Description:FIELD
The present disclosure relates to a process for the preparation of aliphatic amino acid salt.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Hydrolysis of lactams produces corresponding aliphatic amino acid salts, that are critical in the cracking units involved in the conversion of saturated hydrocarbons to unsaturated hydrocarbons. The aliphatic amino acid salts inhibit the polymer formation and dissolve the polymer formed in the caustic tower, thereby enhancing the life of operation of the caustic tower and reduces fouling tendency.
Several methods are known in the art for the preparation of aliphatic amino acids. Conventional methods for the hydrolysis of lactams, including the use of acids such as sulfuric acid and amido-carboxylic acids, require high temperatures such as 150°C to 155°C. The use of sulfuric acid results in the formation of salt with a corresponding amino group of the amino carboxylic form, which requires a tedious process for separation and purification. Moreover, the known process for the hydrolysis of lactams does not provide the complete conversion of lactams and requires a high amount of energy to complete the reaction.
Therefore, there is felt a need to provide a process for the preparation of aliphatic amino acid salts that mitigates the aforestated drawbacks or at least provide an alternative solution.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
An object of the present disclosure is to ameliorate one or more problems of the background or to at least provide a useful alternative.
Another object of the present disclosure is to provide a process for the preparation of aliphatic amino acid salt.
Yet another object of the present disclosure is to provide an energy efficient process for the preparation of aliphatic amino acid salt.
Another object of the present disclosure is to provide a simple, environment friendly, and economical process for the preparation of aliphatic amino acid salt.
Still another object of the present disclosure is to provide a commercially scalable process for the preparation of aliphatic amino acid salt.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure relates to a process for the preparation of aliphatic amino acid salt. The process comprises mixing, either a predetermined amount of solid alkali with a predetermined amount of water followed by adding a predetermined amount of lactam to obtain a mixture having a first predetermined temperature; or mixing a predetermined amount of lactam with a predetermined amount of water followed by adding a predetermined amount of solid alkali to obtain a mixture having a second predetermined temperature. The mixture is heated at a third predetermined temperature for a predetermined time period to obtain the aliphatic amino acid salt.
BRIEF DESCRIPTION OF THE DRAWING
Figure 1 illustrates a graph depicting the temperature variation in accordance with Experiment 1 of the present disclosure;
Figure 2 illustrates a graph depicting the temperature variation in accordance with Experiment 2 of the present disclosure;
Figure 3 illustrates a graph depicting the temperature variation in accordance with Experiment 3 of the present disclosure;
Figure 4 illustrates a 1H NMR of caprolactam in D2O; and
Figure 5 illustrates a 1H NMR of 6-amino hexanoic acid salt (product) in D2O.
DETAILED DESCRIPTION
Embodiments, of the present disclosure, will now be described with reference to the accompanying drawings.
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed elements.
The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.
Several methods are known in the art for the preparation of aliphatic amino acids. Conventional methods for the hydrolysis of lactams, including the use of acids such as sulfuric acid and amido-carboxylic acids, require high temperatures such as 150°C to 155°C. The use of sulfuric acid results in the formation of salt with a corresponding amino group of the amino carboxylic form, which requires a tedious process for separation and purification. Moreover, the known process for the hydrolysis of lactams does not provide the complete conversion of lactams and requires a high amount of energy to complete the reaction.
The process of the present disclosure provides a simple and cost-efficient process for the preparation of aliphatic amino acid salt.
In an aspect of the present disclosure, there is provided a process for the preparation of aliphatic amino acid salt.
The process is described in detail.
In a first step, the process for the preparation of aliphatic amino acid salt comprises the sequential mixing of a predetermined amount of solid alkali, a predetermined amount of water, and a predetermined amount of lactam to obtain a mixture.
In an embodiment of the present disclosure, a predetermined amount of solid alkali is mixed with a predetermined amount of water followed by adding a predetermined amount of lactam to obtain a mixture having a first predetermined temperature.
In another embodiment of the present disclosure, a predetermined amount of lactam is mixed with a predetermined amount of water followed by adding a predetermined amount of solid alkali to obtain a mixture having a second predetermined temperature.
In an embodiment of the present disclosure, the solid alkali is at least one selected from the group consisting of sodium hydroxide, and potassium hydroxide. In an exemplary embodiment of the present disclosure, the solid alkali is sodium hydroxide.
In an embodiment of the present disclosure, the lactam is at least one selected from the group consisting of caprolactam, butyrolactam, valerolactam, and propiolactam. In an exemplary embodiment of the present disclosure, the lactam is caprolactam.
In an embodiment of the present disclosure, the first predetermined temperature is in the range of 40°C to 42°C. In an exemplary embodiment of the present disclosure, the first predetermined temperature is 41.1°C.
In an embodiment of the present disclosure, the second predetermined temperature is in the range of 41°C to 44°C. In an exemplary embodiment of the present disclosure, the second predetermined temperature is 42.2°C.
In an embodiment of the present disclosure, the water is demineralised water.
The demineralised water is preferred over potable water because potable water contains magnesium (Mg) and calcium (Ca) which may adversely affect the process.
In an embodiment of the present disclosure, a mole ratio of the solid alkali to the lactam is in the range of 1.1:1 to 1.3:1. In an exemplary embodiment of the present disclosure, the mole ratio of the solid alkali to the lactam is 1.1:1.
In an embodiment of the present disclosure, the weight ratio of the lactam to the water is in the range of 1:1 to 1:2. In an exemplary embodiment of the present disclosure, the weight ratio of the lactam to water is 1:1.4.
In a final step, the mixture is heated to a third predetermined temperature for a predetermined time period to obtain the aliphatic amino acid salt.
In an embodiment of the present disclosure, the third predetermined temperature is in the range of 75°C to 95°C. In an exemplary embodiment of the present disclosure, the third predetermined temperature is 85°C.
In an embodiment of the present disclosure, the predetermined time period is in the range of 5 hours to 8 hours. In an exemplary embodiment of the present disclosure, the predetermined time period is 6 hours.
The process of the present disclosure effectively utilizes the heat generated by the addition of solid alkali in water, thus reducing the overall energy requirement of the reaction. The process effectively reduces the requirement of external energy by 33% to 35% (Calories) when compared with using the alkali solution. The saving of 33% to 35% of energy (Calories) at the commercial scale provides significant cost savings in the preparation of aliphatic amino acid salts. Thus the process of the present disclosure has the advantage of using exothermic heat produced by the dissolution of solid alkali into the water. The conventional process of mixing all the reactants (alkali solution, lactam, and water) together and raising the temperature from 18°C to 85°C requires a high amount of energy.
The foregoing description of the embodiments has been provided for purposes of illustration and is not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
The present disclosure is further described in light of the following experiments which are set forth for illustration purposes only and not to be construed for limiting the scope of the disclosure. The following experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial scale.
EXPERIMENTAL DETAILS
Experiment I: Preparation of the aliphatic amino acid salt in accordance with the present disclosure
14 gm of solid NaOH flakes were added into a reactor containing 50 ml of demineralised water, being an exothermic reaction the temperature increases from 25.7°C to 68.3°C over a period of 3 minutes to obtain a mixture. To the mixture (at 47.6°), 36 gm of caprolactam was added followed by stirring for 8 minutes to obtain a reaction mass (having a temperature of 41.1°C). The reaction mass was heated from 41.1°C to 85°C under stirring and maintained for 6 hours to obtain a product (6-amino hexanoic acid salt). The temperature variation after the addition of solid NaOH and caprolactam was illustrated in Figure 1.
It is evident from the graph of Figure 1, that the temperature of the reaction rises from 25.7°C to 68.3°C after the addition of solid NaOH flakes in water and then caprolactam was added at 47.6°C and the reaction mass was slowly stabilized at 41.1°C. The heat generated during the dissolution of solid NaOH (exothermic) was effectively utilized, thus leading to energy saving.
Experiment II: Preparation of the aliphatic amino acid salt in accordance with the present disclosure (with a varying sequence of addition)
36 gm of caprolactam was added into a reactor containing 50 ml of demineralised water, being an endothermic reaction the temperature decreases from 24.3°C to 18°C over a period of 4 minutes to obtain a mixture. To the mixture (at 18°C), 14 gm of solid NaOH flakes were added followed by stirring for 6 minutes to obtain a reaction mass (having a temperature of 42.2°C). The reaction mass was heated from 42.2°C to 85°C under stirring and maintained for 6 hours to obtain a product (6-amino hexanoic acid salt). The temperature variation after the addition of caprolactam and NaOH was illustrated in Figure 2.
It is evident from the graph of Figure 2 that the temperature of the reaction decreased from 24.3°C to 18°C after the addition of caprolactam to water. Further, the addition of solid caustic flakes into the mixture of caprolactam and water increases the temperature from 18°C to 47.1°C and slowly stabilized at 42.2°C. The heat generated during the dissolution of solid caustic (exothermic) was effectively utilized, thus leading to energy saving.
Experiment III: Preparation of aliphatic amino acid salt by using aqueous solution (Comparative)
36 gm of caprolactam was charged into a reactor containing 64 gm of aqueous NaOH solution (containing 14g of NaOH) and 50 ml of water to obtain a solution. The temperature of the solution decreased from 23.7°C to 18°C to obtain a stabilized solution. The stabilized solution was heated from 18°C to 85°C under stirring and maintained for 6 hours to obtain a product (6-amino hexanoic acid salt). The temperature variation after the addition of caprolactam and aqueous NaOH solution was illustrated in Figure 3.
It is evident from the graph of Figure 3 that the temperature of the reaction decreases from 23.7°C to 18°C when caprolactam was added to NaOH solution and water. The reaction requires a rising temperature from 18°C to 85°C, which requires a high amount of energy.
Measurement of transmittance of the product:
The reaction product obtained from Experiment I, Experiment II, and Experiment III was evaluated by measuring transmittance% values using a UV-Vis spectrophotometer at a wavelength of 800 nm. The transmittance% values indicate the inhibition of the aldol reaction of acetaldehyde. The results are provided below in Table 1.

Table 1: Transmittance % of the product obtained using different reaction conditions
Experiment No. Reaction Condition 10% NaOH solution (ml) Antipolymerant
Qty (ml) Aldehyde
Qty-Vinyl Acetate (ml) Lab % Transmittance (UV spectroscopy Conversion of
Caprolactam to
Product by NMR
I DM water + solid NaOH pellet + Caprolactam at 85OC 40 2 2 98 99.9
II DM water + Caprolactam+ solid NaOH pellet at 85OC 40 2 2 98 99.9
III
Caustic solution at RT + Caprolactam at 85OC 40 2 2 99 99.9
IV Control
(Caustic solution) 40 - 2 0.1 -

It is evident from the above results that the product of Experiment I and Experiment II (using solid NaOH) has a transmittance value of above 98%, which was comparable to the transmittance value of 99% obtained when a caustic solution was used. Hence, the use of solid NaOH provides a product of similar quality that has been produced using the caustic solution.
Experiment IV:
The amount of conversion of caprolactam was evaluated using proton NMR spectroscopy. The proton peak of caprolactam elucidates the characteristic peaks of -CH2 (3.0 – 3.1 ppm) and -NH (7.5 ppm) as illustrated in Figure 4. Further, it was observed from the proton peaks of the product (obtained in Experiment I) as illustrated in Figure 5, the characteristic peaks at 1.9 – 2.1 ppm for -CH2 and 1.5 ppm for NH2 indicate the formation of 6-amino hexanoic acid salt.
Thus, it is evident from the NMR data that caprolactam was completely converted to the product (6-amino hexanoic acid salt) as illustrated above in Table 1. The data indicates caprolactam conversion of >99.9% of caprolactam to the amino acid product.
Experiment V: Quantification of energy consumption
The quantification of the energy saved by the sequential addition of the solid NaOH flakes was evaluated by using the heat energy method. The energy consumed for the completion of the reaction for Experiments I, II, and III is provided below in Table 2.
Table 2 - Quantification of energy saved
Experiment I
Ingredient Weight/Mass (gm) Cp (Cal/g °C)
T1 °C T2 °C
Delta T °C
Heat Generated/ Used
Calories
(m x Cp x ?T)
Water 50 1 25.7 68.3 42.6 2130
NaOH 14 0.36 25.7 68.3 42.6 215
Caprolactam 36 0.33 47.6 41.1 -6.5
100 0.67 41.1 85 43.9 2941
(Energy consumed by overall reaction)

Experiment II
Ingredient Weight (gm) Cp (Cal/g °C)
T1 °C T2 °C
Delta T °C
Heat Generated/ Used
Calories
(m x Cp x ?T)
Water 50 1 24.3 18 -6.3 -315
Caprolactam 36 0.33 24.3 18 -6.3 -75
NaOH 14 0.36 18 47.1 29.1
100 0.67 42.2 85 42.8 2868
(Energy consumed by overall reaction)

Experiment III
Ingredient Weight (gm) Cp (Cal/g d °C)
T1 °C T2 °C
Delta T °C
Heat Generated/ Used
Calories
(m x Cp x ?T)
Caustic solution 64 0.68 23.7 23.7 0 0
Caprolactam 36 0.33 23.8 18.9 -4.9 -58
100 0.67 18.9 85 66.1 4429
(Energy consumed by overall reaction)
It is evident from the above data that the energy required for Experiment I was 34% less when compared to Experiment III. Similarly, the energy required for Experiment II was 35% less when compared to Experiment III. Thus it is evident that the sequential addition of solid NaOH flakes reduces the energy requirement of the reaction, thereby making the process efficient, economic, and environment friendly.
TECHNICAL ADVANCEMENTS
The present disclosure described hereinabove has several technical advantages including, but not limited to, the realization of a process for the preparation of aliphatic amino acid salt, that:
• uses a reduced amount of heat energy thus energy efficient;
• has comparable antipolymerant performance;
• is environment friendly;
• effectively utilizes the heat energy evolved during the reaction; and
• is simple, and cost-efficient.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.
, Claims:WE CLAIM:

1. A process for the preparation of aliphatic amino acid salt, said process comprising the following steps:
a) mixing:
either
• a predetermined amount of solid alkali in a predetermined amount of water followed by adding a predetermined amount of lactam to obtain a mixture having a first predetermined temperature;
or
• a predetermined amount of lactam in a predetermined amount of water followed by adding a predetermined amount of solid alkali to obtain a mixture having a second predetermined temperature;
and
b) heating said mixture to a third predetermined temperature for a predetermined time period to obtain said aliphatic amino acid salt.
2. The process as claimed in claim 1, wherein said solid alkali is at least one selected from the group consisting of sodium hydroxide, and potassium hydroxide.
3. The process as claimed in claim 1, wherein said lactam is at least one selected from the group consisting of caprolactam, butyrolactam, valerolactam, and propiolactam.
4. The process as claimed in claim 1, wherein water is a demineralised water.
5. The process as claimed in claim 1, wherein said first predetermined temperature is in the range of 40°C to 42°C.
6. The process as claimed in claim 1, wherein said second predetermined temperature is in the range of 41°C to 44°C.
7. The process as claimed in claim 1, wherein said third predetermined temperature is in the range of 75°C to 95°C.
8. The process as claimed in claim 1, wherein said predetermined time period is in the range of 5 hours to 8 hours.
9. The process as claimed in claim 1, wherein a mole ratio of said solid alkali to said lactam is in the range of 1.1:1 to 1.3:1.
10. The process as claimed in claim 1, wherein a weight ratio of said lactam to water is in the range of 1:1 to 1:2.

Dated this 18th day of May, 2023

_______________________________
MOHAN RAJKUMAR DEWAN, IN/PA – 25
of R.K. DEWAN & CO.
Authorized Agent of Applicant

TO,
THE CONTROLLER OF PATENTS
THE PATENT OFFICE, AT MUMBAI