass. Performed atmospheric distillation to separate the solute, followed by negative pressure distillation to get pure product (37.3g, Purity: 98.00%, Yield: 90%).

,CLAIMS:

WE CLAIM:
1. A process for preparation of an aromatic amine, comprising a step of reducing a nitro substituted aromatic compound using hydrogen in presence of encapsulated metal catalyst.
2. The process as claimed in claim 1, wherein the encapsulated metal catalyst is based on Palladium and Nickel.
3. The process as claimed in claim 2, wherein the encapsulated metal catalyst is selected from Palladium and Nickel comprising 4% encapsulated Palladium, Graphene encapsulated Pd @ C, Graphene encapsulated Ni @ C, Ni Encat, Ni Encat TM PRO+, Pd Encat 30 NP, Pd Encat 30 and Pd Encat 40.
4. The process as claimed in claim 1, wherein the encapsulated metal catalyst is spherical, cylindrical or granule.
5. The process as claimed in claim 1, wherein the encapsulated metal catalyst is recovered and reused.
6. The process as claimed in claim 1, wherein the step of reduction is carried out in a solvent selected from a group consisting of methanol, ethanol, propanol, 2-propanol, butanol, and 2-methyl-2-propanol or a mixture thereof.
7. The process as claimed in claim 1, wherein the step of reduction is carried out at a temperature selected in the range of 50 to 70oC.
8. The process as claimed in claim 1, wherein the step of reduction is carried out at a pressure selected in the range of 10 to 20 bars.
9. The process as claimed in claim 1, which comprises the step of reducing a nitro substituted aromatic compound of formula II using hydrogen in presence of encapsulated metal catalyst to obtain the aromatic amine compound of formula I,

Formula I Formula II

wherein X is one or more independently selected from a group consisting of hydrogen, chlorine, bromine, fluorine and C1-C3 alkyl.

Dated this 20th day of December 2022.