Method for stably preparing biodiesel

Abstract

The invention provides a method for stably preparing biodiesel. The method comprises the steps: (1) performing a contact reaction on grease of a low acid value, monohydric alcohol and a metal carboxylate catalyst, separating biodiesel from the reaction products, and recovering the catalyst; and (2) when the decrease extent of the yield of the biodiesel obtained in the step (1) exceeds a tolerancevalue, adding the recovered carboxylate catalyst to a system comprising the grease of a low acid value and the monohydric alcohol, adding C1-C24 carboxylic acid or grease of a high acid value, and performing a reaction at a reaction temperature of 100-200 DEG C and a pressure of 0.1-3 MPa. Through the method, the activity of the catalyst can be increased rapidly at the low reaction temperature andpressure, the deactivated catalyst can be regenerated in situ, and the yield of the product can exceed the initial yield.

Description

technical field [0001] The invention relates to a method for preparing biodiesel by reacting oil and monoalcohol. Background technique [0002] Biodiesel can be obtained through the transesterification reaction of oil and monohydric alcohol. The reaction products include fatty acid monoalkyl esters (ie biodiesel), monoglycerides, diglycerides, glycerol, and unreacted alcohols and oils (ie triglycerides). The preparation methods of biodiesel in the prior art can be divided into acid catalysis method, base catalysis method, enzyme catalysis method and supercritical method. [0003] CN1473907A adopts the leftovers of vegetable oil refining and edible recovered oil as raw materials, and the catalyst is compounded by sulfuric acid, hydrochloric acid, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, naphthalenesulfonic acid and other inorganic or organic acids. , continuous dehydration, esterification, layering, vacuum distillation and other processes for production, the pre...

AI Technical Summary

Problems solved by technology

The shortcomings of using enzyme catalysts are: long reaction time, low efficiency, high cost of enzyme catalysts, and easy deactivation in high-purity methanol

This method can reduce the reaction temperature to 100-200 °C and the pressure to 0.1-2 MPa, and the carboxylate catalyst is a solid catalyst, which is easy to separate from the product, and the post-treatment process is simplified, but the carboxylate catalyst is used for low acid value When preparing biodiesel from oil, the activity of the catalyst decreases rapidly. Usually, when the raw oil treatment capacity per gram of catalyst reaches 100-200 grams, the yield of biodiesel will drop significantly