RU2425863C2 - Procedure for re-etherification of vegetable oil by alcoholysis - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: procedure consists in introduction of vegetable oil and solution of potassium hydroxide in methyl alcohol into reactor with ferro-magnetic particles. Amount of ferro-magnetic particles is 1/5 of reactor volume. Produced mass is subjected to effect of rotating magnetic field generating a vortex layer of ferro-magnetic particles at rate of 15-50 s^-1 and value of magnetic induction 0.12-0.15 tesla. Produced mass is settled with separation of upper layer, neutralised with solution of phosphorus acid and flushed with water.

EFFECT: intensified reaction of alcoholysis and, development of efficient continuous process for production of components of bio-diesel fuel.

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Description

The invention relates to a method for producing methyl esters of higher aliphatic acids from vegetable oils by the transesterification reaction (more precisely, alcoholysis) of vegetable oil triacylglycerols and can be used to obtain components of liquid biodiesel synthesized from renewable raw materials of plant origin.

A known method of carrying out the alcoholysis reaction is to mix a heated (up to 50-80 ° C) vegetable oil and a solution of alkali (catalyst) in alcohol. The reaction mass is stirred for some time, then defend until complete separation of the ether and glycerol phases. The upper ether layer is separated, neutralized with an inorganic acid solution, washed with water (Stopsky N.A. Chemistry of fats and processed products of fatty raw materials: Textbook / N.A. Stopsky. - M .: Kolos, 1992. - 285 p.). The duration of the reaction and the yield of the target product of alcoholysis depend on the presence of impurities in the starting vegetable oil, such as alcohol and catalyst, the temperature of the reaction mixture, and the duration of mixing. The duration of the process of alcoholysis is due to the fact that the components of the reaction mass - vegetable oil and alcohol - are immiscible reaction reagents. At the initial stage, the reaction mass consists of two phases (alcohol and lipid). Heterogeneous reactions do not occur in the entire volume of the system, but only in the volume of one of the phases (in this case, the lipid) as a result of the diffusion of a component from another phase (alcohol) into it. Therefore, the kinetics of the process at the beginning of the reaction is controlled by the mass transfer of reagents by diffusion. Esters of higher aliphatic acids and monohydric alcohols are soluble in both vegetable oil and alcohol. When they appear in the reaction mass, they act as a co-solvent, therefore, some time after the start of the reaction, the system becomes homogeneous and the kinetics of the process are controlled by the chemical reaction (the reaction passes from the diffusion region to the kinetic). Methods of improving the alcoholysis reaction may differ in the type of catalyst (RU 2263660 C2, C07C, 67/03, 69/24, 69/52, C11C 3/10, 10/19/2000), the presence of an additional stage of washing the reaction mass with glycerol (RU 2127251 C1, C07C 67/03, 69/24, 69/52, 01/19/1994) or an additional stage of esterification of free fatty acids (RU 2287519 C2, C07C 67/03, 69/24, 69/52, C11C 3/10, 10/05/2001) . There is a known method of transesterification, according to which a decrease in the reaction time is achieved by introducing an alcohol ester and a higher aliphatic (fatty) acid in such an amount that a single-phase reaction mass is formed as a result (patent application RU 2003128074 A, C11C 3/04, 07/02/2002) .

Significant disadvantages of the known methods are: a long reaction time (from 1 h or more), complexity of execution, high energy consumption (for example, in patent RU 2263660 it is proposed to heat the reaction mass to 135 ° C, maintaining a pressure of 5 bar, while the degree of conversion of triacylglycerols vegetable oils does not exceed 70%), the impossibility of a continuous process. Due to the low reaction rate, an excess of alcohol is used during the alcoholysis reaction (up to 35% by weight of oil or about 9 mol of alcohol per 1 mol of triacylglycerol oil instead of 3 mol) or a rather significant amount of catalyst (2% or more by weight of oil). Currently, the reaction of alcoholysis (often with the use of methyl alcohol - methanolysis) is becoming increasingly important, because methyl esters of higher aliphatic acids are used as an alternative biodiesel fuel having better environmental characteristics compared to petroleum fuels. The production of biodiesel fuel is increasing every year, the search for ways to intensify the reaction, which makes it possible to conduct a continuous technological process of its production with high quality and lower cost of reagents, is an urgent task.

The objective of the present invention is to intensify the process of transesterification of vegetable oils by the reaction of alcoholysis, leading to a decrease in the time of alcoholysis by an order of magnitude and a significant reduction in resources for the synthesis process.

The solution to this problem is achieved by the fact that alcoholysis is carried out by applying a rotating electromagnetic field that creates a vortex layer of ferromagnetic particles. The presence in the reaction mass of ferromagnetic particles in the amount of 1/5 of the reactor volume, intensively moving in a rotating electromagnetic field and forming a vortex layer of ferromagnetic particles with a speed of 15-50 s ^-1 and a magnetic induction of 0.12-0.15 Tesla, leads to an increase in the dispersion of the two-phase lipid-alcohol system and, as a consequence, an increase in the area of contact between the alcohol and lipid phases. In addition, with the intensification of mixing under the action of friction, the thickness of the boundary layer decreases, which leads to an increase in the numerical values of the diffusion coefficient. After the emergence of methyl esters, which play the role of a co-solvent, the reaction mass becomes homogeneous and the reaction passes from the diffusion region to the kinetic. Exposure to the electromagnetic field leads to an increase in the energy of the reacting particles, which reduces the activation energy of the alcoholysis reaction and increases its speed.

The intensification of the reaction, which leads to a decrease in activation energy, can reduce the amount used for the synthesis of alcohol (up to 20% by weight of oil) and catalyst (up to 1.4% by weight of oil).

The method is as follows.

The reacting substances are introduced into the reactor with ferromagnetic particles: vegetable oil and a solution of potassium hydroxide (catalyst) in methyl alcohol. The reaction mass is exposed to a rotating electromagnetic field. Duration of exposure - 10 seconds.

An inductor with three windings (having the same number of turns) was used, the axes of which were mutually shifted by an angle of 120 °. Equal in amplitude values, but shifted by a quarter of the period (90 °) sinusoidal currents, which excited an alternating electromagnetic field in the windings, were passed through the windings. During one period, the electromagnetic field of the inductor was rotated 360 °: there was a continuous and uniform change in the direction of the magnetic field in time. The rotation speed of the magnetic field varied from 15 to 50 s ^-1 , the magnitude of the magnetic induction varied from 0.12 to 0.15 Tesla. Steel cylinders with a diameter of 1 mm and a length of 10 to 15 mm were used as ferromagnetic particles. Ferromagnetic particles filled 1/5 of the volume of the working chamber.

The essence of the proposed method with the best results obtained is described in the following example.

Example

100 g of rapeseed oil heated to a temperature of 60 ° C are introduced into the reactor, a solution of 1.4 g of potassium hydroxide in 20 g of methyl alcohol is added; then the reaction mass is exposed to a rotating electromagnetic field (angular velocity of rotation of the magnetic field 30 s ^-1 , the magnitude of the magnetic induction of 0.13 Tesla) for 10 s. The reaction mass is defended, the upper ether layer is separated, neutralized with a solution of phosphoric acid, washed with water. A mixture of biodiesel components (methyl esters of higher aliphatic acids) is obtained in a yield of 99%.

Using the proposed method for transesterification of vegetable oils allows you to intensify the reaction of alcoholysis and create cost-effective continuous technology for the production of biodiesel components.

Claims (1)

A method for transesterification of vegetable oils by alcoholysis, characterized in that it involves the introduction of a vegetable oil and a solution of potassium hydroxide in methyl alcohol into a reactor with ferromagnetic particles, the amount of ferromagnetic particles being 1/5 of the reactor volume, the resulting mass is subjected to a rotating electromagnetic field, which creates a vortex ferromagnetic particles layer at a rate of 15-50 s ^-1 and the value of magnetic induction 0.12-0.15 T, the resulting mass is settled upper layer was separated, neutrals izuyut phosphoric acid solution and washed with water.