Title of Invention	A PROCESS FOR THE PREPARATION OF PLATINUM/SILICA CATALYST USEFUL FOR HYDROGENATION REACTIONS.
Abstract	This invention relates to a process for the preparation of new platinum/silica catalyst useful for hydrogenation reactions. The catalyst prepared by the process of the present invention is useful mainly for the catalytic hydrogenation of unsaturated hydrocarbons. As the catalyst produced by the process of the present invention is reusable, it is of commercial value and the process is cost-effective since it employs very small quantity of platinum, a precious metal. The catalyst prepared by the process of the present invention has surface area in the range 400-480 m2/g, mean pore diameter in the range 180-220 A and 0.8-1.2 µm,

Title of Invention

A PROCESS FOR THE PREPARATION OF PLATINUM/SILICA CATALYST USEFUL FOR HYDROGENATION REACTIONS.

Abstract

Full Text	This invention relates to a process for the preparation of new platinum/silica catalyst useful for hydrogenation reactions . The catalyst prepared by the process of the present invention is useful mainly for the catalytic hydrogenation of unsat-urated hydrocarbons. As the catalyst produced by the process of the present invention is reusable, it is of commercial value and the process is cost-effective since it employs very small quantity of platinum, a precious metal. The catalyst prepared by the process of the present invention has surface area in the range 400-480 m2/g, mean pore diameter in the range 180- 220 Ǻ and 0.8-1.2 µm, with atleast 80% of the pore volume contained in the pores of 0.8-1.2µm. The porous catalyst consists of a network of capilliary channels and has more acidic silanol groups. These silanol groups present in the capillary channels, being acidic attract the base i.e unsaturated hydrocarbons like cyclohexene during hydrogenation towards platinum having adsorbed hydrogen, thus making the hydrogenation more effective Catalysts are generally employed in chemical reactions. Catalyst can be compounds or metals supported on substrates. It is known that metallic catalysts supported on activated carbons have been employed for the production of various chemicals and petrochemicals. However, it has been found that these carbon supported catalysts suffer from the serious draw back of decomposition of the substrate at temperatures as low as 300°C and this restricts the use of carbon supported catalysts at temperatures higher than 300°C. To overcome this problem, silica was thought to be a substrate since silica is stable at high temperatures and is resistant to most of the common acids used in the reactions. Incorporation of metals into the silica is generally achieved by impregnation or by coating using solution of the metallic compounds. The metals in these catalyst carriers can easily be removed since they are present only on the surface. Another method reported in a Dutch patent (DE 4316508) used for the preparation of ceramic based catalytic supports and catalysts employing sol-gel process uses aerogels i.e hyper-critically dried gels. Aerogel is prepared by removal of liquid from the pores of an alcogels by heating the gel in an autoclave beyond the critical temperature and pressure of the liquid. This procedure is called as hypercritical drying. Hypercritical drying for an alcogel generally require a temperature of 300°C and a pressure of about 20MPa of an autoclave. This method is not easily accessible since use of costly equipment like autoclave is essential for this process. Another method using sol-gel process reported in British patent GB 8303574 describes the preparation of primary particles by vapor phase condensation method. By "vapor phase condensation method" is meant a method which involves a vapor phase intermediate. Examples of vapor phase condensation method are hydrolysis of volatile halides or alkoxides, evaporation and condensation using electron beam, D.C. arc or RF plasma heating and metal oxidation to give a smoke which is then condensed. These particles are then dispersed in a liquid, for example water, to form a sol containing colloidal particles which are then processed through sol-gel technique and impregnated with metal to get catalyst. This is a multistep process and require expensive equipments. It is well known that many unsaturated hydrocarbons are evolved during naphtha cracking. The conversion of unsaturated hydrocarbons to saturated hydrocarbons is effected by employing catalyst for hydrogenation reactions. Platinum catalyst supported on carbon/ceramic supports are generally used in hydrogenation reactions. However the choice of catalyst support is one factor influencing the technical, economic and commercial success of catalytic hydrogenation process. In addition, it is very desirable that the catalyst should be so formulated that it enjoys a long life even under hard conditions. Hence there is an urgent need to develope platinum/silica which is reusable, cost effective and withstand higher temperatures of the order of 500°C. The main object of the present invention is therefore to provide a process for the preparation of platinum/silica catalyst useful for hydrogenation reactions which obviates the drawback of the hitherto known processes. Another object of the present invention is to provide a process for the preparation of platinum/silica catalyst by hydrolytic-polycondensation of alkoxides. Yet another object of the present invention is to provide a process for the preparation of platinum/silica catalyst wherein Pt is incorporated in a silica polynetwork consisting of Si-O-Si linkages and Si-OH groups. Yet another object of the present invention is to provide a process for the preparation of platinum/silica catalyst using porous silica polynetwork consisting of Si-O-Si linkages and Si-OH groups which has cage like structure with highly reactive silanol groups. Yet another object of the present invention is to provide a process for the preparation of silica polynetwork consisting of Si-O-Si linkages and Si-OH groups as catalyst carrier, using silicon alkoxides mixture to give carrier high efficiency of catalytic metal particles. The process of the present invention involves preparation of silica polynetwork consisting of Si-O-Si linkages and Si-OH groups by sol gel technique in the presence of platinum salt at room temperature. The gel prepared is referred as doped gel and has the metal in its structure and when sintered in an inert atmosphere and air and then activated in hydrogen atmosphere yields platinum/silica (Pt/SiO2) catalyst in which Pt is incor porated in chemical structure. The reaction mechanism of the process for the preparation of platinum/silica catalyst is explained below in the following steps. Silicon alkoxides dissolved in alcohols are hydrolyzed in the presence of platinum salt: (R)nSi(OR1)4-n > (R)nSi(OR)14-n-m (OH)m The hydrolysed species condense among themselves to give the silica network in which platinum is incorporated in the chemical structure. (R)nSi (OR1) 4-n-m(OH)m — > [(R)nSiO2-n/2] (Pt) (OH) The polynetwork thus obtained is heated in nitrogen and in air which is followed by activation in hydrogen to give the platinum/silica catalyst. [(R)nSiO2-n/2] (Pt) (OH)n > [SiO2] (Pt) (OH) Accordingly the present invention provides A process for the preparation of platinum/silica catalyst useful for hydrogenation reactions which comprises reacting a mixture of silicon alkoxide and alkyl substituted silicon alkoxides with aqueous solution of a mineral acid except sulphuric and phosphoric acid in the presence of a polar organic solvent and a soluble platinum salt, to obtain a sol, maintaining the reaction mixture at a temperature in the range of 40-65°C to get a gel, heating the resultant gel at a temperature in the range of 650 to 750°C in an inert atmosphere till completion of the carbonization of alkyl groups, cooling to room temperature in the inert atmosphere, reheating the resultant gel to a temperature not exceeding 430 to 570°C in the presence of air for a period not exceeding seven hours, cooling to room temperature and activating by heating at a temperature of 380 to 420°C in hydrogen atmosphere to obtain the platinum/ silicon catalyst. The mixture of silicon alkoxides and alkyl substituted silicon alkoxide used consists of alkoxysilane, monoalkylalkoxysilane, dialkylalkoxysilane be in a molar ratio in the range of (9-11) : (2-6) : (0.4-2) respectively. The mineral acid, other than sulphuric and phosphoric acid, water and polar organic solvent used in a molar ratio in the range of (0.005-0.1) : (4-8): (2-8) respectively. The polar organic solvent used may be such as methuanol, ethanol, propanol, acetonitrile, 2-methoxyethanol, 1-2 dimethoxyethane. The soluble platinum salt used may be such as chloroplatinic acid, platinic chloride, platanous chloride and ammonium platinum chloride. The hydrolytic-polycondensation reaction of mixture of alkooxysilanes is effected at room temperature. The inert atmosphere may be provided by using an inert gas such as nitrogen, argon, helium. The process of the present invention is given in detail below A mixture containing alkoxysilane, monoalkylalkoxysilane, dialkylalkoxysilane, and solvent is stirred preferably magneti- cally. To this homogenous mixture aqueous solution of the mineral acid is added and again stirred well to obtain homogeneous solution. Required amount of platinum in the form of its salt is added and stirred for a period not exceeding five hours at a temperature in the range of 40° C to 65° C. The sol thus obtained is maintained at a temperature in the range of 40°C to 60 C for gelling, aging, and drying. The dried gel is heated in an inert atmosphere in the temperature range of 700+50°C and cooled to room temperature in the inert atmosphere and further heated in air at a temperature in the range of 500±70°C for a period up to seven hours and activated by heating in the temperature range of 400±20°C under the stream of hydrogen to get platinum/silica catalyst. The following examples are given by way of illustration and should not be construed to limit the scope of the present invention EXAMPLE 1: A mixture containing 25 ml tetraethoxysilane, 8 ml methyl-triethoxysilane, 2 ml dimethyldiethoxysilane, 15 ml water, 0.5 ml HCl, 20 ml acetonitrile and 200 mg of platinum as chloro-platinic acid is magentically stirred for about five hours at 50°C and gelled at 60°C. The gel is heated in nitrogen atmosphere at 650°C and further heated in air at 500°C. The catalyst is activated by heating at 420°C it under the stream of hydrogen gas, cooled to room temperature and taken out from the heating chamber. The catalyst is subjected to surface analysis studies, surface area of the catalyst developed by this process is found to be 410 m2/g EXAMPLE 2 : The gel is prepared by magnetically stirring 60 ml tetrae-thoxysilane, 25 ml methyltriethoxysilane, 5 ml dimethyldiethox-ysilane, 20 ml of water, 40 ml of ethanol, 0.9 ml of HC1 and 900 mg platinum chloride for about five hours at 45°C. The sol obtained is kept at 50°C for gelling, aging and drying. The dried gel is heated to 700°C in nitrogen atmosphere and at 550°C in air for a period of four hours and activated at 400°C under hydrogen atmosphere. The resultant is cooled to room temperature and taken out from the heating chamber as platinum silica catalyst. When this catalyst was subjected to surface area analysis, the surface area is found to be 470 m2/g The main advantages of the process of the present invention are 1. The catalyst contains platinum content less than 5% by weight and consist of catalytically active form of platinum in the chemical structure of modified silica polynetwork. There fore catalyst of the present invention is economical. 2. The catalyst prepared can be reused after activation as platinum can not be removed during the hydrogenation reactions due to its incorporation in the chemical structure of modified silica polynetwork. 3. The process does not require costly equipments and is a simple process. 4. The catalyst is resistant to most of the acids and also can be used at temperatures upto 500°C, so that the catalyst has wider applications. We Claim: 1. A process for the preparation of platinum/silica catalyst useful for hydrogenation reactions which comprises reacting a mixture of silicon alkoxide and alkyl substituted silicon alkoxides with aqueous solution of a mineral acid except sulphuric and phosphoric acid in the presence of a polar organic solvent and a soluble platinum salt, to obtain a sol, maintaining the reaction mixture at a temperature in the range of 40-65°C to get a gel, heating the resultant gel at a temperature in the range of 650 to 750°C in an inert atmosphere till completion of the carbonization of alkyl groups, cooling to room temperature in the inert atmosphere, reheating the resultant gel to a temperature not exceeding 430 to 570°C in the presence of air for a period not exceeding seven hours, cooling to room temperature and activating by heating at a temperature of 380 to 420°C in hydrogen atmosphere to obtain the platinum/ silicon catalyst. 2. A process as claimed in claim 1 wherein the mixture of silicon alkoxides and alkyl substituted silicon alkoxide used consists of alkoxysilane, monoalkylalkoxysilane, dialkylalkoxysilane in a molar ratio in the range of (9-11) : (2-6) : (0.4-2) respectively. 3. A process as claimed in claims 1 and 2 wherein the mineral acid, other than sulphuric and phosphoric acid, water and polar organic solvent used is in a molar ratio in the range of (0.005-0.1) : (4-8) : (2-8) respectively. 4. A process as claimed in claims 1-3 wherein the polar organic solvent used is selected from methanol, ethanol, propanol, acetonitrile, 2-methoxyethanol, 1- 2dimethoxyethane. 5. A process as claimed in claims 1-4 wherein the soluble platinum salt used is selected from chloroplatinic acid, platinic chloride, platanous chloride and ammonium platinum chloride. 6. A process as claimed in claims 1-5 wherein the hydrolyticpolycondensaiton reaction of mixture of alkoxysilanes is effected at room temperature. 7. A process as claimed in claims 1-6 wherein the inert atmosphere is provided by using nitrogen, argon, or helium. 8. A process for the preparation of platinum/silica catalyst useful fro hydrogenation reactions substantially as herein described with references to the examples.

Full Text

This invention relates to a process for the preparation of new platinum/silica catalyst useful for hydrogenation reactions .
The catalyst prepared by the process of the present invention is useful mainly for the catalytic hydrogenation of unsat-urated hydrocarbons. As the catalyst produced by the process of the present invention is reusable, it is of commercial value and the process is cost-effective since it employs very small quantity of platinum, a precious metal.
The catalyst prepared by the process of the present invention has surface area in the range 400-480 m2/g, mean pore diameter in the range 180- 220 Ǻ and 0.8-1.2 µm, with atleast 80% of the pore volume contained in the pores of 0.8-1.2µm. The porous catalyst consists of a network of capilliary channels and has more acidic silanol groups. These silanol groups present in the capillary channels, being acidic attract the base i.e unsaturated hydrocarbons like cyclohexene during hydrogenation towards platinum having adsorbed hydrogen, thus making the hydrogenation more effective
Catalysts are generally employed in chemical reactions. Catalyst can be compounds or metals supported on substrates. It is known that metallic catalysts supported on activated carbons have been employed for the production of various chemicals and petrochemicals. However, it has been found that these carbon supported catalysts suffer from the serious draw back of decomposition of the substrate at temperatures as low as 300°C and

this restricts the use of carbon supported catalysts at temperatures higher than 300°C. To overcome this problem, silica was thought to be a substrate since silica is stable at high temperatures and is resistant to most of the common acids used in the reactions.
Incorporation of metals into the silica is generally achieved by impregnation or by coating using solution of the metallic compounds. The metals in these catalyst carriers can easily be removed since they are present only on the surface.
Another method reported in a Dutch patent (DE 4316508) used for the preparation of ceramic based catalytic supports and catalysts employing sol-gel process uses aerogels i.e hyper-critically dried gels. Aerogel is prepared by removal of liquid from the pores of an alcogels by heating the gel in an autoclave beyond the critical temperature and pressure of the liquid. This procedure is called as hypercritical drying. Hypercritical drying for an alcogel generally require a temperature of 300°C and a pressure of about 20MPa of an autoclave. This method is not easily accessible since use of costly equipment like autoclave is essential for this process.
Another method using sol-gel process reported in British patent GB 8303574 describes the preparation of primary particles by vapor phase condensation method. By "vapor phase condensation method" is meant a method which involves a vapor phase intermediate. Examples of vapor phase condensation method

are hydrolysis of volatile halides or alkoxides, evaporation and condensation using electron beam, D.C. arc or RF plasma heating and metal oxidation to give a smoke which is then condensed. These particles are then dispersed in a liquid, for example water, to form a sol containing colloidal particles which are then processed through sol-gel technique and impregnated with metal to get catalyst. This is a multistep process and require expensive equipments.
It is well known that many unsaturated hydrocarbons are evolved during naphtha cracking. The conversion of unsaturated hydrocarbons to saturated hydrocarbons is effected by employing catalyst for hydrogenation reactions. Platinum catalyst supported on carbon/ceramic supports are generally used in hydrogenation reactions. However the choice of catalyst support is one factor influencing the technical, economic and commercial success of catalytic hydrogenation process. In addition, it is very desirable that the catalyst should be so formulated that it enjoys a long life even under hard conditions. Hence there is an urgent need to develope platinum/silica which is reusable, cost effective and withstand higher temperatures of the order of 500°C.
The main object of the present invention is therefore to provide a process for the preparation of platinum/silica catalyst useful for hydrogenation reactions which obviates the drawback of the hitherto known processes.

Another object of the present invention is to provide a process for the preparation of platinum/silica catalyst by hydrolytic-polycondensation of alkoxides.
Yet another object of the present invention is to provide a process for the preparation of platinum/silica catalyst wherein Pt is incorporated in a silica polynetwork consisting of Si-O-Si linkages and Si-OH groups.
Yet another object of the present invention is to provide a process for the preparation of platinum/silica catalyst using porous silica polynetwork consisting of Si-O-Si linkages and Si-OH groups which has cage like structure with highly reactive silanol groups.
Yet another object of the present invention is to provide a process for the preparation of silica polynetwork consisting of Si-O-Si linkages and Si-OH groups as catalyst carrier, using silicon alkoxides mixture to give carrier high efficiency of catalytic metal particles.
The process of the present invention involves preparation of
silica polynetwork consisting of Si-O-Si linkages and Si-OH
groups by sol gel technique in the presence of platinum salt at
room temperature. The gel prepared is referred as doped gel and
has the metal in its structure and when sintered in an inert
atmosphere and air and then activated in hydrogen atmosphere
yields platinum/silica (Pt/SiO2) catalyst in which Pt is incor
porated in chemical structure.

The reaction mechanism of the process for the preparation of platinum/silica catalyst is explained below in the following steps.
Silicon alkoxides dissolved in alcohols are hydrolyzed in the presence of platinum salt:
(R)nSi(OR1)4-n > (R)nSi(OR)14-n-m (OH)m
The hydrolysed species condense among themselves to give the silica network in which
platinum is incorporated in the chemical structure. (R)nSi (OR1) 4-n-m(OH)m — >
[(R)nSiO2-n/2] (Pt) (OH)
The polynetwork thus obtained is heated in nitrogen and in air which is followed by activation in hydrogen to give the platinum/silica catalyst.
[(R)nSiO2-n/2] (Pt) (OH)n > [SiO2] (Pt) (OH)
Accordingly the present invention provides A process for the preparation of platinum/silica catalyst useful for hydrogenation reactions which comprises reacting a mixture of silicon alkoxide and alkyl substituted silicon alkoxides with aqueous solution of a mineral acid except sulphuric and phosphoric acid in the presence of a polar organic solvent and a soluble platinum salt, to obtain a sol, maintaining the reaction mixture at a temperature in the range of 40-65°C to get a gel, heating the resultant gel at a temperature in the range of 650 to 750°C in an inert atmosphere till completion of the carbonization of alkyl groups, cooling to room temperature in the inert atmosphere, reheating the resultant gel to a temperature not exceeding 430 to 570°C in the presence of air for a period not exceeding seven hours, cooling to room temperature and activating by heating at a temperature of 380 to 420°C in hydrogen atmosphere to obtain the platinum/ silicon catalyst.

The mixture of silicon alkoxides and alkyl substituted silicon alkoxide used consists of alkoxysilane, monoalkylalkoxysilane, dialkylalkoxysilane be in a molar ratio in the range of (9-11) : (2-6) : (0.4-2) respectively.
The mineral acid, other than sulphuric and phosphoric acid, water and polar organic solvent used in a molar ratio in the range of (0.005-0.1) : (4-8): (2-8) respectively.
The polar organic solvent used may be such as methuanol, ethanol, propanol, acetonitrile, 2-methoxyethanol, 1-2 dimethoxyethane.
The soluble platinum salt used may be such as chloroplatinic acid, platinic chloride, platanous chloride and ammonium platinum chloride.
The hydrolytic-polycondensation reaction of mixture of alkooxysilanes is effected at room temperature.
The inert atmosphere may be provided by using an inert gas such as nitrogen, argon, helium.
The process of the present invention is given in detail below
A mixture containing alkoxysilane, monoalkylalkoxysilane, dialkylalkoxysilane, and solvent is stirred preferably magneti-

cally. To this homogenous mixture aqueous solution of the mineral acid is added and again stirred well to obtain homogeneous solution. Required amount of platinum in the form of its salt is added and stirred for a period not exceeding five hours at a temperature in the range of 40° C to 65° C. The sol thus obtained is maintained at a temperature in the range of 40°C to 60 C for gelling, aging, and drying. The dried gel is heated in an inert atmosphere in the temperature range of 700+50°C and cooled to room temperature in the inert atmosphere and further heated in air at a temperature in the range of 500±70°C for a period up to seven hours and activated by heating in the temperature range of 400±20°C under the stream of hydrogen to get platinum/silica catalyst.
The following examples are given by way of illustration and should not be construed to limit the scope of the present invention
EXAMPLE 1:
A mixture containing 25 ml tetraethoxysilane, 8 ml methyl-triethoxysilane, 2 ml dimethyldiethoxysilane, 15 ml water, 0.5 ml HCl, 20 ml acetonitrile and 200 mg of platinum as chloro-platinic acid is magentically stirred for about five hours at 50°C and gelled at 60°C. The gel is heated in nitrogen atmosphere at 650°C and further heated in air at 500°C. The catalyst is activated by heating at 420°C it under the stream of hydrogen gas, cooled to room temperature and taken out from the

heating chamber. The catalyst is subjected to surface analysis studies, surface area of the catalyst developed by this process is found to be 410 m2/g
EXAMPLE 2 :
The gel is prepared by magnetically stirring 60 ml tetrae-thoxysilane, 25 ml methyltriethoxysilane, 5 ml dimethyldiethox-ysilane, 20 ml of water, 40 ml of ethanol, 0.9 ml of HC1 and 900 mg platinum chloride for about five hours at 45°C. The sol obtained is kept at 50°C for gelling, aging and drying. The dried gel is heated to 700°C in nitrogen atmosphere and at 550°C in air for a period of four hours and activated at 400°C under hydrogen atmosphere. The resultant is cooled to room temperature and taken out from the heating chamber as platinum silica catalyst. When this catalyst was subjected to surface area analysis, the surface area is found to be 470 m2/g
The main advantages of the process of the present invention are
1. The catalyst contains platinum content less than 5% by
weight and consist of catalytically active form of platinum in
the chemical structure of modified silica polynetwork. There
fore catalyst of the present invention is economical.
2. The catalyst prepared can be reused after activation as
platinum can not be removed during the hydrogenation reactions

due to its incorporation in the chemical structure of modified silica polynetwork.
3. The process does not require costly equipments and is a
simple process.
4. The catalyst is resistant to most of the acids and also can
be used at temperatures upto 500°C, so that the catalyst has
wider applications.

We Claim:
1. A process for the preparation of platinum/silica catalyst useful for hydrogenation
reactions which comprises reacting a mixture of silicon alkoxide and alkyl
substituted silicon alkoxides with aqueous solution of a mineral acid except
sulphuric and phosphoric acid in the presence of a polar organic solvent and a
soluble platinum salt, to obtain a sol, maintaining the reaction mixture at a
temperature in the range of 40-65°C to get a gel, heating the resultant gel at a
temperature in the range of 650 to 750°C in an inert atmosphere till completion of
the carbonization of alkyl groups, cooling to room temperature in the inert
atmosphere, reheating the resultant gel to a temperature not exceeding 430 to
570°C in the presence of air for a period not exceeding seven hours, cooling to
room temperature and activating by heating at a temperature of 380 to 420°C in
hydrogen atmosphere to obtain the platinum/ silicon catalyst.
2. A process as claimed in claim 1 wherein the mixture of silicon alkoxides and
alkyl substituted silicon alkoxide used consists of alkoxysilane,
monoalkylalkoxysilane, dialkylalkoxysilane in a molar ratio in the range of (9-11)
: (2-6) : (0.4-2) respectively.
3. A process as claimed in claims 1 and 2 wherein the mineral acid, other than
sulphuric and phosphoric acid, water and polar organic solvent used is in a molar
ratio in the range of (0.005-0.1) : (4-8) : (2-8) respectively.
4. A process as claimed in claims 1-3 wherein the polar organic solvent used is
selected from methanol, ethanol, propanol, acetonitrile, 2-methoxyethanol, 1-
2dimethoxyethane.
5. A process as claimed in claims 1-4 wherein the soluble platinum salt used is
selected from chloroplatinic acid, platinic chloride, platanous chloride and
ammonium platinum chloride.
6. A process as claimed in claims 1-5 wherein the hydrolyticpolycondensaiton
reaction of mixture of alkoxysilanes is effected at room temperature.
7. A process as claimed in claims 1-6 wherein the inert atmosphere is provided by
using nitrogen, argon, or helium.
8. A process for the preparation of platinum/silica catalyst useful fro hydrogenation
reactions substantially as herein described with references to the examples.

Documents:

1806-del-1996-abstract.pdf

1806-del-1996-claims.pdf

1806-del-1996-complete specification (granted).pdf

1806-del-1996-correspondence-others.pdf

1806-del-1996-correspondence-po.pdf

1806-del-1996-description (complete).pdf

1806-del-1996-form-1.pdf

1806-del-1996-form-2.pdf

1806-del-1996-form-4.pdf

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Patent Number

218116

Indian Patent Application Number

1806/DEL/1996

PG Journal Number

40/2008

Publication Date

03-Oct-2008

Grant Date

31-Mar-2008

Date of Filing

14-Aug-1996

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	VIRENDRA KUMAR PARASHAR	NATIONAL PHYSICAL LABORATORY, DR. K.S. KRISHNAN MARG, NEW DELHI-110012, INDIA.
2	VASANTHA RAMAN	NATIONAL PHYSICAL LABORATORY, DR. K.S. KRISHNAN MARG, NEW DELHI-110012, INDIA.
3	OM PRAKASH BAHL	NATIONAL PHYSICAL LABORATORY, DR. K.S. KRISHNAN MARG, NEW DELHI-110012, INDIA.

PCT International Classification Number

C07C 5/02

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA