Title of Invention

PROCESS FOR RECOVERY OF SULFUR FROM SOUR/NATURAL GAS USING BIODEGRADABLE CARBOXYLIC ACID METAL CHELATES

Abstract A process for recovery of sulfur from sour/natural gas using biodegradable carboxylic acid metal chelate This invention relates to a process for recovery of sulfur from sour/natural gas stream containing H2S is described. It involves contacting the stream with an aqueous solution of biodegradable water soluble carboxylic acid metal chelate. This carboxylic acid metal chelate contains an oxidizing polyvalent metal e.g. Fe (III) and one of the acid from gluconic acid, malic acid, citric acid, succinic acid, oxalic acid. The hydrogen sulfide gas is reduced to hydrogen and elemental sulfur, which is recovered as precipitate. The iron in the metal chelate is reduced in the process and can be regenerated by oxidation.
Full Text tons pThis invention relates to an improved process for the recovery of sulfur from sour/natural gas using biodegradable carboxylic acid metal chelate. More particularly it relates to the recovery of sulfur from sour/natural gas contaminated with H2S or a mixture of gases containing H2S using biodegradable chelates. The reduced chelated metal mass is oxidized with air or oxygen and the precipitated elemental sulfur is separated. The regenerated chelated metal mass is recycled and reused for the conversion of H2S to elemental sulfur. Background of the invention
In chemistry chelate or chelating agents are compounds, which form coordinate covalent bonds with a metal ion. Chelates are thus coordination compounds in which a central metal atom is bounded to two or more other atoms in at least one other molecule or ion (called ligand) such that at least one hetro-cyclic ring is formed with the metal atom as part of each ring.
Chelants are used in variety of applications including food processing, soaps, detergents, cleaning products, pharmaceuticals, pulp and paper processing, water treatment, metalworking and metal plating solutions, textile processing solutions, fertilizers, animal feeds, herbicides, rubber and polymer chemistry, photofinishing, oilfield chemistry. Some of these activities result in chelants entering the environment. For instance, agricultural uses or detergent uses may result in measurable quantities of the chelants being in water. It is therefore, desirable that chelants degrade after use. Biodegradability, that is susceptibility to degradation by microbes, is particularly useful because the microbes are generally naturally present in environments. Commonly used chelant like EDTA (Ehtylenediamine tetraacetic acid) is biodegradable, but the rate is somewhat slower. It would be desirable to have a chelating agent, which degrades faster than EDTA or other commonly used chelants like HEDTA (Hydroxyethylethylene-diaminetriacetic acid), NTA (Nitrilotriacetic acid), DTPA (Diethylenetriaminepentaacetic acid), etc.
Natural gas as well as refiner gas streams are commonly contaminated with sulfur compounds, especially hydrogen sulfide. If substantial amounts of hydrogen sulfide are present, regulatory restrictions dictate that special precautions must be taken to purify the gas streams. In non-populated areas, generally a maximum of two

Summary of the invention
Accordingly the present invention provides a process for recovery of sulfur from
sour/natural gas using biodegradable carboxylic acid metal chelate such as herein
described , which comprises contacting the sour/natural gas flow with an aqueous
solution of a biodegradable water-soluble carboxylic acid metal chelate containing an
oxidizing polyvalent metal salt and carboxylic acid selected from the group consisting
of succinic acid, citric acid, malic acid, gluconic acid and oxalic acid at ambient
temperature and atmospheric pressure, the said solution is maintained at the pH of 7.0
to 9.0 using a hydroxide of an alkaline earth element selected from the group
consisting of Na, K and Mg, continuing contacting till the sour/natural gas coming
out of the solution is free from H2S, reoxidising the carboxylic metal chelate solution
by passing a source of oxygen through the solution, separating the suspended form of
sulfiir obtained and drying to obtain sulfur.
In one embodiment of the invention, the metal chelate comprises a polyvalent metal chelatable in both oxidized and reduced states.
In a fiirther embodiment of the invention, the polyvalent metal is selected from the group consisting of tin, lead, copper, manganese, platinum, tungsten, nickel, palladium, chromium, cobalt, vanadium, titanium, tantalum, zirconium and molybdenum.
In another embodiment of the invention the carboxylic acid metal chelate is a transition metal chelate of iron selected from the group consisting of solution of sulfates, nitrates, thiosulfates, chlorides, acetates, oxalates and phosphates.
In another embodiment of the invention, the transition metal salt is chelated with a carboxylic acid.
In another embodiment of the invention, the carboxylic acid is selected from the group consisting of mono-, di- and tri-carboxylic acids obtained from biodegradable source.
In a fiirther embodiment of the invention, the carboxylic acid is selected from the group consisting of succinic acid, citric acid, malic acid, gluconic acid and oxalic acid.
In another embodiment of the invention, the solution is maintained at the pH of 7.0 to 9.0 using a hydroxide of an alkaline earth element selected from the group consisting of Na, K and Mg.
In another embodiment of the invention, the oxygen source is selected from air and molecular oxygen.
In another embodiment of the invention, the process for recovery of elemental sulfiir is selected from a continuous stirred reactor process, bubble column reactor process, airlift type reactor process and a batch process.

er day of sulfur is allowed to be vented as sulfur oxides flare-off gas per
processing plant. In populated areas even more stringent restrictions are applied.
Gas desulfurization using iron chelates is a commercial process where the
liquid redox chemistry of alternate reduction and oxidation of iron complex is
gainfully utilized. McManus and Martell (1997) provide a comprehensive review of
this technology in the article. We shall therefore provide additional major
developments since there.
C. Pagella et.al. "H2S gas treatment by iron bioprocess", Chemical
Engineering Sciences 55(2000) 2185-2194 discussed a novel chemical-biological
process based on combination of absorption with chemical reaction and biological
oxidation.
C.A. Lieder has reported in U.S. Pat. No. 4332781 a process for the removal
of FS gas and CaS from gas stream in a staged procedure characterized by
conversion of the F^S to produce sulfur in aqueous solution or suspension. The
reactant material includes polyvalent metal bound to monomeric chelate.
F. Engelhardt et.al. in U. S. Pat No. 4518745 disclosed a number of metal
chelates of water soluble copolymer, The copolymers are useful as dyestuff auxiliaries
and leather retanning agents.
U. S. Pat. No. 5741555 discloses use of polyamino disuccinic acids for
effective chelants for use in photography and gas conditioning but polyamino acids
take longer time for biodegradation.
Polyamino disuccinic acids, despite possessing some chelating properties have
not found wide usage. For instance, a better known member of family, namely
ethylenediamine disuccinic acid (HDDS) has not been a widely used chelants. The
preparation of polyamino disuccinic acids is discussed by Kezeodan et.al. in U. S. Pat.
No. 3158635 where their use in rust removal is disclosed. Atkinson in U. S. Pat. No.
4704233 disclosed use of HDDS in detergents to enhance removal of organic stains
and mention about its biodegradability.
U. S. Pat. No. 4889609 discloses a process in solution for removing H2S from
a stream of natural gas. Sodium nitrite in the solution serves as an oxidizing agent for
H^S. in absence of a catalyst, the process suffers from conversion of nitrite ion into
NHs. This conversion is suppressed by the incorporation of a transition metal chelate
complex. The metal is preferably chromium, copper or iron and the chelate complex
is preferably EDTA or TEA, with acceptable performance obtained from HEDTA or
NTA. Use of EDTA and TEA however generate streams that are slow or nonbiodegradable.
U. S. Pat. No. 5152970 discloses a process for removal of hydrogen sulfide
from sour gas by passing the gases in the presence of oxygen and steam over a
catalytic absorption mass, which contains inert porous support material and
catalytically active metal sulfldes and/or metal oxides. The elemental sulfur formed
gets simultaneously deposited on the absorption mass, which is then regenerated. The
whole process is carried out at higher temperature.
J. O. Porath in U. S. Pat. No. 4423158 discloses a process for introducing a
chelate-forming group into a polymer such as polystyrene. The adsorbent for bivalent
or multivalent metal ions so obtained are useful in ion exchange chromatography.
Grinstead et.al. in U.S.Pat.No. 4859437 describe a cyclic continuous process for
reduction of hydrogen sulfide by using organic polymeric chelate to sulfur. The
process includes removal of elemental sulfur and ultrafilteration or dialysis to
regenerate reduced polyvalent metal. The regeneration of polyvalent metal is
expensive.
In view of the above state of the art the need for providing an improved
process for the removal of sulfur from sour/natural gas using biodegradable metal
chelates is clearly evident.
It is also desirable that the biodegradability of the chelate be many times more
than the conventionally used chelates.
Objects of the invention
The main object of the present invention is to provide a process for the
recovery of sulfur from sour/natural gas which is eco-friendly.
It is another object of the invention to provide an improved process for the
removal of sulfur from sour/natural gas waste streams using water soluble chelated
metal, where hydrogen sulfide having been absorbed into an alkaline solution of
chelated metal is converted to yield both elemental sulfur and hydrogen.
Another objective of the present invention is to decompose poisonous gas such
as hydrogen sulfide into separate amounts of hydrogen and sulfur.
The third objective is to provide a process for the removal of sulfur from
sour/natural gas using chelated metal and chelating agent which is easily
biodegradable and eco-friendly.
Summary of the invention
Accordingly the present invention provides an improved process for recovery
of sulfur from sour/natural gas, which comprises contacting the sour/natural gas flow
with an aqueous solution of a biodegradable water-soluble carboxylic acid metal
chelate till the sour/natural gas coming out of the solution is free from H2S,
reoxidising the carboxylic metal chelate solution by passing a source of oxygen
through the solution, separating the suspended form of sulfur obtained and drying to
obtain sulfur.
In one embodiment of the invention, the metal chelate comprises a polyvalent
metal cheiatable in both oxidized and reduced states.
In a further embodiment of the invention, the polyvalent metal is selected from
the group consisting of tin, lead, copper, manganese, platinum, tungsten, nickel,
palladium, chromium, cobalt, vanadium, titanium, tantalum, zirconium and
molybdenum.
In another embodiment of the invention the carboxylic acid metal chelate is a
transition metal chelate of iron selected from the group consisting of solution of
sulfates, nitrates, thiosulfates, chlorides, acetates, oxalates and phosphates.
In another embodiment of the invention, the transition metal salt is chelated
with a carboxylic acid.
In another embodiment of the invention, the carboxylic acid is selected from
the group consisting of mono-, di- and tri-carboxylic acids obtained from
biodegradable source.
In a further embodiment of the invention, the carboxylic acid is selected from
the group consisting of succinic acid, citric acid, malic acid, gluconic acid and oxalic
acid.
In another embodiment of the invention, the solution is maintained at the pH
of 7.0 to 9.0 using a hydroxide of an alkaline earth element selected from the group
consisting of Na, K and Mg.
In another embodiment of the invention, the oxygen source is selected from air
and molecular oxygen.
In another embodiment of the invention, the process for recovery of elemental
sulfur is selected from a continuous stirred reactor process, bubble column reactor
process, airlift type reactor process and a batch process.
In another embodiment of the invention, the concentration of the chelating
agent is in the range of 500 ppm to 20000 ppm.
In another embodiment of the invention, the sour/natural gas is contacted with
the metal chelate solution at ambient temperature and atmospheric pressure.
Detailed description of the invention
The present disclosure is directed to biodegradable aqueous carboxylic acid
metal chelate oxidizer, which is used in an aqueous solution for removal of F^S from
sour/natural gas. With its signature 'rotten egg' smell, fyS is not only odorous, but
corrosive and neuro-toxic too. It is produced naturally, by anaerobic decomposition of
sulfur-bearing materials and synthetically, by a host of chemical process operations,
including hydrogenation and hydrodesulfurization and coking. Most people can detect
concentration even as small as 0.01 PPM. The gas is toxic in relatively light
concentrations and should be removed from natural gas as soon as possible. Many
processes have been developed to convert fyS to some innocuous forms, such as
elemental sulfur and sulfates.
The sour/natural gas is introduced into an aqueous solution of biodegradable
carboxylic acid metal chelate. The present process is typically carried out at room
temperature and atmospheric pressure and the pH of chelated metal solution is
maintained in the range 7.0 to 9.0. The sour/natural gas is bubbled through the reactor
containing the solution of aqueous metal chelate.
Generally, any polyvalent metal chelatable in both oxidized and reduced states
can be used as the metal component of polymeric chelate. In the present invention
ferric iron salts of sulfate, nitrate, chloride are particularly preferred. The polyvalent
metal chelate should be capable of oxidizing hydrogen sulfide (FhS) while being
reduced itself to the corresponding chelate of the metal in a lower valence state and
should then be oxidizable by oxygen or similar oxidation means to chelate of the
metal in higher valence state in a typical redox reactions. Other polyvalent metals
which can be used include tin, lead, copper, manganese, platinum, tungsten, nickel,
palladium, chromium, cobalt, vanadium, titanium, tantalum, zirconium and
molybdenum.
The chelate is preferably biodegrada^., carboxylic acids like gluconic acid,
citric acid, succinic acid, malic acid and oxalic acid.
The solution should be preferably maintained at pH range from about 7.0 to
about 9.0. The pH of the resulting iron chelate solution can be adjusted with an
alkaline material such as ammonia solution, sodium carbonate or dilute caustic i.e.
sodium hydroxide solution. Contact of H2S. with the chelate takes place in the pH
range from about 6 to about 10. The more preferred range of pH is from about 6.5 to
about 9.0 and the most preferred range of pH is from 7.0 to 9.0. In general highest
portion of the range is preferred in order to operate at high efficiency of H2S
absorption. Since the H2S is an acid gas, there is tendency for the H2S to lower the pH
of the aqueous alkaline solution. Lower pH is preferable in the presence of CCh to
reduce absorption thereof. Optimum pH also depends upon stability of a particular
polyvalent metal chelate. At the pH values below about 6.0 the efficiency of H2S
absorption is low so as to be generally impractical. At pH values greater than 10.0, for
instance with iron as the polyvalent metal, the precipitation of insoluble iron
hydroxide may occur resulting in decomposition of the iron chelate.
Any inert water-soluble biodegradable chelate capable of chelating an
oxidizing polyvalent metal is suitable in the present process. " Inert", in this context,
is defined as not detrimentally reactive in the system to an intolerable extent. The
carboxylic acids like citric acid, gluconic acid, malic acid, succinic acid, oxalic acid
are used in combination with ferric iron salts like ferric sulfate, ferric nitrate and ferric
chloride. The combination of above said each salt is made with above said each
carboxylic acid in stiochoimetric proportions in aqueous medium. Concentrations of
iron chelate for H2S removal is made from range about 500 PPM to 20,000 PPM. The
pH of the solution is maintained at about 7.0 to about 9.0.
The present invention therefore provides an improved process for recovery of
sulfur from sour/natural gas, which comprises contacting the sour/natural gas flow
with an aqueous solution of a biodegradable water-soluble carboxylic acid metal
chelate at a pH in the range of about 7.0 to 9.0, at atmospheric pressure till the
sour/natural gas coming out of the solution is free from H2S, reoxidising the
carboxylic metal chelate solution by passing through the said solution a source of
oxygen, separating the sulfur obtained in the suspended form by conventional
methods and drying the sulfur by conventional methods to obtain sulfur.
The carboxylic acid metal chelate may be the transition metal chelate of iron
such as solution of sulfates, nitrates, thiosulfates, chlorides, acetates, oxalates,
phosphates. The transition metal salt used is chelated with carboxylic acids selected
from mono-, di-, tri-carboxylic acids from biodegradable source exemplified by
succinic acid, citric acid, malic acid, gluconic acid and oxalic acid.
The solution is maintained at the pH of about 7.0 to 9.0 by using hydroxides of
alkaline earth elements such as Na. K. and Mg.
The source of oxygen may be air or molecular oxygen. In a feature of the
present invention the process used for the recovery of elemental sulfur may be a
continuous stirred reactor, bubble column reactor, or airlift type reactor or a batch
process.
The process of the present invention is described hereinbelow with reference
to examples which are illustrative only and should not be construed to limit the scope
of the present invention in any manner whatsoever.
Example-1
500 ml of water was placed in a container with 10 grams of ferric nitrate. On
total dissolution of salt. 31.01 ml of gluconic acid solution was added to it. Add 10%
extra acid for complete and proper chelation of metal salt. The pH of the solution was
checked and 5N NaOH solution was added to maintain the pH in the range 7.0 to
about 9.0. The forgoing was mixed at room temperature and atmospheric pressure to
form true solution. The H2S gas was then slowly bubbled through the solution at
constant flow rate. While the test contents began initially as a true solution, the
solution soon becomes dark in color, showing slurry of precipitated sulfur. Continue
to pass the feed gas through the solution until no more precipitation of sulfur occurs.
This is readily tested by passing the outlet gas through a tube containing AgNOs
solution which begun to turn black. Pass the H2S gas for 10 more minutes so as to
ensure complete conversion of H2S to elemental sulfur. While conversion of H2S to
elemental sulfur occurs the Fe (III) simultaneously gets reduced to Fe (II) and so to
reoxidize Fe (II) to Fe (III) excess air or oxygen was sparged through solution. On
oxidation of chelated solution the color of the precipitated sulfur turns to off-white.
Total sulfur recovery on completion of the process was 90 milligrams of 99% purity
(as evaluated using microanalysis).
Example-2
500 ml of water was placed in a container with concentration of ferric nitrate
solution varying from 10,000 PPM to about 1000 PPM. On total dissolution of salt,
gluconic acid solution was added to it in proportion. Add 10% extra acid for complete
and proper chelation of metal salt. The pH of the solution was checked and 5N NaOH
solution was added to maintain the pH in the range 7.0 to about 9.0. The forgoing was
mixed at room temperature and atmospheric pressure to form true solution. The H2S
gas was then slowly bubbled through the solution at constant flow rate. While the test
contents began initially as a true solution, the solution soon becomes dark in color,
showing slurry of precipitated sulfur. Continue to pass the feed gas through the
solution until no more precipitation of sulfur occurs. This is readily tested by passing
the outlet gas through a tube containing AgNOs solution which begun to turn black.
Pass the F^S gas for 10 more minutes so as to get maximum conversion of H?S to
elemental sulfur. While conversion of HiS to elemental sulfur occurs the Fe (III)
simultaneously gets reduced to Fe (II) and so to reoxidize Fe (II) to Fe (III) excess air
or oxygen was sparged through solution. On oxidation of chelated solution the color
of the precipitated sulfur turns to off-white. The total sulfur recovered was of the 99%
purity (as evaluated using microanalysis), in the range of 13 milligrams to 117
milligrams per gram of chelated metal.
Example-3
500 ml of water was placed in a container with concentration of ferric sulfate
solution varying from 20,000 PPM to about 1000 PPM. On total dissolution of salt,
malic acid solution was added to it in proportion from 9.024 grams to 0.4512 grams.
Add 10% extra acid for complete and proper chelation of metal salt. The pH of the
solution was checked and 5N NaOH solution was added to maintain the pH in the
range 7.0 to about 9.0. The forgoing was mixed at room temperature and atmospheric
pressure to form true solution. The F^S {.-• is then slowly bubbled through the
solution at constant flow rate. While the test contents began initially as a true solution,
the solution soon becomes dark in color, showing slurry of precipitated sulfur.
Continue to pass the feed gas through the solution until no more precipitation of sulfur
occurs. This is readily tested by passing the outlet gas through a tube containing
AgNO} solution which begun to turn black. Pass the FbS gas for 10 more minutes so
as to get maximum conversion of H?S to elemental sulfur. While conversion of HaS to
elemental sulfur occurs the Fe (III) simultaneously gets reduced to Fe (II) and so to
reoxidize Fe (II) to Fe (HI) excess air or oxygen was sparged through solution. On
oxidation of chelated solution the color of the precipitated sulfur turns to off-white.
The total sulfur recovered was of the 99% purity (as evaluated using microanalysis),
in the range of 25 milligrams to 84 milligrams per gram of chelated metal.
EXAMPLE-4
500 ml of water was placed in a container with concentration of ferric chloride
solution varying from 20.000 PPM to about 1000 PPM. On total dissolution of salt,
malic acid solution was added to it in proportion from 13.6059 grams to 0.6802
grams. Add 10% extra acid for complete and proper chelation of metal salt. The pH of
the solution was checked and 5N NaOH solution was added to maintain the pH in the
range 7.0 to about 9.0. The forgoing was mixed at room temperature and atmospheric
pressure to form true solution. The HaS gas was then slowly bubbled through the
solution at constant flow rate. While the test contents began initially as a true solution,
the solution soon becomes dark in color, showing slurry of precipitated sulfur.
Continue to pass the feed gas through the solution until no more precipitation of sulfur
occurs. This is readily tested by passing the outlet gas through a tube containing
AgNOa solution which begun to turn black. Pass the FfeS gas for 10 more minutes so
as to get maximum conversion of FhS to elemental sulfur. While conversion of HaS to
elemental sulfur occurs the Fe (III) simultaneously gets reduced to Fe (II) ,::nd so to
reoxidize Fe (II) to Fe (III) excess air or oxygen was sparged through solution. On
oxidation of chelated solution the color of the precipitated sulfur turns to off-white.
The total sulfur recovered was of the 99% purity (as evaluated using microanalvsis),
in the range of 59 milligrams to 127 milligrams per gram of chelated metal.
EXAMPLE-5
500 ml of water was placed in a container with concentration of ferric chloride
solution varying from 20,000 PPM to about 1000 PPM. On total dissolution of salt,
citric acid solution was added to it in proportion from 14.2153 grams to 0.7107 grams.
Add 10% extra acid for complete and proper chelation of metal salt. The pH of the
solution was checked and 5N NaOH solution was added to maintain the pH in the
range 7.0 to about 9.0. The forgoing was mixed at room temperature and atmospheric
pressure to form true solution. The H2S gas was then slowly bubbled through the
solution at constant flow rate. While the test contents began initially as a true solution,
the solution soon becomes dark in color, showing slurry of precipitated sulfur.
Continue to pass the feed gas through the solution until no more precipitation of sulfur
occurs. This is readily tested by passing the outlet gas through a tube containing
AgNO3 solution which begun to turn black. Pass the H2S gas for 10 more minutes so
as to get maximum conversion of H2S to elemental sulfur. While conversion of H2S to
elemental sulfur occurs the Fe (III) simultaneously gets reduced to Fe (II) and so to
reoxidize Fe (II) to Fe (III) excess air or oxygen was sparged through solution. On
oxidation of chelated solution the color of the precipitated sulfur turns to off-white.
The total sulfur recovered was of the 100% purity (as evaluated using microanalysis),
in the range of 40 milligrams to 72 milligrams per gram of chelated metal.
During the experimental runs it was observed that the rate of precipitation of
sulfur varies with the concentration and type of metal salt and carboxylic acid used. In
other words the time required for completion of process varies from case to case for
otherwise similar operating conditions. Dynamic studies and rigorous optimization
may further improve the yield and recovery of sulfur. In any case, the recovery and its
rate are almost always better than that obtained using conventional EDTA process.
Experimental runs were also conducted in continuous mode of reactor operation for a
constant flow of HiS laden gas and chelating solution. Similar quantitative results
were obtained for the continuous reactor. The comparative rate of recovery for an
improved biodegradability of carboxylic acid metal chelates shall prove to be useful
for commercial exploitation of this process.





We claim:
1. A process for recovery of sulfur from sour/natural gas using biodegradable carboxylic acid metal chelate such as herein described, which comprises contacting the sour/natural gas flow with an aqueous solution of a biodegradable water-soluble carboxylic acid metal chelate containing an oxidizing polyvalent metal salt and carboxylic acid selected from the group consisting of succinic acid, citric acid, malic acid, gluconic acid and oxalic acid at ambient temperature and atmospheric pressure, the said solution is maintained at the pH of 7.0 to 9.0 using a hydroxide of an alkaline earth element selected from the group consisting of Na, K and Mg, continuing contacting till the sour/natural gas coming out of the solution is free from H2S, reoxidising the carboxylic metal chelate solution by passing a source of oxygen through the solution, separating the suspended form of sulfur obtained and drying to obtain sulfur.
2. A process as claimed in claim 1, wherein the polyvalent metal is chelatable in both oxidized and reduced states.
3. A process as claimed in claim 1, wherein the polyvalent metal is selected from the group consisting of iron,tin, lead, copper, manganese, platinum, tungsten, nickel, palladium, chromium, cobalt, vanadium, titanium, tantalum, zirconium and molybdenum.
4. A process as claimed in claim 1, wherein the polyvalent metal salt is sulfates, nitrates, thiosulfates, chlorides, acetates, oxalates and phosphates.
5. A process as claimed in claim 1, wherein the oxygen source is selected from air and molecular oxygen.
6. A process as claimed in claim 1, wherein the process for recovery of elemental sulfur is selected from a continuous stirred reactor process, bubble column reactor process, airlift type reactor process and a batch process.
7. A process as claimed in claim 1, wherein the concentration of the chelating agent is in the range of 500 ppm to 20000 ppm.
8. A process for recovery of sulfur from sour/natural gas using biodegradable carboxylic acid metal chelate substantially as herein describe with reference to examples accompanying this specification.


Documents:

1366-DEL-2003-Abstract-(02-01-2009).pdf

1366-del-2003-abstract.pdf

1366-DEL-2003-Claims-(02-01-2009).pdf

1366-DEL-2003-Claims-(25-02-2009).pdf

1366-del-2003-claims.pdf

1366-del-2003-complete specification (granted).pdf

1366-DEL-2003-Correspondence-Others-(02-01-2009).pdf

1366-DEL-2003-Correspondence-Others-(12-01-2009).pdf

1366-DEL-2003-Correspondence-Others-(25-02-2009).pdf

1366-del-2003-correspondence-others.pdf

1366-del-2003-correspondence-po.pdf

1366-del-2003-description (complete)(25-02-2009).pdf

1366-DEL-2003-Description (Complete)-(02-01-2009).pdf

1366-del-2003-description (complete).pdf

1366-del-2003-form-1.pdf

1366-del-2003-form-18.pdf

1366-del-2003-form-2.pdf

1366-DEL-2003-Form-3-(02-01-2009).pdf

1366-del-2003-form-3.pdf

1366-DEL-2003-Petition-137-(12-01-2009).pdf


Patent Number 233617
Indian Patent Application Number 1366/DEL/2003
PG Journal Number 18/2009
Publication Date 01-May-2009
Grant Date 31-Mar-2009
Date of Filing 06-Nov-2003
Name of Patentee COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH
Applicant Address RAFI MARG, NEW DELHI-110 001, INDIA
Inventors:
# Inventor's Name Inventor's Address
1 ANIRUDDHA SUBHASH DESHPANDE NATIONAL CHEMICAL LABORATORY, PUNE-411008, MAHARASHTRA, INDIA
2 NARENDRA VASANT SANKPAL NATIONAL CHEMICAL LABORATORY, PUNE-411008, MAHARASHTRA, INDIA
3 BHASKAR DATTATRAYA KULKARNI NATIONAL CHEMICAL LABORATORY, PUNE-411008, MAHARASHTRA, INDIA
PCT International Classification Number C01B 17/027
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA