A method for determining the epoxide value of an epoxidized vegetable oil

Abstract

The application discloses a method for determining the epoxy value of epoxy vegetable oil, and comprises the following steps: infrared spectrum determination is performed on the epoxy vegetable oil; characteristic peak positions of epoxy functional groups and ester group functional groups are calibrated in the infrared spectrum; peak areas are calculated and are respectively recorded as A 环氧 and A 酯基 ; the ratio of the peak areas is calculated and is defined as an epoxy index m, i.e., m=A 环氧 / A 酯基 ; a hydrochloric acid-acetone method is used to determine the epoxy value M of the corresponding epoxy vegetable oil; a scatter plot is formed by the m and M values of the corresponding epoxy vegetable oil, a standard curve is fitted, and a polynomial fitting equation of M and m is obtained; the epoxy index m of the to-be-detected epoxy vegetable oil is obtained, and the epoxy value M of the to-be-detected epoxy vegetable oil can be obtained by substituting the epoxy index m into the fitting equation. The application has the advantages of simple operation, easy control, small error and good application effect.

Description

Technical Field

[0001] This invention belongs to the field of epoxy value testing technology, specifically relating to a method for determining the epoxy value of epoxy-enriched vegetable oils. Background Technology

[0002] Epoxidized vegetable oil, as a vegetable oil-based derivative, is widely used due to its non-toxicity, harmlessness, and low raw material cost. The main component of epoxidized vegetable oil is fatty acids, with a long-chain molecular structure. Therefore, it does not produce carcinogenic polycyclic aromatic compounds during practical use, making it more environmentally friendly than aromatic oils. Furthermore, the regeneration effect of epoxidized vegetable oil regenerators is similar to that of aromatic oils, effectively improving the low-temperature performance of asphalt and enhancing the plasticity of aged asphalt. Therefore, epoxidized vegetable oil can serve as a substitute for aromatic oils in the regeneration of aged asphalt. Traditional regenerators, aromatic oils, are highly carcinogenic and unstable, easily volatile, while epoxidized vegetable oils are safe and non-toxic, overcoming some of the drawbacks of aromatic oils. Other studies have shown that epoxidized vegetable oil can reduce the viscosity of asphalt; therefore, using vegetable oil as a warm mix agent and a pretreatment solvent for rubber is feasible.

[0003] However, regardless of whether epoxy vegetable oil is used as a regenerator, warm mix agent, or pretreatment solvent for rubber, its epoxy value will affect its practical application effect. Studies have shown that epoxy vegetable oils with lower epoxy values ​​have better regeneration effects on aged asphalt. Traditional methods for determining epoxy value are mainly chemical analysis methods, commonly including the hydrochloric acid-acetone method, hydrochloric acid-pyridine method, hydrochloric acid-dioxane method, and direct titration of ammonium bromide salts. These methods are complex to operate, prone to human error, and can only measure epoxy vegetable oils with relatively small molecular weights. Therefore, there is an urgent need to invent a simple, convenient, and highly reliable method for determining epoxy value. Summary of the Invention

[0004] Technical problem solved: To address the above-mentioned technical problem, this invention provides a method for determining the epoxy value of epoxidized vegetable oils. This method is simple to operate, easy to control, has small errors, and has good application effects.

[0005] Technical solution: A method for determining the epoxy value of epoxidized vegetable oil, comprising the following steps:

[0006] Step 1: Perform infrared spectroscopy on the epoxidized vegetable oil;

[0007] Step 2: Identify the characteristic peak positions of epoxy and ester functional groups in the infrared spectrum;

[0008] Step 3: Calculate the peak areas of the epoxy functional group and the ester functional group, and denote them as A. 环氧 and A 酯基 ;

[0009] Step 4: Calculate the ratio of the peak areas of epoxy functional groups to those of ester functional groups, defined as the epoxy index m, i.e., m = A. 环氧 / A 酯基 ;

[0010] Step 5: Determine the epoxy value M of the corresponding epoxidized vegetable oil using the hydrochloric acid-acetone method;

[0011] Step 6: Create a scatter plot of the m and M values ​​of the corresponding epoxidized vegetable oils, and fit the standard curve to obtain the polynomial fitting equation of M and m.

[0012] Step 7: Repeat steps 1 to 4 for the epoxy vegetable oil to be tested to obtain the epoxy index m. Substitute this m into the polynomial fitting equation obtained in step 6 to obtain the epoxy value M of the epoxy vegetable oil to be tested.

[0013] Preferably, in step one, the infrared spectrum of the epoxidized vegetable oil is characterized using a Fourier transform infrared spectrometer.

[0014] Preferably, in step two, the characteristic peak positions of the epoxy functional group and the ester functional group are 820 cm⁻¹. -1 and 1746cm -1 .

[0015] Preferably, the formula for calculating the epoxy value M in step five is as follows:

[0016]

[0017] In the formula: M represents the epoxy value of the corresponding sample;

[0018] V represents the volume of sodium hydroxide standard titration solution consumed in the blank test, in milliliters;

[0019] V1 represents the volume of sodium hydroxide standard titration solution consumed in the sample test, in milliliters;

[0020] V2 represents the volume of sodium hydroxide standard titration solution consumed in determining the acid value of the sample, in milliliters;

[0021] N represents the concentration of the sodium hydroxide standard titration solution, in moles per liter;

[0022] W represents the sample mass, in grams;

[0023] G represents the mass of the sample when determining the acid value, in grams;

[0024] 0.016 represents the molar mass of oxygen, expressed in grams per mole per liter.

[0025] Preferably, the polynomial fitting equation in step six is ​​a quadratic polynomial fitting equation with a correlation coefficient greater than 0.9.

[0026] Preferably, the epoxy vegetable oil used for each scatter point in step six is ​​defined as the sample point, and the epoxy vegetable oil used for all scatter points is defined as the sample set, wherein the sample set contains no less than 6 groups of sample points.

[0027] Furthermore, the sample points are epoxidized rapeseed oil, epoxidized sunflower seed oil, epoxidized peanut oil, epoxidized soybean oil, epoxidized rapeseed oil, epoxidized camellia oil, epoxidized cottonseed oil, or epoxidized olive oil.

[0028] Furthermore, the sample points are high-oleic acid epoxidized rapeseed oil, high-oleic acid epoxidized peanut oil, or high-oleic acid epoxidized soybean oil.

[0029] Beneficial effects: This invention provides a simple, convenient, and highly reliable method for determining the epoxy value of epoxy vegetable oils based on infrared spectroscopy combined with the hydrochloric acid-acetone method. For the epoxy vegetable oil to be tested, only its infrared spectrum needs to be measured to quickly determine the corresponding epoxy value, thereby improving the application efficiency of epoxy vegetable oils as regenerators or warm mix additives in road asphalt pavements.

[0030] Since the main component of vegetable oil is triglycerides, the double bonds in the triglycerides open after epoxidation, becoming epoxy groups. The ester functional group is very stable and does not change. Therefore, this invention selects the characteristic peaks of epoxy functional groups and ester functional groups as the basis for detection, which has universality for the detection of epoxidized vegetable oils and has better application effect and wider application range. Attached Figure Description

[0031] Figure 1 These are the infrared spectra of the various epoxy plant oils used in this invention;

[0032] Figure 2 This is a diagram of the main molecular structure of epoxidized vegetable oil;

[0033] Figure 3 These are the scatter plots and their fitting equations for each point in this invention. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0035] Example 1

[0036] A method for determining the epoxy value of epoxidized vegetable oil, comprising the following steps:

[0037] Step 1: The infrared spectra of epoxidized vegetable oils were measured using a Fourier transform infrared spectrometer. The sample set included no fewer than six sample points selected from epoxidized rapeseed oil, epoxidized sunflower seed oil, epoxidized peanut oil, epoxidized soybean oil, epoxidized rapeseed oil, epoxidized camellia oil, epoxidized cottonseed oil, epoxidized olive oil, high-oleic acid epoxidized rapeseed oil, high-oleic acid epoxidized peanut oil, and high-oleic acid epoxidized soybean oil. Specifically, the infrared spectra of each sample point in this embodiment are shown below. Figure 1 As shown;

[0038] Step Two, Combining Figure 2 Based on the molecular structure of triglycerides, the main functional groups of epoxidized vegetable oils are epoxy and ester groups. Therefore, the characteristic peak positions of the epoxy and ester groups were determined in the infrared spectrum, specifically at 820 cm⁻¹. -1 and 1746cm -1 nearby;

[0039] Step 3: Calculate the peak areas of the epoxy and ester functional groups using the Analysis module in Origin software, and denote them as A. 环氧 and A 酯基 ;

[0040] Step 4: Calculate the ratio of the peak areas of epoxy functional groups to ester functional groups using Excel, and define it as the epoxy index m, i.e., m = A. 环氧 / A 酯基 The area ratios of epoxidized vegetable oil at each sample point are shown in Table 1.

[0041] Table 1. Epoxy Index of Different Epoxidized Vegetable Oils

[0042] Epoxy vegetable oil <![CDATA[A 820 ]]> <![CDATA[A 1746 ]]> Epoxy Index Epoxidized Rapeseed Oil No. 1 465.160 4726.304 0.098 Epoxidized rapeseed oil No. 2 491.447 4705.626 0.104 High oleic acid epoxidized rapeseed oil 826.098 6394.048 0.129 Epoxidized sunflower seed oil 413.565 3798.120 0.108 Epoxidized Soybean Oil No. 1 371.772 3503.225 0.106 Epoxidized Soybean Oil No. 2 190.111 2387.681 0.079

[0043] Step 5: Determine the epoxy value M of the corresponding epoxidized vegetable oil using the hydrochloric acid-acetone method. The specific process is as follows:

[0044] (1) Prepare the solution: ① 1.8g concentrated HCl + 80-100ml acetone; ② 2g cresol red + 80ml ethanol;

[0045] (2) Weigh 0.2g of epoxidized vegetable oil into Erlenmeyer flasks No. 1 and No. 2 respectively (record the actual amount weighed);

[0046] (3) Take 25 ml of solution ① and solution ② with a pipette and place them in No. 1, No. 2 and a blank conical flask (when using the pipette, first wash it with anhydrous ethanol, and then rinse it with solution ① and solution ② respectively).

[0047] (4) Titrate with a 1 mol / L NaOH standard solution (rinse the burette with NaOH solution before using it). The titration standard is that the solutions in tubes 1, 2 and the blank tube turn purple. Then record the volume of NaOH solution used.

[0048] (5) Calculate the epoxy value according to the following formula:

[0049]

[0050] In the formula: M represents the epoxy value of the corresponding sample;

[0051] V represents the volume of sodium hydroxide standard titration solution consumed in the blank test, in milliliters;

[0052] V1 represents the volume of sodium hydroxide standard titration solution consumed in the sample test, in milliliters;

[0053] V2 represents the volume of sodium hydroxide standard titration solution consumed in determining the acid value of the sample, in milliliters;

[0054] N represents the concentration of the sodium hydroxide standard titration solution, in moles per liter;

[0055] W represents the sample mass, in grams;

[0056] G represents the mass of the sample when determining the acid value, in grams;

[0057] 0.016 represents the molar mass of oxygen, expressed in grams per mole per liter.

[0058] The epoxy values ​​are shown in Table 2.

[0059] Table 2. Epoxy values ​​of different epoxidized vegetable oils

[0060] Epoxy vegetable oil V(mL) <![CDATA[V1(mL)]]> <![CDATA[V2(mL)]]> W(g) G(g) Epoxy value Epoxidized Rapeseed Oil No. 1 42.1 25.6 29.7 0.1 0.01 5.38 Epoxidized rapeseed oil No. 2 45.6 28.6 27.3 0.1 0.01 5.05 Epoxidized high-oleic rapeseed oil 42.5 23.2 22.8 0.1 0.01 4.29 Epoxidized sunflower seed oil 42.3 20.3 28.6 0.1 0.01 5.22 Epoxidized Soybean Oil No. 1 40.3 21.6 29.9 0.1 0.01 5.39 Epoxidized Soybean Oil No. 2 41.1 23.8 30.6 0.1 0.01 5.52

[0061] Step Six: Using Origin software, generate a scatter plot of the m and M values ​​for the corresponding epoxidized vegetable oils, and fit it to the standard curve to obtain the polynomial fitting equation for M and m. (See [link to Origin software]). Figure 3 Among the equations obtained by fitting the scatter plot, only the polynomial fitting equation has the largest correlation coefficient. Figure 3 (a) is 0.9185, indicating that its fitted curve is closest to the relationship between epoxy value and epoxy index. Other fitted equations, whether linear or not, are not comparable. Figure 3 (b) or exponential fitting ( Figure 3 (c) Log-fitting Figure 3 (d) and the power term fitting equation ( Figure 3The correlation coefficients of (e) are all around 0.6 to 0.7. Therefore, the fitting equation in this invention adopts a quadratic polynomial fitting equation, i.e., M = -585.99m. 2 +97.89m+1.428, where M is the epoxy value and m is the epoxy index.

[0062] Step 7: Repeat steps 1 to 4 with the epoxy vegetable oil to be tested to obtain the epoxy index m, and substitute it into the polynomial fitting equation obtained in step 6: M = -585.99m 2 The epoxy value M of the epoxy vegetable oil to be tested can be obtained from +97.89m+1.428.

[0063] Example 2

[0064] Infrared spectroscopy tests were conducted on epoxidized vegetable oils with different epoxy values. The area of ​​the corresponding peaks for each epoxidized vegetable oil in Table 3 was obtained by integral calculation, along with the calculated epoxy index and epoxy value calculated according to the formula proposed in this invention.

[0065] Table 3. Epoxy Index and Epoxy Value of Different Epoxidized Vegetable Oils

[0066] Epoxy vegetable oil <![CDATA[A 820 ]]> <![CDATA[A 1746 ]]> Epoxy Index Epoxy value Epoxidized Sunflower Seed Oil No. 1 235.160 2026.304 0.116 4.896 Epoxidized rapeseed oil 451.986 4065.652 0.111 5.068 High oleic acid epoxidized peanut oil 526.098 3394.089 0.155 2.522 Epoxidized Sunflower Seed Oil No. 2 405.565 4056.755 0.100 5.358 Epoxidized cottonseed oil 371.772 2803.263 0.133 4.104 Epoxidized Camellia Oil 456.111 2883.698 0.158 2.251

[0067] The calculation results in Table 3 were verified using the hydrochloric acid-acetone method. The epoxy values ​​and relative errors of various epoxidized vegetable oils measured using the hydrochloric acid-acetone method are shown in Table 4.

[0068] Table 4. Epoxy values ​​of various epoxidized vegetable oils determined by the hydrochloric acid-acetone method.

[0069] Epoxy vegetable oil V(mL) <![CDATA[V1(mL)]]> <![CDATA[V2(mL)]]> W(g) G(g) Epoxy value relative error Epoxidized Sunflower Seed Oil No. 1 46.3 26.8 26.2 0.1 0.01 4.890 0.1％ Epoxidized rapeseed oil 41.9 22.3 27.6 0.1 0.01 5.051 0.3％ High oleic acid epoxidized peanut oil 19.3 18.6 14.1 0.1 0.01 2.535 0.5％ Epoxidized Sunflower Seed Oil No. 2 40.1 18.6 29.6 0.1 0.01 5.358 0 Epoxidized cottonseed oil 45.9 18.6 21.2 0.1 0.01 4.097 0.2％ Epoxidized Camellia Oil 17.3 18.6 12.5 0.1 0.01 2.247 0.2％

[0070] As can be seen from the table, the error between the epoxy value calculated according to the method proposed in this invention and the epoxy value measured according to the hydrochloric acid-acetone method is within 1%, indicating that the method for determining the epoxy value of epoxidized vegetable oil proposed in this invention is very accurate, and the epoxy value of epoxidized vegetable oil can be calculated in the future according to the method proposed in this invention.

Claims

1. A method for determining the epoxy value of epoxidized vegetable oil, characterized in that, The steps include the following: Step 1: Perform infrared spectroscopy on the epoxidized vegetable oil; Step 2: Identify the characteristic peak positions of epoxy and ester functional groups in the infrared spectrum; Step 3: Calculate the peak areas of the epoxy functional group and the ester functional group, and denote them as A. 环氧 and A 酯基 ; Step 4: Calculate the ratio of the peak areas of epoxy functional groups to those of ester functional groups, defined as the epoxy index m, i.e., m = A. 环氧 / A 酯基 ; Step 5: Determine the epoxy value M of the corresponding epoxidized vegetable oil using the hydrochloric acid-acetone method. The calculation formula is as follows: ， In the formula: M represents the epoxy value of the corresponding sample; V represents the volume of sodium hydroxide standard titration solution consumed in the blank test, in milliliters; V1 represents the volume of sodium hydroxide standard titration solution consumed in the sample test, in milliliters; V2 represents the volume of sodium hydroxide standard titration solution consumed in determining the acid value of the sample, in milliliters; N represents the concentration of the sodium hydroxide standard titration solution, in moles per liter; W represents the sample mass, in grams; G represents the mass of the sample when determining the acid value, in grams; 0.016 represents the molar mass of oxygen, expressed in grams per mole per liter; Step 6: Create a scatter plot of the m and M values ​​of the corresponding epoxidized vegetable oils, and fit the standard curve to obtain the polynomial fitting equation of M and m. Step 7: Repeat steps 1 to 4 for the epoxy vegetable oil to be tested to obtain the epoxy index m. Substitute this m into the polynomial fitting equation obtained in step 6 to obtain the epoxy value M of the epoxy vegetable oil to be tested.

2. The method for determining the epoxy value of an epoxidized vegetable oil according to claim 1, characterized in that, In step one, Fourier transform infrared spectroscopy is used to characterize the infrared spectrum of the epoxidized vegetable oil.

3. The method for determining the epoxy value of an epoxidized vegetable oil according to claim 1, characterized in that, In step two, the characteristic peak positions of the epoxy functional group and the ester functional group are 820 cm⁻¹, respectively. -1 and 1746cm -1 .

4. The method for determining the epoxy value of an epoxidized vegetable oil according to claim 1, characterized in that, In step six, the polynomial fitting equation is a quadratic polynomial fitting equation with a correlation coefficient greater than 0.

9.

5. The method for determining the epoxy value of an epoxidized vegetable oil according to claim 1, characterized in that, Define the epoxy vegetable oil used for each scatter point in step six as the sample point, and the epoxy vegetable oil used for all scatter points as the sample set, wherein the sample set shall have no less than 6 sets of sample points.

6. The method for determining the epoxy value of an epoxidized vegetable oil according to claim 5, characterized in that, The sample points are epoxidized rapeseed oil, epoxidized sunflower seed oil, epoxidized peanut oil, epoxidized soybean oil, epoxidized rapeseed oil, epoxidized camellia oil, epoxidized cottonseed oil, or epoxidized olive oil.

7. The method for determining the epoxy value of an epoxidized vegetable oil according to claim 6, characterized in that, The sample points are high-oleic acid epoxidized rapeseed oil, high-oleic acid epoxidized peanut oil, or high-oleic acid epoxidized soybean oil.

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