Method for continuously and efficiently synthesizing citral based on fixed bed reactor
By continuously reacting the use of load -type metal catalysts in a fixed bed reactor, the problem of low catalytic conversion rate and complex reaction process in the existing citizens synthesis process, and achieve high -efficiency preparation and environmental protection of high -purity citizens.
Patent Information
- Application Number
- CN202411453270.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-17
- Publication Date
- 2025-01-24
AI Technical Summary
The existing citral synthesis process has problems such as low catalytic conversion rate, complex reaction process, long time and frequent wastewater generation, which is difficult to meet the efficient and environmental protection needs of industrial production.
The load -type metal catalyst continues to react in a fixed bed reactor. By shortening the process steps, the complex multi -step process is reduced to a continuous reaction in a reactor to achieve high -efficiency synthesis of citizens.
It achieves efficient preparation of high-purity citral, shortens the process time by at least 50%, reduces equipment investment and wastewater generation, and meets the economic and environmental protection requirements of modern industrial production.
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Figure CN119350146A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of organic chemical industry and pharmaceutical intermediate synthesis, and specifically to the method of directly realizing continuous and efficient synthesis of citral in a fixed bed reactor by using a certain supported metal catalyst. Background Art
[0002] Citral is a colorless to pale yellow oily liquid with a strong lemon aroma. 10 H 16 O, its fragrance helps to concentrate and improves people's mood. Citral has a wide range of uses, mainly used in the preparation of lemon, citrus and assorted fruit flavors, and is also the main raw material for synthesizing ionones and vitamins. Citral has a relatively active chemical property and is prone to redox reactions to produce geranic acid or geraniol / nerol.
[0003] Citral can be separated and extracted from plant essential oils and prepared by chemical synthesis. It is obtained by vacuum distillation of Litsea cubeba oil. This method has harsh process conditions, a long production process and a low extraction rate. Especially with the expansion of the use of citral, citral made from natural resources can no longer meet the needs of market development and is not suitable for large-scale production. The chemical synthesis method can be divided into the dehydrogenation linalool transposition method and the condensation rearrangement synthesis method of 2 C5 enols and enal. At present, the industrial production of citral is mainly chemical synthesis. The reaction process is as follows: Figure 1 shown.
[0004] The synthesis method based on the condensation and rearrangement of two C5 enols and enals uses isopentenol and isopentenal as raw materials, condenses to obtain acetal, and then obtains citral through cracking and rearrangement. Although the yield exceeds 95%, this process is an intermittent production process, which has the disadvantages of large floor space, long synthesis time, and complicated synthesis steps.
[0005] Fixed bed reactors are also called packed bed reactors. They are filled with solid catalysts or solid reactants to achieve multiphase reactions. Solids are usually in granular form and piled up into a bed layer of a certain height (or thickness). The bed layer is stationary and the fluid reacts through the bed layer. It is generally used for heterogeneous catalytic reactions, and the fixed filler is a solid catalyst. Fixed bed reactors have the advantages of less mechanical wear of the catalyst, less catalyst dosage, controllable reaction temperature, higher selectivity and conversion rate. In recent years, it has been widely used in the field of heterogeneous catalytic synthesis.
[0006] In summary, in the process of preparing citral by the batch method, there are disadvantages such as low catalytic conversion rate, easy occurrence of side reactions, affecting product yield, acidic substances are corrosive to equipment, high requirements for equipment materials, increased equipment investment in industrial production, complex reaction process, and cumbersome equipment cleaning. In addition, the reaction solution is acidic when an acidic catalyst is used for catalytic reaction. After the reaction, the reaction solution needs to be neutralized, which will produce a large amount of wastewater, which does not conform to the development concept of economic and environmental protection in modern industrial production.
[0007] Therefore, based on efficient catalyst technology, making full use of the advantages of fixed bed reactors, there is an urgent need to develop a citral synthesis system with high activity, good selectivity, easy separation, high production efficiency, economy and environmental protection, which also has great reference value for the industrial production of citral. Summary of the invention
[0008] The existing system for synthesizing citral has the disadvantages of low conversion rate, low citral selectivity, complicated reaction process and long reaction time. The present invention can greatly shorten the process of the existing process by applying a supported metal catalyst to the synthesis of citral, and reduce the complicated multi-step process to a continuous reaction in a reaction vessel through a fixed bed catalytic technology, so as to efficiently prepare high-purity citral.
[0009] In order to achieve the above object, the present invention adopts the following technical solution:
[0010] A method for continuously and efficiently synthesizing citral in a fixed bed reactor uses a metal-supported catalyst to directly achieve efficient synthesis of citral from acetal in a fixed bed reactor. The supported metal catalyst is prepared as follows: one or more common metals or transition metals such as iron, sodium, potassium, aluminum, magnesium, copper, zinc, titanium, gold, platinum, palladium, nickel, rhodium, osmium, ruthenium, vanadium, cobalt, chromium, molybdenum, etc. are loaded into alumina, magnesium oxide, ceramics, diatomaceous earth, or a molecular sieve carrier by an impregnation method or a coprecipitation method.
[0011] The citral synthesis process of the invention comprises the following steps: filling a catalyst into a fixed bed reactor, introducing acetal under certain conditions for reaction, and directly and efficiently obtaining high-purity citral after staged cooling.
[0012] Preferably, the gas flow rate in the fixed bed reactor is 60-150 ml / min, the raw material flow rate is not less than 0.2 ml / min, the preheating temperature is 200-250°C, the ventilation time is 0.5-1.0h, the reaction temperature is controlled at 300-400°C, the reaction time is controlled at 0.5-3.0h, the cooling temperature is 160-180°C, and the reaction process is as follows: Figure 2 shown.
[0013] The beneficial effects of the present invention are as follows:
[0014] The present invention applies a supported metal catalyst to the synthesis of citral, so that the cracking and two-step rearrangement reactions are carried out in the same fixed bed reactor, which can greatly shorten the process of the existing process. The fixed bed catalytic technology reduces the complex multi-step process to a continuous reaction in a reaction vessel, and can efficiently prepare high-purity citral. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 Schematic diagram of the reaction process of citral.
[0016] Figure 2 Schematic diagram of the continuous and efficient synthesis of citral based on a fixed bed reactor. DETAILED DESCRIPTION
[0017] The following description is only a preferred embodiment of the present invention and does not limit the present invention. For those skilled in the art, various changes and variations are possible. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
[0018] Example 1
[0019] Fill 0.50g of catalyst into a fixed bed reactor, heat the preheating section of the reaction bed to 250℃, the reaction section to 350℃, and the cooling section to 160-180℃. Let air in at a flow rate of 100ml / min. After 0.5h of ventilation, pump acetal in at a rate of 0.2ml / min. Keep the air flow rate unchanged, and continue the reaction for 1.0h to obtain citral with a purity of 94.1% and a yield of 95.5%.
[0020] Example 2
[0021] Fill 0.50g of catalyst into a fixed bed reactor, heat the preheating section of the reaction bed to 250℃, the reaction section to 400℃, and the cooling section to 160-180℃. Let air in at a flow rate of 100ml / min. After 0.5h of ventilation, pump acetal in at a rate of 0.2ml / min. Keep the air flow rate unchanged, and continue the reaction for 3.0h to obtain citral with a purity of 93.2% and a yield of 91.3%.
[0022] Example 3
[0023] Fill 0.50g of catalyst into a fixed bed reactor, heat the preheating section of the reaction bed to 200℃, the reaction section to 350℃, and the cooling section to 160-180℃. Let air in at a flow rate of 100ml / min. After 0.5h of ventilation, pump acetal in at a rate of 0.2ml / min. Keep the air flow rate unchanged, and continue the reaction for 3.0h to obtain citral with a purity of 86.7% and a yield of 90.5%.
[0024] Example 4
[0025] Fill 0.50g of catalyst into a fixed bed reactor, heat the preheating section of the reaction bed to 250℃, the reaction section to 350℃, and the cooling section to 160-180℃. Let air in at a flow rate of 80ml / min. After 0.5h of ventilation, pump acetal in at a rate of 0.5ml / min. Keep the air flow rate constant and react continuously for 3.0h to obtain citral with a purity of 84.1% and a yield of 85.0%.
[0026] Example 5
[0027] Fill 0.50g of catalyst into a fixed bed reactor, heat the preheating section of the reaction bed to 230℃, the reaction section to 350℃, and the cooling section to 160-180℃, introduce air at a flow rate of 100ml / min, and after ventilation for 0.5h, pump in acetal at a rate of 0.2ml / min. The air flow rate remains unchanged, and the reaction is continued for 3.0h to obtain citral with a purity of 95.3% and a yield of 95.9%.
[0028] Example 6
[0029] Fill 0.50g of catalyst into a fixed bed reactor, heat the preheating section of the reaction bed to 230℃, the reaction section to 350℃, and the cooling section to 160-180℃, introduce air at a flow rate of 100ml / min, and after ventilation for 0.5h, pump in acetal at a rate of 0.2ml / min. The air flow rate remains unchanged, and the reaction is continued for 2.0h to obtain citral with a purity of 95.3% and a yield of 95.9%.
[0030] Example 7
[0031] Fill 0.50g of catalyst into a fixed bed reactor, heat the preheating section of the reaction bed to 250℃, the reaction section to 350℃, and the cooling section to 160-180℃. Pass nitrogen at a flow rate of 100ml / min. After ventilation for 0.5h, pump acetal into the reactor at a rate of 0.2ml / min. Keep the nitrogen flow rate unchanged, and react continuously for 3.0h to obtain citral with a purity of 94.7% and a yield of 95.5%.
[0032] Example 8
[0033] Fill 0.50g of catalyst into a fixed bed reactor, heat the preheating section of the reaction bed to 250℃, the reaction section to 350℃, and the cooling section to 160-180℃. Let air in at a flow rate of 150ml / min. After 0.5h of ventilation, pump acetal in at a rate of 0.2ml / min. Keep the air flow rate constant, and react continuously for 3.0h to obtain citral with a purity of 88.7% and a yield of 92.1%.
[0034] Example 9
[0035] Fill 0.60g of catalyst into a fixed bed reactor, heat the preheating section of the reaction bed to 250℃, the reaction section to 350℃, and the cooling section to 160-180℃. Let air in at a flow rate of 100ml / min. After 0.5h of ventilation, pump acetal in at a rate of 0.3ml / min. Keep the air flow rate unchanged, and continue the reaction for 3.0h to obtain citral with a purity of 90.1% and a yield of 85.6%.
[0036] Example 10
[0037] Fill 0.50g of catalyst into a fixed bed reactor, heat the preheating section of the reaction bed to 250℃, the reaction section to 350℃, and the cooling section to 160-180℃. Let air in at a flow rate of 100ml / min. After 1.0h of ventilation, pump acetal in at a rate of 0.2ml / min. Keep the air flow rate constant, and continue the reaction for 0.5h to obtain citral with a purity of 95.3% and a yield of 95.9%.
[0038] Summary of Examples
[0039]
[0040] As can be seen from the tables of Examples 1-10, the existing system for synthesizing citral has problems such as low conversion rate and cumbersome discontinuous process operation. The present invention applies a supported metal catalyst to the synthesis of citral, so that the cracking and two-step rearrangement reactions are carried out in the same fixed bed reactor. In the synthesis process of citral, the complex multi-step process is reduced to a continuous reaction in a reaction vessel, the process of distilling and cracking intermediates is reduced, the time is shortened by at least 50%, and high-purity citral can be prepared efficiently and in large quantities.
Claims
1. A method for continuously and efficiently synthesizing citral based on a fixed bed reactor, characterized in that: Using metal-supported catalysts, efficient synthesis of citral from acetal can be achieved directly in a fixed bed reactor.
2. The method according to claim 1, characterized in that The metal elements in the supported metal catalyst include one or more common metals or transition metals such as iron, sodium, potassium, aluminum, magnesium, copper, zinc, titanium, gold, platinum, palladium, nickel, rhodium, osmium, ruthenium, vanadium, cobalt, chromium, and molybdenum.
3. The method according to claim 1, characterized in that The carrier of the supported metal catalyst is one of aluminum oxide, magnesium oxide, ceramics, diatomaceous earth and molecular sieve.
4. The method according to claim 1, characterized in that: The cracking and two-step rearrangement reactions are carried out in the same fixed bed reactor.
5. The method according to claim 1, characterized in that The reaction gas flow rate is 80-150 ml / min, the raw material flow rate is not less than 0.2 ml / min, the preheating temperature is 200-250°C, the ventilation time is 0.5-1.0h, the reaction temperature is controlled at 300-400°C, the reaction time is controlled at 0.5-3.0h, and the cooling temperature is 160-180°C.
6. The method according to claim 1, characterized in that A metal-supported catalyst is filled into a fixed bed reactor, and the raw material acetal is introduced, and the citral product is directly obtained after staged cooling.