RU2533419C1 - Method of biodiesel production - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of biodiesel production is realised by the re-etherification in mixing natural oil, alcohol and a catalyst and following separation of the target product. The method is characterised by the fact that at the first stage of the re-etherification iron sulphate (II) is applied as the catalyst, after which iron sulphate and precipitated glycerol are separated and the mixture of alcohol, oil and ethers of fatty acids are supplied to the second stage of the re-etherification, at which as the catalyst used is an enzyme - lipase, immobilised on the surface, after which glycerol and the enzyme catalyst are separated and the mixture of alcohol and biodiesel is directed to a stage of the target product separation.

EFFECT: method makes it possible to simplify the process of the re-etherification reaction and increase the completeness of the reaction process.

6 cl, 1 tbl

Description

The invention relates to a method for producing fatty acid esters - biodiesel, which can be used as an alternative biofuel.

From a chemical point of view, biodiesel is a mixture of fatty acid esters. In its production, during the transesterification process, oils and fats react with alcohol in the presence of a catalyst (usually KOH, NaOH). The catalyst is used to improve speed and reaction, and yield. A byproduct of the reaction is glycerin. Transesterification refers to the redistribution of acyl groups in fat triglycerides. Transesterification allows you to change the molecular (glyceride) composition of fat or a mixture of fats, without changing their fatty acid composition. A change in the glyceride composition of fat leads to a change in its physical properties (melting point, hardness, etc.).

Quality requirements for biodiesel according to GOST R and EN are given in the Table.

Table Indicator EN590: 2000 Requirements Requirements GOST 523865-2005 Method of measurement Flash point ° C - - GOST 12.1.044-89 (ISO 4589-84) Flash point ° C more than 55 more than 55 EN ISO 2719 Pour point, ° C - - GOST 20287-91 Cetane number not less than 51 not less than 51 EN ISO 4264 Density at 15 ° C, kg / m ³ 820-845 820-845 EN ISO 3675, EN ISO 12185

Indicator EN590: 2000 Requirements Requirements GOST 523865-2005 Method of measurement Sulfur mg / kg less than 50 less than 350 EN ISO 20846, EN ISO 20847, EN ISO 20884 Ash% 0.01 0.01 EN ISO 6245 The water content, mg / kg 200 200 EN ISO 12937 Viscosity at 40 ° C, mm ² / s 2-4.5 2-4.5 EN ISO 3104

The mechanism of the transesterification reaction is the interaction of the carbonyl group of the C — O ester with the alcohol groups of di- and monoglycerides.

The main drawback of biodiesel production technologies using a catalyst is the removal of catalyst and saponification products after the reaction, which is very important for the purity of the product obtained, the use of an alkaline catalyst is associated with certain problems that do not change dramatically when adding an acid catalyst stage. The problem is, with an increased content of water and free fatty acids (FFA), soap forms, which destroys the catalyst and reduces its effectiveness, all of which as a result reduces the conversion of fats to esters. Alkaline catalysis:

- increases the quality requirements of the feedstock for the content of FFA, which leads to the need for its refinement. At the same time, the cost of high-purity raw materials determines the cost of the final product;

- includes additional stages of vacuum or steam distillation, increasing the energy intensity of production technology.

A known method of producing fatty acid esters (State educational institution of higher professional education Russian state. (RF Patent No. 2365625).

This method consists in the fact that rapeseed oil is transesterified with ethyl alcohol with the separation of the obtained products into fractions. The resulting homogeneous mixture is fed to a first separator to separate glycerol from the target product, and then the target product is fed to a second separator to separate the fatty acid ethyl ester from carbon dioxide, which is recycled. According to the invention, rapeseed oil is used as vegetable oil, and ethanol is used as alcohol obtained by sparging the biomass of immobilized granulated yeast with carbon dioxide at a ratio of 1:12 to a homogeneous state, the resulting mixture is sent to a transesterification reactor, in which the transesterification is carried out at a temperature of 350 -400 ° C and a pressure of 35-50 MPa for 20 minutes, cool the mixture and fed to the extractor, in which the reaction mixture is subjected to temperature control to a temperature tours 250 ° C, then carbon dioxide extraction is carried out under supercritical conditions at a flow rate of carbon dioxide of 40 l / h at a temperature of 350 ° C and a pressure of 35 MPa, the resulting homogeneous mixture is fed to the first separator to separate glycerol from the target product at a pressure of 0.5 MPa and a temperature of 20-30 ° C, the target product is fed to a second separator to separate the fatty acid ethyl ester from carbon dioxide at a pressure of 0.2 MPa and a temperature of 15 ° C.

The proposed method allows to simplify the process and improve the environment through the use of supercritical ethyl alcohol and to obtain the target product with a conversion of 95% and higher.

The disadvantages of this method is the use of ethyl alcohol, which in itself is a valuable biofuel, and supercritical conditions, which increases the complexity of the technology and leads to a more expensive process.

Also known is the technology for processing vegetable oil and producing biodiesel and glycerol as a by-product (Unit S-Saratov Limited Liability Company. (RF Patent for Utility Model No. 82579). It consists in the following. Capacities designed to store the starting components, filled with potassium alkali, methanol, purified vegetable oil. To start the production of biodiesel and glycerin from containers, the starting components are fed into a hydrodynamic mixer in accordance with a given dosage. As the components pass through the flow-through hydrodynamic mixer, they obtain a biodiesel mixture, which is supplied to the cavitator pump. At the exit of the cavitator pump, as a result of activation of cavitation processes, a biodiesel emulsion is obtained, which is sent to the buffer device. The emulsion is transported under pressure through the pipeline of the buffer device, it is stabilized and fed to a centrifugal cleaner to separate the emulsion into biodiesel and glycerin. As a result of the cleaning process, two final products are obtained, which are fed into storage tanks for storage and further sale.

The disadvantage of this method is its technological complexity, associated, firstly, with the use of alkali as a catalyst, which necessitates the prospect of industrial use of the organization of alkaline farming, which leads to an increase in the complexity of servicing the installation, qualification requirements for staff, and second use of cavitation pumps, which are extremely unreliable.

The technical result to which the invention is directed is:

- simplification of catalyst removal technology, as the catalyst precipitates with glycerol,

- improving the quality of the target product by reducing side substances such as saponification products,

- simplification of the industrial implementation of the technology, due to the refusal to organize an additional reagent farm, reducing the requirements for the quality of feedstock, simplifying the hardware design of the process, the technology uses only industrially manufactured equipment.

To this end, a method for the production of biodiesel by transesterification by mixing vegetable oil, alcohol and a catalyst and the subsequent isolation of the target product is proposed, while in the first stage of transesterification, iron sulfate is used as a catalyst (11), after which iron sulfate and precipitated glycerol are separated and a mixture of alcohol, oil and fatty acid esters is sent to the second stage of transesterification, in which the enzyme is used as a catalyst - a lipase immobilized on the surface, after which lyayut glycerol and enzyme catalyst, a mixture of alcohol and biodiesel is sent to the step of isolating the desired product.

Wherein:

- methanol is used as alcohol.

- the first stage of transesterification is carried out for 12 hours and a temperature of 35-40 ° C with a ratio of vegetable oil - methanol - 1: 6 (mol.) and a catalyst - iron (II) sulfate at the rate of 5 g per 1 kg of oil.

- Novozym 435, or Lipozyme TL, or Lipozyme RM, or Lipase AK, or Lipase PS, or their analogues are used as an enzyme catalyst.

- solid surfaces such as silicon dioxide, macroporous resin, sepiolite, cell wall of living microorganisms are used as a surface for immobilizing lipase.

Lipases are serine hydrolases that act on the interface and are capable of catalyzing both the hydrolysis of triglycerides and the reverse reactions of esterification, transesterification, alcoholysis and acidolysis. In the series of hydrolytic enzymes used as catalysts for organochemical transformations, lipases occupy a special place because of the possibility of their use both in hydrolysis of lipids and esters, and in reactions of enantioselective esterification and transesterification in organic solvents or in aqueous-organic systems. In this technology, lipase is immobilized on the surface (it can be a macroporous resin, a cell wall of a living microorganism, etc.).

The method is as follows.

At the first stage, a mixture of vegetable oil and methanol is fed into a standard stirred reactor (the advantage of methanol is that it is cheaper and has physical and chemical advantages (polar, short-chain alcohol)) in a ratio of 1: 6 (mol.) In accordance with stoichiometry of the chemical reaction (theoretically, the esterification reaction is equilibrium, therefore, an excess amount of methanol is used to shift the reaction to the right and form more methyl esters as the target product, respectively s according to the stoichiometry of 1: 3) and the catalyst ferric sulfate (II) - the rate of 5 g per 1 kg of oil (ratio chosen empirically based on the results of the experiments conducted). The reaction proceeds within 12 hours, the stirrer speed is 30 rpm. Process temperature 47 ° C. The process parameters are determined empirically, based on the results of the experiments. The precipitate (iron sulfate and glycerol) is heavier than the liquid, and is collected at the bottom after several hours of settling or centrifuged and discharged through the lower part of the reactor, and the liquid fraction (containing methanol and oil in a ratio of approximately 3: 1, the ratio was determined empirically, based on the results conducted experiments) is discharged from above into the second reactor of a similar design. As a catalyst in the second stage, an enzyme is used - lipase (the only currently known enzyme capable of catalyzing the transesterification reaction) immobilized on any surface t - silicon dioxide, macroporous resin, sepiolite, including the cell walls of living microorganisms. As a catalyst, Novozym 435 or an analogue can be used. The second stage also lasts 12 hours, the stirrer speed is 30 rpm. Process temperature 35-40 ° C. The parameters of this process are also determined empirically, based on the results of experiments. After this, the precipitate (glycerol and catalyst) is discharged through the lower part of the reactor, and a mixture of methanol (which was taken in excess relative to the stoichiometry of the reaction) and the resulting fatty acid esters (biodiesel) is discharged from the upper part of the reactor and sent for further separation.

The proposed method allows to simplify the process of the transesterification reaction and tentatively increase the completeness of the reaction to 96-98%.

Thus, this method will allow due to the proposed catalysts to avoid the presence of saponification products characteristic of alkaline catalysis, to simplify the technology of removal of the catalyst - iron sulfate, it precipitates along with glycerol. In addition, reduced requirements on the quality of the feedstock. The presence in the oil of water and free fatty acids does not lead to the formation of side substances that interfere with the extraction of the target product. As a result, the proposed method will simplify the process of transesterification reaction and approximately increase the completeness of the reaction to 96-98%.

Claims (6)

1. A method of producing biodiesel by transesterification by mixing vegetable oil, alcohol and a catalyst and subsequent isolation of the target product, characterized in that in the first stage of transesterification, iron sulfate is used as a catalyst (11), after which iron sulfate and precipitated glycerol are separated, and a mixture of alcohol, oil and fatty acid esters is sent to the second stage of transesterification, in which the enzyme is used as a catalyst, a lipase immobilized on the surface, and then separated litserol and enzyme catalyst, a mixture of alcohol and biodiesel is sent to the step of isolating the desired product. 2. The method according to claim 1, characterized in that methanol is used as the alcohol. 3. The method according to claim 1 and 2, characterized in that the first stage of transesterification is carried out for 12 hours and a temperature of 35-40 ° C with a ratio of vegetable oil - methanol - 1: 6 (mol.) And a catalyst - iron sulfate (II ) at the rate of 5 g per 1 kg of oil. 4. The method according to claim 1, characterized in that as the enzyme catalyst using drugs Novozym 435, or Lipozyme TL, or Lipozyme RM, or Lipase AK, or Lipase PS, or their analogues. 5. The method according to claim 1, characterized in that as a solid surface for the immobilization of lipase using silicon dioxide, or a macroporous resin, or sepiolite, or the cell wall of living microorganisms. 6. The method according to claim 1, characterized in that the second stage of transesterification is carried out for 12 hours and a temperature of 35-40 ° C.