Method for efficiently and simultaneously synthesizing dipentene and isoterpinene

Abstract

The invention belongs to the technical field of organic synthesis, and particularly discloses a method for efficiently and simultaneously synthesizing dipentene and isoterpinene, which comprises the following steps of: adding alpha-pinene, an acid catalyst and an alkaline auxiliary agent into a reaction kettle according to a ratio for heating reaction, and after the reaction, directly rectifying to obtain dipentene and isoterpinene finished products. The raw material alpha-pinene used in the method is easy to obtain and low in price, and both acid and alkali are mainstream raw materials in the market, so that the production cost is greatly reduced. According to the method, the raw material conversion rate is high, the selectivity is good, the alpha-pinene conversion rate is 100%, the dipentene selectivity is 60%, the isoterpinene selectivity is 30%, and the effective yield is high. And after the rectification is finished, the catalyst and the auxiliary agent are left in kettle residues and can be applied to the next batch of reaction.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, relates to the synthesis of dipentene and terpinene, and particularly relates to a method for simultaneously and efficiently synthesizing dipentene and terpinene. Background Art

[0002] Carvacrol, also known as 2-paracymene, isothymol, isothymol, and p-isopropyl-o-cresol, is found naturally in thyme oil (approximately 70%), oregano oil (approximately 80%), and sweet oregano oil. It is a colorless to pale yellow, slightly viscous oil. As a commonly used food additive and fragrance, it is low-toxic and natural, and has been approved as a safe food additive in the United States and Europe. Natural carvacrol is primarily found in various plants of the Lamiaceae family, such as thyme and oregano. Carvacrol has a wide range of functions and applications. It inhibits the growth of bacteria, yeasts, fungi, insects, and mites by altering the cell membrane structure or mycelium structure of pathogenic bacteria, or by effectively inhibiting conidia activity, exhibiting excellent antibacterial and insecticidal effects. It is also an active ingredient in thyme that promotes blood circulation and removes blood stasis, and activates platelets by mediating the signaling pathway of antihistamines via the G13 protein-linked RhoA / Rho-kinase. These effects make it widely used as a natural antibacterial preservative in food, medicine, cosmetics and other products.

[0003] In industry, dipentene is often used as a raw material. Carveol is obtained through epoxidation and ring opening, followed by orphenamine oxidation to carvone, and finally acidic rearrangement to carvacrol. Therefore, how to efficiently synthesize dipentene has always been a hot topic for researchers.

[0004]

[0005] Terpinene is a monoterpene compound and an isomer of dipentene. Terpinene has a refreshing woody, pine-like, and slightly floral aroma and is commonly used in perfumes, essential oils, and air fresheners. It is also used in soaps, shampoos, and skincare products to provide fragrance and enhance cleaning. It is also added to insect repellents to repel mosquitoes. Studies have shown that terpinene has inhibitory effects on certain bacteria and fungi, making it useful as an antibacterial and preservative agent. Another important use of terpinene is as a starting material, ultimately yielding carvacrol through epoxidation, ring opening, and rearrangement. Therefore, the efficient synthesis of terpinene holds significant research and industrial potential.

[0006]

[0007] Synthetic dipentene and terpinene are mainly obtained by α-pinene isomerization, but because α-pinene chemical properties are relatively active, the side reactions in the isomerization reaction are more numerous, which also causes dipentene and terpinene productive rates to be lower, often no more than 50%, and is also accompanied by the generation of by-products amphene, terpinene, and propinolene. For example, patent CN109721451A discloses a method for preparing limonene from a α-pinene isomerization using a catalyst having a core of aluminum oxide nanoparticles, and obtains a reaction solution containing 29% to 42% of dipentene by isomerization. The method selects the aluminum oxide nanoparticles prepared by oneself as a catalyst, and the catalyst is difficult for realizing application, and the dipentene product content is lower after the isomerization, and can only reach 42% at the highest. Patent CN102343277A describes a high-performance α-pinene isomerization catalyst and its application, utilizing alkali-treated Betα molecular screening. Subsequently, a homemade catalyst is obtained by calcining at 550 degrees Celsius. α-pinene isomerizes under this catalyst to produce a mixture primarily composed of camphene. When α-pinene conversion reaches 97%, the camphene selectivity is 40%, the dipentene selectivity is 31.6%, and the terpinene selectivity is 11.5%. Although this method is simple to manufacture, the product after α-pinene isomerization is a mixture, with the majority being camphene, and therefore, its industrialization prospects are worrying. Patent CN108002973A describes a method for producing limonene using zirconium oxide microcapsules loaded with acidic ionic liquids as catalysts. Self-synthesized zirconium oxide microcapsules loaded with acidic ionic liquids are used as catalysts, achieving an α-pinene isomerization conversion rate of 90% and a dipentene selectivity of 84%. Although this method achieves high dipentene selectivity, the catalyst preparation is cumbersome, zirconium oxide is difficult to form as a support, and the acidic ionic liquids used are N-methylimidazole chloroacetic acid and ammonium metatungstate, both of which are expensive organic reagents. Therefore, this patent cannot be applied industrially. Wang Shifa et al. (Forest Products Chemistry and Industry, 1996, 16:32-38) reported that the main product of 13X sodium molecular sieve was dipentene when treated with hydrochloric acid at a concentration of 0.1 mol / L and a mass ratio of α-pinene to catalyst of 20:1. The optimal selectivity was 54.6% (the conversion of α-pinene was 74.0%). This method exhibited low selectivity for both α-pinene and dipentene. Chinese patent CN109701591B discloses a catalyst for the isomerization reaction of α-pinene and its preparation method. The catalyst uses a commercial 13X molecular sieve modified with alkali solution and then baked to produce a molecular sieve. The catalyst achieves an α-pinene conversion rate of over 94% and a dipentene yield of over 56%. While the report achieves a dipentene selectivity of nearly 60%, it also produces 10% terpinene and over 20% camphene as a byproduct. Camphene cannot ultimately be synthesized into carvacrol, resulting in an effective yield of only 65%, lower than the 90% reported in the patent. Furthermore, the molecular sieve has a short lifespan.Chinese Patent CN 102126904B discloses a method for isomerizing α-pinene. The method uses γ-alumina, silica, silica-alumina, or a silica-alumina molecular sieve as a catalyst support and a solid-supported chloride as an activator. The reaction is carried out in a liquid-solid heterogeneous stirred reactor or a fixed-bed reactor at atmospheric pressure to isomerize α-pinene to dipentene. The method has a trans-dipentene selectivity of 56%, but a camphene selectivity of nearly 30%. (Chinese Patent CN)

[0008] 102126904A adopts solid acid catalyst, by active components such as halides are grafted and immobilized on molecular sieve surface, reaction temperature is at 40 DEG C, the mass ratio of α-pinene and catalyst is 20:1, reaction times is 2h, main product is amphene and dipentene, and wherein the best yield of dipentene is 51.6% (now the transformation efficiency of α-pinene is 98.4%). The same dipentene productive rate of the method only has 50%, and by product is mainly amphene.

[0009] In summary, currently, the most effective method for synthesizing dipentene and terpinene is through the rearrangement of α-pinene under acidic conditions. However, the above patents and literature reports have disadvantages such as expensive catalysts and low combined yield of dipentene and terpinene. Therefore, an efficient, simple and highly selective method for synthesizing dipentene and terpinene is still needed. Dipentene and terpinene can both be used as raw materials to ultimately synthesize carvacrol. Therefore, the method for efficiently synthesizing dipentene and terpinene has good process application value and economic prospects. Summary of the Invention

[0010] In view of the shortcomings of the prior art, the present invention aims to provide a method for the efficient simultaneous synthesis of dipentene and terpinene. The method successfully synthesizes dipentene and terpinene from α-pinene by regulating an acid catalyst, an auxiliary agent, and a temperature. The synthesis method of the present invention has a high conversion rate, and the combined selectivity and combined yield of dipentene and terpinene are high.

[0011] The present invention is achieved through the following technical solutions:

[0012] A highly efficient method for simultaneously synthesizing dipentene and terpinene comprises the following steps:

[0013] Alpha-pinene, an acid catalyst and an alkaline auxiliary agent are added into a reactor in proportion for heating reaction. After the reaction, dipentene and terpinene are directly distilled to obtain finished products.

[0014] The reaction equation is as follows:

[0015]

[0016] A further improvement of the present invention is:

[0017] The acid catalyst is one or a mixture of two or more of benzoic acid, salicylic acid, o-toluic acid, p-toluic acid, o-nitrobenzoic acid, p-nitrobenzoic acid, o-methoxybenzoic acid, p-methoxybenzoic acid, chloroacetic acid, dichloroacetic acid, bromoacetic acid or D-lactic acid.

[0018] Preferably, the acid catalyst is one or a mixture of two or more of benzoic acid, salicylic acid, o-nitrobenzoic acid or chloroacetic acid.

[0019] Furthermore, the alkaline auxiliary agent is one or a mixture of two or more of formamide, acetamide, propionamide, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, benzamide, and phenylacetamide.

[0020] Preferably, the alkaline auxiliary agent is one or a mixture of two or more of formamide, acetamide, N,N-dimethylformamide, benzamide, and phenylacetamide.

[0021] Furthermore, the amount of the acid catalyst accounts for 1% to 10% of the total mass of the system.

[0022] Furthermore, the amount of the alkaline auxiliary agent accounts for 0.5% to 10% of the total mass of the system.

[0023] Furthermore, the temperature of the heating reaction is 90° C. to 160° C., and the reaction time is 2 to 12 hours.

[0024] Furthermore, the reaction mixing method can be a one-pot reaction or 30% of α-pinene can be mixed with the acid catalyst and the alkaline auxiliary agent first, and then the remaining 70% of α-pinene can be added dropwise within 4 hours.

[0025] Furthermore, after the reaction is completed, dipentene and terpinene are obtained by direct distillation, and the acid catalyst and alkaline auxiliary agent remain in the still residue, and new α-pinene is added to the still residue to carry out a new round of isomerization reaction; the still residue can be reused twice, and the reaction conversion rate drops significantly in the third time.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The method of the present invention has high raw material conversion rate and good selectivity, with the conversion rate of α-pinene reaching 100%, the selectivity of dipentene reaching 60%, and the selectivity of terpinene reaching 30%. The effective yield reaches 90%.

[0028] (2) The method of the present invention uses an organic acid as a catalyst and an organic base as an auxiliary agent. The reaction is a homogeneous reaction with good catalytic effect. The amount of catalyst used accounts for 1% to 10% of the system, and the amount of auxiliary agent used accounts for 0.5% to 10% of the system. The acid and base used are both mainstream raw materials on the market, which greatly reduces the production cost.

[0029] (3) After the distillation is completed, the catalyst and auxiliary agent remain in the kettle residue and can be applied to the next batch of reactions, up to twice. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below with reference to specific embodiments.

[0031] Example 1

[0032] To a 2L three-necked flask, add 1000g of α-pinene, 80g of benzoic acid, and 50g of formamide in sequence for a one-pot reaction. The kettle temperature was then raised to 120°C and maintained. The reaction was stopped after complete conversion of the α-pinene. High vacuum distillation was then performed to yield 450g of dipentene and 200g of terpinene. The dipentene selectivity was 45% and the GC content was 99.5%. The terpinene selectivity was 20% and the GC content was 99.2%. The kettle liquid, including the catalyst, was retained for the next batch.

[0033] Example 2

[0034] To a 2L three-necked flask, 1000g of α-pinene, 100g of o-methylbenzoic acid, and 30g of acetamide were added sequentially for a one-pot reaction. The kettle temperature was then raised to 140°C and maintained. The reaction was stopped after complete conversion of the α-pinene. High vacuum distillation was then performed to yield 250g of dipentene and 100g of terpinene. The dipentene selectivity was 25% and the GC content was 99.1%. The terpinene selectivity was 10% and the GC content was 99.0%. The kettle liquid, including the catalyst, was retained for the next batch.

[0035] Example 3

[0036] To a 2L three-necked flask, add 1000g of α-pinene, 60g of salicylic acid, and 10g of acetamide in sequence for a one-pot reaction. The kettle temperature was then raised to 150°C and maintained. The reaction was stopped after complete conversion of the α-pinene. High vacuum distillation was then performed to yield 550g of dipentene and 270g of terpinene. Dipentene selectivity was 55% and the GC content was 99.4%. Terpinene selectivity was 27% and the GC content was 99.2%. The kettle liquid, including the catalyst, was retained for the next batch.

[0037] Example 4

[0038] To a 2L three-necked flask, add 300g of α-pinene, 80g of o-nitrobenzoic acid, and 20g of phenylacetamide. Raise the kettle temperature to 160°C. Add the remaining 700g of α-pinene dropwise over 4 hours. Maintain the temperature at 160°C until all α-pinene is converted. Stop the reaction and then directly distill under high vacuum to obtain 600g of dipentene and 300g of terpinene. Dipentene selectivity is 60% and the GC content is 99.1%. Terpinene selectivity is 30% and the GC content is 99.0%. The kettle liquid, including the catalyst, is retained for the next batch.

[0039] Example 5

[0040] Based on Example 4, the catalyst was re-used multiple times as shown in the following table. The first re-use resulted in unchanged α-pinene conversion and selectivities for dipentene and terpinene. The second re-use resulted in a slightly lower α-pinene conversion of 95%, 56% dipentene selectivity, and 28% terpinene selectivity. The third re-use resulted in a significant decrease in catalyst activity, with α-pinene conversion of only 80%, dipentene selectivity of 40%, and terpinene selectivity of 22%. Therefore, the catalyst and additive can be re-used a maximum of two times.

[0041]

[0042] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A method for simultaneously synthesizing dipentene and terpinene with high efficiency, characterized in that: The following steps are involved: Alpha-pinene, an acid catalyst and an alkaline auxiliary agent are added into a reactor in proportion for heating reaction. After the reaction, dipentene and terpinene are directly distilled to obtain finished products.

2. The method for simultaneously synthesizing dipentene and terpinene efficiently according to claim 1, wherein: The acid catalyst is one or a mixture of two or more of benzoic acid, salicylic acid, o-toluic acid, p-toluic acid, o-nitrobenzoic acid, p-nitrobenzoic acid, o-methoxybenzoic acid, p-methoxybenzoic acid, chloroacetic acid, dichloroacetic acid, bromoacetic acid or D-lactic acid.

3. The method for efficiently synthesizing dipentene and terpinene simultaneously according to claim 2, wherein: The acid catalyst is one or a mixture of two or more of benzoic acid, salicylic acid, o-nitrobenzoic acid or chloroacetic acid.

4. The method for simultaneously synthesizing dipentene and terpinene efficiently according to claim 1, wherein: The alkaline auxiliary agent is one or a mixture of two or more of formamide, acetamide, propionamide, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, benzamide, and phenylacetamide.

5. The method for simultaneously synthesizing dipentene and terpinene efficiently according to claim 4, wherein: The alkaline auxiliary agent is one or a mixture of two or more of formamide, acetamide, N,N-dimethylformamide, benzamide, and phenylacetamide.

6. The method for simultaneously synthesizing dipentene and terpinene efficiently according to claim 1, wherein: The amount of the acid catalyst accounts for 1% to 10% of the total mass of the system.

7. The method for simultaneously synthesizing dipentene and terpinene efficiently according to claim 1, wherein: The amount of the alkaline auxiliary agent used accounts for 0.5% to 10% of the total mass of the system.

8. The method for simultaneously synthesizing dipentene and terpinene efficiently according to claim 1, wherein: The temperature of the heating reaction is 90° C. to 160° C., and the reaction time is 2 to 12 hours.

9. The method for simultaneously synthesizing dipentene and terpinene efficiently according to claim 1, wherein: The mixing method of the reaction can be a one-pot reaction or 30% of the α-pinene can be mixed with the acid catalyst and the alkaline auxiliary agent first, and then the remaining 70% of the α-pinene is added dropwise within 4 hours.

10. The method for simultaneously synthesizing dipentene and terpinene efficiently according to claim 1, characterized in that: After the reaction is completed, dipentene and terpinene are obtained by direct distillation, and the acid catalyst and alkaline auxiliary agent remain in the still residue. New α-pinene is added to the still residue for a new round of isomerization reaction; the still residue can be used twice.

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