Method for preparing biodiesel by taking sludge as raw material

Abstract

The invention discloses a method for preparing biodiesel by taking sludge as a raw material based on a solid acid catalyst. The method comprises the following steps: (1) taking the sludge obtained bya sewage treatment plant as a raw material; filtering, precipitating and drying to obtain dry sludge; (2) taking methanol as an ester exchange agent; carrying out heterotopic ester exchange reaction on the dry sludge under the catalysis of a solid acid catalyst, so as to obtain a mixed solution after heterotopic ester exchange; (3) extracting the mixed solution by taking n-hexane as an extractingagent and collecting supernatant; (4) washing the supernatant by utilizing a potassium bicarbonate solution; collecting an upper-layer n-hexane phase; (5) filtering, evaporating and collecting a product. According to the method disclosed by the invention, a sludge drying technology is subjected to energy-saving optimization and sludge pre-treatment is carried out by adopting a hot drying method; aheterotopic ester exchange method is adopted, and the solid acid catalyst is used for catalyzing the ester exchange reaction after crude fat in the sludge is extracted; after the reaction is finished, the solid catalyst can be recycled and repeatedly utilized; meanwhile, the problem that acidic waste liquid generated by concentrated sulfuric acid catalyzed ester exchange reaction can be discharged after being neutralized is also avoided.

Description

technical field [0001] The invention belongs to the fields of clean energy development and waste recycling, and in particular relates to a method for preparing biodiesel from sludge. Background technique [0002] Catalysts for the production of biodiesel from biomass generally fall into two categories: homogeneous and heterogeneous catalysts. Homogeneous and heterogeneous catalysts are each subdivided into acidic catalysts, basic catalysts, and other types of catalysts. At present, the most widely used sludge-to-biodiesel laboratory is the homogeneous acid catalyst, such as concentrated sulfuric acid, and biological enzymes are also used. The homogeneous acid catalyst can be used for ex-situ and in-situ transesterification of the sludge. In the laboratory research, the lipid conversion rate of the sludge can reach 99%, and the purity of the obtained fatty acid methyl ester can reach more than 96%. However, the use of an acid catalyst requires a large amount of concentrated...

AI Technical Summary

Problems solved by technology

However, the use of an acid catalyst requires a large amount of concentrated sulfuric acid, and it is difficult to recycle and reuse it. Afterwards, it needs to be neutralized with an alkaline reagent, which consumes a lot of reagents; the acid catalyst is used for transesterification, and the reaction time is longer. ; The separation of the final product from the residue and other by-products is not easy, the color of the product is darker, and more refining steps are required; the use of concentrated sulfuric acid, a strong acid and corrosive agent, requires a lot of safety costs in industrial production