RU2665041C2 - Method for obtaining biodiesel fuel - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to the production of fuels from renewable raw materials. This method for producing biodiesel fuel lies in the fact that oil is mixed with a low alcohol to obtain a mixture, then the transesterification process is carried out using water and a catalytically active membrane consisting of a diffusion layer made on the basis of a polymer that is permeable to low alcohols and glycerol, as well as a connecting layer made of a porous polymer and a catalytically active layer formed by a lipolytic microorganism, wherein the porous polymer is selected from woven or non-woven materials of polyethylene fibers, polypropylene, polytetrafluoroethylene, polyamide, wherein said mixture is brought into contact with the catalytically active membrane layer and the water is brought into contact with the diffusion layer of the membrane, after which the product of the contact of said mixture with the catalytically active layer is subjected to evaporation to remove unreacted alcohol to obtain the desired biodiesel fuel, and the product of the contact of water with the diffusion layer is separated into water and glycerin.

EFFECT: improvement of the technology for obtaining biodiesel fuel, which is provided by the lipolytic microorganism, which is in active state during the entire contact time, and the product is obtained in a sufficiently high yield.

1 cl, 5 ex

Description

The invention relates to the field of producing fuels from renewable raw materials, in particular, to the field of producing biodiesel from vegetable oils.

Biodiesel is understood to mean mixtures of fatty acid esters, especially methyl and ethyl fatty acid esters.

Known methods for producing biodiesel using an inorganic catalyst - acid or alkali (US 6211390, 2001, WO 2005/093015, 2005; US 5713965, 1998; US 5525126, 1996). A common and significant drawback of these solutions is the need to purify the products from the inorganic catalyst by washing with water and subsequent neutralization. In addition, the disadvantages include the formation of a large number of alkaline or acidic effluents, which negatively affects the environmental performance of the process as a whole.

Also described are methods for producing biodiesel using biocatalysts: enzymes or native cells of various lipolytic microorganisms. These methods avoid the presence of inorganic impurities in the products, however, such indicators as the yield and conversion of the feedstock for the described methods are not large, since when using a biocatalyst it is impossible to use a large excess of alcohol in the feed mixture. In addition, the biocatalyst loses its activity during the reaction due to the formation of glycerol.

Thus, there is a known method for producing biodiesel using a bioreactor containing a semipermeable membrane of regenerated cellulose and immobilized on a Candida antarctica lipase B lipase carrier (KR 101143313, 2012).

The disadvantages of this method are the need to use expensive isolated lipase, as well as the need for immobilization of lipase, which leads to a partial loss of catalytic activity.

Closest to the invention is a method for producing biodiesel (CN 101265413, 2008) using lipase immobilized on a porous membrane. The membrane, in this case, is made in the form of a hollow fiber inside the reactor. A mixture of oil and alcohol circulates in the reactor volume, water in the fiber cavity. Glycerin formed as a product penetrates the membrane and is removed from the reaction medium, providing an equilibrium shift in the transesterification reaction. In addition, water circulating through the cavity of the membrane fiber, partially penetrating into the reaction volume, provides high activity of the immobilized lipase.

The disadvantages of this method are the need to use expensive lipase, as well as the complexity of the process of immobilization of the latter.

The technical problem is to simplify the technology for producing biodiesel and reduce the cost of its production.

The problem posed is solved by the described method for producing biodiesel, which consists in mixing the oil with lower alcohol to obtain a mixture and carrying out the transesterification process using water and a catalytically active membrane consisting of a diffusion layer based on a polymer permeable to lower alcohols and glycerin, a connecting layer made of a porous polymer, and a catalytically active layer formed by a lipolytic microorganism, wherein said mixture contact with the catalytically active layer of the membrane, and water with the diffusion layer of the membrane, after which the product of contacting the mixture with the catalytically active layer is evaporated to remove unreacted alcohol to obtain the target biodiesel, and the product of contacting water with a diffusion layer is separated into water and glycerol.

The technical result consists in increasing the surface area of the contacting of a mixture of oil with alcohol with a catalytically active layer through the use of a lipolytic microorganism that is in an active state for the entire time of contacting.

The method of producing biodiesel is as follows.

The oil is mixed with lower alcohol to obtain a mixture and the transesterification process is carried out using water and a catalytically active membrane consisting of a diffusion layer made on the basis of a polymer permeable to lower alcohols and glycerin, a connecting layer made of a porous polymer and a catalytically active a layer formed by a lipolytic microorganism.

The diffusion layer of the membrane is a layer of polymeric material permeable to lower alcohols, including polyhydric alcohols, in particular glycerol. As the polymer, it is possible to use any polymer materials compatible with aqueous solutions of alcohols, for example, cellulose acetate, polycarbonate, polytetrafluoroethylene.

The connecting layer is made of a porous polymer inert to the reagents and lipolytic microorganisms used in the method. As the specified porous polymer, it is possible, for example, to use foamed polymers, in particular polyurethane foam, as well as woven and non-woven materials from polymer fibers, for example, woven or non-woven materials from fibers of polyethylene, polypropylene, polytetrafluoroethylene, polyamide fibers (nylon, capron), cellulose fibers.

The catalytically active membrane layer is formed by a lipolytic microorganism.

Used in the described method, the catalytically active membrane is prepared as follows.

Pre-prepared nutrient medium for the cultivation of lipolytic microorganisms.

The composition of the nutrient medium is selected in accordance with the species of the used lipolytic microorganism. It is preferable to use a thickened nutrient medium containing mineral salts necessary for the growth of the microorganism, a carbon source, a nitrogen source and a polysaccharide to thicken the medium. Mineral salts are selected in accordance with the species of the lipolytic microorganism used. So, if fungi of the Aspergillus niger species or yeast of the Yarrowia lipolytica species are used as a lipolytic microorganism, it is possible to use tap water as a source of mineral salts for preparing the nutrient medium.

The carbon source is selected from the series: sunflower oil, rapeseed oil, glucose, fructose, glucose-fructose syrup, molasses, malt extract.

The nitrogen source is selected from the series: soy flour, yeast extract, peptone, tryptone, urea.

The polysaccharide for thickening the medium is selected from the range: agar, sodium alginate, carboxymethyl cellulose.

The resulting thickened nutrient medium is distributed over the surface of the connecting layer of the membrane, which consists of two layers - a diffusion layer made on the basis of a polymer permeable to lower alcohols and glycerin and a connecting layer made of a porous polymer.

In this case, spores or cells of lipolytic microorganisms can be impregnated into a thickened nutrient medium before or after its distribution over the surface of the connecting layer of this membrane.

Then, the membrane with the thickened nutrient medium distributed over the surface of the connecting layer is kept in the presence of air at thermostating at a temperature suitable for the growth of the selected lipolytic microorganism for 20-200 hours. Preferably, thermostating is carried out at a temperature optimal for the growth of the selected lipolytic microorganism.

Thus, the surface of the initial membrane is uniformly overgrown with a lipolytic microorganism to obtain a catalytically active membrane consisting of three layers — a diffusion layer made on the basis of a polymer permeable to lower alcohols and glycerin, a connecting layer made of a porous polymer, and a catalytically active a layer formed by a lipolytic microorganism.

The resulting membrane can be made in the form of a hollow fiber (tubes) or in the form of a polymer film.

In this case, it is possible to use any microorganism as a lipolytic microorganism, characterized in that it synthesizes lipases - enzymes that catalyze the hydrolysis, esterification and transesterification of lipids, including triglycerides of fatty acids, free fatty acids and their esters. Such microorganisms may include, for example, bacteria, archaea and eukaryotes, including unicellular fungi (yeast) and mycelial fungi. It is also possible to use genetically modified microorganisms. Preferably, mycelial fungi are used as the lipolytic microorganism, characterized in that they synthesize lipases. Most preferably, Aspergillus niger species and Yarrowia lipolytica are used.

As an oil, it is possible to use vegetable oils (for example, sunflower oil, rapeseed oil, palm oil, camelina oil and others), as well as mixtures of vegetable oils with animal fats, including those with a high content of free fatty acids.

As the alcohol, it is possible to use various lower alcohols, preferably methyl and ethyl alcohols are used.

Most preferably (in the case of using Aspergillus niger fungi as a lipolytic microorganism), agar-thickened medium of the following composition is used as a nutrient medium: yeast extract - 6.2 g / l, soy flour - 7.4 g / l, sunflower oil - 13 , 2 g / l, bacteriological agar - 15 g / l. The specified environment is prepared on the basis of tap water.

Further, a mixture of oil with a lower alcohol, preferably in a mass ratio of 3: 1 to 20: 1, is brought into contact with the catalytically active layer of the membrane formed by the lipolytic microorganism, and water with the diffusion layer of the membrane. The process is carried out in batch or continuous mode. When carrying out the specified contacting, the contacting product is recycled with the addition of lower alcohol, preferably based on a ratio of 1: 3 to 1:20 in mass fractions relative to the mass of oil for each recirculation cycle. After a sufficient number of recycling cycles, the product of contacting the mixture of oil with a lower alcohol with a catalytically active layer of the membrane is evaporated to remove unreacted alcohol to obtain the target biodiesel fuel. The number of recirculation cycles is determined based on the total consumption of lower alcohol, which is preferably from 1: 2 to 1: 5 with respect to the weight of the oil. The product of contacting water with a diffusion layer is separated into water and glycerin. In this case, the separated water can be sent for recycling, and glycerin can be used as a commercial product.

The implementation of the described method can be carried out using any known apparatus, preferably reactors, for example, membrane reactors.

Below are examples illustrating the described method, but not limiting it.

Example 1

Nutrient medium of the following composition is preliminarily prepared: yeast extract - 6.2 g, soy flour - 7.4 g, sunflower oil - 13.2 g, bacteriological agar - 15 g; tap water - up to a volume of 1 liter. Bacteriological agar is dissolved with constant heating and stirring, then the medium in a glass vessel is placed in an autoclave and sterilized under excessive pressure. After sterilization is complete, the liquid medium is cooled to a temperature of 50-60 ° C. Then, under sterile conditions, the obtained thickened nutrient medium is distributed over the surface of the connecting layer of the membrane, which consists of two layers - a diffusion layer made on the basis of a polymer permeable to lower alcohols and glycerin - cellulose acetate and a connecting layer made of a porous polymer - polypropylene and incubated at room temperature until solidified.

The resulting membrane is placed in a membrane bioreactor. The volumes of the bioreactor from the side of the connecting layer of the membrane with the hardened thickened nutrient medium and from the side of the diffusion layer are filled with sterilized tap water. The volume of the bioreactor from the side of the connecting layer is inoculated with Aspergillus niger spores, air is supplied there and thermostated for 20 hours at a temperature of 30 ° C. During thermostating, the mycelium of the fungus uniformly covers the membrane, forming a catalytically active layer.

Thus, after thermostating, a catalytically active membrane is obtained, which consists of three layers - a diffusion layer made on the basis of a polymer permeable to lower alcohols and glycerin - cellulose acetate, a connecting layer made of a porous polypropylene polymer, and a catalytically active layer, formed by a lipolytic microorganism - Aspergillus niger fungus.

Then the mixture of oil with lower alcohol is brought into contact with the catalytically active layer of the obtained membrane, and water with the diffusion layer of this membrane as follows.

A mixture of rapeseed oil and methanol taken in a mass ratio of 10: 1 is fed into the reaction volume of the bioreactor (from the catalytically active layer of the membrane). Distilled water is supplied to the volume of the bioreactor from the side of the diffusion layer and at the same time water enriched in glycerin is removed from it.

The transesterification process is carried out at a temperature of 20-22 ° C during the recirculation of the mixture inside the reaction volume. Recirculation of the mixture is carried out with the addition of methanol at a rate of 1:10 in mass fractions with respect to the mass of oil for each recirculation cycle until a total methanol consumption of 1: 3 with respect to the mass of oil is reached. After the end of the transesterification process, the product of contacting the mixture with the catalytically active layer of the membrane is replaced with a new portion of the mixture of oil and alcohol and the process is repeated.

The product of contacting the mixture with a catalytically active layer of the membrane is subjected to evaporation, namely, heating under vacuum to remove unreacted alcohol. The product obtained after evaporation is biodiesel. The product of contacting water with a diffusion layer is separated into water and glycerin. In this case, the separated water can be sent for recycling, and glycerin can be used as a commercial product.

The yield of biodiesel is 68% of the weight of the original rapeseed oil.

Example 2

The nutrient medium of the composition of Example 1 is preliminarily prepared. The bacteriological agar is dissolved with constant heating and stirring, then the medium in a glass vessel is placed in an autoclave and sterilized under excessive pressure. After sterilization is completed, the nutrient medium is cooled to a temperature of 50-60 ° C and spores of Aspergillus niger fungus are introduced into it with stirring. Then, under sterile conditions, the obtained thickened nutrient medium is evenly distributed over the surface of the membrane, consisting of a diffusion layer (polycarbonate) and a connecting layer (polyethylene), from the side of the connecting layer and kept at room temperature until solidified. The resulting membrane is placed in a membrane bioreactor. The volumes of the bioreactor from the side of the nutrient layer and from the diffusion layer are filled with sterilized tap water. Air is fed into the bioreactor volume from the nutrient layer and thermostated for 50 hours at a temperature of 25 ° C. During thermostating, the mycelium of the fungus uniformly covers the membrane, forming a catalytically active layer.

Thus, after temperature control, a catalytically active membrane is obtained, which consists of three layers - a diffusion layer made on the basis of a polymer permeable to lower alcohols and glycerol - polycarbonate, a connecting layer made of a porous polymer - polyethylene, and a catalytically active layer, formed by a lipolytic microorganism - Aspergillus niger fungus.

Then the mixture of oil with lower alcohol is brought into contact with the catalytically active layer of the obtained membrane, and water with the diffusion layer of this membrane as follows.

A mixture of sunflower oil and ethanol taken in a mass ratio of 5: 1 is fed into the reaction volume of the bioreactor (from the catalytically active layer of the membrane). Distilled water is supplied to the volume of the bioreactor from the side of the diffusion layer and at the same time water enriched in glycerin is removed from it.

The transesterification process is carried out continuously at a temperature of 20-22 ° C, while recirculating the mixture in the reaction volume with the addition of ethanol at a ratio of 1: 5 in mass fractions relative to the mass of oil for each recirculation cycle. In this case, recirculation is carried out until a total ethanol consumption of 1: 2 with respect to the weight of the oil is achieved. After the end of the transesterification process, the product of contacting the mixture with the catalytically active layer of the membrane is replaced with a new portion of the mixture of oil and alcohol and the process is repeated.

The product of contacting the mixture with a catalytically active layer of the membrane is subjected to evaporation, namely, heating under vacuum to remove unreacted alcohol. The product obtained after evaporation is biodiesel. The product of contacting water with a diffusion layer is separated into water and glycerin. In this case, the separated water can be sent for recycling, and glycerin can be used as a commercial product.

The yield of biodiesel is 66% of the mass of the original sunflower oil.

Example 3

The nutrient medium of the composition of Example 1 is preliminarily prepared. The bacteriological agar is dissolved with constant heating and stirring, then the medium in a glass vessel is placed in an autoclave and sterilized under excessive pressure. After sterilization is complete, the liquid medium is cooled to a temperature of 50-60 ° C. Then, under sterile conditions, the nutrient medium is evenly distributed over the surface of the connecting layer of the membrane, which consists of a diffusion layer (cellulose acetate) and a connecting layer (polypropylene) and molded in the form of a tube so that the diffusion layer forms the inner surface of the tube, and the connecting layer forms the outer surface tube, and incubated at room temperature until solidified. The resulting membrane in the form of a tube is placed in a membrane bioreactor. The volume of the bioreactor external to the membrane tubes, as well as the internal volume of the membrane tubes, is filled with sterilized tap water. The external volume of the bioreactor is seeded with Aspergillus niger spores, air is also fed there and thermostated for 96 hours at 25 ° C. During thermostating, the mycelium of the fungus uniformly covers the surface of the connecting layer of the membrane, forming a catalytically active layer.

Thus, after temperature control, a catalytically active membrane is obtained, which consists of three layers - a diffusion layer made on the basis of a polymer permeable to lower alcohols and glycerol - polycarbonate, a connecting layer made of a porous polymer - polyethylene, and a catalytically active layer, formed by a lipolytic microorganism - Aspergillus niger fungus.

Then the mixture of oil with lower alcohol is brought into contact with the catalytically active layer of the obtained membrane, and water with the diffusion layer of this membrane as follows.

A mixture of camelina and ethanol oil, taken in a mass ratio of 15: 1, is fed into the reaction volume of the bioreactor (from the catalytically active layer of the membrane).

The transesterification process is carried out at a temperature of 20-22 ° C during the recirculation of the specified mixture, carried out with the addition of ethanol at a rate of 1:15 in mass fractions relative to the mass of oil for each recirculation cycle. In this case, recirculation is carried out until a total ethanol consumption of 1: 2 with respect to the weight of the oil is achieved. Distilled water is continuously supplied into the inner volume of the membrane tubes and at the same time water enriched in glycerin is taken off.

After the end of the transesterification process, the reacted mass in the volume of the bioreactor is replaced with a new portion of the mixture of oil and alcohol and the process is repeated.

The product of contacting the mixture with a catalytically active layer of the membrane is subjected to evaporation, namely, heating under vacuum to remove unreacted alcohol. The product obtained after evaporation is biodiesel. The product of contacting water with a diffusion layer is separated into water and glycerin. In this case, the separated water can be sent for recycling, and glycerin can be used as a commercial product.

The yield of biodiesel fuel is 62% of the mass of the original oil of camelina.

Example 4

The nutrient medium of the composition of Example 1 is preliminarily prepared. The bacteriological agar is dissolved with constant heating and stirring, then the medium in a glass vessel is placed in an autoclave and sterilized under excessive pressure. After sterilization is complete, the liquid medium is cooled to a temperature of 30-40 ° C and the Yarrowia lipolytica yeast cells are introduced into it with stirring. Then, under sterile conditions, the nutrient medium is evenly distributed over the surface of the connecting layer of the membrane, which consists of a diffusion layer (polytetrafluoroethylene) and a connecting layer (fibrous polytetrafluoroethylene) and molded in the form of a tube so that the diffusion layer forms the inner surface of the tube, and the connecting layer forms the outer surface tube, and incubated at room temperature until solidified. The obtained membrane in the form of a tube is placed in a membrane bioreactor. The volume of the bioreactor external to the membrane tubes, as well as the internal volume of the membrane tubes, is filled with sterilized tap water. Air is supplied to the external volume of the bioreactor and thermostated for 150 hours at a temperature of 30 ° C. During temperature control, the yeast evenly covers the surface of the connecting layer of the membrane, forming a catalytically active layer.

Thus, after temperature control, a catalytically active membrane is obtained, which consists of three layers - a diffusion layer made on the basis of a polymer permeable to lower alcohols and glycerol - polycarbonate, a connecting layer made of a porous polymer - polyethylene, and a catalytically active layer, formed by a lipolytic microorganism - Yarrowia lipolytica yeast cells.

Then the mixture of oil with lower alcohol is brought into contact with the catalytically active layer of the obtained three-layer membrane, and water with the diffusion layer of this membrane as follows.

In the reaction volume of the bioreactor (from the catalytically active layer of the membrane) serves a mixture of camelina oil and methanol, taken in a mass ratio of 5: 1.

The transesterification process is carried out continuously at a temperature of 30-32 ° C during the recirculation of the mixture with the addition of methanol at a ratio of 1: 5 in mass fractions relative to the mass of oil for each recirculation cycle. Recirculation is carried out until a total methanol consumption of 1: 3 with respect to the weight of the oil is reached. Distilled water is continuously supplied into the inner volume of the membrane tubes and at the same time water enriched in glycerin is taken off.

After the end of the transesterification process, the contact product is replaced with a new portion of a mixture of oil and alcohol and the process is repeated.

The product of contacting the mixture with a catalytically active layer of the membrane is subjected to evaporation, namely, heating under vacuum to remove unreacted alcohol. The product obtained after evaporation is biodiesel. The product of contacting water with a diffusion layer is separated into water and glycerin. In this case, the separated water can be sent for recycling, and glycerin can be used as a commercial product.

The yield of biodiesel fuel is 55% of the mass of the original oil of camelina.

Example 5

The nutrient medium of the composition of Example 1 is preliminarily prepared. The bacteriological agar is dissolved with constant heating and stirring, then the medium in a glass vessel is placed in an autoclave and sterilized under excessive pressure. After sterilization is complete, the liquid medium is cooled to a temperature of 50-60 ° C. Then, under sterile conditions, the nutrient medium is evenly distributed over the surface of the connecting layer of the membrane, consisting of a diffusion layer (cellulose acetate) and a connecting layer (nylon) and molded in the form of a tube so that the diffusion layer forms the inner surface of the tube, and the connecting layer forms the outer surface tube, and incubated at room temperature until solidified. The obtained membrane in the form of a tube is placed in a membrane bioreactor. The volume of the bioreactor external to the membrane tubes, as well as the internal volume of the membrane tubes, is filled with sterilized tap water. A seed culture of Yarrowia lipolytica yeast is introduced into the external volume of the bioreactor, air is also supplied thereto and thermostated for 200 hours at a temperature of 30 ° C. During temperature control, the yeast evenly covers the surface of the connecting layer of the membrane, forming a catalytically active layer.

Thus, after temperature control, a catalytically active membrane is obtained, which consists of three layers — a diffusion layer made on the basis of a polymer permeable to lower alcohols and glycerol — cellulose acetate, a connecting layer made of a porous polymer — nylon, and a catalytically active layer. formed by a lipolytic microorganism - Yarrowia lipolytica yeast cells.

Then the mixture of oil with lower alcohol is brought into contact with the catalytically active layer of the obtained three-layer membrane, and water with the diffusion layer of this membrane as follows.

In the reaction volume of the bioreactor (from the catalytically active layer of the membrane) serves a mixture of camelina oil and ethanol, taken in a mass ratio of 20: 1.

The transesterification process is carried out at a temperature of 30-32 ° C, in a continuous mode, when the mixture is recycled in the external volume of the bioreactor with the addition of ethanol at a rate of 1:20 in mass fractions with respect to the mass of oil for each recirculation cycle. The specified recirculation is carried out until the total ethanol consumption equal to 1: 2 in relation to the mass of oil. Distilled water is continuously supplied into the inner volume of the membrane tubes and at the same time water enriched in glycerin is taken off.

After the end of the transesterification process, the reacted mass - the contact product in the volume of the bioreactor is replaced with a new portion of the mixture of oil and alcohol and the process is repeated.

The resulting product of contacting the mixture with a catalytically active layer of the membrane is subjected to evaporation, namely, heating under vacuum to remove unreacted alcohol. The product obtained after evaporation is biodiesel. The product of contacting water with a diffusion layer is separated into water and glycerin. In this case, the separated water can be sent for recycling, and glycerin can be used as a commercial product.

The yield of biodiesel fuel is 70% of the mass of the original oil of camelina.

A method for producing biodiesel using other lipolytic microorganisms, other feedstock leads to similar results.

Thus, the method according to the invention allows to simplify the process of producing biodiesel and reduces the cost of its production by eliminating the use of expensive preparations of purified lipolytic enzymes with a high yield of the target product.

Claims (1)

The method of producing biodiesel fuel, which consists in mixing oil with lower alcohol to obtain a mixture, and then transesterifying using water and a catalytically active membrane consisting of a diffusion layer based on a polymer permeable to lower alcohols and glycerol, a connecting layer made of a porous polymer and a catalytically active layer formed by a lipolytic microorganism, the porous polymer selected from woven or non-woven materials h fibers of polyethylene, polypropylene, polytetrafluoroethylene, polyamide, while the specified mixture is brought into contact with the catalytically active layer of the membrane, and water with the diffusion layer of the membrane, after which the product of contacting the specified mixture with the catalytically active layer is subjected to evaporation to remove unreacted alcohol to obtain the target alcohol biodiesel, and the product of contacting water with a diffusion layer is divided into water and glycerin.