Method for preparing fatty acid methyl ester by using waste edible oil

Abstract

The invention aims to provide a process for preparing fatty acid methyl ester. According to the process, glycerol is used for replacing methanol, no acid catalyst is added, and direct esterification is carried out for deacidifying and deodorizing waste oil through gas stripping dehydration by using an inert gas. The process is a clean production method which is characterized in that raw materials do not need to be pretreated, water generated during reaction is taken out of a reaction system during reaction, the yield of the fatty acid methyl ester is increased, and no waste water or waste gas is emitted. The process comprises the steps of mixing the waste edible oil (acid value of 30-160mgKoH / g) with glycerol in a molar ratio of fatty acid of 1:(1-2) and adding the mixture into a reaction kettle, introducing the inert gas nitrogen, reacting for 1-4h under the conditions that the reaction temperature is 140-200 DEG C and the vacuum pressure of the reaction kettle is 30-50 KPa, reducing the acid value of an esterification product to be below 3.0mgKoH / g; and preparing the fatty acid methyl ester from materials by adopting the traditional base catalysis ester exchange reaction after the esterification is ended. Because a process of directly esterifying the waste edible oil through acid-free catalysis is adopted, the conversion rate of fatty acid is high, the content of the fatty acid in the waste edible oil is low, and the base catalysis ester exchange is complete.

Description

technical field [0001] The invention relates to a method for preparing fatty acid methyl esters from waste edible oils and fats. In particular, using waste edible oils (gutter oil, acidified oil) as raw materials, the process of synthesizing fatty acid methyl esters by air stripping without using acid catalysts. Background technique [0002] Waste edible oils and fats refer to a series of oil wastes that lose their edible value produced during the deep processing of natural vegetable oils, animal fats and oils. They are also commonly known as gutter oils and acidified oils. According to expert calculations, the amount of these waste edible oils accounts for about 20-30% of the total amount of edible oil consumption. Based on the average annual consumption of edible oil in my country of 21 million tons, 4-8 million tons of waste oil is produced every year. The amount of waste fats and oils that can be collected as resources is about 4 million tons. Waste oil contains a lot...

AI Technical Summary

Problems solved by technology

Although the above two methods avoid the process of liquid acid catalysts such as sulfuric acid reacting with the reaction equipment in a kettle and washing to remove the liquid acid as a catalyst, there are still raw materials that need to be pretreated, the reaction alcohol-oil ratio is large, the process flow is long, and the energy consumption is high. Disadvantages: In addition, when fatty acid is esterified with methanol to generate fatty acid methyl ester, a part of water will be generated at the same time. Water and acidic catalyst exist in the reaction system at the same time, and fatty acid methyl ester will be hydrolyzed into fatty acid, resulting in the one-way yield of the reaction product fatty acid methyl ester. low rate