Method for continuously rectifying high-purity linalool from linalool

Abstract

The invention discloses a method for continuously rectifying high-purity linalool from linalool, and belongs to the technical field of linalool extraction. The linalool extraction method provided by the invention comprises the following steps: by taking linalool essential oil as a raw material, purifying through double-tower coupling continuous rectification: passing a stainless steel corrugated packing layer light component with a high specific surface area of a rectifying section and a low specific surface area in a stripping section in a first rectifying tower, and collecting a tower kettle to obtain a first middle fraction; the second rectifying tower is used for separating heavy components by stainless steel corrugated packing with similar gradient specific surface areas, and collecting tower top fractions in combination with nitrogen protection and refractive index monitoring. The two towers are both provided with falling film type reboilers, the refractive index of the second tower is stabilized to be 1.469-1.471, and collection is performed after the refractive index lasts for 5 min. Through cooperation of gradient packing and double-tower parameters, high-precision separation is achieved, the product purity is larger than or equal to 99%, the mass transfer efficiency is high, energy consumption is low, operation is stable, and support is provided for industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of linalool extraction, and particularly relates to a method for continuously rectifying high-purity linalool from linalyl oil. BACKGROUND

[0002] Linalool, with the chemical name of 3,7-dimethyl-1,6-octadien-3-ol, is a kind of monoterpene alcohol compound with fresh lily fragrance, and is widely used in the fields of perfume essence, medicine, cosmetics and food additives. In the manufacture of high-end perfume, high-purity linalool is the core raw material for blending natural fragrance, and its fragrance is soft and lasting, which can significantly improve the grade and market competitiveness of products. In the field of medicine, linalool has the pharmacological activities of antibacterial, anti-inflammatory and sedative, and is a key ingredient for synthesizing drug intermediates such as vitamin E and vitamin A, and the purity directly affects the efficacy and safety of drugs. With the continuous improvement of the quality requirements of downstream industries, the market demand for high-purity linalool continues to grow, which promotes the iteration and upgrading of extraction and purification technology.

[0003] Linalool can be extracted from natural plants or prepared by chemical synthesis. In daily perfumery, natural linalool has pure, round and sweet fragrance, which is difficult to compare with synthetic linalool. In the application of medicine, natural linalool is more excellent than synthetic linalool (racemic) in “biological potency” due to its optical activity. At present, one of the main sources of producing natural linalool is the branches, leaves and fruits of linalyl tree, and the linalyl oil is extracted by distillation or solvent extraction and then purified. Therefore, the purification process of linalyl oil becomes the core link to determine the quality and production cost of linalool products. Of course, the purification technology of linalool in linalyl oil mainly includes solvent extraction method, molecular distillation method, adsorption method and rectification method, etc., among which the rectification method has the advantages of high separation efficiency, stable product purity and easy industrialization, and becomes the current mainstream purification technology.

[0004] Early linalool rectification and purification mostly adopts single-tower batch rectification process, which takes linalyl oil as raw material and realizes the separation of linalool and impurities by controlling parameters such as temperature and pressure in a single rectification tower. The core defect of this process is very prominent: the components such as α-terpinene and geraniol contained in linalyl oil have close boiling points with linalool, and the limited separation precision of single tower is difficult to realize complete separation, so the product purity is generally lower than 95%, which cannot meet the requirements of high-end perfumes and medicines. At the same time, batch processing of materials is required for intermittent operation, which has low production efficiency, and the parameters such as temperature and pressure are easy to fluctuate in the start-stop process, resulting in poor product quality stability. Frequent thermal cycling also aggravates the decomposition loss of linalool, and the raw material utilization rate is usually low, which is difficult to adapt to the demand of industrial large-scale production.

[0005] In order to improve the disadvantages of single-tower batch rectification, the single-tower continuous rectification process is developed in the industry, which realizes continuous feeding and fraction collection by setting multiple packing layers in the single tower, and the production efficiency is improved compared with the batch type. However, this process still has the essential limitation of single-tower separation: the light component and heavy component impurities need to be treated at the same time, and the parameter regulation is contradictory. If the tower top temperature is increased to strengthen the removal of light components, the loss of linalool will increase as the light components are distilled out; if the temperature is reduced to reduce the loss of linalool, the light component residue will exceed the standard.

[0006] Although the molecular distillation method can improve the purity of linalool to more than 97%, the equipment investment is higher than that of the rectification method, the daily processing capacity of a single set of equipment is low, and the core component of the wiper is easy to wear and tear, and the annual maintenance cost is high, which is only suitable for small batch high-end customization and lacks industrialization universality. The adsorption method relies on the selective interception of impurities by activated carbon and other adsorbents, but due to the non-specific adsorption of the adsorbent to linalool, the yield is reduced, and the adsorbent needs to be replaced frequently, which is high in operation cost and difficult to balance the purity and efficiency.

[0007] In summary, due to the principle limitation, economic inefficiency or design defects, the existing technologies cannot achieve the industrialization goal of high purity, high yield and controllable cost, and there is a technical gap. SUMMARY

[0008] The present application is directed to the above-mentioned deficiencies, and provides a method for continuously rectifying high-purity linalool from linaloe oil, which solves the problems of low separation precision, high energy consumption and insufficient product purity of traditional processes by using double-tower staged rectification and gradient ratio surface area stainless steel corrugated packing.

[0009] In order to achieve the above technical purposes, the present application adopts the following technical solutions:

[0010] A method for continuously rectifying high-purity linalool from linaloe oil, comprising the following steps:

[0011] (1) Raw material preparation: using linaloe essential oil (linalool content ≥ 80%) as raw material;

[0012] (2) First continuous rectification: sending the linaloe essential oil into the first rectification tower, controlling the tower top temperature at 35-50℃, the tower bottom temperature at 85-95℃, and the reflux ratio (2-4):1 under the system absolute pressure of 15-25 kPa, rectifying through the mixed packing layer, collecting the tower top fraction to remove the light component impurities with a boiling point lower than linalool, and collecting the tower bottom fraction as the first intermediate fraction;

[0013] (3) Second continuous distillation: The first intermediate fraction is fed into the second distillation column. Under the absolute pressure of the system of 5-10 kPa, the top temperature of the column is controlled at 95-105℃, the bottom temperature at 115-125℃, and the reflux ratio is (4-6):1. The distillation is carried out through the mixed packing layer, and the top fraction is collected to obtain linalool product with a purity of ≥99%.

[0014] Preferably, in step (2), the mixed packing layer of the first distillation column is stainless steel corrugated packing with different specific surface areas, which is divided into a rectification section and a stripping section from top to bottom; the rectification section is stainless steel corrugated packing with high specific surface area; the stripping section is composed of stainless steel corrugated packing with medium specific surface area in the middle section and stainless steel corrugated packing with low specific surface area in the lower section.

[0015] Preferably, in step (3), the mixed packing layer of the second distillation column is stainless steel corrugated packing with different specific surface areas, which is divided into a rectification section and a stripping section from top to bottom; the rectification section is stainless steel corrugated packing with high specific surface area; the stripping section is composed of stainless steel corrugated packing with medium specific surface area in the middle section and stainless steel corrugated packing with low specific surface area in the lower section.

[0016] Preferably, the height of the high specific surface area stainless steel corrugated packing in the rectification section of the first distillation column is 1.0-2.0m.

[0017] Preferably, the total height of the stripping section of the first distillation column is 1.2-1.8m, wherein the height ratio of the medium specific surface area stainless steel corrugated packing in the middle section to the low specific surface area stainless steel corrugated packing in the lower section is (1-1.5):1.

[0018] Preferably, the height of the high specific surface area stainless steel corrugated packing in the rectification section of the second distillation column is 1.2-2.2m.

[0019] Preferably, the total height of the stripping section of the second distillation column is 1.0-1.5m, wherein the height ratio of the medium specific surface area stainless steel corrugated packing in the middle section to the low specific surface area stainless steel corrugated packing in the lower section is (1-2):1.

[0020] Preferably, in the continuous distillation process of steps (2) and (3), nitrogen gas with a purity of ≥99.99% is introduced into the top reflux tanks of the first and second distillation columns as protective gas, and the nitrogen gas introduction rate is 0.5-1.5 L / min.

[0021] Preferably, in step (3), when collecting the top fraction, an online refractometer is used to monitor the refractive index of the fraction in real time. When the refractive index is stable in the range of 1.469-1.471 and lasts for 5 minutes, the collection of the top fraction is started.

[0022] Preferably, both the first and second distillation columns are equipped with falling film reboilers.

[0023] Compared with the prior art, the present invention has the following advantages and technical effects:

[0024] I. Constructing a New Dual-Tower Coupled Precision Distillation System

[0025] This invention overcomes the limitations of existing linalool extraction processes with its novel dual-tower segmented functionalized distillation and gradient surface area stainless steel corrugated packing. Existing technologies for linalool distillation often employ single-tower batch operation or continuous distillation with homogeneous packing, failing to achieve precise separation and adaptation to the boiling point differences between light and heavy components and linalool. This invention, through a segmented design—a first distillation column for directional collection of light components and a second distillation column for precise separation of heavy components—combined with independent pressure, temperature, and reflux ratio parameters for coordinated control of the two columns, forms a continuous process chain for effective separation of light components and deep purification of target components, filling the gap in existing technologies for fractional distillation technology targeting multi-component impurities in linalool essential oil.

[0026] Meanwhile, this invention innovatively designs the mixed packing layer as a stainless steel corrugated packing structure with a gradient distribution of high specific surface area in the rectification section and low specific surface area in the stripping section, replacing traditional homogeneous packing or adsorption-type composite packing. This design is based on the gradient requirements of vapor-liquid mass transfer during rectification, achieving a balance between mass transfer efficiency and energy consumption through precise matching of specific surface areas. It overcomes the technical bottleneck of existing technologies where packing functions are singular and mass transfer and energy consumption are difficult to balance, representing an innovative design for distillation packing applied to the field of linalool extraction.

[0027] II. Achieving a dual breakthrough in separation efficiency and product quality

[0028] Compared with existing technologies, this invention demonstrates outstanding creativity in both technical conception and technical effect. From the perspective of technical conception, existing technologies generally suffer from the technical contradiction of conflicting separation accuracy and energy consumption, and the difficulty in balancing continuous operation and purity: single-tower distillation processes cannot simultaneously adapt to the separation requirements of light and heavy components, resulting in low product purity or excessive yield loss; although traditional composite packing distillation attempts to improve separation efficiency, the introduction of adsorbed components can easily cause entrainment or contamination of the target product, and the excessive drop in packing resistance leads to a surge in energy consumption.

[0029] This invention resolves contradictions through three-dimensional synergy: First, differentiated design of dual-tower parameters: the first tower uses mild conditions of medium-low pressure and low reflux ratio to collect light components, avoiding linalool volatilization loss; the second tower uses precise conditions of low pressure and high reflux ratio to separate heavy components, ensuring purification accuracy, forming a scientific process of mild pretreatment and precise purification; Second, functional adaptation of gradient specific surface area packings: high specific surface area packings in the rectification section enhance vapor-liquid contact and improve separation accuracy; medium-low specific surface area packings in the stripping section reduce resistance drop and energy consumption, achieving synergy of high-precision separation and low-energy operation; Third, auxiliary protection with nitrogen gas and online refractive index monitoring effectively inhibits linalool oxidation and decomposition, accurately captures target fractions, and avoids purity fluctuations caused by transition fractions.

[0030] The organic integration of the above-mentioned technologies is not a simple superposition of existing technologies, but an innovative optimization based on the mass transfer mechanism of linalool distillation. It ultimately achieves a technological breakthrough with a purity of ≥99%. Compared with existing single-tower processes or traditional packed processes, it has achieved a qualitative leap in separation efficiency, product quality and energy consumption control, and is creative.

[0031] III. Providing a reliable solution for the industrial-scale production of high-purity linalool.

[0032] This invention has strong industrial applicability and can effectively solve many practical technical problems in existing linalool extraction processes. First, addressing the issues of poor continuity and low production efficiency in existing processes, this invention adopts a fully continuous dual-tower coupling design, ensuring continuous operation from raw material feeding to finished product output. This avoids time-consuming steps such as heating and cooling and material transfer in intermittent operations, significantly improving production efficiency and adapting to the needs of large-scale industrial production.

[0033] Secondly, it addresses the industry pain points of unstable product purity and excessive impurity residues in existing processes. Through the synergistic effect of segmented distillation and gradient packing, it achieves efficient separation of light and heavy components. Combined with nitrogen protection to suppress the generation of oxidative impurities and online refractive index monitoring for precise distillation control, it ensures that the product purity consistently reaches over 99%, meeting the quality requirements for high-purity linalool in high-end fields such as fragrances and pharmaceuticals.

[0034] Furthermore, it effectively alleviates the problems of high energy consumption and high operating costs in existing processes. The design of low specific surface area packing in the stripping section reduces vapor-liquid mass transfer resistance and reduces the heating load on the reboiler; the optimized pressure gradient of the dual towers reduces the distillation operating temperature, reduces the thermal decomposition loss of linalool, and improves energy utilization efficiency. Compared with traditional processes, it significantly reduces the energy consumption per unit product, providing technical support for enterprises to reduce production costs and achieve green production.

[0035] Furthermore, the stainless steel corrugated packing used in this invention has strong chemical stability and long service life, avoiding the problems of adsorption saturation and replacement costs of traditional adsorption packing. Moreover, the process operation parameters are clear, the control is simple, and the equipment is highly adaptable. Existing distillation production lines can be applied with appropriate modifications, making it extremely valuable for promotion and industrialization. Detailed Implementation

[0036] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0037] In this invention, a method for continuous distillation of high-purity linalool from linalool oil includes the following steps:

[0038] (1) Raw material preparation: using linalool essential oil (linalool content ≥80%) as raw material;

[0039] (2) First continuous distillation: The linalool essential oil is fed into the first distillation column. Under the absolute pressure of the system of 15-25 kPa, the top temperature of the column is controlled at 35-50℃, the bottom temperature at 85-95℃, and the reflux ratio is (2-4):1. The distillation is carried out through a mixed packing layer. The top fraction is collected to remove light component impurities with boiling points lower than linalool. The bottom fraction is collected as the first intermediate fraction.

[0040] (3) Second continuous distillation: The first intermediate fraction is fed into the second distillation column. Under the absolute pressure of the system of 5-10 kPa, the top temperature of the column is controlled at 95-105℃, the bottom temperature at 115-125℃, and the reflux ratio is (4-6):1. The distillation is carried out through the mixed packing layer, and the top fraction is collected to obtain linalool product with a purity of ≥99%.

[0041] The mechanisms of action of each preparation step are as follows:

[0042] I. Raw material preparation steps

[0043] This invention selects raw materials with high base content, which can reduce ineffective mass transfer processes and allow subsequent distillation operations to focus on the precise separation of trace impurities. This provides initial material assurance for the final product purity of ≥99%, while reducing energy consumption and process cycle, reflecting the design logic of precise pretreatment and efficient separation.

[0044] II. First Continuous Distillation

[0045] The core function of the first distillation column is to directionally collect light components with boiling points lower than linalool. Its process parameters and the design of the mixed packing layer work synergistically. From a pressure perspective, the design of an absolute pressure of 15-25 kPa lowers the boiling point of linalool while increasing the relative volatility of the light components compared to linalool. The gradient control of the top temperature (35-50℃) and the bottom temperature (85-95℃) creates a top-to-bottom temperature field within the column, causing the light components to be enriched and vaporized at the top, while linalool flows with the liquid phase to the bottom, avoiding the loss of the target component due to entrainment by the light components.

[0046] The reflux ratio design of (2-4):1 balances separation efficiency and energy consumption. The mixed packing layer precisely matches the mass transfer requirements in the column through a gradient structure of high specific surface area in the rectification section and low specific surface area in the stripping section: the high specific surface area stainless steel corrugated packing in the rectification section can enhance vapor-liquid contact and improve the capture efficiency of light components; the low specific surface area packing in the stripping section reduces liquid flow resistance, accelerates the accumulation of linalool in the column bottom, avoids separation lag caused by excessive mass transfer resistance, and achieves the dual goals of efficient separation of light components and low loss retention of linalool.

[0047] III. Second Continuous Distillation

[0048] The second distillation column, as the core link in the purification of the target component, is designed around the separation of heavy components and the precise capture of linalool, with various technologies working synergistically in multiple dimensions. A lower absolute pressure of 5-10 kPa further reduces the boiling point of linalool to 95-105℃, avoiding oxidative decomposition of linalool caused by high temperatures; the temperature control of 115-125℃ in the reboiler keeps the heavy components in a liquid phase, achieving vapor-liquid separation from linalool. The high reflux ratio design (4-6):1 is based on the characteristic that the boiling points of linalool and heavy components are relatively similar—a high reflux ratio increases the number of times the top fraction circulates, enhances the depth of vapor-liquid mass transfer, ensures that trace amounts of heavy components are fully retained, and improves product purity.

[0049] The gradient specific surface area design of the mixed packing layer creates more precise mass transfer enhancement in this stage: the high specific surface area packing in the rectification section achieves efficient separation of linalool and trace heavy components through dense vapor-liquid contact interfaces; the low specific surface area packing in the stripping section is suitable for the lower section conditions with higher heavy component content, reducing pressure drop while avoiding accumulation and blockage of heavy components on the packing surface. This packing design, in conjunction with pressure and temperature parameters, resolves the contradiction between high separation accuracy and low energy consumption in existing technologies, achieving complete separation of heavy components and efficient capture of linalool.

[0050] IV. Overall Technical Effects of Synergistic Effects

[0051] The steps in this invention are not isolated operations, but rather form a complete and synergistic system encompassing raw material adaptation, light component collection, heavy component separation, and quality assurance. High raw material content parameters reduce the burden on subsequent distillation; the separation of light components in the first column clears obstacles for deep purification in the second column; the matching of the gradient packing layer with pressure and reflux ratio parameters maximizes mass transfer efficiency; and nitrogen protection and precise monitoring ensure product purity and stability. This synergistic mechanism solves the core problems of low product purity, high oxidation loss, and high energy consumption in existing technologies, demonstrating outstanding creativity and practicality, and providing a reliable technical path for the industrial production of high-purity linalool.

[0052] To make the present invention more fully disclosed, more specific embodiments are described below.

[0053] Example 1

[0054] A method for continuous distillation of high-purity linalool from linalool oil includes the following steps:

[0055] (1) Raw material preparation: Provide 1000g of linalool-containing essential oil raw material with a linalool content of 88.2% and place it in the raw material storage tank for later use.

[0056] (2) First Continuous Distillation: Linalool essential oil is continuously fed into the first distillation column at a rate of 10 kg / h via a feed pump. The column is 3.5 m high and 0.25 m in diameter, and is equipped with a falling film reboiler. The system absolute pressure is set at 20 kPa. By adjusting the heating power of the reboiler and the cooling water flow rate of the condenser at the top of the column, the top temperature is controlled to be stable at 42℃, the bottom temperature at 90℃, and the reflux ratio at 3:1. The mixed packing layer inside the column is stainless steel corrugated packing with different specific surface areas, which is divided into a rectification section and a stripping section from top to bottom; the rectification section is filled with high specific surface area stainless steel corrugated packing (specific surface area 450 m²). 2 / m 3 The column has a height of 1.5m; the stripping section has a total height of 0.8m, consisting of a middle section of medium specific surface area stainless steel corrugated packing and a lower section of low specific surface area stainless steel corrugated packing (height ratio 1:1). The bottom fraction is collected as the first intermediate fraction, weighing 860g (calculated to contain approximately 92.0% linalool).

[0057] (3) Second Continuous Distillation: The first intermediate fraction is continuously fed into the second distillation column at a rate of 8.8 kg / h via a transfer pump. The column is 4.5 m high and 0.2 m in diameter, and is equipped with a falling film reboiler. The system absolute pressure is set at 8 kPa, and the column top temperature is controlled to be stable at 100 °C, the column bottom temperature at 120 °C, and the reflux ratio at 5:1. The mixed packing layer inside the column is stainless steel corrugated packing with different specific surface areas, which is divided into a rectification section and a stripping section from top to bottom; the rectification section is filled with high specific surface area stainless steel corrugated packing (specific surface area 550 m²). 2 / m3 The first and second distillation columns each have a height of 2.0m; the stripping section has a total height of 1.2m and consists of a middle section with medium specific surface area stainless steel corrugated packing and a lower section with low specific surface area stainless steel corrugated packing (height ratio 1:1). Nitrogen gas with a purity ≥99.99% was introduced as a protective gas into the reflux tanks at the top of both columns at a controlled rate of 1.0L / min. The refractive index of the top fraction of the second distillation column was monitored in real time using an online refractometer. Once the refractive index stabilized within the range of 1.470±0.001 for 5 minutes, the top fraction was collected, yielding 748g of linalool.

[0058] Test results: Gas chromatography analysis showed that the final product of this embodiment had a linalool purity of 99.6%, was a colorless and transparent liquid, and possessed the characteristic aroma of pure linalool. Based on the total amount of linalool in the raw materials, the overall yield was 84.47%.

[0059] Single-factor experimental design and results of key process parameters

[0060] (I) Experimental Design Principles

[0061] Using Example 1 as the baseline, single-factor experiments were conducted on the absolute pressure of the first distillation column, the reflux ratio of the second distillation column, and the nitrogen inlet rate. Only the target parameter was changed, while the other parameters were the same as in Example 1.

[0062] (II) Summary of Single-Factor Experiment Results

[0063] The results of the single-factor experiments are shown in Tables 1-3.

[0064]

[0065] (III) Analysis of Single-Factor Experiment Results

[0066] 1. Absolute pressure of the first distillation column

[0067] As shown in Table 1:

[0068] (1) Below 15 kPa: The low pressure causes the boiling point of the light component to drop sharply, and the boiling point difference with linalool is reduced. During the distillation process, some linalool is vaporized along with the light component and distilled off from the top of the column, resulting in a yield of 79.2%. At the same time, the gas velocity in the column is too fast under low pressure, and the purity is only 98.9%.

[0069] (2) Above 25 kPa: Excessive pressure inhibits the gasification of light components, making it difficult to separate light components such as α-pinene from the liquid phase. Some of them remain in the bottom of the column and enter the middle fraction, causing the residual amount of light components to soar to 0.45%. High pressure also causes the bottom temperature of the column to rise implicitly, resulting in slight oxidation of linalool, reducing the purity to 98.7%, and the yield to 78.5% as the proportion of impurities increases.

[0070] (3) Conclusion: 15-25 kPa is the equilibrium range between complete separation of light components and low loss of linalool. 20 kPa is the optimal value. Under this pressure, the light components are fully vaporized and linalool is stably retained, achieving the best results of 99.6% purity and 84.47% yield.

[0071] 2. Reflux ratio of the second distillation column

[0072] As shown in Table 2:

[0073] (1) Below 4:1: Insufficient reflux ratio leads to a shortened gas-liquid contact time between the top fraction and the packing material in the column. Heavy components such as citronellol cannot be fully separated from linalool, and some are distilled out with linalool, with a residual amount of heavy components as high as 0.62%. Insufficient separation precision results in a purity of only 98.5%. Although the yield is slightly improved due to insufficient separation, the product quality does not meet the standards.

[0074] (2) Higher than 6:1: The excessively high reflux ratio causes a large amount of the top distillate to return to the column, and linalool is repeatedly distilled and retained in the column. Some of it is discharged with the heavy components in the bottom of the column, and the yield drops sharply to 77.8%. At the same time, the high reflux ratio increases the energy consumption in the column, while the residual amount of heavy components only decreases from 0.12% to 0.10%, and the purity improvement is less than 0.2 percentage points, which is extremely low cost performance.

[0075] (3) Conclusion: 4:1-6:1 is the balance range between sufficient separation and low energy consumption, and 5:1 is the optimal value. Under this reflux ratio, the gas-liquid mass transfer is sufficient, the residual amount of heavy components is only 0.12%, and the purity and yield reach 99.6% and 84.47% respectively, thus maximizing the benefits.

[0076] 3. Nitrogen introduction rate

[0077] As shown in Table 3:

[0078] (1) Below 0.5L / min: The nitrogen flow rate is insufficient and cannot completely replace the air in the top reflux tank, forming a local oxygen environment. The enol structure of linalool is easily oxidized to aldehydes, and the content of oxidation impurities is as high as 0.25%. The oxidation products affect the purity of the product, reducing the purity to 99.1%, and the yield is slightly lower due to oxidation loss.

[0079] (2) Above 1.5L / min: Excessive nitrogen flow rate causes airflow disturbance, which carries away some of the linalool fraction from the top of the column, resulting in direct loss of linalool and a sharp drop in yield to 79.5%. Although the content of oxidized impurities drops to 0.06%, the purity is only 99.4%, and the nitrogen consumption increases by 3 times, resulting in a significant increase in production.

[0080] (3) Conclusion: 0.5-1.5 L / min is the balance range between sufficient inert protection and low entrainment loss. 1.0 L / min is the optimal value. At this rate, a stable inert atmosphere can be constructed, the content of oxidizing impurities is only 0.08%, and the entrainment of distillate is avoided. The purity and yield are 99.6% and 84.47%, respectively.

[0081] Example 2

[0082] A method for continuous distillation of high-purity linalool from linalool oil includes the following steps:

[0083] (1) Raw material preparation: Provide 1000g of linalool-containing essential oil raw material with a linalool content of 88.2% and place it in the raw material storage tank for later use.

[0084] (2) First Continuous Distillation: Linalool essential oil is continuously fed into the first distillation column at a rate of 12 kg / h via a feed pump. The column is 3.2 m high and 0.25 m in diameter, and a falling film reboiler is installed in the reboiler. The system absolute pressure is set at 15 kPa, and the column top temperature is controlled to be stable at 35 °C, the column bottom temperature at 85 °C, and the reflux ratio at 2:1. The mixed packing layer inside the column is stainless steel corrugated packing with different specific surface areas, which is divided into a rectification section and a stripping section from top to bottom; the rectification section is filled with high specific surface area stainless steel corrugated packing (specific surface area 450 m²). 2 / m 3 The column has a height of 1.2m; the stripping section has a total height of 0.6m, consisting of a middle section with medium specific surface area stainless steel corrugated packing and a lower section with low specific surface area stainless steel corrugated packing (height ratio 1:1). 850g of the first intermediate fraction (linalool content approximately 91.5%) is collected from the bottom of the column.

[0085] (3) Second Continuous Distillation: The first intermediate fraction is continuously fed into the second distillation column at a rate of 9.0 kg / h via a transfer pump. The column is 4.5 m high and 0.2 m in diameter, and is equipped with a falling film reboiler. The system absolute pressure is set at 5 kPa, and the column top temperature is controlled to be stable at 95 °C, the column bottom temperature at 115 °C, and the reflux ratio at 5:1. The mixed packing layer inside the column is stainless steel corrugated packing with different specific surface areas, which is divided into a rectification section and a stripping section from top to bottom; the rectification section is filled with high specific surface area stainless steel corrugated packing (specific surface area 550 m²). 2 / m 3The first and second distillation columns each have a height of 2.0m; the stripping section has a total height of 1.2m and consists of a middle section with medium specific surface area stainless steel corrugated packing and a lower section with low specific surface area stainless steel corrugated packing (height ratio 1:1). Nitrogen gas with a purity ≥99.99% was introduced as a protective gas into the reflux tanks at the top of both columns at a controlled rate of 1.0L / min. The refractive index of the top fraction of the second distillation column was monitored in real time using an online refractometer. Once the refractive index stabilized within the range of 1.470±0.001 for 5 minutes, the top fraction was collected, yielding 730g of linalool.

[0086] Test results: Gas chromatography analysis showed that the final product of this embodiment had a linalool purity of 99.3%, was a colorless and transparent liquid, and possessed the characteristic aroma of pure linalool. Based on the total amount of linalool in the raw materials, the overall yield was 82.19%.

[0087] Example 3

[0088] A method for continuous distillation of high-purity linalool from linalool oil includes the following steps:

[0089] (1) Raw material preparation: Provide 1000g of linalool-containing essential oil raw material with a linalool content of 88.2% and place it in the raw material storage tank for later use.

[0090] (2) First Continuous Distillation: Linalool essential oil is continuously fed into the first distillation column at a rate of 10 kg / h via a feed pump. The column is 3.5 m high and 0.25 m in diameter, and a falling film reboiler is installed in the reboiler. The system absolute pressure is set at 20 kPa, and the column top temperature is controlled to be stable at 42℃, the column bottom temperature at 90℃, and the reflux ratio at 3:1. The mixed packing layer inside the column is stainless steel corrugated packing with different specific surface areas, which is divided into a rectification section and a stripping section from top to bottom; the rectification section is filled with high specific surface area stainless steel corrugated packing (specific surface area 450 m²). 2 / m 3 The first intermediate fraction, 1.5m high, is collected from the bottom of the column. The total height of the stripping section is 0.8m, consisting of medium specific surface area stainless steel corrugated packing in the middle section and low specific surface area stainless steel corrugated packing in the lower section (height ratio 1:1). 860g of the first intermediate fraction is collected from the bottom of the column.

[0091] (3) Second Continuous Distillation: The first intermediate fraction is continuously fed into the second distillation column at a rate of 8.8 kg / h via a transfer pump. The column is 4.8 m high and 0.2 m in diameter, and is equipped with a falling film reboiler. The system absolute pressure is set at 8 kPa, and the column top temperature is controlled to be stable at 100 °C, the column bottom temperature at 120 °C, and the reflux ratio at 6:1. The mixed packing layer inside the column is stainless steel corrugated packing with different specific surface areas, which is divided into a rectification section and a stripping section from top to bottom; the rectification section is filled with high specific surface area stainless steel corrugated packing (specific surface area 550 m²). 2 / m3 The first and second distillation columns each have a height of 2.2m; the stripping section has a total height of 1.0m and consists of a middle section with medium specific surface area stainless steel corrugated packing and a lower section with low specific surface area stainless steel corrugated packing (height ratio 1:1). Nitrogen gas with a purity ≥99.99% was introduced as a protective gas into the reflux tanks at the top of both columns at a controlled rate of 1.0L / min. The refractive index of the top fraction of the second distillation column was monitored in real time using an online refractometer. Once the refractive index stabilized within the range of 1.471±0.001 for 5 minutes, the top fraction was collected, yielding 735g of linalool.

[0092] Test results: Gas chromatography analysis showed that the final product of this embodiment had a linalool purity of 99.4%, was a colorless and transparent liquid, and possessed the characteristic aroma of pure linalool. Based on the total amount of linalool in the raw materials, the overall yield was 82.83%.

[0093] Example 4

[0094] A method for continuous distillation of high-purity linalool from linalool oil includes the following steps:

[0095] (1) Raw material preparation: Provide 1000g of linalool-containing essential oil raw material with a linalool content of 88.2% and place it in the raw material storage tank for later use.

[0096] (2) First Continuous Distillation: Linalool essential oil is continuously fed into the first distillation column at a rate of 10 kg / h via a feed pump. The column is 3.5 m high and 0.25 m in diameter, and a falling film reboiler is installed in the reboiler. The system absolute pressure is set at 20 kPa, and the column top temperature is controlled to be stable at 42℃, the column bottom temperature at 90℃, and the reflux ratio at 3:1. The mixed packing layer inside the column is stainless steel corrugated packing with different specific surface areas, which is divided into a rectification section and a stripping section from top to bottom; the rectification section is filled with high specific surface area stainless steel corrugated packing (specific surface area 450 m²). 2 / m 3 The first intermediate fraction, 1.5m high, is collected from the bottom of the column. The total height of the stripping section is 0.8m, consisting of medium specific surface area stainless steel corrugated packing in the middle section and low specific surface area stainless steel corrugated packing in the lower section (height ratio 1:1). 860g of the first intermediate fraction is collected from the bottom of the column.

[0097] (3) Second Continuous Distillation: The first intermediate fraction is continuously fed into the second distillation column at a rate of 8.8 kg / h via a transfer pump. The column is 4.5 m high and 0.2 m in diameter, and is equipped with a falling film reboiler. The system absolute pressure is set at 8 kPa, and the column top temperature is controlled to be stable at 100 °C, the column bottom temperature at 120 °C, and the reflux ratio at 5:1. The mixed packing layer inside the column is stainless steel corrugated packing with different specific surface areas, which is divided into a rectification section and a stripping section from top to bottom; the rectification section is filled with high specific surface area stainless steel corrugated packing (specific surface area 550 m²).2 / m 3 The first and second distillation columns each have a height of 2.0m; the stripping section has a total height of 1.2m and consists of a middle section with medium specific surface area stainless steel corrugated packing and a lower section with low specific surface area stainless steel corrugated packing (height ratio 1:1). Nitrogen gas with a purity ≥99.99% was introduced as a protective gas into the reflux tanks at the top of both columns at a controlled rate of 1.0L / min. The refractive index of the top fraction of the second distillation column was monitored in real time using an online refractometer. Once the refractive index stabilized within the range of 1.470±0.001 for 5 minutes, the top fraction was collected, yielding 725g of linalool.

[0098] Test results: Gas chromatography analysis showed that the final product of this embodiment had a linalool purity of 99.5%, was a colorless and transparent liquid, and possessed the characteristic aroma of pure linalool. Based on the total amount of linalool in the raw materials, the overall yield was 81.79%.

[0099] Example 5

[0100] A method for continuous distillation of high-purity linalool from linalool oil includes the following steps:

[0101] (1) Raw material preparation: Provide 1000g of linalool-containing essential oil raw material with a linalool content of 88.2% and place it in the raw material storage tank for later use.

[0102] (2) First Continuous Distillation: Linalool essential oil is continuously fed into the first distillation column at a rate of 10 kg / h via a feed pump. The column is 3.5 m high and 0.25 m in diameter, and a falling film reboiler is installed in the reboiler. The system absolute pressure is set at 20 kPa, and the column top temperature is controlled to be stable at 42℃, the column bottom temperature at 90℃, and the reflux ratio at 3:1. The mixed packing layer inside the column is stainless steel corrugated packing with different specific surface areas, which is divided into a rectification section and a stripping section from top to bottom; the rectification section is filled with high specific surface area stainless steel corrugated packing (specific surface area 450 m²). 2 / m 3 The first intermediate fraction, 1.5m high, is collected from the bottom of the column. The total height of the stripping section is 0.8m, consisting of medium specific surface area stainless steel corrugated packing in the middle section and low specific surface area stainless steel corrugated packing in the lower section (height ratio 1:1). 860g of the first intermediate fraction is collected from the bottom of the column.

[0103] (3) Second Continuous Distillation: The first intermediate fraction is continuously fed into the second distillation column at a rate of 8.8 kg / h via a transfer pump. The column is 4.5 m high and 0.2 m in diameter, and is equipped with a falling film reboiler. The system absolute pressure is set at 8 kPa, and the column top temperature is controlled to be stable at 100 °C, the column bottom temperature at 120 °C, and the reflux ratio at 6:1. The mixed packing layer inside the column is stainless steel corrugated packing with different specific surface areas, which is divided into a rectification section and a stripping section from top to bottom; the rectification section is filled with high specific surface area stainless steel corrugated packing (specific surface area 550 m²). 2 / m 3 The first distillation column has a total height of 2.0m; the stripping section has a total height of 1.2m, consisting of a middle section of medium specific surface area stainless steel corrugated packing and a lower section of low specific surface area stainless steel corrugated packing (height ratio 1:1). Nitrogen gas with a purity ≥99.99% is introduced into the reflux tank at the top of the first distillation column as a protective gas at a rate controlled at 0.8L / min; nitrogen gas is introduced into the reflux tank at the top of the second distillation column at a rate controlled at 1.2L / min. The refractive index of the top fraction of the second distillation column is monitored in real time using an online refractometer. When the refractive index stabilizes within the range of 1.469±0.001 for 5 minutes, the top fraction is collected, yielding 740g of linalool.

[0104] Test results: Gas chromatography analysis showed that the final product of this embodiment had a linalool purity of 99.2%, was a colorless and transparent liquid, and possessed the characteristic aroma of pure linalool. Based on the total amount of linalool in the raw materials, the overall yield was 83.23%.

[0105] II. Comparative Example

[0106] Comparative Example 1

[0107] (1) Raw material preparation: Take 1000g of linalool essential oil (linalool content 88.2%) from the same batch as in the example.

[0108] (2) Single-tower continuous distillation: Linalool essential oil was fed into a single distillation column, with the system absolute pressure set at 12 kPa, and the top temperature controlled at 75°C, the bottom temperature at 130°C, and the reflux ratio at 4:1. The column was packed with ceramic corrugated packing (the segmented design of stainless steel corrugated packing with different specific surface areas of this invention was not adopted). Under these general conditions, the separation of light and heavy components from linalool was difficult to be complete. The target fraction was collected, yielding 724 g of linalool product.

[0109] Test results: Linalool purity 95.8%, yield 78.64%.

[0110] Comparative Example 2

[0111] (1) Raw material preparation: Take 1000g of linalool essential oil (linalool content 88.2%) from the same batch as in the example.

[0112] (2) First continuous distillation: The operating parameters are the same as in Example 1, but the mixed packing layer is not designed with stainless steel corrugated packing of different specific surface areas in the rectification-stripping section; instead, it is filled with only a single type of composite packing. The distillate in the bottom of the column is collected and weighed to obtain 847g.

[0113] (3) Second continuous distillation: The operating parameters are the same as in Example 1, but the mixed packing layer is not designed with stainless steel corrugated packing with different specific surface areas for the rectification-stripping section. Instead, it is filled with a single type of activated carbon packing and nitrogen is not introduced. The top fraction is collected to obtain 702g of linalool product.

[0114] Test results: Linalool purity 96.5%, yield 76.81%.

[0115] Comparative Example 3

[0116] (1) Raw material preparation: Take 1000g of linalool essential oil (linalool content 88.2%) from the same batch as in the example.

[0117] (2) Single-tower batch distillation: Heating under atmospheric pressure, controlling the top temperature of the column at 198℃ to collect the fraction, with a reflux ratio of 3:1. The dual-tower coupling design and the segmented structure of stainless steel corrugated packing with different specific surface areas of the present invention were not adopted, resulting in partial decomposition of linalool at high temperature. The target fraction was collected, yielding 636g of linalool product.

[0118] Test results: Linalool purity 94.5%, yield 67.92%.

[0119] III. Summary of Experimental Results:

[0120] (a) Test Results

[0121] The detection results of Examples 1-5 and Comparative Examples 1-3 are shown in Table 4.

[0122]

[0123] (II) Data Comparison and Analysis

[0124] 1. Purity Analysis

[0125] As shown in Table 4, the linalool purity of Examples 1-5 ranged from 99.2% to 99.6%, with Example 1 achieving the optimal purity of 99.6%. In contrast, the purity of Comparative Examples 1-3 ranged from 94.5% to 96.5%, with a maximum of only 96.5%. The purity of Example 1 was 3.97% higher than Comparative Example 1, 3.21% higher than Comparative Example 2, and 5.40% higher than Comparative Example 3. This purity advantage stems from the multi-component synergistic purification system constructed in this invention, the core technical mechanism of which is as follows:

[0126] From a process design perspective, this invention employs a coupled model of dual-tower functional division and gradient specific surface area packing, resolving the core pain point of conflict between light and heavy component separation in traditional processes. The first distillation column focuses on light component separation, utilizing stainless steel corrugated packing in a high specific surface area rectification section and a medium-to-low specific surface area stripping section. The high specific surface area in the rectification section maximizes the vapor-liquid contact area, enhancing mass transfer separation of light components and linalool; the medium-to-low specific surface area packing in the stripping section reduces vapor-liquid flow resistance, ensuring uniform material distribution and avoiding incomplete separation due to localized stagnation. The second distillation column specifically removes heavy components. Its rectification section uses stainless steel corrugated packing with an even higher specific surface area to further improve separation accuracy, while the medium-to-low specific surface area packing in the stripping section balances mass transfer efficiency and energy consumption, achieving efficient retention of heavy components.

[0127] In contrast, Comparative Example 1, with its single-tower distillation, could not simultaneously meet the separation requirements of light and heavy components. The ceramic corrugated packing had a single specific surface area and low mass transfer efficiency, resulting in a significantly higher residual amount of light and heavy components compared to the example. Although Comparative Example 2 adopted a dual-tower structure, the packing lacked a gradient specific surface area design, leading to a mismatch in mass transfer efficiency between the rectification and stripping sections. Furthermore, the absence of nitrogen protection caused linalool to undergo oxidation during distillation, generating trace amounts of oxidized impurities, resulting in a lower purity than the example. Comparative Example 3 employed atmospheric pressure high-temperature single-tower batch distillation. The high temperature not only exacerbated the decomposition of linalool but also resulted in low fraction collection accuracy during batch operation, with a large amount of transition fraction mixed into the product, ultimately leading to the lowest purity.

[0128] 2. Overall Yield Analysis

[0129] As shown in Table 4, the overall yield of Examples 1-5 ranged from 81.79% to 84.47%, with Example 1 achieving the optimal yield of 84.47%. In contrast, the overall yield of Comparative Examples 1-3 ranged from 67.92% to 78.64%, with a maximum of only 78.64%. The yield of Example 1 was 7.41% higher than Comparative Example 1, 10.00% higher than Comparative Example 2, and 24.37% higher than Comparative Example 3. This yield advantage is the result of the precise control of separation efficiency and material loss in this invention. The core technical mechanism is as follows:

[0130] Firstly, the synergistic optimization of the two distillation columns reduces material loss. The first distillation column operates under mild conditions of 15-25 kPa medium-low pressure and a 2-4:1 reflux ratio, ensuring sufficient vaporization and separation of light components while preventing linalool from azeotropically distilling out with the light components. The second distillation column operates under precise conditions of 5-10 kPa low pressure and a 4-6:1 reflux ratio, enhancing the separation of heavy components while reducing the residence time of linalool in the column and minimizing wall adsorption losses. The matching design of the feed and withdrawal rates of the two columns achieves material balance, further reducing process losses.

[0131] Secondly, gradient surface area packing reduces adsorption and entrainment losses. Stainless steel corrugated packing has strong chemical stability; high surface area packing in the rectification section enhances the separation of target components, while low surface area packing in the stripping section reduces vapor-liquid flow resistance, avoiding losses caused by linalool mist entrainment, thus achieving a synergistic effect of high-efficiency separation and low loss.

[0132] Third, continuous operation and precise control improve yield stability. The fully continuous process avoids losses caused by heating and cooling, material transfer, etc. in batch operation; the 5-minute stabilization period monitoring of the online refractometer avoids the misjudgment and discarding of high-purity linalool fractions; the uniform heating design of the falling film reboiler reduces the decomposition loss of linalool caused by local overheating, further improving the overall yield.

[0133] In Comparative Example 1, due to parameter conflicts, a high reflux ratio of 4:1 had to be used for single-tower distillation, resulting in a large amount of linalool remaining in the tower and being discharged with the bottom residue, leading to a low yield. In Comparative Example 2, due to the lack of a gradient design in the packing, the mass transfer efficiency was uneven, and some linalool was excessively adsorbed by the packing. Furthermore, the lack of nitrogen protection led to oxidation loss, further reducing the yield. In Comparative Example 3, the atmospheric pressure and high temperature operation caused linalool volatilization loss, and the inaccuracy of intermittent sampling resulted in the rejection of some qualified fractions. At the same time, the high temperature triggered the decomposition of linalool, ultimately resulting in the lowest yield.

[0134] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for continuously rectifying high purity linalool from linaloe oil, characterized by, The method comprises the following steps: (1) raw material preparation: using linalyl oil as raw material; (2) first continuous rectification: sending the linalyl oil into a first rectification tower, controlling the tower top temperature at 35-50 DEG C, the tower kettle temperature at 85-95 DEG C, the reflux ratio (2-4):1 under the system absolute pressure of 15-25 kPa, rectifying through mixed filler layer, collecting the tower top fraction to remove light components with boiling point lower than linalyl alcohol, and collecting the tower kettle fraction as the first intermediate fraction; (3) second continuous rectification: sending the first intermediate fraction into a second rectification tower, controlling the tower top temperature at 95-105 DEG C, the tower kettle temperature at 115-125 DEG C, the reflux ratio (4-6):1 under the system absolute pressure of 5-10 kPa, rectifying through mixed filler layer, and collecting the tower top fraction to obtain linalyl alcohol product with purity ≥99%.

2. The method of continuously rectifying high purity linalool from linaloe oil according to claim 1, characterized in that, The mixed filler layer of the first rectification tower in step (2) is stainless steel corrugated filler with different specific surface areas, which is sequentially divided into rectification section and stripping section from top to bottom; the rectification section is high specific surface area stainless steel corrugated filler; the stripping section is composed of middle section medium specific surface area stainless steel corrugated filler and lower section low specific surface area stainless steel corrugated filler.

3. The method of claim 1, wherein the method is characterized by, The mixed filler layer of the second rectification tower in step (3) is stainless steel corrugated filler with different specific surface areas, which is sequentially divided into rectification section and stripping section from top to bottom; the rectification section is high specific surface area stainless steel corrugated filler; the stripping section is composed of middle section medium specific surface area stainless steel corrugated filler and lower section low specific surface area stainless steel corrugated filler.

4. The method of claim 2, wherein the method is characterized by, The high specific surface area stainless steel corrugated filler in the rectification section of the first rectification tower has a height of 1.0-2.0 m.

5. The method of claim 2, wherein the method is characterized by, The total height of the stripping section of the first rectification tower is 1.2-1.8 m, wherein the height ratio of the middle section medium specific surface area stainless steel corrugated filler to the lower section low specific surface area stainless steel corrugated filler is (1-1.5):

1.

6. The method of claim 3, wherein the method is characterized by, The high specific surface area stainless steel corrugated filler in the rectification section of the second rectification tower has a height of 1.2-2.2 m.

7. The method of claim 3, wherein the method is characterized by, The total height of the stripping section of the second rectification tower is 1.0-1.5 m, wherein the height ratio of the middle section medium specific surface area stainless steel corrugated filler to the lower section low specific surface area stainless steel corrugated filler is (1-2):

1.

8. The method of claim 1, wherein the method is characterized by, In the continuous rectification process of steps (2) and (3), pure nitrogen with purity ≥99.99% is introduced into the tower top reflux tank of the first rectification tower and the second rectification tower as protective gas, and the nitrogen introduction rate is 0.5-1.5 L / min.

9. The method of claim 1, wherein the method is characterized by, In step (3), when collecting the tower top fraction, an online refractometer is used to monitor the refractive rate of the fraction in real time, and when the refractive rate is stable in the range of 1.469-1.471 and lasts for 5 min, the tower top fraction is collected.

10. The method of claim 1, wherein the method is characterized by, The tower kettle of the first rectification tower and the second rectification tower is respectively provided with a falling film type reboiler.

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