A SULFONATING MIXTURE FOR SYNTHESIS OF ACRYLAMIDO TERTIARY BUTYL SULFONIC ACID AND PREPARATION PROCESS THEROF

CROSS-REFERENCE TO RELATED APPLICATIONS AND PRIORITY

The present application claims priority from Indian complete patent application no. 202121060666 filed on the 24 December 2021, the details of which are incorporated herein by a reference.

TECHNICAL FIELD

The present subject matter described herein, in general, relates to a sulfonating mixture for the synthesis of acrylamido tertiary butyl sulfonic acid (ATBS) monomer and a process for the preparation of the said sulfonating mixture.

BACKGROUND

Acrylamido tertiary butyl sulfonic acid monomer (herein after referred to as “ATBS”) is a white, needle-like crystal at a normal state and has a melting point of 185° C. ATBS has wide applications in the fields of oil industry, mineral industry, construction, water treatment, fibres, plastics, printing and dyeing, coating, static inhibitor, pottery, washing auxiliary detergent, ion exchange, gas separations and cosmetics.

In current state of art, the processes for the synthesis of ATBS involves a first step of preparation of sulfonating mixture, a second step of the reacting the sulfonating mixture prepared in first step with excess of acrylonitrile (ACRN) in controlled temperature and pressure conditions to obtain ACRN- sulfate. Further, the ACRN-sulfate obtained in the second step is reacted with Isobutylene (IB) to obtain ATBS slurry. The ATBS slurry obtained can be further filtered and purified to remove impurities from the final product. ATBS can be represented by the following formula,

In the existing art, in the first step of preparation of sulfonating mixture which happens to be one of primary reagent in the synthesis of ATBS, liquid SO3 is used. However, such conventional processes of preparing the sulfonating mixture in the synthesis of ATBS liquid SO3 suffers from several drawbacks or challenges. Firstly, during the preparation of the sulfonating mixture by using liquid SO3, fumes of SO3 are generated affecting the environment. Further, use of liquid SO3 results in inconsistent acid number of the sulfonating mixture and large variation in oleum strength which in turn affects the overall quality and yield of the end product, i.e. ATBS. It should be noted that consistency in the acid number is significant in order to achieve good quality as well as higher yield of the ATBS. Further, the variation in the strength of the oleum affects the color and yield of the ATBS. Furthermore, in the conventional process of synthesis of ATBS, along with the main reaction for the synthesis of ATBS there is a higher yield of by-products and impurities due to the side reactions. The impurities present in the ATBS strongly affects, the molecular weight of the ATBS during polymerization and hence further to its usage.

Therefore, there is a long felt need for an providing an improved sulfonating mixture for the synthesis of ATBS and preparation process thereof in order to alleviate at least the aforementioned challenges/drawbacks of the existing/conventional processes.

OBJECTS OF THE INVENTION

The principal object of this invention is to provide a highly reactive sulfonating mixture and preparation process thereof enabled to provide high yield and high purity of acrylamido tertiary butyl sulfonic acid (ATBS).

Another object of this invention is to provide a highly reactive sulfonating mixture and preparation process thereof enabled to limit or avoid variation in oleum strength.

Another object of this invention is to provide a highly reactive sulfonating mixture and preparation process thereof enabled to produce ATBS with reduced amount of impurities.

Another object of this invention is to develop environment friendly process for the production of ATBS by reducing the amount of toxic gases like SO3 going into the atmosphere.

SUMMARY

This summary is provided to introduce concepts related to a sulfonating mixture for the synthesis of acrylamido tertiary butyl sulfonic acid (ATBS). This summary is not intended to identify essential features of the claimed subject matter, nor it is intended for use in determining or limiting the scope of the disclosed subject matter.

In one embodiment, a sulfonating mixture for the synthesis of acrylamido tertiary butyl sulfonic acid monomer (ATBS) is disclosed. The said sulfonating mixture may comprise 30% oleum and 98% sulphuric acid (H2SO4), wherein a ratio of 30% oleum to 98% Sulphuric acid (H2SO4) may be between 0.10-0.25:1.

In another embodiment, a process for preparation of sulfonating mixture for the synthesis of ATBS is disclosed. The process of preparation of said sulfonating mixture may comprise various steps. The said process may comprise a step of adding a predetermined amount of 98% sulphuric acid (H2SO4) into a reactor. Further, the said process may comprise a step of circulating the 98% sulphuric acid (H2SO4) in the reactor. Further, the said process may comprise a step of adding a predetermined amount of 30% oleum into the reactor to mix with the circulating 98% sulphuric acid (H2SO4). Further, the said process may comprise a step of circulating a mixture of 30% oleum and 98% sulphuric acid (H2SO4) at a predetermined temperature and pressure for a predetermined period of time. Furthermore, the said process may comprise a step of removing an excess moisture content from the sulphuric acid (H2SO4) and oleum to obtain a moisture free sulfonating mixture.

List of Abbreviations

ATBS- Acrylamido tertiary butyl sulfonic acid

AM- Acrylamide

ACRN- Acrylonitrile

IBDSA- Isobutyl disulfonic acid

IBSA- Isobutyl sulfonic acid

TBA-Tertiary butyl acrylamide

AMPDSA- Acrylamido methyl propane disulfonic acid

IB - Isobutylene

MT- Metric tones

BRIEF DESCRIPTION OF DRAWINGS

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

Figure 1 depicts a process (100) of preparation of a sulfonating mixture in the synthesis of acrylamido tertiary butyl sulfonic acid monomer (ATBS), in accordance with an embodiment of the present subject matter. Figure 2 depicts a system (200) for preparation of the sulfonating mixture in the synthesis of acrylamido tertiary butyl sulfonic acid monomer (ATBS), in accordance with an embodiment of the present subject matter.

Figure 3 depicts the effect of 30% oleum to 98% H2SO4 ratio on the yield of the acrylamido tertiary butyl sulfonic acid (ATBS), based on sulphonating mixture as a limiting reactant in accordance with an embodiment of the present subject matter.

Figure 4 depicts the effect of 30% oleum to 98% H2SO4 ratio on the yield of the acrylamido tertiary butyl sulfonic acid (ATBS), based on Isobutylene (IB) in accordance with an embodiment of the present subject matter.

DETAILED DESCRIPTION

Reference throughout the specification to “various embodiments,” “some embodiments,” “one embodiment,” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in various embodiments,” “in some embodiments,” “in one embodiment,” or “in an embodiment” in places throughout the specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

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

Various modifications to the embodiment may be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. However, one of ordinary skill in the art may readily recognize that the present disclosure is not intended to be limited to the embodiments illustrated but is to be accorded the widest scope consistent with the principles and features described herein. The detailed description of the invention will be described hereinafter referring to accompanied drawings.

In accordance with an embodiment of the present subject matter, a sulfonating mixture for the synthesis of acrylamido tertiary butyl sulfonic acid monomer (ATBS) is described herein. The said sulfonating mixture may comprise 30% oleum and 98% sulphuric acid (H2SO4).

In one embodiment, a mixing ratio of 30% oleum to 98% Sulphuric acid (H2SO4) may be within a range of 0.10-0.25:1, and more preferably within a range of 0.12-0.2:1.

In one embodiment, the said sulfonating mixture may be in liquid form.

In one embodiment, the strength of the said sulfonating mixture may be between 99.8% to 99.9%.

In one embodiment, an acid number of the said sulfonating mixture may be consistent and may be within a range of 35-37.

In one embodiment, the synthesized ATBS may comprise impurities including, acrylamide (AM) within a range of 610- 670 ppm, acrylonitrile (ACRN) within a range of 180-250 ppm, isobutyl disulfonic acid (IBDSA) within a range of 35-75 ppm, isobutyl sulfonic acid (IBSA) within a range of 50-80 ppm, tertiary butyl acrylamide (TBA) within a range of 1500-1600 ppm, and acrylamido methyl propane disulfonic acid (AMPDSA) within a range of 0.20- 0.50 %.

In one embodiment, yield of the synthesized ATBS may be at least within a range of 79-81% and purity of synthesized ATBS may be within a range of 98-99.50%.

Now, referring to Figures 1 and 2, a process (100) for preparation of said sulfonating mixture for the synthesis of ATBS is illustrated in accordance with an embodiment of the present subject matter. The said process (100) for preparation of the sulfonating mixture may be implemented by a system (200) comprising a reactor (203). The said process (100) for the preparation of the said sulfonating mixture comprises of various steps.

In one embodiment, the process (100) for preparation of said sulfonating mixture may comprise a step of adding (101) a predetermined amount of 98% sulphuric acid (H2SO4) into a reactor (203) from a H2SO4 storage tank (201). Further, the said process (100) may comprise a step of circulating (102) the 98% sulphuric acid (H2SO4) in the reactor (203). Further, the said process (100) may comprise a step of adding (103) a predetermined amount of 30% oleum from oleum storage tank (202) into the reactor (203) to mix with the circulating 98% sulphuric acid (H2SO4). Further, the said process (100) may comprise a step of circulating (104) a mixture of 30% oleum and 98% sulphuric acid (H2SO4) at a predetermined temperature and pressure for a predetermined period of time. Further, the said process (100) may comprise a step of removing (105) an excess moisture content from the sulphuric acid (H2SO4) and oleum to obtain a moisture free sulfonating mixture having strength at least 99.89%.

In one embodiment, a rate of circulating (102) the 98% sulphuric acid (H2SO4) may be 20 m ³ /hr for a batch size of 20-30 MT.

In one embodiment, a rate of adding (103) the predetermined amount of 30% oleum may be between 2500-2700 kg/hr for a batch size of 20-30 MT.

In one embodiment, the said reactor (203) may be a static batch reactor.

In one embodiment, the step of circulating (102) the 98% sulphuric acid (H2SO4) may be carried out by means of a centrifugal pump.

In one embodiment, the step of circulating (104) a mixture of 30% oleum and 98% sulphuric acid (H2SO4) may be carried out at a temperature between 40-50°C and pressure between 30-50 mmHg.

In one embodiment, the step of circulating (104) a mixture of 30% oleum and 98% sulphuric acid (H2SO4) may be carried out for a time period of 1 to 4 hours.

In one embodiment, a mixing ratio of 30% Oleum to 98% Sulphuric acid (H2SO4) may be within a range of 0.090-0.25:1, and preferably between 0.12- 0.20: 1.

In one embodiment, the acid number of the sulfonating mixture may be consistently maintained within a range of 35-37.

In another embodiment, the said sulfonating mixture obtained in accordance with the present subject matter may be used as a reaction intermediate in the production of chemical compounds including but not limited to the acrylamido tertiary butyl sulfonic acid monomer (ATBS). In an embodiment of the invention, refering to Figure 4, the yield of ATBS may be consistent in between the ratio of 30% Oleum to 98% H2SO4 which may be within a range of 0.14 to 0.20.

In one embodiment, the sulfonating mixture is enabled to produce high yield of ATBS with improved quality.

The instant subject matter is further described by the following examples:

Experimental Details:

Example 1: Preparation of sulfonating mixture by using 30% Oleum

In one exemplary embodiment, the process for the preparation of sulfonating mixture involves a batchwise mixing of 30% oleum in 98% H2SO4. A batch quantity of 98% H2SO4 is transferred in a static batch reactor (203). The transferred H2SO4is then circulated in the said reactor (203) by means of a centrifugal pump. As the circulation is established, in the next step, the controlled addition of 30% oleum is triggered in order to facilitate uniform mixing of 30% oleum and 98% FhSC to obtain a concentrated sulfonating mixture. In this exemplary embodiment, the mixing ratio of 30% Oleum to 98% H2SO4is within a range of 0.12 to 0.2:1.

In this exemplary embodiment, the time period for the addition of 30% oleum into the reactor (203), containing the circulating H2SO4 (98%), is between 1.5 to 3 hrs. During the step of circulation, the heat of mixing is removed by means of a heat exchanger mounted in the circulation line. As the addition of 30% oleum is completed, the strength of sulfonating mixture obtained in the reactor (203) is checked. If the strength of sulfonating mixture is well within the desired range, then the complete batch of sulfonating mixture is transferred to the storage tank (206). The whole process is monitored and controlled from an optimized distributed control system (not showing in figure).

Example 2: Effect of use of 30% Oleum on yield of ATBS process

In another exemplary embodiment, a comparative effect utilizing sulfonating mixture obtained in accordance with the Example 1 by using 30% oleum on yield of the ATBS (based on the limiting reactants Isobutylene and 98% H2SO4) is tabulated below. The percentage yield of ATBS obtained using the sulfonating mixture in accordance with the Example 1 is compared with the percentage yield ATBS obtained using liquid SO3 in the conventional process.

1. % ATBS yield when liquid SO3 is in use: of mixture by SO ₃ The process involves the batchwise mixing of predetermined amount of liquid SO3 in 98% H2SO4. A batch quantity of 98% H2SO4 is transferred in an agitated batch reactor. As the agitation is established, in the next step, the controlled addition of liquid SO3 is triggered in order to facilitate uniform mixing of liquid SO3 and 98% H2SO4 to obtain a concentrated sulfonating mixture. The mixing ratio of liquid SO3 to 98% H2SO4 is within a range of 0.03 to 0.07. The time period for the addition of liquid SO3 into the reactor containing H2SO4(98%) is between 0.5 to 1 hr. During the step of mixing, the heat of mixing is removed by means of cooling water provided to limpet coil of the batch reactor. As the addition of liquid SO3 is completed, the strength of sulfonating mixture obtained in the reactor is checked. If the strength of sulfonating mixture is well within the desired range, then the complete batch of sulfonating mixture is transferred to storage tank. The whole process is monitored and controlled from an optimized distributed control system (DCS system).

Table 1: ATBS yield when liquid SO3 is used for the preparation of sulfonating mixture as per the conventional process

2. ATBS yield when 30% oleum is in use in accordance with present subject matter:

Preparation of sulfonating mixture by using liquid 30% oleum In one exemplary embodiment, the sulfonating mixture is prepared in accordance with the details mentioned in the aforementioned Example 1.

Table 2: ATBS yield data when 30% oleum is used for the preparation of sulfonating mixture By referring to table 2, the amount of IB and the amount of sulfonating mixture comprising 30% oleum and 98% sulfuric acid in accordance with the present invention to produce 1 kg of ATBS is provided. The IB concentration is optimized in order to achieve reaction parameters and formation of impurities and side products during ATBS synthesis.

By referring to table 2, the yield of ATBS monomer based on Isobutylene (IB) and sulphonating mixture as limiting reactants is provided, wherein the limiting reactants are totally consumed at the end of the reaction and therefore a yield calculation of amount of ATBS monomer product formed is limited by Isobutylene (IB) and sulphonating mixture.

Table 3: Comparative summary of results

Referring to Tables 2-3, it is evident that the yield of ATBS monomer based on Isobutylene (IB) and sulphonating mixture as limiting reactant by using 30% oleum is better as compared to the yield obtained using liquid SO3. Specifically, the yield of ATBS is improved from 79.29% to 80.34% based on IB as limiting reactant and from 77.62% to 81.51% based on sulphonating mixture of table 2 is considered as limiting reactant.

Further, ref ering to Figure 3 and 4, it can be seen that the yield of ATBS based on IB and sulphonating mixture as limiting reactants is consistent in between the ratio of 30% Oleum to 98% H2SO4 which is 0.14 to 0.20.

Example 3: Effect of use of 30% Oleum on quality of ATBS product

In another exemplary embodiment, the effect on quality of the ATBS synthesized using the sulfonating mixtures prepared in accordance to Example 1 and Example 2 is evaluated. One of the major by-product formed in ATBS synthesis process is Tertiary butyl acrylamide (TBA). A comparative reduction in formation of TBA and other impurities such as acrylamide (AM), acrylonitrile (ACRN), Isobutyl disulfonic acid (IBDSA), Isobutyl sulfonic acid (IBSA), and Acrylamido methyl propane disulfonic acid (AMPDSA) is observed while using 30% oleum in predefined mixing ratio in the preparation of sulfonating mixture. The comparative qualitative data while using liquid SO3 and 30% oleum is tabulated below.

Table 4: Qualitative data while using liquid SO3 in the preparation of sulfonating mixture:

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Table 5: Qualitative data while using 30% Oleum in the preparation of sulfonating mixture

Table 6: Comparative impurity profile while using liquid SQ3 and 30% oleum is tabulated below: Refering to Tables 4-6, it is evident that the concentration of TBA is reduced in case of use of 30% Oleum in the preparation of sulfonating mixture as compared to the conventional process of using liquid SO3 in the preparation of sulfonating mixture. Further, it can be seen that the impurities like AM, ACRN and IBSA are also reduced. Thus, the purity of ATBS is improved. The reduction in the formation of impurities lead to the reduction of yellow color of ATBS and a white colored or clear ATBS is obtained unlike the conventional process which results in yellow colored ATBS product.

Example 4: Effect of 30% Oleum to 98% H2SQ4 ratio

In another exemplary embodiment, the effect of 30% Oleum to 98% H2SO4 ratio on the yield of ATBS is evaluated. The experimental results at different ratio are tabulated below.

Table 7: Effect of 30% Oleum to 98% H2SO4 ratio

Refering to figure 3, figure 4 and table 7, it is evident that the yield of ATBS is quite steady in the ratio of 30% Oleum to 98% H2SO4 between 0.09 to 0.23. The percentage yield of ATBS is within the range of 78-81% (based on IB as limiting reactant) and the percentage yield of ATBS is within the range of 80-82% based on sulphonating mixture as limiting reactant, wherein the ratio of 30% Oleum to 98% H2SO4 is adjusted between 0.09 to 0.23.

Example 5: Reduction in fumes during preparation of sulfonating mixture

In another exemplary embodiment, it is observed that venting of fumes through scrubber is reduced in case when 30% Oleum in predetermined ratio is used for the preparation of sulfonating mixture. In the conventional process of preparation of sulfonating mixture, significant amount of venting of fumes of SO3 was observed. In the contrary, by using 30% oleum in predetermined ratio this venting of fumes from scrubbing system is substantially reduced. This reduction in fumes is realized and appreciated from the fact that while the replacement of scrubber solution was required in every 4-5 days in the preparation of sulfonating mixture using the conventional process employing liquid SO3, in case of using 30% oleum for the preparation of sulfonating mixture in predetermined ratio, the time period of replacing the scrubber solution is increased up to 10-15 days. The comparative time period of replacing the scrubber solution clearly indicates the reduction in venting of fumes. The preparation method is more environment friendly than conventional method.

Example 6: Determination of the strength of sulfonating mixture

The strength of the sulfonating mixture prepared in accordance with the present invention is determined by ASTM D664-04 method.

In another embodiment, the said sulfonating mixture may be enabled to decrease the production of by-products in the synthesis of ATBS, wherein the said by-products may be a tertiary butyl acrylamide (TBA) formed during the process of ATBS synthesis.

In another embodiment of the invention, the said sulfonating mixture may be enabled to decrease the amount of impurities in the synthesized ATBS, wherein the said impurities may be one or more of Acrylamide (AM), acrylonitrile (ACRN), and Isobutyl sulfonic acid (IB SA).

In another embodiment of the invention, the said sulfonating mixture may be enabled to obtain the ATBS slurry with reduced yellowness and to obtain white colored ATBS slurry with reduced iron content.

The embodiments, examples and alternatives of the preceding paragraphs or the description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.

Although implementations for a sulphonating mixture for synthesis of acrylamido tertiary butyl sulfonic acid (ATBS) have been described in language specific to structural features and/or processes, it is to be understood that the appended claims are not necessarily limited to the specific features or processes described. Rather, the specific features and processes are disclosed as examples of implementations a sulphonating mixture for synthesis of acrylamido tertiary butyl sulfonic acid (ATBS).