Method for preparing biodiesel by using waste grease split-phase method

Abstract

The invention provides a method for preparing biodiesel by using a waste grease split-phase method, which comprises the following steps of: firstly, heating waste grease to 80 DEG C; adding concentrated sulfuric acid which accounts for 0.3 percent of the weight of the grease and is 98 percent in concentration and stirring for 20min; then, adding high-salt-hot water which accounts for 5 percent of the weight of the grease and is 2 percent in concentration; stirring for 30min; performing centrifugal separation to obtain degummed waste grease; adding methanol to the degummed waste grease in proportion that the molar ratio of the grease to the methanol is 1:1.5; stirring for 30min at the temperature of 30 DEG C; standing to separate glyceride from fatty acid; adding the methanol to the glyceride in proportion that the molar ratio of the glyceride to the methanol is 1:4.5; meanwhile, adding solid sodium hydroxide which accounts for 0.8 percent of the weight of the glyceride and stirring; reacting for 1h under at the temperature of 70 DEG C; standing to separate a glycerine layer in a reaction mixture; then separating to obtain crude biodiesel, crude glycerine and sodium sulfate; washing, drying and filtering the separated crude biodiesel to prepare the biodiesel; adding the methanol to the fatty acid; then, adding H2SO4 for catalysis, wherein the weight ratio of the fatty acid to the methanol to the H2SO4 is 1:0.45:0.03; performing esterification at the temperature of 60-65 DEG C stage by stage for 30min respectively; performing vacuum dealcoholization and dewatering between the two stages of reaction; and finally cooling and filtering to prepare the biodiesel.

Description

technical field [0001] The invention belongs to the technical field of chemical industry or the technical field of comprehensive utilization of agricultural product processing waste, and specifically relates to a method for preparing biodiesel from biological resources, in particular to a method for preparing biodiesel by using waste oil phase separation. Background technique [0002] Biodiesel is a renewable green energy. It can be a liquid fuel made from vegetable oil crops or engineered microalgae and animal fats. It is a high-quality substitute for petroleum diesel. Since our country is a country with insufficient resources, it is impossible to use a large amount of vegetable or animal oils as raw materials for biodiesel. At the same time, 4-5 million tons of waste oil and acidified oil discharged from household consumption, catering, fast food restaurants, market vendors, fried food industry, oil refining, food processing and oil retailing in China can be used as Biodi...

AI Technical Summary

Problems solved by technology

[0003] Currently, domestic waste oil biodiesel technology patents generally adopt the pre-esterification method, that is, first esterify high-acid value oil and methanol under the action of an acid catalyst, and after a long reaction, the acid value of the mixture decreases, and the acid catalyst ( If it is inorganic acids such as sulfuric acid, it needs to be neutralized by adding alkali or washed and dried), methanol is supplemented and an alkaline catalyst is added to carry out the alcoholysis reaction until the reaction is completed. The reaction time of this method is longer, the catalyst consumed is more, and the energy consumption higher

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