Title of Invention	AN IMPROVED SOLVENT EXTRACTION PROCESS FOR THE PRODUCTION OF SPECIAL BOILING SOLVENTS USING NPM SOLVENT
Abstract	This invention relates to an improved process for the exraction of special boiling point (SBP) solvents from naphtha range petroleum fractions which comprises, (a) Dearomatizating a naphtha range petroleum fractions by passing countercurrently N-methylpyrolodone (NMP) containing water in an amount ranging from 2 to 15% by weight to extract the aromatics, at a temperature between 25 and 60°C (b) Distilling the extract phase obtained above in a distillation column (solvent recovery column) under atmospheric pressure and at a temperature ranges from 100 to 160°C, recovering the aromatics extract from the overhead and recovering the solvent and utilizing it in step (a), (c) Washing with water the top raffinate phase in a raffinate wash column, at a temperature between 25 and 60°C (d) Subjecting the washed raffinate to fractionation to separate the 63-69°C fraction as food grade hexane and 55/115°C fraction as (SBP) solvent.

Title of Invention

AN IMPROVED SOLVENT EXTRACTION PROCESS FOR THE PRODUCTION OF SPECIAL BOILING SOLVENTS USING NPM SOLVENT

Abstract

This invention relates to an improved process for the exraction of special boiling point (SBP) solvents from naphtha range petroleum fractions which comprises, (a) Dearomatizating a naphtha range petroleum fractions by passing countercurrently N-methylpyrolodone (NMP) containing water in an amount ranging from 2 to 15% by weight to extract the aromatics, at a temperature between 25 and 60°C (b) Distilling the extract phase obtained above in a distillation column (solvent recovery column) under atmospheric pressure and at a temperature ranges from 100 to 160°C, recovering the aromatics extract from the overhead and recovering the solvent and utilizing it in step (a), (c) Washing with water the top raffinate phase in a raffinate wash column, at a temperature between 25 and 60°C (d) Subjecting the washed raffinate to fractionation to separate the 63-69°C fraction as food grade hexane and 55/115°C fraction as (SBP) solvent.

Full Text	This invention relates to an improved process for the extraction of special boiling point(SBP) solvent from naphtha range petroleum fractions. Aromatics and non-aromatics from naphtha fractions with boiling points below 160°C are employed as solvents for a variety of industrial purposes such as oil seed extraction, in the preparation of certain lacquers and printing inks, in the manufacture of polyolefins, synthetic rubber and pharmaceuticals, and are often tailored to the needs of the customers. For this reason special boiling point (SBP) solvent are usually manufactured in comparatively small batches or short runs. Besides, a strict specification on boiling range, a specification on aromatics content often also exists. These specifications can either be a maximum allowable (e.g. for benzene) or ask for certain range required for itsspecific use. Such requirements can hardly ever be met by straight run distillates. The selection of the most attractive processing route is dependent on the number of solvents required as well as on product specifications. The latter point especially is often the determining factor. The manufacturing processes that are still in use are oleum treatment, extractive distillation, adsorption, hydrogenation and solvent extraction. In oleum treatment prcess hexane fraction is contacted with oleum up to 160% at ambient conditions wherein aromatics are converted to sulphonates forming the acid sludge. Despite these stringent conditions benzene can not be reduced below 1%. A serious disadvantage of the process is the problem of disposal of the sludge. Oleum is highly corrosive and poses serious handling problems. Moreover, the aromatics are also lost with the acid sludge. Extractive Distillation method employs selective solvent e.g. sulpholane in the distillation operation to separate aromatics from non-aromatics hydrocarbons. It poses problem in processing feedstocks with low benzene concentrations where the number of stages required in the distillation column is large to get the desired product. The solvent-to-feed ratio required is about three times compared to solvent extraction. The distillation column operates at high temperatures and therefore, the utility costs will be high. In adsorption process aromatics are removed by using selective adsorbents such as silica gel, activated carbon and zeolite. The process, however, operates in semi-batch and costs involved in stripping the aromatics from the loaded adsorbent are often high and determines the economics of the process. Operating costs are mainly dependent on the aromatic content of the starting material. In hydrogenation process aromatics are converted in to naphthenes in presence of catalyst containing noble metals. In this process aromatics are lost due to coversion hich sometimes are the valuable components for hydrocarbon solvents. Since the catalysts used in this process are usually sulphur-sensitive, a preceding hydrodesulphurization step is required. Thus, hydrogen requirements, depending upon the aromatic content of the feed contribute substantially to the operating costs. The solvent extraction process is very suitable for aromatics removal from light distillate fractions. The use of high boiling solvents such as sulpholane, N-methylpyrolidone (NMP) has particular advantages, since the operating costs are only marginally influenced by the quality of the starting material. Moreover, the aromatics can be obtained in a pure form and as such have a high value either as a gasoline component, as high aromatic solvent or as starting material for the manufacture of pure aromatics. The main objective of this invention is to provide an improved process for the preparation of special boiling solvents using N-methylpyrolidone (NMP) solvent, from feedstocks of naphtha range petroleum fractions. According to the present invention it has been found that liquid-liquid extraction for the removal of aromatics is more advantageous with solvents which has very high capacity and low viscosity, particularly NMP. Sulpholane and glycols are very viscous solvents compared to NMP and are poorly dispersed at low temperatures. This decreases mass transfer rate at interface and as a result efficiency decreases. Thus, for dearomatization purposes extraction is to be carried out at high temperature or to use low viscosity solvents like NMP. The operation at high temperature such as 70°C is disadvantageous as it decreases the solvent selectivity and increases utility requirements. Accordingly, the present invention provides an improved process for the extraction of special boiling point (SBP) solvent from naphtha range petroleum fractions which comprises, (a) Dearomatizing a naphtha range petroleum fractions by passing countercurrently N-methylpyrolodone (NMP) containing water in an amount ranging from 2 to 15% by weight to extract the aromatics, at a temperature between 25 and 60°C (b)Distilling the extract phase obtained above in a distillation column (solvent recovery column) under atmospheric pressure and at a temperature ranges from 100 to 160°C, recovering the aromatics extract from the overhead and recovering the solvent and utilizing it in step (a), ( c) Washing with water the top raffinate phase in a raffinate wash column, at a temperature between 25 and 60°C d) Subjecting the washed raffinate to fractionation to separate the 63-69°C fraction as food grade hexane and 55/115°C fraction as (SBP) solvent The extraction in the extractor is preferably carried out in multistage packed extraction columns. The naphtha feed is contacted countercurrently with NMP solvent in the extractor. The solvent contains some amount of water as antisolvent ranging between 2% and 20% by wt, preferably between 5 to 15% by wt, The extract phase, thus obtained, is distilled in a distillation column under atmospheric pressure to recover the extract hydrocarbons while the solvent is recirculated back to the extractor. The raffinate phase is water washed in a raffinate wash column and then fractionated to get food grade hexane (63-69°C) and SBP solvents. The solvent-to-naphtha feed ratio may range from 0.5 to 5 by weight and preferably between 1 and 3 by weight. The temperature of extraction may range within wide limits provided it is above the melting temperatures of both feed and solvent. The temperature in the contacting zone may range between 25°C to 60°C, preferably from 30 to 40°C. In the raffinate wash column the temperature may range between 30 to 40°C. The temperature in the distillation column ranges from 50-150°C, i.e, the bubble point of NMP + water combination, while solvent left behind will be recirculated to the extractor. Under the conditions employed in the process of the invention, the aromatics were left in traces in the dearomatized naphtha. However, after fractionation the 63-69°C cut so obtained contained 0.1 wt.% benzene while the SBP solvent had the aromatics in traces. The flow diagram of this process of the present invention is shown in Fig.-l of the drawing accompanying the provisional specification. The naphtha stream is introduced through line (1) into the contact zone (2) and lean solvent is introduced via line (3) where the two streams meet countercurrently. The contact zone may comprise either a packed column or a plate or a rotating disc contactor. The raffinate and extract phase, thus produced, are separately withdrawn through lines (4) and (5) respectively. The top raffinate phase which leaves the contacting zone (2) via line (4) is water washed in raffinate wash column (6) and then enters the distillation column (fractionator) (8) via line (7) where it gets fractionated to 63-69°C hexane cut and SBP solvent. The top 55 ° C- and 1150+ fractions are collected separately from top and bottom of the distillation column (8) respectively. The 55-115°C fraction is sent to another fractionator (15) via line (16) where 55-63° fraction is collected separately and later on mixed with 69-115°C fraction via line (17). The 63-115°C cut from the bottom of the fractionator (15) goes to another fractionator (18) where top 63-69°C cut is collected via line (19) and bottom 69-115°C cut is mixed with 55-63°C cut via line (20) to get 55/115°C SBP solvent. The wash water containing NMP from line (9) is recycled to SRC and part of it can be used for water makeup in the recycled NMP through line (3). The extract phase obtained from the contact zone (2) is introduced via line (5) in the distillation column (10) for solvent recovery from where solvent-free extract is withdrawn through line (11) and recovered solvent is withdrawn through line (12) and joined to line (3) for recycling. A slip-stream of solvent is taken from line (12) and fed to the NMP regeneration column (13) from where the regenerated NMP is taken through line (14) and put back into NMP recycled line (3). The invention is described in the following examples which are provided by way of illustration only and therefore should not be construed to limit the scope of the invention. Example-1 The naphtha fraction (IBP-120oC) containing about 22.7 wt.% of total aromatics is fed into the bottom of a packed liquid-liquid extraction column at a rate of 2.57 kg/hr where it is contacted countercurrently with the solvent stream of NMP containing 5 wt.% water flowing in from the top of the extraction column at a rate of about 5.48 kg/hr. The temperature in the column is maintained at 40°C. The resulting raffmate stream is withdrawn from the top of the column at a rate of 1.45 kg/hr and the extract stream is withdrawn from the bottom at a rate of 6.60 kg/hr. The raffmate stream from the extraction column which contains about 7.33 wt.% of the solvent is water washed in the raffmate wash column (RWC). The water washed raffmate stream is withdrawn from the top of RWC at a rate of 1.33 kg/hr. The total aromatics in the washed raffmate were in traces. The washed raffmate is then fed to the fractionator where it is fractionated to 63- 69°C hexane cut and 55/115° SBP solvent. The benzene concentration in hexane cut was found to be 0.1 wt.% while total aromatics in the 55/115° SBP solvent was in traces. The respective yields of hexane cut and 55/115° SBP solvent are 5.49 and 35.60% by weight respectively. The wash water containing solvent from the bottom of RWC is fed into the solvent recovery column (SRC) as stripper water. The extract phase from the bottom of the extraction column contains about 19.6 wt.% of hydrocarbons out of which 45.3% by weight are total aromatics, and is fed into a distillation column (SRC) operating with a bottom temperature of 130°C and a top temperature of 95°C. Wash water from the RWC is also fed into this column at a point below the feed entry point. The overhead vapours on condensation gives a hydrocarbon layer and a water layer. The hydrocarbon layer is withdrawn as extract produced at a rate of 1.24 kg/hr. A part of the water layer is returned to the distillation column top as reflux. The bottom product from the SRC contains no hydrocarbons and is recycled back to the extractor as lean solvent. Example-2 The naphtha fraction (IBP-160oC) containing about 24.2 wt.% of total aromatics is fed into the bottom of a packed liquid-liquid extraction column at a rate of 2.08 kg/hr where it is contacted countercurrently with the solvent stream of NMP containing 5 wt.% water flowing in from the top of the extraction column at a rate of about 5.45 kg/hr. The temperature in the column is maintained at 40°C. The resulting raffinate stream is withdrawn from the top of the column at a rate of 1.09 kg/hr and the extract stream is withdrawn from the bottom at a rate of 6.44 kg/hr. The raffinate stream from the extraction column which contains about 8.19 wt.% of the solvent is pumped to the bottom of another packed extraction column, the raffinate wash column (RWC), where it comes in contact with water flowing in from the top. The operation is at 40°C. The water washed raffinate stream is withdrawn from the top of RWC at a rate of about 1.00 kg/hr. The total aromatics in the washed raffinate were in traces. The washed raffinate is then fed to the fractionator where it is fractionated to 63-69°C hexane cut and 55/115° SBP solvent respectively. The benzene concentration in hexane cut was found to be 0.1 wt.% while total aromatics in the 55/115° SBP solvent was in traces. The yield of food grade hexane cut, thus produced was 4.12% by weight. The wash water containing solvent from the bottom of RWC is fed into the solvent recovery column (SRC) as stripper water. The extract phase from the bottom of the extraction column contains about 18.14 wt.% of hydrocarbons out of which 43.5% by weight are total aromatics, and is fed into a distillation column (SRC) operating with a bottom temperature of 130°C and a top temperature of 96°C. Wash water from the RWC is also fed into this column at a point below the feed entry point. The overhead vapours on condensation gives a hydrocarbon layer and a water layer. The hydrocarbon layer is withdrawn as extract produced at a rate of 1.24 kg/hr. A part of the water layer is returned to the distillation column top as reflux. The bottom product from the SRC is withdrawn which contains no hydrocarbons and is recycled to the extractor as lean solvent. The main advantages of the present invention over the sulpholane extraction process are : NMP has very low viscosity at ambient temperature and as such it can be used at temperatures close to ambient. Due to low viscosity of NMP the extraction efficiency is higher compared to other solvents. Since the extraction temperature is close to ambient the solvent selectivity is very high. NMP has high capacity and is always used with 5 to 15 wt.% water which can be adjusted at will depending upon the aromatics content of the feed to achieve desired separation. Since it has high capacity low solvent-to-feed (S/F) ratio is required. Since S/F ratio is low the diameters of extraction and recovery columns will be small resulting in low capital and utility costs. The solvent recovery column (SRC) operates at relatively lower temperatures and atmospheric pressure, hence solvent losses due to degradation is minimized. Water is not required to be distilled off in the SRC and as such no additional energy is required. Use of water with NMP further reduces the NMP inventory cost. NMP has lower boiling point than other industrial solvents and therefore, utility consumption in the solvent regeneration section will be low. Due to low viscosity of NMP the energy requirement to pump the solvent will be low. The process throughout operates at lower temperature and lower S/F, therefore, utility requirements will be low. We Claim : 1. An improved process for the extraction of special boiling point (SBP) solvents from naphtha range petroleum fractions which comprises, (a) Dearomatizating a naphtha range petroleum fractions by passing countercurrently N-methylpyrolodone (NMP) containing water in an amount ranging from 2 to 15% by weight to extract the aromatics, at a temperature between 25 and 60°C (b) Distilling the extract phase obtained above in a distillation column (solvent recovery column) under atmospheric pressure and at a temperature ranges from 100 to 160°C, recovering the aromatics extract from the overhead and recovering the solvent and utilizing it in step (a), (c) Washing with water the top raffinate phase in a raffinate wash column, at a temperature between 25 and 60°C (d) Subjecting the washed raffinate to fractionation to separate the 63-69°C fraction as food grade hexane and 55/115°C fraction as (SBP) solvent 2. A process as claimed in claim 1 wherein the solvent-to-neptha (hydrocarbon) feed ratio ranges from 0.5 to 5 by weight. 3. A process as claimed in claims 1 and 2 wherein in the step (a) is affected at a temperature between 30 and 40°C. 4. A process as claimed in claims 1 to 3 wherein the temperature in the raffinate wash column ranges between 30 to 40°C. 5. A process as claimed in claims 1 to 4 wherein the temperature in the recovery column ranges from 120 to 150°C. 6. An unproved process for the extraction of special boiling point (SBP) solvent from naphtha range petroleum fractions subatantially as herein described with reference to the examples and drawing accompanying this provisional specification.

Full Text

This invention relates to an improved process for the extraction of special boiling point(SBP) solvent from naphtha range petroleum fractions.
Aromatics and non-aromatics from naphtha fractions with boiling points below 160°C are employed as solvents for a variety of industrial purposes such as oil seed extraction, in the preparation of certain lacquers and printing inks, in the manufacture of polyolefins, synthetic rubber and pharmaceuticals, and are often tailored to the needs of the customers. For this reason special boiling point (SBP) solvent are usually manufactured in comparatively small batches or short runs. Besides, a strict specification on boiling range, a specification on aromatics content often also exists. These specifications can either be a maximum allowable (e.g. for benzene) or ask for certain range required for itsspecific use. Such requirements can hardly ever be met by straight run distillates. The selection of the most attractive processing route is dependent on the number of solvents required as well as on product specifications. The latter point especially is often the determining factor. The manufacturing processes that are still in use are oleum treatment, extractive distillation, adsorption, hydrogenation and solvent extraction.
In oleum treatment prcess hexane fraction is contacted with oleum up to 160% at ambient conditions wherein aromatics are converted to sulphonates forming the acid sludge. Despite these stringent conditions benzene can not be reduced below 1%. A serious disadvantage of the process is the problem of disposal of the sludge. Oleum is highly corrosive and poses serious handling problems. Moreover, the aromatics are also lost with the acid sludge.
Extractive Distillation method employs selective solvent e.g. sulpholane in the distillation operation to separate aromatics from non-aromatics hydrocarbons. It poses problem in processing feedstocks with low benzene concentrations where the number of stages required in the distillation column is large to get the desired product. The solvent-to-feed ratio required is about three times compared to solvent extraction. The distillation column operates at high temperatures and therefore, the utility costs will be high.
In adsorption process aromatics are removed by using selective adsorbents such as silica gel, activated carbon and zeolite. The process, however, operates in semi-batch and costs involved in stripping the aromatics from the loaded adsorbent are often high and determines the economics of the process. Operating costs are mainly dependent on the aromatic content of the starting material.
In hydrogenation process aromatics are converted in to naphthenes in presence of catalyst containing noble metals. In this process aromatics are lost due to coversion hich sometimes are the valuable components for hydrocarbon solvents. Since the catalysts used in this process are usually sulphur-sensitive, a preceding hydrodesulphurization step is required. Thus,
hydrogen requirements, depending upon the aromatic content of the feed contribute substantially to the operating costs.
The solvent extraction process is very suitable for aromatics removal from light distillate fractions. The use of high boiling solvents such as sulpholane, N-methylpyrolidone (NMP) has particular advantages, since the operating costs are only marginally influenced by the quality of the starting material. Moreover, the aromatics can be obtained in a pure form and as such have a high value either as a gasoline component, as high aromatic solvent or as starting material for the manufacture of pure aromatics.
The main objective of this invention is to provide an improved process for the preparation of special boiling solvents using N-methylpyrolidone (NMP) solvent, from feedstocks of naphtha range petroleum fractions. According to the present invention it has been found that liquid-liquid extraction for the removal of aromatics is more advantageous with solvents which has very high capacity and low viscosity, particularly NMP. Sulpholane and glycols are very viscous solvents compared to NMP and are poorly dispersed at low temperatures. This decreases mass transfer rate at interface and as a result efficiency decreases. Thus, for dearomatization purposes extraction is to be carried out at high temperature or to use low viscosity solvents like NMP. The operation at high temperature such as 70°C is disadvantageous as it decreases the solvent selectivity and increases utility requirements.
Accordingly, the present invention provides an improved process for the extraction of special boiling point (SBP) solvent from naphtha range petroleum fractions which comprises,
(a) Dearomatizing a naphtha range petroleum fractions by passing countercurrently N-methylpyrolodone (NMP) containing water in an amount ranging from 2 to 15% by weight to extract the aromatics, at a temperature between 25 and 60°C
(b)Distilling the extract phase obtained above in a distillation column (solvent recovery column) under atmospheric pressure and at a temperature ranges from 100 to 160°C, recovering the aromatics extract from the overhead and recovering the solvent and utilizing it in step (a),
( c) Washing with water the top raffinate phase in a raffinate wash column, at a temperature between 25 and 60°C
d) Subjecting the washed raffinate to fractionation to separate the 63-69°C fraction as food grade hexane and 55/115°C fraction as (SBP) solvent
The extraction in the extractor is preferably carried out in multistage packed extraction columns. The naphtha feed is contacted countercurrently with NMP solvent in the extractor. The solvent contains some amount of water as antisolvent ranging between 2% and 20% by wt, preferably between 5 to 15% by wt, The extract phase, thus obtained, is distilled in a distillation column under atmospheric pressure to recover the extract hydrocarbons while the solvent is recirculated back to the extractor. The raffinate phase is water washed in a raffinate wash column and then fractionated to get food grade hexane (63-69°C) and SBP solvents.
The solvent-to-naphtha feed ratio may range from 0.5 to 5 by weight and preferably between 1 and 3 by weight. The temperature of extraction may range within wide limits provided it is above the melting temperatures of both feed and solvent. The temperature in the contacting zone may range between 25°C to 60°C, preferably from 30 to 40°C. In the raffinate wash column the temperature may range between 30 to 40°C. The temperature in the distillation column ranges from 50-150°C, i.e, the bubble point of NMP + water combination, while solvent left behind will be recirculated to the extractor.
Under the conditions employed in the process of the invention, the aromatics were left in traces in the dearomatized naphtha. However, after fractionation the 63-69°C cut so obtained contained 0.1 wt.% benzene while the SBP solvent had the aromatics in traces.
The flow diagram of this process of the present invention is shown in Fig.-l of the drawing accompanying the provisional specification.
The naphtha stream is introduced through line (1) into the contact zone (2) and lean solvent is introduced via line (3) where the two streams meet countercurrently. The contact zone may comprise either a packed column or a plate or a rotating disc contactor. The raffinate and extract phase, thus produced, are separately withdrawn through lines (4) and (5) respectively. The top raffinate phase which leaves the contacting zone (2) via line (4) is water washed in raffinate wash column (6) and then enters the distillation column (fractionator) (8) via line (7) where it gets fractionated to 63-69°C hexane cut and SBP solvent. The top 55 ° C- and 1150+ fractions are collected separately from top and bottom of the distillation column (8) respectively. The 55-115°C fraction is sent to another fractionator (15) via line (16) where 55-63° fraction is collected separately and later on mixed with 69-115°C fraction via line (17). The 63-115°C cut from the bottom of the fractionator (15) goes to another fractionator (18) where top 63-69°C cut is collected via line (19) and bottom 69-115°C cut is
mixed with 55-63°C cut via line (20) to get 55/115°C SBP solvent. The wash water containing NMP from line (9) is recycled to SRC and part of it can be used for water makeup in the recycled NMP through line (3).
The extract phase obtained from the contact zone (2) is introduced via line (5) in the distillation column (10) for solvent recovery from where solvent-free extract is withdrawn through line (11) and recovered solvent is withdrawn through line (12) and joined to line (3) for recycling. A slip-stream of solvent is taken from line (12) and fed to the NMP regeneration column (13) from where the regenerated NMP is taken through line (14) and put back into NMP recycled line (3).
The invention is described in the following examples which are provided by way of illustration only and therefore should not be construed to limit the scope of the invention.
Example-1
The naphtha fraction (IBP-120oC) containing about 22.7 wt.% of total aromatics is fed into the bottom of a packed liquid-liquid extraction column at a rate of 2.57 kg/hr where it is contacted countercurrently with the solvent stream of NMP containing 5 wt.% water flowing in from the top of the extraction column at a rate of about 5.48 kg/hr. The temperature in the column is maintained at 40°C. The resulting raffmate stream is withdrawn from the top of the column at a rate of 1.45 kg/hr and the extract stream is withdrawn from the bottom at a rate of 6.60 kg/hr.
The raffmate stream from the extraction column which contains about 7.33 wt.% of the solvent is water washed in the raffmate wash column (RWC). The water washed raffmate stream is withdrawn from the top of RWC at a rate of 1.33 kg/hr. The total aromatics in the washed raffmate were in traces. The washed raffmate is then fed to the fractionator where it is fractionated to 63- 69°C hexane cut and 55/115° SBP solvent. The benzene concentration in hexane cut was found to be 0.1 wt.% while total aromatics in the 55/115° SBP solvent was in traces. The respective yields of hexane cut and 55/115° SBP solvent are 5.49 and 35.60% by weight respectively. The wash water containing solvent from the bottom of RWC is fed into the solvent recovery column (SRC) as stripper water.
The extract phase from the bottom of the extraction column contains about 19.6 wt.% of hydrocarbons out of which 45.3% by weight are total aromatics, and is fed into a distillation column (SRC) operating with a bottom temperature of 130°C and a top temperature of 95°C. Wash water from the RWC is also fed into this column at a point below the feed entry point.
The overhead vapours on condensation gives a hydrocarbon layer and a water layer. The hydrocarbon layer is withdrawn as extract produced at a rate of 1.24 kg/hr. A part of the water layer is returned to the distillation column top as reflux. The bottom product from the SRC contains no hydrocarbons and is recycled back to the extractor as lean solvent.
Example-2
The naphtha fraction (IBP-160oC) containing about 24.2 wt.% of total aromatics is fed into the bottom of a packed liquid-liquid extraction column at a rate of 2.08 kg/hr where it is contacted countercurrently with the solvent stream of NMP containing 5 wt.% water flowing in from the top of the extraction column at a rate of about 5.45 kg/hr. The temperature in the column is maintained at 40°C. The resulting raffinate stream is withdrawn from the top of the column at a rate of 1.09 kg/hr and the extract stream is withdrawn from the bottom at a rate of 6.44 kg/hr.
The raffinate stream from the extraction column which contains about 8.19 wt.% of the solvent is pumped to the bottom of another packed extraction column, the raffinate wash column (RWC), where it comes in contact with water flowing in from the top. The operation is at 40°C. The water washed raffinate stream is withdrawn from the top of RWC at a rate of about 1.00 kg/hr. The total aromatics in the washed raffinate were in traces. The washed raffinate is then fed to the fractionator where it is fractionated to 63-69°C hexane cut and 55/115° SBP solvent respectively. The benzene concentration in hexane cut was found to be 0.1 wt.% while total aromatics in the 55/115° SBP solvent was in traces. The yield of food grade hexane cut, thus produced was 4.12% by weight. The wash water containing solvent from the bottom of RWC is fed into the solvent recovery column (SRC) as stripper water.
The extract phase from the bottom of the extraction column contains about 18.14 wt.% of hydrocarbons out of which 43.5% by weight are total aromatics, and is fed into a distillation column (SRC) operating with a bottom temperature of 130°C and a top temperature of 96°C. Wash water from the RWC is also fed into this column at a point below the feed entry point. The overhead vapours on condensation gives a hydrocarbon layer and a water layer. The hydrocarbon layer is withdrawn as extract produced at a rate of 1.24 kg/hr. A part of the water layer is returned to the distillation column top as reflux. The bottom product from the SRC is withdrawn which contains no hydrocarbons and is recycled to the extractor as lean solvent.
The main advantages of the present invention over the sulpholane extraction process are :
NMP has very low viscosity at ambient temperature and as such it can be used at temperatures close to ambient.
Due to low viscosity of NMP the extraction efficiency is higher compared to other solvents.
Since the extraction temperature is close to ambient the solvent selectivity is very high.
NMP has high capacity and is always used with 5 to 15 wt.% water which can be adjusted at will depending upon the aromatics content of the feed to achieve desired separation. Since it has high capacity low solvent-to-feed (S/F) ratio is required.
Since S/F ratio is low the diameters of extraction and recovery columns will be small resulting in low capital and utility costs.
The solvent recovery column (SRC) operates at relatively lower temperatures and atmospheric pressure, hence solvent losses due to degradation is minimized. Water is not required to be distilled off in the SRC and as such no additional energy is
required. Use of water with NMP further reduces the NMP inventory cost.
NMP has lower boiling point than other industrial solvents and therefore, utility consumption in the solvent regeneration section will be low.
Due to low viscosity of NMP the energy requirement to pump the solvent will be low.
The process throughout operates at lower temperature and lower S/F, therefore, utility requirements will be low.

We Claim :
1. An improved process for the extraction of special boiling point (SBP) solvents from
naphtha range petroleum fractions which comprises,
(a) Dearomatizating a naphtha range petroleum fractions by passing countercurrently N-methylpyrolodone (NMP) containing water in an amount ranging from 2 to 15% by weight to extract the aromatics, at a temperature between 25 and 60°C
(b) Distilling the extract phase obtained above in a distillation column (solvent recovery column) under atmospheric pressure and at a temperature ranges from 100 to 160°C, recovering the aromatics extract from the overhead and recovering the solvent and utilizing it in step (a),
(c) Washing with water the top raffinate phase in a raffinate wash column, at a temperature between 25 and 60°C
(d) Subjecting the washed raffinate to fractionation to separate the 63-69°C fraction as food grade hexane and 55/115°C fraction as (SBP) solvent
2. A process as claimed in claim 1 wherein the solvent-to-neptha (hydrocarbon) feed
ratio ranges from 0.5 to 5 by weight.
3. A process as claimed in claims 1 and 2 wherein in the step (a) is affected at a
temperature between 30 and 40°C.
4. A process as claimed in claims 1 to 3 wherein the temperature in the raffinate wash
column ranges between 30 to 40°C.
5. A process as claimed in claims 1 to 4 wherein the temperature in the recovery column ranges from 120 to 150°C.
6. An unproved process for the extraction of special boiling point (SBP) solvent from naphtha range petroleum fractions subatantially as herein described with reference to the examples and drawing accompanying this provisional specification.

Documents:

603-del-1995-abstract.pdf

603-del-1995-claims.pdf

603-del-1995-correspondence-others.pdf

603-del-1995-correspondence-po.pdf

603-del-1995-description (complete).pdf

603-del-1995-drawings.pdf

603-del-1995-form-1.pdf

603-del-1995-form-2.pdf

603-del-1995-form-4.pdf

603-del-1995-form-5.pdf

603-del-1995-form-6.pdf

603-del-1995-form-9.pdf

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Patent Number

191005

Indian Patent Application Number

603/DEL/1995

PG Journal Number

37/2003

Publication Date

13-Sep-2003

Grant Date

22-Mar-2004

Date of Filing

31-Mar-1995

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI 110001,INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	B.S.RAWAT	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA
2	M.K.KHANNA	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA
3	S.M. NANOTI	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA
4	GURU PRASAD	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA
5	JYOTSNA NAITHANI	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA
6	DHARAM PAUL	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA
7	B. R. NAUTIYAL	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA
8	T.S.R. PRASADA RAO	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA

PCT International Classification Number

C07C 015/02

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA