Method for preparing high-purity biodiesel

Abstract

The invention relates to a method for preparing high-purity biodiesel with crude oil. The method comprises: pretreating the raw material of crude oil to remove impurities; subjecting the pretreated crude oil raw material to pre-esterification with concentrated sulfuric acid as a catalyst; then conducting transesterification with the presence of a base catalyst; recovering methanol and separating glycerin, thus obtaining coarse fatty acid methyl ester; subjecting the obtained coarse fatty acid methyl ester to purification, distillation, and segmentation so as to obtain high-purity fatty acid methyl ester.

Description

technical field [0001] The invention relates to a method for preparing high-purity biodiesel, which uses cheap raw materials such as crude oil (such as waste oil, acidified oil, etc.) to obtain high-purity fatty acid methyl ester (ie biodiesel) through pre-esterification and transesterification. Background technique [0002] Energy is the lifeblood of national development. With the rapid development of society and economy, fossil resources such as petroleum, natural gas, and coal, which are widely used at present, are increasingly in short supply. At the same time, the use of a large number of fossil resources has brought many harms to the environment, such as the greenhouse effect and acid rain. In addition, the catering industry, food industry and other related industries produce a large amount of waste animal and vegetable oil every day. These waste oils generally contain a lot of impurities, some of which are recycled for making soap, and some are directly discharged wi...

AI Technical Summary

Problems solved by technology

In this method, esterification and transesterification are carried out in different reactors, and the intermediate product is separated by two sedimentation separators, which increases equipment cost and energy consumption; this method needs water washing and neutralization after transesterification, and the The total amount of concentrated sulfuric acid reaches 9.5% of the raw material, resulting in a large amount of acid water in the washing process, so a large amount of alkali is required for neutralization in the later sewage treatment, which increases the treatment cost; on the other hand, sodium hydroxide is used alone as a catalyst There are some problems in practical application: 1. The dissolution time of sodium hydroxide and methanol is long, and the dissolution rate is low; 2. The transesterification reaction is not sufficient; 3. The sodium salt is easy to agglomerate. During the exchange reaction, there will be serious blockage of the pipeline, so it cannot be widely applied to various raw materials; 4. The separation speed of glycerin and fatty acid methyl esters generated by the reaction is relatively slow

Although this method does not require neutralization and washing, it also requires two separation steps to separate the solid acid catalyst and solid base catalyst, respectively.

In addition, there is no distillation in this process, no matter how thorough the transesterification reaction is, the neutral oil (triglyceride) cannot be completely converted into fatty acid methyl ester

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