阅读说明：本技术 三甘油脂肪酸酯酯交换甲酯化衍生的方法 (Method for ester exchange and methyl esterification derivation of triglycerol fatty acid ester ) 是由 叶活动 曾庆平 徐兴烟 陈丹 林成雄 曹文辉 于 2020-04-02 设计创作，主要内容包括：本发明公开了一种三甘油脂肪酸酯酯交换甲酯化衍生的方法。以浓盐酸作催化剂、甲醇作酯交换甲酯化试剂、2,2-二甲氧基丙烷作甘油去除剂将酯交换甲酯化生成的甘油转换为丙酮缩甘油并去除水；先取三甘油脂肪酸酯试样并置于圆底烧瓶内,随后向圆底烧瓶内加入甲醇、2,2-二甲氧基丙烷和浓盐酸,加入量按体积比三甘油脂肪酸酯：甲醇：2,2-二甲氧基丙烷：浓盐酸＝1：200～400：40～80：2～4,振荡混合开始酯交换甲酯化、去除甘油和去除水反应；再将圆底烧瓶置于超声波清洗机内超声30-90min,以加快步骤二的化学反应；最后通过水浴蒸除甲醇、2,2-二甲氧基丙烷、丙酮和盐酸,得到脂肪酸甲酯丙酮缩甘油液体混合物。该三甘油脂肪酸酯酯交换甲酯化衍生的方法无毒、环保、高效、适用范围广。(The invention discloses a method for ester exchange and methyl esterification derivation of triglycerol fatty acid ester. Converting glycerol generated by ester exchange methyl esterification into acetone glycerol and removing water by using concentrated hydrochloric acid as a catalyst, methanol as an ester exchange methyl esterification reagent and 2, 2-dimethoxypropane as a glycerol remover; taking a triglycerol fatty acid ester sample, placing the triglycerol fatty acid ester sample into a round-bottom flask, and then adding methanol, 2-dimethoxypropane and concentrated hydrochloric acid into the round-bottom flask, wherein the addition amounts are as follows according to the volume ratio: methanol: 2, 2-dimethoxypropane: concentrated hydrochloric acid 1: 200-400: 40-80: 2-4, oscillating and mixing to start ester exchange methyl esterification, glycerin removal and water removal reaction; placing the round-bottom flask in an ultrasonic cleaner for ultrasonic treatment for 30-90min to accelerate the chemical reaction in the second step; and finally, removing the methanol, the 2, 2-dimethoxypropane, the acetone and the hydrochloric acid by water bath evaporation to obtain a fatty acid methyl ester acetone glycidol liquid mixture. The method for the transesterification methyl esterification derivation of the triglycerol fatty acid ester has the advantages of no toxicity, environmental protection, high efficiency and wide application range.)

1. A method for deriving triglyceride fatty acid ester exchange methyl esterification, it changes glycerin produced by ester exchange methyl esterification reaction into acetonide glycerin and removes the water in the supplies through adopting concentrated hydrochloric acid as catalyst, methanol as ester exchange methyl esterification reagent, 2-dimethoxy propane as glycerin remover; the operation steps are as follows:

the method comprises the following steps: transferring a triglycerin fatty acid ester sample by using a liquid transfer device and placing the sample into a round-bottom flask;

step two: adding methanol, 2-dimethoxypropane and concentrated hydrochloric acid into a round-bottom flask, wherein the addition amount of the triglycerol fatty acid ester is as follows according to the volume ratio: methanol: 2, 2-dimethoxypropane: concentrated hydrochloric acid 1: 200-400: 40-80: 2-4, oscillating and mixing, and starting chemical reactions of ester exchange methyl esterification, glycerin removal and water removal;

step three: placing the round-bottom flask in an ultrasonic cleaner for 30-90min to accelerate the chemical reaction in the second step;

step four: placing the round-bottom flask on a rotary evaporator, and removing methanol, 2-dimethoxypropane, acetone and hydrochloric acid by water bath evaporation; to obtain a liquid mixture of fatty acid methyl ester acetonide glycidol.

Technical Field

The invention relates to a method for analyzing grease, in particular to a method for the transesterification and methyl esterification derivation of triglycerol fatty acid ester.

Background

The triglycerol fatty acid ester is compounded with various carbon chain fatty acids and glycerin, is the main component of animal and vegetable oil, is an important part of human food, is the main source of energy intake, can provide essential fatty acid for human body, and is an indispensable substance for maintaining life activity and growth and development. With the improvement of living standard of people, the problems of edible safety and nutrition of oil and fat are increasingly emphasized, wherein fatty acid is one of important indexes for determining the quality of animal and vegetable oil, the nutritional value of the animal and vegetable oil can be intuitively reflected, and the composition and the proportion of the fatty acid determine the nutritional value to a great extent, so that the composition and the content of the fatty acid in the animal and vegetable oil are very necessary to be accurately determined. Because the triglyceride fatty acid ester has a high boiling point under normal pressure and cannot be directly analyzed by gas chromatography for composition and content, it is usually necessary to perform gas chromatography after transesterification methyl esterification of the triglyceride fatty acid ester to obtain fatty acid methyl ester with a lower boiling point. At present, there are many methods for the transesterification methyl esterification derivation, but the derivation methods applicable to the transesterification methyl esterification of the triglyceride fatty acid ester in the prior art mainly include the following methods:

1. boron trifluoride-methanol process: GB/T17376 animal and vegetable oil fatty acid methyl ester preparation stipulates the method, firstly triglycerides fatty acid ester is saponified in sodium hydroxide methanol solution, and the generated fatty acid salt reacts with boron trifluoride methanol solution to generate fatty acid methyl ester. The defects are as follows: the reagent boron trifluoride is colorless gas with irritant odor, high toxicity and both hydrogen fluoride and boron toxicity, and boron trifluoride methanol solution needs to be prepared in advance and stored in a refrigerator.

2. Trimethyl sulfur hydroxide-methanol process: the preparation of the fatty acid methyl ester of the animal and vegetable oil GB/T17376 stipulates the method, and the defects are that: the used reagent trimethyl sulfur hydroxide methanol solution is toxic and needs to be prepared and stored in a refrigerator in advance.

3. Acetyl chloride-methanol method: the determination of fatty acids in food products according to national standard for food safety of GB 5009.168 stipulates that the method is suitable for samples with a water content of less than 5%, and has the following defects: the reagent acetyl chloride is irritant, and the acetyl chloride methanol solution needs to be prepared before use.

4. Alkali-methanol process: in the method, triglycerol fatty acid ester and methanol are subjected to transesterification methyl esterification reaction in the presence of alkali to generate fatty acid methyl ester and glycerol. However, the method is only applicable to oils and fats having a free fatty acid content of less than 2%, and saponification easily occurs when water is contained in the oils and fats.

5. Sulfuric acid-methanol process: in the method, triglycerol fatty acid ester and methanol are subjected to transesterification methyl esterification reaction in the presence of sulfuric acid to generate fatty acid methyl ester and glycerol. The defects are as follows: the transesterification reaction rate of the method is far lower than that of the alkali-methanol method, and a side reaction that sulfuric acid dehydrates methanol to generate dimethyl ether may exist.

Disclosure of Invention

Aiming at the defects of the transesterification methyl esterification derivation method, the invention aims to provide a method for the transesterification methyl esterification derivation of the triglycerol fatty acid ester, which is non-toxic, environment-friendly, high-efficiency and wide in application range.

In order to achieve the purpose, the method for the ester exchange and methyl esterification derivation of the triglycerol fatty acid ester adopts concentrated hydrochloric acid as a catalyst, methanol as an ester exchange and methyl esterification reagent and 2, 2-dimethoxypropane as a glycerol remover to convert glycerol generated by the ester exchange and methyl esterification reaction into acetonide and remove water in materials; the operation steps are as follows:

the method comprises the following steps: transferring a triglycerin fatty acid ester sample by using a liquid transfer device and placing the sample into a round-bottom flask;

step two: adding methanol, 2-dimethoxypropane and concentrated hydrochloric acid into a round-bottom flask, wherein the addition amount of the triglycerol fatty acid ester is as follows according to the volume ratio: methanol: 2, 2-dimethoxypropane: concentrated hydrochloric acid 1: 200-400: 40-80: 2-4, oscillating and mixing, and starting chemical reactions of ester exchange methyl esterification, glycerin removal and water removal;

step three: placing the round-bottom flask in an ultrasonic cleaner for 30-90min to accelerate the chemical reaction in the second step;

step four: placing the round-bottom flask on a rotary evaporator, and removing methanol, 2-dimethoxypropane, acetone and hydrochloric acid by water bath evaporation; to obtain a liquid mixture of fatty acid methyl ester acetonide glycidol.

Performing gas chromatography analysis on the fatty acid methyl ester acetone-glycerol acetal liquid mixture obtained in the step four according to SH/T0796 gas chromatography (content determination method for free glycerol and total glycerol in B-100 biodiesel fatty acid methyl ester-gas chromatography), determining that the sum of the contents of fatty acid monoglyceride, fatty acid diglyceride and fatty acid triglyceride in the fatty acid methyl ester is the total amount of unconverted glycerol fatty acid ester, and calculating the transesterification methyl esterification efficiency of the triglyceride fatty acid ester; the calculation formula is as follows:

the sum of the contents of fatty acid monoglyceride, fatty acid diglyceride and fatty acid triglyceride which are not converted into fatty acid methyl ester is less than or equal to 0.5%, so that the efficiency of the transesterification methyl esterification of the refined soybean oil is more than or equal to 99.5%, and the transesterification methyl esterification efficiency is high.

The chemical reaction equation for transesterification methyl esterification in the related chemical reaction is as follows:

the chemical reaction equation for removing glycerol in the related chemical reaction is as follows:

the chemical reaction equation for water removal in the related chemical reaction is as follows:

the method for the ester exchange and methyl esterification derivation of the triglycerol fatty acid ester adopts concentrated hydrochloric acid as a catalyst, methanol as an ester exchange and methyl esterification reagent and 2, 2-dimethoxypropane as a glycerol remover, and has the following technical characteristics and beneficial effects:

1. 2, 2-dimethoxypropane can be used as a glycerol remover to convert glycerol generated by the ester exchange methyl esterification reaction into acetone glycerol, so that the ester exchange methyl esterification reaction is carried out in the forward and reverse reaction directions, and the efficiency is higher;

2. the solubility of the triglycerol fatty acid ester in methanol is low, so that the triglycerol fatty acid ester is uniformly dispersed by the aid of ultrasonic treatment to increase the contact area and accelerate the reaction speed;

3. the method is suitable for water-containing samples, has the characteristics of wide application range, simple and convenient operation, mild reaction conditions, easily obtained used reagents and small pollution, and simultaneously, the transesterification methyl esterification reaction is more thorough.

Detailed Description