CN106977383B - Method for preparing citral - Google Patents
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- C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
- C07C45/51—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by pyrolysis, rearrangement or decomposition
- C07C45/511—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by pyrolysis, rearrangement or decomposition involving transformation of singly bound oxygen functional groups to >C = O groups
- C07C45/513—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by pyrolysis, rearrangement or decomposition involving transformation of singly bound oxygen functional groups to >C = O groups the singly bound functional group being an etherified hydroxyl group
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- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
- C07C45/61—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by reactions not involving the formation of >C = O groups
- C07C45/67—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by reactions not involving the formation of >C = O groups by isomerisation; by change of size of the carbon skeleton
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Abstract
The invention provides a method for preparing citral, which comprises the following steps: cis/trans-isopentenyl-3-methyl butadiene ether is subjected to Claisen rearrangement to obtain 2,4, 4-trimethyl-3-formyl-1, 5-hexadiene, and then subjected to Cope rearrangement to obtain citral (3, 7-dimethyl-2, 6-octadiene-1-aldehyde). The method comprises adding esters as side reaction inhibitor to raw materials and adjusting reaction rate. The method has high selectivity and high reaction rate, and the residence time of the whole process is 1-15 min.
Description
Technical Field
The invention relates to a method for preparing citral. Cis/trans-isopentenyl-3-methyl butadiene ether is used as a raw material to carry out Claisen rearrangement reaction to obtain 2,4, 4-trimethyl-3-formyl-1, 5-hexadiene, and then Cope rearrangement is carried out to obtain citral (3, 7-dimethyl-2, 6-octadiene-1-aldehyde).
Background
Citral is not only a commonly used fragrance product per se, but also as a raw material for a variety of fine chemicals. The downstream products include vitamins, valuable flavors, etc. U.S. Pat. No. 4,88636 discloses a process for preparing cis/trans-prenyl-3-methyl-butadiene ether as an intermediate product of citral, which comprises thermally cracking prenyl alcohol to obtain prenyl-3-methyl-butadiene ether and prenol, and continuously distilling off prenol to obtain cis/trans-prenyl-3-methyl-butadiene ether. The cis/trans-isopentenyl-3-methyl butadiene ether is subjected to rearrangement reaction to prepare citral. However, cis/trans-isopentenyl-3-methyl butadiene ether is easy to generate polymerization reaction at higher temperature, and experiments prove that the byproduct isopentenol can generate condensation reaction with cis/trans-isopentenyl-3-methyl butadiene ether Claisen rearrangement reaction products 2,4, 4-trimethyl-3-formyl-1, 5-hexadiene and citral, so that the final yield is influenced.
Patent publication WO2008037693 describes optimization of citral production by simultaneously distilling off prenyl-3-methyl-butadiene ether and prenol, which are products after cracking cis/trans-prenyl-3-methyl-butadiene ether, to shorten the heating time of cis/trans-prenyl-3-methyl-butadiene ether, and then separating the two by rectification, but cis/trans-prenyl-3-methyl-butadiene ether in actual production usually contains a part of prenol which is not separated. And then, taking cis/trans-isopentenyl-3-methyl butadiene ether as a raw material to obtain citral through two-step rearrangement reaction. However, the method still has the following defects: 1. the rearrangement process is violent in heat release, reaction heat is difficult to remove by a common reactor, and safety accidents are easy to occur in the actual production process. 2. When the system contains alcohols, significant side reactions occur. The reaction is generally carried out at the temperature of more than 150 ℃, the reaction time is generally 20-40 min, the selectivity is 90% -97%, and the longer the reaction time is, the lower the product selectivity is.
Therefore, a new method for preparing citral is required to improve the selectivity and reaction rate of the product.
Disclosure of Invention
The patent aims to provide a method for preparing citral, which has high selectivity and high reaction rate.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a method for preparing citral uses cis/trans-isopentenyl-3-methyl butadiene ether as a raw material to obtain 2,4, 4-trimethyl-3-formyl-1, 5-hexadiene through a Claisen rearrangement reaction in the presence of an inhibitor, and then performs a Cope rearrangement reaction to obtain citral (3, 7-dimethyl-2, 6-octadiene-1-aldehyde). Cis/trans-prenyl-3-methyl-butadiene ether refers to cis-prenyl-3-methyl-butadiene ether and trans-prenyl-3-methyl-butadiene ether.
In the present invention, the inhibitor is an ester, particularly a hindered alcohol-derived ester, preferably a tert-butanol-derived ester and/or a trityl alcohol-derived ester, more preferably one or more of tert-butyl formate, tert-butyl acetate, tert-butyl isoamylene, trityl formate, trityl acetate and trityl isoamylene, and still more preferably tert-butyl formate and/or trityl formate. The inhibitor is used in an amount of 0.02 to 10mol%, preferably 0.5 to 5mo1 to 1%, based on the molar amount of the starting material to be rearranged.
In the present invention, the main side reaction is due to the presence of a small amount of alcohol (mainly prenol) in the reaction raw materials, in an amount of 0.1wt% to 20wt%, based on the total weight of the reaction raw materials. Alcohols react with raw materials or intermediate products to generate hemiacetals, acetals and other by-products, and in addition, because the raw material molecules have a plurality of double bonds, polymerization of the double bonds at high temperature is also one of the side reactions. The esters have the effect of inhibiting side reactions because the esters can perform transesterification with alcohols to generate new alcohols with higher steric hindrance, so that the side reactions are difficult to occur. In addition, the ester also reduces the concentration of carbon free radicals, carbon positive ions and the like in the system, and slows down the occurrence of polymerization reaction to a certain extent. The selectivity of the final product is obviously improved by selecting the esters which are optimized in the invention, the highest selectivity can reach 99%, and the reaction is mild and easy to control.
As a preferable technical scheme, the method for preparing the citral by using the microreactor and the micro heat exchanger system or the micro heat exchanger system strengthens heat and mass transfer by using the microreactor and the micro heat exchanger system and adds (side reaction) inhibitor to enable cis/trans-isopentenyl-3-methyl butadiene ether to generate Claisen rearrangement and Cope rearrangement, so that the citral is quickly and highly selectively obtained.
Compared with the traditional reactor, the micro-reactor and the micro-heat exchanger system or the micro-heat exchanger system adopted by the invention have the advantages that the channel sizes of the micro-reactor and the micro-heat exchanger are in the micrometer to millimeter level, and the micro-reactor and the micro-heat exchanger have larger specific surface areas and smaller volumes. On the premise of ensuring better mixing effect, the larger specific surface area ensures better heat transfer effect; the smaller volume makes the reaction liquid in the equipment small, thereby reducing the accident risk.
In the invention, the micro-reactor and micro-heat exchanger system consists of a feeding pump, a preheating pipeline, a micro-reactor, a micro-heat exchanger and a time delay pipeline, and the micro-heat exchanger system consists of a feeding pump, a preheating pipeline, a micro-heat exchanger and a time delay pipeline. The reaction process is as follows: the raw material enters a preheating pipeline through a feeding pump, preheated raw material liquid and an inhibitor are simultaneously and respectively pumped into the microreactor, and the raw material liquid and the inhibitor are fully mixed in the microreactor and then stay for a short time and then enter the micro-heat exchanger, or preheated mixed liquid directly enters the micro-heat exchanger. The micro heat exchanger removes most of reaction heat and then enters a delay pipeline section, and after the delay pipeline section keeps a certain temperature and residence time, reaction liquid is decompressed and cooled by a decompression valve and then enters a product storage tank. The feeding flow of the feeding pump is 1-100 mL/min, and the tolerance pressure is 0.1-15 MPa (absolute pressure). The length of the preheating pipeline is 0.5-20 m, and the inner diameter is 1-8 mm. The flow rate of the micro-reactor is 0.5-70 mL/min, the withstand pressure is 0.1-3 MPa (absolute pressure), and the residence time is 0.1-5 s. The flow rate of the micro heat exchanger is 0.5-50 mL/min, the withstand pressure is 0.1-50 MPa (absolute pressure), and the residence time is 0.1-60 s. The length of the delay pipeline is 0.5-100 m, and the inner diameter is 1-8 mm.
In the invention, the temperature of the constant-temperature circulating bath outside the preheating pipeline is 150-220 ℃, the temperature of the constant-temperature circulating bath outside the microreactor is 180-300 ℃, the temperature of the constant-temperature circulating bath outside the micro-heat exchanger is 120-180 ℃, and the temperature of the constant-temperature circulating bath outside the delay pipeline is 150-220 ℃. The residence time of the whole reaction process is 1-15 min, preferably 4-8 min.
In the invention, the inhibitor is added by respectively pumping the preheated raw materials into the micro-reactor and the micro-heat exchanger or the micro-heat exchanger. The reason for this is: the reaction rate of the preheated raw materials is obviously accelerated, the heat release is severe, the pumped inhibitor absorbs part of the reaction heat, and in addition, the added inhibitor has the effects of slowing down the reaction rate and reducing the heat release peak value. The reason is that the raw material firstly undergoes a Claisen rearrangement reaction, an electron-withdrawing group is arranged in the molecule of the raw material to facilitate the reaction, and the added ester inhibitors, particularly tert-butyl formate and trityl formate disperse the electronegativity of oxygen atoms in the raw material molecule to reduce the electron cloud density, so that the reaction rate is slowed down, and the reaction can be better controlled.
In the invention, the reaction raw material is cis/trans-isopentenyl-3-methyl butadiene ether or cis/trans-isopentenyl-3-methyl butadiene ether solution with the concentration of 10-99 wt%, preferably cis/trans-isopentenyl-3-methyl butadiene ether.
In the present invention, the solvent of the cis/trans-isopentenyl-3-methylbutadiene ether solution is inert aliphatic alkane, aromatic hydrocarbon, ether, halogenated alkane, etc. which do not react with the raw material, such as n-heptane, toluene, 1, 2-dichloroethane, 1, 4-dioxane, etc.
In the invention, the structural formulas of the cis/trans-isopentenyl-3-methylbutadiene ether are (Ia) and (Ib), the structural formula of the 2,4, 4-trimethyl-3-formyl-1, 5-hexadiene is (II), and the structural formula of the citral (3, 7-dimethyl-2, 6-octadiene-1-aldehyde) is (III).
The invention has the positive effects that: the invention provides a method for preparing citral with high selectivity and high speed, wherein specific esters are added in raw materials to serve as side reaction inhibitors and play a role in regulating reaction rate. The selectivity of the product is obviously improved by selecting inhibitors and optimizing reaction conditions (mainly feeding sequence). The selectivity reaches 95-99%, preferably 97-99%, and the reaction time is shortened to 1-15 min. In the preferred scheme, the whole process is carried out in a micro reactor and/or a micro heat exchanger system, and the heat and mass transfer effects are enhanced, so that the whole reaction time is further shortened to 4-8 min, and the side reaction time is shortened.
Detailed Description
The method according to the invention will be further illustrated by the following examples, but the invention is not limited to the examples listed, but also encompasses any other known modification within the scope of the claims of the invention.
Gas chromatograph: agilent7820A, column HP-5(30 m.times.320. mu.m.times.0.25 μm), injection port temperature: 150 ℃; the split ratio is 50: 1; carrier gas flow: 1.5 ml/min; temperature rising procedure: keeping at 40 deg.C for 1min, heating to 90 deg.C at 10 deg.C/min for 0min, heating to 160 deg.C at 5 deg.C/min for 0min, heating to 280 deg.C at 30 deg.C/min for 6 min. Detector temperature: 280 ℃.
Micro-reactor and micro-heat exchanger: purchased from Dalian Mikay chemical Co.
The type of the microreactor is as follows: CPMM-R300-so
The type of the micro heat exchanger is as follows: HX204
EXAMPLE 1 preparation of cis/trans-isopentenyl-3-methylbutadiene ether
774g of isopentenol (about 9mol), 84g of isopentenal (about 1mol) and 1.15g of phosphoric acid (85 mass percent, about 0.01mol) are added into a tower kettle of a rectifying tower, the number of theoretical plates of the rectifying tower is 9, the temperature of the tower bottom is 110 ℃, the vacuum degree of the tower top is 5KPa, the reflux ratio is 1: 10, collecting the isopentenol and water at the top of the tower, heating the bottom of the tower for 5 hours, and stopping heating when the top of the tower almost has no reflux. The product obtained at the bottom of the tower is isopentenol-condensed isopentenal, and the content of acetal is detected by gas phase to be 99%. Heating the tower kettle to 150 ℃, keeping the vacuum degree at the top of the tower at 2KPa, and keeping the reflux ratio at 1: 3, collecting cis/trans-isopentenyl-3-methyl butadiene ether and isopentenol from the tower top. And (3) distilling the tower top liquid under reduced pressure, wherein the external temperature of the reduced pressure distillation is 90 ℃, and the pressure is 200Pa, and the prenol is distilled out to obtain cis/trans-prenyl-3-methyl butadiene ether, wherein the content of the prenol is 2.5%.
Example 2
The length of the preheating pipe of the microreactor is 0.5m, the inner diameter of the preheating pipe is 1mm, and the temperature of the constant-temperature circulating bath outside the preheating pipe is 180 ℃. The temperature of the constant-temperature circulating bath outside the micro-reactor is 200 ℃, and the temperature of the constant-temperature circulating bath outside the micro-heat exchanger is 120 ℃. The length of the delay line is 6m and the inner diameter is 4 mm. The temperature of the constant temperature circulating bath outside the delay line is 180 ℃. Raw materials (the mass content of cis/trans-isopentenyl-3-methyl butadiene ether is 97 percent, the content of isopentenol is 2.5 percent) are fed through a preheating pipeline at the speed of 15mL/min, tert-butyl formate and the raw materials with the amount of 0.5mo1 percent are pumped into a microreactor simultaneously and respectively, and the tert-butyl formate flows through a micro-heat exchanger and a time-delay pipeline (the pressure after the micro-heat exchanger is 0.15MPa, and the residence time of reaction liquid in the microreactor and the micro-heat exchanger is 4s and 60s respectively). And sampling after the system runs stably for 2 h. The conversion rate of the raw materials is 85 percent, the selectivity is 97 percent, and the reaction residence time is 8 min.
Example 3
The length of the preheating pipe of the micro heat exchanger is 0.5m, the inner diameter is 1mm, the temperature of the constant-temperature circulating bath outside the preheating pipe is 200 ℃, the reaction liquid directly enters the micro heat exchanger, and the temperature of the constant-temperature circulating bath outside the micro heat exchanger is 150 ℃. The length of the delay line is 6m and the inner diameter is 4 mm. The temperature of the constant temperature circulating bath outside the delay line is 180 ℃. Raw materials (the mass content of cis/trans-isopentenyl-3-methyl butadiene ether is 97 percent, the content of isopentenol is 2.5 percent) are fed at the speed of 20mL/min and pass through a preheating pipeline, tert-butyl acetate and the raw materials are pumped into a micro heat exchanger at the same time and respectively according to the amount of 2.0mo1 percent of the raw materials, and then enter a delay pipeline (the pressure behind the micro heat exchanger is 0.2MPa, and the residence time of reaction liquid in the micro reactor and the micro heat exchanger is 3s and 45s respectively). And sampling after the system runs stably for 2 h. The conversion rate of the raw materials is 95%, the selectivity is 95%, and the reaction residence time is 6 min.
Example 4
The length of the preheating pipe of the microreactor is 1.0m, the inner diameter of the preheating pipe is 1mm, and the temperature of the constant-temperature circulating bath outside the preheating pipe is 220 ℃. The temperature of the constant-temperature circulating bath outside the micro-reactor is 250 ℃, and the temperature of the constant-temperature circulating bath outside the micro-heat exchanger is 150 ℃. The length of the delay line is 6m and the inner diameter is 4 mm. The temperature of the constant temperature circulating bath outside the delay line is 180 ℃. Raw materials (cis/trans-isopentenyl-3-methyl butadiene ether with the mass content of 19 percent, isopentenol with the mass content of 0.5 percent, a diluting solvent of n-heptane and n-heptane with the mass content of 79 percent) are fed at the speed of 30mL/min and pass through a preheating pipeline, tert-butyl isopentene with the amount of 10mo1 percent of the raw materials and the raw materials are simultaneously and respectively pumped into a microreactor, and sequentially pass through the microreactor, a micro heat exchanger and a time delay pipeline (the pressure after the micro heat exchanger is 0.3MPa, and the residence time of reaction liquid in the microreactor and the micro heat exchanger is respectively 2s and 30 s). And sampling after the system runs stably for 2 h. The conversion rate of the raw materials is 93 percent, the selectivity is 98 percent, and the reaction residence time is 4 min.
Example 5
The length of the preheating pipe of the microreactor is 0.5m, the inner diameter of the preheating pipe is 1mm, and the temperature of the constant-temperature circulating bath outside the preheating pipe is 180 ℃. The temperature of the constant temperature circulating bath outside the micro-reactor is 250 ℃, and the temperature of the constant temperature circulating bath outside the micro-heat exchanger is 170 ℃. The length of the delay line was 3m and the inner diameter was 4 mm. The temperature of the constant temperature circulating bath outside the delay line is 200 ℃. Raw materials (the mass content of cis/trans-isopentenyl-3-methyl butadiene ether is 97 percent, the content of isopentenol is 2.5 percent) are fed at the speed of 15mL/min and pass through a preheating pipeline, trityl formate and the raw materials are pumped into a microreactor at the same time and respectively in the amount of 3.0mo1 percent of the raw materials, and the raw materials sequentially pass through the microreactor, a micro heat exchanger and a time delay pipeline (the pressure behind the micro heat exchanger is 0.15MPa, and the residence time of reaction liquid in the microreactor and the micro heat exchanger is 4s and 60s respectively). And sampling after the system runs stably for 2 h. The conversion rate of the raw materials is 99.9 percent, the selectivity is 99 percent, and the reaction residence time is 5 min.
Example 6
The length of the preheating pipe of the microreactor is 0.5m, the inner diameter of the preheating pipe is 1mm, and the temperature of the constant-temperature circulating bath outside the preheating pipe is 180 ℃. The temperature of the constant-temperature circulating bath outside the micro-reactor is 250 ℃, and the temperature of the constant-temperature circulating bath outside the micro-heat exchanger is 150 ℃. The length of the delay line is 12m, and the inner diameter is 4 mm. The temperature of the constant temperature circulating bath outside the delay line is 200 ℃. Raw materials (the mass content of cis/trans-isopentenyl-3-methyl butadiene ether is 97 percent, the content of isopentenol is 2.5 percent) are fed at the speed of 50mL/min and pass through a preheating pipeline, the triphenylmethyl isopentenyl acid and the raw materials are pumped into a microreactor at the same time and respectively in the amount of 5.0mo1 percent of the raw materials, and sequentially pass through the microreactor, a micro heat exchanger and a time delay pipeline (the pressure behind the micro heat exchanger is 0.45MPa, and the residence time of reaction liquid in the microreactor and the micro heat exchanger is 1.2s and 18s respectively). And sampling after the system runs stably for 2 h. The conversion rate of the raw materials is 97 percent, the selectivity is 97 percent, and the reaction residence time is 5 min.
Example 7
The length of the preheating pipe of the microreactor is 1.0m, the inner diameter of the preheating pipe is 1mm, and the temperature of the constant-temperature circulating bath outside the preheating pipe is 220 ℃. The temperature of the external constant-temperature circulating bath of the micro-reactor is 270 ℃, and the temperature of the external constant-temperature circulating bath of the micro-heat exchanger is 160 ℃. The length of the delay line is 6m and the inner diameter is 4 mm. The temperature of the constant-temperature circulating bath outside the delay line is 220 ℃. Raw materials (the mass content of cis/trans-isopentenyl-3-methyl butadiene ether is 98 percent, the content of isopentenol is 1.5 percent) are fed through a preheating pipeline at the speed of 35mL/min, tert-butyl formate is pumped into a microreactor, a micro-heat exchanger and a delay pipeline respectively at the same time with the raw materials by the amount of 2.0mo1 percent of the raw materials (the pressure behind the micro-heat exchanger is 0.32MPa, and the residence time of reaction liquid in the microreactor and the micro-heat exchanger is 1.7s and 26s respectively). And sampling after the system runs stably for 2 h. The conversion rate of the raw materials is 99.5 percent, the selectivity is 98 percent, and the reaction residence time is 4 min.
Example 8
The tubular reactor is placed in an oil bath of a reaction kettle to be heated to 210 ℃, the rotating speed of the reaction kettle is 500r/min to enhance heat transfer, and the outer diameter of the coil is 8mm, the inner diameter of the coil is 6mm, and the total diameter is 10 m. The reaction liquid outlet is quenched by using condensed water. The trityl formate was mixed with the raw material (cis/trans-isopentenyl-3-methylbutadiene ether content 98% by mass, isopentenol content 1.5%) in an amount of 1.5mo 1% and fed through the tubular reactor at a rate of 50mL/min, and the system was operated stably for 2 hours and then sampled. The conversion rate of the raw materials is 79.5 percent, the selectivity is 95 percent, and the reaction residence time is 23 min.
COMPARATIVE EXAMPLE 1 (COMPARATIVE WITH EXAMPLE 2)
The length of the preheating pipe of the microreactor is 0.5m, the inner diameter of the preheating pipe is 1mm, and the temperature of the constant-temperature circulating bath outside the preheating pipe is 180 ℃. The temperature of the constant-temperature circulating bath outside the micro-reactor is 200 ℃, and the temperature of the constant-temperature circulating bath outside the micro-heat exchanger is 120 ℃. The length of the delay line is 6m and the inner diameter is 4 mm. The temperature of the constant temperature circulating bath outside the delay line is 180 ℃. Raw materials (the mass content of cis/trans-isopentenyl-3-methyl butadiene ether is 97 percent, the content of isopentenol is 2.5 percent) are fed at the speed of 15mL/min and pass through a preheating pipeline, then are pumped into a microreactor, and flow through a micro-heat exchanger and a delay pipeline (the pressure after the micro-heat exchanger is 0.15MPa, and the residence time of reaction liquid in the microreactor and the micro-heat exchanger is 4s and 60s respectively). And sampling after the system runs stably for 2 h. The conversion rate of the raw materials is 89%, the selectivity is 91%, and the reaction residence time is 8 min.
COMPARATIVE EXAMPLE 2 (COMPARATIVE WITH EXAMPLE 6)
The length of the preheating pipe of the microreactor is 0.5m, the inner diameter of the preheating pipe is 1mm, and the temperature of the constant-temperature circulating bath outside the preheating pipe is 180 ℃. The temperature of the constant-temperature circulating bath outside the micro-reactor is 250 ℃, and the temperature of the constant-temperature circulating bath outside the micro-heat exchanger is 150 ℃. The length of the delay line is 12m, and the inner diameter is 4 mm. The temperature of the constant temperature circulating bath outside the delay line is 200 ℃. The method comprises the steps of mixing 5.0mo 1% of triphenylmethyl isopentenyl acid with raw materials (the mass content of cis/trans-isopentenyl-3-methyl butadiene ether is 97%, and the content of isopentenyl alcohol is 2.5%), feeding the mixture at the speed of 50mL/min to pass through a preheating pipeline, and sequentially passing through a microreactor, a micro-heat exchanger and a time delay pipeline (the pressure behind the micro-heat exchanger is 0.45MPa, and the residence time of reaction liquid in the microreactor and the micro-heat exchanger is 1.2s and 18s respectively). And sampling after the system runs stably for 2 h. The conversion rate of the raw materials is 91 percent, the selectivity is 94 percent, and the reaction residence time is 5 min.
COMPARATIVE EXAMPLE 3 (COMPARATIVE WITH EXAMPLE 8)
The tubular reactor is placed in an oil bath of a reaction kettle to be heated to 210 ℃, the rotating speed of the reaction kettle is 500r/min to enhance heat transfer, and the outer diameter of the coil is 8mm, the inner diameter of the coil is 6mm, and the total diameter is 10 m. The reaction liquid outlet is quenched by using condensed water. Raw materials (cis/trans-isopentenyl-3-methyl butadiene ether content 98% by mass and isopentenol content 1.5%) are fed through a tubular reactor at a rate of 50mL/min, and a sample is taken after the system is stably operated for 2 hours. The conversion rate of the raw materials is 85.7 percent, the selectivity is 89 percent, and the reaction residence time is 23 min.
Claims (12)
1. The method for preparing the citral is characterized in that cis/trans-isopentenyl-3-methyl butadiene ether is used as a raw material and undergoes Claisen rearrangement and Cope rearrangement reactions in the presence of an inhibitor to obtain the citral; the inhibitor is tert-butyl alcohol derivative ester and/or triphenyl methanol derivative ester sterically hindered alcohol derivative ester; the rearrangement reaction is carried out in a microreactor and a micro-heat exchanger system or in a micro-heat exchanger system.
2. The method of claim 1, wherein the inhibitor is one or more of t-butyl formate, t-butyl acetate, t-butyl isovalerate, trityl formate, trityl acetate, and trityl isovalerate.
3. The method according to claim 1, wherein the inhibitor is used in an amount of 0.02 mol% to 10mol% based on the molar amount of the reaction raw materials.
4. The process according to claim 1, characterized in that the inhibitor is used in an amount of 0.5mo1% to 5mo1% based on the molar amount of the reaction starting materials.
5. The method of claim 1 wherein the microreactor and the micro-heat exchanger system are comprised of a feed pump, preheat lines, microreactor and micro-heat exchanger, time delay lines; the micro heat exchanger system consists of a feed pump, a preheating pipeline, a micro heat exchanger and a delay pipeline; the raw materials enter a preheating pipeline through a feeding pump, the preheated raw materials and the inhibitor are simultaneously and respectively pumped into the microreactor and then enter a micro heat exchanger, or the preheated raw materials and the inhibitor are simultaneously and respectively pumped into the micro heat exchanger, then the mixed liquid enters a delay pipeline section, and finally the reaction liquid flows out from the delay pipeline to obtain the product.
6. The method of claim 5, wherein: the temperature of the external constant-temperature circulating bath of the preheating pipeline is 150-220 ℃, the temperature of the external constant-temperature circulating bath of the microreactor is 180-300 ℃, the temperature of the external constant-temperature circulating bath of the micro-heat exchanger is 120-180 ℃, and the temperature of the external constant-temperature circulating bath of the delay pipeline is 150-220 ℃.
7. The method of claim 5, wherein: the residence time of the whole reaction process is 1-15 min.
8. The method of claim 7, wherein: the residence time of the whole reaction process is 4-8 min.
9. The method of claim 1, wherein: the content of the prenol in the cis/trans-isopentenyl-3-methyl butadiene ether serving as the reaction raw material is 0.1-20 wt%, based on the total weight of the raw materials.
10. The method according to claim 1 or 9, characterized in that: the cis/trans-isopentenyl-3-methyl butadiene ether is a cis/trans-isopentenyl-3-methyl butadiene ether solution with the concentration of 10wt% -99 wt%.
11. The method of claim 10, wherein: the solvent of the cis/trans-isopentenyl-3-methyl butadiene ether solution is one or more of inert aliphatic alkane, aromatic hydrocarbon, ether and alkyl halide which do not react with the cis/trans-isopentenyl-3-methyl butadiene ether.
12. The method of claim 11, wherein: the solvent of the cis/trans-isopentenyl-3-methylbutadiene ether solution is one or more of n-heptane, toluene, 1, 2-dichloroethane and 1, 4-dioxane.
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| CN111018682A (en) * | 2019-12-17 | 2020-04-17 | 南通天泽化工有限公司 | Preparation method of citral |
| CN111807936B (en) * | 2020-07-22 | 2022-11-08 | 万华化学集团股份有限公司 | Preparation method of prenyl isopentenyl ether |
| CN112225655B (en) * | 2020-09-10 | 2024-02-27 | 万华化学集团营养科技有限公司 | Preparation method of citral |
| CN112574018B (en) * | 2020-11-30 | 2022-07-12 | 万华化学集团股份有限公司 | Low-color-number citral and preparation method thereof |
| CN112574015B (en) * | 2020-12-11 | 2022-09-20 | 万华化学集团股份有限公司 | Method for preparing cyclocitral from C10 unsaturated aldehyde rectifying tower bottoms |
| CN114133321A (en) * | 2021-12-06 | 2022-03-04 | 万华化学集团股份有限公司 | Preparation method of citral |
| CN114773168B (en) * | 2022-04-28 | 2024-08-13 | 江苏宏邦化工科技有限公司 | Method for synthesizing cis/trans-prenyl-3-methyl butadiene ether by using methyl butynol and isopentenol |
| CN115160113B (en) * | 2022-07-06 | 2024-10-18 | 江苏宏邦化工科技有限公司 | Method for simultaneously synthesizing two citral intermediates |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4288636A (en) * | 1979-06-30 | 1981-09-08 | Basf Aktiengesellschaft | Preparation of citral |
| CN1255480A (en) * | 1998-10-07 | 2000-06-07 | Basf公司 | Process for preparing citral |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4288636A (en) * | 1979-06-30 | 1981-09-08 | Basf Aktiengesellschaft | Preparation of citral |
| CN1255480A (en) * | 1998-10-07 | 2000-06-07 | Basf公司 | Process for preparing citral |
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