DESC:FIELD
The present disclosure relates to a process for the recovery of aromatic compounds from hydrocarbon feed. The present disclosure particularly relates to a process for the recovery of aromatic compounds from C5-C11 hydrocarbon fraction from different refinery streams.
DEFINITIONS
As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicate otherwise.
Extractive Distillation: The term “Extractive Distillation” refers to a separation technique in which a solvent is added to a mixture to enhance the separation based on the difference in affinities of mixture components towards the solvent.
n-paraffins: The term “n-paraffins”, also known as normal paraffins refer to a group of hydrocarbons that consist of straight-chain saturated alkanes (alkanes with single bonds between carbon atoms). They have the general formula CnH2n+2, where "n" is the number of carbon atoms in the molecule. N-paraffins are typically derived from petroleum and natural gas and are used as fuels (e.g., gasoline), solvents, and in the production of various chemicals.
Iso-paraffins: The term “iso-paraffins” also known as isoparaffins refer to branched-chain saturated hydrocarbons. They are similar to N-paraffins (normal paraffins) in that they consist of only carbon and hydrogen atoms with single bonds, but differ from n-paraffins by having one or more branches in the carbon chain.
Naphthenes: The term “naphthenes” refer to a class of saturated hydrocarbons containing one or more cyclic structures having single bonds between the carbon atoms.
Olefins: The term “olefins”, also known as alkenes, refer to a class of unsaturated hydrocarbons that contain one or more carbon-carbon double bonds (C=C).
Aromatic compounds: The term “aromatic compounds” refer to a class of organic compounds that contain a benzene ring or similar structure, characterized by its unique arrangement of alternating single and double bonds.
C5-C11 hydrocarbon fraction: The term “C5-C11 hydrocarbon fraction” refers to a group of hydrocarbons containing five to eleven carbon atoms per molecule. This fraction includes alkanes (paraffins) and alkenes (olefins), along with aromatics, depending on the source and the refining process.
C5-C11 non-aromatic compounds: The term “C5-C11 range non-aromatic compounds” refer to alkanes (paraffins), alkenes (olefins), and cycloalkanes (naphthenes), which are hydrocarbons without aromatic rings and have C5 to C11 carbon range.
C6-C11 aromatic compounds: The term “C6-C11 aromatic compounds” refer to hydrocarbons that contain one or more benzene rings (or derivatives of benzene) and have C6 to C11 carbon range.
C4 hydrocarbons: The term “C4 hydrocarbons” refer to hydrocarbons that contain four carbon atoms in their molecular structure. These can include alkanes, and alkenes.
C5 hydrocarbons: The term “C5 hydrocarbons” refer to hydrocarbons containing five carbon atoms in their molecular structure and include alkanes, alkenes, and cycloalkanes.
Marangoni effect: The term “Marangoni effect” refers to a phenomenon where surface tension differences drive fluid motion along an interface. In case of a variation in surface tension along a liquid surface, the liquid flows from regions of lower surface tension to regions of higher surface tension, trying to equalize the surface tension across the interface, resulting in the foam formation.
Zuiderweg negative: The term “Zuiderweg negative” refers to the working of the Marangoni effect to suppress foam formation rather than enhance it. When a surface tension gradient develops, the liquid moves in a way that disrupts foam stabilization, causing bubbles to collapse.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
C5-C11 hydrocarbon fraction typically consists of n-paraffins, iso-paraffins, n-olefins, di-olefins, naphthenes, and aromatic (benzene and alkyl benzene) types of hydrocarbons, commonly found in petroleum refining processes. C5-C11 hydrocarbon fraction is usually obtained from different units in refinery such as catalytic cracking, hydrocracking, thermal cracking, delayed coking, crude distillation, and naphtha reforming. This hydrocarbon fraction serves as a valuable feedstock for the production of gasoline and other important fuels. Additionally, C5-C11 hydrocarbon fraction can play an important role as a building block in the synthesis of chemicals used in various industries such as solvents, lubricants, and other chemical products.
Therefore, it is important to maximize the recovery of aromatics from the hydrocarbon feed. The overall yield can be enhanced by two means. The first means involve separating aromatics from non-aromatics compounds. The non-aromatics stream is then recycled back to mother processing unit (catalytic or thermal cracking unit, fluidized catalytic cracking unit, multi-zone catalytic cracking unit, delayed coking unit, naphtha reforming and the like). The second means involve a benzene free raffinate stream, that can be directed to gasoline pool. The recovery of aromatic compounds from C5-C11 hydrocarbon feed valorises/enhances the C5-C11 fraction.
Generally, C5-C11 hydrocarbon fraction is blended into the gasoline pool or charged to refinery units like naphtha reforming to enhance its Octane number. The aromatic hydrocarbons present in C5-C11 hydrocarbon move freely in the naphtha reforming units or sometimes they undergo de-alkylation/ side chain cracking reactions to produce undesired lighter aromatic molecules. The lighter aromatic molecules, such as benzene are known to have health and environmental concerns due to their toxicity and potential carcinogenicity. The removal of such lighter aromatic compounds from C5-C11 hydrocarbon feed can create space to process additional feed, which can increase the overall yield of higher aromatic molecules. However, the known methods recover lighter aromatic compounds from the hydrocarbon feed, with the higher aromatic compounds remaining in the hydrocarbon feed.
There is, therefore, felt a need to provide a process for the recovery of aromatic compounds from C5-C11 hydrocarbon feed that mitigates the drawbacks mentioned hereinabove and at least provides a useful alternative solution.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.
An object of the present disclosure is to ameliorate one or more problems of the background or to at least provide a useful alternative.
Another object of the present disclosure is to provide a process for the recovery of aromatic compounds from a hydrocarbon feed.
Yet another object of the present disclosure is to provide a process for the recovery of aromatic compounds from C5-C11 hydrocarbon fraction.
Still another object of the present disclosure is to provide a process for the recovery of aromatic compounds from C5-C11 hydrocarbon fraction of different refinery streams.
Yet another object of the present disclosure is to provide a simple and environmental friendly process for the recovery of aromatic compounds from a hydrocarbon 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 recovering aromatic compounds from a hydrocarbon feed comprising a mixture of aromatic and non-aromatic compounds. The process comprises the following steps:
a. introducing a preheated hydrocarbon feed and a solvent system into an extractive distillation column to obtain an overhead raffinate phase comprising the non-aromatic compounds and a bottom extract phase comprising a mixture of the solvent system and the aromatic compounds;
b. condensing the overhead raffinate phase to obtain the non-aromatic compounds;
c. separately, introducing the bottom extract phase from the extractive distillation column into a middle portion of a solvent recovery column; and
d. introducing steam into a bottom portion to the solvent recovery column to obtain a bottom stream comprising the solvent system and an overhead stream comprising the aromatic compounds.
In an embodiment of the present disclosure, the extractive distillation column has an upper portion and a lower portion, and wherein
? the upper portion of the extractive distillation column has a temperature in the range of 80 °C to 100 °C; and
? the lower portion of the extractive distillation column is maintained at a temperature in the range of 140 °C to 175 °C.
In an embodiment of the present disclosure, the preheated hydrocarbon feed is introduced into the lower portion of the extractive distillation column.
In an embodiment of the present disclosure, the solvent system is introduced into the upper portion of the extractive distillation column.
In an embodiment of the present disclosure, prior to introducing the hydrocarbon feed into the extractive distillation column, the hydrocarbon feed is subjected to distillation to separate C4 and C5 hydrocarbons from the hydrocarbon feed.
In an embodiment of the present disclosure, the distillation is carried out at a temperature in the range of 110 °C to 120 °C and at a pressure in the range of 1 bar to 2 bar.
In an embodiment of the present disclosure, the overhead stream obtained in step (d) is washed to remove the solvent system and to obtain the aromatic compounds.
In an embodiment of the present disclosure, the washing is carried out at a temperature in the range of 80 °C to 90 °C.
In an embodiment of the present disclosure, the hydrocarbon feed comprises:
? n-paraffins in an amount in the range of 1 mass% to 15 mass%;
? iso-paraffins in an amount in the range of 2 mass% to 22 mass%;
? olefins in an amount in the range of 5 mass% to 12 mass%;
? naphthenes in an amount in the range of 4 mass% to 22 mass%; and
? aromatic compounds in an amount in the range of 35 mass% to 80 mass%,
wherein the mass% of each component is with respect to the total mass of the hydrocarbon feed.
In an embodiment of the present disclosure, the overhead raffinate phase comprises:
? non-aromatic compounds in an amount in the range of 93 mass% to 99.5 mass%; and
? aromatic compounds in an amount in the range of 0.5 mass% to 7 mass%,
wherein the mass% of each component is with respect to the total mass of the raffinate phase.
In an embodiment of the present disclosure, the bottom extract phase comprises:
? non-aromatic compounds in an amount in the range of 5 mass% to 15 mass%; and
? aromatic compounds in an amount in the range of 85 mass% to 95 mass%,
wherein the mass% of each component is with respect to the total mass of the bottom extract phase.
In an embodiment of the present disclosure, the ratio of the solvent system to the hydrocarbon feed is in the range of 2:1 to 5:1.
In an embodiment of the present disclosure, the solvent system comprises a primary solvent and a co-solvent.
In an embodiment of the present disclosure, the primary solvent is selected from N-methyl pyrrolidone (NMP) and N-formyl morpholine (NFM).
In an embodiment of the present disclosure, the co-solvent is selected from the group consisting of anti-foaming agents, water and sulfolane.
In an embodiment of the present disclosure, the co-solvent is present in an amount in the range of 0 to 10 mass% with respect to the primary solvent.
In an embodiment of the present disclosure,
? the preheated hydrocarbon feed has a temperature in the range of 90 °C to 110 °C;
? the solvent system has a temperature in the range of 65 °C to 75 °C;
? steam has a temperature in the range of 180 °C to 220 °C; and
? the solvent recovery column has a temperature maintained in the range of 170 °C to 180 °C.
In an embodiment of the present disclosure,
? the preheated hydrocarbon feed has a flowrate in the range of 1 Kg/hr to 4 Kg/hr;
? the solvent system has a flowrate in the range of 2.5 Kg/hr to 5 Kg/hr; and
? the bottom extract phase has a flowrate in the range of 2.8 Kg/hr to 23.2 Kg/hr.
In an embodiment of the present disclosure, the ratio of steam to a hydrocarbon content of the bottom extract phase is in the range of 0.5:1 to 1.5:1.
In an embodiment of the present disclosure,
? the extractive distillation column has a pressure maintained in the range of 0.5 bar to 2.0 bar; and
? the solvent recovery column has a pressure maintained in the range of 0.3 bar to 0.7 bar
In an embodiment of the present disclosure, the hydrocarbon feed comprises C5-C11 hydrocarbon fraction.
In an embodiment of the present disclosure, the overhead raffinate phase comprises C5-C11 non-aromatic compounds.
In an embodiment of the present disclosure, the bottom extract phase comprises C6-C11 aromatic compounds.
In an embodiment of the present disclosure, the overhead stream comprises C6-C11 aromatic compounds.
In an embodiment of the present disclosure,
? the non-aromatic compounds are recycled to the extractive distillation column;
? the bottom stream from the solvent recovery column is recycled to the extractive distillation column; and
? the overhead stream from the solvent recovery column is recycled to the extractive distillation column.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The present disclosure will now be described with reference to the accompanying drawing, in which:
Figure 1 illustrates a schematic diagram for the recovery of aromatic compounds from hydrocarbon feed in accordance with the present disclosure, wherein EDC refers to Extractive Distillation Column, SRC refers to Solvent Recovery Column, WS refers to Water Stripper and WB refers to Water Boiler in accordance with the present disclosure.
DETAILED DESCRIPTION
The present disclosure relates to a process for the recovery of aromatic compounds from hydrocarbon feed. The present disclosure particularly relates to a process for the recovery of aromatic compounds from C5-C11 hydrocarbon fraction from different refinery streams.
Embodiments, of the present disclosure, will now be described with reference to the accompanying drawings.
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 the 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.
As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed elements.
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.
C5-C11 hydrocarbon fraction typically consists of n-paraffins, iso-paraffins, n-olefins, di-olefins, naphthenes, and aromatics (benzene and alkyl benzene) types of hydrocarbons, commonly found in petroleum refining processes. C5-C11 hydrocarbon fraction is usually obtained from different units in refinery such as catalytic cracking, hydrocracking, thermal cracking, delayed coking, crude distillation, and naphtha reforming. This hydrocarbon fraction serves as a valuable feedstock for the production of gasoline and other important fuels. Additionally, C5-C11 hydrocarbon fraction can play an important role as a building block in the synthesis of chemicals used in various industries such as solvents, lubricants, and other chemical products.
Therefore, it is important to maximize the recovery of aromatics from the hydrocarbon feed. The overall yield can be enhanced by two means. The first means involve separating aromatics from non-aromatics compounds. The non-aromatics stream is then recycled back to mother processing unit (catalytic or thermal cracking unit, fluidized catalytic cracking unit, multi-zone catalytic cracking unit, delayed coking unit, naphtha reforming and the like). The second means involve a benzene free raffinate stream, that can be directed to gasoline pool. The recovery of aromatic compounds from C5-C11 hydrocarbon feed valorises/enhances the C5-C11 fraction.
Generally, C5-C11 hydrocarbon fraction is blended into the gasoline pool or charged to refinery units like naphtha reforming to enhance its Octane number. The aromatic hydrocarbons present in C5-C11 hydrocarbon move freely in the naphtha reforming units or sometimes they undergo de-alkylation/ side chain cracking reactions to produce undesired lighter molecules. The removal of aromatic compounds from C5-C11 hydrocarbon feed can create space to process additional feed, which can increase the overall aromatics yield. Moreover, the aromatic compounds, such as benzene are known to have health and environmental concerns due to their toxicity and potential carcinogenicity.
Further, the known methods recover lighter aromatic compounds from the hydrocarbon feed, with the higher aromatic compounds remaining in the hydrocarbon feed.
The present disclosure provides a process for the recovery of aromatic compounds from C5-C11 hydrocarbon fraction of different refinery streams by extractive distillation using a selective solvent system.
In an aspect of the present disclosure, there is provided a process for recovering aromatic compounds from a hydrocarbon feed comprising a mixture of aromatic and non-aromatic compounds. The process comprises the following steps:
a. introducing a preheated hydrocarbon feed and a solvent system into an extractive distillation column to obtain an overhead raffinate phase comprising the non-aromatic compounds and a bottom extract phase comprising a mixture of the solvent system and the aromatic compounds;
b. condensing the overhead raffinate phase to obtain the non-aromatic compounds;
c. separately, introducing the bottom extract phase from the extractive distillation column into a middle portion of a solvent recovery column; and
d. introducing steam into a bottom portion to the solvent recovery column to obtain a bottom stream comprising the solvent system and an overhead stream comprising the aromatic compounds.
The process is described herein below in detail.
In the first step, a preheated hydrocarbon feed and a solvent system are introduced into an extractive distillation column to obtain an overhead raffinate phase comprising the non-aromatic compounds and a bottom extract phase comprising a mixture of solvent system and the aromatic compounds.
In an embodiment of the present disclosure, the hydrocarbon feed can be obtained from catalytic cracking unit or thermal cracking unit, gas oil/residue hydrocracking unit, crude distillation unit or combinations thereof. In another embodiment, the hydrocarbon can be obtained from feeds such as waste plastic recycle, biomass conversion, and the like.
In an embodiment of the present disclosure, the hydrocarbon feed comprises C5-C11 range hydrocarbon fraction.
In an embodiment of the present disclosure, the C5-C11 hydrocarbon fraction includes paraffin, iso-paraffin, naphthenes, aromatics and olefins and other known suitable hydrocarbons.
In an embodiment of the present disclosure, the hydrocarbon feed comprises:
? n-paraffins in an amount in the range of 1 mass% to 15 mass%;
? iso-paraffins in an amount in the range of 2 mass% to 22 mass%;
? olefins in an amount in the range of 5 mass% to 12 mass%;
? naphthenes in an amount in the range of 4 mass% to 22 mass%; and
? aromatic compounds in an amount in the range of 35 mass% to 80 mass%,
wherein the mass% of each component is with respect to the total mass of the hydrocarbon feed.
In an embodiment of the present disclosure, prior to introducing the hydrocarbon feed into the extractive distillation column, the hydrocarbon feed is subjected to distillation to separate C4 and C5 hydrocarbons from the hydrocarbon feed.
In an embodiment of the present disclosure, the C5-C11 hydrocarbon fraction is pre-topped to reduce the light ends such as C4 and C5 hydrocarbons in order to reduce the foaming due to Marangoni effect and to ensure the distillation system to be Zuiderweg negative.
In an embodiment of the present disclosure, the distillation is carried out at a temperature in the range of 110 °C to 120 °C and at a pressure in the range of 1 bar to 2 bar. In an exemplary embodiment of the present disclosure, the distillation is carried out at a temperature of 115 °C and at a pressure of 1.3 bar.
In an embodiment of the present disclosure, the C5-C11 hydrocarbon fraction is introduced into the extractive distillation column from a suitable position to maximize the recovery of aromatic compounds.
In an embodiment of the present disclosure, the extractive distillation column has an upper portion and a lower portion, wherein
? the upper portion of the extractive distillation column has a temperature in the range of 80 °C to 100 °C; and
? the lower portion of the extractive distillation column is maintained at a temperature in the range of 140 °C to 175 °C.
In an exemplary embodiment of the present disclosure, the temperature of the upper portion of the extractive distillation column is 85 °C. In another exemplary embodiment of the present disclosure, the temperature of the upper portion of the extractive distillation column is 90 °C. In still another exemplary embodiment of the present disclosure, the temperature of the upper portion of the extractive distillation column is 95 °C.
In an exemplary embodiment of the present disclosure, the lower portion of the extractive distillation column is maintained at 145 °C. In another exemplary embodiment of the present disclosure, the lower portion of the extractive distillation column is maintained at 170 °C. In still another exemplary embodiment of the present disclosure, the lower portion of the extractive distillation column is maintained at 162 °C.
The lower portion of the extractive distillation column is maintained at a temperature within the range of 145°C to 170°C, ensuring efficient separation of aromatic and non-aromatic compounds.
In an embodiment of the present disclosure, the hydrocarbon feed is introduced into the lower portion of the extractive distillation column.
In an embodiment of the present disclosure, the solvent system is introduced into the upper portion of the extractive distillation column.
The extractive distillation column (EDC) comprises a number of trays. The trays in the EDC provides the surface area for vapor-liquid contact, which helps in the separation of components present in the mixture.
In an exemplary embodiment of the present disclosure, the solvent system is introduced into few trays below top tray in top section of the extractive distillation column.
When the preheated hydrocarbon feed (comprising a mixture of aromatic and non-aromatic compounds) comes in contact with the solvent system, a change in the polarity of the solvent system takes place resulting in the separation of the non-aromatic into the overhead raffinate phase and the aromatics along with the solvent system go into the bottom extract phase.
In an embodiment of the present disclosure, the solvent system comprises a primary solvent and a co-solvent. Other suitable solvent systems can also be used.
In an embodiment of the present disclosure, the primary solvent is selected from N-methyl pyrrolidone (NMP), and N-formyl morpholine (NFM). In an exemplary embodiment of the present disclosure, the primary solvent is N-methyl pyrrolidones (NMP).
The primary solvent, selected from N-methyl pyrrolidone (NMP), and N-formyl morpholine (NFM), plays a critical role in selectively dissolving aromatic compounds while minimizing interactions with non-aromatics. Among these, NMP is particularly preferred due to its high capacity, thermal stability, and superior solvent power for aromatic hydrocarbons.
In an embodiment of the present disclosure, the co-solvent is selected from the group consisting of anti-foaming agents, water, and sulfolane. In an exemplary embodiment of the present disclosure, the co-solvent is water.
In an embodiment of the present disclosure, the co-solvent is present in an amount in the range of 0 mass% to 10 mass% with respect to the total amount of the primary solvent. The co-solvent in the present disclosure is incorporated in a controlled amount to optimize the efficiency of the extractive distillation process, allowing for flexibility in process conditions based on the feed composition and operational requirements.
In an exemplary embodiment of the present disclosure, the solvent system is devoid of the co-solvent, relying solely on the primary solvent for aromatic separation.
In another exemplary embodiment of the present disclosure, the co-solvent is present in an amount of 5 mass% with respect to the total amount of the primary solvent to enhance solvent performance.
In still another exemplary embodiment of the present disclosure, the co-solvent is present in an amount of 1 mass% with respect to the total amount of the primary solvent, providing a balance between improved separation efficiency and minimizes the non-aromatics in the bottom extract phase.
Thus, the adjustable co-solvent concentration ensures that the process remains efficient, while achieving high-purity aromatic recovery.
In an embodiment of the present disclosure, the ratio of the solvent system to hydrocarbon feed is in the range of 2:1 to 5:1. In an exemplary embodiment of the present disclosure, the ratio of the solvent system to hydrocarbon feed is 3.1:1. In another exemplary embodiment of the present disclosure, the ratio of the solvent system to hydrocarbon feed is 2.6:1. In still another exemplary embodiment of the present disclosure, the ratio of the solvent system to hydrocarbon feed is 4.0:1.
In an embodiment of the present disclosure, the temperature of the preheated hydrocarbon feed is in the range of 90 °C to 120 °C. In an exemplary embodiment of the present disclosure, the temperature of the preheated hydrocarbon feed is 110 °C.
In an embodiment of the present disclosure, the temperature of the solvent system is in the range of 65 °C to 75 °C. In an exemplary embodiment of the present disclosure, the temperature of the solvent system is 70 °C.
In an embodiment of the present disclosure, the flowrate of the preheated hydrocarbon feed is in the range of 1 Kg/hr to 4 Kg/hr. In an exemplary embodiment of the present disclosure, the flowrate of the preheated hydrocarbon feed is 1 Kg/hr.
In an embodiment of the present disclosure, the flowrate of the solvent system is in the range of 2.5 Kg/hr to 5 Kg/hr. In an exemplary embodiment of the present disclosure, the flowrate of the solvent system is 3 Kg/hr.
In an embodiment of the present disclosure, the pressure of the extractive distillation unit is maintained in the range of 0.5 bar to 2.0 bar. In an exemplary embodiment of the present disclosure, the pressure of the extractive distillation unit is maintained at 1 bar.
In an embodiment of the present disclosure, the overhead raffinate phase is rich in C5-C11 range non-aromatic compounds.
In an embodiment of the present disclosure, the bottom extract phase is rich in C6-C11 aromatic compounds.
In an embodiment of the present disclosure, the overhead raffinate phase is washed to remove traces of solvent.
In an embodiment of the present disclosure, the overhead raffinate is washed with water to remove traces of solvent.
In the second step, the so-obtained overhead raffinate phase is condensed to obtain non-aromatic compounds.
In an embodiment of the present disclosure, the overhead raffinate phase comprises:
? non-aromatic compounds in an amount in the range of 93 mass% to 99.5 mass%; and
? aromatic compounds in an amount in the range of 0.5 mass% to 7 mass%,
wherein the mass% of each component is with respect to the total mass of the raffinate phase.
In an embodiment of the present disclosure, the so obtained non-aromatic compounds can be fed to processes such as catalytic cracking, thermal cracking, residue/gas oil hydrocracking, or any other conversion process to meet the future requirements for reducing or eliminating the gasoline production.
In an embodiment of the present disclosure, the obtained non-aromatic compounds can be recycled back as a feed to the extractive distillation column.
In another embodiment of the present disclosure, the non-aromatic compounds are recycled to the extractive distillation column. This is done in case the aromatic loss is higher in the overhead raffinate phase, recycling the overhead raffinate phase to the extractive distillation column will improve the aromatics recovery.
In an embodiment of the present disclosure, the so obtained non-aromatic contain higher olefins, n-paraffins and cycloparaffins and can be used to produce products such as special boiling point solvents.
In an embodiment of the present disclosure, the bottom extract phase comprises:
? non-aromatic compounds in an amount in the range of 5 mass% to 15 mass%; and
? aromatic compounds in an amount in the range of 85 mass% to 95 mass%,
wherein the mass% of each component is with respect to the total mass of the bottom extract phase.
In the third step, the bottom extract phase obtained at the bottom of the extractive distillation column is separately introduced into a middle portion of a solvent recovery column.
In the fourth step, steam is introduced into a bottom portion of the solvent recovery column to obtain a bottom stream comprising the solvent system and an overhead stream comprising the aromatic compounds.
In an embodiment of the present disclosure, the ratio of steam to a hydrocarbon content of the bottom extract phase is in the range of 0.5:1 to 1.5:1. In an exemplary embodiment of the present disclosure, the ratio of steam to the hydrocarbon content of the bottom extract phase is 1:1.
In accordance with the embodiments of the present disclosure the hydrocarbon content comprises the non-aromatic compounds and the aromatic compounds.
In an embodiment of the present disclosure, the flowrate of the bottom extract phase is in the range of 2.82 Kg/hr to 23.2 Kg/hr. In an exemplary embodiment of the present disclosure, the flowrate of the bottom extract phase is 3.6 Kg/hr.
In an embodiment of the present disclosure, the pressure in the solvent recovery column is maintained in the range of 0.3 bar to 0.7 bar. In an exemplary embodiment of the present disclosure, the pressure of the solvent recovery column is maintained at 0.5 bar.
In accordance with the embodiments of the present disclosure, the temperature of steam is in the range of 180 °C to 275 °C. In an embodiment of the present disclosure, the temperature of steam is in the range of 180 °C to 220 °C. In an exemplary embodiment of the present disclosure, the temperature of steam is 200 °C.
In an embodiment of the present disclosure, the overhead stream obtained in step (d) is washed with water to remove the solvent system and obtain the aromatic compounds.
In an embodiment of the present disclosure the washing is carried out at a temperature in the range of 80 °C to 90 °C. In an exemplary embodiment, the washing is carried out at 85 °C.
In an embodiment of the present disclosure, the condensed water from the extractive distillation column (overhead raffinate phase) and the solvent recovery column is routed to the water stripper.
In an embodiment of the present disclosure, the separation of the aromatic compounds from the C5-C11 hydrocarbon feed is for the enhancement of aromatics production in the refinery.
In an embodiment of the present disclosure, the so obtained overhead stream from the solvent recovery column has C6-C11 aromatic compounds.
In an embodiment of the present disclosure, the bottom stream obtained from the solvent recovery column is free from aromatic compounds and consists of the primary solvent and the co-solvent.
In an embodiment of the present disclosure, the obtained overhead steam from the solvent recovery column is sent to the aromatics pool, for the recovery of the aromatic compounds.
In an embodiment of the present disclosure, the overhead stream from the solvent recovery column is recycled to the extractive distillation column. The overhead stream is recycled to the extractive distillation column due to the operational flexibilities in the system.
In an embodiment of the present disclosure, the so obtained bottom stream from the solvent recovery column is recycled back as a circulating solvent to the extractive distillation column.
The process of the present disclosure is efficient and provides recovery of aromatic compounds from various hydrocarbon feeds. The process of the present disclosure is capable of recovering C6 range of aromatic compounds along with higher fractions of branched aromatic hydrocarbons (up to C11 fraction of aromatic hydrocarbons). The process of the present disclosure not only provides recovery of aromatic compounds, but also recycles the solvents to the extractive distillation column for subsequent use and also with withdrawal of non-aromatic fractions from the overhead raffinate phase.
The process of the present disclosure provides an efficient approach for recovering aromatic compounds from a C5-C11 hydrocarbon feed, significantly enhancing the yield of the aromatic compounds. One of key features of the present disclosure is the application of extractive distillation using a selective solvent system, which enables precise separation of aromatic and non-aromatic compounds. Unlike conventional methods that rely on energy-intensive fractionation techniques, the process of the present disclosure optimizes solvent affinity to selectively extract aromatic compounds while minimizing losses in the raffinate phase. The solvent system, comprising a primary solvent such as N-methyl pyrrolidone (NMP) or N-formyl morpholine (NFM), ensures superior separation efficiency and recyclability, making the process both economically and environmentally sustainable.
Another feature of the present disclosure is the incorporation of a pre-distillation step that removes light-end hydrocarbons (C4 and C5 fractions) before being introduced into the extractive distillation column. This pre-treatment step effectively mitigates foaming issues caused by the Marangoni effect, ensuring stable operation and high separation efficiency. Additionally, the process optimizes operating conditions within the extractive distillation column by maintaining a controlled temperature gradient (80 °C to 100 °C in the upper portion to 140 °C to 175°C in the lower portion) thereby maximizing aromatic recovery and minimizing solvent degradation.
Furthermore, the process of the present disclosure provides a solvent recovery system that efficiently separates the solvent from the extracted aromatic compounds using a solvent recovery column and controlled steam introduction. This ensures that the solvent can be recycled back into the system, significantly reducing operational costs and environmental impact. The integration of water washing at the final stage removes residual solvent traces, ensuring high-purity aromatic products suitable for downstream applications. Additionally, the non-aromatic raffinate stream can be directed back into refinery units or repurposed for gasoline blending, demonstrating the process's ability to maximize resource utilization.
The process of the present disclosure is a scalable and industrially viable solution for enhancing aromatic yields in refineries. By integrating selective extractive distillation, optimized thermal control, and efficient solvent recycling, the process achieves a high level of separation efficiency with reduced energy consumption. Its ability to recover C6-C11 aromatic hydrocarbons while minimizing aromatic content in the raffinate phase addresses both economic and regulatory concerns.
The foregoing description of the embodiments has been provided for purposes of illustration and is 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
Example 1: Process for recovery of aromatic compounds from a hydrocarbon feed in accordance with the present disclosure
Step-I: Distillation of the hydrocarbon feed to separate C4 and C5 hydrocarbons from the hydrocarbon feed in accordance with the present disclosure
Hydrocarbon feed was subjected to distillation at 115 °C and at a pressure of 1.5 bar to obtain hydrocarbon feed comprising C5-C11 hydrocarbon fraction, wherein maximum portion of C4 and C5 were separated from the hydrocarbon feed.
Step-II: Recovery of the aromatic compounds from the hydrocarbon feed in accordance with the present disclosure
Aromatic compounds were recovered from the hydrocarbon feed as illustrated in Figure 1. The hydrocarbon feed comprising C5-C11 hydrocarbon fraction obtained in Step-I was used as the feed, wherein the C4 and C5 fractions were removed.
Oldershaw column was used as the extractive distillation column (EDC), having 50 tray configuration for recovering the aromatic compounds. N-methyl pyrrolidone (NMP) was used as the primary solvent along with water as the co-solvent. Different solvent to hydrocarbon feed ratios, and EDC temperatures (upper portion and lower portion) were studied and are summarized in Table 1. The amount of solvent system used was based on the quantity of feed and was dependent on the solvent system to hydrocarbon feed ratio (S/F) ratio.
Table 1: Process details for aromatic compounds recovery in accordance with the present disclosure
Case No. Case-1 Case-2 Case-3
S/F ratio (w/w) (solvent system to feed ratio) 3.1 2.6 4.0
Co-Solvent (mass %) 0 5.0 1.0
EDC (lower portion) Temperature (°C) 170 145 162
EDC (upper portion) Temperature (°C) 95 85 90

The composition of the hydrocarbon feeds used for recovering the aromatic compounds is summarized in Table 2.
Table 2: Composition of hydrocarbon feed in accordance with the present disclosure
Hydrocarbon Feed
Case-1 Case-2 Case-3
n-Paraffins (Wt%) 13.97 13.50 1.74
i-Paraffins (Wt%) 11.35 20.58 3.32
Olefins (Wt%) 8.57 19.59 5.26
Naphthenes (Wt%) 8.23 7.63 10.68
Aromatics (Wt%) 57.89 38.70 79.00
Unknown (Wt%) 0.830 0.937 0.546

Preheated hydrocarbon feed (HC feed) (110 °C) was introduced into the extractive distillation column (EDC) from the lower portion at a flowrate of 1 Kg/hr and the solvent system was introduced into the upper portion of the EDC at a flowrate of 3 Kg/hr to obtain an overhead raffinate phase comprising non-aromatic compounds and a bottom extract phase comprising a mixture of solvent system and aromatic compounds.
When the preheated hydrocarbon feed (comprising a mixture of aromatic and non-aromatic compounds) comes in contact with the solvent system, a change in polarity of the solvent system takes place resulting in the separation of the non-aromatic into the overhead raffinate phase and the aromatics along with the solvent system go into the bottom extract phase.
The bottom extract phase from the bottom of the extractive distillation column (EDC) was introduced into a solvent recovery column at a flowrate of 3.6 Kg/hr. Steam (200 °C) (steam: bottom extract phase ratio of 1:1) was introduced into the bottom portion of the solvent recovery column to obtain a bottom stream comprising the solvent system and an overhead stream comprising the aromatic compounds.
Water boiler was used to generate steam for SRC to strip out (separate) aromatics hydrocarbon from extract stream coming from EDC bottom.
The overhead stream was washed with water (85 °C) to obtain the aromatic compounds to remove traces of solvent system.
The composition of the overhead raffinate phase and the bottom extract phase is summarized in Table 3.
Table 3: Composition of overhead raffinate phase and bottom extract phase, in accordance with the present disclosure
Overhead Raffinate Phase
Case-1 Case-2 Case-3
Non -Aromatics (Wt %) 99.10 92.06 98.57
Aromatics (Wt %) 0.90 7.94 1.43

Bottom Extract Phase
Case-1 Case-2 Case-3
Non-Aromatics (Wt %) 10.60 4.84 7.82
Aromatics (Wt %) 89.40 95.16 92.18
It is seen from Table 3 that the overhead raffinate phase is rich in non-aromatic compounds, whereas the bottom extract phase is rich in aromatic compounds.
It is seen from Tables 1-3 that the maximum amount of aromatic compounds (95.16%) were recovered for Case-2, with the following process parameters: solvent/ feed ratio of 2.6, 5 mass% of co-solvent, EDC lower portion temperature of 145 °C, and EDC upper portion temperature of 85 °C. Further, maximum aromatic compounds were separated for the same process parameters.
The process of the present disclosure is capable of recovering C6 range of aromatic along with higher fractions of branched aromatic hydrocarbons (up to C11 fraction of aromatic hydrocarbons).
TECHNICAL ADVANCEMENTS:
The present disclosure described hereinabove has several technical advantages including, but not limited to, the realization of a process for the recovery of aromatic compounds from a hydrocarbon feed that:
• can increase the overall aromatic yield in naphtha reforming units;
• can recover C6-C11 range of aromatic compounds;
• maximizes the recovery of aromatic compounds in the C5-C11 hydrocarbon feed; and
• can separate aromatic and non-aromatic compounds that can be reused in preparation of other solvents and chemicals.
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 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 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. ,CLAIMS:WE CLAIM:
1. A process for recovering aromatic compounds from a hydrocarbon feed comprising a mixture of aromatic and non-aromatic compounds, said process comprising the following steps:
a. introducing a preheated hydrocarbon feed and a solvent system into an extractive distillation column to obtain an overhead raffinate phase comprising said non-aromatic compounds; and a bottom extract phase comprising a mixture of said solvent system and said aromatic compounds;
b. condensing said overhead raffinate phase to obtain said non-aromatic compounds;
c. separately, introducing said bottom extract phase from said extractive distillation column into a middle portion of a solvent recovery column; and
d. introducing steam into a bottom portion to said solvent recovery column to obtain a bottom stream comprising said solvent system and an overhead stream comprising said aromatic compounds.
2. The process as claimed in claim 1, wherein said extractive distillation column has an upper portion and a lower portion, and wherein
? said upper portion of said extractive distillation column has a temperature in the range of 80 °C to 100 °C; and
? said lower portion of said extractive distillation column is maintained at a temperature in the range of 140 °C to 175 °C.
3. The process as claimed in claim 1, wherein said preheated hydrocarbon feed is introduced into said lower portion of said extractive distillation column.
4. The process as claimed in claim 1, wherein said solvent system is introduced into said upper portion of said extractive distillation column.
5. The process as claimed in claim 1, wherein prior to introducing said hydrocarbon feed into said extractive distillation column, said hydrocarbon feed is subjected to distillation to separate C4 and C5 hydrocarbons from said hydrocarbon feed.
6. The process as claimed in claim 5, wherein said distillation is carried out at a temperature in the range of 110 °C to 120 °C and at a pressure in the range of 1 bar to 2 bar.
7. The process as claimed in claim 1, wherein said overhead stream obtained in step (d) is washed to remove said solvent system and to obtain said aromatic compounds.
8. The process as claimed in claim 7, wherein said washing is carried out at a temperature in the range of 80 °C to 90 °C.
9. The process as claimed in claim 1, wherein said hydrocarbon feed comprises:
? n-paraffins in an amount in the range of 1 mass% to 15 mass%;
? iso-paraffins in an amount in the range of 2 mass% to 22 mass%;
? olefins in an amount in the range of 5 mass% to 12 mass%;
? naphthenes in an amount in the range of 4 mass% to 22 mass%; and
? aromatic compounds in an amount in the range of 35 mass% to 80 mass%,
wherein the mass% of each component is with respect to the total mass of said hydrocarbon feed.
10. The process as claimed in claim 1, wherein said overhead raffinate phase comprises:
? non-aromatic compounds in an amount in the range of 93 mass% to 99.5 mass%; and
? aromatic compounds in an amount in the range of 0.5 mass% to 7 mass%,
wherein the mass% of each component is with respect to the total mass of said overhead raffinate phase.
11. The process as claimed in claim 1, wherein said bottom extract phase comprises:
? non-aromatic compounds in an amount in the range of 5 mass% to 15 mass%; and
? aromatic compounds in an amount in the range of 85 mass% to 95 mass%,
wherein the mass% of each component is with respect to the total mass of said bottom extract phase.
12. The process as claimed in claim 1, wherein the ratio of said solvent system to said hydrocarbon feed is in the range of 2:1 to 5:1.
13. The process as claimed in claim 1, wherein said solvent system comprises a primary solvent and a co-solvent.
14. The process as claimed in claim 13, wherein said primary solvent is selected from N-methyl pyrrolidone (NMP) and N-formyl morpholine (NFM).
15. The process as claimed in claim 13, wherein said co-solvent is selected from the group consisting of anti-foaming agents, water and sulfolane.
16. The process as claimed in claim 13, wherein said co-solvent is present in an amount in the range of 0 to 10 mass% with respect to the amount of said primary solvent.
17. The process as claimed in claim 1, wherein
? said preheated hydrocarbon feed has a temperature in the range of 90 °C to 110 °C;
? said solvent system has a temperature in the range of 65 °C to 75 °C;
? steam has a temperature in the range of 180 °C to 220 °C; and
? said solvent recovery column has a temperature maintained in the range of 170 °C to 180 °C.
18. The process as claimed in claim 1, wherein
? said preheated hydrocarbon feed has a flowrate in the range of 1 Kg /hr to 4 Kg/hr;
? said solvent system has a flowrate in the range of 2.5 Kg/hr to 5 Kg/hr; and
? said bottom extract phase has a flowrate in the range of 2.8 Kg/hr to 23.2 Kg/hr.
19. The process as claimed in claim 1, wherein the ratio of steam to a hydrocarbon content of said bottom extract phase is in the range of 0.5:1 to 1.5:1.

20. The process as claimed in claim 1, wherein
? said extractive distillation column has a pressure maintained in the range of 0.5 bar to 2.0 bar; and
? said solvent recovery column has a pressure maintained in the range of 0.3 bar to 0.7 bar.
21. The process as claimed in claim 1, wherein said hydrocarbon feed comprises C5-C11 hydrocarbon fraction.
22. The process as claimed in claim 1, wherein said overhead raffinate phase comprises C5-C11 non-aromatic compounds.
23. The process as claimed in claim 1, wherein said bottom extract phase comprises C6-C11 aromatic compounds.
24. The process as claimed in claim 1, wherein said overhead stream comprises C6-C11 aromatic compounds.
25. The process as claimed in claim 1, wherein
? said non-aromatic compounds are recycled to said extractive distillation column;
? said bottom stream from said solvent recovery column is recycled to said extractive distillation column; and
? said overhead stream from said solvent recovery column is recycled to said extractive distillation column.

Dated this 15th Day of February 2025

_______________________________
MOHAN RAJKUMAR DEWAN, IN/PA – 25
OF R. K. DEWAN & CO.
AUTHORIZED AGENT OF APPLICANT