Title of Invention	A PROCESS FOR THE PREPARATION OF IMPROVED FIBROUS ACTIVATED CARBON USEFUL FOR THE FILTRATION OF CARCINOGENIC VAPOURS IN TOBACCO BASED SMOKING DEVICES
Abstract	A process for the preparation of improved fibrous activated carbon useful for the filtration of carcinogenic vapours in tobacco based smoking devices by impregnating fibrous activated carbon with water of the type as herein described by conventional methods, subjecting the resultant water impregnated fibrous activated carbon to vacuum at a pressure in the range of 1 to 0.0001 ton- for a period of at least 10 minutes at a temperature in the range of 200-700OC to obtain the improved activated carbon.

Title of Invention

A PROCESS FOR THE PREPARATION OF IMPROVED FIBROUS ACTIVATED CARBON USEFUL FOR THE FILTRATION OF CARCINOGENIC VAPOURS IN TOBACCO BASED SMOKING DEVICES

Abstract

A process for the preparation of improved fibrous activated carbon useful for the filtration of carcinogenic vapours in tobacco based smoking devices by impregnating fibrous activated carbon with water of the type as herein described by conventional methods, subjecting the resultant water impregnated fibrous activated carbon to vacuum at a pressure in the range of 1 to 0.0001 ton- for a period of at least 10 minutes at a temperature in the range of 200-700OC to obtain the improved activated carbon.

Full Text	This invention relates to a process for the preparation of improved fibrous activated carbon useful for the filtration of carcinogenic vapours in tobacco based smoking devices. This invention more particularly relates to a process for the preparation of fibrous activated carbon having meso pores which will be useful for trapping molecules greater than 7-8 A° in size such as benzene. Flexible activated carbon prepared by the process of the present invention is particularly useful in adsorptive filtration devices for the filtration of carcinogenic vapours and gases. The products obtained by the process of the present invention are used at the ends of tobacco based smoking devices for the adsorption of harmful vapours thus significantly reducing the health risk to the users. Existing filtering materials like cotton and natural and synthetic fabrics perfomi mainly mechanical filtenng as these materials have a negligible adsorption capacity. Porous materials which have a large surface area, like activated carbons, zeolites etc., have a very high adsorption capacity and thus are more suitable in filtering devices. In addition the adsorption of gases and vapours on high surface area materials is, in general, extremely fast as the adsorption process is physical in nature and occurs spontaneously. In UK Patent Application GB 2, 164, 870 (1986), a two stage granular activated carbon fluid filter is described which can be used for the removal of noxious substances fi-om air and other gases. The filter assembly consists of a pleated paper layer for mechanical filtering in series with activated carbon granules to purify air and other gases. A carbon filter for purification of solvent containing air is described in Swedish patent SE 425,632 (1981). This filter, which can be regenerated with steam, consists of a bed of carbon contained in a vessel that has an inlet for contaminated air, an outlet for purified air, an inlel for steam and a bottom opening for drawing condensate. In German patents DE 3,813,562 (1989) and DE 3,813,564 (1989). activated carbon filter for gas masks are described. The filtering element consists of granular or spherical activated carbon particles having diameter in the range of 0.1-1.0 mm. The activated carbon particles can optionally be impregnated with metal compounds. French patent (FR 2599761; 1987) describes textile fibers for manufacture of high surface area activated carbon based filtering bed and its use. The textile fiber comprises of an inert core surrounded by carbonized and activated fibers, which after activation have a specific surface area (>1000 m2/g). The above patents describe two and/or three stage filtering devices utilizing activated carbons. The fibrous activated carbon obtained by the process of the present invention can be used as single stage filters. The textile morphology that is retained in the fibers obtained by the process of the present invention results in ease of handling and shaping of the filtering devices for example as rolls and disks. In addition, the fibrous forms of activated carbon have a higher adsorption capacity and higher rate of adsorption as compared to granular forms of activated carbon. In our Indian patent ,No. 175522 we have described and claimed an improved process for the preparation of activated carbon fibres /cloth. The products obtained by the said patent are microporous in nature and are usefiil only for general purpose filteration of pollutants and needs modifications in the properties to be used for particular pollutants. The main objective of the present invention is to provide a process for the preparation of improved fibrous activated carbon usefiil for the filtration of carcinogenic vapours in tobacco based smoking devices. Another objective of the present invention is to provide a process for the preparation of fibrous activated carbon having micro and mesopores with enhanced filtering capacity for toxic vapours like tarry materials, nicotine and polycyclic aromatic hydrocarbons. The present invention is based on the high efficiency and high adsorptive capacity of fibrous activated carbon for adsorbing organic vapours. The fibrous forms of activated carbon have a well developed internal pore structure and a high specific surface area thus rendering the material suitable for adsorption for organic vapours. The pore structure of the fibrous activated carbon can be tailored according to the nature of the adsorbates and the conditions under which adsorption takes place. Thus, for large organic molecules the pore size in the fibrous activated carbon can be increased to include supermicropores or even mesopores. An inherent characteristic of physical adsorption is that it involves only weak vander waals/dispersion forces of attraction between the adsorbate molecules and the adsorbent surface thus making the adsorptive process reversible with no accompanying structural changes taking place. Accordingly, the present invention provides a process for the preparation of improved fibrous activated carbon useful for the filtration of carcinogenic vapours in tobacco based smoking devices which comprises impregnating fibrous activated carbon with water of the t>'pe as herein described by conventional methods, subjecting the resultant water impregnated fibrous activated carbon to vacuum at a pressure in the range of 1 to 0.0001 torr for a period of at least 10 minutes at a temperature in the range of 200-700'C to obtain the improved activated carbon. The fibrous activated carbon used may be such as microporous, supermicroporous. or a combination thereof The water used may be such as clean tap water, distilled water or deionized water. The impregnation of fibrous activated carbon may be effected using conventional methods such as underwater boiling of the fibrous activated carbon, or subjecting the immersed fibrous activated carbon to low pressure, immersing the fibrous activated carbon in water and allow It to soak fully. The fibrous activated carbon may be subjected to vacuum at a pressure of at least 1 ton for a period of at least 10 minutes. In the process of the present invention the modified activated carbon provides high efficiency adsorption of toxic organic vapours dueto the enlarged pores of the fibrous activated carbon. In the process of the present invention activated carbon fibres are impregnated with water either by immersing in water till fully soaked or by immersing in water under reduced pressure or boiled in water so that the existing pores in the predominantly microporous fibres are completely filled with water. The fibres thus impregnated with water are subjected to a vacuum in the range of Itorr- .0001 torr at a temperature in the range of 200 to 700 °C for a period of 10 to 60 min to induce sputtering and steam oxidation which results in increase of pores size. The sputtering and steam oxidation may be effected in a vacuum oven maintained at a temperature in the range of 200-700 C for a period of 10-60 min. at a pressure of at least 1 torr. The drying process involves the explosive evolution of the water trapped in the pores of the fibrous activated carbon thereby increasing the size of the micropores to either supermicropores or even mesopores which are suitable for the adsorption of long chain organic vapours like poly-aromatic hydrocarbons (PAH.) The following examples are given by way of illustration of the present invention and should not be construed to limit the scope of the present invention. Example 1 As-received activated carbon cloth was dipped in distilled water and subjected to reduced pressure of 1 torr by means of a rotary vacuum pump for a period of 10 minutes. The water impregnated activated carbon cloth was then placed in a preheated chamber (temperature of chamber 200 °C). The chamber was immediately evacuated with a vacuum pump for a period of 20 minutes to a pressure of 0.1 torr and maintained for a period of ,20 minutes. The dried activated carbon cloth was cut into 0.8 cm X 5.0 cm pieces. The pieces were rolled and attached to the ends of cigarettes. Comparative studies of different filters was done. Example 2 As-received activated carbon cloth was dipped in distilled water and subjected to reduced pressure by means of a rotary vacuum pump for a period of 20 minutes. The wetted activated carbon cloth was then placed in a preheated chamber (temperature of chamber 300 °C). The chamber was immediately evacuated with a vacuum pump for a period of 45 minutes at a pressure of 0.05 torr. The dried activated carbon cloth was cut into 0.8 cm X 5.0 cm pieces. The pieces were rolled into cylinders and attached to the ends of cigarettes. The main advantages of the process of the present invention are 1. The products obtained by the present process have a high capacity of adsorption for organic vapours such as methanol, toluene,acetone. 2. The products obtained by the present process are inherently hydrophobic so that water vapour, which is not harmful to the human body, is not adsorbed. 3. The products obtained by the present process retain their flexibility making the material easy to handle and store. We claim 1. A process for the preparation of improved fibrous activated carbon useful for the filtration of carcinogenic vapours in tobacco based smoking devices which comprises impregnating fibrous activated carbon with water of the type as herein described by conventional methods, subjecting the resultant water impregnated fibrous activated carbon to vacuum at a pressure in the range of 1 to 0.0001 torr for a period of at least 10 minutes at a temperature in the range of 200-700oC to obtain the improved activated carbon. 2. A process as claimed in claim 1 wherein the fibrous activated carbon used is microporous, supermicroporous, mesoporous or a combination thereof. 3. A process as claimed in claims 1-2 wherein the water used for impregnating the fibrous activated carbon is such as tap water, dieonized water or distilled water. 4. A process for the preparation of improved fibrous activated carbon useful for the filtration of carcinogenic vapours in tobacco based smoking devices substantially as herein described with reference to the examples.

Full Text

This invention relates to a process for the preparation of improved fibrous activated carbon useful for the filtration of carcinogenic vapours in tobacco based smoking devices. This invention more particularly relates to a process for the preparation of fibrous activated carbon having meso pores which will be useful for trapping molecules greater than 7-8 A° in size such as benzene. Flexible activated carbon prepared by the process of the present invention is particularly useful in adsorptive filtration devices for the filtration of carcinogenic vapours and gases.
The products obtained by the process of the present invention are used at the ends of tobacco based smoking devices for the adsorption of harmful vapours thus significantly reducing the health risk to the users.
Existing filtering materials like cotton and natural and synthetic fabrics perfomi mainly mechanical filtenng as these materials have a negligible adsorption capacity. Porous materials which have a large surface area, like activated carbons, zeolites etc., have a very high adsorption capacity and thus are more suitable in filtering devices. In addition the adsorption of gases and vapours on high surface area materials is, in general, extremely fast as the adsorption process is physical in nature and occurs spontaneously.
In UK Patent Application GB 2, 164, 870 (1986), a two stage granular activated carbon fluid filter is described which can be used for the removal of noxious substances fi-om air and other gases. The filter assembly consists of a pleated paper layer for mechanical filtering in series with activated carbon granules to purify air and other gases.
A carbon filter for purification of solvent containing air is described in Swedish patent SE 425,632 (1981). This filter, which can be regenerated with steam, consists of a bed of carbon contained in a vessel that has an inlet for contaminated air, an outlet for purified air, an inlel for steam and a bottom opening for drawing condensate.
In German patents DE 3,813,562 (1989) and DE 3,813,564 (1989). activated carbon filter for
gas masks are described. The filtering element consists of granular or spherical activated carbon particles having diameter in the range of 0.1-1.0 mm. The activated carbon particles can optionally be impregnated with metal compounds.
French patent (FR 2599761; 1987) describes textile fibers for manufacture of high surface area activated carbon based filtering bed and its use. The textile fiber comprises of an inert core surrounded by carbonized and activated fibers, which after activation have a specific surface area (>1000 m2/g).
The above patents describe two and/or three stage filtering devices utilizing activated carbons. The fibrous activated carbon obtained by the process of the present invention can be used as single stage filters. The textile morphology that is retained in the fibers obtained by the process of the present invention results in ease of handling and shaping of the filtering devices for example as rolls and disks. In addition, the fibrous forms of activated carbon have a higher adsorption capacity and higher rate of adsorption as compared to granular forms of activated carbon. In our Indian patent ,No. 175522 we have described and claimed an improved process for the preparation of activated carbon fibres /cloth. The products obtained by the said patent are microporous in nature and are usefiil only for general purpose filteration of pollutants and needs modifications in the properties to be used for particular pollutants.
The main objective of the present invention is to provide a process for the preparation of improved fibrous activated carbon usefiil for the filtration of carcinogenic vapours in tobacco based smoking devices.
Another objective of the present invention is to provide a process for the preparation of fibrous activated carbon having micro and mesopores with enhanced filtering capacity for toxic vapours like tarry materials, nicotine and polycyclic aromatic hydrocarbons.
The present invention is based on the high efficiency and high adsorptive capacity of fibrous
activated carbon for adsorbing organic vapours. The fibrous forms of activated carbon have a well developed internal pore structure and a high specific surface area thus rendering the material suitable for adsorption for organic vapours. The pore structure of the fibrous activated carbon can be tailored according to the nature of the adsorbates and the conditions under which adsorption takes place. Thus, for large organic molecules the pore size in the fibrous activated carbon can be increased to include supermicropores or even mesopores. An inherent characteristic of physical adsorption is that it involves only weak vander waals/dispersion forces of attraction between the adsorbate molecules and the adsorbent surface thus making the adsorptive process reversible with no accompanying structural changes taking place.
Accordingly, the present invention provides a process for the preparation of improved fibrous activated carbon useful for the filtration of carcinogenic vapours in tobacco based smoking devices which comprises impregnating fibrous activated carbon with water of the t>'pe as herein described by conventional methods, subjecting the resultant water impregnated fibrous activated carbon to vacuum at a pressure in the range of 1 to 0.0001 torr for a period of at least 10 minutes at a temperature in the range of 200-700'C to obtain the improved activated carbon.
The fibrous activated carbon used may be such as microporous, supermicroporous. or a combination thereof The water used may be such as clean tap water, distilled water or deionized water.
The impregnation of fibrous activated carbon may be effected using conventional methods such as underwater boiling of the fibrous activated carbon, or subjecting the immersed fibrous activated carbon to low pressure, immersing the fibrous activated carbon in water and allow It to soak fully.
The fibrous activated carbon may be subjected to vacuum at a pressure of at least 1 ton for a period of at least 10 minutes.
In the process of the present invention the modified activated carbon provides high efficiency
adsorption of toxic organic vapours dueto the enlarged pores of the fibrous activated carbon.
In the process of the present invention activated carbon fibres are impregnated with water either
by immersing in water till fully soaked or by immersing in water under reduced pressure or boiled
in water so that the existing pores in the predominantly microporous fibres are completely filled
with water. The fibres thus impregnated with water are subjected to a vacuum in the range of
Itorr- .0001 torr at a temperature in the range of 200 to 700 °C for a period of 10 to 60 min to
induce sputtering and steam oxidation which results in increase of pores size. The sputtering and
steam oxidation may be effected in a vacuum oven maintained at a temperature in the range of
200-700 C for a period of 10-60 min. at a pressure of at least 1 torr. The drying process involves
the explosive evolution of the water trapped in the pores of the fibrous activated carbon thereby
increasing the size of the micropores to either supermicropores or even mesopores which are
suitable for the adsorption of long chain organic vapours like poly-aromatic hydrocarbons
(PAH.)
The following examples are given by way of illustration of the present invention and should not
be construed to limit the scope of the present invention.
Example 1
As-received activated carbon cloth was dipped in distilled water and subjected to reduced
pressure of 1 torr by means of a rotary vacuum pump for a period of 10 minutes. The water
impregnated activated carbon cloth was then placed in a preheated chamber (temperature of
chamber 200 °C). The chamber was immediately evacuated with a vacuum pump for a period of
20 minutes to a pressure of 0.1 torr and maintained for a period of ,20 minutes. The dried
activated carbon cloth was cut into 0.8 cm X 5.0 cm pieces. The pieces were rolled and attached
to the ends of cigarettes. Comparative studies of different filters was done.
Example 2
As-received activated carbon cloth was dipped in distilled water and subjected to reduced pressure by means of a rotary vacuum pump for a period of 20 minutes. The wetted activated carbon cloth was then placed in a preheated chamber (temperature of chamber 300 °C). The chamber was immediately evacuated with a vacuum pump for a period of 45 minutes at a pressure of 0.05 torr. The dried activated carbon cloth was cut into 0.8 cm X 5.0 cm pieces. The pieces were rolled into cylinders and attached to the ends of cigarettes. The main advantages of the process of the present invention are
1. The products obtained by the present process have a high capacity of adsorption for organic vapours such as methanol, toluene,acetone.
2. The products obtained by the present process are inherently hydrophobic so that water vapour, which is not harmful to the human body, is not adsorbed.
3. The products obtained by the present process retain their flexibility making the material easy to handle and store.

We claim
1. A process for the preparation of improved fibrous activated carbon useful for the filtration of carcinogenic vapours in tobacco based smoking devices which comprises impregnating fibrous activated carbon with water of the type as herein described by conventional methods, subjecting the resultant water impregnated fibrous activated carbon to vacuum at a pressure in the range of 1 to 0.0001 torr for a period of at least 10 minutes at a temperature in the range of 200-700oC to obtain the improved activated carbon.
2. A process as claimed in claim 1 wherein the fibrous activated carbon used is microporous, supermicroporous, mesoporous or a combination thereof.
3. A process as claimed in claims 1-2 wherein the water used for impregnating the fibrous activated carbon is such as tap water, dieonized water or distilled water.
4. A process for the preparation of improved fibrous activated carbon useful for the filtration of carcinogenic vapours in tobacco based smoking devices substantially as herein described with reference to the examples.

Documents:

1263-del-1997-abstract.pdf

1263-del-1997-claims.pdf

1263-del-1997-correspondence-others.pdf

1263-del-1997-correspondence-po.pdf

1263-del-1997-description (complete).pdf

1263-del-1997-form-1.pdf

1263-del-1997-form-19.pdf

1263-del-1997-form-2.pdf

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Patent Number

254077

Indian Patent Application Number

1263/DEL/1997

PG Journal Number

38/2012

Publication Date

21-Sep-2012

Grant Date

18-Sep-2012

Date of Filing

13-May-1997

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	JAGAN NATH BOHRA	NATIOANAL PHYSICAL LABORATORY NEW DELHI, INDIA.
2	RANJAN KOTHARI	NATIOANAL PHYSICAL LABORATORY NEW DELHI, INDIA.
3	RAJIV KUMAR SAXENA	NATIOANAL PHYSICAL LABORATORY NEW DELHI, INDIA.
4	RANBIR SINGH	NATIOANAL PHYSICAL LABORATORY NEW DELHI, INDIA.
5	ERODE SUBRAMANIAN RAJA GOPAL	NATIOANAL PHYSICAL LABORATORY NEW DELHI, INDIA.

PCT International Classification Number

B01D 39/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA