The present invention relates to an aerosol-forming substrate, an aerosol-generating article including a substrate portion comprising the aerosol-forming substrate and a system comprising the aerosol forming article and an aerosol-generating device including a heating chamber for inserting the aerosol-generating article.

It is known to provide an aerosol-generating article including an aerosol-forming substrate which comprises aerosol-formers, such as polyhydric alcohols and nicotine. The aerosol-generating article is inserted into the heating chamber of an aerosol-generating device and is heated to a temperature at which one or more components of the aerosol-forming substrate are volatilised without burning the aerosol-forming substrate. These non-liquid aerosol-generating articles may or may not comprise tobacco. It is known that aldehydes, in particular unwanted formaldehyde can be formed when burning tobacco in traditional cigarettes. However, aldehydes also may be formed when heating aerosol-generating articles without burning the aerosol-forming substrate. Therefore, there is a need for reducing the formation of unwanted aldehydes in the aerosol produced by heating aerosol-forming substrates without burning.

According to an embodiment of the invention there is provided an aerosol-forming substrate comprising: a) one or both of cellulose and cellulose derivatives, b) an aerosol-former, c) from 0 weight percent to 5 weight percent, preferably from 0 weight percent to 3 weight percent, more preferred from 0 weight percent to 1 weight percent, most preferred from 0 weight percent to 0.5 weight percent of tobacco on a dry weight basis based on the total amount of the aerosol-forming substrate, and d) a nitrogen-containing nucleophilic compound.

It was surprisingly found that aerosol-forming substrates not containing tobacco or that are substantially free of tobacco, but comprising one or both of cellulose and cellulose derivatives may produce an aerosol having a high concentration of aldehydes, in particular formaldehyde. The aerosol-forming substrate may comprise from 0.1 weight percent to 3 weight percent, from 0.2 weight percent to 2.5 weight percent, or from 0.3 weight percent to 2 weight percent of tobacco. The concentration of formaldehyde in the aerosol formed from such an aerosol-forming substrate may be several times higher than the concentration of formaldehyde in the aerosol of aerosol generating articles containing a higher amount of tobacco of more than 70 weight percent. The nitrogen-containing nucleophilic compound may provide an aerosol reduced in the amount of aldehydes compared to an aerosol-forming substrate which does not contain the nitrogen-containing nucleophilic compound. Further, the nitrogen-containing nucleophilic compound may provide an aerosol free of aldehydes. Without being bound by any theory, the nitrogen-containing nucleophilic compound may either react with the aldehyde in the aerosol or reduce or prohibit the formation of the aldehyde in the aerosol-forming substrate in situ. Thus, the nitrogen-containing nucleophilic compound may serve as an aldehyde scavenger. Therefore, any aerosol resulting from the above-mentioned aerosol-forming substrate may comprise less aldehydes compared to aerosol-forming substrates of the same composition, but lacking the nitrogen-containing nucleophilic compound.

Without being bound by any theory, the nitrogen-containing nucleophilic compound may via the nitrogen-atom react with aldehydes, in particular formaldehyde, present in the aerosol. The compound may be particularly nucleophilic owing to the lone electron pair of the nitrogen-atom.

The nitrogen-containing nucleophilic compound may comprise groups such as ^* -NH ₂ , ^* -NH- ^* , ^* -CN, NH ₄ ⁺ , or ^* -C(=0)-NH-*, wherein the bond indicates a bond to further moieties of the nitrogen-containing nucleophilic compound. Without being bound by any theory, these nitrogen-atom containing groups may particularly well react with any aldehyde formed upon heating of the aerosol-forming substrate or with chemical precursors to these aldehydes.

According to another embodiment of the invention, the nitrogen-containing nucleophilic compound may be one or both of an organic or inorganic compound. In particular, the nitrogen- containing nucleophilic compound may be selected from a group consisting of:

- an organic compound with an amino or amide group, preferably an amino group, nitrogen-containing saccharide and polysaccharide, or a nitrogen-containing plastic, and inorganic ammonium compound,

- or a combination thereof.

According to a further embodiment of the invention the nitrogen-containing nucleophilic compound may be selected from at least one of:

- an amino acid being selected from a group consisting of lysine, glycine, cysteine, arginine, or homocysteine or a combination thereof,

- a tripeptide, including glutathione,

- urea or an urea derivative or a combination thereof,

- nitrogen-containing saccharide and polysaccharide being selected from a group consisting of: glucosamine, galactosamine, or chitosan, or a combination thereof, - a nitrogen-containing plastic being selected from polyethylene-imine, polystyrene- acrylonitrile or polyacrylonitrile butadiene-styrene or a combination thereof.

These compounds may be particularly well suited to react with the aldehyde. Thus, these compounds may reduce the concentration of the aldehydes, in particular the formaldehyde in the aerosol formed from these aerosol-forming substrates.

Particularly preferred may be compounds such as lysine, urea, chitosan, polyethylene- imine and di-ammonium phosphate or a combination thereof.

The tripeptide including glutathione may preferably be glutathione.

The urea derivatives may be selected from derivatives, wherein some or all of the hydrogen atoms of the -NH ₂ groups are replaced by either Ci- to Ci ₂ -alkyl groups, aryl groups, hydrogen-groups or alkyl-hydroxy groups. Concrete examples may be N-hydroxy urea, N-alkyl urea or N-aryl urea or any combination thereof.

The aerosol-forming substrate may contain from 0.1 weight percent to 10 weight percent, 0.2 weight percent to 9 weight percent preferably from 0.5 weight percent to 8 weight percent, most preferred from 1 weight percent to 5 weight percent, even more preferred from 1 weight percent to 4 weight percent, or 1 .5 weight percent to 3 weight percent of the nitrogen- containing nucleophilic compound on a dry weight basis based on the total amount of the aerosol-forming substrate. These weight percent ranges may be particularly advantageous to reduce the amount of the aldehydes, in particular the formaldehyde in the aerosol formed. Particularly preferred also may be a weight percent-range of 2 weight percent to 4 weight percent. Such a range may reduce or completely eliminate the aldehyde in the aerosol formed.

The cellulose present in the aerosol-forming substrate of the present invention may serve as a filler. In particular the cellulose may serve as a matrix for the aerosol-former which may be present in the aerosol-forming substrate. The cellulose may include particles with size of less than 100 micrometers. The cellulose may be in powder-form.

Cellulose may also comprise cellulose fibers. The cellulose fibers may have at length of larger than 200 micrometers. The fiber lengths may vary from 200 to 2000 micrometers. The fiber widths may vary from 14 to 32 micrometers. The cellulose fibers may serve as an agent reinforcing the aerosol-forming substrate.

The cellulose derivatives may be derivatives wherein at least partly or completely the - OH groups of the D-glucose units of cellulose have been replaced by groups other than -OH groups. In preferred embodiments the cellulose derivatives may be cellulose esters and cellulose ethers.

Typical cellulose esters may be cellulose acetate, cellulose propionate or cellulose sulfate. Typical cellulose ethers may be cellulose ethers, wherein some or all of the hydrogen atoms of the -OH groups have been replaced by alkyl-groups, or carboxy alkyl groups. Suitable examples of the group of cellulose ethers may be methyl cellulose, ethyl cellulose, hydroxy ethyl cellulose, hydroxy propyl cellulose, ethyl hydroxy ethyl cellulose or carboxymethyl cellulose (CMC) or any combination thereof. Particularly preferred may be carboxymethyl cellulose. The cellulose derivatives may serve as binder in the aerosol-forming substrate.

The one or both of cellulose and cellulose derivatives may be present in an amount of 15 weight percent to 85 weight percent, preferably 20 weight percent to 80 weight percent, more preferred 25 weight percent to 70 weight percent on a dry weight basis based on the total amount of the aerosol-forming substrate. These weight percent-ranges may be particularly suited for the one or both of cellulose and cellulose derivatives in order to serve as a binder or as a filler.

In particular, cellulose may be present in an amount of 30 weight percent to 70 weight percent, preferably in an amount of 35 weight percent to 65 weight percent, more preferred in an amount of 30 weight percent to 58 weight percent, even more preferably in an amount of 40 weight percent to 60 weight percent, most preferred in an amount of 40 weight percent to 50 weight percent. In particular, an amount of 45 weight percent to 58 weight percent of cellulose on a dry weight basis based on the total amount of the aerosol-forming substrate may be present. These weight percent ranges are preferred for cellulose and enable cellulose to particularly well serve as a filler in the aerosol-forming substrate.

The cellulose derivatives may be present in an amount of 1 weight percent to 15 weight percent, or 1 .5 weight percent to 12 weight percent, preferably in an amount of 2 weight percent to 10 weight percent, more preferably in an amount of 2.5 to 8 weight percent, more preferably in an amount of 3 to 5 weight percent on a dry weight basis based on the total amount of the aerosol-forming substrate.

The cellulose fibers may be present in an amount of 0.5 weight percent to 10 weight percent, preferably an amount of 1 weight percent to 8 weight percent, more preferably in an amount of 2 weight percent to 6 weight percent, most preferred in an amount of 2.5 weight percent to 5.5 weight percent on a dry weight basis based on the total amount of the aerosol forming substrate. These weight percent-ranges enable the fibers to particularly well serve as the re-enforcing agent for the aerosol-forming substrate.

In a further embodiment of the invention, one, two or all of cellulose powder, cellulose fibers and cellulose derivative may be present in the aerosol-forming substrate. For example, the aerosol-forming substrate may comprise a combination of cellulose powder and a cellulose derivative, such as carboxymethyl cellulose. Alternatively, the aerosol-forming substrate may comprise combination of cellulose powder and cellulose fibers. In another alternative, the aerosol-forming substrate may comprise combination of cellulose fibers cellulose derivatives. Furthermore, the aerosol-forming substrate may only comprise the cellulose powder. The aerosol-forming substrate may also only comprise the cellulose fibers or the cellulose derivatives. In particular, cellulose powder, cellulose fibers and cellulose derivatives, such as carboxymethyl cellulose may be included in the aerosol-forming substrate. The presence of all three components may particularly well enable these components to serve as a reinforcing agent, as a filler and as a binder.

The aerosol-forming substrate may comprise at least one aerosol-former. An aerosol- former is any suitable known compound or mixture of compounds that, in use, facilitates formation of a dense and stable aerosol and that is substantially resistant to thermal degradation at the temperature of operation of the aerosol-generating system. Suitable aerosol-formers may include, but are not limited to: polyhydric alcohols, such as triethylene glycol, 1 ,3-butanediol and glycerine; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. Aerosol formers may be polyhydric alcohols or mixtures thereof, such as triethylene glycol, 1 ,3-butanediol and glycerine. The aerosol- former may be propylene glycol. The aerosol former may include both glycerine and propylene glycol. The aerosol former may only include glycerine.

The aerosol-former may be present in an amount of 20 weight percent to 58 percent, preferably 25 weight percent to 45 weight percent, more preferred 30 weight percent to 38 weight percent on a dry weight basis based on the total amount of the aerosol-forming substrate. The term “dry weight basis ” throughout the application refers to the weight of the aerosol-forming substrate calculated with the water removed via Karl-Fischer titration, for example after being heated to a temperature of 110 degrees Celsius at standard conditions for temperature and pressure and using potentiometry to determine the endpoint. The end point is detected by a bipotentiometric titration method. A second pair of Pt electrodes is immersed in the anode solution. The detector circuit maintains a constant current between the two detector electrodes during titration. Prior to the equivalence point, the solution contains I-, but little . At the equivalence point, excess I2 appears and an abrupt voltage drop marks the endpoint. The amount of charge needed to generate I2 and reach the endpoint can then be used to calculate the amount of water in the original sample. The aerosol-former content can be measured by gas chromatography in combination with a flame ionization detector.

In some embodiments, the aerosol-forming substrate may further include a disaccharide. In a preferred embodiment, the aerosol-forming substrate may include a disaccharide. Without being bound by any theory, the disaccharide may serve to facilitate the conduction of heat from an outside heating element into the aerosol-forming substrate. Thus, the disaccharide may assist in a reliable formation of the aerosol once the aerosol-forming substrate is heated in a heating chamber by any outside heating element. Furthermore, without being bound by any theory, the disaccharide may serve to modify the release of the aerosol-former during the course of different puffs taken by a user. For example, the presence of the disaccharide may enable the release of the aerosol-former, for example glycerine over a longer, extended period of time. In particular, it may be possible for a user to even enjoy an aerosol generated from the aerosol-forming substrate after having taken more than 6, 7 or 8 puffs. Normally, the amount of aerosol generated during these later puffs is reduced in comparison to the 3 ^rd or 4 ^th puff of the user.

The disaccharide may be selected from sucrose, lactose or maltose or a combination thereof. In preferred embodiments, the disaccharide is sucrose.

The disaccharide may be present in an amount of 0.1 weight percent to 15 weight percent, preferably 0.5 weight percent to 12 weight percent, more preferred 1 weight percent to 10 weight percent on a dry weight basis based on the total amount of the aerosol-forming substrate. These weight percent-ranges may enable the disaccharide to particularly well extend the release of the aerosol-former during the puffs taken by a user. Furthermore, these weight percent-ranges may also be well suited to enable the conduction of heat into the aerosol-forming substrate.

In some embodiments, the aerosol-forming substrate furthermore may further comprise nicotine. Nicotine may form an important part of the aerosol generated from the aerosol forming substrate upon heating.

The aerosol-forming substrate may comprise nicotine in an amount of 0.1 weight percent to 10 weight percent, preferably 0.5 weight percent to 8 weight percent, more preferred 1 weight percent to 3 weight percent on a dry weight basis based on the total amount of the aerosol forming substrate. The nicotine content of the “dry weight’ can also be detected by gas chromatography in combination with a flame ionization detector.

The aerosol-forming substrate may additionally comprise at least one carboxylic acid, preferably C ₃ to C _& alkyl hydroxy carboxylic acid, an alkyl keto carboxylic acid or an aryl carboxylic acid. This at least one carboxylic acid may protonate any nicotine present in the aerosol-forming substrate. Concrete examples of the carboxylic acid may be lactic acid, benzoic acid, citric acid, malic acid, tartaric acid, 2-methyl butyric acid, levulinic acid or any combination thereof. Preferably, the nicotine is protonated with the acid in a solution to yield the nicotinate. The nicotinate may then be employed with the other components, such as the cellulose or cellulose derivatives in order to produce the aerosol-forming substrate. For example, nicotine may be used as 10 weight percent solution in glycerine and 2 molar equivalents of lactic acid may be added into slurry of remaining ingredients and mixed. The one or more protonated nicotine salts may have a higher solubility in water compared to the nicotine free base. Preferably the one or more nicotine salt may be selected from the list consisting of nicotine citrate, nicotine pyruvate, nicotine bitartrate, nicotine pectates, nicotine alginates, and nicotine salicylate. Nicotine in these salt forms is more stable than liquid freebase nicotine typically used. Thus, aerosol-forming substrates comprising these one or more nicotine salts may have longer shelf lives than typical aerosol-forming substrates.

The at least one carboxylic acid may be present in an amount of 0.1 weight percent to 10 weight percent, preferably 0.5 weight percent to 8 weight percent, more preferred 1 weight percent to 3 weight percent on a dry weight basis based on the total amount of the aerosol forming substrate.

The aerosol-forming substrate may comprise non-tobacco volatile flavour compounds. These non-tobacco volatile flavour compounds may form an aerosol together with the aerosol- former upon heating of the aerosol-forming substrate. For example, non-tobacco volatile flavour compounds may comprise menthol. As used herein, the term ‘menthol’ denotes the compound 2-isopropyl-5-methylcyclohexanol in any of its isomeric forms. The non-tobacco volatile flavour compounds may provide a flavour selected from the group consisting of menthol, lemon, vanilla, orange, wintergreen, cherry, and cinnamon.

The amount of the non-tobacco volatile flavour compounds in the aerosol-forming substrate may be between 0.1 weight percent to 54 weight percent, preferably between 0.5 weight percent to 30 weight percent on a dry weight basis based on the total amount of the aerosol-forming substrate.

According to a further embodiment of the invention, the aerosol-forming substrate may comprise from 0.1 weight percent to 3 weight percent of tobacco, preferably from 0.1 weight percent to 2 weight percent of tobacco.

According to a further embodiment of the invention, the aerosol-forming substrate is substantially free, more preferred free of any tobacco. In this case, the aerosol may be formed by the aerosol-former and - if present - by one or both of nicotine and the non-tobacco volatile flavour compounds. Tobacco flavour compounds may not substantially or not at all contribute to the formation of the aerosol, when the aerosol-forming substrate is heated.

The one or both of cellulose and cellulose derivatives also may be derived from cellulose sources other than tobacco. For example, trees or non-tobacco plants may serve sources for cellulosic materials. The one or both of cellulose and cellulose derivatives therefore may not be derived from tobacco.

The presence and also the absence of tobacco in the aerosol-forming substrate can be positively identified by DNA barcoding. Methods for performing DNA barcoding based on the nuclear gene ITS2 (internal transcribed spacer 2) of tobacco, the rbcL and matK system as well as the plastid intergenic spacer trnFI-psbA, are well known in the art and can be used (Chen S, Yao FI, Flan J, Liu C, Song J, et al. (2010) Validation of the ITS2 Region as a Novel DNA Barcode for Identifying Medicinal Plant Species. PLoSONE 5(1): e8613; Hollingsworth PM, Graham SW, Little DP (2011) Choosing and Using a Plant DNA Barcode. PLoS ONE 6(5): e19254).

The substrate portion comprising the aerosol-forming substrate may be formed as a sheet, preferably a cast sheet. The sheets of aerosol-former may be formed by a casting process of the type generally comprising casting a slurry comprising one or both of cellulose and cellulose derivatives, and - optionally - aerosol-former and the nitrogen-containing nucleophilic compound onto a conveyor belt or other support surface, drying the cast slurry to form a sheet of the aerosol-forming substrate and removing the sheet of aerosol-forming substrate from the support surface. For example, in certain embodiments sheets of the aerosol forming substrate for use in the invention may be formed from a slurry comprising cellulose, cellulose fibers, carboxy methyl cellulose and optionally glycerine by a casting process. Additionally, the slurry may comprise additional components selected from: nicotine, nicotine salts, the disaccharide.

In one embodiment, a slurry including the at least one of cellulose and cellulose derivatives, the aerosol-former, the nitrogen-containing nucleophilic compound and - if present - the tobacco is formed. The ingredients in the slurry may have a concentration of between 15 weight percent to 25 weight percent, preferably 20 weight percent on a dry weight basis. Casted sheets may be formed from the slurry. The casted sheets may be formed by drying. The target sheet thickness may be between 200 micrometers to 300 micrometers, preferably 250 micrometers. The sheet weight may be between 160 to 180 grams/square meter.

Alternatively, the casting process for forming the sheet of non-tobacco material may only employ one or both of cellulose and the cellulose derivative. The cast sheet may subsequently serve as a cellulosic absorbent substrate for absorbing one or both of the nicotine, preferably the nicotine salt and the aerosol-former onto the sheet. Additionally, one or both of the nitrogen-containing nucleophilic compound and the disaccharide also may be absorbed on the absorbent substrate or may be present during the casting process.

The nicotine, preferably the nicotine salt and the aerosol-former may be combined with water as a liquid formulation. The liquid formulation may further comprise any of the above- mentioned non-tobacco volatile flavour compounds. Such a liquid formulation may then be absorbed by the sorbent substrate or coated onto the surface of the sorbent substrate.

The substrate portion comprising the aerosol-forming substrate may be formed as a rod. The substrate portion may be provided comprising a gathered sheet of non-tobacco material formed by the above-mentioned casting process including at least the one or both of cellulose and cellulose derivatives. The substrate portion may be circumscribed by a wrapper. The sheet of non-tobacco material may be textured or crimped and may comprise a sorbent substrate, a nicotine salt, and an aerosol-former. The gathered sheet of material non-tobacco preferably extends along substantially the entire length of the substrate portion and across substantially the entire transverse cross-sectional area of the substrate portion. The sheet may further comprise water.

The aerosol-forming substrate may comprise up to 5 weight percent of tobacco on a dry weight basis based on the total amount of the aerosol-forming substrate. This tobacco may comprise cast leaf tobacco, reconstituted tobacco, tobacco paper, tobacco powder, blended tobacco, strips, sheets, shredded tobacco, or any other suitable form of tobacco. The tobacco may be produced of sheets of homogenised tobacco materials by a reconstitution process. These include, but are not limited to: paper-making processes of the type described in, for example, US-A-3,860,012 or casting or ‘cast leaf processes of the type described in, for example, US-A-5,724,998. For example, in certain embodiments homogenized sheets including tobacco material for use in the invention may be formed from a slurry additionally comprising particulate tobacco in addition to the other components for the slurry mentioned above.

As used herein, the term ‘gathered’ may denote that the sheet of aerosol-forming substrate is convoluted, folded, or otherwise compressed or constricted substantially transversely to the cylindrical axis of the rod.

The term ‘sheet’ may denote a laminar element having a width and length substantially greater than the thickness thereof.

Another embodiment of the present invention is directed to an aerosol-generating article comprising a substrate portion containing an aerosol-forming substrate as described herein. Preferably, the substrate portion in the article may be in the form of a rod.

The aerosol-generating article may further comprise a connect portion. The connect portion preferably may have a tubular hollow core. Such a tubular hollow core may be located downstream of the substrate portion and may abut the aerosol-forming substrate.

The connect portion may be formed from any suitable material or combination of materials. For example, the connect portion may be formed from one or more materials selected from the group consisting of: cellulose acetate; cardboard; crimped paper, such as crimped heat resistant paper or crimped parchment paper; and polymeric materials, such as low-density polyethylene (LDPE). In a preferred embodiment, the connect portion may be formed from cellulose acetate and preferably may be a hollow cellulose acetate tube.

The connect portion preferably has an external diameter that is approximately equal to the external diameter of the aerosol-generating article.

The aerosol-generating article further may comprise a tipping paper arranged at least partly wrapped around the connect portion and the substrate portion to overlap the connect portion and the substrate portion. Such a tipping paper may increase the stability of an aerosol generating article.

A further aspect of the invention is directed to an aerosol-generating system comprising the aerosol-generating article as described herein and an aerosol-generating device. The aerosol-generating device may comprise a heating element and a heating chamber for receiving said aerosol-generating article. The heating element may be configured to heat the aerosol-generating article to a temperature ranging from 220 degrees Celsius to 400 degrees Celsius, preferably from 250 degrees Celsius to 290 degrees Celsius. At these temperatures an aerosol may be generated from the aerosol-forming substrate included in the aerosol generating article. This aerosol may be reduced in aldehydes due to the presence of the nitrogen-containing nucleophilic compound.

The aerosol-generating device may heat, but not combust the aerosol-generating article. Such electrically heated heat-not-burn aerosol-generating systems heat the aerosol generating article to a temperature sufficient to produce an aerosol from the substrate without combusting the substrate.

As used herein, the terms ‘upstream’ and ‘downstream’ are used to describe the relative positions of components, or portions of components, of the aerosol-generating device and the aerosol-generating article in relation to the direction in which a user draws on the aerosol-generating article inserted into the heating chamber of the aerosol-generating device during use thereof.

The aerosol-generating article may comprise a mouth end through which in use an aerosol exits the aerosol-generating system and is delivered to a user. The mouth end may also be referred to as the downstream end. In use, a user draws on the downstream or mouth end of the aerosol-generating system, in particular the aerosol-generating article in order to inhale an aerosol generated by the aerosol-generating system. The aerosol-generating system comprises an upstream end opposed to the downstream or mouth end.

In some aspects of the disclosure, the heating element may comprise an electrically resistive material. Suitable electrically resistive materials include but are not limited to: semiconductors such as doped ceramics, electrically "conductive" ceramics (such as, for example, molybdenum disilicide), carbon, graphite, metals, metal alloys and composite materials made of a ceramic material and a metallic material. Such composite materials may comprise doped or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbides. Examples of suitable metals include titanium, zirconium, tantalum platinum, gold and silver. Examples of suitable metal alloys include stainless steel, nickel-, cobalt-, chromium-, aluminium- titanium- zirconium-, hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese-, gold- and iron-containing alloys, and super-alloys based on nickel, iron, cobalt, stainless steel, Timetal® and iron-manganese-aluminium based alloys. In composite materials, the electrically resistive material may optionally be embedded in, encapsulated or coated with an insulating material or vice-versa, depending on the kinetics of energy transfer and the external physicochemical properties required.

In another embodiment, heated aerosol-generating articles may be used comprising a combustible heat source and an aerosol-generating substrate downstream of the combustible heat source. For example, aerosol-generating articles with aerosol-generating substrates in heated aerosol-generating articles of the type disclosed in WO-A-2009/022232 may be employed, which comprise a combustible carbon-based heat source, an aerosol-generating substrate downstream of the combustible heat source, and a heat-conducting element around and in contact with a rear portion of the combustible carbon-based heat source and an adjacent front portion of the aerosol-generating substrate. However, it will be appreciated that aerosol generating articles as described herein may also be used in heated aerosol-generating articles comprising combustible heat sources having other constructions.

As described, in any of the aspects of the disclosure, the heating element may be part of the aerosol-generating device. The aerosol-generating device may comprise an internal heating element or an external heating element, or both internal and external heating elements, where "internal" and "external" refer to the aerosol-generating article. An internal heating element may take any suitable form. For example, an internal heating element may take the form of a heating blade. Alternatively, the internal heater may take the form of a casing or substrate having different electro-conductive portions, or an electrically resistive metallic tube. Alternatively, the internal heating element may be one or more heating needles or rods that run through the center of the substrate portion of the aerosol-generating article. Other alternatives include a heating wire or filament, for example a Ni-Cr (Nickel-Chromium), platinum, tungsten or alloy wire or a heating plate. Optionally, the internal heating element may be deposited in or on a rigid carrier material. In one such embodiment, the electrically resistive heating element may be formed using a metal having a defined relationship between temperature and resistivity. In such an exemplary device, the metal may be formed as a track on a suitable insulating material, such as ceramic material, and then sandwiched in another insulating material, such as a glass. Heaters formed in this manner may be used to both heat and monitor the temperature of the heating elements during operation.

An external heating element may take any suitable form. For example, an external heating element may take the form of one or more flexible heating foils on a dielectric substrate, such as polyimide. The flexible heating foils can be shaped to conform to the perimeter of the heating chamber for receiving the aerosol-generating article. Alternatively, an external heating element may take the form of a metallic grid or grids, a flexible printed circuit board, a molded interconnect device (MID), ceramic heater, flexible carbon fibre heater or may be formed using a coating technique, such as plasma vapour deposition, on a suitable shaped substrate. An external heating element may also be formed using a metal having a defined relationship between temperature and resistivity. In such an exemplary device, the metal may be formed as a track between two layers of suitable insulating materials. An external heating element formed in this manner may be used to both heat and monitor the temperature of the external heating element during operation.

The internal or external heating element may comprise a heat sink, or heat reservoir comprising a material capable of absorbing and storing heat and subsequently releasing the heat over time to the substrate portion of the aerosol-generating article. The heat sink may be formed of any suitable material, such as a suitable metal or ceramic material. In one embodiment, the material has a high heat capacity (sensible heat storage material), or is a material capable of absorbing and subsequently releasing heat via a reversible process, such as a high temperature phase change. Suitable sensible heat storage materials include silica gel, alumina, carbon, glass mat, glass fibre, minerals, a metal or alloy such as aluminium, silver or lead, and a cellulose material such as paper. Other suitable materials which release heat via a reversible phase change include paraffin, sodium acetate, naphthalene, wax, polyethylene oxide, a metal, metal salt, a mixture of eutectic salts or an alloy. The heat sink or heat reservoir may be arranged such that it is directly in contact with the substrate portion of the aerosol-generating article and can transfer the stored heat directly to the substrate. Alternatively, the heat stored in the heat sink or heat reservoir may be transferred to the substrate portion of the aerosol-generating article by means of a heat conductor, such as a metallic tube.

Alternatively, to an electrically resistive heating element, the heating element may be configured as an induction heating element. The induction heating element may comprise an induction coil and a susceptor. In general, the susceptor is a material that is capable of absorbing electromagnetic energy and converting it to heat. When located in an alternating electromagnetic field, typically eddy currents are induced and hysteresis losses occur in the susceptor causing heating of the susceptor. Changing electromagnetic fields generated by one or several induction coils heat the susceptor, which then transfers the heat to the aerosol generating article, such that an aerosol is formed. The heat transfer may be mainly by conduction of heat. Such a transfer of heat is best, if the susceptor is in close thermal contact with the aerosol-generating article.

The susceptor may be formed from any material that can be inductively heated to a temperature sufficient to generate an aerosol from the aerosol-forming substrate. A preferred susceptor may comprise or consist of a ferromagnetic material, for example a ferromagnetic alloy, ferritic iron, or a ferromagnetic steel or stainless steel. A suitable susceptor may be, or comprise, aluminium. Preferred susceptors may be heated to a temperature in excess of 250 degrees Celsius.

Preferred susceptors are metal susceptors, for example stainless steel. However, susceptor materials may also comprise or be made of graphite, molybdenum, silicon carbide, aluminum, niobium, Inconel alloys (austenite nickel-chromium-based superalloys), metallized films, ceramics such as for example zirconia, transition metals such as for example iron, cobalt, nickel, or metalloids components such as for example boron, carbon, silicon, phosphorus, aluminium.

Preferably, the susceptor material is a metallic susceptor material. The susceptor may also be a multi-material susceptor and may comprise a first susceptor material and a second susceptor material. In some embodiments, the first susceptor material may be disposed in intimate physical contact with the second susceptor material. The second susceptor material preferably has a Curie temperature that is below the ignition point of the aerosol-forming substrate. The first susceptor material is preferably used primarily to heat the susceptor when the susceptor is placed in a fluctuating electromagnetic field. Any suitable material may be used. For example, the first susceptor material may be aluminium, or may be a ferrous material such as a stainless steel. The second susceptor material is preferably used primarily to indicate when the susceptor has reached a specific temperature, that temperature being the Curie temperature of the second susceptor material. The Curie temperature of the second susceptor material can be used to regulate the temperature of the entire susceptor during operation. Suitable materials for the second susceptor material may include nickel and certain nickel alloys.

By providing a susceptor having at least a first and a second susceptor material, the heating of the aerosol-forming substrate and the temperature control of the heating may be separated. Preferably the second susceptor material is a magnetic material having a second Curie temperature that is substantially the same as a desired maximum heating temperature. That is, it is preferable that the second Curie temperature is approximately the same as the temperature that the susceptor should be heated to in order to generate an aerosol from the aerosol-forming substrate.

When an induction heating element is employed, the induction heating element may be configured as an internal heating element as described herein or as an external heater as described herein. If the induction heating element is configured as an internal heating element, the susceptor element is preferably configured as a pin or blade for penetrating the aerosol generating article. If the induction heating element is configured as an external heating element, the susceptor element is preferably configured as a cylindrical susceptor at least partly surrounding the heating chamber or forming the sidewall of the heating chamber.

The heating element may heat the substrate portion of the aerosol-generating article by means of conduction. The heating element may be at least partially in contact with the substrate, or the carrier on which the substrate is deposited. Alternatively, the heat from either an internal or external heating element may be conducted to the substrate by means of a heat conductive element.

During operation, the aerosol-generating article may be completely contained within the aerosol-generating device. In that case, a user may puff on a mouthpiece of the aerosol generating device. Alternatively, during operation only the substrate portion of the aerosol generating article may be contained within the aerosol-generating device. In that case, the user may puff directly on the aerosol-generating article.

The aerosol-generating device may comprise electric circuitry. The electric circuitry may comprise a microprocessor, which may be a programmable microprocessor. The microprocessor may be part of a controller. The electric circuitry may comprise further electronic components. The electric circuitry may be configured to regulate a supply of power to the heating element. Power may be supplied to the heating element continuously following activation of the aerosol-generating device or may be supplied intermittently, such as on a puff- by-puff basis. The power may be supplied to the heating element in the form of pulses of electrical current. The electric circuitry may be configured to monitor the electrical resistance of the heating element, and preferably to control the supply of power to the heating element dependent on the electrical resistance of the heating element.

The aerosol-generating device may comprise a power supply, typically a battery, within a main body of the aerosol-generating device. In one embodiment, the power supply is a Lithium-ion battery. Alternatively, the power supply may be a Nickel-metal hydride battery, a Nickel cadmium battery, or a Lithium based battery, for example a Lithium-Cobalt, a Lithium- Iron-Phosphate, Lithium Titanate or a Lithium-Polymer battery. As an alternative, the power supply may be another form of charge storage device such as a capacitor. The power supply may require recharging and may have a capacity that enables to store enough energy for one or more usage experiences; for example, the power supply may have sufficient capacity to continuously generate aerosol for a period of around six minutes or for a period of a multiple of six minutes. In another example, the power supply may have sufficient capacity to provide a predetermined number of puffs or discrete activations of the heating element.

Another aspect of the present invention is directed to a method of operating the aerosol generating system as described herein, comprising the method steps:

A) inserting said aerosol-generating article into the heating chamber, B) heating said aerosol-generating article via the heating element, thereby generating an aerosol and in aldehydes, wherein the aldehyde reacts with nitrogen-containing nucleophilic compound, resulting in an aldehyde reduced aerosol.

During the heating of said aerosol-generating article an aerosol may be provided which is substantially free or completely free of the aldehyde.

During heating of said aerosol-generating article, formaldehyde may be formed as an aldehyde, wherein the formaldehyde reacts with said nitrogen-containing nucleophilic compound, resulting in a formaldehyde reduced aerosol. Formaldehyde may be one primary aldehyde formed during the generation of an aerosol from the aerosol-forming substrates of the present invention.

An aerosol-generating article comprising an aerosol-forming substrate according to any embodiments of the present invention may preferably comprise one or both of urea and lysine in the aerosol forming substrate as a nitrogen-containing nucleophilic compound.

A further aspect of the present invention is also directed to the use of a nitrogen- containing nucleophilic compound for removing an aldehyde from an aerosol formed by a heating of an aerosol-generating article as described herein.

During the use of the nitrogen-containing nucleophilic compound the aerosol may be heated to a temperature between 220 degrees Celsius to 400 degrees Celsius, preferably from 250 degrees Celsius to 290 degrees Celsius.

Features described in relation to one embodiment may equally be applied to other embodiments of the invention.

The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

Fig. 1 shows a column chart of the formaldehyde contents of different aerosol generating articles containing tobacco as well as non-tobacco aerosol-forming substrates;

Fig. 2 depicts a column chart of the formaldehyde content of different aerosol generating articles including different concentrations of urea;

Fig. 3 shows a column chart of the formaldehyde content of different aerosol-generating articles including tobacco or other non-tobacco aerosol-forming substrate with sucrose and lysine;

Fig. 4 shows the release of the aerosol-former glycerine during the course of 12 puffs taken by a user depending on the amount of the disaccharide sucrose in the aerosol-forming substrate;

Fig. 5 depicts a schematic of an aerosol-generating system comprising an aerosol generating device and an aerosol-generating article. Fig. 1 depicts a column chart wherein the amount of formaldehyde detected in an aerosol generated from various aerosol-generating articles having a heating element at a temperature of 350 degrees Celsius. The substrate portion containing the aerosol-forming substrate of the aerosol-generating article was heated by an internal blade. In general, formaldehyde in smoke can be detected by trapping the aerosol in a DNPH derivatization solution (2,4-dinitrophenylhydrazine) using a smoking machine. Pyridine is added to quench the derivatization reaction, maximum 15 minutes after the end of the aerosol collection. A solution containing an internal standard is added to the stabilized aerosol extracts before being analyzed using ultra performance liquid chromatography with MS-MS detection with an ESI (Electrospray ionization) source in a negative mode. In this figure and also in the Fig. 2 and 3 the vertical axis denotes the amount of formaldehyde detected in micrograms/aerosol generating article. The column denoted with 10 shows that 3.7 micrograms formaldehyde were detected in the aerosol of an aerosol-generating article including 75 weight percent of a tobacco blend, 18 weight percent of glycerine as aerosol-former with the remainder being binder. In contrast to the tobacco containing aerosol-generating article, 15.4 micrograms of formaldehyde could be detected in the aerosol of an aerosol generating article including 45 weight percent cellulose, 30 weight percent inositol, 20 weight percent glycerine and the remainder being binder (column denoted with 12). The inositol serves as a plasticizer. The data show that up to 4-times more formaldehyde is released from non-tobacco-containing aerosol-forming substrates in comparison to substrates containing tobacco. The columns denoted with 14 and 16 show that no formaldehyde could be detected in the aerosol of aerosol generating articles including 45 weight percent cellulose, 26.25 weight percent inositol, 20 weight percent glycerine and either 3.75 weight percent urea (column denoted with 14) or 3.75 weight percent lysine (column denoted with 16). Thus, both urea and lysine can act as nitrogen- containing nucleophilic compounds reacting with formaldehyde, thereby eliminating formaldehyde from the aerosol.

Fig. 2 depicts a column chart of the formaldehyde detected in the aerosol generated from various aerosol-generating articles having a heating element at a temperature of 350 degrees Celsius. The column denoted with 18 shows that 3.5 micrograms of formaldehyde could be detected in the aerosol formed from an aerosol generating article including 75 weight percent of a tobacco blend, 18 weight percent glycerine and the remainder being binder. 2.11 micrograms formaldehyde was found in the aerosol of an aerosol generating article containing 56 weight percent cellulose, 5 weight percent carboxy methyl cellulose, 1 weight percent urea, 3 weight percent cellulose fibers and 35 weight percent glycerine (column denoted with 20). Thus, the amount of formaldehyde in the aerosol could be reduced by 39percent when including 1 weight percent urea as a formaldehyde-scavenger. No formaldehyde could be detected in the aerosol of the aerosol generating article containing 49 weight percent cellulose, 8 weight percent carboxy methyl cellulose, 5 weight percent urea, 3 weight percent cellulose fibers and 35 weight percent glycerine (column denoted with 22).

Fig. 3 shows a column chart of the formaldehyde detected in the aerosol of various aerosol generating articles with different compositions. 3.31 micrograms formaldehyde could be detected in an aerosol generating article at 350 degrees Celsius of the heating element including 75 weight percent of a tobacco blend including the other components as mentioned above for figure 2 (column denoted with 24). An aerosol generating article containing 58 weight percent cellulose, 35 weight percent glycerine, 4 weight percent carboxy methyl cellulose and 3 weight percent cellulose fibers generates 1.68 micrograms formaldehyde (column denoted with 26). In contrast to that, more formaldehyde, 2.61 micrograms is detected in the aerosol of an aerosol generating article in which 10 weight percent cellulose have been replaced by 10 weight percent sucrose (column denoted with 28). This suggests that the presence of the disaccharide, sucrose, increases the amount of formaldehyde. The release of formaldehyde associated with the disaccharide can reliably be reduced or suppressed by including the nitrogen-containing nucleophilic compounds of the present invention in the aerosol-forming substrates. The column denoted with 30 shows, that no formaldehyde could be detected in the aerosol of an aerosol generating article including 56 weight percent cellulose, 35 weight percent glycerin, 2 weight percent lysine as a nitrogen-containing nucleophilic compound, 4 weight percent carboxy methyl cellulose and 3 weight percent cellulose fibers.

Similar results, which are not shown in the Figures were achieved, when aerosol generating articles with an aerosol forming substrate weighing 0.5 grams and comprising 42 weight percent cellulose, 28 weight percent sorbitol, 20 weight percent glycerin, and either 5 weight percent the ammonium phosphate, 5 weight percent chitosane , 5 weight percent lysine, 5 weight percent urea or 5 weight percent polyethylene imine with the remainder being cellulose fibers and guar gum were heated to 350 degrees Celsius for 6 minutes. In all these cases no formaldehyde could be detected with TG-GC-MS analysis.

Fig. 4 shows a graph, wherein the vertical axis depicts the amount of glycerin per puff (micrograms/puff) detected by FT-IR and the horizontal axis denotes the number of puffs. The graph depicts the amount of glycerol detected in the aerosol during the course of 12 consecutive puffs at a temperature of 250 degrees Celsius of the heating element. The graph denoted with 32 shows the amount of glycerine released from a tobacco containing aerosol generating article with 75 weight percent tobacco, 18 weight percent glycerine and the remainder being binder for comparison. The graph denoted with 34 shows the release of glycerine from an aerosol generating article containing 58 weight percent cellulose, 35 weight percent glycerine, 4 weight percent carboxy methyl cellulose, and 3 weight percent cellulose fibers. The further graphs show the release of glycerine from aerosol generating articles, wherein either 10 weight percent cellulose has been replaced by 10 weight percent sucrose (graph denoted with 36) or wherein 20 weight percent cellulose has been replaced by 20 weight percent sucrose (graph denoted with 38). It can clearly be seen that the addition of sucrose results in a delay of the release of glycerine, so that more glycerine is released at a later stage beginning with puff number 7 or 8.

Fig. 5 depicts a schematic of an aerosol-generating system comprising an aerosol generating device 46 and an aerosol-generating article 40. The aerosol-generating article 40 includes a substrate portion 42 and a connect portion 44. The substrate portion 42 includes the aerosol-forming substrate of the present invention and is located upstream in the direction of the aerosol-generating article. The downstream connect portion 44 may comprise a tubular hollow portion, such as a hollow acetate tube. The aerosol-generating article 40 can be inserted into the heating chamber 48 of the aerosol-generating device 46 in such a way, that the substrate portion 42 is neighbouring the heating element 50 of the heating chamber. Additional elements are present in the aerosol-generating device 46, for example circuitry 52, such as a microprocessor and a power supply 54, for example a battery. The power supply and the circuitry as well as the heating elements can be electrically connected via electrical connections 56. During use of the aerosol-generating device user may draw on the downstream end of the aerosol-generating article 40, which might be the connect portion 44 or an additional mouthpiece or filter, not shown in Fig. 5 for inhaling the aerosol formed during the heating of the substrate portion 42. The aerosol may comprise a reduced concentration of aldehyde due to the presence of the nitrogen-containing nucleophilic compound in the aerosol forming substrate of the substrate portion 42.