EP0141097A2 - Process for preparing low-nicotine tobacco by high-pressure extraction - Google Patents

Abstract

The nicotine content of tobacco can be reduced by partially withdrawing the nicotine and by increasing the filling capacity, i.e. the specific volume of tobacco. Nicotine removal is accomplished by high pressure extraction using compressed gaseous solvents. To increase the filling capacity, the tobacco is impregnated with liquid or supercritical gases, then relaxed and post-treated. A disadvantage of the previous methods for nicotine removal by means of high-pressure extraction is that flavorings are also extracted. In order to at least largely leave the aroma substances in the tobacco, solvent, a mixture of nitrogen and carbon dioxide with 50 to 80% nitrogen content is used. The optimum pressures of 250 to 600 bar, which are suitable for selective nicotine extraction, are at the same time optimally suitable for increasing the filling capacity of the tobacco by relaxing it immediately after the extraction and subjecting it to a thermal aftertreatment.

Description

The invention relates to a process for the production of nicotine-free tobacco by high-pressure extraction of the nicotine with the aid of a compressed gaseous solvent, and optionally also to increase the filling capacity of the tobacco.

With the help of various gaseous solvents under high pressure, nicotine can be largely removed from tobacco. The pressures used can be so high that the solvents are in the liquid state or in the supercritical state. DE-OS 2 043 537 mentions, for example, CO ₂ , N _z O and Ar as suitable gaseous solvents. A disadvantage of this method is that in addition to nicotine, other, for. B. partially flavor-extracting ingredients will. According to a process known from DE-OS 2 142 205, this disadvantage is avoided in that the flavoring substances are extracted separately before the nicotine removal and the flavoring substances are added to the tobacco again after the nicotine extraction. This procedure is relatively complex and it cannot be ruled out that the sometimes complicated and sensitive aroma substances are adversely affected by such manipulations.

Another way of reducing the nicotine content in tobacco products is to improve the filling capacity of the tobacco used, ie to increase its specific volume (cm ³ / g). For this purpose, the tobacco is impregnated with liquid or supercritical gases under pressure, then relaxed and thermally treated by increasing the temperature. Suitable impregnation gases for this purpose are mentioned in DE-OS 2 903 300 N ₂ or Ar, in US Pat. No. 4,258,729 liquid CO ₂ .

However, these methods of tobacco bloating only lead to a doubling of the specific volume or filling capacity. The nicotine content in such pretreated tobacco products can therefore only be reduced by up to about 50%.

The invention has for its object to provide a process for the production of low-nicotine tobacco by high pressure extraction, which allows a largely isolated removal of nicotine without other ingredients, in particular aroma components, are also removed. In an advantageous development, the invention is intended to allow the filling capacity of the tobacco to be increased immediately after the nicotine extraction by lowering the pressure and thermal treatment and thus further reducing the specific nicotine content.

Starting from the prior art taken into account in the preamble of claim 1, this object is achieved according to the invention with the features specified in the characterizing part of claim 1.

Advantageous developments of the invention are specified in the subclaims.

The invention is essentially based on the finding that, surprisingly, mixtures of nitrogen and carbon dioxide of a certain composition have an almost selective solubility towards nicotine, although nitrogen alone has no or only an extremely small solvency, at least in the pressure range up to 500 bar. For all other ingredients in tobacco, however, the nitrogen-carbon dioxide mixtures behave like pure nitrogen and are therefore an extremely poor solvent. The mixtures of nitrogen and carbon dioxide stand out extremely advantageously compared to pure carbon dioxide, the solubility of which for nicotine, even at low pressures is excellent, but which also releases numerous tobacco ingredients such as waxes and flavorings.

A particular advantage of the process according to the invention is that the pressure and the composition of the nitrogen-carbon dioxide mixture can be selected such that relaxation and thermal aftertreatment of the tobacco can be carried out from a pressure which is optimal for the selective extraction of the nicotine this method is to increase the filling capacity of the tobacco. After the selective nicotine extraction, there is therefore no longer any need to change the pressure. Rather, the known inflation process can be carried out directly from the existing pressure. Through this this results in an economically extremely favorable overall process.

The choice of the optimum pressure for the process according to the invention depends primarily on the moisture content of the tobacco and the solvent. As a rule, working temperatures above 50 ° C are required, but in special cases temperatures down to 40 ° C may already be sufficient.

The extracted nicotine can be separated by changing the pressure and / or temperature of the solvent. The deposition of the nicotine can be effected particularly advantageously by adding another component to the solvent or by changing the composition of the solvent by adding one of the two components nitrogen or carbon dioxide.

The process according to the invention is carried out with solvent throughputs of at least 5 kg of solvent per kg of raw material, preferably with the assertion of 15 to 25 kg of solvent per kg of raw material. This leads to a reduction in the nicotine content in the raw material of at least 80 to over 90%. A further reduction in the nicotine content can be achieved if the raw material is released from the extraction pressure immediately after the extraction and is then subjected to a thermal aftertreatment. A short-term increase in temperature to at least 100 ° C., preferably to 150 to 350 ° C., is sufficient for this. The rapid outgassing of the gas components dissolved in the raw material leads to an increase in the specific volume of at least 20%, usually from 40 to 70%. The invention is explained in more detail with reference to the drawings.

• Fig. 1 den Druck maximaler Nikotinlöslichkeit als Funktion der Lösungsmittel-Zusammensetzung;
• Fig. 2 die Nikotinlöslichkeit als Funktion des Druckes für reines Kohlendioxid, reinen Stickstoff und ein Gemisch aus 75 % Stickstoff und 25 % Kohlendioxid;
• Fig. 3 zeigt die Abhängigkeit der relativen Extraktausbeuten und die der relativen maximalen Nikotin-Konzentrationen als Funktion der Lösungsmittelzusammensetzung;
• Fig. 4 zeigt ein Verfahrensschema des erfindungsgemäßen Verfahrens.

Show it:

• 1 shows the pressure of maximum nicotine solubility as a function of the solvent composition;
• 2 shows the nicotine solubility as a function of the pressure for pure carbon dioxide, pure nitrogen and a mixture of 75% nitrogen and 25% carbon dioxide;
• 3 shows the dependence of the relative extract yields and that of the relative maximum nicotine concentrations as a function of the solvent composition;
• 4 shows a process diagram of the process according to the invention.

1 shows the optimum pressures p _m in bar for the nicotine extraction with dry carbon dioxide as a function of the composition of the nitrogen-carbon dioxide mixture. The pressures of maximum nicotine solubility are given at a temperature of 50 ° C. Figure 2 shows nicotine solubility as a function of pressure at 50 ° C for the various solvents. Curve 1 indicates the solubility of carbon dioxide, curve 2 that of nitrogen and curve 3 that of a mixture according to the invention of 75% nitrogen and 25% carbon dioxide. As the illustration shows, pure nitrogen is practically unusable as a solvent, while pure carbon dioxide itself is an excellent solvent even at low pressures. Pure carbon dioxide also extracts other ingredients in addition to nicotine. Surprisingly, this is not the case with a solvent mixture of 75% and 25% carbon dioxide according to the invention. Although the overall solubility is lower than that of pure carbon dioxide and higher extraction pressures are required, a practically selective extraction of the nicotine is possible. The high pressures required can also be used directly to increase the filling capacity of the raw material.

wobei in etwa p₀ = (150 - 50) bar und p_g,T = (400 ± 50) bar gilt. Die genauen Werte hängen von der Feuchtigkeit des Rohstoffes und des Lösungsmittels ab sowie von der Art und Vorbehandlung des Tabaks.For the dependence of the optimal pressure on the composition of the solvent, the approximate formula at 50 ° C can be given:

p ₀ = (150 - 50) bar and p _g , T = (400 ± 50) bar. The exact values depend on the moisture of the raw material and the solvent as well as on the type and pretreatment of the tobacco.

Fig. 3 shows the dependence of the relative extract yields and that of the relative maximum nicotine concentrations as a function of the solvent composition at 50 ° C. Curve 4 shows the relative extract yield E (N _{2 /} CO ₂ ) / E (CO ₂ ). E (C0 ₂ ) is the total extract yield with a throughput of 10 kg of carbon dioxide per kilogram of raw material, E (N _{2 /} CO ₂ ), the extract obtained with a throughput of 10 kg of nitrogen-carbon dioxide mixture at the optimum pressure for the respective composition. Curve 5 indicates the relative nicotine saturation concentration c _N (N ₂ / CO ₂ ) / CN (CO ₂ ) as a function of solvent composition at 50 ° C. While the extract yield falls rapidly and continuously with increasing nitrogen content in the solvent mixture, the nicotine solubility is still at a good 40% of the value for pure carbon dioxide even at 75% nitrogen content, although nitrogen has practically no nicotine solubility at 450 bar and shows hardly measurable values even at 520 bar .

The advantages of the method according to the invention are immediately apparent from the figures. The composition of the solvent mixture of nitrogen and carbon dioxide extremely influences the selectivity of the extraction process in favor of nicotine and shifts the pressure that is optimal for the extraction of nicotine to values that make a subsequent improvement in filling capacity through thermal aftertreatment very effective.

Fig. 4 shows an embodiment of the inventive method by way of _V experienced schemas. The starting material for the nicotine extraction was commercial pipe tobacco.

• Trockensubstanzgehalt: TS = 85,6 %
• TS-Nikotingehalt bez. auf C _{Nik. =} ^{0,94 %}

Analysis data:

• Dry matter content: TS = 85.6%
• TS nicotine content on C _{Nik. =} ^0.94%

The tobacco is moistened to approx. 25% DM and the solvent that is taken from the storage tank 6 flows through in the extractor. The pressure of the solvent was increased accordingly in the compressor 4 and the corresponding temperature increase was carried out in the heat exchanger 5. The separation is effected via relaxation (valve 3), the extract is removed from the separator 2. The extraction and separation conditions are given in Table 1, the extraction result in Table 2.

With a similar nicotine reduction, there was a significant difference in the qualitative and sensory evaluation of the raw material after extraction: the tobacco treated with CO ₂ was significantly drier (DM 92%) and almost flavorless. In contrast, the tobacco treated with N _{2 /} CO _{2 was distinguished} by an almost unchanged aroma content and the moisture content was insignificantly reduced. In both trials, the treated tobacco was somewhat bloated. However, the increase in the specific volume only becomes clear after a thermal aftertreatment following the extraction and relaxation.

Claims (5)

1. Process for the production of nicotine-free tobacco by high-pressure extraction of the nicotine with the aid of a compressed gaseous solvent,
characterized,
that a mixture of nitrogen and carbon dioxide with 50 to 80% nitrogen content is used as solvent and the extraction is carried out at pressures between 250 and 600 bar and temperatures above 50 ° C. 2. The method according to claim 1,
characterized,
that the nitrogen content of the solvent is 70 to 80% and the extraction is carried out at pressures of 300 to 600 bar. 3. The method according to claim 1 or 2,
characterized,
that the deposition of the nicotine from the solvent is effected by changing the solvent composition after leaving the extraction container. 4. The method according to any one of claims 1 to 3,
characterized,
that to increase the filling capacity of the tobacco, it relaxes after the extraction of the nicotine and is subjected to a thermal aftertreatment at temperatures between 100 and 300 ° C. 5. The method according to claim 4,
characterized,
that the thermal aftertreatment is carried out at temperatures between 150 and 300 ° C.

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