Title of Invention	"PROCESS FOR OXIDATIVE DESULPHURIZATION OF LIQUID HYDROCARBON FUELS BY USING CARBOXYLIC ACID-ALKALI METAL PEROXOBORATE AS OXIDATION SYSTEM"
Abstract	The present invention relates to a process_for the oxidative desulphurization of liquid hydrocarbon fuel such as diesel fuel, gasoline, jet fuel, fuel oil, coal liquids and similar petroleum products reducing the sulphur content to less than 10 ppm. It consists of oxidizing the sulphur compounds present in hydrocarbon fuels by organosulphonic or carboxylic acid and oxygen containing species in the range of 2-10 mole times of sulphur to sulphones or sulphoxides followed by their removal by extraction followed by adsorption or adsorption only.

Title of Invention

"PROCESS FOR OXIDATIVE DESULPHURIZATION OF LIQUID HYDROCARBON FUELS BY USING CARBOXYLIC ACID-ALKALI METAL PEROXOBORATE AS OXIDATION SYSTEM"

Abstract

The present invention relates to a process_for the oxidative desulphurization of liquid hydrocarbon fuel such as diesel fuel, gasoline, jet fuel, fuel oil, coal liquids and similar petroleum products reducing the sulphur content to less than 10 ppm. It consists of oxidizing the sulphur compounds present in hydrocarbon fuels by organosulphonic or carboxylic acid and oxygen containing species in the range of 2-10 mole times of sulphur to sulphones or sulphoxides followed by their removal by extraction followed by adsorption or adsorption only.

Full Text	The present invention relates to a process for oxidative desulphurization of liquid hydrocarbon fuels by using carboxylic acid-alkali metal peroxoborate as oxidation system. Particularly the present invention relates to a process for oxidative desulphurization of liquid hydrocarbon fuels such as diesel fuel, gasoline, jet fuel, fuel oil, coal liquids and similar petroleum products to ultra low sulphur hydrocarbon fuels with sulphur content less than 10 ppm. More particularly, the invention relates to a process for oxidative desulphurization of hydrotreated liquid hydrocarbon fuels such as diesel fuel, gasoline, jet fuel, fuel oil, coal liquids containing condensed thiophene, benzothiophene, dibenzothiophene type sulphur compounds which are refractory in nature, to ultra low sulphur liquid hydrocarbon fuels having sulphur content less than 30 ppm and comprises of oxidation of sulphur compounds present in liquid hydrocarbon fuels with an oxidizing solution consisting of carboxylic acid containing small amounts of alkali metal peroxoborate to sulphones followed by removal of sulphones from the hydrocarbon fuel by solvent extraction and final finishing by passing through a bed of alumina/silica/clay or alternatively removing the sulphones from hydrocarbon fuels by adsorption on solid alumina/silica. Because of their high energy densities and convenient physical form liquid hydrocarbon fuels such as diesel fuel, gasoline, jet fuel, fuel oil and coal liquids are presently being consumed in vast quantities and their consumption continues to grow at alarming rates. Inevitably, this high consumption is having a major impact on the global environment. Most notably, transport hydrocarbon fuels like diesel fuel, gasoline, and jet fuel are receiving the highest scrutiny due to increased environmental concerns. There is an increasing demand to reduce sulphur content in the liquid hydrocarbon fuels to produce products, which have very low sulphur content and are thereby marketable in the even more demanding marketplace. Conventionally, hydrodesulphurization of liquid hydrocarbon fuels which involves contacting of hydrogen with hydrocarbon stream in presence of a catalyst at elevated temperature and pressure to convert sulphur compounds present therein to hydrogen sulfide is used to produce hydrocarbon fuels with lower sulphur content. Hydrodesulphurization can easily remove sulphur from several common classes of sulphur compounds such as sulphides, disulphides and thiols present in hydrocarbon fuels because these are easily accessible to contact with hydrodesulphurization catalyst, however, sulphur compounds like 4,6-dimethyldibenzothiophene (4,6-DMDBT) and other similar thiophene species are rigid to hydrodesulphurization and therefore difficult to remove. Conventional hydro desulphurization of diesel for example that operates at moderate temperatures (315-400°C) and hydrogen pressure 3.0~8.0 MPa with Co/Mo/Al2O3 as catalyst can bring down the sulphur content in the range 300-500 ppm easily. However, to bring down sulphur content further below 100 ppm deep hydrodesulphurization of diesel required very severe conditions like the use of high temperature, high hydrogen pressure, more active catalyst and long residence time. Deep hydrodesulphurization yields negative effects such as reduced catalyst life, high hydrogen consumption and high yield loss thereby resulting in higher operating cost. Apart from the cost involved, the energy requirements for implementation of hydroprocessing technology also leads to increased level of CO2 emissions from refinery itself. The USEPA has released new regulations that require the sulphur content in the diesel fuel used in highway vehicles to be limited to 30 ppm by 2005 and 15 ppm effective by 2006. Similarly, in European countries the sulphur content in the diesel fuel will be limited to 30-50 ppm by 2005. The necessity has therefore been felt for a process complementary to hydro desulphurization to remove condensed thiophene, benzothiophene and dibenzothiophene type sulphur compounds present in hydrodesulphurized hydrocarbon fuels to yield ultra low hydrocarbon fuels It is known that sulphur compounds present in liquid hydrocarbon fuels can be oxidized to sulphones / sulphoxides and subsequently removed by taking advantage of their different chemical and physical characteristics (Tetsuo Aida et al. 20th American Chemical Society meeting at San Diego, California Mar 13-17 1994). US Pat No 5,958,224 discloses a process for removal of refractory sulphur compounds from hydrotreated hydrocarbon streams by oxidizing them to sulphoxides and sulphones with peroxometal complexes like LMO(O2)2 where M is selected from the groups consisting of Mo, W, Cr and L is alkyl phosphoric triamide like hexamethyl-phosphoric triamide followed by adsorption on solid adsorbents like activated carbon, bauxite, clay, coke, alumina or silica gel. The peroxometal complexes were prepared by reacting metal complexes with hydrogen peroxide Collins et al. (J. Mol. Catal A: Chem 117 (1977) 397) reported their studies on oxidation of sulphur compounds present in gas oil with hydrogen peroxide using phosphotungstic acid as catalyst, and subsequent removal of the sulphones formed by solvent extraction using y-butyrolactone as solvent or by adsorption on silica gel to obtain ultra low sulphur gas oil. However large amounts of hydrogen peroxide were used for the oxidation of sulphur compounds present in gas oil. Mei et al. (Fuel 82 (2003) 405) reported their ultrasound assisted studies on oxidative desulphurization of diesel using hydrogen peroxide as oxidant, phosphotungstic acid as catalyst, methanol as solvent for extraction of sulphones and obtained 66.4% overall sulphur removal after 2.5h reaction. The sulphur removal efficiency could be improved to 97.8% by increasing the reaction time to 4 hours and using silica adsorption instead of solvent extraction to remove sulphones from diesel. US patent No 6368495 discloses a process for oxidative desulpurization of petroleum fractions like gasoline, diesel fuel, kerosene which involves oxidation of thiophene and thiophene derivatives present in petroleum fractions to sulphones with alkyl hydroperoxide in presence of molybdenum on alumina as catalyst followed by decomposition of sulphones using catalyst like double layer hydroxides, molecular sieves, inorganic metal oxides or a mixture thereof. Ishihara et al. (Applied Catal. A: Gen. 279 (2004) 279) reported oxidative desulphurization of desulphurized light gas oil with sulphur content 39 ppm involving oxidation of the sulphur compounds present therein with tert-butylhydroperoxide in presence of 16 wt% MoO3/ A12O3 as catalyst followed by removal of the sulphones formed by adsorption over silica gel to obtain light gas oil with sulphur content less than 5 ppm. WO patent No 2004029179 describes a process for oxidative desulphurization of hydrotreated hydrocarbon mixture boiling range 180-360°C containing less than 350 ppm thiophene sulphur involving oxidation of sulphur compounds with organic peroxide in presence of a catalytic composition containing completely amorphous micro and/or meso porous mixed oxides comprising a matrix selected from silica, alumina, ceria, magnesia and mixture thereof wherein one or more metal oxides selected from transition metal oxides and group IVA metal oxides are uniformly dispersed followed by separation of the suphur oxygenated product from the hydrocarbon mixture. Otsuki et al. (Energy and fuel 14 (2000) 1232) studied the oxidation of the model sulphur compounds with a mixture of hydrogen peroxides and formic acid and found the reactivity of dibenzothiophene derivative to increase with the increase of electron density. Thus the reactivity order for oxidation was found to be 4,6-dimethyldibenzothiophene> 4-methyldibenzothiophene>dibenzothiophene which is reversed to the order of reactivity for hydrodeslphurization. They further studied the oxidative desulphurization of light gas oil and vacuum gas oil using formic acid-hydrogen peroxide mixture as oxidant and N,N-diethylformamide, acetonitrile, methanol, dimethylsulphoxides, sulpholane as solvents for extraction of sulphones. European patent No. 0565324A1 describes a method for recovery of organic sulphur compounds from liquid oil, which involves oxidation of sulphur compounds present in liquid oil by a number of oxidants including formic acid and peroxides followed by removal of organic sulphones by adsorption on alumina or silica. WO patent No.2005019386 discloses a process for desulphurization of hydro carbonaceous oil which involve hydrodesulphurization to reduce sulphur level to a relatively low level, then oxidation of sulphur compounds present in hydrodesulphurized hydro carbonaceous oil to sulphones with an aqueous oxidizing solution like acetic acid, hydrogen peroxide mixture, decomposing residual oxidizing agent on supported transition metal and removal of sulphone by adsorption. US patent 6402940 discloses a process for desulphurization of fuels such as diesel oil and similar products to reduce sulphur contents to a range of from about 2 to 15 ppm which involves oxidation of sulphur compounds present in fuels with a oxidizing solution of formic acid, a small amount of commercial hydrogen peroxide preferably and not more than about 14 wt% of water at slightly elevated temperature followed by separation of fuel from aqueous acid, flashed removal of residual acid / water, neutralization of remaining acid with caustic solution or with anhydrous calcium oxide and removal of sulphones by adsorption on alumina. It is hitherto known that mixture of formic acid and commercial hydrogen peroxide (30%/50%) forms performic acid which is very powerful oxidant for oxidation of various types of sulphur compounds including 4,6-dimethyldibenzothiophene and other condensed thiophene derivatives which are most refractory in hydrodesulphurization, present in hydrocarbon fuels to their corresponding sulphones. It is also hitherto known that sulphones/sulphoxides being more polar can be removed from hydrocarbon fuels either by solvent extraction using polar solvents like N- dimethylformamide, acetonitrile, methanol, dimethylsulfoxides, sulpholane followed by final finishing by passing through alumina/silica/clay or by adsorption alumina/silica to obtain ultra low sulphur hydrocarbon fuels. It is also hitherto know that oxidizing solution of formic acid and hydrogen peroxide should not contain preferably more than 14 wt% water and beyond this formic acid has to be purified by distillation for its reuse (US 6402940) The oxidizing solution used for oxidation of sulphur compounds present in fuels is prepared by mixing formic acid and commercial hydrogen peroxide, which is normally 30% or 50% solution of hydrogen peroxide in water. Hydrogen peroxide solution of more than 50% strength is not safe to handle at industrial scale. With the use of this 30% or 50% solution of hydrogen peroxide large amount of water contained in it also goes to formic acid which necessitate the frequent purification of formic acid to keep water content in oxidizing solution preferably below 14%. Further formic acid is a strong acid and its handling needs special metallurgy equipments. The weak acid like acetic acid when used in place of formic acid for preparation of oxidizing solution did not oxidize sulphur compounds present in hydrocarbon fuels due to the fact that peroxyacetic acid is not formed from acetic acid and commercial hydrogen peroxide (J. Prakt. Chem. 131 (1931) 357. Alkali metal peroxoborates like sodium/potassium peroxoborate are white crystalline solids formed with sodium/potassium tetraborate is treated with commercial 30%/50% aqueous hydrogen peroxide under alkaline conditions. Due to their ease of preparation, commercial availability and reasonably high stability alkali metal peroxoborates find wide applications in oxidations reactions as a substitute for highly concentrated unsafe hydrogen peroxide (J. Chem. Soc., Perkin Trans 1, (2000) 1471; Tetrahedron 51 (1995) 6145; Ullmann's Encyclopedia of Industrial Chemistry Vol. A 19, 177) The main objective of the present invention is to provide a process for oxidative desulphurization of liquid hydrocarbon fuels by using carboxylic acid-alkali metal peroxoborate as oxidation system which obviates the drawbacks as detailed above. Another objective of the present invention is to provide a process for oxidative desulphurization of liquid hydrocarbon fuels such as diesel fuel, gasoline, jet fuel, fuel oil, coal liquids and similar petroleum products to ultra low sulphur hydrocarbon fuels with sulphur content less than 10 ppm. Accordingly the present invention provides a process for oxidative desulphurization of liquid hydrocarbon fuels by using carboxylic acid-alkali metal peroxoborate as oxidation system which comprises oxidation of sulphur compounds present in hydrocarbons fuels, in the temperature range 20-150 °C pressure atmospheric to 10 kg/cm2 for 2 to 60 min in a continuous or batch manner with oxidizing solution consisting of carboxylic acid containing 2-10 moles of alkali metal peroxoborate per mole of sulphur, to sulphones/sulphoxides followed by separation of hydrocarbon fuel from oxidizing solution, water washing and removal of sulphones/sulphoxides from hydrocarbon fuel by solvent extraction and final finishing by passing through a bed of alumina/ silica/clay or alternatively removing the sulphones from hydrocarbon fuels by adsorption on solid alumina/silica. In an embodiment of the present invention liquids hydrocarbon fuels such as diesel fuel, gasoline, jet fuel, fuel oil, coal liquids and similar petroleum products may be both untreated or hydrotreated containing condensed thiophene, benzothiophene and dibenzothiophene type sulphur compounds which are refractory in nature in hydro desulphurization (HDS) most preferably hydrodesulphurized diesel boiling range 167-376°C containing 4,6-dimethyldibenzothiophene and other similar alkyl dibenzothiophene sulphur compounds with total sulphur content less than 500 ppm. In yet another embodiment of the present invention the carboxylic acid used is selected from formic acid, acetic acid, propionic acid, butyric acid preferably formic and acetic acid. In yet another embodiment of the present invention the alkali metal peroxoborate used is selected from sodium, potassium, magnesium, calcium, barium and strontium peroxoborate most preferable sodium peroxoborate. In yet another embodiment of the present invention the oxidation of the sulphur compounds present in hydrocarbon fuels is carried out in the temperature range 20-150 °C preferably 30-100 °C at atmospheric pressure. In yet another embodiment of the present invention the alkali metal peroxoborate used is 2 to 10 mole preferably 2 to 5 mole times of the sulphur present in the hydrocarbon fuels. In yet another embodiment of the present invention the water content of the oxidizing solution consisting of carboxylic acid and alkali metal peroxoborate is preferably 0 to 14%. In yet another embodiment of the present invention the carboxylic acid used is preferably 2 to 20 wt% of the hydrocarbon fuel. In yet another embodiment of the present invention the mole ratio of carboxylic acid to alkali metal peroxoborate is 5:1 to 50:1 preferably 10:1 to 30:1. In yet another embodiment of the present invention as the consumption of alkali metal peroxoborate is dependent upon the sulphur present in the hydrocarbon fuel and cost of this material can have a negative effect on the economics of the process. Therefore this process is most suitable for removal of small amounts of sulphur present in liquid hydrocarbon fuels preferable less than 500 ppm sulphur. In yet another embodiment of the present invention the desulphurized ultra low sulphur hydrocarbon fuel obtained contains total sulphur below 10 ppm. In yet another embodiment of the present invention although this process is capable of removing all types of sulphur such as thiols, disulphide, sulphide and thiophenic from the liquid hydrocarbon fuels, the process is more suitable for liquid hydrocarbon fuels containing condensed thiophene, benzothiophene, dibenzothiophene and alkylated dibenzothiophene type sulphur which is refractory to hydrodesulphurization. Process description: In one of our pending patent application we have described in detail a process along with flow sheet for oxidative desulphurization of liquid hydrocarbon fuels to ultra low sulphur hydrocarbon fuels with sulphur content less than 10 ppm which comprise oxidation of sulphur compounds present in hydrocarbon fuels to more polar sulphones / sulphoxides in a continuous counter current oxidation reactor preferably in the temperature range 30-100 °C at atmospheric pressure preferably for 5-30 minutes with an oxidizing solution consisting of carboxylic acid containing 2 to 10 moles of active oxygen containing species like commercial aqueous hydrogen peroxide, alkali metal peroxoborate, alkaline earth peroxides per mole of sulphur, washing of the oxidized hydrocarbon fuels with alkaline water to remove carboxylic acid present, followed by extraction of sulphones / sulphoxides in a counter current extraction with N-methylpyrolidinone (NMP) containing 5-15 wt% water as antisolvent, water washing to remove entrained NMP, drying through salt filter and final finishing through a bed of alumina, silica or clay. In the oxidative desulphurization process herein contemplated the oxidation of sulphur compounds present in hydrocarbon fuels to more polar sulphones / sulphoxides is carried out in the temperature range 20-150°C with a oxidizing solution consisting of carboxylic acid containing 2 to 10 moles of alkali metal peroxoborate per mole of sulphur, followed by removal of sulphones / sulphoxides from hydrocarbon fuel by solvent extraction and final finishing by passing through a bed of alumina/silica/clay or alternatively removing the sulphones / sulphoxides from hydrocarbon fuel by adsorption on solid alumina/silica/clay The following examples are given by way of illustration and thereof should not be construed to limit the scope of this investigation. Examples: Studies were carried out by using HDS diesel obtained from an Indian refinery as feedstock and its characteristics are given in Table 1 Table:1 (Table Removed) Example 1 As the oxidizing solution consisting of carboxylic acid containing 2 to 10 moles of alkali metal peroxoborate adduct per mole of sulphur has role only in the oxidation of sulphur compounds present in liquid hydrocarbon fuels to sulphones / sulphoxides, experiments were carried out to access its efficiency. Experiments were carried out in a jacketed mixer settler equipped with mechanical stirrer, condenser, thermowel, neck for addition of the reactants and drain valve. The temperature of the reactants was maintained at desired level by circulating by hot fluid in the jacket of the mixer settler. HDS diesel feedstock (100 ml, 83.34 g) was added to the mixer settler and stirrer, hot fluid from circulatory bath were started to keep the temperature of the reactants at 50 °C. Formic acid (5 g) was then added to the diesel in the mixer settler followed by addition of sodium perborate tetrahydrate (1.8 g, 10 mole times of sulphur). The mixture was stirred vigorously at 50 °C for 30 minutes and then taken out in the separating funnel through drain valve. The two layers namely hydrocarbon layer and formic acid layer were then separated. The diesel layer was then washed with water, aqueous sodium bicarbonate and again with water to remove entrained formic acid. The washed diesel layer was then dried on anhydrous sodium sulphate and analyzed by GC SCD, which showed quantitative oxidation of sulphur compounds present to sulphones / sulphoxides. The oxidized diesel thus obtained was extracted with NMP containing 10% water as antisolvent at solvent to feed ratio 2 and the hydrocarbon phase after separation, washing with water, drying on anhydrous sodium sulphate gave sulphur content 45 ppm. The dry low sulphur diesel sample thus obtained on passing through adsorption column filled with silica gel yielded ultra low sulphur diesel containing 5 ppm total sulphur. We claim: 1. A process for oxidative desulphurization of liquid hydrocarbon fuels by using carboxylic acid-alkali metal peroxoborate as oxidation system which comprises of oxidation of sulphur compound present in hydrocarbon fuel in the temperature range 20-150°C, pressure atmospheric to 10kg/cm2 for 2 to 60 min in a continuous or batch manner, with an oxidizing solution consisting of carboxylic acid containing alkali metal peroxoborate in the range of 2-10 mole times of sulphur present in hydrocarbon fuel, to sulphones/sulphoxides, followed by separation of hydrocarbon fuel from oxidizing solution, water washing and removal of sulphones/sulphoxides from hydrocarbon fuel by solvent extraction and final finishing by passing through a bed of alumina/silica/clay or alternatively removing sulphones from hydrocarbon fuels by adsorption on solid alumina/silica. 2. A process as claimed in claim 1, wherein liquid hydrocarbon fuel includes diesel fuel, gasoline, jet fuel, fuel oil, coal liquids and similar petroleum products. 3. A process as claimed in claim 1 wherein liquid hydrocarbon fuels are both untreated or hydrotreated containing condensed thiophene, benzothiophene, dibenzothiophene type sulphur compounds which are refractory in nature in hydrodesulphurization (HDS), preferably hydrotreated liquid hydrocarbon fuels containing less than 500 ppm sulphur. 4. A process as claimed in claim 1, wherein alkali metal peroxoborate is selected from sodium, potassium, magnesium, calcium, barium and strontium peroxoborate most preferably sodium peroxoborate. 5. A process as claimed in claim 1 wherein carboxylic acid used is selected from formic acid, acetic acid, propionic acid and butyric acid preferably formic and acetic acid. 6. A process as claimed in claim 1, wherein alkali metal peroxoborate used is 2-10 mole times of sulphur present in hydrocarbon fuel preferably 2-5 mole times of sulphur present in hydrocarbon fuel. 7. A process as claimed in claim 1, wherein oxidation of sulphur compounds present in liquid hydrocarbon fuels is carried out in the temperature range 20-150°C, pressure atmospheric to 10kg/cm2 preferably in the temperature range 30-100 °C at atmospheric pressure. 8. A process as claimed in claim 1, wherein water content of the oxidizing solution consisting of carboxylic acid and alkali metal peroxoborate is preferably in the range 0-14%. 9. A process as claimed in claim 1, wherein the mole ratio of carboxylic acid to alkali metal peroxoborate in the oxidizing solution used is in the range of 5:1 to 50:1 preferably 10:1 to 30:1. 10. A process as claimed in claim 1, wherein the oxidation of sulphur compounds present in hydrocarbon fuel is affected in 2 to 60 minutes preferably in 7 to 20 minutes. 11. A process as claimed in claim 1, wherein the solvents used for extraction of sulphones /sulphoxides from oxidized hydrocarbon fuel is selected from N,N- dimethylformamide, acetonitrile, methanol, dimethylsulfoxide, sulpholane, N- methylpyrolidinone containing 2-20 % water as antisolvent. 12. A process for oxidative desulphurization of liquid hydrocarbon fuels by using carboxylic acid-alkali metal peroxoborate as oxidation system substantially as herein described with reference to the examples accompanying this specification.

Full Text

The present invention relates to a process for oxidative desulphurization of liquid hydrocarbon fuels by using carboxylic acid-alkali metal peroxoborate as oxidation system.
Particularly the present invention relates to a process for oxidative desulphurization of liquid hydrocarbon fuels such as diesel fuel, gasoline, jet fuel, fuel oil, coal liquids and similar petroleum products to ultra low sulphur hydrocarbon fuels with sulphur content less than 10 ppm.
More particularly, the invention relates to a process for oxidative desulphurization of hydrotreated liquid hydrocarbon fuels such as diesel fuel, gasoline, jet fuel, fuel oil, coal liquids containing condensed thiophene, benzothiophene, dibenzothiophene type sulphur compounds which are refractory in nature, to ultra low sulphur liquid hydrocarbon fuels having sulphur content less than 30 ppm and comprises of oxidation of sulphur compounds present in liquid hydrocarbon fuels with an oxidizing solution consisting of carboxylic acid containing small amounts of alkali metal peroxoborate to sulphones followed by removal of sulphones from the hydrocarbon fuel by solvent extraction and final finishing by passing through a bed of alumina/silica/clay or alternatively removing the sulphones from hydrocarbon fuels by adsorption on solid alumina/silica.
Because of their high energy densities and convenient physical form liquid hydrocarbon fuels such as diesel fuel, gasoline, jet fuel, fuel oil and coal liquids are presently being consumed in vast quantities and their consumption continues to grow at alarming rates. Inevitably, this high consumption is having a major impact on the global environment. Most notably, transport hydrocarbon fuels like diesel fuel, gasoline, and jet fuel are receiving the highest scrutiny due to increased environmental concerns. There is an increasing demand to reduce sulphur content in the liquid hydrocarbon fuels to produce products, which have very low sulphur content and are thereby marketable in the even more demanding marketplace.
Conventionally, hydrodesulphurization of liquid hydrocarbon fuels which involves contacting of hydrogen with hydrocarbon stream in presence of a catalyst at elevated temperature and pressure to convert sulphur compounds present therein to hydrogen sulfide is used to produce hydrocarbon fuels with lower sulphur content. Hydrodesulphurization can easily remove sulphur from several common classes of sulphur compounds such as sulphides,
disulphides and thiols present in hydrocarbon fuels because these are easily accessible to contact with hydrodesulphurization catalyst, however, sulphur compounds like 4,6-dimethyldibenzothiophene (4,6-DMDBT) and other similar thiophene species are rigid to hydrodesulphurization and therefore difficult to remove. Conventional hydro desulphurization of diesel for example that operates at moderate temperatures (315-400°C) and hydrogen pressure 3.0~8.0 MPa with Co/Mo/Al2O3 as catalyst can bring down the sulphur content in the range 300-500 ppm easily. However, to bring down sulphur content further below 100 ppm deep hydrodesulphurization of diesel required very severe conditions like the use of high temperature, high hydrogen pressure, more active catalyst and long residence time. Deep hydrodesulphurization yields negative effects such as reduced catalyst life, high hydrogen consumption and high yield loss thereby resulting in higher operating cost. Apart from the cost involved, the energy requirements for implementation of hydroprocessing technology also leads to increased level of CO2 emissions from refinery itself. The USEPA has released new regulations that require the sulphur content in the diesel fuel used in highway vehicles to be limited to 30 ppm by 2005 and 15 ppm effective by 2006. Similarly, in European countries the sulphur content in the diesel fuel will be limited to 30-50 ppm by 2005. The necessity has therefore been felt for a process complementary to hydro desulphurization to remove condensed thiophene, benzothiophene and dibenzothiophene type sulphur compounds present in hydrodesulphurized hydrocarbon fuels to yield ultra low hydrocarbon fuels
It is known that sulphur compounds present in liquid hydrocarbon fuels can be oxidized to sulphones / sulphoxides and subsequently removed by taking advantage of their different chemical and physical characteristics (Tetsuo Aida et al. 20th American Chemical Society meeting at San Diego, California Mar 13-17 1994). US Pat No 5,958,224 discloses a process for removal of refractory sulphur compounds from hydrotreated hydrocarbon streams by oxidizing them to sulphoxides and sulphones with peroxometal complexes like LMO(O2)2 where M is selected from the groups consisting of Mo, W, Cr and L is alkyl phosphoric triamide like hexamethyl-phosphoric triamide followed by adsorption on solid adsorbents like activated carbon, bauxite, clay, coke, alumina or silica gel. The peroxometal complexes were prepared by reacting metal complexes with hydrogen peroxide Collins et al. (J. Mol. Catal A: Chem 117 (1977) 397) reported their studies on oxidation of sulphur compounds present in
gas oil with hydrogen peroxide using phosphotungstic acid as catalyst, and subsequent removal of the sulphones formed by solvent extraction using y-butyrolactone as solvent or by adsorption on silica gel to obtain ultra low sulphur gas oil. However large amounts of hydrogen peroxide were used for the oxidation of sulphur compounds present in gas oil.
Mei et al. (Fuel 82 (2003) 405) reported their ultrasound assisted studies on oxidative desulphurization of diesel using hydrogen peroxide as oxidant, phosphotungstic acid as catalyst, methanol as solvent for extraction of sulphones and obtained 66.4% overall sulphur removal after 2.5h reaction. The sulphur removal efficiency could be improved to 97.8% by increasing the reaction time to 4 hours and using silica adsorption instead of solvent extraction to remove sulphones from diesel.
US patent No 6368495 discloses a process for oxidative desulpurization of petroleum fractions like gasoline, diesel fuel, kerosene which involves oxidation of thiophene and thiophene derivatives present in petroleum fractions to sulphones with alkyl hydroperoxide in presence of molybdenum on alumina as catalyst followed by decomposition of sulphones using catalyst like double layer hydroxides, molecular sieves, inorganic metal oxides or a mixture thereof.
Ishihara et al. (Applied Catal. A: Gen. 279 (2004) 279) reported oxidative desulphurization of desulphurized light gas oil with sulphur content 39 ppm involving oxidation of the sulphur compounds present therein with tert-butylhydroperoxide in presence of 16 wt% MoO3/ A12O3 as catalyst followed by removal of the sulphones formed by adsorption over silica gel to obtain light gas oil with sulphur content less than 5 ppm.
WO patent No 2004029179 describes a process for oxidative desulphurization of hydrotreated hydrocarbon mixture boiling range 180-360°C containing less than 350 ppm thiophene sulphur involving oxidation of sulphur compounds with organic peroxide in presence of a catalytic composition containing completely amorphous micro and/or meso porous mixed oxides comprising a matrix selected from silica, alumina, ceria, magnesia and mixture thereof wherein one or more metal oxides selected from transition metal oxides and group IVA metal oxides are uniformly dispersed followed by separation of the suphur oxygenated product from the hydrocarbon mixture.
Otsuki et al. (Energy and fuel 14 (2000) 1232) studied the oxidation of the model sulphur compounds with a mixture of hydrogen peroxides and formic acid and found the

reactivity of dibenzothiophene derivative to increase with the increase of electron density. Thus the reactivity order for oxidation was found to be 4,6-dimethyldibenzothiophene> 4-methyldibenzothiophene>dibenzothiophene which is reversed to the order of reactivity for hydrodeslphurization. They further studied the oxidative desulphurization of light gas oil and vacuum gas oil using formic acid-hydrogen peroxide mixture as oxidant and N,N-diethylformamide, acetonitrile, methanol, dimethylsulphoxides, sulpholane as solvents for extraction of sulphones.
European patent No. 0565324A1 describes a method for recovery of organic sulphur compounds from liquid oil, which involves oxidation of sulphur compounds present in liquid oil by a number of oxidants including formic acid and peroxides followed by removal of organic sulphones by adsorption on alumina or silica.
WO patent No.2005019386 discloses a process for desulphurization of hydro carbonaceous oil which involve hydrodesulphurization to reduce sulphur level to a relatively low level, then oxidation of sulphur compounds present in hydrodesulphurized hydro carbonaceous oil to sulphones with an aqueous oxidizing solution like acetic acid, hydrogen peroxide mixture, decomposing residual oxidizing agent on supported transition metal and removal of sulphone by adsorption.
US patent 6402940 discloses a process for desulphurization of fuels such as diesel oil and similar products to reduce sulphur contents to a range of from about 2 to 15 ppm which involves oxidation of sulphur compounds present in fuels with a oxidizing solution of formic acid, a small amount of commercial hydrogen peroxide preferably and not more than about 14 wt% of water at slightly elevated temperature followed by separation of fuel from aqueous acid, flashed removal of residual acid / water, neutralization of remaining acid with caustic solution or with anhydrous calcium oxide and removal of sulphones by adsorption on alumina.
It is hitherto known that mixture of formic acid and commercial hydrogen peroxide (30%/50%) forms performic acid which is very powerful oxidant for oxidation of various types of sulphur compounds including 4,6-dimethyldibenzothiophene and other condensed thiophene derivatives which are most refractory in hydrodesulphurization, present in hydrocarbon fuels to their corresponding sulphones.
It is also hitherto known that sulphones/sulphoxides being more polar can be removed from hydrocarbon fuels either by solvent extraction using polar solvents like N-
dimethylformamide, acetonitrile, methanol, dimethylsulfoxides, sulpholane followed by final finishing by passing through alumina/silica/clay or by adsorption alumina/silica to obtain ultra low sulphur hydrocarbon fuels.
It is also hitherto know that oxidizing solution of formic acid and hydrogen peroxide should not contain preferably more than 14 wt% water and beyond this formic acid has to be purified by distillation for its reuse (US 6402940)
The oxidizing solution used for oxidation of sulphur compounds present in fuels is prepared by mixing formic acid and commercial hydrogen peroxide, which is normally 30% or 50% solution of hydrogen peroxide in water. Hydrogen peroxide solution of more than 50% strength is not safe to handle at industrial scale. With the use of this 30% or 50% solution of hydrogen peroxide large amount of water contained in it also goes to formic acid which necessitate the frequent purification of formic acid to keep water content in oxidizing solution preferably below 14%. Further formic acid is a strong acid and its handling needs special metallurgy equipments. The weak acid like acetic acid when used in place of formic acid for preparation of oxidizing solution did not oxidize sulphur compounds present in hydrocarbon fuels due to the fact that peroxyacetic acid is not formed from acetic acid and commercial hydrogen peroxide (J. Prakt. Chem. 131 (1931) 357.
Alkali metal peroxoborates like sodium/potassium peroxoborate are white crystalline solids formed with sodium/potassium tetraborate is treated with commercial 30%/50% aqueous hydrogen peroxide under alkaline conditions. Due to their ease of preparation, commercial availability and reasonably high stability alkali metal peroxoborates find wide applications in oxidations reactions as a substitute for highly concentrated unsafe hydrogen peroxide (J. Chem. Soc., Perkin Trans 1, (2000) 1471; Tetrahedron 51 (1995) 6145; Ullmann's Encyclopedia of Industrial Chemistry Vol. A 19, 177)
The main objective of the present invention is to provide a process for oxidative desulphurization of liquid hydrocarbon fuels by using carboxylic acid-alkali metal peroxoborate as oxidation system which obviates the drawbacks as detailed above.
Another objective of the present invention is to provide a process for oxidative desulphurization of liquid hydrocarbon fuels such as diesel fuel, gasoline, jet fuel, fuel oil,
coal liquids and similar petroleum products to ultra low sulphur hydrocarbon fuels with sulphur content less than 10 ppm.
Accordingly the present invention provides a process for oxidative desulphurization of liquid hydrocarbon fuels by using carboxylic acid-alkali metal peroxoborate as oxidation system which comprises oxidation of sulphur compounds present in hydrocarbons fuels, in the temperature range 20-150 °C pressure atmospheric to 10 kg/cm2 for 2 to 60 min in a continuous or batch manner with oxidizing solution consisting of carboxylic acid containing 2-10 moles of alkali metal peroxoborate per mole of sulphur, to sulphones/sulphoxides followed by separation of hydrocarbon fuel from oxidizing solution, water washing and removal of sulphones/sulphoxides from hydrocarbon fuel by solvent extraction and final finishing by passing through a bed of alumina/ silica/clay or alternatively removing the sulphones from hydrocarbon fuels by adsorption on solid alumina/silica.
In an embodiment of the present invention liquids hydrocarbon fuels such as diesel fuel, gasoline, jet fuel, fuel oil, coal liquids and similar petroleum products may be both untreated or hydrotreated containing condensed thiophene, benzothiophene and dibenzothiophene type sulphur compounds which are refractory in nature in hydro desulphurization (HDS) most preferably hydrodesulphurized diesel boiling range 167-376°C containing 4,6-dimethyldibenzothiophene and other similar alkyl dibenzothiophene sulphur compounds with total sulphur content less than 500 ppm.
In yet another embodiment of the present invention the carboxylic acid used is selected from formic acid, acetic acid, propionic acid, butyric acid preferably formic and acetic acid.
In yet another embodiment of the present invention the alkali metal peroxoborate used is selected from sodium, potassium, magnesium, calcium, barium and strontium peroxoborate most preferable sodium peroxoborate.
In yet another embodiment of the present invention the oxidation of the sulphur compounds present in hydrocarbon fuels is carried out in the temperature range 20-150 °C preferably 30-100 °C at atmospheric pressure.
In yet another embodiment of the present invention the alkali metal peroxoborate used is 2 to 10 mole preferably 2 to 5 mole times of the sulphur present in the hydrocarbon fuels.
In yet another embodiment of the present invention the water content of the oxidizing solution consisting of carboxylic acid and alkali metal peroxoborate is preferably 0 to 14%.
In yet another embodiment of the present invention the carboxylic acid used is preferably 2 to 20 wt% of the hydrocarbon fuel.
In yet another embodiment of the present invention the mole ratio of carboxylic acid to alkali metal peroxoborate is 5:1 to 50:1 preferably 10:1 to 30:1.
In yet another embodiment of the present invention as the consumption of alkali metal peroxoborate is dependent upon the sulphur present in the hydrocarbon fuel and cost of this material can have a negative effect on the economics of the process. Therefore this process is most suitable for removal of small amounts of sulphur present in liquid hydrocarbon fuels preferable less than 500 ppm sulphur.
In yet another embodiment of the present invention the desulphurized ultra low sulphur hydrocarbon fuel obtained contains total sulphur below 10 ppm.
In yet another embodiment of the present invention although this process is capable of removing all types of sulphur such as thiols, disulphide, sulphide and thiophenic from the liquid hydrocarbon fuels, the process is more suitable for liquid hydrocarbon fuels containing condensed thiophene, benzothiophene, dibenzothiophene and alkylated dibenzothiophene type sulphur which is refractory to hydrodesulphurization. Process description:
In one of our pending patent application we have described in detail a process along with flow sheet for oxidative desulphurization of liquid hydrocarbon fuels to ultra low sulphur hydrocarbon fuels with sulphur content less than 10 ppm which comprise oxidation of sulphur compounds present in hydrocarbon fuels to more polar sulphones / sulphoxides in a continuous counter current oxidation reactor preferably in the temperature range 30-100 °C at atmospheric pressure preferably for 5-30 minutes with an oxidizing solution consisting of carboxylic acid containing 2 to 10 moles of active oxygen containing species like commercial aqueous hydrogen peroxide, alkali metal peroxoborate, alkaline earth peroxides per mole of sulphur, washing of the oxidized hydrocarbon fuels with alkaline water to remove carboxylic acid present, followed by extraction of sulphones / sulphoxides in a counter current extraction with N-methylpyrolidinone (NMP) containing 5-15 wt% water as antisolvent, water washing
to remove entrained NMP, drying through salt filter and final finishing through a bed of
alumina, silica or clay.
In the oxidative desulphurization process herein contemplated the oxidation of sulphur
compounds present in hydrocarbon fuels to more polar sulphones / sulphoxides is carried out
in the temperature range 20-150°C with a oxidizing solution consisting of carboxylic acid
containing 2 to 10 moles of alkali metal peroxoborate per mole of sulphur, followed by
removal of sulphones / sulphoxides from hydrocarbon fuel by solvent extraction and final
finishing by passing through a bed of alumina/silica/clay or alternatively removing the
sulphones / sulphoxides from hydrocarbon fuel by adsorption on solid alumina/silica/clay
The following examples are given by way of illustration and thereof should not be construed
to limit the scope of this investigation.
Examples:
Studies were carried out by using HDS diesel obtained from an Indian refinery as feedstock
and its characteristics are given in Table 1
Table:1
(Table Removed)
Example 1
As the oxidizing solution consisting of carboxylic acid containing 2 to 10 moles of alkali metal peroxoborate adduct per mole of sulphur has role only in the oxidation of sulphur compounds present in liquid hydrocarbon fuels to sulphones / sulphoxides, experiments were carried out to access its efficiency. Experiments were carried out in a jacketed mixer settler equipped with mechanical stirrer, condenser, thermowel, neck for addition of the reactants and drain valve. The temperature of the reactants was maintained at desired level by circulating by hot fluid in the jacket of the mixer settler. HDS diesel feedstock (100 ml, 83.34 g) was added to the mixer settler and stirrer, hot fluid from circulatory bath were started to keep the temperature of the reactants at 50 °C. Formic acid (5 g) was then added to the diesel in the mixer settler followed by addition of sodium perborate tetrahydrate (1.8 g, 10 mole times of sulphur).
The mixture was stirred vigorously at 50 °C for 30 minutes and then taken out in the separating funnel through drain valve. The two layers namely hydrocarbon layer and formic acid layer were then separated. The diesel layer was then washed with water, aqueous sodium bicarbonate and again with water to remove entrained formic acid. The washed diesel layer was then dried on anhydrous sodium sulphate and analyzed by GC SCD, which showed quantitative oxidation of sulphur compounds present to sulphones / sulphoxides. The oxidized diesel thus obtained was extracted with NMP containing 10% water as antisolvent at solvent to feed ratio 2 and the hydrocarbon phase after separation, washing with water, drying on anhydrous sodium sulphate gave sulphur content 45 ppm. The dry low sulphur diesel sample thus obtained on passing through adsorption column filled with silica gel yielded ultra low sulphur diesel containing 5 ppm total sulphur.

We claim:
1. A process for oxidative desulphurization of liquid hydrocarbon fuels by using
carboxylic acid-alkali metal peroxoborate as oxidation system which comprises of
oxidation of sulphur compound present in hydrocarbon fuel in the temperature range
20-150°C, pressure atmospheric to 10kg/cm2 for 2 to 60 min in a continuous or batch
manner, with an oxidizing solution consisting of carboxylic acid containing alkali
metal peroxoborate in the range of 2-10 mole times of sulphur present in hydrocarbon
fuel, to sulphones/sulphoxides, followed by separation of hydrocarbon fuel from
oxidizing solution, water washing and removal of sulphones/sulphoxides from
hydrocarbon fuel by solvent extraction and final finishing by passing through a bed of
alumina/silica/clay or alternatively removing sulphones from hydrocarbon fuels by
adsorption on solid alumina/silica.
2. A process as claimed in claim 1, wherein liquid hydrocarbon fuel includes diesel fuel,
gasoline, jet fuel, fuel oil, coal liquids and similar petroleum products.
3. A process as claimed in claim 1 wherein liquid hydrocarbon fuels are both untreated
or hydrotreated containing condensed thiophene, benzothiophene, dibenzothiophene
type sulphur compounds which are refractory in nature in hydrodesulphurization
(HDS), preferably hydrotreated liquid hydrocarbon fuels containing less than 500
ppm sulphur.
4. A process as claimed in claim 1, wherein alkali metal peroxoborate is selected from
sodium, potassium, magnesium, calcium, barium and strontium peroxoborate most
preferably sodium peroxoborate.
5. A process as claimed in claim 1 wherein carboxylic acid used is selected from formic
acid, acetic acid, propionic acid and butyric acid preferably formic and acetic acid. 6. A process as claimed in claim 1, wherein alkali metal peroxoborate used is 2-10 mole
times of sulphur present in hydrocarbon fuel preferably 2-5 mole times of sulphur
present in hydrocarbon fuel. 7. A process as claimed in claim 1, wherein oxidation of sulphur compounds present in
liquid hydrocarbon fuels is carried out in the temperature range 20-150°C, pressure
atmospheric to 10kg/cm2 preferably in the temperature range 30-100 °C at atmospheric pressure.
8. A process as claimed in claim 1, wherein water content of the oxidizing solution
consisting of carboxylic acid and alkali metal peroxoborate is preferably in the range
0-14%.
9. A process as claimed in claim 1, wherein the mole ratio of carboxylic acid to alkali
metal peroxoborate in the oxidizing solution used is in the range of 5:1 to 50:1
preferably 10:1 to 30:1.
10. A process as claimed in claim 1, wherein the oxidation of sulphur compounds present
in hydrocarbon fuel is affected in 2 to 60 minutes preferably in 7 to 20 minutes.
11. A process as claimed in claim 1, wherein the solvents used for extraction of sulphones
/sulphoxides from oxidized hydrocarbon fuel is selected from N,N-
dimethylformamide, acetonitrile, methanol, dimethylsulfoxide, sulpholane, N-
methylpyrolidinone containing 2-20 % water as antisolvent.
12. A process for oxidative desulphurization of liquid hydrocarbon fuels by using carboxylic acid-alkali metal peroxoborate as oxidation system substantially as herein described with reference to the examples accompanying this specification.

Documents:

1894-del-2005-Abstract-(22-05-2012).pdf

1894-del-2005-abstract.pdf

1894-del-2005-claims.pdf

1894-del-2005-Correspondence Others-(22-05-2012).pdf

1894-del-2005-correspondence-others.pdf

1894-del-2005-description (complete).pdf

1894-del-2005-Form-1-(22-05-2012).pdf

1894-del-2005-form-1.pdf

1894-del-2005-form-18.pdf

1894-del-2005-form-2.pdf

1894-del-2005-Form-3-(22-05-2012).pdf

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Patent Number

253487

Indian Patent Application Number

1894/DEL/2005

PG Journal Number

30/2012

Publication Date

27-Jul-2012

Grant Date

25-Jul-2012

Date of Filing

20-Jul-2005

Name of Patentee

COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	TUMULA VENKATESHWAR RAO	INDIAN INSTITUTE OF PETROLEUM, MOHKAMPUR, DEHRADUN 248005, UTTRANCHAL, INDIA.
2	BIR SAIN	INDIAN INSTITUTE OF PETROLEUM, MOHKAMPUR, DEHRADUN 248005, UTTRANCHAL, INDIA.
3	NAUTIYAL BHAGAT RAM	INDIAN INSTITUTE OF PETROLEUM, MOHKAMPUR, DEHRADUN 248005, UTTRANCHAL, INDIA.
4	DHARAM PAUL	INDIAN INSTITUTE OF PETROLEUM, MOHKAMPUR, DEHRADUN 248005, UTTRANCHAL, INDIA.
5	SHARMA YOGENDRA KUMAR	INDIAN INSTITUTE OF PETROLEUM, MOHKAMPUR, DEHRADUN 248005, UTTRANCHAL, INDIA.
6	NANOTI SHRIKANT MADHUSUDAN	INDIAN INSTITUTE OF PETROLEUM, MOHKAMPUR, DEHRADUN 248005, UTTRANCHAL, INDIA.
7	GARG MADHUKAR ONKARNATH	INDIAN INSTITUTE OF PETROLEUM, MOHKAMPUR, DEHRADUN 248005, UTTRANCHAL, INDIA.
8	GUPTA ASHOK KUMAR	INDIAN INSTITUTE OF PETROLEUM, MOHKAMPUR, DEHRADUN 248005, UTTRANCHAL, INDIA.

PCT International Classification Number

C01B 3/50

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA