Synthesis method of 2, 2, 4-trimethyl-1, 3-pentanediol monoisobutyrate

Abstract

The invention discloses a synthesis method of 2, 2, 4-trimethyl-1, 3-pentanediol monoisobutyrate, which comprises the following steps: 1) adding a raw material isobutyraldehyde and a catalyst sodium isobutyrate powder into a reaction kettle according to a certain proportion; 2) sealing the reaction kettle, replacing with nitrogen, stirring, heating to a reaction temperature, keeping the temperature to react for a certain time, and cooling to room temperature; and 3) filtering the catalyst, directly applying the catalyst, rectifying the reaction liquid to recover the isobutyraldehyde and obtain the product, and applying the isobutyraldehyde to the secondary kettle. Sodium isobutyrate is used as a catalyst, waste is turned into wealth, energy is saved, emission is reduced, economic benefits are improved, a water washing procedure is omitted in the technological process, no sodium isobutyrate salt water is generated, post-treatment procedures such as acidification reaction and acidizing fluid rectification are omitted, energy is saved, emission is reduced, and the method is environmentally friendly.

Description

Technical Field

[0001] The present invention belongs to the field of organic synthesis, and particularly relates to a method for synthesizing 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate. Background Art

[0002] Dodecyl alcohol ester (2,2,4-trimethyl-1,3-pentanediol monoisobutyrate) has been widely used as a film-forming aid in the waterborne coating industry in recent years. It has good film-forming properties. The latex paint formulated with it as a film-forming aid has excellent leveling property, anti-sagging property and good color development property, and can significantly reduce the glass transition temperature of the polymer. At the same time, dodecyl alcohol ester is green and environmentally friendly, meeting the requirements of regulations on VOC (volatile organic compounds) in countries such as the European Union and China. Currently, the preparation of dodecyl alcohol ester is usually carried out by gradually polymerizing isobutyraldehyde through aldol condensation reaction, Cannizzaro reaction, etc. under the catalysis of strong base to form 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate.

[0003] For example, in the production process of using isobutyraldehyde as a reactant and NaOH as a catalyst to prepare dodecyl alcohol ester, the intermediate product 2,2,4-trimethyl-3-hydroxypentanal generated reacts with isobutyraldehyde to form 2,2,4-trimethyl-1,3-pentanediol and isobutyric acid, and then 2,2,4-trimethyl-1,3-pentanediol and isobutyric acid are esterified under alkaline conditions to synthesize dodecyl alcohol ester. A small amount of intermediate isobutyric acid reacts with the catalyst NaOH to form sodium isobutyrate, resulting in an increase in the content of 2,2,4-trimethyl-1,3-pentanediol in the reaction solution. The reaction solution is washed with water to obtain an oil phase and an aqueous phase. The oil phase undergoes a series of distillation operations to obtain dodecyl alcohol ester product and the intermediate 2,2,4-trimethyl-1,3-pentanediol. The sodium isobutyrate in the aqueous phase needs to undergo sulfuric acid acidification reaction, distillation process, etc. to obtain isobutyric acid and sodium sulfate. The main chemical reaction equations are as follows:

[0004]

[0005] Currently, the main problems in the process of synthesizing dodecyl alcohol ester using sodium hydroxide as a catalyst are:

[0006] 1. The reaction solution needs to be washed with water and generates a large amount of organic salt wastewater containing sodium isobutyrate (about 2500 t / year), and the subsequent acidification, distillation and other treatment costs are relatively high.

[0007] 2. The sodium hydroxide catalyst is used once and cannot be recycled, and the catalyst cost is relatively high. Secondly, the catalyst consumes intermediate isobutyric acid, increasing the unit consumption of raw material isobutyraldehyde.

[0008] 3. Since the intermediate isobutyric acid reacts with sodium hydroxide to form sodium isobutyrate, the content of the intermediate 2,2,4-trimethyl-1,3-pentanediol increases, and it needs to be rectified and recovered in the later stage. The recovery cost is relatively high and the quality indicators are difficult to meet the customer requirements.

[0009] Based on the above problems, the present patent application is proposed. Summary of the Invention

[0010] In view of the problems existing in the prior art, the present invention provides a method for synthesizing 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (dodecyl alcohol ester). The method provided by the present invention uses isobutyraldehyde as a raw material and polymerizes it into 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate under the catalysis of a weak base salt (sodium isobutyrate).

[0011] Based on the above object, the present invention adopts the following technical solutions:

[0012] A method for synthesizing 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, and its chemical reaction equation is as follows:

[0013]

[0014] It includes the following steps:

[0015] 1) Add the raw material isobutyraldehyde and the catalyst sodium isobutyrate powder into the autoclave in a certain proportion;

[0016] 2) Seal the reaction kettle and displace it with nitrogen. Start stirring and heat up to the reaction temperature. After maintaining the reaction for a certain time, slowly cool it to room temperature;

[0017] 3) Filter. The filter cake is the catalyst and can be directly reused. The filtrate is rectified to obtain isobutyraldehyde and the target product, and the isobutyraldehyde is reused in the next kettle.

[0018] Specifically, the sodium isobutyrate powder in step 1) is obtained by concentrating, recrystallizing and recovering from the dodecyl alcohol ester production workshop, with a purity ≥ 98.0% and a particle size of 50 - 1000 mesh; the mass ratio of isobutyraldehyde to sodium isobutyrate is 100:(0.5 - 15), preferably 100:(1 - 10).

[0019] Specifically, in step 2), the nitrogen displacement is carried out until the oxygen content ≤ 0.5 v%; the stirring is a downward propeller mechanical stirring, and the rotation speed is the conventional rotation speed for organic reactions; the reaction temperature is 120 - 250 °C, preferably 150 - 220 °C; the reaction time is 6 - 20 h.

[0020] Specifically, when the catalyst is reused in step 3), a certain amount of new catalyst should be added, and the added amount is equal to the filtration loss. Based on the above steps, the present invention also lists a series of examples.

[0021] Compared with the prior art, the process features and advantages of using sodium isobutyrate as a catalyst in the present invention are as follows:

[0022] (1) Using sodium isobutyrate as a catalyst turns waste into treasure, saves energy and reduces emissions, and improves economic benefits.

[0023] (2) Sodium isobutyrate can be recycled more than 20 times, solving the problem of disposable use of sodium hydroxide catalyst and reducing costs.

[0024] (3) The process reduces the water washing process, does not produce sodium isobutyrate brine, and reduces post-treatment processes such as acidification reaction and acidification liquid rectification, saving energy, reducing emissions and being environmentally friendly.

[0025] (4) There are few by-products, and the product selectivity can reach more than 92%. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is the process flow chart of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] The main process schematic diagram for implementing this method is as shown above. In the examples, the reaction temperature, reaction time, catalyst addition ratio, and recycling times were investigated respectively. The following is a detailed description of the present invention.

[0028] Example 1

[0029] Add 100 g of isobutyraldehyde to a 200 mL autoclave. As Figure 1 shown, then add sodium isobutyrate (4 g, purity 98.5%, particle size 800 mesh) which is 4% of the mass of isobutyraldehyde to the autoclave, and displace with nitrogen until the oxygen content ≤ 0.5 v%. Stir and heat up to 180 °C for reaction. The stirring is a lower propeller mechanical stirring with a stirring speed of 900 rpm. Keep the temperature constant at 180 °C and react for 8 h (when the reaction time is less than 8 h, the conversion rate of isobutyraldehyde < 27.5%. The longer the reaction time, the higher the conversion rate, and the selectivity changes little.). After sampling and testing, the conversion rate is 24.5% and the selectivity is 92.5%. After the reaction is completed, the reaction solution is cooled, and sodium isobutyrate will precipitate from the reaction solution and be filtered. The filter cake is sodium isobutyrate for recycling, and the filtrate is directly used for the subsequent rectification.

[0030] Examples 2 - 4

[0031] The process is the same as that in Example 1, only changing the amount of sodium isobutyrate to 5%, 6%, and 8% of the mass of isobutyraldehyde. The reaction conditions and results are shown in the following table:

[0032]

[0033] From the experimental results, it can be seen that when the addition ratio of sodium isobutyrate is 5 - 8%, the conversion rate is 27.5 - 32.5%, and the selectivity is 93.1 - 93.4%.

[0034] Examples 5 - 7

[0035] The process is the same as that in Example 1, only the reaction temperatures are changed to 190°C, 210°C, and 220°C. The reaction conditions and results are as follows in the table:

[0036]

[0037] From the experimental results, it can be seen that when the reaction temperature is 190 - 220°C, the conversion rate is 28.5 - 32.3%, and the selectivity is 93.0 - 93.8%.

[0038] Examples 8 - 10

[0039] The process is the same as that in Example 1, only the reaction times are changed to 10 h, 14 h, and 16 h. The reaction conditions and results are as follows in the table:

[0040]

[0041] From the experimental results, it can be seen that when the reaction time is 10 - 16 h, the conversion rate is 27.4 - 34.9%, and the selectivity is 93.3 - 93.5%. From the above three tables, it can be seen that the conversion rate of isobutyraldehyde is the highest when the addition ratio of sodium isobutyrate is 8%, the reaction temperature is 220°C, and the reaction time is 16 h.

[0042] Example 11

[0043] The comparative experimental results of the above - screened catalyst ratio, reaction temperature, reaction time, the process conditions with the highest conversion rate, and the industrial reaction conditions are as follows in the table:

[0044]

[0045] Note: The data of Example 12 is from Puyang Shengkai Environmental Protection Technology Co., Ltd.

[0046] From the above table, it can be seen that in this application, using isobutyraldehyde as the raw material and sodium isobutyrate as the catalyst, the molar yield of dodecyl alcohol ester under the optimal conditions is 45.5%×93.8%≈42.68%, which is comparable to the molar yield of 45.5%×93.8%≈42.6% for the preparation of dodecyl alcohol ester using sodium hydroxide as the catalyst in the current industry.

[0047] Examples 13 - 17

[0048] The process is the same as that in Example 1, and the catalyst is reused once, twice, three times, fifteen times, and twenty times. The reaction conditions and results are as follows in the table:

[0049]

[0050]

[0051] Note: The additional amount of sodium isobutyrate of 2% refers to the additional amount being 2% of the mass of the catalyst added for the first time (in the first reactor).

[0052] From the experimental results, it can be seen that when the catalyst is reused 20 times, the conversion rate is 23.5 - 24.4%, and the selectivity is 92.1 - 93.1%.

[0053] It should be noted that the above-described embodiments are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described by referring to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than limiting words. Modifications can be made to the present invention within the scope of the claims of the present invention as provided, and the present invention can be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A method for synthesizing 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, characterized in that: The following steps are involved: Adding raw material isobutyraldehyde and catalyst sodium isobutyrate powder into the reactor in a certain proportion; Seal the reactor and replace it with nitrogen, stir and heat it to the reaction temperature, keep the temperature for a certain period of time and then cool it down to room temperature; Filter, use the filter cake as a catalyst directly, distill the filtrate to obtain isobutyraldehyde and the target product, and use the isobutyraldehyde in the next kettle.

2. The method for synthesizing 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate according to claim 1, characterized in that: Step 1) The sodium isobutyrate powder is recovered from the dodecanol ester production workshop by concentration and recrystallization, with a purity of ≥98.0% and a particle size of 50-1000 meshes.

3. The method for synthesizing 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate according to claim 1, characterized in that: In step 1), the mass ratio of isobutyraldehyde to sodium isobutyrate is 100:(0.5-15).

4. The method for synthesizing 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate according to claim 1, characterized in that: In step 2), the reaction temperature is 120-250° C., and the reaction time is 6-20 h.

5. The method for synthesizing 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate according to claim 1, characterized in that: Step 2) The nitrogen is replaced until the oxygen content is ≤ 0.5%.

6. The method for synthesizing 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate according to claim 1, characterized in that: Step 3) When the catalyst is applied, a certain amount of new catalyst should be added, and the amount of addition is equal to the filtration loss.

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