CN103687848A - A sustainable chemical approach for the separation of naphthalenesulfonic acid compounds using intrinsic recycling of all acidic streams generated during separation and washing - Google Patents

Abstract

The separation of the naphthalene sulfonic acid compound is effected by acidifying the alkali melt mixture with dilute sulfuric acid under predetermined conditions of temperature, time and pH to produce a precipitate, and the naphthalene sulfonic acid compound is separated by precipitation as a partial alkali metal salt and by filtration. The filtrate containing the soluble naphthalenesulfonic acid compound and/or its salt obtained after the recycling treatment is used as the starting reaction medium, the topping reaction medium, the dilution reaction medium for the subsequent separation of the naphthalenesulfonic acid compound after the recycling treatment. Separation of the naphthalene sulfonic acid can be achieved by two methods, i.e., forward separation and reverse separation.

Description

A sustainable chemical approach for the separation of naphthalenesulfonic acid compounds using intrinsic recycling of all acidic streams generated during separation and washing

technical field

The present invention relates to a process for isolating part of the naphthalenesulfonic acid compounds in the form of alkali metal salts using intrinsic type recycle of all acid streams produced.

More specifically, the present invention relates to obtaining H acid in the form of a partial alkali metal salt by mixing molten agglomerates with acid (for brevity, the precipitate produced by mixing molten agglomerate with acid is hereinafter referred to as "acidified precipitate" ) while subjecting an alkali molten mixture to precipitation to separate the naphthalenesulfonic acid compound, characterized in that the acidification precipitation is carried out by mixing the molten mass with the dilute acid, and the precipitated naphthalenesulfonic acid partial alkali metal salt is separated by filtration , and the intrinsic type recycle of the resulting filtrate containing soluble naphthalenesulfonic acid compounds and/or salts thereof is used as the reaction medium of the separation process.

Background technique

Separation (broadly defined as separation of products) is the formation of a basic substance with an acidic solution following a chemical process in which a soluble product is separated by known methods. Separation is an important chemical method widely used in the preparation of many molecules.

Separation of molecules finds applications in various chemical groups including pharmaceuticals, dyes and pigments, agrochemicals, specialty chemicals, fine chemicals and explosives.

Disadvantages of current separation methods:

Naphthalenesulfonic acid compounds have long been prepared and used as intermediates in the production of dyes and pigments. A general method for isolating naphthalenesulfonic acid compounds involves obtaining an alkali-melting amine from naphthalene, followed by acidification with dilute acid and precipitation.

The problem with this method is that the overall yield of naphthalenesulfonic acid compounds from naphthalene is low and a large amount of acid and base etc. are required.

According to the method as described on pages 533 to 536 of Yutaka HOSODA "Senryo Kagaku (Dye Chemistry)", the amount of caustic soda used for alkali melting 1 mole of the trisodium salt of Koch's acid is 8.6 moles, which corresponds to the theoretically required 4.3 times the amount (2 moles). Thus, for 1 mole of Koch acid, the amount of sulfuric acid required to obtain H acid in the form of the monosodium salt from the molten mass amounted to 5.8 moles.

A disadvantage of these methods is that they generate large volumes of acid waste which are difficult to recycle. These methods require environmentally unsustainable reaction conditions regarding pH, temperature, concentration, reagents and media, etc., and leave unsustainable impacts on the environment, especially on our water bodies.

These methods have disadvantages such as low conversion and low yields, making them uneconomical and environmentally unsustainable.

Furthermore, a further disadvantage of all the methods described above is that unwanted organic and inorganic by-products are always formed as a result of these methods. The types of by-products formed and their amounts vary according to the process and molecule. This difficulty during recirculation of the mother liquor results in a large liquid effluent.

Another disadvantage of the above-mentioned methods is that, in some cases, also large amounts of inorganic solid waste are generated. These solid wastes are contaminated with organic compounds such as starting materials, products and by-products and pose serious pollution problems. Often these wastes are viscous solids that are cumbersome to handle, difficult to dispose of, and known to industry as non-green solid wastes.

The above method still has other disadvantages. Because of the large volumes of liquid effluent and non-green solid waste generated, the above-mentioned methods require large facilities for effluent treatment and disposal of solid waste. These factors impose site-related constraints, forcing these methods to be carried out only in designated industrial areas suitable for handling particular chemicals.

Therefore, these methods are non-green, unsustainable, uneconomical, and damage the environment to a very large extent, which has become a focus of attention worldwide.

Therefore, there is a need to provide a method for the green separation of naphthalenesulfonic acid compounds using intrinsic type recycling of acid mother liquor, thereby avoiding the above-mentioned drawbacks and disadvantages and providing an environmentally sustainable and economical recycling solution.

Contents of the invention

The inventors have developed a new method for the isolation of naphthalenesulfonic acid compounds using commercially available custom formulations, such as R-Cat1 and R-Cat2, with intrinsic recirculation of washes and mother liquors generated during the process.

According to the inventors' follow-up, the use of such excess auxiliary material (eg acid) in each separation step is to some extent unavoidable. It has been found that it is almost impossible to substantially reduce the amount of these auxiliary materials used without compromising the other advantages of the method, although there is still room for improving the method.

The use of an excess of auxiliary material (eg, acid) in the separation step results in the use of a large amount of another auxiliary material (eg, base) to neutralize the liquid stream produced after separation of the naphthalenesulfonic acid compound. Therefore, most of the cost of raw materials and processed materials for the preparation of naphthalenesulfonic acid compounds is absorbed by the cost of acids and bases. At the same time, the economic burden of generating a large amount of effluent containing spent acid or inorganic salts and disposing of them cannot be ignored.

The object of the process of the present invention is to provide an environmentally friendly (green) process that overcomes the problem of large amounts of acid waste generation caused by conventional methods of separation of naphthalenesulfonic acid compounds.

Therefore, avoiding the limitations encountered in the isolation of naphthalenesulfonic acid compounds from alkali-fused pellets is the main object of the present invention.

Another object is to provide a green process for the separation of naphthalenesulfonic acids which is not only inexpensive to operate but also leads to high quality products.

Another object of the present invention is to provide an improved process for the production of naphthalenesulfonic acid with recycling of the acidic stream generated during separation, separation and washing of the product, resulting in zero discharge of liquid waste.

Another object of the present invention is to provide economy by reducing the consumption of auxiliary materials such as acid and alkali for neutralizing the acidic liquid effluent by utilizing the recycle of the acidic stream generated during precipitation, separation and washing of the product.

Another object of the present invention is to provide a process in which the content of unwanted by-products, organic and inorganic impurities is substantially reduced by virtue of the reaction medium recirculation capability, which leads to a continuous formation of purer products.

The advantage of the present invention is that the possibility of generating by-products in the acidic mother liquor during recirculation is less due to the use of the patented formulation R-Cat-1 & R-Cat2 since the number and amount of organic and inorganic impurities are relatively small. This fact effectively enables an infinite number of acid mother liquor cycles in our process.

Another advantage of the process of the present invention is that the product separation process disclosed herein ensures that the spent solids formed in the process of the present invention unexpectedly have low levels of organic compounds and are therefore green in nature. Thus, the methods described herein do not require any liquid outflow treatment facilities or the use of solid waste disposal facilities. A further advantage of the method according to the invention over the prior art is that it is not restricted in terms of plant location, since it does not necessarily have to be carried out in an industrial area.

Yet another advantage of the present invention is that the methods disclosed herein are performed under milder reaction conditions and atmospheric pressure, which is safer.

Another advantage of the present invention is that it is possible to fully recycle the acidic liquid stream using the patented reaction formulations developed by the inventors, namely R-Cat1 & R-Cat2 or any other similar formulations used in the process of the present invention.

Another advantage of the method of the present invention is that its internal thermodynamic conditions defined by the pressure, temperature, pH, concentration and various reactants of the reaction components are close to the conditions occurring in nature respectively, thus making the method of the present invention Benign and environmentally friendly.

Carrying out the process at such temperatures and pH values makes it energy saving and thus economical for the process, and it is greener since the production of energy often leads to batch contamination.

Summary of the invention:

Isolation of the naphthalenesulfonic acid compound is achieved by acidifying the base molten mixture with dilute sulfuric acid at predetermined conditions of temperature, time and pH to produce a precipitate, and the naphthalenesulfonic acid compound is separated by precipitation as part of the alkali metal salt and isolated by filtration. The filtrate containing the soluble naphthalenesulfonic acid compound and/or its salt obtained after the recycling treatment is used as the initial reaction medium for the subsequent separation of the naphthalenesulfonic acid compound, filling up the reaction medium, and diluting the reaction medium.

The separation of naphthalenesulfonic acid can be achieved by two methods, forward separation and reverse separation. Detailed method descriptions for forward and reverse separations are clearly shown in A & B, respectively.

Description of drawings

Figure 1 shows a schematic representation of the overall process of the invention.

Figure 2 shows the reaction sequence for the forward separation part of the method.

Figure 3 shows a simplified diagrammatic relationship between the separation and cycling procedures of the present invention.

Figure 4 shows a schematic representation of the complete process in which various streams and products are produced.

Figure 5 shows the reaction sequence for a single cycle of reverse separation of a large number of recirculation loops.

Figure 6 shows a schematic diagram of the cycle procedure.

Detailed ways

We'll start by defining some key terms.

Terms used in the description of the invention:

To aid in the understanding of the methods described herein, several terms are explicitly defined.

Forward Separation - Forward Separation can be defined as "in a reaction procedure in which fresh water or reaction medium and sulfuric acid are considered as the starting reaction medium and subsequently added to the molten agglomerate (starting material) The addition of the molten agglomerate is carried out by addition or batch addition or by any other known addition method.

Reverse Separation - Reverse Separation can be defined as "a separation reaction procedure in which fresh water or reaction medium and molten mass (starting material) are considered to start the reaction medium and then sulfuric acid is added under predetermined separation conditions to continuously add The addition of the sulfuric acid solution is performed either batchwise or by any other known addition method.

• The reaction medium (RM) is the mother liquor or dilute acid or acidic aqueous phase or a combination thereof used in the separation process.

• Fresh reaction medium (FRM) is fresh water or fresh dilute acid or fresh acidic aqueous phase or a combination thereof used in the reaction.

• Reaction Medium Factor (RMF) is the ratio of the weight of FRM or RM used in the process to the weight of the molten mass.

• Mother Liquor (ML) is the liquid stream produced after performing a specific step. Already in cycles following its first cycle, the mother liquor is used as reaction medium (RM) in the various stages of the process of the invention.

• Separation RM is a mixture of acidic pH within the specified range for H acid separation, which is aqueous and miscible for phase separation.

• The Cooling Curve (CC) is a graph of temperature versus time.

• The pH curve is a plot of pH versus the amount of sulfuric acid required to separate the H acids.

• Seeding - is the crystallization or isolation initiator that gives the desired result.

·Salt addition-is to add salt externally to improve the salting-out rate.

The method disclosed in the present invention is a sustainable chemical process for the separation of naphthalenesulfonic acid compounds using intrinsic type recycling of all acid streams generated during separation and washing.

The separation of naphthalenesulfonic acid compounds can be carried out in two ways, namely:

A: Forward Separation - Forward separation can be defined as "in a reaction procedure where fresh water or reaction medium and sulfuric acid are considered to initiate the reaction medium and are subsequently added to the molten mass (starting material) under predetermined separation conditions".

In the forward separation of naphthalenesulfonic acid compounds from the molten mass, the molten mass was added to the starting acid solution using two different methods (ie continuous addition, batch addition).

B: Reverse Separation - Reverse separation can be defined as "a separation reaction procedure in which fresh water or reaction medium and molten agglomerate (starting material) are considered to start the reaction medium and then sulfuric acid is added under predetermined separation conditions".

In the reverse separation of naphthalenesulfonic acid compounds from molten agglomerates, sulfuric acid solution was added to the starting molten agglomerate solution using two different methods (ie, continuous addition, batch addition).

The present method uses a proprietary chemistry, namely R-Cat1 & R-Cat2 for separation and recycle. R-Cat1 & R-Cat2 are multifunctional chemical recycling formulations which mainly contain fine iron powder (ranging from 0% (w/w) to 95% (w/w)), tin, copper, titanium and zinc or any combination thereof , depending on the molten mass to be acidified (ranging from 0% (w/w) to 10% (w/w)). The purity of all components ranged from 50% (w/w) to 100% (w/w). These patented catalysts were finalized and optimized after various studies to effectively remove organic and inorganic impurities with various R-Cats namely R-Cat A, Al, A2, A3, A4, A5, 1, 2.

R-Cat1 & R-Cat2 also contain various metals with multiple valence states such as sodium, magnesium, calcium, iron, nickel, cobalt, tin, Electrolyte salts of zinc, titanium, copper, manganese and any other metal. The purity of the salt is variable and ranges from 50% (w/w) to 100% (w/w). R-Cat1 & R-Cat2 also contain custom grade activated carbon in the range of 0% (w/w) to 5% (w/w); filter aid in the range of 0%-95% and /w) to 5% (w/w) depigmentation agent.

R-Cat1 & R-Cat2 also contain calcium or hydroxides of alkali metals such as magnesium, barium, sodium, potassium in the range of 0% (w/w) to 95% (w/w); ) to 5% (w/w) of custom grade activated carbon; filter aids in the range of 5% (w/w) to 95% (w/w) and Depigmentation agent in the range of 5% (w/w) and iron powder in the range of 5% (w/w) to 25% (w/w).

R-Cat1 & R-Cat2 also contain special additives such as polyelectrolytes, defoamers, dispersants, emulsifiers, mass transfer enhancers, anti-caking agents, UV stabilizers, solubilizers and antioxidants and other such agents.

The method of the present invention also uses commercial grade sodium salt in the range of 0% (w/w) to 95% (w/w), depending on the range of 0% (w/w) to 10% (w/w) of the fused mass to be acidified for salting out from the mother liquor. The purity of the precipitated salt is in the range of 10% (w/w) to 90% (w/w), more precisely in the range of 30-60%. The sodium salt is precipitated from the mother liquor by a predetermined method at a predetermined time period and at a predetermined temperature. This precipitated salt is recycled back into the process at predetermined stages and at predetermined processes. The present invention includes the use of the sodium salt in the range of 0% to 50% (w/w), more preferably in the range of 10-40% (w/w).

This application also discloses a sustainable chemical method for the green separation of naphthalenesulfonic acid compounds utilizing intrinsic type recycling of all acidic liquid streams produced under the same conditions.

The chemical process of the present invention essentially involves the treatment of the acidic mother liquor and the internal bulk recycle of all streams produced during any cycle. Each cycle also contains two programs - a green reaction program and a green separation program.

One of the novel features of the process of the invention relates to the reaction medium used in the various stages of the process.

Referring to Figure 1, in the first cycle of the process of the present invention, FRM is used as the reaction medium in the steps of start-up (step 1.1) and reaction (step 1.2), and is used for steps including stirring & cooling, stirring & separation, filtration & washing (steps 2.1, 2.2, 2.3, 2.4) steps. As a key feature of the present invention, the liquid stream produced in the various steps of the recycle of the first cycle is used as the reaction medium in the subsequent cycles. However, the use of these liquid streams as reaction media is optional and the FRM can be used as reaction media in all cycles.

The streams produced at the various stages of the invention are now defined. As shown in Figure 1, stream A is produced after filtration in (step 2.3) after the reaction step. Stream B is produced after washing the product in step 2.4. The stream resulting from co-processing of streams A & B with R-Cat1 is defined as stream C and transferred to 2nd processing. After the 2nd treatment of stream C, the resulting stream is stored in a storage tank and is defined as stream D. The treated mother liquor stream D is used in various stages such as start-up, reaction, stirring & cooling, stirring & separation, separation into stream E.

Some amount of FRM or any other suitable liquid stream, or combination thereof, is used as make-up liquid during the wash step to compensate for various liquid losses through handling, evaporation, etc.

Details of the steps involved in the two procedures forming a typical cycle of the method of the invention are described below with reference to FIGS. 1 , 2 , 3 and 4 .

A preferred embodiment and various other embodiments of the invention are now described.

In another embodiment of the invention where starting materials are added in a different procedure as described in embodiment A, the simultaneous production and fate of all steps in these two embodiments are the same.

Changes in the procedure of raw material addition were made to understand and optimize the naphthalenesulfonic acid compound separation process parameters to establish and maintain process sustainability to set up an internal infinite recirculation loop of the reaction medium and consistency of product quality.

Program 1.0 - Green Reaction Program:

The green reaction procedure is carried out with two different methods, such as (A) forward separation (B) reverse separation. The following is a detailed description of the method of the present invention. The two methods differ only in the steps initiation (step 1.1) and reaction (step 1.2), all other steps (1.3, 1.4, 2.1, 2.2, 2.3, 2.4, 3.1 & 3.2) are in these two separation methods is common.

A: -forward separation-

As shown in Figure 2, the procedure consists of four steps, namely initiation, reaction, isolation & isolation. Each of these steps is described below.

One of the key features of this procedure is the reaction medium used in the various steps. A predetermined amount of reaction medium is added as appropriate. The reaction medium together with the resulting specific conditions as defined by temperature, pressure, pH, agitation and other such parameters lead to the unique internal recyclability of the process of the invention.

The total amount of reaction medium required in this procedure (hereinafter referred to as Q _RT ) for a typical cycle is determined by the requirement for the conversion of the molten agglomerate to the naphthalenesulfonic acid compound. Q _RT is determined by the weight ratio of the reaction medium (weight ratio) _RA , which is the weight of the reaction medium W _RA required in a single cycle of the process of the invention to the weight of the total amount of molten mass to be converted in a single cycle Ratio of W _{to N.} For a single loop it is:

(weight ratio) _RA =W _RA /W _N Formula 1

Q _RT is such that its weight is equal to W _RA determined from Equation 1.

In a preferred embodiment of the present invention, (weight ratio) _RA is preferably in the range of 0.25 to 25, more preferably in the range of 0.5 to 2.5.

Step 1.1 - Start-up: This step is carried out in a reaction vessel with a stirrer and required accessories known to those skilled in the art. As shown in Figure 2, at the beginning of the first cycle of the process of the invention, a suitable amount of RM is added to the reaction vessel.

In a preferred embodiment of the invention, FRM is used as the reaction medium. The total amount of reaction medium required for a typical cycle (hereinafter referred to as Q _RMT ) is determined by the solubility of the naphthalenesulfonic acid compound. This amount is determined by the weight ratio of the FRM or reaction medium (indicated as (weight ratio) _RM ), which is the weight W _RM of the FRM or reaction medium required in a single cycle to the total weight of the molten mass to be converted in a single cycle Amount to weight ratio of W _{to N.} Right now-

(weight ratio) _RM =W _RM /W _N Formula 2

Q _RMT is such that its weight is equal to W _RM determined from Equation 2.

The amount of FRM or reaction medium used in step 1.1 (indicated as Q _RM1.1 ) was variable.

In a preferred embodiment, (weight ratio) _RM is preferably in the range of 5 to 100, more preferably in the range of 10 to 75, and Q _{RM 1.1} is 0% (w/w )-40% (w/w) range.

A suitable acid is added in a suitable amount and in a suitable form while maintaining the temperature of the reaction mixture in the reaction vessel in the range of 0°C to 200°C, preferably in the range of 30°C to 100°C. In a preferred embodiment of the invention sulfuric acid is used. In another embodiment of the present invention, the temperature at which the acid is added is in the range of 10°C to 100°C, more preferably 50°C to 100°C.

The mixture is stirred for a predetermined time, which is in the range of 0 minutes to 5 hours, more preferably 0.5 hours to 2.5 hours. During the stirring phase, the pH of the reaction mixture is maintained at a predetermined level, which ranges from 1 to 9, preferably ranges from 1 to 7, and most preferably ranges from 1 to 2.

At the end of the mixing phase, the appropriate amount of molten mass is added. It is added in its entirety required amount or in any number of batches of any size, or continuously, or any combination thereof. The molten mass is added at a predetermined temperature and a predetermined pH for a predetermined period of time. The time for adding the molten agglomerate is in the range of 0 minutes to 5 hours, more preferably 0.5 hours to 2.5 hours. The temperature at which the molten mass is added is in the range of 0°C to 200°C. The pH at the time of adding the molten agglomerate is in the range of 1 to 9, preferably in the range of 1 to 7, more preferably in the range of 1 to 2.

In subsequent cycles of the process according to the invention, stream E is used as reaction medium instead of FRM in start-up (step 1.1).

In another embodiment of the present invention, the temperature at which the reaction medium is added is in the range of 10°C to 100°C, more preferably 30°C to 70°C.

In another embodiment of the invention, the addition of the reaction medium and/or the acid, and the molten mass is done in any procedure.

Step 1.2 - Reaction: The molten mass to be converted is added continuously to the reaction vessel in its entirety or in any number of batches. The total amount of molten mass to be converted is added at suitable intervals (depending on the molecules to be separated) within 0 to 5 hours, more preferably within 0.5-1.5 hours.

An appropriate amount of reaction medium is added to the reaction vessel while maintaining the temperature, and the pH of the mixture within their respective predetermined ranges. The temperature at which the reaction medium is added is in the range of 0°C to 200°C, more preferably in the range of 50-100°C. The pH at the time of addition of the reaction medium is in the range from 1 to 9, preferably in the range from 2 to 5. In a preferred embodiment of the invention, FRM is used as reaction medium in step 1.2 of the first cycle of the process of the invention. For subsequent cycles, stream E is used as reaction medium for this step.

The amount of FRM or reaction medium used in step 1.2 (indicated as _QRM1.2 ) can be varied in the range of 0% (w/w) - 40% (w/w) of the total amount _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. A suitable form of acid is added while maintaining the temperature of the reaction mixture in the reaction vessel in the range of 0°C to 200°C.

When the pH of the reaction mixture is at a predetermined value in the range of 1 to 9, preferably in the range of 1 to 2, the molten mass is added to the reaction mixture. Add the molten mass required for step 1.2 in a single batch or batchwise, or continuously, or any combination of these addition methods.

The reaction mixture at all stages of this step is optionally stirred with a stirrer rotating at a rate of 0 to 500 RPM. This step can even be carried out successfully without stirring.

B: -reverse separation-

In the reverse separation of naphthalenesulfonic acid compound, there is only a change in step No.1.1 & 1.2, as shown in Figure 5, all other steps in the reaction program 1.3 & 1.4 are the same as those in the forward separation. The procedure consists of four steps, namely initiation, reaction, isolation & isolation.

One of the key features of this procedure is the reaction medium used in the various steps. A predetermined amount of reaction medium is added as appropriate. The reaction medium together with the resulting specific conditions as defined by temperature, pressure, pH, agitation and other such parameters lead to the unique internal recyclability of the process of the invention.

The total amount of reaction medium required in this procedure (hereinafter referred to as Q _RT ) for a typical cycle is determined by the requirement for the conversion of the molten agglomerate to the naphthalenesulfonic acid compound. Q _RT is determined by the weight ratio of the reaction medium (weight ratio) _RA , which is the weight of the reaction medium W _RA required in a single cycle of the process of the invention to the weight of the total amount of molten mass to be converted in a single cycle Ratio of W _{to N.} For a single loop it is:

(weight ratio) _RA =W _RA /W _N Formula 1

Q _RT is such that its weight is equal to W _RA determined from Equation 1.

In a preferred embodiment of the present invention, (weight ratio) _RA is preferably in the range of 0.25 to 25, more preferably in the range of 0.5 to 2.5.

Step 1.1 - Start-up: This step is carried out in a reaction vessel with a stirrer and required accessories known to those skilled in the art. As shown in Figure 5, at the beginning of the first cycle of the process of the invention, a suitable amount of RM is added to the reaction vessel.

In a preferred embodiment of the invention, FRM is used as the reaction medium. The total amount of reaction medium required for a typical cycle (hereinafter referred to as Q _RMT ) is determined by the solubility of the naphthalenesulfonic acid compound. This amount is determined by the weight ratio of the FRM or reaction medium (indicated as (weight ratio) _RM ), which is the weight W _RM of the FRM or reaction medium required in a single cycle to the total weight of the molten mass to be converted in a single cycle Amount to weight ratio of W _{to N.} Right now

(weight ratio) _RM =W _RM /W _N Formula 2

Q _RMT is such that its weight is equal to W _RM determined from Equation 2.

The amount of FRM or reaction medium used in step 1.1 (indicated as Q _RM1.1 ) was variable.

In a preferred embodiment, (weight ratio) _RM is preferably in the range of 5 to 100, more preferably in the range of 10 to 75, and Q _{RM 1.1} is 0% (w/w )-40% (w/w) range.

A suitable acid is added in a suitable amount and in a suitable form while maintaining the temperature of the reaction mixture in the reaction vessel in the range of 0°C to 200°C, preferably in the range of 30°C to 100°C. In a preferred embodiment of the invention sulfuric acid is used. In another embodiment of the present invention, the temperature at which the acid is added is in the range of 10°C to 100°C, more preferably 50°C to 100°C.

The mixture is stirred for a predetermined time, which is in the range of 0 minutes to 5 hours, more preferably 0.5 hours to 2.5 hours. During the stirring phase, the pH of the reaction mixture is maintained at a predetermined level, which ranges from 1 to 9, preferably ranges from 1 to 7, and most preferably ranges from 1 to 2.

At the end of the mixing phase, the appropriate amount of molten mass is added. It is added in its entirety required amount or in any number of batches of any size, or continuously, or any combination thereof. The molten mass is added at a predetermined temperature and a predetermined pH for a predetermined period of time. The time for adding the molten agglomerate is in the range of 0 minutes to 5 hours, more preferably 0.5 hours to 2.5 hours. The temperature at which the molten mass is added is in the range of 0°C to 200°C. The pH at the time of adding the molten agglomerate is in the range of 1 to 9, preferably in the range of 1 to 7, more preferably in the range of 1 to 2.

In subsequent cycles of the process according to the invention, stream E is used as reaction medium instead of FRM in start-up (step 1.1).

In another embodiment of the present invention, the temperature at which the reaction medium is added is in the range of 10°C to 100°C, more preferably 30°C to 70°C.

In another embodiment of the invention, the addition of the reaction medium and/or the acid, and the molten mass is done in any procedure.

Step 1.2 - Reaction: The molten mass to be converted is added to the reaction vessel in its entirety or in any number of batches. The total amount of molten mass to be converted is added at suitable intervals (depending on the molecules to be separated) over a period of 0 to 5 hours.

An appropriate amount of reaction medium is added to the reaction vessel while maintaining the temperature, and the pH of the mixture within their respective predetermined ranges. The temperature at which the reaction medium is added is in the range of 0°C to 200°C, more preferably in the range of 50-100°C. The pH at the time of addition of the reaction medium is in the range of 1 to 9, preferably in the range of 1 to 2. In a preferred embodiment of the invention, FRM is used as reaction medium in step 1.2 of the first cycle of the process of the invention. For subsequent cycles, stream E is used as reaction medium for this step.

The amount of FRM or reaction medium used in step 1.2 (indicated as _QRM1.2 ) can be varied in the range of 0% (w/w) - 40% (w/w) of the total amount _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. A suitable form of acid is added while maintaining the temperature of the reaction mixture in the reaction vessel in the range of 0°C to 200°C.

When the pH of the reaction mixture is at a predetermined value in the range of 1 to 9, preferably in the range of 1 to 2, the molten mass is added to the reaction mixture. Add the molten mass required for step 1.2 in a single batch or batchwise, or continuously, or any combination of these addition methods.

The reaction mixture at all stages of this step is optionally stirred with a stirrer rotating at a rate of 0 to 500 RPM. This step can even be carried out successfully without stirring.

Forward and reverse separations are only different in step 1.1 & 1.2 and the rest of the process performed in step 1.3 (separation) and step 1.4 (separation) is the same in both separations, refer to Figures 2 & 5.

Step 1.3 - Separation: After completion of the addition of the molten mass at the end of step 1.2, an appropriate amount of a suitable reaction medium is optionally added to the reaction vessel. The decision to add reaction medium depends on the consistency of the solids. The amount of reaction medium used in step 1.3 (indicated as QRM _1.3 ) can be varied in the range of 0% (w/w) - 40% (w/w) of the total amount Q _RMT used in the cycle.

In a preferred embodiment of the invention, FRM is used as reaction medium in the first cycle of the procedure, and for subsequent cycles subjected to the process of the invention, FRM is replaced by stream E.

The reaction mixture at all stages of this step is optionally stirred with a stirrer rotating at a rate of 0 to 500 RPM. This step can even be carried out successfully without stirring.

In a preferred embodiment where _SO2 (sulfur dioxide) gas generated during the separation reaction is completely removed, the reaction is then heated with stirring to a temperature in the range of 0 to 200°C, preferably 0 to 100°C, more preferably 70 to 100°C Predetermined temperature for a duration in the range of 0 hours to 10 hours, preferably 30 minutes to 8 hours, more preferably 30 minutes to 5 hours for a predetermined time.

Step 1.4 - Separation: In a preferred embodiment of the invention, FRM is used as the reaction medium in the first cycle of the procedure. The decision to add reaction medium depends on consistency of product concentration and uniform crystal formation. The amount of reaction medium used in step 1.4 (indicated as QRM _1.4 ) can be varied in the range of 0% (w/w) - 40% (w/w) of the total amount Q _RMT used in the cycle. The resulting mixture is called a separation mixture.

In a preferred embodiment of the invention, the separation temperature is in the range of 0 to 200° C. and the separation pH is in the range of 1 to 12, preferably 1 to 2.

In a preferred embodiment, the pH and temperature conditions are maintained at predetermined levels of pH and temperature for a period ranging from 0 hours to 24 hours, preferably ranging from 30 minutes to 5 hours.

For subsequent cycles subjected to the method of the invention, the FRM is replaced by stream E.

In all the above steps of steps 1.1 to 1.4, optionally sulfuric acid is used as a preferred suitable acid.

In another embodiment of the invention, FRM is used as the reaction medium in the first cycle of the procedure. The amount of FRM or reaction medium used in step 1.4 (QRM _1.4 ) can be varied in the range of 0% (w/w) to 40% (w/w) of Q _RMT used in this cycle.

The reaction mixture at all stages of this step is optionally stirred with a stirrer rotating at a rate of 0 to 500 RPM. This step can even be carried out successfully without stirring.

The green reaction program for a single cycle is completed at the end of step 1.4.

In another embodiment of the present invention, the separation temperature is preferably from 0°C to 100°C.

Program 2.0 - Green Separation Program:

As shown in Fig. 3, the procedure includes four steps, namely, stirring & cooling, stirring & separation, filtration and washing steps. Describe each of these steps in detail.

Step 2.1 - Stirring & Cooling: As shown in Fig. 3, a suitable amount of reaction medium (referred to as the first settling RM) is optionally added to the reaction vessel at a suitable temperature and pH obtained at the end of step 1.4 mixture, said temperature is in the range of 0 to 200°C and said pH is in the range of 1 to 11, preferably 2 to 5, and more preferably 1 to 2. The mixture thus formed is allowed to stir by maintaining it at the first stirring temperature for a certain stirring time.

In a preferred embodiment of the present invention, the first stirring pH is in the range of 1 to 11, preferably 2 to 5, more preferably 1 to 2; the first stirring temperature is 0°C to 200°C, preferably 0°C to 100°C and at a temperature ranging from 0°C to 100°C, the first stirring time is from 1 minute to 10 hours, preferably from 30 minutes to 3 hours.

The liquid layer formed due to the stirring method is cooled at a first cooling temperature, a first cooling pH, and a first cooling time.

In a preferred embodiment of the invention, FRM is used as reaction medium in the first cycle, and for subsequent cycles subjected to the process of the invention, FRM is replaced by stream E.

The amount of FRM or reaction medium used in step 2.1 (indicated as Q _RM2.1 ) can be varied in the range of 0% (w/w) to 60% (w/w) of Q _RMT used in this cycle.

Step 2.2 - Stirring and Separation: At the end of step 2.1 of the first cycle, a predetermined amount of reaction medium ( Known as Stir & Separate RM). Stir the mixture. Agitation is continued by maintaining the mixture at a predetermined first agitation continuation temperature, a predetermined first agitation continuation pH, for a predetermined first agitation continuation time.

In a preferred embodiment of the invention, the FRM is used as stirring and separating RM in the first cycle, and for subsequent cycles subjected to the process of the invention, the FRM is replaced by stream C; the value of the stirring temperature is between 0°C and 200°C, preferably In the range of 0°C to 100°C; the value of separation pH is in the range of 1 to 11, preferably in the range of 2 to 5, more preferably in the range of 1 to 2; the value of time and separation time is in the range of 5 minutes to 5 hours, preferably 30 minutes to within 3 hours.

The amount of FRM or reaction medium used in step 2.2 (indicated as Q _RM2.2 ) can be varied in the range of 0% (w/w) - 40% (w/w) of Q _RMT used in this cycle.

Step 2.3 - Filtering:

The separated mass formed at the end of step 2.2 of the first cycle is then filtered by solid-liquid separation methods known to those skilled in the art at a predetermined filtration temperature, predetermined filtration pH; for a predetermined filtration time. The liquid stream obtained at the end of step 2.3 is fed as stream A to the mother liquor storage tank.

In a preferred embodiment of the invention, the isolated mass is filtered at a value in the filtration temperature range of 0°C to 200°C, preferably 40°C to 100°C; the filtration time is 5 minutes to 5 hours; preferably 30 minutes to 3 hours within range.

Step 2.4 - Washing and Filtration: The total mass obtained from step 2.3 at the predetermined separation temperature and predetermined separation pH is then washed and filtered by methods known to those skilled in the art, where a suitable amount of FRM is defined as stream B.

At the beginning of any cycle, liquid is stored with wash (streams A & B) in storage tanks containing liquid and then transferred to a recirculation treatment vessel for R-Cat1 treatment and subsequently for R-Cat2 treatment.

In a preferred embodiment, the separation temperature is from 0°C to 200°C, preferably from 40°C to 100°C, and the pH is from 1 to 11, preferably from 2 to 5.

A key advantageous feature of the present invention is the recirculation of a suitable amount of a portion of the storage liquid (the portion defined as stream E) to the various steps of the next cycle of the process of the invention (steps 1.1 to 1.3 and 2.2).

The amount of FRM used in step 2.2 (indicated as Q _RM2.2 ) can be varied in the range of 0% (w/w) - 40% (w/w) of Q _RMT used in this cycle.

A typical cycle of the method of the present invention is a cycle consisting of a green reaction procedure and a green separation procedure, so far. A key feature of the invention is that all steps of a typical cycle are performed at atmospheric pressure.

As a key advantageous feature of the present invention, the reaction medium is taken from the mother liquor and the various streams generated during the process of the invention in cycles following the first cycle using both the green reaction procedure and the green separation procedure. In other words, the FRM used in the various stages of the first cycle (steps 1.1 to 1.4 and 2.1 to 2.4) was replaced by the appropriate reaction medium in all subsequent cycles.

In step 2.4, the FRM is used at all cycles to replenish losses from previous cycles in the method of the invention.

The inventors of the present invention have found that the purity of the product naphthalenesulfonic acid compound so formed after any cycle of drying varies in the range of 75% to 100%, preferably 78% to 80%.

The mother liquor and the aqueous washes obtained during the various steps described above are stored for treatment in another cycle, usually in numbers ranging from 5 to 100 and above.

Surprisingly, the inventors have found that the isolation of naphthalenesulfonic acid compounds from molten agglomerates by the method described above can produce inorganic by-products in any cycle, the ratio of their weight to the molten agglomerate to be converted of the above procedure In the range of 0.25 to 25, it is crystalline and non-sticky in nature. The color of these by-products varies from white to off-white to pale yellow, especially off-white. The pH of the inorganic by-products is in the range of 4.0 to 6.0. The moisture content of the inorganic by-products is in the range of 5% to 50%, with a specific range of 10% to 30%.

Recycling treatment of naphthalenesulfonic acid compound mother liquor and washings

Both the mixed mother liquor and the wash are collected for recycling to source treatment. The combined mother liquor was then treated with the first treatment agent (R-Cat1 ) and the second treatment agent (R-Cat2 ) along with sodium sulfate according to the methods discussed herein below. For a single cycle of the present invention, reference is made to the processing cycle of FIG. 6 .

Step No.3.1 - Recycling treatment with R-Cat1

The filtrate flow A & washing flow B in steps 2.3 & 2.4 are combined respectively, and added to the R-Cat processing vessel, and then carry out solid-liquid separation known to those skilled in the art at a predetermined filtration temperature, predetermined filtration pH, and predetermined filtration time method, as shown in Figure 6.

In a preferred embodiment of the present invention, the combined mother liquor is heated in the treatment vessel to a predetermined temperature ranging from 0°C to 200°C, preferably from 40°C to 100°C; its predetermined treatment time is between 5 minutes and 5 hours, preferably 30 minutes to 3 hours. After the desired temperature is reached, the predetermined amount of R-Cat1 and the salt are added completely or in batches at the predetermined addition temperature and under stirring within the predetermined addition time.

The amount of R-Cat1 and salt used for the recycling process in step 3.1 (indicated as Q _R-Cat3.1 ) can be 0% (w/v)-40% (w/v) of the Q _RMT used in this cycle v), more preferably 0% (w/v) to 20% (w/v).

In a preferred embodiment of the present invention, fresh salt is only used in the fresh cycle and the following cycle, the salt recovered from step 3.2, ie R-Cat2 treatment, is recycled in both process steps 3.1 & 3.2.

The entire treated mass is maintained under agitation at a predetermined temperature preferably in the range 0°C to 200°C, preferably 40°C to 100°C, at a predetermined pH in the range of preferably 1 to 7, more preferably 2 to 5; for The predetermined treatment time is in the range of 5 minutes to 5 hours, preferably 30 minutes to 3 hours.

In a preferred embodiment of the present invention, the processed The Baume of the slurry is adjusted to a predetermined Baume in the range of preferably 0 to 50, more preferably 10 to 35.

In a preferred embodiment of the present invention, at a predetermined filtration pH preferably in the range 1 to 7, more preferably 2 to 5, at a predetermined filtration temperature preferably in the range 0°C to 200°C, preferably 40°C to 100°C Known filtration methods filter the total mother liquor; for a predetermined filtration time ranging from 5 minutes to 5 hours, preferably from 30 minutes to 3 hours. Spent R-Cat1 isolated as residue was set aside for safe disposal.

The filtrate mother liquor stream obtained after R-Cat1 treatment was defined as stream C and then transferred to another treatment vessel for R-Cat2 treatment.

Step No.3.2 - Recycling treatment with R-Cat2

The filtrate mother liquor stream C received from the first R-Cat process step 3.1 is fed to the R-Cat2 process vessel at a predetermined temperature, at a predetermined pH, as shown in FIG. 6 .

In a preferred embodiment of the invention, stream C is cooled to a predetermined temperature in the range of 0°C to 50°C, preferably 10°C to 40°C; a predetermined freezing duration in the range of 5 minutes to 5 hours, preferably 30 minutes to 3 hours time. After the desired temperature is reached, the predetermined amount of R-Cat2 and the salt are added completely or in batches at the predetermined addition temperature and under stirring within the predetermined addition time.

The amount of R-Cat2 and salt used in step 3.2 (indicated as C _R-Cat3.2 ) can range from 0% (w/w) to 20% (w/w) of the Q _RMT used in this cycle Variety.

In a preferred embodiment of the invention, fresh salt is only used in the fresh cycle and the following cycle, the salt recovered from the same step, ie step 3.2 in the fresh cycle and the following cycle, is recycled in the process step 3.2.

The entire treated mass is maintained at a predetermined temperature preferably in the range 0°C to 50°C, preferably 10°C to 40°C, at a predetermined pH in the preferred range of 1 to 7, more preferably 4 to 6; The predetermined treatment time ranges from minutes to 5 hours, preferably from 30 minutes to 3 hours.

In a preferred embodiment of the present invention, the processed The Baume of the slurry is adjusted to a predetermined Baume in the range of preferably 0 to 50, more preferably 10 to 35.

In a preferred embodiment of the present invention, at a predetermined filtration pH preferably in the range 1 to 7, more preferably 4 to 6, at a predetermined filtration temperature preferably in the range 0°C to 50°C, preferably 10°C to 40°C Filtration of the treated mother liquor by known filtration methods; for a predetermined filtration time ranging from 5 minutes to 5 hours, preferably from 30 minutes to 3 hours. Salts recovered together with spent R-Cat2 are separated by known filtration methods and stored for recycling in the next cycle.

The filtrate mother liquor stream after R-Cat2 treatment is defined as stream D and then transferred to the mother liquor storage tank, which is then recycled back as stream E in the next cycle.

It should be noted that in the process as described above, the molten mass and/or acid is added to step 1.2 in its entirety or in batches of any size at any interval.

It is further noted that in the methods described above, said first and second treating agents are selected from the group comprising alkali metal hydroxides, carbonates or bicarbonates alone, or combinations thereof; said The preferred sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium hydroxide of hydroxide; The preferred sodium carbonate, potassium carbonate, calcium carbonate or lithium carbonate of described carbonate; The preferred sodium, potassium bicarbonate, lithium bicarbonate.

It should also be noted that the methods described above are applicable to the isolation of similar classes of sulfonic acid products, including 1,8-dihydroxynaphthalene-4-sulfonic acid, 1-amino-8-naphthol-5,7-disulfonic acid , 1-amino-8-naphthol-2,4-disulfonic acid (Chicago acid), 2-amino-8-naphthol-3,6-disulfonic acid (γ-disulfonic acid), 2-amino-5 -Naphthol-7-sulfonic acid (J-acid), 2-naphthol-6-sulfonic acid (Schiffer's acid), 2-amino-5-naphthol-1,7-disulfonic acid (J-di sulfonic acid), 2-phenylamino-5-naphthol-7-sulfonic acid (phenyl J-acid), 1-naphthylamine-8-sulfonic acid (peri-acid), 2-aminonaphthalene-4, 8-disulfonic acid (C-acid), 1-amino-8-naphthol-4,6-disulfonic acid (K-acid), 1,8-dihydroxynaphthalene-3,6-disulfonic acid (chromium acid), 1-naphthylamine-3,6,8-trisulfonic acid (Koch acid), 1-naphthylamine-6-sulfonic acid (Klevic acid), 1-naphthylamine-7- Sulfonic acid (Klev acid), R-acid, G-acid, amino G-acid, 2-amino-8-naphthol-6-sulfonic acid (gamma acid), 2-amino-5-naphthol-7 -sulfonic acid (iso-gamma acid), M-acid, 1-amino-8-naphthol-5-sulfonic acid, 1-naphthylamine-4,7-disulfonic acid and , hydroxyl, sulfonic acid, carboxyl, benzyl, phenyl, ketone, aldehyde, etc. all similar naphthalenesulfonic acid and β-naphthol derivatives.

The following examples illustrate some of the advantages mentioned herein.

Many dyes and dyestuffs, fine chemicals have naphthalenesulfonate as one of the structural units and are currently used in the preparation of various dyes and colorants and pharmaceutical intermediates.

In the conventional H-acid preparation method, the amount of caustic soda used to alkali-melt 1 mole of Koch's acid trisodium salt is 8.6 moles, which corresponds to 4.3 times the theoretically required amount (2 moles). Thus, for 1 mole of Koch acid, the amount of sulfuric acid required to obtain H acid in the form of the monosodium salt from the molten mass amounted to 5.8 moles.

In order to overcome the above-mentioned disadvantages of current methods, the inventors have developed an environmentally friendly, safe and non-toxic method, as shown in the examples below.

Example 1:

In this example, the forward separation reaction procedure for H-acid is described with the following recycle.

Fresh cycle: 181 ml of water and 50 g of sulfuric acid were added to a 0.5 liter 4 necked round bottom flask equipped with a stir bar, condenser, thermometer and addition port arranged in a suitable heating/cooling system and heated to 60°C. 125 g of the molten mass were slowly added to the dilute acid at 90°C over 20 minutes with continuous stirring. The reaction mass was further heated to 95°C to 100°C for SO2 gas evolution and confirmation. Completion of SO2 evolution was checked by the Congo red test. The reaction mass was cooled to 70°C and filtered after adjusting the Baume of the mass to 25°Be. The wet cake of H-acid was washed with 125 ml of water. The H-acid was dried at 110°C to dry 17 g of off-white to pink H-acid with a nitration value (NV) of 80%. The total filtrate, ie reaction medium and washings, is collected and recycled in subsequent batches after treatment.

First recycle (R1) : In the same setup as above, 61 ml of fresh water, 120 ml of treated mother liquor produced in the fresh cycle and 48 g of sulfuric acid were heated to 60°C. 125 g of the molten mass were slowly added to the dilute acid at 90°C over 20 minutes with continuous stirring. The reaction mass was further heated to 95°C-100°C for SO2 gas evolution and confirmation. Completion of SO2 evolution was checked by the Congo red test. The reaction mass was cooled to 70°C and filtered after adjusting the Baume of the mass to 28°Be. The wet cake of H-acid was washed with 125 ml of water. The H-acid was dried at 110°C to dry 18.0 g of off-white acid to pink H-acid with a nitration value (NV) of 79.40%. The total filtrate, ie reaction medium and washings, is collected and recycled in subsequent batches after treatment.

Fifth recycle (R5) : In the same setup as above, 33ml of fresh water, 148ml of treated mother liquor and 76ml of wash mother liquor produced in the fourth recycle and 49g of sulfuric acid were heated to 60°C. 125 g of the molten mass were slowly added to the dilute acid at 90°C over 20 minutes with continuous stirring. The reaction mass was further heated to 95°C-100°C for SO2 gas evolution and confirmation. Completion of SO2 evolution was checked by the Congo red test. The reaction mass was cooled to 70°C and filtered after adjusting the Baume of the mass to 28°Be. The wet cake of H-acid was washed with 125 ml of water. The H-acid was dried at 110°C to dry 17.5 g of a dark pink H-acid with a nitration value (NV) of 76.63%. The total filtrate, ie reaction medium and washings, is collected and recycled in subsequent batches after treatment.

Tenth recycle (R10) : In the same setup as above, 26ml of fresh water, 155ml of treated mother liquor produced in the ninth recycle and 48g of sulfuric acid were heated to 60°C. 125 g of the molten mass were slowly added to the dilute acid at 90°C over 20 minutes with continuous stirring. The reaction mass was further heated to 95°C-100°C for SO2 gas evolution and confirmation. Completion of SO2 evolution was checked by the Congo red test. The reaction mass was cooled to 70°C and filtered after adjusting the Baume of the mass to 28°Be. The wet cake of H-acid was washed with 125 ml of water. The H-acid was dried at 110°C to dry 22 g of a light brown H-acid with a nitration value (NV) of 76.3%. The total filtrate, ie reaction medium and washings, is collected and recycled in subsequent batches after treatment.

Fifteenth recycle (R15) : In the same setup as above, 32ml of fresh water, 149ml of treated mother liquor produced in the fourteenth recycle and 48g of sulfuric acid were heated to 60°C. 125 g of the molten mass were slowly added to the dilute acid at 90°C over 20 minutes with continuous stirring. The reaction mass was further heated to 95°C-100°C for SO2 gas evolution and confirmation. Completion of SO2 evolution was checked by the Congo red test. The reaction mass was cooled to 70°C and filtered after adjusting the Baume of the mass to 27°Be. The wet cake of H-acid was washed with 125 ml of water. The H-acid was dried at 110°C to dry 19.5 g of L. brown H-acid with a nitration value (NV) of 74.11%. The total filtrate, ie reaction medium and washings, is collected and recycled in subsequent batches after treatment.

Twentieth recycle (R20): In the same setup as above, 74ml of fresh water, 107ml of treated mother liquor produced in the nineteenth recycle, 74ml of water and 48g of sulfuric acid were heated to 60°C. 125 g of the molten mass were slowly added to the dilute acid at 90°C over 20 minutes with continuous stirring. The reaction mass was further heated to 95°C-100°C for SO2 gas evolution and confirmation. Completion of SO2 evolution was checked by the Congo red test. The reaction mass was cooled to 70°C and filtered after adjusting the Baume of the mass to 27°Be. The wet cake of H-acid was washed with 125 ml of water. The H-acid was dried at 110°C to dry 20.5 g of a light brown H-acid with a nitration value (NV) of 72.64%. The total filtrate, ie reaction medium and washings, is collected and recycled in subsequent batches after treatment.

The following table (Table 01) shows the frugality of the amount of fresh water used in the reaction of the present invention, forward separation (continuous addition of molten mass )

The mother liquor produced in each cycle of the forward separation procedure was treated with R-Cat1 & sodium sulfate; details of the 1st treatment are mentioned in Table 2 below.

Table 02 below shows the precipitation of impurities in the 1st recycle for source treatment with R-Cat1 & sodium sulfate in the reaction of the invention in the forward separation.

The mother liquor produced after the 1st treatment is then treated with R-Cat2 & Sodium Sulphate and then recycled in the other cycle of the present invention. Its details are mentioned in Table 3.

Table 03 below shows the precipitation of impurities in the 2nd recycle and the savings in the amount of fresh water used in the reaction of the invention in the forward separation when source treatment is performed with R-Cat2.

Example 2:

In this example, the reverse separation reaction procedure for H-acid is described with the following recycle.

Fresh Cycle: Divide a total of 1086g of water into two equal portions of 543ml each. 200.0g of 98% sulfuric acid was diluted with a 543ml portion of water to make a volume of 640ml. The 500.0 g molten mass was diluted with the remaining portion of water to make a volume of 840 ml.

Into a 2.0 L 4 necked round bottom flask equipped with a stir bar, condenser, thermometer and addition port arranged in a suitable heating/cooling system was charged the diluted molten mass and heated to 90°C. The dilute acid slurry was then added in 10 equal batches (each containing 64ml) for 5 minutes each. The reaction mass was further heated to 95°C to 100°C for SO2 gas evolution and confirmation. Completion of SO2 evolution was checked by the Congo red test. The reaction mass was cooled to 70°C and filtered after adjusting the Baume of the pellet to 30°Be by further evaporating the pellet. The wet cake of H-acid was washed with 500 ml of water. The H-acid was dried at 110°C to dry 86 g of off-white to pink H-acid with a nitration value (NV) of 77.03%. The total filtrate, ie reaction medium and washings, is collected and recycled in subsequent batches after treatment.

First recycle (R1) : 386.4 g of treated mother liquor produced in the fresh cycle was topped up with 699.6 g of water, making a total mass of 1086 g. The resulting volume of 1045ml was divided into two equal batches of 522.5ml each. 194.77g of 98% sulfuric acid was diluted with a 522.5ml portion of ML to make a volume of 610ml. The 500.0 g fused mass was diluted with the remaining portion of ML to make a volume of 830 ml. The diluted fused mass was added in the same setup as above and heated to 90°C. The dilute acid slurry was then added in 10 equal batches (61 ml each) for 5 minutes each. The reaction mass was further heated to 95°C to 100°C for SO2 gas evolution and confirmation. Completion of SO2 evolution was checked by the Congo red test. The reaction mass was cooled to 70°C and filtered after adjusting the Baume of the pellet to 30°Be by further evaporating the pellet. The wet cake of H-acid was washed with 500 ml of water. The H-acid was dried at 110°C to dry 88 g of off-white to pink H-acid with a nitration value (NV) of 76.36%. The total filtrate, ie reaction medium and washings, is collected and recycled in subsequent batches after treatment.

Fifth recycle (R5) : 489.3 g of the treated mother liquor produced in the third recycle was topped up with 596.7 g of water to make a total mass of 1086 g. The volume to make 1000ml was divided into two equal batches of 500ml each. A volume of 600ml was made by diluting 189.92g of 98% sulfuric acid with a 500ml portion of ML. The 500.0 g fused mass was diluted with the remaining portion of ML to make a volume of 850 ml.

The diluted fused mass was added in the same setup as above and heated to 90°C. Dilute Acid Slurry The dilute acid slurry was then added in 10 equal batches (each containing 60ml) for 5 minutes per batch. The reaction mass was further heated to 95°C to 100°C for SO2 gas evolution and confirmation. Completion of SO2 evolution was checked by the Congo red test. The reaction mass was further heated to 95°C to 100°C for SO2 gas evolution and confirmation. Completion of SO2 evolution was checked by the Congo red test. The reaction mass was cooled to 70°C and filtered after adjusting the Baume of the mass to 30°Be. The wet cake of H-acid was washed with 500 ml of water. The H-acid was dried at 110°C to dry 94 g of off-white to pink H-acid with a nitration value (NV) of 74.70%. The total filtrate, ie reaction medium and washings, is collected and recycled in subsequent batches after treatment.

Table 04 below shows the savings in the amount of fresh water used in the reverse separation inventive reaction.

The mother liquor produced in each cycle of the reverse separation procedure was treated with R-Cat1 & sodium sulfate; details of the 1st treatment are mentioned in Table 5 below.

Table 05 below shows the precipitation of impurities in the 1st recycle for source treatment with R-Cat1 & sodium sulfate in the reverse separation inventive reaction.

The mother liquor produced after the 1st treatment is then treated with R-Cat2 & Sodium Sulphate and then recycled in the other cycle of the present invention. Its details are mentioned in Table 6.

Table 06 below shows the precipitation of impurities in the 2nd recycle and the savings in the amount of fresh water used in the reaction of the invention in reverse separation when source treatment is performed with R-Cat2.

From the above discussion it is clear that the present invention consists of the following clauses:

1. A chemical process for separating naphthalenesulfonic acid from molten agglomerates, wherein said molten agglomerates contain said naphthalenesulfonic acid salts, characterized in that said method is a sustainable process comprising the following procedures:

A reaction procedure wherein the molten mass is reacted with an acid,

followed by an isolation procedure in which isolation of the reaction product is accomplished,

This is followed by a recycle treatment sequence wherein the impure mother liquor is treated for further recycling in said reaction sequence and said separation sequence, and further wherein said reaction sequence and said separation sequence are in steady state in multiple cycles in a closed loop of conditions where fresh water is added only to make up for systemic losses, for example due to evaporation, where said closed loop enables intrinsic and intrinsic Recycling, the mother liquor used in the process is any one of reaction medium, extraction medium or washing medium, or any combination thereof, as shown in FIG. 4 .

2. The method according to clause 1, wherein said molten agglomerate is preferably greater than 3, more preferably greater than 15, even more preferably greater than 30 in number of said plurality of cycles.

3. The method of claim 1, wherein said naphthalenesulfonic acid in said molten mass is H-acid.

4. The process as described in clauses 1 to 3, wherein for any single cycle, the reaction procedure is carried out with stages of separately preparing diluted molten agglomerate and dilute acid, mixing together diluted molten agglomerate and dilute acid , characterized in that the phases are carried out in the following phases:

Stage 1.1a - adding a first start-up reaction medium to a first vessel with a stirrer and adding an acid, preferably sulfuric acid, to it while maintaining the acid at a temperature of at most 200°C and at a pH between 1 and 7, wherein The amount of the first starting reaction medium is at most 40% (w/w) of the total amount of reaction medium used in the whole cycle, and the total amount of the first starting reaction medium used in the whole cycle is to be separated in the current cycle 5 to 100 times, preferably 10 to 75 times, the total molten mass,

Stage 1.1b - Adding the second start-up reaction medium to a second reaction vessel with a stirrer and adding thereto an amount of molten mass such that the pH of the mixture in said second reaction vessel is between 8 and 14, preferably Between 9 and 13, and wherein the amount of the second start-up reaction medium is at most 40% (w/w) of the total amount of reaction medium used in the whole cycle, and the total amount of the second start-up reaction medium used in the whole cycle The amount is 5 to 100 times, preferably 10 to 75 times, the total molten mass to be separated in the current cycle,

stage 1.1c - stirring the mixture of the first and second reaction vessel for a duration of at most 5 hours, preferably 30 minutes to 2.5 hours, while maintaining the temperature of the respective mixture at most 200°C,

Step 1.2 - adding the diluted molten mass of the second reaction vessel to the dilute acid of the first reaction vessel and optionally the first reducing reaction medium over a period of up to 5 hours and maintaining the The temperature of the mixture is at most 200° C. and the pH is maintained between 1 and 9, characterized in that the first and second start-up reaction medium are taken from the mother liquor storage tank for all cycles starting from the second cycle of the process , storing the mother liquor recycled from the recycling process in the mother liquor storage tank, and

The reaction mixture obtained at the end of step 1.2 is withdrawn to complete the reaction procedure, followed by isolation of the product resulting from the reaction, followed by further recycling of the resulting mother liquor.

5. The process as described in clauses 1 to 3, wherein for any single cycle, the reaction procedure is carried out with stages of separately preparing diluted molten agglomerate and dilute acid, mixing together diluted molten agglomerate and dilute acid , characterized in that said stage is carried out in the following steps:

Stage 1.1a - Adding the first start-up reaction medium to a first reaction vessel with a stirrer and adding thereto an amount of molten mass so that the pH of the mixture in said second reaction vessel is between 8 and 14, preferably 9 to 13, and wherein the amount of the first start-up reaction medium is at most 40% (w/w) of the total amount of reaction medium used throughout the cycle, and the total amount of the second start-up reaction medium used throughout the cycle 5 to 100 times, preferably 10 to 75 times, the total molten mass to be separated in the current cycle,

Stage 1.1b - adding the second start-up reaction medium to a second vessel with a stirrer and adding thereto an acid, preferably sulfuric acid, while maintaining the acid at a temperature of at most 200°C and at a pH between 1 and 7, wherein The amount of the second start-up reaction medium is at most 40% (w/w) of the total amount of reaction medium used in the whole cycle, and the total amount of the first start-up reaction medium used in the whole cycle is the current cycle to be separated 5 to 100 times, preferably 10 to 75 times, the total molten mass,

stage 1.1c - stirring the mixture of the first and second reaction vessel for a duration of at most 5 hours, preferably 30 minutes to 2.5 hours, while maintaining the temperature of the respective mixture at most 200°C,

Step 1.2 - Adding the dilute acid of the second reaction vessel to the molten mass of the first reaction vessel and optionally adding a first reducing reaction medium and maintaining the mixture over a period of up to 5 hours at a temperature of at most 200° C. and maintaining a pH between 1 and 9, characterized in that for all cycles starting from the second cycle of the process, both the first and the second start-up reaction medium are withdrawn from the mother liquor storage tank, storing said mother liquor recycled from a recycling process in said mother liquor storage tank, and

The reaction mixture obtained at the end of step 1.2 is withdrawn to complete the reaction procedure, followed by isolation of the product resulting from the reaction, followed by further recycling of the resulting mother liquor.

6. The process as described in clauses 4 to 5, wherein for any cycle of said process, the reaction mixture obtained at the end of step 1.2 is withdrawn to complete the reaction procedure as described below:

Step 1.3 - optionally adding a second reaction medium to said first reaction vessel in an amount of at most 40% (w/w) of the total amount of reaction medium used throughout the cycle, while The mixture is optionally stirred at up to 500 RPM and by maintaining the temperature of the reaction mixture at most 200°C, preferably at most 100°C, and performing said stirring for at most 10 hours, preferably 30 minutes to 8 hours to completely remove the sulfur dioxide generated during the reaction , and the Baume value is 10 to 50,

Step 1.4 - Adding a third reaction medium to said first reaction medium in the first cycle as fresh reaction medium in an amount not exceeding 40% (w/w) of the total amount of reaction medium used throughout the current cycle container, thereby forming the separation mixture, while maintaining the temperature of said separation mixture at most 200°C, preferably at most 100°C and maintaining the pH between 1 and 7, while stirring said separation mixture for at most 24 hours, preferably at most 5 hours, which Characterized in that said third reaction medium for all subsequent cycles is selected from said mother liquor storage tank.

7. The method as described in clauses 1 to 6, wherein for any cycle of the method, the separation procedure comprises the following steps:

Step 2.1 - Adding the first stirred reaction medium to said first reaction vessel as fresh reaction medium in an amount not exceeding 60% (w/w) of the total amount of reaction medium used in said current cycle, while The mixture is cooled to a temperature of 70° C. and the pH is maintained between 1 and 7 while continuously stirring the mixture for up to 10 hours, characterized in that for all subsequent cycles the first stirred reaction medium is taken from the mother liquor storage tank,

Step 2.2 - maintaining the temperature of the reaction mixture at 70°C and the pH between 1 and 7 by optionally adding a fourth reaction medium in the form of fresh reaction medium in the first cycle while stirring the reaction mixture for up to 24 hours, preferably up to 5 hours, characterized in that for all subsequent cycles said first stirred reaction medium is taken from said mother liquor storage tank,

Step 2.3 - Filtration of the separated mass formed at the end of step 2.2 at a temperature of about 70° C. and a pH of 1 to 7, and a first filtrate stream A is produced as a result of said filtration process, which is carried out at most 5 hours of time,

Step 2.4 - Wash all the pellets obtained at the end of step 2.3 at a temperature of about 70° C. and a pH of 1 to 7 using fresh reaction medium and generate wash stream B.

8. The process as described in clauses 1 to 7, wherein for any cycle of the process, the first filtrate stream A and the wash stream B are combined and subjected to catalytic treatment as follows:

Step 3.1 - Heating the combined streams A and B to a temperature of at most 100°C, preferably 70°C, in a first treatment vessel for at most 5 hours, followed by addition of a first treatment agent and a first sulfate, wherein the first treatment The amount of agent is at most 40% (w/v) of the total amount of reaction medium used in the current cycle, so that the Baume value of the mixture is kept at most 50, while the temperature of the mixture is maintained at Up to 50°C and maintaining a pH between 1 and 7, where a second filtrate in the form of a mother liquor stream C is produced and waste to be disposed of, characterized in that fresh sulphate is used only in the first cycle of this step, and in the following The salt generated from step 3.2 is used in the cycle,

Step 3.2 - Adding said second filtrate stream C to a second treatment vessel, wherein said second filtrate is cooled to a temperature of at most 25°C for at most 5 hours, followed by addition of a second treatment agent and sulfate, wherein said The amount of said second treatment agent and sulfate is at most 20% (w/v) of the total amount of reaction medium used in the current cycle, while maintaining the Baume value of the mixture at most 50, and maintaining the pH at 1 to 7, Preferably between 4 and 6, characterized in that in the first cycle of the process fresh salt is used and in all subsequent cycles the salt recovered at the end of step 3.2 is used, wherein

9. The method of any one of clauses 2 to 8, wherein the acid is sulfuric acid.

10. The method as described in Clause 9, wherein said first and second treatment agents are any proprietary reagents.

11. The method according to any one of clauses 2 to 10, wherein the molten mass and/or acid is added to step 1.2 in its entirety or in batches of any size at any interval.

12. The method of any one of clauses 2 to 11, wherein the first and second treating agents of steps 3.1 & 3.2 are selected from alkali metal-containing hydroxides, carbonates or bicarbonates, Or the group of the combination of hydroxide, carbonate or bicarbonate of alkali metal; The preferred sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium hydroxide of described hydroxide; The preferred sodium carbonate of described carbonate , potassium carbonate, calcium carbonate or lithium carbonate; The preferred sodium bicarbonate, potassium bicarbonate, lithium bicarbonate of described bicarbonate.

13. The method as described in any one of clauses 2 to 12 can also be applied to the separation of similar kinds of sulfonic acid products, such as 1,8-dihydroxynaphthalene-4-sulfonic acid, 1-amino-8-naphthol -5,7-disulfonic acid, 1-amino-8-naphthol-2,4-disulfonic acid (Chicago acid), 2-amino-8-naphthol-3,6-disulfonic acid (γ-disulfonic acid acid), 2-amino-5-naphthol-7-sulfonic acid (J-acid), 2-naphthol-6-sulfonic acid (Scheffer’s acid), 2-amino-5-naphthol-1,7 -disulfonic acid (J-disulfonic acid), 2-phenylamino-5-naphthol-7-sulfonic acid (phenyl J-acid), 1-naphthylamine-8-sulfonic acid (peri-acid) , 2-aminonaphthalene-4,8-disulfonic acid (C-acid), 1-amino-8-naphthol-4,6-disulfonic acid (K-acid), 1,8-dihydroxynaphthalene-3 ,6-disulfonic acid (chromic acid), 1-naphthylamine-3,6,8-trisulfonic acid (Koch acid), 1-naphthylamine-6-sulfonic acid (Klev acid), 1-naphthylamine-7-sulfonic acid (Klev acid), R-acid, G-acid, amino G-acid, 2-amino-8-naphthol-6-sulfonic acid (gamma acid), 2- Amino-5-naphthol-7-sulfonic acid (iso-gamma acid), M-acid, 1-amino-8-naphthol-5-sulfonic acid, 1-naphthylamine-4,7-disulfonic acid and All similar naphthalenesulfonic acid and β-naphthol derivatives with functional groups such as amino, nitro, halo, hydroxyl, sulfonic acid, carboxyl, benzyl, phenyl, ketone, aldehyde, etc.

14. The method of any one of clauses 1-6 and 6-12, wherein the number of cycles is greater than 100.

15. The method of any one of clauses 8-14, wherein the first and second treating agents are added in small batches when the temperature of the reaction mixture reaches 0°C to 100°C, preferably 70 to 20°C Either the addition, or the two reagents are added together once the temperature reaches 0°C to 100°C, preferably 70 to 20°C.

While the above description contains many specificities, these should not be construed as limitations on the scope of the invention, but as exemplifications of preferred embodiments thereof. It must be appreciated that modifications and variations are possible in light of the disclosure given above without departing from the spirit and scope of the invention. Accordingly, the scope of the present invention should be determined not by the illustrated embodiments, but by the appended claims and their legal equivalents.

Claims (15)

1. A chemical process for separating naphthalenesulfonic acid from molten agglomerates, wherein said molten agglomerates contain said naphthalenesulfonic acid salts, characterized in that said method is a sustainable process comprising the following procedures: A reaction procedure wherein the molten mass is reacted with an acid, followed by an isolation procedure in which isolation of the reaction product is accomplished, This is followed by a recycle treatment procedure in which the impure mother liquor is treated for further recycling in said reaction procedure and said separation procedure, And further, wherein said reaction procedure and said separation procedure are performed in multiple cycles in a closed loop in a steady state state, wherein fresh water is added only to make up for systemic losses such as due to evaporation, wherein said closed loop The method is capable of intrinsic and intrinsic recirculation at the source level of all mother liquors produced, said mother liquors used in said process being any of the reaction medium, extraction medium or scrubbing medium, or any of them combination, as shown in Figure 4. 2. The method according to claim 1, wherein said molten agglomerate is, said number of cycles is preferably greater than 3, more preferably greater than 15, even more preferably greater than 30. 3. The method of claim 1, wherein said naphthalenesulfonic acid in said molten mass is H-acid. 4. A process as claimed in claims 1 to 3, wherein for any single cycle the reaction is programmed with stages of separately preparing diluted molten agglomerate and dilute acid, mixing together diluted molten agglomerate and dilute acid Carried out, characterized in that said stage is carried out in the following stages: Stage 1.1a - adding a first start-up reaction medium to a first vessel with a stirrer and adding an acid, preferably sulfuric acid, to it while maintaining the acid at a temperature of at most 200°C and at a pH between 1 and 7, wherein The amount of the first starting reaction medium is at most 40% (w/w) of the total amount of reaction medium used in the whole cycle, and the total amount of the first starting reaction medium used in the whole cycle is to be separated in the current cycle 5 to 100 times, preferably 10 to 75 times, the total molten mass, Stage 1.1b - Adding the second start-up reaction medium to a second reaction vessel with a stirrer and adding thereto an amount of molten mass such that the pH of the mixture in said second reaction vessel is between 8 and 14, preferably Between 9 and 13, and wherein the amount of the second start-up reaction medium is at most 40% (w/w) of the total amount of reaction medium used in the whole cycle, and the total amount of the second start-up reaction medium used in the whole cycle The amount is 5 to 100 times, preferably 10 to 75 times, the total molten mass to be separated in the current cycle, stage 1.1c - stirring the mixture of the first and second reaction vessel for a duration of at most 5 hours, preferably 30 minutes to 2.5 hours, while maintaining the temperature of the respective mixture at most 200°C, Step 1.2 - adding the diluted molten mass of the second reaction vessel to the dilute acid of the first reaction vessel and optionally the first reducing reaction medium over a period of up to 5 hours and maintaining the The temperature of the mixture is at most 200° C. and the pH is maintained between 1 and 9, characterized in that the first and second start-up reaction medium are taken from the mother liquor storage tank for all cycles starting from the second cycle of the process , storing the mother liquor recycled from the recycling process in the mother liquor storage tank, and The reaction mixture obtained at the end of step 1.2 is withdrawn to complete the reaction procedure, followed by isolation of the product resulting from the reaction, followed by further recycling of the resulting mother liquor. 5. A process as claimed in claims 1 to 3, wherein for any single cycle the reaction is programmed with stages of separately preparing diluted molten agglomerate and dilute acid, mixing together diluted molten agglomerate and dilute acid Carry out, it is characterized in that said stage is carried out in the following steps: Stage 1.1a - Adding the first start-up reaction medium to a first reaction vessel with a stirrer and adding thereto an amount of molten mass so that the pH of the mixture in said second reaction vessel is between 8 and 14, preferably Between 9 and 13, and wherein the amount of the first starting reaction medium is at most 40% (w/w) of the total amount of reaction medium used in the whole cycle, and the total amount of the second starting reaction medium used in the whole cycle The amount is 5 to 100 times, preferably 10 to 75 times, the total molten mass to be separated in the current cycle, Stage 1.1b - adding the second start-up reaction medium to a second vessel with a stirrer and adding thereto an acid, preferably sulfuric acid, while maintaining the acid at a temperature of at most 200°C and at a pH between 1 and 7, wherein The amount of the second start-up reaction medium is at most 40% (w/w) of the total amount of reaction medium used in the whole cycle, and the total amount of the first start-up reaction medium used in the whole cycle is the current cycle to be separated 5 to 100 times, preferably 10 to 75 times, the total molten mass, stage 1.1c - stirring the mixture of the first and second reaction vessel for a duration of at most 5 hours, preferably 30 minutes to 2.5 hours, while maintaining the temperature of the respective mixture at most 200°C, Step 1.2 - Adding the dilute acid of the second reaction vessel to the molten mass of the first reaction vessel and optionally adding a first reducing reaction medium and maintaining the mixture over a period of up to 5 hours at a temperature of at most 200° C. and maintaining a pH between 1 and 9, characterized in that for all cycles starting from the second cycle of the process, both the first and the second start-up reaction medium are withdrawn from the mother liquor storage tank, storing said mother liquor recycled from a recycling process in said mother liquor storage tank, and The reaction mixture obtained at the end of step 1.2 is withdrawn to complete the reaction procedure, followed by isolation of the product resulting from the reaction, followed by further recycling of the resulting mother liquor. 6. The process as claimed in claims 4 to 5, wherein for any cycle of the process, the reaction mixture obtained at the end of step 1.2 is withdrawn to complete the reaction sequence as follows: Step 1.3 - optionally adding a second reaction medium to said first reaction vessel in an amount of at most 40% (w/w) of the total amount of reaction medium used throughout the cycle, while The mixture is optionally stirred at up to 500 RPM and by maintaining the temperature of the reaction mixture at most 200°C, preferably at most 100°C, and performing said stirring for at most 10 hours, preferably 30 minutes to 8 hours to completely remove the sulfur dioxide generated during the reaction , and the Baume value is 10 to 50, Step 1.4 - Adding a third reaction medium to said first reaction medium in the first cycle as fresh reaction medium in an amount not exceeding 40% (w/w) of the total amount of reaction medium used throughout the current cycle container, thereby forming the separation mixture, while maintaining the temperature of said separation mixture at most 200°C, preferably at most 100°C and maintaining the pH between 1 and 7, while stirring said separation mixture for at most 24 hours, preferably at most 5 hours, which Characterized in that said third reaction medium for all subsequent cycles is selected from said mother liquor storage tank. 7. A method as claimed in claims 1 to 6, wherein for any cycle of the method, the separation procedure comprises the steps of: Step 2.1 - Adding the first stirred reaction medium to said first reaction vessel as fresh reaction medium in an amount not exceeding 60% (w/w) of the total amount of reaction medium used in said current cycle, while The resulting mixture is cooled to a temperature of 70° C., and the pH is maintained between 1 and 7, while continuously stirring the mixture for up to 10 hours, characterized in that for all subsequent cycles, the first stirred reaction medium is taken from the The mother liquor storage tank, Step 2.2 - maintaining the temperature of the reaction mixture at 70°C and the pH between 1 and 7 by optionally adding a fourth reaction medium in the form of fresh reaction medium in the first cycle while stirring the reaction mixture for up to 24 hours, preferably up to 5 hours, characterized in that for all subsequent cycles said first stirred reaction medium is taken from said mother liquor storage tank, Step 2.3 - Filtration of the separated mass formed at the end of step 2.2 at a temperature of about 70° C. and a pH of 1 to 7, and a first filtrate stream A is produced as a result of said filtration process, which is carried out at most 5 hours of time, Step 2.4 - Wash all the pellets obtained at the end of step 2.3 at a temperature of about 70° C. and a pH of 1 to 7 using fresh reaction medium and generate wash stream B. 8. A process as claimed in claims 1 to 7, wherein for any cycle of the process the first filtrate stream A and the wash stream B are combined and catalytically treated as follows: Step 3.1 - Heating the combined streams A and B to a temperature of at most 100°C, preferably 70°C, in a first treatment vessel for at most 5 hours, followed by addition of a first treatment agent and a first sulfate, wherein the first treatment The amount of agent is at most 40% (w/v) of the total amount of reaction medium used in the current cycle, so that the Baume value of the mixture is kept at most 50, while the temperature of said mixture after addition of reagent is kept at most 50°C and maintaining a pH between 1 and 7, where a second filtrate in the form of a mother liquor stream C is produced as well as waste to be disposed of, characterized in that fresh sulphate is used only in the first cycle of this step, and in the following cycles Use the salt generated from step 3.2 in, Step 3.2 - Adding said second filtrate stream C to a second treatment vessel, wherein said second filtrate is cooled to a temperature of at most 25°C for at most 5 hours, followed by addition of a second treatment agent and sulfate, wherein said The amount of said second treatment agent and sulfate is at most 20% (w/v) of the total amount of reaction medium used in the current cycle, while maintaining the Baume value of the mixture at most 50, and maintaining the pH at 1 to 7, Preferably between 4 and 6, characterized in that fresh salt is used in the first cycle of the process and the salt recovered at the end of step 3.2 is used in all subsequent cycles. 9. A method as claimed in any one of claims 2 to 8, wherein the acid is sulfuric acid. 10. The method as claimed in claim 9, wherein said first and second treatment agents are any proprietary agents. 11. A process as claimed in any one of claims 2 to 10, wherein the molten mass and/or acid is added to step 1.2 in its entirety or in batches of any size at any interval. 12. The method according to any one of claims 2 to 11, wherein said first and second treating agents of steps 3.1 & 3.2 are selected from hydroxides, carbonates or bicarbonates comprising alkali metals , or alkali metal hydroxides, carbonates or hydrogen carbonates; the preferred hydroxides are sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium hydroxide; the preferred carbonic acid carbonates Sodium, potassium carbonate, calcium carbonate or lithium carbonate; Described bicarbonate is preferably sodium bicarbonate, potassium bicarbonate, lithium bicarbonate. 13. The method as claimed in any one of claims 1 to 12 is also applicable to the separation of similar types of sulfonic acid products such as 1,8-dihydroxynaphthalene-4-sulfonic acid, 1-amino-8-naphthalene Phenol-5,7-disulfonic acid, 1-amino-8-naphthol-2,4-disulfonic acid (Chicago acid), 2-amino-8-naphthol-3,6-disulfonic acid (γ di sulfonic acid), 2-amino-5-naphthol-7-sulfonic acid (J-acid), 2-naphthol-6-sulfonic acid (Scheffer's acid), 2-amino-5-naphthol-1, 7-disulfonic acid (J-disulfonic acid), 2-phenylamino-5-naphthol-7-sulfonic acid (phenyl J-acid), 1-naphthylamine-8-sulfonic acid (peri-acid ), 2-aminonaphthalene-4,8-disulfonic acid (C-acid), 1-amino-8-naphthol-4,6-disulfonic acid (K-acid), 1,8-dihydroxynaphthalene- 3,6-disulfonic acid (chromic acid), 1-naphthylamine-3,6,8-trisulfonic acid (Koch acid), 1-naphthylamine-6-sulfonic acid (Klev acid) , 1-naphthylamine-7-sulfonic acid (Klev acid), R-acid, G-acid, amino G-acid, 2-amino-8-naphthol-6-sulfonic acid (gamma acid), 2 -amino-5-naphthol-7-sulfonic acid (isogamma acid), M-acid, 1-amino-8-naphthol-5-sulfonic acid, 1-naphthylamine-4,7-disulfonic acid and All similar naphthalenesulfonic acid and β-naphthol derivatives having functional groups such as amino, nitro, halo, hydroxyl, sulfonic acid, carboxyl, benzyl, phenyl, ketone, aldehyde, etc. 14. The method of any one of claims 1-6 and 7-12, wherein the number of cycles is greater than 100. 15. The method according to any one of claims 8-14, wherein the first and second treating agents are added in a small amount when the temperature of the reaction mixture reaches 0° C. to 100° C., preferably 70 to 20° C. The addition is done together in batches, or the two reagents are added together once the temperature reaches 0°C to 100°C, preferably 70 to 20°C.

Images