Process for preparing undecylenic acid by microwave heating enzymatic hydrolysis under negative pressure

Abstract

The present invention discloses a process for preparing undecylenic acid by microwave heating enzymatic hydrolysis under negative pressure, that is, water and methyl undecylenate are enzymatically catalyzed to hydrolyze into undecylenic acid and methanol under microwave heating and negative pressure conditions. This process uses biological enzymes as catalysts, shortening the process of traditional saponification and acidification processes, improving the reaction rate and selectivity. At the same time, the mild reaction conditions are more friendly to equipment and the environment; under negative pressure conditions, the removal of methanol is accelerated, effectively improving the reaction rate and conversion rate of hydrolysis; the use of the thermal effect and non-thermal effect of microwave heating improves the reaction rate and conversion rate. The reaction temperature is only 40 °C, the reaction time is 2 hours, and the conversion rate reaches more than 95%. At the same time, the energy consumption of the process is also relatively low. The present invention provides a new process for preparing undecylenic acid, effectively improving the reaction rate and conversion rate, and achieving the purposes of energy conservation, consumption reduction and environmental protection in the process.

Description

Technical Field

[0001] The present invention relates to the field of oil and fat chemical industry, and particularly to a process for preparing undecylenic acid by microwave heating enzymatic hydrolysis under negative pressure. Background Art

[0002] Undecylenic acid is an important chemical intermediate, which can be used to prepare nylon 11, pharmaceuticals, spices, etc. It can be obtained by cracking castor oil or directly cracking ricinoleic acid, or by saponifying and acidifying methyl undecylenate. In the process of directly cracking to prepare undecylenic acid using castor oil or ricinoleic acid as raw materials, there are technical problems such as high cracking energy consumption, many by-products, easy coking and low yield. When preparing undecylenic acid from methyl undecylenate after cracking of methyl ricinoleate, generally, a saponification and acidification process is required (Zhao Xuejing. Chemical Principles and Preparation of Undecylenic Acid Derived from Castor Oil [J]. Modern Food, 2015(22): 38-43.). This requires a large amount of lye and acid solution, which will cause corrosion to the equipment and also bring problems in the treatment of waste salt and wastewater.

[0003] Undecylenic acid can also be prepared by hydrolyzing methyl undecylenate. The process described in Chinese Patent CN 116063171 A uses pressurized high temperature to produce undecylenic acid. Adding a catalyst can accelerate the chemical reaction rate, but the temperature is high, the energy consumption is large, and there is also a problem of reprocessing the catalyst. Chinese Patent CN 115784866 A uses a bubble cap tower as a reactor, which can reduce the energy loss caused by mechanical stirring, and through the contact of the upper and lower liquids for mixing and heat exchange, saving energy. However, pressurized and high temperature conditions still require a large amount of energy consumption.

[0004] In recent years, due to the mild reaction conditions and fast reaction rate of biological enzymes, they have been widely used in oil hydrolysis. In Chinese Patent CN 101294170A, Chinese Patent CN 101100628 A and Chinese Patent CN 102417916 B, lipase is used to hydrolyze oil and fat. Under relatively mild conditions, the reaction process is accelerated, the hydrolysis rate is increased, and the enzyme can be reused. However, since the hydrolysis reaction is generally a reversible reaction, there are still problems of low conversion rate and insufficient reaction rate in the enzymatic hydrolysis process. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies existing in the prior art, and to provide a process for catalytic hydrolysis of fatty acid methyl ester to produce fatty acid by using microwave heating to strengthen the reaction under negative pressure conditions and using biological enzyme as a catalyst, which is a new process with low energy consumption, high yield and low pollution. The present invention relates to a new process for preparing undecylenic acid by microwave heating enzymatic hydrolysis under negative pressure.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A process for preparing undecylenic acid by microwave heating enzymatic hydrolysis under negative pressure, comprising the following steps:

[0008] Step 1: Add water, methyl undecylenate and biological enzyme into a microwave hydrolysis reactor, and continuously stir; the biological enzyme is lipase, which refers to an enzyme that can catalyze the hydrolysis of the ester bond of grease, and its form is solid or liquid enzyme;

[0009] Step 2: Evacuate the microwave hydrolysis reactor to make the reaction system under negative pressure conditions, then turn on the microwave heating. By adjusting the microwave heating power and the pressure of evacuation, make the reaction system reach the required reaction temperature and maintain a constant temperature state, so that the hydrolysis reaction occurs under microwave radiation and stirring;

[0010] Step 3: During the reaction process, water and the generated methanol vapor are continuously distilled out and condensed and collected, and water is timely replenished into the reaction system to keep the liquid level of the reaction system at the initial level;

[0011] Step 4: After the reaction is completed, separate and recover the biological enzyme from the reaction solution to obtain a stock solution containing undecylenic acid product, and the separated biological enzyme is reused in the next batch of reactions.

[0012] Further, the microwave heating power is 5 - 10 kW / kg of methyl undecylenate. That is to say, the microwave heating power is determined according to the mass of methyl undecylenate. For example: when the dosage of methyl undecylenate during the hydrolysis reaction is 1 kg, the microwave heating power is 5 - 10 kW; if the dosage of methyl undecylenate is 2 kg, the microwave heating power is 10 - 20 kW, and so on.

[0013] Further, the negative pressure condition in the reaction system is an absolute pressure of 5 - 20 kPa.

[0014] Further, in Step 1, the feeding mass ratio of the reaction raw materials water and methyl undecylenate is 3:1 - 6:1.

[0015] Further, in the hydrolysis reaction of Step 2, the reaction temperature is 40 - 60 °C.

[0016] Further, the reaction time of the hydrolysis reaction is 1 - 3 hours.

[0017] Further, the stirring speed in the hydrolysis reaction of Step 2 is 400 - 700 rpm.

[0018] Further, the mass concentration of the biological enzyme in the reaction system is 0.5 - 20 %.

[0019] Further, the biological enzyme is immobilized lipase Novozym 435, and the mass concentration of the biological enzyme in the reaction system is 0.5 - 3%.

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0021] Using bio - enzyme as a catalyst greatly improves the reaction rate and selectivity of methyl undecylenate hydrolysis. At the same time, the mild reaction conditions are more friendly to equipment and the environment; under negative pressure conditions, the removal of methanol is accelerated, effectively improving the reaction rate and conversion rate of hydrolysis; the use of the thermal effect and non - thermal effect of microwave heating improves the reaction rate. At a relatively low temperature (reaction temperature is 40 °C) and a reaction time of 2 hours, a conversion rate of over 96% can be achieved, reducing the process energy consumption. This process has mild reaction conditions and a simple process flow, achieving high reaction rate, high conversion rate, and high yield of methyl undecylenate hydrolysis under the conditions of low energy consumption and environmental friendliness. Specific Embodiments

[0022] The following further illustrates the present invention with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0023] The immobilized lipase Novozym 435 is from Novozymes A / S, Denmark.

[0024] Example 1: Add the immobilized lipase Novozym 435 into a hydrolysis reactor. Add water and methyl undecylenate into the hydrolysis reactor at a mass ratio of 4:1, and the mass concentration of the enzyme in the feed liquid is 1%. The mass of methyl undecylenate in the hydrolysis reactor is 30 g. Start stirring at a speed of 500 rpm, and at the same time, turn on the water - bath heating, set the water - bath temperature to 40 °C, keep the reaction temperature stable at 40 °C, and start the reaction. After 4 hours of reaction, the conversion rate of methyl undecylenate is 54.93%, and the yield of undecylenic acid is 54.93%.

[0025] Example 2: Add the immobilized lipase Novozym 435 into a microwave hydrolysis reactor. Add water and methyl undecylenate into the microwave hydrolysis reactor at a mass ratio of 4:1, and the mass concentration of the enzyme in the feed liquid is 1%. The mass of methyl undecylenate in the microwave hydrolysis reactor is 30 g. Start stirring at a speed of 500 rpm, and at the same time, turn on the microwave heating, with a microwave power of 189 W. Heat the reaction feed liquid at a microwave heating power of 6.3 kW / kg of methyl undecylenate and keep the temperature at 40 °C, and start the reaction. After 4 hours of reaction, the conversion rate of methyl undecylenate is 59.54%, and the yield of undecylenic acid is 59.54%.

[0026] Comparing Comparative Example 1 and Example 2, under the conditions of the same hydrolysis raw material ratio, reaction temperature, stirring speed, and enzyme dosage, compared with water bath heating, microwave heating has a higher heating efficiency, which speeds up the reaction rate, and the yield of undecylenic acid increases by 4.61%. The possible reason is that the non-thermal effect of microwave heating changes the reaction path and reduces the activation energy of the reaction.

[0027] Example 3: Add immobilized lipase Novozym 435 to the hydrolysis reactor. Add water and methyl undecylenate to the hydrolysis reactor at a mass ratio of 4:1. The mass concentration of the enzyme in the feed liquid is 1%. The mass of methyl undecylenate in the hydrolysis reactor is 30 g. Start stirring at a speed of 500 rpm. Turn on the water bath heating, set the water bath temperature to 41 °C, and at the same time evacuate to vacuum. Heat the reaction feed liquid to boiling and maintain the temperature at 40 °C. At this time, the pressure in the hydrolysis reactor is maintained at 10 kPa, and the reaction starts. During the reaction, make up water in time to ensure that the reaction liquid level remains at the initial liquid level. After reacting for 4 hours, the conversion rate of methyl undecylenate is 83.88%, and the yield of undecylenic acid is 83.88%.

[0028] Comparing Comparative Example 1 and Example 3, under the condition that other conditions remain unchanged, after applying negative pressure, methanol can be removed in time, which is beneficial to the forward progress of the reaction, the hydrolysis reaction rate is accelerated, and the yield of undecylenic acid increases by 28.95%. This shows that the negative pressure condition can effectively improve the conversion rate of the reaction.

[0029] Example 4: Add immobilized lipase Novozym 435 to the hydrolysis reactor. Add water and methyl undecylenate to the hydrolysis reactor at a mass ratio of 4:1. The mass concentration of the enzyme in the feed liquid is 1%. The mass of methyl undecylenate in the hydrolysis reactor is 30 g. Start stirring at a speed of 500 rpm. Turn on the water bath heating, set the water bath temperature to 50 °C, and at the same time evacuate to vacuum. Heat the reaction feed liquid to boiling and maintain the temperature at 40 °C. At this time, the pressure in the hydrolysis reactor is maintained at 5 kPa, and the reaction starts. During the reaction, make up water in time to ensure that the reaction liquid level remains at the initial liquid level. After reacting for 4 hours, the conversion rate of methyl undecylenate is 93.75%, and the yield of undecylenic acid is 93.75%.

[0030] Example 5: Immobilized lipase Novozym 435 was added to the hydrolysis reactor. Water and methyl undecylenate were added to the hydrolysis reactor at a mass ratio of 4:1, and the mass concentration of the enzyme in the feed liquid was 1%. The mass of methyl undecylenate in the hydrolysis reactor was 30 g. Stirring was started at a speed of 500 rpm. Water bath heating was turned on, and the water bath temperature was set at 55 °C. At the same time, vacuum was applied to heat the reaction feed liquid to boiling and maintain the temperature at 40 °C. At this time, the pressure in the hydrolysis reactor was maintained at 2.5 kPa, and the reaction was started. During the reaction, water was replenished in a timely manner to ensure that the reaction liquid level remained at the starting level. After reacting for 4 hours, the conversion rate of methyl undecylenate was 95.39%, and the yield of undecylenic acid was 95.39%.

[0031] Example 6: Immobilized lipase Novozym 435 was added to the hydrolysis reactor. Water and methyl undecylenate were added to the hydrolysis reactor at a mass ratio of 4:1, and the mass concentration of the enzyme in the feed liquid was 1%. The mass of methyl undecylenate in the hydrolysis reactor was 30 g. Stirring was started at a speed of 500 rpm. Water bath heating was turned on, and the water bath temperature was set at 60 °C. At the same time, vacuum was applied to heat the reaction feed liquid to boiling and maintain the temperature at 40 °C. At this time, the pressure in the hydrolysis reactor was maintained at 1.5 kPa, and the reaction was started. During the reaction, water was replenished in a timely manner to ensure that the reaction liquid level remained at the starting level. After reacting for 4 hours, the conversion rate of methyl undecylenate was 95.48%, and the yield of undecylenic acid was 95.48%.

[0032] Comparing Comparative Example 3, Example 4, Example 5 and Example 6, at the same reaction temperature, by increasing the temperature of water bath heating and reducing the pressure in the reaction system, the evaporation amount of water and the removal amount of methanol were increased, the mass transfer process was accelerated, the hydrolysis proceeded in the forward direction, the reaction rate was accelerated, and the yield of undecylenic acid was increased.

[0033] Example 7: Immobilized lipase Novozym 435 was added to the microwave hydrolysis reactor. Water and methyl undecylenate were added to the microwave hydrolysis reactor at a mass ratio of 4:1, and the mass concentration of the enzyme in the feed liquid was 1%. The mass of methyl undecylenate in the hydrolysis reactor was 30 g. Stirring was started at a speed of 500 rpm, and microwave heating was turned on. The microwave power was 189 W, and heating was started at a power of 6.3 kW / kg of methyl undecylenate. At the same time, vacuum was applied to heat the reaction feed liquid to boiling and stabilize the temperature at 40 °C. At this time, the pressure in the microwave hydrolysis reactor was maintained at 10 kPa, and the reaction was started. During the reaction, water was replenished in a timely manner to ensure that the reaction liquid level remained at the starting level. After reacting for 100 min, the conversion rate of methyl undecylenate was 94.97%, and the yield of undecylenic acid was 94.97%.

[0034] Comparing Example 3 and Example 7, under the same negative pressure condition, the reaction rate of microwave heating is fast and the conversion rate is high. Microwave heating reaches a conversion rate of 94.97% within 100 min, which is 31.49% higher than the yield of undecylenic acid under water bath heating conditions. The results of the yields of undecylenic acid at different reaction times in Examples 1 - 5 and Example 7 are summarized in Table 1.

[0035] Table 1 Yields of undecylenic acid at different reaction times in different examples

[0036] 。

[0037] The comparison of the reaction conditions of Examples 1 - 7, as well as the results of the conversion rate and the total mass of the distilled water and methanol vapor at different times, are summarized in Table 2.

[0038] Table 2 Comparison of the conditions and conversion rates of the hydrolysis of methyl undecylenate

[0039] 。

[0040] In addition, comparing Example 5 and Example 7, in terms of the amount of the distilled water and methanol vapor, the energy consumption of microwave heating is the least, and the evaporation rate of water and methanol is only about 64.7 g / h. It shows that compared with water bath heating, to achieve the same high conversion rate and high yield, water bath heating requires greater heating power and lower pressure.

[0041] Example 8: Add immobilized lipase Novozym 435 to the microwave hydrolysis reactor. Add water and methyl undecylenate to the microwave hydrolysis reactor at a mass ratio of 4:1, and the mass concentration of the enzyme in the feed liquid is 1%. The mass of methyl undecylenate in the hydrolysis reactor is 30 g. Start stirring at a speed of 500 rpm, turn on the microwave heating, the microwave power is 240 W, start heating at a power of 8 kW / kg of methyl undecylenate, and at the same time evacuate, heat the reaction feed liquid to boiling, and keep the temperature stable at 40 °C. At this time, the pressure in the microwave hydrolysis reactor is maintained at 9 kPa, and the reaction starts. Make up water in time during the reaction to ensure that the reaction liquid level remains at the starting liquid level. After reacting for 1.7 hours, the conversion rate of methyl undecylenate is 99.02%, and the yield of undecylenic acid is 99.02%.

[0042] The content described in this specification is only a list of the implementation forms of the inventive concept, and the protection scope of the present invention should not be regarded as limited to the specific forms stated in the embodiments.

Claims

1. A process for preparing undecylenic acid by microwave heating enzymatic hydrolysis under negative pressure, characterized in that The following steps are involved: Step 1: adding water, methyl undecylenate and biological enzyme into a microwave hydrolysis reactor and stirring continuously; the biological enzyme is lipase, which refers to an enzyme that can catalyze the hydrolysis of ester bonds of oils and fats, and is in the form of solid or liquid enzyme; the biological enzyme is immobilized lipase Novozym 435; Step 2: After evacuating the microwave hydrolysis reactor to place the reaction system under negative pressure, microwave heating is started, and the reaction system is placed at a desired reaction temperature by adjusting the microwave heating power and the evacuation pressure, and the temperature is maintained constant to allow the hydrolysis reaction to proceed under microwave radiation and stirring; Step 3: During the reaction, water and the generated methanol vapor are continuously evaporated and condensed and collected, and water is added to the reaction system in a timely manner to maintain the liquid level of the reaction system at the initial level; Step 4: After the reaction is completed, the biological enzyme is separated and recovered from the reaction solution to obtain a feed solution containing the undecylenic acid product, and the separated biological enzyme is repeatedly used for the next batch of reactions.

2. The process for preparing undecylenic acid by microwave heating enzymatic hydrolysis under negative pressure as claimed in claim 1, characterized in that The microwave heating power is 5-10 kW / kg methyl undecylenate.

3. The process for preparing undecylenic acid by microwave heating enzymatic hydrolysis under negative pressure as claimed in claim 1, characterized in that The negative pressure condition in the reaction system is an absolute pressure of 5-20 kPa.

4. The process for preparing undecylenic acid by microwave heating enzymatic hydrolysis under negative pressure as claimed in claim 1, characterized in that In step 1, the mass ratio of the reaction raw materials water and methyl undecylenate is 3:1-6:

1.

5. The process for preparing undecylenic acid by microwave heating enzymatic hydrolysis under negative pressure as claimed in claim 1, characterized in that In the hydrolysis reaction of step 2, the reaction temperature is 40-60°C.

6. The process for preparing undecylenic acid by microwave heating enzymatic hydrolysis under negative pressure as claimed in claim 1, characterized in that The stirring speed of the hydrolysis reaction in step 2 is 400-700 rpm.

7. The process for preparing undecylenic acid by microwave heating enzymatic hydrolysis under negative pressure as claimed in claim 1, characterized in that The mass concentration of the biological enzyme in the reaction system is 0.5%-20%.

8. The process for preparing undecylenic acid by microwave heating enzymatic hydrolysis under negative pressure as claimed in claim 1, characterized in that The reaction time of the hydrolysis reaction is 1-3 hours.

9. The process for preparing undecylenic acid by microwave heating enzymatic hydrolysis under negative pressure as claimed in claim 1, characterized in that The mass concentration of the biological enzyme in the reaction system is 0.5%-3%.