FIELD

The present disclosure relates to a process for reducing the content of asphaltene and unsubstituted polynuclear aromatics of heavy hydrocarbons.

BACKGROUND

The background information herein below relates to the present disclosure but is not necessarily prior art.

Conventionally, heavy hydrocarbons, such as heavy coker gas oil (HCGO), vacuum gas oil (VGO), heavy vacuum gas oil (HVGO), and heavy atmospheric gas oil (HAGO) can be converted to lighter feedstocks by hydrotreating or fluidized catalytic cracking (FCC). Lighter feedstocks are easy to crack and require less capital input for refining. Heavy hydrocarbons comprise paraffins, substituted polynuclear aromatics (substituted PNAs), unsubstituted polynuclear aromatics (unsubstituted PNAs), as well as coke precursors such as asphaltene. Paraffins, and substituted polynuclear aromatics (substituted PNAs) can be converted to useful lower hydrocarbons.

However, the presence of coke precursors and unsubstituted polynuclear aromatics (unsubstituted PNAs) in heavy hydrocarbons pose certain problems. Coke precursors produce coke, which deactivates the catalyst, thereby reducing the catalyst life. The presence of unsubstituted PNAs necessitates carrying out hydrotreating at a high hydrogen partial pressure. The use of high hydrogen partial pressure increases the capital cost of the equipment or may require expensive revamps of low pressure units. Furthermore, the presence of asphaltene and unsubstituted PNAs reduce the yields of useful FCC products and decrease gross refinery margin (GRM) during fluid catalytic cracking (FCC).

There is, therefore, felt a need to provide a process for reducing the content of asphaltene and unsubstituted PNAs of heavy hydrocarbons. OBJECTS

Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.

It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.

It is another object of the present disclosure to reduce content of asphaltene in heavy hydrocarbons.

It is yet another object of the present disclosure to reduce the content of unsubstituted polynuclear aromatics (unsubstituted PNAs) in heavy hydrocarbons feed. Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.

SUMMARY

The present disclosure relates to a process for reducing content of asphaltene and unsubstituted polynuclear aromatics in a heavy hydrocarbon feed. The present disclosure provides a two stage process comprising reducing the asphaltene content of heavy hydrocarbon feed using a hydrocarbon fluid medium; followed by separating from heavy hydrocarbon feed with/ without reduced asphaltene content, an aromatic fraction containing unsubstituted polynuclear aromatics to obtain the heavy hydrocarbon feed with the reduced content of asphaltene and unsubstituted polynuclear aromatics. Typically, the step of separating an aromatic fraction from heavy hydrocarbon feed either follows or precedes process step of reducing the asphaltene content of heavy hydrocarbon feed.

Typically, the heavy hydrocarbon feed in step is hydrocarbon feed with/ without reduced content of unsubstituted polynuclear aromatics.

In the first stage the heavy hydrocarbon feed is mixed with the hydrocarbon fluid medium in a mixer to obtain a first resultant mixture. The first resultant mixture is introduced in a settler and allowed to settle to obtain a first biphasic mixture comprising a hydrocarbon phase comprising heavy hydrocarbon feed with reduced asphaltene content and the solid phase comprising asphaltene. The solid phase is separated from the first biphasic mixture to obtain the hydrocarbon phase comprising the heavy hydrocarbon feed with reduced asphaltene content.

In the second stage the heavy hydrocarbon feed is mixed with a polar fluid medium to obtain a second resultant mixture. The second resultant mixture is introduced in a settler and allowed it to settle to obtain a second biphasic mixture comprising an upper layer comprising a paraffin fraction with reduced content of aromatics, and the lower layer comprising an aromatic fraction containing unsubstituted polynuclear aromatics. The upper layer is separated from the second biphasic mixture to obtain the paraffin fraction with reduced aromatics content and the aromatic fraction containing unsubstituted polynuclear aromatics.

The paraffin fraction is mixed with water and allowed to settle to obtain a third biphasic mixture comprising a first organic phase containing paraffins and a first aqueous phase containing polar fluid medium and water. Similarly, the aromatic fraction is mixed with water and allowed to settle to obtain a fourth biphasic mixture comprising a second organic phase containing aromatics and a second aqueous phase containing polar fluid medium and water.

The process of the present disclosure improves a compositional quality of the heavy hydrocarbon feed, which further helps in improving yield of FCC unit and life of hydro-treating catalyst.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

The present disclosure will now be described with the help of the accompanying drawing, in which:

Figure 1 is a schematic representation of a process for reducing asphaltene content of a heavy hydrocarbon in accordance with the present disclosure; and

Figure 2 is a schematic representation of a process for reducing the content of unsubstituted polynuclear aromatics (unsubstituted PNAs) of a heavy hydrocarbon in accordance with the present disclosure.

DETAILED DESCRIPTION

Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.

The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising,"“including,” and“having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.

The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.

The present disclosure therefore, discloses a two stage process for reducing content of asphaltene and unsubstituted polynuclear aromatics of heavy hydrocarbon feed.

The present disclosure provides a two stage process comprising reducing the asphaltene content of heavy hydrocarbon feed using a hydrocarbon fluid medium; followed by separating from heavy hydrocarbon feed with/ without reduced asphaltene content, an aromatic fraction containing unsubstituted polynuclear aromatics to obtain the heavy hydrocarbon feed with the reduced content of asphaltene and unsubstituted polynuclear aromatics. Typically, the step of separating an aromatic fraction from heavy hydrocarbon feed either follows or precedes process step of reducing the asphaltene content of heavy hydrocarbon feed.

Typically, the heavy hydrocarbon feed in step is hydrocarbon feed with/ without reduced content of unsubstituted polynuclear aromatics. In the first stage the heavy hydrocarbon feed is mixed with the hydrocarbon fluid medium in a mixer to obtain a first resultant mixture. The first resultant mixture is introduced in a settler and allowed to settle to obtain a first biphasic mixture comprising a hydrocarbon phase comprising heavy hydrocarbon feed with reduced asphaltene content and the solid phase comprising asphaltene. The solid phase is separated from the first biphasic mixture to obtain the hydrocarbon phase comprising the heavy hydrocarbon feed with reduced asphaltene content.

In the second stage the heavy hydrocarbon feed is mixed with a polar fluid medium to obtain a second resultant mixture. The second resultant mixture is introduced in a settler and allowed it to settle to obtain a second biphasic mixture comprising an upper layer comprising a paraffin fraction with reduced content of aromatics, and the lower layer comprising an aromatic fraction containing unsubstituted polynuclear aromatics. The upper layer is separated from the second biphasic mixture to obtain the paraffin fraction with reduced aromatics content and the aromatic fraction containing unsubstituted polynuclear aromatics.

The paraffin fraction is mixed with water and allowed to settle to obtain a third biphasic mixture comprising a first organic phase containing paraffins and a first aqueous phase containing polar fluid medium and water. Similarly, the aromatic fraction is mixed with water and allowed to settle to obtain a fourth biphasic mixture comprising a second organic phase containing aromatics and a second aqueous phase containing polar fluid medium and water.

In accordance with the embodiments of the present disclosure, the process further comprises mixing the first aqueous phase and the second aqueous phase and introducing the combined aqueous phase to a distillation unit for recovery of the polar fluid medium.

In accordance with the embodiments of the present disclosure, the heavy hydrocarbon feed is at least one selected from the group consisting of heavy coker gas oil (HCGO), vacuum gas oil (VGO), heavy vacuum gas oil (HVGO) and heavy atmospheric gas oil (HA GO). In accordance with the exemplary embodiment of the present disclosure, the heavy hydrocarbon feed is heavy coker gas oil (HCGO).

In first stage, the present disclosure provides a process for reducing the content of asphaltene in a heavy hydrocarbon. The process is described with the help of Figure-1, which depicts a schematic representation of the process for reducing asphaltene content of a heavy hydrocarbon in accordance with the present disclosure.

A heavy hydrocarbon feed (102) is mixed with a hydrocarbon fluid medium (104) in a first mixer (106) to obtain a first resultant mixture (108).

The first resultant mixture (108) is then introduced in a first settler (110) and allowed to settle to obtain a first biphasic mixture comprising a hydrocarbon phase comprising heavy hydrocarbons with reduced asphaltene content and the solid phase comprising asphaltene. The solid phase (114) is separated from the first biphasic mixture to obtain the hydrocarbon phase comprising the heavy hydrocarbons with reduced asphaltene content (112). The step of separation involves filtration to remove suspended asphaltene particles. In accordance with the embodiments of the present disclosure, the hydrocarbon fluid medium is at least one selected from the group consisting of n-propane, n-pentane, n-hexane, n-heptane and light coker naphtha and de-iso-pentanizer side draw. In accordance with an exemplary embodiment of the present disclosure, the hydrocarbon fluid medium is n-pentane.

In accordance with the embodiments of the present disclosure, the step of reducing the asphaltene content of heavy hydrocarbon feed is carried out at a temperature in the range of 50 °C to 250 °C, and the pressure in the range of 2 to 20 MPa.

The asphaltene content of the heavy hydrocarbon is reduced by an amount in the range of 80 weight% to 99.9 weight% by the process of the present disclosure.

In accordance with the embodiments of the present disclosure, the hydrocarbon fluid medium is recovered and reused, thereby providing economical and eco-friendly process.

In second stage, the present disclosure provides a process for reducing the content of unsubstituted polynuclear aromatics (unsubstituted PNAs) of a heavy hydrocarbon. The process is described with the help of Figure-2, which is a schematic representation of the process for reducing the content of unsubstituted polynuclear aromatics (unsubstituted PNAs) of a heavy hydrocarbon in accordance with the present disclosure.

A heavy hydrocarbon feed (202) is mixed with a polar fluid medium (204) in a second mixer (206) to obtain a second resultant mixture (208).

The second resultant mixture (208) is introduced in a second settler (210), and is allowed to settle to obtain a second biphasic mixture comprising an upper layer containing a paraffin fraction with reduced content of aromatics, and the lower layer comprising an aromatic fraction containing unsubstituted polynuclear aromatics, and polar fluid medium. The upper layer is separated from the second biphasic mixture to obtain the paraffin fraction with reduced content of aromatics (212).

The separated upper layer contains a small fraction of the polar fluid medium, which is separated with the help of water. A typical procedure for separating water is provided herein below.

The separated upper layer (212) is mixed with water (216) with the help of a third mixer (218) to obtain a first admixture (220). The first admixture is introduced in a third settler (222), and is allowed to settle to obtain a third biphasic mixture comprising a first organic phase containing paraffins and substituted PNAs and the first aqueous phase containing water and the trace amount of the polar fluid medium. The first aqueous phase (228) is separated from the third biphasic mixture to obtain the first organic phase (226). In accordance with the embodiments of the present disclosure, the lower layer comprising an aromatic fraction containing unsubstituted polynuclear aromatics is admixed with water (234) with the help of a fourth mixer (236) to obtain a second admixture (238). The second admixture is introduced in a settler (240) and allowed to settle to obtain a fourth biphasic mixture comprising a second organic phase containing unsubstituted PNAs and the second aqueous phase containing the polar fluid medium and water. The second organic phase (242) is separated from the fourth biphasic mixture to obtain the second organic phase (242) and the second aqueous phase (244). The first aqueous phase (228) and the second aqueous phase (244) are combined and the combined aqueous phase (246) can be introduced in a distillation unit (248). The combined aqueous phase can be distilled to obtain a top fraction comprising water (250) and a bottom fraction containing the polar fluid medium (252). In accordance with the embodiments of the present disclosure, the polar fluid medium is at least one selected from the group consisting of furfural, N-methyl-2-pyrrolidone (NMP), sulfolane, dimethyl formamide (DMF), dimethyl sulphoxide (DMSO), water and combinations thereof. In accordance with the exemplary embodiment of the present disclosure, the polar fluid medium is N-methyl-pyrrolidone (NMP). In accordance with another exemplary embodiment of the present disclosure, the polar fluid medium is a combination of N-methyl-pyrrolidone (NMP) and water.

In accordance with the embodiments of the present disclosure, the step of separating heavy hydrocarbon feed into paraffin fraction and aromatic fraction is carried out at a temperature in the range of 50 °C to 250 °C, and the pressure in the range of 2 to 20 MPa.

The lower layer (214) obtained from the second biphasic mixture comprises majority of the polar fluid medium. The polar fluid medium is recovered reused.

The unsubstituted PNAs obtained in the process of the present disclosure may further be converted to useful lower hydrocarbons. The second organic phase (242) comprising unsubstituted PNAs can be hydrotreated to obtain reduced products. The reduced products so obtained can be subjected to ring opening reactions to obtain a mixture comprising paraffins. This mixture can be cracked to obtain useful lower hydrocarbons. In accordance with one embodiment of the present disclosure, this mixture can be mixed with the heavy hydrocarbon with reduced content of asphaltene and unsubstituted PNAs, and the combined mixture can be cracked.

In accordance with the embodiments of the present disclosure, the polar fluid medium is recovered and reused, thereby providing economical and eco-friendly process.

In another embodiment, the process involves separating heavy hydrocarbon feed into paraffin fraction with reduced content of unsubstituted polynuclear aromatics and aromatic fraction, followed by reducing the asphaltene content of the aromatic fraction using a hydrocarbon fluid medium to obtain heavy hydrocarbon with reduced asphaltene content.

If the step of reducing the asphaltene content of heavy hydrocarbon feed is carried out first, it can be carried out at ambient temperature as dissolved paraffins will be in liquid state and paraffin will not solidify at ambient conditions. However, coke particle and other inorganic particles will be discarded first, and viscosity of mixture will be reduced drastically which will improve feed filters performance. But the disadvantages come from handling higher amount of hydrocarbon fluid medium.

If step of reducing the asphaltene content of heavy hydrocarbon feed is carried out after separation of paraffin fraction and aromatic fraction, process will have to be carried out at greater than congealing temperature of VGO. Further, asphaltenes separation will require additional capex for handling of hydrocarbon fluid medium and it’s separation and recovery. But this process will discard asphaltenes and reduce catalyst deactivation by metals and coking. It will also reduce or mitigate the VGOHT feed filter problems. The reduction in the content of asphaltene and unsubstituted PNAs of the heavy hydrocarbon leads to an increase in the life of the hydrotreating catalyst and FCC catalyst which are contacted with the heavy hydrocarbon. Further, the FCC process with the hydrocarbon steam having reduced asphaltene content and enriched with paraffins and substituted PNAs have higher yield of useful lower hydrocarbons. The unsubstituted PNAs can be subjected to hydrotreatment, followed by ring opening reaction to obtain paraffins. Thus, the loss of heavy hydrocarbon in the form of unsubstituted PNAs is prevented, thereby leading to high the gross refinery margin (GRM).

The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure. The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial scale. EXPERIMENTAL DETAILS

Experiments 1: Reduction of content of asphaltene and unsubstituted polynuclear aromatics from heavy hydrocarbons

In the first step, heavy coker gas oil (HCGO) was obtained from coker unit. The typical properties of the v are summarized below in Table 1. Table 1: Properties and composition of the heavy hydrocarbon feed

HCGO was mixed with n-pentane to obtain a first resultant mixture. The so obtained first resultant mixture was then introduced in a first settler and allowed to settle to obtain a first biphasic mixture comprising a hydrocarbon phase, and a solid phase.

The solid phase was separated from the first biphasic mixture by filtration to obtain a separated hydrocarbon phase with reduced asphaltene content and the solid phase comprising asphaltene. The comparison between the heavy hydrocarbon feed and separated hydrocarbon phase with reduced asphaltene content is given below in Table 2.

Table 2: Composition of heavy hydrocarbon feed and separated hydrocarbon phase

It was observed that the asphaltene content was reduced by 99%. The so obtained hydrocarbon phase with reduced asphaltene content was further sent for separation of paraffin fraction and aromatic fraction by liquid extraction method.

The hydrocarbon phase was mixed with N-methyl pyrrolidone (NMP) to obtain a second resultant mixture. The second resultant mixture was introduced in a second settler and allowed to settle to obtain a second biphasic mixture comprising an upper layer comprising paraffin fraction and a lower layer comprising aromatic fraction.

The upper layer was separated from the second biphasic mixture to obtain paraffin fraction with reduced content of aromatics and the aromatic fraction comprising unsubstituted polynuclear aromatics and polar fluid medium.

The comparison between the heavy hydrocarbon feed, separated paraffin fraction with reduced aromatics content and aromatic fraction is given below in Table 3.

Table 3: Composition of heavy hydrocarbon feed, aromatic fraction and paraffin fraction

It was observed that paraffin layer also comprises small amount of mono, di- aromatics with long paraffin chain. Due to presence of long paraffin chain, these molecules behave like paraffin and are rejected by solvent. However, these types of molecules are useful in FCC as these molecules can undergo cracking. TECHNICAL ADVANCEMENTS

The present disclosure described herein above has several technical advantages including, but not limited to, the realization of: a process for reducing asphaltene content in a heavy hydrocarbon feed; a process for reducing unsubstituted PNA content in a heavy hydrocarbon feed; and - increase in the life of the hydrotreating catalyst and FCC catalyst which are contacted with the heavy hydrocarbon feed for cracking.

The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

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

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.

Any discussion of documents, acts, materials, devices, articles or 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.

The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary. While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.