U.S. patent application number 15/882350 was filed with the patent office on 2018-09-06 for process for the desulfurization of petroleum oil.
The applicant listed for this patent is ADITYA BIRLA SCIENCE & TECHNOLOGY CO. LTD., SKI CARBON BLACK (INDIA) PRIVATE LIMITED. Invention is credited to Sandeep Vasant Chavan, Ranjan Ghosal, Bir Kapoor, Harshad Ravindra Kini.
Application Number | 20180251687 15/882350 |
Document ID | / |
Family ID | 46879832 |
Filed Date | 2018-09-06 |
United States Patent
Application |
20180251687 |
Kind Code |
A1 |
Chavan; Sandeep Vasant ; et
al. |
September 6, 2018 |
PROCESS FOR THE DESULFURIZATION OF PETROLEUM OIL
Abstract
A process for desulphurization of petroleum oil, comprising the
step of diluting the feed oil with a suitable organic solvent prior
to the desulphurization reaction, is disclosed. The organic solvent
is selected from alkanes, alkenes, cyclic alkenes and alkynes, and
particularly selected from n-hexane, cyclohexane, heptane, pentene,
hexene, heptene, octene, toluene and xylene. The solvent
concentration in the mixture of feed oil and solvent is in the
range of 0.1-70%.
Inventors: |
Chavan; Sandeep Vasant;
(Mumbai, IN) ; Kini; Harshad Ravindra; (Mumbai,
IN) ; Kapoor; Bir; (Mumbai, IN) ; Ghosal;
Ranjan; (Navi Mumbai, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SKI CARBON BLACK (INDIA) PRIVATE LIMITED
ADITYA BIRLA SCIENCE & TECHNOLOGY CO. LTD. |
Mumbai
Mumbai |
|
IN
IN |
|
|
Family ID: |
46879832 |
Appl. No.: |
15/882350 |
Filed: |
January 29, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14006803 |
Sep 23, 2013 |
|
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PCT/IN12/00188 |
Mar 20, 2012 |
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15882350 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10G 31/09 20130101;
C10G 29/00 20130101; C10G 29/04 20130101; C10G 2300/202 20130101;
C10G 21/14 20130101; C10G 45/02 20130101; C10G 2300/44
20130101 |
International
Class: |
C10G 21/14 20060101
C10G021/14; C10G 45/02 20060101 C10G045/02; C10G 29/04 20060101
C10G029/04; C10G 29/00 20060101 C10G029/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 23, 2011 |
IN |
845/MUM/2011 |
Claims
1. A process for desulphurization of petroleum oils, said process
comprising the following steps: diluting petroleum oil with a
hydrocarbon organic solvent selected from the group consisting of
alkanes, alkenes, cyclic alkenes and alkynes, to obtain an
oil-solvent mixture, wherein the organic solvent concentration in
the oil-solvent mixture is in the range of 0.1-70%; transferring
the oil-solvent mixture to a reactor vessel; adding solid sodium
metal to the oil-solvent mixture in the reactor vessel, wherein the
sodium concentration is between 0.1-20% of the petroleum oil
concentration; reacting the oil-solvent mixture with sodium at a
temperature in the range of 240-350.degree. C. and a pressure in
the range of 0-500 psig for 15 minutes-4 hours under mixing to
obtain a resultant mixture; cooling and settling the resultant
mixture; and decanting the cooled mixture and filtering the
decanted solution of desulfurized petroleum oil.
2. The process as claimed in claim 1, wherein the hydrocarbon
organic solvent is selected from the group consisting of n-hexane,
cyclohexane, heptane, pentene, hexene, heptene, octene, toluene and
xylene.
3. The process as claimed in claim 1, which includes the step of
purging the reactor vessel with hydrogen gas at a pressure in the
range of 0-500 psig.
4. The process as claimed in claim 1, which includes the step of
separating the organic solvent from desulfurized petroleum oil by
distillation.
5. The process as claimed in claim 1, which includes the step of
mixing sodium with the oil-solvent mixture in the reactor vessel by
using high shear mixing by means of a mixer selected from an inline
mixer, a mechanical mixer, a pump around loop and an ultrasonic
mixer.
6. The process as claimed in claim 1, which includes the step of
removing residual sodium metal by: treating the desulfurized
petroleum oil with 0.1-10% carboxylic acid in an organic solvent at
a temperature in the range of 50-150.degree. C. for 30 minutes to
90 minutes under vigorous stirring; and filtering the resultant
mixture to obtain desulfurized petroleum oil having sodium content
between 10-50 ppm.
7. The process as claimed in claim 6, wherein the carboxylic acid
is selected from acetic acid, formic acid and propionic acid.
8. The process as claimed in claim 6, wherein the organic solvent
is selected from alkanes, alkenes, cyclic alkenes, alkynes and
alcohol.
9. The process as claimed in claim 6, wherein the organic solvent
is xylene.
10. The process as claimed in claim 1, which includes the step of
removing residual sodium metal by purging the desulfurized
petroleum oil with air at a temperature in the range of
30-150.degree. C.
Description
FIELD OF DISCLOSURE
[0001] The present disclosure relates to desulphurization
processes.
[0002] Particularly, the disclosure relates to a process for
desulphurization of petroleum heavy oils and residual petroleum
oils, more particularly carbon black feed oil.
BACKGROUND
[0003] Petroleum oils are complex mixtures of primarily
hydrocarbons and other carbon containing compounds. The overall
composition of the petroleum oil or crude oil is known to vary
significantly from its origin or geographical location of the
refinery. The elemental composition of these oils consists of about
carbon (84-87%), hydrogen (12-14%) along with oxygen, nitrogen,
sulfur, moisture and ash. The sulfur content may vary substantially
from 0.2-8%. In addition to these main components, there are traces
of metal impurities, that may be present initially or get
associated with the oil during various refinery processing steps.
The crude oils may also contain hydrocarbons, paraffins,
asphaltenes, resins and ash. The crude oil compositions can be
differentiated into various individual fractions at different
boiling ranges. The low boiling fractions (<170.degree. C.) are
typically napthas, those between 180-250.degree. C. are kerosene
and the ones boiling in the range of 250-350.degree. C. are termed
as gas oils. The fractions boiling above 350.degree. C. are
generally termed as residues and are obtained after all or most of
the distillable products have been removed from the petroleum oil.
These residue fractions could be further distinguished as light
vacuum gas oils, heavy vacuum gas oils and vacuum residues. Each of
these different fractions has different molecular distribution of
various hydrocarbon species and related compounds. In particular,
one of the significant aspects is the distribution of sulfur
containing species in these fractions. The use of the petroleum oil
residues includes heating (as a fuel), and as a feedstock for the
manufacture of carbon black. The presence of sulfur in the
petroleum oil residue has a number of shortcomings. During the
complete or partial combustion of the petroleum residue, sulfur
gets converted to SO.sub.2 and SO.sub.3. These cause major
environmental issues in the form of acid rains and adversely affect
health. Further, the sulfur species cause poisoning of catalyst
systems used in the refineries. These are also known to be the
primary cause of corrosion of equipments and exhaust. The presence
of sulfur in the residue fraction has further ramifications in case
of use of this as raw material for carbon black manufacturing.
Apart from significant air pollution, these species remain
associated with the final carbon black product which is detrimental
to various applications. Furthermore, high sulfur content affects
the throughput of the manufacturing process.
[0004] Carbon black feed oil (CBFO) is a raw material used for
manufacturing carbon black, an important material used in the tyre
industry. Carbon black feedstock is a mixture of C.sub.12 and
higher components rich in naphthalene, methylindenes, anthracene,
fluorene and other poly-aromatic components. CBFO is essentially
procured either from oil refineries or from coal tar distillers.
There are two types of CBFO viz. High BMCI type and General type.
"BMCI" (Bureau of Mines Co-relation Index) effectively measures the
degree yield of carbon black. Higher the BMCI, better the yield of
carbon black. High BMCI CBFO is used as a raw material by carbon
black manufacturers while the other grade is used by various
consumers to manufacture rubber process oils, incense sticks
etc.
[0005] Sulfur content in CBFO reduces the effective BMCI value.
Moreover, this sulfur gets carried to the final carbon black
product as an impurity. Hence, it is of interest to reduce the
sulfur content of the CBFO. Hence, it would be of interest to
discover a method for reducing the sulfur content of the petroleum
oil residue to be used as CBFO.
[0006] A desulphurization process is usually carried out to remove
sulfur (S) from natural gas and petroleum products such as gasoline
or petrol, jet fuel, kerosene, diesel fuel and fuel oils. The
refinery feedstock (naphtha, kerosene, diesel oil and heavier oils)
contains a wide range of organic sulfur compounds, including
thiols, thiophenes, organic sulfides, disulfides and many others.
These organic sulfur compounds are the products of degradation of
sulfur containing biological components, present during the natural
formation of the fossil fuel, petroleum crude oil. The purpose of
removing sulfur is to reduce sulfur dioxide (SO.sub.2) emissions
that result from using these fuels in automotive vehicles,
aircrafts, railroad locomotives, ships, gas or oil burning power
plants, residential and industrial furnaces, and other forms of
equipment using fuel for combustion.
[0007] A number of techniques including catalytic transformation
processes such as hydrodesulfurization and physico-chemical
processes such as solvent extraction, alkylation, oxidation,
precipitation, adsorption, and the like, have been worked in order
to reduce the sulfur content from various fractions of the
petroleum oils. The hydro-desulfurization is commonly used for this
purpose. This process is based on catalytic hydrogenation of the
sulfur species to convert it into H.sub.2S. However, the
hydro-desulfurization is known to work efficiently on lower boiling
fractions such as gasoline, naptha, kerosene, and the like. The
catalyst systems generally include transition metals such as Ni,
Co, Mo supported on Al.sub.2O.sub.3. Several efforts have been made
in the past to provide a hydro-desulfurization technique. Some
typical prior art examples are disclosed in U.S. Pat. No.
2,516,877, U.S. Pat. No. 2,604,436, U.S. Pat. No. 2,697,682, U.S.
Pat. No. 2,866,751, U.S. Pat. No. 2,866,752, U.S. Pat. No.
2,911,359, U.S. Pat. No. 2,992,182, U.S. Pat. No. 3,620,968, U.S.
Pat. No. 3,668,116, U.S. Pat. No. 4,193,864, U.S. Pat. No.
4,328,127, U.S. Pat. No. 4,960,506 and U.S. Pat. No. 5,677,259.
Most of these processes are highly suitable for treating lower
boiling fractions or crude oils. However, their efficiency drops
when treating high boiling fractions or vacuum residues. This is
due to the fact that lower boiling oil fractions primarily contain
sulfur in the form of mercaptans or lower membered ring compounds,
which are relatively easier to desulfurize. However, the high
boiling fractions or resids contain sulfur species that are part of
the more stable ring compounds such as substituted benzothiophenes
and higher derivatives or large molecule ring compounds which are
extremely difficult to desulfurize. Some prior art examples for
treating residues by hydro-desulfurization include U.S. Pat. No.
2,640,011, U.S. Pat. No. 2,992,182, U.S. Pat. No. 4,328,127 and
U.S. Pat. No. 4,576,710. In most of the cases, the treatment
parameters are extreme i.e. use of high temperatures in excess of
400.degree. C. and pressures in excess of 1000 psig. Moreover, the
desulfurization efficiencies are low. Further, due to these
difficult processing conditions hydro-desulfurization results in
coke formation, leading to deactivation of the catalyst systems. In
addition, the hydro-desulfurization process results in the
formation of H.sub.2S, which again cannot be disposed, off due its
environmental concerns. This H.sub.2S needs to be further treated
by the Claus process at high temperature of about 800.degree. C. in
presence Al.sub.2O.sub.3 catalyst to convert to elemental
sulfur.
[0008] In addition to hydro-desulfurization, there are several
other techniques that are being explored for the desulfurization of
the petroleum oils. These include oxidative, adsorptive, solvent
extraction and bio-enzymatic processes. Some typical prior art
examples of oxidative desulfurization process are disclosed in U.S.
Pat. No. 3,816,301, U.S. Pat. No. 3,163,593, U.S. Pat. No.
3,413,307, U.S. Pat. No. 3,505,210, U.S. Pat. No. 3,816,301, U.S.
Pat. No. 3,847,800, U.S. Pat. No. 6,274,785, U.S. Pat. No.
6,277,271, U.S. Pat. No. 7,144,499, U.S. Pat. No. 7,179,368, U.S.
Pat. No. 7,276,152, U.S. Pat. No. 7,314,545, US20050189261,
US200600226049, US20080308463 and US20090148374. The common
oxidizing agents used are H.sub.2O.sub.2 or H.sub.2O.sub.2 in
combination with acetic acid and in the presence of an oxidizing
catalyst system. In addition, tert-butyl hydroperoxide can also be
used as an oxidant as it tends to be soluble in oil. The adsorptive
processes generally use absorbents such as clay, Al.sub.2O.sub.3,
bauxite, transition metal oxides systems supported on silica or
alumina, zeolites, activated carbon, etc. Some typical examples of
these processes are disclosed in U.S. Pat. No. 2,436,550, U.S. Pat.
No. 2,537,756, U.S. Pat. No. 2,988,499, U.S. Pat. No. 3,620,969,
U.S. Pat. No. 4,419,224, U.S. Pat. No. 4,695,366, U.S. Pat. No.
5,219,542, U.S. Pat. No. 5,310,717, U.S. Pat. No. 6,558,533, U.S.
Pat. No. 6,500,219, U.S. Pat. No. 7,291,259, US20030029777,
US20030188993, US20060283780 and US20090000990. The solvent
extraction processes use various solvent systems such as dimethyl
formamide, dimethyl sulfoxide, phenols, dichloroethers,
nitrobenzene, and the like. Some typical prior art processes are
disclosed in U.S. Pat. No. 2,486,519, U.S. Pat. No. 2,623,004, U.S.
Pat. No. 2,634,230 and U.S. Pat. No. 3,779,895. However, most of
the above mentioned processes are aimed at desulfurization of crude
oils or low boiling fractions. Similarly, most of the above
mentioned processes (except bio-enzymatic) are aimed at targeting
and removing the entire sulfur containing molecule rather than
removal of the sulfur atom specifically. This may not have a
significant effect while considering desulfurization of crude oil
or lower boiling fractions as the net sulfur content is less and
also the sulfur would be distributed over small number of low
molecule weight compounds. However, in case of resids where the
sulfur content can be as high as 4-5%, the sulfur appears to be
essentially distributed over a majority of the molecules contained
in the oil. Thus, removing the entire sulfur containing molecule
would result in substantial material loss of the oil part.
[0009] Another such desulfurization process is based on the use of
alkali metal, especially sodium metal as the desulfurizing agent.
In this process, the sulfur is primarily removed as a metal sulfide
instead of the removal of the entire sulfur containing molecule.
Some typical prior art examples of this process are U.S. Pat. No.
1,938,672, U.S. Pat. No. 1,952,616, U.S. Pat. No. 2,902,441, U.S.
Pat. No. 3,004,912, U.S. Pat. No. 3,093,575, U.S. Pat. No.
3,617,530, U.S. Pat. No. 3,755,149, U.S. Pat. No. 3,787,315, U.S.
Pat. No. 4,003,824, U.S. Pat. No. 4,120,779, U.S. Pat. No.
4,123,350, U.S. Pat. No. 4,147,612, U.S. Pat. No. 4,248,695, U.S.
Pat. No. 4,437,980, U.S. Pat. No. 6,210,564, U.S. Pat. No.
7,192,516, U.S. Pat. No. 7,507,327, U.S. Pat. No. 7,588,680. These
documents thus describe the desulfurization of crude oils and
resids by sodium metal. The sodium metal can be used as pure metal
or in an alloy, supported on inert species, or as dissolved in
solvent such as ammonia. Also, these processes use hydrogen at high
pressures in combination to the sodium metal for desulfurization.
In some processes, sodium-based compounds such as NaHS, NaNH.sub.2,
and the like, are used for the desulfurization. A major product
formed as a reaction of the sodium metal with the sulfur in the
feed oil is sodium sulfide (Na.sub.2S). Some of the above-mentioned
prior art documents also describe the regeneration of sodium from
Na.sub.2S. These processes report the effectiveness of
desulfurization of recalcitrant sulfur especially from that of high
boiling resid oils. However, these sodium-based desulfurization
processes are associated with limitations such as low yield of
desulphurized feed oil, formation of large amount of insoluble
sludge, requirement of hydrogen and safety concerns. The inherent
high viscosity of heavy oils and petroleum residues makes it
difficult for the processing and separation operations before and
after the desulphurization process. A large amount of valuable
residual feed oil remains associated with the precipitated sodium
sulfide residue or the unreacted sodium in the form of a highly
viscous sludge. Also, the sludge is extremely difficult to filter
and separate due to its inherent viscosity and sticky nature. Thus,
there is a substantial loss of feed during the process, especially
during filtration or separation. Furthermore, due to lower density
of sodium metal as compared to that of the residual oil, the sodium
metal may tend to float at the surface of the oil and may lead to a
hazardous situation during failed reactions or during incomplete
mixing.
[0010] Thus, the known desulphurization processes are associated
with a number of limitations such as low yield of desulphurized
feed oil, formation of large amount of insoluble sludge,
requirement of hydrogen and safety issues. The inherent high
viscosity of heavy oils and petroleum residues makes it difficult
for the processing and separation operations before and after the
desulphurization process. A large amount of valuable residual feed
oil remains associated to the precipitated sulfur residue or
unreacted sodium in the form of a highly viscous sludge. Also, the
sludge is extremely difficult to filter and separate due to its
inherent viscosity and sticky nature. There is a substantial loss
of feed during the process, especially during filtration or
separation. Further, it was observed that the sodium-based
desulfurization processes result in retention of sodium metal in
the oil. The presence of sodium metal, even at concentration as low
as <100 ppm, results in change in the morphology of the carbon
black during the manufacturing processes. Therefore, there is felt
a need to develop a process to minimize the loss of feed during
desulphurization of petroleum oils. The present invention is an
improved process for petroleum oil desulphurization, especially
carbon black feed oil (CBFO) desulfurization, which reduces the
sulfur content in the oil.
OBJECTS
[0011] An object of the present disclosure is to provide a process
for desulphurization of carbon black feed oil which provides
improved yield and high quality of desulphurized oil.
[0012] Another object of the present disclosure is to provide a
process for desulphurization of carbon black feed oil with improved
processing and handling operations.
[0013] Yet another object of the present disclosure is to provide a
process for desulphurization of carbon black feed oil without the
use of hydrogen.
[0014] Another object of the present disclosure is to provide a
process for further treatment of the desulfurized oil for removal
of the residual sodium content.
SUMMARY
[0015] In accordance with the present disclosure, there is provided
a process for desulphurization of petroleum oils, said process
comprising the following steps: [0016] diluting petroleum oil with
a hydrocarbon organic solvent selected from the group consisting of
alkanes, alkenes, cyclic alkenes and alkynes, to obtain an
oil-solvent mixture, wherein the organic solvent concentration in
the oil-solvent mixture is in the range of 0.1-70%; [0017]
transferring the oil-solvent mixture to a reactor vessel; [0018]
adding solid sodium metal to the oil-solvent mixture in the reactor
vessel, wherein the sodium concentration is between 0.1-20% of the
petroleum oil concentration; [0019] reacting the oil-solvent
mixture with sodium at a temperature in the range of
240-350.degree. C. and a pressure in the range of 0-500 psig for 15
minutes-4 hours under mixing to obtain a resultant mixture; [0020]
cooling and settling the resultant mixture; and [0021] decanting
the cooled mixture and filtering the decanted solution of
desulfurized petroleum oil.
[0022] Typically, in accordance with the present disclosure, the
hydrocarbon organic solvent is selected from a group consisting of
n-hexane, cyclohexane, heptane, pentene, hexene, heptene, octene,
toluene and xylene.
[0023] Preferably, in accordance with the present disclosure, the
process includes the step of purging the reactor vessel with
hydrogen gas at a pressure in the range of 0-500 psig.
[0024] Typically, in accordance with the present disclosure, the
process includes the step of separating the organic solvent from
desulfurized petroleum oil by distillation.
[0025] Preferably, in accordance with the present disclosure, the
process includes the step of mixing sodium with the oil-solvent
mixture in the reactor vessel by using high shear mixing by means
of a mixer selected from an inline mixer, a mechanical mixer, a
pump around loop and an ultrasonic mixer.
[0026] In accordance with the present disclosure, there is provided
a process for removing residual sodium metal, said process
including the steps of: treating the desulfurized petroleum oil
with 0.1-10% carboxylic acid in an organic solvent at a temperature
in the range of 50-150.degree. C. for 30 minutes to 90 minutes
under vigorous stirring; and filtering the resultant mixture to
obtain desulfurized petroleum oil having sodium content between
10-50 ppm.
[0027] Typically, in accordance with the present disclosure, the
carboxylic acid is selected from acetic acid, formic acid and
propionic acid.
[0028] Preferably, in accordance with the present disclosure, the
organic solvent is selected from alkanes, alkenes, cyclic alkenes,
alkynes and alcohol. More preferably, the organic solvent is
xylene.
[0029] In accordance with the present disclosure, there is provided
a process for removing residual sodium metal by purging the
desulfurized petroleum oil with air at a temperature in the range
of 30-150.degree. C.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0030] The present disclosure relates to a process for
desulphurization of carbon black feed oil (CBFO). The feed oil
(CBFO) has high viscosity at ambient conditions. The process
comprises diluting the feed oil with a suitable organic solvent,
prior to the desulphurization reaction. The organic solvent can be
selected from the group of hydrocarbon solvents consisting of
alkanes, alkenes, cyclic alkenes and alkynes. Similarly, other oils
such as petrol, kerosene, crude oil, and the like, can also be used
for diluting the feed oil. The organic solvent is particularly
selected from the group consisting of n-hexane, cyclohexane,
heptane, pentene, hexene, heptene, octene, toluene and xylene,
preferably the solvent is xylene. The solvent concentration used is
in the range of 0.1-70%, preferably in the range of 0.1-50%, more
preferably in the range of 1-30%, in the mixture of CBFO and
solvent.
[0031] The feed to the process of the present disclosure is carbon
black feed oil having a sulfur content in the range of 0.1%-20%.
The process of the present disclosure can also be used for
petroleum oils of various boiling fractions. Further, the process
of the present disclosure can be used to desulphurize coal tar,
shale oil or other organic sulfur bearing compounds. The organic
solvent is removed after the desulphurization process. The present
process results in a desulphurized stream (after xylene removal)
with a substantial viscosity reduction. The formation of insoluble
sludge (unusable material) due to polymerization reactions of the
desulphurized species is reduced due to improvement in the feed oil
viscosity. Further, the improvement in the feed oil viscosity
enhances the processing of the feed oils required in applications
such as manufacturing of carbon black product.
[0032] The process results in improvement of feed oil quality by
means of reducing the asphaltene content in the feed oil.
Asphaltenes are considered as the n-heptane insoluble, toulene
soluble components of a carbonaceous material such as crude oil,
bitumen or coal. Asphaltenes are high molecular weight hetero-atom
species that are generally considered detrimental to the quality of
the processed carbon black product.
[0033] The process of the present disclosure is carried out in the
absence of hydrogen at a pressure in the range of 0-500 psig, this
results in an higher C:H ratio of the processed oil as compared to
processes carried in the presence of high pressure hydrogen. This
is beneficial for converting most of the processed oil into carbon
black, as the hydrogen leaves the process in the form of water
vapor without contributing to the formation of product. The process
removes moisture present in the CBFO. The CBFO generally contains
about <1% moisture. Na metal is known to have strong affinity to
water and thereby react with moisture. The present process uses
sodium metal in a concentration between 0.1-20% of the CBFO oil
concentration. Thus, moisture present in the CBFO is completely
removed.
[0034] In one aspect of the present disclosure, the process is
carried out in the presence of hydrogen. The hydrogen added could
be in the range of 0-500 psig, preferably in the range of 0-300
psig, and more preferably in the range of 0-100 psig. In addition,
the hydrogen may not be present in the form of closed system i.e.
under no hydrogen pressure or a pressureless system. Thus, it could
be added in a continuous or a semi continuous flow of hydrogen
gas.
[0035] The process of desulphurization of the present disclosure
gives crystalline sodium sulfide as the by-product. The by-product
so formed is easier to separate and filter and thus results in a
better recovery of the desulfurized oil as well as better
separation and processing efficiency of the desulfurized oil.
[0036] An important aspect of the present disclosure is that it
provides a process for reducing the size of dispersed sodium--as
solid particles or molten form as droplets. Finer dispersion of
sodium metal increases the efficiency of the desulphurization
process. In the conventional process, the by-product, sodium
sulfide tends to cover the surface of sodium metal thereby reducing
the efficiency of the process. Therefore, mixing, preferably high
shear mixing, for a duration in the range of 15 minutes--4 hours at
a temperature in the range of 240-350.degree. C. is provided; high
shear mixing causes the breaking of sodium sulfide and thereby
provides new sodium surfaces for enhancing the reaction. Any form
of mixing may be used, such as an inline mixer, a pump around loop,
a mechanical mixer, or an ultrasonic mixer, that provides the
required amount of dispersion to the sodium metal.
[0037] In the absence of hydrogen, there is formation of insoluble
sludge (unusable material) due to the polymerization reactions
amongst the desulfurized species.
[0038] Furthermore, the pure CBFO has a high viscosity of above
1500 cP at ambient conditions. The process of the present
disclosure results in a desulfurized stream (after xylene/solvent
removal) having a substantial viscosity reduction to the range of
100-150 cP at ambient conditions. Thus, the overall effect is that
the desulphurization process is carried out in the absence of
hydrogen and results in lower loss of feed oil caused by insoluble
sludge formation as well as improvement in the feed oil viscosity
which is further expected to enhance the characteristics of the
processed carbon black product. Further, if the process is carried
out in the presence of hydrogen, there may be a reduction in the
aromatic content of the feed due to hydrogenation (reduced C:H
ratio), resulting in lower yield of the carbon black product. Thus,
if the process is carried out in the absence of hydrogen the C:H
ratio of the treated feed would increase thereby increasing the
carbon black product yield. It may be noted that the process of the
present disclosure can also be extended by means of carrying the
desulphurization with Na and organic solvent, along with hydrogen.
These results with simultaneous presence of organic solvent and
hydrogen before desulphurization also show benefits in terms of
product quality and yield, wherein the desulfurized feed oil yield
is greater by 15-20% as against the known processes. The scope of
our process could thus be further extended as an improved
desulphurization process involving simultaneous use of organic
solvent and hydrogen, however, in an optimized combination (or
absence) of each of the reactants.
[0039] Another aspect of the process of the present disclosure is
the by-product formation and processing after the desulphurization
reaction. The desulphurization of feed oil using Na metal, results
in the formation of Na.sub.2S as the by-product. However, a large
amount of valuable residual CBFO is lost as it remains associated
to this Na.sub.2S residue or unreacted sodium in the form of a
highly viscous sludge. The presence of organic solvent in the feed
oil prior to the desulphurization reaction, results in the
formation of a crystalline and pure by-product. This product is
easier to separate and filter as there is substantially less CBFO
loss. This results in a better recovery of the desulphurized oil as
well as a better separation and processing efficiency post the
desulphurization reaction.
[0040] The present disclosure uses high shear mixing apparatus
aimed at reducing the size of dispersed sodium--as solid particles
or molten form as droplets. This gives finer dispersion of sodium
metal in the feed oil which increases the desulphurization
efficiency of the process. Secondly, during the desulphurization
process, the by-product formed tends to cover the surface of sodium
metal thereby reducing the efficiency. The high shear mixing helps
in breaking these surfaces and bringing new sodium surfaces for
enhancing the reaction. Any form of mixing may be used, such as an
inline mixer, a pump around loop, a mechanical mixer, or an
ultrasonic mixer, that provides the required amount of dispersion
to the sodium metal.
[0041] The carbon black feed oil is highly viscous with a viscosity
of above 1500 cP at ambient conditions. Addition of organic solvent
prior to desulphurization reduces its viscosity to a substantial
extent (less than 50 cP at ambient conditions, depending upon the
amount of solvent added), making it simpler to transfer and handle
as well as facilitate better mixing and contact with other
reactants. Apart from viscosity, the density of CBFO is also high,
typically between 1.01-1.08 g/cm.sup.3. The density of sodium solid
at 30.degree. C. is about 0.96 g/cm.sup.3 and that of molten sodium
is about 0.927 g/cm.sup.3. Thus, there is a tendency for the sodium
to remain floating at the top of CBFO surface. Thus, in order to
carry the reaction, it is to be ensured that the sodium remains
well immersed in the liquid, primarily by means of a continuous
stirring mechanism. This may lead to severe safety concerns in case
stirring fails or whenever the reaction fails. The result will be
that all of the sodium (due to low density) will rise to the top of
the feed and may come in contact with atmospheric moisture.
Addition of appropriate amount of organic solvent (say xylene
having a density of about 0.86 g/cm.sup.3), lowers the density of
CBFO to less than that of sodium and ensures that all of the sodium
remains well immersed in the liquid feed at all times.
[0042] A process for removal of residual sodium metal from the
desulphurized oil is also disclosed. During the desulphurization
process the sodium metal gets finely dispersed in the oil. After
the desulphurization process completes, some sodium metal
invariably remains in the system either as a suspension or bound to
the molecular chain in the oil. The separation or removal of this
sodium from the oil system is considerably difficult by means of
pure mechanical processes. The presence of this residual sodium
even in trace quantities has serious implications on the overall
quality of product for the carbon black Industry. The process of
the present disclosure uses acetic acid in the organic solvent
mixture. The role of acetic acid is that of scavenging the sodium
metal and the organic solvent promotes a better mixing between the
feedstock oil and acetic acid. Alternatively, apart from acetic
acid, various carboxylic acids such as formic acid, propanoic acid,
and mixtures thereof, can be used. In addition, ethanol and such
alcohols can also be used for scavenging the sodium. Still further,
the residual sodium removal was also achieved by purging the oil
with air at elevated temperatures between 30-150.degree. C. Such
treatment is not limited to air alone and would cover other gaseous
agents such as oxygen, ozone, etc.
[0043] The disclosure will now be described with reference to the
following examples which do not limit the scope and ambit of the
disclosure. The description provided is purely by way of
illustration.
EXAMPLE 1
[0044] The experiments were carried on CBFO and xylene mixtures of
varying proportion, to evaluate the effect of xylene amount on the
CBFO yield. All the following three examples (listed in TABLE 1)
were carried in the presence of hydrogen atmosphere. In example 1,
150 g of CBFO was mixed with 150 ml of xylene. This resulted in the
mixture as CBFS:Xylene=50:50 (weight volume basis). The solution
was mixed thoroughly and then transferred to a high pressure
reactor. 9 gm of sodium metal was weighed separately. The sodium
metal was then cut into small pieces of 0.5-1.0 cm and added to the
CBFS/xylene solution in the reactor. The reactor vessel was first
purged with nitrogen to remove air, and then the vessel was purged
with hydrogen gas. The reactor was then pressurized up to 300 psi
with hydrogen. The reactor was subsequently heated to a temperature
of 290.degree. C. The reaction was carried out at this temperature
for a period of 4 h. The entire solution was allowed to cool down
to room temperature and then the CBFO was decanted. The decanted
solution was filtered out and analyzed for sulfur content by XRF
(X-ray Fluorescence Spectroscopy). Similarly, the desulfurization
process was carried for other varying CBFO:Xylene ratios viz.
70:30, 80:20 (as shown in examples 2 and 3 in TABLE 1). The results
with respect to these different compositions are tabulated in TABLE
1. The CBFO, xylene and sodium content used is also tabulated
below, along with the desulfurization efficiency for each of the
different CBFS:Xylene ratios.
TABLE-US-00001 TABLE 1 Amount Amount of of Amount Pressure CBFO
Xylene CBFS:Xylene of Na Temp. Desul. Initial Ex. (g) (ml) ratio
(g:ml) (g) (.degree. C.) Time (h) (%) (psig) 1. 150 150 50:50 9.0
290 4 86 300 2. 210 90 70:30 13.5 290 4 70 300 3. 240 60 80:20 15.5
290 4 75 300
It was observed that more than 70% desulfurization was obtained in
all the cases.
Viscosity
[0045] The sample from example 2, after desulphurization and xylene
distillation was analyzed for viscosity as a function of
temperature. The sample was initially heated to about 175.degree.
C. and the viscosity measurements were noted at different
temperatures as the sample was cooled. Similarly measurements were
noted for a second sample of untreated or raw CBFO. The results are
tabulated in TABLE 2.
TABLE-US-00002 TABLE 2 CBFO- Untreated CBFO-Treated Sr. No Temp cP
cP 1. 150.degree. C. 20 14 2. 100.degree. C. 53 23 3. 50.degree. C.
280 70 4. 35.degree. C. 2800 120
[0046] Thus, it was observed that a substantial reduction in the
viscosity of the desulfurized sample especially at the lower
temperature range of below 50.degree. C. was obtained. The basic
advantages of viscosity reduction could include easier processing
of the oil, thereby reduction in energy cost as well as improvement
in quality of carbon black product due to formation of finer
droplets during the nebulization process.
Asphaltine Content
[0047] The samples were further tested for the asphaltene content
of the oil. Asphaltenes are found to be detrimental for the carbon
black quality as well as manufacturing processes during carbon
black formation. Thus, the asphaltene content for treated oil and
untreated oil was carried by determining the n-heptane insoluble
content in both the oils. It was observed that the asphaltene
content of untreated oil was 10.59%. However, the asphaltene
content of the treated oil was substantially reduced to 4.65%. This
indicated that our process is capable of reducing the asphaltene
content by over 50%.
EXAMPLE 2
[0048] Following experiments were carried out to optimize the time,
temperature and pressure parameters for the desulfurization
process. These studies were decided to be carried on the
CBFO:Xylene ratio of 70:30. These optimization studies are
discussed in example 4-11 listed in TABLE 3.
[0049] TABLE 3 below describes the effect of temperature on the
desulfurization efficiency. Thus, in each case the CBFO:Xylene
ratio is kept constant to 70:30. The batch contained 210 g CBFO and
90 ml of xylene. 13.5 g of sodium metal was added in each of the
samples. All the reagents were taken in high pressure reactor
vessel and then pressurized with hydrogen (about 300 psig). The
reactions were carried at a temperature of 290.degree. C. with
different residence time intervals of 3 h, 1 h, 45 min, 30 min and
10 min for the examples 4-8, respectively. The reactor was then
cooled and the CBFO was decanted and analyzed for each case by XRF.
These desulfurization results are tabulated in TABLE 3. It was
observed that the desulfurization efficiency practically remains
same for residence durations of 3 h, 1 h and 45 min respectively,
with overall desulfurization efficiency of 70%. However, the
desulfurization efficiency is drastically reduced to 59 and 50% for
reduced residence time of 30 min and 10 min, respectively.
TABLE-US-00003 TABLE 3 Concentration (CBFO:Xylene) Na amount
Hydrogen % Ex. Wt vs Vol. (g) Time Temperature Pressure
Desulfurization 4. 70:30 13.5 3 h 290.degree. C. 300 psi 70 5.
70:30 13.5 1 h 290.degree. C. 300 psi 70 6. 70:30 13.5 45 min
290.degree. C. 300 psi 68 7. 70:30 13.5 30 min 290.degree. C. 300
psi 59 8. 70:30 13.5 10 min 290.degree. C. 300 psi 50 9. 70:30 13.5
1 h 240.degree. C. 300 psi 10 10. 70:30 13.5 1 h 290.degree. C. 500
psi 70 11. 70:30 13.5 1 h 290.degree. C. 100 psi 62
[0050] Further, the desulfurization was carried out at a reduced
temperature of 240.degree. C., to understand the effect of
temperature on the desulfurization efficiency. Thus in Example 9,
appropriate amounts of CBFO:Xylene (70:30) mixture was taken in the
high pressure reactor. 13.5 g of Na metal was added and the reactor
was pressurized with hydrogen to a pressure of about 300 psig. The
reactor was then heated to a temperature of 240.degree. C. with a
residence time of 1 h. The reactor was cooled and the CBFO decanted
and analyzed for the sulfur content. A desulfurization efficiency
of 10% was obtained in this case suggesting that the minimum
temperature where effective desulfurization can be carried out was
240.degree. C.
[0051] These studies were further extended to understand the effect
of partial pressure of hydrogen on the desulfurization
efficiency.
[0052] In examples 10 & 11 different hydrogen pressures of 500
psig and 100 psig were maintained. The temperature was raised to
290.degree. C. with a residence time of about 1 h. The reactor was
cooled and the samples decanted and analyzed for sulfur content. It
was observed that there was only a marginal improvement in the
overall desulfurization efficiency at high hydrogen partial
pressures.
[0053] Thus, it was observed that the minimum temperature required
for the desulfurization reaction was about 250.degree. C. Further,
a residence time of 1 h was found to be sufficient for optimum
desulfurization to occur. It was also observed that the residence
time could be further reduced by increasing the sodium content
above stochiometric or also by means of increasing the reaction
temperature to above 300.degree. C. The effect of hydrogen partial
pressure was not found to affect the desulfurization efficiency
significantly.
EXAMPLE 3
[0054] Desulfurization experiments were carried out in the presence
and absence of hydrogen and xylene. It was observed that the
presence of xylene has a significant impact on the processing as
well as the by-product formation. Similarly, it was important to
understand the effect of hydrogen on the overall desulfurization
process. Thus, in order to study the effect of hydrogen and xylene
individually and also in combination, the following schemes were
investigated: example 12--desulfurization in the presence of xylene
and in the absence of H.sub.2; example 13--desulfurization in the
presence of xylene and in the presence of H.sub.2; example
14--desulfurization in the absence of xylene and in the absence of
H.sub.2.
[0055] In case of example 12, 210 g of CBFO and 90 ml of xylene
were taken in the high pressure reactor. No hydrogen was added to
the reactor. For example 13, 210 g of CBFO and 90 ml of xylene were
taken in the high pressure reactor and about 300 psig of hydrogen
was added to the reactor. For example 14, 210 g of CBFO was taken
and no xylene or hydrogen was added. In all the examples 12-14,
stoichiometric amount of sodium metal were added. The reaction
temperature was kept to 290.degree. C. for a residence time of 1 h.
Thus, after the reaction the samples were cooled and decanted for
each of the cases. All schemes resulted in free CBFO and sludge
(Na.sub.2S+CBFO) in varying proportions. The decanted CBFO was
weighed; the yields are given in TABLE 4.
TABLE-US-00004 TABLE 4 Ex. Composition Desulfurized CBFO yield (%)
12. No H.sub.2 + Xylene 72 13. H.sub.2 + Xylene 78 14. No H.sub.2 +
No Xylene 54
[0056] It was observed that when xylene was used the CBFO yield was
higher as compared to when no xylene was added. Further, to reduce
the sodium content from the desulfurized oil, 5% mixture of acetic
acid in xylene was prepared. The acetic acid solution was added to
the treated or desulfurized oil. The mixture was then heated at
100.degree. C. for 1 hr under vigorous stirring. The mixture was
then allowed to cool down and filtered. The treatment resulted in
significant reduction in sodium content from 2000 ppm to <50
ppm. Alternatively, the treatment of desulfurized oil can also be
achieved by purging the oil with air under elevated temperatures.
For this, 100 ml of desulfurized CBFO was taken in a glass air
treatment tube and in this tube compressed air was continuously
purged for a period of 30 minutes. This air reacts with the excess
of Na present in the oil to form a precipitated mass which can be
filtered out. It was found that this treatment resulted in
reduction in Na content by around 50% (from 2000 ppm to 900 ppm).
Further to optimize the treatment, same reaction was carried out at
elevated temperature at 50.degree. C. It was found that the
treatment resulted in significant reduction in Na content by around
96% (from 2200 ppm to 90 ppm).
[0057] Experiments were performed to check the effect of heavy
shear mixing in which samples were mixed at a low agitation mixing
(200-300 rpm) with a stirrer having blunt edged blades (made of
Teflon/plastic) and samples were mixed under higher agitation
speeds (700-800 rpm) mixing in a parr reactor with metal blades
with relatively sharp edges. It was observed that higher
desulfurization was obtained when the agitator is capable of
breaking the Na.sub.2S particles that are formed and bringing new
Na metal surfaces in contact with the CBFO for further
reaction.
TECHNICAL ADVANTAGES
[0058] A process for desulphurization of carbon black feed oil, as
described in the present disclosure has several technical
advantages including but not limited to the realization of: the
process does not require hydrogen; the process does not require
high pressure conditions; the process reduces the loss of feed oil;
the process gives a reduction in the asphaltene content of the
petroleum oil by >50%; the process improves the viscosity of the
desulphurized oil to <200 cP; the process reduces the residual
sodium content to <10 ppm; the process enhances the processing
and handling conditions of the CBFO; the process provides easy
filtration and separation of the desulfurized oil and by-products
thereof; and the process is safe as it lowers the density of oil in
comparison with sodium metal.
[0059] Throughout this specification the word "comprise", or
variations such as "comprises" or "comprising", will be understood
to imply the inclusion of a stated element, integer or step, or
group of elements, integers or steps, but not the exclusion of any
other element, integer or step, or group of elements, integers or
steps.
[0060] 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 invention to
achieve one or more of the desired objects or results.
[0061] 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 invention.
It is not to be taken as an admission that any or all of these
matters form part of the prior art base or were common general
knowledge in the field relevant to the invention as it existed
anywhere before the priority date of this application.
[0062] 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. Wherever a range of values
is specified, a value up to 10% below and above the lowest and
highest numerical value respectively, of the specified range, is
included in the scope of the disclosure.
[0063] While considerable emphasis has been placed herein on the
specific steps of the preferred process, it will be appreciated
that additional steps can be made and that many changes can be made
in the preferred steps without departing from the principles of the
disclosure. These and other changes in the preferred steps 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.
* * * * *