KR20100097543A - Process for producing biofuel from algae - Google Patents

Abstract

PURPOSE: A method for producing a biofuel using sea algae is provided to produce mixture alcohol at high yield using organic ingredient including protein and lipid. CONSTITUTION: A method for producing biofuel from sea algae comprises: a step of fermenting sea algae under anaerobic condition to obtain organic acid; a step of esterifying the organic acid to obtain ester; and a step of adding hydrogen to ester to obtain mixture alcohol. The fermentation is performed by culturing anaerobic microorganism in a medium composition containing inorganic salt. The sea algae are brown algae, red algae, or green algae. The mixture alcohol contains ethanol, propanol, and butanol.

Description

Process for producing biofuel from algae

The present invention relates to a method for producing biofuel using seaweed, and more particularly, to ferment algae under anaerobic conditions to obtain an organic acid and converting the obtained organic acid into mixed alcohol through esterification and hydrogenation. It relates to a method for producing biofuel.

Biofuel is a fuel obtained from biomass and includes not only living organisms but also metabolic byproducts such as animal excretion. Biofuel is also used to refer to a combination of bioalcohol and biodiesel.

Recently, as the problems of greenhouse effect and oil depletion due to global warming have emerged, interest in biofuels has been focused. Sugar cane juice or corn starch is used to produce bioethanol, which is typically used among biofuels. However, the raw materials face many problems, such as competition with food and livestock feed, saturation of the growing area.

In order to overcome this, research has been made on a method of producing energy from various biomass resources. In particular, algae (macroalgae) has a low lignin content, has a dense structure, is easy to process, exhibits high productivity per unit area (up to 700 tons / ha), and has great potential as an unexplored field compared to land resources. As a result, research is being conducted to produce natural fuel using the same.

Seaweeds are divided into green algae, brown algae, and red algae according to the color of the algae, and have a compositional characteristic as shown in Table 1 below.

Brown algae Red algae Green algae Representative species Seaweed, kelp, maternity Laver Blue, hearing Water content 75-90 wt% 70-80 wt% 70-85 wt% mineral 30-50 wt% 25-35 wt% 10-25% by weight carbohydrate
(chief ingredient) 30-50% by weight
(Alginate, fucoidan) 30-60 wt%
(Agar, carrageenan) 25-50% by weight
(Cellulose, starch) protein 7-15% by weight 7-15% by weight 10-15 wt% Fat 2-5% by weight 1-5% by weight 1-5% by weight

Korean Patent Laid-Open Publication No. 10-2008-113990 discloses a method for producing bioethanol through pretreatment of algae and saccharification and alcohol fermentation. However, the method does not have a high yield of ethanol, and organic components other than carbohydrates cannot be used as raw materials.

Recently, research on the application of anaerobic digestion processes applied to wastewater or organic waste treatment has been conducted. In particular, Japanese Laid-Open Patent Publication No. 2005-245443 discloses a method and apparatus for producing methane gas by anaerobic fermentation by microorganisms after heat treatment of algae and low molecular weight. Research into the technology to advance the development. However, the fermentation period is long, such as 15 to 25 days until the methane production, and there is a problem that close to 30% of the carbon component in the fermentation step from organic acid to methane is lost to CO ₂ and the like.

U.S. Patent No. 5,874,263 discloses a method of fermenting wood and herbaceous plants in an anaerobic environment to obtain an organic acid, and a method of converting the organic acid to alcohol through a hydrogenation reaction is known. In addition, US Pat. No. 7,351,559 shows a method of obtaining acetic acid through enzymatic digestion and fermentation followed by esterification and hydrogenation. However, wood, herb, etc. containing a large amount of lignin is not good for the production efficiency of organic acids, such as takes several months to break down and fermentation, competition with food and livestock feed, saturation of cultivated area is raised.

Therefore, the present inventors conducted and researched to develop a method for producing biofuel using algae, and as a result, fermented algae under anaerobic conditions to obtain an organic acid, esterification thereof, and hydrogenated reaction to obtain a mixed alcohol. By discovering, the present invention has been completed.

Therefore, an object of the present invention is to provide a method for producing biofuel using seaweed.

The present invention,

1) fermenting algae under anaerobic conditions to obtain an organic acid;

2) esterifying the organic acid to obtain an ester; And

3) adding hydrogen to the ester to obtain a mixed alcohol

Characterized by a method of producing a biofuel from algae comprising a.

Unlike the saccharification platform, the method of producing mixed alcohol according to the present invention has little limitation on the type of seaweed used, and does not require the development of a specific enzyme and also uses a high yield using all organic components such as proteins and fats other than carbohydrates. Mixed alcohols can be prepared. In addition, the present invention is excellent in productivity compared to the production of methane gas by conventional methane fermentation, and can generate more energy from the same biomass, it is expected to contribute significantly to the production of bio-energy utilizing water biomass in the future do.

The present invention relates to a method of fermenting algae under anaerobic conditions and producing biofuels of mixed alcohols through esterification and hydrogenation. The overall flow of the invention is shown briefly in FIG.

The algae used in the present invention is not limited to any kind, and may be used for all kinds of algae including green algae, brown algae, and red algae, preferably Laminaria and seaweed ( Undaria ). pinnatifida ), Sargassum fulvellum ), flirt ( Gracilaria verrucosa ), 톳 ( Hizikia fusiforme ) or Gelidium amansii .

Wood-based biomass is very hard because of the lignin contained in it, so it requires a separate pretreatment such as acid and alkali treatment, but since algae does not contain lignin, it can be processed immediately after a simple grinding process.

Fermenting the algae under anaerobic conditions produces organic acids by anaerobic digestion. Anaerobic digestion refers to a process of decomposing degradable organic matter in an oxygen-free state with little oxygen, and is finally converted to methane through hydrolysis and acid fermentation. Anaerobic digestion is currently being applied to recover methane as energy at the same time as wastewater or waste treatment, and in the present invention organic acid is obtained from seaweed using some of the commonly known anaerobic digestion processes.

The anaerobic microorganisms used in the anaerobic digestion of the present invention are not limited to specific microorganisms, and any anaerobic microorganism capable of producing an organic acid under anaerobic conditions may be used. Under anaerobic conditions, bacteria that hydrolyze organic matter and produce organic acids include Clostridium sp. And Acetobacterium woody. woodii ), Selenomonas rumintium ), Propionibacterium arabinosum arabinosum ), Butyribacterium methyltropycum methylotrophicum ) and Lactobacillus amylophilus are known.

The medium composition used for the cultivation of anaerobic microorganisms is used as a constituent of the cells, and preferably contains inorganic salts which play an important role in regulating the pH and osmotic pressure of the medium. More preferably, a medium composition containing ammonium salt, calcium salt, magnesium salt, sodium salt and the like is used.

By the anaerobic digestion, organic acids such as acetic acid, propionic acid, butyric acid are produced, and the distribution of the generated organic acids may vary depending on conditions such as pH, temperature, and type of seaweed used.

Anaerobic digestion produces organic acids and carbon dioxide and hydrogen together as by-products. In the case of generated hydrogen, impurities can be removed with an adsorbent such as activated carbon or zeolite or separated with high purity using an appropriate separator, and the separated hydrogen can be used in a hydrogenation reaction described later.

However, the methane production process in which the organic acid is decomposed into methane and water by the methane-producing bacterium after the production of the organic acid may proceed, but in the present invention, only the organic acid is converted into alcohol through esterification and hydrogenation. It is desirable to inhibit additive methane production. The methane production process can be inhibited by adding a methane fermentation inhibitor to the medium composition, the methane fermentation inhibitor may be used, such as iodoform (bromoform), bromoethanesulfonic acid (bromoethanesulfonic acid) have.

The organic acid produced by the above process includes carboxylic acids such as acetic acid, propionic acid, butyric acid and lactic acid, and acetic acid is the main product.

Esterification (esterification) process of converting the resulting organic acid to an ester is well known, and is made as shown in formula (1).

The esterification takes place in the liquid phase in the reactor and the equilibrium constant of the reaction is approximately 4.0. As the acid catalyst of the esterification reaction, sulfuric acid, methane sulfonic acid, acid ion exchange resin, zeolite and carbonic acid produced by dissolution of CO ₂ may be used. In addition, since the acid catalyst has an inorganic salt in the medium composition, the carboxylic acid produced by anaerobic digestion may be converted into a carboxylate salt, and thus separated into carboxylic acid to allow the esterification reaction to occur. It also plays a role.

The reaction rate of the esterification reaction is affected by the type and concentration of the catalyst, the reaction temperature, the degree of equilibrium shift, and the like, and the alcohol used for the esterification is not limited. However, it is preferable in terms of cost to separately separate and recycle high molecular weight alcohols of low value as biofuels among the mixed alcohols finally produced by the production method of the present invention.

The obtained ester is converted to alcohol by hydrogenation. The hydrogenation reaction is performed as in the following formula (2) in the presence of a catalyst.

The hydrogenation reaction may be carried out in a liquid phase or gas phase, it is preferably made at 150 ~ 250 ℃, 15 ~ 40 atm conditions. In addition, in the hydrogenation reaction, reduced copper oxide-zinc oxide (CuO / ZnO), copper-chromite, nickel, Raney nickel, ruthenium or Platinum is used, preferably copper oxide-zinc oxide, copper chromite, nickel, Raney nickel. In addition, when the reaction is performed in the liquid phase, it is preferable to use an alcohol solvent such as ethanol, and when the reaction is performed in the gas phase, it is preferable to vaporize the produced ester and react with hydrogen gas to lower the temperature to obtain a liquid alcohol. .

Hydrogen added in the hydrogenation reaction can be obtained by methods well known in the art such as partial oxidation of hydrocarbons, partial oxidation of coal or electrolysis of water. In the present invention, however, the algae may be fermented under anaerobic conditions to proceed with the addition of hydrogen generated in the step of obtaining an organic acid.

Finally, a mixed alcohol is produced by hydrogenation, and the mixed alcohol includes ethanol, propanol, butanol, pentanol, and many other alcohols. The resulting mixed alcohol is separated into low molecular weight alcohol and high molecular weight alcohol while passing through an alcohol separation column, and low molecular weight alcohols such as ethanol, propanol, butanol and pentanol, which are valuable as biofuels, are separated and used as fuel. Alcohol is preferably used as the alcohol required in the esterification reaction.

The esterification process, hydrogenation process and separation of the mixed alcohol is shown in FIG.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are intended to illustrate the present invention and do not limit the present invention.

[Example]

Example 1 Generation of Organic Acids

In order to check the degree of organic acid produced by anaerobic digestion of each seaweed, the experiment was carried out as follows. 1 g of seaweed with a dry weight of 1 g was added to a 250 mL Erlenmeyer flask, and 10 mL of an inorganic salt solution having a composition as shown in Table 2 and 10 mL of pH 6.0 1M phosphate buffer solution were added thereto. Grinded for minutes. At this time, using a sawdust with a dry weight of 1g as a comparative example was tested in the same manner as above.

The pulverized mixed solution was put back into the flask and aerated with nitrogen gas for 10 minutes to remove oxygen from the solution. After adding 10 mL of anaerobic digester sludge supernatant from Seongnam wastewater treatment plant, the total amount of acetic acid and acetic acid, propionic acid, butyric acid, lactic acid, etc. Was measured. The microorganism included as a dominant species in the sludge supernatant of the anaerobic digester used was Clostridium thermoaceticum , Clostridium formicoaceticum , Clostridium thermoautotropium ), Acetobacterium woodii and Selenomonas rumintium . The results of measuring the amount of organic acid produced are shown in Table 3 below.

ingredient Concentration (g / L) ingredient Concentration (g / L) NH ₄ HCO ₃ 20 Na ₂ MoO ₄ .2H ₂ O 0.1 KH ₂ PO ₄ 10 CaCl ₂ .2H ₂ O 0.1 MgSO ₄ .7H ₂ O One MnSO ₄ .7H ₂ O 0.15 NaCl 0.1 FeCl ₂ 0.028 Iodoform 0.1

1 day (g / L) 2 days (g / L) 3 days (g / L) Acetic acid Total organic acid Acetic acid Total organic acid Acetic acid Total organic acid Kelp 0.67 0.95 0.88 1.26 0.90 1.15 Seaweed 0.75 0.84 0.85 0.96 0.82 0.98 Flirt ND ND 0.34 0.44 0.67 0.92 Mother and child 0.12 0.12 0.29 0.34 0.35 0.50 톳 0.76 1.26 0.81 1.61 1.02 1.85 Kim ND ND 0.24 0.39 0.36 0.52 sawdust ND ND ND ND 0.01 0.02

In the experiment, algae were fermented under anaerobic conditions for 3 days to produce organic acids including acetic acid at high speed, but sawdust was confirmed that fermentation was hardly performed. This is because sawdust has a high lignin content and a dense tissue, so that the decomposition is relatively slow.

Example 2 Production of Organic Acids and Hydrogen by Anaerobic Digestion of Seaweeds in a Continuous Reactor

100 g of kelp (87% by weight of moisture, 14.7% of ignition loss) was pulverized finely with a blender, and then 100 mL of an inorganic salt solution having the composition of Table 2 was mixed, and distilled water was added so that the total volume was 900 mL. The mixed solution was placed in a 2L experimental fermentor (COBIOTECH) and then aerated for 10 minutes with nitrogen gas to remove oxygen from the mixed solution and the reactor. 100 mL of the anaerobic digester sludge supernatant of the Seongnam wastewater treatment plant used in Example 1 was added thereto, followed by stirring while stirring at 35 ° C. at 100 rpm. The pH in the reactor was maintained at 6.0 by adding 100 mM caustic soda solution. After 3 days of reaction, 200 mL of the reaction solution was removed every day, and 40 g of kelp and 20 mL of the inorganic salt solution of Table 2 were mixed and 200 mL of a feed solution made by adding distilled water was further added to the reactor.

The concentration of organic acid in the reaction solution and the volume of hydrogen generated in the reactor were measured from 10 days to 25 days after the start of showing stable results. The concentration of the organic acid containing acetic acid was measured by HPLC (Shimadzu), and the hydrogen production rate was also obtained by measuring the volume and hydrogen content of the generated gas using gas chromatography. The average and standard deviation of the measured values are shown in Table 4 below.

Item Average Standard Deviation Volatile Organic Concentration (g / L) ¹⁾ 22.2 Organic acid concentration (g / L) 10.5 2.3 Organic acid yield (%) ²⁾ 47.3 9.7 Organic acid formation rate (mmol / day) ³⁾ 38 7.5 Gas generation amount (mL / day) 880 93.1 Hydrogen content in gas (%) 60.5 7.2 Hydrogen production rate (mmol / day) 24 3.5 (mole hydrogen) / (mole organic acid) (%) ⁴⁾ 63.1 4.5

1) Kelp concentration in feed solution x (1-kelp moisture content) x (1-ignition loss)

2) (organic acid concentration) / (volatile organic substance concentration)

3) Calculation based on acetic acid (molecular weight 60)

4) (hydrogen generation rate) / (organic acid generation rate)

Example 3: Esterification and Hydrogenation of Organic Acids

After 10 days from the reaction in Example 2, 1L of the reaction solution was extracted from the reactor, placed in an esterification reactor, and reacted with alcohol to proceed with esterification. Hexanol was used as the alcohol.

After esterification of the reaction solution in which the organic acid is produced, hydrogenation is performed in an ethanol solvent. The hydrogenation reaction was performed by supplying hydrogen to an ester present in an ethanol solvent at 150 ° C. and 25 atm under a CuO / ZnO catalyst. Table 5 shows the amounts of organic acids in the organic acid reaction solution and the amount produced in each alcohol in the finally prepared mixed alcohol.

Organic Acid Used (g) Produced Mixed Alcohol (g) ethanol Propanol Butanol Pentanol Etc 10.5 4.2 0.6 1.2 0.1 0.2

Through the experiments, it was confirmed that the mixed alcohol production method according to the present invention can produce an alcohol that can be used as a fuel in high yield from seaweeds.

Figure 1 is a simplified schematic of the process from the algae to the mixed alcohol is produced.

Figure 2 shows the esterification process, hydrogenation process and separation of the mixed alcohol in the present invention.

Claims (9)

1) fermenting algae under anaerobic conditions to obtain an organic acid; 2) esterifying the organic acid to obtain an ester; And 3) adding hydrogen to the ester to obtain a mixed alcohol Method of producing a biofuel from algae comprising a. The method of claim 1, wherein the added hydrogen comprises hydrogen produced during the fermentation of step 1). According to claim 1 or 2, wherein the finally produced mixed alcohol is separated according to the molecular weight to extract the low molecular weight alcohol of ethanol, propanol, butanol and pentanol and the remaining high molecular weight alcohol in the esterification of step 2) Using the method. The method according to claim 1 or 2, wherein the fermentation of step 1) is performed by culturing anaerobic microorganisms in a medium composition containing inorganic salts. The method of claim 4, wherein the medium composition further comprises a methane fermentation inhibitor selected from iodine form, bromoform, bromoethanesulfonic acid. The method of claim 4, wherein the anaerobic microorganism is Clostridium thermoaceticum (Clostridium thermoaceticum), Clostridium formicoaceticum (Clostridium formicoaceticum), Clostridium thermoautotropium, Acetobacterium Acetobacterium woodii, Selenomonas rumintium, Propionibacterium arabinosum, Butyribacterium methylotrophicum and Lactobacillus amylophilus amylophilus amylophilus 1 or 2 or more microorganisms selected from the method. The method according to claim 1 or 2, wherein the algae are brown algae, red algae or green algae.  The method of claim 1 or 2, wherein the organic acid comprises acetic acid, propionic acid, butyric acid and lactic acid.  3. Process according to claim 1 or 2, wherein the finally produced mixed alcohol comprises ethanol, propanol and butanol.

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