CROSS-REFERENCE TO RELATED APPLICATIONS AND PRIORITY

The present application claims priority from Indian complete patent application no. 202121060667 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, about an agitator reactor used in the synthesis of Acrylamido tertiary butyl sulfonic acid (ATBS).

BACKGROUND

Acrylamido tertiary butyl sulfonic acid (hereinafter 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 the 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 the current state of the art, the processes for the synthesis of ATBS are described. The process for the synthesis of ATBS involves the first step of the preparation of the sulfonating mixture. The second step in the preparation of ATBS involves the reaction of sulfonating mixture prepared in step 1 with an excess of acrylonitrile (ACRN) in controlled temperature and pressure conditions to obtain acrylonitrile- sulphate (ACRN-sulfate). Further, the ACRN-sulfate obtained in the second step is reacted with Isobutylene (IB) to obtain the 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,

Earlier, ATBS was produced via two methods. In the first method, single-step synthesis or one-pot synthesis was used. In the second method, a two-step synthesis was used in which ACRN- sulphate was prepared in the first step and in the second step, ACRN-sulphate was treated with isobutylene (IB) to produce ATBS. These two steps were carried out in separate reactors. The agitator reactor, which is the second reactor, plays an important role to control the yield and purity of ATBS. In-state of the art, the conventional reactor and processes of preparing reaction mixture in the synthesis of ATBS lack in many aspects such as improper heat transfer due to improper mixing of the reactants, and the proper and efficient heat transfer is vital in order to achieve good quality as well as higher yield of the ATBS. In the conventional reactor and process implemented thereon, 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. Impurities present in the ATBS strongly affects the polymerization and molecular weight of ATBS.

Therefore, there is a long-felt need for an improved agitator reactor that facilitates improved heat transfer and proper mixing and process for the preparation of ATBS thereof and thereby improving overall quality and yield of the final product, i.e., ATBS.

OBJECTS OF THE INVENTION

The principal object of this invention is to provide an agitator reactor enabled to provide high yield and high purity of acrylamido tertiary butyl sulfonic acid (ATBS).

Another object of this invention is to provide a process for the preparation of said ATBS with high yield and purity.

Another object of this invention is to provide a process to produce ATBS with a reduced amount of impurities.

SUMMARY

This summary is not intended to identify essential features of the claimed subject matter, nor is it intended for use in determining or limiting the scope of the claimed subject matter. This summary is provided to introduce concepts related to an agitator reactor system and process for the production of ATBS, and the concepts are further described below in the detailed description.

In one embodiment, an agitator reactor system facilitating improved heat transfer and mixing of ACRN sulphate and isobutylene in order to obtain 80-85% yield of the 2-acrylamido-2- methylpropane sulfonic acid having purity at least 99.5% is disclosed. The said agitator reactor system may comprise a first inlet dip pipe configured to receive ACRN sulphate solution from an external reactor. The first inlet dip pipe may be positioned at the top, at a predetermined distance from a central axis, and extended up to the predefined length of the reactor. Further, the said agitator reactor system a second inlet dip pipe configured to receive isobutylene (IB) in liquified form. The second inlet dip pipe may be positioned at the top, at a predetermined distance from the central axis, and extended till the bottom of the reactor. The said agitator reactor system may further comprise a sparger positioned at the bottom of the reactor and in connection with the second inlet dip pipe. The said sparger may be configured to sparge IB in gaseous form, received at the bottom of the second inlet dip pipe, in order to facilitate the reaction of the IB gas with the ACRN sulphate solution for a residence time of 40-80 minutes. Furthermore, the said agitator reactor system may comprise a shaft comprising one or more pairs of propellers rotated at a speed of 170- 185 rpm and a tip speed of 2-5 m/sec to facilitate the proper mixing of the acrylonitrile sulphate and the isobutylene, thereby obtaining a reaction mass/slurry of ATBS.

In another embodiment, a process carried out in an agitator reactor system for facilitating improved heat transfer and mixing of ACRN sulphate and isobutylene in order to obtain 80-85% yield of the 2-acrylamido-2-methylpropane sulfonic acid having a purity of at least 99.5% is disclosed. The said process may comprise adding acrylonitrile sulphate solution at a predetermined flow rate through a first inlet dip pipe positioned at the top of the reactor and extended up to the predefined length of the reactor. The said process may further comprise adding isobutylene (IB) in the liquified form at a predetermined rate through a second inlet dip pipe positioned at the top of the reactor and extended till the bottom of the reactor. Further, the said process may comprise spraying IB in gaseous form over the acrylonitrile sulphate via a sparger positioned at the bottom of the reactor and connected to the second inlet dip pipe to react the IB gas with the ACRN-sulphate solution for a residence time of 40-80 minutes. Furthermore, the said process may comprise facilitating the proper mixing of the acrylonitrile sulphate and the isobutylene via one or more pairs of propellers rotated at a speed of 170-190 rpm and a tip speed of 2-5 m/sec, thereby obtaining a reaction mass/slurry of ATBS.

In one embodiment, the said agitator reactor for the synthesis of ATBS may be a vertical tubular type.

In one embodiment, the said agitator reactor for the synthesis of ATBS may be a continuous flow reactor. In another embodiment of the present disclosure, the first dip pipe maybe 3/4* of the length of the reactor.

In another embodiment of the invention, the sparger may be configured to sparge IB in gaseous form, received at the bottom of the second inlet dip pipe, in order to facilitate the reaction.

In another embodiment of the present disclosure, the said agitation system consists of a solid shaft bearing one or more pairs of propellers and rotated with the help of an electric motor.

In another embodiment of the invention, propellers are selected from at least one of turbine type and paddle type for better heat transfer and turbulent mixing.

In one embodiment of the invention, the said agitator reactor consists of a plurality of baffles, attached internally to the outer wall of the vessel, arranged at 90°, equally apart from each other and running throughout the length of the reactor. The width and thickness of baffles are adjusted in such a way that it breaks the swirl generated due to agitation to ensure thorough mixing.

In another embodiment of the invention, the process carried out in an agitator reactor facilitates improved heat transfer and mixing of ACRN-sulphate and isobutylene.

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

In another embodiment of the invention, the yield of ATBS may be at least 80-85%, and purity of ATBS may be up to 99.50%.

In one embodiment of the present invention, the said process may comprise a step of adding a predetermined amount of ACRN-sulphate into a reactor. Further, the said process may comprise a step of circulating the ACRN-sulphate in the reactor. Further, the said process may comprise a step of adding a predetermined amount of IB into the reactor to mix with the circulating ACRN- sulphate. Further, the said process may comprise a step of circulating a mixture of IB and ACRN- sulphate at a predetermined temperature and pressure for a predetermined period of time.

In one embodiment of the present invention, the rate of circulating the ACRN-sulphate may be 6000-10200 kg/hr.

In one embodiment of the present invention, the rate of adding the predetermined amount of IB may be between 400-600 kg/hr.

In one embodiment of the present invention, the said reactor may be a continuous flow reactor.

In one embodiment of the present invention, the step of circulating the ACRN-sulphate may be carried out by means of a centrifugal pump.

In one embodiment of the present invention, the step of circulating a mixture of IB and ACRN-sulphate may be carried out at a temperature between 50-60 °C and pressure between 0-0.05 kg/cm ² (g).

In one embodiment of the present invention, the step of circulating a mixture of IB and ACRN-sulphate may be carried out for a time period of 40-80 minutes.

List of Abbreviations

A TBS- 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 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 illustrates an implementation of an agitator reactor system 100 and components thereof for facilitating improved heat transfer and proper mixing in the synthesis of acrylamido tertiary butyl sulfonic acid (ATBS), in accordance with an embodiment of the present subject matter.

Figure 2 illustrates a process 200 carried out in the agitator reactor system 100 for facilitating improved heat transfer and mixing of ACRN-sulphate and IB in the synthesis of acrylamido tertiary butyl sulfonic acid (ATBS), 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 accompanying drawings.

Referring to figure 1, an agitator reactor 100 for facilitating improved heat transfer and proper mixing in the synthesis of acrylamido tertiary butyl sulfonic acid (ATBS) is illustrated, in accordance with an embodiment of the present subject matter.

In one embodiment of the invention, as shown in Figure 1, the said system may comprise a vertical tubular reactor 117, a first inlet dip pipe 101, a second inlet dip pipe 102, a sparger 113, a cooling jacket 118, and an agitation system 116 comprising of a motor 110, a shaft 111 and one or more pair of propellers 112.

In one embodiment of the present disclosure, the said first inlet dip pipe 101 may be configured to receive ACRN sulphate solution from an external reactor (not shown). In one embodiment, the external reactor is a continuous flow reactor equipped with an agitation system which is configured to prepare the said ACRN sulphate solution by mixing ACRN with the sulfonating mixture prepared by using 30% Oleum. The first inlet dip pipe 101 may be positioned at the top, at a predetermined distance from a central axis, and extended up to the predefined length of the reactor. In an embodiment of the present disclosure, the first dip pipe maybe 3/4 ^th of the length of the reactor.

In one embodiment of the present disclosure, the significance of having the first inlet dip pipe 101 of 3/4 ^th length of the reactor is to discharge the fresh ACRN-sulphate near to the position of sparger.

In one embodiment of the present disclosure, the second inlet dip pipe 102 may be positioned at the top, at a predetermined distance from the central axis, and extended till the bottom of the reactor. In an embodiment, the said second inlet dip pipe may be configured to receive isobutylene (IB) in liquified form.

In one embodiment of the present disclosure, the second inlet dip pipe 102 may be in connection with the sparger 113 positioned at the bottom of the reactor. In an embodiment, the sparger 113 may be configured to sparge IB in gaseous form, received at the bottom of the second inlet dip pipe 102, in order to facilitate the reaction of the IB gas with the ACRN sulphate solution for a residence time of 40-80 minutes.

In one embodiment of the present disclosure, the sparger positioned at the bottom sprays IB in the gaseous form, thereby facilitating the IB to travel from bottom to top through the reaction mixture. This, in turn, provides sufficient time to react IB with the ACRN- sulphate, ultimately increasing the yield of the ATBS monomer.

In one embodiment of the present disclosure, the said sparger may be a perforated ring-type sparger having a diameter of 750-850mm, a pore size of 1.5-2.5mm, and the number of pores between 45-60.

In one embodiment of the present disclosure, the said shaft 111 may be solid shaft may be arranged centrally with a motor unit at the top of the reactor and is extended to the 3/4* of the length of the reactor. In another embodiment of the present disclosure, the said solid shaft 111 comprises one or more pairs of propellers 112 rotated at a speed of 170-185 rpm and a tip speed of 2-5 m/sec to facilitate the proper mixing of the acrylonitrile sulphate and the isobutylene thereby obtaining a reaction mass/slurry of ATBS. In one embodiment of the present disclosure, the said one or more pairs of propellers 112 are selected from at least one of turbine type and paddle type for better heat transfer and turbulent mixing. In another embodiment of the present disclosure, the outer cooling jacket 118 may be configured to control reaction temperature between 50 to 60 °C.

In one embodiment of the present disclosure, the paddle type impellers are used for simpler mixing. The advantage of a paddle type impeller is to prevent the deposits on the heat transfer surface.

In another embodiment of the present disclosures, the turbine type impellers are effective over a wide range of viscosities. The turbines generate strong currents both radially and tangentially that persist throughout the agitator vessel. There is a zone of rapid currents and high turbulence near the impeller.

In one embodiment of the invention, the said agitator reactor consists of a plurality of baffles, attached internally to the outer wall of the vessel, arranged at 90°, equally apart from each other and running throughout the length of the reactor. The width and thickness of baffles are adjusted in such a way that it breaks the vortexing generated due to agitation to ensure thorough mixing.

In one embodiment of the present disclosure, the outer cooling jacket 118 is provided with external limpet coils 115 having inlet 107 and outlet 108 and internal coils 114 having inlet 105 and outlet 106. These inlets are flooded with chilled brine to control the reaction temperature. In another embodiment of the present disclosure, the said agitator reactor further comprises a drainpipe 103 for collecting the reaction mass/slurry from one of the sides at the top of the reactor.

In another embodiment of the present disclosure, the said agitator reactor further comprises a drain 104 for collecting the reaction residue from the bottom side of the reactor.

In another embodiment of the present disclosure, the said agitator reactor further comprises with the plurality of sensors like resistance temperature detector (RTD) 109 and level transmitter (LT) 118 for monitoring and collecting the respective data.

Now referring to figure 2, a process (200) carried out in the agitator reactor system 100 for facilitating improved heat transfer, and proper mixing in the synthesis of acrylamido tertiary butyl sulfonic acid (ATBS) is depicted, in accordance with the embodiment of the present invention.

The said process 200 for the synthesis of ATBS is implemented by the aforementioned system 100 comprising reactor 117. The said process 200 involves the mixing of reactants, i.e., ACRN-sulphate and IB with distinct inlet feed pipes at predefined flow rates in the said reactor in order to obtain of ATBS monomer having 80-85% yield and of at least 99.5% purity.

As shown in figure 2, at step 201, the first inlet dip pipe 101 may be configured for the addition of acrylonitrile sulphate. In one embodiment of the present disclosure, the first inlet dip pipe 101 is positioned at the top of the reactor and extended up to the predefined length of the reactor. At step 202, the second inlet dip pipe may be configured for the addition of isobutylene (IB) in the liquified form at a predetermined rate. In one embodiment of the present disclosure, the second inlet dip pipe 102 may be positioned at the top of the reactor and extended till the bottom of the reactor.

At step 203, the sparger 113 may be configured for spraying IB in gaseous form over the ACRN-sulphate. In one embodiment of the present disclosure, the sparger 113 may be positioned at the bottom of the reactor and connected to the second inlet dip pipe 102 to facilitate the reaction of IB gas with the ACRN-sulphate solution for a residence time of 40-80 minutes.

At step 204, the proper mixing of the ACRN-sulphate and the IB may be facilitated via one or more pairs of propellers 112 rotated at a speed of 170-190 rpm and a tip speed of 2-5 m/sec, thereby obtaining a reaction mass/slurry of ATBS.

At step 205, white-colored ATBS is collected after pressure filtration.

In another embodiment of the present disclosure, the mixing ratio of isobutylene to Oleum to acrylonitrile may be within a predefined range of 0.25-0.60:1:10-15, preferably may be within a range of 0.54:1:11-15.

In another embodiment of the present disclosure, the process further comprises maintaining the reaction temperature between 50 to 60 °C. In another embodiment, the whole agitation process is monitored and controlled from an optimized distributed control system (DCS system).

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

In another embodiment of the invention, the yield of ATBS may be at least 80-85%, and the purity of ATBS may be up to 99.50%. The instant invention is further described by the following experimental section:

Experimental Details:

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

The process for the preparation of sulfonating mixture involves the batchwise mixing of 30% oleum in 98% H2SO4. A batch quantity of 98% H2SO4 is transferred in a static batch reactor. The transferred H2SO4 is then circulated in the said reactor by means of a centrifugal pump. As the circulation is established in the next step, the controlled addition of 30% oleum is started in order to uniform mixing of 30% oleum and 98% H2SO4 to obtain a concentrated sulfonating mixture. The mixing ratio of 30% Oleum to 98% H2SO4is typically within the range of 0.12 to 0.20:1.

The addition time for the addition of 30% oleum into the reactor (containing 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 is checked. If the strength of sulfonating mixture is well within the desired range, then the complete batch of the sulfonating mixture is transferred to the storage tank. The whole process is monitored and controlled from an optimized distributed control system (DCS system).

Example 2: Preparation of ACRN-sulphate by using sulphonating mixture and ACRN

The process for the preparation of ACRN-sulphate involves the continuous mixing of the sulfonating mixture in ACRN. This continuous mixing is done in a continuous flow reactor equipped with an agitation system. The ACRN is pumped in the said reactor by means of a pump at a predetermined flow rate. The transferred ACRN is then chilled in the said reactor by means of internal cooling coils and maintaining the temperature between -15 to -5°C.

In the next step, the controlled addition of sulphonating mixture at a predetermined rate is enabled by spraying over the ACRN via a sparger positioned at the top of the reactor.

The addition time for the addition of the sulphonating mixture into the reactor (containing the circulating ACRN) is between 30-60 minutes. During the step of mixing, the heat of mixing is removed by means of a heat exchanger mounted as cooling jacket 118. The agitation system facilitates the proper mixing of the sulphonating mixture and the ACRN via one or more pairs of propellers rotated at a speed of 100-110 rpm and a tip speed of 4.21-4.63 m/s thereby obtaining ACRN-sulphate.

In the next step, the ACRN-sulphate is transferred to another reactor (e.g., agitator reactor system 100) for carrying out the next process for the preparation of ATBS. The whole process is monitored and controlled from an optimized distributed control system (DCS system).

Example 3: Determination of mixing time and better heat transfer (mixing) using IB sparging :

The reaction time or residence time of a reactor depends upon the volumetric capacity of the reactor to the volume of inlet/outlet mass.

Thus, residence time (RT)= (volume of reactor) / (Total volumetric feed rate).

The residence time obtained from this equation is in hours. As in this present invention, the reaction is carried out with certain mass ratios.

In one embodiment, considering the feed ratios of reactants Oleum, Isobutylene & Acrylonitrile are as given below. a) Ratio of Acrylonitrile to Isobutylene = 11 :0.54 b) Ratio of Acrylonitrile to Isobutylene = 15:0.54

From the above ratios, the residence time is calculated as below for different feed rates of Oleum. a. For ACRN to IB ratio = 11 :0.54 b. For ACRN to IB ratio = 15:0.54

Example 4: Determination of the impurities

The effect on the quality of the ATBS product synthesized using agitator reactor 100 is depicted herein. One of the major by-products formed in the ATBS synthesis process is Tertiary butyl acrylamide (TBA). A comparative reduction in the 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 and tabulated below.

Table 1: Qualitative data of impurities generated during mixing in agitator reactor

Table 2: Qualitative data of impurities generated during mixing in a conventional reactor

Table 3: Comparative impurity profile

By referring to tables 1-3, it is evident that the concentration of TBA is reduced in the case of the agitator reactor as compared to the conventional reactor. Also, the impurities like AM, ACRN and IBSA are reduced. Thus, ATBS product purity is also improved. The reduction in the formation of impurities lead to the reduction of the yellow-color of ATBS, and a white-colored ATBS is obtained.

In another embodiment of the invention, the said process enabled to decrease the production of byproducts during 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 process enabled to reduce the number of impurities in the synthesized ATBS, wherein the said impurities may be one or more of Acrylamide (AM), acrylonitrile (ACRN), Isobutyl sulfonic acid (IBSA).

In another embodiment of the invention, the said process is enabled to obtain the ATBS slurry with reduced yellowness and to obtain white colored ATBS slurry with reduced iron content. In another embodiment of the invention, the process in accordance with the present invention may have the following advantages, including but not limited to:

• Improved and consistent yield of ATBS

• Improved quality and purity of ATBS • Decreased number of impurities in the ATBS synthesized using a sulfonating mixture

• Consistency in Acid numbers, moisture of filtrate and color of ATBS product

• Decreased amount of moisture in ATBS.

Although implementations for an agitator reactor system and process implemented thereon for the synthesis of acrylamido tertiary butyl sulfonic acid monomer 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 of an agitator reactor system and process implemented thereon for the synthesis of acrylamido tertiary butyl sulfonic acid monomer.