AN BUFFER REACTOR FOR THE PREPARATION OF ACRN-SULPHATE FOR SYNTHESIS OF ACRYLAMIDO TERTIARY BUTYL SULFONIC ACID AND PROCESS

IMPLEMENTED THEREON

CROSS-REFERENCE TO RELATED APPLICATIONS AND PRIORITY

The present application claims priority from Indian complete patent application no. 202121060668 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, is about a buffer reactor for the preparation of ACRN-sulphate 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 preparation of the sulfonating mixture, the second step in the preparation of ATBS involves the reaction of the sulfonating mixture prepared in step 1 is with an 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 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, ACRN-sulphate for the synthesis of ATBS has been produced via two methods. In the first method, single-step synthesis or one-pot synthesis was used. In this one-pot synthesis, all the reactants like sulphuric acid or Oleum and acrylonitrile were mixed. In the second method, the mixing of sulphonating mixture and acrylonitrile were done in a continuous channel (feed pipe) having an outer cooling covering and draining the sulphonated ACRN into a reaction chamber. Instate of the art, the conventional reactor, and processes of preparing reaction mixture for the synthesis of ATBS lack in many aspects such as improper heat transfer due to improper mixing of the reactants, wherein the heat transfer is vital in order to achieve good quality as well as higher yield of the 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. Impurities present in the ATBS strongly affects the polymerization and molecular weight of ATBS.

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

OBJECTS OF THE INVENTION

The principal object of this invention is to provide a buffer reactor enabled to provide ACRN- sulphate, which is further used to give 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 ACRN-sulphate, which further gives ATBS with high yield and purity.

Another object of this invention is to provide a process to produce ACRN-sulphate, which further gives ATBS with the 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 a buffer reactor system and process for the production of ACRN-sulphate used in the synthesis of Acrylamido tertiary butyl sulfonic acid (ATBS) monomer, and the concepts are further described below in the detailed description. In one embodiment, the buffer reactor system facilitating improved heat transfer and mixing of acrylonitrile (ACRN) and sulphonating mixture (Oleum) in order to obtain at least 80-85% yield of a 2-acrylamido-2-methylpropane sulfonic acid having purity at least 99.50%, is disclosed. The said buffer reactor system may comprise a first inlet dip pipe configured to receive ACRN from an external storage tank. 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 buffer reactor system a second inlet dip pipe configured to receive Oleum. The second inlet dip pipe may be positioned at the top, at a predetermined distance from the central axis. The said buffer reactor system may further comprise a sparger positioned at the top of the reactor and in connection with the second inlet dip pipe. The sparger may be configured to spray the Oleum over the ACRN in order to facilitate the reaction of the Oleum with the ACRN for a residence time of 30-60 minutes. Furthermore, said buffer reactor system may comprise a shaft comprising one or more pairs of propellers rotated at a speed of 100-110 rpm and a tip speed of 4.21 to 4.63 m/s to facilitate the proper mixing of the ACRN and the Oleum, thereby obtaining an ACRN- sulphate which is further mixed with Isobutylene (IB) in a separate reactor in order to obtain a reaction mass/slurry of ATBS.

In another embodiment, a process carried out in a buffer reactor facilitating improved heat transfer and mixing of acrylonitrile (ACRN) and sulphonating mixture (Oleum) in order to obtain at least 80-85% yield of a 2-acrylamido-2-methylpropane sulfonic acid having a purity of at least 99.50%, is disclosed. The said process may comprise adding acrylonitrile at a predetermined flow rate through a first inlet dip pipe positioned at the top of the reactor and extended up to the 3/4th of the length of the reactor. The said process may further comprise adding Oleum at a predetermined rate through a second inlet dip pipe positioned at the top of the reactor. Further, the said process may comprise spraying Oleum over the ACRN via a sparger positioned at the top of the reactor and connected to the second inlet dip pipe to react the Oleum with the ACRN for a residence time of 30- 60 minutes. Furthermore, the said process may comprise facilitating the proper mixing of the Oleum 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 to 4.63 m/s, thereby obtaining an ACRN-sulphate, which is further mixed with Isobutylene (IB) in a separate reactor in order to obtain a reaction mass/slurry of ATBS.

In one embodiment, the said buffer reactor for the production of ACRN-sulphate used in the synthesis of ATBS may be a vertical tubular type. In one embodiment, the said buffer reactor for the production of ACRN-sulphate used in the synthesis of ATBS may be a continuous flow reactor.

In another embodiment of the present disclosure, the first dip pipe maybe 3/4 ^lh of the length of the reactor.

In another embodiment of the invention, the sparger may be configured to sparge sulphonating mixture (Oleum) received at the top of the second inlet dip pipe in order to facilitate the reaction

In another embodiment of the present disclosure, the said buffer reactor 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 buffer 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 a buffer reactor facilitates improved heat transfer and mixing of ACRN and sulphonating mixture.

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

In one embodiment of the present invention, the said process may comprise a step of adding a predetermined amount of ACRN into a reactor. Further, the said process may comprise a step of circulating the ACRN in the reactor. Further, the said process may comprise a step of adding a predetermined amount of sulphonating mixture (i.e., Oleum) into the reactor to mix with the circulating ACRN. Further, the said process may comprise a step of circulating a mixture of Oleum and ACRN 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 maybe 5000- 9000 kg/hr.

In one embodiment of the present invention, the rate of adding the predetermined amount of sulphonating mixture may be between 900-1100 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 may be carried out by means of a centrifugal pump.

In one embodiment of the present invention, the step of circulating a mixture of sulphonating mixture and ACRN may be carried out at a temperature between -15 to -5 °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 sulphonating mixture and ACRN may be carried out for a time period of 30-60 minutes.

List of Abbreviations

ATBS- Acrylamide 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 a buffer reactor system 100 and components thereof for enabling to produce ACRN-sulphate used in the ATBS synthesis, in accordance with an embodiment of the present subject matter.

Figure 2 illustrates a process 200 carried out in the buffer reactor system 100 for facilitating improved heat transfer and mixing of ACRN and sulphonating mixture 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 accompanied drawings.

Referring to figure la, buffer reactor system 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 111, a cooling jacket 118, and an agitation system 116 comprising of a motor 112, a shaft 113 and one or more pair of propellers 114.

In another embodiment of the present disclosure, the said first inlet dip pipe 101 may be configured to receive ACRN from an external reservoir (not shown). 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 may be at least 3/4 ^th of the length of the reactor. In an embodiment of the present disclosure, the first dip pipe is extended up to 90% of the length of the reactor. In one embodiment of the present disclosure, the significance of the 3/4* length of the first inlet dip pipe 101 is to discharge the fresh ACRN near to the bottom of the reactor.

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 top of the reactor. In an embodiment, the said second inlet dip pipe may be configured to receive sulphonating mixture in liquified form from the external storage tank or from the oleum reactor. In one embodiment, the external reactor may be a batch or continuous flow reactor, which is configured to prepare the said sulphonating mixture by mixing of 98% H2SO4 with 30% Oleum.

In one embodiment of the present disclosure, the second inlet dip pipe 102 may be in connection with the sparger 111 positioned at the top of the reactor. In an embodiment, the sparger 111 may be configured to sparge sulphonating mixture, received at the top of the second inlet dip pipe 102, in order to facilitate the reaction of the sulphonating mixture with the ACRN for a residence time of 30-90 minutes.

In one embodiment of the present disclosure, the sparger positioned at the top sprays sulphonating mixture in the liquid form, thereby facilitating the sulphonating mixture to travel from top to bottom through the reaction mixture. Thus, in turn, it provides sufficient time to react sulphonating mixture with the ACRN to provide ACRN-sulphate, which ultimately increases the yield of the ATBS monomer.

In one embodiment of the present disclosure, the said sparger 111 may be a perforated ringtype sparger having a diameter of 600-650 mm, a pore size of 1.5-2.5mm, and the number of pores between 45-60.

In another embodiment of the present disclosure, the said shaft 113 may be solid shaft may be arranged centrally with a motor unit 112 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 113 comprises one or more pairs of propellers 114 rotated at a speed of 100-100 rpm and a tip speed of 4.21-4.63m/sec to facilitate the proper mixing of the ACRN and the sulphonating mixture thereby obtaining a reaction mass/slurry of ATBS. In one embodiment of the present disclosure, the said one or more pairs of propellers 114 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 -15 to -5 °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 one embodiment of the invention, the said 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 119 having inlet 107 and outlet 103 and internal coils 115 having inlet 106 and outlet 105. These inlets are flooded with chilled brine to control the reaction temperature. In another embodiment of the present disclosure, the said buffer reactor further comprises a drainpipe 104 for collecting the ACRN-sulphate from one of the sides at the top of the reactor. In another embodiment of the present disclosure, the drainpipe 104 is selected from at least one of U-type and L-type. The side nozzle 108 is connected to U-type or L-type drainpipe for pressure balancing.

In another embodiment of the present disclosure, the said buffer reactor further comprises with the plurality of sensors like resistance temperature detector (RTD) 109 and level transmitter (LT) 110 for monitoring and collecting the respective data.

Now referring to figure 2, a process (200) carried out in the agitator reactor system 100 for enabling the preparation of ACRN-sulphate used 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 production of ACRN-sulphate is implemented by the aforementioned system 100 comprising the reactor 117. The said process 200 involves the mixing of reactants, i.e., ACRN and sulphonating mixture with distinct inlet feed pipes at predefined flow rates in the said reactor in order to obtain ACRN-sulphate, which is further used in the synthesis 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. In one embodiment of the present disclosure, the first inlet dip pipe 101 may be 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 sulphonating mixture 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.

At step 203, the sparger 111 may be configured for spraying sulphonating mixture over the ACRN. In one embodiment of the present disclosure, the sparger 111 may be positioned at the top of the reactor and connected to the second inlet dip pipe 102 to facilitate the reaction of sulphonating mixture with the ACRN for a residence time of 30-60 minutes.

At step 204, the proper mixing of the ACRN and the sulphonating mixture may be facilitated via one or more pairs of propellers 114 rotated at a speed of 100-110 rpm and a tip speed of 4.21-4.63 m/sec, thereby obtaining a reaction mass/slurry of ATBS.

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

In another embodiment of the present disclosure, the process further comprising maintaining the reaction temperature between -15 to -5 °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) within the predefined range of 610- 670 ppm, acrylonitrile (ACRN) within the predefined range of 180-250 ppm, isobutyl disulfonic acid (IBDSA) within the predefined range of 35-75 ppm, isobutyl sulfonic acid (IBSA) within the predefined range of 50- 80 ppm, tertiary butyl acrylamide (TBA) within the predefined range of 1500-1600 ppm, and acrylamido methyl propane disulfonic acid (AMPDSA) 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%.

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 98% H2SO4) 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 115 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/secthereby obtaining ACRN-sulphate.

In the next step, the ACRN-sulphate is transferred to another reactor for carrying out the next process for the synthesis of the ATBS monomer. 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) 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 from ACRN-sulphate using buffer 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 (IB DS A), Isobutyl sulfonic acid (IBSA), and Acrylamido methyl propane disulfonic acid (AMPDSA) is observed and tabulated below.

Table 1: Qualitative data of impurities generated during ATBS synthesis using buffer reactor 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 a buffer 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 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 by-products 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 a buffer reactor system and process implemented thereon for the preparation of ACRN-sulphate used in 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 a buffer reactor system and process implemented thereon for the preparation of ACRN-sulphate used in the synthesis of acrylamido tertiary butyl sulfonic acid monomer.