Description:TECHNICAL FIELD
The present disclosure relates to the field of processing of carbonaceous material for the production of coal tar pitch. More particularly, the present disclosure provides a method for producing an isotropic, low softening point pitch, free of primary quinoline insoluble (QI) particles, using tar as starting material. Further provided herein is an isotropic, low softening point pitch prepared by the said method.

BACKGROUND OF THE DISCLOSURE
Low softening point pitches are excellent intermediates for the preparation of more advanced carbon materials since such pitches contain low molecular weight compounds susceptible to be transformed, by additional steps into advanced carbonaceous materials, therefore increasing the overall yield of the processing.

For certain applications, such as preparation of carbon fibers, elimination of primary quinoline insoluble particles present in coal tar is desired. Other “impurities” to be eliminated from the final low softening point pitches include any mesophase content produced during pitch formation, usually as a result of thermal treatment at high temperature of the aromatic feedstock.

While there exist several methods for the preparation of aromatic pitches free of QI particles from aromatic tar, efficient separation of the QI particles is still a challenge. Some examples for such methods include addition of suitable solvents which, however, is expensive and requires additional steps for removal of the solvent after completion of the process. Other examples include multiple filtration steps, pre-treatment of feed material to remove QI particles or reliance on auxiliary agents, each of which again reduce the process economy.

In view of the need in the art for an efficient and economical process to produce isotropic pitch free of primary QI particles, the present disclosure provides a method to eliminate QI particles present naturally in coal tars while polymerizing their components to produce a pitch with low softening point.

STATEMENT OF THE DISCLOSURE
Addressing the aforesaid need in the art for an efficient and economical method to produce isotropic pitch free of primary QI particles, the present disclosure provides a method for preparing an isotropic pitch having low softening point, comprising
a) subjecting coal tar to pressurized heating to allow formation of an incipient mesophase;
b) subjecting the heated coal tar of step (a) to depressurization at a temperature of about 100°C to about 350°C; and
c) separating the mesophase from the depressurized tar of step (b) to obtain the isotropic pitch having low softening point.

In some embodiments, the pressurized heating is at a temperature ranging from about 390°C to about 500°C.

In some embodiments, the pressurized heating is conducted at a pressure ranging from about 0.5 bar to about 10 bar.

In some embodiments, the pressurized heating is conducted for about 2 hours to about 5 hours.

In some embodiments, the pressurized heating is conducted in an inert atmosphere.

In some embodiments, the depressurization is conducted at a rate of about 0.1 bar h-1 to about 15 bar h-1.

In some embodiments, the depressurization is conducted for about 20 minutes to about 1 hour.
In some embodiments, temperature of the heated coal tar of step(a) is reduced from a range of about 390°C to about 500°C to a range of about 100 ºC to about 350ºC, followed by depressurization of the cooled tar.

In some embodiments, the mesophase is separated by method selected from a group comprising filtration and centrifugation, or a combination thereof.

In some embodiments, the softening point of the obtained pitch is less than or equal to about 100°C.

In some embodiments, the softening point of the obtained pitch ranges from about 70°C to about 95°C.

In some embodiments, the QI content of the obtained pitch ranges from about 3.6 wt% to about 6.7 wt%.

In some embodiments, the TI content of the obtained pitch ranges from about 25 wt% to about 40 wt%.

Further provided herein, is a low softening point, isotropic pitch prepared by the method as described above.

In some embodiments, the softening point of the pitch is less than or equal to about 100°C.

In some embodiments, the softening point of the pitch ranges from about 70°C to about 95°C.

In some embodiments, the QI content of the pitch ranges from about 3.6 wt% to about 6.7

In some embodiments, the TI content of the pitch ranges from about 25 wt% to about 40 wt%.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
In order that the disclosure may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying figures. The figures together with detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, where:
Figure 1 depicts optical images (lens x20 and x50 magnifications) of reaction products obtained as per the method of the present disclosure using raw tars CT1, CT2, CT3 and CT4.
Figure 2 depicts optical micrographs (lens x20) of filtered products produced by the method of the present disclosure i.e. Product-CT1-cold, Product-CT2-cold, Product-CT3-cold, Product-CT4-cold, wherein the filtration is through a 1µm mesh filter.
Figure 3 depicts optical images (lens x50 magnifications) of the ALCAN residues obtained for the primary QI-free pitches obtained from CT1, CT2, CT3 and CT4 via the method of the present disclosure.
Figure 4 depicts optical images (lens x20 and x50 magnifications) of the sample retained during filtering in the reaction from CT3 in the stirred reactor at 420 °C for 4 h at 3 bar, followed by depressurization at 200ºC.
Figure 5 depicts optical images (lens x50) of reaction products obtained in the reaction from CT3 in the stirred reactor at 420°C for 4 hours at 3 bar, followed by depressurization at 200ºC i.e. Product-CT1-hot (a) and Product-CT2-hot (b).
Figure 6 depicts optical images (lens x50) of raw tars (left) and filtered reaction products (CTP1-QIF-hot and CTP2-QIF-hot) after ALCAN analysis, from CTP1 (up) and CTP2 (down), wherein the filtration is through filters of mesh size 25 and 5 µm.
Figure 7 depicts optical micrographs (lens x10) of filtered products Product-CT1-hot and Product-CT2-hot, wherein the filtration is through a 5 µm mesh filter.
Figure 8 depicts optical microscopy images (x 50) of ALCAN residues obtained from tar CT1: (a) as received and filtered using (b) a single filter mesh of 5 µm, (c) a single filter mesh of 1 µm, (d) two overlapped filters of 1 µm (e) three overlapped filters of 1 µm, (f) a single filter mesh 0.5 µm after filtering from (e).

DETAILED DESCRIPTION OF THE DISCLOSURE
As used herein, ‘coal tar’ or ‘tar’, used interchangeably, refer to a thick dark liquid which is a by-product of the production of coke and coal gas from coal.

The terms ‘primary quinoline insoluble free’, ‘primary QI free, ‘QI free’, ‘QIF’ and ‘Quinoline insoluble free’ or obvious variants thereof, used interchangeably in the context of the present disclosure, have been used in reference to a pitch free of ‘primary quinoline insoluble particles’, wherein said primary quinoline insoluble particles are eliminated along with mesophase spheres to yield an isotropic, primary QI particle free pitch.

As used herein, the term ‘primary QI particles’ or ‘primary quinoline insoluble particles’ refers to a variety of solid carbonaceous particles such as but not limited to coal powder, coke powder, ash particles, and silica particles generally having a diameter of < 1 µm that are already present in the tar used as starting material and are a result of the carbonization and refining process. As the name suggests, these particles are insoluble in quinoline when used as a solvent. These primary QI particles strongly influence the behaviour of pitches derived from the coal tar.

The term ‘quinolone insoluble content’ or ‘QI content’ referred to in the context of the characterization of the final pitch obtained from the method of the present disclosure, refers to QI insoluble material composed of large molecules (i.e. having diameter >1 µm, as opposed to the primary QI particles) formed during the thermal treatment which are insoluble in such solvent.

The term ‘parent tar’, in the context of the present disclosure, refers to the starting material i.e. the coal tar used as raw material in the method for preparing the isotropic, low softening point pitch.

As used herein, the term ‘isotropic pitch’ refers to a pitch characterized by absence of mesophase spheres.

As used herein, the term ‘incipient mesophase’ refers to the initial formation of an ordered liquid crystal phase, initially in the form of spheres (mesophase spheres), that begin to develop from isotropic phase as a result of thermal treatment of coal tar. By optical analysis of the mixture comprising the incipient mesosphere and the isotropic phase using polarized light, the mesophase can be visualized as a coloured phase separate from the isotropic phase. The isotropic phase without the mesophase is composed of molecules which are disordered both in position and orientation and this later is seen a plain coloured phase, in the absence of the mesophase.

The term ‘low softening point’, in the context of the present disclosure, refers to softening point of obtained pitch less than or equal to about 100ºC.

As used herein, the term ‘comprising’ when placed before the recitation of steps in a method means that the method encompasses one or more steps that are additional to those expressly recited, and that the additional one or more steps may be performed before, between, and/or after the recited steps. For example, a method comprising steps a, b, and c encompasses a method of steps a, b, x, and c, a method of steps a, b, c, and x, as well as a method of steps x, a, b, and c. Furthermore, the term ‘comprising’ when placed before the recitation of steps in a method does not (although it may) require sequential performance of the listed steps, unless the content clearly dictates otherwise. For example, a method comprising steps a, b, and c encompasses, for example, a method of performing steps in the order of steps a, c, and b, the order of steps c, b, and a, and the order of steps c, a, and b, etc.

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity. The suffix ‘(s)’ at the end of any term in the present disclosure envisages in scope both the singular and plural forms of said term.
As used in this specification and the appended claims, the singular forms ‘a’, ‘an’ and ‘the’ includes both singular and plural references unless the content clearly dictates otherwise. The use of the expression ‘at least’ or ‘at least one’ suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results. As such, the terms ‘a’ (or ‘an’), ‘one or more’, and ‘at least one’ can be used interchangeably herein.

Numerical ranges stated in the form ‘from x to y’ include the values mentioned and those values that lie within the range of the respective measurement accuracy as known to the skilled person. If several preferred numerical ranges are stated in this form, of course, all the ranges formed by a combination of the different end points are also included.

The terms ‘about’ or ‘approximately’ as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, are meant to encompass variations of and from the specified value, such as variations of +/-10% or less, +/-5% or less, +/-1% or less, and +/-0.1% or less of and from the specified value, insofar such variations are appropriate to perform in the disclosed invention. It is to be understood that the value to which the modifier ‘about’ or ‘approximately’ refers is itself also specifically, and preferably, disclosed.

As used herein, the terms ‘include’, ‘have’, ‘comprise’, ‘contain’ etc. or any form said terms such as ‘having’, ‘including’, ‘containing’, ‘comprising’ or ‘comprises’ are inclusive and will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

As regards the embodiments characterized in this specification, it is intended that each embodiment be read independently as well as in combination with another embodiment. For example, in case of an embodiment 1 reciting 3 alternatives A, B and C, an embodiment 2 reciting 3 alternatives D, E and F and an embodiment 3 reciting 3 alternatives G, H and I, it is to be understood that the specification unambiguously discloses embodiments corresponding to combinations A, D, G; A, D, H; A, D, I; A, E, G; A, E, H; A, E, I; A, F, G; A, F, H; A, F, I; B, D, G; B, D, H; B, D, I; B, E, G; B, E, H; B, E, I; B, F, G; B, F, H; B, F, I; C, D, G; C, D, H; C, D, I; C, E, G; C, E, H; C, E, I; C, F, G; C, F, H; C, F, I, unless specifically mentioned otherwise.

As mentioned in the above section, the present disclosure is directed towards a method to facilitate the preparation of an isotropic pitch that is free of primary QI particles. The present disclosure provides a method that utilizes the capability of primary QI particles to coalesce with a very incipient mesophase to form a mixture containing a separatable mesophase that is surrounded by primary QI particles, in order to yield an isotropic pitch by separating the isotropic matrix from the mesophase particles.

Provided herein is a method for preparing an isotropic pitch having low softening point, comprising
a) subjecting tar to pressurized heating to allow formation of an incipient mesophase
b) subjecting the heated tar of step (a) to depressurization at a temperature of about 100°C to about 350°C; and
c) separating the mesophase from the depressurized tar of step (b) to obtain the isotropic pitch having low softening point.

In some embodiments, the tar used as starting material is coal tar. The use of coal tar as a starting material has several advantages over graphite and other graphitic materials at least from the perspective of economy, environmental impact and energy consumption of the process.

Accordingly, in some embodiments, the method for preparing an isotropic pitch having low softening point, comprises -
a) subjecting coal tar to pressurized heating to allow formation of an incipient mesophase;
b) subjecting the heated coal tar of step (a) to depressurization at a temperature of about 100°C to about 350°C; and
c) separating the mesophase from the depressurized tar of step (b) to obtain the isotropic pitch having low softening point.
In some embodiments, the method for preparing an isotropic pitch having low softening point, consists of -
a) subjecting coal tar to pressurized heating to allow formation of an incipient mesophase;
b) subjecting the heated coal tar of step (a) to depressurization at a temperature of about 100°C to about 350°C; and
c) separating the mesophase from the depressurized tar of step (b) to obtain the isotropic pitch having low softening point.

In some embodiments, the coal tar has primary quinoline insoluble (QI) content ranging from about 0.3 wt% to about 8 wt.%.

In some embodiments, the coal tar has primary quinoline insoluble (QI) content of about 0.3 wt%, about 0.5 wt%, about 1, about 1.5 wt%, about 2 wt%, about 2.5 wt%, about 3 wt%, about 3.5 wt%, about 4 wt%, about 4.5 wt%, about 5 wt%, about 5.5 wt%, about 6.5 wt%, about 7 wt%, about 7.5 wt% or about 8 wt.%.

In some embodiments, the pressurized heating in step (a) is at a temperature ranging from about 390°C to about 500°C.

In some embodiments, the pressurized heating in step (a) is at a temperature of about 390°C, about 400°C, about 410°C, about 420°C, about 430°C, about 440°C, about 450°C, about 460°C, about 470°C, about 480°C, about 490°C or about 500°C.

In an exemplary embodiment, the pressurized heating in step (a) is conducted at a temperature ranging between about 400ºC to about 460ºC.

Pressurized heating is conducted to avoid a massive release of volatiles and so as to increase the yield of the reaction. In some embodiments, the pressurized heating is conducted at a pressure ranging from about 0.5 bar to about 10 bar.

In some embodiments, the pressurized heating is conducted at a pressure of about 0.5 bar, about 1 bar, about 1.5 bar, about 2 bar, about 2.5 bar, about 3 bar, about 3.5 bar, about 4 bar, about 4.5 bar, about 5 bar, about 5.5 bar, about 6 bar, about 6.5 bar, about 7 bar, about 8 bar, about 8.5 bar, about 9 bar, about 9.5 bar, or about 10 bar.

In some embodiments, the thermal treatment of the coal tar is carried out in a stainless-steel reactor able to operate under inert atmosphere.
In some embodiments, the pressurized heating is conducted in an inert atmosphere.

In some embodiments, the pressurized heating is conducted in an inert atmosphere selected from but not limited to nitrogen, neon and argon inert atmosphere or any combination thereof.

In an exemplary embodiment, step (a) of the above-mentioned method is carried out under nitrogen pressure.

In a preferred embodiment the nitrogen pressure is set, but not restricted to, between 0.5-10 bar, preferably about 3 bar.

In some embodiments, the pressurized heating is conducted in the presence of agitation.

In some embodiments, the pressurized heating is conducted in a stirred reactor.

In a non-limiting embodiment, the pressurized heating is conducted for about 2 hours to about 5 hours.

In some embodiments, the pressurized heating is conducted for about 2 hours, about 2.5 hours, about 3 hours, about 3.5 hours, about 4 hours, about 4.5 hours or about 5 hours.

In some embodiments, the pressurized heating is conducted such that the mesophase formed is maintained at an initial stage of formation, at a low concentration.

Accordingly, in some embodiments, the concentration of the incipient mesophase formed in step (a) is maintained below about 5 wt%.

In an exemplary embodiment, the concentration of the incipient mesophase formed in step (a) is maintained below about 3 wt%.

In a non-limiting embodiment, the incipient mesophase formed in step (a) has a concentration of about 0.5 wt%, about 1 wt%, about 1.5 wt%, about 2 wt%, about 2.5 wt% or about 3 wt%.
In some embodiments, the depressurization step (b) is conducted for about 20 minutes to about 1 hour.
In some embodiments, the depressurization in step (b) is conducted for about 20 minutes, about 25 minutes, about 30 minutes, about 35 minutes, about 40minutes, about 45 minutes, about 50 minutes, about 55 minutes or about 60 minutes.

In some embodiments, the depressurization in step (b) is conducted at a rate ranging from about 0.1 bar h-1 to about 15 bar h-1.

In some embodiments, the depressurization in step (b) is conducted at a rate of about 0.1 bar h-1 , about 0.5 bar h-1 , about 1 bar h-1 , about 1.5 bar h-1 , about 2 bar h-1 , about 2.5 bar h-1 , about 3 bar h-1 , about 3.5 bar h-1 , about 4 bar h-1 , about 4.5 bar h-1 , about 5 bar h-1 , about 5.5 bar h-1 , about 6 bar h-1 , about 6.5 bar h-1 , about 7 bar h-1 , about 7.5 bar h-1, about 8 bar h-1, about 8.5 bar h-1, about 9 bar h-1, about 9.5 bar h-1, about 10 bar h-1, about 10.5 bar h-1, about 11 bar h-1, about 11.5 bar h-1, about 12 bar h-1, about 12.5 bar h-1, about 13.5 bar h-1, about 14 bar h-1, about 14.5 bar h-1 or about 15 bar h-1.

In some embodiments, temperature of the heated tar of step(a) is reduced from a range of about 390°C to about 500°C to a range of about 100 ºC to about 350ºC, followed by depressurization of the cooled tar.

In an exemplary embodiment, temperature of the heated tar of step(a) is reduced from a range of about 390°C to about 500°C to a range of about 150ºC to about 250ºC, followed by depressurization of the cooled tar.

Accordingly, in some embodiments, the method for preparing an isotropic pitch having low softening point, comprises -
a) subjecting tar to pressurized heating at a temperature of 390°C to about 500°C to allow formation of an incipient mesophase;
b) reducing the temperature of the pressurized tar to about 150ºC to about 250ºC;
c) subjecting the tar of step (b) to depressurization; and
d) separating the mesophase from the depressurized tar of step (c) to obtain the isotropic pitch having low softening point.

In some embodiments, the method for preparing an isotropic pitch having low softening point, consists of -
a) subjecting tar to pressurized heating at a temperature of 390°C to about 500°C to allow formation of an incipient mesophase;
b) reducing the temperature of the pressurized tar to about 150ºC to about 250ºC;
c) subjecting the tar of step (b) to depressurization; and
d) separating the mesophase from the depressurized tar of step (c) to obtain the isotropic pitch having low softening point.

In some embodiments, the temperature of the depressurized tar of step (b) is optionally further reduced to about 25°C to about 40°C for ease of handling.

Accordingly, in some embodiments, the method for preparing an isotropic pitch having low softening point– comprises -
a) subjecting tar to pressurized heating at a temperature of 390°C to about 500°C to allow formation of an incipient mesophase;
b) subjecting the heated tar of step (a) to depressurization at a temperature of about 100°C to about 350°C;
c) reducing the temperature of the depressurized tar of step (b) to about 25°C to about 40°C; and
d) separating the mesophase from the depressurized tar of step (c) to obtain the isotropic pitch having low softening point.

The present disclosure utilizes the incipient mesophase formed as a result of the pressurized heating as a co-adjuvant to facilitate coalescence of the QI particles. The said tendency of the primary QI particles to coalesce with the very incipient mesophase results in a filterable mixture that allows separation of the mesophase from the isotropic matrix.

In some embodiments, the process for preparing an isotropic pitch further comprises moderate heating of the depressurized tar, after the optional reduction of temperature to about 25°C to about 40°C for fluidization of the depressurized mixture, followed by separation of mesophase.

In some embodiments, the moderate heating is performed at a temperature that is about 10ºC to about 50ºC above the softening point of the mixture formed in step (b).
In some embodiments, the moderate heating is performed at a temperature that is about 10ºC, about 20ºC, about 30ºC, about 40ºC or about 50ºC above the softening point of the mixture formed in step (b).

Therefore, in some embodiments, after step (b), the temperature of the depressurized tar is reduced to about 25°C to about 40°C and subsequently the said tar is heated to a temperature of about 80ºC to about 180ºC for fluidization before the separation of the mesophase.

In some embodiments, the depressurized tar is heated to a temperature of about 80ºC, about 100ºC, about 120ºC, about 140ºC, about 160ºC or about 180ºC for fluidization before the separation of the mesophase.

Accordingly, in some embodiments, the method for preparing an isotropic pitch having low softeningpoint, comprises -
a) subjecting tar to pressurized heating at a temperature of 390°C to about 500°C to allow formation of an incipient mesophase;
b) subjecting the heated tar of step (a) to depressurization at a temperature of about 100°C to about 350°C;
c) reducing the temperature of the depressurized tar of step (b) to about 25°C to about 40°C;
d) heating the cooled depressurized tar of step (c) to about 80°C to about 180°C for fluidization of the depressurized tar; an
e) separating the mesophase from the heated depressurized tar of step (d) to obtain the isotropic pitch having low softening point.

In some embodiments, the method for preparing an isotropic pitch having low softening point, consists of -
a) subjecting tar to pressurized heating at a temperature of 390°C to about 500°C to allow formation of an incipient mesophase;
b) subjecting the heated tar of step (a) to depressurization at a temperature of about 100°C to about 350°C;
c) reducing the temperature of the depressurized tar of step (b) to about 25°C to about 40°C;
d) heating the cooled depressurized tar of step (c) to about 80°C to about 180°C for fluidization of the depressurized tar; and
e) separating the mesophase from the heated depressurized tar of step (d) to obtain the isotropic pitch having low softening point.

In some embodiments, the mesophase is separated by method(s) selected from a group comprising filtration and centrifugation or a combination thereof.

In some embodiments, the filtration is conducted through one or more filters.

In some embodiments, the filtration is through filter(s) having mesh size ranging from about 1 micron to about 25 microns.

In some embodiments, the filtration is through filter(s) having mesh size of about 1 micron, about 5 micron, about 10 micron, about 15 micron, about 20 micron or about 25 micron.
In an exemplary embodiment, the filtration is through filter(s) having mesh size ranging from about 1 micron to about 10 microns.

In a non-limiting embodiment, the filter is a stainless-steel filter.

In some embodiments, the method for preparing an isotropic pitch having low softening point comprises
a) subjecting tar to pressurized heating at a temperature of about 390°C to about 500°C and pressure of about 0.5 bar to about 10 bar;
b) reducing the temperature of the heated tar to about 350 ºC to about 100ºC;
c) depressurizing the tar of step (b) at a rate of about 0.1 bar h-1 to about 15 bar h-1;
d) optionally, allowing the depressurized tar of step (c) to cool to 25°C to about 40°C;
e) optionally, heating the cooled depressurized tar of step (d) to a temperature of about 80ºC to about 180ºC for fluidization; and
f) filtering the heated depressurized/fluidized tar through filter(s) having mesh size ranging from about 1 micron to about 10 microns
to obtain a filtrate comprising the isotropic pitch having low softening point.

In some embodiments, the method for preparing an isotropic pitch having low softening point consists of
a) subjecting tar to pressurized heating at a temperature of about 390°C to about 500°C and pressure of about 0.5 bar to about 10 bar;
b) reducing the temperature of the heated tar to about 350 ºC to about 100ºC;
c) depressurizing the tar of step (b) at a rate of about 0.1 bar h-1 to about 15 bar h-1;
d) optionally, allowing the depressurized tar of step (c) to cool to 25°C to about 40°C;
e) optionally, heating the cooled depressurized tar of step (d) to a temperature of about 80ºC to about 180ºC for fluidization; and
f) filtering the heated depressurized/fluidized tar through filter(s) having mesh size ranging from about 1 micron to about 10 microns
to obtain a filtrate comprising the isotropic pitch having low softening point.

In some embodiments, the softening point of the obtained isotropic pitch is less than or equal to about 100°C.

In some embodiments, the softening point of the obtained isotropic pitch ranges from about 70°C to about 95°C.

In some embodiments, the softening point of the obtained isotropic pitch is about 70°C, about 75°C, about 80°C, about 85°C, about 90°C or about 95°C.

One of the objectives of the present disclosure is to provide a method that allows removal of primary QI particles from the parent tar to yield an isotropic, primary QI free, low softening point pitch.

In some embodiments, the fraction of the obtained QI free pitch which is insoluble in quinoline, referred to as ‘QI content’ of the pitch, which is composed of organic molecules of large size (and not particles having diameter <1 µm) formed during the thermal heating of the tar and was measured after the elimination of the primary QI particles, ranges from about 3.6 wt% to about 6.7 wt%.

In some embodiments, the QI content of the pitch is about 3.6 wt%, about 4 wt%, about 4.5 wt%, about 5 wt%, about 5.5 wt% or about 6.7 wt%.

In some embodiments, provided herein is a method to remove primary QI particles from coal tar, said method comprising steps of
a) subjecting the coal tar to pressurized heating to allow formation of an incipient mesophase;
b) subjecting the heated tar of step (a) to depressurization at a temperature of about 100°C to about 350°C; and
c) separating the mesophase from the depressurized tar of step (b) to obtain the isotropic pitch free of primary QI particles.

In some embodiments, the present disclosure provides a primary quinoline insoluble (QI) particle free, low softening point, isotropic pitch prepared–by a method comprising -
a) subjecting coal tar to pressurized heating to allow formation of an incipient mesophase;
b) subjecting the heated coal tar of step (a) to depressurization at a temperature of about 100°C to about 350°C; and
c) separating the mesophase from the depressurized tar of step (b) to obtain the isotropic pitch having low softening point.

In some embodiments, the present disclosure further provides a primary quinoline insoluble (QI) particle free, low softening point, isotropic pitch prepared by the method as described above.

In some embodiments, the pitch is in a solid form.

In some embodiments, depending on the tar used as the starting material, the primary quinoline insoluble (QI) particle free, low softening point, isotropic pitch has a carbon content ranging from about 92.7 wt.%to about 93.0 wt.%.

In some embodiments, depending on the tar used as the starting material, the primary quinoline insoluble (QI) particle free, low softening point, isotropic pitch has a carbon content of about 92.7 wt.%, about 92.8 wt.%, about 92.9 wt.% or about 93.0 wt.%.

In some embodiments, depending on the tar used as the starting material, the primary quinoline insoluble (QI) particle free, low softening point, isotropic pitch has a H content ranging from about 4.7 wt.% to about 4.8 wt.%.

In some embodiments, depending on the tar used as the starting material, the primary quinoline insoluble (QI) particle free, low softening point, isotropic pitch has a H content of about 4.7 wt.% or about 4.8 wt.%.

In some embodiments, depending on the tar used as the starting material, the primary quinoline insoluble (QI) particle free, low softening point, isotropic pitch has a N content of about 1.4 wt% to about 1.6 wt.%.

In some embodiments, depending on the tar used as the starting material, the primary quinoline insoluble (QI) particle free, low softening point, isotropic pitch has a N content of about 1.4 wt%, about 1.5 wt% or about 1.6 wt.%.

In some embodiments, depending on the tar used as the starting material, the primary quinoline insoluble (QI) particle free, low softening point, isotropic pitch has an oxygen content ranging from about 0.8 wt.% to about 1 wt.%.

In some embodiments, depending on the tar used as the starting material, the primary quinoline insoluble (QI) particle free, low softening point, isotropic pitch has an oxygen content of about 0.8 wt.%, about 0.85 wt.%, about 0.9 wt.%, about 0.95 wt.% or about 1 wt.%.

In some embodiments, softening point of the pitch is less than or equal to about 100°C.

In some embodiments, softening point of the pitch ranges from about 70°C to about 95°C.

In some embodiments, softening point of pitch ranges is about 70°C, about 75°C, about 80°C, about 85°C, about 90°C or about 95°C.

In some embodiments, depending on the tar used as the starting material, the QI content (i.e. QI molecules having size > 1µm) of the obtained primary QI free pitch ranges from about 3.6 wt% to about 6.7 wt%.

In some embodiments, depending on the tar used as the starting material, the QI content of the primary QI free pitch is about 3.6 wt%, about 4 wt%, about 4.5 wt%, about 5 wt%, about 5.5 wt% or about 6.7 wt%.

In some embodiments, depending on the tar used as the starting material, the Toluene insoluble (TI) content of the obtained primary QI free pitch ranges from about 25 wt% to about 40 wt%.
As mentioned above, the characteristics of the pitch, such as elemental composition, QI and TI content are dependent on the tar used as starting material. Therefore, the above ranges provided for the QIF pitch are non-limiting and prone to deviation based on the tar used as starting material. Thus, the above ranges are depictive of the observations for the QIF pitch obtained from the tar characterized in Table 1 in the Examples section of the present disclosure and are in no way considered to be limiting.

In an embodiment, the foregoing descriptive matter is illustrative of the disclosure and not a limitation. Providing working examples for all possible combinations of optional elements in the composition and process parameters such as but not limiting to time and temperature of hot dipping, is considered redundant.

While the present disclosure is susceptible to various modifications and alternative forms, specific aspects thereof have been shown by way of examples and drawings and are described in detail below. However, it should be understood that it is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and the scope of the invention as defined by the appended claims.

EXAMPLES:

Materials and methods
All the examples were carried out using up to four coal tars as starting material. Properties of the said coal tars are summarized in Table 1:

Table 1: Elemental composition, solubility parameters and carbon yield of the four coal tars used as raw materials
Sample Elemental Analysis (wt.%)
C H N S O TI QI CY
CT1 90.4 5.6 1.6 0.6 1.8 6.7 0.7 23.0
CT2* 88.6 5.3 1.5 0.8 3.8 6.5 2.4 26.3
CT3 91.0 5.4 1.5 0.6 1.5 9.0 1.8 25.3
CT4** 82.2 5.4 1.3 0.6 10.5 10.0 5.1 28.8
* contains 29% of liquid fraction immiscible in the parent tar (hereinafter referred to as supernatant)
** contains 15% of liquid fraction immiscible in the parent tar (hereinafter referred to as supernatant)
TI, toluene insoluble content (wt.%)
QI, primary QI particles content (wt.%)
CY, carbon yield (wt.%) determined by ALCAN analysis

Methods used for analysis -
Elemental Analysis: The carbon, hydrogen, nitrogen and sulphur contents of the tars were determined by elemental analysis with a LECO-CHNS-932 microanalyzer. The oxygen content of the samples was determined directly in a LECO-TF-900 furnace coupled to a LECO-CHNS-932 microanalyzer. The analyses were performed using about 1mg of ground sample. The results were quoted from an average of the values of four determinations. In all cases, the experimental error was < 0.5% of the absolute value. Tar samples can contain some occluded water. Therefore, the oxygen content in them was determined by difference from the C,H,N,S total percentage content.

Determination of Toluene Insoluble Content: Solubility of the samples in toluene was determined according to the Pechiney B-16 (series PT-7/79 of STPTC) standard. About 2 g of representative sample and about 100 mL of toluene were placed in a ?ask, heated to the boiling point, and maintained under re?ux for about 30 minutes. Filtering was carried out with a porous ceramic plate No. 4 and the residue washed with hot toluene to complete the removal of toluene soluble fraction, and then with about 10 mL of acetone. The experiments were performed in duplicates and the result was taken as the average of both determinations.

Determination of Quinoline Insoluble content: Solubility in quinoline was determined according to the ASTM2318 standard. About 0.5g to about 2 g of representative sample (tar or soft pitches in this work) and about 25 mL of quinoline were placed in a ?ask and heated to about 75 °C for about 20 minutes. The filtering was carried out with a porous ceramic plate No. 5 (for as received tars, additional use of a filter membrane of 0.1 µm was required) and the residue was washed with hot toluene and acetone to complete the total removal of the quinoline. The experiments were performed in duplicates and the result was taken as the average of both determinations.

The quinolone insoluble content in the parent tar represents the amount of ‘primary’ QI particles present in the tar having particle diameter less than 1µm.

In the formed pitches, which are free of these primary QI particles as confirmed by additional methods (such as optical spectroscopy), ‘QI content’ accounts for carbonaceous molecules of large size formed during the previous thermal treatment.

Carbon yield: Carbon yield of samples was calculated by adopting the Alcan method (ASTM D4715 standard). About 1 g of sample was place in a 30 mL porcelain crucible covered with a lid. The porcelain crucible was embedded in calcined petroleum coke (< 1mm particle size) within a 130 mL lidded nickel crucible. The set was then placed in an oven preheated to about 550 °C. After about 150 min, the set was removed from the oven and freely cooled. The carbon yield was determined from the weight of the carbonaceous residue. The experiments were performed in duplicates and the result was taken as the average of both determinations.

Optical microscopy: Optical microscopy was performed on polished samples embedded in epoxy resin, using a Zeiss Axioplan microscope. The microscope was equipped with one lambda retarder plate to generate interference colours. Representative micrographs of each sample were taken using objectives with lens of x10 (air), x20 (oil) and x50 (oil) magnifications.

EXAMPLE 1: Thermal treatment of coal tar under pressure followed by depressurization in cold temperature (200ºC) followed by filtration
Thermal treatment of coal tars to form reaction products
Thermal treatment of tars was carried out in a stainless-steel reactor able to operate under inert atmosphere and even under gaseous pressure (nitrogen). The reactor containing the selected coal tar (CT1, CT2, CT3 and CT4) was heated according to the following conditions: heating to about 420°C, at about 3 bar of nitrogen pressure and for a residence time of about 4 hours. After finishing the treatment, the temperature was decreased to about 200ºC, and the pressure was removed. The depressurization was performed for about 20-30 minutes. At these conditions, a soft product was obtained in all cases, hereinafter referred to as Product-CT1-cold, Product-CT2-cold, Product-CT3-cold and Product-CT4-cold. The yields of these reaction products are summarized in Table 2. The yields in all reactions were found to vary from about 47wt% to about 67wt.%.

Table 2: Yields (reaction and filtration) and softening points of reaction products from coal tars in the stirred reactor
Sample Product Yield (wt.%) Softening point
(ºC)
CT1 62.2 79
CT2 47.5 80
CT3 66.4 78
CT4 65.9 90

The reaction products were obtained as semi-solid samples. This allowed study of their optical texture before proceeding with the filtering step and importantly, to confirm the presence, in all products obtained, of mixtures of mesophase spheres surrounded by primary QI particles within the isotropic matrix.

Results of said optical are summarized in Figure 1. By using lens x20 the presence of mixtures of isotropic phase (purple background) and mesophase spheres in all the reaction products obtained was observed (Figure 1, left). The images suggest higher evolution of mesophase in samples with the largest amount of primary QI particles (for example from tar CT4, Table 1). At higher magnifications using lens x50, the primary QI particles surrounding the spheres were also visible, disrupting the theoretically perfect round surface of the spheres (Figure 1, right).

Filtration of reaction products to form the pitches
The reaction products prepared as described above were filtered to separate the primary QI particles and the mesophase spheres from the isotropic phase. The products obtained are hereinafter referred to as Product-CT1-cold, Product-CT2-cold, Product-CT3-cold and Product-CT4-cold.

Product-CT1-cold and Product-CT3-cold were filtered directly through a 1 µm mesh filter. However, Product-CT2-cold and Product-CT4-cold required a pre-filtering step using filter of mesh size 25 µm to prevent filter blockage in view of the higher content of primary QI particles in the starting material, post which, the pre-filtered reaction products passed through the 1 µm mesh filter. The obtained pitches are hereinafter referred to as CTP1-QIF-cold, CTP2-QIF-cold, CTP3-QIF-cold and CTP4-QIF-cold.

The filtration results are summarized in Table 3. The results clearly indicate that products from CT1 and CT3, the coal tars with the lowest amount of primary QI particles, have similar (and relatively higher) filtration yields (~83 wt.%), this yield decreasing in samples prepared from coal tars having higher primary QI particle content, for example CT2 (providing a yield of about 50 wt.%) and CT4 (providing a yield of about 33 wt.%).

In order to prove the isotropic nature of the pitches obtained, the filtrates were further characterized by optical microscopy with polarized light (Figure 2). The optical images confirmed that the obtained pitches were completely isotropic. The process also eliminated almost all the primary QI particles in the pitches. In order to further confirm this, also considering that QI particles are more visible within an anisotropic matrix (and that their evaluation as insolubility in quinoline is not possible in the pitch since the pitch also contains molecules of large size formed by polymerization during the thermal treatment that are also insoluble in such solvent, ALCAN analysis of the as obtained primary QI-free pitches was performed to analyse the residue (coke) by optical microscopy. The results, summarized in Figure 3 (lens x 50), confirmed the absence of the primary QI particles in the coke (and by extension, in the parent pitch), along with a texture in the obtained coke which is explained by the coalescence of mesophase spheres during growing, allowed by the absence of primary QI particles in the pitch.

For CTP3-QIF-cold, the optical texture of the retained fraction was determined (Figure 4) confirming that the retained fraction was primarily composed of mesophase spheres and primary QI particles.

The QIF pitches so obtained were further characterized (Table 3). The softening point of the obtained pitches were found to range from about 76ºC for CTP3-QIF-cold to about 90 ºC on CTP4-QIF-cold. The elemental composition of all primary QI-free pitches was found to be quite similar, with the carbon content varying from about 92.7 wt% to about 93.0 wt.%, the H content between about 4.7 wt% to about 4.8 wt.% and the N content in all of them of being about 1.5 wt.%. The oxygen content was also low about 1.0 wt% to about 0.8 wt.%. The pitches were assessed for carbon yield (determined by means of the ALCAN method), which was slightly higher for CTP1-QIF-cold and CTP4-QIF-cold (about 53.3 wt.%) than for CTP3-QIF-cold (about 48.8 wt.%) and CTP2-QIF-cold (about 48.3 wt.%). The pitches were further characterized by the solubility parameters. The quinoline insoluble content, which now accounts for the larger molecules formed during the thermal treatment and not for primary QI particles, was quite similar for CTP3-QIF-cold and CTP2-QIF-cold, and comparatively lower for CTP1-QIF-cold. In the case of CTP4-QIF-cold, this value could not be estimated since the filter was blocked, which is indicative of a higher polymerization degree of its components. The toluene insoluble content of CTP3-QIF-cold was found to be relatively higher, in a similar range as that observed for CTP4-QIF-cold, in line with TI values of their respective starting materials.

Table 3: Elemental analysis, solubility parameters, carbon yield and softening points of the primary QI-free pitches obtained from CT1, CT2, CT3 and CT4 via the conditions of Example 1
Sample Elemental Analysis (wt.%) TI QI CY Filtration yield
(Wt%) Softening point (ºC)
C H N S O (wt.%) (wt.%) (Wt.%)
CTP1-QIF-cold 92.7 4.8 1.5 0.4 1.0 28.7 3.6 53.3 83 79
CTP2-QIF-cold 92.9 4.8 1.5 0.5 0.8 27.0 6.2 48.3 50 77
CTP3-QIF-cold 92.9 4.8 1.5 0.4 0.8 36.5 6.7 48.8 83 76
CTP4-QIF-cold 93.0 4.7 1.5 0.5 0.8 34.4 -* 53.3 33 90
TI, toluene insoluble content (wt.%)
QI, quinoline insoluble content (wt.%) after primary QI particle elimination
CY, carbon yield (wt.%) determined by ALCAN analysis
*Filter blocked

EXAMPLE 2: Thermal treatment of coal tar under pressure followed by depressurization at the same high temperature followed by filtration (comparative example)
Thermal treatment of coal tars to form reaction products
CTP1 and CTP2 coal tars were thermally treated in a stainless steel reactor at a temperature of about 420 °C and at about 3 bar of nitrogen pressure. After about 2 hours at this temperature, pressure was gradually removed until reaching atmospheric conditions (hot depressurization). After that, the thermal treatment at about 420 °C was prolonged for about 2 more hours, but under atmospheric pressure. The reaction products obtained (hereinafter referred to as Product-CT1-hot and Product CT2-hot) were, at these conditions, solid samples, having softening points of about 137ºC and about 169ºC, respectively (i.e. higher than softening points observed in example 1). The yields obtained were higher for Product-CT1-hot i.e. about 50 wt.% as compared to about 34 wt.% for Product-CT2-hot. This could be due to the supernatant fraction (not reactive under these conditions).

Said yield is lower than that obtained in Example 1, which could be attributed to the differences in the depressurization method, more particularly the temperature at which the depressurization was performed.

Table 4: Yields (reaction and filtration) and softening point of reaction products and pitches from coal tars CT1 and CT2 obtained after depressurization at 420ºC -
Coal Tar Product Yield (wt.%) Softening point of Product
(ºC)
CT-1 49 137
CT-2 34 169

The final product of the thermal treatment was subjected to optical analysis to understand the presence of isotropic and/or mesophase. The optical images (Figure 5) confirm that the products were obtained as a mixture of isotropic phase and incipient mesophase spheres.

Filtration of reaction products to form the pitches
The reaction products obtained in previous step were thermally heated at moderate temperature (to fluidify the pitches) and filtered through 25 µm (CTP2) and 1 (CTP2 and CTP1) µm mesh filters consecutively. The filtration temperature was about 160 ºC for Product-CT1-hot and 200 ºC for Product-CT2-hot. After filtration, the filtrate (pitch) was recovered and labeled as CTP1-QIF-hot and CTP2-QIF-hot.

Optical characterization of each filtrate was performed after their ALCAN carbonization. The obtained images of the ALCAN residues after filtration are summarized in Figure 6.

The results indicate that the filtration of reaction products from CT1 and CT2 at the processing conditions carried out in example 2 was successful, confirming that both pitches were free of primary QI particles (not black spots were observed in images of CTP1 and CTP2 after filtering with 5 µm. However, CTP2-QIF-hot required the initial use of filters of higher mesh size (25 µm) and a subsequent filtration through 5 µm mesh size filter.

The filtrate itself was characterized by optical microscopy with polarized light results of which as shown in Figure 7. The results indicate that both pitches were isotropic.

The softening point was measured for the obtained pitches CTP1-QIF-hot and CTP2-QIF-hot (Table 5), being 135ºC and 165ºC respectively. These results show that the experimental conditions of example 2, which includes a depressurization of the thermally treated tar under pressure at a higher temperature yields primary QI free isotropic pitches but having softening point above values expected for a low softening point pitch (defined as about 100ºC).

Table 5: Softening points of the QI-free pitches obtained from CT1 and CT2 via the conditions of Example 2
Sample Softening point (ºC) ALCAN Filtration yield
Wt.% (wt.%)
CTP1-QIF-hot 136 1.0 83
CTP2-QIF-hot 167 1.1 50

EXAMPLE 3: Thermal treatment of coal tar under pressure followed by depressurization at room temperature and filtration (Comparative example)
CTP1 and CTP2 coal tars were thermally treated in a stainless-steel reactor at about 420 °C and about 3 bar of nitrogen pressure for about 4 hours. After cooling up to room temperature of about 25ºC, pressure was gradually removed until reaching atmospheric conditions The depressurization was performed for a total time of about 20-30 min). The reaction products obtained (hereinafter referred to as Product-CT1-RT and Product CT2-RT) were, at these conditions, completely liquid samples having yields of about 63 wt.% and about 74 wt.%, respectively.

After filtering the products, no residue was observed in the mesh and consequently liquid materials (hereinafter referred to as CTP1-QIF-RT or CTP2-QIF-RT) were obtained (instead of solid sample as in the case of Example 1).

This indicated that the obtained product contained the primary QI particles.

Table 6: Product yield and softening points of the QI-free pitches obtained from CT1 and CT2 after depressurization at room temperature
Sample Product yield
(wt%) Softening point (ºC)
CTP1-QIF-RT 63 NA (Obtained as liquid)
CTP2-QIF-RT 74 NA (Obtained as liquid)

EXAMPLE 4: Filtration of coal tar to remove primary QI particles without thermal treatment
Parent tars as employed as starting material in Examples 1-3 were subjected to filtration using filtering meshes of different having size ranging from 5µm to 0.5µm, without any thermal treatment. The results are summarized in Table 7. The presence of the primary QI particles was directly visualized by optical microscopy in the ALCAN residue derived from the filtered tars, which appears as isotropic spots also disrupting the coalescence of the fluid anisotropic domains. The images obtained are depicted in Figure 8.

Table 7: Filtration conditions studied with CT1 tar without the presence of mesophase in its composition.
Run no. Mesh filter
(µm) Temperature
(°C) Mass
(g) Pressure
(bar) Observations
1 5 80 25 1 Primary QI presence
2 1 80 25 1 Primary QI presence
3 2 filters together:
1µm +1µm 80 25 1 Primary QI presence
4 3 filters together:
1µm+1µm +1µm 80 25 1 Primary QI presence
5 Filtrate of run 4 filtered through 0.5µm 60 25 1 Primary QI free

It was possible to filter CT1 through a 5 µm mesh filter at about 80ºC and 1 bar and in less than 5 minutes. In a second experiment, the 5 µm mesh filter was replaced by a 1µm mesh filter, keeping constant the other parameters of the process.

Studies carried out by light microscopy on the ALCAN residue (coke) derived from the filtered tar of runs 1 and 2 (Figures 8 b,c) revealed that primary QI particles remained in similar amounts like the coke obtained from original tar (Figure 8a). The use of two, and even three, overlapped 1 µm mesh filters only produced a little reduction in the amount of primary QI particles (Figure 8d and Figure 8e).

It was only after the use of a further filter mesh of 0.5 µm (cost of such filters being extremely high) through which the filtrate of run using 1µm +1µm +1µm mesh filters was passed that the QI particles in the tar were eliminated in great proportion (Figure 8f). Although the QI particles seemed to be even of lower size that 0.5 µm, the effectiveness of the filtering process could be related to the effect of mesh size reduction by the carbonaceous material (or particle accumulation) during the filtering process. Despite that, it is obvious that the absence of any mesophase sphere requires the usage of multiple filters of larger size, thereby increasing the process time and reducing process economy and efficiency.

Additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based on the description provided herein. The embodiments herein provide various features and advantageous details thereof in the description. Descriptions of well-known/conventional methods and techniques are omitted so as to not unnecessarily obscure the embodiments herein.

The foregoing description fully reveals the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments in this disclosure have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein, without departing from the principles of the disclosure.

Any discussion of documents, acts, materials, devices, articles and the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
, C , C , C , C , C , C , C , C , Claims:1. A method for preparing a primary quinoline insoluble (QI) particle free, isotropic pitch having low softening point, comprising
a) subjecting coal tar to pressurized heating to allow formation of an incipient mesophase;
b) subjecting the heated coal tar of step (a) to depressurization at a temperature of about 100°C to about 350°C; and
c) separating the mesophase from the depressurized tar of step (b) to obtain the isotropic pitch having low softening point.

2. The method as claimed in claim 1, wherein the coal tar has primary quinoline insoluble particles (QI) content of about 0.3 wt% to about 8 wt.%.

3. The method as claimed in claim 1, wherein the pressurized heating is at a temperature ranging from about 390°C to about 500°C.

4. The method as claimed in claim 1, wherein the pressurized heating is conducted at a pressure ranging from about 0.5 bar to about 10 bar.

5. The method as claimed in claim 1, wherein the pressurized heating is conducted in an inert atmosphere.

6. The method as claimed in claim 1, wherein the pressurized heating is conducted in a stirred reactor.

7. The method as claimed in claim 1, wherein the pressurized heating is conducted for about 2 hours to about 5 hours.

8. The method as claimed in claim 1, wherein the depressurization is conducted at a rate of about 0.1 bar h-1 to about 15 bar h-1.

9. The method as claimed in claim 1, wherein the depressurization is conducted for about 20 minutes to about 1 hour.

10. The method as claimed in claim 1, wherein temperature of the heated coal tar of step(a) is reduced from a range of about 390°C to about 500°C to a range of about 100 ºC to about 350ºC, followed by depressurization of the cooled tar.

11. The method as claimed in claim 1, wherein the mesophase is separated by method selected from a group comprising filtration and centrifugation, or a combination thereof.

12. The method as claimed in claim 11, wherein the filtration is through filter(s) having mesh size ranging from about 1 micron to about 10 microns.

13. The method as claimed in claim 1, comprising
a) subjecting coal tar to pressurized heating at a temperature of about 390°C to about 500°C and pressure of about 0.5 bar to about 10 bar;
b) reducing the temperature of the heated coal tar to about 350 ºC to about 100ºC;
c) depressurizing the tar of step (b) at a rate of about 0.1 bar h-1 to about 15 bar h-1;
d) filtering the coal tar obtained in step (d) through filter(s) having mesh size ranging from about 1 micron to about 10 microns.
to obtain a filtrate comprising the isotropic pitch having low softening point.

14. The method as claimed in claim 1, wherein the softening point of the pitch is less than or equal to about 100°C.

15. The method as claimed in claim 14, wherein the softening point of the pitch ranges from about 70°C to about 95°C.

16. The method as claimed in claim 1, wherein the QI content of the pitch ranges from about 3.6 wt% to about 6.7 wt%.

17. The method as claimed in claim 1, wherein the TI content of the pitch ranges from about 25 wt% to about 40 wt%.

18. A primary quinoline insoluble (QI) particle free, low softening point, isotropic pitch prepared by the method as claimed in claim 1.
19. The primary quinoline insoluble (QI) particle free, low softening point, isotropic pitch as claimed in claim 18, wherein the softening point of the pitch is less than or equal to about 100°C.

20. The primary quinoline insoluble (QI) particle free, low softening point, isotropic pitch as claimed in claim 19, wherein the softening point of the pitch ranges from about 70°C to about 95°C.

21. The primary quinoline insoluble (QI) particle free, low softening point, isotropic pitch as claimed in claim 18, wherein the QI content of the pitch ranges from about 3.6 wt% to about 6.7 wt%.

22. The primary quinoline insoluble (QI) particle free, low softening point, isotropic pitch as claimed in claim 18, wherein the TI content of the pitch ranges from about 25 wt% to about 40 wt%.