A process for the preparation of isooctyl nitrate

Abstract

The application belongs to the technical field of organic synthesis, and particularly relates to a preparation method of isooctyl nitrate. The method uses cyclohexane as a solvent, uses urea as a stabilizer, and uses a composite aerogel as a catalyst, so that isooctanol is nitrified by concentrated nitric acid to generate isooctyl nitrate. The method can avoid the use of sulfuric acid, and the prepared isooctyl nitrate has high yield and high purity, the whole preparation process is safe and environmentally friendly, and safe and efficient preparation of isooctyl nitrate can be realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic synthesis, and particularly relates to a preparation method of isooctyl nitrate. BACKGROUND

[0002] Isooctyl nitrate is a colorless transparent liquid with strong volatility and irritating odor, and is widely used. It can be used as a gasoline additive to effectively improve the combustion performance of diesel and reduce the ignition energy. It can also be used in the pharmaceutical field. Due to its special effect on expanding blood vessels, it is used to prepare drugs for preventing and treating heart disease.

[0003] In the prior art, isooctyl nitrate is generally synthesized by using mixed acid (for example, CN1017146A), that is, isooctyl alcohol is added to mixed acid for reaction within a certain temperature range, and the product is obtained by separating the reaction product. However, the reaction process is not easy to control, the heat is concentrated, the danger is great, side reactions and over-reactions are easy to occur, the production efficiency is low, and an excessive amount of sulfuric acid is required, which is accompanied by a large amount of waste acid. In recent years, using a micro-channel reactor to continuously synthesize isooctyl nitrate is a relatively safe and effective method (for example, CN110683953A), which can reduce the use amount of raw material acid, greatly reduce the amount of waste water produced, and reduce the danger, but the use of sulfuric acid cannot be avoided in essence. Therefore, it is particularly important to provide a method for safely and efficiently preparing isooctyl nitrate which can avoid the use of sulfuric acid. SUMMARY

[0004] In view of the problems in the prior art, the application provides a preparation method of isooctyl nitrate, which can avoid the use of sulfuric acid, and has high yield and purity of isooctyl nitrate, is safe and environmentally friendly in the whole preparation process, and can realize safe and efficient preparation of isooctyl nitrate.

[0005] Specifically, the application provides a preparation method of isooctyl nitrate, which uses cyclohexane as a solvent, urea as a stabilizer, and a composite aerogel as a catalyst to generate a nitration product under the nitration of concentrated nitric acid from isooctyl alcohol.

[0006] The nitration product is allowed to stand and separate into layers, and the organic phase is separated out, washed with water, washed with alkali, washed with water again to neutral, and then distilled and dried to obtain isooctyl nitrate.

[0007] The preparation method of the composite aerogel catalyst comprises the following steps:

[0008] S1: mixing tetraethyl orthosilicate, anhydrous ethanol, deionized water and hydrochloric acid, and performing hydrolysis in a water bath at a temperature of 60-70 DEG C for 5-6 hours, then adding p-toluenesulfonic acid and carboxymethyl cellulose, and fully stirring to form a mixed solution;

[0009] S2: drop ammonia water into the mixed solution, and gelation reaction is carried out by rapid stirring, and after filtration and washing, supercritical carbon dioxide drying is carried out to obtain aerogel;

[0010] S3: the aerogel is immersed in cerium nitrate solution, and after standing, drying and calcination, a composite aerogel catalyst is obtained.

[0011] Further, the addition ratio of cyclohexane, urea, composite aerogel, isooctanol and concentrated nitric acid is 30-50 mL: 0.05-0.1 mol: 2-5 g: 1 mol: 1-1.2 mol; the mass fraction of concentrated nitric acid is 65-80%.

[0012] Further, in the process of generating nitric acid isooctyl ester under the nitration of isooctanol in concentrated nitric acid, the reaction temperature is 20-25℃, and the time is 3-5h.

[0013] Further, the molar ratio of tetraethyl orthosilicate, anhydrous ethanol, deionized water and hydrochloric acid is 1:5-10:6-8:0.02-0.04.

[0014] Further, the molar ratio of tetraethyl orthosilicate, p-toluenesulfonic acid and carboxymethyl cellulose is 1:0.2-0.3:0.1.

[0015] Further, the concentration of ammonia water is 0.6-0.8 mol / L, and the volume ratio of ammonia water to mixed solution is 1-2:10.

[0016] Further, after the ammonia water is dropped, the gelation reaction is carried out by rapid stirring for 5-10 min.

[0017] Further, when supercritical carbon dioxide drying is carried out, the pressure is 10-20 MPa, the temperature is 40-50℃, the pressure holding time is 5-6h, and the pressure relief rate is 4-5 MPa / h.

[0018] Further, in step S3, the concentration of cerium nitrate solution is 0.5 mol / L; the standing time is 6-8h, the drying temperature is 70-80℃, the calcination temperature is 450-500℃, and the calcination time is 2-3h.

[0019] The beneficial effects of one or more technical solutions of the above application are as follows:

[0020] 1.The preparation method of isooctyl nitrate provided by the present application, the composite aerogel catalyst is prepared by gel method combined with impregnation process, the obtained aerogel material contains porous structure, which is not only beneficial to the diffusion of the reactant isooctyl alcohol, but also provides large specific surface area, fully loads sulfonic acid group and cerium in the structure system, and then forms rich catalytic active sites, thereby effectively improving the yield of isooctyl nitrate. Based on the composite aerogel catalyst, isooctyl nitrate can be efficiently prepared, the yield of isooctyl nitrate is more than 98.91%, and the purity is more than 99.5%.

[0021] 2.The large number of pores of the composite aerogel also has a strong structure guiding effect, which inhibits the agglomeration and shedding of active components in the reaction, and enhances the stability of the catalyst. At the same time, carboxymethyl cellulose is used to participate in the preparation of the composite aerogel, which not only promotes the dispersion of the sulfonic acid group in the system, but also forms a three-dimensional network of fiber staggered distribution in the aerogel, which can further effectively improve the stability of the catalyst structure, prolong the service life of the catalyst, and thereby reduce the cost of industrial production of isooctyl nitrate. After the composite aerogel catalyst prepared by the present application is operated for 216h, the yield of isooctyl nitrate decreases very little and can be maintained above 97%, and even after 480h of cyclic use, the yield can still be maintained above 90%. DETAILED DESCRIPTION

[0022] In order for those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in combination with specific examples and comparative examples.

[0023] Example 1

[0024] The present embodiment provides a preparation method of isooctyl nitrate, the specific steps are as follows:

[0025] (1) Preparation of composite aerogel catalyst:

[0026] S1: Mix tetraethyl orthosilicate, anhydrous ethanol, deionized water and hydrochloric acid (the molar ratio of tetraethyl orthosilicate, anhydrous ethanol, deionized water and hydrochloric acid is 1:5:6:0.02), hydrolyze in water bath at 60℃ for 6h, then add p-toluenesulfonic acid and carboxymethyl cellulose (the molar ratio of tetraethyl orthosilicate, p-toluenesulfonic acid and carboxymethyl cellulose is 1:0.2:0.1), and fully stir to form a mixed solution;

[0027] S2: Drop 0.8mol / L ammonia water into the mixed solution, the volume ratio of ammonia water to mixed solution is 1:10, quickly stir for 5min for gelation reaction, after filtration and washing, perform supercritical carbon dioxide drying (pressure is 10MPa, temperature is 50℃, pressure maintaining time is 5h, pressure releasing rate is 4MPa / h), and obtain aerogel;

[0028] S3: The aerogel is immersed in a cerium nitrate solution with a concentration of 0.5 mol / L, and is left to stand for 6 h, dried at 70°C, and calcined at 500°C for 2 h to obtain a composite aerogel catalyst.

[0029] (2) Preparation of isooctyl nitrate:

[0030] Into 30 mL of cyclohexane, 0.05 mol of urea, 2 g of the composite aerogel, 1 mol of isooctyl alcohol, and 1 mol of concentrated nitric acid (the mass fraction of the concentrated nitric acid is 65%) are added, and a nitration reaction is carried out at 25°C, with a reaction time of 5 h;

[0031] The nitration product is left to stand to separate layers, and the organic phase is separated, washed with water, washed with alkali, washed with water again until neutral, and then distilled, dried, to obtain isooctyl nitrate.

[0032] Example 2

[0033] The present embodiment provides a preparation method of isooctyl nitrate, and the specific steps are as follows:

[0034] (1) Preparation of a composite aerogel catalyst:

[0035] S1: Tetraethyl orthosilicate, anhydrous ethanol, deionized water, and hydrochloric acid are mixed (the molar ratio of tetraethyl orthosilicate, anhydrous ethanol, deionized water, and hydrochloric acid is 1:10:8:0.04), and hydrolysis is carried out in a water bath at a temperature of 70°C for 6 h, then p-toluenesulfonic acid and carboxymethyl cellulose are added (the molar ratio of tetraethyl orthosilicate, p-toluenesulfonic acid, and carboxymethyl cellulose is 1:0.3:0.1), and the mixture is fully stirred to form a mixed solution;

[0036] S2: Ammonia water with a concentration of 0.8 mol / L is added dropwise to the mixed solution, the volume ratio of the ammonia water to the mixed solution is 1:10, and rapid stirring is carried out for 10 min to carry out a gelation reaction, and after filtration and washing, supercritical carbon dioxide drying is carried out (the pressure is 20 MPa, the temperature is 40°C, the pressure maintaining time is 5 h, and the pressure release rate is 4 MPa / h) to obtain an aerogel;

[0037] S3: The aerogel is immersed in a cerium nitrate solution with a concentration of 0.5 mol / L, and is left to stand for 6 h, dried at 70°C, and calcined at 450°C for 3 h to obtain a composite aerogel catalyst.

[0038] (2) Preparation of isooctyl nitrate:

[0039] Into 30 mL of cyclohexane, 0.06 mol of urea, 3 g of the composite aerogel, 1 mol of isooctyl alcohol, and 1.1 mol of concentrated nitric acid (the mass fraction of the concentrated nitric acid is 65%) are added, and a nitration reaction is carried out at 25°C, with a reaction time of 5 h;

[0040] The nitration product is allowed to stand to separate into layers, the organic phase is separated, washed with water, washed with alkali, washed with water again until neutral, distilled, and dried to obtain isooctyl nitrate.

[0041] Example 3

[0042] The embodiment provides a preparation method of isooctyl nitrate, and specific steps are as follows:

[0043] (1) Preparation of the composite aerogel catalyst:

[0044] S1: tetraethyl orthosilicate, anhydrous ethanol, deionized water and hydrochloric acid are mixed (the molar ratio of the tetraethyl orthosilicate, the anhydrous ethanol, the deionized water and the hydrochloric acid is 1:8:7:0.04), hydrolysis is performed in a water bath at a temperature of 70 DEG C for 5h, then p-toluenesulfonic acid and carboxymethyl cellulose are added (the molar ratio of the tetraethyl orthosilicate, the p-toluenesulfonic acid and the carboxymethyl cellulose is 1:0.2:0.1), and a mixed solution is formed by fully stirring;

[0045] S2: ammonia water with a concentration of 0.6 mol / L is added dropwise into the mixed solution, the volume ratio of the ammonia water to the mixed solution is 1:5, rapid stirring is performed for 10 min to perform a gelation reaction, after filtration and washing, supercritical carbon dioxide drying is performed (the pressure is 20 MPa, the temperature is 50 DEG C, the pressure maintaining time is 6h, and the pressure releasing rate is 5 MPa / h), and an aerogel is obtained;

[0046] S3: the aerogel is immersed in a cerium nitrate solution with a concentration of 0.5 mol / L, is allowed to stand for 8h, is dried at 80 DEG C, and is calcined at 450 DEG C for 3h to obtain the composite aerogel catalyst.

[0047] (2) Preparation of isooctyl nitrate:

[0048] 0.1 mol of urea, 5g of the composite aerogel, 1 mol of isooctanol and 1.2 mol of concentrated nitric acid (the mass fraction of the concentrated nitric acid is 65%) are added into 50 mL of cyclohexane, and nitration reaction is performed at 25 DEG C, and the reaction time is 5h;

[0049] The nitration product is allowed to stand to separate into layers, the organic phase is separated, washed with water, washed with alkali, washed with water again until neutral, distilled, and dried to obtain isooctyl nitrate.

[0050] Example 4

[0051] The embodiment provides a preparation method of isooctyl nitrate, and specific steps are as follows:

[0052] (1) Preparation of the composite aerogel catalyst:

[0053] S1: mixing tetraethyl orthosilicate, anhydrous ethanol, deionized water and hydrochloric acid (the molar ratio of tetraethyl orthosilicate, anhydrous ethanol, deionized water and hydrochloric acid is 1:6:7:0.04), hydrolyzing at 70℃ for 5h in a water bath, then adding p-toluenesulfonic acid and carboxymethyl cellulose (the molar ratio of tetraethyl orthosilicate, p-toluenesulfonic acid and carboxymethyl cellulose is 1:0.2:0.1), and fully stirring to form a mixed solution;

[0054] S2: dropping 0.6mol / L ammonia water into the mixed solution, the volume ratio of ammonia water to the mixed solution is 1:5, stirring rapidly for 10min to carry out gelation reaction, after filtration and washing, carrying out supercritical carbon dioxide drying (pressure is 15MPa, temperature is 40℃, pressure maintaining time is 6h, pressure releasing rate is 5MPa / h), to obtain aerogel;

[0055] S3: immersing the aerogel in 0.5mol / L cerium nitrate solution, standing for 8h, drying at 80℃, and then calcining at 500℃ for 2h to obtain a composite aerogel catalyst.

[0056] (2) Preparation of isooctyl nitrate:

[0057] Adding 0.05mol urea, 3g composite aerogel, 1mol isooctyl alcohol and 1mol concentrated nitric acid (the mass fraction of concentrated nitric acid is 80%) into 50mL cyclohexane, and carrying out nitration reaction at 25℃ for 3h;

[0058] After the nitration product is allowed to stand and separate into layers, the organic phase is separated out, washed with water, washed with alkali, washed with water again until neutral, and then distilled and dried to obtain isooctyl nitrate.

[0059] Comparative Example 1

[0060] The comparative example provides a preparation method of isooctyl nitrate, and the specific steps are as follows:

[0061] Adding 0.1mol urea, 5g p-toluenesulfonic acid, 1mol isooctyl alcohol and 1.2mol concentrated nitric acid (the mass fraction of concentrated nitric acid is 65%) into 50mL cyclohexane, and carrying out nitration reaction at 25℃ for 5h;

[0062] After the nitration product is allowed to stand and separate into layers, the organic phase is separated out, washed with water, washed with alkali, washed with water again until neutral, and then distilled and dried to obtain isooctyl nitrate.

[0063] Comparative Example 2

[0064] The comparative example provides a preparation method of isooctyl nitrate, and the specific steps are as follows:

[0065] (1) Preparation of composite aerogel catalyst:

[0066] S1: mixing tetraethyl orthosilicate, anhydrous ethanol, deionized water and hydrochloric acid (the molar ratio of tetraethyl orthosilicate, anhydrous ethanol, deionized water and hydrochloric acid is 1:8:7:0.04), hydrolyzing in a water bath at a temperature of 70°C for 5h, then adding p-toluenesulfonic acid (the molar ratio of tetraethyl orthosilicate and p-toluenesulfonic acid is 1:0.2), and fully stirring to form a mixed solution;

[0067] S2: dropping 0.6mol / L ammonia water into the mixed solution, rapidly stirring for 10min to perform a gelation reaction, and then performing supercritical carbon dioxide drying (the pressure is 20MPa, the temperature is 50°C, the pressure maintaining time is 6h, and the pressure releasing rate is 5MPa / h) after filtering and washing to obtain a composite aerogel catalyst.

[0068] (2) Preparation of isooctyl nitrate:

[0069] adding 0.1mol urea, 5g composite aerogel, 1mol isooctyl alcohol and 1.2mol concentrated nitric acid (the mass fraction of concentrated nitric acid is 65%) into 50mL cyclohexane, and performing nitration at 25°C for 5h;

[0070] separating the nitration product by layering, performing water washing, alkali washing, and then water washing until neutral, and then performing distillation and drying to obtain isooctyl nitrate.

[0071] Comparative Example 3

[0072] The present comparative example provides a preparation method of isooctyl nitrate, and the specific steps are as follows:

[0073] (1) Preparation of a composite aerogel catalyst:

[0074] S1: mixing tetraethyl orthosilicate, anhydrous ethanol, deionized water and hydrochloric acid (the molar ratio of tetraethyl orthosilicate, anhydrous ethanol, deionized water and hydrochloric acid is 1:8:7:0.04), hydrolyzing in a water bath at a temperature of 70°C for 5h, then adding p-toluenesulfonic acid and carboxymethyl cellulose (the molar ratio of tetraethyl orthosilicate, p-toluenesulfonic acid and carboxymethyl cellulose is 1:0.2:0.1), and fully stirring to form a mixed solution;

[0075] S2: dropping 0.6mol / L ammonia water into the mixed solution, rapidly stirring for 10min to perform a gelation reaction, and then performing supercritical carbon dioxide drying (the pressure is 20MPa, the temperature is 50°C, the pressure maintaining time is 6h, and the pressure releasing rate is 5MPa / h) after filtering and washing to obtain a composite aerogel catalyst.

[0076] (2) Preparation of isooctyl nitrate:

[0077] Into 50 mL of cyclohexane, 0.1 mol of urea, 5 g of composite aerogel, 1 mol of isooctanol, and 1.2 mol of concentrated nitric acid (65% of mass fraction) were added to carry out a nitration reaction at 25°C, and the reaction time was 5 h.

[0078] The nitration product was allowed to stand and separate into layers, and the organic phase was separated, washed with water, washed with alkali, washed with water again until neutral, and then distilled and dried to obtain isooctyl nitrate.

[0079] Comparative Example 4

[0080] The present comparative example provides a preparation method of isooctyl nitrate, and the specific steps are as follows:

[0081] S1: concentrated nitric acid and concentrated sulfuric acid were mixed in a molar ratio of 1:1 (80% of mass fraction of concentrated nitric acid and 98% of mass fraction of concentrated sulfuric acid) to obtain a mixed acid solution;

[0082] S2: urea and isooctanol were added to the mixed acid solution (the molar ratio of concentrated nitric acid, urea, and isooctanol was 1:0.1:1), the reaction temperature was 20°C, and the stirring reaction was carried out for 1 h, then the nitration product was allowed to stand and separate into layers, the organic phase was separated, washed with water, washed with alkali, washed with water again until neutral, and then distilled and dried to obtain isooctyl nitrate.

[0083] Performance test:

[0084] Table 1 shows the yield (%) and purity (%) of isooctyl nitrate finally obtained in Examples 1-4 and Comparative Examples 1-4.

[0085] Table 1

[0086]

[0087] As shown in Table 1, by using the preparation method provided by the present application, the yield of isooctyl nitrate is above 98.91%, and the purity is above 99.5%, compared with the traditional mixed acid method in Comparative Example 4, the yield and purity are significantly improved, which indicates that the preparation method provided by the present application can efficiently prepare isooctyl nitrate.

[0088] Table 2 shows the change of the yield (%) of isooctyl nitrate after the composite aerogel catalyst prepared in Examples 1-4 and Comparative Examples 2 and 3 was operated for a period of time.

[0089] Table 2

[0090]

[0091] It can be seen that after the catalysts in Examples 1-4 are operated for 216 h, the yield of isooctyl nitrate decreases slightly and can be maintained above 97%, and until after 480 h of repeated use, the yield can still be maintained above 90%, proving that the composite aerogel catalyst prepared in the application has excellent catalytic activity while maintaining good stability, can be repeatedly used in the industrial production of isooctyl nitrate, thereby effectively reducing production costs.

Claims

1. A process for the preparation of isooctyl nitrate, characterized in that: The cyclohexane is used as the solvent, the urea is used as the stabilizer, and the composite aerogel is used as the catalyst, so that the isooctanol is nitrated by concentrated nitric acid to generate the nitration product; The nitration product is layered after standing, and the organic phase is separated out, and then is subjected to water washing, alkali washing, re-water washing to neutral, and then is subjected to distillation and drying, so that the isooctyl nitrate is obtained. The preparation method of the composite aerogel catalyst comprises the following steps: S1: mixing tetraethyl orthosilicate, anhydrous ethanol, deionized water and hydrochloric acid, and then performing hydrolysis in a water bath at a temperature of 60-70 DEG C for 5-6 h, and then adding p-toluenesulfonic acid and carboxymethyl cellulose to form a mixed solution; S2: dropping ammonia water into the mixed solution, and then rapidly stirring to perform gelation reaction, and then performing filtration and washing, and then performing supercritical carbon dioxide drying to obtain the aerogel; S3: immersing the aerogel in a cerium nitrate solution, and then standing, drying and calcining to obtain the composite aerogel catalyst; The addition ratio of cyclohexane, urea, composite aerogel, isooctanol and concentrated nitric acid is 30-50 mL:0.05-0.1 mol:2-5 g:1 mol:1-1.2 mol; and the mass fraction of the concentrated nitric acid is 65-80%. The molar ratio of tetraethyl orthosilicate, anhydrous ethanol, deionized water and hydrochloric acid is 1:5-10:6-8:0.02-0.

04. The molar ratio of tetraethyl orthosilicate, p-toluenesulfonic acid and carboxymethyl cellulose is 1:0.2-0.3:0.

1.

2. The process for the preparation of isooctyl nitrate as claimed in claim 1, wherein: In the process of generating the isooctyl nitrate from the isooctanol under the nitration of the concentrated nitric acid, the reaction temperature is 20-25 DEG C, and the time is 3-5 h.

3. The process for the preparation of isooctyl nitrate as claimed in claim 1, wherein: The concentration of the ammonia water is 0.6-0.8 mol / L, and the volume ratio of the ammonia water to the mixed solution is 1-2:

10.

4. The process for the preparation of isooctyl nitrate as claimed in claim 1, wherein: After the ammonia water is dropped, the gelation reaction is performed by rapidly stirring for 5-10 min.

5. The process for the preparation of isooctyl nitrate as claimed in claim 1, wherein: In the supercritical carbon dioxide drying, the pressure is 10-20 MPa, the temperature is 40-50 DEG C, the pressure maintaining time is 5-6 h, and the pressure releasing rate is 4-5 MPa / h.

6. The process for the preparation of isooctyl nitrate as claimed in claim 1, wherein: In step S3, the concentration of the cerium nitrate solution is 0.5 mol / L; the standing time is 6-8 h, the drying temperature is 70-80 DEG C, the calcination temperature is 450-500 DEG C, and the calcination time is 2-3 h.

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