Method for preparing eugenol from clove oil plants

Abstract

The invention relates to the technical field of separation and purification, in particular to a method for preparing eugenol from clove oil plants, which comprises the following steps: (a) mixing clove buds or leaves with perlite according to a mass ratio of 1: (1.5-2) to obtain a mixture; (b) an anti-oxidation composite liquid is added into the mixed material, the mixture is stirred to be uniform and then left to stand, a pretreated material is obtained, and the anti-oxidation composite liquid comprises ascorbic acid, citric acid and glycerin; (c) loading the pretreated material into a distillation device, carrying out gradient heating steam distillation, and collecting condensate; (d) performing low-temperature vacuum concentration on the condensate to obtain crude eugenol; and (e) mixing the crude eugenol with a molecular sieve according to a mass ratio of 1: (3-5), adsorbing, and filtering to obtain refined eugenol. The invention provides an efficient, stable and environment-friendly eugenol purification method, by introducing a novel protective agent system and a staged temperature control rectification technology, the occurrence rate of thermal decomposition and oxidation reaction is remarkably reduced, and the product purity and the production efficiency are improved.

Description

Technical Field

[0001] This invention relates to the field of separation and purification technology, and specifically to a method for preparing eugenol from plants of the genus Eugenia. Background Technology

[0002] Eugenol is an important natural compound widely used in fragrances, pharmaceuticals, and pesticides. Extraction from clove plants is one of its main preparation methods. However, existing extraction processes still have certain shortcomings in terms of efficiency, cost, and product purity, hindering its large-scale application. Patent CN104628542B discloses a method for preparing eugenol from clove leaf oil through steps such as vacuum distillation, reaction treatment under alkaline conditions, metal ion complexation, and rectification. While this method can significantly reduce the metal ion content and improve anti-discoloration properties, its process is lengthy, involving multiple complex steps, resulting in low production efficiency. Furthermore, the chemical treatment under alkaline conditions may corrode equipment, increasing maintenance costs. In addition, the rectification step consumes a large amount of energy, which is detrimental to environmental protection and energy conservation requirements. Patent CN105294409B discloses a synthesis method for eugenol from guaiacol and allyl chloride through a novel composite catalyst THLD. Although this method has a high conversion rate and yield, it uses chemical synthesis instead of direct extraction from natural plants, which may not meet the market demand for naturally sourced eugenol. At the same time, the use of chemical reagents such as allyl chloride increases the cost of raw materials and may cause environmental pollution problems. In addition, the preparation and recovery process of the catalyst is relatively complex, which further increases the difficulty of the process and the economic cost.

[0003] The aforementioned existing technologies indicate that methods for extracting eugenol from clove plants still have significant shortcomings in terms of process simplification, energy consumption reduction, environmental friendliness, and meeting the demand for natural products. In particular, the traditional steam distillation extraction process presents several key challenges that urgently need to be addressed: First, eugenol is prone to oxidation or polymerization during high-temperature distillation, affecting its aroma and bioactivity; the oxidation rate of traditional methods is approximately 15%. Second, other components in clove oil have boiling points close to eugenol, leading to severe co-distillation and low crude oil purity, requiring multiple subsequent purification steps. Finally, steam distillation requires continuous heating; on an industrial scale, energy consumption accounts for 30%–40% of the total cost, significantly increasing production costs. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide an efficient, stable and environmentally friendly eugenol purification method that addresses the shortcomings of existing eugenol purification methods in terms of thermal decomposition inhibition, antioxidant performance improvement and process efficiency optimization. By introducing a novel protective agent system and staged temperature-controlled distillation technology, the occurrence rate of thermal decomposition and oxidation reactions is significantly reduced, thereby improving product purity and production efficiency.

[0005] The technical solution adopted by this invention to solve its technical problem is: The technical problem to be solved by this invention is to provide an efficient, environmentally friendly and simple method for extracting eugenol from plants of the genus Syringa, which addresses the shortcomings of existing eugenol extraction methods, such as quality degradation due to high temperature, impurity co-distillation affecting purity, high energy consumption and complex operation.

[0006] The technical solution adopted by this invention to solve its technical problem is: A method for preparing eugenol from plants of the genus *Cephalotaxus* includes the following steps: (a) Mix lilac buds or leaves with perlite at a mass ratio of 1:1.5~2 to obtain a mixture; (b) Add antioxidant complex liquid to the mixture, stir evenly and let stand for 1 hour to obtain pretreated material, wherein the antioxidant complex liquid contains ascorbic acid, citric acid and glycerol; (c) Load the pretreated material into a distillation apparatus and perform gradient heating steam distillation to collect the condensate; (d) The condensate was concentrated under low temperature vacuum to obtain crude eugenol; (e) Crude eugenol is mixed with molecular sieve at a mass ratio of 1:3~5 and adsorbed for 1 hour, then filtered to obtain refined eugenol.

[0007] This scheme establishes the core process for eugenol preparation: First, material loosening is achieved through crushing and mixing with perlite, effectively avoiding the problem of uneven vapor distribution caused by material agglomeration during traditional distillation. Then, an antioxidant complex is introduced, significantly reducing the oxidation rate and polymerization risk of eugenol at high temperatures. The composition ratio of the antioxidant complex is based on a complementary mechanism of redox potential and molecular polarity: ascorbic acid, as a proton donor, quenches free radicals through reduction; citric acid, with its carboxyl complexation ability, blocks the catalytic activity of metal ions; and glycerol, relying on its polyhydroxy structure, forms a steric hindrance layer. These three components construct a dynamic synergistic protective network through intermolecular forces; an imbalance in their ratio will disrupt electron transport pathways and phase interface stability. This scheme achieves a balance between efficient extraction and high-quality assurance, forming a complete green process chain.

[0008] Preferably, the amount of antioxidant compound solution added in step (b) is 0.5~0.8g of ascorbic acid, 0.3~0.5g of citric acid, and 1.0~1.5g of glycerol per 100g of mixture.

[0009] Preferably, during the settling period in step (b), the ambient humidity is maintained at 60%~70%, and nitrogen gas is introduced for protection at a flow rate of 0.2~0.5L / min.

[0010] A constant humidity environment maintains the turgor pressure of plant cells to ensure the penetration efficiency of antioxidants. Nitrogen protection replaces oxygen molecules in the atmosphere with inert gas laminar flow, thus inhibiting both enzymatic browning and non-enzymatic oxidation reactions. Its core function is to block the oxygen diffusion and mass transfer pathway and reduce the activation energy of the oxidation reaction.

[0011] Preferably, the antioxidant composite liquid in step (b) is evenly distributed on the surface of the mixture by spraying.

[0012] Atomized spraying forms micro-droplet clusters that cover the material surface. By leveraging the surface tension of the liquid, the antioxidant-material contact interface is maximized. This process increases the specific surface area by reducing the droplet size, thereby achieving a monolayer adsorption advantage distribution of antioxidant molecules on the solid surface.

[0013] Preferably, the gradient heating steam distillation in step (c) is divided into two stages: the first stage is controlled at 90~95℃ for 20 min, and the second stage is controlled at 98~100℃ for 40 min.

[0014] The gradient temperature sequence follows the difference in vaporization enthalpy of volatile components: in the low-temperature stage, heat-sensitive low-molecular-weight substances are selectively vaporized to avoid molecular thermal decomposition; in the high-temperature stage, excess latent heat of vaporization is provided to drive the phase transition of high-boiling-point components, and the differential escape of components is achieved by utilizing the positive correlation between boiling point and vapor pressure.

[0015] Preferably, the conditions for low-temperature vacuum concentration in step (d) are a temperature of 35~40℃ and a vacuum degree of 0.08~0.09MPa.

[0016] Sub-ambient temperature vacuum concentration reduces the saturated vapor pressure of the system, causing volatile components to undergo liquid-gas phase equilibrium transfer at temperatures below atmospheric pressure boiling points. Essentially, it is the Le Chatelier principle for the directional control of phase equilibrium, avoiding molecular isomerization caused by high temperatures.

[0017] Preferably, the molecular sieve in step (e) is a type 3A molecular sieve with an activation temperature of 300°C and an activation time of 2 hours.

[0018] High-temperature activation of molecular sieves removes adsorbates through lattice vibration, resets the ion exchange sites of the surface silica-alumina oxide rings, restores the pore size sieving efficiency, and creates a size exclusion effect between the dynamic diameter of water molecules and the sieve pores.

[0019] Preferably, the crude eugenol in step (e) is mixed with the molecular sieve and the adsorption operation is carried out in a sealed container.

[0020] A sealed container is used to construct a closed adsorption system, eliminating the interference of atmospheric humidity and oxygen on the adsorption isotherm, and enabling selective van der Waals bonding between the electrostatic force on the surface of the molecular sieve and the polar groups of the target molecule.

[0021] Preferably, the perlite in step (a) has a particle size range of 100-150 mesh, and the lilac buds or leaves, after being crushed, have a particle size of 80 mesh or more.

[0022] In summary, the implementation of this solution is also based on: 1. The formulation control of the antioxidant complex liquid achieves molecular-level protection through a ternary synergistic mechanism: ascorbic acid, as an electron transfer medium, sacrificially captures free radicals; citric acid chelates catalytic metal ions to interrupt the oxidation chain reaction; and glycerol forms an oxygen-repellent barrier through a hydrogen bond network. The dynamic balance of these three ensures the stability of the phenolic structure. Humidity and nitrogen environment control during the static stage constitute a physical-chemical dual isolation system. Humidity regulation maintains cell membrane permeability to facilitate antioxidant penetration, while nitrogen flow continuously replaces gaseous oxygen molecules, inhibiting oxidation kinetics from the diffusion source. The spraying process enhances the effect through the atomization interface, ensuring the antioxidant liquid uniformly coats the material surface, forming a micron-level protective film. 2. The temperature sequence design of gradient distillation follows the principle of different component volatility: in the initial low-temperature stage, heat-sensitive low-boiling-point substances are selectively released to avoid molecular rearrangement; in the subsequent high-temperature stage, the diffusion kinetic energy of high-boiling-point components is stimulated, and full-spectrum extraction is achieved by utilizing the vapor pressure difference. Vacuum concentration operates at sub-ambient temperature, relying on the phase change principle of reducing the solvent boiling point by pressure, so that volatile components are mildly enriched in the liquid state, and volume monitoring is based on the law of conservation of mass to provide real-time feedback on the phase change process; 3. Molecular sieve activation optimizes adsorption sites through lattice energy resetting. Its pore size sieving effect precisely intercepts water molecules and polar impurities, while the sealed adsorption environment blocks atmospheric interference, allowing van der Waals forces and capillary interactions to efficiently purify target molecules within a closed system. Raw material particle size and carrier particle size control are based on the principle of positive correlation between surface area and diffusion efficiency. A specific mesh size increases the mass transfer interface, while the multi-level porous structure of perlite directionally guides the vapor penetration path, together forming the basis for optimized extraction kinetics.

[0023] Compared to existing technologies, the advantages of this solution are: The core of the process lies in the fact that the ratio control of the antioxidant composite liquid achieves molecular-level protection through a ternary synergistic mechanism. Furthermore, the temperature and timing design of gradient distillation follows the difference in volatility of components, and the activation of molecular sieves optimizes adsorption sites through lattice energy reset, which synergistically solves the problems of low purity and low efficiency of steam distillation products. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1

[0026] A method for preparing eugenol from plants of the genus *Cephalotaxus* includes the following steps: (a) Crush clove buds or leaves to 100 mesh and mix them with 120 mesh perlite at a mass ratio of 1:1.5 to obtain a mixture; (b) Add 0.5g of ascorbic acid, 0.3g of citric acid and 1.0g of glycerol to every 100g of mixture. The antioxidant compound solution is evenly distributed on the surface of the mixture by spraying. After stirring evenly, maintain the ambient humidity at 60% and purge with nitrogen at a flow rate of 0.2L / min. Let stand for 1h to obtain the pretreated material. (c) Load the pretreated material into a distillation apparatus and perform gradient heating steam distillation. The temperature is controlled at 90°C for 20 min in the first stage and at 98°C for 40 min in the second stage. Collect the condensate. (d) The condensate was concentrated under low temperature vacuum conditions of 35°C and 0.08 MPa to obtain crude eugenol; (e) Crude eugenol was mixed with 3A molecular sieve activated at 300℃ for 2h at a mass ratio of 1:3, and the mixture was adsorbed in a sealed container for 1h and then filtered to obtain refined eugenol.

[0027] Example 2

[0028] A method for preparing eugenol from plants of the genus *Cephalotaxus* includes the following steps: (a) Crush clove buds or leaves to 100 mesh and mix them with 120 mesh perlite at a mass ratio of 1:2 to obtain a mixture; (b) Add 0.8g of ascorbic acid, 0.5g of citric acid and 1.5g of glycerol to every 100g of mixture. The antioxidant compound solution is evenly distributed on the surface of the mixture by spraying. After stirring evenly, maintain the ambient humidity at 70% and purge with nitrogen at a flow rate of 0.5L / min. Let stand for 1 hour to obtain the pretreated material. (c) Load the pretreated material into a distillation apparatus and perform gradient heating steam distillation. The temperature is controlled at 95°C for 20 min in the first stage and at 100°C for 40 min in the second stage. Collect the condensate. (d) The condensate was concentrated under low temperature vacuum conditions of 40℃ and 0.09MPa to obtain crude eugenol; (e) Crude eugenol was mixed with 3A molecular sieve activated at 300℃ for 2h at a mass ratio of 1:5, and the mixture was adsorbed in a sealed container for 1h and then filtered to obtain refined eugenol.

[0029] Example 3

[0030] A method for preparing eugenol from plants of the genus *Cephalotaxus* includes the following steps: (a) Crush clove buds or leaves to 100 mesh and mix them with 120 mesh perlite at a mass ratio of 1:1.8 to obtain a mixture; (b) Add 0.6g of ascorbic acid, 0.4g of citric acid and 1.2g of glycerol to every 100g of mixture. The antioxidant compound solution is evenly distributed on the surface of the mixture by spraying. After stirring evenly, maintain the ambient humidity at 65% and purge with nitrogen at a flow rate of 0.3L / min. Let stand for 1 hour to obtain the pretreated material. (c) Load the pretreated material into a distillation apparatus and perform gradient heating steam distillation. The temperature is controlled at 92°C for 20 min in the first stage and at 99°C for 40 min in the second stage. Collect the condensate. (d) The condensate was concentrated under low temperature vacuum at a temperature of 38°C and a vacuum of 0.085 MPa to obtain crude eugenol; (e) Crude eugenol was mixed with 3A molecular sieve activated at 300℃ for 2h at a mass ratio of 1:4, and the mixture was adsorbed in a sealed container for 1h and then filtered to obtain refined eugenol.

[0031] Comparative Example 1 The difference from Example 1 is that it was prepared using conventional methods: A method for preparing eugenol from plants of the genus *Cephalotaxus* includes the following steps: (a) Crush clove buds or leaves to 100 mesh and mix them with 120 mesh perlite at a mass ratio of 1:1.5 to obtain a mixture; (b) Add 1.0g of pure water to every 100g of mixture, and distribute it evenly on the surface of the mixture by spraying. After stirring evenly, let it stand for 1 hour to obtain the pretreated material. (c) Load the pretreated material into a distillation apparatus and perform steam distillation, controlling the temperature at 95°C for 60 minutes, and collect the condensate. (d) The condensate was concentrated under low temperature vacuum conditions of 35°C and 0.08 MPa to obtain crude eugenol; (e) Crude eugenol is directly filtered to obtain refined eugenol.

[0032] Comparative Example 2 The difference from Example 1 is that the antioxidant complex liquid only contains antioxidants: A method for preparing eugenol from plants of the genus *Cephalotaxus* includes the following steps: (a) Crush clove buds or leaves to 100 mesh and mix them with 120 mesh perlite at a mass ratio of 1:1.5 to obtain a mixture; (b) Add 0.5g of ascorbic acid to every 100g of mixture. The antioxidant compound solution is evenly distributed on the surface of the mixture by spraying. After stirring evenly, maintain the ambient humidity at 60% and purge with nitrogen at a flow rate of 0.2L / min. Let stand for 1 hour to obtain the pretreated material. (c) Load the pretreated material into a distillation apparatus and perform gradient heating steam distillation. The temperature is controlled at 90°C for 20 min in the first stage and at 98°C for 40 min in the second stage. Collect the condensate. (d) The condensate was concentrated under low temperature vacuum conditions of 35°C and 0.08 MPa to obtain crude eugenol; (e) Crude eugenol was mixed with 3A molecular sieve activated at 300℃ for 2h at a mass ratio of 1:3, and the mixture was adsorbed in a sealed container for 1h and then filtered to obtain refined eugenol.

[0033] Comparative Example 3 The difference from Example 1 is that citric acid in the antioxidant complex solution is replaced with malic acid: A method for preparing eugenol from plants of the genus *Cephalotaxus* includes the following steps: (a) Crush clove buds or leaves to 100 mesh and mix them with 120 mesh perlite at a mass ratio of 1:1.5 to obtain a mixture; (b) Add 0.5g of ascorbic acid, 0.3g of malic acid and 1.0g of glycerol to every 100g of mixture. The antioxidant compound solution is evenly distributed on the surface of the mixture by spraying. After stirring evenly, maintain the ambient humidity at 60% and purge with nitrogen at a flow rate of 0.2L / min. Let stand for 1 hour to obtain the pretreated material. (c) Load the pretreated material into a distillation apparatus and perform gradient heating steam distillation. The temperature is controlled at 90°C for 20 min in the first stage and at 98°C for 40 min in the second stage. Collect the condensate. (d) The condensate was concentrated under low temperature vacuum conditions of 35°C and 0.08 MPa to obtain crude eugenol; (e) Crude eugenol was mixed with 3A molecular sieve activated at 300℃ for 2h at a mass ratio of 1:3, and the mixture was adsorbed in a sealed container for 1h and then filtered to obtain refined eugenol.

[0034] Comparative Example 4 The difference from Example 1 is that fractional distillation was not performed: A method for preparing eugenol from plants of the genus *Cephalotaxus* includes the following steps: (a) Crush clove buds or leaves to 100 mesh and mix them with 120 mesh perlite at a mass ratio of 1:1.5 to obtain a mixture; (b) Add 0.5g of ascorbic acid, 0.3g of citric acid and 1.0g of glycerol to every 100g of mixture. The antioxidant compound solution is evenly distributed on the surface of the mixture by spraying. After stirring evenly, maintain the ambient humidity at 60% and purge with nitrogen at a flow rate of 0.2L / min. Let stand for 1h to obtain the pretreated material. (c) Load the pretreated material into a distillation apparatus and perform steam distillation, controlling the temperature at 95°C for 60 minutes, and collect the condensate. (d) The condensate was concentrated under low temperature vacuum conditions of 35°C and 0.08 MPa to obtain crude eugenol; (e) Crude eugenol was mixed with 3A molecular sieve activated at 300℃ for 2h at a mass ratio of 1:3, and the mixture was adsorbed in a sealed container for 1h and then filtered to obtain refined eugenol.

[0035] Comparative Example 5 The difference from Example 1 is that molecular sieves were not used: A method for preparing eugenol from plants of the genus *Cephalotaxus* includes the following steps: (a) Crush clove buds or leaves to 100 mesh and mix them with 120 mesh perlite at a mass ratio of 1:1.5 to obtain a mixture; (b) Add 0.5g of ascorbic acid, 0.3g of citric acid and 1.0g of glycerol to every 100g of mixture. The antioxidant compound solution is evenly distributed on the surface of the mixture by spraying. After stirring evenly, maintain the ambient humidity at 60% and purge with nitrogen at a flow rate of 0.2L / min. Let stand for 1h to obtain the pretreated material. (c) Load the pretreated material into a distillation apparatus and perform gradient heating steam distillation. The temperature is controlled at 90°C for 20 min in the first stage and at 98°C for 40 min in the second stage. Collect the condensate. (d) The condensate was concentrated under low temperature vacuum conditions of 35°C and 0.08 MPa to obtain crude eugenol; (e) Crude eugenol is directly filtered to obtain refined eugenol.

[0036] Comparative Example 6 The difference from Example 1 is that the molecular sieve was not activated: A method for preparing eugenol from plants of the genus *Cephalotaxus* includes the following steps: (a) Crush clove buds or leaves to 100 mesh and mix them with 120 mesh perlite at a mass ratio of 1:1.5 to obtain a mixture; (b) Add 0.5g of ascorbic acid, 0.3g of citric acid and 1.0g of glycerol to every 100g of mixture. The antioxidant compound solution is evenly distributed on the surface of the mixture by spraying. After stirring evenly, maintain the ambient humidity at 60% and purge with nitrogen at a flow rate of 0.2L / min. Let stand for 1h to obtain the pretreated material. (c) Load the pretreated material into a distillation apparatus and perform gradient heating steam distillation. The temperature is controlled at 90°C for 20 min in the first stage and at 98°C for 40 min in the second stage. Collect the condensate. (d) The condensate was concentrated under low temperature vacuum conditions of 35°C and 0.08 MPa to obtain crude eugenol; (e) Crude eugenol was mixed with 120-mesh 3A molecular sieve at a mass ratio of 1:3, and the mixture was adsorbed in a sealed container for 1 hour and then filtered to obtain refined eugenol.

[0037] Comparative Example 7 The difference from Example 1 is that the proportion of perlite is too small: A method for preparing eugenol from plants of the genus *Cephalotaxus* includes the following steps: (a) Crush clove buds or leaves to 100 mesh and mix them with 120 mesh perlite at a mass ratio of 1:1 to obtain a mixture; (b) Add 0.5g of ascorbic acid, 0.3g of citric acid and 1.0g of glycerol to every 100g of mixture. The antioxidant compound solution is evenly distributed on the surface of the mixture by spraying. After stirring evenly, maintain the ambient humidity at 60% and purge with nitrogen at a flow rate of 0.2L / min. Let stand for 1h to obtain the pretreated material. (c) Load the pretreated material into a distillation apparatus and perform gradient heating steam distillation. The temperature is controlled at 90°C for 20 min in the first stage and at 98°C for 40 min in the second stage. Collect the condensate. (d) The condensate was concentrated under low temperature vacuum conditions of 35°C and 0.08 MPa to obtain crude eugenol; (e) Crude eugenol was mixed with 3A molecular sieve activated at 300℃ for 2h at a mass ratio of 1:3, and the mixture was adsorbed in a sealed container for 1h and then filtered to obtain refined eugenol.

[0038] Comparative Example 8 The difference from Example 1 is that maintaining ambient humidity and purging with nitrogen were not performed. A method for preparing eugenol from plants of the genus *Cephalotaxus* includes the following steps: (a) Crush clove buds or leaves to 100 mesh and mix them with 120 mesh perlite at a mass ratio of 1:1.5 to obtain a mixture; (b) Add 0.5g of ascorbic acid, 0.3g of citric acid and 1.0g of glycerin to every 100g of mixture. The antioxidant compound solution is evenly distributed on the surface of the mixture by spraying. After stirring evenly, let it stand for 1 hour to obtain the pretreated material. (c) Load the pretreated material into a distillation apparatus and perform gradient heating steam distillation. The temperature is controlled at 90°C for 20 min in the first stage and at 98°C for 40 min in the second stage. Collect the condensate. (d) The condensate was concentrated under low temperature vacuum conditions of 35°C and 0.08 MPa to obtain crude eugenol; (e) Crude eugenol was mixed with 3A molecular sieve activated at 300℃ for 2h at a mass ratio of 1:3, and the mixture was adsorbed in a sealed container for 1h and then filtered to obtain refined eugenol.

[0039] Detection method: Eugenol purity determination: High performance liquid chromatography; Eugenol yield: Yield = (mass of crude eugenol / mass of raw material) × 100%; Moisture content: GB 5009.3-2016; Total distillation time: Record the total time from the start of heating to the completion of condensate collection.

[0040] The test results are shown in Table 1.

[0041] Table 1. Detection results of the examples and comparative examples. Group Eugenol purity (%) Eugenol yield (%) Moisture content (%) Total distillation time (min) Example 1 92.3±1.1 12.1±0.8 0.8±0.1 60 Example 2 93.5±1.0 12.5±0.7 0.7±0.1 65 Example 3 92.8±1.2 12.3±0.6 0.75±0.1 62 Comparative Example 1 85.2±1.5 9.5±0.6 2.5±0.3 90 Comparative Example 2 88.1±1.3 10.2±0.7 1.8±0.2 85 Comparative Example 3 89.5±1.2 10.8±0.6 1.2±0.1 82 Comparative Example 4 88.1±1.3 10.2±0.7 1.8±0.2 85 Comparative Example 5 89.5±1.2 10.8±0.6 1.2±0.1 65 Comparative Example 6 84.7±1.6 8.9±0.5 2.1±0.2 67 Comparative Example 7 83.2±1.7 8.5±0.6 1.9±0.2 75 Comparative Example 8 82.7±1.8 8.9±0.5 2.1±0.2 62 The core of the purity improvement in Examples 1-3 lies in the composite antioxidant inhibiting the formation of oxidation byproducts, combined with the deep adsorption of moisture and small molecule impurities by activated molecular sieves, resulting in a purity of 92.3%~93.5% in the examples. The yield advantage stems from nitrogen protection reducing phenolic oxidation and degradation, and molecular sieve adsorption reducing the loss of target substances, with a yield of 12.1%~12.5% ​​in the examples. Moisture control directly relies on the efficient dehydration capability of molecular sieve activation and regeneration. The optimized distillation time is achieved by separating impurities and target substances in stages through gradient temperature, combined with perlite carrier to enhance mass transfer efficiency, requiring only 60~65 minutes in the examples.

[0042] The core reason why Example 1 achieved better results than Comparative Examples 1-7 lies in its multi-dimensional process optimization, which synergistically improved the purity and yield of eugenol: Compared to Comparative Example 1, Example 1 used gradient distillation to first remove low-boiling-point impurities at low temperature, and then concentratedly distilled eugenol at high temperature. Combined with molecular sieve adsorption, it deeply removed water and small molecule impurities, significantly reducing impurity residue and shortening distillation time; Compared to Comparative Example 2, which only added ascorbic acid, the composite antioxidant in Example 1, ascorbic acid + citric acid + glycerol, synergistically inhibited the oxidation of raw materials, reduced the formation of oxidation byproducts, and improved purity; Compared to Comparative Example 3, which replaced citric acid with malic acid, the strong antioxidant properties of citric acid in Example 1 more effectively inhibited the oxidation reaction and reduced impurity accumulation; Compared to Comparative Example 4, which did not use segmented distillation, Example 1 implemented... The segmented heating strategy in Example 1 achieved stepwise separation of low-boiling-point impurities and eugenol, avoiding the mixing of high-boiling-point impurities with the target compound. Compared to Comparative Example 5 without molecular sieves, the activated molecular sieve in Example 1 efficiently adsorbed moisture and residual impurities in the condensate, reducing the moisture content and minimizing the dissolution loss of eugenol. Compared to Comparative Example 6 with unactivated molecular sieves, the fully activated molecular sieve in Example 1 showed significantly enhanced adsorption activity, resulting in more thorough removal of moisture and impurities. Compared to Comparative Example 7 with an excessively low perlite ratio, the reasonable ratio of perlite to raw materials in Example 1 enhanced the mass transfer efficiency of the mixture and shortened the distillation time. Compared to Comparative Example 8, the nitrogen protection and humidity control in Example 1 effectively inhibited the oxidation of raw materials, preventing the formation of oxidation byproducts, thereby comprehensively improving the purity and yield of eugenol.

Claims

1. A method for preparing eugenol from plants of the genus *Cephalotaxus*, characterized in that, Includes the following steps: (a) Mix lilac buds or leaves with perlite at a mass ratio of 1:1.5~2 to obtain a mixture; (b) Add an antioxidant complex to the mixture, stir evenly and let stand to obtain a pretreated material, wherein the antioxidant complex contains ascorbic acid, citric acid and glycerol; (c) Load the pretreated material into a distillation apparatus and perform gradient heating steam distillation to collect the condensate. (d) The condensate was concentrated under low temperature vacuum to obtain crude eugenol; (e) Crude eugenol is mixed with molecular sieve at a mass ratio of 1:3~5, adsorbed, and then filtered to obtain refined eugenol.

2. The method as described in claim 1, characterized in that: The amount of antioxidant compound solution added in step (b) is 0.5~0.8g of ascorbic acid, 0.3~0.5g of citric acid, and 1.0~1.5g of glycerol per 100g of mixture.

3. The method as described in claim 1, characterized in that: During the settling period in step (b), maintain the ambient humidity at 60%~70% and purge with nitrogen gas for protection at a flow rate of 0.2~0.5L / min.

4. The method as described in claim 1, characterized in that: The antioxidant composite liquid described in step (b) is evenly distributed on the surface of the mixture by spraying.

5. The method as described in claim 1, characterized in that: In step (c), the gradient heating steam distillation is divided into two stages: the first stage is controlled at 90~95℃ for 20 min, and the second stage is controlled at 98~100℃ for 40 min.

6. The method as described in claim 1, characterized in that: The conditions for low-temperature vacuum concentration in step (d) are a temperature of 35~40℃ and a vacuum degree of 0.08~0.09MPa.

7. The method as described in claim 1, characterized in that: The molecular sieve mentioned in step (e) is a type 3A molecular sieve.

8. The method as described in claim 7, characterized in that: The molecular sieve described in step (e) is activated at 300°C for 2 hours.

9. The method as described in claim 1, characterized in that: In step (e), the crude eugenol is mixed with the molecular sieve and the adsorption operation is carried out in a sealed container.

10. The method as described in claim 1, characterized in that: The perlite in step (a) has a particle size range of 100-150 mesh, and the lilac buds or leaves, after being crushed, have a particle size of 80 mesh or more.