A method for continuously preparing 3-methyl-2-butene-1-aldehyde diisoprenylacetal

Abstract

The present invention provides a method for continuously preparing 3 methyl 2 butylene 1 aldehyde diisopentenyl acetals, the method comprising the steps of: mixing raw material isopentanol and isopentenyl aldehyde according to a certain ratio to obtain a mixture, then the mixture is continuously fed from the middle part of the reaction section of a reactive distillation tower after being preheated by a heat exchanger into a tower for condensation reaction, wherein the reaction section is loaded with a modified SAPO 34 molecular sieve catalyst; and the water generated by the reaction and unreacted raw material are separated in a tower top oil-water separator, the oil phase is transported to a designated storage tank, and the aqueous phase is discharged as waste water, and the reactor obtains a higher content of 3 methyl 2 butylene 1 aldehyde diisopentenyl acetals. The present invention uses modified SAPO 34 molecular sieve catalysts to reduce reaction temperature, improve selectivity, reduce production energy consumption, extend catalyst life, and is conducive to industrialized production under the premise of ensuring high activity.

Description

Technical Field

[0001] The invention belongs to the technical field of fine chemicals, and particularly relates to a method for continuously preparing 3-methyl-2-butene-1-aldehyde diisopentenyl acetal. Background Art

[0002] 3-Methyl-2-butene-1-aldehyde diisoprenylacetal is an important intermediate in the synthesis of citral. The traditional method is to use inorganic acids such as nitric acid and phosphoric acid or lithium chloride as catalysts under negative pressure conditions to prepare it.

[0003] The chemical equation for the reaction is as follows:

[0004]

[0005] US Patent No. 4133836A discloses a method for preparing acetal by reactive distillation, wherein nitric acid (with a concentration of 1x10 -6 The condensation reaction is carried out under process conditions of 2-200 mmHg (absolute pressure) and 15-100°C. When the reaction substrates are prenol and prenal, the conversion rate of prenal exceeds 97%. However, the disadvantages of this method are that the nitric acid catalyst is unevenly distributed in the reactive distillation column, the reaction amount is difficult to control, and the equipment requirements are relatively high.

[0006] U.S. Patent No. 5,177,265A uses phosphoric acid as a catalyst and toluene as a water carrier, conducting a condensation reaction at a pressure of 8,000 to 14,000 Pa (absolute pressure) and a temperature of 60 to 90°C. The conversion of isopentenal is 83%, and the yield of 3-methyl-2-butene-1-aldehyde diisopentenyl acetal is 75.6%. However, its disadvantages are that the reaction product contains toluene, and the excess acid catalyst requires neutralization, which increases the subsequent separation process.

[0007] U.S. Patent No. 4,933,500 discloses a condensation reaction using aluminum chloride as a catalyst in an inert solvent at a reaction temperature of 70-100°C and a pressure of 20-100 mmHg (2.7-13.3 kPa) (absolute pressure), resulting in a conversion rate of greater than 75% to isopentenal. However, this method has the following disadvantages: the aluminum chloride catalyst is highly corrosive, requires high equipment requirements, and is cumbersome to process.

[0008] Chinese patent CN104788295A discloses a method using a tubular reactor or fixed-bed reactor for pre-reaction, followed by subsequent reaction and separation and purification in a bulkhead reaction distillation column. The catalysts used are one or more of nitric acid, formic acid, acetic acid, propionic acid, and isopentenic acid. The reaction temperature is 70-90°C, and the conversion rate of isopentenal is 98.7%, with a selectivity of 99.2% for 3-methyl-2-butene-1-aldehyde diisopentenyl acetal. However, the method uses a low-boiling acid as the catalyst, making it difficult to accurately control the amount used, and requires post-reaction neutralization of the catalyst, making the operation cumbersome.

[0009] Chinese patent CN112299962A discloses a method using a fixed-bed reactor with a chiral phosphoric acid-supported solid catalyst, preheating the feedstock to 150°C, operating at a reaction temperature of 80-90°C and a pressure of 1.0 kPa. The method achieves a conversion rate of 96.7% for isopentenal and a selectivity of 99.5% for 3-methyl-2-butene-1-aldehyde diisopentenyl acetal. However, the reaction requires preheating the feedstock to 150°C, and the reaction temperature is also relatively high, at 80-90°C, resulting in high energy consumption.

[0010] Chinese patent CN101497556B discloses the use of a solid superacid as a catalyst, with an aldehyde or ketone as the reaction reagent for acetalization, and a condensation reaction with 1,3-propylene glycol to generate a water-insoluble acetal product. In the preparation of the solid superacid catalyst, the doping metal cation is one or more of tungsten, lanthanum, molybdenum, aluminum, iron, platinum, zirconium, or manganese, and the molar ratio of the doping metal cation to silicon, tin, zirconium, or titanium is 1:0.01 to 100. The doped metal cation mainly serves to strengthen the L-acid and B-acid centers. However, the substrates isopentenol and isopentenal in the present invention are extremely unstable in the presence of a solid superacid, and side reactions such as dehydration and polymerization may occur. Therefore, the solid superacid is not suitable as a condensation catalyst of the present invention.

[0011] In summary, the liquid acid used in existing processes is difficult to recycle, corrosive to equipment, and has cumbersome post-processing steps. Furthermore, the reaction temperature in existing processes is between 80 and 120°C, resulting in high energy consumption and numerous side reactions. Summary of the Invention

[0012] The present invention provides a method for continuously synthesizing 3-methyl-2-butene-1-aldehyde diisopentenyl acetal using a reactive distillation process. This method uses a modified SAPO-34 molecular sieve as a condensation catalyst. While maintaining high activity, this method can lower the reaction temperature, improve selectivity, and reduce production energy consumption. Furthermore, the use of a solid catalyst solves the problems of cumbersome product post-processing steps and equipment corrosion in conventional processes.

[0013] To achieve the above objectives, the present invention provides a method for continuously preparing 3-methyl-2-butene-1-aldehyde diisoprenylacetal using the modified SAPO-34 molecular sieve as a condensation catalyst and prenol and prenaldehyde as raw materials. The method comprises the following steps: 1) mixing the raw materials, prenol and prenaldehyde, in a certain proportion to obtain a mixed material, and then preheating the mixed material through a heat exchanger and continuously feeding the mixed material into a reactive distillation tower from the middle of a reaction section thereof for a condensation reaction, wherein the reaction section is filled with a modified SAPO-34 molecular sieve catalyst; and 2) separating the water generated by the reaction and the unreacted raw materials in an oil-water separator at the top of the tower, conveying the oil phase to a designated storage tank, discharging the water phase as wastewater, and obtaining a high content of 3-methyl-2-butene-1-aldehyde diisoprenylacetal in the bottom of the tower.

[0014] In a preferred technical solution of the method of the present invention, preferably, the reaction distillation tower is divided into an upper distillation section, a middle reaction section and a lower stripping section, the modified SAPO-34 molecular sieve catalyst is loaded in the middle reaction section, the distillation section and the stripping section are packed towers, the number of theoretical plates of the distillation section of the reaction distillation tower is 6 to 10; the number of theoretical plates of the stripping section of the reaction distillation tower is 8 to 12; the height of the reaction section of the reaction distillation tower is 1 / 2 to 2 / 3 of the height of the entire tower.

[0015] In a preferred technical solution of the method of the present invention, preferably, in step 1), the feeding molar ratio of isopentenol to isopentenal is 2 to 2.5:1, and the temperature of the condensation reaction is 40 to 70°C.

[0016] In a preferred technical solution of the method of the present invention, preferably, in step 1), the top pressure (absolute pressure) of the reaction is 500-1000 Pa.

[0017] In the preferred technical solution of the method of the present invention, preferably, in step 1), the feed liquid volume space velocity of the mixed material is 1 to 2 h -1 .

[0018] In a preferred technical solution of the method of the present invention, the present invention also provides a method for preparing a modified SAPO-34 molecular sieve catalyst, which comprises the following steps: first, subjecting the SAPO-34 molecular sieve to steam treatment; then, impregnating and modifying the SAPO-34 molecular sieve after the steam treatment with an aqueous solution of a rare earth metal salt; and finally, drying and calcining to obtain the modified SAPO-34 molecular sieve catalyst.

[0019] In the preferred technical solution of the method of the present invention, preferably, the temperature of the water vapor treatment is 300-500°C, the time of the water vapor treatment is 2-5 hours, and the mass space velocity of the water vapor treatment is 0.2-0.5h -1Preferably, the temperature of the steam treatment is 350-450°C.

[0020] In a preferred technical solution of the method of the present invention, preferably, the rare earth metal salt is selected from one or more of the nitrates of lanthanum, cerium, praseodymium and neodymium.

[0021] In a preferred technical solution of the method of the present invention, preferably, the concentration of the rare earth metal salt aqueous solution is 0.3-1.0 wt %; the immersion temperature is 20-50° C.; and the immersion time is 5-24 hours.

[0022] In a preferred technical solution of the method of the present invention, preferably, the drying temperature is 100-120°C, and the drying time is 8-20 hours; the calcining temperature is 400-600°C, and the calcining time is 2-5 hours. Preferably, the calcining temperature is 450-550°C.

[0023] Compared with Chinese patent CN112299962A, the catalyst of the present invention can effectively reduce the reaction temperature to 40-70°C, thereby reducing energy consumption. At the same time, the reduction in reaction temperature can extend the life of the catalyst.

[0024] The present invention is different from the solid superacid in Chinese patent CN101497556B. The catalyst of the present invention has suitable medium-strength acidity and acidity after being treated with water vapor and then modified with a rare earth metal, thereby being able to obtain 3-methyl-2-butene-1-aldehyde diisoprenylacetal in high yield.

[0025] The present invention has the following advantages: 1) The modified SAPO-34 molecular sieve catalyst can lower the reaction temperature while maintaining high activity, thereby improving selectivity, reducing production energy consumption, and extending catalyst life. 2) The use of a solid catalyst solves the problems of cumbersome post-processing steps and equipment corrosion in traditional processes, making it environmentally friendly and conducive to industrial production. DETAILED DESCRIPTION

[0026] The specific implementation methods of the technical solutions of the present invention are described in detail below, but the present invention is not limited to the following descriptions.

[0027] Example 1

[0028] 100 g of SAPO-34 molecular sieve was loaded into a fixed bed reactor with a bed temperature of 400 °C and a metering pump at a mass space velocity of 0.3 h -1 Deionized water was introduced into the fixed bed at a flow rate of 100 μg / min for 4 hours, and then nitrogen was used for 1 hour to remove moisture from the bed. The temperature was cooled to room temperature under nitrogen protection to obtain a steam-treated SAPO-34 molecular sieve catalyst, which was labeled SAPO-34-W.

[0029] Example 2

[0030] 80 g of the SAPO-34-W catalyst prepared in Example 1 was added to 100 g of a 1.0 wt% cerium nitrate aqueous solution, allowed to stand and impregnate at 30° C. for 15 hours, then filtered and dried at 100° C. for 20 hours. Finally, the modified SAPO-34 molecular sieve catalyst was obtained at 550° C. in a muffle furnace for 4 hours, which was labeled SAPO-34-W-1.0Ce-550.

[0031] Example 3

[0032] 80 g of the SAPO-34-W catalyst prepared in Example 1 was added to 100 g of a 0.6 wt% cerium nitrate aqueous solution, allowed to stand and impregnate at 30° C. for 15 hours, then filtered and dried at 100° C. for 8 hours. Finally, the modified SAPO-34 molecular sieve catalyst was obtained at 550° C. in a muffle furnace for 2 hours, which was labeled SAPO-34-W-0.6Ce-550.

[0033] Example 4

[0034] 80 g of the SAPO-34-W catalyst prepared in Example 1 was added to 100 g of a 0.3 wt% cerium nitrate aqueous solution, allowed to stand and impregnate at 30° C. for 15 hours, then filtered and dried at 100° C. for 15 hours, and finally calcined in a muffle furnace at 550° C. for 4 hours to obtain a modified SAPO-34 molecular sieve catalyst, labeled SAPO-34-W-0.3Ce-550.

[0035] Example 5

[0036] 80 g of the SAPO-34-W catalyst prepared in Example 1 was added to 100 g of a 0.6 wt% lanthanum nitrate aqueous solution, allowed to stand and soak at 20° C. for 24 hours, then filtered and dried at 100° C. for 20 hours, and finally calcined in a muffle furnace at 550° C. for 4 hours to obtain a modified SAPO-34 molecular sieve catalyst, labeled SAPO-34-W-0.6La-550.

[0037] Example 6

[0038] 80 g of the SAPO-34-W catalyst prepared in Example 1 was added to 100 g of a 0.6 wt% praseodymium nitrate aqueous solution, allowed to stand and soak at 50° C. for 5 hours, then filtered and dried at 120° C. for 20 hours, and finally calcined in a muffle furnace at 550° C. for 5 hours to obtain a modified SAPO-34 molecular sieve catalyst, labeled SAPO-34-W-0.6Pr-550.

[0039] Example 7

[0040] 80 g of the SAPO-34-W catalyst prepared in Example 1 was added to 100 g of a 0.6 wt% neodymium nitrate aqueous solution, allowed to stand and impregnate at 30° C. for 15 hours, then filtered and dried at 100° C. for 20 hours, and finally calcined in a muffle furnace at 550° C. for 4 hours to obtain a modified SAPO-34 molecular sieve catalyst, labeled SAPO-34-W-0.6Nd-550.

[0041] Example 8

[0042] 80 g of the SAPO-34-W catalyst prepared in Example 1 was added to 100 g of a 0.6 wt% cerium nitrate aqueous solution, allowed to stand and impregnate at 30° C. for 15 hours, then filtered and dried at 100° C. for 20 hours. Finally, the mixture was calcined in a muffle furnace at 400° C. for 4 hours to obtain a modified SAPO-34 molecular sieve catalyst, labeled SAPO-34-W-0.6Ce-400.

[0043] Example 9

[0044] 80 g of the SAPO-34-W catalyst prepared in Example 1 was added to 100 g of a 0.6 wt% cerium nitrate aqueous solution, allowed to stand and impregnate at 30° C. for 15 hours, then filtered and dried at 100° C. for 20 hours. Finally, the mixture was calcined in a muffle furnace at 600° C. for 4 hours to obtain a modified SAPO-34 molecular sieve catalyst, labeled SAPO-34-W-0.6Ce-600.

[0045] Example 10 (Comparative Example)

[0046] A 20mm inner diameter, 1m long distillation column was loaded with 25cm Raschig rings, 50cm SAPO-34 molecular sieve catalyst, and 25cm Raschig rings, respectively, corresponding to the stripping, reaction, and rectification sections of the reactive distillation column. The rectification and stripping sections each had 8 theoretical plates. Isopentenol and isopentenal were mixed in a molar ratio of 2.2:1. The mixture was then preheated to 60°C in a heat exchanger and fed into the column from the middle of the reaction section for reaction. The liquid volumetric space velocity of the feed mixture was 1.5h / min. -1 The tower top pressure was 800 Pa, and the reaction zone temperature was controlled between 50 and 60°C. The generated water and unreacted raw materials were separated in an overhead oil-water separator. The oil phase was transported to a designated storage tank, and the aqueous phase was discharged as wastewater. A high content of 3-methyl-2-butene-1-aldehyde diisoprenylacetal was obtained in the bottom of the tower. Gas chromatography was used to analyze the components of the overhead and bottom materials. The conversion and yield are shown in Table 1 (conversion calculated based on isopentenal, selectivity and yield calculated based on 3-methyl-2-butene-1-aldehyde diisoprenylacetal). See Table 1.

[0047] Examples 11 to 18

[0048] The reaction conditions and process were the same as in Example 10, except that the reaction section was loaded with catalysts prepared under different conditions. Specific reaction results are shown in Table 1, which shows the results of the catalytic performance of different catalysts under the same process conditions.

[0049] Table 1

[0050]

[0051]

[0052] Examples 19-23

[0053] The catalyst in Example 10 was replaced with SAPO-34-W-0.6Ce-550, and the alcohol-to-aldehyde ratio and feed amount of the feed were adjusted to a certain extent. Other parameters remained unchanged. The reaction results are shown in Table 2, which shows the results of investigating different process parameters under the same catalyst.

[0054] Table 2

[0055]

[0056] Example 24

[0057] The inventors have demonstrated through pilot tests that, after 1000 hours of continuous operation using the catalyst and process parameters of Example 21, the reaction yield showed no significant decrease, demonstrating the catalyst's excellent stability. To obtain data on catalyst activation and regeneration, SAPO-34-W-0.6Ce-550 was subjected to a destructive test. Specifically, the catalyst was subjected to a reaction using an aldehyde-alcohol feedstock high in heavy components, reducing its catalytic activity to 90% of that of a new catalyst. The catalyst was then calcined at 450°C for 2 hours for activation and regeneration, and this procedure was repeated three times. Specific data are shown in Table 3, which summarizes the results of the catalyst activation and regeneration study.

[0058] Table 3

[0059] Catalyst regeneration times Catalyst activity before regeneration Catalyst activity after regeneration 0 100％ 100％ 1 90％ 96％ 2 90％ 95％ 3 90％ 92％

[0060] Note: The activities in the table are relative to new catalysts.

[0061] From the above examples, it can be concluded that the modified catalyst has moderate acidity, which can ensure high activity while lowering the reaction temperature, thereby improving selectivity and reducing production energy consumption. In addition, the catalyst has high stability and regeneration, which is conducive to large-scale industrial production.

[0062] It should be noted that the above invention content and specific embodiments are intended to demonstrate the practical application of the technical solutions provided by the present invention and should not be interpreted as limiting the scope of protection of the present invention. Those skilled in the art will be able to make various modifications, equivalent substitutions, or improvements within the spirit and principles of the present invention.

Claims

1. A method for continuously preparing 3-methyl-2-butene-1-aldehyde diisoprenylacetal, the method comprising the steps of: 1) mixing the raw materials of isopentenol and isopentenal in a certain proportion to obtain a mixture, and then preheating the mixture in a heat exchanger and continuously feeding the mixture into the reaction distillation tower from the middle of the reaction section to perform a condensation reaction, wherein: The reaction section is filled with a modified SAPO-34 molecular sieve catalyst. The preparation method of the modified SAPO-34 molecular sieve catalyst comprises the following steps: first, subjecting the SAPO-34 molecular sieve to steam treatment; then, impregnating the steam-treated SAPO-34 molecular sieve with an aqueous solution of a rare earth metal salt for modification; and finally, drying and calcining to obtain the modified SAPO-34 molecular sieve catalyst, wherein the rare earth metal salt is selected from one or more nitrates of lanthanum, cerium, praseodymium, and neodymium. and 2) The water generated by the reaction and the unreacted raw materials are separated in an oil-water separator at the top of the tower, the oil phase is transported to a designated storage tank, the water phase is discharged as wastewater, and a high content of 3-methyl-2-butene-1-aldehyde diisoprenylacetal is obtained in the bottom of the tower.

2. The method according to claim 1, characterized in that The reaction distillation tower is divided into an upper distillation section, a middle reaction section and a lower stripping section. The modified SAPO-34 molecular sieve catalyst is loaded in the middle reaction section. The distillation section and the stripping section are packed towers. The number of theoretical plates of the distillation section of the reaction distillation tower is 6 to 10; the number of theoretical plates of the stripping section of the reaction distillation tower is 8 to 12; the height of the reaction section of the reaction distillation tower is 1 / 2 to 2 / 3 of the height of the entire tower.

3. The method according to claim 1 or 2, characterized in that In step 1), the feeding molar ratio of isopentenol to isopentenal is 2-2.5:1, and the temperature of the condensation reaction is 40-70°C.

4. The method according to claim 1 or 2, characterized in that In step 1), the tower top pressure of the reaction is 500-1000 Pa.

5. The method according to claim 1 or 2, characterized in that In step 1), the feed liquid volume space velocity of the mixed material is 1 to 2 h -1 .

6. The method according to claim 1, characterized in that: The temperature of the water vapor treatment is 300-500° C., the time of the water vapor treatment is 2-5 hours, and the mass space velocity of the water vapor treatment is 0.2-0.5 h -1 .

7. The method according to claim 1, characterized in that The concentration of the rare earth metal salt aqueous solution is 0.3-1.0 wt %; the immersion temperature is 20-50° C.; and the immersion time is 5-24 hours.

8. The method according to claim 1, characterized in that The drying temperature is 100-120° C., and the drying time is 8-20 hours; the roasting temperature is 400-600° C., and the roasting time is 2-5 hours.

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