Method for preparing biodiesel

Abstract

The invention discloses a method for preparing biodiesel. Pretreated animal fat and vegetable fat are taken as raw oil, and the method comprises the following steps of: adding methanol into a reaction kettle according to a methanol / oil ratio of 4:1-8:1, and adding concentrated sulfuric acid with stirring to make the acid value in the system less than 3mgKOH / g to complete pre-esterification; adding water for neutralization and washing, dehydrating to removing impurities, drying, putting into the reaction kettle again, raising the temperature to 75DEG C, adding 3 percent ethanol solution of NaOH with stirring to make the acid value in the system 1mgKOH / g to complete ester exchange, and separating out glycerin methanol solution of a lower layer to obtain coarse biodiesel; and finally performing three-stage molecular distillation to obtain fatty acid methyl ester containing C16 and C18 and fatty acid methyl ester containing C20 and C22, namely the biodiesel. The method is relatively simple in process and wide in raw material range, and has the time consumption of only 4 hours and the esterification rate of over 98 percent; and the procedures such as decolorization, deodorization and degasification are completed simultaneously, the flow is shortened and the cost is reduced.

Description

technical field [0001] The invention belongs to the technical field of preparing liquid hydrocarbon mixtures from oxygen-containing organic matter, and relates to a method for preparing biodiesel, in particular to a method for continuously preparing diesel by using waste animal and vegetable oils with high acid value as raw materials. Background technique [0002] Biodiesel is fatty acid methyl ester, which is made by transesterification reaction of animal and vegetable oil (triglyceride fatty acid) and methanol. At present, there are many patent applications related to the preparation of biodiesel. Generally speaking, most of them are in the preliminary research and development stage, and the technology is not yet mature. Some of them cannot realize industrial production due to harsh process conditions or high equipment requirements. For example: Chinese patent CN1654601 discloses "a method for preparing biodiesel", which performs transesterification in an ultrasonic reacto...

AI Technical Summary

Problems solved by technology

At present, there are many patent applications related to the preparation of biodiesel. Generally speaking, most of them are in the preliminary research and development stage, and the technology is not yet mature. Some of them cannot realize industrial production due to harsh process conditions or high equipment requirements. For example: Chinese patent CN1654601 discloses "a method for preparing biodiesel", which performs transesterification in an ultrasonic reactor, and requires the water content of the raw material oil to be below 0.06%; some conversion rates are low, the production cost is high, and the time is too long Long, for example: Chinese patent CN1986740 discloses "preparation biodiesel method", its esterification reaction is nearly 15 hours