Method for efficiently extracting Chinese fir essential oil

Abstract

The present application belongs to the technical field of plant essential oil extraction, and particularly relates to a method for efficiently extracting Chinese fir essential oil, which comprises the following steps: performing water pre-impregnation treatment on Chinese fir sawdust to obtain pre-impregnated raw materials; performing fractional distillation on the pre-impregnated raw materials by using superheated steam, and obtaining Chinese fir essential oil after oil-water separation, wherein the fractional distillation comprises primary distillation and secondary distillation performed in sequence, and the temperature of the primary distillation is lower than that of the secondary distillation. The present application has the beneficial effect that pre-impregnation can make the dry and dense cell walls of Chinese fir sawdust soften by absorbing water, reopen the micropores and pit holes closed due to water loss, and actively push the essential oil out from the inside. Fractional distillation first extracts heat-sensitive and low-boiling-point components at a lower temperature to avoid their decomposition or polymerization due to long-time high-temperature heating, and then forcibly extracts high-boiling-point main components (such as cedrol) at a higher temperature. The synergy of the two achieves a substantial improvement in the extraction rate and quality of essential oil.

Description

Technical Field

[0001] This invention belongs to the field of plant essential oil extraction technology, specifically relating to a method for efficiently extracting cedar essential oil. Background Technology

[0002] Chinese fir is one of my country's important fast-growing commercial timber species, accounting for 20% to 25% of the country's total commercial timber production. However, a large amount of fir sawdust is generated annually during timber processing, which is not fully utilized, resulting in a significant waste of resources. Fir sawdust is rich in essential oils, the main components of which are cedrene and cedreol, which can be used in the pharmaceutical, fragrance, and fine chemical industries. Therefore, extracting and utilizing the essential oils from fir sawdust can save resources, protect the environment, and increase the economic value of Chinese fir.

[0003] Currently, common methods for extracting cedarwood essential oil include organic solvent extraction, supercritical CO2 extraction, dry distillation, and steam distillation. Organic solvent extraction suffers from solvent residue issues; supercritical CO2 extraction yields high-cost oil; dry distillation produces oil with a burnt taste and dark color, affecting product quality; steam distillation produces clear, transparent cedarwood essential oil with a pure aroma, and is currently the widely used method. However, atmospheric pressure steam distillation at lower temperatures results in low oil yields; pressurized steam distillation can increase the temperature, thus improving the oil yield, but requires equipment such as a high-pressure boiler. Superheated steam distillation can increase the distillation temperature at atmospheric pressure, thereby increasing the oil yield and effectively solving the problems of equipment investment and safety.

[0004] In existing technologies, researchers have attempted to improve the extraction process by using hot water soaking and variable-temperature distillation. For example, Chinese patent document CN112159726A discloses a method for producing cedar bio-essential oil from cedar sawdust, which involves soaking in 40°C hot water with the addition of surfactants (such as ethylene oxide, ethanolamine, or butylphenol), followed by three-stage variable-temperature distillation (120~165°C). However, this method has the following drawbacks: First, surfactants must be added as auxiliaries, which not only increases the cost of raw materials and the burden of subsequent separation, but also the residue of chemical auxiliaries may affect the natural quality of the essential oil, and the sawdust residue after extraction is difficult to reuse directly; Second, its distillation temperature is relatively low (maximum only 165°C), which cannot fully extract the high-boiling-point essential oil components (such as cedarwood alcohol with a boiling point of 294°C) from the cedar sawdust, resulting in a limited total oil yield; Third, it uses atmospheric pressure steam instead of superheated steam, resulting in low thermal efficiency.

[0005] Therefore, developing a method for extracting cedar essential oil that requires no chemical additives, uses simple equipment, and can both improve the oil yield and ensure the high quality of the essential oil is of great practical significance. Summary of the Invention

[0006] The purpose of this invention is to provide a highly efficient method for extracting cedar essential oil, in order to solve the following problems existing in the prior art: the decrease in moisture content of dried cedar wood chips leads to the closure of cell wall micropores and capillary channels, resulting in reduced cell permeability and increased mass transfer resistance, making it difficult for superheated steam to effectively break through the dry, dense, and hydrophobic cell wall barrier; at the same time, prolonged high-temperature distillation easily damages low-boiling-point and heat-sensitive chemical components, resulting in a decrease in essential oil extraction rate and quality.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for efficiently extracting cedarwood essential oil, comprising the following steps: Pre-impregnated fir sawdust with water to obtain pre-impregnated raw material; The pre-impregnated raw material is subjected to fractional distillation using superheated steam, and cedar essential oil is obtained after oil-water separation. The fractional distillation includes a first-stage distillation and a second-stage distillation performed sequentially, with the temperature of the first-stage distillation being lower than that of the second-stage distillation.

[0008] Furthermore, in the above-mentioned method for efficiently extracting cedarwood essential oil, the temperature of the first-stage distillation is 130~220℃, and the time is 1~5 h.

[0009] Furthermore, in the above-mentioned method for efficiently extracting cedarwood essential oil, the temperature of the first-stage distillation is 160~190℃, and the time is 1~5 h.

[0010] As described above, this temperature range can gently distill out heat-sensitive and low-boiling-point components (such as some terpenes) from cedar wood chips, avoiding decomposition, oxidation, or discoloration caused by excessively high temperatures or prolonged times; at the same time, sufficient time ensures the sufficiency of extraction in the low-temperature range.

[0011] Furthermore, in the above-mentioned method for efficiently extracting cedarwood essential oil, the temperature of the secondary distillation is 220~280℃, and the time is 3~6 h.

[0012] As described above, after the first distillation, the temperature is increased to this range, utilizing the high enthalpy of superheated steam to forcibly extract essential oil components with high boiling points (such as cypressin, boiling point 294℃) that remain deep within the cell walls. This temperature and time range ensures the full distillation of high-boiling-point components, which is key to achieving a significant increase in the overall extraction rate.

[0013] Furthermore, in the above-mentioned method for efficiently extracting cedarwood essential oil, the temperature of the first-stage distillation is 190℃ and the time is 3 hours; the temperature of the second-stage distillation is 250℃ and the time is 5 hours.

[0014] As described above, under these conditions, the total extraction rate of essential oil and the extraction rate of cypress alcohol both reach their optimal values, and the resulting essential oil is clear, transparent, and has a pure aroma.

[0015] Furthermore, in the above-mentioned method for efficiently extracting cedar essential oil, the flow rate of the superheated steam is 865~2465 mL / h.

[0016] As described above, the parameter settings ensure sufficient contact time between the steam and the sawdust particles, thereby improving extraction efficiency.

[0017] Furthermore, in the above-mentioned method for efficiently extracting cedar essential oil, the mass ratio of cedar wood chips to water is 1:1 to 1:3.

[0018] As described above, this ratio range ensures sufficient pre-impregnation. If the water content is too low (e.g., below 1:1), the sawdust will not absorb enough water, the cell walls will not soften sufficiently, and the mass transfer channels will be limited. If the water content is too high (e.g., above 1:3), it may lead to increased energy consumption in subsequent distillation or clumping of raw materials.

[0019] Furthermore, in the above-mentioned method for efficiently extracting cedar essential oil, the particle size of the cedar wood chips is 0.15~2.0 mm.

[0020] As described above, this particle size range takes into account both mass transfer efficiency and operational feasibility: if the particle size is too small, it can easily lead to clogging of the distillation column, short circuit of the gas flow, or dust entrainment; if the particle size is too large, the internal mass transfer distance is too long, and the essential oil is difficult to diffuse from the center of the particle to the surface, resulting in incomplete extraction.

[0021] Furthermore, in the above-mentioned method for efficiently extracting cedar essential oil, the cedar wood chips are cedar processing residues that are naturally air-dried or oven-dried to a moisture content of less than 15%.

[0022] As described above, conventional steam distillation of this type of sawdust has extremely low extraction efficiency due to the closure of cell wall channels. The pre-impregnation step of this invention is specifically designed for this particular raw material state, effectively "activating" the mass transfer channels that have closed due to water loss, thus overcoming the shortcomings of existing technologies in terms of low extraction efficiency of dried raw materials.

[0023] The beneficial effects of this invention are as follows: The efficient method for extracting cedar essential oil utilizes a combination of water pre-impregnation and staged superheated steam distillation to achieve the following effects: First, pre-impregnation softens the cell walls of dried cedar wood chips and opens mass transfer channels. Combined with the micro-explosion effect generated by the vaporization of water within the cells due to heat, this increases the total extraction rate of essential oil compared to direct distillation without pre-impregnation. Second, staged distillation first protects heat-sensitive and low-boiling-point components at a lower temperature, then extracts high-boiling-point components at a higher temperature, increasing the extraction rate of the key active ingredient, cedrol. The resulting essential oil is clear, transparent, has a pure aroma, and is free of burnt odor. Furthermore, pre-impregnation using only water eliminates the need for any surfactants or other chemical additives, simplifying the process and reducing separation costs. It also avoids additive residues, and the extracted wood chip residue is free of chemical pollution and can be safely reused. This invention uses forestry processing residues such as cedar wood chips as raw materials, which is beneficial for environmental protection and the recycling of forest resources. Attached Figure Description

[0024] Figure 1 A schematic diagram of cell permeability of ray parenchyma cells, axial tracheids and pits in cedar wood chips at different water contents; Figure 2 Gas chromatograms of direct distillation in Comparative Example 1 and fractional distillation (190 / 250) in Example 1, which are specific embodiments of the present invention. Figure 3 Gas chromatograms of direct distillation in Comparative Example 2 and fractional distillation (160 / 250) in Example 2, which are specific embodiments of the present invention; Figure 4 Gas chromatograms of direct distillation in Comparative Example 3 and fractional distillation (220 / 250) in Example 3, which are specific embodiments of the present invention. Detailed Implementation

[0025] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0026] This invention investigated the changes in the extraction rate of cedarwood essential oil and the relative content of cedarwood alcohol. The results showed that the pre-impregnation process helps improve the permeability of ray parenchyma cells, axial tracheids, and pits in cedarwood sawdust (see reference). Figure 1 This process effectively constructs mass transfer channels, reduces the barrier effect of cell walls, and promotes the exudation of essential oils. Furthermore, the localized vaporization of water inside the cells due to heat generates minute "explosive" forces, which also "push" the essential oils out from the inside, thereby increasing the extraction rate. Fractional distillation can reduce the decomposition, hydrolysis, or polymerization of heat-sensitive components caused by prolonged high-temperature distillation, thus improving the extraction rate and quality of essential oils. The pre-impregnation-fractional distillation technique combines the effects of pre-impregnation and fractional distillation, further contributing to improved essential oil extraction rate and quality.

[0027] Example 1 A method for efficiently extracting cedarwood essential oil, the preparation steps of which are as follows: (1) Select fir wood chips with a particle size of 0.15~2.0 mm as raw materials (the fir wood chips are naturally air-dried and have a moisture content of less than 15%). (2) The cedar wood chips from step (1) are pre-impregnated with water at a mass ratio of 1:2. The mixture is soaked at room temperature for 60 minutes to form pre-impregnated raw material (semi-dry material). (3) Place the pre-impregnated raw material from step (2) evenly in a distillation vessel, and introduce superheated steam into the distillation vessel for fractional distillation. The flow rate of superheated steam is 1470 mL / h, and the distillation is carried out at atmospheric pressure. The fractional distillation is as follows: first-stage distillation temperature 190℃, time 3 h, second-stage distillation temperature 250℃, time 5 h. (4) Introduce all the oil-water mixture distilled in step (3) into the condenser, cool it to obtain an oil-water mixture, and then separate the oil-water mixture to obtain cedar essential oil.

[0028] Results: The extraction rate of cedarwood essential oil obtained in this example was 1.20% (of which the first-stage distillation extraction rate was 0.357% and the second-stage distillation extraction rate was 0.843%).

[0029] Comparative Example 1 (As a control of Example 1, the same raw materials were used but no pre-impregnation and fractional distillation were performed.) A method for extracting cedarwood essential oil, the preparation steps of which are as follows: (1) Select fir wood chips with a particle size of 0.15~2.0 mm as raw materials (the fir wood chips are naturally air-dried and have a moisture content of less than 15%). (2) Place the cedar wood chips from step (1) into a distillation vessel and pass superheated steam at a rate of 1470 mL / h into the vessel for direct distillation to extract cedar wood essential oil. The direct distillation is carried out at a distillation temperature of 250℃ for 8 h.

[0030] (3) The oil-water mixture distilled in step (2) is introduced into the condenser and cooled to obtain an oil-water mixture liquid. The oil-water mixture liquid is then separated to obtain cedar essential oil.

[0031] In Comparative Example 1, the process of direct one-step distillation to 250℃ resulted in an essential oil extraction rate of only 0.95%.

[0032] Comparative analysis of Example 1 and Comparative Example 1: The extraction rate of cedarwood essential oil obtained in Example 1 was 1.20% (0.357% for primary grade and 0.843% for secondary grade), which was 26.3% higher than that of direct distillation to 250°C without pre-impregnation (extraction rate 0.95%). The extraction rate of cedarwood alcohol increased from 0.56% to 0.71%, an increase of 26.8%. Figure 2 ).

[0033] The essential oil obtained in Example 1 was clear and transparent, pale yellow in color, with a pure cedarwood aroma, and free from any burnt odor or residual chemical odor. (See gas chromatogram for reference.) Figure 2 Analysis of the essential oil yield showed that the content of low-boiling-point components in the essential oil obtained by the method in Example 1 was significantly higher than that of direct distillation in Comparative Example 1, indicating that heat-sensitive components were effectively protected.

[0034] Example 2 A method for efficiently extracting cedarwood essential oil, the preparation steps of which are as follows: (1) Select fir wood chips with a particle size of 0.15~2.0 mm as raw materials. (The fir wood chips are naturally air-dried with a moisture content of less than 15%) (2) The cedar wood chips from step (1) are pre-impregnated with water at a mass ratio of 1:1.5. The mixture is soaked at room temperature for 60 minutes to form pre-impregnated raw material (semi-dry material). (3) Place the pre-impregnated raw material from step (2) evenly in a distillation vessel, and introduce superheated steam into the distillation vessel for fractional distillation. The flow rate of the superheated steam is 1195 mL / h, and the distillation is carried out at atmospheric pressure. The fractional distillation is as follows: first-stage distillation temperature 160℃, time 4 h, second-stage distillation temperature 250℃, time 4 h. (4) The oil-water mixture distilled in step (3) is introduced into the condenser and cooled to obtain an oil-water mixture. The oil-water mixture is then separated to obtain cedar essential oil.

[0035] Results: The extraction rate of cedar essential oil obtained in this example was 1.03% (0.324% for primary grade and 0.706% for secondary grade).

[0036] Comparative Example 2 (As a control of Example 2, the same raw materials were used but no pre-impregnation and fractional distillation were performed.) A method for extracting cedarwood essential oil, the preparation steps of which are as follows: (1) Select fir wood chips with a particle size of 0.15~2.0 mm as raw materials. (The fir wood chips are naturally air-dried with a moisture content of less than 15%) (2) Place the cedar wood chips from step (1) into a distillation vessel and pass superheated steam at a rate of 1195 mL / h into the vessel for direct distillation to extract cedar wood essential oil. The direct distillation is carried out at a distillation temperature of 250℃ for 8 h.

[0037] (3) The oil-water mixture distilled in step (2) is introduced into the condenser and cooled to obtain an oil-water mixture liquid. The oil-water mixture liquid is then separated to obtain cedar essential oil.

[0038] In Comparative Example 2, the process of direct one-step distillation to 250℃ resulted in an essential oil extraction rate of only 0.86%.

[0039] Comparative analysis of Example 2 and Comparative Example 2: The extraction rate of cedarwood essential oil obtained in Example 2 was 1.03% (0.324% for primary grade and 0.706% for secondary grade), which was 19.8% higher than that of Comparative Example 2, which involved direct distillation to 250°C without pre-impregnation (extraction rate of 0.86%). The extraction rate of cedarwood alcohol increased from 0.50% to 0.61%, an increase of 22.0% (refer to...). Figure 3 ).

[0040] Example 3 A method for efficiently extracting cedarwood essential oil, the preparation steps of which are as follows: (1) Select fir wood chips with a particle size of 0.15~2.0 mm as raw materials. (The fir wood chips are naturally air-dried with a moisture content of less than 15%) (2) The cedar wood chips from step (1) are pre-impregnated with water at a mass ratio of 1:1. The mixture is soaked at room temperature for 60 minutes to form pre-impregnated raw material (semi-dry material). (3) Place the pre-impregnated raw material from step (2) evenly in a distillation vessel, and introduce superheated steam into the distillation vessel for fractional distillation. The flow rate of superheated steam is 1830 mL / h, and the distillation is carried out at atmospheric pressure. The fractional distillation is as follows: first-stage distillation temperature 220℃, time 4 h, second-stage distillation temperature 250℃, time 3 h. (4) The oil-water mixture distilled in step (3) is introduced into the condenser and cooled to obtain an oil-water mixture. The oil-water mixture is then separated to obtain cedar essential oil.

[0041] Results: The extraction rate of cedar essential oil obtained in this example was 0.813% (0.323% for primary grade and 0.490% for secondary grade).

[0042] Comparative Example 3 (As a control of Example 3, the same raw materials were used but no pre-impregnation and fractional distillation were performed.) A method for extracting cedarwood essential oil, the preparation steps of which are as follows: (1) Select fir wood chips with a particle size of 0.15~2.0 mm as raw materials. (The fir wood chips are naturally air-dried with a moisture content of less than 15%) (2) Place the cedar wood chips from step (1) into a distillation vessel and pass superheated steam at a rate of 1830 mL / h into the vessel for direct distillation to extract cedar wood essential oil. The direct distillation is carried out at a distillation temperature of 250℃ for 8 h.

[0043] (3) The oil-water mixture distilled in step (2) is introduced into the condenser and cooled to obtain an oil-water mixture liquid. The oil-water mixture liquid is then separated to obtain cedar essential oil.

[0044] In Comparative Example 3, the process of direct one-step distillation to 250℃ resulted in an essential oil extraction rate of only 0.73%.

[0045] Comparative analysis of Example 3 and Comparative Example 3: The extraction rate of cedarwood essential oil obtained in Example 3 was 0.81% (0.323% for primary grade and 0.490% for secondary grade). Compared with the process of Comparative Example 3, which involved direct distillation to 250°C without pre-impregnation (extraction rate of 0.73%), the extraction rate was increased by 11.4%. The extraction rate of cedarwood alcohol increased from 0.44% to 0.47%, an increase of 6.82% (refer to...). Figure 4 Furthermore, compared to Example 1, the primary distillation temperature of 220°C in Example 3 is too high, causing the decomposition, hydrolysis, or polymerization of heat-sensitive components in the essential oil, thereby reducing the yield and quality of the essential oil.

[0046] Example 4 A method for efficiently extracting cedarwood essential oil, the preparation steps of which are as follows: (1) Select fir wood chips with a particle size of 0.15~2.0 mm as raw materials. (The fir wood chips are naturally air-dried with a moisture content of less than 15%) (2) The cedar wood chips from step (1) are pre-impregnated with water at a mass ratio of 1:1. The mixture is soaked at room temperature for 60 minutes to form pre-impregnated raw material (semi-dry material). (3) Place the pre-impregnated raw material from step (2) evenly in a distillation vessel, and introduce superheated steam into the distillation vessel for fractional distillation. The flow rate of superheated steam is 1470 mL / h, and the distillation is carried out at atmospheric pressure. The fractional distillation is as follows: first-stage distillation temperature 130℃, time 3 h, second-stage distillation temperature 250℃, time 5 h. (4) The oil-water mixture distilled in step (3) is introduced into the condenser and cooled to obtain an oil-water mixture. The oil-water mixture is then separated to obtain cedar essential oil.

[0047] Results: The extraction rate of cedar essential oil obtained in this example was 0.91% (0.264% for primary grade and 0.646% for secondary grade).

[0048] Comparative Example 4 (Pre-impregnation is performed only, without grading, and the temperature is directly increased to 250°C for distillation in one step.) A method for extracting cedarwood essential oil, the preparation steps of which are as follows: (1) Select fir wood chips with a particle size of 0.15~2.0 mm as raw materials. (The fir wood chips are naturally air-dried with a moisture content of less than 15%) (2) The cedar wood chips from step (1) are pre-impregnated with water at a mass ratio of 1:2. The mixture is soaked at room temperature for 60 minutes to form pre-impregnated raw material (semi-dry material). (3) Place the pre-impregnated raw material from step (2) into a distillation vessel, and pass superheated steam at a rate of 1470 mL / h into the distillation vessel for direct distillation to extract cedar essential oil. The direct distillation is carried out at a distillation temperature of 250℃ for 8 h.

[0049] (4) The oil-water mixture distilled in step (3) is introduced into the condenser and cooled to obtain an oil-water mixture. The oil-water mixture is then separated to obtain cedar essential oil.

[0050] In Comparative Example 4, the extraction rates of cedarwood essential oil and cypress alcohol were 1.03% and 0.63%, respectively, both lower than the 1.20% and 0.71% in Example 1, indicating that the pre-impregnation-fractional distillation technology of the present invention helps to improve the yield and quality of cedarwood essential oil.

[0051] Comparative Example 5 (No pre-impregnation is performed; dry sawdust is used directly, but fractional distillation is carried out at 190℃ / 250℃.) A method for extracting cedarwood essential oil, the preparation steps of which are as follows: (1) Select fir wood chips with a particle size of 0.15~2.0 mm as raw materials (the fir wood chips are naturally air-dried and have a moisture content of less than 15%). (2) Place the fir wood chips from step (1) into a distillation kettle, and introduce superheated steam into the distillation kettle for fractional distillation. The flow rate of superheated steam is 1470 mL / h, and the distillation is carried out at atmospheric pressure. The fractional distillation is as follows: first-stage distillation temperature 190℃, time 3 h, second-stage distillation temperature 250℃, time 5 h. (3) The oil-water mixture distilled in step (2) is introduced into the condenser and cooled to obtain an oil-water mixture. The oil-water mixture is then separated to obtain cedar essential oil.

[0052] In Comparative Example 5, the extraction rates of cedarwood essential oil and cypress alcohol were 1.17% and 0.69%, respectively, both lower than the 1.20% and 0.71% in Example 1, indicating that the pre-impregnation-fractional distillation technology of the present invention helps to improve the yield and quality of cedarwood essential oil.

[0053] In summary, comparing the results of each embodiment with the comparative examples, it can be seen that the method of pre-impregnation combined with fractional superheated steam distillation (Examples 1-3) of the present invention has significantly better total essential oil extraction rate (0.81%-1.20%) and juniperol extraction rate (0.47%-0.71%) than the direct one-step distillation control without pre-impregnation (Comparative Examples 1-3, extraction rate 0.73%-0.95%, juniperol 0.44%-0.56%). More importantly, the extraction rates of Comparative Example 4 (pre-impregnation only + one-step distillation) and Comparative Example 5 (fractional distillation only + no pre-impregnation) (1.03% and 1.17%, respectively) and juniperol extraction rates (0.63% and 0.69%, respectively) are lower than those of Example 1 (1.20% and 0.71%), indicating that there is a significant synergistic effect between pre-impregnation and fractional distillation, and the combined effect of the two exceeds the simple summation of their individual effects.

[0054] Meanwhile, the essential oils obtained in Examples 1-3 were clear and transparent with a pure aroma and no chemical additive residues, while the essential oils obtained by direct one-step distillation in Comparative Examples 1-3 were slightly darker in color (due to the destruction of heat-sensitive components). These results fully demonstrate that the present invention, through water pre-impregnation + staged superheated steam distillation, can significantly improve the extraction rate, key active ingredient content, and product quality of cedarwood essential oil without the need for any chemical additives.

[0055] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for efficiently extracting cedarwood essential oil, characterized in that, Includes the following steps: Pre-impregnated fir sawdust with water to obtain pre-impregnated raw material; The pre-impregnated raw material is subjected to fractional distillation using superheated steam, and cedar essential oil is obtained after oil-water separation. The fractional distillation includes a first-stage distillation and a second-stage distillation performed sequentially, with the temperature of the first-stage distillation being lower than that of the second-stage distillation.

2. The method for efficiently extracting cedarwood essential oil according to claim 1, characterized in that, The first-stage distillation is carried out at a temperature of 130~220℃ for 1~5 hours.

3. The method for efficiently extracting cedarwood essential oil according to claim 1, characterized in that, The first-stage distillation is carried out at a temperature of 160-190℃ for 1-5 hours.

4. The method for efficiently extracting cedarwood essential oil according to claim 1, characterized in that, The secondary distillation is carried out at a temperature of 220-280℃ for 3-6 hours.

5. The method for efficiently extracting cedarwood essential oil according to claim 1, characterized in that, The first-stage distillation is carried out at a temperature of 190°C for 3 hours; the second-stage distillation is carried out at a temperature of 250°C for 5 hours.

6. The method for efficiently extracting cedarwood essential oil according to claim 1, characterized in that, The flow rate of the superheated steam is 865~2465 mL / h.

7. The method for efficiently extracting cedarwood essential oil according to claim 1, characterized in that, The mass ratio of the cedar wood chips to water is 1:1 to 1:

3.

8. The method for efficiently extracting cedarwood essential oil according to claim 1, characterized in that, The particle size of the cedar wood chips is 0.15~2.0 mm.

9. The method for efficiently extracting cedarwood essential oil according to claim 1, characterized in that, The cedar wood chips are the processing residues of cedar wood that have been naturally air-dried or oven-dried to a moisture content of less than 15%.

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