Title of Invention

A PROCESS FOR THE EXTRACTION OF AROMATICS FROM AROMATIC RICH PETROLEUM STREAMS

Abstract A process for the extraction of aromatics from aromatic rich petroleum streams The invention relates to an improved process for the extraction of aromatics from aromatic rich petroleum streams. In this process, aromatics are extracted from aromatic rich petroleum stream such as heavy naphtha, kerosene and gas oil range petroleum fractions using polar organic solvent and further re-extracting the extract phase with C6-C7 paraffinic solvent. Refinery cut light naphtha is used as re-extraction solvent. The unique process of this invention provides feasibility to dearomatize three feedstocks of different boiling range using an eco-friendly solvent N-methyl-pyrrolidone in the same unit using block out operation..
Full Text The invention particularly relates to the extraction of aromatics from heavy
naphtha, kerosene and gas oil range petroleum fractions with the aid of a
suitable polar organic solvent and re-extracting the extract phase with a Ce-C/
paraffinic solvent7
Different petroleum fractions obtained in crude distillation unit contain varying
concentration of aromatics depending upon crude oil source. These aromatics
are required to be removed to produce various end products meeting the
specifications with respect to aromatics. For example:
Naphtha used as feedstock in petrochemical industry for the production of olefins
should not contain more than 5% of aromatics due to refractory nature of
aromatics. While in the case of fertiliser industry limitation of aromatics ( naphtha feedstock is due to higher carbon to hydrogen ratio which in turn affects
the hydrogen yield.
Refining of kerosene fractions is done in order to produce superior kerosene
(SK)/ aviation turbine fuel (ATF). These end products should meet BIS
specification requirements of smoke point, freezing point (for ATF) and aromatic
content on which performance of these products depends.
High aromatic content in gas oil fraction results in lowering of cetane number. In
order to improve the cetane number the reduction of aromatics is essential.
Hydrofming and solvent extraction are the conventional processes for
dearomatization. However, severe operating conditions such as high partial
pressure of hydrogen and high hydrogen consumption are required for high
aromatic feed stocks, which make the process highly capital cost intensive
compared to solvent extraction. For example for dearomatisation of kerosene
fractions from Assam crude oils, being rich in aromatics solvent extraction is
employed. Presently, there are three refineries in the eastern part of our country
where kerosene fractions are dearomatized using liquid sulphur dioxide as the
solvent (Edeleanu, L. British Patent 11,140 May 22, 1908). Considering present
growth in technology development and environment awareness, this is an
obsolete process. It has several drawbacks. The main drawbacks are :
(1) Liquid sulphur dioxide is highly corrosive in presence of traces of water,
therefore, drying of feed and solvent is an important step.
(2) There is occasional failure of ATF produced by this process.
(3) The number of columns used for solvent recovery from raffinate and
extract phases is too large.
(4) Extraction temperature is as low as -15°C thus requires refrigeration
To overcome the above drawbacks Indian Institute of Petroleum, Dehra
Dun, Engineers India Limited, New Delhi and Hindustan Petroleum Corporation
Limited, Mumbai have jointly developed a process for refining kerosene fraction
(140-240°C) which uses sulpholane as the solvent (Patent No. 170747, 23 Mar
1987) employing conventional extraction route. In this process scheme the
recovery of solvent from extract phase is carried out by distillation. This approach
is successful for systems constituting feed and solvents having wide difference of
boiling points. However, this process consumes significant energy for the
recovery of hydrocarbons, due to requirement of stringent operating conditions.
Moreover, processing of feeds having wide boiling range e.g. naphtha to gas oil
in the same unit using block out operations is not feasible due to over lapping of
boiling points with the solvent. For such application solvent extraction in
combination with re-extraction route for solvent recovery is feasible approach.
Re-extraction concept for the recovery of aromatics from extract phase is
reported to have been used commercially e.g., for the production of pure
benzene and toluene by Dimethyl sulphoxide (DMSO) process [Hydrocarbon
Processing, 45, (5), 188, 1966]. Handling of low thermal stability solvent is the
main drawback of this process. Improvement of cetane number of LCCO
[Hydrocarbon Processing, 46, (9), 134, 1967] using Dimethyl formamide (DMF),
production of high boiling aromatics by using N-Formyl Morpholine (NFM)
[Hydrocarbon Processing, 51, (4), 141,1972], production of pure benzene and
toluene from pyrolysis gasoline by using Tetraethyleneglycol [DE 3,409,307 Sept
1985 and ISEC 1971] have also been tried. Re-extraction of aromatics from
extract phase of kerosene fractions is also reported by Muller, et. at. [DE
3,207,404; 8 Sept 1983] and Lobov [Nauchn. Osn. Pererab.Negti Gaza
Neftekhim., Tezisy Dokl., Vses. Knof. 234-5, 1977]. The solvent tried in the
former work was N-Methyl pyrolidinone (NMP) containing 6% water while the reextraction
was done by n-hexane, while in the latter work the feed used was
kerosene fraction 200-270°C and solvent used was DMF while the re-extraction
solvent was n-heptane. In all these processes the lean solvent obtained from
bottom of the re-extraction column is directly re-circulated back to the main
extraction column without removing the re-extraction solvent. Drawbacks of this
process scheme are:
- Difficulty in maintaining the extraction solvent composition
- Contamination of raffmate phase with re-extraction solvent
- Requirement of additional fractionator for removal of re-extraction
solvent from raffinate
- Requirement of stringent operating conditions in water-solvent
fractionator due to higher boiling point of solvents
- RE-extraction solvent such as n-hexane & n-heptane being pure
hydrocarbons are costly
in the present work a modified process scheme has been developed for the
extraction of aromatics from petroleum fractions i.e. naphtha, kerosene and gas
oil, using re-extraction route for recovery of solvent. The novelty of the present
invention lies in:
- Proposed invention provides unique feasibility to dearomatize three
feed stocks of different boiling range namely Heavy Naphtha,
Kerosene and Gas Oil using an eco-friendly solvent such as NMP.
- Single plant can be used in blocked out mode of operation to produce
additional products such as high octane benzene free stock for
gasoline pool, high Cetane Diesel, high aromatic solvent and feedstock
for needle coke production. This is the unique feature of the
invention as no such process has been reported so far to produce
these value-added products from a single unit.
- Use of refinery cut light naphtha cut as re-extraction solvent
- The invention facilitates the controllability of the severity of extraction
while in operation, through manipulating anti-solvent composition
depending upon feed characteristics and target product specification.
- The invention allows the production; of dearomatised raffinate free of
re-extraction solvent.
The main object of the present invention is to provide an improved process for
the extraction of aromatics from petroleum streams, which obviates the
drawbacks as detailed above.
Another objective of the present invention is to provide modified process wherein
solvent extraction of aromatics from aromatic rich petroleum fractions to obtain
the products e.g. high octane aromatic extract for Motor Sprit pool, superior
kerosene, high cetane gas oil and speciality solvents for particular end use.
Yet another objective of the process is to achieve savings in capital cost by
eliminating raffinate-re-extraction solvent fractionator.
Still another objective is to reduce operating cost by saving in utilities by using
heat integration of hot and cold streams.
Yet another objective of the process is to produce superior quality special boiling
point solvents.
In the present invention therefore, the aromatics are separated from nonaromatics
from the feedstocks by extraction using polar organic solvent. The
solvent used here is N-Methyl pyrolidinone admixed with water, glycols,
sulpholane etc.
The flow diagram of the present invention is shown in Fig.1 of the drawing
accompanying this specification.
The petroleum fraction stream is introduced through line (1) and lean solvent is
introduced via line (2) into the extractor-A where the two streams meet
countercurrently. The extract phase, thus produced, is introduced via line (4) in
the extractor-B, which meets the Ce-C? petroleum fraction (63-69°C cut) countercurrently,
entering via line (5). The raffinate phase produced is fed to raffinate
wash column-E via line (3) where it is washed with water. The two contact zones
may comprise either a packed or a sieve plate column.
The top phase which leaves the extractor-B via line (6) is water washed in extract
wash column-C and then enters via line (8) in the distillation column-D where it is
fractionated to yield aromatic extract which is collected via line (11) and C6-C7
petroleum fraction, which is re-circulated to extractor-B via line (5). The bottom of
extractor-B enters to solvent recovery column-F via line (7). Hydrocarbons from
the top of solvent recovery column (SRC) are routed to column-D via line (15).
One part of water is recycled back to extract wash column-C via line (10).

Another part of water is recycled back to raffinate wash column-E routed through water stripper-G via line (14). Washed raffinate is taken from line (12). The lean solvent from the bottom of solvent recovery column-F is re-circulated back to extractor-A via line (2). Water containing the solvent is fed to solvent recovery column-F via lines (9) and (13) used as striping stream.
Accordingly the present invention provides a process for the extraction of aromatics
from aromatic rich petroleum streams which comprises:
a) Characterized in that contacting aromatic rich petroleum streams feed with a polar organic solvent containing 2-20 wt% anti solvent at a temperature in the range of 20 - 80°C in a extractor-A column to obtain a extract phase and a raffinate phase,
b) contacting the said extract phase obtained from step (a) with 1-6 vol% of secondary solvent consisting of C6-C7 paraffinic petroleum fraction in the extractor-B column at a temperature in the range of 20-60°C to recover the extract hydrocarbons,
c) distilling the bottom stream of extractor-B obtained in step (b) in column-F at reboiler temperature of 90-180°C to recover the extraction solvent for further recycling
d) washing the top stream of extractor-B obtained in step (b) with water in column-C at a temperature in the range of 20-60°C, followed by fractionating the resultant hydrocarbons at a temperature in the range of 100-400°C to obtain the extract hydrocarbons and secondary solvent and further recycling the secondary solvent to extractor-B,
e) washing the raffinate phase obtained from step (a) in column-E at a temperature
in the range of 20-60°C, by conventional method to obtain raffinate hydrocarbons.
In an embodiment of the present invention, aromatic rich petroleum stream used is petroleum fraction having boiling temperature in the range of 90-360°C.
In another embodiment of the present invention, the aromatics extracted from aromatic rich petroleum streams are benzene, toluene, xylene, alkyl benzene, naphthalenes, alkyl naphthalenes and depends on boiling range of feedstock.
In an embodiment of the present invention, wherein the resultant hydrocarbons is a mixture of C6-C7 paraffins, secondary solvent and aromatic hydrocarbons.

In another embodiment of the present invention the selective solvent used is
N-Methyl pyrolidinone admixed with 2.0 to 15wt % water or sulpholane or
glycol.
In yet another embodiment of the present invention ratio of solvent mixture to
feed is in the range of 1:1 to 5:1wt%.
In still another embodiment of the present invention feed and extraction
solvent is contacted countercurrently in a extractor-A at a temperature of 30 -
80°C.
In still another embodiment of the present invention recovery of aromatics
from extract phase is affected countercurrently in a extractor-B using
secondary solvent selected from C6-C7 petroleum fraction at a temperature
of 30 - 60°C.
In still another embodiment of the present invention the ratio of secondary
solvent to extract phase is in the range of 1 to 4 by volume.
In still another embodiment of the present invention recovery of solvent from
top phase of extractor-B and raffinate phase is done by known method such
as water washing at a temperature of 30-40°C.
In still another embodiment of the present invention recovery of secondary
solvent from top of the extractor-B is affected by using conventional method
such as distillation at atmospheric pressure at a temperature of 110 - 300 °C
In still another embodiment of the present invention recovery of residual
hydrocarbons in bottom phase of extractor-B is done by using conventional
method such as distillation at reboiler temperature of 100-160°C.
The following examples are given by way of illustration and therefore should not
be construed to limit the scope of the present invention.
Example-1
For the extraction step the model mixture of propyl benzene-decane with 6.0
wt.% propyl benzene, was admixed with an equal weight of NMP (Pure) at
40°C. Two liquid phases under equilibrium were formed. Each phase was
separated, made solvent-free and analysed. The extract phase contained 2.6
wt.% propyl benzene, while its concentration reduced to 4.1 wt.% in the raffinate
phase with 89.0 wt.% yield.
Example-2
For the extraction step the model mixture of propyl benzene-decane with 6.0
wt.% propyl benzene, was admixed with an equal weight of NMP +20%
sulpholane at 40°C. Two liquid phases under equilibrium were formed. Each
phase was separated, made solvent-free and analysed. The extract phase
contained 2.2 wt.% propyl benzene, while its concentration reduced to 4.8 wt.%
in the raffinate phase with 94.5 wt.% yield.
Example-3
3.3 kgs/hr of heavy naphtha fraction (100-200°C) from Assam crude, containing
30.2 wt.% aromatic is fed to packed extractor-A. It was counter-currently
contacted with the selective solvent (NMP+10% water) at 40°C entering the
column at a rate of 7.7 kgs/hr. The extract phase produced at a rate of about 8.6
kgs/hr.
4.1 kgs/hr of extract phase produced as above containing 0.54 kgs/hr of total
hydrocarbons is fed to packed extractor-B and counter currently contacted with
C6-C7 paraffinic petroleum fraction entering at a rate of 6.1 kgs/hr. Phase
produced at a rate of 7.0 kgs/hr from the top of extractor-B contains 0.49 kgs/hr
of NMP. The phase is water washed and fractionated yielding 0.55 kgs/hr of
naphtha extract containing 77.2 wt% of aromatics. The recovered C6-C7
paraffinic petroleum fraction is circulated back to extractor-B. The bottom of the
extractor-B contains 3.15 kgs/hr of lean solvent and 0.011 kgs/hr of naphtha
hydrocarbons.
2.3 kgs/hr of the raffinate phase produced from extractor-A contains about 0.133
kgs/hr of NMP was water washed in raffinate wash column -E, yielding 2.16
kgs/hr of dearomatized heavy naphtha with 7.8 wt.% aromatics.
Example-4
2.0 kgs/hr of gas oil fraction (240-400°C) from Assam crude, containing 39.2
wt.% aromatic is fed to packed extractor-A. It was counter-currently contacted
with the selective solvent (NMP+10% water) at 40°C entering the column at a
rate of 7.4 kgs/hr. The extract phase produced at a rate of about 8.2 kgs/hr.
4.7 kgs/hr of extract phase produced as above containing 0.377 kgs/hr of total
hydrocarbons is fed to packed extractor-B and counter currently contacted with
Ce-C/ paraffinic petroleum fraction entering at a rate of 6.8 kgs/hr. Phase
produced at a rate of 7.6 kgs/hr from the top of extractor-B contains 0.56 kgs/hr
of NMP. The phase is water washed and fractionated yielding 0.345 kgs/hr of
gas oil extract containing 86.9 wt% of aromatics. The recovered Ce-C7 paraffinic
petroleum fraction is circulated back to extractor-B. The bottom of the extractor-B
contains 4.07 kgs/hr of lean solvent and 0.02 kgs/hr of gas oil hydrocarbons.
1.38 kgs/hr of the raffinate phase produced from extractor-A contains about
0.059 kgs/hr of NMP was water washed in raffinate wash column -E, yielding
1.32 kgs/hr of dearomatized gas oil with 16.2 wt.% aromatics.
10
The main advantages of the present invention are as follows :
1. Use of environmentally friendly solvent such as NMP in an admixure with
anti solvents such as water, glycols, sulpholane etc.
2. Use of conventional metallurgy such as carbon steel
3. Highly simplified and flexible flowsheet
4. Lower capital cost
5. High capacity solvent like NMP inspite of its boiling point overlap with that
of the feed can be used since the hydrocarbons are recovered from the
extract phase by re-extraction route.
6. Flexibility in handing wide range of petroleum fractions (naphtha to gas
oil) in the same unit by using block out operation is possible
7. Elimination of energy intensive distillation step of aromatic recovery from
extract phase will lead to considerable savings in the utility.
8. Operation of re-extraction column at ambient temperature will result in
requirement of lower utilities and minimize solvent degradation. This will
also minimize the corrosion problem.
9. Production of good quality aromatic rich extract for various end uses e.g.
gasoline blending, insecticide formulation.
•10. Feasibility of producing superior quality speciality solvents by
incorporation of water stripper
11. Availability of additional extraction column operating parameters (e.g.
anti solvent composition and extraction temperature) due to
incorporation of solvent recovery column




We Claim:
1. A process for the extraction of aromatics from aromatic rich petroleum streams
which comprises:
a) Characterized in that contacting aromatic rich petroleum streams with a polar organic solvent containing 2-20 wt% anti solvent at a temperature in the range of 20 - 80°C in a extractor-A column to obtain a extract phase and a raffmate phase,
b) contacting the said extract phase obtained from step (a) with 1-6 vol% of secondary solvent consisting of C6-C7 paraffinic petroleum fraction in the extractor-B column at a temperature in the range of 20-60°C to recover the extract hydrocarbons,
c) distilling the bottom stream of extractor-B obtained in step (b) in column-F at reboiler temperature of 90-180°C to recover the extraction solvent for further recycling
d) washing the top stream of extractor-B obtained in step (b) with water in column-C at a temperature in the range of 20-60°C, followed by fractionating the resultant hydrocarbons at a temperature in the range of 100-400 C to obtain the extract hydrocarbons and secondary solvent and further recycling the secondary solvent to extractor-B,
e) washing the raffmate phase obtained from step (a) in column-E at a temperature in the range of 20-60°C, by conventional method to obtain raffmate hydrocarbons.

2. A process as claimed in claim 1, wherein aromatic rich petroleum stream used is petroleum fraction selected from heavy naphtha, kerosene, and gas oil having boiling temperature in the range of 90-360°C.
3. A process as claimed in claim 1, wherein the aromatics extracted from aromatic rich petroleum streams are benzene, toluene, xylene, alkyl benzene, naphthalenes, alkyl naphthalenes and depends on boiling range of feedstock.
4. A process as claimed in claim 1 ,wherein the resultant hydrocarbons is a mixture of C6-C7 paraffins, secondary solvent and aromatic hydrocarbons.
5. A process as claimed in claim 1, wherein the polar organic solvent used is N-Methyl pyrolidinone admixed with 2.0 to 15wt% water or sulpholane or glycol.

6. A process as claimed in claim 1, wherein ratio of solvent mixture to aromatic rich petroleum stream is in the range of 1:1 to 5:1 wt%.
7. A process as claimed in claim 1, wherein aromatic rich petroleum stream and extraction solvent is contacted counter currently in a extractor-A at a temperature of 30-80°C,
8. A process as claimed in claim 1, wherein recovery of aromatics from extract phase is affected counter currently in an extractor-B using secondary solvent selected from C6-C7 petroleum fraction at a temperature of 30-60°C.
9. A process as claimed in claim 1, wherein the ratio of secondary solvent to extract phase is in the range of 1 to 4 by volume.

Documents:

372-DEL-2002-Abstract-(10-10-2008).pdf

372-DEL-2002-Abstract-(20-11-2008).pdf

372-del-2002-abstract.pdf

372-DEL-2002-Claims-(10-10-2008).pdf

372-DEL-2002-Claims-(20-11-2008).pdf

372-del-2002-claims.pdf

372-del-2002-correspondence others.pdf

372-del-2002-correspondence po.pdf

372-DEL-2002-Correspondence-Others-(10-10-2008).pdf

372-DEL-2002-Correspondence-Others-(20-11-2008).pdf

372-DEL-2002-Description (Complete)-(10-10-2008).pdf

372-del-2002-description (complete).pdf

372-del-2002-drawing.pdf

372-DEL-2002-Form-1-(20-11-2008).pdf

372-del-2002-form-1.pdf

372-del-2002-form-18.pdf

372-DEL-2002-Form-2-(20-11-2008).pdf

372-del-2002-form-2.pdf

372-DEL-2002-Form-3-(10-10-2008).pdf

372-del-2002-form-3.pdf

372-DEL-2002-Petition-137-(10-10-2008).pdf


Patent Number 231486
Indian Patent Application Number 372/DEL/2002
PG Journal Number 13/2009
Publication Date 27-Mar-2009
Grant Date 05-Mar-2009
Date of Filing 28-Mar-2002
Name of Patentee COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH
Applicant Address RAFI MARG, NEW DELHI-110 001, INDIA.
Inventors:
# Inventor's Name Inventor's Address
1 BHAGAT RAM NAUTIYAL INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248 005, INDIA.
2 DHARAM PAUL INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248 005, INDIA.
3 MADHUKAR ONKARNATH GARG INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248 005, INDIA.
4 ALOK K SAXENA INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248 005, INDIA.
5 PRADEEP KUMAR INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248 005, INDIA.
6 MOHAN KRISHAN KHANNA INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248 005, INDIA.
7 SHRIKANT MADHUSUDAN NANOTI INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248 005, INDIA.
8 BACHAN SINGH RAWAT INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248 005, INDIA.
9 GURU PRASAD INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248 005, INDIA.
PCT International Classification Number C10G 21/14
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA