Description:FIELD OF INVENTION
[0001] The present invention relates to a process for producing an oxygen rich carbon fiber precursor pitch suitable for preparation of carbon fiber.

BACKGROUND
[0002] Carbon fibers possesses a unique combination of properties like low bulk density and high tensile strength and tensile modulus. These properties made carbon fiber, a new age material for the application in many industries like automotive, aerospace, sporting goods, wind turbine.
[0003] Carbon fibers are made from feedstocks that has a high carbon content. These carbonaceous feedstocks are termed as precursor material. Polyacrylonitrile, commonly known as PAN, and pitch derived from either coal tar or petroleum is widely used as precursor for carbon fiber manufacturing. Pitch based carbon fiber precursors must have some key characteristics like high softening point and viscosity, low primary Quinoline insoluble (QI) content and homogeneity. Precursor materials are melt spun above their softening point to produce green fiber. Green fiber is then stabilized by controlled oxidation to make it thermoset and then it is pyrolyzed at high temperature to make carbon fiber.
[0004] Hence, preparation of suitable precursor material from any carbonaceous feedstock is the first crucial step towards carbon fiber manufacturing. Prior art discloses several unique methods of precursor preparation. Based on these methods, precursors can be classified in two categories i.e. anisotropic or mesophase precursor and isotropic precursor. However, any process related to modification of feedstock results in loss of some material in forms of volatile matters. This increases the cost of precursor and the cost of carbon fiber. Therefore, it is desirable to prepare a precursor with high yield to reduce the price of the carbon fiber.
[0005] Prime important characteristic of any precursor is softening point. Prior arts confirm that attempts have been made to increase the softening point of feedstocks at a desired range so that spinning becomes less troublesome. For example, in U.S. Pat. No. 7,318,890, a process is disclosed for increasing the softening point of raw pitch. The said pitch is subjected to heat treatment by direct contact with molten metal. Metal chosen for the purpose was Bismuth, Indium, Gallium etc. Melting point of any combination of two metals are in the range of 118-227 °C. A pitch with 285 °C softening point was obtained by this method. Although raising softening point is important, but it has also been a concern that very high softening point might lead to difficulties in melt spinning.
[0006] One of the most important parameters of the precursor is the primary QI content. Theoretically, primary QI content in the precursor should be zero to avoid breakage of green fiber during spinning. Coal tar exhibits presence of primary QI particles. Attempts have been made to remove primary QI from the pitch. For example, in U.S. Pat. No. 4,482,452, a process for producing coal tar pitch with primary QI content less than 300 ppm is disclosed. Coal tar is mixed with aromatic solvent and polyoxyethylenated surfactant followed by centrifugation. Coal tar pitch is obtained by distillation of the clean tar and solvent is also recovered.
[0007] Once QI free pitch is obtained, it is important to convert the raw pitch into spinnable precursors. Both petroleum pitch and coal tar pitch are considered as good starting material for precursor preparation process. There are various ways to prepare precursors from petroleum pitch. For example, in U.S. Pat. No. 4,460,455, a process is disclosed where spinnable precursor pitch is produced from vacuum residue oil of petroleum feedstock. Oil obtained from vacuum distillation of heavy residue is hydrogenated and is mixed with hydrogenated residue oil. Mixture is catalytically cracked. This catalytically cracked oil is distilled to obtain an oil of 300 °C boiling point. This oil is then treated thermally to get spinnable precursor pitch. Further simplification of precursor preparation is disclosed in U.S. Pat. No. 4,575,411. Where, the vacuum gas oil is at first hydrogenated and distilled to obtain petroleum pitch. This pitch is then subjected to thin film evaporation at 350 °C for 8 minutes under 2 mm Hg vacuum. A precursor with 287 °C softening point and 85 % anisotropic content is obtained by this method. Apart from vacuum residues, naphtha cracked oil derived pitch is also used as an alternative way to produce precursor. In U.S. Pat. No. 4,579,645, naphtha cracked oil derived pitch is mixed with methanol insoluble benzene soluble pitch. Pitch mixture is heated at 430 °C under 10 kg/cm2 pressure to obtain a precursor pitch with 280 °C softening point and 80 % anisotropic content. However, not only the anisotropic pitch, isotropic pitch is also produced from the petroleum feedstock. In U.S. Pat. No. 4,608,150, a heavy residue oil derived pitch is heated up to 420 °C for 30 minutes at 10 mm Hg pressure to produce the isotropic pitch. This isotropic pitch is then heated to 460 °C for 20 minutes under 1 mm Hg vacuum to produce the anisotropic pitch precursor.
[0008] Coal middle distillates or coal tar is also modified through different methods to produce isotropic and mesophase pitch. For example, U.S. Pat. No. 4,448,670, disclosed a method where coal tar pitch with 80 to 100 % toluene insoluble content is heated up to 430 °C and vacuum stripped at 420 °C to obtain a precursor with greater than 80 % anisotropic content. U.S. Pat. No. 4,533,535 and 4,596,652, reported various heat treatment methods for mixture of coal tar pitch and petroleum pitch. In the former, coal tar is mixed with oil produced from catalytic cracking of petroleum residue and is subjected to heat treatment at 370 to 460 °C under 2 to 50 kg/cm2 pressure to produce precursor material. In the later, both coal tar pitch and petroleum pitch is subjected to heat treatment at 400-500 °C while introducing hydrogen donating solvent like tetralin or tetrahydroquinoline in the pitch. Precursor obtained had 50 % QI content and 40 to 100 % anisotropy content. It is not necessary to obtain anisotropic pitch from coal tar pitch to derive carbon fiber. Isotropic pitch is also suitable for producing carbon fiber with high tensile strength.
[0009] Several methods for producing isotropic pitch are described in prior art. For example, U.S. Pat. No. 4,927,620, isotropic pitch with SP of 250 °C is produced by solvent extraction of catalytically heated pitch. In another example, U.S. Pat. No. 9,222,027, described a process in which steam reaction of petroleum pitch is done in a high-speed tubular reactor. Post reaction, the admixture is subjected to flash evaporation in a flash drum under 500 mm Hg pressure. It is claimed in the said art that the softening point of the precursor can be controlled by controlling the flash drum pressure and the steam ratio. To obtain isotropic pitch, it is necessary to remove macromolecules from the raw pitch and treating the pitch in a substantially low temperature in which formation of mesogens is suppressed. Hence, solvent extraction or flash separation have proven to be an effective method. Another method to strip off the volatiles from the raw pitch is described in European patent 0,508,318. Coal tar pitch is subjected to air blowing treatment. Two-step air blowing of coal tar pitch is described in detail. First step consists of air blowing the coal tar pitch at 300-370 °C for 132 hours under atmospheric pressure. Reason for this long treatment of pitch is slow kinetics of the oxygen insertion reaction in the aromatic molecules. After obtaining the desired pitch, it is further air blown at the same temperature range for 10 to 300 minutes of time but under reduced pressure of 100 torr. A complete isotropic pitch with 250 °C softening point is obtained by this method.
[0010] Prior investigations discussed up to this point indicates that preparation of isotropic or anisotropic pitch are two different processes. However, several investigations confirm that both isotropic and anisotropic pitch can be obtained by the same process. Separation and further treatment of the separated pitch is an additional step to produce both type of pitches. For example, European Patent 0,358,048, disclosed a process where coal tar pitch and petroleum pitch are heated up to 400-600 °C under 0.2 to 9.9 MPa pressure. Resultant pitch is extracted with monocyclic aromatic compound Xylene. Xylene insoluble pitch obtained after extraction is hydrogenated at 400-460 °C by using hydrogen donating solvent. This pitch solvent mixture is distilled to recover the solvent and to remove lighter components. Distilled isotropic pitch is then again heat treated to at 350-400 °C to produce the mesophase pitch. On the other hand, Xylene soluble pitch is distilled to remove the solvent and the lighter components and then heat treated at the same temperature to produce the isotropic pitch. In another example, Canadian patent 2,202,525, a method is described where a mixture of Xylene and Heptane in 7:3 ratio is used to extract isotropic pitch. Isotropic pitch was prepared by heating of a clean aromatic feedstock. Heating was done at 200 °C under 76 psi pressure. Extract insoluble part was then dried and heat soaked at 360 °C. Process claimed to produce a mesophase pitch with 330 °C softening point.
[0011] Prior arts described discloses several methods to produce low QI pitch from raw coal tar feedstock. Methods to produce suitable precursors for carbon material development have also mentioned herein. Challenge was to develop methods which can increase softening point of the raw material and can enhance the coking value. In all the prior arts, extraction of selected fractions through various solvents and heat treatment of extracted parts to strip off the light components are focused. Hence, these steps in turn reduces the yield of the precursor from the raw feedstock. To address this challenge, a process is henceforth described where a complete precursor pitch (isotropic pitch) is obtained with a greater yield.

OBJECTIVE OF INVENTION
[0012] It is an object of the invention to solve the aforementioned problems of the prior art and to provide a process of producing an oxygen rich carbon fiber precursor pitch for the production of carbon fibers having improved yield of the precursor from the raw feedstock, heat stability, spinnability and infusibility.
[0013] Another objective of the present invention is to produce an oxygen rich precursor pitch having a higher bond strength compared to the raw coal tar pitch.
[0014] Another object of this invention is to produce a precursor from coal tar pitch with a high softening point which is suitable for melt spinning process.
[0015] It is further object of this invention to produce an isotropic precursor pitch suitable for producing general purpose carbon fiber with yield of about 100 % through a process which involves treatment of coal tar pitch with a radical initiator chemical such as hydrogen peroxide solution.
SUMMARY OF INVENTION
[0016] This summary is provided to introduce concepts related to a process for producing an oxygen rich carbon fiber precursor pitch. The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[0017] In one aspect of the present invention, a process of producing an oxygen rich precursor pitch for carbon fiber is disclosed. The process comprises distilling coal tar at atmospheric pressure to produce coal tar pitch. The process also comprises mixing the said coal tar pitch with a solution having compound comprising peroxy linkage. The process further comprises deagglomerating the mixture of coal tar pitch and the solution having compounds comprising peroxy linkage using ultrasonication to prepare a dispersed pitch solution. The process comprises heating the said dispersed pitch solution under controlled temperature to prepare an oxidized coal tar pitch solution. The process also comprises filtering the said oxidized coal tar pitch solution with a filter to obtain a filter cake and to remove excess solution. The process further comprises washing the said filter cake with water to obtain a washed cake. The process comprises drying and crushing the said washed cake to obtain the oxygen rich precursor pitch.
[0018] In an embodiment, the solution having compound comprising peroxy linkage is hydrogen peroxide solution. In an embodiment, the hydrogen peroxide solution is of concentration 5% - 30% v/v.
[0019] In an embodiment, wherein the distilling of coal tar is performed in a temperature range of 380°C - 420°C. In an embodiment, the distilling of coal tar is performed for 0 - 30 mins.
[0020] In an embodiment, the coal tar pitch is mixed with the hydrogen peroxide solution in a pulp density of 0.0167 g/ml – 0.5 g/ml.
[0021] In an embodiment, deagglomeration of the mixture of coal tar pitch and the hydrogen peroxide solution using ultrasonication is performed for 10 – 60 mins.
[0022] In an embodiment, the filtering of the reaction mixture is done using wire mesh of 200-500-micron size.
[0023] In an embodiment, the washing of the filter cake with water is performed for 60 - 180 mins.
[0024] In an embodiment, drying of the washed coke is performed in a temperature range of 50°C - 120°C. In an embodiment, drying of the washed coke is performed for 30 - 360 mins.
[0025] In an embodiment, the coal tar contains less than 2.5 % by the weight of quinoline insoluble portion.
[0026] In an embodiment, the coal tar pitches have a softening point of 70°C - 100°C. In an embodiment, the coal tar pitches have a Carbon to Hydrogen atomic ratio less than 2. In an embodiment, the coal tar pitches have a particle size of less than 250 micron.
[0027] In an embodiment, the carbon fiber precursor pitches have a softening point in the range of 150 °C – 200 °C. In an embodiment, the precursor pitches have fixed carbon content in the range of 53-58 percent by weight.
[0028] In an embodiment, the carbon fiber precursor pitches have oxygen content in the range of 4.5-7.0 percent by weight on dry mineral matter free basis.
[0029] In an embodiment, the carbon fiber precursor pitches have Carbon to Hydrogen atomic ratio in the range of 2.2 - 3.2.
[0030] In an embodiment, the carbon fiber precursor pitches have average molecular weight of 3000-3200 Da.
[0031] In an embodiment, the carbon fiber precursor pitches have aromaticity value of 0.40 - 0.45 measured from Fourier Transformed Infrared spectroscopy.
[0032] In an embodiment, the overall yield of the carbon fiber precursor pitch from the coal tar pitch is approximately 100 %.
[0033] In another aspect of the present invention, a process of producing an oxygen rich precursor pitch for carbon fiber is disclosed. The process comprises distilling coal tar at 380-420 °C, for 0 to 30 minutes under atmospheric pressure to produce coal tar pitch having a softening point of 70 -100 °C. The process also comprises mixing the said coal tar pitch in a pulp density of 0.0167 g/ml – 0.5 g/ml with a hydrogen peroxide solution of concentration 5% - 30% v/v. The process further comprises deagglomerating the admixture of coal tar pitch and the hydrogen peroxide solution using ultrasonication for 10 – 60 mins to prepare a dispersed pitch solution. The process comprises heating the said dispersed pitch solution to initiate reaction within the dispersed pitch solution under controlled temperature of 50°C - 120°C for 30 - 360 mins to prepare an oxidized coal tar pitch solution. The process also comprises filtering the said oxidized coal tar pitch solution with a 500-mesh filter to obtain a filter cake and to remove excess solution. The process further comprises washing the said filter cake with demineralized water for 60-180 minutes to obtain a washed cake. The process comprises drying of the said washed cake at 90-120 °C temperature for 4 to 6 hours followed by crushing to obtain the oxygen rich carbon fiber precursor pitch.
[0034] Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1 is a flowchart which illustrates the process of producing an oxygen rich carbon fiber precursor pitch, according to an embodiment of the present invention.
[0036] The drawings referred to in this description are not to be understood as being drawn to scale except if specifically noted, and such drawings are only exemplary in nature.

DETAILED DESCRIPTION
[0037] The detailed description of various exemplary embodiments of the disclosure is described herein with reference to the accompanying drawings. It should be noted that the embodiments are described herein in such details as to clearly communicate the disclosure. However, the amount of details provided herein is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0038] It is also to be understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and embodiments of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof.
[0039] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.
[0040] It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may, in fact, be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
[0041] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
[0042] Figure 1 illustrates an exemplary process (100) for producing an oxygen rich carbon fiber precursor useful as a raw material for carbon fibers. At step (102), coal tar is distilled at atmospheric pressure to produce coal tar pitch (coal tar pitch formation step). At step (104), the coal tar pitch formed in the coal tar pitch formation step is mixed with a solution having compound comprising peroxy linkage (mixing step). At step (106), the admixture of coal tar pitch and the solution having compound comprising peroxy linkage formed after mixing step is deagglomerated using ultrasonication to prepare dispersed pitch solution (deagglomerating step). At step (108), the dispersed pitch solution formed after deagglomerating step is heated under controlled temperature to obtain oxidized coal tar pitch (heating step). At step (110), the oxidized coal tar pitch obtained after heating step is filtered to obtain filter cake (filtering step). At step (112), the filter cake obtained after filtering step is washed with water to obtain washed cake (washing step). At step (114), the washed cake obtained after washing step is dried and crushed to get the desired pitch precursor (drying and crushing step).
[0043]
[0044] In the coal tar pitch formation step, coal tar is distilled to at atmospheric pressure to produce coal tar pitch. In the preferred embodiment, the coal tar used to produce the coal tar pitch has density in between 1.12 to 1.18 g/cc and preferably in between 1.14 to 1.16 g/cc. In the preferred embodiment, the coal tar used has viscosity in between 150 to 480 cP at room temperature and preferably in between 160 to 470 cP in room temperature. In the preferred embodiment, quantity of quinoline insoluble content, present in the coal tar used is less than 2.5 percent by weight and preferably less than 0.5 percent by weight. In the preferred embodiment, the coal tar has a pitch yield in between 40 to 60 % at 400 °C and preferably 50 % at 400 °C.
[0045] The coal tar is distilled at 380-420 °C, preferably at 390-410 °C, for 0 to 30 minutes under atmospheric pressure to produce coal tar pitch. The coal tar pitch having the following properties is preferred to be produced so as to use it as raw coal tar pitch for further processing. The coal tar pitch having very low ash content, less than 0.1 percent by weight. The coal tar pitch having a fixed carbon content, in between 40 to 45 percent by weight. The coal tar pitch having a softening point in between 70 to 100 °C, preferably between 90 to 100 °C. The coal tar pitch having an atomic ratio of carbon to hydrogen less than two, preferably in between 1.9 to 2. The coal tar pitch in powder form with particle size less than 250 micron and 80 % passing through 60 mesh screen of Tyler standard.
[0046]
[0047] In the mixing step, the coal tar pitch formed in the coal tar pitch formation step is mixed with a solution having compound comprising peroxy linkage. In the preferred embodiment, the solution having compound comprising peroxy linkage is hydrogen peroxide solution. The hydrogen peroxide solution is essentially a radical initiator which provides nascent oxygen during reaction. In the preferred embodiment, hydrogen peroxide solution is of concentration 5% - 30% v/v. For preparation of hydrogen peroxide solution, concentrated hydrogen peroxide of 30 % v/v is mixed with demineralized water in a ratio such that the final concentration of the hydrogen peroxide solution is in between 5 to 30 % v/v. In the preferred embodiment, the coal tar pitch is mixed with the hydrogen peroxide solution in a pulp density of 0.0167 g/ml – 0.5 g/ml. In another example, the compound comprising peroxy linkage may be any compound which releases nascent oxygen, without limiting the scope of the invention.
[0048] < Deagglomerating step>
[0049] In the deagglomerating step, the admixture formed in the mixing step is deagglomerated using ultrasonication for 10 to 60 minutes, preferably for 20 to 50 minutes to prepare a dispersed pitch solution. Objective of ultrasonication is to disperse the coal tar pitch particles in the hydrogen peroxide solution.
[0050]
[0051] In the heating/reacting step, the dispersed pitch solution is subjected to oxidation reaction through controlled heating. The dispersed pitch solution is placed and heated in a reactor vessel, kept at temperature in the range of 50 °C to 120 °C, preferably between 90 to 110 °C and having a stirring speed kept in between 40 to 50 RPM. Heating the dispersed pitch solution initiates reaction within the dispersed pitch solution. The reaction takes place under controlled temperature of 50°C - 120°C for 30 - 360 mins, preferably between 240 to 360 minutes to obtain an oxidized coal tar pitch solution.
[0052] The reaction is done to convert the lower chain aromatic compounds present in the coal tar pitch, into longer chain compounds. During the reaction, hydrogen peroxide molecules breakdown to generate nascent oxygen. This nascent oxygen reacts with the coal tar pitch in the active state. Coal tar pitch in the active state is obtained by increasing the temperature of the reaction. Coal tar pitch in active state releases hydrogen from the cyclic ring and creates an active site. Nascent oxygen present in the admixture reacts with the active sites and produces oxygen containing compounds. The oxygen-containing compounds further reacts internally to produce the long chain compounds.
[0053] Presence of quinoline insoluble materials in the coal tar pitch hinders the reaction. This is solely because these are inert materials which does not participate in the reaction. Removing quinoline insoluble contents from the product is difficult. So, it is important that the coal tar or the coal tar pitch chosen for the process must have low QI content. Otherwise, removal of quinoline insoluble contents from the coal tar or the coal tar pitch is recommended. Process for removal of quinoline insoluble is well known in the art and will not be described in detail in here.
[0054]
[0055] In the filtering step, the oxidized coal tar pitch solution (pitch solvent mixture) is separated by filtration to obtain a filter cake and remove excess reactant solution. In the preferred embodiment, the filtration is done using wire mesh of 200-500-micron size, preferably 400-500-micron size.
[0056]
[0057] In the washing step, the filter cake is washed with demineralized water for removal of any residual reactant solution. Washing is done for 60-180 minutes preferably for 120 to 150 minutes, to obtain a washed cake.
[0058]
[0059] In the drying and crushing step, the washed cake is dried to remove the moisture from precursor pitch. Drying temperature is set between 90 to 120 °C, preferably 100-110 °C. Weight of the sample is monitored at each hour of drying to ensure there is no change of weight with time. This step confirms the completion of drying process. Preferred time taken for drying is 4 to 6 hours. Once the sample is dried, the lump precursor pitch is crushed to less than 25-micron particle size to obtain oxygen rich precursor pitch.
[0060] The product obtained by the above-mentioned process is an isotropic precursor pitch suitable for preparation of carbon fiber. The resultant precursor pitch product has a rich oxygen content preferably between 4.5 to 7.0 percent by weight in dry mineral matter free basis. High oxygen content also signifies high softening point of the precursor pitch in the range of 150 to 200 °C. Therefore, the fixed carbon content of the resultant product also increased in the range of 53 to 58 percent by weight. Increase in oxygen content is due to the substitution of the hydrogen atom present in the benzene ring, by the nascent oxygen atoms. Hence, decrease in hydrogen content also results in increase in the carbon to hydrogen atomic ratio in the range of 2.2 to 3.2. Increase in oxygen content also results in increase in the chemical stability of the product. Chemical stability is measured in terms of aromaticity value calculated based on Fourier Transformed Infrared spectroscopy. Aromaticity value of the resultant precursor pitch product is in the range of 0.40 to 0.45. Oxygen insertion also resulted in macromolecule formation in the resultant pitch matrix. The average molecular weight of the precursor pitch is in between 3000 to 3500 Da, preferably between 3000-3300 Da.
[0061] The main advantage of the invention is (a) it does not require any high temperature operation to remove light components or volatile matters. Maximum temperature require is within 120 °C which is comparatively lower than the methods discussed in the prior art. (b) Yield of the process is 100 % of the raw pitch. In this process, lighter components are converted into macromolecules by oxygen insertion reaction. Hence, it is not stripped of from the raw coal tar pitch and the whole coal tar pitch is converted into the resultant precursor pitch.
[0062] Following examples further illustrates the details of the present invention. However, the present invention is comprised of but not limited to these illustrations.
EXAMPLE 1
[0063] A coal tar with quinoline insoluble content of 2.4 percent by weight was distilled to produce a coal tar pitch. 120 mL of coal tar was distilled at 400 °C for 1 hour to obtain 54 g of coal tar pitch having a softening point of 97 °C along with fixed carbon content of 42.8 % percentage by weight and oxygen content of 1.93 percent by weight in dry mineral matter free basis. The coal tar pitch containing Carbon to Hydrogen atomic ratio of 1.92. 10 g of the coal tar pitch was mixed with 600 mL of hydrogen peroxide solution of 15 % volume by volume concentration. Hydrogen peroxide solution was prepared by mixing 300 mL of 30 % concentrated hydrogen peroxide solution in 300 mL demineralized water. The admixture of coal tar pitch and hydrogen peroxide solution was then ultrasonicated for 30 minutes. After dispersing the coal pitch in peroxide by sonication, the dispersed pitch solution was transferred to the reaction vessel. Reaction was carried out at 100 °C for 2 hours and the rotation speed of the reaction vessel was maintained at 45 RPM and an oxidized coal tar pitch solution was obtained. The oxidized coal tar pitch solution was then filtered through 500 stainless steel wire mesh to obtain the filter cake. The filter cake was washed with 500 mL water for 120 minutes and then dried for 240 minutes at 110 °C. Dried product was crushed and screened through 60 mesh screen of Tyler standard to obtain precursor pitch. The resultant precursor pitch product had a softening point of 117 °C with fixed carbon content of 46 percent by weight. Further the resultant precursor pitch product had a Carbon to Hydrogen atomic ratio 2.01 and Oxygen content also increased to 2.12 percent by weight in dry mineral matter free basis.
COMPARATIVE EXAMPLE 1
[0064] Coal tar pitch mentioned in example 1 was treated in same manner as described in example 1. Concentration of hydrogen peroxide solution was increased from 15 % to 30 % volume by volume. 600 mL of 30 % concentrated hydrogen peroxide solution was taken. Water was not added into it. The resultant precursor pitch product had a softening point of 162 °C with fixed carbon content of 55.5 percent by weight. Further the resultant precursor pitch product had a Carbon to Hydrogen atomic ratio of 3.09 and Oxygen content also increased to 6.38 percent by weight in dry mineral matter free basis.
COMPARATIVE EXAMPLE 2
[0065] Coal tar Pitch mentioned in example 1 was treated in same manner as described in comparative example 1. Only difference was that the admixture was not ultrasonicated prior to reaction. The resultant precursor pitch product had a softening point of 138 °C with fixed carbon content of 43.8 percent by weight. Further the resultant precursor pitch product had a Carbon to Hydrogen atomic ratio of 2.74 and Oxygen content obtained was 6.01 percent by weight in dry mineral matter free basis. This example signifies the effect of ultrasonication prior to the reaction. Ultrasonication is required for dispersing the pitch in the hydrogen peroxide matrix, as pitch is not soluble in hydrogen peroxide, dispersing helps in creating a homogeneous mixture.
COMPARATIVE EXAMPLE 3
[0066] Coal tar Pitch mentioned in example 1 was treated in same manner as mentioned in comparative example 1. To change the stoichiometry of the reaction, 50 g of the coal tar pitch was mixed with 500 mL of 30 % volume by volume hydrogen peroxide solution. Reaction conditions maintained was same as comparative example 1. The resultant precursor pitch product had a softening point of 160 °C with fixed carbon content of 45 percent by weight. Further the resultant precursor pitch product had a Carbon to Hydrogen atomic ratio of 2.21 and Oxygen content also increased to 4.61 percent by weight in dry mineral matter free basis. Hence, it was determined that the pulp density can be increased to 1 g of coal tar pitch per 10 mL of hydrogen peroxide solution, from 1 g of coal tar pitch per 60 mL of hydrogen peroxide solution, without significantly varying the softening point of the resultant product.
COMPARATIVE EXAMPLE 4
[0067] Coal tar pitch mentioned in example 1 was treated in same manner as mentioned in comparative example 3. Reaction time was increased to 6 hours to understand the effect of time on reaction kinetics, other parameters were kept same as mentioned in comparative example 3. The resultant precursor pitch product had a softening point of 180 °C with fixed carbon content of 58.2 percent by weight. Further the resultant precursor pitch product had a Carbon to Hydrogen atomic ratio of 2.95 and Oxygen content also increased to 6.62 percent by weight in dry mineral matter free basis. Hence, it was observed that, increase in reaction time, increases the softening point and fixed carbon of the product significantly.
COMPARATIVE EXAMPLE 5
[0068] Coal tar pitch mentioned in example 1 was treated in same manner as mentioned in comparative example 3. To see the stoichiometry of the reaction, pulp density of the reaction mixture was further increased. 100 g of the coal tar pitch was mixed with 500 mL of 30 % volume by volume hydrogen peroxide solution. Reaction conditions maintained was same as comparative example 1. The resultant precursor pitch product had a softening point of 165 °C with fixed carbon content of 56.5 percent by weight. Further the resultant precursor pitch product had a Carbon to Hydrogen atomic ratio of 1.78 and Oxygen content also increased to 4.83 percent by weight in dry mineral matter free basis. Hence, it was determined that the increase in pulp density to 1 g of coal tar pitch per 5 mL of hydrogen peroxide solution, from 1 g of coal tar pitch per 10 mL of hydrogen peroxide solution, significantly varies the softening point of the product. Hence, it was recommended that pulp density of 1 g of pitch per 10 mL of hydrogen peroxide solution is ideal for carrying out the said reaction.
EXAMPLE 2
[0069] Coal tar pitch mentioned in example 1 was taken for further experiments. 50 g of the coal tar pitch was mixed with 500 mL of hydrogen peroxide solution of 30 % volume by volume concentration. This admixture was then ultrasonicated for 30 minutes. After dispersing the pitch in peroxide by sonication, mixture was transferred to the reaction vessel. Reaction was carried out at 110 °C for 4 hours and the rotation speed was maintained at 45 RPM and an oxidized coal tar pitch solution was obtained. Filtering, drying and crushing of the oxidized coal tar pitch solution was carried out in the same manner as described in example 1. The resultant precursor pitch product had a softening point of 192 °C with fixed carbon content of 58 percent by weight. Further the resultant precursor pitch product had a Carbon to Hydrogen atomic ratio of 2.96 and Oxygen content also increased to 6.75 percent by weight in dry mineral matter free basis.
COMPARATIVE EXAMPLE 6
[0070] Coal tar pitch mentioned in example 1 was treated in same manner as described in example 2. Only the reaction time was increased from 4 hours to 6 hours for comparison. The resultant precursor pitch product had a softening point that was beyond 270 °C and was not detected. Fixed carbon content of 58 percent by weight was obtained. Further the resultant precursor pitch product had a Carbon to Hydrogen atomic ratio of 3.11 and Oxygen content also increased to 6.70 percent by weight in dry mineral matter free basis.
EXAMPLE 3
[0071] A coal tar with quinoline insoluble content of 0.5 percent by weight was distilled to produce coal tar pitch. 120 mL coal tar was distilled at 400 °C for 1 hour to obtain 50 g of coal tar pitch having a softening point of 87 °C along with fixed carbon content of 38.9 % percentage by weight and oxygen content of 2.24 percent by weight in dry mineral matter free basis. Carbon to Hydrogen atomic ratio was 2.12. The coal tar pitch was processed in the same manner as described in example 2. The resultant precursor pitch product had a softening point of 167 °C with fixed carbon content of 53 percent by weight. Further the resultant precursor pitch product had Carbon to Hydrogen atomic ratio of 2.73 and Oxygen content also increased to 6.13 percent by weight in dry mineral matter free basis.
[0072] Properties of different tars and pitches are listed in Table 1 and Table 2.
Tar Density (g/cc) Viscosity (cP) QI (% weight)
Example 1 1.16 470 2.4
Example 3 1.14 160 0.5
TABLE 1

TABLE 2
Pitch Softening point
(°C) Fixed carbon (% weight) C/H ratio Oxygen content (% weight)
Raw pitch in example 1 97 42.8 1.92 1.93
Raw pitch in example 3 87 38.9 2.12 2.24
Product in example 1 117 46 2.01 2.12
Product in comparative example 1 162 55 3.09 6.38
Product in comparative example 2 138 43.8 2.74 6.01
Product in comparative example 3 160 45 2.21 4.61
Product in comparative example 4 180 58.2 2.95 6.62
Product in comparative example 5 165 56.5 1.78 4.83
Product in example 2 192 58 2.76 6.75
Product in comparative example 6 >270 58 3.11 6.70
Product in example 3 167 53 2.73 6.13

[0073] The precursor pitch produced using the above process is suitable for preparation of carbon fibers which are used for manufacturing any component relating to any industry, without departing from the scope of the present invention. The process improves yield of the precursor from the raw feedstock, and improves heat stability, spinnability and infusibility of the resultant product.
[0074] Furthermore, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.
[0075] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.
[0076] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

Claims:We claim:
1. A process (100) of producing an oxygen rich precursor pitch for carbon fiber, the process comprising:
distilling coal tar at atmospheric pressure to produce coal tar pitch;
mixing the said coal tar pitch with a solution having compound comprising peroxy linkage;
deagglomerating the admixture of coal tar pitch and the solution having compound comprising peroxy linkage using ultrasonication to prepare a dispersed pitch solution;
heating the said dispersed pitch solution under controlled temperature to prepare an oxidized coal tar pitch solution;
filtering the said oxidized coal tar pitch solution with a filter to obtain a filter cake and to remove excess solution;
washing the said filter cake with water to obtain a washed cake; and
drying and crushing the said washed cake to obtain the oxygen rich precursor pitch.
2. The process (100) of producing the oxygen rich precursor pitch for carbon fiber as claimed in claim 1, wherein the solution having compound comprising peroxy linkage is hydrogen peroxide solution.
3. The process (100) of producing the oxygen rich precursor pitch for carbon fiber as claimed in claim 2, wherein the hydrogen peroxide solution is of concentration 5% - 30% v/v.
4. The process (100) of producing the oxygen rich precursor pitch for carbon fiber as claimed in claim 1, wherein the distilling of coal tar is performed in a temperature range of 380°C - 420°C.
5. The process (100) of producing the oxygen rich precursor pitch for carbon fiber as claimed in claim 1, wherein the distilling of coal tar is performed for 0 - 30 mins.
6. The process (100) of producing the oxygen rich precursor pitch for carbon fiber as claimed in claim 1, wherein the coal tar pitch is mixed with the hydrogen peroxide solution in a pulp density of 0.0167 g/ml – 0.5 g/ml.
7. The process (100) of producing the oxygen rich precursor pitch for carbon fiber as claimed in claim 1, wherein deagglomeration of the mixture of coal tar pitch and the hydrogen peroxide solution using ultrasonication is performed for 10 – 60 mins.
8. The process (100) of producing the oxygen rich precursor pitch for carbon fiber as claimed in claim 1, wherein the filtering of the oxidized coal tar pitch solution is done with using wire mesh of 200-500-micron size.
9. The process (100) of producing the oxygen rich precursor pitch for carbon fiber as claimed in claim 1, wherein the washing of the filter cake with water is performed for 60 - 180 mins.
10. The process (100) of producing the oxygen rich precursor pitch for carbon fiber as claimed in claim 1, wherein drying of the washed coke is performed in a temperature range of 50°C - 120°C.
11. The process (100) of producing the oxygen rich precursor pitch for carbon fiber as claimed in claim 1, wherein drying of the washed coke is performed for 30 - 360 mins.
12. The process (100) of producing the oxygen rich precursor pitch for carbon fiber as claimed in claim 1, wherein the coal tar contains less than 2.5 % by the weight of quinoline insoluble portion.
13. The process (100) of producing the oxygen rich precursor pitch for carbon fiber as claimed in claim 1, wherein the coal tar pitches have a softening point of 70°C - 100°C.
14. The process (100) of producing the oxygen rich precursor pitch for carbon fiber as claimed in claim 1, wherein the coal tar pitches have a Carbon to Hydrogen atomic ratio less than 2.
15. The process (100) of producing the oxygen rich precursor pitch for carbon fiber as claimed in claim 1, wherein the coal tar pitches have a particle size of less than 250 micron.
16. The process (100) of producing the oxygen rich precursor pitch for carbon fiber as claimed in claim 1, wherein the precursor pitches have a softening point in the range of 150 °C – 200 °C.
17. The process (100) of producing the oxygen rich precursor pitch for carbon fiber as claimed in claim 1, wherein the precursor pitches have fixed carbon content in the range of 53-58 percent by weight.
18. The process (100) of producing the oxygen rich precursor pitch for carbon fiber as claimed in claim 1, wherein the precursor pitches have oxygen content in the range of 4.5-7.0 percent by weight on dry mineral matter free basis.
19. The process (100) of producing the oxygen rich precursor pitch for carbon fiber as claimed in claim 1, wherein the precursor pitches have Carbon to Hydrogen atomic ratio in the range of 2.2 - 3.2.
20. The process (100) of producing the oxygen rich precursor pitch for carbon fiber as claimed in claim 1, wherein the precursor pitches have average molecular weight of 3000-3200 Da.
21. The process (100) of producing the oxygen rich precursor pitch for carbon fiber as claimed in claim 1, wherein the precursor pitches have aromaticity value of 0.40 - 0.45 measured from Fourier Transformed Infrared spectroscopy.
22. The process (100) of producing the oxygen rich precursor pitch for carbon fiber as claimed in claim 1, wherein the overall yield of the said precursor pitch from the said coal tar pitch is approximately 100 %.
23. A process (100) of producing an oxygen rich precursor pitch for carbon fiber, the process comprising:
distilling coal tar at 380-420 °C, for 0 to 30 minutes under atmospheric pressure to produce coal tar pitch having a softening point of 70 -100 °C;
mixing the said coal tar pitch in a pulp density of 0.0167 g/ml – 0.5 g/ml with a hydrogen peroxide solution of concentration 5% - 30% v/v;
deagglomerating the admixture of coal tar pitch and the hydrogen peroxide solution using ultrasonication for 10 – 60 mins to prepare a dispersed pitch solution;
heating the said dispersed pitch solution to initiate reaction within the dispersed pitch solution under controlled temperature of 50°C - 120°C for 30 - 360 mins to prepare an oxidized coal tar pitch solution;
filtering the said oxidized coal tar pitch solution with a mesh filter to obtain a filter cake and to remove excess solution;
washing the said filter cake with demineralized water for 60-180 minutes to obtain a washed cake; and
drying of the said washed cake at 90-120 °C temperature for 4 to 6 hours followed by crushing to obtain the oxygen rich precursor pitch.
24. The process (100) of producing the oxygen rich precursor pitch for carbon fiber as claimed in claims 1 and 23, wherein the process (100) further comprises screening through 60 mesh screen of Tyler standard to obtain the oxygen rich precursor pitch.