Process for reducing acid value of biodiesel

Abstract

A method for reducing the acid value of biodiesel oil is characterized in that: rectification of crude fatty acid methyl ester or fatty acid ethyl ester is carried out; a deacidification agent occupying 0.02 to 4 percent of the total weight of fine fatty acid methyl ester or fatty acid ethyl ester is added after the rectification; the mixture is gradually heated up to 60 to 80 DEG C inside a stirring reaction kettle, and is put in a settling tank when the stirring reaction is carried out for 0.2 to 0.5 hours; after 2-hour settlement, the lower-layer deacidification agent is discharged; the acid value of an upper layer is measured, and the upper layer is put in a finished product tank after the acid value is up to standard; and the deacidification agent can be used repeatedly. The method is simple and does not need complex equipment; meanwhile, the method has low production cost and ideal deacidification effect, and the diesel oil manufactured by the method accords with national standard; the separated deacidification agent can be used repeatedly to produce naphthenic acid amide which is a chemical raw material and can increase the economic benefits of a biodiesel oil enterprise. Tests and a standard method adopted to measure the acid value of biodiesel oil before and after deacidification show that the acid value of biodiesel oil can be reduced more than 90 percent when deacidified through adopting the method.

Description

1. Technical field [0001] The invention relates to a method for reducing acid value in biodiesel. 2. Background technology [0002] As the storage of mineral diesel oil decreases year by year, all countries are looking for renewable bio-energy sources. Since fatty acid methyl esters are the closest to mineral diesel oil in terms of combustion performance and characteristics, developed countries such as Europe and the United States have developed vegetable oils as raw materials. biodiesel. [0003] There are also people in my country who are working on this aspect, such as Chinese patent application 92114795.3, which uses natural oils to produce biodiesel through alkali as a catalyst, and the acid value can reach the standard, but cannot be used for production and use because of the high price of raw materials; Recycling high-acid-value fatty acids to produce biodiesel, the acid value can only reach 4.5mgKOH / g, which does not meet the national BD100 standard; Chinese patent a...

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Problems solved by technology

[0003] There are also people in my country who are working on this aspect, such as Chinese patent application 92114795.3, which uses natural oils to produce biodiesel through alkali as a catalyst, and the acid value can reach the standard, but cannot be used for production and use because of the high price of raw materials; Recycling high-acid-value fatty acids to produce biodiesel, the acid value can only reach 4.5mgKOH / g, which does not meet the national BD100 standard; Chinese patent application CN 1031070C uses acid as a catalyst for pre-esterification. After the reaction is completed, alcohol and excess The alkali neutralizes the acidic catalyst and the residual free fatty acid, and the remaining alkali is used as the production process of the transesterification reaction. However, the amount of catalyst used in the above two-step method will increase, the processing time will be doubled, the equipment investment will be large, and the energy consumption will increase significantly. In addition, The alkaline catalyst needs to be removed from the product, a large amount of alkali-containing wastewater is produced, pollutes the environment, it is difficult to recover glycerin, and the production cost is too high