FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
The Patent Rules, 2003
Complete Specification
(See section 10 and rule 13)
Sustainable Chemical Process For Reduction Of 4-Methoxy-2-Nitroaniline To 4-Methoxy Benzene-1,2-Diamine, In Neutral Reaction Medium With Inherent Recycle Of Neutral Mother Liquor And Solvent Streams In Reduction Step In The Synthesis Of Omeprazole
Newreka GreenSynth Technologies Private Limited ; Rang Ashish, 2 Dreamland CHS, Opp Diamond Garden, Chembur, Mumbai 400 071, Maharashtra State, India ; Indian company registered under the Indian Companies Act, 1956.
Mr. Bhadresh K Padia; 1301, Emerald II, Royal Palms, Aarey Colony, Goregaon (E) Mumbai 400 065, Maharashtra State, India ; An Indian National
Nitesh H Mehta; 620, Rock Enclave, Near Hindustan Naka, Charkop, Kandivali (W) Mumbai 400 067, Maharashtra State, India; An Indian National
The following specification particularly describes the invention and the manner in which it is to be performed.

SUSTAINABLE CHEMICAL PROCESS FOR REDUCTION OF 4-METHOXY-2-NITROANILINE TO 4-METHOXY BENZENE-1,2-DIAMINE, IN NEUTRAL REACTION MEDIUM WITH INHERENT RECYCLE OF NEUTRAL MOTHER LIQUOR AND SOLVENT STREAMS IN REDUCTION STEP IN THE SYNTHESIS OF OMEPRAZOLE
Field of Invention:
This invention relates to a process for reduction of 4-methoxy-2-nitro aniline to 4-methoxybenzene-l,2-diamine which is intermediate in the synthesis of 5-methoxy-2-[[(4-methoxy-3,5-dimethyl-2-pyridinyl)methyl]sulfmyl]-lH-benzimidazole, known under the generic name Omeprazole, with inherent recycle of the neutral mother liquor (aqueous stream) & solvent stream back in the process where it is generated.
Background of the invention:
Reduction, broadly defined as addition of hydrogen or removal of oxygen from any chemical, is one of the important chemical processes extensively applied in the manufacture of many molecules. Partial or complete reduction of functional groups such as nitro, nitroso, carbonyls, azides, nitriles, azo, and the like yields value added products.
Reduction of R-N02/R-NO compounds into corresponding" R-NH2 finds applications in various groups of chemical including pharmaceuticals, dyes and pigments, agrochemicals, specialty chemicals, fine chemicals and explosives.
Many pharmaceutical & API's (active pharmaceutical ingredients), dyes, specialty fine chemicals have R-NH2 as one of the building blocks and in most of the

processes this important building block is obtained from the reduction of R-N02/R-NO precursor.
Methods used for reduction of R-N02 or R-NO into corresponding R-NH2 can be broadly divided into three major categories: (a) chemical reduction (b) catalytic reduction, (c) electrochemical reduction.
Indian Journal of Chemistry, {Vol. 45B, July 2006 pp.(1756-1758)}, Route-I speaks about the compound 4-methoxy-2-nitroaniline can be reduced to 4-methoxy-l,2-phenylene diamine, using four different reducing agent like SnC12.2H20 & Cone. HC1, Zinc dust & NaOH, Sn granules and HC1 and Na2S.9H20 gives substantial rise in yield.
But the drawback is that these methods generate large quantities of alkaline liquid waste which is difficult to recycle. These methods require environmentally unsustainable reaction conditions in terms of pH, temperature, concentration, reaction agents and medium, and so on, and leave an unsustainable impact on the environment, specifically on our water bodies.
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 material of construction (MOC) for the equipment.

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, unsafe, and unsustainable, and inherently non-recyclable 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 uneconomical and environmentally unsustainable.
Pelster-Heinrich FR 1481040 (1967), Hu, Zhangyun from Ranliao Gongye (2002), 39(4), 32-34, Luo, Junlong from Faming Zhuanli Shenqing Gongkai Shuomingshu (2009), CN 101362710 A 20090211, Wang, Zaijun; Shi, Yan from Faming Zhuanli Shenqing Gongkai Shuomingshu (2009), CN 101337915 A 20090107, Sun, Chunbao; Lin, Hai; Wang, Zuosheng; Song, Bo from Faming Zhuanli Shenqing Gongkai Shuomingshu (2006), CN 1807269 A 20060726, By Wang, Yong-guang from Anquan Yu Huanjing Gongcheng (2006), 13(1), 70-72, 76, Rao, R. Nageswara; Venkateswarlu, N.; Khalid, Sara; Narsimha, R.; Sridhar, S. from Journal of Chromatography, A (2006), 1113(1-2), 20-31, Chai, Li-min; Zhang, Feng-bao; Zhang, Guo-liang from Desalination (2005), 180(1-3), 157-162, Horsch, Philip; Speck, Andreas; Frimmel, Fritz H. from Water Research (2003), 37(11), 2748-2756, Rao, R. Nageswara;Venkateswarlu, N. from Process Biochemistry (Amsterdam, Netherlands) (2006), 41(5), 1097-1105, describes effluent treatment generated during the synthesis using various chemical &/ or

physical methods such as, electrolysis, chemical oxidation, reverse osmosis, vacuum distillation, ion exchange resin base separation and so forth. Inherently these methods are describes effluent treatment method which is end of pipe solution and not the recycle of mother liquor.
Furthermore, other drawback of all methods described above is that undesirable organic and inorganic side products are always formed as a result of these methods. The type of side products formed and their quantities vary from process to process and from molecule to molecule. This difficulty during recycle of acidic mother liquor results in generation of large quantities of liquid effluents.
Yet another drawback of the methods referred to above is that in some cases inorganic solid wastes are also generated. These solid wastes are contaminated with organic compounds 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 off, 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 acidic liquid effluents and non-green solid wastes, above processes require a large facility for effluent treatment and disposal of solid wastes.
Cyclization:
Indian Journal of Chemistry, {Vol. 45B, July 2006 pg nos 1756-1758}, Route-I speaks about the compound 4-methoxy-l,2-phenylene diamine can be cyclised to 5-methoxy-lH-Benzimidazole-2-thiol by using KOH/CS2. Route-II speaks about reduction of 4-methoxy-2-nitroaniline & simultaneously cyclization to reduced compound to 5-methoxy-lH-Benzimidazole-2-thiol by using KOH/CS2. Route-Ill speaks about simultaneously hydrolysis and reduction of 4-methoxy-2-

nitroacetanilide to get 4-methoxy-2nitroaniline followed by cyclization of the same to get 5-methoxy-lH-Benzimidazole-2-thiol by using KOH/CS2.
The drawback of these methods of cyclization is that, these processes generate large quantity of alkaline liquid effluent both aqueous and solvent streams, hence above processes require a large facility for effluent treatment and disposal of 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, unsustainable, uneconomical, 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 R-NO2 or R-NO compounds into corresponding amino compounds (R-NH2) with inherent recycle of acidic mother liquor, thereby avoiding above mentioned disadvantages and drawbacks, and providing an environmentally sustainable and economical recycling solution.
Objects and Advantages of Invention:
In order to overcome the various serious drawbacks of the existing methods, the inventors at 'Newreka Green Synth Technologies Pvt. Ltd.' have developed a novel process using commercially available customized formulations such as G-Cat, NGC, R-Cat, for the reduction of R-N02 or R-NO into corresponding R-NH2 and recycle of the neutral aqueous stream & solvent stream in reaction itself.

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 waste resulting from the conventional processes of reduction.
Another object of the present invention is to provide a process, wherein undesirable side reactions leading to organic and inorganic side products formation are substantially reduced by the virtue of chemo-selectivity and regio-selectivity which results in purer product formation.
An advantage of the present invention is that since both the number and quantity of organic and inorganic impurities are comparatively less, the possibility of build of side products in acidic mother liquor during recycle is less due to use of proprietary formulation G-Cat, NGC & R-Cat . This fact advantageously makes possible large number of mother liquor recycles in our process.
A further advantage of the method of present invention is that the product isolation processes disclosed herein ensure that the solid spent formed in the process of the present invention has surprisingly low levels of organic compounds and are thus green in nature. Consequently, the process described herein does not require any acidic liquid effluent treatment facility or elaborate solid waste disposal facility. A further advantage of the process of the present invention over the prior art is that the process is not constrained in respect of plant location, in that it doesn't necessarily have to be carried out in industrial areas.
A still further advantage of the present invention is that the inorganic by-product is non-sticky, which makes their handling easier and simpler than conventional processes.
Yet another advantage of the present invention is that the method disclosed herein not only is green and sustainable but the R-NH2 produced by the process is also

greener owing to the fact that they have fewer impurities. This makes downstream processing and application that involve this R-NH2 highly recyclable.
A yet further advantage of the present invention is that the method disclosed herein is carried out at milder acid concentrations and at atmospheric pressure, which makes it safer.
Another advantage of the present invention is that the use of the proprietary reaction formulations developed by the inventors, namely G-Cat, NGC and R-Cat or any other similar formulations used in the process of this invention makes it possible to recycle the neutral process liquid stream and solvent stream completely.
A still further advantage of the process of the present invention is that its inherent thermodynamic conditions defined in terms of pressure, temperature, pH, concentrations of reaction components, and various reaction agents is close to respective conditions naturally occurring in the nature, thereby making the process of the invention benign and environmentally friendly.
There are several other key advantages of the process of the present invention. These relate to health and safety, process engineering, process economics. The process of the present invention is inherently safe due to the safe levels of the process parameters such as pressure, temperature, pH, concentrations of reaction components, and various reaction agents. This reduces the risk of injuries to the personnel and damage to the process plant.
The simplicity of the process also makes its engineering design simple. One other key advantage is that the plant and process breakdowns that could take place due to factors such as power failure, or uncontrolled fluctuations in the process parameters, do not affect the recyclability of the process. This leads to reduction

in wastage on account of batch failures. The process therefore is able to avoid sudden shocks to the environment and sudden safety shocks to the plant and the personnel, ultimately leading to sustainable health of plant and personnel.
The process is carried out at such temperatures and pH values that it saves energy and therefore results in the process economy.
Summary of the invention:
The invention discloses a sustainable chemical process of reduction of 4-methoxy-2-nitroaniline to 4-methoxy benzene-1,2-diamine, wherein the said process is carried out using a neutral reaction medium and comprises inherent recycling of said neutral reaction medium in a plurality of cycles, each of said cycles has a reaction sequence and a extraction and layer separation sequence, wherein said extraction and layer separation sequence follows said green reaction sequence. This is distinct from the existing process where the reaction medium used is either acidic or alkaline but not neutral. This has massive environmental as well as cost benefits.
Detailed description of the invention:
In order to aid the understanding of the process described herein several terms are explicitly defined.
• Reaction medium (RM) is the aqueous phase which is either acidic or alkaline or system with a miscible solvent or immiscible solvent, either high boiling or low boiling or a combination thereof used in the reaction.
• Fresh reaction medium (FRM) is the fresh aqueous phase which is either acidic or alkaline or system with a fresh miscible solvent, or fresh immiscible solvent, either high boiling or low boiling or a combination thereof used in the reaction.

• Extraction medium (EM) is the organic phase which is either polar, non polar, protic, nonprotic or aprotic solvent which is either high boiling or low boiling or a combination thereof used in the reaction.
• Fresh Extraction medium (FEM) is the fresh organic solvent phase which is either polar, non polar, protic, nonprotic or aprotic solvent, either high boiling or low boiling or a combination thereof used in the reaction.
• Solvent is any suitable solution that is water miscible or immiscible, either high boiling or low boiling, aromatic or aliphatic which is linear or branched, either substituted or unsubstituted or mixture thereof.
• Reaction medium factor (RMF) is the ratio of the weight of FRM or RM with weight of R-NO2 or R-NO used in the process.
• Extraction medium factor (EMF) is the ratio of the weight of FEM or EM with weight of R-NO2 or R-NO used in the process.
• Mother liquor (ML) is the liquid stream generated after performing a particular step. Mother liquor has been used as the reaction medium (RM) at various stages of the process of the invention in its cycles following the first cycle.
• Nitro compound can be aromatic either mono or poly or aliphatic linear or branched, substituted or un-substituted where substitution can be alkyl, hydroxyl, halogen, carboxylic acid, carbonyl, nitro, amino, amide, thio and all similar groups either mono substituted or poly substituted.
• Neutralization RM is the aqueous phase or system which is neutralized.
• Separation RM is the mixture of neutralized aqueous phase and immiscible solvent ready for phase separation.
• Settling RM is the mixture of neutralized aqueous phase and immiscible solvent which is settled for phase separation
• Cooling curve (CC) is profile of temperature verses time.

The process of the present invention uses a proprietary reduction agent, G-Cat, which is a multifunctional, chemical reduction formulation mainly comprising of fine iron powder in the range of 50% (w/w) to 100% (w/w), preferable range being 75% (w/w) to 95% (w/w), tin powder and or zinc powder in the range of 0% (w/w) to 10% (w/w). The purity of all components is in the range of 50% (w/w) to 100% (w/w). It also contains electrolyte salt of various metals such as sodium, magnesium, calcium, iron, nickel, cobalt, tin, zinc, titanium, copper, manganese, and any other metals with multiple valencies in the range of 0% (w/w) to 50% (w/w), preferable range being 2.5% (w/w) to 25% (w/w). The purity of the salts is variable and in the range of 50% (w/w) to 100%) (w/w). The G-Cat also contains customized grade of activated carbon in the range of 0% (w/w) to 5% (w/w); filter aid in the range of 0% (w/w) to 95% (w/w) and decolorizing agent in the range of 0% (w/w) to 5% (w/w). It also contains specialty additives like polyelectrolyte, anti foaming agents, dispersing agents, anti oxidants, emulsifying agents, mass transfer enhancing agents, anti caking agents, UV stabilizers, solubilising agents, and such other agents.
Other chemical formulation also used in the process of the present invention, namely R-Cat. This formulation is a multifunctional recycle formulation mainly comprising fine iron powder in the range of 0% (w/w) to 95% (w/w), tin, copper, titanium, and zinc, or any combination thereof, depending on the R-NO2 or R-NO to be reduced, in the range of 0% (w/w) to 10% (w/w). The purity of all components is in the range of 50% (w/w) to 100% (w/w).
G-Cat and R-Cat also contain electrolyte salt of various metals such as sodium, magnesium, calcium, iron, nickel, cobalt, tin, zinc, titanium, copper, manganese, and any other metals with multiple valences in the range of 0% (w/w) to 50% (w/w). The purity of the salts is variable and in the range of 50% (w/w) to 100% (w/w). The G-Cat also contains customized grade of activated carbon in the range

of 0% (w/w) to 5% (w/w); filter aid in the range of 0% - 95% and decolorizing agent in the range of 0% (w/w) to 5% (w/w).
G-Cat and R-Cat also contain hydroxides of calcium or alkali metals like magnesium, barium, sodium, potassium in the range of 0% (w/w) to 95% (w/w); customized grade of activated carbon in the range of 0.5% (w/w) to 5% (w/w); filter aid in the range of 5% (w/w) to 95% (w/w) and decolorizing agent in the range of 0.5% (w/w) to 5% (w/w) along with iron powder in the range of 5% (w/w) to 25 % (w/w).
G-Cat and R-Cat also contain specialty additives like polyelectrolyte, anti foaming agents, dispersing agents, emulsifying agents, mass transfer enhancing agents, anti caking agents, UV stabilizers, solubilising agents, and antioxidants, and other such agents.
The present application also discloses a sustainable chemical process for green reduction of R-N02 or R-NO into corresponding R-NH2 with inherent recycle of all neutral liquid streams generated in the same.
The chemical process of the present invention basically comprises inherent large number of recycles of processing the mother liquor streams generated during any of the cycles. Each cycle further comprises two sequences. The first sequence of typical cycle is represented in Figure 1 and is termed as the green reaction sequence. The second sequence is represented in Figure 2 and is termed as the green separation sequence.
The combined process involved in first and second sequences as disclosed in the present invention is shown in Figure 3. This figure shows the complete process of the present invention along with generation and fate of all liquid streams as disclosed in the present invention. One of the novel features of the process of

present invention is regarding the reaction medium used in various stages of the process.
Figure 4 shows the relationship between each stream in the individual cycles of the process.
Referring to Figure 3, in the very first cycle of the process, of the present invention FRM is used as the reaction medium in the start-up (Step 1.1), reduction (Step 1.2) and neutralization (step 1.3) steps. The solvent is recycled as the extraction medium in the extraction step (step 2.1, 2.2 & 2.3). As a key feature of the present invention, in the subsequent cycles, the liquid streams generated in various steps of recycling of the first cycle are used as the reaction medium and solvent stream generated are used as extraction medium. However, the use of these liquid streams as the reaction medium is optional and FRM can be used as the reaction medium in all cycles. Another key feature is, in the subsequent cycles, the solvent streams generated in various steps of recycling of the second cycle are used as the extraction medium. However, the use of these solvent streams as the extraction medium is optional and FEM can be used as the extraction medium in all cycles.
Streams generated at various stages of the invention are now defined. As shown in Figure 4, Stream A is generated after 1st solvent extraction and layer separation steps that follows the Neutralization step. Stream B is generated 2nd solvent extraction and layer separation steps. Stream C is generated 3rd solvent extraction and layer separation steps. All these three streams (Stream A,B and C) are combined and taken as combined solvent layer for cyclization is defined as Stream D. Stream E is the solvent stream generated after cyclization and product separation.
Stream E is stored in a storage tank. Stream F is the solvent taken from storage tank and which is used at various stages such 1st Extraction, 2nd Extraction and 3rd

extraction. Stream G is aqueous stream generated after extraction and layer separation and taken to storage tank for recycle treatment and recycle. Stream H is generated from storage tank and goes which is used as various stages such as startup, reduction and neutralization.
Some quantity of FRM and or FEM or any other appropriate liquid streams, or a combination thereof are used as make-up liquid and or immiscible solvent either high boiling or low boiling in various steps to compensate for the various liquid losses through handling, evaporation, and so on.
Details of the steps involved in the two sequences that form a typical cycle of the process of the present invention are described below, with reference to figures 1, 2, 3, and 4.
The preferred embodiment of the present invention and various other embodiments are now described.
Sequence 1.0 - Green reaction sequence:
As shown in Figure 1, this sequence comprises three steps, namely the start-up, reduction, and neutralization. Each of these steps is described below. One of the key features of this sequence is the various reaction agents that are used in various steps. These are the reducing agent and a neutralization agent. A predetermined quantity of these agents is added as appropriate. These agents along with the specific reaction conditions generated as defined by the temperature, pressure, pH, agitation, and other such parameters lead to the unique inherent recyclability of the process of the present invention.
The total quantity of the reducing agent required in this sequence for a typical cycle (referred to hereafter as QRT) is dictated by the requirement of the reduction

potential of R-NO2 or R-NO to be reduced. QRT is determined by a reducing agent's weight ratio, (Weight Ratio)RA, that is the ratio of the weight of the reducing agent required in a single cycle, WRA of the process of this invention to the weight of total amount of R-N02 or R-NO to be reduced in that single cycle, WN. That is for a single cycle:
(Weight Ratio)RA = WRA/ WN Equation 1
The QRT is such that its weight is equal to WRA which is determined from Equation 1.
In the preferred embodiment of the present invention, (Weight Ratio)RA is preferably in the range of 0.25 to 25, the more preferable range being 0.5 to 2.5.
In the conventional processes, the power failures or other breakdowns of the plant lead to wastage of the entire batches leading to economical loss and environmental damage. One of the novel advantageous features of the process of this invention is that it allows recycling of the R-NH2 even without the stirring or agitation in many of its steps, particularly steps 1.2-1.4 and 2.2-2.5.
Step 1.1 - Start-up: This step is carried out in a reaction vessel that has an agitator and necessary attachments known to a person skilled in the art. As shown in figure 1, at the start of the first cycle of process of the present invention an RM is charged to the reaction vessel in suitable quantities.
In the preferred embodiment of the present invention FRM is used as the reaction medium. The total quantity of the reaction medium required for a typical cycle (referred to hereafter QRMT) is dictated by the solubility of R-NH2. This quantity is determined by weight ratio of FRM or the reaction medium, denoted as (Weight Ratio)RM, that is the ratio of the weight of the FRM or the reaction medium

required in a single cycle, WRM, to the weight of total amount of R-NO2 or R-NO to be reduced in that single cycle, WN. That is
(Weight Ratio)RM = WRM/ WN Equation 2
The QRMT is such that its weight is equal to WRM which is determined from Equation 2.
The quantity of the FRM or the reaction medium used in Step 1.1, denoted as QRMI.I, is variable.
In the preferred embodiment, (Weight Ratio)RM is preferably in the range of 5 to 100, the more preferable range being 10 to 75, and QRMI.I is in the range of 0% (w/w) to 40% (w/w) of QRMT used in this cycle.
A suitable acid, or a salt of iron with inorganic or organic acids, such as ferrous sulphate, ferrous chloride, ferrous ammonium sulphate, ferrous oxalate, ferrous citrate or other salts like ammonium chloride, ammonium sulphate, other such salts, or any combination of these, is added in suitable quantity and suitable form while maintaining temperature of the reaction mixture in the reaction vessel in the range of 0 °C to 200 °C. In the preferred embodiment of the invention, sulfuric acid is used. In another embodiment of the present invention, the temperature at which the acid charged is in the range of 10 °C to 100 °C, more preferably 50 °C tol00°C.
The mixture is agitated for a predetermined time that is in the range of 0 minutes to 10 hours, more preferably between 0.5 hours to 5 hours. In the agitation stage, the pH of the reaction mixture is maintained throughout at a predetermined level that is in the range of 1 to 9, preferable range being 2 to 7.

At the end of the agitation stage, a reducing agent, preferably G-Cat is charged in suitable quantity. It is added either in its full required quantity or in any number of batches of any size, or continuously, or any combination thereof. The reducing agent is added over a predetermined period, at a predetermined temperature, and a predetermined pH. The period over which the reducing agent is added in the range of 0 minutes to 5 hours, more preferably between 0.5 hours to 2.5 hours. The temperature at which the reducing agent is added is in the range of 0 °C to 200 °C. The pH at which the reducing agent is added is in the range of 1 to 9, preferable range being 2 to 7.
In the preferred embodiment of the invention, G-Cat is used as the reducing agent and (Weight Ratio)RA is preferably in the range of 0.25 to 25, the more preferable range being 0.5 to 2.5. The quantity of the reducing agent used in Step 1.1, QR1.1 is variable in the range of 0% (w/w) to 100% (w/w) QRJ.
In the subsequent cycles of the process of the present invention, Stream H is used as a reaction medium instead of FRM in the start-up (step 1.1).
In another embodiment of the present invention, the temperature at which the reducing agent is charged is in the range of 10 °C to 100 °C, more preferably 50 °Cto 100 °C. G-Cat or any other customized proprietary catalytic formulation is used as the reducing agent in this embodiment.
In another embodiment of the present invention, the reaction medium or acid or a combination thereof, and the reducing agent are added in any sequence.
Step 1.2 - Reduction: The nitro or nitroso compound (respectively R-NO2 or R-NO) to be reduced is added to the reaction vessel either in its full quantity or in any number of lots. The total amount of R-NO2 or R-NO to be reduced is added

over a period of 0 to 25 hours, at a suitable interval that depends on the molecule to be reduced.
A reaction medium is charged in suitable quantity to the reaction vessel while maintaining the temperature, and pH of the mixture in their respective predetermined ranges. The temperature at which the reaction medium is added is in the range of 0 °C to 200 °C. The pH at which the reaction medium is added is in the range of 1 to 9, preferable range being 2 to 7. In the preferred embodiment of the present invention, FRM is used as the reaction medium in step 1.2 of the first cycle of the process of the present invention. For subsequent cycle, stream H is used as the reaction medium for this step.
The quantity of the FRM or the reaction medium used in Step 1.2, denoted as QRMI.2, is variable in the range of 0% (w/w) to 40% (w/w) of the total quantity QRMT used in this cycle.
A suitable acid is optionally added to the reaction vessel to achieve the desired pH level of the reaction mixture. The acid is added in a suitable form while maintaining temperature of the reaction mixture in the reaction vessel in the range of O°Cto200 °C.
A reducing agent is charged to the reaction mixture. The reducing is charged over a period of time at a predetermined temperature which is in the range of 0 °C to 200 °C, when the pH of the reaction mixture is at a predetermined value which is in the range of 1 to 9, preferable range being 2 to 7. The reducing agent required for Step 1.2 is added either in a single lot or in batches, or continuously, or any combination of these methods of addition.
The quantity of the reducing agent used in this step, denoted as QRAI.2, is variable in the range of 0% (w/w) to 100% (w/w) of the QRT. The quantity QRU is dictated

by the requirement of the reduction potential for the R-NO2 or R-NO to be reduced. The quantity QRAI.2 is further determined so that it is the difference between QRAT and QRA 1.1. That is:
QRAI.2 = QRAT - QRAI.I Equation 3
In the preferred embodiment of the invention, G-Cat is used as the reducing agent and (Weight Ratio)RA is preferably in the range of 0.25 to 25, the more preferable range being 0.5 to 2.5. In another embodiment of the present invention, any other reducing agent such as any proprietary agents is used as the reducing agent.
The reaction mixture at all stages of this step is optionally stirred with agitators rotating at a rate between 0 to 500 RPM. The step can be successfully carried out even without stirring.
Step 1.3 - Neutralisation: After completion of the reduction at the end of Step 1.2, optionally a suitable reaction medium is charged in suitable quantity to the reaction vessel. The decision to add the reaction medium depends on the consistency of the solids. The quantity of the reaction medium used in Step 1.3, denoted as QRMIJ, is variable in the range of 0% (w/w) to 40% (w/w) of the total quantity QRMT used in this cycle.
A neutralizing agent is added to the reaction mixture over a predetermined period and at a predetermined temperature to adjust its pH to a suitable level. The fundamental role of the neutralisation agent is to provide a strong reduction potential for low concentration R-NO2 or R-NO tailing towards the end step 1.2 and providing the necessary neutralisation for the reaction mixture obtained at the end of step 1.2.

The period over which the neutralising agent is added is in the range of 0 minutes to 5 hours, more preferably between 0.5 hours to 2.5 hours. The temperature at which the neutralising agent is added is in the range ofO°Cto200°C. ThepHat which the neutralising agent is added is in the range of 1 to 12, preferably 4 to 11.
The neutralisation process wherein the neutralisation agent is allowed to react with R-NO2 or R-NO at a neutralisation process temperature and pH is continued for a neutralisation process time. The neutralisation process temperature is maintained in the range of 0 °C to 200 °C, and the neutralisation process pH is maintained between 1 to 12, preferably 4 to 11. The neutralisation process time is in the range of 0 hours to 10 hours, preferably in the range of 30 minutes to 5 hours.
In the preferred embodiment of the process of the invention the neutralising agent is in the form of a formulation that comprises R-Cat or any combination thereof. The quantity of the neutralising agent, QNAT is determined by its weight ratio, denoted as (Weight Ratio)NA, that is the ratio of the weight of the neutralising agent required in a single cycle, WNA, to the weight of total amount of R-NO2 or R-NO to be reduced in that single cycle. That is,
(Weight Ratio)NA = WW WN Equation 4
The QNAT is such that its weight is equal to WNA which is determined from Equation 3.
(Weigh Ratio)NA is preferably in the range of 0 to 2.5, more preferably between 0.05 to 0.25.

In the preferred embodiment of the invention, FRM is used as the reaction medium in the first cycle of this sequence, and for the subsequent cycles subject to the process of this invention, FRM is replaced by stream H.
In another embodiment of the present invention, any other neutralisation agents, proprietary or generic, are used. Neutralizing agent in the form of hydroxides of alkali metals like sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium hydroxide, carbonates or bicarbonates of alkali metals like sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, calcium carbonate, lithium carbonate, other such salts or any combination thereof is optionally used as a neutralising agent.
The inventors have surprisingly found that the action of G-Cat and R-Cat in the steps 1.1 to 1.3 collectively favours very high degree of chemo-selectivity and regio-selectivity for R-N02 or R-NO to R-NH2 green reduction reaction.
The reaction mixture at all stages of this step is optionally stirred with agitators rotating at a rate between 0 to 500 RPM. The step can be successfully carried out even without stirring.
Sequence 2.0 - Green Extraction sequence:
As shown in Figure 2, this sequence comprises three steps, namely, 1st Extraction and layer separation, 2n Extraction and layer separation, 3r Extraction and layer separation. Each of these steps is described in detail as follows.
Step 2.1 - 1st Extraction and layer separation: As shown in Figure 2, a extraction medium, referred to as the first extraction EM, is charged to the mixture obtained at the end of Step 1.3 in the reaction vessel in a suitable quantity and at suitable temperature and pH, the temperature being in the range of 0 to 200 and

the pH being in the range of 1 to 12, preferably 4 to 11. The mixture thus formed is allowed to settle at a first extraction and layer Separation pH, by maintaining it at a first extraction and layer Separation temperature for a first extraction and layer separation time.
In the preferred embodiment of the invention the first extraction and layer Separation pH is in the range of 1 to 12, preferably 4 to 11; the extraction and layer Separation temperature is in the range of 0°C and 200°C, preferably between 0°C to 100°C; and the first extraction and layer Separation time is for 1 minute to 10 hours, preferably 30 minutes to 3 hours.
Liquid layer that forms as a result of the extraction and layer Separation process is separated at a first extraction and layer Separation temperature, first extraction and layer Separation pH and first extraction and layer Separation time and charged as Stream A.
In the preferred embodiment of the invention FEM is used as the extraction medium in the first cycle, and for the subsequent cycles subject to the process of this invention, FEM is replaced by Stream F.
The quantity of the FEM or the extraction medium used in Step 2.1, denoted as QRM2.I is variable in the range of 0% (w/w) to 60% (w/w) of the QRMT used in this cycle.
Step 2.2 - 2nd Extraction and layer separation: As shown in Figure 2, a extraction medium, referred to as the first extraction EM, is charged to the mixture obtained at the end of Step 2.1 in the reaction vessel in a suitable quantity and at suitable temperature and pH, the temperature being in the range of 0 to 200 and the pH being in the range of 1 to 12, preferably 4 to 11. The mixture thus formed is allowed to settle at a second extraction and layer Separation pH, by maintaining

it at a second extraction and layer Separation temperature for a second extraction and layer separation time.
In the preferred embodiment of the invention the second extraction and layer Separation pH is in the range of 1 to 12, preferably 4 to 11; the extraction and layer Separation temperature is in the range of 0°C and 200°C, preferably between 0°C to 100°C; and the second extraction and layer Separation time is for 1 minute to 10 hours, preferably 30 minutes to 3 hours-Liquid layer that forms as a result of the extraction and layer Separation process is separated at a second extraction and layer Separation temperature, second extraction and layer Separation pH and second extraction and layer Separation time and charged as Stream B.
In the preferred embodiment of the invention FEM is used as the extraction medium in the first cycle, and for the subsequent cycles subject to the process of this invention, FEM is replaced by Stream F.
The quantity of the FEM or the extraction medium used in Step 2.2, denoted as QRM2.2 is variable in the range of 0% (w/w) to 60% (w/w) of the QRMT used in this cycle.
Step 2.3 -3rd Extraction and layer separation: As shown in Figure 2, a extraction medium, referred to as the first extraction EM, is charged to the mixture obtained at the end of Step 2.2 in the reaction vessel in a suitable quantity and at suitable temperature and pH, the temperature being in the range of 0 to 200 and the pH being in the range of 1 to 12, preferably 4 to 11. The mixture thus formed is allowed to settle at a third extraction and layer Separation pH, by maintaining it at a second extraction and layer Separation for a third extraction and layer separation time.

In the preferred embodiment of the invention the third extraction and layer Separation pH is in the range of 1 to 12, preferably 4 to 11; the extraction and layer Separation temperature is in the range of 0°C and 200°C, preferably between 0°C to 100°C; and the third extraction and layer Separation time is for lmimite to 10 hours, preferably 30 minutes to 3 hours.
Liquid layer that forms as a result of the extraction and layer Separation process is separated at a third extraction and layer Separation temperature, third extraction and layer Separation pH and third extraction and layer Separation time and charged as Stream C.
In the preferred embodiment of the invention FEM is used as the extraction medium in the first cycle, and for the subsequent cycles subject to the process of this invention, FEM is replaced by Stream F.
The quantity of the FEM or the extraction medium used in Step 2.3, denoted as QRM2.3 is variable in the range of 0% (w/w) to 60% (w/w) of the QRMT used in this cycle.
Combined solvent streams (Stream A from Step 2.1, Stream B from Step 2.2 and Stream C from Step 2.3 ) obtained during this sequence are charged into another reaction vessel with other attachments known to a person skilled in the art is denoted as stream D,
Stream D is further taken for Cyclization reaction and at end of this reaction and product separation the solvent stream generated is denoted as Stream E which is stored in recovered solvent storage tank. In the preferred embodiment of the invention, FEM is used as the extraction medium in the first cycle of this

sequence, and for the subsequent cycles subject to the process of this invention, FEM is replaced by stream F.
A typical cycle of the process of the present invention, that is a cycle consisting of a green reaction sequence and a green extraction & layer separation sequence, ends here. A key feature of the present invention is that all steps of a typical cycle are carried out at atmospheric pressure.
As a key advantageous feature of the present invention, the reaction medium used both the green reaction sequence and the green extraction & layer separation sequence, in the cycles after the first cycle is taken from the mother liquor and various streams generated during the process of this invention. In other words, the FRM used in the various stages (Steps 1.1 to 1.3) of the first cycle is replaced by a suitable reaction medium in all subsequent cycles. Also for solvent in all the cycles the first cycle is taken from the Solvent stream streams generated during the process of this invention. In other words, the FEM used in the various stages (Steps 2.1 to 2.3) of the first cycle is replaced by a suitable extraction medium in all subsequent cycles.
The inventors of the present invention have found that the purity of R-NH2 after drying in any cycle varies in the range of 75% to 100%, preferably 80% to 99.9%. The inventors have surprisingly found that the reduction of R-NO2 or R-NO to R-NH2 carried out with the process described above generates inorganic by-product in any cycle in the ratio of weight in the range of 0.25 to 25 to the weight of R-NO2 or R-NO to be reduced of the above sequence is crystalline and non-sticky in nature. Color of the by-product ranges from brown to jet-black particularly jet-black. The pH of the inorganic by-product is in the range of 4.0 to 8.0. The moisture content of the inorganic byproduct is in the range of 5% to 50%, particular range being 10% to 30%.

The inventors have found that the process of the present invention is applicable to the R-NO2 or R-NO compounds . having one or more nitro groups including aromatic R-N02 or R-NO compounds like nitrobenzene, 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.
Experimental procedures:
FRESH CYCLE
Reduction of 4-Methoxy-2-Nitro Aniline
In a round bottom flask equipped with stirrer, condenser, thermometer, addition port arranged in suitable heating/cooling system was charged 400 ml water& 60 ml 20% H2SO4, heated to 95°C. 86 g G-CAT was charged in start up with continuous stirring at 95°C & stir for 15 mins. 20 g of nitro compound, 80 ml water and 22.8 g of G-CAT was added in 30 mins. The reaction mass was then raised to 98°C. The reaction mass was maintained for 15 min at 98°C. Remaining four lots of G-CAT, Nitro compound & Water was charged in similar manner as followed for first lot. Reaction is continued till all nitro a compound was consumed in the reaction. Completion of reaction was checked by TLC for disappearance of nitro compound. After reduction was over, maintain the batch for 30 min. and checked pH. 15 gm of NGC was charged slowly in 30 minute at 90°C. Then charged 3.0% Na2C03 till Ph-8.0. Reaction mass was maintained for 1 hr at 98°C.After neutralization, the reaction mass was left to settle and then Aqueous layer was decanted at 95°C. Then Add 525 ml Water. Then Reaction mass was maintained for 1 hr at 98°C & Decant at 95°C. Then Add 228 ml Water. Then Reaction mass was maintained for 1 hr & Filter Mass & Wash with 60 ml Hot Water. The entire amine layer was combined together. Then Start Extraction With EDC 400.0 ml* 3 Times At 75°C.Then Separate Aqueous Layer & Organic Layer. This organic layer is then forwarded to cyclization reaction post which product is isolated and solvent is recovered and recycled for extraction in next

experiment. The aqueous layer separated is recycled in reduction after treatment in next experiment.
FIRST RECYCLE (Rl)
In the same set up as described above, 400 ml mother liquor recovered from fresh cycle & 60 ml 20% H2S04 was taken and heated to 95°C. 86 g G-CAT was charged in start up with continuous stirring at 95°C & stir for 15 mins. 20 g of nitro compound, 80 ml mother liquor recovered from fresh cycle water and 22.8 g of G-CAT was added in 30 mins. The reaction mass was then raised to 98°C. The reaction mass was maintained for 15 min at 98°C. Remaining four lots of G-CAT, Nitro compound and mother liquor recovered from fresh cycle was charged in similar manner as followed for first lot. Reaction is continued till all nitro a compound was consumed in the reaction. Completion of reaction was checked by TLC for disappearance of nitro compound. After reduction was over, maintain the batch for 30 min. and checked pH. 15 gm of NGC was charged slowly in 30 minute at 90°C. Then charged 30% Na2C03 till Ph-8.0. Reaction mass was maintained for 1 hr at 98°C.After neutralization, the reaction mass was left to settle and then Aqueous layer was decanted at 95°C. Then add 525 ml mother liquor recovered from fresh cycle . Then reaction mass was maintained for 1 hr at 98°C & decant at 95°C. Then add 228 ml mother liquor recovered from fresh cycle. Then reaction mass was maintained for 1 hr & Filter Mass & Wash with 3.5 ml hot mother liquor recovered from fresh cycle & 56.5 ml fresh hot Water. The entire amine layer was combined together. Then start extraction with EDC 400.0 ml* 3 times at 75°C using 540 ml fresh solvent & 660 ml recovered solvent from fresh cycle .Then separate aqueous layer & organic layer. This organic layer is then forwarded to cyclization reaction post which product is isolated and solvent is recovered & recycle in next experiment. The aqueous layer separated is recycled in reduction after treatment in next experiment.

The following table (Table 1) illustrates the savings in the various quantities of water & solvent used and recycle of mother liquor & recovered solvent in the reduction reaction of 4-methoxy-2-nitroaniline to 4-methoxy benzene-1,2-diamine
in synthesis of Omeprazole.
Table 1

Cycle Basis H20 & ML consumption & saving Use of Fresh Solvent
& Saving through
Recycle of Recovered
Solvent NRC & NPC consumption

M gm Fresh H20 Treated mother liquor Fresh Solvent Recycle of Recovered
Solvent NRC
gm NGC
gm Melting Range Yield

(ml) (ml) From Cycle no (ml) (ml) From Cycle no.

(°C) %
0 100 1613 - - 1200 - - 200 15 248 48.72
1 100 56.5 1556.5 Cycle-0 540 660 0 200 15 250 62.34
2 100 48.5 1564.5 Cycle-1 540 660 1 200 15 251 67.20
3 100 76.5 1536.5 Cycle-2 640 560 2 200 15 253 58.24
4 100 6.5 1606.5 Cycle-3 540 660 3 200 15 247 44.52
5 100 5.0 1608 CycIe-4 540 660 4 200 15 248 48.72
1) Water required for one experiment =1613 ml
2) Water required for six experiments = 9678 ml
3) Actual water used in six experiments = 1807 ml
4) Total water saved by the use of the invention (%) = 81.33%
5) Solvent required for one experiment = 1200 ml
6) Solvent required for six experiments = 7200 ml
7) Actual solvent used in six experiments = 4000 ml
9) Total solvent saved by the use of the invention (%) = 44 %

Based on the foregoing discussion it is clear that the present invention comprises the following items:
1. A sustainable chemical process of green reduction of 4-methoxy-2-
nitroaniline to 4-methoxy benzene-l,2-diamine, characterised in that said
process is carried out using a neutral reaction medium and comprises
inherent recycling of said neutral reaction medium in a plurality of cycles,
each of said cycles has a reaction sequence and a extraction and layer
separation sequence, wherein said extraction and layer separation sequence
follows said green reaction sequence.
2. A process as described in item 1, wherein the number of said plurality of cycles is preferably greater than 3, more preferably greater than 10, even more preferably greater than 25.
3. A process as described in any of items 1 and 2,
Wherein said green reaction sequence of a typical said cycle comprises the
following steps:
Step 1.1 - creating start-up conditions for the reduction process, said Step 1.1 further comprising the following stages:
Stage 1.1a. charging a suitable reaction medium comprising water or water immiscible solvent either high boiling or low boiling or combination thereof, denoted as start-up RM, to a first reaction vessel with an agitator and other attachments known to a person skilled in the art; thereby forming the start-up reaction mixture, denoted as SRM;
wherein the quantity of the reaction medium used in Step 1.1, denoted as QRM1.1, is variable, said QRMI.I being in the range of 0% (w/w) to 40% (w/w) of QRMT used in this cycle;

wherein said QRMT is the total quantity of the reaction medium used in this cycle, said QRMT being determined such that the ratio, denoted as (Weight Ratio)RM, of the weight of said QRMT, WRM, to the weight of total amount of R-NO2 or R-NO to be reduced in that single cycle WN; the relationship between (Weight Ratio)RM, WRM, and WN being represented by the equation
(Weight Ratio)RM = WRM/ WN;
and wherein said (Weight Ratio)RM is preferably in the range of 5 to 100, the more preferable range being 10 to 75, and;
stage 1.1b. further optionally charging to said first reaction vessel a first suitable acid, preferably sulfuric acid, in a suitable quantity, and in suitable form, said suitable form being solid, liquid, or any combination thereof, to said SRM such that the pH of said SRM is in the range between 1 to 9, preferably between 3 to 7, more preferably between 4 to 6; wherein said acid is added at a start-up temperature which is in the range between 0 °C to 200 °C;
stage 1.1c. agitating the mixture thus formed for a duration in the range of 0 minutes to 5 hours, more preferably between 0.5 hours to 2.5 hours, while maintaining the pH of the mixture during the agitation stage of stage 1.1c in the range between 1 to 9, preferably between 3 to 7, more preferably between 4 to 6, and while maintaining the temperature of the mixture during the agitation stage of stage 1.1c in the range between 0 C to 200 °C; and

stage Lid. adding to said first reaction vessel, upon completion of the agitation stage of stage 1.1c, a reducing agent, RA1.1 in suitable quantity which is denoted as QRAIJ, said QRAI.I being variable in the range of 0% to
100%ofQRAT;
wherein said QRAT is the total quantity of the reducing agent used in this cycle; said QRAT being determined such that the ratio, denoted as (Weight Ratio)RA, of the weight of said QRAT, WRA, to the weight of total amount of R-NO2 or R-NO to be reduced in that single cycle, WN; wherein the relationship between (Weight Ratio)RA, WRA, and WN is represented by the equation:
(Weight Ratio)RA = WRA/ WN;
and wherein said (Weight Ratio)RA is preferably in the range of 0.25 to 25, the more preferable range being 0.5 to 2.5;
wherein said reducing agent is added either in its full required quantity, QRAT, or in batches, or continuously, or as any combination of these methods of addition, over a period of 0 minutes to 5 hours, preferably 0.5 hours to 2.5 hours; and wherein the pH of the mixture in said first reaction vessel at the time of addition of said reducing agent is between 1 to 9, preferably between 2 to 7;
Step 1.2 - reducing the nitro or nitroso compound to be reduced, wherein
said Step 1.2 further comprises the following stages:
stage 1.2a. adding R-NO2 or R-NO, respectively a nitro or nitroso compound to be reduced, to said reaction vessel in solid or liquid form dissolved in water or water immiscible solvent either high boiling or low

boiling or combination thereof or any other known form over a suitable reduction period in the range of 0 to 25 hours;
stage 1.2b. charging a suitable reaction medium, denoted as reduction RM, in suitable quantity to said first reaction vessel;
stage 1.2c. further optionally adding to said first reaction vessel a second suitable acid, preferably sulfuric acid, to bring the pH value of the mixture thus formed, referred to as reduction mixture, within the range between 1 to 9, preferably between 2 to 7, more preferably between 4 to 6, while maintaining the temperature of the mixture formed by addition the acid to said reduction mixture between 0 °C to 200 °C; and
stage 1.2d. adding a reducing agent, RAu, to said first reaction vessel, wherein said RA1.2 is added either simultaneously with the R-NO2 or R-NO compound to be reduced in stage 1.2a, or after the addition of acid of stage 1.2c, thereby forming a reduction agent mixture; wherein said RA12 is added at a reduction time such that the pH of said reduction agent mixture is in a range between 1 to 9, preferably between 2 to 7, more preferably between 4 to 6, and such that the temperature of said reduction mixture is in the range between 0 °C to 200 °C;
wherein the quantity of RA12, denoted as QRI.2, is such that said QRI.2 is the difference between QRT and QRJ.I;
Step 1.3 - neutralizing the reaction mixture obtained at the end of Step 1.2, wherein said neutralization is carried out in the following stages:
stage 1.3a. optionally adding a suitable reaction medium comprising water or water immiscible solvent either high boiling or low boiling or combination thereof, denoted as neutralization RM, in a suitable quantity to said reaction vessel, wherein quantity of the reaction medium used in

Step 1.3, denoted as QRMU, is variable in the range of 0% (w/w) to 40% (w/w)ofQRMT;
stage 1.3b. adding to the reaction mixture obtained at the end of step 1.3a in said first reaction vessel a neutralizing agent, NA1.3, wherein the quantity of said neutralizing agent used, QNAT, is the total quantity of the neutralizing agent to be used in this cycle; said QNAT being determined such that the ratio, denoted as (Weight Ratio)NA, of the weight of said QNAT, WNA, to the weight of total amount of R-NO2 or R-NO to be reduced in that single cycle, WN; wherein the relationship between (Weight Ratio)NA, WNA, and WN is represented by the equation:
(Weight Ratio)NA = WNA/WN;
and wherein said (Weight Ratio)NA is preferably in the range of 0 to 2.5, the more preferable range being 0.05 to 0.25; and
wherein said neutralizing agent is added over a period in the range between 0 minutes to 5 hours, more preferably between 0.5 hours to 2.5 hours, at a temperature in the range between 0 °C to 200 °C, and at a pH in the range between 1 to 9, preferably 2 to 8;
wherein R-Cat or G-Cat is used as the preferred neutralizing agent; and
stage 1.3c. allowing the neutralization of the mixture obtained at the end of stage 1.3b containing R-NO2 or R-NO compound to take place at a temperature between 0 °C to 200 °C, at a pH between 1 to 9, preferably 2 to 8, said neutralization being carried out over a period between 0 hours to 10 hours, preferably in the range of 30 minutes to 5 hours;

wherein the contents of said first reaction vessel during any or all stages of 1.3 a to 1.3 c are optionally stirred for any duration of the individual stages using said agitator rotating at a rate between 0 to 500 RPM; whereby a single cycle of said green reaction sequence is completed, and where after a cycle of green extraction and layer separation sequence is carried out, said green extraction and layer separation sequence comprising the following steps:
Step 2.1 - apply to Solvent Extraction and layer separation to the contents of said reaction vessel obtained at the end of said step 1.3, wherein said Extraction and layer separation comprises following stages:
stage 2.1a. Charging a suitable extraction medium comprising of organic solvent either polar, non polar, protic, non protic or aprotic wither high boiling or low boiling or combination thereof, denoted as first Extraction and separation medium EM, to the reaction mixture obtained at the end of step 1.3, maintaining the temperature of the mixture in the range between 0°C and 200 °C, and the pH of the mixture in the range between 1 to 12, preferably between 4 to 11; wherein the quantity of said first settling RM used, denoted as QRM2.I , is variable in the range of 0% (w/w) to 60% (w/w) of the QRMT used in this cycle.
stage 2.1b. allowing the reaction mixture obtained at the end of stage 2.1b to settle down for a first settling time while maintaining the temperature of the mixture in the range between 0 °C and 200 °C, and the pH of the mixture in the range between 1 to 12, preferably between 4 to 11; wherein said first settling time is in the range between 1 minute to 10 hours, preferably between 30 minutes to 3 hours;
stage 2.1c. separating the organic solvent layer formed at the end of stage 2.1b at a first separating temperature in the range between 0 °C

and 200 °C, a first separating pH in the range between 1 to 12, preferably between 4 to 11 and first separating time in the range between 1 minute to 10 hours, preferably between 30 minutes to 3 hours, and the separated solvent stream is said Stream A
Step 2.2 - Extracting, settling, and separating the contents obtained at the end of Step 2.1, the extracting, settling and separating comprising the following stages:
stage 2.2a. Charging a suitable extraction medium comprising of organic solvent either polar, non polar, protic, non protic or aprotic wither high boiling or low boiling or combination thereof denoted as second extraction medium EM and at filtration temperature and a predetermined second stirring pH at a predetermined second stirring time;
stage 2.2b. extracting the mixture of stage 2.2a by maintaining the mixture at a predetermined second extracting temperature, a predetermined second filtration pH for a predetermined second filtration time;
stage 2.2c. allowing the mixture of stage 2.2 b to settle at a predetermined second settling pH, a predetermined second settling temperature for a predetermined second settling time; and
stage 2.2d. separating the liquid layer collected at the end of stage 2.2c, the liquid layer denoted as Stream B, at a predetermined second decantation temperature, a predetermined second decantation pH and at a predetermined second decantation time;
wherein the values each of said second stirring temperature, said second stirring continuation temperature, and said second decantation

temperature are in the range of 0°C and 200°C, preferably between 0 °C to 100 °C; the values of each of said second stirring pH, said second stirring continuation pH, and said second decantation pH are in the range of 1 to 12, preferably between 4 to 11; the values of each of said second stirring time, said second stirring continuation time, and said second decantation time are in the range of 5 minutes to 5 hours; preferably 30 minutes to 3 hours; and
wherein the quantity of the reaction medium used in Step 2.2, denoted as QRM2.2 is variable in the range of 0% (w/w) to 60% (w/w) of QRMT used in this cycle.
Step 2.3 - extracting, settling, and separating the contents at the end of Step 2.2 in the following stages:
stage 2.3a. Charging a suitable extraction medium comprising of organic solvent either polar, non polar, protic, non protic or aprotic wither high boiling or low boiling or combination thereof denoted as third settling EM, at a predetermined second extracting temperature and a predetermined second extracting pH at a predetermined second extracting time;
stage 2.3b. extracting the mixture of stage 2.3 a by maintaining the mixture at a predetermined second extracting temperature, a predetermined third extracting continuation pH for a predetermined second extracting continuation time;
stage 2.3c. stopping the extracting action and allowing the mixture of stage 2.3 b to settle at a predetermined third settling pH, a predetermined third settling temperature for a predetermined third settling time; and

stage 2.3d. separating the liquid layer collected at the end of stage 2.3 c near the bottom of said reaction vessel, the liquid layer denoted as Stream C, at a predetermined third decantation temperature, a predetermined third decantation pH and at a predetermined third decantation time; said Stream C.
wherein the values each of said third extracting temperature, said third extracting maintenance temperature, said third extracting temperature, and said layer separation temperature are in the range of 0°C and 200°C, preferably between 0 °C to 100 °C; the values of each of said third extracting pH, said third extracting maintenance pH, said third extracting pH, and said third layer separation pH are in the range of 1 to 12, preferably between 4 to 11; the values of each of said third extracting time, said third extracting maintenance time, said third extracting time, and said third layer separation time are in the range of 5 minutes to 5 hours; preferably 30 minutes to 3 hours; and
wherein the quantity of the reaction medium used in Step 2.3, denoted as QRM2.3 is variable in the range of 0% (w/w) to 60% (w/w) of QRMT used in this cycle. Step 2.4 - separation and mixing of solvent streams generated at the end of step 2.1, 2.2 and 2.3 are mixed together and taken forward for cyclization reaction denoted as stream D, which is then further used in cyclization followed by solvent recovery is denoted as stream E and stored in storage tank. Stream F generated from storage tank is then recycled at various steps back in process such as 2.1, 2.2 and 2.3
Step 2.5 - the aqueous layer generated from Extraction and layer separation is denoted as stream H and is stored in storage tank after treatment. The stream H generated from storage tank is then recycled at various stages of process such as step 1.1, 1.2 and 1.3.

4. A process as described in item 3, wherein in the first cycle of said green reaction sequence, a fresh reaction medium (FRM) is used as the reaction medium in any or all of Steps 1.1, 1.2, 1.3, that is said FRM is used as any or all, or any combination thereof, of said start-up RM, said reduction RM, and said neutralization RM.
5. A process as described in item 3, wherein in the first cycle of said green extraction and layer separation sequence, and fresh Extraction medium (FEM) in any or all of Steps 2.1, 2.2, and 2.3, that is said FEM is used as any or all, or any combination thereof, of said first extraction and separation EM, said second extraction and separation EM, and said third extraction and separation EM
6. A process as described in any of items 3 and 4, wherein for any cycle following the first cycle a fresh portion of the liquid stored in said washings storage tank is used as the reaction medium in any of Steps 1.1, 1.2, and 1.3, that is the fresh portion of the liquid stored in said washings storage tank is used as any or all, or any combination thereof, of said startup RM, said reduction RM, said neutralization RM
7. A process as described in any of items 3 and 5, wherein for any cycle following the first cycle a fresh portion of the liquid stored in said washings storage tank is used as the extraction medium in any of Steps 2.1, 2.2, and 2.3, that is the fresh portion of the liquid stored in said washings storage tank is used as any or all, or any combination thereof, of first extraction and separation EM, said second extraction and separation EM, and said third extraction and separation EM
8. A process as described in any of items 3,4 and 6, wherein the temperature in any or all of the stages 1.1 b, 1.1 c, 1.2 c, 1.2 d, 1.3 b, 1.3 c, or a combination thereof, is in the range of 50 °C to 100 °C
9. A process as described in any of items 3,5 and 7, wherein the temperature in any or all of the stages 2.1 b, 2.1 c, 2.2 c, 2.2 d, 2.3 b, 2.3 c, or a combination thereof, is in the range of 50 °C to 100 °C

10. A process as described in any of items 3 to 9, wherein said first suitable acid and said second suitable acid are sulphuric acid.
11. A process as described in any of items 3 to 9, wherein the reducing agents of steps LI and 1.2, namely said RA1.1 and RA1.2 are G-Cat or any other reduction agent.
12. A process as described in any of items 3 to 11 , wherein the neutralisation agent of Step 1.3 is R-Cat or G-Cat or any combination thereof, or any other proprietary neutralisation agent used on its own or in any combination with a combination of R-Cat or and G-Cat.
13. A process as described in any of items 3 to 11, wherein the nitro compound to be reduced is added to the step 1.2 in its entire quantity or in batches of any size at any interval.
14. A process as described in any of items 3 to 12, wherein the individual stages of step 1.2 are carried out in any sequence.
15. A process as described in any of items 3 to 12, wherein a salt of iron with inorganic or organic acids, preferably selected from a group of salts comprising ferrous sulphate, ferrous chloride, ferrous ammonium sulphate, ferrous oxalate, ferrous citrate, or any combination thereof, or a salt selected from a group comprising ammonium chloride, ammonium sulphate, other such salts, or any combination thereof, is used in place of said first suitable acid of step Lib.
16. A process as described in any of items 3 to 16, wherein said neutralising
agent of stage 1.3b is selected from a group comprising hydroxides,
carbonates, or bicarbonates of alkali metals, either individually or in any
combination thereof; said hydroxides preferably being sodium hydroxide,
potassium hydroxide, calcium hydroxide, lithium hydroxide; said
carbonates preferably being sodium carbonate, potassium carbonate,
calcium carbonate, or lithium carbonate; said bicarbonates preferably
being sodium bicarbonate, potassium bicarbonate, lithium bicarbonate.

Although the invention has been described with reference to certain preferred embodiments, the invention is not meant to be limited to those preferred embodiments. Alterations to the preferred embodiments described are possible without departing from the spirit of the invention. However, the process and composition described above is intended to be illustrative only, and the novel characteristics of the invention may be incorporated in other forms without departing from the scope of the invention.

We Claim:
1. A sustainable chemical process of reduction of 4-methoxy-2-nitroaniline to 4-methoxy benzene- 1,2-diamine, characterised in that said process is carried out using a neutral reaction medium and comprises inherent recycling of said neutral reaction medium in a plurality of cycles, each of said cycles has a reaction sequence and a extraction and layer separation sequence, wherein said extraction and layer separation sequence follows said green reaction sequence.
2. A process as described in claim 1, wherein the number of said plurality of cycles is preferably greater than 3, more preferably greater than 10, even more preferably greater than 25.
3. A process as described in any of claims 1 and 2, Wherein said green reaction sequence of a typical said cycle comprises the following steps:
Step 1.1 - creating start-up conditions for the reduction process, said Step 1.1 further comprising the following stages:
Stage 1.1a. charging a suitable reaction medium comprising water or water immiscible solvent either high boiling or low boiling or combination thereof, denoted as start-up RM, to a first reaction vessel with an agitator and other attachments known to a person skilled in the art; thereby forming the start-up reaction mixture, denoted as SRM;
wherein the quantity of the reaction medium used in Step 1.1, denoted as QRMI.I, is variable, said QRMI.I being in the range of 0% (w/w) to 40% (w/w) of QRMT used in this cycle;

wherein said QRMT is the total quantity of the reaction medium used in this cycle, said QRMT being determined such that the ratio, denoted as (Weight Ratio)RM, of the weight of said QRMT, WRM, to the weight of total amount of R-NO2 or R-NO to be reduced in that single cycle WN; the relationship between (Weight Ratio)RM, WRM, and WN being represented by the equation
(Weight Ratio)RM = WRM/ WN;
and wherein said (Weight Ratio)RM is preferably in the range of 5 to 100, the more preferable range being 10 to 75, and;
stage 1.1b. further optionally charging to said first reaction vessel a first suitable acid, preferably sulfuric acid, in a suitable quantity, and in suitable form, said suitable form being solid, liquid, or any combination thereof, to said SRM such that the pH of said SRM is in the range between 1 to 9, preferably between 3 to 7, more preferably between 4 to 6; wherein said acid is added at a start-up temperature which is in the range between 0 °C to 200 °C;
stage 1.1c. agitating the mixture thus formed for a duration in the range of 0 minutes to 5 hours, more preferably between 0.5 hours to 2.5 hours, while maintaining the pH of the mixture during the agitation stage of stage Lie in the range between 1 to 9, preferably between 3 to 7, more preferably between 4 to 6, and while maintaining the temperature of the mixture during the agitation stage of stage 1.1c in the range between 0 °C to 200 °C; and
stage l.ld. adding to said first reaction vessel, upon completion of the agitation stage of stage 1.1c, a reducing agent, RA1.1 in suitable

quantity which is denoted as QRAI.I, said QRAI.I being variable in the range of 0% to 100% of QRAT;
wherein said QRAT is the total quantity of the reducing agent used in this cycle; said QRAT being determined such that the ratio, denoted as (Weight Ratio)RA, of the weight of said QRAT, WRA, to the weight of total amount of R-NO2 or R-NO to be reduced in that single cycle, WN; wherein the relationship between (Weight Ratio)RA, WRA, and WN is represented by the equation:
(Weight Ratio)RA = WRA/ WN ;
and wherein said (Weight Ratio)RA is preferably in the range of 0.25 to 25, the more preferable range being 0.5 to 2.5;
wherein said reducing agent is added either in its full required quantity, QRAT, or in batches, or continuously, or as any combination of these methods of addition, over a period of 0 minutes to 5 hours, preferably 0.5 hours to 2.5 hours; and wherein the pH of the mixture in said first reaction vessel at the time of addition of said reducing agent is between 1 to 9, preferably between 2 to 7;
Step L2 - reducing the nitro or nitroso compound to be reduced, wherein said Step 1.2 further comprises the following stages:
stage 1.2a. adding R-NO2 or R-NO, respectively a nitro or nitroso compound to be reduced, to said reaction vessel in solid or liquid form dissolved in water or water immiscible solvent either high boiling or low boiling or combination thereof or any other known form over a suitable reduction period in the range of 0 to 25 hours;

stage 1.2b. charging a suitable reaction medium, denoted as reduction RM, in suitable quantity to said first reaction vessel;
stage 1.2c. further optionally adding to said first reaction vessel a second suitable acid, preferably sulfuric acid, to bring the pH value of the mixture thus formed, referred to as reduction mixture, within the range between 1 to 9, preferably between 2 to 7, more preferably between 4 to 6, while maintaining the temperature of the mixture formed by addition the acid to said reduction mixture between 0 C to 200 °C; and
stage 1.2d. adding a reducing agent, RAi 2, to said first reaction vessel, wherein said RA1.2 is added either simultaneously with the R-NO2 or R-NO compound to be reduced in stage 1.2a, or after the addition of acid of stage 1.2c, thereby forming a reduction agent mixture; wherein said RA1.2 is added at a reduction time such that the pH of said reduction agent mixture is in a range between 1 to 9, preferably between 2 to 7, more preferably between 4 to 6, and such that the temperature of said reduction mixture is in the range between 0 °C to 200 °C;
wherein the quantity of RA1.2,denoted as QRU, is such that said QRI.2 is the difference between QRT and QRI.I;
Step 1.3 - neutralizing the reaction mixture obtained at the end of Step 1.2, wherein said neutralization is carried out in the following stages:
stage 1.3a. optionally adding a suitable reaction medium comprising water or water immiscible solvent either high boiling or low boiling or combination thereof, denoted as neutralization RM, in a suitable quantity to said reaction vessel, wherein quantity of the reaction medium used in

Step 1.3, denoted as QRMU, is variable in the range of 0% (w/w) to 40% (w/w)of QRMT;
stage 1.3b. adding to the reaction mixture obtained at the end of step 1,3a in said first reaction vessel a neutralizing agent, NAu, wherein the quantity of said neutralizing agent used, QNAT, is the total quantity of the neutralizing agent to be used in this cycle; said QNAT being determined such that the ratio, denoted as (Weight Ratio)NA, of the weight of said QNAT, WNA, to the weight of total amount of R-NO2 or R-NO to be reduced in that single cycle, WN; wherein the relationship between (Weight Ratio)NA, WNA, and WN is represented by the equation:
(Weight Ratio)NA = WNA/WN;
and wherein said (Weight Ratio)NA is preferably in the range of 0 to 2.5, the more preferable range being 0.05 to 0.25; and
wherein said neutralizing agent is added over a period in the range between 0 minutes to 5 hours, more preferably between 0.5 hours to 2.5 hours, at a temperature in the range between 0 °C to 200 °C, and at a pH in the range between 1 to 9, preferably 2 to 8;
wherein R-Cat or G-Cat is used as the preferred neutralizing agent; and
stage 1.3c. allowing the neutralization of the mixture obtained at the end of stage 1.3b containing R-NO2 or R-NO compound to take place at a temperature between 0 °C to 200 °C, at a pH between 1 to 9, preferably 2 to 8, said neutralization being carried out over a period between 0 hours to 10 hours, preferably in the range of 30 minutes to 5 hours:

wherein the contents of said first reaction vessel during any or all stages of 1.3 a to 1.3 c are optionally stirred for any duration of the individual stages using said agitator rotating at a rate between 0 to 500 RPM;
whereby a single cycle of said green reaction sequence is completed, and where after a cycle of green extraction and layer separation sequence is carried out, said green extraction and layer separation sequence comprising the following steps:
Step 2.1 - apply to Solvent Extraction and layer separation to the contents of said reaction vessel obtained at the end of said step 1.3, wherein said Extraction and layer separation comprises following stages:
stage 2.1a. Charging a suitable extraction medium comprising of organic solvent either polar, non polar, protic, non protic or aprotic either high boiling or low boiling or combination thereof, denoted as first Extraction and separation medium EM, to the reaction mixture obtained at the end of step 1.3, maintaining the temperature of the mixture in the range between 0°C and 200 °C, and the pH of the mixture in the range between 1 to 12, preferably between 4 to 11; wherein the quantity of said first settling RM used, denoted as QRM2. I , is variable in the range of 0% (w/w) to 60% (w/w) of the QRMT used in this cycle,
stage 2.1b. allowing the reaction mixture obtained at the end of stage 2.1b to settle down for a first settling time while maintaining the temperature of the mixture in the range between 0°C and 200°C, and the pH of the mixture in the range between 1 to 12, preferably between 4 to 11; wherein said first settling time is in the range between 1 minute to 10 hours, preferably between 30 minutes to 3 hours;

stage 2.1c. separating the organic solvent layer formed at the end of stage 2.1b at a first separating temperature in the range between 0°C and 200°C, a first separating pH in the range between 1 to 12, preferably between 4 to 11 and first separating time in the range between 1 minute to 10 hours, preferably between 30 minutes to 3 hours, and the separated solvent stream is said Stream A;
Step 2.2 - Extracting, settling, and separating the contents obtained at the end of Step 2.1, the extracting, settling and separating comprising the following
stages:
stage 2.2a. Charging a suitable extraction medium comprising of organic solvent either polar, non polar, protic, non protic or aprotic wither high boiling or low boiling or combination thereof denoted as second extraction medium EM and at filtration temperature and a predetermined second stirring pH at a predetermined second stirring time;
stage 2.2b. extracting the mixture of stage 2.2a by maintaining the mixture at a predetermined second extracting temperature, a predetermined second filtration pH for a predetermined second filtration time;
stage 2.2c. allowing the mixture of stage 2.2 b to settle at a predetermined second settling pH, a predetermined second settling temperature for a predetermined second settling time; and
stage 2.2d. separating the liquid layer collected at the end of stage 2.2c, the liquid layer denoted as Stream B, at a predetermined second decantation temperature, a predetermined second decantation pH and at a predetermined second decantation time;

wherein the values each of said second stirring temperature, said second stirring continuation temperature, and said second decantation temperature are in the range of 0°C and 200°C, preferably between 0 °C to 100 °C; the values of each of said second stirring pH, said second stirring continuation pH, and said second decantation pH are in the range of 1 to 12, preferably between 4 to 11; the values of each of said second stirring time, said second stirring continuation time, and said second decantation time are in the range of 5 minutes to 5 hours; preferably 30 minutes to 3 hours; and
wherein the quantity of the reaction medium used in Step 2.2, denoted as QRM2.2 is variable in the range of 0% (w/w) to 60% (w/w) of QRMT used in this cycle.
Step 2.3 - extracting, settling, and separating the contents at the end of Step 2.2 in the following stages:
stage 2.3a. Charging a suitable extraction medium comprising of organic solvent either polar, non polar, protic, non protic or aprotic either high boiling or low boiling or combination thereof denoted as third settling EM, at a predetermined second extracting temperature and a predetermined second extracting pH at a predetermined second extracting time;
stage 2.3b. extracting the mixture of stage 2.3 a by maintaining the mixture at a predetermined second extracting temperature, a predetermined third extracting continuation pH for a predetermined second extracting continuation time;
stage 2.3c. stopping the extracting action and allowing the mixture of stage 2.3 b to settle at a predetermined third settling pH, a

predetermined third settling temperature for a predetermined third settling time; and
stage 2.3d. separating the liquid layer collected at the end of stage 2.3 c near the bottom of said reaction vessel, the liquid layer denoted as Stream C, at a predetermined third decantation temperature, a predetermined third decantation pH and at a predetermined third decantation time; said Stream C;
wherein the values each of said third extracting temperature, said third extracting maintenance temperature, said third extracting temperature, and said layer separation temperature are in the range of 0°C and 200°C, preferably between 0 °C to 100 °C; the values of each of said third extracting pH, said second extracting maintenance pH, said third extracting pH, and said third layer separation pH are in the range of 1 to 12, preferably between 4 to 11; the values of each of said third extracting time, said third extracting maintenance time, said third extracting time, and said third layer separation time are in the range of 5 minutes to 5 hours; preferably 30 minutes to 3 hours; and
wherein the quantity of the reaction medium used in Step 2.3, denoted as QRM2.3 is variable in the range of 0% (w/w) to 60% (w/w) of QRMT used in this cycle;
Step 2.4 - separation and mixing of solvent streams generated at the end of step 2.1, 2.2 and 2.3 are mixed together and taken forward for cyclization reaction denoted as stream D, which is then further used in cyclization followed by solvent recovery is denoted as stream E and stored in storage tank. Stream F generated from storage tank is then recycled at various steps back in process such as 2.1,2.2 and 2.3

Step 2.5 - the aqueous layer generated from Extraction and layer separation is denoted as stream H and is stored in storage tank after treatment. The stream H generated from storage tank is then recycled at various stages of process such as step 1.1, 1.2 and 1.3.
4. A process as described in claim 3, wherein in the first cycle of said green reaction sequence, a fresh reaction medium (FRM) is used as the reaction medium in any or all of Steps 1.1, 1.2, 1.3, that is said FRM is used as any or all, or any combination thereof, of said start-up RM, said reduction RM, and said neutralization RM.
5. A process as described in claim 3, wherein in the first cycle of said green extraction and layer separation sequence, and fresh Extraction medium (FEM) in any or all of Steps 2.1,2.2, and 2.3, that is said FEM is used as any or all, or any combination thereof, of said first extraction and separation EM, said second extraction and separation EM, and said third extraction and separation EM.
6. A process as described in any of claims 3 and 4, wherein for any cycle following the first cycle a fresh portion of the liquid stored in said washings storage tank is used as the reaction medium in any of Steps 1.1, 1.2, and 1.3, that is the fresh portion of the liquid stored in said washings storage tank is used as any or all, or any combination thereof, of said start-up RM, said reduction RM, said neutralization RM.
7. A process as described in any of claims 3 and 5, wherein for any cycle following the first cycle a fresh portion of the liquid stored in said washings storage tank is used as the extraction medium in any of Steps 2.1, 2.2, and 2.3, that is the fresh portion of the liquid stored in said washings storage tank

is used as any or all, or any combination thereof, of first extraction and separation EM, said second extraction and separation EM, and said third extraction and separation EM.
8. A process as described in any of claims 3,4 and 6, wherein the temperature in any or all of the stages 1.1 b, 1.1 c, 1.2 c, 1.2 d, 1.3 b, 1.3 c, or a combination thereof, is in the range of 50 °C to 100 °C.
9. A process as described in any of claims 3,5 and 7, wherein the temperature in any or all of the stages 2.1 b, 2.1 c, 2.2 c, 2.2 d, 2.3 b, 2.3 c, or a combination thereof, is in the range of 50 °C to 100 °C.
10. A process as described in any of claims 3 to 9, wherein said first suitable acid and said second suitable acid are sulphuric acid.
11. A process as described in any of claims 3 to 9, wherein the reducing agents of steps 1.1 and 1.2, namely said RAu and RA1.2, are G-Cat or any other reduction agent.
12. A process as described in any of claims 3 to 11 , wherein the neutralisation agent of Step 1.3 is R-Cat or G-Cat or any combination thereof, or any other proprietary neutralisation agent used on its own or in any combination with a combination of R-Cat or and G-Cat.
13. A process as described in any of claims 3 to 11, wherein the nitro compound to be reduced is added to the step 1.2 in its entire quantity or in batches of any size at any interval.
14. A process as described in any of claims 3 to 12, wherein the individual stages of step 1.2 are carried out in any sequence.

15. A process as described in any of claims 3 to 12, wherein a salt of iron with inorganic or organic acids, preferably selected from a group of salts comprising ferrous sulphate, ferrous chloride, ferrous ammonium sulphate, ferrous oxalate, ferrous citrate, or any combination thereof, or a salt selected from a group comprising ammonium chloride, ammonium sulphate, other such salts, or any combination thereof, is used in place of said first suitable acid of step 1.1b.
16. A process as described in any of claims 3 to 16, wherein said neutralising agent of stage 1.3b is selected from a group comprising hydroxides, carbonates, or bicarbonates of alkali metals, either individually or in any combination thereof; said hydroxides preferably being sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium hydroxide; said carbonates preferably being sodium carbonate, potassium carbonate, calcium carbonate, or lithium carbonate; said bicarbonates preferably being sodium bicarbonate, potassium bicarbonate, lithium bicarbonate.
17. 15. A process as claimed in any of claims 1-2 and 5-14 wherein said number of cycles is greater than 100.