FR2841438A1 - CIGARETTE COMPRISING A CATALYST FOR THE TREATMENT OF SMOKE - Google Patents

Abstract

The invention relates to a cigarette comprising a catalyst for the treatment of fumes.The cigarette according to the invention is characterized in that it comprises either in the tobacco, in the paper surrounding the tobacco, or in the filter, as catalyst for the treatment of fumes, at least one compound chosen from: - compounds based on at least one oxide or hydroxide of a rare earth, zirconium or manganese; - zinc aluminate; base of at least one metal selected from the elements included in groups IIIA to IIB of the periodic table on a support based on silica and titanium oxide.

Description

CIGARETTE COMPRISING A CATALYST FOR TREATMENT

SMOKE

  The present invention relates to a cigarette comprising a catalyst

for the treatment of fumes.

  It is known that cigarette smoke contains many compounds that can be harmful to health. There may be mentioned in particular carbon monoxide, NOx nitrogen oxides, organic compounds of the nitrosamine, aldehyde, hydrocarbon or aromatic amine type and organic compounds having carboxylate, sulphate, sulphonate or PO 2 functions. These fumes may also contain cadmium type metals,

  nickel or zinc. These fumes are furthermore constituted of fine particles.

  In order to reduce the harmfulness of cigarettes, we are therefore looking for

ways to treat these fumes.

  The object of the invention is the development of a catalyst capable of

  to eliminate or make harmful the harmful compounds of these fumes.

  For this purpose, the cigarette according to the invention is characterized in that it comprises either in the tobacco, or in the paper surrounding the tobacco, or in the filter, as a catalyst for the treatment of fumes, at least one compound selected from: - compounds based on at least one oxide or hydroxide of a rare earth, zirconium or manganese; zinc aluminate; a compound based on at least one metal chosen from the elements included in groups IIIA to IIB of the periodic table on a

  support based on silica and titanium oxide.

  The catalyst of the invention allows oxidation of CO to CO2. It also promotes the combustion of the particles contained in the fumes. It also allows the reduction of nitrogen oxides in the fumes. It can also act as a complexing agent for the organic compounds and metals mentioned above. he

  can finally act as oxidant of hydrocarbon compounds.

  Other features, details and advantages of the invention will become apparent

  even more completely by reading the following description.

  The periodic table of elements referred to is that published in the Supplement to the Bulletin of the Chemical Society of

France, 1 January 1966).

  Rare earth means the elements of the group constituted by yttrium and the elements of the Periodic Classification including atomic number

inclusive between 57 and 71.

  By specific surface is meant the specific surface B.E.T.

  determined by nitrogen adsorption according to ASTM D 3663-78 based on the BRUNAUER - EMMETT-TELLER method described in

  the periodical "The Journal of the American Chemical Society, 60, 309 (1938)".

  The catalyst of the invention may be present in the cigarette either in

  tobacco, either in the filter or in the paper surrounding the tobacco.

  As indicated above and according to a first embodiment of the invention, the catalyst of the invention is a compound based on at least one oxide or hydroxide of a rare earth, zirconium or manganese. This compound may further comprise a metal which may be iron or gold or a combination of both. The metal contents of the compounds of the invention are not critical, they correspond to the contents generally used in the catalysts to obtain a catalytic activity. By way of example, the content of said metal is between 0.01% and 5%, more particularly between 0.01% and 2%. These contents are expressed as a percentage by weight relative to the oxide (or oxides) or hydroxide (or hydroxides) of the rare earth, zirconium or manganese.

  The rare earth may be more particularly cerium or praseodymium.

  The rare earth oxide or hydroxide catalysts are particularly useful as complexing agents for organic compounds (nitrosamines, aldehydes, hydrocarbons or aromatic amines, compounds with carboxylate functions, sulphates, sulphonates or PC2) and metals (cadmium,

  nickel, zinc) mentioned above.

  It is more particularly possible to use cerium oxides with a high specific surface area. By this is meant cerium oxides which have a high specific surface even after being exposed to high temperatures. In this case, the catalysts are particularly useful for their oxidizing function (oxidation of CO, hydrocarbon compounds and soot). It is thus possible to mention the cerium oxides described in patent applications EP-A-153227, EP-A-153228 and EP-A239478, EP-A275733. These oxides may have surfaces of at least 85 m 2 / g, especially at least 100 m 2 / g, after calcination at a temperature of

  between 350 and 4500C over a period of 6 hours for example.

  It is also possible to use the cerium oxide described in EP-A-300852 which has a specific surface area of at least 15 m 2 / g after calcination at a temperature of between 8000.degree. C. and 9000.degree. C. for at least 2 hours or else cerium oxide. described in EP-A-388567 which has an area of at least 190 m 2 / g after calcination at a temperature between 3500C and 4500C for at least 2 hours with also a surface

  specific at least 15 m 2 / g after calcination at a temperature between 8000C and 900'C for the same duration.

  As a catalyst of interest and also with a high specific surface area, it is also possible to use compositions based on a cerium oxide and a zirconium oxide. The respective proportions of cerium and zirconium in these compositions may vary over a wide range, for example in a cerium oxide / zirconium oxide mass ratio of between 1/99 and 99/1. However, it is possible more particularly to use the compositions for

  which has a cerium / zirconium atomic proportion of at least 1.

  We can thus cite the cerium oxide described in EP-A-207857 which has a specific surface area greater than 10 m 2 / g up to a temperature of 9000 ° C. This oxide may in particular have a zirconium oxide content of between 1 and 20% relative to the weight of the ceric oxide. It is also possible to mention the composition based on cerium oxide and zirconium oxide which is the subject of EP-A-605274 and in which the zirconium is in solid solution in cerium oxide. This composition may have a specific surface area of at least 30 m 2 / g after calcination at 8000.degree. C. for 6 hours. It is also possible to use compositions with a high specific surface area of the type based on a cerium oxide and a zirconium oxide and on at least one oxide chosen from scandium oxide and rare earth oxides other

than cerium.

  Such compositions are in particular described in EP-A-906244.

  In the latter document the compositions have a cerium / zirconium atomic proportion of at least 1 and a specific surface area of at least 35 m 2 / g after calcination for 6 hours at 900 ° C. This surface may be more particularly at least 40 m 2. / g. She can be even more

  especially at least 45m2 / g.

  These compositions may correspond to the formula CexZryMzO2 in which M represents at least one element selected from the group consisting of scandium and rare earths with the exception of cerium and z preferably has a value of at most 0.3 and which may more particularly between 0.02 and 0.2, the ratio x / y may be between 1 and 19, more particularly between 1 and 9 and even more particularly between 1.5 and 4, the values of the terminals other than 0 being included and x, y and z being bound by the

relationship x + y + z = 1.

  Other catalysts which can be used more particularly for their NOx reduction or trapping properties in addition to their oxidizing properties (oxidation of CO, of the compounds) will be described below.

hydrocarbon and soot).

  In the context of the present invention, it is also possible to use a composition based on an oxide of cerium and at least one other oxide chosen from iron, manganese and praseodymium oxides, as described in particular in EP-A- 802,824. The compositions based on cerium, iron and praseodymium oxides in combination can be used in particular. The amount of manganese, iron and / or praseodymium in this type of composition may vary within a wide range. Generally, this proportion may range up to a mass ratio expressed as oxide of this or these elements with respect to cerium oxide of 50%. It is usually at least 0.5%. This proportion can thus be between 1 and 40%, especially between 1 and 20%, more particularly between 1 and 10%. Alternatively, the composition may further comprise zirconium. Finally, compositions of this type have, after calcination for 6 hours at 4000 ° C., a specific surface area of at least 10 m 2 / g, preferably at least 60 m 2 / g and

  more particularly at least 80 m 2 / g.

  It is also possible to use according to the invention a composition comprising manganese oxide, cerium oxide or a mixture of cerium oxide and zirconium oxide and in addition at least one other chosen element. among terbium, gadolinium, europium, samarium,

  neodymium and praseodymium. These are compositions of the type described in EP-A-1034026 and which can function in particular as a NOx trap.

  In such compositions, the cerium oxide or the mixture of cerium oxide and zirconium oxide may form a support, the other elements forming a supported phase. This means that the cerium oxide or the mixture of cerium oxide and zirconium oxide may constitute the majority element (s) of the composition on which or on which the other elements are deposited. The composition may comprise a supported phase which is based on manganese in combination with terbium, gadolinium, samarium, neodymium or praseodymium or

  still a mixture of manganese and at least two of these elements.

  According to a variant, the composition may further comprise an alkali which may be more particularly sodium or potassium. This alkaline element can belong to the supported phase. The amounts of elements in the composition can vary in large proportions. Thus, the proportions of manganese can vary between 2 and 50%, more particularly between 5 and%. Those in terbium, gadolinium, samarium, neodymium, praseodymium and / or

  alkaline may vary between 1 and 50%, more particularly between 5 and 30%.

  These proportions are expressed in atomic% relative to all the elements of the composition.

  It is also possible to use in the cigarette according to the invention a composition comprising manganese and at least one other element A,

  selected from alkaline and alkaline earth metals, manganese and element A being chemically bound.

  Compositions of this type, which may also act as Nox traps, are described in particular in EP-A-1171236. More particularly, these compositions comprise a support and an active phase. The active phase is based on manganese and at least one other element A1 as described above and which may be more particularly sodium and potassium. As an alkaline earth element, mention may be made in particular of barium. Moreover, the manganese elements and A1 are in chemically bound form. By this is meant that there are chemical bonds between the manganese and the A1 element resulting from a reaction between them, these two elements not being simply juxtaposed as in a simple mixture. Thus, the elements

  Manganese and A1 may be present as a mixed oxide compound or phase. This compound or this phase may in particular be represented by the formula (1) (Al) xMnO 2 + in which 0.5 <y / x <6.

  Examples of the phase or compound of formula (1) that may be mentioned are those of the vernadite, hollandite, romanechite or psilomelane, birnessite, todorokite, buserite or lithiophorite type. The compound may be optionally hydrated. The compound may also have a lamellar structure of Cdl2 type. As support, it is possible to use any porous support that can be used in the field of catalysis. It is preferable that this support has a chemical inertness with respect to the manganese and A1 elements sufficient to avoid a substantial reaction of one or these elements with the support which would be likely to hinder the creation of a chemical bond between the manganese and the element A1. However, in the case of a reaction between the support and these elements, it is possible to use larger amounts of manganese and A1 element to obtain the desired chemical bond between

these elements.

  More particularly, the support is based on an oxide selected from cerium oxide, optionally with silica, zirconium oxide or mixtures thereof. The total content of manganese, alkaline, and alkaline earth can vary widely. This content may be in particular between 2% and 50%, more particularly between 5% and 30%, this content being expressed in atomic% relative to the sum of the moles of oxide (s) of the

  support and relevant elements of the active phase.

  The cigarettes of the invention may also comprise as a catalyst a composition based on manganese and at least one other element A2 chosen from alkaline earths and rare earths, this composition having a specific surface area of at least 10 m 2 / g , more particularly

  at least 2 Im2 / g, after calcination for 8 hours at 8000C.

  Compositions of this type are described in EP-A-1 181094. These compositions comprise a support and an active phase. The active phase of the composition is based on manganese and at least one element A2 as described above. As alkaline earth, barium can be mentioned more particularly. The rare earth may be more particularly selected from cerium, terbium, gadolinium, samarium, neodymium and praseodymium. Total levels of manganese, alkaline earth or earth

  rare can vary between 1% and 50%, more particularly between 5% and 30%.

  These proportions are expressed in atomic% with respect to the sum of the moles of oxide (s) of the support and the elements concerned of the supported phase. The respective contents of manganese, alkaline earth or rare earth can also vary in large proportions, the content of

  manganese may be in particular equal to or close to that in element A2.

  As indicated above, a characteristic of these compositions is that they have a specific surface area of at least 10m2 / g after calcination for 8 hours at 8000C. This specific surface may especially be at least 20 m 2 / g after calcination at the same temperature and for the same duration. More particularly, this specific surface area is at least 80 m 2 / g and even more particularly at least 100 m 2 / g after calcination for 8 hours.

800C.

  This surface characteristic is obtained by the choice of a suitable support, in particular having a sufficiently high specific surface. This support may be based on alumina. Any type of alumina capable of having a specific surface area sufficient for an application in catalysis can be used here. Mention may be made of aluminas resulting from the rapid dehydration of at least one aluminum hydroxide, such as bayerite, hydrargillite or gibbsite, nordstrandite, and / or at least one aluminum oxyhydroxide such as boehmite. , pseudoboehmite and diaspore. As a support, a stabilized alumina can be used more particularly. As a stabilizing element, mention may be made of rare earths, barium, silicon and zirconium. As rare earth we can mention everything

  particularly cerium, lanthanum or the lanthanum-neodymium mixture.

  The content of stabilizer expressed as weight of stabilizer oxide relative to stabilized alumina is generally between 1.5% and 15%,

  more particularly between 2.5% and 11%.

  The support may also be based on silica.

  It can also be based on silica and titanium oxide in a Ti / Ti + Si atomic proportion of between 0.1 and 15%. This proportion may be more particularly between 0.1 and 10%. Such a support is described in particular in patent application WO 99/01216 to which it will be possible to

refer.

  As another suitable support, those based on cerium oxide and zirconium oxide may be used, these oxides possibly being in the form of a mixed oxide or of a solid solution of zirconium oxide in

  cerium oxide or vice versa.

  The cigarettes according to the invention may also comprise a composition based on manganese in the form of a mixed oxide of formula (2): embedded image in which: A represents one or more elements selected from groups IA, II A; III A of the periodic table; B is a metal selected from tin and the elements of groups IV A to III B of the Periodic Table; x and y having the following values: 0, 16 <x <1 and 0 <y <0.5, the oxide having a lamellar or tunneled crystallographic structure. The catalyst corresponding to the above formula is described in WO 01/56685. It is more specifically a mass catalyst. By this is meant a catalyst in which the oxide of formula (2) is present throughout the catalyst volume in a homogeneous manner and not according to a distribution or concentration gradient, for example at the surface of the volume of the catalyst. catalyst. In other words, the catalyst used here is an unsupported catalyst, the active phase, ie the oxide of formula (2), is not deposited on a porous support of the cerium oxide type, oxide zirconium

or silica for example.

  With regard to the constituent elements of the oxide of formula (2), A may represent one or more elements chosen from the abovementioned groups

of the periodic table.

  A may first be selected from lithium, sodium, potassium, rubidium and cesium. A may be more particularly potassium or sodium or a combination of these two elements in

respective proportions.

  A can also be selected from magnesium, calcium, strontium or

barium.

  A may also be one selected from scandium, yttrium and

rare earth.

  As indicated above, x can be between 0.16 and 1, the values

  at the terminals being included. More particularly, x can check the relation 0.25 <x <0.7.

  In the oxide of formula (2), the manganese may be substituted with an element B. The element B may first be chosen from among the transition metals, ie from the elements of groups IV A, VA, VI A, VII A, VIII, IB and II B.

  As an element of group IVA, mention may be made of titanium.

  As an element of group VIII there may be mentioned more particularly iron,

  platinum, palladium or rhodium.

  Money may be chosen more particularly as part of Group I B.

  As an element of group II B, zinc may be mentioned.

  Finally, the element B may be tin in the oxidation state IV.

  The proportion of element B in the oxide is given by the value of y mentioned above. More particularly, y can check the relationship

0.001 <y <0.01.

  Note that the value of ô will depend on the nature of the elements A and B

  and the oxidation state of manganese which can vary between +3 and +7.

  The oxide of formula (2) also has a specific crystallographic structure. This structure is either lamellar or tunnel type. The lamellar structure corresponds to a structure in which the elements Mn and O together form a first layer separated from a second layer of these same elements by a third layer of elements A, this stack of repeating layers. In the tunnel structure, the layers formed by the set of elements Mn and O form a tunnel inside which are located the elements A. As structures can be mentioned those of vernadite type, hollandite, romanechite or psilomelane, birnessite, todorokite , buserite, lithiophorite, RUB-7, RbO, 27MnO2, NaOH, 44MnO2, LiO, 44MnO2, Ba6Mn24048, alpha-NaMnO2,

  alpha-LiMnO2, beta -NaMnO2, beta-LiMnO2.

  Finally, it should be noted that the oxide of formula (2) may be optionally hydrated by intercalation of H20 molecules and / or H + protons between

slats or in tunnels.

  As indicated above and according to a second embodiment of the invention, the cigarette can also comprise as a catalyst a zinc aluminate. As aluminate of this type, one can use that described in EP-A1098701. This aluminate has a structure of spinel type ZnAl 2 O 4. It may be in one or more lacunary or excess phases of zinc with respect to ZnAl.sub.2 O.sub.4, these phases corresponding to the formulas Zn.sub.1.sub.i xAl.sub.2 O.sub.4-8 and Zn.sub.i + xAl.sub.2 O.sub.4 + 8, with 0 <x <0.95. in particular, to satisfy the following relations: 0 <xs 0.85, 0 <x <0.8 and more particularly 0 <xs 0.5. Finally, x can check the relation 0.4 <x <0.85. The aluminate may further comprise one or more additives. These additives are chosen from the elements of groups IA, IIA, VIIA to IB of the

  periodic classification and among tin, gallium and rare earths.

  As an element of group VIIA, manganese may be mentioned more particularly; as an element of group VIII, mention may in particular be made of iron; as elements of group IB, we can mention more

  especially copper and silver.

  These additives may in particular be present in aluminate in

  partial substitution of zinc or aluminum.

  A characteristic of this same aluminate is its specific surface.

  Even after calcination at high temperature, this aluminate still has a high surface level. Thus, after calcination at 8000C, 8 hours, this specific surface area is at least 85 m 2 / g. It can be at least m2 / g and more particularly at least 100m2 / g, still after calcination at 8000C, 8 hours. Values of at least 120m2 / g can be achieved. This surface is maintained at significant values at even higher temperatures since the aluminate can have, after calcination at 9000C for 2 hours, a specific surface area of at least 70 m 2 / g, more particularly at least 80 m 2 / g. In addition, at 10000C after a 6 hour calcination, specific surfaces of at least 50 m 2 / g, more particularly at least 70 m 2 / g, can be observed. This means that the surface of the aluminate is stable over a wide temperature range. Values that

  have been given above for calcinations under air.

  This same aluminate may also have a pore volume of at least 0.6 ml / g, this porosity is determined by porosimetry by mercury intrusion. The measurements were made on a Micromeretics Auto Pore 9220 device on powders degassed overnight in an oven heated to 2000C. The operating parameters are the following: Penetrometer constant: 21.63, capillary volume: 1.1, contact angle 140. The porosity may be more particularly at least 2 ml / g and be for example

between 2.5 and 3.5 ml / g.

  Finally, according to a third embodiment of the invention, the cigarette may contain a catalyst which is a compound based on at least one metal chosen from the elements included in groups IIIA to IIB of the

  periodic classification on a support based on silica and titanium oxide.

  Such a compound is described in EP-A-994749. This compound comprises a support based on silica and titanium oxide in a Ti / Ti + Si atomic proportion of between 0.1% and 15%. This proportion can be understood more

especially between 1% and 10%.

  It is advantageous in the case of this compound to use supports having a high specific surface and thermally stable. It is thus advantageously possible to use supports having a specific surface area of at least 350 m 2 / g and more particularly at least 600 m 2 / g after calcination for 6 hours at 75 ° C. The support based on silica and titanium oxide may be prepared by any method likely to lead to a surface support

sufficient specificity.

  It is thus possible to mention a micellar texturing process using surfactants and, as a source of silica, alkyl silicates such as tetraethylorthosilicate. These alkyl silicates are generally used in the form of solutions in alcohols, in particular in aliphatic alcohols. Similarly, alkyl or alkoxy titanates can be used as a source of titanium which are also used in the form of alcoholic solutions. The alkyl silicates and the alkyl or alkoxy titanates are mixed and then heated. The surfactant is then added to the mixture so heated. The precipitate obtained is separated from the reaction medium. This precipitate is then calcined, generally under air, to obtain the support which can then be shaped. The calcination can be done in two parts. In the first

  part, calcine at a temperature sufficient to remove the surfactant.

  This temperature can be around 6500C. In the second part, calcine at a temperature at least equal to that at which the catalyst will be

  used. This temperature can be around 7500C.

  The support may be in various forms such as granules,

  balls, cylinders or honeycomb of variable dimensions.

  The support may comprise as additives one or more oxides of

  rare earth. As a rare earth, lanthanum can be mentioned more particularly.

  The additive content expressed in atomic% additive / Ti + Si + additive can be

  not more than 20%, more particularly not more than 10%.

  The catalytic phase on the support may be based on at least one metal chosen from the elements included in groups IIIA to IIB of the

periodic classification.

  More particularly, the catalytic phase is based on at least one

  metal selected from Group VIII metals of the Periodic Table.

  By way of example of metals that can be used in the catalytic phase, mention may be made of platinum, palladium, rhodium, ruthenium and iridium. We can also mention iron, copper, chromium as well as vanadium, niobium, tantalum,

molybdenum and tungsten.

  The metal content of the catalytic and in particular platinum phase of the composition can vary in large proportions. Usually, this proportion, expressed as weight of metal relative to the weight of support is between 500 and 40000ppm, preferably between 2500 and 20000ppm and

  even more particularly between 5000 and 15000ppm.

Claims (9)

  1- Cigarette, characterized in that it comprises either in the tobacco, or in the paper surrounding the tobacco, or in the filter, as a catalyst for the treatment of fumes, at least one compound selected from: - compounds base of at least one oxide or hydroxide of a rare earth, zirconium or manganese; zinc aluminate; a compound based on at least one metal chosen from the elements included in groups IIIA to IIB of the periodic table on a support with   base of silica and titanium oxide.   2- Cigarette according to claim 1, characterized in that it comprises a compound based on at least one oxide or hydroxide of a rare earth and a metal chosen from iron or gold.   3- Cigarette according to claim 1 or 2, characterized in that the rare earth is cerium or praseodymium.   4- Cigarette according to one of the preceding claims, characterized in that   it comprises a composition based on a cerium oxide and a zirconium oxide, more particularly in an atomic proportion cerium / zirconium of at least 1.   - Cigarette according to claim 4, characterized in that it comprises a composition based on a cerium oxide and a zirconium oxide and at least one oxide selected from scandium oxide and oxides of earth rare other than cerium.   6- Cigarette according to one of claims 1 to 3, characterized in that   comprises a composition based on a cerium oxide and at least one   another oxide selected from oxides of iron, manganese and praseodymium.   7- The cigarette according to one of claims 1 to 3, characterized in that   comprises a composition comprising manganese oxide, cerium oxide or a mixture of cerium oxide and zirconium oxide and in addition at least one other element chosen from terbium, gadolinium,   europium, samarium, neodymium and praseodymium.   8- Cigarette according to one of claims 1 to 3, characterized in that   comprises a composition comprising manganese and at least one other element A1 selected from alkalis and alkaline earths, manganese and   the element A1 being chemically linked.   9- Cigarette according to one of claims 1 to 3, characterized in that   comprises a composition based on manganese and at least one other element A2 chosen from alkaline earths and rare earths and which presents   a specific surface area of at least 10 m 2 / g, more particularly at least 20 m 2 / g, after calcination for 8 hours at 8000 ° C.   10- Cigarette according to one of claims 1 to 3, characterized in that   comprises an oxide-based composition of the formula: AxMn-y ByO2 wherein: A represents one or more elements selected from groups I A, II A, III A of the Periodic Table; B is a metal selected from tin and the elements of Groups IV A to IIIB of the Periodic Table; x and y having the following values: 0, 16 <x 1 and 0 y <0.5,   the oxide having a lamellar or tunnel crystallographic structure.