Method for preparing biodiesel without by-product of glycerin by utilization of high acid value waste oil

Abstract

The invention relates to a method for preparing biodiesel without a by-product of glycerin by the utilization of high acid value waste oil, comprising the following steps: carrying out a reaction between waste oil with the acid value of 10-200mgKOH / g and an ester exchanger of carbonic ester according to the mol ratio of 1:2-1:30 in the presence of a composite catalyst at the reaction temperature 20-100 DEG C for 6-48h; filtering to remove the catalyst and distilling to remove excess ester exchanger so as to prepare biodiesel, wherein the addition amount of the composite catalyst accounts for 1%-40% of the weight of the waste oil, and the mass ratio of immobilized enzyme to super absorbent resin in the composite catalyst is 1:1-3:1. According to the preparation method, the composite catalyst is adopted. The catalyst has good reusability and efficient catalytic activity. The color of the obtained biodiesel is light. The preparation method has adnvatages of no by-product of glycerin, no need in washing and no generation of waste liquid. By the adoption of the preparation method, problems, existing in the traditional biodiesel preparation technology, such as high cost of preprocessing a lot of raw oil, environmental burden and the like, are solved.

Description

technical field [0001] The invention belongs to the field of biodiesel preparation, and in particular relates to a method for preparing biodiesel without glycerol by-product from waste oil with high acid value. Background technique [0002] Due to the depletion of oil resources, in order to reduce dependence on oil, scientists are trying to find alternative fuels for oil, which has greatly promoted the pace of research and development of diesel alternative fuels in countries around the world. Biodiesel refers to an organic fatty acid ester fuel obtained by transesterifying vegetable oil and animal oil with short-chain alcohols. Compared with ordinary fossil fuels, it has a high cetane number, no sulfur and The advantages of aromatic compounds, biodegradable, non-toxic and renewable, and higher flash point than petrochemical diesel have attracted more and more attention from various countries (especially European and American countries), especially in the 1990s, the developme...

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Problems solved by technology

[0010] However, since the free fatty acid in the high-acid value oil will react with the new carbonate-based transesterification reagent to generate a certain amount of water (from the decomposition of carbonic acid), and the presence of water will irreversibly inhibit the activity of the immobilized enzyme catalyst. It is of great significance to develop some water-absorbing materials and immobilized enzymes to form composite catalysts. It is of great significance to apply enzyme catalysts to high-acid value oils and new transesterification reagents to prepare biodiesel. In the study of enzyme-catalyzed methanol and high-acid value oils, It has been reported in the literature that adding a certain amount of molecular sieve and silica gel to remove the water generated after the esterification reaction of methanol and free fatty acid, these water-absorbing agents have limited water absorption capacity, and after each reaction, it is necessary to recover the molecular sieve for high-temperature water removal, otherwise the next The catalytic activity of batches will be greatly reduced, and the separation of immobilized enzymes and molecular sieves is difficult, which is very unfavorable in industry

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