High-purity plant essential oil separation method based on molecular distillation technology

Abstract

The invention belongs to the technical field of plant essential oil separation, and provides a plant essential oil high-purity separation method based on a molecular distillation technology, which comprises the following steps: firstly obtaining a free path of a substance molecule to be extracted in a raw material, sequencing to obtain a free path gradient, then converting into a temperature gradient, and dividing into a gradient adjacent part and a non-gradient adjacent part overlapped temperature domain. And for the non-gradient adjacent part overlapping temperature domain, constructing a non-gradient temperature change curve, analyzing the stability, and performing regulation and control when the stability is not stable. The method comprises the following steps: uniformly dividing an overlapped temperature domain of a gradient adjacent part into subintervals, carrying out heating-constant temperature-cooling circulation on each subinterval, collecting a first fraction product by using an independent condenser, carrying out secondary and multiple molecular distillation, and dynamically adjusting the boundary of the subintervals in combination with GC-MS analysis so as to remove impurities. According to the method, high-purity separation of the plant essential oil is realized through association of a molecular free path and temperature in combination with multi-interval circulating distillation and real-time monitoring, the problem of insufficient separation purity in the prior art is solved, and the product purity is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of plant essential oil separation, in particular to a high-purity plant essential oil separation method based on molecular distillation technology. Background Art

[0002] In the field of plant essential oil separation technology, traditional separation methods such as distillation and extraction have obvious shortcomings and it is difficult to achieve high-purity separation; plant essential oils are usually composed of multiple components such as monoterpenes, sesquiterpenes, and phenylpropanoids. The molecular free paths of each component are different, and temperature range overlap is prone to occur during the separation process; when the temperature ranges of substance A and substance B overlap but not completely, traditional methods cannot accurately handle the separation problem of such gradient adjacent partially overlapping temperature domains, resulting in cross-contamination of fractions and insufficient separation purity.

[0003] In addition, during the separation process, the stability of temperature changes is crucial to the separation effect; if the temperature changes are unstable, it may lead to incomplete separation of the target components or thermal decomposition, affecting the quality of the product; at the same time, for the collected distillate products, traditional methods lack effective secondary and multiple purification means, and it is difficult to remove low-boiling point, same-boiling point impurities and chiral isomers, etc., and cannot meet the purification needs of high-value-added plant essential oils.

[0004] Therefore, how to accurately process the overlapping areas in the temperature gradient based on molecular distillation technology to achieve high-purity separation of plant essential oils is a technical problem that needs to be solved urgently in this field;

[0005] To this end, the present invention provides a high-purity separation method of plant essential oils based on molecular distillation technology. Summary of the Invention

[0006] In order to make up for the deficiencies of the prior art, at least one technical problem raised in the background technology is solved.

[0007] The technical solution adopted by the present invention to solve its technical problem is:

[0008] In a first aspect, the present invention provides a method for separating plant essential oils with high purity based on molecular distillation technology, comprising:

[0009] S1: Obtain the molecular free paths of all substances to be extracted from the plant essential oil raw material, analyze all the molecular free paths, and integrate them to obtain the molecular free path gradient of the substances to be extracted;

[0010] S2: According to the molecular free path theory, the molecular free path gradient of the substance to be extracted is converted into a temperature gradient. Based on the temperature gradient, the temperature gradient is divided into multiple temperature domains with overlapping adjacent gradient portions and overlapping adjacent non-gradient portions;

[0011] S3: Based on any non-gradient adjacent partially overlapping temperature domain, construct a non-gradient temperature change curve, and perform stability analysis on the non-gradient temperature change curve. If it is unstable, adjust the non-gradient temperature change curve;

[0012] S4: Based on any overlapping temperature domain of adjacent gradient parts, the overlapping temperature domain is divided into multiple sub-intervals, and a heating-constant temperature-cooling cycle is implemented in each sub-interval. Each sub-interval is equipped with an independent condenser to collect the first fraction product, and the collected first fraction product is subjected to secondary and multiple molecular distillations to further remove fraction impurities.

[0013] As a further improvement of the present invention: the process of integrating and obtaining the molecular free path gradient of the substance to be extracted is:

[0014] The molecular free paths of all substances to be extracted in the plant essential oil raw material are obtained, and the molecular free paths of all substances to be extracted in the plant essential oil raw material are sorted from small to large to obtain a molecular free path gradient.

[0015] As a further improvement of the present invention: the specific process of converting the free path gradient of the molecules of the substance to be extracted into a temperature gradient is as follows:

[0016] Molecular free path and temperature ,pressure , molecular diameter There is a relationship, which is expressed as: ,in, is the Boltzmann constant, is the molecular diameter, is the system pressure, = pi. In a constant pressure system, the free path of molecules is linearly positively correlated with temperature. For each substance to be extracted from the plant essential oil raw material, its accurate molecular diameter is obtained. , where di represents the molecular diameter of the i-th substance to be extracted;

[0017] Based on molecular free path gradient Each free path value in The expression used is: Calculate the corresponding temperature value , where Ti represents the temperature value corresponding to the i-th free path. Based on the multiple temperature values calculated in the constant pressure system, the temperature gradient is constructed by arranging the multiple temperature values in ascending order.

[0018] As a further improvement of the present invention, the specific process of dividing the temperature gradient into a plurality of gradient adjacent partially overlapping temperature domains and non-gradient adjacent partially overlapping temperature domains is as follows:

[0019] Obtain two substances to be extracted whose temperature ranges partially overlap;

[0020] The free path ranges of the two substances to be extracted are used to determine whether there is an overlapping free path interval between the two substances to be extracted. If so, the temperature intervals corresponding to the two substances to be extracted are calculated based on the overlapping free path intervals and combined with the molecular free path theory.

[0021] The temperature ranges of the adjacent overlapping gradients are the temperature ranges of the two substances to be extracted, and the corresponding temperatures must meet the following requirements: The overlapping interval is ; The non-gradient adjacent partially overlapping temperature domain is the temperature range of the two adjacent materials that meets of the region, where and Respectively represent the minimum and maximum values within the temperature range corresponding to the substance A to be extracted, and They respectively represent the minimum and maximum values in the temperature range corresponding to the substance B to be extracted.

[0022] As a further improvement of the present invention: the process of constructing the non-gradient temperature change curve is:

[0023] Based on any non-gradient adjacent partially overlapping temperature domain, the temperature changes during the separation process of the extracted substance are analyzed, and the temperature value in the temperature change is used as the Y-axis and the time change as the X-axis to construct a non-gradient temperature change curve.

[0024] As a further improvement of the present invention, the specific process of performing stability analysis on the non-gradient temperature change curve is as follows:

[0025] A reference line parallel to the X-axis is drawn with the maximum temperature of the substance to be extracted as the reference point, and is recorded as the first reference line. Below the first reference line, a straight line parallel to the first reference line is set, and is recorded as the second reference line. A prediction reference line is set at the halfway point between the first reference line and the second reference line.

[0026] The non-gradient temperature change curve is analyzed in real time to predict whether the non-gradient temperature change curve will exceed the first reference line during the purification period.

[0027] As a further improvement of the present invention, the specific process of performing stability analysis on the non-gradient temperature change curve includes:

[0028] The time point when the non-gradient temperature change curve reaches the predicted baseline is recorded as the arrival time point;

[0029] If the arrival time point is greater than the midpoint of the purification time period, it means that the non-gradient temperature change curve will not exceed the first reference line during the purification time period. If the arrival time point is less than or equal to the midpoint of the purification time period, the slope analysis of the non-gradient temperature change curve is performed.

[0030] As a further improvement of the present invention, the specific process of performing stability analysis on the non-gradient temperature change curve also includes slope analysis, specifically:

[0031] In the time interval from when the non-gradient temperature change curve first breaks through the second reference line to when it reaches the prediction baseline, the non-gradient temperature change curve is divided into multiple non-gradient temperature change curve segments according to the minute-level time dimension, the slopes of the multiple non-gradient temperature change curve segments are calculated, the slopes of the multiple non-gradient temperature change curve segments are averaged to obtain a curve segment mean slope, and the curve segment mean slope is compared and analyzed with the curve segment mean slope threshold;

[0032] If the mean slope of the curve segment is less than or equal to the mean slope threshold of the curve segment, it means that the non-gradient temperature change curve will not exceed the first reference line during the purification time period. If the mean slope of the curve segment is greater than the mean slope threshold of the curve segment, it means that the non-gradient temperature change curve will exceed the first reference line during the purification time period, and an alarm signal is generated.

[0033] As a further improvement of the present invention: the specific process of regulating the non-gradient temperature change curve is:

[0034] Based on the generated alarm signal, the heating is stopped, and when the temperature drops to the second reference line, the heating process is performed again.

[0035] As a further improvement of the present invention, the specific process of performing secondary molecular distillation on the collected first fraction product is as follows:

[0036] The fraction products are collected from each subinterval and distilled again. The composition of each fraction is analyzed by GC-MS. The boundary of the temperature subinterval is dynamically adjusted. The dynamically adjusted temperature subinterval is subjected to a heating-constant temperature-cooling cycle to further remove impurities in the fraction.

[0037] In a second aspect, the present invention provides a high-purity plant essential oil separation system based on molecular distillation technology, comprising:

[0038] Free path gradient analysis module: obtains the molecular free paths of all substances to be extracted from the plant essential oil raw materials, analyzes all molecular free paths, and integrates them to obtain the molecular free path gradient of the substances to be extracted;

[0039] Temperature gradient construction module: According to the molecular free path theory, the molecular free path gradient of the substance to be extracted is converted into a temperature gradient. Based on the temperature gradient, the temperature gradient is divided into multiple temperature domains with overlapping gradient adjacent parts and overlapping non-gradient adjacent parts;

[0040] Temperature gradient stability analysis module: Based on any non-gradient adjacent partially overlapping temperature domain, a non-gradient temperature change curve is constructed and stability analysis is performed on the non-gradient temperature change curve. If it is unstable, the non-gradient temperature change curve is regulated;

[0041] Secondary distillation module: Based on any overlapping temperature domain of adjacent gradients, the overlapping temperature domain is divided into multiple sub-intervals. A heating-constant temperature-cooling cycle is implemented in each sub-interval. Each sub-interval is equipped with an independent condenser to collect the first fraction product. The collected first fraction product is then subjected to secondary and multiple molecular distillations to further remove fraction impurities.

[0042] The beneficial effects of the present invention are as follows:

[0043] By converting the molecular free path gradient into a temperature gradient, the overlapping temperature domains of adjacent gradients are precisely divided. A sub-interval heating-constant temperature-cooling cycle and multiple molecular distillations are used to break through the cross-contamination bottleneck caused by temperature overlap in traditional methods. A non-gradient temperature change curve is constructed. Through slope analysis and a dual reference line early warning mechanism, the risk of temperature fluctuations is predicted in real time. When the temperature is abnormal, a heating-cooling cycle is automatically triggered to ensure a stable separation process and avoid thermal decomposition of components. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention will be further described below with reference to the accompanying drawings.

[0045] Figure 1 is a flow chart of the steps of the present invention;

[0046] Figure 2 It is a system module diagram of the present invention. DETAILED DESCRIPTION

[0047] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0048] Example 1

[0049] like Figure 1 As shown, the method for separating plant essential oils with high purity based on molecular distillation technology according to an embodiment of the present invention comprises:

[0050] S1: Obtain the molecular free paths of all substances to be extracted from the plant essential oil raw material, analyze and process all the molecular free paths, and integrate them to obtain the molecular free path gradient of the substances to be extracted;

[0051] The plant essential oils include, but are not limited to, monoterpenes, sesquiterpenes, phenylpropanoids, phenols, benzyl alcohol, methyl salicylate, alcohols, aldehydes, acids, esters and other substances;

[0052] The essential oil raw materials are a mixture of monoterpenes, sesquiterpenes, phenylpropanoids, phenols, benzyl alcohol, methyl salicylate, alcohols, aldehydes, acids, esters and other substances;

[0053] Obtaining the molecular free paths of all substances to be extracted from the plant essential oil raw material, and sorting the molecular free paths of all substances to be extracted from the obtained plant essential oil raw material from small to large;

[0054] For example, for a mixture of plant essential oil raw materials composed of substances A, B, C, D, E, F, etc. to be extracted from the plant essential oil raw materials;

[0055] Based on the molecular free path theory, the molecular free paths of the substances to be extracted A, B, C, D, E, and F are sorted from small to large. For example, ; The substances to be extracted from the plant essential oil raw materials are sorted from small to large according to the molecular free path theory to obtain the molecular free path gradient;

[0056] S2: According to the molecular free path theory, the molecular free path gradient of the substance to be extracted is converted into a temperature gradient. Based on the temperature gradient, the temperature gradient is divided into multiple temperature domains with overlapping adjacent gradient portions and overlapping adjacent non-gradient portions;

[0057] In the kinetic theory of gases, the molecular free path and temperature ,pressure , molecular diameter There is a relationship, which is expressed as: ,in, is the Boltzmann constant, is the molecular diameter, is the system pressure, is pi;

[0058] In a constant pressure system, that is, the pressure system of the molecular distillation equipment is constant, the free path of the molecule and the temperature show a linear positive correlation, that is: ;

[0059] For each substance to be extracted from the plant essential oil raw material, such as monoterpenes, sesquiterpenes, phenylpropanoids, etc., obtain its accurate molecular diameter , where di represents the molecular diameter of the i-th substance to be extracted;

[0060] The method of obtaining the accurate molecular diameter of each substance to be extracted from the plant essential oil raw material The methods include but are not limited to: consulting relevant chemical databases, literature or using experimental measurement methods;

[0061] Based on molecular free path gradient Each free path value in The expression used is: Calculate the corresponding temperature value , multiple temperature values calculated based on a constant pressure system , multiple temperature values are arranged in order from small to large to construct a temperature gradient;

[0062] Based on the constructed temperature gradient, the temperature gradient is divided into a plurality of gradient adjacent partially overlapping temperature domains and non-gradient adjacent partially overlapping temperature domains;

[0063] The gradient adjacent partially overlapping temperature domain specifically means that the temperature ranges of substance A and substance B overlap partially, but not completely, the minimum temperature value of substance A is less than the minimum temperature value of substance B, the maximum temperature value of substance A is less than the maximum temperature value of substance B, and the maximum temperature value of substance A is greater than the minimum temperature value of substance B;

[0064] For example, the free path range of substance A is ,in, Represents the minimum free path value of substance A, The maximum free path value of substance A and the free path range of B are ,in, Represents the minimum free path value of substance B, Represents the maximum free path value of substance B; ; Then the overlapping free path interval is: , which means taking the smaller value of the right endpoints of the two intervals, , which means taking the larger value of the left endpoints of the two intervals;

[0065] like , it means there is no overlapping free path interval, so there is no need to calculate the overlapping part;

[0066] like , it means there are overlapping free path intervals, and the overlapping parts need to be calculated;

[0067] Using the molecular free path theory, we can calculate the overlap interval of substance A and substance B and the temperature interval of substance A. The formula is: , calculate the temperature range of substance B, the formula is: ,when and When , the temperature overlap range of substance A and substance B is: ,in, It means taking the larger value of the left endpoints of the two intervals. It means taking the smaller value of the right endpoints of the two intervals;

[0068] The temperature overlap interval between substance A and substance B is recorded as the overlapping temperature domain;

[0069] More specifically, the temperature domain of the adjacent gradient overlaps, and the temperature range of the two adjacent substances satisfies: The overlapping interval is , corresponding to the free path overlapping interval ,in, and Respectively represent the minimum and maximum values within the temperature range corresponding to the substance A to be extracted, and Respectively represent the minimum and maximum values within the temperature range corresponding to the substance B to be extracted;

[0070] The non-gradient adjacent partially overlapping temperature domain is the temperature range of the two adjacent materials that satisfies In the region of , the corresponding free paths have no overlap, and separation can be achieved directly through temperature gradient;

[0071] It should be noted that according to the molecular free path theory, in the ideal gas model, the molecular free path is an average statistical result. In reality, the movement of gas molecules follows the Maxwell-Boltzmann distribution. At the same temperature, the molecular velocity has a distribution range, such as the normal distribution, and is not a single value. Even if the pressure is constant, the molecular free path itself is a range, and the corresponding temperature must also be an interval.

[0072] Then from the minimum temperature value of material A To the starting point of the temperature overlap interval Expressed as: ;

[0073] like , then from the minimum temperature value of material A The starting point of the overlapping interval is , which corresponds to the independent fraction stage of substance A, and there is no interference from substance B at this time;

[0074] like , then from the minimum temperature value of material A The starting point of the overlapping interval is , then the fractionation stage of substance A is interfered by substance B, and the temperature range of substance A completely contains the starting temperature of substance B;

[0075] From the end point of the temperature overlap interval To the maximum temperature of material B Expressed as: ;

[0076] like , then from the end point of the temperature overlap interval The maximum temperature of substance B is , which corresponds to the independent distillation stage of substance B, without the interference of substance A;

[0077] like , then from the end point of the temperature overlap interval The maximum temperature of substance B is , at this time, the temperature range of substance B completely includes the starting temperature of substance A;

[0078] S3: Based on any non-gradient adjacent partially overlapping temperature domain, construct a non-gradient temperature change curve, and perform stability analysis on the non-gradient temperature change curve. If it is unstable, adjust the non-gradient temperature change curve;

[0079] Specifically, based on any non-gradient adjacent partially overlapping temperature domain, the temperature change during the separation process of the extracted substance is analyzed, and the temperature value in the temperature change is used as the Y-axis and the time change as the X-axis to construct a non-gradient temperature change curve;

[0080] Taking the maximum temperature value of the substance to be extracted as the reference point, draw a reference line parallel to the X-axis and record it as the first reference line. Below the first reference line, set a straight line parallel to the first reference line and record it as the second reference line. The second reference line is a reference line set by technical personnel in this industry based on production experience. This reference line is a purification baseline set based on long-term production practice. Its temperature threshold has been verified by multiple batch processes and can be used as a critical reference to ensure purification effect and quality. When the distillation temperature exceeds this threshold, it can ensure the effective separation of the target component under the molecular free path gradient, while avoiding the risk of cross-contamination of fractions caused by insufficient temperature. A prediction baseline is set at halfway between the first reference line and the second reference line.

[0081] Analyze the non-gradient temperature change curve in real time to predict whether the non-gradient temperature change curve will exceed the first reference line during the purification period;

[0082] dividing the non-gradient temperature change curve into a plurality of non-gradient temperature change curve segments within a purification time period;

[0083] It should be noted that the purification time period refers to the effective operating time interval for high-purity separation of the target component in the distillation process;

[0084] When the non-gradient temperature change curve exceeds the second reference line for the first time, predicting whether the non-gradient temperature change curve will exceed the first reference line during the remaining purification time period;

[0085] When the non-gradient temperature change curve exceeds the second reference line for the first time, continuously observing the time point when the non-gradient temperature change curve reaches the predicted baseline, and recording the time point when the non-gradient temperature change curve reaches the predicted baseline as the arrival time point;

[0086] If the arrival time point is greater than the midpoint of the purification time period, it means that the non-gradient temperature change curve will not exceed the first reference line during the purification time period;

[0087] If the arrival time point is less than or equal to the midpoint of the purification time period, further analysis is performed on the non-gradient temperature change curve;

[0088] The specific further analysis process is as follows:

[0089] In the time interval from when the non-gradient temperature change curve first breaks through the second reference line to when it reaches the prediction baseline, the non-gradient temperature change curve is divided into multiple non-gradient temperature change curve segments according to the minute-level time dimension;

[0090] Calculating the slopes of multiple non-gradient temperature change curve segments to obtain the slopes of multiple non-gradient temperature change curve segments;

[0091] Performing average processing on the obtained multiple non-gradient temperature change curve segment slopes to obtain the curve segment average slope;

[0092] Compare and analyze the mean slope of the curve segments with the mean slope threshold of the curve segments;

[0093] If the curve segment mean slope is less than or equal to the curve segment mean slope threshold, it indicates that the non-gradient temperature change curve will not exceed the first reference line during the purification period;

[0094] If the curve segment mean slope is greater than the curve segment mean slope threshold, it indicates that the non-gradient temperature change curve will exceed the first reference line during the purification period, and an alarm signal is generated;

[0095] Based on the generated alarm signal, heating is stopped, and heating is performed again when the temperature drops to a second reference line;

[0096] S4: Based on any overlapping temperature domain of adjacent gradients, the overlapping temperature domain is divided into multiple sub-intervals, a heating-constant temperature-cooling cycle is implemented in each sub-interval, and each sub-interval is equipped with an independent condenser to collect the first fraction product, and the collected first fraction product is subjected to secondary molecular distillation to further remove fraction impurities;

[0097] Divide the overlapping temperature domain into n subintervals, , a heating-maintaining-cooling cycle is implemented in each sub-interval, heating to the target temperature and maintaining the temperature to fully evaporate the target substance, followed by rapid cooling to suppress the volatilization of coexisting impurities, and configuring an independent condenser for each sub-interval to collect the first fraction product;

[0098] The fractions collected from each sub-interval were redistilled, and the composition of each fraction was analyzed by GC-MS, and the boundaries of the temperature sub-intervals were dynamically adjusted;

[0099] The dynamically adjusted temperature sub-interval is subjected to a heating-constant temperature-cooling cycle to further remove impurities in the distillate;

[0100] The technical solution of the embodiment of the present invention is: obtaining the molecular free path of all substances to be extracted in the plant essential oil raw material, analyzing all the molecular free path, integrating to obtain the molecular free path gradient of the substance to be extracted, converting the molecular free path gradient of the substance to be extracted into a temperature gradient according to the molecular free path theory, dividing the temperature gradient into multiple gradient adjacent partially overlapping temperature domains and non-gradient adjacent partially overlapping temperature domains based on the temperature gradient, constructing a non-gradient temperature change curve based on any non-gradient adjacent partially overlapping temperature domain, and performing stability analysis on the non-gradient temperature change curve. If it is unstable, regulating the non-gradient temperature change curve, dividing the overlapping temperature domain into multiple sub-intervals based on any gradient adjacent partially overlapping temperature domain, implementing a heating-constant temperature-cooling cycle in each sub-interval, and equipping each sub-interval with an independent condenser to collect the first distillation product, and performing secondary and multiple molecular distillations on the collected first distillation product to further remove distillate impurities.

[0101] Example 2

[0102] like Figure 2 As shown, based on Example 1, the present invention provides a high-purity plant essential oil separation system based on molecular distillation technology, comprising:

[0103] Free path gradient analysis module: obtains the molecular free paths of all substances to be extracted from the plant essential oil raw materials, analyzes all molecular free paths, and integrates them to obtain the molecular free path gradient of the substances to be extracted;

[0104] Temperature gradient construction module: According to the molecular free path theory, the molecular free path gradient of the substance to be extracted is converted into a temperature gradient. Based on the temperature gradient, the temperature gradient is divided into multiple temperature domains with overlapping gradient adjacent parts and overlapping non-gradient adjacent parts;

[0105] Temperature gradient stability analysis module: Based on any non-gradient adjacent partially overlapping temperature domain, a non-gradient temperature change curve is constructed and stability analysis is performed on the non-gradient temperature change curve. If it is unstable, the non-gradient temperature change curve is regulated;

[0106] Secondary distillation module: Based on any overlapping temperature domain of adjacent gradients, the overlapping temperature domain is divided into multiple sub-intervals. A heating-constant temperature-cooling cycle is implemented in each sub-interval. Each sub-interval is equipped with an independent condenser to collect the first fraction product. The collected first fraction product is then subjected to secondary and multiple molecular distillations to further remove fraction impurities.

[0107] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-purity separation method for plant essential oils based on molecular distillation technology, characterized in that: include: S1: Obtain the molecular free paths of all substances to be extracted from the plant essential oil raw material, analyze all the molecular free paths, and integrate them to obtain the molecular free path gradient of the substances to be extracted; S2: According to the molecular free path theory, the molecular free path gradient of the substance to be extracted is converted into a temperature gradient. Based on the temperature gradient, the temperature gradient is divided into multiple temperature domains with overlapping adjacent gradient portions and overlapping adjacent non-gradient portions; S3: Based on any non-gradient adjacent partially overlapping temperature domain, construct a non-gradient temperature change curve, and perform stability analysis on the non-gradient temperature change curve. If it is unstable, adjust the non-gradient temperature change curve; S4: Based on any overlapping temperature domain of adjacent gradient parts, the overlapping temperature domain is divided into multiple sub-intervals, and a heating-constant temperature-cooling cycle is implemented in each sub-interval. Each sub-interval is equipped with an independent condenser to collect the first fraction product, and the collected first fraction product is subjected to secondary and multiple molecular distillations to further remove fraction impurities.

2. the plant essential oil high-purity separation method based on molecular distillation technology according to claim 1, is characterized in that: The process of integrating and obtaining the molecular free path gradient of the substance to be extracted is: The molecular free paths of all substances to be extracted in the plant essential oil raw material are obtained, and the molecular free paths of all substances to be extracted in the plant essential oil raw material are sorted from small to large to obtain a molecular free path gradient.

3. the plant essential oil high-purity separation method based on molecular distillation technology according to claim 1, is characterized in that: The specific process of converting the free path gradient of the molecules of the substance to be extracted into a temperature gradient is as follows: Molecular free path and temperature ,pressure , molecular diameter There is a relationship, which is expressed as: ,in, is the Boltzmann constant, is the molecular diameter, is the system pressure, = pi. In a constant pressure system, the free path of molecules is linearly positively correlated with temperature. For each substance to be extracted from the plant essential oil raw material, its accurate molecular diameter is obtained. , where di represents the molecular diameter of the i-th substance to be extracted; Based on molecular free path gradient Each free path value in The expression used is: Calculate the corresponding temperature value , where Ti represents the temperature value corresponding to the i-th free path. Based on the multiple temperature values calculated in the constant pressure system, the temperature gradient is constructed by arranging the multiple temperature values in ascending order.

4. the plant essential oil high-purity separation method based on molecular distillation technology according to claim 1, is characterized in that: The specific process of dividing the temperature gradient into a plurality of gradient adjacent partially overlapping temperature domains and non-gradient adjacent partially overlapping temperature domains is as follows: Obtaining a substance A to be extracted and a substance B to be extracted whose temperature ranges partially overlap; The free path ranges of the two substances to be extracted are used to determine whether there is an overlapping free path interval between the two substances to be extracted. If so, the temperature intervals corresponding to the two substances to be extracted are calculated based on the overlapping free path intervals and combined with the molecular free path theory. The temperature ranges of the adjacent overlapping gradients are the temperature ranges of the two substances to be extracted, and the corresponding temperatures must meet the following requirements: The overlapping interval is ; The non-gradient adjacent partially overlapping temperature domain is the temperature range of the two adjacent materials that meets of the region, where and Respectively represent the minimum and maximum values within the temperature range corresponding to the substance A to be extracted, and They respectively represent the minimum and maximum values in the temperature range corresponding to the substance B to be extracted.

5. the plant essential oil high-purity separation method based on molecular distillation technology according to claim 1, is characterized in that: The process of constructing the non-gradient temperature change curve is as follows: Based on any non-gradient adjacent partially overlapping temperature domain, the temperature changes during the separation process of the extracted substance are analyzed, and the temperature value in the temperature change is used as the Y-axis and the time change as the X-axis to construct a non-gradient temperature change curve.

6. The method for separating high-purity plant essential oils based on molecular distillation technology according to claim 1, wherein: The specific process of performing stability analysis on the non-gradient temperature change curve is as follows: A reference line parallel to the X-axis is drawn with the maximum temperature of the substance to be extracted as the reference point, and is recorded as the first reference line. Below the first reference line, a straight line parallel to the first reference line is set, and is recorded as the second reference line. A prediction reference line is set at the halfway point between the first reference line and the second reference line. The non-gradient temperature change curve is analyzed in real time to predict whether the non-gradient temperature change curve will exceed the first reference line during the purification period.

7. The method for separating plant essential oils with high purity based on molecular distillation technology according to claim 6, wherein: The specific process of performing stability analysis on the non-gradient temperature change curve includes: The time point when the non-gradient temperature change curve reaches the predicted baseline is recorded as the arrival time point; If the arrival time point is greater than the midpoint of the purification time period, it means that the non-gradient temperature change curve will not exceed the first reference line during the purification time period. If the arrival time point is less than or equal to the midpoint of the purification time period, the slope analysis of the non-gradient temperature change curve is performed.

8. The method for separating high-purity plant essential oils based on molecular distillation technology according to claim 6, wherein: The specific process of performing stability analysis on the non-gradient temperature change curve also includes slope analysis, specifically: In the time interval from when the non-gradient temperature change curve first breaks through the second reference line to when it reaches the prediction baseline, the non-gradient temperature change curve is divided into multiple non-gradient temperature change curve segments according to the minute-level time dimension, the slopes of the multiple non-gradient temperature change curve segments are calculated, the slopes of the multiple non-gradient temperature change curve segments are averaged to obtain a curve segment mean slope, and the curve segment mean slope is compared and analyzed with the curve segment mean slope threshold; If the mean slope of the curve segment is less than or equal to the mean slope threshold of the curve segment, it means that the non-gradient temperature change curve will not exceed the first reference line during the purification time period. If the mean slope of the curve segment is greater than the mean slope threshold of the curve segment, it means that the non-gradient temperature change curve will exceed the first reference line during the purification time period, and an alarm signal is generated.

9. The method for separating high-purity plant essential oils based on molecular distillation technology according to claim 1, wherein: The specific process of regulating the non-gradient temperature change curve is as follows: Based on the generated alarm signal, the heating is stopped, and when the temperature drops to the second reference line, the heating process is performed again.

10. The method for separating plant essential oils with high purity based on molecular distillation technology according to claim 1, wherein: The specific process of performing secondary molecular distillation on the collected first fraction product is as follows: The fraction products are collected from each subinterval and distilled again. The composition of each fraction is analyzed by GC-MS. The boundary of the temperature subinterval is dynamically adjusted. The dynamically adjusted temperature subinterval is subjected to a heating-constant temperature-cooling cycle to further remove impurities in the fraction.

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