A method for preparing benzaldehyde and anisaldehyde by steam distillation and gas-phase ozone catalytic oxidation of cinnamaldehyde and anethole

Abstract

The present invention discloses a method for preparing benzaldehyde and anisaldehyde by steam distillation and gas-phase ozone catalytic oxidation of cinnamaldehyde and anethole, comprising the following steps: (1) introducing water vapor and ozone mixed gas into a distillation kettle containing cinnamon branches and leaves, star anise branches and leaves, or star anise fruits, and extracting cinnamon oil or anise oil with the mixed vapor and ozone mixed gas to undergo homogeneous oxidation reaction in a gas channel; (2) directly introducing water vapor and ozone mixed gas into a re-distillation tank containing a cinnamic aldehyde or anethole aqueous solution to carry out gas-phase oxidation reaction; (3) condensing and separating the oxidized vapor to obtain an oil phase containing benzaldehyde or anisaldehyde, and purifying the oil phase by normal pressure or vacuum steam distillation in a distillation tower to obtain benzaldehyde and anisaldehyde. The process of the present invention directly performs gas-phase homogeneous ozone oxidation from the distillation extraction process of branches and leaves, and the oxidation product does not need to be reduced. The product is purified by steam distillation, and the process route is short, energy-saving, and equipment investment is small, which is environmentally friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of deep processing of agricultural and forestry chemical products, and in particular relates to a method for preparing benzaldehyde and anisaldehyde by steam distillation, gas-phase ozone catalytic oxidation of cinnamaldehyde and anethole. Background Art

[0002] The industrial preparation method of cinnamon oil is mainly to obtain it through steam distillation of cinnamon branches and leaves, and its main component is trans-cinnamaldehyde. The industrial preparation method of fennel oil is mainly to obtain it through steam distillation of star anise branches and leaves, and its main component is trans-anethole. Cinnamaldehyde and anethole can react with ozone mixed gas to prepare benzaldehyde and anisaldehyde equivalent to natural products. Domestic Yi Fengping et al. used cinnamon oil and ethanol as solvent to ozonate at 0°C, and then used thiourea oxalic acid reduction hydrolysis and vacuum distillation to obtain benzaldehyde with a purity of 80.12%, with a yield of 62.32%; Luo Xuan et al. used an oxide of V, Ti, Ag, Ba, Mg or two or three composite oxides as catalysts, introduced O2 or air as oxygen source, and cinnamaldehyde was reacted with compressed air or oxygen After atomization, the mixture enters a fixed-bed reactor, where a gas-solid catalytic continuous reaction is carried out at atmospheric pressure and 120-200°C. The product is purified by molecular distillation to obtain benzaldehyde. Luo Xuan et al. then used cinnamaldehyde as the raw material, added a mixed solution of cinnamaldehyde and anhydrous ethanol in a mass ratio of 1:3 to the ozonation reactor, added 1.0-3.0wt% Ca(OH)2 as a catalyst, and introduced 0.05-0.15g of ozone per gram of cinnamaldehyde per hour. The ozonation reaction was carried out at 0°C. While the ozonation reaction was taking place, a water control device generated a pressure difference through a peristaltic pump, causing ethanol and water to pass through the reverse osmosis membrane into the dehydration pipeline. After passing through the desiccant, the dehydrated ethanol was re-transported into the ozonation reactor. The resulting crude product was treated with molecular distillation to obtain natural benzaldehyde with a purity of 85%. Qin Zuzeng and others used two or three composite oxides of Fe, Mo, W, Mn, Ca, Al, Cu, Zn, etc. as catalysts, introduced O2 or air as oxygen source, and after cinnamaldehyde was vaporized at 260°C, it entered a fixed bed reactor for gas-solid catalytic continuous reaction, and the product was purified by molecular distillation to obtain benzaldehyde. The above process is mainly a heterogeneous gas-solid or gas-liquid oxidation reaction. The gas-solid oxidation reaction requires a relatively high temperature for the vaporization of cinnamaldehyde. Cinnamaldehyde must be heated to above 260°C for high-temperature boiling and gasification, which can easily lead to carbon deposition on the solid catalyst. The generation of water during the oxidation process can also affect the performance of the solid catalyst. Gas-liquid reactions generally require solvents, and the use of solvents needs to be recycled, which leads to increased costs. Ozonation of olefins can easily generate ozonides and peroxides. Direct heating and distillation without detecting the thermal stability of the oxidation product after the reaction may cause thermal decomposition of the peroxide, which may cause thermal runaway and pose a safety hazard. Figure 1As shown in FIG. 1 , the DSC (differential scanning calorimetry) diagram of the solvent product of cinnamaldehyde under vacuum recovery at room temperature using ethanol as solvent is shown. The DSC conditions are: 3.46 mg injection volume, nitrogen flow rate of 50.0 mL / min, and heating rate of 5°C / min. Figure 1 As can be seen from the data, the product decomposition temperature (T0) after ozonation of cinnamaldehyde with vacuum solvent recovery is 78.7°C, the self-accelerating decomposition temperature (SADT) is 104.54°C, the maximum decomposition temperature is 131.69°C, and the heat release is 967.3 J / g. Excessive peroxides in the oxidation product can release significant amounts of heat during storage, distillation, and heating, posing a potentially hazardous risk. Separating the product benzaldehyde from unreacted cinnamaldehyde requires additional heat via vacuum distillation. Separating cinnamaldehyde requires higher temperatures, which can lead to side reactions such as polymerization. Molecular distillation separation and purification requires high vacuum equipment, which is costly. Using cinnamon oil or cinnamaldehyde as raw materials incurs higher transportation costs compared to cinnamon oil manufacturers.

[0003] Yi Fengping et al., Liu Lihua et al., Wang Qingjun et al. used anise oil or anethole in a solvent for ozonation and reduction, followed by distillation to produce anisaldehyde. Yu Jing et al. used a mixture of water, acetone, and anethole for ozonation, followed by extraction with ethyl acetate and direct distillation without reduction to produce anisaldehyde. Dai Huifang et al.'s patent discloses a method for producing anisaldehyde by continuous microchannel ozonation. The method uses anise oil as the raw material and ozone as the oxidant in the presence of an organic solvent or no solvent, conducting an oxidation reaction in a first microchannel reactor. The oxidation reaction is then carried out with the reducing agent NaHSO3 in a second microchannel reactor, achieving a continuous reduction reaction to produce anisaldehyde. Xie Yu et al. added natural anethole, ethanol, and water to a three-necked flask, continuously introduced oxygen into the reaction mixture for oxidation, and controlled the reaction temperature at 40-55°C. After 40-80 minutes of reaction, the resulting reaction product containing anisaldehyde was then distilled and purified. The above process is mainly a heterogeneous gas-liquid oxidation reaction. Generally, a solvent is used to enhance gas-liquid mass transfer. The solvent needs to be recovered. Direct heating and distillation without testing the thermal stability of the peroxide after the oxidation reaction may cause the peroxide to thermally decompose and run away, posing a safety hazard. The differential scanning calorimetry (DSC) results of the direct ozonation product of anethole at room temperature are shown in the attached figure. Figure 2 , where DSC conditions are: 5.74 mg injection volume, nitrogen flow rate of 50.0 mL / min, and heating rate of 5°C / min. Figure 2 It can be seen that the initial decomposition temperature T0 of the direct ozonation product of anethole is 73.75℃, the self-accelerating decomposition temperature SADT is 100.57℃, the maximum decomposition temperature is 136.34℃, and the heat release is 815.0J / g. Its thermal decomposition will release a large amount of heat, and the potential danger is relatively high.

[0004] In response to the safety risks posed by the use of solvents, solid catalysts, and heterogeneous reactions in the above processes, the generated ozonides pose a safety hazard. This method utilizes the equipment and steam heat energy used in cinnamon and anise oil production to introduce an ozone mixture into a still for a homogeneous vapor-phase reaction with a cinnamaldehyde or anethole oil / gas mixture. The oxidation product is separated into volatile oils and less volatile components through a distillation tower, and its thermal stability is tested to ensure production safety. The entire process is short and requires minimal equipment investment. The heat source, generated by burning steam from distilled branches and leaves, requires no additional energy, solvents, or catalysts. Ozonides readily decompose in the presence of water at 100°C, preventing subsequent thermal decomposition and thermal runaway, making the production process environmentally friendly. Summary of the Invention

[0005] The present invention provides a method for preparing benzaldehyde and anisaldehyde by steam distillation and gas-phase ozone catalytic oxidation of cinnamic aldehyde and anethole. The technical problem to be solved is to utilize cinnamon oil and anise oil production equipment to directly perform a one-step ozone catalytic oxidation reaction, wherein cinnamic aldehyde and anethole are subjected to a gas-phase homogeneous oxidation reaction with an ozone mixture. Steam is used as a heating agent for rectification, separation, and purification of the oxidation products.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A method for preparing benzaldehyde and anisaldehyde by steam distillation and gas-phase ozone catalytic oxidation of cinnamaldehyde and anethole, characterized by comprising the following steps:

[0008] (1) introducing water vapor into a distillation kettle containing cinnamon branches and leaves, star anise branches and leaves, or star anise fruits, and simultaneously introducing an ozone mixture, so that the mixed vapor of the extracted cinnamon oil or anise oil and the ozone mixture undergo a homogeneous oxidation reaction in the gas channel;

[0009] (2) directly passing a mixed gas of water vapor and ozone into a re-distillation tank containing an aqueous solution of cinnamaldehyde or anethole, while distilling out cinnamaldehyde or anethole, while performing a gas-phase oxidation reaction;

[0010] (3) The vapor after oxidation in step (1) and step (2) or step (1) and step (2) is condensed and separated into oil and water to obtain an oil phase containing benzaldehyde or anisaldehyde, which is then purified by a steam distillation tower or a vacuum distillation tower to obtain benzaldehyde, anisaldehyde and unreacted cinnamaldehyde and anethole. The cinnamaldehyde and anethole can be reused for further oxidation.

[0011] Furthermore, the volume ratio of the ozone mixed gas to water vapor in step (1) is 0.05-0.2.

[0012] Furthermore, the ozone mixed gas is a mixed gas obtained by preparing oxygen through air separation, preparing oxygen through molecular sieve, or air passing through an ozone generator.

[0013] Furthermore, the re-distillation tank in step (2) is a device for re-distilling the water after oil-water separation to reduce the dissolution loss of cinnamon oil in water.

[0014] Furthermore, the re-distillation tank contains re-distilled water: cinnamaldehyde or anethole = 500 mL: 80-100 g.

[0015] Furthermore, the re-distilled water refers to the water after the oil-water separation by steam distillation in the last time, in which a certain amount of cinnamon oil or anise oil components are dissolved.

[0016] Furthermore, the amount of cinnamaldehyde or anethole added to the re-distillation tank in step (2) is greater than the amount of cinnamaldehyde or anethole distilled out by the introduction of water vapor, that is, cinnamaldehyde or anethole is still in the re-distillation tank at the end of the reaction, so as to maintain the stability of the oxidation process.

[0017] Furthermore, the thermal stability of the obtained oxidation product needs to be tested by heating to ensure production safety.

[0018] Furthermore, the distillation tower in step (3) is a packed tower or a sieve plate tower.

[0019] Furthermore, the purification method in step (3) is direct atmospheric pressure steam distillation or vacuum distillation.

[0020] Compared with the prior art, the technology of the present invention has the following advantages:

[0021] (1) Utilizing the existing industrial cinnamon oil and anise oil steaming equipment, ozone mixed gas is introduced during steam distillation of cinnamon oil and anise oil, and the oil-water mixed gas and ozone mixed gas produced by distillation undergo gas phase homogeneous oxidation reaction in the gas channel, and after condensation, oil and water are separated to obtain an oil layer containing benzaldehyde and anisaldehyde, and the thermal stability of the oxidation product is tested to ensure production safety, and then the benzaldehyde and anisaldehyde product is obtained by steam distillation and purification, and the unreacted cinnamic aldehyde and anethole can be recycled for re-oxidation; the entire oxidation process has a short process route, a fast reaction, and no harmful substances are introduced during the reaction process, which is green and environmentally friendly.

[0022] (2) Ozone acts as an oxidation catalyst or initiator. Under normal pressure and water vapor at 100°C, ozone reacts with cinnamaldehyde and anethole to produce ozonides. Ozonates have a low self-accelerating decomposition temperature and decompose quickly at high temperatures. The free radicals produced accelerate the oxidation reaction of the carbon-carbon double bond connected to the benzene ring. Compared with the risk of thermal runaway of peroxides produced by direct oxidation or ozonation of cinnamaldehyde and anethole, the oil-water mixture produced by steam distillation of branches and leaves has a low proportion of oil, and the large thermal enthalpy of water vapor plays a safe role in diluting the heat of peroxide decomposition during the oxidation process. It also slows down the oxidation of cinnamaldehyde to cinnamic acid, benzaldehyde to benzoic acid, and anisaldehyde to anisic acid. The oxidation product has good thermal stability after testing, indicating that it has been decomposed and does not need to be reduced.

[0023] (3) Separation of reaction products. After the reaction of the mixture of cinnamaldehyde, anethole and water produced by distillation with the ozone mixture is completed, steam distillation is performed using the thermal energy of water vapor to separate volatile components such as benzaldehyde, cinnamaldehyde, anethole and anisaldehyde. The bottom of the tower contains the by-products benzoic acid and cinnamic acid and other products with low volatility.

[0024] (4) In view of the problems that the current ozone oxidation of cinnamic aldehyde and anethole to prepare benzaldehyde and anisaldehyde requires solvents, catalysts, and the ozonide is prone to thermal decomposition and thermal runaway and needs to be reduced, the inventors have established a method for preparing benzaldehyde and anisaldehyde by steam distillation gas-phase ozone catalytic oxidation of cinnamic aldehyde and anethole by making full use of cinnamon oil distillation equipment and the heat energy of distilled water vapor. Cinnamic aldehyde and anethole are added to a distillation kettle filled with cinnamon leaves and star anise branches or in a double steamer. Ozone mixed gas is introduced while water vapor is introduced for gas-phase oxidation. The oxidation reaction product is directly introduced into a distillation tower for separation or condensed for oil-water separation and then distilled to separate benzaldehyde, unreacted cinnamic aldehyde, benzoic acid or unreacted anethole, anisaldehyde or anisic acid. By adopting the present invention, various products equivalent to natural products such as benzaldehyde, benzoic acid, anisaldehyde and anisic acid can be obtained through steam distillation gas-phase ozone catalytic oxidation and separation and purification. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The DSC graph of the product after ozonation of cinnamaldehyde with ethanol as solvent and vacuum solvent recovery;

[0026] Figure 2 This is the DSC diagram of the direct ozonation product of anethole;

[0027] Figure 3 This is a process flow chart of the method for preparing benzaldehyde and anisaldehyde by steam distillation and gas-phase ozone oxidation of the present invention;

[0028] Figure 4 This is a diagram showing the temperature rise process of the product after cinnamaldehyde + ethanol ozonation and vacuum concentration of the solvent;

[0029] Figure 5 This is a diagram showing the temperature rise process of the solvent-free direct ozonation products of anethole. DETAILED DESCRIPTION

[0030] 1. Application Examples

[0031] Example 1 Effect of different ozone mixture and water vapor volume ratios on the oxidation reaction of cinnamaldehyde

[0032] according to Figure 3Connect the device as shown in the process flow, weigh 2kg of cinnamon leaves and crush them into about 1.5cm pieces, soak them in water for 8h, then put the leaves into a 5L distillation tank, add 500mL of distilled water and 100g of cinnamaldehyde into a 1.5L re-distillation pot, and use a steam generator to pass a flow rate of 2.72m 3 / h water vapor. When the distillation tower begins to evaporate, open the ozone generator to introduce oxygen to produce ozone mixture. Different ozone mixture and water vapor volume ratios are used, as shown in the table below. The distillation tower does not reflux, and the top fraction is directly condensed into the product collection tank. After reacting for 2 hours, turn off the ozone machine, continue to pass oxygen through the ozone pipe for 3 minutes, then turn off the oxygen and stop introducing water vapor. After the distillate oil and water are separated, separate the lower oil layer and quantify it by gas chromatography peak area normalization method. Gas chromatography conditions: chromatographic column is non-polar capillary column RTX-1

[0033] (0.25 mm × 30 m × 0.25 μm); carrier gas (high-purity N2); column temperature 35°C; detector temperature 250°C; injection port temperature 250°C; injection volume 0.2 μL, split ratio 50:1 (split injection); FID (hydrogen flame ionization detector); heating program: 35°C (10°C / min) → 100°C (8°C / min) → 160°C (15°C / min) → 200°C. The needle-like solid precipitated at the bottom of the kettle was filtered and weighed. The experimental results are shown in the following table:

[0034]

[0035] As shown in the table above, the yield is calculated by feeding 100g cinnamaldehyde+2kg branches and leaves of the retort with 20g cassia oil (cinnamaldehyde 80%), which means that the cinnamaldehyde raw material is converted into 116g. The benzaldehyde yield increases with the increase in the ratio of ozone mixed gas and water vapor, and the maximum value is 50.91%, while the cinnamaldehyde transformation efficiency increases with the increase of volume ratio. The solid (cinnamic acid benzoic acid crystal) at the bottom of the still also increases, and the aldehyde is oxidized to the acid ratio and increases. The increase of the ozone mixed gas can obviously accelerate the oxidation reaction rate, but has also increased the yield of the solid at the bottom of the still.

[0036] Example 2 Effect of the amount of cinnamaldehyde added to the retort on the reaction

[0037] according to Figure 3 Connect the device as shown in the process flow, weigh 2kg of cinnamon leaves and crush them into about 1.5cm pieces and soak them in water for 8h, then put the leaves into a 5L distillation tank, add 500mL of distilled water and different masses of cinnamaldehyde (50g, 100g, 150g, see the table below) into a 1.5L re-distillation pot, and use a steam generator to pass a flow rate of 2.72m 3 / h water vapor. When the distillation tower begins to evaporate, open the ozone generator to introduce oxygen to produce ozone mixed gas with a flow rate of 0.13m 3 / h, the distillation tower was not refluxed, and the overhead fraction was directly condensed into a product collection tank. The fraction was collected every 30 minutes. After reacting for 2 hours, the ozone generator was turned off, and oxygen was continued to flow through the ozone pipe for 3 minutes. After that, the oxygen was turned off and the water vapor was stopped. After the oil and water fractions were separated, the lower oil layer was separated and weighed, and quantified by gas chromatography peak area normalization method. The chromatographic conditions were the same as in Example 1. The experimental results are shown in the following table:

[0038] Cinnamaldehyde feeding amount in retort (g) 50 100 150 Benzaldehyde yield% 36.51 40.03 22.21 Unreacted cinnamaldehyde% 38.87 40.10 67.86 Oil content in 30min fraction g 24.13 25.41 25.56 Oil content in 60min fraction g 23.32 25.13 24.31 Oil content in 90min fraction g 15.57 24.25 25.71 Oil content in 120min fraction g 8.36 23.78 25.36

[0039] From the results in the table above, we can see that the yield is calculated based on the amount of cinnamaldehyde added to the retort and 20g of cinnamon oil is obtained. The flow rate is 2.72m 3 / h water vapor condensation capacity in half an hour is about 500g, when the ozone mixed gas flow rate is 0.13m 3 Under conditions of 100 mL / h, steam extraction removes approximately 25 g of oil every 30 minutes. This indicates that production capacity is related to the amount of material added to the re-evaporator and the amount of water vapor introduced. It's best to add more cinnamaldehyde to the re-evaporator than the amount of cinnamaldehyde evaporated in 2 hours. Otherwise, insufficient material will lead to increased ozone concentration in the exhaust gas. Under these experimental conditions, the optimal re-evaporator feed ratio is 500 mL of re-evaporated water: 100 g of cinnamaldehyde, meaning the optimal amount of cinnamaldehyde added to the re-evaporator is 100 g.

[0040] Example 3 Thermal Stability of Cinnamaldehyde Oxidation Products in Ozone Mixtures of Different Concentrations

[0041] As shown in the table below, 0.5g of the oxidation product obtained by mixing ozone with water vapor at different volume ratios and 0.5g of the product obtained by ozonating cinnamaldehyde and ethanol after vacuum concentration of the solvent were heated from room temperature to 140°C in a 25mL sealed container under nitrogen over 130 minutes to examine their thermal stability, that is, whether there was any significant thermal decomposition or thermal runaway during the heating process. The results of the thermal stability test of the steam distillation gas-phase oxidation products are shown in the following table:

[0042]

[0043] The temperature rise process of the product after cinnamaldehyde + ethanol ozonation and vacuum concentration of solvent is as follows Figure 4 shown.

[0044] From the above table and Figure 4 The results show that: when the temperature of the vapor phase oxidation product of steam distillation rises from room temperature to 140℃ in 130min, the temperature and pressure increase with time basically in a linear relationship, and there is no sudden change in temperature and pressure, that is, it is stable in this temperature range without violent thermal decomposition; while the product of cinnamaldehyde + ethanol after room temperature ozonation and vacuum concentration of solvent has a sudden and rapid increase in temperature and pressure in a short time when the temperature is raised to 100℃, which is consistent with the characteristics of the above. Figure 1The results of differential scanning calorimetry (DSC) tests indicate a risk of thermal runaway. The ozonation product of cinnamaldehyde must undergo thermal stability testing to confirm its stability before thermal distillation. The oxidation product of the steam distillation vapor-phase oxidation system is stable from room temperature to 140°C.

[0045] Example 4 Separation and purification of different benzaldehyde and cinnamaldehyde compositions by steam distillation

[0046] 100g of raw materials with different benzaldehyde to cinnamaldehyde mass ratios were added to the 2L distillation tower kettle, as shown in the table below. The tower section diameter was 3cm, the stainless steel packing was 40cm high, and the flow rate of the steam generator was 0.8m 3 / h water vapor, set total reflux when a fraction emerges, and after 5 minutes of total reflux, set the reflux ratio R to 1. Use collection flask 1 to collect the front fraction benzaldehyde. When the oil content in the fraction decreases, evacuate the flask and set the pressure to 80.2kPa. Use collection flask 2 to collect the cinnamaldehyde fraction. When no oil content evaporates, end the distillation. Quantitative analysis was performed using the gas chromatography normalization method, and the chromatographic conditions were the same as in Example 1. The experimental results are shown in the following table:

[0047]

[0048] As shown in the table above, the greater the benzaldehyde to cinnamaldehyde mass ratio, the higher the benzaldehyde content obtained by steam distillation. When the mass ratio reaches 50%, the benzaldehyde purity reaches 99.06%. This means that higher benzaldehyde content in the oil feed composition leads to higher content in a 40cm distillation tower with a packing height of 40cm. The distilled cinnamaldehyde content is generally between 96% and 98%, indicating that benzaldehyde and cinnamaldehyde can be separated and purified using steam distillation.

[0049] Example 5 Optimization of process conditions

[0050] From the results of the above examples 1-4, it can be seen that the main influencing factor is the volume ratio of ozone mixture to water vapor. Figure 3 Connect the device as shown in the process flow, weigh 2kg of cinnamon leaves and crush them into about 1.5cm pieces, soak them in water for 8h, then put the leaves into a 5L distillation tank, add 500mL of distilled water and 100g of cinnamaldehyde into a 1.5L re-distillation pot, and use a steam generator to pass a flow rate of 2.72m 3 / h water vapor. When the distillation tower begins to evaporate, open the ozone generator to introduce oxygen to produce an ozone mixture. Different volume ratios of ozone mixture and water vapor are used, as shown in the table below. The distillation tower does not reflux, and the top fraction is directly condensed into the product collection tank. After reacting for 2 hours, turn off the ozone machine, continue to pass the oxygen exhaust pipe for 3 minutes to ozone, then turn off the oxygen and stop introducing water vapor. After the distillate oil and water layers are separated, the lower oil layer is separated and weighed. The oil layer is separated and purified by water vapor distillation according to Example 4, and quantified by gas chromatography peak area normalization method. The chromatographic conditions are the same as in Example 1. The experimental results are as follows:

[0051]

[0052] As can be known from the above table result: get 20g cassia oil (cinnamic aldehyde 80%) by the 100g cinnamaldehyde+2kg branches and leaves that feed intake of multiple steamer and calculate, promptly converting to the cinnamic aldehyde raw material and feeding intake is 116g, by 0.05 volume ratio a phenylaldehyde yield in the table is 116 * 40.25%=46.69g, also having 116 * 32.61%=37.83g cinnamic aldehyde unreacted, reuse a phenylaldehyde gets 37.83 * 40.25%=15.23g, also having 37.83 * 32.61%=12.34g cinnamic aldehyde unreacted, calculating reuse 3 times of phenylaldehyde and divided by cinnamic aldehyde raw material 116 by this is the phenylaldehyde total yield. When the volume ratio of ozone mixture to water vapor reaches 0.08, the total yield of benzaldehyde is 66.78%. As the volume ratio of ozone mixture to water vapor increases, the total yield of benzaldehyde decreases slightly. Therefore, the optimal volume ratio of ozone mixture to water vapor is 0.08.

[0053] Example 6 Effects of Different Ozone Mixture and Water Vapor Volume Ratios on Anethole Oxidation

[0054] according to Figure 3 Connect the device as shown in the process flow, weigh 2kg of star anise branches and leaves, crush them into about 1.5cm pieces, and put them into a 5L distillation tank. Add 500mL of distilled water and 80g of anethole into a 1.5L re-distillation pot, and use a steam generator to pass a flow rate of 2.72m 3 / h of water vapor. When distillate began to evaporate from the distillation column, an ozone generator was turned on to introduce oxygen to produce an ozone mixture. Different ozone mixture: water vapor volume ratios were used (see the table below). The distillation column was not refluxed, and the overhead fraction was directly condensed into a product collection tank. After 2 hours of reaction, the ozone generator was turned off, and oxygen was continued to flow through the ozone pipe for 3 minutes. After that, the oxygen was turned off and the water vapor flow was stopped. After the oil and water fractions were separated, the lower oil layer was separated and quantified by gas chromatography peak area normalization. GC conditions: RTX-5 elastic quartz capillary column, dimensions 0.25μm × 0.25nm × 30m; temperature program: 40°C for 1 minute, then to 250°C (15°C / min); carrier gas: high-purity helium at a flow rate of 1mL / min; injection volume: 0.1μL, split ratio 80:1, inlet temperature 250°C, interface temperature 250°C. The needle-like solid precipitated from the bottom of the kettle was filtered and weighed. The experimental results are shown in the following table:

[0055]

[0056] The results in the table above show that the yield is calculated based on a retort charge of 80g anethole + 2kg star anise branches and leaves to yield 20g of anise oil (85% anethole), equivalent to 97g of anethole. The anisaldehyde yield increases with increasing ozone mixture:water vapor ratio, but the increase decreases after a certain point, reaching a maximum of 53.24%. Anethole conversion increases with increasing volume ratio, as does the amount of solid anisic acid crystals at the bottom of the kettle, indicating an increase in the proportion of aldehyde oxidized to acid. Increasing the ozone mixture significantly accelerates the oxidation reaction rate, but also increases the yield of solids at the bottom of the kettle. The table above shows that the optimal volume ratio of ozone mixture to water vapor is 0.111.

[0057] Example 7 Effect of the amount of anethole added to the retort on the reaction

[0058] according to Figure 3 Connect the device as shown in the process flow, weigh 2kg of star anise branches and leaves, crushed into about 1.5cm, and put them into a 5L distillation tank. Add 500mL of distilled water and different masses of anethole (50g, 80g, and 120g, respectively, see the table below) into a 1.5L re-distillation pot, and use a steam generator to pass a flow rate of 2.72m 3 / h water vapor. When the distillation tower begins to evaporate, open the ozone generator to introduce oxygen to produce ozone mixed gas with a flow rate of 0.2m 3 / h, the distillation tower is not refluxed, and the overhead fraction is directly condensed into the product collection tank. After reacting for 2 hours, the ozone machine is turned off, and the oxygen is continued to be passed through the ozone pipe for 3 minutes, and then the oxygen is turned off and the water vapor is stopped. After the oil and water fractions are separated, the lower oil layer is separated and quantified by gas chromatography peak area normalization method. The gas chromatography conditions are as in Example 6. The needle-shaped solid precipitated at the bottom of the kettle is filtered and weighed. The experimental results are as follows:

[0059] Anethole feeding amount in double steamer (g) 50 80 120 Anisaldehyde yield% 30.11 40.03 20.81 Unreacted anethole% 45.89 39.50 80.86 Oil content in 30min fraction g 20.33 20.46 20.32 Oil content in 60min fraction g 20.28 20.73 20.61 Oil content in 90min fraction g 16.47 20.25 20.35 Oil content in 120min fraction g 8.73 20.78 20.61

[0060] From the results in the table above, we can see that the yield is calculated based on the amount of anethole added to the retort + 2kg of star anise branches and leaves to get 20g of anise oil (85% anethole), and the flow rate is 2.72m 3 / h water vapor condensation capacity in half an hour is about 500g, when the ozone mixed gas flow rate is 0.15m 3 / h, steam extraction yielded approximately 20g of oil every 30 minutes. This indicates that production capacity is related to the amount of material added to the re-evaporator and the amount of water vapor introduced. Ideally, the amount of anethole added to the re-evaporator should be greater than the amount of cinnamaldehyde evaporated in 2 hours. Otherwise, insufficient material in the later stages will lead to increased ozone concentration in the exhaust gas. Under these experimental conditions, the optimal re-evaporator feed ratio is 500mL of re-evaporated water: anethole: 80g, meaning the optimal amount of anethole added to the re-evaporator is 80g.

[0061] Example 8 Thermal Stability of Anethole Oxidation Products During Heating Process in Ozone Mixtures of Different Concentrations

[0062] As shown in the table below, 0.5g of the oxidation product obtained by mixing ozone with water vapor at different volume ratios and 0.5g of the product obtained by ozonating cinnamaldehyde and ethanol after vacuum concentration of the solvent were heated from room temperature to 140°C in a 25mL sealed container under nitrogen over 130 minutes to examine their thermal stability, that is, whether there was any significant thermal decomposition or thermal runaway during the heating process. The results of the thermal stability test of the steam distillation gas-phase oxidation products are shown in the following table:

[0063]

[0064] The heating process of the solvent-free direct ozonation product of anethole is as follows Figure 5 shown.

[0065] From the above table and Figure 5 The results show that when the temperature of the vapor phase oxidation product of steam distillation is raised from room temperature to 180℃ in 2.5h, the temperature and pressure increase with time in a basically linear relationship, and there is no sudden change in temperature and pressure, that is, it is stable in this temperature range without violent thermal decomposition; while the temperature and pressure of the product of cinnamaldehyde + ethanol ozonation vacuum concentrated solvent suddenly increase rapidly in a short period of time when the temperature is raised to 70℃, which is consistent with the characteristics of the above. Figure 2 The results of differential scanning calorimetry (DSC) tests indicate a risk of thermal runaway. The anethole ozonation product must undergo thermal stability testing to confirm stability before thermal distillation. The steam distillation vapor-phase oxidation system shows stable oxidation products from room temperature to 180°C.

[0066] Example 9 Separation and Purification of Anethole and Anisaldehyde with Different Compositions by Steam Distillation

[0067] 100 g of raw materials with different mass ratios of anethole and cinnamaldehyde were added to the bottom of a 2 L distillation tower (see the table below). The tower section diameter was 3 cm, the stainless steel packing was 80 cm high, and the flow rate of the steam generator was 0.8 m 3 / h water vapor. When a fraction emerges, total reflux is set. After 5 minutes of total reflux, the reflux ratio R is set to 1.2. The front fraction, anethole, is collected in collection flask 1. When the oil content in the fraction decreases, vacuum is applied and the pressure is set to 80.2 kPa. The anisaldehyde fraction is then collected in collection flask 2. The distillation is terminated when no more oil is evaporated. Quantification is performed using the gas chromatography normalization method, using the same chromatographic conditions as in Example 6. The experimental results are shown in the following table:

[0068] Anethole:anisaldehyde (mass ratio) / % 80 60 40 20 10 Anethole mass / g 77.92 57.54 37.31 20.54 12.44 Anethole content / % 98.22 97.32 96.36 96.01 95.67 Anisaldehyde mass / g 16.01 35.75 54.49 70.23 82.85 Anisaldehyde content / % 96.10 97.25 98.31 99.01 99.12

[0069] The results in the table above show that the lower the mass ratio of anethole to anisaldehyde, the higher the anisaldehyde content obtained by steam distillation. When the mass ratio reaches 20%, the purity of the distilled benzaldehyde reaches 99.12%. In other words, the higher the anisaldehyde content in the oil feed composition, the higher the content obtained in the distillation tower with a packing height of 80 cm. The anethole content ranges from 95.67% to 98.22%, indicating that anethole and anisaldehyde can be separated and purified by steam distillation.

[0070] Example 10 Optimization of process conditions for steam distillation and gas phase ozone oxidation of star anise branches and leaves

[0071] From the results of Examples 6-9, it can be seen that the main influencing factor is the volume ratio of ozone mixture to water vapor. Figure 3 Connect the device as shown in the process flow, weigh 2kg of star anise branches and leaves, crush them into about 1.5cm pieces, and put them into a 5L distillation tank. Add 500mL of distilled water and 80g of anethole into a 1.5L re-distillation pot, and use a steam generator to pass a flow rate of 2.72m 3 / h water vapor, when the distillation tower begins to evaporate, open the ozone generator to introduce oxygen to produce ozone mixture, using different ozone mixture and water vapor volume ratios, see the table below, the distillation tower does not reflux, the top fraction is directly condensed into the product collection tank, after reacting for 2h, turn off the ozone machine, continue to pass the oxygen exhaust pipe for 3min ozone, then turn off the oxygen, and stop passing water vapor. After the distillate oil and water layers are separated, the lower oil layer is separated and weighed. The oil layer is separated and purified by steam distillation according to the conditions of Example 9, and quantified by gas chromatography peak area normalization method, and the chromatographic conditions are as in Example 6. The experimental results are as follows:

[0072]

[0073]

[0074] From the results in the above table, it can be seen that 20g of anise oil (85% anethole) is obtained by adding 80g of anethole + 2kg of branches and leaves to the retort, which is equivalent to 97g of cinnamaldehyde raw material. According to the volume ratio of 0.05 in the table, the yield of anisaldehyde once is 97×36.52%=35.42g, and 97×48.21%=46.76g of anethole remains unreacted. The anisaldehyde is recycled once to obtain 46.76×36.52%=17.08g, and 46.76×48.21%=22.54g of anethole remains unreacted. According to this calculation, the sum of the anisaldehyde recycled three times divided by the anethole raw material 97 is the total anisaldehyde yield. When the volume ratio of ozone mixture to water vapor reaches 0.14, the total yield of anisaldehyde is 75.55%. As the volume ratio of ozone mixture to water vapor increases, the total yield of anisaldehyde decreases slightly. Therefore, the optimal volume ratio of ozone mixture to water vapor is 0.14.

[0075] 2. Obtain the best process route by optimizing the process parameters according to Examples 1-10

[0076] ① The process flow chart is shown in Figure 3. Cassia twigs and leaves or star anise twigs and leaves are placed in a distillation pot. To increase the yield of benzaldehyde or anisaldehyde, re-distilled water and cinnamic aldehyde or anethole are added to the re-distillation pot in a certain proportion, and then a mixture of water vapor and ozone is introduced in a certain proportion. ② The mixed gas after the gas-phase homogeneous oxidation reaction is directly condensed or enters a distillation tower. The volatile benzaldehyde, anisaldehyde, anethole, and cinnamic aldehyde are evaporated at the top of the tower, and the oil and water are separated to obtain an oil layer. Non-volatile substances such as benzoic acid, anisic acid, and cinnamic acid can be obtained in the bottom of the tower. ③ To obtain high-purity benzaldehyde and anisaldehyde, the oil layer in ② is subjected to atmospheric pressure steam distillation or vacuum distillation. According to the best optimized process, 1% cinnamon oil is distilled from cassia twigs and leaves, and the cinnamon oil contains 80% cinnamaldehyde. The yield of benzaldehyde calculated based on cinnamon aldehyde can reach 66.78%. 1% fennel oil is distilled from star anise twigs and leaves, and the anethole content in the fennel oil is 85%. The yield of anisealdehyde calculated based on anethole can reach 75.55%.

Claims

1. A method for preparing benzaldehyde and anisaldehyde by steam distillation and gas-phase ozone catalytic oxidation of cinnamaldehyde and anethole, characterized in that: The following steps are involved: (1) introducing water vapor into a distillation kettle containing cinnamon branches and leaves, star anise branches and leaves, or star anise fruits, and simultaneously introducing an ozone mixture, so that the mixed vapor of the extracted cinnamon oil or anise oil and the ozone mixture undergo a homogeneous oxidation reaction in the gas channel; (2) directly passing a mixed gas of water vapor and ozone into a re-distillation tank containing an aqueous solution of cinnamaldehyde or anethole, while distilling out cinnamaldehyde or anethole, while performing a gas-phase oxidation reaction; (3) The vapor after oxidation in step (1) and step (2) or step (1) and step (2) is condensed and separated into oil and water to obtain an oil phase containing benzaldehyde or anisaldehyde, which is purified by a steam distillation tower or a vacuum distillation tower to obtain benzaldehyde, anisaldehyde and unreacted cinnamaldehyde and anethole, and the cinnamaldehyde and anethole can be reused for further oxidation; The volume ratio of the ozone mixture to water vapor in step (1) is 0.05-0.2; The ozone mixed gas is an ozone mixed gas produced by introducing oxygen into an ozone generator.

2. The method for preparing benzaldehyde and anisaldehyde by steam distillation and gas-phase ozone catalytic oxidation of cinnamaldehyde and anethole according to claim 1, characterized in that: The re-distillation tank in step (2) is a device for re-distilling the water after the oil-water separation to reduce the dissolution loss of cinnamon oil in water.

3. The method for preparing benzaldehyde and anisaldehyde by steam distillation and gas-phase ozone catalytic oxidation of cinnamaldehyde and anethole according to claim 2, characterized in that: The re-distilled water in the re-distillation tank: cinnamaldehyde or anethole = 500mL: 80-100g.

4. The method for preparing benzaldehyde and anisaldehyde by steam distillation and gas-phase ozone catalytic oxidation of cinnamaldehyde and anethole according to claim 3, characterized in that: The re-distilled water refers to the water obtained after the oil and water are separated by steam distillation, in which a certain amount of cinnamon oil or anise oil components are dissolved.

5. The method for preparing benzaldehyde and anisaldehyde by steam distillation and gas-phase ozone catalytic oxidation of cinnamaldehyde and anethole according to claim 1, characterized in that: The amount of cinnamaldehyde or anethole added to the re-distillation tank in step (2) is greater than the amount of cinnamaldehyde or anethole distilled out by the introduction of water vapor, that is, cinnamaldehyde or anethole is still in the re-distillation tank at the end of the reaction to maintain the stability of the oxidation process.

6. The method for preparing benzaldehyde and anisaldehyde by steam distillation and gas-phase ozone catalytic oxidation of cinnamaldehyde and anethole according to claim 1, characterized in that: The obtained oxidation product needs to be tested for its thermal stability by heating to ensure production safety.

7. The method for preparing benzaldehyde and anisaldehyde by steam distillation and gas-phase ozone catalytic oxidation of cinnamaldehyde and anethole according to claim 1, characterized in that: The distillation tower in step (3) is a packed tower or a sieve plate tower.

8. The method for preparing benzaldehyde and anisaldehyde by steam distillation and gas-phase ozone catalytic oxidation of cinnamaldehyde and anethole according to claim 1, characterized in that: The purification method in step (3) is direct atmospheric pressure steam distillation or vacuum distillation.

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