Title of Invention	A CATALYST COMPOSITION FOR HYDROPURIFICATION OF CRUDE TEREPHTHALIC ACID AND A METHOD THEREOF
Abstract	ABSTRACT The present invention discloses a catalyst composition for hydropurification of crude terephthalic acid and a process for providing the catalyst composition. The catalyst composition of the present invention comprises: a carrier material having a porous absorptive surface with a BET surface area of 200 - 400 m /g and a pore volume of 1 to 2.5 cm /g; and a Group VIII noble metal in the form of nanoparticles (100) with particle size between 10 - 20 nm impregnated on the carrier material. The present invention further discloses a process for hydropurification of crude terephthalic acid using the catalyst composition.

Title of Invention

A CATALYST COMPOSITION FOR HYDROPURIFICATION OF CRUDE TEREPHTHALIC ACID AND A METHOD THEREOF

Abstract

ABSTRACT The present invention discloses a catalyst composition for hydropurification of crude terephthalic acid and a process for providing the catalyst composition. The catalyst composition of the present invention comprises: a carrier material having a porous absorptive surface with a BET surface area of 200 - 400 m /g and a pore volume of 1 to 2.5 cm /g; and a Group VIII noble metal in the form of nanoparticles (100) with particle size between 10 - 20 nm impregnated on the carrier material. The present invention further discloses a process for hydropurification of crude terephthalic acid using the catalyst composition.

Full Text	FORM-2 THE PATENTS ACT, 1970 (39 of 1970) THE PATENTS RULES, 2006 COMPLETE Specification (See Section 10 and Rule 13) A CATALYST COMPOSITION FOR HYDROPURIFICATION OF CRUDE TEREPHTHALIC ACID AND A METHOD THEREOF RELIANCE INDUSTRIES LIMITED an Indian Company of Reliance Technology Group, Building No. 7, B Wing, Ground Floor Reliance Corporate Park, Thane-Belapur Road, Ghansoli, Navi - Mumbai: 400 701, Maharashtra, India. The following specification particularly describes the invention and the manner in which it is to be performed. FIELD OF THE INVENTION The present invention relates to the field of catalysts for purification of crude terephthalic acid and a method thereof DEFINITIONS As used in the present specification, the following words and phrases are generally intended to have the meanings as set forth below, except to the extent that the context in which they are used indicates otherwise. The term "catalyst activity" is defined as a measure of the catalyst's ability to convert 4-carboxybenzaldehyde at a specified set of reaction parameters, viz. temperature, pressure, reaction time, and reactant feed composition. Catalyst activity is expressed as moles of 4-carboxybenzaldehyde reduced per mole of noble metal in the catalyst. The term "porous absorptive surface" is defined as a surface having pores being able to absorb a fluid or solid media thereon. The term "mesopores" are defined as pores having a diameter between 2-50 nm. The term "pore volume" is defined as the ratio of a porous material's air volume to a porous material's total volume. The term "functionalization" is defined as creation of chemical functional groups on the surface of a carrier material for chemically modifying the surface of the carrier material. The chemical functional groups on a carrier material help bind metal onto the surface of the carrier material. The term "BET surface area" is defined as Brunauer, Emmett, and Teller surface area, using the BET analysis to obtain the surface area of a solid by physical adsorption of gas molecules: The total surface area (SBET,totai), units m2/g, and the specific surface area (SBET), units m2/g, is evaluated using the following equations: Where, N : Avogadro's Number s : adsorption cross section, unit nm2; V: molar volume of adsorbent gas, unit m3/mol; a : molar mass of adsorbed species, unit g/mol; vm : monolayer adsorbed gas quantity; Where, A : Value of Slope I: y-intercept of the line The term "functionalized carrier material" is defined as a carrier material having oxygen-containing groups (C02 and CO) formed on the surface. Functionalized carrier material shows hydrophilic behavior which has higher specific surface area than the carrier material. Repulsion forces are generated on the surface which help in debundling the carrier material, and provide enhanced interaction of the carrier material with organic solvents. The term "magnetic stirring" is defined as stirring by using magnetic stirrers which employ a rotating magnetic field to cause a stir bar immersed in a liquid to spin. The rotating magnetic field can be created by a rotating bar magnet or a set of stationary electromagnets placed beneath the vessel with the liquid. BACKGROUND OF THE INVENTION & PRIOR ART Terephthalic acid is an important chemical used as a raw material in the production of poly (ethylene terephthalate) which is used in the manufacture of polyester fiber, films, and resins for bottles and containers. Liquid phase oxidation of alkyl aromatic compound gives carboxylic acid which contains a variety of impurities e.g. oxidation of 1,4-dimethylbenzene gives terephthalic acid with substantial amount of 4- carboxybenzaldehyde as an impurity which is only tolerated up to 20 ppm in the terephthalic acid product. The 4-carboxybenzaldehyde present in the terephthalic acid is known to cause chain termination in the polyester synthesis and also leads to undesirable coloration of the polymer. Catalytic hydrogenation is an important process in the purification of crude terephthalic acid. The process for purification of the crude terephthalic acid involves hydrogenation of an aqueous solution of crude terephthalic acid at an elevated temperature to keep it in dissolved state over a bed of catalyst containing a noble metal anchored on a support such as activated carbon. However, the carbon support used in the conventional catalyst has the following disadvantages. 1) The carbon support undergoes attrition losses resulting in corresponding loss of the noble metal; (2) Most of the noble metal particles anchored on to the granular carbon support remain in the micropores which are difficult to access for an organic compounds such as 4-carboxybenzaldehyde. Several attempts have been made to provide a catalyst for purification of crude terephthalic acid and a method thereof to overcome the aforementioned drawbacks; some of the related systems are discussed in the following section dealing with the prior art. The publication in J. Phys. Chem. C, 112 (2008) 13463, discloses the application of carbon nanotubes as support for catalysts in a variety of reactions due to their nanostructure and interesting electrical and mechanical properties. The large specific surface area of the metal particles and the high mechanical strength of carbon nanotubes significantly enhance the activity and life of the catalysts. US Patent No. 4415479 discloses a catalyst for purification of crude terephthalic acid which reduces the 4-carboxybenzaldehyde content to less than 100 ppm. The catalyst is prepared by contacting an aqueous solution of palladium amine complex with a porous carbonaceous material such as granular coconut shell carbon. US Patent No. 4421676 discloses preparation of palladium on carbon catalyst by contacting an aqueous solution of sodium tetranitritopalladate with a porous carbonaceous support such a granular coconut shell carbon. Hydrogenation of an aqueous solution of crude terephthalic acid in the presence of the catalyst reduced the 4-carboxybenzaldehyde content to less than 100 ppm. US Patent No. 4476242 discloses a catalyst preparation by supporting palladium on porous activated carbonaceous material such as coconut shell charcoal wherein the palladium crystallites are predominantly less than 3 5A. The catalyst is prepared by depositing palladium on the carbon support from a solution of palladium salt in an organic solvent in the absence of hydrogen. Hydrogenation in the presence of this catalyst reduced the 4-carboxybenzaldehyde concentration in the crude terephthalic acid to less than 100 ppm. US Patent No. 4317923 discloses rhenium deposited on carbon as a catalyst for purification of crude aromatic dicarboxylic acids such as those obtained by oxidation of 1,4-dimethylbenzene. Treatment of the crude dicarboxylic acids containing 4-carboxybenzaldehyde as impurity under nitrogen atmosphere results into decarbonylation of the aldehyde functionality and thus converting the 4-carboxybenzaldehyde to benzoic acid which is easily removed during recrystallization process. EP Patent No. 219288 discloses preparation of catalyst comprising rhodium supported on granular carbon and its application to purification of crude terephthalic acid. The catalyst reduces the impurities such as 4-carboxybenzaldehyde and exhibits reduced rate of decomposition of terephthalic acid as compared to the commercially available rhodium catalyst. US Patent No. 4629715 discloses a process for purification of crude terephthalic acid that uses two different catalyst beds in the hydrogenation reactor to give high purity terephthalic acid product. The top bed of primary catalyst comprises of palladium on active carbon which catalyzes hydrogenation of 4-carboxybenzaldehyde to /?-toluic acid. The secondary catalyst bed located downstream of the first bed comprises of rhodium supported on carbon catalyst which is believed to affect decarbonylation of the remainder of the 4-carboxybenzaldehyde to give benzoic acid. EP Patent No. 222500 discloses purification of crude terephthalic acid by hydrogenation of its aqueous solution in a catalyst bed containing two layers of catalysts. The first layer of the catalyst comprises of Group VIII metal such as rhodium supported on active carbon support. The second catalyst layer comprises of palladium supported on active carbon. The feed enters the first catalyst layer and then contacts the second layer. The carbon monoxide generated in the reactor due to decarbonylation of 4-carboxybenzaldehyde is a poison to the catalyst. In this process the carbon monoxide is reduced by Fischer-Tropsch type reaction to give hydrocarbons such as methane. US Patent No. 4394299 discloses a bimetallic catalyst for purification of crude terephthalic acid which reduces concentration of 4-carboxybenzaldehyde from 10,000 ppm to less than 100 ppm. The catalyst is prepared by fast absorbing palladium on a porous carbonaceous support such as granular coconut charcoal from a solution of palladium salt formed by reaction with amine and acetic acid followed by deposition of rhodium form an aqueous solution of sodium hexanitritorhodate. GB Patent No. 2018252 discloses a process for purification of crude terephthalic acid containing organic impurities such as 4-carboxybenzaldehyde by hydrogenation over a catalyst made from the alloy of palladium and ruthenium in the form of a membrane. The aqueous solution of impure terephthalic acid is contacted with the membrane catalyst at a temperature high enough to keep the terephthalic acid in aqueous solution. The catalyst is claimed to be stable under the condition of hydrogenation and its use eliminates hot filtration of the solution underpressure. WO 2006/071407A1 describes a process for purification of impure aromatic dicarboxylic acid product by catalytic hydrogenation using a stable catalyst prepared by depositing a noble metal such as palladium on high surface area silicon carbide support. The abrasion and attrition resistant support provides catalyst with longer life time, improved process stability and reduced presence of catalyst particles in the product as compared to the processes using carbon-supported catalysts. Therefore, there is felt a need to provide a catalyst for purification of crude terephthalic acid and a method thereof which exhibits better catalytic properties, provides higher surface area, the metal particles in the catalyst are easily accessible to the reactants, minimizes impurities in the terephthahc acid, and has a long life, as compared to the existing catalysts and methods discussed in the prior art. OBJECTS OF THE INVENTION An object of the present invention is to provide a catalyst composition for hydropurification of crude terephthalic acid. Another object of the present invention is to provide a catalyst composition for hydrogenation of 4-carboxybenzaldehyde in the crude terephthalic acid. Still another object of the present invention is to provide a catalyst composition for hydropurification of crude terephthalic acid having a high catalytic performance. Yet another object of the present invention is to provide a catalyst composition for hydropurification of crude terephthalic acid having a large external surface area for enhancing exposure to the reactants. One more object of the present invention is to devise a catalyst composition for hydropurification of crude terephthalic acid which provides optimum efficiency. Still one more object of the present invention is to provide a catalyst composition in which the carrier material has a high mechanical strength and minimum catalyst is lost due to attrition, thus, the catalyst composition has a long life. Yet one more object of the present invention is to provide a method for making a catalyst for hydropurification of crude terephthalic acid. An additional object of the present invention is to provide a method for making terephthalic acid. SUMMARY OF THE INVENTION In accordance with the present invention, a catalyst composition is provided for hydropurification of crude terephthalic acid, said catalyst composition comprising: • a carrier material having a porous absorptive surface with a BET surface area of 200 to 400 m2/g and a pore volume of 1 to 2.5 cm3/g; and • a Group VIII noble metal impregnated in the mesopores of the carrier material, wherein the Group VIII noble metal is in the form of nanoparticles with particle size in the range of 10-20 nm. Typically, in accordance with the present invention, the carrier material is selected from the group consisting of single-walled carbon nanotubes, multi-walled carbon nanotubes, rope carbon nanotubes, and the like. Additionally, in accordance with the present invention, the carrier material is a multi-walled carbon nanotubes having 3-15 walls. Preferably, in accordance with the present invention, the Group VIII noble metal is palladium. Preferably, in accordance with the present invention, the multi-walled carbon nanotubes have an outer diameter of 13 - 16 nm, an inner diameter of 2 - 5 nm and a length of 1 - 10 μm. Typically, in accordance with the present invention, the carrier material is functionalized by nitric acid before impregnating the noble metal thereon. Additionally, in accordance with the present invention, the catalyst composition contains 0.01 - 5 % (by weight) of the noble metal. In accordance with the present invention, the BET surface area of the carrier material is in the range Additionally, in accordance with the present invention, the BET surface area of the functionalized carrier material is in the range of 370 - 430 m /g. Preferably, in accordance with the present invention, the BET surface area of the metal impregnated functionalized carrier material is in the range of 260 -290 m2/g. In accordance with the present invention, the carrier material is in the form of spheres, pills, cakes, extrudates, powders, granules, and the like. Typically, in accordance with the present invention, the metal impregnated functionalized carrier material is treated with 5-10 equivalents of sodium borohydride. In accordance with the present invention, a process is disclosed for providing a catalyst composition for hydropurification of crude terephthalic acid, said process comprising the following steps: (i) functionalizing a carrier material having a porous absorptive surface with nitric acid by magnetically stirring at a temperature of 100 - 180 °C for 6-24 hours to provide a suspension containing functionalized carrier material; (ii) cooling the suspension to a temperature in the range of 25 - 35 °C to provide a cooled suspension; (iii) centrifuging the cooled suspension for 15 - 45 minutes and separating the functionalized carrier material; (iv) washing the functionalized carrier material with deionized water and tetrahydrofuran; (v) drying the functionalized carrier material at 75 - 150 °C for 1 - 6 hours to provide dry functionalized carrier material; (vi) dissolving a Group VIII noble metal compound in deionized water to prepare a solution; (vii) pouring the solution on the dry functionalized carrier material to obtain a blend and magnetically stirring the blend for 1 - 5 hours; (viii) distributing nanosized particles of the noble metal compound in the mesopores of the functionalized carrier material; (ix) filtering the blend to separate metal compound impregnated functionalized carrier material; (x) washing the metal compound impregnated functionalized carrier material with deionized water and ethanol; (xi) drying the metal compound impregnated functionalized carrier material at a temperature of 40 - 60 °C for 6 - 10 hours to provide dried metal compound impregnated functionalized carrier material; (xii) treating the dried metal compound impregnated functionalized carrier material with 5-10 equivalents of sodium borohydride and magnetically stirring for 15 - 45 minutes to provide a reduced catalyst composition; (xiii) filtering the reduced catalyst composition and washing it with deionized water and dry ethanol to obtain a purified catalyst composition; and (xiv) drying the purified catalyst composition at 100 - 150 °C under vacuum for 6 - 10 hours to provide the catalyst composition. In accordance with the present invention, a process is disclosed for hydropurification of crude terephthalic acid using a catalyst composition, said process comprising the following steps: (i) charging a reaction mixture comprising terephthalic acid having 2000 - 6000 ppm of 4-carboxybenzaldehyde, deionized water, and the catalyst composition in an autoclave; (ii) purging the autoclave first with nitrogen gas and then with hydrogen gas; (iii) filling the autoclave with hydrogen gas to 100 - 200 psig pressure; (iv) heating the hydrogen gas filled autoclave to a temperature of 150 -300°C; (v) agitating the autoclave for a predetermined duration of the reaction time; (vi) stopping the agitator and cooling the autoclave while allowing the reaction mixture to stand in the autoclave for 8 - 16 hours; (vii) venting the hydrogen gas from the autoclave and purging the autoclave with nitrogen gas; (viii) discharging the reaction mixture from the autoclave and filtering the reaction mixture under suction to provide a precipitate; and (ix) drying a deionized water washed precipitate under vacuum at a temperature of 60 - 85 °C for 1 - 5 hours, to obtain purified terephthalic acid. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING The invention will now be described with the help of the accompanying drawing, in which, FIGURE 1 illustrates the Transmission Electron Micrograph image of Pd nanoparticles (black spot) in the range of 10-20 nm supported on multi-walled carbon nanotubes (MWCNT). DETAILED DESCRIPTION OF THE INVENTION The present invention envisages a catalyst composition comprising a carrier material having a porous absorptive surface with a high surface area and a Group VIII noble metal impregnated thereon and application of the catalyst composition for purification of crude terephthalic acid, specifically for hydrogenation of 4-carboxybenzaldehyde, to obtain pure terephthalic acid of the grade suitable as a co-monomer for the manufacturing of poly(ethylene terephthalate) used in fiber, films, bottles, and containers. The high catalytic performance of the catalyst composition of the present invention is attributed to the high external surface area of the carrier material, typically, carbon nanotubes, compared to that of the conventional activated carbon support wherein a large part of the surface area is micropores which are not easily accessible to the reactants, especially in the liquid phase where high diffusional limitations are predominant. The catalytic properties of the catalyst composition are further enhanced due to the phase of the noble metal on the carrier material and the mesoporous property of the carrier material. Also, when the carrier material is a carbon nanotubes, nanosized particles of the noble metal are impregnated thereon, which further enhances the catalytic properties of the catalyst composition. The efficiency of the catalyst composition in the aforementioned condition is higher than when the carrier material is activated carbon in which the metal particles are much bigger. Typically, in accordance with the present invention, palladium is supported on multi-walled carbon nanotubes, which showed higher catalytic activity compared to the commercially available 0.5% palladium supported on activated carbon, under conditions similar to the plant operations. Further, carbon nanotubes posses outstanding physical, chemical and mechanical properties like lightweight, thermal and electrical conductivity, and high tensile strength, thus, the catalyst composition in accordance with the present invention has a longer life compared to the commercially available catalysts used for purifying crude terephthalic acid. The catalyst composition in accordance with the present invention is used for hydropurification of crude terephthalic acid, wherein the catalyst composition comprises a carrier material having a porous absorptive surface with a high BET surface area of 200 to 400 m /g and a pore volume of 1 to 2.5 cm /g and a Group VIII noble metal, preferably palladium in the form of nanoparticles, impregnated in the mesopores of the carrier material. Transmission electron micrograph of the catalyst shows palladium particles of particle size in the range of 10-20 nm supported on multi-walled carbon nanotubes (refer Figure 1). The porous carrier material is typically selected from single-walled carbon nanotubes, multi-walled carbon nanotubes, rope carbon nanotubes. Typically, carbon nanotubes are used, wherein, a multi-walled carbon nanotubes having 3-15 walls are preferred. The carbon nanotubes exhibit outstanding physical, chemical and mechanical properties such as lightweight, excellent thermal and electrical conductivity, and high tensile strength; thus, minimizing losses of the catalyst due to attrition. Further, the carbon nanotubes keep the metal particles predominantly anchored in the mesopores, thus, increasing the accessible surface area of the metal particles. The preferred carrier material can be prepared in any suitable manner from synthetic or naturally occurring raw material. Further, the carrier material can be formed in any desired shape such as spheres, pills, cakes, extrudates, powders, granules, and the like; and the carrier material can be utilized in any particle size. Preferably, the multi-walled carbon nanotubes chosen as the carrier material has an outer diameter of 13 - 16 nm and an inner diameter of 2 - 5 nm and a length of 1 - 10 μm. The carrier material is functionalized with nitric acid before impregnating the noble metal thereon. The carrier material is functionalized by nitric acid by magnetically stirring at a temperature of 100 - 180 °C for 6-24 hours. A concoction containing the fimctionalized carrier material is obtained which is cooled to a temperature of 25 - 35 °C and centrifuged for 15 - 45 minutes to conveniently separate the functionalized carrier material which is subsequently washed with deionized water and small portions of tetrahydrofuran (THF) and dried at a temperature of 75-150 °C for 1 - 6 hours, to obtain the usable functionalized carrier material. The noble metal compound is deposited on the functionalized carrier material. The final catalyst composition consists 0.01 to 5 % (by weight) of the noble metal, preferably, 0.1 - 0.5 % (by weight) of noble metal is provided in the catalyst composition. The noble metal, preferably palladium, in the active state of the catalyst composition is present substantially in the elemental state with or without chemical interaction with the carrier material, depending upon the method of preparation. Nanosized particles of the noble metal are desirably distributed in the mesopores of the functionalized carrier material to impart enhanced intrinsic properties to the catalyst composition. Typically, palladium is used as the active metal component, wherein, palladium chloride (PdCb) is preferred as the palladium precursor. The metal compound is dissolved in deionized water to obtain a solution which is poured on the functionalized carrier material to obtain a blend. The blend is magnetically stirred for 1 - 5 hours allowing the metal compound from the solution to deposit on the functionalized carrier material. Finally, the blend is filtered and the metal compound impregnated functionalized carrier material, thus obtained, is washed with deionized water and ethanol and dried at a temperature of 40 - 60 °C for 6 - 10 hours to obtain dried metal compound impregnated functionalized carrier material. The dried metal compound impregnated functionalized carrier material, thus obtained, is reduced by treating with a reducing agent, preferably 5-10 equivalents of sodium borohydride (NaBH4), and magnetically stirring the reactants for 15 - 45 minutes to provide a reduced catalyst composition. The reduced catalyst composition is filtered, washed with deionized water and dry ethanol to obtain a purified catalyst composition which is dried at 100 - 150 °C under vacuum for 6 - 10 hours to provide the catalyst composition in accordance with the present invention. The surface area of the carrier material increased after fiinctionalization and decreased after noble metal impregnation. Experimental results for the BET surface area showed that carbon nanotubes in accordance with the present invention have a BET surface area in the range of 320 - 360 m7g, while functionalized carbon nanotubes have a BET surface area in the range of 370 - 430 m2/g, and the palladium impregnated functionalized carbon nanotubes have a BET surface area of 260 - 290 m /g. The surface area of the carbon nanotubes is mainly due to the external surface and the space between the graphene layers is too small to allow access to the metal particles. On the other hand, activated carbon has considerable inner pore volume which is accessible to the metal particles. The catalyst composition of the present invention is used for hydropurification of crude terephthalic acid containing considerably high concentration of 4-carboxybenzaldehyde, to provide purified terephthalic acid having substantially reduced levels of 4-carboxybenzaldehyde. The process for hydropurification of crude terephthalic acid in accordance to the present invention comprises charging crude terephthalic acid containing 2000 to 6000 ppm of 4-carboxybenzaIdehyde, deionized water, and appropriate quantity of the catalyst composition in an autoclave, typically a Parr reactor. The autoclave is purged first with nitrogen gas and then with hydrogen gas, to remove impurities in the autoclave. Further, the autoclave is filled with hydrogen gas to 100 - 200 psig pressure. The reactions were continued at a specified temperature and for a predetermined time. Primarily, the autoclave was heated to a temperature in the range of 150 - 300 °C and once heated the agitator was started to initiate and continue the reaction. Once the reaction time was completed, the agitator was stopped and the heating device was switched off. The autoclave was allowed to cool while the reaction mixture was made to stand for 8 - 16 hours. The hydrogen gas from the autoclave was vented and the autoclave was purged with nitrogen gas. The reaction mixture was discharged from the autoclave and filtered under suction to provide a precipitate. The precipitate was washed with deionized water and dried under vacuum at a temperature of 60 - 85 °C for 1 - 5 hours, to obtain the purified terephthalic acid in accordance with the present invention. EXAMPLES The invention will now be described with reference to the following examples to further exemplify the process of the invention; these examples do not limit the scope and ambit of the invention. EXAMPLE 1: The example illustrates functionalization of carbon nanotubes. 450 mg of the multi-walled CNTs and 45 ml of 3M nitric acid were placed in a 100 ml round bottom flask fitted with a reflux condenser. The contents of the flask were magnetically stirred at 100 °C for 24 h. The mixture was cooled to room temperature and centrifuged on an ultra centrifuge for 30 min. The material was washed with distilled water and twice with small quantity of THF. The functionalized carbon nanotubes thus obtained were dried at 100 °C for 4 hours. EXAMPLE 2: The example demonstrates preparation of the palladium supported carbon nanotubes. A wet impregnation method was used for the preparation of palladium on multi-walled carbon nanotubes (Pd/CNTs) catalyst composition. PdCl2 (17,5 mg) was dissolved in 50 ml of distilled water and 9.5 ml of the solution was added to 100 mg of the functionalized multi-walled carbon nanotubes. The mixture was magnetically stirred at room temperature for 4 hours. The solids were filtered, washed thoroughly with distilled water followed by three small portions of ethanol and dried at 45 °C for 8 hours. The palladium impregnated functionalized nanotubes were magnetically stirred with 1 ml of 0.25 M aqueous NaBH4 (10 equivalents) for 30 min. The solution was filtered and washed with 100 ml of distilled water, followed by small amount of dry ethanol and dried at 110 °C under vacuum (1-2 mm) for 8 hours. ICP analysis showed that the palladium content of the CNT catalyst composition was 0.15% w/w. EXAMPLE 3: The example describes hydrogenation of 4- carboxybenzaldehyde mixed with pure terephthalic acid using the Pd/CNT as catalyst. Pure terephthalic acid (3 g), 4-carboxybenzaldehyde (15 mg), distilled water (40 ml), and 0.15% Pd/CNT catalyst (6 mg) were charged to the Parr reactor of 100 ml capacity. The reactor was assembled and purged with high purity nitrogen gas by five pressurizing (20-30 psig) -depressurizing cycles followed by similar purging with hydrogen gas. The autoclave was filled with hydrogen to 200 psig pressure. The temperature on the control panel was set to 250 °C and the heating device was switched on. When the temperature reached to 250 °C the agitator was started which was set to 240 rpm. The time count was started at this point. Heat and agitation were stopped at the end of the specified reaction time and the reactor left overnight. Next day, the hydrogen gas was carefully vented and the vessel purged with nitrogen. The contents of the reactor were filtered under suction, the precipitate washed with distilled water and dried at 75 °C under vacuum (2-3 mm) for 2 hours. The dried solid was subjected to estimation of 4-carboxybenzaldehyde. EXAMPLE 4: The example demonstrates hydrogenation of 4-carboxybenzaldehyde mixed with pure terephthalic acid using 0.5% palladium on activated carbon (Pd/C) as catalyst. Pure terephthalic acid (3 g), 4-carboxybenzaldehyde (15 mg), distilled water (40 ml) and 0.5% Pd/C catalyst (24 mg) were charged to the Parr reactor of 100 ml capacity. The reactor was assembled and purged with high purity nitrogen gas by five pressurizing (20-30 psig)-depressurizing cycles followed by similar purging with hydrogen gas. The autoclave was filled with hydrogen to 200 psig pressure. The temperature on the control panel was set to 250 °C and the heating devices started which was set to 240 rpm. The time count was started was switched on. When the temperature reached to 250 °C the agitator wa at this point. At the end of the specified reaction time heating and agitation were stopped and the reactor left overnight. Next day, the hydrogen gas was carefully vented and the vessel was purged with nitrogen. The contents of the reactor were filtered under suction, the precipitate washed with distilled water and dried at 75 °C under vacuum (2-3 mm) for 2 hours. The dried solid was subjected to estimation of 4-carboxybenzaldehyde. EXAMPLE 5: The example describes hydrogenation of crude terephthalic acid containing 3200 ppm of 4-carboxybenzaldehyde, obtained from a commercial plant, using 0.15% Pd/CNT as catalyst. Crude terephthalic acid containing 3200 ppm of 4-carboxybenzaldehyde (3 g), distilled water (40 ml), and 0.15% Pd/CNT catalyst (6 mg) were charged to the Parr reactor of 100 ml capacity. The reactor was assembled and purged with high purity nitrogen gas by five pressurizing (20-30 psig)-depressurizing cycles followed by similar purging with hydrogen gas. The autoclave was filled with hydrogen to 200 psig pressure. The temperature on the control panel was set to 250 °C and the heating device was switched on. When the temperature reached to 250 °C the agitator was started which was set to 240 rpm. The time count was started at this point. Heat and agitation were stopped at the end of the specified reaction time and the reactor left overnight. Next day, the hydrogen gas was carefully vented and the vessel purged with nitrogen. The contents of the reactor were filtered under suction, the precipitate washed with distilled water and dried at 75 °C under vacuum (2-3 mm) for 2 hours. The dried solid was subjected to estimation of 4-carboxybenzaldehyde. EXAMPLE 6t The example illustrates hydrogenation of crude terephthalic acid containing 3200 ppm of 4-carboxybenzaldehyde, obtained from a commercial plant, using 0.5% Pd/C as catalyst. Crude terephthalic acid containing 3200 ppm of 4-carboxybenzaldehyde (3 g), distilled water (40 ml), and 0.5% Pd/C catalyst . (24 mg) were charged to the Parr reactor of 100 ml capacity. The reactor was assembled and purged with high purity nitrogen gas by five pressurizing (20-30 psig)-depressurizing cycles followed by similar purging with hydrogen gas. The autoclave was filled with hydrogen to 200 psig pressure. The temperature on the control panel was set to 250 °C and the heating device was switched on. When the temperature reached to 250 °C the agitator was started which was set to 240 rpm. The time count was started at this point. At the end of the specified reaction time heating and agitation were stopped and the reactor left overnight. Next day, the hydrogen gas was carefully vented and the vessel purged with nitrogen. The contents of the reactor were filtered under suction, the precipitate washed with distilled water and dried at 75 °C under vacuum (2-3 mm) for 2 hours. The dried solid was subjected to estimation of 4-carboxybenzaldehyde. EXPERIMENTAL DATA The estimation of 4-carboxybenzaldehyde in the experimental samples of the purified terephthalic acid were done with the help of a polarographic analysis. Voltametric technique in differential polarizing mode on a mercury graphite electrode was used in accordance with an analytical signal with a maxima at the potential of-1.07 v proportional to 4-carboxybenzaldehyde in terephthalic acid. Table 1 shows comparison of catalytic activity of 0.15% Palladium (Pd) & Carbon nanotubes (CNT) catalyst composition with that of a commercial 0.5% Pd & activated carbon (C) catalyst for the hydrogenation of 4-carboxybenzaldehyde present in terephthalic acid. 24 mg of the commercial 0.5 % Pd/C catalyst was used in these experiments in order to get conversions of 4-carboxybenzaldehyde comparable to that using 6 mg of the 0.15% Pd/CNT catalyst composition. TABLE 1: Comparison of the catalyst activity of 0.15 % Pd/CNT and 0.5 Pd/C Experiment No. Catalyst, (mg) Reaction Time (h) Feed Reduction of4-CBA (%) Catalyst Activity 1 0.15% Pd/CNT (6) 0.25 A 64 757 2 0.15% Pd/CNT (6) 1 A 75 844 3 0.15% Pd/CNT (6) 3 A 91 1076 4 0.15% Pd/CNT (6) 6 A 92 1088 5 0.5% Pd/C (24) 3 A 83 70 6 0.15% Pd/CNT (6) .3 B 81 610 7 0.5% Pd/C (24) 3 B 88 51 Feed A = 3 gm of pure terephthalic acid and 15 mg (4975 ppm) of 4- carboxybenzaldehyde; and Feed B = 3 gm of crude terephthalic acid containing 3200 ppm of 4- carboxybenzaldehyde. * Catalyst activity is moles of 4-carboxybenzaldehyde reduced per mole of palladium. Reaction conditions for the experiments: Deionized water 40 ml, Autoclave temperature 250 °C, Hydrogen pressure 200 psig, Agitation speed 240 rpm. The experiments 1 to 5 in Table 1 relate to hydrogenation of 4-carboxybenzaldehyde (about 5000 ppm) present in pure terephthalic acid. The experiments 1 to 4 show the effect of variation of the reaction time on the activity of the 0.15% Pd/CNT catalyst composition for the reduction of 4-carboxybenzaldehyde under the set of aforementioned reaction conditions. Increasing the reaction time from 0.25 hour to 3 hours led to significant increase in the reduction of 4-carboxybenzaldehyde (experiments 1 to 3 in Table 1). However, further increase in the time (up to 6 hours), as seen in the experiment no. 4 in Table 1, had very little effect on the conversion of 4-carboxybenzaldehyde. Thus, the reduction of 4-carboxybenzaldehyde has practically reached the maximum in 3 hours with catalyst activity reaching to 1076 in experiment no. 3. Comparison of the activity of 0.15% Pd/CNT catalyst composition and 0.5% Pd/C catalyst over a period of 3 hours (experiments no. 3 and 5) shows that the Pd/CNT catalyst exhibits 15.4 times higher activity than the Pd/C. The activities of these catalysts were also compared for the hydrogenation of crude terephthalic acid from a commercial plant which has 3200 ppm of 4-carboxybenzaldehyde (experiments no. 6 and 7). Crude terephthalic acid from a commercial plant contains several reducible impurities in addition to 4-carboxybenzaldehyde and testing of the hydropurification catalyst using crude terephthalic acid represents conditions closer to the commercial plant operation. The results for the experiments no. 6 and 7 show that 0.15% Pd/CNT catalyst composition shows 12 times higher catalyst activity for the reduction of 4-carboxybenzaldehyde than the commercial 0.5% Pd/C catalyst. TECHNICAL ADVANCEMENTS A catalyst composition for hydropurification of crude terephthalic acid and a method thereof, in accordance with the present invention has several technical advantages including but not limited to the realization of: • distributing the Group VIII noble metal in the mesopores of the carrier material to provide easy accessibility to the reactants during the hydropurification of crude terephthalic acid; • the carrier material, typically, multi-walled carbon nanotubes has a high BET surface area of 200 - 400 m /g and pore volume of 1 - 2.5 cm /g; • the noble metal, typically palladium, is in the form of nanoparticles to provide high catalytic performance; • higher catalytic activity in hydrogenation of 4-carboxybenzaldehyde to P-toluic acid; • the carrier material exhibits outstanding physical, chemical, and mechanical properties such as lightweight, excellent electrical and thermal conductivity, and high tensile strength; and • minimal metal is lost due to attrition because of high tensile strength of the carrier material, thus, the catalyst composition has a long life. 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 invention, unless there is a statement in the specification specific to the contrary. In view of the wide variety of embodiments to which the principles of the present invention can be applied, it should be understood that the illustrated embodiments are exemplary only. While considerable emphasis has been placed herein on the particular features of this invention, 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 principle of the invention. These and other modifications in the nature of the invention 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 invention and not as a limitation. We Claim: 1. A catalyst composition for hydropurification of crude terephthalic acid, said catalyst composition comprising: • a carrier material having a porous absorptive surface with a BET surface area of 200 to 400 m /g and a pore volume of 1 to 2.5 cm3/g; and • a Group VIII noble metal impregnated in the mesopores of the carrier material, wherein the Group VIII noble metal is in the form of nanoparticles with particle size in the range of 10-20 nm. 2. The catalyst composition as claimed in claim 1, wherein the carrier material is selected from the group consisting of single-walled carbon nanotubes, multi-walled carbon nanotubes, rope carbon nanotubes, and the like. 3. The catalyst composition as claimed in claim 1, wherein the carrier material is multi-walled carbon nanotubes having 3-15 walls. 4. The catalyst composition as claimed in claim 1, wherein the Group VIII noble metal is palladium. 5. The catalyst composition as claimed in claim 4, wherein the multi-walled carbon nanotubes have an outer diameter of 13 - 16 nm and an inner diameter of 2 - 5 nm. 6. The catalyst composition as claimed in claim 4, wherein the multi-walled carbon nanotubes support has a length of 1 - 10 μrn. 7. The catalyst composition as claimed in claim 1, wherein the carrier material is fiinctionalized by nitric acid before impregnating the noble metal thereon. 8. The catalyst composition as claimed in claim 1, wherein the catalyst composition contains 0.01 ~5% (by weight) of the noble metal. 9. The catalyst composition as claimed in claim 1, wherein the BET surface area of the carrier material is in the range of 320 - 360 m2/g. 10.The catalyst composition as claimed in any of the above claims, wherein the BET surface area of the fiinctionalized carrier material is in the range of 370 - 430 m2/g. 11.The catalyst composition as claimed in any of the above claims, wherein the BET surface area of the metal impregnated functionalized carrier material is in the range of 260 - 290 m2/g. 12.The catalyst composition as claimed in claim I, wherein the carrier material is in the form of spheres, pills, cakes, extrudates, powders, granules, and the like. 13.The catalyst composition as claimed in any of the above claims, wherein the metal impregnated functionalized carrier material is treated with 5-10 equivalents of sodium borohydride. 14. A process for providing a catalyst composition for hydropurification of crude terephthalic acid, said method comprising the following steps: (i) functionalizing a carrier material having a porous absorptive surface with nitric acid by magnetically stirring at a temperature of 100 - 180 °C for 6-24 hours to provide a suspension containing functionalized carrier material; (ii) cooling the suspension to a temperature in the range of 25 - 35 °C to provide a cooled suspension; (iii) centrifuging the cooled suspension for 15 - 45 minutes and separating the functionalized carrier material; (iv) washing the functionalized carrier material with deionized water and tetrahydrofuran; (v) drying the functionalized carrier material at 75 - 150 °C for 1 - 6 hours to provide dry functionalized carrier material; (vi) dissolving a Group VIII noble metal compound in deionized water to prepare a solution; (vii) pouring the solution on the dry functionalized carrier material to obtain a blend and magnetically stirring the blend for 1 - 5 hours; (viii) distributing nanosized particles of the noble metal compound in the mesopores of the functionalized carrier material; (ix) filtering the blend to separate metal compound impregnated functionalized carrier material; (x) washing the metal compound impregnated functionalized carrier material with deionized water and ethanol; (xi) drying the metal compound impregnated functionalized carrier material at a temperature of 40 - 60 °C for 6 - 10 hours to provide dried metal compound impregnated functionalized carrier material; (xii) treating the dried metal compound impregnated functionalized carrier material with 5-10 equivalents of sodium borohydride and magnetically stirring for 15 - 45 minutes to provide a reduced catalyst composition; (xiii) filtering the reduced catalyst composition and washing it with deionized water and dry ethanol to obtain a purified catalyst composition; and (xiv) drying the purified catalyst composition at 100 - 150 °C under vacuum for 6 - 10 hours to provide the catalyst composition. 15.A process for hydropurification of crude terephthalic acid using a catalyst composition, said process comprising the following steps: (i) charging a reaction mixture comprising terephthalic acid having 2000 - 6000 ppm of 4-carboxybenzaldehyde, deionized water, and the catalyst composition in an autoclave; (ii) purging the autoclave first with nitrogen gas and then with hydrogen gas; (iii) filling the autoclave with hydrogen gas to 100 - 200 psig pressure; (iv) heating the hydrogen gas filled autoclave to a temperature of 150-300 °C; (v) agitating the autoclave for a predetermined duration of the reaction time; (vi) stopping the agitator and cooling the autoclave while allowing the reaction mixture to stand in the autoclave for 8 - 16 hours; (vii) venting the hydrogen gas from the autoclave and purging the autoclave with nitrogen gas; (viii) discharging the reaction mixture from the autoclave and filtering the reaction mixture under suction to provide a precipitate; and (ix) drying a deionized water washed precipitate under vacuum at a temperature of 60 - 85 °C for 1 - 5 hours, to obtain purified terephthalic acid.

Full Text

FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
THE PATENTS RULES, 2006
COMPLETE
Specification
(See Section 10 and Rule 13)
A CATALYST COMPOSITION FOR HYDROPURIFICATION OF CRUDE TEREPHTHALIC ACID AND A METHOD THEREOF
RELIANCE INDUSTRIES LIMITED
an Indian Company
of Reliance Technology Group,
Building No. 7, B Wing, Ground Floor
Reliance Corporate Park, Thane-Belapur Road,
Ghansoli, Navi - Mumbai: 400 701,
Maharashtra, India.
The following specification particularly describes the invention and the manner in which it
is to be performed.

FIELD OF THE INVENTION
The present invention relates to the field of catalysts for purification of crude terephthalic acid and a method thereof
DEFINITIONS
As used in the present specification, the following words and phrases are generally intended to have the meanings as set forth below, except to the extent that the context in which they are used indicates otherwise.
The term "catalyst activity" is defined as a measure of the catalyst's ability to convert 4-carboxybenzaldehyde at a specified set of reaction parameters, viz. temperature, pressure, reaction time, and reactant feed composition. Catalyst activity is expressed as moles of 4-carboxybenzaldehyde reduced per mole of noble metal in the catalyst.
The term "porous absorptive surface" is defined as a surface having pores being able to absorb a fluid or solid media thereon.
The term "mesopores" are defined as pores having a diameter between 2-50 nm.
The term "pore volume" is defined as the ratio of a porous material's air volume to a porous material's total volume.

The term "functionalization" is defined as creation of chemical functional
groups on the surface of a carrier material for chemically modifying the
surface of the carrier material. The chemical functional groups on a carrier
material help bind metal onto the surface of the carrier material.
The term "BET surface area" is defined as Brunauer, Emmett, and Teller
surface area, using the BET analysis to obtain the surface area of a solid by
physical adsorption of gas molecules:
The total surface area (SBET,totai), units m2/g, and the specific surface area
(SBET), units m2/g, is evaluated using the following equations:

Where,
N : Avogadro's Number
s : adsorption cross section, unit nm2;
V: molar volume of adsorbent gas, unit m3/mol;
a : molar mass of adsorbed species, unit g/mol;
vm : monolayer adsorbed gas quantity;

Where,
A : Value of Slope
I: y-intercept of the line

The term "functionalized carrier material" is defined as a carrier material having oxygen-containing groups (C02 and CO) formed on the surface. Functionalized carrier material shows hydrophilic behavior which has higher specific surface area than the carrier material. Repulsion forces are generated on the surface which help in debundling the carrier material, and provide enhanced interaction of the carrier material with organic solvents.
The term "magnetic stirring" is defined as stirring by using magnetic stirrers which employ a rotating magnetic field to cause a stir bar immersed in a liquid to spin. The rotating magnetic field can be created by a rotating bar magnet or a set of stationary electromagnets placed beneath the vessel with the liquid.
BACKGROUND OF THE INVENTION & PRIOR ART
Terephthalic acid is an important chemical used as a raw material in the production of poly (ethylene terephthalate) which is used in the manufacture of polyester fiber, films, and resins for bottles and containers.
Liquid phase oxidation of alkyl aromatic compound gives carboxylic acid which contains a variety of impurities e.g. oxidation of 1,4-dimethylbenzene gives terephthalic acid with substantial amount of 4- carboxybenzaldehyde as an impurity which is only tolerated up to 20 ppm in the terephthalic acid product. The 4-carboxybenzaldehyde present in the terephthalic acid is known to cause chain termination in the polyester synthesis and also leads to undesirable coloration of the polymer. Catalytic hydrogenation is an

important process in the purification of crude terephthalic acid. The process for purification of the crude terephthalic acid involves hydrogenation of an aqueous solution of crude terephthalic acid at an elevated temperature to keep it in dissolved state over a bed of catalyst containing a noble metal anchored on a support such as activated carbon.
However, the carbon support used in the conventional catalyst has the following disadvantages. 1) The carbon support undergoes attrition losses resulting in corresponding loss of the noble metal; (2) Most of the noble metal particles anchored on to the granular carbon support remain in the micropores which are difficult to access for an organic compounds such as 4-carboxybenzaldehyde.
Several attempts have been made to provide a catalyst for purification of crude terephthalic acid and a method thereof to overcome the aforementioned drawbacks; some of the related systems are discussed in the following section dealing with the prior art.
The publication in J. Phys. Chem. C, 112 (2008) 13463, discloses the application of carbon nanotubes as support for catalysts in a variety of reactions due to their nanostructure and interesting electrical and mechanical properties. The large specific surface area of the metal particles and the high mechanical strength of carbon nanotubes significantly enhance the activity and life of the catalysts.

US Patent No. 4415479 discloses a catalyst for purification of crude terephthalic acid which reduces the 4-carboxybenzaldehyde content to less than 100 ppm. The catalyst is prepared by contacting an aqueous solution of palladium amine complex with a porous carbonaceous material such as granular coconut shell carbon.
US Patent No. 4421676 discloses preparation of palladium on carbon catalyst by contacting an aqueous solution of sodium tetranitritopalladate with a porous carbonaceous support such a granular coconut shell carbon. Hydrogenation of an aqueous solution of crude terephthalic acid in the presence of the catalyst reduced the 4-carboxybenzaldehyde content to less than 100 ppm.
US Patent No. 4476242 discloses a catalyst preparation by supporting palladium on porous activated carbonaceous material such as coconut shell charcoal wherein the palladium crystallites are predominantly less than 3 5A. The catalyst is prepared by depositing palladium on the carbon support from a solution of palladium salt in an organic solvent in the absence of hydrogen. Hydrogenation in the presence of this catalyst reduced the 4-carboxybenzaldehyde concentration in the crude terephthalic acid to less than 100 ppm.

US Patent No. 4317923 discloses rhenium deposited on carbon as a catalyst for purification of crude aromatic dicarboxylic acids such as those obtained by oxidation of 1,4-dimethylbenzene. Treatment of the crude dicarboxylic acids containing 4-carboxybenzaldehyde as impurity under nitrogen atmosphere results into decarbonylation of the aldehyde functionality and thus converting the 4-carboxybenzaldehyde to benzoic acid which is easily removed during recrystallization process.
EP Patent No. 219288 discloses preparation of catalyst comprising rhodium supported on granular carbon and its application to purification of crude terephthalic acid. The catalyst reduces the impurities such as 4-carboxybenzaldehyde and exhibits reduced rate of decomposition of terephthalic acid as compared to the commercially available rhodium catalyst.
US Patent No. 4629715 discloses a process for purification of crude terephthalic acid that uses two different catalyst beds in the hydrogenation reactor to give high purity terephthalic acid product. The top bed of primary catalyst comprises of palladium on active carbon which catalyzes hydrogenation of 4-carboxybenzaldehyde to /?-toluic acid. The secondary catalyst bed located downstream of the first bed comprises of rhodium supported on carbon catalyst which is believed to affect decarbonylation of the remainder of the 4-carboxybenzaldehyde to give benzoic acid.
EP Patent No. 222500 discloses purification of crude terephthalic acid by hydrogenation of its aqueous solution in a catalyst bed containing two layers

of catalysts. The first layer of the catalyst comprises of Group VIII metal such as rhodium supported on active carbon support. The second catalyst layer comprises of palladium supported on active carbon. The feed enters the first catalyst layer and then contacts the second layer. The carbon monoxide generated in the reactor due to decarbonylation of 4-carboxybenzaldehyde is a poison to the catalyst. In this process the carbon monoxide is reduced by Fischer-Tropsch type reaction to give hydrocarbons such as methane.
US Patent No. 4394299 discloses a bimetallic catalyst for purification of crude terephthalic acid which reduces concentration of 4-carboxybenzaldehyde from 10,000 ppm to less than 100 ppm. The catalyst is prepared by fast absorbing palladium on a porous carbonaceous support such as granular coconut charcoal from a solution of palladium salt formed by reaction with amine and acetic acid followed by deposition of rhodium form an aqueous solution of sodium hexanitritorhodate.
GB Patent No. 2018252 discloses a process for purification of crude terephthalic acid containing organic impurities such as 4-carboxybenzaldehyde by hydrogenation over a catalyst made from the alloy of palladium and ruthenium in the form of a membrane. The aqueous solution of impure terephthalic acid is contacted with the membrane catalyst at a temperature high enough to keep the terephthalic acid in aqueous solution. The catalyst is claimed to be stable under the condition of hydrogenation and its use eliminates hot filtration of the solution underpressure.

WO 2006/071407A1 describes a process for purification of impure aromatic dicarboxylic acid product by catalytic hydrogenation using a stable catalyst prepared by depositing a noble metal such as palladium on high surface area silicon carbide support. The abrasion and attrition resistant support provides catalyst with longer life time, improved process stability and reduced presence of catalyst particles in the product as compared to the processes using carbon-supported catalysts.
Therefore, there is felt a need to provide a catalyst for purification of crude terephthalic acid and a method thereof which exhibits better catalytic properties, provides higher surface area, the metal particles in the catalyst are easily accessible to the reactants, minimizes impurities in the terephthahc acid, and has a long life, as compared to the existing catalysts and methods discussed in the prior art.
OBJECTS OF THE INVENTION
An object of the present invention is to provide a catalyst composition for hydropurification of crude terephthalic acid.
Another object of the present invention is to provide a catalyst composition for hydrogenation of 4-carboxybenzaldehyde in the crude terephthalic acid.
Still another object of the present invention is to provide a catalyst composition for hydropurification of crude terephthalic acid having a high catalytic performance.

Yet another object of the present invention is to provide a catalyst composition for hydropurification of crude terephthalic acid having a large external surface area for enhancing exposure to the reactants.
One more object of the present invention is to devise a catalyst composition for hydropurification of crude terephthalic acid which provides optimum efficiency.
Still one more object of the present invention is to provide a catalyst composition in which the carrier material has a high mechanical strength and minimum catalyst is lost due to attrition, thus, the catalyst composition has a long life.
Yet one more object of the present invention is to provide a method for making a catalyst for hydropurification of crude terephthalic acid.
An additional object of the present invention is to provide a method for making terephthalic acid.
SUMMARY OF THE INVENTION
In accordance with the present invention, a catalyst composition is provided for hydropurification of crude terephthalic acid, said catalyst composition comprising:
• a carrier material having a porous absorptive surface with a BET
surface area of 200 to 400 m2/g and a pore volume of 1 to 2.5
cm3/g; and

• a Group VIII noble metal impregnated in the mesopores of the carrier material, wherein the Group VIII noble metal is in the form of nanoparticles with particle size in the range of 10-20 nm.
Typically, in accordance with the present invention, the carrier material is selected from the group consisting of single-walled carbon nanotubes, multi-walled carbon nanotubes, rope carbon nanotubes, and the like.
Additionally, in accordance with the present invention, the carrier material is a multi-walled carbon nanotubes having 3-15 walls.
Preferably, in accordance with the present invention, the Group VIII noble metal is palladium.
Preferably, in accordance with the present invention, the multi-walled carbon nanotubes have an outer diameter of 13 - 16 nm, an inner diameter of 2 - 5 nm and a length of 1 - 10 μm.
Typically, in accordance with the present invention, the carrier material is functionalized by nitric acid before impregnating the noble metal thereon.
Additionally, in accordance with the present invention, the catalyst composition contains 0.01 - 5 % (by weight) of the noble metal.

In accordance with the present invention, the BET surface area of the carrier material is in the range
Additionally, in accordance with the present invention, the BET surface area of the functionalized carrier material is in the range of 370 - 430 m /g.
Preferably, in accordance with the present invention, the BET surface area of the metal impregnated functionalized carrier material is in the range of 260 -290 m2/g.
In accordance with the present invention, the carrier material is in the form of spheres, pills, cakes, extrudates, powders, granules, and the like.
Typically, in accordance with the present invention, the metal impregnated functionalized carrier material is treated with 5-10 equivalents of sodium borohydride.
In accordance with the present invention, a process is disclosed for providing a catalyst composition for hydropurification of crude terephthalic acid, said process comprising the following steps:
(i) functionalizing a carrier material having a porous absorptive
surface with nitric acid by magnetically stirring at a temperature of 100 - 180 °C for 6-24 hours to provide a suspension containing functionalized carrier material;

(ii) cooling the suspension to a temperature in the range of 25 - 35
°C to provide a cooled suspension; (iii) centrifuging the cooled suspension for 15 - 45 minutes and
separating the functionalized carrier material; (iv) washing the functionalized carrier material with deionized water
and tetrahydrofuran; (v) drying the functionalized carrier material at 75 - 150 °C for 1 - 6
hours to provide dry functionalized carrier material; (vi) dissolving a Group VIII noble metal compound in deionized
water to prepare a solution; (vii) pouring the solution on the dry functionalized carrier material to
obtain a blend and magnetically stirring the blend for 1 - 5
hours; (viii) distributing nanosized particles of the noble metal compound in
the mesopores of the functionalized carrier material; (ix) filtering the blend to separate metal compound impregnated
functionalized carrier material; (x) washing the metal compound impregnated functionalized carrier
material with deionized water and ethanol; (xi) drying the metal compound impregnated functionalized carrier
material at a temperature of 40 - 60 °C for 6 - 10 hours to
provide dried metal compound impregnated functionalized
carrier material; (xii) treating the dried metal compound impregnated functionalized
carrier material with 5-10 equivalents of sodium borohydride

and magnetically stirring for 15 - 45 minutes to provide a
reduced catalyst composition; (xiii) filtering the reduced catalyst composition and washing it with
deionized water and dry ethanol to obtain a purified catalyst
composition; and (xiv) drying the purified catalyst composition at 100 - 150 °C under
vacuum for 6 - 10 hours to provide the catalyst composition.
In accordance with the present invention, a process is disclosed for hydropurification of crude terephthalic acid using a catalyst composition, said process comprising the following steps:
(i) charging a reaction mixture comprising terephthalic acid having
2000 - 6000 ppm of 4-carboxybenzaldehyde, deionized water,
and the catalyst composition in an autoclave; (ii) purging the autoclave first with nitrogen gas and then with
hydrogen gas; (iii) filling the autoclave with hydrogen gas to 100 - 200 psig
pressure; (iv) heating the hydrogen gas filled autoclave to a temperature of 150
-300°C; (v) agitating the autoclave for a predetermined duration of the
reaction time; (vi) stopping the agitator and cooling the autoclave while allowing
the reaction mixture to stand in the autoclave for 8 - 16 hours;

(vii) venting the hydrogen gas from the autoclave and purging the
autoclave with nitrogen gas; (viii) discharging the reaction mixture from the autoclave and filtering
the reaction mixture under suction to provide a precipitate; and (ix) drying a deionized water washed precipitate under vacuum at a
temperature of 60 - 85 °C for 1 - 5 hours, to obtain purified
terephthalic acid.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The invention will now be described with the help of the accompanying drawing, in which,
FIGURE 1 illustrates the Transmission Electron Micrograph image of Pd nanoparticles (black spot) in the range of 10-20 nm supported on multi-walled carbon nanotubes (MWCNT).
DETAILED DESCRIPTION OF THE INVENTION
The present invention envisages a catalyst composition comprising a carrier material having a porous absorptive surface with a high surface area and a Group VIII noble metal impregnated thereon and application of the catalyst composition for purification of crude terephthalic acid, specifically for hydrogenation of 4-carboxybenzaldehyde, to obtain pure terephthalic acid of the grade suitable as a co-monomer for the manufacturing of poly(ethylene terephthalate) used in fiber, films, bottles, and containers. The high catalytic performance of the catalyst composition of the present invention is attributed

to the high external surface area of the carrier material, typically, carbon nanotubes, compared to that of the conventional activated carbon support wherein a large part of the surface area is micropores which are not easily accessible to the reactants, especially in the liquid phase where high diffusional limitations are predominant. The catalytic properties of the catalyst composition are further enhanced due to the phase of the noble metal on the carrier material and the mesoporous property of the carrier material. Also, when the carrier material is a carbon nanotubes, nanosized particles of the noble metal are impregnated thereon, which further enhances the catalytic properties of the catalyst composition. The efficiency of the catalyst composition in the aforementioned condition is higher than when the carrier material is activated carbon in which the metal particles are much bigger. Typically, in accordance with the present invention, palladium is supported on multi-walled carbon nanotubes, which showed higher catalytic activity compared to the commercially available 0.5% palladium supported on activated carbon, under conditions similar to the plant operations. Further, carbon nanotubes posses outstanding physical, chemical and mechanical properties like lightweight, thermal and electrical conductivity, and high tensile strength, thus, the catalyst composition in accordance with the present invention has a longer life compared to the commercially available catalysts used for purifying crude terephthalic acid.
The catalyst composition in accordance with the present invention is used for hydropurification of crude terephthalic acid, wherein the catalyst composition comprises a carrier material having a porous absorptive surface with a high

BET surface area of 200 to 400 m /g and a pore volume of 1 to 2.5 cm /g and a Group VIII noble metal, preferably palladium in the form of nanoparticles, impregnated in the mesopores of the carrier material. Transmission electron micrograph of the catalyst shows palladium particles of particle size in the range of 10-20 nm supported on multi-walled carbon nanotubes (refer Figure 1). The porous carrier material is typically selected from single-walled carbon nanotubes, multi-walled carbon nanotubes, rope carbon nanotubes. Typically, carbon nanotubes are used, wherein, a multi-walled carbon nanotubes having 3-15 walls are preferred. The carbon nanotubes exhibit outstanding physical, chemical and mechanical properties such as lightweight, excellent thermal and electrical conductivity, and high tensile strength; thus, minimizing losses of the catalyst due to attrition. Further, the carbon nanotubes keep the metal particles predominantly anchored in the mesopores, thus, increasing the accessible surface area of the metal particles. The preferred carrier material can be prepared in any suitable manner from synthetic or naturally occurring raw material. Further, the carrier material can be formed in any desired shape such as spheres, pills, cakes, extrudates, powders, granules, and the like; and the carrier material can be utilized in any particle size. Preferably, the multi-walled carbon nanotubes chosen as the carrier material has an outer diameter of 13 - 16 nm and an inner diameter of 2 - 5 nm and a length of 1 - 10 μm. The carrier material is functionalized with nitric acid before impregnating the noble metal thereon.
The carrier material is functionalized by nitric acid by magnetically stirring at a temperature of 100 - 180 °C for 6-24 hours. A concoction containing the

fimctionalized carrier material is obtained which is cooled to a temperature of 25 - 35 °C and centrifuged for 15 - 45 minutes to conveniently separate the functionalized carrier material which is subsequently washed with deionized water and small portions of tetrahydrofuran (THF) and dried at a temperature of 75-150 °C for 1 - 6 hours, to obtain the usable functionalized carrier material. The noble metal compound is deposited on the functionalized carrier material.
The final catalyst composition consists 0.01 to 5 % (by weight) of the noble metal, preferably, 0.1 - 0.5 % (by weight) of noble metal is provided in the catalyst composition. The noble metal, preferably palladium, in the active state of the catalyst composition is present substantially in the elemental state with or without chemical interaction with the carrier material, depending upon the method of preparation. Nanosized particles of the noble metal are desirably distributed in the mesopores of the functionalized carrier material to impart enhanced intrinsic properties to the catalyst composition. Typically, palladium is used as the active metal component, wherein, palladium chloride (PdCb) is preferred as the palladium precursor. The metal compound is dissolved in deionized water to obtain a solution which is poured on the functionalized carrier material to obtain a blend. The blend is magnetically stirred for 1 - 5 hours allowing the metal compound from the solution to deposit on the functionalized carrier material. Finally, the blend is filtered and the metal compound impregnated functionalized carrier material, thus obtained, is washed with deionized water and ethanol and dried at a temperature of 40 - 60 °C for 6 - 10 hours to obtain dried metal compound

impregnated functionalized carrier material. The dried metal compound impregnated functionalized carrier material, thus obtained, is reduced by treating with a reducing agent, preferably 5-10 equivalents of sodium borohydride (NaBH4), and magnetically stirring the reactants for 15 - 45 minutes to provide a reduced catalyst composition. The reduced catalyst composition is filtered, washed with deionized water and dry ethanol to obtain a purified catalyst composition which is dried at 100 - 150 °C under vacuum for 6 - 10 hours to provide the catalyst composition in accordance with the present invention.
The surface area of the carrier material increased after fiinctionalization and decreased after noble metal impregnation. Experimental results for the BET surface area showed that carbon nanotubes in accordance with the present invention have a BET surface area in the range of 320 - 360 m7g, while functionalized carbon nanotubes have a BET surface area in the range of 370 - 430 m2/g, and the palladium impregnated functionalized carbon nanotubes have a BET surface area of 260 - 290 m /g. The surface area of the carbon nanotubes is mainly due to the external surface and the space between the graphene layers is too small to allow access to the metal particles. On the other hand, activated carbon has considerable inner pore volume which is accessible to the metal particles.
The catalyst composition of the present invention is used for hydropurification of crude terephthalic acid containing considerably high concentration of 4-carboxybenzaldehyde, to provide purified terephthalic acid having substantially reduced levels of 4-carboxybenzaldehyde. The process

for hydropurification of crude terephthalic acid in accordance to the present invention comprises charging crude terephthalic acid containing 2000 to 6000 ppm of 4-carboxybenzaIdehyde, deionized water, and appropriate quantity of the catalyst composition in an autoclave, typically a Parr reactor. The autoclave is purged first with nitrogen gas and then with hydrogen gas, to remove impurities in the autoclave. Further, the autoclave is filled with hydrogen gas to 100 - 200 psig pressure. The reactions were continued at a specified temperature and for a predetermined time. Primarily, the autoclave was heated to a temperature in the range of 150 - 300 °C and once heated the agitator was started to initiate and continue the reaction. Once the reaction time was completed, the agitator was stopped and the heating device was switched off. The autoclave was allowed to cool while the reaction mixture was made to stand for 8 - 16 hours. The hydrogen gas from the autoclave was vented and the autoclave was purged with nitrogen gas. The reaction mixture was discharged from the autoclave and filtered under suction to provide a precipitate. The precipitate was washed with deionized water and dried under vacuum at a temperature of 60 - 85 °C for 1 - 5 hours, to obtain the purified terephthalic acid in accordance with the present invention.
EXAMPLES
The invention will now be described with reference to the following examples to further exemplify the process of the invention; these examples do not limit the scope and ambit of the invention.

EXAMPLE 1:
The example illustrates functionalization of carbon nanotubes. 450 mg of the multi-walled CNTs and 45 ml of 3M nitric acid were placed in a 100 ml round bottom flask fitted with a reflux condenser. The contents of the flask were magnetically stirred at 100 °C for 24 h. The mixture was cooled to room temperature and centrifuged on an ultra centrifuge for 30 min. The material was washed with distilled water and twice with small quantity of THF. The functionalized carbon nanotubes thus obtained were dried at 100 °C for 4 hours.
EXAMPLE 2:
The example demonstrates preparation of the palladium supported carbon nanotubes. A wet impregnation method was used for the preparation of palladium on multi-walled carbon nanotubes (Pd/CNTs) catalyst composition. PdCl2 (17,5 mg) was dissolved in 50 ml of distilled water and 9.5 ml of the solution was added to 100 mg of the functionalized multi-walled carbon nanotubes. The mixture was magnetically stirred at room temperature for 4 hours. The solids were filtered, washed thoroughly with distilled water followed by three small portions of ethanol and dried at 45 °C for 8 hours. The palladium impregnated functionalized nanotubes were magnetically stirred with 1 ml of 0.25 M aqueous NaBH4 (10 equivalents) for 30 min. The solution was filtered and washed with 100 ml of distilled water, followed by small amount of dry ethanol and dried at 110 °C under vacuum (1-2 mm) for 8 hours. ICP analysis showed that the palladium content of the CNT catalyst composition was 0.15% w/w.

EXAMPLE 3:
The example describes hydrogenation of 4- carboxybenzaldehyde mixed with pure terephthalic acid using the Pd/CNT as catalyst. Pure terephthalic acid (3 g), 4-carboxybenzaldehyde (15 mg), distilled water (40 ml), and 0.15% Pd/CNT catalyst (6 mg) were charged to the Parr reactor of 100 ml capacity. The reactor was assembled and purged with high purity nitrogen gas by five pressurizing (20-30 psig) -depressurizing cycles followed by similar purging with hydrogen gas. The autoclave was filled with hydrogen to 200 psig pressure. The temperature on the control panel was set to 250 °C and the heating device was switched on. When the temperature reached to 250 °C the agitator was started which was set to 240 rpm. The time count was started at this point. Heat and agitation were stopped at the end of the specified reaction time and the reactor left overnight. Next day, the hydrogen gas was carefully vented and the vessel purged with nitrogen. The contents of the reactor were filtered under suction, the precipitate washed with distilled water and dried at 75 °C under vacuum (2-3 mm) for 2 hours. The dried solid was subjected to estimation of 4-carboxybenzaldehyde.
EXAMPLE 4:
The example demonstrates hydrogenation of 4-carboxybenzaldehyde mixed with pure terephthalic acid using 0.5% palladium on activated carbon (Pd/C) as catalyst. Pure terephthalic acid (3 g), 4-carboxybenzaldehyde (15 mg), distilled water (40 ml) and 0.5% Pd/C catalyst (24 mg) were charged to the Parr reactor of 100 ml capacity. The reactor was assembled and purged with high purity nitrogen gas by five pressurizing (20-30 psig)-depressurizing cycles followed by similar purging with hydrogen gas. The autoclave was

filled with hydrogen to 200 psig pressure. The temperature on the control panel was set to 250 °C and the heating devices started which was set to 240 rpm. The time count was started was switched on. When the temperature reached to 250 °C the agitator wa at this point. At the end of the specified reaction time heating and agitation were stopped and the reactor left overnight. Next day, the hydrogen gas was carefully vented and the vessel was purged with nitrogen. The contents of the reactor were filtered under suction, the precipitate washed with distilled water and dried at 75 °C under vacuum (2-3 mm) for 2 hours. The dried solid was subjected to estimation of 4-carboxybenzaldehyde.
EXAMPLE 5:
The example describes hydrogenation of crude terephthalic acid containing 3200 ppm of 4-carboxybenzaldehyde, obtained from a commercial plant, using 0.15% Pd/CNT as catalyst. Crude terephthalic acid containing 3200 ppm of 4-carboxybenzaldehyde (3 g), distilled water (40 ml), and 0.15% Pd/CNT catalyst (6 mg) were charged to the Parr reactor of 100 ml capacity. The reactor was assembled and purged with high purity nitrogen gas by five pressurizing (20-30 psig)-depressurizing cycles followed by similar purging with hydrogen gas. The autoclave was filled with hydrogen to 200 psig pressure. The temperature on the control panel was set to 250 °C and the heating device was switched on. When the temperature reached to 250 °C the agitator was started which was set to 240 rpm. The time count was started at this point. Heat and agitation were stopped at the end of the specified reaction time and the reactor left overnight. Next day, the hydrogen gas was carefully

vented and the vessel purged with nitrogen. The contents of the reactor were filtered under suction, the precipitate washed with distilled water and dried at 75 °C under vacuum (2-3 mm) for 2 hours. The dried solid was subjected to estimation of 4-carboxybenzaldehyde.
EXAMPLE 6t
The example illustrates hydrogenation of crude terephthalic acid containing 3200 ppm of 4-carboxybenzaldehyde, obtained from a commercial plant, using 0.5% Pd/C as catalyst. Crude terephthalic acid containing 3200 ppm of 4-carboxybenzaldehyde (3 g), distilled water (40 ml), and 0.5% Pd/C catalyst . (24 mg) were charged to the Parr reactor of 100 ml capacity. The reactor was assembled and purged with high purity nitrogen gas by five pressurizing (20-30 psig)-depressurizing cycles followed by similar purging with hydrogen gas. The autoclave was filled with hydrogen to 200 psig pressure. The temperature on the control panel was set to 250 °C and the heating device was switched on. When the temperature reached to 250 °C the agitator was started which was set to 240 rpm. The time count was started at this point. At the end of the specified reaction time heating and agitation were stopped and the reactor left overnight. Next day, the hydrogen gas was carefully vented and the vessel purged with nitrogen. The contents of the reactor were filtered under suction, the precipitate washed with distilled water and dried at 75 °C under vacuum (2-3 mm) for 2 hours. The dried solid was subjected to estimation of 4-carboxybenzaldehyde.

EXPERIMENTAL DATA
The estimation of 4-carboxybenzaldehyde in the experimental samples of the purified terephthalic acid were done with the help of a polarographic analysis. Voltametric technique in differential polarizing mode on a mercury graphite electrode was used in accordance with an analytical signal with a maxima at the potential of-1.07 v proportional to 4-carboxybenzaldehyde in terephthalic acid.
Table 1 shows comparison of catalytic activity of 0.15% Palladium (Pd) & Carbon nanotubes (CNT) catalyst composition with that of a commercial 0.5% Pd & activated carbon (C) catalyst for the hydrogenation of 4-carboxybenzaldehyde present in terephthalic acid. 24 mg of the commercial 0.5 % Pd/C catalyst was used in these experiments in order to get conversions of 4-carboxybenzaldehyde comparable to that using 6 mg of the 0.15% Pd/CNT catalyst composition.
TABLE 1: Comparison of the catalyst activity of 0.15 % Pd/CNT and 0.5 Pd/C

Experiment
No. Catalyst, (mg) Reaction Time (h) *Feed Reduction of4-CBA
(%) *Catalyst Activity
1 0.15% Pd/CNT (6) 0.25 A 64 757
2 0.15% Pd/CNT (6) 1 A 75 844
3 0.15% Pd/CNT (6) 3 A 91 1076

4 0.15% Pd/CNT (6) 6 A 92 1088
5 0.5% Pd/C (24) 3 A 83 70
6 0.15% Pd/CNT (6) .3 B 81 610
7 0.5% Pd/C (24) 3 B 88 51

*Feed A = 3 gm of pure terephthalic acid and 15 mg (4975 ppm) of 4-
carboxybenzaldehyde; and
*Feed B = 3 gm of crude terephthalic acid containing 3200 ppm of 4-
carboxybenzaldehyde.
* Catalyst activity is moles of 4-carboxybenzaldehyde reduced per mole of
palladium.
Reaction conditions for the experiments: Deionized water 40 ml, Autoclave temperature 250 °C, Hydrogen pressure 200 psig, Agitation speed 240 rpm.
The experiments 1 to 5 in Table 1 relate to hydrogenation of 4-carboxybenzaldehyde (about 5000 ppm) present in pure terephthalic acid. The experiments 1 to 4 show the effect of variation of the reaction time on the activity of the 0.15% Pd/CNT catalyst composition for the reduction of 4-carboxybenzaldehyde under the set of aforementioned reaction conditions.

Increasing the reaction time from 0.25 hour to 3 hours led to significant increase in the reduction of 4-carboxybenzaldehyde (experiments 1 to 3 in Table 1). However, further increase in the time (up to 6 hours), as seen in the experiment no. 4 in Table 1, had very little effect on the conversion of 4-carboxybenzaldehyde. Thus, the reduction of 4-carboxybenzaldehyde has practically reached the maximum in 3 hours with catalyst activity reaching to 1076 in experiment no. 3. Comparison of the activity of 0.15% Pd/CNT catalyst composition and 0.5% Pd/C catalyst over a period of 3 hours (experiments no. 3 and 5) shows that the Pd/CNT catalyst exhibits 15.4 times higher activity than the Pd/C. The activities of these catalysts were also compared for the hydrogenation of crude terephthalic acid from a commercial plant which has 3200 ppm of 4-carboxybenzaldehyde (experiments no. 6 and 7). Crude terephthalic acid from a commercial plant contains several reducible impurities in addition to 4-carboxybenzaldehyde and testing of the hydropurification catalyst using crude terephthalic acid represents conditions closer to the commercial plant operation. The results for the experiments no. 6 and 7 show that 0.15% Pd/CNT catalyst composition shows 12 times higher catalyst activity for the reduction of 4-carboxybenzaldehyde than the commercial 0.5% Pd/C catalyst.
TECHNICAL ADVANCEMENTS
A catalyst composition for hydropurification of crude terephthalic acid and a method thereof, in accordance with the present invention has several technical advantages including but not limited to the realization of:

• distributing the Group VIII noble metal in the mesopores of the carrier material to provide easy accessibility to the reactants during the hydropurification of crude terephthalic acid;
• the carrier material, typically, multi-walled carbon nanotubes has a high BET surface area of 200 - 400 m /g and pore volume of 1 - 2.5 cm /g;
• the noble metal, typically palladium, is in the form of nanoparticles to provide high catalytic performance;
• higher catalytic activity in hydrogenation of 4-carboxybenzaldehyde to P-toluic acid;
• the carrier material exhibits outstanding physical, chemical, and mechanical properties such as lightweight, excellent electrical and thermal conductivity, and high tensile strength; and
• minimal metal is lost due to attrition because of high tensile strength of the carrier material, thus, the catalyst composition has a long life.
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 invention, unless there is a statement in the specification specific to the contrary.
In view of the wide variety of embodiments to which the principles of the present invention can be applied, it should be understood that the illustrated embodiments are exemplary only. While considerable emphasis has been placed herein on the particular features of this invention, 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 principle of the invention. These and other modifications in the nature of the invention 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 invention and not as a limitation.

We Claim:
1. A catalyst composition for hydropurification of crude terephthalic acid,
said catalyst composition comprising:
• a carrier material having a porous absorptive surface with a BET surface area of 200 to 400 m /g and a pore volume of 1 to 2.5 cm3/g; and
• a Group VIII noble metal impregnated in the mesopores of the carrier material, wherein the Group VIII noble metal is in the form of nanoparticles with particle size in the range of 10-20 nm.

2. The catalyst composition as claimed in claim 1, wherein the carrier material is selected from the group consisting of single-walled carbon nanotubes, multi-walled carbon nanotubes, rope carbon nanotubes, and the like.
3. The catalyst composition as claimed in claim 1, wherein the carrier material is multi-walled carbon nanotubes having 3-15 walls.
4. The catalyst composition as claimed in claim 1, wherein the Group VIII noble metal is palladium.
5. The catalyst composition as claimed in claim 4, wherein the multi-walled carbon nanotubes have an outer diameter of 13 - 16 nm and an inner diameter of 2 - 5 nm.

6. The catalyst composition as claimed in claim 4, wherein the multi-walled carbon nanotubes support has a length of 1 - 10 μrn.
7. The catalyst composition as claimed in claim 1, wherein the carrier material is fiinctionalized by nitric acid before impregnating the noble metal thereon.
8. The catalyst composition as claimed in claim 1, wherein the catalyst composition contains 0.01 ~5% (by weight) of the noble metal.
9. The catalyst composition as claimed in claim 1, wherein the BET surface area of the carrier material is in the range of 320 - 360 m2/g.
10.The catalyst composition as claimed in any of the above claims, wherein the BET surface area of the fiinctionalized carrier material is in the range of 370 - 430 m2/g.
11.The catalyst composition as claimed in any of the above claims, wherein the BET surface area of the metal impregnated functionalized carrier material is in the range of 260 - 290 m2/g.
12.The catalyst composition as claimed in claim I, wherein the carrier material is in the form of spheres, pills, cakes, extrudates, powders, granules, and the like.

13.The catalyst composition as claimed in any of the above claims, wherein the metal impregnated functionalized carrier material is treated with 5-10 equivalents of sodium borohydride.
14. A process for providing a catalyst composition for hydropurification of crude terephthalic acid, said method comprising the following steps: (i) functionalizing a carrier material having a porous absorptive
surface with nitric acid by magnetically stirring at a
temperature of 100 - 180 °C for 6-24 hours to provide a
suspension containing functionalized carrier material; (ii) cooling the suspension to a temperature in the range of 25 - 35
°C to provide a cooled suspension; (iii) centrifuging the cooled suspension for 15 - 45 minutes and
separating the functionalized carrier material; (iv) washing the functionalized carrier material with deionized
water and tetrahydrofuran; (v) drying the functionalized carrier material at 75 - 150 °C for 1 -
6 hours to provide dry functionalized carrier material; (vi) dissolving a Group VIII noble metal compound in deionized
water to prepare a solution; (vii) pouring the solution on the dry functionalized carrier material
to obtain a blend and magnetically stirring the blend for 1 - 5
hours; (viii) distributing nanosized particles of the noble metal compound in
the mesopores of the functionalized carrier material;

(ix) filtering the blend to separate metal compound impregnated
functionalized carrier material; (x) washing the metal compound impregnated functionalized
carrier material with deionized water and ethanol; (xi) drying the metal compound impregnated functionalized carrier
material at a temperature of 40 - 60 °C for 6 - 10 hours to
provide dried metal compound impregnated functionalized
carrier material; (xii) treating the dried metal compound impregnated functionalized
carrier material with 5-10 equivalents of sodium borohydride
and magnetically stirring for 15 - 45 minutes to provide a
reduced catalyst composition; (xiii) filtering the reduced catalyst composition and washing it with
deionized water and dry ethanol to obtain a purified catalyst
composition; and (xiv) drying the purified catalyst composition at 100 - 150 °C under
vacuum for 6 - 10 hours to provide the catalyst composition.
15.A process for hydropurification of crude terephthalic acid using a catalyst composition, said process comprising the following steps: (i) charging a reaction mixture comprising terephthalic acid having 2000 - 6000 ppm of 4-carboxybenzaldehyde, deionized water, and the catalyst composition in an autoclave; (ii) purging the autoclave first with nitrogen gas and then with hydrogen gas;

(iii) filling the autoclave with hydrogen gas to 100 - 200 psig
pressure; (iv) heating the hydrogen gas filled autoclave to a temperature of
150-300 °C; (v) agitating the autoclave for a predetermined duration of the
reaction time; (vi) stopping the agitator and cooling the autoclave while allowing
the reaction mixture to stand in the autoclave for 8 - 16 hours; (vii) venting the hydrogen gas from the autoclave and purging the
autoclave with nitrogen gas; (viii) discharging the reaction mixture from the autoclave and
filtering the reaction mixture under suction to provide a
precipitate; and (ix) drying a deionized water washed precipitate under vacuum at a
temperature of 60 - 85 °C for 1 - 5 hours, to obtain purified
terephthalic acid.

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Patent Number

269559

Indian Patent Application Number

2457/MUM/2010

PG Journal Number

44/2015

Publication Date

30-Oct-2015

Grant Date

27-Oct-2015

Date of Filing

03-Sep-2010

Name of Patentee

RELIANCE INDUSTRIES LIMITED

Applicant Address

RELIANCE TECHNOLOGY GROUP. BUILDING NO.7, B WING, GROUND FLOOR, RELIANCE CORPORATE PARK, THANE-BELAPUR ROAD, GHANSOLI, NAVI - MUMBAI: 400 701, MAHARASHTRA, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	GANESHPURE PRALHAD AMBADAS	B-21, KINNARI DUPLEX, ELLORA PARK, VADODARA-390023, GUJARAT, INDIA.
2	LANDE, SHARAD VASUDEORAO	SARASWATI NIWAS, RENUKA NAGAR, DABAKI ROAD, AKOLA - 444002, MAHARASHTRA, INDIA.

PCT International Classification Number

B01J 23/40; B01J 23/44

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA