JP4789247B2 - Methods for analyzing acylglycerides and fatty acid esters - Google Patents

Description

  The present invention relates to an analytical method for measuring the content of a compound group in a sample in which acylglyceride and / or fatty acid ester compounds are mixed, such as in a biodiesel fuel production process, and more specifically, obtained by transesterification of acylglyceride and alcohol. The present invention relates to a method for quantifying fatty acid esters and acylglycerides in the reaction mixture.

Biodiesel fuel refers to fatty acid esters obtained by transesterification of glycerol and alcohol in fats and oils, as represented by methyl esters of fatty acids produced by alcoholysis (methanolysis) of animal and vegetable fats and oils.
As a method for producing a fatty acid ester, an alkali catalyst is generally used. In addition, an enzyme reaction using lipase and a non-catalytic reaction in which alcohol is brought into contact with fats and oils in a supercritical or subcritical state are known. ing.

  When producing biodiesel fuel, that is, in the reaction mixture of the step of producing fatty acid ester by transesterification of animal and vegetable fats and alcohol, fatty acid ester (FE), triacylglyceride (TG), diacylglyceride (DG), Since monoacylglyceride (MG), glycerin, and alcohol are contained, it is important to know whether the reaction has progressed to a purity suitable for each use. However, since these are made from animal and vegetable oils and have fatty acid groups of various structures, there are reaction intermediates and fatty acid esters having fatty acid groups of various structures in the reaction mixture after completion of the reaction. The composition is complicated.

The analysis method of the composition in the reaction mixture should be measured by gas chromatography (GC) analysis because fatty acid esters are relatively volatile, and by liquid chromatography (LC) analysis because glycerides are hardly volatile substances. Has been done.
In these analysis methods, each compound group must be collected, analyzed by applying a plurality of pretreatments, and various analysis methods must be combined for measurement. In addition, various analyzes are laborious operations such as creating a calibration curve for each standard compound and correcting it.

  Examples of using LC include measurement of a lipophilic group constituting a surfactant (Patent Document 1), analysis method of hydrocarbon oil containing an aromatic compound (Patent Document 2), analysis method of polyglycerin (Patent Document) 3) Although various methods have been proposed, from highly volatile compounds to less volatile compounds, such as reaction liquids in the process of producing fatty acid esters by transesterification of animal and vegetable oils and alcohols In a system in which is mixed, a method for measuring the content of each compound group has not been proposed.

A refractive index (RI) detector used in high-performance liquid chromatography (HPLC) is a highly versatile detector for detecting a refractive index that is a characteristic value of a substance, but an ultraviolet absorptiometric (UV) detector. It is said that the sensitivity difference between the compounds is small compared with the sensitivity. Since the RI detector has a sensitivity almost proportional to the difference in refractive index between the mobile phase solvent and the sample component and shows a response proportional to the concentration of the target component, for example, in HPLC, the polarity of the mobile phase solvent is changed to change the gradient. It is possible to separate each compound by separation, and a method for treating the eluent has been proposed (Patent Document 4). However, since the refractive index of the mobile phase also changes at that time, quantification with an RI detector is possible. Analysis was difficult.
Japanese Patent Laid-Open No. 10-73578 Japanese Patent No. 3073757 Japanese Patent No. 3339147 JP-A-9-229920

  When producing biodiesel fuel, it is not necessary to capture the amount of each compound produced, but grasp the amount of FE as a reaction product and TG as a raw material for each compound group, including MG and DG as reaction intermediate products. It is important to do. An analysis method for measuring the content of a compound group by a simple analysis method for a sample containing each of these compound groups has not been proposed. The present invention solves these problems and provides a method for quantifying TG, DG, MG, and FE by a simple method.

  The present inventor has found that the RI detection sensitivity of each compound group has a good correlation with the sample unsaturation rate when the analysis of the sample containing TG, DG, MG and FE is quantified with an RI detector. . As a result, it was discovered that each compound group can be quantified without calibrating the RI sensitivity of each individual compound, and the present invention has been achieved.

  That is, the present invention quantifies a sample containing two or more different compounds selected from the four compound groups of triacylglyceride (TG), diacylglyceride (DG), monoacylglyceride (MG) and fatty acid ester (FE). In doing so, (A) a step of measuring the unsaturation rate of the sample, (B) a step of obtaining an output value of the compound group separated by liquid chromatography using a refractive index detector, and (C) an unsaturation rate and a predetermined relational expression. And (D) an analysis method for acylglycerides and fatty acid esters, including the step of calculating the content of the compound group in the sample using the output value and the refractive index sensitivity ratio.

  Further, in the step of producing a fatty acid ester by transesterification of animal and vegetable oils and fats and alcohol, the reaction product is analyzed by the above-described method, and the transesterification reaction is monitored.

  According to the present invention, quantification for each compound group in a sample in which four kinds of compound groups of triacylglyceride (TG), diacylglyceride (DG), monoacylglyceride (MG) and fatty acid ester (FE) are mixed, It is possible to carry out without measuring the RI sensitivity of each compound, and by applying this analytical method to the monitoring of the process of producing a fatty acid ester by transesterification of animal and vegetable fats and alcohols, a fatty acid ester production process It can be applied to reaction control of products and quality control of products.

  The present invention relates to a method for quantifying a sample containing two or more different compounds selected from four types of compound groups of TG, DG, MG and FE. If the sample to be analyzed contains two or more kinds of compounds contained in different compound groups of the above compound groups, even natural-derived animal and vegetable oils and fats may contain specific acylglycerides and alcohols (lower alcohols such as methanol and ethanol). A reaction liquid for transesterification may be used.

  The unsaturation rate in step (A) of the present invention is defined as unsaturation rate (X) = number of carbon-carbon double bonds of fatty acid group / molecular weight. In a mixture composed of a plurality of compounds, the molecular weight is the sample. The average molecular weight and the number of carbon / carbon double bonds of the fatty acid group may be read as the average number of carbon / carbon double bonds of the fatty acid group contained in the sample.

  Here, there is no restriction | limiting in particular in the process of measuring an unsaturation rate, You may obtain | require an unsaturation rate from what kind of method. If the reaction system can specify the unsaturation rate of the raw material triacylglyceride in advance, the unsaturation rate of the raw material can be used without measuring the unsaturation rate of the product. In the case of a mixed system of various compounds, analysis necessary for obtaining the unsaturation rate is performed by a known method. For example, in order to determine the number of double bonds in a sample, the fatty acid composition in the sample may be measured, and fats and oils are subjected to alkali saponification decomposition, methyl esterified by a boron trifluoride-methanol method or the like and subjected to GC analysis. What is necessary is just to obtain | require using conventional methods, such as.

  It is preferable to obtain the unsaturation rate for each compound group. However, since operations such as fractionation into each compound group and pretreatment operations according to the volatility of each compound become complicated, biodiesel fuel production If the fatty acid composition of the raw material can be regarded as constant, the unsaturation rate of one compound group is measured and the other compounds are measured without measuring the unsaturation rate of all compound groups in the reaction process liquid. It can be used as the group unsaturation.

  In the step (B), the step of obtaining the output value of the compound group separated by LC with the RI detector is the integration of the output signal of the RI detector for each compound group separated by LC and the compound group such as relative area value The step of obtaining an output value correlated with the amount of.

  LC includes adsorption column chromatography using silica gel column (also called normal phase chromatography) and distribution column chromatography using octadecylsilane-bonded column (also called reverse phase chromatography). Size exclusion chromatography (SEC), which is a method of separating by solute size (molecular weight) using the molecular sieving effect of the filler, is preferably used.

  For the separation of each compound group, it is preferable to use a polystyrene column having a molecular weight of 2000 or less. Examples of columns include columns with a molecular weight of 2000 or less, such as Polymer Laboratories, 50 、 columns, Tosoh's TSKgel G1000H8.

  As the LC mobile phase, general-purpose organic solvents such as tetrahydrofuran (THF), dichloromethane, and chloroform can be used.

  A Hewlett Packard 1050 was used as the LC analyzer, a system instruments 480 data processing system was used as the data processing system, a water detector 410 was used as the RI detector, a polymer laboratory 50 liter was used as the column, and the mobile phase FIG. 1 shows a chromatogram when each reagent manufactured by SIGMA is subjected to size exclusion chromatography analysis under the measurement conditions of 1.0 mL / min of THF, a column temperature of 25 ° C., and a sample injection amount of 100 μL. TG, DG, MG, and FE compound groups can be fractionated in order from the one with the highest retention time. Although not shown here, glycenline and methanol are separated after the retention time of FE.

The predetermined relational expression in the step (C) will be described.
Since the RI sensitivity varies depending on the compound structure, the accurate content cannot be obtained without performing sensitivity correction for each compound. Therefore, it is necessary to obtain and correct the RI sensitivity of each compound in advance. However, it is difficult to measure the RI sensitivity of each compound for a sample made of a mixture of various compounds, and it is practical. Not. The present inventor has found a method capable of easily calculating the RI sensitivity ratio when measuring the content of each compound group.

The background of the experiment will be explained below.
First, each compound having a different fatty acid structure was obtained as a reagent, and the SEC was subjected to SEC under the same conditions, and the RI sensitivity ratio with respect to a specific reference compound was determined from the output value (relative area value).
Here, a method using trilinolein (C ₅₇ H ₉₈ O ₆ molecular weight) which is a triacylglyceride composed of linoleic acid which is an unsaturated fatty acid having 18 carbon atoms as a reference compound is shown as an example. Table 1 shows the RI sensitivity ratio (Y) of each compound based on trilinolein. For example, 0.87 for triolein (C ₅₇ H ₁₀₄ O ₆ ), 0.92 for 1,3-diolein (C ₃₉ H ₇₂ O ₅ ), and 0 for 1-monoolein (C ₂₁ H ₄₀ O ₄ ). 90, 0.63 for methyl oleate (C ₁₉ H ₃₆ O ₂ ).

From these experimental results, the RI sensitivity ratio (Y) of each compound alone has a correlation with the above-described unsaturation rate (X), and as shown in a predetermined relational expression, in this example, the RI sensitivity (1). It has been found that the ratio (Y) is arranged as a quadratic function of the unsaturation rate (X).
Y = 0.47 + (Z × 0.23) + 54.2X-1595X ² (1)
Here, Z is the number of glycerin skeletons in the compound group.

  In this example, the same fatty acid that binds to the glycerin skeleton was used, but the above results revealed that there is a predetermined relational expression between the unsaturation rate and the RI sensitivity. Even if it exists, it turns out that RI sensitivity ratio (Y) for each compound group is easily computable from said unsaturation rate (X) and said predetermined relational expression (1).

  Since the unsaturation rate (X) and the RI sensitivity ratio (Y) have a high correlation, even if the measurement conditions are different, the unsaturation rate can be determined by defining this predetermined relational expression, particularly a quadratic function, for each measurement system. The RI sensitivity ratio (Y) can be obtained from (X).

  The step (D) is a step of calculating the content of the compound group in the sample using the output value obtained in the step (B) and the RI sensitivity ratio obtained in the step (C). Usually, a value corrected by dividing the output value obtained in the step (B) by the RI sensitivity ratio obtained in the step (C) for each compound group is calculated as a fraction of all samples.

  Further, the present invention provides a fatty acid characterized in that, in the step of producing a fatty acid ester by transesterification between animal and vegetable fats and oils, the reaction product is analyzed by the aforementioned analysis method and the transesterification reaction is monitored. It is a manufacturing method of ester.

The transesterification reaction is monitored by the analysis method described above, grasping the amount of reaction product produced, determining whether the desired reaction rate has been reached, and determining the reaction temperature, reaction time, stirring conditions, etc. Determining whether to change various conditions related to the reaction.
For example, when performing transesterification reaction between animal and vegetable fats and oils and methanol in batch mode, the reaction solution is analyzed over time by the above analysis method, and the reaction time is extended if the production amount of fatty acid ester does not reach the predetermined amount. Or changing the reaction temperature.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

(Example 1, Comparative Example 1)
30.0 parts by weight of trilinolein, 13.5 parts by weight of triolein, 50.0% by weight of triglyceride (TG) consisting of 6.2 parts by weight of tripalmitin, 30.3 parts by weight of methyl linoleate, 13. Sample 1 consisting of 50.0% by weight of fatty acid ester (FE) consisting of 6.2 parts by weight of 5 parts by weight of methyl palmitate was prepared.

The sample 1 was subjected to liquid chromatography (1050, manufactured by Hewlett Packard, data processing system: System Instruments 480 data processing system) equipped with an RI detector (410, manufactured by Waters), and 50 mm (300 mm, manufactured by Polymer Laboratories) as a column. × 7.5 mmφ), SEC analysis was performed under the measurement conditions of 1.0 mL / min of THF as a mobile phase, a column temperature of 25 ° C., and a sample injection amount of 100 μL.
The measurement results obtained from the relative area values by SEC are shown in Table 2 as Comparative Example 1.

  In Example 1, the relational expression (1) based on the RI sensitivity ratio (Y) based on the RI sensitivity of trilinolein was used. Further, the degree of unsaturation (X) was determined by comparing sample 2 consisting of 30.3 parts by weight of methyl linoleate, 13.5 parts by weight of methyl oleate, and 6.2 parts by weight of methyl palmitate, which is the composition of FE in the sample. Fatty acid composition was analyzed using GC (Shimadzu Corporation GC-17A: detector FID) equipped with a capillary column (DB-1: J & W Science, 0.25 mmφ × 30 m), and the unsaturation rate (X ) Unsaturation rate (X) was 0.0050.

The average molecular weight of FE in the material is 292.07, and the RI sensitivity ratio (Y _FE ) is Y = 0 in the equation (1) using the unsaturation rate (X) = 0.050 determined previously. _FE is calculated as 0.70. When the unsaturation rate was calculated from the theoretical value, the unsaturation rate (X _FE ) was 0.0051.
Similarly, the average molecular weight of TG is 872.13, the RI sensitivity ratio (Y _TG ) is Z = 1 in the formula (1), and the unsaturation rate (X) can be considered that the fatty acid composition ratio is constant between TG and FE. It calculates by substituting the unsaturation rate (X) of FE, and becomes _YTG = 0.94. The unsaturation rate (X _TG ) calculated from the theoretical value was 0.0051.

The concentrations of TG and FE in the output value (Comparative Example 1) of each compound group determined from the area value by SEC were A _TG : 57.6 wt% and A _FE : 42.4 wt%. When the content of each compound group was determined by calculating using each output value and each RI sensitivity ratio (Y), it was TG: 50.3% by weight and FE: 49.7% by weight.

SEC analysis chromatogram of each compound

Claims (3)

In quantifying a sample containing two or more different compounds selected from four types of compound groups of triacylglyceride, diacylglyceride, monoacylglyceride and fatty acid ester, (A) a step of measuring the unsaturation rate of the sample; B) A step of obtaining an output value of a compound group separated by liquid chromatography with a refractive index detector, (C) RI of the compound with respect to a reference compound with respect to a reference compound under the same conditions as in the liquid chromatography analysis for compounds having different known fatty acid structures A sensitivity ratio is obtained, a quadratic function formula is determined by correlation between the unsaturation rate of the compound and the RI sensitivity ratio of the compound, and then the unsaturation rate of the sample measured in the step (A) and the quadratic function obtaining a refractive index sensitivity ratio of the sample based on the equation, obtained by (D) wherein (B) said output value obtained in the step (C) step Acyl glyceride and fatty acid esters analysis method comprising the step of using a refractive index sensitivity ratio of the sample to calculate the content of the compounds in the sample. In quantifying a sample containing two or more different compounds selected from four types of compound groups of triacylglyceride, diacylglyceride, monoacylglyceride and fatty acid ester, (A) a step of measuring the unsaturation rate of the sample; B) Refractive index detection of compound groups separated by liquid chromatography under the measurement conditions of polystyrene column with a molecular weight of 2000 or less, THF as the transfer phase, 1.0 mL / min, column temperature of 25 ° C., sample injection volume of 100 μL A step of obtaining an output value by a vessel, (C) a step of obtaining a refractive index sensitivity ratio (Y) of the sample based on the unsaturation rate (X) of the sample measured in the step (A ) and the formula (1),
Y = 0.47 + (Z × 0.23) + 54.2X-1595X ² (1)
X is the unsaturation rate of the sample, Y is the refractive index sensitivity ratio of the sample, Z is the number of glycerin skeletons in the compound group (D) The output value obtained in the step (B) and the step (C) A method for analyzing acylglycerides and fatty acid esters, comprising calculating the content of compound groups in a sample using the refractive index sensitivity ratio of the sample.
In the process of producing the fatty acid esters by transesterification of animal or vegetable fats and oils and alcohols, the reaction products were analyzed by the method of claim 1 or 2 wherein, prior Symbol of fatty acid ester, which comprises the monitoring of the transesterification Production method.