Method for preparing biodiesel by virtue of two-step catalytic conversion of microalgae with high acid value

Abstract

The invention relates to a method for preparing biodiesel by virtue of two-step catalytic conversion of microalgae with high acid value. The method comprises the following steps of: adding a certain amount of solid acid catalyst and methyl alcohol into the high acid value microalgae raw material, heating to certain temperature, carrying out esterification reaction for 40-60 minutes, then filtering the solid acid, continuously adding a basic catalyst (KOH-potassium hydroxide) into the reaction system for catalysis esterification reaction of the second stage, after reaction, absorbing supernatant liquid through normal hexane, then removing the normal hexane, and obtaining the biodiesel. The method can be used for both improving the yield of the biodiesel and shortening the reaction time, and is beneficial to promotion and application.

Description

1. Technical field [0001] The invention belongs to the field of bioengineering and energy, and in particular relates to a method for preparing biodiesel by in-situ two-step catalytic conversion of high acid value microalgae. 2. Background technology [0002] With the rapid development of the economy, the shortage of global fossil energy and the continuous deterioration of the environment, there is an urgent need to replace new resources. Microalgae are characterized by fast growth rate, strong renewability, high photosynthetic efficiency, short doubling time, and high yield per unit area. It is dozens of times higher than higher plants, does not occupy arable land, and can be cultivated by using beaches, saline-alkali land and organic wastewater. It has high oil content and absorbs CO 2 It has become the focus and hot issue of people's research because of its advantages such as carbon source, not competing with the people for grain and land, and high oil content. The energy...

AI Technical Summary

Problems solved by technology

Since the catalytic efficiency of basic catalysts is hundreds or even thousands of times that of acidic catalysts, basic catalysts are generally used in industrial production, but if the content of free fatty acids is high, the basic catalysts will first undergo saponification reaction with free fatty acids. Not only the yield of biodiesel is reduced, but also the generated saponification product is mixed in the biodiesel, which makes the subsequent separation process of the product complicated and costly

It has been reported in the literature that after a period of storage of microalgae and algae powder, part of the oil in it is converted into free fatty acids under the action of enzymes, resulting in the content of free fatty acids in microalgae as high as 70% or more; for microalgae with high acid value, Man Kee Lam et al. use sulfuric acid as a catalyst, but due to the low catalytic efficiency of the acid catalyst, the entire reaction process lasts up to 6 hours, and the amount of methanol is large, and the alcohol-oil molar ratio reaches 180:1; the reaction is not only long, but also consumes a large amount of methanol