Preparation method of citral

Abstract

The invention discloses a preparation method of citral. The preparation method comprises the following steps: reacting 3-methyl-2-butene-1-aldehyde diisopentenyl acetal in a film cracking reactor with a nitrogen gas stripping function to obtain prenyl alcohol and prenyl isopentenyl ether, adding a mixture of the prenyl alcohol and the prenyl isopentenyl ether into a reactive rectifying tower, continuously extracting the prenyl alcohol from the top of the tower and continuously extracting from the citral from the bottom of the tower. According to the method, the residence time of an intermediate under high-temperature and acidic conditions can be remarkably shortened, byproducts are reduced, and the citral selection performance can be more than 98%.

Description

technical field [0001] The invention relates to a preparation method of citral. Background technique [0002] Citral exists in essential oils such as lemongrass oil and eucalyptus oil, and has a strong lemon aroma. It is widely used in the food industry and daily chemicals. More importantly, citral is the main raw material for the synthesis of ionone, and it is also an important raw material for the production of vitamin E, vitamin A, isophytol or β-citronone. A natural spice with broad application prospects. [0003] The synthesis methods of citral generally include the following: alcohol and aldehyde condensation, rearrangement method, dehydrolinalool direct rearrangement method, geraniol gas phase oxidation method, isoprene method, acetone method and nitrogen oxide method. [0004] Alcohol and aldehyde condensation and rearrangement method: This method first condenses prenyl alcohol and prenyl aldehyde to generate 3-methyl-2-butene-1-aldehyde di-prenyl acetal, and then ...

AI Technical Summary

Problems solved by technology

The disadvantages of this patent are: 1. 3-methyl-2-butene-1-aldehyde di-isopentenyl acetal is used in a large amount; 2. The amount of phosphoric acid is small, the control is difficult, and it is difficult to carry out continuous production

[0010] 1. The side stream production fluid contains citral. Because citral is unstable under acidic conditions, it is prone to polymerization reaction, and the residence time is 5min-2h. If the reaction time is too long, the selectivity of the reaction will be affected;

[0011] 2. The content of citral and intermediates in the side stream production fluid is greatly affected by the catalyst concentration, pressure and temperature changes of the reaction device, and the composition of the reaction liquid is prone to fluctuations that affect the residence time of subsequent rearrangement reactions, resulting in low conversion rates of intermediates or Decreased selectivity of citral;

[0012] 3. Since the cleavage reaction of 3-methyl-2-butene-1-aldehyde di-prenyl acetal is a first-order reaction, if prenyl alcohol and prenyl isopentenyl ether reaction product cannot be obtained from Timely removal in the reaction system will reduce the concentration of 3-methyl-2-butene-1-aldehyde di-isopentenyl acetal, making 3-methyl-2-butene-1-aldehyde diisoamyl acetal The rate of cleavage reaction of pentenyl acetal decreases

[0015] 1. For the preparation of citral by gas phase cracking, the preparation of the catalyst used in the fixed bed is cumbersome and needs to be replaced frequently; Lithium chloride is used as a catalyst, which is highly corrosive;

[0016] 2. When the side line is used for extraction, the rectification tower needs more plates. At the same time, because the intermediate extracted from the side line is a mixture, its composition is greatly affected by the catalyst concentration, the operating pressure and temperature of the rectification tower. Continuous production process It is easy to cause the conversion rate of intermediates to be low or the selectivity of citral to decrease;

[0017] 3. Citral is unstable under acidic conditions. Due to the use of reactors such as kettles, the residence time is too long, which will also affect the reaction selectivity

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