FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
The Patent Rules, 2003
Provisional Specification
(See section 10 and rule 13)
GREEN REDUCTION OF NITRO - COMPOUNDS INTO CORRESPONDING AMINO - COMPOUNDS WITH INHERENT INFINITE RECYCLE OF PROCESS MOTHER LIQUOR
1. Newreka Chemicals Private Limited
Rang Ashish, 2 Dreamland CHS, Opp Diamond Garden, Chembur,
Mumbai 400 071, Maharashtra State, India
An Indian company registered under the Companies Act, 1956.
2. Mr. Padia, Bhadresh K.
Rang Ashish, 2 Dreamland CHS, Opp Diamond Garden, Chembur, Mumbai 400 071, Maharashtra State, India. An Indian National.
3. Mr. Mehta, Nitesh H.
4 Shri Sanman, Juhu Versova Link Road, Andheri (W), Mumbai 400 053, Maharashtra State, India. An Indian National.
The following specification describes the invention:

GREEN REDUCTION OF NITRO - COMPOUNDS INTO
CORRESPONDING AMINO - COMPOUNDS WITH INHERENT
INFINITE RECYCLE OF PROCESS MOTHER LIQUOR
Field of Invention:
This invention relates to a process for the reduction in general and in particular to reduction of aromatic nitro compounds into the corresponding aromatic amines with total recycle of mother liquor.
Background of Invention:
Reduction is one of the important chemical processes extensively applied in the manufacture of many molecules. Partial or complete reduction of functional groups such as carbonyls, azides, nitriles, azo, nitro and the like yields value added products.
Reduction of aromatic nitro compounds into corresponding aromatic amines finds applications in various groups of chemical including pharmaceuticals, dyes, agrochemicals, explosives, specialty chemicals, and fine chemicals. Many life saving drugs have aromatic amine as one of the building blocks and in most of the processes this important building block is obtained from the reduction of aromatic nitro precursor. One such important drug being currently used to fight against deadly 'AIDS' is 'Nevirapine' [129618-40-2].
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Some of the important amino precursors are, 2-Chloro-3-amino-4-methylpyridine [133627-45-9], m-Aminoacetophenone [99-03-6], o-Aminophenol [95-55-6], p-Aminophenol [51-78-5], 2-Amino-4-picoline [695-34-1], o-Chloroaniline [95-51-2], p-Chloroaniline [106-47-8], o-Phenylendiamine [95-54-5], p-Phenylendiamine [106-50-3], 2-Fluoroaniline [348-54-9], 3-Fluoroaniline [372-19-0].
Methods used for reduction of aromatic nitro compounds into corresponding aromatic amines can be broadly divided into three major categories: (a) chemical reduction (b) catalytic reduction, (c) electrochemical reduction
Skipka, G. et. al., Ger. Offen. DE 2930754 (1981); Skalicky, P. et. al., Czech. CS 248864 Bl (1988), Laucoiner, M. et. al. in Appl. Catal., A, 172(1), 141-148 (1998) disclose methods of chemical reduction, which include metal and acid reduction such as Bechamp reduction, sulfide reduction, metal hydride reduction, hydrazine hydrate reduction and the like. Some of the drawbacks of these methods are that these processes require extreme pH conditions, handling of strong acids/strong alkalis, working in poisonous H2S / SO2 atmosphere, handling of pyrophoric and/or explosive material, and expensive MOC for the equipment. Another drawback is that these methods generate large quantities of liquid waste which is difficult to recycle, resulting in processes involving extreme pH conditions and having lot of negative impact on the environment.
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Shimanzu, K. et. al. JP 9,132,536 (1997); Kuo, E. et. al. in Syn. Commun. 15(7), 599 (1985), disclose methods of catalytic reduction. The drawbacks of these methods, which normally use noble metal catalysts, are that they use highly inflammable hydrogen gas and require high pressure and/or high temperature. Further drawbacks of these methods are that they involve catalyst poisoning and regeneration, handling of pyrophoric catalysts, high cost due to use of pressure reactors and noble metal catalysts resulting in expensive and unsafe processes.
Gunawardena, N. E. et. al., Acta. Chem. Scand., Ser. B, B37 (6), 549-53 (1983); Starke, C. et. al. in Chem. Tech. (Leipzig), 35(9), 463-5 (1983) describe electrochemical reduction methods. These methods suffer from drawbacks such as poor conversion rates and low yields, and that these methods require large quantum of electricity, rendering these methods quite uneconomical.
Furthermore, another drawbacks of all methods described above is that undesirable side products are always formed. The type of side products formed and their quantities vary from process to process and from molecule to molecule. The side products build-up during recycles and after these side products reach certain concentration, they start contaminating the product inhibiting further recycles. This difficulty during recycle of mother liquor results in generation of large quantities of liquid effluents.
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Yet another drawback of the methods referred to above is that in some cases solid wastes are also generated, especially in iron reduction. These solid wastes are contaminated with organic compound like starting material, product and side products and pose a serious pollution problem. Normally these wastes are sticky solids and are tedious to handle and are difficult to dispose, and are known in the industry as non-green solid wastes.
There are still further drawbacks of the above methods. Because of generation of large quantities of liquid effluents and non-green solid wastes, above processes require a large facility for effluent treatment and disposal of solid wastes. These factors impose location related constraints making it mandatory for these processes to be carried out only in designated industrial areas, suitable for handling special chemicals.
Thus, these methods are non-green and harm the environment to a very large extent, which has worldwide become a major concern.
Hence there is a need for providing a process of green reduction of nitro compounds into corresponding amino compounds with inherent infinite recycle of process mother liquid, thereby avoiding above mentioned disadvantages and drawbacks.
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Objects and Advantages of Invention:
The inventors of Newreka Chemicals Pvt. Ltd. have developed a novel process for the reduction of aromatic nitro compounds into corresponding aromatic amines.
An object of the process of the present invention is to provide an environmentally friendly (green) process that overcomes the problem of generation of large quantities of liquid wastes resulting from the conventional processes of reduction.
Another object of the present invention is to provide a process, wherein side reactions leading to side products formation are totally avoided which results in purer product formation.
An advantage of the present invention is that since side products are not formed, the possibility of build-up of side products in mother liquor during recycles is nil. This fact advantageously makes possible infinite number of mother liquor recycles in our process.
A further advantage of the method of present invention is that the product isolation and purification disclosed herein makes sure that the solid spent formed in the process of the present invention are not contaminated with organic compounds and thus are green in nature.
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A still further advantage of the present invention is that the spent is non-brown in colour and is non-sticky, which makes their handling easier and simpler than conventional processes. Solid spent formed in the process of the present invention is environmentally friendly and moreover finds applications in construction industry specifically in manufacture of bricks and cement.
Consequently, the process described herein does not require any effluent treatment facility or solid waste disposal facility and does not have any location constraints unlike existing processes. This is a further advantage over the conventional processes.
As yet another advantage of the present invention is that the method disclosed herein not only is green but the aromatic amines produced at the end of the process are also greener owing to the fact that they have fewer impurities.
A yet further advantage of the present invention is that the method disclosed herein is carried out at milder pH conditions and at atmospheric pressure, which makes it safer.
Summary of the invention:
The method of the present invention creates a closed water loop. The waste stream
generated is recycled completely in the reaction making our process a zero liquid
waste process.
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In short, this invention relates to a green process for the reduction of aromatic nitro compounds into corresponding aromatic amines that produces greener aromatic amines in good yields with infinite recycles of mother liquor and has a wide scope since it can be applied to many molecules.
Brief Description of Figures:
Figure 1 shows a green reaction sequence with complete and infinite number of
mother liquor recycles.
Figure 2 shows green isolation and purification sequence with complete and
infinite number of mother liquor and washings streams.
Figure 3 shows green complete sequence with complete and infinite number of
recycles of all the liquid streams, schematically represented as a close loop as
disclosed in the present invention.
Detailed description of the invention:
The process of the present invention basically comprises two sequences. The first sequence is represented in Figure 1 and is termed as the green reaction sequence with complete and infinite number of mother liquor recycles.
The second sequence is represented in Figure 2 and is termed as the green
isolation and purification sequence with complete and infinite number of mother
liquor and washings streams.
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The combined process involved in first and second sequences as disclosed in the present invention is shown in Figure 3.
Details of the steps involved in the process are described below, with reference to figures 1, 2, and 3.
Step 1.1 - Start-up: As shown in figure 1, a portion of the mother liquor (in the range of 1 to 25 factor, preferably in the range of 4 to 8 factor) from the earlier run is charged into a round bottom flask equipped with stirrer having speed of 5 to 100 rpm, heat exchanger, thermometer;' and charging port arranged in heating/cooling system. Sulfuric acid is added and total mass is heated to temperature in the range of 0°C to 100°C, preferable range being 50°C to 100°C during 0 hours to 5 hours at the pH range of 2 to 9, preferable pH range being 4 to 8. NRC or customized proprietary catalytic formulation or any other reducing agent is charged.
Step 1.2 - Reduction: R-NO2 (1 factor), NRC / Reducing agent and portion of
mother liquor (in the range of 5 to 25 factor, preferably in the range of 8 to 16) in
any number of lots, preferably in the range of in 0 to 20 lots in given or different
sequence at temperature range of 0°C to 100°C, preferable range being 50°C to
100°C at the pH range of 2 to 12, more preferable pH range being 4 to 8, still
more preferable pH range being 5 to 6 is charged to the reaction mixture.
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Step 1.3 - Neutralisation: After completion of the reaction pH is adjusted in the range of 2 to 12, preferable pH range being 6.5 to 7.0, more preferable pH being 7, by charging NPC or NGC or customized proprietary neutralizing formulation or any other neutralizing agent at temperature range of 0°C to 100°C, preferable range being 50°C to 100°C, during 0 hours to 5 hours.
Step 1.4 - Purification: Activated carbon is charged to the reaction mixture at the pH range of 2 to 12, preferable pH range being 4 to 8, typical pH range being 5 to 6, at the temperature range of 0°C to 100°C, preferable range being 50°C to 100°C during 0 hours to 10 hours under stirring.
Sequence 2.0 - Green Reaction sequence:
Step 2.1 - Settling and Decantation: Stirring is stopped, at the pH range of 2 to 12, preferable pH range being 4 to 8, more preferable pH range being 5 to 6, the mass is settled for 0 hours to 10 hours at the temperature range of 0°C to 100°C, preferable range being 50°C to 100°C. Upper aqueous layer is decanted at the temperature range of 0°C to 100°C, preferable temperature range being 30°C to 95°C, at the pH range of 2 to 12, preferable pH range being 4 to 8, more preferable pH range being 5 to 6.
Step 2.2 - Stirring, Settling, and Decantation: Remaining portion of mother
liquor (in the range of 5 to 25 factor, preferable range being 8 to 16, more
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preferable range being of 9 to 12) is charged and the total mass is maintained at the temperature range of 0°C to 100°C, preferable range being 50°C to 100°C under stirring for 0 hours to 12 hours at the pH range of 2 to 12, preferable pH range being 4 to 8, more preferable pH range being 5 to 6. Stirring is stopped, the mass is settled for 0 hours 12 hours Upper aqueous layer is decanted at the temperature range of 0°C to 100°C, preferable temperature range being 30°C to 95°C, at the pH range of 2 to 12, preferable pH range being 4 to 8, more preferable pH range being 5 to 6.
Step 2.3 - Stirring, Settling, and Decantation:
Washings from the earlier run (in the range of 5 to 25 factor, preferable range being 8 to 16, more preferable range being of 9 to 12) is charged and the total mass is maintained at the temperature range of 0°C to 100°C, preferable range being 50°C to 100°C under stirring for 0 hours to 12 hours at the pH range of 2 to 12, preferable pH range being 4 to 8, more preferable pH range being 5 to 6. Stirring is stopped, the mass is settled for 0 hours 12 hours Upper aqueous layer is decanted at the temperature range of 0°C to 100°C, preferable temperature range being 30°C to 95°C, at the pH range of 2 to 12, preferable pH range being 4 to 8, more preferable pH range being 5 to 6.
Step 2.4 - Filtration and Washing: After filtration of the solid, fresh water (in
the range of 1 to 10 factor, preferable range being 2 to 8, more preferable range
being of 4 to 6) is charged to the wet cake of the solid washing for washing the
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wet cake at the temperature range of 0°C to 100°C, preferable range being 0°C to 100°C at the pH range of 2 to 12, more preferable pH range being 4 to 8, still more preferable pH range being 5 to 6.
Step 2.5 - Crystallisation: Combined aqueous mass at the pH range of 2 to 12, preferable pH range being 4 to 8, more preferable pH range being 5 to 6. is maintained under stirring at the temperature range of-10°C to 100°C, preferable range being 0°C to 50°C for 0 hours to 40 hours.
Step 2.6 - Filtration: Crystallized product is then filtered and washed with water (in the range of 1 to 10 factor, preferable range being 2 to 8, more preferable range being of 3 to 5) at the temperature range of 0°C to 100°C, preferable range being 0°C to 100°C at the pH range of 2 to 12, preferable pH range being 4 to 8, more preferable pH range being 5 to 6.
The solid is dried by any method selected from known methods of drying in the temperature range of 0°C to 100°C during 0 hours to 20 hours
The mother liquor and washings are stored for recycle in different steps for infinite number of times, particularly at least for 100 times.
The solid spent generated in the above sequence (in the range of 1 to 10, typical
range being 3 to 6) is crystalline and non-sticky in nature. Colour of the spent
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ranges from gray to jet-black, particularly the colour is black. The pH of the spent is in the range of 6.5 to 7.0. The moisture content is in the range of 5% to 50%, particular range being 10% to 20%.
The present invention is generally applicable to processes with the following parameters:
1. Temperature range of 0°C to any temperature, preferable temperature range being 50°C to 100°C.
2. pH range of 1 to 14, preferable pH range being 3 to 9.
3. Preferably NRC or any other customized Proprietary Catalytic Formulation or any other reducing agent loading in the range of 0.5% to 50%.
4. Preferably NPC & NGC or any other customized Proprietary Catalytic Formulations or any other neutralizing agent loading in the range of 1% to 30%.
5. Any pressure, preferable being atmospheric pressure.
6. Preferable water factor in the range of 1 to 25 for the reaction and 1 to 75 for the isolation of the product.
7. Temperature for crystallization in the range of-10°C to any temperature, preferable range being 0°C to 50°C.
8. Solvents for the reaction and isolation of the product include water miscible, water immiscible, aromatic, aliphatic or mixture thereof in any combination and any composition or otherwise, preferable solvent being water.
9. Liquid streams recycle in the range of 1 to 100, extendable to any number of
recycles. ,
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10. For the amines with solubility in the range of 0.1% to 100%
11. Colour of the spent generated in the range of gray to jet black, typically black.
12. pH of the spent in the range of 6 to 8, typically the range being 6.5 to 7.0.
13. Nature of the spent is non-sticky and crystalline.

14. Moisture content in the spent in the range of 5% to 50%, typical range being 10% to 20%
15. For the nitro compounds having one or more nitro groups including aromatic nitro compound like nirobenzenes, nitronaphthalenes, nitroanthracenes, nitrophenanthrenes, heterocyclic nitro compounds with one or more hetero atoms either same or different, aliphatic nitro compounds and all such other nitro compounds.

Dated this 04th Day of April, 2006
(Mr. Tase, Sharatchandra Dattatraya) Applicant's patent agent Registration Number IN/PA 879
To,
The Controller of patents
The Patent Office Branch at Mumbai.
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