Low-temperature extraction separation method of natural tobacco essential oil and essential oil thereof

Abstract

This invention discloses a low-temperature extraction and separation method for natural tobacco essential oil and the resulting essential oil, belonging to the field of natural product extraction and separation technology. The method first uses liquefied butane as a solvent to perform low-temperature continuous phase change extraction on tobacco raw materials; subsequently, two-stage molecular distillation is performed. The first-stage molecular distillation separates and removes insoluble heavy resins and pigments; the second-stage molecular distillation removes nicotine as a heavy component, and the light component is the high-purity, nicotine-free natural tobacco essential oil. This invention achieves efficient dealkalization through molecular distillation, resulting in an essential oil with a natural and pure aroma and extremely low nicotine content. It achieves high aroma, ultra-low nicotine, green and residue-free production, low cost, and industrial applicability, suitable for the high-end flavor and fragrance industry.

Description

Technical Field

[0001] This invention belongs to the field of natural product extraction and separation technology and cigarette technology, specifically relating to a low-temperature extraction and separation method for natural tobacco essential oil and the essential oil thereof. Background Technology

[0002] Tobacco is not only an economic crop, but it also contains abundant natural aroma components, which have high application value in the food, flavoring, and cosmetic industries. However, nicotine in tobacco is an addictive and toxic alkaloid, which severely limits the application of tobacco essential oils in a wider range of fields.

[0003] Currently, traditional methods for extracting essential oils from tobacco include steam distillation, solvent extraction, and supercritical CO2 extraction. However, these methods have several drawbacks: Steam distillation requires high operating temperatures (usually exceeding 100°C), which can cause the decomposition, oxidation, or isomerization of heat-sensitive aroma components in tobacco, thus affecting the natural aroma and quality of the essential oil. Conventional solvent extraction uses solvents such as ethanol and petroleum ether, achieving high extraction rates but leaving solvent residues and exhibiting poor selectivity. It also extracts large amounts of non-target components such as pigments, waxes, and nicotine along with the essential oil, making subsequent purification steps complex. Supercritical CO2 extraction, while operating at lower temperatures and offering better selectivity, has high equipment investment and operating costs, and requires extremely high operating pressures (typically 20-30 MPa), limiting its large-scale industrial application. Furthermore, the tobacco extracts obtained by these methods typically have high nicotine content, requiring additional and complex nicotine removal processes, such as acid-base treatment and chromatographic separation. These processes involve numerous steps, potentially introducing chemical reagents again and leading to the loss of aroma components.

[0004] Therefore, developing a novel extraction and separation method that can be carried out at low temperatures, is highly efficient and energy-saving, has good selectivity, and can fundamentally and effectively separate nicotine to obtain high-quality, high-purity natural tobacco essential oil is of great industrial significance. Summary of the Invention

[0005] This invention provides a novel extraction and separation method that can be carried out at low temperatures, is highly efficient and energy-saving, has good selectivity, leaves no solvent residue, and can fundamentally and effectively separate nicotine to directly obtain high-quality natural tobacco essential oil.

[0006] This invention provides a low-temperature extraction and separation method for natural tobacco essential oil, comprising the following steps:

[0007] S1: Using liquefied butane as the extraction solvent, continuous phase change extraction was carried out on tobacco raw materials at 25℃~50℃ and 0.3MPa~0.8MPa to obtain crude oleoresin extract; S2: The crude oleoresin extract obtained in step S1 is subjected to primary molecular distillation at a temperature of T1 and a pressure of 50 Pa to 200 Pa to collect the light fraction, which is recorded as the primary light fraction. S3: The primary light component obtained in step S2 is subjected to secondary molecular distillation at a temperature of T2 and a condition of 5 Pa to 15 Pa, where T2 > T1. The light component is collected to obtain the nicotine-free natural tobacco essential oil.

[0008] Furthermore, in step S1, the extraction time is 60 to 120 minutes.

[0009] Furthermore, in step S1, the tobacco raw material is one or both of flue-cured tobacco and sun-cured tobacco.

[0010] Further, in step S1, the tobacco raw material is pre-dried to a moisture content of ≤8% and pulverized to 20-60 mesh.

[0011] Furthermore, in step S1, after extraction is completed, liquefied butane is recovered by heating and reducing pressure.

[0012] Furthermore, in step S1, the continuous phase change extraction is countercurrent extraction.

[0013] Furthermore, in step S2 and / or step S3, the molecular distillation is a scraped-film molecular distillation.

[0014] Furthermore, the temperature T1 is 80°C to 100°C; in step S3, the temperature T2 is 120°C to 140°C.

[0015] In another aspect, the present invention provides a natural tobacco essential oil prepared by any of the above methods. The tobacco essential oil prepared by the method of the present invention is of high quality and high purity, with a nicotine content of less than 10 ppm.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention innovatively employs a two-stage molecular distillation process. The first-stage molecular distillation removes polymer resins and waxes, achieving preliminary purification. The second-stage molecular distillation utilizes the difference in saturated vapor pressure between nicotine and essential oil components to achieve precise separation under high vacuum, removing nicotine as a heavy component. The nicotine content can be reduced to below 10 ppm, achieving the "nicotine-free" level.

[0017] 2. Low-temperature butane continuous phase change extraction is adopted. The entire process is carried out at near room temperature (25℃-50℃), which maximizes the protection of the natural structure and activity of heat-sensitive aroma components in tobacco and avoids aroma damage caused by high temperature. The resulting essential oil has a pure and natural aroma and a high yield, which improves the essential oil yield without destroying the aroma.

[0018] 3. This invention uses butane as a natural solvent, which is non-toxic and harmless, and is highly volatile. It can be recycled through a recovery system with a recovery rate of ≥95%, eliminating the risk of solvent residue and meeting the requirements of green chemistry and safe production.

[0019] 4. The present invention can achieve continuous or semi-continuous operation from extraction to separation. The process is simple, easy to operate, and suitable for large-scale industrial production.

[0020] 5. This invention combines low-temperature butane continuous phase change extraction with two-stage molecular distillation. Low-temperature butane extraction provides a clean crude extract with a low nicotine background. The first-stage molecular distillation provides a feedstock for the second-stage distillation without heavy interference. The second-stage molecular distillation achieves ultra-deep nicotine removal. All three are indispensable and work synergistically. This invention is applicable to various raw materials such as flue-cured tobacco and sun-cured tobacco, with high yield and complete aroma retention, combining economy and practicality. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A process flow diagram of the low-temperature extraction and separation method for natural tobacco essential oil shown in Embodiment 1 of the present invention is illustrated. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] The following persistent pain points remain unresolved in existing tobacco essential oil extraction technologies: 1) Incompatibility between aroma quality and yield: While high-temperature steam distillation is inexpensive, it leads to the decomposition of heat-sensitive aroma components, resulting in low yield. Supercritical CO2 extraction, although enabling low-temperature operation, requires 8-10 times the equipment investment of butane extraction equipment with equivalent capacity, creating a dilemma of "high temperature failing to preserve aroma, low temperature being too costly." 2) Incomplete nicotine removal: Traditional processes typically yield essential oils with nicotine content ranging from hundreds to thousands of ppm, far from meeting the tobacco industry's requirement of "nicotine-free" (usually <10 ppm). 3) Fragmented process chain: Extraction and dealkalization are often performed as two independent unit operations, lacking an integrated continuous solution, resulting in lengthy processes and increased aroma loss. 4) Significant industrialization bottlenecks: Supercritical methods are too expensive, steam and solvent methods have poor quality, and while laboratory-level chromatography can achieve precise separation, it is difficult to scale up. These pain points are considered "natural" technical contradictions. High quality, low nicotine, low cost, and scalability cannot be simultaneously achieved. For a long time, those skilled in the art have tended to make local optimizations within the existing process framework (such as adjusting the distillation temperature or changing the extraction solvent). This invention systematically integrates "low-temperature liquefied butane extraction" with "functionally differentiated two-stage molecular distillation," innovatively adopting a two-stage molecular distillation process. Through the synergy of low-temperature continuous butane phase change extraction and two-stage molecular distillation, it achieves a simultaneous breakthrough in achieving four goals: "high aroma, ultra-low nicotine, green and residue-free, and low-cost industrialization."

[0025] This invention provides a low-temperature extraction and separation method for natural tobacco essential oil, comprising the following steps: S1: Using liquefied butane as the extraction solvent, continuous phase change extraction was carried out on tobacco raw materials at 25℃~50℃ and 0.3MPa~0.8MPa to obtain crude oleoresin extract; S2: The crude oleoresin extract obtained in step S1 is subjected to primary molecular distillation at a temperature T1 and a vacuum of 50 Pa to 200 Pa to collect the light fraction, which is recorded as the primary light fraction. T1 is 80 °C to 100 °C. S3: The primary light component obtained in step S2 is subjected to secondary molecular distillation at a temperature of T2 and a vacuum of 5 Pa to 15 Pa, where T2 > T1. The light component is collected to obtain the natural tobacco essential oil.

[0026] Light components refer to substances with smaller molecular weights and lower boiling points that are more likely to escape from the liquid surface and be condensed and collected under given temperature and vacuum conditions during molecular distillation. In this invention, during the first-stage molecular distillation in step S2, aroma components (terpenes, ketones, esters, etc.) and most nicotine are considered "light components" due to their relatively low boiling points; heavy resins, waxes, pigments, etc., with larger molecular weights and higher boiling points are retained and removed as "heavy components." During the second-stage molecular distillation in step S3, aroma components with relatively lower boiling points are considered "light components," while nicotine with higher boiling points is considered a "heavy component" and is separated and removed.

[0027] In another embodiment, the tobacco raw material is pretreated before extraction. The tobacco raw material is pre-dried to a moisture content of ≤8% and pulverized to 20-60 mesh. Suitable raw material particle size and moisture content can significantly improve the penetration and dissolution efficiency of liquefied butane for aroma components, achieving optimal raw material permeability, more complete extraction, minimal impurity introduction, and improved yield.

[0028] In another embodiment, the tobacco raw materials applicable to this invention are selected from one or more of flue-cured tobacco and sun-cured tobacco.

[0029] In another embodiment, the extraction time can be 60–120 minutes. This ensures extraction efficiency while avoiding excessive dissolution of impurities due to prolonged extraction, resulting in a more optimal proportion of aroma components in the crude extract.

[0030] In another embodiment, the continuous phase change extraction can be countercurrent extraction. Countercurrent extraction maximizes the contact efficiency between the solvent and the feedstock, further shortening the extraction time and increasing the yield.

[0031] In another embodiment, in step S1, after extraction, liquefied butane is recovered by heating and reducing pressure. The recovered butane can be recycled, with a recovery rate of ≥95%, achieving near-complete solvent recovery, eliminating residues, meeting the requirements of green industrial production, and significantly reducing operating costs.

[0032] In another embodiment, in step S2, the temperature T1 is 80°C to 100°C; in step S3, T2 is 120°C to 140°C. After extraction, the crude tobacco oleoresin extract undergoes two-stage molecular distillation. The first-stage molecular distillation is carried out at a temperature of 80°C–100°C and a vacuum of 50Pa–200Pa to remove heavy resins, waxy impurities, and pigments without losing the essential oil. The second-stage molecular distillation is carried out at a temperature of 120°C–140°C and a vacuum of 5Pa–15Pa to separate nicotine as a heavy component, collecting the light component to obtain nicotine-free natural tobacco essential oil. This achieves precise separation of essential oil and nicotine, removing nicotine to below 10 ppm without damaging the aroma.

[0033] In another embodiment, in steps S2 and S3, the molecular distillation can be a scraped-film molecular distillation. Scraped-film distillation can form an extremely thin and constantly renewed liquid film, which greatly improves mass transfer and separation efficiency, ensuring the precise removal of heavy impurities and nicotine while maintaining the integrity of the aroma, without affecting the yield.

[0034] like Figure 1 As shown, this embodiment of the invention provides a low-temperature extraction and separation method for natural tobacco essential oil. Step S1 specifically involves drying and pulverizing the tobacco raw material (moisture content controlled below 8%, pulverized to 20-60 mesh), then feeding it into a continuous phase change extraction device. Liquid butane is used as the extraction solvent, and continuous countercurrent extraction is performed under low-temperature conditions: extraction temperature 25°C to 50°C, extraction pressure 0.3 MPa to 0.8 MPa, and extraction time 60-120 minutes. Under these conditions, butane selectively dissolves oil-soluble aroma components and some resins in the tobacco, obtaining a crude extract of tobacco oleoresin rich in natural aroma components.

[0035] Step S2 can be performed by primary molecular distillation of the crude tobacco oil resin extract obtained in step S1 to separate insoluble heavy resins: distillation temperature 80℃ to 100℃, system vacuum degree 50Pa to 200Pa. Under these conditions, the light essential oil components and most of the nicotine are distilled off and collected as light components; while high molecular weight resins, pigments, and waxes are retained and separated as heavy components, thereby achieving preliminary purification.

[0036] Specifically, step S3 involves performing a second-stage molecular distillation on the light fraction obtained from the primary molecular distillation in step S2 to precisely separate nicotine from the target essential oil components: the distillation temperature is 120°C to 140°C, and the system vacuum is 5Pa to 15Pa. Under these conditions, the tobacco essential oil components with relatively low boiling points are preferentially distilled out and collected, which is the nicotine-free natural tobacco essential oil; while the nicotine with higher boiling points and a small amount of residual heavy components are effectively removed as heavy components.

[0037] The tobacco essential oil obtained in the embodiments of the present invention not only has a nicotine content of ≤10ppm, but also fully retains the natural aroma spectrum of tobacco, with no solvent residue, and can be directly used in the fields of cigarettes and high-end flavorings and fragrances.

[0038] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0039] Example 1 1) Take flue-cured tobacco from Guangdong, dry it until the moisture content is ≤6%, and grind it to 40 mesh.

[0040] 1 kg of the above-mentioned tobacco powder was added to a continuous phase change extraction device, liquefied butane was introduced, and the extraction temperature was controlled at 35°C, the extraction pressure at 0.5 MPa, and dynamic extraction was performed for 90 minutes. After extraction, the extract was separated by analysis to obtain 85 g of dark brown crude tobacco oleoresin extract.

[0041] 2) First-stage molecular distillation: The above 85g crude extract was subjected to scraped-film molecular distillation. The distillation temperature was set to 90℃ and the system vacuum to 100Pa. 71g of light components and 7g of heavy components (mainly resin) were collected.

[0042] 3) Secondary molecular distillation: The 78g light fraction obtained from the primary distillation was subjected to a second scraped-film molecular distillation. The distillation temperature was set at 130℃ and the system vacuum at 10Pa. Under these conditions, the collected light fraction, which is the target product—nicotine-free natural tobacco essential oil, weighed 55g; the remaining heavy fraction (rich in nicotine) weighed 13g.

[0043] Product testing: GC-MS analysis and nicotine content determination were performed on 55g of the final tobacco essential oil. Results showed that it had a rich aroma, exhibiting typical characteristics of flue-cured tobacco. The nicotine content, determined by high-performance liquid chromatography (HPLC), was 8 ppm, with a yield (relative to the dry weight of the raw material) of 5.5%.

[0044] Example 2 1) Take Guangdong sun-dried tobacco, dry it until the moisture content is ≤7%, and grind it to 60 mesh.

[0045] 1 kg of tobacco powder was added to the apparatus, liquefied butane was introduced, and the extraction temperature was controlled at 25℃, the extraction pressure at 0.5 MPa, and dynamic extraction was performed for 90 minutes. 92 g of crude tobacco oleoresin extract was obtained.

[0046] 2) Primary molecular distillation: Distillation temperature 80℃, system vacuum 50Pa. Collect 86g of light fraction.

[0047] 3) Secondary molecular distillation: Distillation temperature 120℃, system vacuum 5Pa. Collect 71g of light fraction.

[0048] Product testing: The obtained essential oil has a sweet aroma, a nicotine content of 6 ppm, and a yield of 7.1%.

[0049] Example 3 1) Take Yunnan flue-cured tobacco, dry it until the moisture content is ≤5%, and grind it to 20 mesh.

[0050] Low-temperature continuous phase change extraction: 1 kg of tobacco powder was added to the apparatus, liquefied butane was introduced, and the extraction temperature was controlled at 50℃, the extraction pressure at 0.3 MPa, and dynamic extraction was performed for 60 minutes. 78 g of crude tobacco oleoresin extract was obtained.

[0051] 2) Primary molecular distillation: Distillation temperature 100℃, system vacuum 200Pa. Collect 68g of light components.

[0052] 3) Secondary molecular distillation: Distillation temperature 140℃, system vacuum 15Pa. Collect 54g of light fraction.

[0053] Product testing: The obtained essential oil has a rich aroma, a nicotine content of 9 ppm, and a yield of 5.4%.

[0054] Comparative Example 1 Take 1 kg of Guangdong flue-cured tobacco from the same batch as in Example 1, and use the traditional steam distillation method: place the tobacco powder in a volatile oil extractor, soak it in water, heat and distill for 4 hours, collect the distillate, extract it with ether to remove the solvent, and obtain a light yellow essential oil.

[0055] Results: The yield was only 0.2% (2g), and the essential oil had a distinct burnt and grassy odor. HPLC analysis revealed a nicotine content as high as 1520ppm. This was because the high-temperature steam destroyed the heat-sensitive aroma components, and some of the nicotine evaporated with the steam, making effective separation impossible.

[0056] Comparative Example 2 One kilogram of Guangdong flue-cured tobacco from the same batch as in Example 1 was extracted twice with 6 times the amount of 95% ethanol at 60°C for 2 hours each time. The extracts were combined, and the ethanol was recovered under reduced pressure to obtain 185g of dark green crude extract. This crude extract was directly subjected to first-stage molecular distillation (conditions as in step 2 of Example 1: 90°C, 100Pa), and the light fraction was collected. This light fraction was then subjected to second-stage molecular distillation (conditions as in step 3 of Example 1: 130°C, 10Pa), and the final light fraction was collected. Results: 22g of essential oil was finally obtained, with a yield of 2.2%. The nicotine content was found to be 340ppm, and the essential oil contained residual ethanol solvent odor and some waxy odor, indicating that the aroma was not pure enough. This shows that even after molecular distillation, single-solvent extraction cannot completely remove nicotine and unpleasant odors, and the yield is low.

[0057] Comparative Example 3 Take 1 kg of Guangdong flue-cured tobacco from the same batch as in Example 1, and extract it twice at 50°C for 2 hours each time with 6 times the amount of petroleum ether with a boiling range of 60-90°C. Combine the extracts and recover the petroleum ether under reduced pressure to obtain 76 g of tobacco oleoresin. Directly steam distill the resin (100°C) to remove residual solvent and some light components to obtain essential oil.

[0058] Results: Yield was 3.1% (31g). Petroleum ether residue (0.5%) was detected in the essential oil, which does not meet relevant requirements. Nicotine content was 860ppm, and the aroma had a slight chemical solvent odor. This indicates that petroleum ether has poor selectivity, and the problem of solvent residue is difficult to solve.

[0059] Comparative Example 4 One kilogram of Guangdong flue-cured tobacco from the same batch as in Example 1 was used for supercritical CO2 extraction: extraction pressure 25 MPa, extraction temperature 40°C, CO2 flow rate 20 L / h, extraction time 2 hours, separation vessel pressure 6 MPa, and separation temperature 35°C. 52 g of orange-yellow tobacco extract was collected.

[0060] The extract was directly subjected to primary molecular distillation (same as step 2 of Example 1, primary conditions) and secondary molecular distillation (same as step 3 of Example 1, secondary conditions) to collect the final light fraction. Result: 38g of essential oil was finally obtained, with a yield of 3.8%.

[0061] Testing revealed a nicotine content of 45 ppm, with a pure aroma. Although the nicotine content is relatively low, the equipment investment is enormous (the cost of supercritical equipment is approximately 8-10 times that of butane extraction equipment with the same capacity), the operating pressure is high, and the energy consumption is large, thus limiting its industrial-scale promotion.

[0062] Comparative Example 5 Take 1 kg of Guangdong flue-cured tobacco from the same batch as in Example 1, and obtain 85 g of crude tobacco oleoresin extract by following step 1 of Example 1 (low-temperature continuous phase change extraction).

[0063] Molecular distillation: The crude extract was directly subjected to molecular distillation (90℃, 100Pa), and 78g of the light fraction was collected.

[0064] Results: 78g of product was obtained, with a yield of 7.8%. The product contained a high nicotine content of 520ppm, as well as some heavy components. It was dark in color, had poor flowability, and lacked a pronounced aroma. This indicates that single-stage molecular distillation alone cannot effectively remove nicotine; two-stage molecular distillation under high vacuum is necessary to achieve precise separation of nicotine from the target essential oil.

[0065] Table 1. E-liquid yield and quality under different extraction and separation methods

[0066] Example 1 of this invention demonstrates the best overall performance in terms of yield, nicotine removal efficiency, aroma quality, safety, and economy. Although Comparative Example 4 (supercritical CO2 method) also achieves a low nicotine content, its equipment investment and operating costs are far higher than those of this invention, and its yield is also lower. While Comparative Example 5 has a higher yield, its nicotine content is severely excessive, failing to meet the requirements for nicotine-free products. The combined process of "low-temperature butane continuous phase change extraction + two-stage molecular distillation" in this invention exhibits a significant synergistic effect, simultaneously achieving the four objectives of "high aroma, ultra-low nicotine, green and residue-free, and low-cost industrialization."

[0067] Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the invention. The scope of the present invention is defined by the appended claims and their equivalents.

[0068] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A low-temperature extraction and separation method for natural tobacco essential oil, characterized in that, Includes the following steps: S1: Using liquefied butane as the extraction solvent, continuous phase change extraction was carried out on tobacco raw materials at 25℃~50℃ and 0.3MPa~0.8MPa to obtain crude oleoresin extract; S2: The crude oleoresin extract obtained in step S1 is subjected to primary molecular distillation at a temperature T1 and a vacuum of 50 Pa to 200 Pa to collect the light fraction, which is recorded as the primary light fraction. T1 is 80 °C to 100 °C. S3: The primary light component obtained in step S2 is subjected to secondary molecular distillation at a temperature of T2 and a vacuum of 5 Pa to 15 Pa to collect the light component, thereby obtaining the natural tobacco essential oil, where T2 > T1.

2. The method according to claim 1, characterized in that, The nicotine content of the natural tobacco essential oil obtained in step S3 is below 10 ppm.

3. The method according to claim 1, characterized in that, In step S1, the extraction time is 60–120 minutes.

4. The method according to claim 1, characterized in that, In step S1, the tobacco raw material is pre-dried to a moisture content of ≤8% and pulverized to 20-60 mesh.

5. The method according to claim 1, characterized in that, In step S1, after extraction is completed, liquefied butane is recovered by heating and reducing pressure.

6. The method according to claim 1, characterized in that, In step S2 and / or step S3, the molecular distillation is a scraped-film molecular distillation.

7. The method according to claim 1, characterized in that, In step S2, the temperature T1 is 80°C to 100°C; in step S3, the temperature T2 is 120°C to 140°C.

8. The method according to claim 1, characterized in that, The tobacco raw materials are selected from one or more types of flue-cured tobacco and sun-cured tobacco.

9. The method according to claim 1, characterized in that, In step S1, the continuous phase change extraction is countercurrent extraction.

10. A natural tobacco essential oil, characterized in that, Prepared by the method described in any one of claims 1 to 9.

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