Method of lowering acid value of oil and fat

Abstract

The present invention provides a method for reducing acid value of oil. Said method includes the following steps: making oil with high acid value and monohydric alcohol with C1-C6 produce reaction in fixed bed reactor under the condition of 170-280 deg.C and 5-12MPa, and collecting oil mixture whose acid value is reduced.

Description

technical field [0001] The invention relates to a method for reducing the acid value of oil. Background technique [0002] Biodiesel can be produced by transesterification of fats and monohydric alcohols (generally low-carbon alcohols, such as C1-C6 monohydric alcohols). When oil and methanol undergo transesterification, the reaction product includes fatty acid methyl ester, namely biodiesel, and by-products such as monoglyceride, diglyceride, and glycerin. [0003] Before preparing biodiesel with high acid value oils and fats, it is generally necessary to reduce the acid value of the raw materials. For example, the method of pre-esterification is adopted. 50-120°C, esterify the free fatty acid with alcohol, and pre-esterify the oil. (2) The reaction mixture is separated into an alcohol phase containing catalyst and water and an oil phase. (3) Remove the water in the oil phase by extraction. (4) In the presence of a basic catalyst, the extracted oil phase is subjected to ...

AI Technical Summary

Problems solved by technology

[0005] Adopt the above-mentioned pre-esterification process, the left over acid catalyst will be neutralized by alkali, the consumption of alkali metal catalyst will increase, the processing flow will be longer, equipment investment, energy consumption will rise sharply, in addition, the basic catalyst needs to be removed from the product, There is a lot of waste water

Difficulty recovering glycerin

[0006] US2494366 uses excess alkali to neutralize free fatty acids to reduce the acid value in high acid value oils and carry out methyl esterification reaction. After methyl esterification, the soap formed by alkali and free fatty acids is counter-neutralized with sulfuric acid to release free acids. This part of the free Under the action of acid catalysis, the acid is esterified again, and the final product is neutralized, filtered and rectified to obtain the methyl ester product. This process has many steps, long process, large material loss and many inorganic wastes.

[0007] It can be seen from the prior art that for oils with higher acid value, such as the acid value is greater than 1.0mgKOH / g, it is generally necessary to carry out esterification treatment on the oil in advance to change the free fatty acids into fatty acid methyl esters. This process, such as using sulfuric acid etc. as a catalyst, the corrosion is serious, and a large amount of waste acid and waste water will be produced; if solid acid is used as a catalyst, there are problems that the catalyst is more expensive and the service life is shorter