Process for the preparation of a 2,5-tetrahydrofurandimethanol difatty acid ester and its use in a diesel additive

Abstract

A process for the preparation of a 2,5-tetrahydrofurandimethanol difatty acid ester, comprising the following steps: providing a reaction system containing 2,5-tetrahydrofurandimethanol with a monobasic acid, wherein the structural formula of the monobasic acid is R-COOH, where R is an alkyl group from C5 to C20; esterification in the presence of a catalyst to obtain the 2,5-tetrahydrofurandimethanol difatty acid ester, wherein the catalyst is at least one of calcium acetate, tetraalkoxytitanium, manganese acetate, cobalt acetate, aluminum oxide, zinc oxide, and zinc-aluminum spinel; wherein the 2,5-tetrahydrofurandimethanol difatty acid ester has a structural formula as shown in Formula I, characterized in that the calcium acetate, tetraalkoxytitanium, manganese acetate, cobalt acetate, aluminum oxide, zinc oxide, and zinc-aluminum spinel have a particle size of have less than or equal to 80 mesh, and the reaction system includes a solvent,wherein the solvent is at least one of dimethyl sulfoxide and dimethylformamide.

Description

TECHNICAL AREA

[0001] The present application relates to the technical field of diesel fuel additives, in particular to a bio-based 2,5-tetrahydrofurandimethanol difatty acid ester and a process for its production. STATE OF THE ART

[0002] Diesel fuel is a component obtained from crude oil through catalytic cracking, hydrocatalysis, coking, and similar processes after distillation. During operation, diesel engines place stricter demands on the ignition performance and explosion resistance of the diesel fuel. A key indicator for measuring ignition performance and explosion resistance is the cetane number. The cetane number affects pollutant emissions, starting performance, and fuel consumption. Higher cetane numbers result in significantly lower pollutant emissions and reduced engine knocking during starting and driving compared to diesel with a lower cetane number. Therefore, using diesel with a high cetane number reduces engine damage and lowers fuel consumption.

[0003] Currently, the most commonly used additives on the market for improving the cetane number of diesel fuel include nitrates, azide compounds, peroxy compounds, ethers, and esters. Most of these additives consist of non-renewable, petroleum-based chemicals. Given the depletion of fossil fuels and environmental pollution, it is necessary to find renewable resources that can replace them. CONTENT OF THE PRESENT INVENTION

[0004] According to one aspect of the present application, a process for the preparation of a 2,5-tetrahydrofurandimethanol di fatty acid ester and its use in a diesel additive are provided.

[0005] 5-Hydroxymethylfurfural (HMF) is a carbohydrate derived from biomass. When sugars, glucose, starch, and cellulose are obtained through dehydration, they are known as one of the most important basic compounds because they can be oxidized or reduced to various high-value monomers. Although many 5-hydroxymethylfurfural (HMF) derivatives, such as ethers, acetals, and lactones, can be used as biomass-derived fuels and additives, the direct esterification of these compounds for the production of biofuels is less explored.

[0006] 2,5-Tetrahydrofurandimethanol (DHMTHF) can be produced by the hydrogenation of 5-hydroxymethylfurfural (HMF). Due to its symmetrical structure and good thermal stability, it can be esterified with monobasic acids at elevated temperatures. Adding the resulting dibasic acid ester to diesel fuel can effectively increase its cetane number. Therefore, it has significant practical importance for the development and use of clean energy.

[0007] Preferably, the process for the preparation of a 2,5-tetrahydrofurandimethanol difatty acid ester comprises the following steps: In the presence of a catalyst, a reaction system containing 2,5-tetrahydrofurandimethanol is esterified with a monobasic acid to obtain the 2,5-tetrahydrofurandimethanol difatty acid ester. where the structural formula of the monobasic acid is R-COOH, where R is an alkyl group from C5-C20.

[0008] Preferably, R is an alkyl group from C7-C14.

[0009] Preferably, the monobasic acid is selected from at least one of the n-octanoic acid, n-nonanoic acid, N-decanoic acid, undecanoic acid, dodecanoic acid and tetradecanoic acid.

[0010] Preferably, the catalyst is selected from at least one of the Candida lipase B, calcium acetate, tetraalkoxytitanium, manganese acetate, cobalt acetate, aluminium oxide, zinc oxide and zinc-aluminium spinel.

[0011] Preferably, tetraalkoxytitanium is selected from at least one of tetraethoxytitanium.

[0012] Preferably, the Candida Lipase B is used after drying.

[0013] Preferably, the drying process comprises the following steps: Candida Lipase B is placed in the flask and stored with phosphorus pentoxide for 16-24 hours at room temperature and high vacuum, and used after drying. Preferably, calcium acetate, tetraalkoxytitanium, manganese acetate, cobalt acetate, aluminium oxide, zinc oxide and zinc-aluminium spinel have a particle size of less than or equal to 80 mesh.

[0014] Preferably, the molar ratio of the monobasic acid to the 2,5-tetrahydrofurandimethanol is 2-4:1.

[0015] Preferably, the molar ratio of the monobasic acid to the 2,5-tetrahydrofurandimethanol is 2:1, 3:1, 4:1 or a range value between any two ratios.

[0016] Preferably, the mass ratio of 2,5-tetrahydrofurandimethanol to the catalyst is 50-200:1.

[0017] Preferably, the reaction system is a solvent system, or the reaction system also includes a solvent, wherein the solvent is selected from at least one of dimethyl sulfoxide and dimethylformamide, wherein the volume ratio of the solvent to the 2,5-tetrahydrofurandimethanol is 10-20:1.

[0018] Preferably, the reaction temperature is 60-120 °C and the reaction time is 10-24 hours.

[0019] Preferably, the upper limit of the reaction temperature is selected from 70 °C, 80 °C, 90 °C, 100 °C, 110 °C or 120 °C, and the lower limit of the reaction temperature is selected from 60 °C, 70 °C, 80 °C, 90 °C, 100 °C or 110 °C.

[0020] Preferably, the upper limit of the reaction time is selected from 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours or 24 hours, with the lower limit of the reaction time being selected from 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours or 23 hours.

[0021] Preferably, the water produced during the esterification reaction is removed by distillation under reduced pressure.

[0022] Preferably, the mixture obtained after the esterification reaction is purified to obtain the diesel additive. the cleaning process includes washing with an alkaline solution, drying, and distillation in an organic solvent, wherein the alkaline solution comprises at least one of sodium carbonate solution and potassium carbonate solution, wherein the organic solvent is selected from at least one of ethanol, ethyl acetate and petroleum ether.

[0023] Preferably, the cleaning process should include the following steps: The resulting mixture is washed with sodium carbonate solution and water, dried with anhydrous sodium sulfate and steamed by rotating with at least one of ethanol, ethyl acetate and petroleum ether.

[0024] According to another aspect of the present application, a use of manufactured 2,5-tetrahydrofurandimethanol difatty acid ester in a diesel additive is provided according to one of the above methods for its preparation.

[0025] Preferably, the amount added to diesel is 5-10% by weight of the 2,5-tetrahydrofurandimethanol difatty acid ester.

[0026] Preferably, the 2,5-tetrahydrofurandimethanol difatty acid ester is used as a diesel additive.

[0027] In the present application, CALB refers to Candida Lipase B.

[0028] In the present application, C5-C20, C7-C14 etc. refer to the number of carbon atoms contained in the group.

[0029] In the present application, the term alkyl refers to a group formed by the loss of a hydrogen atom on an alkane compound molecule.

[0030] The advantageous effects of the present application include: 1) According to the use of the 2,5-tetrahydrofurandimethanol difatty acid ester in a diesel additive in the present application, the obtained bio-based difatty acid ester is added to diesel, thereby effectively increasing the cetane number of diesel, which has high application value. 2) According to the process for producing a 2,5-tetrahydrofurandimethanol difatty acid ester in the present application, 2,5-tetrahydrofurandimethanol is used with a catalyst to produce bio-based difatty acid esters with monobasic acids of different chain lengths. The process according to the present invention has low equipment and technology requirements, so that the production process is simple, the selectivity is high, and the purification process is simple. List of characters Fig. 1 is a theoretical reaction process of 2,5-tetrahydrofurandimethanol with a monobasic acid having different chain lengths according to an embodiment of the present application. Fig. 2 is a time-of-flight mass spectrum of 2,5-tetrahydrofurandimethanol didecanoic acid ester produced by the reaction of 2,5-tetrahydrofurandimethanol with n-decanoic acid according to embodiment 7 of the present application. Fig. 3 is a time-of-flight mass spectrum of 2,5-tetrahydrofurandimethanol monodecanoic acid ester produced by the reaction of 2,5-tetrahydrofurandimethanol with n-decanoic acid according to embodiment 7 of the present application. Fig. Figure 4 is a liquid chromatogram of 2,5-tetrahydrofurandimethanol didecanoic acid ester and 2,5-tetrahydrofurandimethanol monodecanoic acid ester produced by the reaction of 2,5-tetrahydrofurandimethanol with n-decanoic acid according to embodiment 7 of the present application. DETAILED DESCRIPTION

[0031] The present application is described in detail below in conjunction with exemplary embodiments, but the present application is not limited to the exemplary embodiments presented.

[0032] Unless otherwise stated, the raw materials and catalysts in the embodiments of this application are obtained through commercial channels.

[0033] The analysis method in the embodiments of the present application is as follows: Flight mass spectrometry is performed using a Model 4600 flight mass spectrometer manufactured by AB Sciex, USA.

[0034] Gas phase mass spectrometry is performed using a gas phase mass spectrometer of model 7890B-7977A, manufactured by Agilent, USA.

[0035] Liquid phase analysis is performed using a high-performance liquid chromatograph, model 1260, manufactured by Agilent, USA.

[0036] In the exemplary embodiment, the conversion rate of 2,5-tetrahydrofurandimethanol = the mass of 2,5-tetrahydrofurandimethanol after the reaction / the mass of 2,5-tetrahydrofurandimethanol after the initial reaction.

[0037] In the exemplary embodiment, the selectivity of 2,5-tetrahydrofurandimethanol dioic acid ester = the mass of 2,5-tetrahydrofurandimethanol dioic acid ester / the mass of the total reaction product.

[0038] In the exemplary embodiment, the yield of 2,5-tetrahydrofurandimethanol diic acid ester = the mass of 2,5-tetrahydrofurandimethanol diic acid ester after purification / the mass xx of 2,5-tetrahydrofurandimethanol diic acid ester after theoretical production.

[0039] The concentration of the sodium carbonate solution in the exemplary embodiment is 2 mol / l.

[0040] According to one embodiment of the present application, the use of 2,5-tetrahydrofurandimethanol difatty acid ester in a diesel additive is provided. The 2,5-tetrahydrofurandimethanol difatty acid ester can be used as a bio-based diesel additive to increase the cetane number of diesel and improve its combustion performance.

[0041] According to one embodiment of the present application, the process for the preparation of the 2,5-tetrahydrofurandimethanol difatty acid ester comprises the following steps: S100: The esterification reaction is carried out after mixing 2,5-tetrahydrofurandimethanol and monobasic acid with different chain lengths in a specific ratio, wherein the molar ratio of the monobasic acid with different chain lengths to the 2,5-tetrahydrofurandimethanol is 2:1-4:1, S200: The obtained product is washed, dried, steamed using a rotary process, and the by-product is removed to obtain a difatty acid ester diesel additive.

[0042] In one of the embodiments, the monobasic acid in S100 is one or more of n-octanoic acid, n-nonanoic acid, n-decanoic acid, undecanoic acid, dodecanoic acid and tetradecanoic acid.

[0043] In one embodiment, the catalyst in S100 is one or more of the biological enzyme CALB, calcium acetate, tetraalkoxytitanium, manganese acetate, cobalt acetate, aluminum oxide, zinc oxide, and zinc-aluminum spinel. Due to the good thermal stability of 2,5-tetrahydrofurandimethanol, it can generate difatty acid esters at higher temperatures with improved selectivity.

[0044] In the present application, 2,5-tetrahydrofurandimethanol can be esterified using the biological enzyme catalyst CALB, which has better catalytic activity, or with alkaline compounds such as calcium acetate, tetraalkoxytitanium, or weakly alkaline manganese acetate, cobalt acetate, etc., as esterification reaction catalysts, due to its improved thermal stability at lower temperatures. To ensure complete contact between the catalyst and the reactants, the particle size of the catalyst should be less than or equal to 80 mesh.

[0045] In one embodiment, the system in S 100 consists of one or more solvent-free dimethyl sulfoxide and dimethylformamide. If the esterification reaction is carried out without the addition of a solvent to the system, the manufacturing process is simple and the reaction time is short. However, the disadvantage is that the reaction temperature is high, which necessitates that the reactant does not decompose at this temperature, that the ratio of the reactant is precise, that the viscosity of the reactant is high, that small molecules are not easily removed, and that the reaction equipment is tightly sealed. 2,5-Tetrahydrofurandimethanol, however, oxidizes at higher temperatures to form new byproducts. Therefore, if no solvent is present in the system, the reaction temperature should be strictly controlled to minimize the presence of byproducts.When one or more of dimethyl sulfoxide and dimethylformamide are used as solvents for esterification, the presence of a solvent can reduce the reaction temperature, prevent the decomposition of raw materials and products, and make the reaction stable and easy to control, allowing it to react azeotropically or with the resulting small molecules for removal. The disadvantage is that the presence of a solvent increases the need for separation, refining, solvent recovery, and similar steps in the esterification reaction.

[0046] In one of the embodiments, the biological enzyme catalyst CALB is added to the flask in S100 and stored with phosphorus pentoxide at room temperature and high vacuum for 16-24 hours and used after drying.

[0047] In one of the embodiments, calcium acetate, tetraalkoxytitanium, manganese acetate, cobalt acetate, aluminium oxide, zinc oxide and zinc-aluminium spinel in S 100 have a particle size of less than or equal to 80 mesh.

[0048] In one of the embodiments, the reaction temperature in S100 is 60-120 °C.

[0049] In one of the embodiments, the reaction time in S100 is 10-24 hours.

[0050] In one of the embodiments, the water produced during the reaction in S100 is subjected to distillation under reduced pressure.

[0051] In one of the embodiments, the product in S200 is washed with sodium carbonate solution and water and dried with anhydrous sodium sulfate.

[0052] In one embodiment, one or more molecules of ethanol, ethyl acetate, and petroleum ether are subjected to rotary vaporization in S200. Preferably, the resulting product is washed several times with sodium carbonate solution of a specific concentration and water, and then dried with anhydrous sodium sulfate after excess fatty acid has been removed. Then, one or more molecules of ethanol, ethyl acetate, and petroleum ether are subjected to rotary vaporization to obtain highly purified bio-based fatty acid diesters after complete removal of byproducts. Example 1 (1) 1.32 g of 2,5-tetrahydrofurandimethanol and 2.88 g of n-octanoic acid are added to the three-necked flask, and 0.02 g of manganese acetate (particle size of 80 mesh) is added and the mixture is stirred thoroughly at 100 °C, and the water produced in the system is removed by distillation under reduced pressure to promote the reaction process and increase the conversion rate, and to react completely for 10 hours, the molar ratio of n-octanoic acid to 2,5-tetrahydrofurandimethanol being 2:1. (2) The product obtained in step (1) is washed completely in the configured sodium carbonate solution, then rinsed with deionized water, dried with anhydrous sodium sulfate, and then steam-dried with ethanol solution to remove the by-product, finally yielding 2,5-tetrahydrofurandimethanol dioctanoic acid ester of higher purity. The conversion rate of 2,5-tetrahydrofurandimethanol is 100%. The yield of 2,5-tetrahydrofurandimethanol dioctanoic acid ester is 59%. The selectivity of 2,5-tetrahydrofurandimethanol dioctanoic acid ester is 80%. Example 2 (1) 1.32 g of 2,5-tetrahydrofurandimethanol and 4.32 g of n-octanoic acid are added to the three-necked flask, and 0.02 g of manganese acetate (particle size of 80 mesh) is added and the mixture is stirred thoroughly at 100 °C, and the water produced in the system is removed by distillation under reduced pressure to promote the reaction process and increase the conversion rate, and to react completely for 10 hours, the molar ratio of n-octanoic acid to 2,5-tetrahydrofurandimethanol being 3:1. (2) As in embodiment 1. Compared with embodiment 1, the concentration of n-octanoic acid in the raw material has changed according to the present embodiment, and the other manufacturing conditions have not changed. As the concentration of n-octanoic acid increases, the yield of 2,5-tetrahydrofurandimethanol dioctanoic acid ester ultimately increases. The conversion rate of 2,5-tetrahydrofurandimethanol is 100%. The yield of 2,5-tetrahydrofurandimethanol dioctanoic acid ester is 71%. The selectivity of 2,5-tetrahydrofurandimethanol dioctanoic acid ester is 85%. Example 3 (1) 1.32 g of 2,5-tetrahydrofurandimethanol and 2.88 g of n-octanoic acid are added to the three-necked flask, and 0.02 g of manganese acetate (particle size of 80 mesh) is added and the mixture is stirred thoroughly at 120 °C, and the water produced in the system is removed by distillation under reduced pressure to promote the reaction process and increase the conversion rate, and to react completely for 10 hours, the molar ratio of n-octanoic acid to 2,5-tetrahydrofurandimethanol being 2:1. (2) As in embodiment 1. Compared with embodiment 1, the reaction temperature has changed according to the present embodiment, and the other production conditions have not changed. As the temperature increases, the yield of 2,5-tetrahydrofurandimethanol dioctanoic acid ester ultimately increases. The conversion rate of 2,5-tetrahydrofurandimethanol is 100%. The yield of 2,5-tetrahydrofurandimethanol dioctanoic acid ester is 73%. The selectivity of 2,5-tetrahydrofurandimethanol dioctanoic acid ester is 92%. Example 4 (1) 1.32 g of 2,5-tetrahydrofurandimethanol and 2.88 g of n-octanoic acid are added to the three-necked flask, and 0.02 g of manganese acetate (particle size of 80 mesh) is added and the mixture is stirred thoroughly at 100 °C, and the water produced in the system is removed by distillation under reduced pressure to promote the reaction process and increase the conversion rate and to react completely for 24 hours, the molar ratio of n-octanoic acid to 2,5-tetrahydrofurandimethanol being 2:1. (2) As in embodiment 1. Compared with embodiment 1, the reaction time has changed according to the present embodiment, and the other manufacturing conditions have not changed. As the reaction time increases, the yield of 2,5-tetrahydrofurandimethanol dioctanoic acid ester ultimately increases. The conversion rate of 2,5-tetrahydrofurandimethanol is 100%. The yield of 2,5-tetrahydrofurandimethanol dioctanoic acid ester is 66%. The selectivity of 2,5-tetrahydrofurandimethanol dioctanoic acid ester is 84%. Example 5 (1) 1.32 g of 2,5-tetrahydrofurandimethanol and 3.16 g of n-nonanoic acid are added to the three-necked flask, 10 ml of dimethyl sulfoxide is added, 0.02 g of tetraalkoxytitanium (particle size of 80 mesh) is added and the mixture is stirred thoroughly at 100 °C, and the water produced in the system is removed by distillation under reduced pressure to promote the reaction process and increase the conversion rate and to react completely for 10 hours, with the molar ratio of n-nonanoic acid to 2,5-tetrahydrofurandimethanol being 2:1. (2) The product obtained in step (1) is washed completely in the configured sodium carbonate solution, then rinsed with deionized water, dried with anhydrous sodium sulfate, then steamed by rotating with ethyl acetate solution to remove the by-product, and finally 2,5-tetrahydrofurandimethanoldinonanoic acid ester of higher purity is obtained. Example 6 (1) 1.32 g of 2,5-tetrahydrofurandimethanol and 3.44 g of n-decanoic acid are added to the three-necked flask, 10 ml of dimethylformamide is added, 0.02 g of manganese acetate (particle size of 80 mesh) is added and the mixture is stirred thoroughly at 100 °C, and the water produced in the system is removed by distillation under reduced pressure to promote the reaction process and increase the conversion rate and to react completely for 10 hours, with the molar ratio of n-decanoic acid to 2,5-tetrahydrofurandimethanol being 2:1. (2) The product obtained in step (1) is washed completely in the configured sodium carbonate solution, then rinsed with deionized water, dried with anhydrous sodium sulfate, then steamed with petroleum ether by rotating to remove the by-product, and finally 2,5-tetrahydrofurandimethanol didecanoate ester of higher purity is obtained. Example 7 (1) 1.32 g of 2,5-tetrahydrofurandimethanol and 3.44 g of n-decanoic acid are added to the three-necked flask, and 0.02 g of calcium acetate (particle size of 80 mesh) is added and the mixture is stirred thoroughly at 120 °C, and the water produced in the system is removed by distillation under reduced pressure to promote the reaction process and increase the conversion rate and to react completely for 24 hours, the molar ratio of n-decanoic acid to 2,5-tetrahydrofurandimethanol being 2:1. (2) The product obtained in step (1) is washed completely in the configured sodium carbonate solution, then rinsed with deionized water, dried with anhydrous sodium sulfate, then steamed by rotating with ethyl acetate solution to remove the by-product, and finally 2,5-tetrahydrofurandimethanol didecanoate ester of higher purity is obtained. Example 8 (1) The biological enzyme catalyst CALB is placed in the flask and stored with phosphorus pentoxide at room temperature and high vacuum for 16 hours and used after drying. 1.32 g of 2,5-tetrahydrofurandimethanol and 3.44 g of n-decanoic acid are added to the three-necked flask, and 0.02 g of biological enzyme CALB (particle size of 80 mesh) is added and stirred thoroughly at 60 °C. The water generated in the system is removed by distillation under reduced pressure to promote the reaction process and increase the conversion rate, and to react completely for 24 hours, with the molar ratio of n-decanoic acid to 2,5-tetrahydrofurandimethanol being 2:1. (2) The product obtained in step (1) is washed completely in the configured sodium carbonate solution, then rinsed with deionized water, dried with anhydrous sodium sulfate, and then steam-dried with ethyl acetate solution to remove the by-product, finally yielding 2,5-tetrahydrofurandimethanol didecanoic acid ester of higher purity. The conversion rate of 2,5-tetrahydrofurandimethanol is 100%. The yield of 2,5-tetrahydrofurandimethanol didecanoic acid ester is 85%. The selectivity of 2,5-tetrahydrofurandimethanol didecanoic acid ester is 95%. Example 9 (1) 1.32 g of 2,5-tetrahydrofurandimethanol and 3.72 g of undecanoic acid are added to the three-necked flask, 10 ml of dimethyl sulfoxide is added, 0.02 g of cobalt acetate (particle size of 80 mesh) is added and the mixture is stirred thoroughly at 120 °C, and the water produced in the system is removed by distillation under reduced pressure to promote the reaction process and increase the conversion rate and to react completely for 24 hours, with the molar ratio of undecanoic acid to 2,5-tetrahydrofurandimethanol being 2:1. (2) The product obtained in step (1) is washed completely in the configured sodium carbonate solution, then rinsed with deionized water, dried with anhydrous sodium sulfate, then steamed with ethanol by rotating to remove the by-product, and finally 2,5-tetrahydrofurandimethanolundecanoic acid diester of higher purity is obtained. Example 10 (1) 1.32 g of 2,5-tetrahydrofurandimethanol and 4.00 g of dodecanoic acid are added to the three-necked flask, 10 ml of dimethyl sulfoxide is added, 0.02 g of cobalt acetate (particle size of 80 mesh) is added and the mixture is stirred thoroughly at 120 °C, and the water produced in the system is removed by distillation under reduced pressure to promote the reaction process and increase the conversion rate and to react completely for 24 hours, with the molar ratio of dodecanoic acid to 2,5-tetrahydrofurandimethanol being 2:1. (2) The product obtained in step (1) is washed completely in the configured sodium carbonate solution, then rinsed with deionized water, dried with anhydrous sodium sulfate, then steamed with ethanol by rotary action to remove the by-product, and finally 2,5-tetrahydrofurandimethanoldodecanoic acid diesters of higher purity are obtained. Example 11 (1) 1.32 g of 2,5-tetrahydrofurandimethanol and 4.56 g of tetradecanoic acid are added to the three-necked flask, 10 ml of dimethyl sulfoxide is added, 0.02 g of cobalt acetate (particle size of 80 mesh) is added and the mixture is stirred thoroughly at 120 °C, and the water produced in the system is removed by distillation under reduced pressure to promote the reaction process and increase the conversion rate and to react completely for 24 hours, with the molar ratio of tetradecanoic acid to 2,5-tetrahydrofurandimethanol being 2:1. (2) The product obtained in step (1) is washed completely in the configured sodium carbonate solution, then rinsed with deionized water, dried with anhydrous sodium sulfate, then rotary steamed with ethanol to remove the by-product, and finally 2,5-tetrahydrofurandimethanoltetradecanoic acid diester of higher purity is obtained. Example 12

[0053] The bio-based dibasic acid esters produced in embodiments 1 to 11 were tested by time-of-flight mass spectrometry. The test results show that the corresponding products were produced. Typical test results are shown in Fig. 2, Fig. 3 and Fig. 4 shown, which correspond to the product produced in embodiment 7. Fig. Figure 2 shows a molecular ion peak and a fragment ion peak of 2,5-tetrahydrofurandidecanoic acid ester. Fig. Figure 3 shows a molecular ion peak and a fragment ion peak of 2,5-tetrahydrofuran monodecanoic acid ester, which does not react completely. Fig. Figure 4 is a liquid chromatogram with a retention time of 5.17 minutes for 2,5-tetrahydrofuran monodecanoic acid esters of the trans structure, a retention time of 6.13 minutes for 2,5-tetrahydrofuran monodecanoic acid esters of the cis structure, and a retention time of 14.83 minutes for 2,5-tetrahydrofurandidecanoic acid esters. Example 13 Use

[0054] The bio-based difatty acid esters produced in embodiments 1 to 11 are used as diesel additives. The cetane number of the diesel is tested. The diesel used is biodiesel from the Romaglia biodiesel filling station.

[0055] When the amount added of 2,5-tetrahydrofurandimethanoldecanoic acid diester is 5 wt% of the biodiesel mass, the cetane number of diesel is typically 57.4.

[0056] The above are only some embodiments of the present application and do not constitute a limitation of the present application. Although the present application discloses the above preferred embodiments, it is not intended to limit the present application. Any person skilled in the art familiar with the field will make some changes or modifications using the technical content disclosed above without departing from the technical solution of the present application, which corresponds to an equivalent embodiment and falls within the scope of the technical solution.

Claims

[1] Process for the preparation of a 2,5-tetrahydrofuran dimethanol difatty acid ester, characterized by that the process for preparing a 2,5-tetrahydrofuran dimethanol difatty acid ester comprises the following steps: in the presence of a catalyst, a reaction system containing 2,5-tetrahydrofurandimethanol is esterified with a monobasic acid to obtain the 2,5-tetrahydrofurandimethanol difatty acid ester, where the structural formula of the monobasic acid is R-COOH, where R is an alkyl group of C5-C20, wherein the 2,5-tetrahydrofuran dimethanol difatty acid ester has a structural formula as shown in formula I, where R is selected from one of the alkyl groups of C5-C20. [2] A method of manufacturing according to claim 1, characterized by that the monobasic acid is at least one of n-octanoic acid, n-nonanoic acid, N-decanoic acid, undecanoic acid, dodecanoic acid and tetradecanoic acid. [3] A method of manufacturing according to claim 1, characterized by that the catalyst is at least one of Candida Lipase B, calcium acetate, tetraalkoxytitanium, manganese acetate, cobalt acetate, aluminum oxide, zinc oxide and zinc aluminum spinel. [4] A method of manufacturing according to claim 3, characterized by that calcium acetate, tetraalkoxytitanium, manganese acetate, cobalt acetate, aluminum oxide, zinc oxide and zinc aluminum spinel have a particle size of less than or equal to 80 mesh. [5] A method of manufacturing according to claim 1, characterized by that the molar ratio of the monobasic acid to the 2,5-tetrahydrofurandimethanol is 2-4:

1. [6] A method of manufacturing according to claim 1, characterized by that the mass ratio of 2,5-tetrahydrofuran dimethanol to the catalyst is 50-200:

1. [7] A method of manufacturing according to claim 1, characterized bythat the reaction system is a solvent system, or that the reaction system also comprises a solvent, wherein the solvent is at least one of dimethyl sulfoxide and dimethylformamide, wherein the volume ratio of the solvent to the 2,5-tetrahydrofurandimethanol is 10-20:

1. [8] A method of manufacturing according to claim 1, characterized by that the condition of the esterification reaction is that the reaction temperature is 60-120 °C and the reaction time is 10-24 hours. [9] A method of manufacturing according to claim 1, characterized by that the water produced during the esterification reaction is removed by distillation under reduced pressure. [10] A method of manufacturing according to claim 1, characterized by that the mixture obtained after the esterification reaction is purified to obtain the 2,5-tetrahydrofurandimethanol difatty acid ester. [11] A method of manufacturing according to claim 10, characterized by that cleaning comprises washing with alkaline solution, drying and distillation in an organic solvent, wherein the alkaline solution comprises at least one of sodium carbonate solution and potassium carbonate solution, wherein the organic solvent is at least one of ethanol, ethyl acetate and petroleum ether. [12] Use of the 2,5-tetrahydrofurandimethanol difatty acid ester prepared by the process for preparation according to any one of claims 1 to 11 in a diesel additive.