A method for preparing undecylenic acid by catalytic hydrolysis at medium and low temperatures

Abstract

The present invention discloses a method for preparing undecylenic acid by medium and low temperature catalytic hydrolysis. Methyl undecylenate, water and a hydrolysis catalyst enter a hydrolysis reactor through an inlet at the top of the hydrolysis reactor. After hydrolysis, methanol vapor enters a condenser through an outlet at the top of the hydrolysis reactor. After condensation, methanol enters a methanol recovery tank. The upper oil phase in the methanol recovery tank is pressurized by a pump and then returned to the hydrolysis reactor. The upper layer of undecylenic acid in the hydrolysis reactor is introduced into a precipitation tank. Water is added to wash the undecylenic acid in the upper layer in the precipitation tank, and the upper layer of undecylenic acid enters an undecylenic acid refining tower for refining. The lower layer of water and the hydrolysis catalyst in the precipitation tank, together with the lower layer of water in the hydrolysis reactor, enter a process water storage tank. The catalyst in the lower layer of the process water storage tank is discharged and then regenerated for reuse. Methanol is recovered after the reaction, and the process water is recycled. By adopting the medium and low temperature catalytic hydrolysis method, the process flow is shortened, the conversion rate of methyl undecylenate and the yield of undecylenic acid are improved, the energy consumption is reduced, and the discharge of waste water and waste residue is greatly reduced; the problems of excessive addition of acids and alkalis and high treatment costs of sewage and waste residue in the saponification and acidification method are avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparing undecylenic acid, and particularly relates to a method for catalytic hydrolysis at medium and low temperatures to prepare undecylenic acid. Background Art

[0002] The chemical name of nylon 11 is polyundecanamide, and its English name is Polyundecancylamide (abbreviated as PA11). Its chemical structural formula is H[NH(CH2)10CO]nOH. It is a long-chain flexible nylon synthesized from castor oil and is an important variety in polyamide engineering plastics. The production of nylon 11 mainly includes the production of 10-undecylenic acid, the production of 11-aminoundecanoic acid, monomer polymerization, and resin modification.

[0003] There are mainly two processes for producing 10-undecylenic acid from castor oil in China: One is the traditional lead bath cracking technology, in which methyl ricinoleate and steam are mixed and passed into high-temperature lead liquid for cracking. The lead liquid is easily volatilized with the cracking products, causing serious environmental pollution and easy coking. The other is the direct cracking process of castor oil. The castor oil is preheated to 150-200°C and mixed with superheated steam according to a ratio, and then enters a tower cracking furnace and is heated to 500-600°C for thermal cracking to produce 10-undecylenic acid and heptaldehyde products. In this process, due to the high viscosity, poor fluidity and difficulty in gasification of castor oil, coking is even more difficult to control.

[0004] The above two methods are both based on thermal cracking processes. Due to the too high thermal cracking temperature, the side reaction ratios of double bond polymerization and isomerization reactions, secondary cracking of products, coking, etc. are very large, and it is difficult to improve the product yield.

[0005] Castor oil undergoes transesterification with methanol to form methyl ricinoleate; methyl ricinoleate is catalytically cracked to form methyl 10-undecylenate and heptaldehyde; methyl 10-undecylenate and heptaldehyde are separated by vacuum distillation; methyl 10-undecylenate is saponified and acidified to obtain 10-undecylenic acid. In this method, the preparation of undecylenic acid from methyl undecylenate uses the saponification and acidification method, which uses a large amount of strong acids and bases such as sodium hydroxide and sulfuric acid, increasing the difficulty of sewage treatment, and the generated solid salts are difficult to handle, resulting in waste of resources and increased costs.

[0006] At present, the well-known oil hydrolysis methods include atmospheric pressure catalytic hydrolysis method and catalytic or non-catalytic medium pressure hydrolysis method. The atmospheric pressure catalytic hydrolysis method uses an acidic catalyst under atmospheric pressure, adds fresh water or low-concentration glycerol wastewater, and uses direct steam for fractional cooking to hydrolyze the oil. The catalysts used in this method are usually sulfur and sulfuric acid. The disadvantages of the atmospheric pressure hydrolysis method are that due to a very small amount of sulfation or sulfonation, the color of the fatty acids produced by hydrolysis deepens, the steam consumption is large, the hydrolysis reaction time is long, the hydrolysis degree is low, the glycerol content in the wastewater is low, and the cost of glycerol recovery is increased. At the same time, it contains sulfuric acid and sulfonic acid, which has great corrosiveness to equipment.

[0007] The medium pressure non-catalytic hydrolysis method relies on controlling certain pressure, temperature, water addition amount, and hydrolysis time to hydrolyze the oil; the medium pressure catalytic hydrolysis method, in addition to requiring certain conditions such as pressure, temperature, and water addition amount, also needs to add a certain amount of catalyst to increase the solubility of water in the oil phase during the reaction process, improve the reaction rate, and ensure a certain degree of hydrolysis. This method has a relatively long production cycle, large equipment investment, and relatively low hydrolysis degree.

[0008] Since methyl undecylenate has a shorter carbon chain than general oils, at higher temperatures and pressures, side reactions are likely to occur, resulting in a decrease in the yield of undecylenic acid. When the temperature and pressure are lower, the reaction rate is slower, the time consumption is longer, the energy consumption is higher, and at the same time, a longer reaction time will also lead to the occurrence of side reactions. Summary of the Invention

[0009] The purpose of the present invention is to solve the problems of large consumption of acids and alkalis in the existing production system of undecylenic acid by saponification and acidification method, difficult treatment of the generated wastewater and waste residue, and low selectivity in the process of using the traditional high-temperature hydrolysis method for producing undecylenic acid, and to provide a method for preparing undecylenic acid by medium and low temperature catalytic hydrolysis with mild reaction conditions, energy conservation and environmental protection, high selectivity and high yield of undecylenic acid.

[0010] The technical solution adopted by the present invention is as follows for the method of preparing undecylenic acid by medium and low temperature catalytic hydrolysis;

[0011] Methyl undecylenate, water and catalyst enter the hydrolysis reaction kettle from the top inlet of the hydrolysis reaction kettle. After hydrolysis, the methanol vapor enters the condenser through the top outlet of the hydrolysis reaction kettle. After condensation, the methanol enters the methanol recovery tank. The upper oil phase of the methanol recovery tank is pressurized by a pump and returned to the hydrolysis reaction kettle. The lower layer of methanol and water in the methanol recovery tank enter the methanol distillation column for separation;

[0012] The upper layer of undecylenic acid in the hydrolysis reaction kettle is introduced into the precipitation kettle. Water is added to wash the undecylenic acid in the upper layer of the precipitation kettle, and the upper layer of undecylenic acid enters the undecylenic acid refining tower for refining; the lower layer of water and catalyst in the precipitation kettle and the lower layer of water in the hydrolysis reaction kettle enter the process water storage tank together. After the catalyst in the lower layer of the process water storage tank is discharged, it is regenerated and reused, and the reacted process water is recycled.

[0013] Further, the reaction temperature of methyl undecylenate and water in the hydrolysis reactor is 120 - 200 °C.

[0014] Further, during the whole reaction process, the pressure in the hydrolysis reactor is 0.2 - 1.5 MPa.

[0015] Further, the mass ratio of methyl undecylenate to water is 1:0.5 - 4.

[0016] Further, the addition amount of the catalyst is 0.5 - 2% of the mass of methyl undecylenate.

[0017] Further, the catalyst is obtained by calcining a composite oxide support composed of Al, Zr, La, Mg, and Zn and then modifying it with an Al - Si sol. The molar ratio of Al, Zr, La, Mg, and Zn is 80 - 100:40 - 60:5 - 10:40 - 60:20 - 30.

[0018] Further, the preparation method of the catalyst is as follows: Mix the metal precursor salts of the composite oxide support and an equal amount of citric acid to form a sol, then stir it into a gel at 50 - 80 °C, dry it at 80 - 120 °C for 5 - 12 h, calcine it at 350 - 650 °C for 3 - 8 h, and cool it to room temperature to obtain the composite oxide support;

[0019] Immerse the composite oxide support in a sol containing Al and Si, stir and impregnate for 6 - 12 h, filter, dry it at 80 - 120 °C for 5 - 12 h, calcine it at 350 - 650 °C for 3 - 8 h, and cool it to room temperature to obtain the hydrolysis catalyst.

[0020] Further, the Al - Si coating accounts for 5 - 8% of the mass of the catalyst, and the mass ratio of Al2O3 to SiO2 is 1:5 - 8.

[0021] Further, after the catalyst is used, it is filtered and precipitated, then added to a 2% sodium carbonate solution, stirred at room temperature for 2 - 4 h, filtered, washed with an appropriate amount of water, dried at 80 - 150 °C for 5 - 12 h, and calcined at 350 - 650 °C for 3 - 8 h to obtain the regenerated catalyst.

[0022] Compared with the traditional technology, the present invention has the following advantages:

[0023] 1) For the traditional saponification - acidification method for hydrolyzing methyl undecylenate to undecylenic acid, the present invention adopts a medium - low temperature catalytic hydrolysis method, which shortens the process flow, greatly reduces the discharge of wastewater and waste residues; and avoids the problems of excessive addition of acids and bases and high treatment costs of sewage and waste salts in the saponification - acidification method.

[0024] 2) The present invention uses an oxide catalyst. Compared with the traditional medium-pressure and high-pressure grease hydrolysis methods, the reaction pressure and temperature are significantly reduced, the energy consumption is decreased, the occurrence of side reactions under high temperature and pressure is reduced, the selectivity and yield of undecylenic acid are high, and the catalyst can be reused.

[0025] 3) In the method of the present invention, methanol generated by the hydrolysis of methyl undecylenate is removed in a timely manner, which helps the reaction to proceed in the forward direction, increases the hydrolysis conversion rate of undecylenic acid, reduces the reaction time, and is also conducive to the recovery of methanol generated by hydrolysis. The production cost is reduced, and the recovery of by-products also brings certain economic benefits.

[0026] 4) Aiming at the problems existing in the traditional grease hydrolysis catalyst, the active component and the carrier component of the present invention are prepared in one step by the precipitation method, which improves the stability of the catalyst. The introduction of Zr enriches the acid-base sites on the surface of Al, the introduction of La improves the hydrothermal stability of the carrier, and the interaction between Zn and Mn helps the distribution of acid-base sites of the catalyst and increases the base strength. At the same time, the one-step preparation enhances the interaction between each component and improves the hydrothermal stability of the catalyst. Furthermore, the present invention composites Si with Al and uses it for catalyst modification, which is more conducive to improving the hydrothermal and structural stability of the catalyst and increasing the catalyst life. The prepared catalyst has high catalytic activity for the hydrolysis of methyl undecylenate. At a relatively low temperature and pressure, methyl undecylenate is hydrolyzed to form undecylenic acid. Compared with the case without adding a catalyst, the hydrolysis temperature is low, the efficiency is high, the hydrolysis conversion rate of methyl undecylenate can reach more than 99%, and the yield of undecylenic acid can reach more than 98%.

[0027] 5) In the traditional hydrolysis of castor oil to prepare ricinoleic acid, the added catalyst zinc oxide is discarded after being used once. The present invention provides a method for regenerating the catalyst. After being used, the catalyst can be restored to activity after simple alkali washing and calcination, and can be reused three times, and the catalyst activity still remains above 95%, significantly reducing the production cost.

[0028] 6) The hydrolysis temperature of the present invention is low. Using a hydrolysis reaction kettle, the investment is low, the production is flexible, and the production cost is relatively low. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic flow chart of the method for low-temperature catalytic hydrolysis to prepare undecylenic acid in the present invention. DETAILED DESCRIPTION OF THE INVENTION

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

[0031] Example 1

[0032] As Figure 1As shown in the figure, methyl undecylenate, water and catalyst enter the hydrolysis reactor a from the top inlet of the hydrolysis reactor a. After hydrolysis, the methanol vapor enters the condenser b through the top outlet of the hydrolysis reactor a. After condensation, the methanol enters the methanol recovery tank c. The upper oil phase in the methanol recovery tank c is pressurized by a pump and then returned to the hydrolysis reactor a. The lower layer of methanol and water in the methanol recovery tank c enters the methanol distillation column f for separation; during the reaction process, the mass fraction ratio of oil to water is controlled at 1:1, the catalyst addition amount accounts for 1.5% of the mass of methyl undecylenate, the temperature in the hydrolysis tower is controlled at 150 °C, the pressure is controlled at 0.47 MPa, and the stirring speed is controlled at 200 rpm / min.

[0033] The upper layer of undecylenic acid in the hydrolysis reactor a is introduced into the precipitation reactor d. Water is added to wash the undecylenic acid in the upper layer in the precipitation reactor d, and the upper layer of undecylenic acid enters the undecylenic acid refining tower f for refining; the lower layer of water and catalyst in the precipitation reactor d and the lower layer of water in the hydrolysis reactor a enter the process water storage tank e together. After the catalyst in the lower layer of the process water storage tank e is discharged, it is regenerated and reused, and the reacted process water is recycled.

[0034] Preparation method of the catalyst:

[0035] 1) Measure 1 L of a mixed solution of 0.45 mol / L aluminum nitrate, 0.25 mol / L zirconium nitrate, 0.04 mol / L lanthanum nitrate, 0.25 mol / L magnesium nitrate and 0.125 mol / L zinc chloride, add 214 g of citric acid, stir evenly to form a sol, then continue to stir into a gel at 60 °C, dry at 110 °C for 12 h, calcine at 550 °C for 4 h, and cool to room temperature to obtain a composite oxide. The molar ratio of Al, Zr, La, Mg and Zn is 45:25:2.5:25:12.5.

[0036] 2) Add 7 g of aluminum nitrate and 50 g of 20% silica sol by mass concentration to 180 mL of 5% dilute nitric acid by mass concentration. During stirring, add 3 g of urea, 3 g of polyethylene glycol and 3 g of ethanolamine, and age for 12 hours to obtain a stable Al-Si composite sol. The mass ratio of Al2O3 to SiO2 is 1:6.

[0037] 3) Immerse 50 g of the composite oxide support obtained in step 1) into 50 ml of the sol obtained in step 2), stir, dry at 110 °C for 12 h, and calcine at 550 °C for 5 h to obtain a modified catalyst. The addition amount of Al-Si is 6% of the catalyst mass;

[0038] Reaction results: The conversion rate of methyl undecylenate is 99.79%, the selectivity of undecylenic acid is 99.22%, and the yield of undecylenic acid is 99.01%.

[0039] Example 2

[0040] Methyl undecylenate, water and catalyst enter the hydrolysis reactor a from the top inlet of the hydrolysis reactor a. After hydrolysis, the methanol vapor enters the condenser b through the top outlet of the hydrolysis reactor a. After condensation, the methanol enters the methanol recovery tank c. The upper oil phase in the methanol recovery tank c is pressurized by a pump and then returned to the hydrolysis reactor a. The lower layer of methanol and water in the methanol recovery tank c enters the methanol distillation column f for separation; during the reaction process, the mass ratio of oil to water is controlled at 1:2, the catalyst addition amount accounts for 1% of the mass of methyl undecylenate, the temperature in the hydrolysis tower is controlled at 160 °C, the pressure is controlled at 0.6 MPa, and the stirring speed is controlled at 200 rpm / min.

[0041] The upper layer of undecylenic acid in the hydrolysis reactor a is introduced into the precipitation tank d. Water is added to wash the undecylenic acid in the upper layer in the precipitation tank d, and the upper layer of undecylenic acid enters the undecylenic acid refining column f for refining; the lower layer of water and catalyst in the precipitation tank d and the lower layer of water in the hydrolysis reactor a enter the process water storage tank e together. After the catalyst in the lower layer of the process water storage tank e is discharged, it is recycled, and the reacted process water is recycled.

[0042] Preparation method of catalyst:

[0043] 1) Measure 1 L of a mixed solution of 0.4 mol / L aluminum nitrate, 0.25 mol / L zirconium nitrate, 0.025 mol / L lanthanum nitrate, 0.3 mol / L magnesium nitrate and 0.1 mol / L zinc chloride, add 206 g of citric acid, stir evenly to form a sol, then continue to stir into a gel at 60 °C, dry at 110 °C for 12 h, calcine at 450 °C for 8 h, and cool to room temperature to obtain a composite oxide. The molar ratio of Al, Zr, La, Mg and Zn is 40:25:2.5:30:10.

[0044] 2) Add 5 g of aluminum nitrate and 50 g of 20% silica sol by mass to 180 mL of 5% dilute nitric acid by mass. During stirring, add 3 g of urea, 3 g of polyethylene glycol and 3 g of ethanolamine, and age for 12 hours to obtain a stable Al-Si composite sol. The mass ratio of Al2O3 to SiO2 is 1:7.

[0045] 3) Immerse 50 g of the composite oxide support obtained in step 1) into 58 ml of the sol obtained in step 2), stir, dry at 110 °C for 12 h, and calcine at 450 °C for 5 h to obtain a hydrolysis catalyst. The addition amount of Al-Si is 7% of the catalyst mass.

[0046] Reaction results: The conversion rate of methyl undecylenate is 99.71%, the selectivity of undecylenic acid is 99.01%, and the yield of undecylenic acid is 98.72%.

[0047] Example 3

[0048] Methyl undecylenate, water and catalyst enter the hydrolysis reactor a from the top inlet of the hydrolysis reactor a. After hydrolysis, the methanol vapor enters the condenser b through the top outlet of the hydrolysis reactor a. After condensation, the methanol enters the methanol recovery tank c. The upper oil phase in the methanol recovery tank c is pressurized by a pump and then returned to the hydrolysis reactor a. The lower layer of methanol and water in the methanol recovery tank c enters the methanol distillation column f for separation; during the reaction process, the mass ratio of oil to water is controlled at 1:1, the catalyst addition amount accounts for 1.5% of the mass of methyl undecylenate, the temperature in the hydrolysis tower is controlled at 160 °C, the pressure is controlled at 0.6 MPa, and the stirring speed is controlled at 200 rpm / min.

[0049] The upper layer of undecylenic acid in the hydrolysis reactor a is introduced into the precipitation tank d. Water is added to wash the undecylenic acid in the upper layer in the precipitation tank d, and the upper layer of undecylenic acid enters the undecylenic acid refining tower f for refining; the lower layer of water and catalyst in the precipitation tank d and the lower layer of water in the hydrolysis reactor a enter the process water storage tank e together. After the lower layer of catalyst in the process water storage tank e is discharged, it is regenerated and reused, and the reacted process water is recycled.

[0050] Preparation method of catalyst:

[0051] 1) Measure 1 L of a mixed solution of 0.5 mol / L aluminum nitrate, 0.3 mol / L zirconium nitrate, 0.05 mol / L lanthanum nitrate, 0.2 mol / L magnesium nitrate and 0.12 mol / L zinc chloride, add 225 g of citric acid, stir evenly to form a sol, then continue to stir into a gel at 60 °C, dry at 100 °C for 10 h, calcine at 650 °C for 3 h, and cool to room temperature to obtain a composite oxide. The molar ratio of Al, Zr, La, Mg and Zn is 50:30:5:20:12.

[0052] 2) Add 7 g of aluminum nitrate and 50 g of 20% silica sol by mass to 180 mL of 5% dilute nitric acid by mass. During stirring, add 3 g of urea, 3 g of polyethylene glycol and 3 g of ethanolamine, and age for 12 hours to obtain a stable Al-Si composite sol. The mass ratio of Al2O3 to SiO2 is 1:6.

[0053] 3) Immerse 50 g of the composite oxide support obtained in step 1) into 50 ml of the sol obtained in step 2), stir, dry at 110 °C for 12 h, and calcine at 650 °C for 3 h to obtain a hydrolysis catalyst. The addition amount of Al-Si is 6% of the catalyst mass.

[0054] Reaction results: The conversion rate of methyl undecylenate is 99.72%, the selectivity of undecylenic acid is 99.08%, and the yield of undecylenic acid is 98.80%.

[0055] Example 4

[0056] Methyl undecylenate, water and the catalyst enter the hydrolysis reactor a from the top inlet of the hydrolysis reactor a. After hydrolysis, the methanol vapor enters the condenser b through the top outlet of the hydrolysis reactor a. After condensation, the methanol enters the methanol recovery tank c. The upper oil phase in the methanol recovery tank c is pressurized by a pump and returned to the hydrolysis reactor a. The lower layer of methanol and water in the methanol recovery tank c enters the methanol distillation column f for separation; during the reaction process, the mass ratio of oil to water is controlled at 1:0.5, the catalyst addition amount accounts for 2% of the mass of methyl undecylenate, the temperature in the hydrolysis tower is controlled at 170 °C, the pressure is controlled at 0.79 MPa, and the stirring speed is controlled at 200 rpm / min.

[0057] The upper layer of undecylenic acid in the hydrolysis reactor a is introduced into the precipitation tank d. Water is added to wash the undecylenic acid in the upper layer in the precipitation tank d, and the upper layer of undecylenic acid enters the undecylenic acid refining column f for refining; the lower layer of water and the catalyst in the precipitation tank d and the lower layer of water in the hydrolysis reactor a enter the process water storage tank e together. After the lower layer of catalyst in the process water storage tank e is discharged, it is recycled, and the reacted process water is recycled.

[0058] Preparation method of the catalyst:

[0059] 1) Measure 1 L of a mixed solution of 0.4 mol / L aluminum nitrate, 0.2 mol / L zirconium nitrate, 0.025 mol / L lanthanum nitrate, 0.2 mol / L magnesium nitrate and 0.1 mol / L zinc chloride, add 178 g of citric acid, stir evenly to form a sol, then continue to stir into a gel at 60 °C, dry at 80 °C for 12 h, calcine at 550 °C for 4 h, and cool to room temperature to obtain a composite oxide. The molar ratio of Al, Zr, La, Mg and Zn is 40:20:2.5:20:10.

[0060] 2) Add 8.4 g of aluminum nitrate and 50 g of 20% silica sol by mass to 180 mL of 5% dilute nitric acid by mass. Stir and add 3 g of urea, 3 g of polyethylene glycol and 3 g of ethanolamine. Age for 12 hours to obtain a stable Al-Si composite sol. The mass ratio of Al2O3 to SiO2 is 1:5.

[0061] 3) Immerse 50 g of the composite oxide support obtained in step 1) into 42 ml of the sol obtained in step 2), stir, dry at 110 °C for 12 h, and calcine at 550 °C for 5 h to obtain a hydrolysis catalyst. The addition amount of Al-Si is 5% of the catalyst mass.

[0062] Reaction results: The conversion rate of methyl undecylenate is 99.62%, the selectivity of undecylenic acid is 98.86%, and the yield of undecylenic acid is 98.48%.

[0063] Example 5

[0064] Methyl undecylenate, water and the catalyst enter the hydrolysis reactor a from the top inlet of the hydrolysis reactor a. After hydrolysis, the methanol vapor enters the condenser b through the top outlet of the hydrolysis reactor a. After condensation, the methanol enters the methanol recovery tank c. The upper oil phase in the methanol recovery tank c is pressurized by a pump and then returned to the hydrolysis reactor a. The lower layer of methanol and water in the methanol recovery tank c enters the methanol distillation column f for separation; during the reaction process, the mass fraction ratio of oil to water is controlled at 1:3, the catalyst addition amount accounts for 0.5% of the mass of methyl undecylenate, the temperature in the hydrolysis tower is controlled at 180 °C, the pressure is controlled at 1 MPa, and the stirring speed is controlled at 200 rpm / min.

[0065] The upper layer of undecylenic acid in the hydrolysis reactor a is introduced into the precipitation tank d. Water is added to wash the undecylenic acid in the upper layer in the precipitation tank d, and the upper layer of undecylenic acid enters the undecylenic acid refining tower f for refining; the lower layer of water and the catalyst in the precipitation tank d and the lower layer of water in the hydrolysis reactor a enter the process water storage tank e together. After the catalyst in the lower layer of the process water storage tank e is discharged, it is regenerated and reused, and the reacted process water is recycled.

[0066] Preparation method of the catalyst:

[0067] 1) Measure 1 L of a mixed solution of 0.5 mol / L aluminum nitrate, 0.3 mol / L zirconium nitrate, 0.05 mol / L lanthanum nitrate, 0.3 mol / L magnesium nitrate and 0.15 mol / L zinc chloride, add 250 g of citric acid, stir evenly to form a sol, then continue to stir into a gel at 60 °C, dry at 110 °C for 12 h, calcine at 550 °C for 4 h, and cool to room temperature to obtain a composite oxide. The molar ratio of Al, Zr, La, Mg and Zn is 50:30:5:30:15.

[0068] 2) Add 5.25 g of aluminum nitrate and 50 g of 20% silica sol by mass concentration to 180 mL of 5% dilute nitric acid by mass concentration. While stirring, add 3 g of urea, 3 g of polyethylene glycol and 3 g of ethanolamine, and age for 12 hours to obtain a stable Al-Si composite sol. The mass ratio of Al2O3 to SiO2 is 1:8.

[0069] 3) Immerse 50 g of the composite oxide support obtained in step 1) into 67 ml of the sol obtained in step 2), stir, dry at 110 °C for 12 h, and calcine at 550 °C for 5 h to obtain a hydrolysis catalyst. The Al-Si addition amount is 8% of the catalyst mass.

[0070] Reaction results: The conversion rate of methyl undecylenate is 99.18%, the selectivity of undecylenic acid is 98.87%, and the yield of undecylenic acid is 98.06%.

[0071] Example 6

[0072] Methyl undecylenate, water and catalyst enter the hydrolysis reactor a from the top inlet of the hydrolysis reactor a. After hydrolysis, the methanol vapor enters the condenser b through the top outlet of the hydrolysis reactor a. After condensation, the methanol enters the methanol recovery tank c. The upper oil phase in the methanol recovery tank c is pressurized by a pump and returned to the hydrolysis reactor a. The lower layer of methanol and water in the methanol recovery tank c enters the methanol distillation column f for separation; during the reaction process, the mass ratio of oil to water is controlled at 1:3, the catalyst addition amount accounts for 2% of the mass of methyl undecylenate, the temperature in the hydrolysis tower is controlled at 120 °C, the pressure is controlled at 0.2 MPa, and the stirring speed is controlled at 200 rpm / min.

[0073] The upper layer of undecylenic acid in the hydrolysis reactor a is fed into the precipitation kettle d. Water is added to wash the undecylenic acid in the upper layer in the precipitation kettle d, and the upper layer of undecylenic acid enters the undecylenic acid refining tower f for refining; the lower layer of water and catalyst in the precipitation kettle d and the lower layer of water in the hydrolysis reactor a enter the process water storage tank e together. After the catalyst in the lower layer of the process water storage tank e is discharged, it is regenerated and reused, and the reacted process water is recycled.

[0074] Preparation method of the catalyst:

[0075] 1) Measure 1 L of a mixed solution of 0.4 mol / L aluminum nitrate, 0.2 mol / L zirconium nitrate, 0.03 mol / L lanthanum nitrate, 0.25 mol / L magnesium nitrate and 0.14 mol / L zinc chloride, add 196 g of citric acid, stir evenly to form a sol, then continue to stir into a gel at 60 °C, dry at 120 °C for 5 h, calcine at 550 °C for 4 h, and cool to room temperature to obtain a composite oxide. The molar ratio of Al, Zr, La, Mg and Zn is 40:20:3:25:14.

[0076] 2) Add 5 g of aluminum nitrate and 50 g of 20% silica sol by mass concentration to 180 mL of 5% dilute nitric acid by mass concentration. Stir and add 3 g of urea, 3 g of polyethylene glycol and 3 g of ethanolamine, and age for 12 hours to obtain a stable Al-Si composite sol. The mass ratio of Al2O3 to SiO2 is 1:6.

[0077] 3) Immerse 50 g of the composite oxide support obtained in step 1) into 58 ml of the sol obtained in step 2), stir and dry at 110 °C for 12 h and calcine at 550 °C for 5 h to obtain a hydrolysis catalyst. The addition amount of Al-Si is 7% of the catalyst mass.

[0078] Reaction results: The conversion rate of methyl undecylenate is 98.01%, the selectivity of undecylenic acid is 99.18%, and the yield of undecylenic acid is 97.21%.

[0079] Example 7

[0080] Methyl undecylenate, water and the catalyst enter the hydrolysis reactor a from the top inlet of the hydrolysis reactor a. After hydrolysis, the methanol vapor enters the condenser b through the top outlet of the hydrolysis reactor a. After condensation, the methanol enters the methanol recovery tank c. The upper oil phase in the methanol recovery tank c is pressurized by a pump and then returned to the hydrolysis reactor a. The lower layer of methanol and water in the methanol recovery tank c enters the methanol distillation column f for separation; during the reaction process, the mass ratio of oil to water is controlled at 1:3, the catalyst addition amount accounts for 2% of the mass of methyl undecylenate, the temperature in the hydrolysis tower is controlled at 140 °C, the pressure is controlled at 0.36 MPa, and the stirring speed is controlled at 200 rpm / min.

[0081] The upper layer of undecylenic acid in the hydrolysis reactor a is introduced into the precipitation tank d. Water is added to wash the undecylenic acid in the upper layer in the precipitation tank d, and the upper layer of undecylenic acid enters the undecylenic acid refining tower f for refining; the lower layer of water and the catalyst in the precipitation tank d and the lower layer of water in the hydrolysis reactor a enter the process water storage tank e together. After the catalyst in the lower layer of the process water storage tank e is discharged, it is regenerated and used, and the reacted process water is recycled.

[0082] Preparation method of the catalyst:

[0083] 1) Measure 1 L of a mixed solution of 0.4 mol / L aluminum nitrate, 0.3 mol / L zirconium nitrate, 0.04 mol / L lanthanum nitrate, 0.3 mol / L magnesium nitrate and 0.12 mol / L zinc chloride, add 223 g of citric acid, stir evenly to form a sol, then continue to stir into a gel at 60 °C, dry at 110 °C for 12 h, calcine at 550 °C for 4 h, and cool to room temperature to obtain a composite oxide. The molar ratio of Al, Zr, La, Mg and Zn is 40:30:4:30:12.

[0084] 2) Add 7 g of aluminum nitrate and 50 g of 20% silica sol by mass to 180 mL of 5% dilute nitric acid by mass, add 3 g of urea, 3 g of polyethylene glycol and 3 g of ethanolamine during stirring, and age for 12 hours to obtain a stable Al-Si composite sol. The mass ratio of Al2O3 to SiO2 is 1:6.

[0085] 3) Immerse 50 g of the composite oxide support obtained in step 1) into 50 ml of the sol obtained in step 2), stir, dry at 110 °C for 12 h, and calcine at 550 °C for 5 h to obtain a hydrolysis catalyst. The Al-Si addition amount is 6% of the catalyst mass.

[0086] Reaction results: The conversion rate of methyl undecylenate is 98.21%, the selectivity of undecylenic acid is 99.15%, and the yield of undecylenic acid is 97.38%.

[0087] Example 8

[0088] Methyl undecylenate, water and the catalyst enter the hydrolysis reactor a from the top inlet of the hydrolysis reactor a. After hydrolysis, the methanol vapor enters the condenser b through the top outlet of the hydrolysis reactor a. After condensation, the methanol enters the methanol recovery tank c. The upper oil phase in the methanol recovery tank c is pressurized by a pump and returned to the hydrolysis reactor a. The lower layer of methanol and water in the methanol recovery tank c enters the methanol distillation column f for separation; during the reaction process, the mass fraction ratio of oil to water is controlled at 1:4, the catalyst addition amount accounts for 2% of the mass of methyl undecylenate, the temperature in the hydrolysis tower is controlled at 200 °C, the pressure is controlled at 1.5 MPa, and the stirring speed is controlled at 200 rpm / min.

[0089] The upper layer of undecylenic acid in the hydrolysis reactor a is introduced into the precipitation tank d. Water is added to wash the undecylenic acid in the upper layer in the precipitation tank d, and the upper layer of undecylenic acid enters the undecylenic acid refining tower f for refining; the lower layer of water and the catalyst in the precipitation tank d enter the process water storage tank e together with the lower layer of water in the hydrolysis reactor a. After the catalyst in the lower layer of the process water storage tank e is discharged, it is recycled, and the reacted process water is recycled.

[0090] Preparation method of the catalyst:

[0091] 1) Measure 1 L of a mixed solution of 0.45 mol / L aluminum nitrate, 0.25 mol / L zirconium nitrate, 0.045 mol / L lanthanum nitrate, 0.25 mol / L magnesium nitrate and 0.11 mol / L zinc chloride, add 212 g of citric acid, stir evenly to form a sol, then continue to stir into a gel at 60 °C, dry at 110 °C for 12 h, calcine at 550 °C for 4 h, and cool to room temperature to obtain a composite oxide. The molar ratio of Al, Zr, La, Mg and Zn is 45:25:4.5:25:11.

[0092] 2) Add 7 g of aluminum nitrate and 50 g of 20% silica sol by mass concentration to 180 mL of 5% dilute nitric acid by mass concentration. During stirring, add 3 g of urea, 3 g of polyethylene glycol and 3 g of ethanolamine, and age for 12 hours to obtain a stable Al-Si composite sol. The mass ratio of Al2O3 to SiO2 is 1:6.

[0093] 3) Immerse 50 g of the composite oxide support obtained in step 1) into 42 ml of the sol obtained in step 2), stir, dry at 110 °C for 12 h, and calcine at 550 °C for 5 h to obtain a hydrolysis catalyst. The addition amount of Al-Si is 5% of the catalyst mass.

[0094] Reaction results: The conversion rate of methyl undecylenate is 99.12%, the selectivity of undecylenic acid is 98.68%, and the yield of undecylenic acid is 97.81%.

[0095] Comparative example 1

[0096] No catalyst was added, and other conditions were the same as in Example 1.

[0097] Comparative Example 2

[0098] Add zinc oxide catalyst, and the others are the same as in Example 1.

[0099] Comparative Example 3

[0100] Catalyst regeneration, only drying, without calcination, and the others are the same as in Example 1.

[0101] Comparative Example 4

[0102] The used catalyst is not modified, and the others are the same as in Example 1.

[0103] Table 1 Reaction Data

[0104] Methyl undecylenate hydrolysis rate / % Undecylenic acid selectivity / % Undecylenic acid yield / % Example 1 99.79 99.22 99.01 Example 2 99.71 99.01 98.72 Example 3 99.72 99.08 98.80 Example 4 99.62 98.86 98.48 Example 5 99.18 98.87 98.06 Example 6 98.01 99.18 97.21 Example 7 98.21 99.15 97.38 Example 8 99.12 98.68 97.81 Comparative Example 1 62.27 98.32 61.22 Comparative Example 2 70.05 76.11 53.32 Comparative Example 3 99.58 99.02 98.60 Comparative Example 4 99.75 99.18 98.93

[0105] Table 2 Catalyst Regeneration Data

[0106]

[0107] The results of Examples 1-8 in Table 1 show that the process method of the present invention has the advantages of high hydrolysis rate of methyl undecylenate, high selectivity and yield of undecylenic acid. The hydrolysis rate of methyl undecylenate can reach more than 98%, the selectivity of undecylenic acid can reach 98.68-99.22%, and the yield of undecylenic acid can reach 97.21-99.01%. The results of Comparative Example 1 show that in the case of not using a catalyst, the hydrolysis rate of methyl undecylenate decreases significantly, the selectivity of undecylenic acid also decreases slightly, and the yield of undecylenic acid is only 61.22%. The results of Comparative Example 2 show that when using zinc oxide as the hydrolysis catalyst, although the hydrolysis rate increases slightly compared with not using a catalyst, the selectivity of undecylenic acid decreases significantly, only 76.11%, and the yield of undecylenic acid is 53.32%. The results of Comparative Example 3 show that after the catalyst of the present invention is simply dried, its catalytic activity can be partially restored. The results of Comparative Example 4 show that when the catalyst support is not modified, the catalytic activity is equivalent to that after modification. The regeneration results of the catalysts in Example 1 and Comparative Example 4 in Table 2 show that after three regenerations, the yield of undecylenic acid in Example 1 decreases from 99.01% to 96.82%, indicating that the regeneration effect of this catalyst is good and it can be reused repeatedly. This shows that the regeneration method of the present invention has a good regeneration effect. After three regenerations, the yield of undecylenic acid in Comparative Example 4 decreases from 98.93% to 84.59%. It shows that the catalyst modification method of the present invention helps to maintain the stability of the catalyst activity, has a significant improvement effect on the regeneration performance, so that the catalyst can be reused repeatedly after simple regeneration, reducing the production cost.

Claims

1. A method for preparing undecylenic acid by catalytic hydrolysis at medium and low temperatures, characterized in that, The preparation method is as follows; Methyl undecylenate, water and a catalyst enter the hydrolysis reactor (a) from the top inlet of the hydrolysis reactor (a). After hydrolysis, the methanol vapor enters the condenser (b) through the top outlet of the hydrolysis reactor (a). After condensation, the methanol enters the methanol recovery tank (c). The upper oil phase of the methanol recovery tank (c) is pressurized by a pump and then returned to the hydrolysis reactor (a). The lower layer of methanol and water in the methanol recovery tank (c) enters the methanol distillation column (f) for separation; The upper layer of undecylenic acid in the hydrolysis reactor (a) is introduced into the precipitation tank (d). Water is added to wash the undecylenic acid in the upper layer in the precipitation tank (d). The upper layer of undecylenic acid enters the undecylenic acid refining column (f) for refining; the lower layer of water and the catalyst in the precipitation tank (d) and the lower layer of water in the hydrolysis reactor (a) enter the process water storage tank (e) together. After the catalyst in the lower layer of the process water storage tank (e) is discharged, it is regenerated and reused, and the reacted process water is recycled; The catalyst is a composite oxide support of Al, Zr, La, Mg and Zn, which is calcined and then modified with Al-Si sol. The molar ratio of Al, Zr, La, Mg and Zn is 80-100:40-60:5-10:40-60:20-30; the preparation method of the catalyst is: mixing the metal precursor salts of the composite oxide support and an equal amount of citric acid to form a sol, then stirring into a gel at 50-80 °C, drying at 80-120 °C for 5-12 h, calcining at 350-650 °C for 3-8 h, and cooling to room temperature to obtain the composite oxide support; The composite oxide support is impregnated in a sol containing Al and Si, stirred and impregnated for 6-12 h, filtered, dried at 80-120 °C for 5-12 h, calcined at 350-650 °C for 3-8 h, and cooled to room temperature to obtain the catalyst.

2. The method for preparing undecylenic acid by catalytic hydrolysis at medium and low temperatures according to claim 1, wherein The reaction temperature of methyl undecylenate and water in the hydrolysis reactor (a) is 120-200 °C.

3. The method for preparing undecylenic acid by medium and low temperature catalytic hydrolysis according to claim 1, wherein The pressure in the hydrolysis reactor (a) is 0.2-1.5 MPa.

4. The method for preparing undecylenic acid by medium and low temperature catalytic hydrolysis according to claim 1, characterized in that: The mass ratio of methyl undecylenate to water is: 1:0.5-4.

5. The method for preparing undecylenic acid by catalytic hydrolysis at medium and low temperatures according to claim 1, characterized in that, The addition amount of the catalyst is 0.5-2% of the mass of methyl undecylenate.

6. The method for preparing undecylenic acid by medium-low temperature catalytic hydrolysis according to claim 1, wherein The Al-Si coating accounts for 5-8% of the mass of the catalyst, and the mass ratio of Al2O3 to SiO2 is 1:5-8.

7. The method for preparing undecylenic acid by medium and low temperature catalytic hydrolysis according to claim 1, characterized in that, After the hydrolysis catalyst is used, it is filtered, precipitated, added to a 2% sodium carbonate solution by mass, stirred at room temperature for 2-4 h, filtered, washed with an appropriate amount of water, dried at 80-150 °C for 5-12 h, and calcined at 350-650 °C for 3-8 h to obtain the regenerated catalyst.

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