A method for preparing isooctanoic acid by selective oxidation of isooctyl alcohol

Abstract

The invention discloses a method for preparing isooctanoic acid by selective oxidation of isooctyl alcohol, and belongs to the technical field of preparation of isooctyl acid of fine chemicals. The invention uses sodium lignin sulfonate quaternary ammonium salt loaded with phosphotungstic acid as a catalyst, isooctyl alcohol as a raw material, and H2O2 as an oxidant, and synthesizes isooctyl acid by solvent-free one-step reaction. The method for preparing isooctyl acid by selective oxidation reaction of isooctyl alcohol provided by the invention has the advantages of being direct, efficient, and green. Compared with the prior art, the sodium lignin sulfonate quaternary ammonium salt catalyst loaded with phosphotungstic acid prepared and used by the invention and the product isooctyl acid can be separated by a simple solid-liquid separation means, which not only overcomes the defects of needing to use a large amount of strong oxidants (potassium permanganate, nitric acid, etc.) and noble metal catalysts in the process of synthesizing isooctyl acid, and polluting the environment, but also can achieve a high conversion rate of isooctyl alcohol and a high yield of isooctyl acid.

Description

Technical Field

[0001] The invention belongs to the technical field of chemistry and material science, and further belongs to the technical field of preparation of fine chemical isooctonic acid, and specifically relates to a catalyst of quaternary ammonium salt-loaded phosphotungstic acid synthesized from lignin, a synthesis method thereof, and a method for preparing isooctonic acid by selectively oxidizing isooctyl alcohol using the catalyst. Background Art

[0002] Isooctanoic acid is a high value-added fine chemical, mainly used as a drier in the coating industry, a thickener in the ink industry, an accelerator for unsaturated polyester resins, a polyvinyl chloride processing aid, and a metal processing and lubricating aid. Isooctanoic acid can also be used as an intermediate to synthesize a variety of medicines, dyes, pesticides, and spices. In recent years, due to its wide range of uses, the demand for isooctanoic acid in the domestic and foreign markets has increased, the consumer market has continued to expand, and it has high economic benefits. Therefore, the research on the synthesis method of isooctanoic acid has received extensive attention from industry insiders at home and abroad.

[0003] At present, the synthesis research of domestic isooctanoic acid is mainly isooctyl alcohol oxidation method, by using different oxidants and catalysts, obtain different methods.Mainly include potassium permanganate oxidation method, nitric acid oxidation method, ultrasonic radiation method, electrolytic hydrogenation method, dehydrogenation oxidation method, oxygen oxidation method etc.The above various methods, although can guarantee isooctanoic acid output, generally speaking there is long reaction time, poor catalyst selectivity, harsh reaction conditions, high production cost, some methods also can produce three wastes and pollute the environment and other shortcomings.Therefore, it is of great significance to develop a new production technology of isooctanoic acid. Summary of the invention

[0004] Based on the shortcomings in the above-mentioned research process of isooctonic acid synthesis, the present invention proposes a reusable heterogeneous catalyst using sodium lignin sulfonate quaternary ammonium salt loaded with phosphotungstic acid, and adopts isooctyl alcohol oxidation method to prepare isooctyl acid, so as to solve the problems existing in the preparation process of isooctyl acid to meet industrial production.

[0005] In order to realize the selective oxidation reaction of isooctyl alcohol to prepare isooctyl acid, the present invention provides the following technical scheme:

[0006] A method for preparing isooctyl acid by selective oxidation of isooctyl alcohol, comprising: mixing a catalyst, isooctyl alcohol and H2O2, and heating the mixture at 40-120 DEG C in an O2 atmosphere to react, so as to obtain isooctyl acid; the catalyst is a sodium lignin sulfonate quaternary ammonium salt loaded with phosphotungstic acid.

[0007] As a preferred embodiment of the method for preparing isooctanoic acid by selective oxidation of isooctyl alcohol of the present invention, the mass ratio of isooctyl alcohol, H2O2 and catalyst is 1:(1.5-4):(0.04-0.16).

[0008] As a preferred embodiment of the method for preparing isooctyl acid by selective oxidation of isooctyl alcohol of the present invention, the specific operation of mixing the catalyst, isooctyl alcohol and H2O2 is as follows: adding the sodium lignin sulfonate quaternary ammonium salt catalyst loaded with phosphotungstic acid and a magnet to a reaction bottle, and then respectively adding isooctyl alcohol and H2O2 to the reaction bottle, and heating the reaction to obtain isooctyl acid.

[0009] As a preferred embodiment of the method for preparing isooctanoic acid by selective oxidation of isooctyl alcohol of the present invention, the heating reaction time is 6 to 12 hours.

[0010] As a preferred embodiment of the method for preparing isooctanoic acid by selective oxidation of isooctyl alcohol of the present invention, the molar ratio of phosphotungstic acid to chelate sodium lignin sulfonate quaternary ammonium salt is (1-10):1.

[0011] As a preferred embodiment of the method for preparing isooctanoic acid by selective oxidation of isooctyl alcohol of the present invention, the molar ratio of phosphotungstic acid to chelate sodium lignin sulfonate quaternary ammonium salt is (1-2):1.

[0012] As a preferred embodiment of the method for preparing isooctyl acid by selective oxidation of isooctyl alcohol of the present invention, the isooctyl acid is obtained and the light components such as isooctyl alcohol are separated by vacuum distillation to purify the product.

[0013] As a preferred embodiment of the method for preparing isooctanoic acid by selective oxidation of isooctyl alcohol of the present invention, the vacuum distillation temperature is 160°C.

[0014] Another object of the present invention is to provide a method for preparing the catalyst used in the method as described above, the method comprising the following steps:

[0015] S1, epichlorohydrin, concentrated hydrochloric acid, and hexadecyl dimethyl tertiary amine are placed in a flask, heated in a water bath and stirred until fully dissolved, the pH is adjusted to 8-9, and the reaction is continued at this temperature for 3-5 hours to obtain an intermediate of glycidyl hexadecyl dimethyl ammonium chloride;

[0016] S2, mixing sodium lignin sulfonate and deionized water, adjusting the pH to 10-12, heating in a water bath for 20-30 min, adding the intermediate obtained in S1, stirring at the temperature for 3-5 h, filtering, washing, and drying to obtain sodium lignin sulfonate quaternary ammonium salt;

[0017] S3, placing sodium lignin sulfonate quaternary ammonium salt in water, adding an aqueous solution of phosphotungstic acid, heating to react for 1 to 3 hours, cooling and filtering, and washing and drying the obtained solid to obtain a catalyst.

[0018] As a preferred embodiment of the method for preparing the sodium lignin sulfonate quaternary ammonium salt catalyst loaded with phosphotungstic acid according to the present invention, the pH of the system is adjusted using an aqueous NaOH solution.

[0019] As a preferred embodiment of the method for preparing phosphotungstic acid-loaded sodium lignin sulfonate quaternary ammonium salt catalyst of the present invention, the molar ratio of sodium lignin sulfonate, epichlorohydrin and hexadecyldimethyl tertiary amine is 1:(1-5):(1-5).

[0020] As a preferred embodiment of the method for preparing phosphotungstic acid-loaded sodium lignin sulfonate quaternary ammonium salt catalyst of the present invention, the water bath temperature in S1 and S2 is 40-80°C; the heating reaction temperature in S3 is 40-90°C.

[0021] As a preferred embodiment of the method for preparing phosphotungstic acid-loaded sodium lignin sulfonate quaternary ammonium salt catalyst of the present invention, the drying temperature in S2 and S3 is 50-80° C., and the drying time is 6-12 hours.

[0022] As a preferred embodiment of the method for preparing a sodium lignin sulfonate quaternary ammonium salt catalyst loaded with phosphotungstic acid according to the present invention, wherein: using different carbon chain lengths and having a structural formula of (CH3)2N(C n H 2n+1 ) is used to replace hexadecyl dimethyl tertiary amine.

[0023] As a preferred embodiment of the method for preparing the sodium lignin sulfonate quaternary ammonium salt catalyst loaded with phosphotungstic acid of the present invention, alkali lignin or solvent lignin is used to replace the sodium lignin sulfonate.

[0024] As a preferred embodiment of the method for preparing a sodium lignin sulfonate quaternary ammonium salt catalyst loaded with phosphotungstic acid according to the present invention, the catalyst has high stability and can be recycled.

[0025] The present invention uses isooctyl alcohol as a raw material, sodium lignin sulfonate quaternary ammonium salt loaded with phosphotungstic acid as a catalyst, and adopts a solvent-free H2O2 oxidation method to prepare isooctyl acid. The method does not require the use of a solvent, and the catalyst is easy to separate and can be reused, which is more green and efficient. Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The sodium lignin sulfonate quaternary ammonium salt catalyst loaded with phosphotungstic acid prepared by the present invention has higher catalytic activity in the synthesis of isooctonic acid than other phosphotungstic acid quaternary ammonium salt catalysts, and has a high isooctonic acid yield.

[0027] (2) The sodium lignin sulfonate quaternary ammonium salt catalyst loaded with phosphotungstic acid provided by the present invention is simple to prepare, plays a vital role in the selective oxidation reaction of isooctyl alcohol to prepare isooctyl acid, has high stability, and can be recycled.

[0028] (3) The method for preparing isooctanoic acid by selective oxidation of isooctyl alcohol provided by the present invention has the advantages of being direct, efficient, and green. Compared with the prior art, the sodium lignin sulfonate quaternary ammonium salt catalyst loaded with phosphotungstic acid and the product isooctyl acid can be separated by a simple solid-liquid separation method, which not only overcomes the defects of needing to use a large amount of strong oxidants (potassium permanganate, nitric acid, etc.) and precious metal catalysts in the process of synthesizing isooctyl acid, causing environmental pollution, but also achieves a high conversion rate of isooctyl alcohol and a high yield of isooctyl acid.

[0029] (4) The process for preparing isooctyl acid by selective oxidation of isooctyl alcohol provided by the present invention is simple, can be completed at normal pressure and low temperature (below 100° C.), has low energy consumption, and the catalyst used is easy to synthesize, has low raw material cost and good activity, can be reused, and the product is easy to separate, thus solving the problems of using precious metal catalysts and high energy consumption in the synthesis method of the same product. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is the infrared contrast spectra of phosphotungstic acid, sodium lignin sulfonate quaternary ammonium salt and sodium lignin sulfonate quaternary ammonium salt catalyst loaded with phosphotungstic acid;

[0031] Figure 2 The isooctanoic acid prepared in Example 1 1 H NMR spectrum;

[0032] Figure 3 This is the mass spectrum of the isooctanoic acid prepared in Example 1. DETAILED DESCRIPTION

[0033] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0034] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0035] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0036] Unless otherwise specified, the raw materials used in the examples were purchased commercially.

[0037] Example 1

[0038] Step 1: Prepare a sodium lignin sulfonate quaternary ammonium salt catalyst with a hexadecyl chain length loaded with phosphotungstic acid, and the specific process is as follows:

[0039] S1: 0.93 g of epichlorohydrin, 10 mL of concentrated hydrochloric acid (36-38%), and 2.69 g of hexadecyl dimethyl tertiary amine were placed in a flask, stirred evenly, and kept warm at 50°C to allow the solution to fully dissolve. The pH was adjusted to 8-9 using an aqueous NaOH solution, and the reaction was continued for 3 h to obtain an intermediate of glycidyl hexadecyl dimethyl ammonium chloride;

[0040] S2: Add 2.67 g of sodium lignin sulfonate and 15 mL of deionized water into a flask, adjust the pH to 10-12 with NaOH solution, keep warm in a 50°C water bath for 30 min, add the intermediate obtained in step S1 and stir at 50°C for 3 h, filter, wash with deionized water, and dry in a 60°C oven for 12 h to obtain sodium lignin sulfonate quaternary ammonium salt;

[0041] S3: 0.90 g of sodium lignin sulfonate quaternary ammonium salt was placed in 10 mL of deionized water, followed by adding 10 mL of an aqueous solution containing 2.9 g of phosphotungstic acid, and the mixed solution was heated at 60° C. for 1 h, and filtered after cooling. The obtained solid was washed with water and dried in an oven at 60° C. for 12 h to obtain a catalyst, referred to as phosphotungstic acid-sodium lignin sulfonate hexaquaternary ammonium salt.

[0042] The structure of the catalyst was characterized. Figure 1 shown.

[0043] Step 2: Using the catalyst obtained in step 1 to prepare isooctanoic acid, the specific process is as follows:

[0044] Add 0.2g of quaternary ammonium salt catalyst loaded with phosphotungstic acid and magnetron into the reaction tube, and cycle three times of vacuum-oxygen filling. Then, use a syringe to add 2g of isooctyl alcohol and 3.4g of H2O2 into the reaction tube respectively. Heat the reaction at 90°C for 12h to obtain isooctyl acid. After the reaction is completed, pour the reaction liquid and catalyst into a centrifuge tube. After centrifugation for 5min, separate the upper layer of reaction liquid and catalyst, transfer the reaction liquid, and the lower layer of catalyst can be reused after drying. The reaction liquid is extracted with ethyl acetate, the upper organic phase is combined, a small amount of water is removed with anhydrous sodium sulfate, and then qualitative and quantitative analysis is performed by gas chromatograph. The results are as follows: Figure 3 As shown in Table 1, the isooctanoic acid is obtained. 1 H NMR spectra, such as Figure 2 shown.

[0045] Example 2

[0046] The difference between this embodiment and embodiment 1 is that 2.13g of dodecyl dimethyl tertiary amine is used in S1 to replace 2.69g of hexadecyl dimethyl tertiary amine; the mass of the sodium lignin sulfonate quaternary ammonium salt obtained in S2 is 0.84g in S3, and the rest of the operation process and parameter settings are the same as those in embodiment 1. The catalyst obtained in this embodiment is referred to as phosphotungstic acid-sodium lignin sulfonate dodecaquaternary ammonium salt.

[0047] Example 3

[0048] The difference between this embodiment and embodiment 1 is that 2.42g of tetradecyl dimethyl tertiary amine is used in S1 to replace 2.69g of hexadecyl dimethyl tertiary amine; the mass of the sodium lignin sulfonate quaternary ammonium salt obtained in S2 is 0.87g in S3, and the rest of the operation process and parameter settings are the same as those in embodiment 1. The catalyst obtained in this embodiment is referred to as phosphotungstic acid-sodium lignin sulfonate tetradecyl ammonium salt.

[0049] Example 4

[0050] The difference between this embodiment and embodiment 1 is that 2.98g of tetradecyl dimethyl tertiary amine is used in S1 to replace 2.69g of hexadecyl dimethyl tertiary amine; the mass of the sodium lignin sulfonate quaternary ammonium salt obtained in S2 is 0.92g in S3, and the rest of the operation process and parameter settings are the same as those in embodiment 1. The catalyst obtained in this embodiment is referred to as phosphotungstic acid-sodium lignin sulfonate octadecane quaternary ammonium salt.

[0051] Comparative Example 1

[0052] The difference between this comparative example and Example 1 is that S3 contains 2.9g Na7P 11 O 39 The 10 mL aqueous solution containing 2.9 g of phosphotungstic acid was replaced by 10 mL aqueous solution of 10 mL of 2.9 g of phosphotungstic acid, and the remaining operation process and parameter settings were the same as those in Example 1. The catalyst obtained in this example is referred to as Na7P 11 O 39 - Sodium lignin sulfonate 18-quaternary ammonium salt.

[0053] Comparative Example 2

[0054] The difference between this comparative example and Example 1 is as follows: Step 1, prepare the monosodium quaternary ammonium salt catalyst loaded with phosphotungstic acid, the specific process is as follows: weigh 5.760g of phosphotungstic acid in a three-necked flask, add 15mL of deionized water to dissolve it, stir magnetically at room temperature for 1h, add an aqueous solution containing 1.92g of hexadecyltrimethylammonium chloride to the three-necked flask, stir while dripping to make it fully react, slowly generate a white precipitate, continue to stir at room temperature for 4h after the addition is completed, wait for the precipitation to be complete, filter, wash, and dry at 65°C. The obtained catalyst is referred to as phosphotungstic acid-hexadecyltrimethylammonium chloride. The remaining operation process and parameter settings are the same as those in Example 1.

[0055] Comparative Example 3

[0056] The difference between this comparative example and Example 1 is that 2.53 g of alkali lignin is used in S3 to replace 2.67 g of sodium lignin sulfonate, and the remaining operation process and parameter settings are the same as those of Example 1. The catalyst obtained in this example is referred to as phosphotungstic acid-alkali lignin quaternary ammonium salt.

[0057] Comparative Example 4

[0058] The difference between this comparative example and Example 1 is that 2.50g of solvent lignin is used in S1 to replace 2.67g of sodium lignin sulfonate; the mass of the solvent lignin quaternary ammonium salt obtained in S2 is 1.0g, and 10mL of aqueous solution containing 3.0g of phosphotungstic acid is added in S3, and the rest of the operation process and parameter settings are the same as those in Example 1. The catalyst obtained in this example is referred to as phosphotungstic acid-solvent lignin quaternary ammonium salt.

[0059] Example 5

[0060] The catalysts prepared in Comparative Examples 1 to 4 of Examples 1 to 4 were applied to the selective oxidation reaction of isooctyl alcohol, and the isooctyl alcohol conversion rate and isooctyl acid selectivity were characterized. The results are shown in Table 1:

[0061] Table 1 Effect of different catalysts on the selective oxidation reaction of isooctyl alcohol

[0062]

[0063]

[0064] It can be seen from the above table that the sodium lignin sulfonate quaternary ammonium salt catalyst loaded with phosphotungstic acid has a good catalytic effect on the oxidation reaction of isooctyl alcohol.

[0065] Example 6

[0066] The sodium lignin sulfonate quaternary ammonium salt with a hexadecyl chain length loaded with phosphotungstic acid obtained in Example 1 was used as a catalyst. On the basis of Example 1, the heating reaction temperature in step 2 was changed to 70°C, 80°C and 100°C, respectively, to study the effect of the reaction temperature on the conversion rate of isooctyl alcohol and the selectivity of isooctyl acid. The results are shown in Table 2 below:

[0067] Table 2 Effect of changing the reaction temperature in the solvent-free H2O2 oxidation process for preparing isooctanoic acid on the conversion of isooctyl alcohol and selectivity of isooctyl acid

[0068]

[0069] Example 7

[0070] The sodium lignin sulfonate quaternary ammonium salt with a hexadecyl chain length loaded with phosphotungstic acid obtained in Example 1 was used as a catalyst to characterize the stability test of the catalyst after repeated use for multiple times. The specific operation was as follows:

[0071] (1) Taking the sodium lignin sulfonate quaternary ammonium salt with a hexadecyl chain length loaded with phosphotungstic acid in Example 1 as an example, isooctanoic acid was prepared according to the method of Example 1;

[0072] (2) the solution after the reaction is transferred to a centrifuge tube, saturated sodium chloride solution and ethyl acetate are added, and solid-liquid separation is achieved after centrifugation in a centrifuge. The obtained catalyst is dried at 60° C. and is further used as a catalyst for preparing isooctanoic acid;

[0073] (3) The sodium lignin sulfonate quaternary ammonium salt catalyst with a hexadecyl chain length loaded with phosphotungstic acid was repeatedly used 3 times. After each reaction, the isooctyl alcohol conversion rate and isooctyl acid selectivity were analyzed by gas chromatography. The results are shown in Table 3:

[0074] Table 3 Stability test results of preparing isooctanoic acid by selective oxidation of isooctol catalyzed by phosphotungstic acid-sodium lignin sulfonate quaternary ammonium salt

[0075]

[0076] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing isooctanoic acid by selective oxidation of isooctyl alcohol, characterized in that: The catalyst, isooctyl alcohol and H2O2 are mixed, and heated to 80-100°C in an O2 atmosphere to react to obtain isooctyl acid; the catalyst is a sodium lignin sulfonate quaternary ammonium salt loaded with phosphotungstic acid; The preparation method of the sodium lignin sulfonate quaternary ammonium salt loaded with phosphotungstic acid comprises the following steps: S1, epichlorohydrin, concentrated hydrochloric acid, and hexadecyl dimethyl tertiary amine are placed in a flask, heated in a water bath and stirred until fully dissolved, the pH is adjusted to 8-9, and the reaction is continued at this temperature for 3-5 hours to obtain an intermediate of glycidyl hexadecyl dimethyl ammonium chloride; S2, mix sodium lignin sulfonate and deionized water, adjust the pH to 10-12, heat in a water bath for 20-30 min, add the intermediate obtained in S1, keep warm and stir for 3-5 h, filter, wash and dry to obtain sodium lignin sulfonate quaternary ammonium salt; S3, placing sodium lignin sulfonate quaternary ammonium salt in water, adding an aqueous solution of phosphotungstic acid, heating to react for 1-3 hours, cooling and filtering, and washing and drying the obtained solid to obtain a catalyst.

2. The method for preparing isooctanoic acid by selective oxidation of isooctyl alcohol according to claim 1, characterized in that: The mass ratio of isooctyl alcohol, H2O2 and catalyst is 1:(1.5~4):(0.04~0.16).

3. The method for preparing isooctanoic acid by selective oxidation of isooctyl alcohol according to claim 1, characterized in that: The heating reaction time is 6 to 12 hours.

4. The method for preparing isooctanoic acid by selective oxidation of isooctyl alcohol according to claim 1, characterized in that: The molar ratio of phosphotungstic acid to sodium lignin sulfonate quaternary ammonium salt chelate is 1-10:

1.

5. The method for preparing isooctanoic acid by selective oxidation of isooctyl alcohol according to claim 1, characterized in that: The molar ratio of sodium lignin sulfonate, epichlorohydrin and hexadecyl dimethyl tertiary amine is 1:(1-5):(1-5).

6. The method for preparing isooctanoic acid by selective oxidation of isooctyl alcohol according to claim 1, characterized in that: The water bath temperature in S1 and S2 is 40~80℃; the heating reaction temperature in S3 is 40~90℃.

7. The method for preparing isooctanoic acid by selective oxidation of isooctyl alcohol according to claim 1, characterized in that: Dodecyldimethyl tertiary amine, tetradecyldimethyl tertiary amine, or octadecyldimethyl tertiary amine is used in place of hexadecyldimethyl tertiary amine.

8. The method for preparing isooctanoic acid by selective oxidation of isooctyl alcohol according to claim 1, characterized in that: Alkali lignin or solvent lignin is used instead of sodium lignin sulfonate.

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