A method for obtaining eugenol from sygygium species

Abstract

The present application relates to the technical field of separation and purification, and particularly relates to a method for preparing eugenol from syringa oil plants, comprising the following steps: (a) mixing syringa flower buds or leaves with perlite at a mass ratio of 1:1.5-2 to obtain a mixture; (b) adding an antioxidant composite liquid to the mixture, stirring uniformly, and then standing to obtain pretreated material, wherein the antioxidant composite liquid comprises ascorbic acid, citric acid and glycerol; (c) loading the pretreated material into a distillation device, performing gradient heating water vapor distillation, and collecting a condensate; (d) performing low-temperature vacuum concentration on the condensate to obtain crude eugenol; and (e) mixing the crude eugenol with molecular sieves at a mass ratio of 1:3-5, adsorbing and then filtering to obtain refined eugenol. The present application provides an efficient, stable and environmentally-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 significantly reduced, and the product purity and production efficiency are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of separation and purification, and particularly relates to a method for preparing eugenol from Sygygium genus plants. BACKGROUND

[0002] Eugenol is an important natural compound, which is widely used in the fields of perfumery, medicine and pesticide. Extraction of eugenol from Sygygium genus plants is one of the main preparation methods. However, the existing extraction process still has certain deficiencies in efficiency, cost and product purity, which restricts its large-scale application. The patent with publication number CN104628542B discloses a method for preparing eugenol by using Sygygium leaf oil as raw material, through steps of reduced pressure distillation, reaction treatment under alkaline condition, complexing metal ions and rectification. Although this method can significantly reduce the content of metal ions in the product and improve the anti-color change performance, the process flow is relatively long, involving multiple complex operation steps, resulting in low production efficiency; at the same time, the chemical treatment under alkaline condition may cause corrosion to the equipment, increasing the maintenance cost; in addition, the rectification step has large energy consumption, which is not conducive to environmental protection and energy saving requirements. The patent with publication number CN105294409B discloses a synthesis method for preparing eugenol by using guaiacol and allyl chloride as raw materials, through catalytic reaction of a new type of composite catalyst THLD. Although this method has high conversion rate and yield, it uses chemical synthesis instead of direct extraction from natural plants, which may not meet the market demand for natural source eugenol; at the same time, the use of chemical reagents such as allyl chloride increases the raw material cost and may cause environmental pollution problems; in addition, the preparation and recovery process of the catalyst is relatively complex, which further increases the process difficulty and economic cost.

[0003] The above existing technologies show that the method for extracting eugenol from Sygygium genus plants still has obvious deficiencies in process simplification, energy consumption reduction, environmental protection and satisfaction of natural product demand. Especially in the traditional extraction process of water vapor distillation method, there are several core pain points to be solved: first, eugenol is easy to oxidize or polymerize in the high-temperature distillation process, thereby affecting its aroma and biological activity, and the oxidation rate of the traditional method is about 15%; second, other components in eugenol oil have close boiling points with eugenol, resulting in serious co-distillation phenomenon, low purity of crude oil and the need for subsequent multi-step purification; finally, water vapor distillation needs continuous heating, and the energy consumption accounts for 30% to 40% of the total cost under industrial scale, which significantly increases the production cost. SUMMARY

[0004] The technical problem solved by the present application is that the existing eugenol purification method has the problems of heat decomposition inhibition, antioxidant performance improvement and process efficiency optimization, and the present application provides an efficient, stable and environmentally friendly eugenol purification method.

[0005] The technical solution adopted by the present application to solve its technical problem is:

[0006] The technical problem solved by the present application is that the existing eugenol extraction method has the problems of quality degradation at high temperature, impurity co-distillation affecting purity, high energy consumption and complex operation, and the present application provides an efficient, environmentally friendly and simple method for preparing eugenol from eugenol plants.

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

[0008] A method for preparing eugenol from eugenol plants, comprising the following steps:

[0009] (a) mixing clove buds or leaves with perlite at a mass ratio of 1:1.5-2 to obtain a mixture;

[0010] (b) adding an antioxidant composite liquid to the mixture, stirring uniformly and standing for 1h to obtain a pretreated material, the antioxidant composite liquid comprising ascorbic acid, citric acid and glycerol;

[0011] (c) loading the pretreated material into a distillation device and performing gradient heating steam distillation to collect a condensate;

[0012] (d) vacuum concentrating the condensate at low temperature to obtain crude eugenol;

[0013] (e) mixing the crude eugenol with molecular sieves at a mass ratio of 1:3-5, adsorbing for 1h and filtering to obtain refined eugenol.

[0014] The present application provides an efficient, stable and environmentally friendly eugenol purification method, which significantly reduces the occurrence rate of thermal decomposition and oxidation reaction by introducing a new protective agent system and a staged temperature control rectification technology, and improves product purity and production efficiency.

[0015] As preferred, the antioxidant complex solution is added in step (b) in an amount of 0.5-0.8 g ascorbic acid, 0.3-0.5 g citric acid, and 1.0-1.5 g glycerol per 100 g of the mixture.

[0016] As preferred, the ambient humidity is maintained at 60-70% during the standing period in step (b), and nitrogen gas is introduced for protection at a flow rate of 0.2-0.5 L / min.

[0017] The constant humidity environment maintains the turgor pressure of the plant cells to ensure the penetration efficiency of the antioxidants, and the nitrogen protection replaces the oxygen molecules in the gas phase by inert gas laminar flow, which inhibits the enzymatic browning and non-enzymatic oxidation reactions through the double action of blocking the diffusion mass transfer path of oxygen and reducing the activation energy of oxidation.

[0018] As preferred, the antioxidant complex solution is uniformly distributed on the surface of the mixture by spraying in step (b).

[0019] The atomized spraying forms a micro-droplet group covering the surface of the material, and the liquid surface tension is used to maximize the antioxidant-material contact interface. This process increases the specific surface area by reducing the droplet size, and realizes the monolayer adsorption advantage distribution of antioxidant molecules on the solid surface.

[0020] As preferred, the gradient heating water vapor distillation in step (c) is divided into two stages: the first stage controls the temperature at 90-95°C for 20 min, and the second stage controls the temperature at 98-100°C for 40 min.

[0021] The gradient temperature sequence follows the difference in vaporization enthalpy of volatile components: the low-temperature stage selectively vaporizes heat-sensitive low-molecular-weight substances to avoid molecular thermal cracking; the high-temperature stage provides excess latent heat of vaporization to drive the phase change of high-boiling-point components, and uses the positive correlation between boiling point and vapor pressure to realize the differential escape of components.

[0022] As preferred, the low-temperature vacuum concentration in step (d) is performed at a temperature of 35-40°C and a vacuum degree of 0.08-0.09 MPa.

[0023] Sub-ambient vacuum concentration transfers the volatile components from the liquid phase to the gas phase at a temperature lower than the normal pressure boiling point by reducing the system's saturated vapor pressure. The essence is the directional regulation of Le Chatelier's principle on phase equilibrium, which avoids molecular isomerization caused by high temperature.

[0024] As preferred, the molecular sieve in step (e) is a 3A type molecular sieve activated at a temperature of 300°C for 2 h.

[0025] Molecular sieve high-temperature activation removes adsorbates by lattice vibration, resets the ion exchange sites of the surface silicon-aluminum oxygen ring, and restores the pore size sieving efficiency, so that the kinetic diameter of water molecules and the sieve pore size form a size exclusion effect.

[0026] As preferred, the adsorption operation in step (e) is carried out in a sealed container when the crude eugenol is mixed with the molecular sieve.

[0027] The sealed container constitutes a closed adsorption system, eliminating the interference of atmospheric humidity and oxygen on the adsorption isotherm, so that the electrostatic force on the surface of the molecular sieve and the polar group of the target molecule can realize selective van der Waals combination.

[0028] As preferred, the particle size of the perlite in step (a) is in the range of 100-150 mesh, and the particle size of the eugenol flower or leaf after crushing is more than 80 mesh.

[0029] Based on the above, the implementation of the present scheme is also based on:

[0030] 1. The ratio of the antioxidant composite liquid realizes molecular-level protection through a ternary synergistic mechanism: ascorbic acid acts as an electron transfer medium to sacrificially capture free radicals, citric acid chelates catalytic metal ions to interrupt the oxidation chain reaction, and glycerol forms an oxygen barrier through hydrogen bond network, and the dynamic balance of the three ensures the stability of the phenolic structure. The humidity and nitrogen environment control in the standing stage constitute a physical-chemical double isolation system, the humidity adjustment maintains the cell membrane permeability to facilitate the penetration of antioxidants, and the nitrogen flow continuously replaces the oxygen molecules in the gas phase to inhibit the oxidation kinetic process from the diffusion source. The spraying process enhances the effect through the atomization interface, so that the antioxidant liquid uniformly coats the surface of the material, forming a micron-level protective film;

[0031] 2. The temperature time sequence design of gradient distillation follows the volatility difference of components: selective release of heat-sensitive low-boiling-point substances at the initial low-temperature stage to avoid molecular rearrangement; high-boiling-point components are excited to diffuse at the subsequent high-temperature stage, and full-spectrum extraction is achieved by utilizing the vapor pressure difference. Vacuum concentration is operated at sub-temperature, relying on the phase change principle that the boiling point of the solvent is lowered by pressure reduction, so that volatile components are enriched in liquid state, and volume monitoring is based on the law of conservation of mass to feedback the phase change process in real time;

[0032] 3. The activation of molecular sieve optimizes the adsorption sites by resetting the lattice energy, its pore size sieving effect precisely intercepts water molecules and polar impurities, and the sealed adsorption environment blocks atmospheric interference, so that van der Waals force and capillary action efficiently purify target molecules in a closed system. The control of raw material particle size and carrier particle size is based on the principle that surface area and diffusion efficiency are positively correlated, and the specific mesh size of the crushed particle size increases the mass transfer interface, and the multi-level pore structure of perlite directionally guides the steam penetration path, which together constitutes the basis for optimizing the extraction kinetics.

[0033] Compared with the prior art, the present scheme has the following advantages:

[0034] The core of the process flow is that the ratio regulation of the antioxidant composite liquid realizes molecular-level protection through a ternary synergistic mechanism, and the temperature timing design of gradient distillation follows the component volatility difference law and the molecular sieve activation optimizes the adsorption site through lattice energy reset, which solves the problems of low product purity and low efficiency of water vapor distillation. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0036] Embodiment 1

[0037] A method for preparing eugenol from Sygygium genus plants, comprising the following steps:

[0038] (a) crushing Sygygium genus flower buds or leaves to 100 mesh, and mixing with 120 mesh perlite at a mass ratio of 1:1.5 to obtain a mixture;

[0039] (b) adding 0.5 g of ascorbic acid, 0.3 g of citric acid and 1.0 g of glycerol to 100 g of the mixture, uniformly distributing the antioxidant composite liquid on the surface of the mixture by spraying, uniformly stirring, maintaining the environmental humidity at 60%, and introducing nitrogen protection at a flow rate of 0.2 L / min, and standing for 1 h to obtain pretreated material;

[0040] (c) loading the pretreated material into a distillation device, and performing gradient heating water vapor distillation, controlling the temperature at 90℃ for 20 min in the first stage, and controlling the temperature at 98℃ for 40 min in the second stage, and collecting the condensate;

[0041] (d) performing low-temperature vacuum concentration on the condensate under the conditions of a temperature of 35℃ and a vacuum degree of 0.08 MPa to obtain crude eugenol;

[0042] (e) mixing the crude eugenol with 3A type molecular sieve activated at 300℃ for 2 h at a mass ratio of 1:3, filtering after adsorption in a sealed container for 1 h to obtain refined eugenol.

[0043] Embodiment 2

[0044] A method for preparing eugenol from Sygygium genus plants, comprising the following steps:

[0045] (a) crushing Sygygium genus flower buds or leaves to 100 mesh, and mixing with 120 mesh perlite at a mass ratio of 1:2 to obtain a mixture;

[0046] (b) 0.8 g of ascorbic acid, 0.5 g of citric acid and 1.5 g of glycerol were added to 100 g of the mixture, and an antioxidant compound was uniformly distributed on the surface of the mixture by spraying, and after stirring, the ambient humidity was kept at 70%, and nitrogen was introduced for protection at a flow rate of 0.5 L / min, and the mixture was left to stand for 1 h, to obtain pretreated material;

[0047] (c) The pretreated material was loaded into a distillation device, and gradient heating steam distillation was performed, the temperature was controlled at 95°C for 20 min in the first stage, and the temperature was controlled at 100°C for 40 min in the second stage, and the condensate was collected;

[0048] (d) The condensate was concentrated under low temperature and vacuum, at a temperature of 40°C and a vacuum degree of 0.09 MPa, to obtain crude eugenol;

[0049] (e) The crude eugenol was mixed with 3A molecular sieves activated at 300°C for 2 h at a mass ratio of 1:5, and after adsorption in a sealed container for 1 h, filtration was performed, to obtain refined eugenol.

[0050] Example 3

[0051] A method for preparing eugenol from Sygygium genus plants, comprising the following steps:

[0052] (a) Sygygium flower buds or leaves were crushed to 100 mesh, and were mixed with 120 mesh perlite at a mass ratio of 1:1.8, to obtain a mixture;

[0053] (b) 0.6 g of ascorbic acid, 0.4 g of citric acid and 1.2 g of glycerol were added to 100 g of the mixture, and an antioxidant compound was uniformly distributed on the surface of the mixture by spraying, and after stirring, the ambient humidity was kept at 65%, and nitrogen was introduced for protection at a flow rate of 0.3 L / min, and the mixture was left to stand for 1 h, to obtain pretreated material;

[0054] (c) The pretreated material was loaded into a distillation device, and gradient heating steam distillation was performed, the temperature was controlled at 92°C for 20 min in the first stage, and the temperature was controlled at 99°C for 40 min in the second stage, and the condensate was collected;

[0055] (d) The condensate was concentrated under low temperature and vacuum, at a temperature of 38°C and a vacuum degree of 0.085 MPa, to obtain crude eugenol;

[0056] (e) The crude eugenol was mixed with 3A molecular sieves activated at 300°C for 2 h at a mass ratio of 1:4, and after adsorption in a sealed container for 1 h, filtration was performed, to obtain refined eugenol.

[0057] Comparative Example 1

[0058] The difference from Example 1 is that the conventional method was used to prepare:

[0059] A method for preparing eugenol from Sygygium genus plants, comprising the following steps:

[0060] (a) crushing Sygygium genus flower buds or leaves to 100 mesh, and mixing with 120 mesh perlite at a mass ratio of 1:1.5 to obtain a mixture;

[0061] (b) adding 1.0 g of pure water to 100 g of the mixture, and uniformly distributing the mixture on the surface of the mixture by spraying, after uniform stirring, standing for 1 h to obtain a pretreated material;

[0062] (c) loading the pretreated material into a distillation device, and performing water vapor distillation, controlling the temperature at 95℃ for 60 min, and collecting a condensate;

[0063] (d) performing low-temperature vacuum concentration on the condensate under the conditions of a temperature of 35℃ and a vacuum degree of 0.08 MPa to obtain crude eugenol;

[0064] (e) directly filtering the crude eugenol to obtain refined eugenol.

[0065] Comparative Example 2

[0066] The difference from Example 1 is that only an antioxidant is added to the antioxidant composite liquid:

[0067] A method for preparing eugenol from Sygygium genus plants, comprising the following steps:

[0068] (a) crushing Sygygium genus flower buds or leaves to 100 mesh, and mixing with 120 mesh perlite at a mass ratio of 1:1.5 to obtain a mixture;

[0069] (b) adding 0.5 g of ascorbic acid to 100 g of the mixture, and uniformly distributing the mixture on the surface of the mixture by spraying, after uniform stirring, maintaining the ambient humidity at 60%, and introducing nitrogen protection at a flow rate of 0.2 L / min, standing for 1 h to obtain a pretreated material;

[0070] (c) loading the pretreated material into a distillation device, and performing gradient heating water vapor distillation, controlling the temperature at 90℃ for 20 min in the first stage, and controlling the temperature at 98℃ for 40 min in the second stage, and collecting a condensate;

[0071] (d) performing low-temperature vacuum concentration on the condensate under the conditions of a temperature of 35℃ and a vacuum degree of 0.08 MPa to obtain crude eugenol;

[0072] (e) mixing the crude eugenol with 3A type molecular sieves activated at 300℃ for 2 h at a mass ratio of 1:3, and filtering after adsorption in a sealed container for 1 h to obtain refined eugenol.

[0073] Comparative Example 3

[0074] The difference from Example 1 is that the citric acid in the antioxidant composite liquid is replaced by malic acid:

[0075] A method for preparing eugenol from Sygygium genus plants, comprising the following steps:

[0076] (a) crushing Sygygium genus flower buds or leaves to 100 mesh, and mixing with 120 mesh perlite at a mass ratio of 1:1.5 to obtain a mixture;

[0077] (b) adding 0.5 g of ascorbic acid, 0.3 g of malic acid and 1.0 g of glycerol to 100 g of the mixture, uniformly distributing the antioxidant composite liquid on the surface of the mixture by spraying, uniformly stirring, maintaining the environmental humidity at 60%, and introducing nitrogen protection at a flow rate of 0.2 L / min, and standing for 1 h to obtain pretreated material;

[0078] (c) loading the pretreated material into a distillation device, and performing gradient heating steam distillation, controlling the temperature at 90℃ for 20 min in the first stage, and controlling the temperature at 98℃ for 40 min in the second stage, and collecting the condensate;

[0079] (d) performing low-temperature vacuum concentration on the condensate under the condition of a temperature of 35℃ and a vacuum degree of 0.08 MPa to obtain crude eugenol;

[0080] (e) mixing the crude eugenol with 3A type molecular sieves activated at 300℃ for 2 h at a mass ratio of 1:3, filtering after adsorption in a sealed container for 1 h to obtain refined eugenol.

[0081] Comparative Example 4

[0082] The difference from Example 1 is that the step of segmented distillation is not performed:

[0083] A method for preparing eugenol from Sygygium genus plants, comprising the following steps:

[0084] (a) crushing Sygygium genus flower buds or leaves to 100 mesh, and mixing with 120 mesh perlite at a mass ratio of 1:1.5 to obtain a mixture;

[0085] (b) adding 0.5 g of ascorbic acid, 0.3 g of malic acid and 1.0 g of glycerol to 100 g of the mixture, uniformly distributing the antioxidant composite liquid on the surface of the mixture by spraying, uniformly stirring, maintaining the environmental humidity at 60%, and introducing nitrogen protection at a flow rate of 0.2 L / min, and standing for 1 h to obtain pretreated material;

[0086] (c) loading the pretreated material into a distillation device, and performing steam distillation, controlling the temperature at 95℃ for 60 min, and collecting the condensate;

[0087] (d) The condensed liquid is concentrated at low temperature and vacuum, with a temperature of 35°C and a vacuum degree of 0.08 MPa, to obtain crude eugenol;

[0088] (e) The crude eugenol is mixed with 3A molecular sieves activated at 300°C for 2h at a mass ratio of 1:3, filtered after adsorption in a sealed container for 1h, to obtain refined eugenol.

[0089] Comparative Example 5

[0090] The difference from Example 1 is that no molecular sieves are used:

[0091] A method for preparing eugenol from Sygygium genus plants, comprising the following steps:

[0092] (a) The Sygygium genus flower buds or leaves are crushed to 100 mesh and mixed with 120 mesh perlite at a mass ratio of 1:1.5 to obtain a mixture;

[0093] (b) 0.5g of ascorbic acid, 0.3g of citric acid and 1.0g of glycerol are added to every 100g of the mixture, and the antioxidant compound solution is uniformly distributed on the surface of the mixture by spraying. After stirring evenly, the environment is kept at a humidity of 60%, and nitrogen gas is introduced for protection at a flow rate of 0.2L / min. The pre-treatment material is left to stand for 1h;

[0094] (c) The pre-treatment material is loaded into a distillation device for gradient heating steam distillation, with the temperature controlled at 90°C for 20min in the first stage and at 98°C for 40min in the second stage, and the condensed liquid is collected;

[0095] (d) The condensed liquid is concentrated at low temperature and vacuum, with a temperature of 35°C and a vacuum degree of 0.08 MPa, to obtain crude eugenol;

[0096] (e) The crude eugenol is directly filtered to obtain refined eugenol.

[0097] Comparative Example 6

[0098] The difference from Example 1 is that the molecular sieves are not activated:

[0099] A method for preparing eugenol from Sygygium genus plants, comprising the following steps:

[0100] (a) The Sygygium genus flower buds or leaves are crushed to 100 mesh and mixed with 120 mesh perlite at a mass ratio of 1:1.5 to obtain a mixture;

[0101] (b) Add 0.5 g of ascorbic acid, 0.3 g of citric acid and 1.0 g of glycerol per 100 g of the mixture, and uniformly distribute the antioxidant compound on the surface of the mixture by spraying. After stirring, keep the ambient humidity at 60%, and introduce nitrogen protection with a flow rate of 0.2 L / min. Let stand for 1 h to obtain the pretreated material;

[0102] (c) Load the pretreated material into a distillation device, and perform gradient heating steam distillation. Control the temperature at 90°C for 20 min in the first stage, and control the temperature at 98°C for 40 min in the second stage. Collect the condensate;

[0103] (d) Perform low-temperature vacuum concentration on the condensate under the condition of a temperature of 35°C and a vacuum degree of 0.08 MPa to obtain crude eugenol;

[0104] (e) Mix the crude eugenol with 3A molecular sieves activated at 300°C for 2 h at a mass ratio of 1:3, and filter after adsorption in a sealed container for 1 h to obtain refined eugenol.

[0105] Comparative Example 7

[0106] The difference from Example 1 is that the proportion of perlite is too small:

[0107] A method for preparing eugenol from Sygygium genus plants, comprising the following steps:

[0108] (a) Crush Sygygium genus flower buds or leaves to 100 mesh, and mix with 120 mesh perlite at a mass ratio of 1:1 to obtain a mixture;

[0109] (b) Add 0.5 g of ascorbic acid, 0.3 g of citric acid and 1.0 g of glycerol per 100 g of the mixture, and uniformly distribute the antioxidant compound on the surface of the mixture by spraying. After stirring, keep the ambient humidity at 60%, and introduce nitrogen protection with a flow rate of 0.2 L / min. Let stand for 1 h to obtain the pretreated material;

[0110] (c) Load the pretreated material into a distillation device, and perform gradient heating steam distillation. Control the temperature at 90°C for 20 min in the first stage, and control the temperature at 98°C for 40 min in the second stage. Collect the condensate;

[0111] (d) Perform low-temperature vacuum concentration on the condensate under the condition of a temperature of 35°C and a vacuum degree of 0.08 MPa to obtain crude eugenol;

[0112] (e) Mix the crude eugenol with 3A molecular sieves activated at 300°C for 2 h at a mass ratio of 1:3, and filter after adsorption in a sealed container for 1 h to obtain refined eugenol.

[0113] Comparative Example 8

[0114] The difference from Example 1 is that the ambient humidity is not maintained and nitrogen protection is not provided:

[0115] A method for preparing eugenol from Syzygium genus plants, comprising the following steps:

[0116] (a) The Syzygium genus flower buds or leaves are crushed to 100 mesh, and mixed with 120 mesh perlite at a mass ratio of 1:1.5 to obtain a mixture;

[0117] (b) 0.5 g of ascorbic acid, 0.3 g of citric acid, and 1.0 g of glycerol are added to 100 g of the mixture, and the antioxidant compound solution is uniformly distributed on the surface of the mixture by spraying. After stirring and uniform mixing, the mixture is allowed to stand for 1 h to obtain a pretreated material;

[0118] (c) The pretreated material is loaded into a distillation device for gradient heating steam distillation. In the first stage, the temperature is controlled at 90℃ for 20 min, and in the second stage, the temperature is controlled at 98℃ for 40 min. The condensate is collected;

[0119] (d) The condensate is subjected to low-temperature vacuum concentration under the conditions of a temperature of 35℃ and a vacuum degree of 0.08 MPa to obtain crude eugenol;

[0120] (e) The crude eugenol is mixed with 3A molecular sieves activated at 300℃ for 2 h at a mass ratio of 1:3, filtered after adsorption in a sealed container for 1 h to obtain refined eugenol.

[0121] Detection method:

[0122] Purity detection of eugenol: high performance liquid chromatography;

[0123] Yield of eugenol: yield = (mass of crude eugenol / mass of raw material) × 100%;

[0124] Moisture content: GB 5009.3-2016;

[0125] Total distillation time: record the total time from the start of heating to the completion of condensate collection.

[0126] The detection results are shown in Table 1.

[0127] Table 1: Detection results of examples and comparative examples

[0128] 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

[0129] The purity of the examples 1-3 is improved by the complex antioxidant which inhibits the formation of oxidation by-products, combined with the activated molecular sieve which deeply adsorbs moisture and small molecular impurities, so that the purity of the examples is 92.3%-93.5%; the yield advantage is due to the reduction of phenolic oxidative degradation under nitrogen protection, and the loss of target product is reduced by molecular sieve adsorption, and the yield of the examples is 12.1%-12.5%; moisture control directly depends on the high-efficiency dehydration ability of the activated and regenerated molecular sieve; the optimization of distillation time is achieved by gradient temperature separation of impurities and target product, combined with the enhancement of mass transfer efficiency by perlite carrier, and the examples only need 60-65 min.

[0130] The core reason why the example 1 achieves better results than the comparative examples 1-7 is that it synergistically improves the purity and yield of eugenol through multi-dimensional process optimization: compared with comparative example 1, example 1 uses gradient distillation to first evaporate low-boiling-point impurities at low temperature, then evaporate eugenol at high temperature, combined with molecular sieve adsorption, which deeply removes water and small molecular impurities, significantly reduces impurity residues and shortens the distillation time; compared with comparative example 2 which only adds a single ascorbic acid, the complex antioxidant of example 1, ascorbic acid + citric acid + glycerol, synergistically inhibits the oxidation of raw materials, reduces the generation of oxidation by-products, and improves the purity; compared with comparative example 3 which uses citric acid instead of malic acid, the strong antioxidant property of citric acid in example 1 more effectively inhibits the oxidation reaction and reduces impurity accumulation; compared with comparative example 4 which does not segment distillation, the segmented heating strategy of example 1 realizes the step-by-step separation of low-boiling-point impurities and eugenol, avoiding the mixing of high-boiling-point impurities with the target product; compared with comparative example 5 which does not use molecular sieve, the activated molecular sieve in example 1 efficiently adsorbs moisture and residual impurities in the condensate, reducing moisture content and reducing the loss of eugenol; compared with comparative example 6 which does not activate the molecular sieve, the adsorption activity of the molecular sieve in example 1 is significantly improved after being fully activated, and the removal of moisture and impurities is more thorough; compared with comparative example 7 which has too small a proportion of perlite, the reasonable proportion of perlite and raw materials in example 1 enhances the mass transfer efficiency of the mixture and shortens the distillation time; compared with comparative example 8, the nitrogen protection and humidity control of example 1 effectively inhibit the oxidation of raw materials and avoid the generation of oxidation by-products, 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 is ascorbic acid, citric acid and glycerin; The antioxidant compound solution is added at a rate of 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. (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; The conditions for the low-temperature vacuum concentration are a temperature of 35~40℃ and a vacuum degree of 0.08~0.09MPa; (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: 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.

3. 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.

4. 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.

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

6. The method as described in claim 1, characterized in that: The molecular sieve described in step (e) is activated at 300°C for 2 hours.

7. 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.

8. 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.