Description:TECHNICAL FIELD
[001]. The present disclosure generally relates to the field of treating industrial waste. In particular, the present disclosure provides an activated carbon adsorbent and a process for removing impurities found in mono ethylene glycol (MEG), recovered from industrial effluents such as from the manufacture of polyethylene terephthalate (PET) or glycolysis of waste PET fiber, employing the same.

BACKGROUND
[002]. Polyethylene Terephthalate (PET) is usually manufactured by reacting Mono Ethylene Glycol (MEG) with Purified Terephthalic Acid (PTA) using antimony trioxide (Sb2O3) as a catalyst, at around 265?. The commercial process requires employing two moles of MEG for one mole of PTA for production of PET. However, during this process, excess unreacted MEG is left unrecycled due to quality issues in recycling MEG such as presence of suspended solids, dissolved solids, coloring, and other impurities which get carried forward from esterification reaction, and lower pH.
[003]. Similarly, waste fibers received from Polyester Filament Yarn (PFY) plant, Polyester Staple Fibre (PSF) plant, Partially Oriented Yarn (POY) plant and other external sources are subjected to glycolysis in presence of MEG using zinc acetate catalyst at 250? to make PET monomer viz., dihydroxyethyl terephthalate. However, during the glycolysis process, huge quantity of crude or contaminated MEG is generated along with some undissolved solids and moisture in the range of 20-30%. The excess MEG used in such processes could not be reused due to contamination of the MEG with impurities generated in the glycolysis process. MEG thus needs to be purified for reusing it in PET production as well as in glycolysis process.
[004]. At manufacturing sites, standard distillation process is practiced for the purification of MEG, which is an energy intensive process. Further, some impurities which have boiling point closer to MEG, are not easily separated during distillation process.
[005]. Further, adsorptive processes known in the art for purification of MEG are carried out at high temperatures of about 150? and employ several steps, vessels/equipment and adsorbents. Such processes are thereby very cost intensive and complex.
[006]. Thus, there is an unmet need in the art for developing simple, cost-effective and efficient means and method for purification of contaminated MEG. The present disclosure aims to address the same.

SUMMARY
[007]. Accordingly, the present disclosure describes a process for purification of contaminated mono ethylene glycol from a sample, said process comprising act of contacting the sample with activated carbon absorbent, to obtain purified mono ethylene glycol, characterized in that the activated carbon has- surface area ranging from about 800 m2/g to about 1100 m2/g, particle size ranging from about 0.25 mm to 2 mm, Iodine number ranging from about 900 mg/g to 1100 mg/g, and pH ranging from about 5 to 9.
[008]. The disclosure also describes an activated carbon having surface area ranging from about 800 m2/g to about 1100 m2/g, particle size ranging from about 0.25 mm to about 2 mm, Iodine number ranging from about 900 mg/g to about 1100 mg/g, and pH ranging from about 5 to 9.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
[009]. In order that the disclosure may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying figures. The figures together with detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, in accordance with the present disclosure where:
[0010]. Figure 1 depicts low chart indicating the process of manufacture of the activated carbon is illustrated in Figure 1.
[0011]. Figure 2 depicts comparison of HPLC analysis of pure MEG and contaminated MEG.
[0012]. Figure 3 depicts block diagram of the process of the present disclosure.
[0013]. Figure 4 depicts visual comparison of A) Impure MEG feed (%T @ 350nm= 4 to 6, pH = 2 to 3, APHA= > 80) vis-à-vis B) Purified MEG Feed (%T @ 350nm= > 99 %, pH= 6.2-6.7, APHA= < 30).
[0014]. Figure 5 depicts overlay of HPLC analysis of impurities present in (a) waste and treated MEG, and (b) pure, waste and treated MEG.

DESCRIPTION OF THE DISCLOSURE
[0015]. The present disclosure aims to address the drawbacks of the art and provides for a highly efficient activated carbon adsorbent and a process to remove undesirable impurities from contaminated mono ethylene glycol employing the same. The process of the present disclosure aims to be cost-effective, ecofriendly without employing or generating hazardous chemicals, and suitable to be carried out at ambient temperature and atmospheric pressure.
[0016]. Before going into the detailed description, while the following terms are believed to be well understood by one of ordinary skill in the art, the following definitions are set forth to facilitate better understanding of the presently disclosed subject matter.
[0017]. As used herein, the terms “method” and “process” are employed interchangeably and are meant to convey their commonly known dictionary meaning.
[0018]. As used herein, the term “adsorbent of the present disclosure”, “activated carbon of the present disclosure” or “the activated carbon” are used interchangeably to refer to an activated carbon having specific characteristics wherein its surface area ranges from about 800 m2/g to about 1100 m2/g, particle size ranges from about 0.25 mm to about 2 mm, bulk density ranges from about 0.3 g/cc to about 0.8 g/cc, Iodine number is about 900 mg/g to 1100 mg/g, moisture content is about 5 %, and pH is of about 9.
[0019]. As used herein, the term “sample” refers to the input feed containing the contaminated mono ethylene glycol, regardless of the quantity obtained/employed. The sample may be an industrial effluent containing contaminated mono ethylene glycol, obtained from industrial processes such as but not limiting to effluent generated during the manufacture of polyethylene terephthalate or glycolysis of waste fiber.
[0020]. As used herein, the terms “contaminated MEG” or “contaminated mono ethylene glycol” are used interchangeably to refer to MEG which contains impurities associated with it, such as but not limiting to 4-(2-hydroxyethoxy) benzoic acid, bis(2-hydroxyethyl)terephthalate, 2-(2-hydroxyethoxy)ethyl(2-hydroxyethyl)terephthalate etc., which renders it unsuitable for further use in industrial processes.
[0021]. As used herein, the expressions ‘purified mono ethylene glycol’ or ‘treated mono ethylene glycol’ are used interchangeably to refer to the MEG obtained post treatment by the process of the present disclosure.
[0022]. The present disclosure provides for an adsorbent and a process for purification of contaminated mono ethylene glycol. In an embodiment, the present disclosure relates to adsorbents and adsorption process for the purification of contaminated mono ethylene glycol at room temperature and atmospheric pressure.
[0023]. In another embodiment, the present disclosure pertains to an eco-friendly adsorptive process for the purification of contaminated mono ethylene glycol (MEG) obtained from industrial processes/effluents such as generated during the manufacture of polyethylene terephthalate and during the glycolysis of waste PET fiber / fabric. During such industrial processes, various types of impurities are formed such as 4-(2-hydroxyethoxy) benzoic acid, bis(2-hydroxyethyl)terephthalate, 2-(2-hydroxyethoxy)ethyl(2-hydroxyethyl)terephthalate etc. These impurities effect the overall quality of MEG.
[0024]. LC-MS analysis of contaminated MEG shows the presence of several impurities generated in the process which is lowering %T and pH.
[0025]. In order to reuse and recycle the MEG in the process, it is essential to remove the impurities and obtain MEG with desired specifications. Based on impurities present, different types of adsorbents were explored viz., Clay, ion exchange resin and activated carbon. However, the inventors of the present disclosure surprisingly found that the best results, in terms of removal of impurities from MEG, were obtained upon using an activated carbon adsorbent having specific characteristic.
[0026]. In embodiments of the present disclosure, the process for purification of contaminated MEG comprises the act of contacting contaminated monoethylene glycol or a sample/effluent containing the monoethylene glycol with activated carbon adsorbent having porosity ranging from about 2 nm to 50 nm. In some embodiments, the activated carbon employed in the method of the present disclosure further has one or more of characteristics selected from the following:
- a surface area ranging from about 800 m2/g to about 1100 m2/g,
- particle size ranging from about 0.25 mm to about 2 mm,
- bulk density ranging from about 0.3 g/cc to about 0.8 g/cc,
- Iodine number of about 900 mg/g to 1100 mg/g,
- moisture of about 5 %, and
- pH of about 9.
[0027]. In some embodiments of the present disclosure, the activated carbon is in a form selected from a group comprising granules, spherical, flakes and powder or any combination thereof.
[0028]. In an embodiment of the present disclosure, the process for purification of contaminated mono ethylene glycol comprises the act of contacting a sample containing contaminated mono ethylene glycol with the activated carbon adsorbent of the present disclosure, to obtain purified mono ethylene glycol.
[0029]. In an exemplary embodiment, the adsorbent carbon of the present disclosure of any shape such as granules, spherical, flakes etc. is loaded/packed in a column or reactor though which contaminated MEG is passed at room temperature and atmospheric pressure. The treated MEG is subsequently analyzed for its percentage transmittance (%T) and pH.
[0030]. It was observed that adsorption studies conducted at room temperature showed good improvement in % Transmittance at 350 nm (which is related to yellowish colour) and pH over the 80? treated samples.
[0031]. In some embodiments of the present disclosure, the process is carried out by using dynamic mode of adsorption or equilibrium mode of adsorption. The dynamic mode of adsorption is a continuous mode of operation whereas the equilibrium mode of adsorption is operating in a batch mode.
[0032]. In some embodiments of the present disclosure, the dynamic mode of adsorption is carried out in a glass column, or a reactor loaded with the activated carbon adsorbent of the present disclosure.
[0033]. In an exemplary embodiment, the dynamic mode of adsorption is carried out in a glass column, such as but not limiting to a glass column having inner diameter of 22.4 mm. Activated carbon adsorbent bed is prepared in the column wherein the height of the packed bed used is of about 150 mm. Contaminated MEG is passed through the column comprising the adsorbent of the present disclosure. Liquid hourly space velocity (LHSV) employed ranges from about 1 to about 4 h-1.
[0034]. In another exemplary embodiment, the dynamic mode of adsorption is carried out in a reactor such as but not limiting to a packed bed reactor. The activated carbon adsorbent is loaded in the reactor. The adsorbent bed was packed properly by tapping. The reactor is purged under nitrogen gas to remove the fine carbon particles after charging the column with the adsorbent. All the points are checked like metallic stainer filter, 1 micron cartridge filter, pressure gauze and micromotion flow meter. The feed flow is maintained below 1 m3/hr for smooth running of system.
[0035]. In some embodiments, the treated MEG is collected in a separate drum/unit if it has fine carbon particles. This material is passed through a suitable filter, such as but not limiting to a 1micron filter, to remove the fine particles for further usage Thereafter, the treated MEG is collected in storage tank, from where it is consumed in the process to manufacture the PET polymer.
[0036]. In some embodiments, once the adsorbent is exhausted, the bed is kept under nitrogen to desorb the trapped MEG from voids and pores of the activated carbon adsorbent and the spent adsorbent is unloaded from the bottom reactor.
[0037]. In some embodiments of the present disclosure, the process is carried out at a liquid hourly space velocity (LHSV) ranging from about 1h-1 to about 4h-1.
[0038]. In some embodiments of the present disclosure, in the equilibrium mode of adsorption the contaminated MEG is kept in contact with the activated carbon adsorbent for a period of about 30 minutes to about 24 hr, and wherein the mixture is optionally stirred at about 50 rpm to about 250 rpm.
[0039]. In an exemplary embodiment, in the equilibrium mode of adsorption the activated carbon adsorbent is taken in a suitable vessel and contaminated MEG is added to it. The mixture is stirred at 250 rpm, at room temperature.
[0040]. In some embodiments, the treated MEG sample is collected periodically and sent for analysis at Q.C. laboratory to monitor the % transmittance, pH and/or color appearance of the treated MEG, to assess the efficiency of the process.
[0041]. In some embodiments, the purified mono ethylene glycol obtained post treatment by the process of the present disclosure has at least 98% transmittance at a wavelength of 350 nm.
[0042]. In some embodiments, the purified mono ethylene glycol obtained post treatment by the process of the present disclosure has a pH ranging from about 6 to about 7.
[0043]. In some embodiments, the purified mono ethylene glycol obtained post treatment by the process of the present disclosure is suitable for reuse in industrial processes such as PET manufacturing etc., after blending with the virgin MEG in the desired ratio.
[0044]. In some embodiments of the present disclosure, the sample comprising the contaminated mono ethylene glycol is filtered through a micro filter prior to contacting the sample with the activated carbon.
[0045]. In some embodiments, the process for purification of contaminated mono ethylene glycol comprises the acts of:
- filtering a sample containing the contaminated MEG through a suitable filter, such as but not limiting to a micro filter, to obtain filtered sample, and
- contacting the filtered sample with the activated carbon adsorbent of the present disclosure, to obtain purified mono ethylene glycol.
[0046]. In an exemplary embodiment, the contaminated MEG is first passed through a 1 micron filter to remove the suspended and undissolved solids followed by a glass column or reactor loaded with the adsorbent of the present disclosure at LHSV of about 1 to 4 h-1. The process is carried out at room temperature.
[0047]. In some embodiments of the present disclosure, the contaminant present in the MEG is selected from a group comprising 4-(2-hydroxyethoxy) benzoic acid, bis(2-hydroxyethyl)terephthalate and 2-(2-hydroxyethoxy)ethyl(2-hydroxyethyl)terephthalate or any combination thereof.
[0048]. In some embodiments, the process of the present disclosure is carried out at room temperature.
[0049]. In some embodiments, the process of the present disclosure is carried out at atmospheric pressure.
[0050]. After use in the process of the present disclosure, the activated carbon becomes saturated with contaminants. Therefore, the spent carbon material needs to be regenerated for the further utilization. In some embodiments, the spent carbon material of the present disclosure is regenerated for further utilization by techniques including but not limiting to steam regeneration.
[0051]. In an exemplary embodiment, the spent carbon material is regenerated by steam regeneration at a temperature ranging from about 100 to about 140, preferably about 120? at atmospheric pressure of about 2 to about 4 bar. The regeneration was carried out for about 2 h to about 10 h, preferably about 6 h, thereafter the material was cooled at room temperature. Approximately 60% surface area and pore volume of the spent carbon was regenerated after the treatment.
[0052]. The present invention also relates to development of suitable adsorbents for the purification of contaminated mono ethylene glycol. In particular, the activated carbon of the present disclosure has a porosity ranging from about 2 nm to 50 nm. In some embodiments, the activated carbon of the present disclosure is further characterized by one or more of the following characteristics:
I. Surface area: about 800 to 1100 m2/g
II. Particle size: about 0.25 to 2mm
III. Bulk Density: about 0.3 to 0.8 g/cc
IV. Iodine number: about 900-1100 mg/g
V. Moisture: about 1-5 %
VI. pH: 9
[0053]. In some embodiments, the activated carbon of the present disclosure is prepared in two stages, viz., i. carbonization; and ii. activation.
Carbonization: Material with carbon content is pyrolyzed at temperature in range of about 600 ? to 900 ?, in absence of oxygen, in inert atmosphere with gases, such as argon or nitrogen.
Activation/oxidation: Carbonized material is exposed to oxidizing atmospheres (carbon dioxide, oxygen or steam) at temperature above 250 ?, particularly in the temperature range of about 600 ? to 1200 ?.
The flow chart indicating the process of manufacture of the activated carbon is illustrated in Figure 1.
[0054]. In some embodiments, physicochemical properties of the activated carbon of the present disclosure are provided hereunder:
Parameter Unit Activated carbon
Porosity nm About 2-50
Iodine Number mg/g About 900-1100
Molasses Number mg/g About 180-250
Moisture % About 1-5
Density g/cc About 0.40-0.60
Abrasion Value mg/cycle About 50-95

In an exemplary and non-limiting embodiment, the activated carbon of the present disclosure has an Iodine number of about 950 mg/g, molasses number of about 300 mg/g, moisture of about 2 %, density of about 0.54 g/cc and abrasion value of about 75 mg/cycle.
[0055]. ¬ ADVANTAGES/BENEFITS:
The process for purification of contaminated MEG and the adsorbent as described in the present disclosure has several advantages/benefits, including, but not limiting to the following:
1. Single step process: The present disclosure provides for a process which essentially employs a single step, which thereby renders the process simple and easy to follow/commercialize. This is in contrast with the process of the prior arts, such as the distillation process employed for purification of MEG which employs as high as 9 steps, requires several vessels to carry out the process, thereby requiring larger space and has a very high CAPEX cost. Since the process of the present disclosure can be carried out in a single step, it can be conducted using just a single vessel, thereby requiring less space and has a very low CAPEX cost with high recovery.
2. Operated at ambient temperature and atmospheric pressure: Unlike methods of the prior art which require heating at high temperature, such as the distillation process for purification of MEG, the process of the present application does not require heating or high pressure, making the process simpler and more convenient.
3. The process of the present disclosure is thereby easy to handle and safe to operate.
4. Eco-friendly: Minimum loss and environment friendly process compared to reported conventional methods. The adsorptive process of the present disclosure is environmentally friendly as there is no hazardous chemicals used/generated in the process. The process also does not generate any side product.
5. The process of the present disclosure maintains the plant integrity by removing different impurities.
6. Cost effective: Owing to the nature of the process, requiring fewer steps and simpler setups, the process of the present disclosure is highly economical compared to conventional techniques. Also, the continuous adsorptive purification process of the present disclosure would save huge revenue besides maintaining the plant process integrity.
7. Efficient purification of MEG: The process treats MEG with minimal loss and the treated MEG meets the desired specifications which is suitable in CP process for industrial processes such as PET manufacturing, etc.
8. Commercially relevant: The developed process can be easily scaled up and will create the value for the organization.
9. Regeneration of adsorbent: The adsorbent employed can be regenerated and reused.

[0056]. Additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based on the description provided herein. The embodiments herein provide various features and advantageous details thereof in the description. Descriptions of well-known/conventional methods and techniques are omitted so as to not unnecessarily obscure the embodiments herein.
[0057]. The foregoing description of the specific embodiments fully reveals 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 in this disclosure 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.
[0058]. Throughout this specification, the word “comprise”, or variations such as “comprises” or “comprising” wherever used, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. Similarly, terms such as “include” or “have” or “contain” and all their variations are inclusive and will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
[0059]. The terms “about” or “approximately” are used herein to mean approximately, in the region of, roughly, or around. When the term “about” is used in conjunction with a numerical value/range, it modifies that value/range by extending the boundaries above and below the numerical value(s) set forth. In general, the term “about” is used herein to modify a numerical value(s) or a measurable value(s) such as a parameter, an amount, a temporal duration, and the like, above and below the stated value(s) by a variance of +/-20% or less, +/-10% or less, +/-5% or less, +/-1% or less, and +/-0.1% or less of and from the specified value, insofar such variations are appropriate to perform in the disclosed invention, and achieves the desired results and/or advantages as disclosed in the present disclosure. It is to be understood that the value to which the modifier “about” or “approximately” refers is itself also specifically, and preferably, disclosed.
[0060]. With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity. As used in this specification and the appended claims, the singular forms “a,” “an” and “the” includes both singular and plural references unless the content clearly dictates otherwise. 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. As such, the terms “a” (or “an”), “one or more”, and “at least one” can be used interchangeably herein.
[0061]. Numerical ranges stated in the form ‘from x to y’ include the values mentioned and those values that lie within the range of the respective measurement accuracy as known to the skilled person. If several preferred numerical ranges are stated in this form, of course, all the ranges formed by a combination of the different end points are also included.
[0062]. As regards the embodiments characterized in this specification, it is intended that each embodiment be read independently as well as in combination with another embodiment. For example, in case of an embodiment 1 reciting 3 alternatives A, B and C, an embodiment 2 reciting 3 alternatives D, E and F and an embodiment 3 reciting 3 alternatives G, H and I, it is to be understood that the specification unambiguously discloses embodiments corresponding to combinations A, D, G; A, D, H; A, D, I; A, E, G; A, E, H; A, E, I; A, F, G; A, F, H; A, F, I; B, D, G; B, D, H; B, D, I; B, E, G; B, E, H; B, E, I; B, F, G; B, F, H; B, F, I; C, D, G; C, D, H; C, D, I; C, E, G; C, E, H; C, E, I; C, F, G; C, F, H; C, F, I, unless specifically mentioned otherwise.
[0063]. Any discussion of documents, acts, materials, devices, articles and 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.
[0064]. While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications 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 modifications in the nature of the disclosure or the preferred embodiments 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.
[0065]. All references, articles, publications, general disclosures etc. cited herein are incorporated by reference in their entireties for all purposes. However, mention of any reference, article, publication etc. cited herein is not, and should not be taken as, an acknowledgment or any form of suggestion that they constitute valid prior art or form part of the common general knowledge in any country in the world.
[0066]. Further, while the instant disclosure is susceptible to various modifications and alternative forms, specific aspects thereof has been shown by way of examples and drawings and are described in detail below. However, it should be understood that it is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and the scope of the invention.

[0067]. EXAMPLES

[0068]. The present disclosure is further described with reference to the following examples, which are only illustrative in nature and should not be construed to limit the scope of the present disclosure in any manner.

[0069]. Nomenclature Used in The Examples:
[0070]. Activated Carbon: The examples of the present disclosure employ activated carbon having:
I. Surface area: 800 m2/g to 1100 m2/g
II. Particle size: 0.25 mm to 2mm
III. Bulk Density: 0.3 to 0.8 g/cc
IV. Iodine number: 900 mg/g to 1100 mg/g
V. Porosity: 2 nm to 20 nm
VI. Moisture: 1% to 5 %
VII. pH: 5 to 9
[0071]. Contaminated MEG: The contaminated MEG employed in the examples of the present application was obtained from continuous polymerization process. LC-MS analysis of the contaminated MEG, depicted in Figure 2, showed presence of several impurities generated in the process which was lowering %T and pH. Figure 2 depicts complete analysis of waste MEG by HPLC, carried out under the following conditions:
Detector: PDA
Column: Phenomenex, C8, 3.5µm, 4.6 X 150 mm
Mobile Phase: A: MiliQ water with 0.05% Phosphoric acid, B: ACN, C: Methanol
Column temp: 40°C
Injection volume: 10µl
Mobile phase flow rate:1.2 ml/min
Run time: 75 min
Further, the probable impurities identified in the contaminated MEG by LCMS analysis are tabulated below in Table 1.
[0072]. Table 1: Impurities identified by LCMS


[0073]. Source of commercially available activated carbons: NORIT RB-2, NORIT RST-3 and NORIT ROX-0.8 activated carbons were obtained from Norit Carbon; Acticarbon -3SW and Acticarbon -2 SW activated carbons were obtained from Acticarbone company.
[0074]. Adsorption Capacity: Adsorption capacity was carried out to assess the amount of adsorbate taken up by the adsorbent per unit mass (or volume) of the adsorbent. An experiment was carried out under dynamic mode for the purification using a glass column having inner diameter of about 22.4 mm and height of the packed bed was about 150 mm. About 30 g of adsorbent was employed in this experiment. Before passing the waste MEG through the adsorbent column, it was filtered through 1 micron filter to improve the %T.

[0075]. Example 1: Purification of MEG in dynamic mode using activated carbon
A dynamic study was carried out by using glass column having inner diameter of about 22.4 mm. About 30 gm of the activated carbon adsorbent bed was prepared and height of the packed bed used was of about 150 mm. Contaminated MEG was passed through the adsorbent at a liquid hourly space velocity (LHSV) of about 1 h-1. High adsorption capacity of about 47ml/g was observed.

[0076]. Example 2: Purification of MEG Activated carbon in both dynamic and equilibrium mode and equilibrium mode
In an equilibrium mode of process, 5 gm of the activated carbon adsorbent was taken in 250 ml of conical flask and 100 ml of contaminated MEG was added to it. The mixture was stirred for a period of about 2 hours. The solution was kept settling down before pH measurement and %T@ 350 nm. The adsorption capacity was about 20 ml/g with pH close to 7.

[0077]. Example 3: Pilot scale trial for purification of contaminated MEG
In a pilot scale trial, about 45 kg of adsorbent (8) was loaded in packed bed reactor (7). The adsorbent bed was packed properly by tapping. About 6.5 kg each of inert alumina balls (about 3 mm size) (9) was placed at top and bottom of the reactor respectively. The reactor was purged (6) under nitrogen gas (10) to remove fine carbon particles. Recycle/waste MEG feed (1) was passed through a pump (2) and subsequently a pre-filter (4); and thereafter passed through the reactor (7) from bottom to top by maintaining the feed flow in between 25-30 litre per hour at room temperature and at ambient pressure. The flow of the feed, nitrogen, other reactants, treated MEG, side-products and/or spent adsorbent was maintained through flow control valve (3). The purified MEG were passed through a filter (12) and collected in a storage vessel (11). At about 4 hours’ time interval, the purified MEG samples were collected in small bottle & analysed at the site Q.C. to monitor the % transmittance. The detailed process flow diagram is shown in Figure 3 which depicts the block diagram of the exemplary process (100). The results of the pilot plant are given in Table 2. Once the adsorbent was exhausted, the bed was kept under nitrogen to desorb the trapped MEG from voids and pores of the activated carbon adsorbent and the spent adsorbent was unloaded from the bottom reactor to the drain (5).
[0078]. Table 2: Analysis of treated MEG
Properties Pure MEG Waste MEG Pilot plant trial MEG
pH 6.95 3.9 7
Water (%) 0.12 13 16
Floating particles No Yes No
Color Clear Yellow Clear
US-Vis % Transmittance (nm)
220 65 0.00 0.1
275 92 0.00 24
350 98 35.0 97.1

[0079]. Example 4: Commercial scale trial for purification of contaminated MEG
For a commercial scale trial, about 2.2 MT of adsorbent was loaded in packed bed reactor. The adsorbent bed was packed properly by tapping. About 200 kg each of inert alumina balls (of 6 mm and 9 mm size) was placed at top and bottom of the reactor respectively as shown in Table 3. The process parameters employed are depicted in Table 4. The system was checked for hydro test by filling water before loading the adsorbent and inert alumina ball. The hydrotest was carried out at about 3kg/cm2 pressure with a hold time of about 3 minutes before loading of the adsorbent in the column. The reactor was then purged under nitrogen gas to remove the fine carbon particles after charging the column with the adsorbent. Pneumatic test was carried out to verify that the system may be safely subjected to its maximum operating pressure by testing it beyond its designed pressure limit. The pneumatic test was carried out under nitrogen condition (1kg/cm2) for about 40 minutes. All the points were checked like metallic stainer filter, 1 micron cartridge filter, pressure gauze and micromotion flow meter. The feed flow was maintained below 1 m3/hr for smooth running of system. Initially, about 200 to 300 litres of MEG was collected in separate drum because it had fine carbon particles. Thereafter, the treated MEG was collected in storage tank, from where it was consumed in the process to manufacture the PET polymer. The treated MEG sample was collected after about 4 hours’ time interval and sent for analysis at Q.C. laboratory. Figure 4 depicts visual comparison of A) Impure MEG feed (%T @ 350nm= 4 to 6, pH= 2 to 3, APHA= > 80) vis-à-vis B) Purified MEG Feed (%T @ 350nm= > 99 %, pH= 6.2-6.7, APHA= < 30). Further, the results of HPLC analysis comparing the impurities in the waste MEG and treated MEG is depicted in Figure 5. Overlay of the HPLC analysis shows that substantial impurities were removed post treatment with the adsorbent of the present disclosure.

[0080]. Table 3: Adsorbent loading pattern of column
Loading Pattern Particle Size (mm) Length (mm) Bulk density Volume (m3) Amount (kg)
Top Ceramic layers 9 150 1360 0.09 116
6 150 1450 0.09 124
Activated Carbon 1 7886 555 4.49 2494
Bottom Ceramic layers 6 150 1450 0.09 124
9 150 1360 0.09 116

[0081]. Table 4: Process parameter details for the commercialization of the technology
Properties of MEG UOM Value
Density @ 30? Kg/m3 1106
Viscosity @ 30? Pa.s 1.46E-02
Adsorbent Properties UOM Value
Adsorbent Activated Carbon
Particle size (avg) M 1.00E-03
Bulk Density Kg/m3 555.00
Particle Density Kg/m3 1750.00
Adsorption Capacity Kg/kg 50.00
Column Dimensions UOM Value
ID M 0.852
Length M 8.486
Ceramic ball (6mm) height-top M 0.15
Ceramic ball (3mm) height-top m 0.15
Ceramic ball (3mm) height-bottom m 0.15
Ceramic ball (6mm) height-bottom m 0.15
Adsorbent Height (t/t) m 7.886
Adsorbent Volume m3 4.50
Adsorbent Weight Kg 2495
Bed Voidage 0.45

[0082]. Example 5: Study on different adsorbents
A few studies were conducted to compare the efficacy of different adsorbents with the activated carbon black of the present disclosure. Experiments were conducted by using equilibrium adsorption.
[0083]. In Experiment no. 1, about 100 ml of the waste MEG was taken in about 250 ml of conical flask along with 10 gm of activated bauxite and kept for about 2 hours under stirring. The pH of the treated MEG was checked and found to be about 4.1. No improvement was observed in the pH, which shows that activated bauxite is not a suitable adsorbent for removal of impurities from the waste MEG.
[0084]. Similarly, in an Experiment no. 2 about 100 ml of waste MEG was taken in a conical flask and about 10g of silica pellet was used as adsorbent. The equilibration time was kept for 2 hrs. However, the final pH of the treated MEG was found to be 4.0, indicating that use of silica as adsorbent does not improve the pH of the treated MEG, thereby implicating presence of impurities in the treated MEG.
[0085]. The details of the studies of Experiment nos. 1-2 are provided in Table 5 below.
Table 5: Equilibrium study with different adsorbents
Expt. No. Adsorbent Amount of feed processed (ml) Equilibrium Time (hrs) pH
1 Activated bauxite (pellet) 0 4
100 2 4.1
2 Silica pellet 0 4.0
100 2 4.0

[0086]. Further, to remove the impurities associated with MEG, use of various grade of activated carbons (M/s NORIT) was also explored. Experiment no. 3 was conducted by taking about 5 gm pellet of activated carbon along with 50 ml of waste MEG in conical flask and kept at 400 rpm under stirring for 5 hrs. The treated MEG had a pH of 4.8 and was pale yellow in color. Similarly, other experiments, Experiment nos. 4 and 5 were conducted by taking different grade of activated carbon (pellet form), but no improvement was observed in terms of color and pH. Another grade of NORIT ROX-0.8 carbon was also explored by conducting the Experiment no. 6, however, no improvement was observed. The details of the studies of Experiment nos. 3-6 are provided in Table 6 below.
[0087].

Table 6: Equilibrium study on different activated carbon
Expt. No. Activated carbon Amount of feed processed (ml) Equilibrium Time (hrs) pH
3 NORIT RB-2 (Pellets, 400rpm)
Surface area: 800 to 900 m2/g; Particle size: 3 to 4 mm; Porosity: < 2nm; Moisture: 20 %; pH: 4 to 5 0 4.0
50 3 4.7
5 4.8
4 NORIT RB-2
(Powder, 400rpm)
Surface area: 800 to 900 m2/g; Particle size: powder form; Porosity: < 2nm; Moisture: 20 %; pH: 4 to 5 0 4.0
50 3 5.9
5 NORIT RST-3 (Pellet, 700rpm)
Surface area: 800 to 1000 m2/g; Particle size: 2 to 3 mm; Porosity: < 2nm; Moisture: 20 %; pH: 5 to 6 0 4
50 16 4.7
6 NORIT ROX-0.8, (Powder, 400rpm)
Surface area: 800 to 900 m2/g; Particle size: powder form; Porosity: < 2nm; Moisture: 20 %; pH: 4 to 5 0 4
50 3 4
5 4

[0088]. Example 6: Regeneration study
After the use, the activated carbon becomes saturated with contaminants. Therefore, the spent carbon material needs to be regenerated for the further utilization. Steam regeneration process was employed for regeneration of the spent carbon adsorbent, at a temperature of about 120? and pressure of about 3-4 bar. The regeneration was carried out for about 6-8 h under constant steam temperature and pressure. The steam outlet was scrubbed in distilled water and pH was monitored intermittently till the pH of the of the solution came close to neutral pH of about 6 to about 7. Once the pH of the outlet was neutralized, steam was stopped, and the system was kept under nitrogen flow. Thereafter the material was cooled at room temperature. Approximately 60% surface area and pore volume of the spent carbon was regenerated after the treatment. Results of the regeneration studies are tabulated in Table 7 below:

Table 7: Comparison of properties of fresh, spent and regenerated carbon
Description of Samples BET Surface Area (m2/g) Pore Volume (cm3/g)
Fresh activated carbon 940 0.53
Spent carbon 200 0.18
Regenerated carbon 650 0.34
[0089]. Referral Numerals:
Referral Numeral Description
100 Block diagram of the process of the present disclosure
1 Waste mono ethyl glycol
2 Pump
3 Flow control valve or rotameter
4 Pre-filter (1 micron)
5 Drain
6 Pressure gauze (PG)
7 Reactor
8 Adsorbent
9 Ceramic ball support
10 Nitrogen
11 Treated / purified MEG Storge vessel
12 Filter
13 Vent

, C , Claims:We Claim:
1. A process for purification of contaminated mono ethylene glycol from a sample, said process comprising the act of contacting the sample with activated carbon adsorbent, to obtain purified mono ethylene glycol, characterized in that the activated carbon has:
- surface area ranging from about 800 m2/g to about 1100 m2/g,
- particle size ranging from about 0.25 mm to about 2 mm,
- Iodine number of about 900 mg/g to about 1100 mg/g, and
- pH of about 5 to about 9.
2. The process as claimed in claim 1, wherein the activated carbon has porosity ranging from about 2 nm to 20 nm; the activated carbon has bulk density ranging from about 0.3 g/cc to about 0.8 g/cc; and the activated carbon has moisture content ranging from about 1% to 5%.
3. The process as claimed in claim 1, wherein the process is carried out at room temperature and atmospheric pressure.
4. The process as claimed in claim 1 or claim 3, wherein the process is carried out by using dynamic mode of adsorption or equilibrium mode of adsorption.
5. The process as claimed in claim 4, wherein the dynamic mode of adsorption is carried out in glass column loaded with the adsorbent, and by varying the liquid hourly space velocity (LHSV) in the range of 1h-1 to 4h-1.
6. The process as claimed in claim 4, wherein in the equilibrium mode of adsorption the contaminated MEG is kept in contact with the activated carbon adsorbent for a period of about 30 minutes to about 2 h, and wherein the mixture is optionally stirred at about 50 rpm to about 250 rpm.
7. The process as claimed in any one of the preceding claims, wherein the activated carbon is in a form selected from a group comprising granules, spherical, flakes and powder or any combination thereof.
8. The process as claimed in claim 1, wherein the sample comprising the contaminated mono ethylene glycol is filtered through a micro filter prior to contacting the sample with the activated carbon.
9. The process as claimed in claim 1, wherein the sample is an industrial effluent.
10. The process as claimed in claim 8, wherein the industrial effluent is generated during the manufacture of polyethylene terephthalate or glycolysis of waste fiber.
11. The process as claimed in claim 1, wherein the contaminant is selected from a group comprising 4-(2-hydroxyethoxy) benzoic acid, bis(2-hydroxyethyl)terephthalate and 2-(2-hydroxyethoxy)ethyl(2-hydroxyethyl)terephthalate or any combination thereof.
12. The process as claimed in any one of the preceding claims, wherein spent carbon material is regenerated for further utilization by steam regeneration at a temperature ranging from about 100? to about 140?, preferably 120? at atmospheric pressure of about 2 to about 4 bar.
13. The process as claimed in claim 1, wherein the purified mono ethylene glycol has 98% transmittance at a wavelength of 350 nm.
14. An activated carbon having surface area ranging from about 800 m2/g to about 1100 m2/g, particle size ranging from about 0.25 mm to about 2 mm, Iodine number ranging from about 900 mg/g to 1100 mg/g, moisture of about 5 %, and pH of about 5 to 9.
15. The activated carbon as claimed in claim 14, wherein the activated carbon has porosity ranging from about 2 nm to 20 nm; the activated carbon has bulk density ranging from about 0.3 g/cc to about 0.8 g/cc; and the activated carbon has moisture content ranging from about 1% to 5%.

Dated this 07th day of June 2022
Signature:
Name: Sridhar R
To: Of K&S Partners, Bangalore
The Controller of Patents Agent for the Applicant
The Patent Office, at Mumbai IN/PA-2598