A new method for synthesizing peach aldehyde with reduced unit consumption

Abstract

The present application relates to the technical field of perfume synthesis, and specifically discloses a new method for synthesizing peach aldehyde with reduced unit consumption. The method uses n-octanol and acrylic acid as raw materials, di-tert-butyl peroxide as an initiator, introduces a weak alkaline buffer additive in a free radical addition and lactonization tandem reaction system, and after cooling, suction filtration, flash evaporation and vacuum rectification treatment, the peach aldehyde product is obtained. The weak alkaline buffer additive can effectively stabilize the pH of the reaction system, inhibit side reactions such as self-polymerization of acrylic acid and excessive oxidation of n-octanol, significantly reduce the unit consumption of n-octanol raw material, improve the product yield and purity, the recovered n-octanol can be directly recycled and used, reduce the production cost, the process does not produce heavy metal wastewater, the burden of three wastes treatment is small, and is suitable for industrialized production.

Description

Technical Field

[0001] This invention relates to the field of fragrance synthesis technology, and more specifically, to a novel synthesis method for reducing the consumption of peach aldehyde. Background Technology

[0002] Peach aldehyde, chemically known as γ-undecyl lactone, has the molecular formula C2. 11 H 20 O2, a colorless to pale yellow viscous liquid with a strong peach aroma, is an important lactone flavoring compound. Peach aldehyde is listed in my country's "Hygienic Standards for the Use of Food Additives" as a permitted food flavoring compound, and has wide applications in the food, daily chemical, and tobacco industries. Its efficient and low-consumption synthesis methods have always been a research hotspot in the fine chemical field. Currently, the industrial synthesis methods of peach aldehyde are mainly divided into two categories: The first category involves heating ω-undecenoic acid with sulfuric acid, causing double bond transfer from the chain to the β or γ position, followed by lactonization to prepare peach aldehyde. This route has limited raw material sources, harsh process conditions, and numerous side reactions, limiting its industrial application. The second category uses n-octanol and acrylic acid or acrylate as raw materials, undergoing an addition reaction under the action of a free radical initiator to generate the corresponding hydroxy acid or hydroxy ester intermediate, followed by intramolecular dehydration and cyclization or transesterification to obtain the peach aldehyde product. This route has abundant raw material sources and a relatively mature process, and is currently the mainstream method for industrial production of peach aldehyde.

[0003] In the second type of method mentioned above, existing technologies typically use di-tert-butyl peroxide as a free radical initiator and boric acid as a catalyst to induce an addition-lactone tandem reaction between n-octanol and acrylic acid at a relatively high temperature. The Chinese literature "Optimization of Peach Aldehyde Synthesis Process and its Kinetic Study" reports a process for synthesizing peach aldehyde using boric acid as a catalyst, di-tert-butyl peroxide as an initiator, and acrylic acid and n-octanol as raw materials. The process suppresses side reactions by optimizing the reaction temperature and increasing the molar ratio of n-octanol to acrylic acid, but the yield of peach aldehyde remains below 65%, and the raw material consumption is relatively high. Chinese patent CN116102527A discloses a method for photocatalytic synthesis of peach aldehyde using n-octanol and acrylate as raw materials, boric acid as a catalyst, a triazine compound as an initiator, the addition of a divalent nickel complex, and a light source with a wavelength range of 100-450 nm. While this method has some innovation in its technical route, the divalent nickel complex used is expensive, and the photocatalytic synthesis device is difficult to scale up industrially, significantly limiting its practical application value. The aforementioned existing technologies all share the following common defects: First, the reaction temperature is high, and some n-octanol is easily oxidized to octanoic acid. Octanoic acid further esterifies with n-octanol to produce byproducts such as octanoate, resulting in a significantly high consumption of n-octanol raw material. Second, acrylic acid is prone to self-polymerization under high temperature conditions, generating high molecular weight byproducts such as polyacrylic acid, which reduces the effective conversion rate of acrylic acid. Third, the use of catalysts such as boric acid can easily lead to impure aroma in the product, requiring an additional aroma post-treatment process, which increases the complexity of the process and further restricts the improvement of product yield. Typically, the yield of peach aldehyde after one purification is only below 65%. Fourth, none of the existing technologies have a technical solution for actively controlling the pH stability of the reaction system, and the continuous accumulation of acidity in the reaction system has not effectively suppressed the promoting effect of side reactions.

[0004] Weakly basic phosphate compounds such as disodium hydrogen phosphate have been proven to have good pH buffering capacity, stabilizing the acid-base environment of aqueous solutions and organic reaction systems. They also possess certain catalytic properties for ester synthesis and acetalization reactions. However, there are currently no reports on the application of weakly basic phosphate buffers in the free radical addition-lactone synthesis system of peach aldehyde to stabilize the reaction environment and reduce the consumption of n-octanol as a raw material. Their mechanism of action and process optimization schemes in this type of tandem reaction system remain a technological gap. Therefore, this invention provides a novel synthetic method to reduce the consumption of peach aldehyde, thereby solving the aforementioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to provide a new synthesis method that reduces the consumption of phenol, effectively suppresses side reactions such as acrylic acid self-polymerization and excessive oxidation of n-octanol, significantly reduces the consumption of n-octanol raw material, improves product yield and purity, and allows the recovered n-octanol to be directly recycled, reducing production costs. The process does not generate heavy metal wastewater, has a low burden on waste treatment, and is suitable for industrial-scale production.

[0006] This invention provides a novel synthesis method for reducing the consumption of peach aldehyde, employing the following technical solution:

[0007] S1. According to the molar ratio of n-octanol to acrylic acid of (6-10):1, the molar ratio of di-tert-butyl peroxide to acrylic acid of 1:(8-15), and the amount of weak basic buffering agent of 0.1-2.0% of the mass of acrylic acid, weigh n-octanol, acrylic acid, initiator di-tert-butyl peroxide and weak basic buffering agent respectively, and set aside.

[0008] S2. Add a portion of the n-octanol and weakly basic buffer agent weighed in step S1 to the reactor. Heat the reaction system to 170-175℃ at atmospheric pressure and 220-260 rpm to complete the preheating of the feed. Mix the remaining n-octanol, acrylic acid and initiator di-tert-butyl peroxide weighed in step S1 evenly to prepare the reaction mixture to be added dropwise for later use.

[0009] S3. Under the condition of maintaining the temperature inside the reactor at 170-175℃, the reaction mixture is added to the preheated reaction system obtained in step S2 by uniform and continuous dropwise addition. The dropwise addition time is controlled to be 24-26h. After the dropwise addition is completed, the reaction is continued to be stirred at 170-175℃ for 1-3h and then the heating is stopped. The reaction solution is cooled to below 40℃ and the cooled material is filtered to obtain crude liquid containing peach aldehyde.

[0010] S4. Transfer the crude liquid obtained in step S3 into the distillation system. First, recover the unreacted n-octanol through flash distillation, which can be directly recycled for subsequent batch production. Then, perform vacuum distillation on the remaining material after flash distillation to collect the target fraction, namely peach aldehyde.

[0011] Preferably, the weak alkaline buffering agent in step S1 is selected from one of disodium hydrogen phosphate, dipotassium hydrogen phosphate, sodium dihydrogen phosphate, or potassium dihydrogen phosphate, and is used for later use.

[0012] Preferably, the molar ratio of n-octanol to acrylic acid is (6-10):1, the molar ratio of di-tert-butyl peroxide to acrylic acid is 1:(8-15), and the amount of the weakly basic buffering agent is 0.1-2.0% of the mass of acrylic acid.

[0013] Preferably, the feeding and preheating step is as follows: a portion of n-octanol and all of the weakly basic buffer agent are added to the reactor, and the temperature is raised to 170-175°C at atmospheric pressure and 220-260 rpm; the dropping reaction step is as follows: the remaining n-octanol, acrylic acid and di-tert-butyl peroxide are mixed to prepare a reaction mixture, and the mixture is added to the reactor in a uniform and continuous dropping manner while maintaining the temperature inside the reactor at 170-175°C.

[0014] Preferably, the reaction mixture is added dropwise over a period of 24-26 hours, and after the addition is complete, the mixture is kept at 170-175°C and stirred for another 1-3 hours.

[0015] Preferably, the post-processing step is as follows: after the heat preservation is completed, the reaction liquid is cooled to below 40°C, and the cooled material is filtered to remove insoluble solids such as solid weak alkaline buffer agents, so as to obtain crude liquid containing peach aldehyde.

[0016] Preferably, the distillation step is as follows: the crude liquid is first flash-distilled to recover unreacted n-octanol, and the recovered n-octanol can be directly recycled for subsequent batch production. Then, the remaining material after flash distillation is subjected to vacuum distillation to collect the target fraction and obtain the peach aldehyde product.

[0017] In summary, the present invention has the following beneficial effects:

[0018] 1. This invention solves the core problem of excessive raw material consumption in existing processes by introducing a weakly basic buffering agent into the free radical addition and lactone tandem reaction system of peach aldehyde synthesis. The weakly basic buffering agent can continuously stabilize the acid-base environment of the reaction system, avoiding the side reaction catalytic effect caused by the gradual accumulation of acidic substances during the reaction. It effectively inhibits the self-polymerization tendency of acrylic acid under high temperature conditions, improves the effective conversion rate of acrylic acid, and significantly reduces the probability of excessive oxidation of n-octanol to carboxylic acid, reducing the ineffective consumption of raw materials from the source. At the same time, unreacted n-octanol can be directly recycled after simple recovery, greatly reducing the overall raw material loss in the production process.

[0019] 2. This invention significantly improves product quality and simplifies the production process. Due to effective control of side reactions, the generation of various impurities in the reaction system is greatly reduced, resulting in a significant improvement in the quality of crude peach aldehyde. This reduces the difficulty of subsequent distillation and separation, and increases the separation yield and purity of the target product. Furthermore, this invention eliminates the use of boric acid catalysts commonly used in existing technologies, avoiding the problem of impure odor caused by such catalysts. The resulting product has a pure aroma and excellent color, eliminating the need for complex aroma post-treatment and decolorization processes, and effectively shortening the production cycle.

[0020] 3. This invention possesses excellent environmental friendliness and industrial adaptability. The weakly alkaline buffer agent used is a solid inorganic compound, which can be completely separated by simple filtration after the reaction, without introducing heavy metal ions or recalcitrant organic pollutants into the system. No heavy metal wastewater is generated, significantly reducing the burden of waste treatment. This invention improves upon the existing mainstream peach aldehyde production process without altering the original main reaction flow and core production equipment. Technological upgrades can be achieved simply by adding a small amount of auxiliary agent. The process is simple to operate, parameters are controllable, and operational stability is high. It can be directly applied to industrial-scale production without large-scale equipment modifications. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the experimental materials used, unless otherwise specified, were all purchased from conventional biochemical reagent stores. All quantitative experiments in the following examples were performed in triplicate, and the data are the average of the three replicates or the average ± standard deviation.

[0023] The reaction results were detected using gas chromatography, with the specific analytical conditions as follows:

[0024] Gas chromatograph: Agilent 7820A, column HP-5 (30m × 320μm × 0.25μm), injection port temperature: 150℃; split ratio: 50:1; carrier gas flow rate: 1.5ml / min; temperature program: 40℃ for 1 min, ramp to 90℃ at 10℃ / min, hold for 0 min, then ramp to 160℃ at 5℃ / min, hold for 0 min, then ramp to 280℃ at 30℃ / min, hold for 6 min. Detector temperature: 280℃. Mass percentage of each component was calculated using the area normalization method.

[0025] Example 1

[0026] This embodiment provides a novel synthesis method for reducing the consumption of peach aldehyde, employing the following technical solution:

[0027] 1950g of n-octanol and 1.25g of disodium hydrogen phosphate (0.5% of the mass of acrylic acid) were added to a 5L reactor. The mixture was heated to 175℃ under normal pressure and stirring at 240rpm to complete the preheating process. Separately, 750g of n-octanol, 250g of acrylic acid, and 52g of di-tert-butyl peroxide were mixed thoroughly to prepare a reaction mixture for dropwise addition. Maintaining the reactor temperature at 175℃, the reaction mixture was added dropwise continuously and uniformly to the preheated reaction system obtained in step S2, with the addition time controlled at 25h. After the addition was complete, the reaction was continued at 175℃ with stirring for 2h. Before the end of the heat treatment, samples were taken for GC analysis to determine the composition of the reaction solution, and the conversion rate of acrylic acid was calculated. The yield was 98.85%, and the selectivity of peach aldehyde was 98.12%. After the heat preservation was completed, the heating was stopped, and the reaction solution was cooled to below 40°C. After removing insoluble solids such as solid disodium hydrogen phosphate by vacuum filtration, the solution was transferred to a flash evaporator for flash evaporation, yielding 2240g of recovered n-octanol (GC purity 97.5%) and 646g of crude peach aldehyde. GC analysis showed that the mass percentages of each component were: peach aldehyde 96.0%, n-octanol 2.0%, and octyl octanoate and other byproducts totaling 2.0%. The crude product was transferred to a distillation vessel for vacuum distillation, yielding 564g of finished peach aldehyde (GC purity 99.1%), with a single-stage purification yield of 91.0%. The n-octanol consumption was 0.915g, and the acrylic acid consumption was 0.443g.

[0028] Example 2

[0029] This embodiment provides a novel synthesis method for reducing the consumption of peach aldehyde, employing the following technical solution:

[0030] 1950g of n-octanol and 2.0g of disodium hydrogen phosphate (0.8% of the mass of acrylic acid) were added to a 5L reactor. The mixture was heated to 175℃ under normal pressure and stirring at 240rpm to complete the preheating process. Separately, 750g of n-octanol, 250g of acrylic acid, and 52g of di-tert-butyl peroxide were mixed thoroughly to prepare a reaction mixture for dropwise addition. Maintaining the reactor temperature at 175℃, the reaction mixture was added dropwise continuously and uniformly to the preheated reaction system obtained in step S2, with the addition time controlled at 25h. After the addition was complete, the reaction was continued at 175℃ with stirring for 2h. Before the end of the holding period, samples were taken for GC analysis to determine the composition of the reaction solution. The calculated conversion rate of acrylic acid was 9%. The yield was 7.92%, and the selectivity of peach aldehyde was 96.85%. After the heat preservation was completed, the heating was stopped, and the reaction solution was cooled to below 40°C. After removing insoluble solids such as solid disodium hydrogen phosphate by vacuum filtration, the solution was transferred to a flash evaporator for flash evaporation, yielding 2243g of recovered n-octanol (GC purity 97.3%) and 642g of crude peach aldehyde. GC analysis showed that the mass percentages of each component were: peach aldehyde 94.4%, n-octanol 2.5%, and byproducts such as octanoic acid ester totaling 3.1%. The crude product was transferred to a distillation vessel for vacuum distillation, yielding 545g of finished peach aldehyde (GC purity 99.0%), with a single-stage purification yield of 90.0%. The n-octanol consumption was 0.95g, and the acrylic acid consumption was 0.45g.

[0031] Example 3

[0032] This embodiment provides a novel synthesis method for reducing the consumption of peach aldehyde, employing the following technical solution:

[0033] 1950g of n-octanol and 2.5g of disodium hydrogen phosphate (1.0% of the mass of acrylic acid) were added to a 5L reactor. The mixture was heated to 175℃ under normal pressure and stirring at 240rpm to complete the preheating process. Separately, 750g of n-octanol, 250g of acrylic acid, and 52g of di-tert-butyl peroxide were mixed thoroughly to prepare a reaction mixture for dropwise addition. Maintaining the reactor temperature at 175℃, the reaction mixture was added dropwise continuously and uniformly to the preheated reaction system obtained in step S2, with the addition time controlled at 25h. After the addition was complete, the reaction was continued at 175℃ with stirring for 2h. Before the end of the holding period, samples were taken for GC analysis to determine the composition of the reaction solution. The calculated conversion rate of acrylic acid was 9%. The yield was 9.14%, and the selectivity of peach aldehyde was 98.66%. After the heat preservation was completed, the heating was stopped, and the reaction solution was cooled to below 40°C. After removing insoluble solids such as solid disodium hydrogen phosphate by vacuum filtration, the solution was transferred to a flash evaporator for flash evaporation, yielding 2240g of recovered n-octanol (GC purity 97.8%) and 646g of crude peach aldehyde. GC analysis showed that the mass percentages of each component were: peach aldehyde 96.8%, n-octanol 1.7%, and byproducts such as octanoic acid ester totaling 1.5%. The crude product was transferred to a distillation vessel for vacuum distillation, yielding 575g of finished peach aldehyde (GC purity 99.3%), with a single-stage purification yield of 92.0%. The n-octanol consumption was 0.886g, and the acrylic acid consumption was 0.435g.

[0034] Example 4

[0035] This embodiment provides a novel synthesis method for reducing the consumption of peach aldehyde, employing the following technical solution:

[0036] 1950g of n-octanol and 2.5g of dipotassium hydrogen phosphate (1.0% of the mass of acrylic acid) were added to a 5L reactor. The mixture was heated to 175℃ under normal pressure and stirring at 240rpm to complete the preheating process. Separately, 750g of n-octanol, 250g of acrylic acid, and 52g of di-tert-butyl peroxide were mixed thoroughly to prepare a reaction mixture for dropwise addition. Maintaining the reactor temperature at 175℃, the reaction mixture was added dropwise continuously and uniformly to the preheated reaction system obtained in step S2, with the addition time controlled at 25h. After the addition was complete, the reaction was continued at 175℃ with stirring for 2h. Before the end of the holding period, samples were taken for GC analysis to determine the composition of the reaction solution. The calculated conversion rate of acrylic acid was 9%. The yield was 4.52%, and the selectivity of peach aldehyde was 91.35%. After the heat preservation was completed, the heating was stopped, and the reaction solution was cooled to below 40°C. After removing insoluble solids such as solid dipotassium hydrogen phosphate by vacuum filtration, the solution was transferred to a flash evaporator for flash evaporation, yielding 2265g of recovered n-octanol (GC purity 97.0%) and 617g of crude peach aldehyde. GC analysis showed that the mass percentages of each component were: peach aldehyde 89.5%, n-octanol 3.6%, and byproducts such as octanoic acid ester totaling 6.9%. The crude product was transferred to a distillation vessel for vacuum distillation, yielding 491g of finished peach aldehyde (GC purity 98.9%), with a single-stage purification yield of 89.0%. The n-octanol consumption was 1.024g, and the acrylic acid consumption was 0.509g.

[0037] Comparative Example 1

[0038] This comparative example provides a novel synthetic method for reducing the consumption of peach aldehyde, employing the following technical solution:

[0039] 1950g of n-octanol was added to a 5L reactor, and the temperature was raised to 175℃ under normal pressure and stirring at 240rpm. Separately, 750g of n-octanol, 250g of acrylic acid, and 52g of di-tert-butyl peroxide were mixed thoroughly to prepare a reaction mixture for dropwise addition. Maintaining the reactor temperature at 175℃, the reaction mixture was added to the preheated reaction system dropwise at a uniform rate for 25 hours. After the addition was complete, the reaction was continued at 175℃ with stirring for another 2 hours. Before the end of the holding period, samples were taken for GC analysis to determine the composition of the reaction solution. The calculated conversion rate of acrylic acid was 86.45%, and the selection of peach aldehyde was... The purity was 77.20%. After the heat preservation was completed, heating was stopped, and the reaction solution was cooled to below 40°C. After filtration, it was transferred to a flash evaporator for flash evaporation, yielding 2300g of recovered n-octanol (GC purity 96.0%) and 510g of crude peach aldehyde. GC analysis showed that the mass percentages of each component were: peach aldehyde 83.7%, n-octanol 4.9%, and byproducts such as octanoic acid ester totaling 11.4%. The crude product was transferred to a distillation vessel for vacuum distillation, yielding 363g of finished peach aldehyde (GC purity 98.6%). The yield of the first distillation was 85.0%, with n-octanol consumption of 1.36g and acrylic acid consumption of 0.69g.

[0040] A comparison of the test data from Examples 1-4 and Comparative Example 1 shows that the present invention, by creatively introducing an appropriate amount of weakly alkaline buffering agent into the reaction system, has achieved significant optimization of all key process indicators. Specifically, in Comparative Example 1 without the added buffering agent, the acrylic acid conversion rate and peach aldehyde selectivity were only 86.45% and 77.20%, respectively, and the content of byproducts such as octanoate was as high as 11.4%, resulting in a single consumption of 1.36 and 0.69 of n-octanol and acrylic acid, respectively. In contrast, Examples 1-4, by precisely controlling the amount of weakly alkaline buffering agent (such as disodium hydrogen phosphate or dipotassium hydrogen phosphate), effectively stabilized the pH of the system, inhibiting the high-temperature self-polymerization of acrylic acid and the excessive oxidation side reaction of n-octanol from the source. This resulted in the acrylic acid conversion rate reaching a maximum of 99.14%, the peach aldehyde selectivity reaching a maximum of 98.66%, and the byproduct generation significantly reduced to the range of 1.5% to 6.9%. This optimization of the underlying reaction not only stabilized the yield of peach aldehyde to 89.0%~92.0% and the GC purity of the product to over 98.9%, but also reduced the core consumption of n-octanol and acrylic acid to as low as 0.886 and 0.435, respectively. This fully demonstrates that the technical solution adopted in this invention has excellent technical effects in suppressing side reactions, significantly reducing the ineffective loss of raw materials, and improving the overall yield of the target product. It has extremely high industrial application and economic value.

[0041] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A novel synthesis method for reducing the consumption of peach aldehyde, characterized in that, Includes the following steps: Peach aldehyde was prepared by using n-octanol and acrylic acid as raw materials, di-tert-butyl peroxide as an initiator, and adding a weak alkaline buffer to the reaction system, followed by feeding, preheating, dropwise addition, heat preservation, post-treatment, and distillation.

2. The novel synthesis method for reducing peach aldehyde consumption according to claim 1, characterized in that, The weakly basic buffering agent is selected from one of disodium hydrogen phosphate, dipotassium hydrogen phosphate, sodium dihydrogen phosphate, or potassium dihydrogen phosphate.

3. The novel synthesis method for reducing peach aldehyde consumption according to claim 1, characterized in that, The molar ratio of n-octanol to acrylic acid is (6-10):1, the molar ratio of di-tert-butyl peroxide to acrylic acid is 1:(8-15), and the amount of the weakly basic buffering agent is 0.1-2.0% of the mass of acrylic acid.

4. The novel synthesis method for reducing peach aldehyde consumption according to claim 1, characterized in that, The feeding and preheating step is as follows: a portion of n-octanol and all of the weakly basic buffer agent are added to the reactor, and the temperature is raised to 170-175℃ at atmospheric pressure and 220-260 rpm; the dropping reaction step is as follows: the remaining n-octanol, acrylic acid and di-tert-butyl peroxide are mixed to prepare a reaction mixture, and the mixture is added to the reactor in a uniform and continuous dropping manner while maintaining the temperature inside the reactor at 170-175℃.

5. The novel synthesis method for reducing peach aldehyde consumption according to claim 4, characterized in that, The reaction mixture is added dropwise over 24-26 hours, and after the addition is complete, the mixture is kept at 170-175°C and stirred for another 1-3 hours.

6. The novel synthesis method for reducing peach aldehyde consumption according to claim 1, characterized in that, The post-processing steps are as follows: after the heat preservation is completed, the reaction liquid is cooled to below 40°C, and the cooled material is filtered to remove insoluble solids such as solid weak alkaline buffer agents, so as to obtain crude liquid containing peach aldehyde.

7. The novel synthesis method for reducing peach aldehyde consumption according to claim 1, characterized in that, The distillation step is as follows: the crude liquid is first flash-distilled to recover unreacted n-octanol, and the recovered n-octanol can be directly recycled for subsequent batches of production. Then, the remaining material after flash distillation is subjected to vacuum distillation to collect the target fraction and obtain the peach aldehyde product.