A method for separating and extracting citral with high selectivity

Abstract

The invention discloses a method for highly selectively separating and extracting citral, belonging to the fields of biomedicine, food and chemical industry. The present invention adds chitosan powder to litsea cubeba oil or lemongrass oil, heats and stirs, and waits for the solid to become a stable yellow, i.e. obtains chitosan-citral complex-litsea cubeba oil mixture or chitosan-citral complex-lemongrass oil mixture; the obtained mixture is filtered and washed, and the obtained filter residue is added to the acid solution and stirred for reaction, and the oily product is no longer increased, and stirring is stopped, and the upper oily substance is taken after oil-water stratification, and high-purity citral is obtained after dehydration and drying. The purity of citral after purification of the present invention is greater than 92.0%, and the method has low energy consumption and mild conditions, and can replace traditional distillation and rectification methods under high temperature and high negative pressure conditions, and the production and preparation cost of citral can be greatly reduced, and the main reaction involved does not need a solvent, and the overall use amount of the solvent is small, and the chitosan and acid solution used can be repeatedly recycled.

Description

Technical Field

[0001] The invention belongs to the fields of biomedicine, food and chemical industry, and particularly relates to a method for separating and extracting citral with high selectivity. Background Art

[0002] The configuration of natural citral mainly includes α-citral (nerol) and β-citral (geranial), and its sources are mainly lemongrass oil and litsea cubeba oil. Lemongrass is widely planted in tropical areas, and its stems and leaves can be used to extract lemongrass oil for making perfumes and soaps, and it can also be eaten. Litsea cubeba is a kind of forest-source spice plant unique to my country, with abundant resources. The content of natural citral in lemongrass oil and litsea cubeba oil can be as high as 70% or more. Therefore, the development and utilization of natural citral is of great significance for improving the resource utilization rate and added value of lemongrass and litsea cubeba. Citral has broad application prospects in the fields of food, daily chemicals, medicine, etc., and has multiple functions such as flavoring, antibacterial and pheromone. Citral is volatile and has active chemical properties. It is easy to undergo redox reactions to generate substances such as geranic acid or geraniol / nerol. At present, the extraction and separation of citral is mainly a vacuum distillation separation method, which has high equipment investment and high energy consumption. It generally requires high temperature conditions and is easy to cause it to deteriorate. In addition, there are also methods such as organic solvent extraction and supercritical extraction, and the overall preparation cost is high. Therefore, there is a great industrial technology demand for a method to achieve efficient separation of citral at medium to low temperature and normal pressure.

[0003] Chitosan (CTS) is widely available and inexpensive. It is a cationic alkaline amino polysaccharide with good biocompatibility, non-toxicity, non-antigenicity and biodegradability. It is currently widely used in various industries such as medicine, food, feed additives and daily chemicals. Chitosan also has multiple biological activities such as antibacterial, antiviral and anti-tumor. The amino group on chitosan can react with the aldehyde group on citral to form a water-insoluble chitosan-citral complex, which can be further decomposed into chitosan and citral under certain acidic conditions. Utilizing this property, Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the present invention proposes a method for highly selective separation and extraction of citral, the technology mainly comprising: utilizing chitosan to selectively react with citral in litsea cubeba oil or lemongrass oil through Schiff base reaction to generate a water-insoluble chitosan-citral complex precipitate, and then decomposing it with acid to release citral after separation, thereby achieving efficient and selective separation of citral.

[0005] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0006] A method for separating and extracting citral with high selectivity comprises the following steps: adding chitosan powder into litsea cubeba oil or lemongrass oil, heating and stirring, and waiting for the solid to turn into a stable yellow color to obtain a chitosan-citral complex-litsea cubeba oil mixture or a chitosan-citral complex-lemongrass oil mixture; filtering the obtained chitosan-citral complex-litsea cubeba oil mixture or the chitosan-citral complex-lemongrass oil mixture, washing the filter residue with a solvent for several times, adding the filter residue to an acid solution, stirring and reacting until the oily product no longer increases, taking out the upper oily substance after oil and water separation, and dehydrating and drying to obtain high-purity citral.

[0007] Furthermore, the particle size of the chitosan powder is 0.05 μm-200 μm.

[0008] Furthermore, the litsea cubeba oil is a volatile oil obtained by steam distillation of the fruit of the litsea cubeba; and the lemongrass oil is a volatile oil obtained by steam distillation of the leaves of lemongrass.

[0009] Furthermore, the mass ratio of litsea cubeba oil or lemongrass oil to chitosan is 5-100:1.

[0010] Furthermore, the heating and stirring is carried out at a temperature of 30-60°C and for a time of 2-24 hours.

[0011] Furthermore, the washing solvent is selected from one of ethanol, ethyl acetate and acetone; the pH value of the acid is 1-5 and is selected from hydrochloric acid, sulfuric acid, acetic acid, formic acid, citric acid or oxalic acid.

[0012] Furthermore, the method for separating citral with high selectivity comprises the following steps:

[0013] (1) slowly adding chitosan powder of 0.05 μm to 200 μm into litsea cubeba oil or lemongrass oil, and stirring the mixture under heating conditions of 30-60° C. for 2-24 hours, and obtaining a chitosan-citral complex-litsea cubeba oil mixture or a chitosan-citral complex-lemongrass oil mixture when the solid turns into a stable yellow color;

[0014] (2) The chitosan-citral complex-litsea cubeba oil mixture or chitosan-citral complex-lemongrass oil mixture obtained in the first step is filtered, and the filter residue is washed with a solvent for several times, and then the washed filter residue is slowly added to an acid solution with a pH value of 1-5, and the reaction is stirred for 0.1-6 hours at a reaction temperature of 20-60°C. When the oily product no longer increases, the stirring is stopped, and after the oil and water are separated, the upper layer of oil is taken, and high-purity citral is obtained after dehydration and drying.

[0015] Furthermore, high-purity citral is prepared by the above method.

[0016] Furthermore, the obtained citral includes α-citral and β-citral, and the purity of the citral is greater than 92.0%.

[0017] Compared with the prior art, the advantages of this application are:

[0018] 1) The present invention utilizes the reversibility of the Schiff base reaction to generate a water-insoluble chitosan-citral complex under solvent-free conditions, and obtains high-purity citral through precipitation, filtration, acid decomposition, stratification and other methods. The purity of the purified citral (including α-citral and β-citral) is greater than 92.0% (gas chromatography). The method has low energy consumption and mild conditions, and can replace traditional distillation and rectification methods under high temperature and high negative pressure conditions, and can greatly reduce the production and preparation cost of citral.

[0019] 2) The main reaction involved in the present invention does not require an organic solvent, the overall amount of solvent used is small, the chitosan and acid solution used can be recycled multiple times, the preparation method is simple, the process stability is good, and it can be applied to the fields of biomedicine, food, chemical industry, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the formation of chitosan-citral complex by Schiff base reaction and its acid decomposition;

[0021] Figure 2 The gas chromatographic analysis diagram of citral (including α-citral and β-citral) after separation and purification;

[0022] Among them, β-citral, retention time: 27.8668, area percentage: 45.05%; α-citral, retention time: 28.7808, area percentage: 51.22%, and the rest are other impurity peaks. DETAILED DESCRIPTION

[0023] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with specific embodiments.

[0024] Example 1

[0025] A method for highly selectively separating and extracting citral, the steps are as follows:

[0026] (1) Preparation of chitosan-citral complex-litsea cubeba oil mixture:

[0027] 1 g of chitosan powder with a particle size of 0.1 μm-10 μm was slowly added to 20 g of litsea cubeba oil, and the mixture was stirred and reacted at 45° C. for 12 h. When the solid material turned into a stable yellow color, a chitosan-citral complex-litsea cubeba oil mixture was obtained.

[0028] (2) Separation and purification of citral (derived from litsea cubeba oil):

[0029] 21 g of the chitosan-citral complex-litsea cubeba oil mixture obtained in step (1) was filtered, and the filter residue was washed with ethanol 5 times. The washed filter residue was then slowly added into a hydrochloric acid solution with a pH value of 2, and the reaction temperature was 35°C. After stirring for 1 hour, the oily product no longer increased, and the stirring was stopped. After the oil and water layers were separated, the upper layer of oil was absorbed, and after dehydration and drying, citral (including α-citral and β-citral, derived from litsea cubeba oil) with a purity of 97.1% (gas chromatography) was obtained.

[0030] Example 2

[0031] A method for highly selectively separating and extracting citral, the steps are as follows:

[0032] (1) Preparation of chitosan-citral complex-lemongrass oil mixture:

[0033] 1 g of chitosan powder with a particle size of 0.1 μm-10 μm was slowly added to 20 g of lemongrass oil, and the mixture was stirred and reacted at 50° C. for 12 h. When the solid turned into a stable yellow color, a chitosan-citral complex-lemongrass oil mixture was obtained.

[0034] (2) Isolation and purification of citral (derived from lemongrass oil):

[0035] 21 g of the chitosan-citral complex-lemongrass oil mixture obtained in step (1) was filtered, and the filter residue was washed three times with ethyl acetate. The washed filter residue was then slowly added into a sulfuric acid solution with a pH value of 2, and the reaction temperature was 30° C. After stirring for 1 hour, the oily product no longer increased, and the stirring was stopped. After the oil and water layers were separated, the upper oil was absorbed, and after dehydration and drying, citral (including α-citral and β-citral, derived from lemongrass oil) with a purity of 96.1% (gas chromatography) was obtained.

[0036] Example 3

[0037] A method for highly selectively separating and extracting citral, the steps are as follows:

[0038] (1) Preparation of chitosan-citral complex-litsea cubeba oil mixture:

[0039] 1 g of chitosan powder with a particle size of 10 μm-200 μm was slowly added to 5 g of litsea cubeba oil, and the mixture was stirred and reacted at 30° C. for 24 hours. When the solid matter turned into a stable yellow color, a chitosan-citral complex-litsea cubeba oil mixture was obtained.

[0040] (2) Separation and purification of citral (derived from litsea cubeba oil):

[0041] 6 g of the chitosan-citral complex-litsea cubeba oil mixture obtained in step (1) was filtered, and the filter residue was washed with acetone three times. The washed filter residue was then slowly added into an acetic acid solution with a pH value of 5, and the reaction temperature was 60° C. After stirring for 6 hours, the oily product no longer increased, and the stirring was stopped. After the oil and water layers were separated, the upper layer of oil was absorbed, and after dehydration and drying, citral (including α-citral and β-citral, derived from litsea cubeba oil) with a purity of 92.3% (gas chromatography) was obtained.

[0042] Example 4

[0043] A method for highly selectively separating and extracting citral, the steps are as follows:

[0044] (1) Preparation of chitosan-citral complex-lemongrass oil mixture:

[0045] 1 g of chitosan powder with a particle size of 10 μm-100 μm was slowly added to 5 g of lemongrass oil, and the mixture was stirred and reacted at 35° C. for 24 hours. When the solid matter turned into a stable yellow color, a chitosan-citral complex-lemongrass oil mixture was obtained.

[0046] (2) Isolation and purification of citral (derived from lemongrass oil):

[0047] 6 g of the chitosan-citral complex-lemongrass oil mixture obtained in step (1) was filtered, and the filter residue was washed three times with ethyl acetate. The washed filter residue was then slowly added into a formic acid solution with a pH value of 5, and the reaction temperature was 60° C. After stirring for 6 hours, the oily product no longer increased, and the stirring was stopped. After the oil and water layers were separated, the upper layer of oil was absorbed, and after dehydration and drying, citral (including α-citral and β-citral, derived from lemongrass oil) with a purity of 93.0% (gas chromatography) was obtained.

[0048] Example 5

[0049] A method for highly selectively separating and extracting citral, the steps are as follows:

[0050] (1) Preparation of chitosan-citral complex-litsea cubeba oil mixture:

[0051] 1 g of chitosan powder with a particle size of 0.1 μm-1 μm was slowly added to 100 g of litsea cubeba oil, and the mixture was stirred and reacted at 60° C. for 2 h. When the solid matter turned into a stable yellow color, a chitosan-citral complex-litsea cubeba oil mixture was obtained.

[0052] (2) Separation and purification of citral (derived from litsea cubeba oil):

[0053] 101 g of the chitosan-citral complex-litsea cubeba oil mixture obtained in step (1) was filtered, and the filter residue was washed three times with ethanol. The washed filter residue was then slowly added into a hydrochloric acid solution with a pH value of 1, and the reaction temperature was 20°C. After stirring for 0.1 h, the oily product no longer increased, and the stirring was stopped. After the oil and water layers were separated, the upper layer of oil was absorbed, and after dehydration and drying, citral (including α-citral and β-citral, derived from litsea cubeba oil) with a purity of 94.6% (gas chromatography) was obtained.

[0054] Example 6

[0055] A method for highly selectively separating and extracting citral, the steps are as follows:

[0056] (1) Preparation of chitosan-citral complex-lemongrass oil mixture:

[0057] 1 g of chitosan powder with a particle size of 0.1 μm-1 μm was slowly added to 100 g of lemongrass oil, and the mixture was stirred and reacted at 60° C. for 2 h. When the solid matter turned into a stable yellow color, a chitosan-citral complex-lemongrass oil mixture was obtained.

[0058] (2) Isolation and purification of citral (derived from lemongrass oil):

[0059] 101 g of the chitosan-citral complex-lemongrass oil mixture obtained in step (1) was filtered, and the filter residue was washed twice with ethyl acetate. The washed filter residue was then slowly added into a sulfuric acid solution with a pH value of 1, and the reaction temperature was 20° C. After stirring for 0.1 h, the oily product no longer increased, and the stirring was stopped. After the oil and water layers were separated, the upper oil was absorbed, and after dehydration and drying, citral (including α-citral and β-citral, derived from lemongrass oil) with a purity of 94.2% (gas chromatography) was obtained.

[0060] Example 7

[0061] A method for highly selectively separating and extracting citral, the steps are as follows:

[0062] (1) Preparation of chitosan-citral complex-litsea cubeba oil mixture:

[0063] 1 g of chitosan powder with a particle size of 0.1 μm-100 μm was slowly added to 40 g of litsea cubeba oil, and the mixture was stirred and reacted at 50° C. for 12 h. When the solid matter turned into a stable yellow color, a chitosan-citral complex-litsea cubeba oil mixture was obtained.

[0064] (2) Separation and purification of citral (derived from litsea cubeba oil):

[0065] 41 g of the chitosan-citral complex-litsea cubeba oil mixture obtained in step (1) was filtered, and the filter residue was washed three times with ethyl acetate. The washed filter residue was then slowly added into a citric acid solution with a pH value of 3, and the reaction temperature was 45°C. After stirring for 6 hours, the oily product no longer increased, and the stirring was stopped. After the oil and water layers were separated, the upper layer of oil was absorbed, and after dehydration and drying, citral (including α-citral and β-citral, derived from litsea cubeba oil) with a purity of 92.5% (gas chromatography) was obtained.

[0066] Example 8

[0067] A method for highly selectively separating and extracting citral, the steps are as follows:

[0068] (1) Preparation of chitosan-citral complex-lemongrass oil mixture:

[0069] 1 g of chitosan powder with a particle size of 0.1 μm-100 μm was slowly added to 50 g of lemongrass oil, and the mixture was stirred and reacted at 40° C. for 16 h. When the solid matter turned into a stable yellow color, a chitosan-citral complex-lemongrass oil mixture was obtained.

[0070] (2) Isolation and purification of citral (derived from lemongrass oil):

[0071] 51 g of the chitosan-citral complex-lemongrass oil mixture obtained in step (1) was filtered, and the filter residue was washed twice with acetone. The washed filter residue was then slowly added to an oxalic acid solution with a pH value of 2, and the reaction temperature was 40° C. After stirring for 2 hours, the oily product no longer increased, and the stirring was stopped. After the oil and water layers were separated, the upper layer of oil was absorbed, and after dehydration and drying, citral (including α-citral and β-citral, derived from lemongrass oil) with a purity of 94.6% (gas chromatography) was obtained.

[0072] In summary, the highly selective separation and extraction method of citral of the present invention utilizes chitosan to selectively react with citral in litsea cubeba oil or lemongrass oil, through Schiff base reaction, to generate water-insoluble chitosan-citral complex precipitation, and then releases citral through acid decomposition after separation, thereby achieving efficient and selective separation of citral. This technology has the characteristics of mild separation conditions, recyclable materials, low solvent content, and high purity of the obtained product.

Claims

1. A method for separating and extracting citral, characterized in that, Adding chitosan powder with a particle size of 0.05 μm-200 μm into litsea cubeba oil or lemongrass oil, heating and stirring, and waiting for the solid to turn into a stable yellow color to obtain a chitosan-citral complex-litsea cubeba oil mixture or a chitosan-citral complex-lemongrass oil mixture; filtering the obtained chitosan-citral complex-litsea cubeba oil mixture or the chitosan-citral complex-lemongrass oil mixture, washing the filter residue with a solvent for several times, adding it to an acid solution, stirring and reacting until the oily product no longer increases, taking out the upper layer of oil after oil and water are separated, and dehydrating and drying to obtain citral; the citral includes α-citral and β-citral, and the purity of the citral is greater than 92.0%; The mass ratio of the litsea cubeba oil or lemongrass oil to chitosan is 5-100:1; the heating and stirring temperature is 30-60°C and the time is 2-24 hours; the washing solvent is selected from one of ethanol, ethyl acetate and acetone; the pH value of the acid is 1-5 and is selected from hydrochloric acid, sulfuric acid, acetic acid, formic acid, citric acid or oxalic acid.

2. The method for separating and extracting citral according to claim 1, wherein The litsea cubeba oil is a volatile oil obtained by steam distillation of the fruit of the litsea cubeba; and the lemongrass oil is a volatile oil obtained by steam distillation of the leaves of the lemongrass.

3. The method for separating and extracting citral according to any one of claims 1 to 2, characterized in that: Here are the steps: (1) slowly adding chitosan powder of 0.05 μm to 200 μm into litsea cubeba oil or lemongrass oil, and stirring the mixture under heating conditions of 30-60° C. for 2-24 hours, and obtaining a chitosan-citral complex-litsea cubeba oil mixture or a chitosan-citral complex-lemongrass oil mixture when the solid turns into a stable yellow color; (2) Filter the chitosan-citral complex-litsea cubeba oil mixture or chitosan-citral complex-lemongrass oil mixture obtained in the first step, wash the filter residue with a solvent for several times, then slowly add the washed filter residue into an acid solution with a pH value of 1-5, stir and react for 0.1-6h, the reaction temperature is 20-60°C, and the stirring is stopped when the oily product no longer increases. After the oil and water are separated, the upper layer of oil is taken and citral is obtained after dehydration and drying.

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