Claims:1. An apparatus for the purification of crude carboxylic acid, said apparatus comprising:
? a vessel for reacting at least one Lewis base with at least one crude carboxylic acid at a temperature ranging from 50 °C to 200 °C and at a pressure ranging from 1 bar to 10 bar to obtain Lewis base-carboxylic acid adducts dissolved in a resultant mass;
? a crystallizer for crystallizing the at least one Lewis base-carboxylic acid adduct, received from said vessel, at a temperature lower than 200 °C to obtain crystals of the Lewis base-carboxylic acid adduct;
? a filter for separating said Lewis base-carboxylic acid wet adduct, received from said crystallizer, to obtain wet crystals of said Lewis base-carboxylic acid adduct;
? at least one dryer for drying said wet crystals of said Lewis base-carboxylic acid adduct, received from said filter, wherein said wet crystals are heated to a temperature in the range from 50 °C to 250 °C and at a pressure ranging from 0 to 760 mm of Hg to obtain purified carboxylic acid and vapors of said at least one Lewis base;
? at least one scrubber adapted to
o scrub said vapors of said at least one Lewis base from said at least one dryer; and
o recover said at least one Lewis base in liquid phase; and
? a storage unit:
o connected to and in fluid communication with said at least one scrubber; and
o adapted to receive said liquid Lewis base therefrom.
2. An apparatus for purification of crude carboxylic acid, said apparatus comprising:
? a vessel for
o reacting at least one Lewis base with at least one crude carboxylic acid at a temperature ranging from 50 °C to 200 °C and at a pressure ranging from 1 bar to 10 bar to obtain Lewis base-carboxylic acid adducts dissolved in a resultant mass; and subsequently
o crystallizing the at least one Lewis base-carboxylic acid adduct, received from said vessel, at a temperature lower than 200 °C to obtain crystals of said Lewis base-carboxylic acid adduct;
? a filter for separating said Lewis base-carboxylic acid wet adduct, received from said crystallizer, to obtain wet crystals of said Lewis base-carboxylic acid adduct;
? at least one dryer for drying said wet crystals of said Lewis base-carboxylic acid adduct, received from said filter, wherein said wet crystals are heated to a temperature in the range from 50 °C to 250 °C and at a pressure ranging from 0 to 760 mm of Hg to obtain purified carboxylic acid and vapors of said at least one Lewis base;
? at least one scrubber adapted to
o scrub said vapors of said at least one Lewis base from said at least one dryer; and
o recover said at least one Lewis base in liquid phase; and
? a storage unit:
o connected to and in fluid communication with said at least one scrubber; and
o adapted to receive said liquid Lewis base therefrom.
3. The apparatus as claimed in claim 1 or claim 2, further comprising a pump, connected to and in fluid communication with said storage unit and said at least one scrubber, for recycling said Lewis base to said at least one scrubber.
4. The apparatus as claimed in claim 1 or claim 2, wherein said at least one scrubber has an outlet configured on an operative top thereof for venting the left over vapors of water vapor and Lewis base vapor therefrom.
5. The apparatus as claimed in claim 4, wherein said outlet is connected to and in fluid communication with a condensate pot for condensing said left over vapors comprising water vapor and Lewis base vapor therefrom.
6. The apparatus as claimed in claim 4, wherein said at least one scrubber is connected to and in fluid communication with at least one water scrubber via said outlet, wherein said water scrubber is adapted scrub water and Lewis base in said left over vapors comprising water vapor and Lewis base vapor.
7. The apparatus as claimed in any of the preceding claims, wherein said purified carboxylic acid is collected in bags using a storage silo.
8. The apparatus as claimed in any of the preceding claims, wherein said Lewis base is at least one selected from the group consisting of substituted, un-substituted, linear, branched, cyclic, polycyclic, heterocyclic, aromatic and hetero-aromatic Lewis base.
9. The apparatus as claimed in any of the preceding claims, wherein said Lewis base is 1-methylimidiazole.
10. The apparatus as claimed in any of the preceding claims, wherein said crude carboxylic acid is at least one selected from said group consisting of crude terephthalic acid, crude orthophthalic acid, and combinations thereof. , Description:This is a divisional application in furtherance to the first application number 1838/MUM/2014 dated 04/06/2014.
FIELD
The present disclosure relates to an apparatus for the purification of crude carboxylic acid.
BACKGROUND
Terephthalic acid is an organic colorless solid having the formula C6H4-(COOH)2. Terephthalic acid is a known precursor for the preparation of the polyethylene terephthalate (PET); the latter being extensively used for applications such as preparation of clothing items, plastic bottles, and the like.
Commercially, terephthalic acid is produced by the oxidation of para-xylene using air or oxygen rich air as an oxidant in the presence of a catalyst and a promoter and by employing acetic acid as a fluid medium (or solvent).
Wet oxidation process of para-xylene results in crude terephthalic acid as the main product, intermediates such as para-tolualdehyde, para-toluic acid, 4-carboxybenzhaldehyde (4-CBA), and numerous side products such as isophthalic acid, orthophthalic acid, meta or ortho-tolualdehyde, meta or ortho-toluic acid, 2 or 3-carboxybenzhaldehyde, 3 or 4-bromo methyl benzoic acid, benzoic acid, trimellitic acid, trimesic acid, benzaldehyde, phthalaldehyde, ethylbenzaldehyde, methylstyrene, diphenic acid, 2-biphenyl carboxylic acid, hemimellitic acid, dimethyl terephthalate, methyl p-toluate, 3-hydroxy 4-methyl benzoic acid, terephthaldehyde, styrene, phenol, toluene, benzene, ethylbenzene, methylethylbenzene, formaldehyde, 1,3-cyclopentadiene, indene, methylnaphthalene, anthracene, phenanthrene, phenylacetylene, methylbiphenyl, diphenylbutane, naphthalene, 4,4-dimethylbibenzyl, and vinylacetylene are produced.
In order to use terephthalic acid as a starting material, for instance, in the preparation of PET, it is recommended that its 4-CBA content is less than a minimum threshold. Presence of large quantities of 4-CBA in terephthalic acid, acts as a chain terminator during the PET polymerization process, thereby hindering the preparation of PET having desired molecular weight. During the production of terephthalic acid, 4-CBA is typically present between 4000 ppm to 10,000 ppm and para-toluic acid is in the range of 150 ppm to 5000 ppm. Therefore, reducing the 4-CBA content is very crucial for further use of terephthalic acid.
Various apparatuses have been explored to purify crude terephthalic acid. Attempts have also been made to purify the side products such as isophthalic acid and the like. Conventionally, crude terephthalic acid is subjected to hydrogenation to convert 4-CBA into p-toluic acid; the latter is then separated and eliminated from the apparatus. However, these apparatuses have certain drawbacks
There is, thus, felt a need for developing an apparatus for the purification of crude carboxylic acids.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
An object of the present disclosure is to provide an apparatus for the purification of crude carboxylic acid.
Another object of the present disclosure is to provide an apparatus for the continuous purification of the crude carboxylic acid.
Still another object of the present disclosure is to provide an apparatus for the purification of the crude terephthalic acid.
Another object of the present disclosure is to provide an apparatus for the purification of the crude carboxylic acid by reducing the metallic and other impurities to less than or equal to the standard PET specification.
Still another object of the present disclosure is to provide an apparatus for the purification of the crude terephthalic acid to obtain purified terephthalic acid having acceptable 4-CBA content.
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 provides an apparatus for the purification of crude carboxylic acid. In accordance with one embodiment of the present disclosure, an apparatus for purification of crude carboxylic acid is provided, wherein the apparatus comprises
? a vessel for reacting at least one Lewis base with at least one crude carboxylic acid at a temperature ranging from 50 °C to 200 °C and at a pressure ranging from 1 bar to 10 bar to obtain Lewis base-carboxylic acid adducts dissolved in a resultant mass;
? a crystallizer for crystallizing the at least one Lewis base-carboxylic acid adduct, received from the vessel, at a temperature lower than 200 °C to obtain crystals of the Lewis base-carboxylic acid adduct;
? a filter for separating the Lewis base-carboxylic acid wet adduct, received from the crystallizer, to obtain wet crystals of the Lewis base-carboxylic acid adduct;
? at least one dryer for drying the wet crystals of the Lewis base-carboxylic acid adduct, received from the filter, wherein the wet crystals are heated to a temperature in the range from 50 °C to 250 °C and at a pressure ranging from 0 to 760 mm of Hg to obtain purified carboxylic acid and vapors of the at least one Lewis base;
? at least one scrubber adapted to scrub the vapors of the at least one Lewis base from the at least one dryer; and recover the at least one Lewis base in liquid phase; and
? a storage unit connected to and in fluid communication with the at least one scrubber; and adapted to receive the liquid Lewis base therefrom.
In accordance with the present disclosure, the purified carboxylic acid obtained is collected in bags using a storage silo that is provided at the downstream side of the dryer.
In accordance with another embodiment of the present disclosure, the crystallization of the at least one Lewis base-carboxylic acid adduct is carried out in the same vessel in a subsequent step after the formation of the Lewis base-carboxylic acid adducts, that is, there is no provision of a separate crystallizer.
In accordance with another embodiment of the present disclosure, the Lewis base, obtained after the step of separation of the purified carboxylic acid, recovered from the scrubber and collected in the storage unit a first portion of the Lewis base is recycled back to reactor for adduct preparation and second portion of the Lewis base remains in circulation mode to scrub the Lewis base that is received from at least one dryer in vapor form.
In accordance with the present disclosure, at least one water scrubber is connected to and in fluid communication with the at least one scrubber, wherein the water scrubber is adapted scrub water and Lewis base in the left over vapors comprising water vapor and Lewis base vapor.
In accordance with the present disclosure, the
? crude carboxylic acid is at least one selected from the group consisting of crude terephthalic acid, crude orthophthalic acid, and combinations thereof; and
? Lewis base is at least one selected from the group consisting of substituted, un-substituted, linear, branched, cyclic, polycyclic, heterocyclic, aromatic and hetero-aromatic Lewis base.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
Figure 1 illustrates a schematic diagram of an apparatus for purification of crude carboxylic acid in accordance with an embodiment of the present disclosure;
Figure 2 illustrates a schematic diagram of an apparatus for purification of crude carboxylic acid in accordance with another embodiment of the present disclosure; and
Figure 3 illustrates a schematic diagram of an apparatus for purification of crude carboxylic acid in accordance with still another embodiment of the present disclosure.
DETAILED DESCRIPTION
The apparatus for the purification of the crude carboxylic acid of the present disclosure will now be described with reference to the embodiments, which do not limit the scope and ambit of the disclosure.
The embodiments herein, the various features and the 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 that there is no unnecessary confusion about 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 description hereinafter, of the specific embodiments will 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.
Figure 1 illustrates a schematic diagram of an apparatus 100 for the purification of the crude carboxylic acid in accordance with an embodiment of the present disclosure. The apparatus 100 for the purification of the crude carboxylic acid comprises a vessel 101 for reacting at least one Lewis base with the at least one crude carboxylic acid at a temperature in the range from 50 °C to 200 °C and at a pressure ranging from 1 bar to 10 bar to obtain Lewis base-carboxylic acid adducts dissolved in a resultant mass.
The apparatus 100 further comprises a crystallizer 102 for crystallizing the at least one Lewis base-carboxylic acid adduct formed in the vessel 101. The vessel 101 and the crystallizer 102 are connected to and in fluid with the each other, wherein the crystallizer 102 is adapted to receive at least one Lewis base-carboxylic acid adduct formed in the vessel 101. The crystallizer 102 is configured to crystallize the adduct at a temperature that is lower than 200 °C or at a temperature that is lower than the temperature at which the crystals of the adduct are formed to obtain crystals of the Lewis base-carboxylic acid adduct. The crystallizer 102 may be one selected from the group consisting of a single or series of crystallizers and non-limiting examples of crystallizers include Forced Circulation crystallizers, Draft Tube Baffle crystallizers, Oslo Crystallizers, and the like.
Further, the apparatus is provided with a filter 103 for separating the Lewis base-carboxylic acid wet adduct, received from the crystallizer 102, to obtain wet crystals of the at least one Lewis base-carboxylic acid adduct. The filter 103 may be selected from the group consisting of a single or series of filters and non-limiting examples of the filtration system include all types of filters like belt filters, rotary filters, Nutsche filters, and the like, operated under positive, negative or atmospheric pressure.
At least one dryer 104 (figure 1 through 3 shows an exemplary embodiment with two dryers) is connected and in fluid communication with the filter 103, wherein the dryer 104 is adapted to dry the wet crystals of the Lewis base-carboxylic acid adduct, received from the filter 103, wherein the wet crystals are heated to a temperature in the range from 50 °C to 250 °C and at a pressure ranging from 0 to 760 mm of Hg to obtain purified carboxylic acid and vapors of the at least one Lewis base. The purified carboxylic acid which is the final product, so obtained, is further used for various purposes. The dryer 104 may be selected from the group consisting of a series of dryers and non-limiting examples of dryers include fluidized bed, atmospheric tray, vacuum tray, agitated bed, direct rotary, indirect rotary, spray, spouted bed, vibrated bed, drum, belt, plate, vacuum, disc, paddle, column, filter, ring, jet-zone, microwave, freeze, solar and any combinations thereof. Relative motion between the drying medium and solid to be dried can be concurrent, counter current, and mixed flow.
Moreover, at least one scrubber 105 is provided that is connected to and in fluid communication with the at least one dryer 104, wherein the at least one scrubber 105 is adapted to receive the vapors of the at least one Lewis base from the at least one dryer 104. Further, the scrubber 105 is adapted to recover the at least one Lewis base in liquid phase. The at least one Lewis base in liquid phase, so recovered from the scrubber 105 is transferred to a storage unit 106 that is connected to and in fluid communication with the scrubber 105 via a pump 107.
Further, the Lewis base recovered and stored in the storage unit 106 is recycled to the scrubber 105 and the vessel 101.
Furthermore, the at least one scrubber 105 is provided with an outlet 108 that is configured at an operative top of the at least one scrubber 105, wherein the outlet 108 facilitates the removal or exhaust or venting of the left over vapors comprising water vapor and Lewis base vapor from the scrubber 105.
In accordance with the present disclosure, the filter 103 is a solid liquid filter or a solid liquid filtration system that is adapted to filter-out the solid from the liquid.
In accordance with another embodiment of the present disclosure, the vessel 101 and the crystallizer 102 can be one and the same. More specifically, the crystallizer 102 can be removed and the crystallization of the Lewis base-carboxylic acid adducts can be carried out in the vessel 101 itself. The steps of reacting the at least one Lewis base with at least one crude carboxylic acid to obtain adducts of the at least one Lewis base-carboxylic acid and crystallization of the so obtained adducts can be carried out in the vessel 101 in subsequent steps thereby eliminating the use of the crystallizer 102. The reaction and the crystallization conditions (temperature and pressure) remaining the same.
Figure 2 illustrates a schematic diagram of an apparatus 100 for purification of crude carboxylic acid in accordance with another embodiment of the present disclosure. In accordance with this embodiment, the purified carboxylic acid obtained after the drying in the dryer 104 is collected in bags 112, which can be transported, using a storage silo 111.
Further, in accordance with this embodiment the left over vapors vented from the outlet 108 configured on the operative top of the scrubber 105 are condensed using a condensate pot 109. Further, the condensate pot 109 may be provided with an outlet 109a that is in fluid communication with a vacuum pump 110, wherein the vacuum pump 110 facilitates the provision of a desired vacuum required to increase or accelerate rate of de-adduction of terephthalic acid – 1-methyl imidazole adduct to get purified terephthalic acid. The portion of the apparatus 100 from the dryer 104 to the condensate pot 109a remains under vacuum or negative pressure.
The rest of the components of the apparatus 100 herein are similar to that of the embodiment described hereinabove with reference to figure 1.
Figure 3 illustrates a schematic diagram of an apparatus 100 for purification of crude carboxylic acid in accordance with still another embodiment of the present disclosure. The rest of the components of the apparatus 100 herein are similar to that of the embodiment described hereinabove with reference to figure 1 and 2 except that a water scrubber 113 is provided between the scrubber 105 and the condensate pot 109, wherein the water scrubber 113 is adapted to scrub water and Lewis base from the left over vapors comprising the water vapors and the Lewis base vapors vented from the outlet 108 of the scrubber 105. The water scrubber 113 is further in fluid communication with a water tank 114, wherein the water tank 114 is adapted to receive scrubbed water and Lewis base from the water scrubber 113. The water collected in the water tank 114 remains under circulation to the water scrubber 113 with a purge stream that goes to the Lewis base recovery system or to effluent treatment plant (ETP) for purification using a pump 115.
In accordance with the present disclosure, the Lewis base is at least one selected from the group consisting of substituted, un-substituted, linear, branched, cyclic, polycyclic, heterocyclic, aromatic, and hetero-aromatic Lewis base.
In accordance with the present disclosure, the Lewis base is 1-methylimidiazole.
In accordance with the present disclosure, the crude carboxylic acid is at least one selected from the group consisting of crude terephthalic acid, crude orthophthalic acid, and combinations thereof.
TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of an apparatus for the:
? purification of crude carboxylic acid;
? continuous purification of the crude carboxylic acid;
? purification of crude terephthalic acid;
? purification of crude orthophthalic acid;
? purification of the crude carboxylic acid by reducing the metallic and other impurities to less than or equal to the standard PET specification; and
? purification of the crude carboxylic acid (terephthalic acid) to obtain purified terephthalic acid having acceptable 4-CBA content.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, 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.
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 invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.
The numerical values given for various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.