KR101547287B1 - Process for producing biofuel from algae - Google Patents

Abstract

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

The method of producing mixed alcohol according to the present invention is not limited to the kind of seaweed used, unlike the glycation platform, and does not require the development of specific enzymes. In addition, it can be produced at high yields using all organic components such as proteins and fats other than carbohydrates Mixed alcohol can be produced. Further, the present invention is superior to methane gas production by methane fermentation in the past and can generate more energy from the same biomass, and thus can contribute greatly to the production of bioenergy using marine biomass in the future do.

Algae, anaerobic digestion, esterification, hydrogenation

Description

TECHNICAL FIELD The present invention relates to a process for producing biofuel using algae,

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

Biofuel is a fuel from biomass that contains all the byproducts of living organisms as well as metabolic activities such as animal feces. However, biofuel is also used as a combination of bio-alcohol and biodiesel.

Recently, the problem of greenhouse effect and oil depletion caused by global warming is growing, and attention is focused on biofuels. Sugarcane juice or corn starch is used for the production of bioethanol which is typically used as biofuels. However, the above-mentioned raw materials have faced many problems such as competition with food and livestock feed, saturation of cultivation area, and the like.

In order to overcome this, research is being conducted on methods of producing energy from various biomass resources. In particular, macroalgae has a low lignin content and has an unclassified structure, which facilitates its treatment, exhibits high productivity per unit area (up to 700 tons / ha.) And has great potential as an untapped area compared to land resources. Research has been carried out to produce natural fuels by using them.

Seaweeds are classified into green algae, brown algae, and red algae according to their appearing color, and have the composition characteristics shown in Table 1 below.

Brown algae Red algae Green algae A representative species Seaweed, seaweed, mackerel Kim, ukagasari Parasitic, auditory Moisture content 75-90 wt% 70-80 wt% 70-85 wt% mineral 30-50 wt% 25-35 wt% 10-25 wt% carbohydrate
(chief ingredient) 30-50 wt%
(Alginate, fucoidan) 30-60 wt%
(Agar, carrageenan) 25-50 wt%
(Cellulose, starch) protein 7-15 wt% 7-15 wt% 10-15 wt% Fat 2-5 wt% 1-5 wt% 1-5 wt%

Korean Patent Laid-Open No. 10-2008-113990 discloses a method of pretreating seaweeds and producing bioethanol through saccharification and alcohol fermentation. However, the above method has a problem that the yield of ethanol is not high, and organic components other than carbohydrates can not be used as a raw material.

Recently, researches are being conducted on the application of anaerobic digestion process applied to wastewater or organic waste treatment. In particular, Japanese Patent Application Laid-Open No. 2005-245443 discloses a method and apparatus for producing methane gas by anaerobic fermentation by microorganisms after heat treatment of seaweeds to make them low in molecular weight. Research on the development of technology is underway. However, there is a problem that the fermentation period is long to 15 to 25 days until methane gas generation, and that 30% of the carbon components are lost by CO ₂ or the like in the fermentation step from organic acid to methane.

U.S. Patent No. 5,874,263 discloses a method for obtaining organic acids by fermenting woody and herbaceous plants in an anaerobic environment, and a method of converting the organic acids into alcohols through hydrogenation is known. In addition, U.S. Patent No. 7,351,559 discloses a method of obtaining acetic acid through enzymatic degradation and fermentation of grains, followed by ethanolation through esterification and hydrogenation. However, the production efficiency of organic acids such as woody, herbaceous and the like, which takes a few months to decompose and ferment, is not good, and competition with food and livestock feed and saturation of growing area arise.

Accordingly, the present inventors have made efforts to develop a method for producing biofuel using seaweeds. As a result, they have found that algae can be fermented under anaerobic conditions to obtain an organic acid, which can be esterified and hydrogenated to obtain a mixed alcohol The present invention has been completed by finding out.

Accordingly, it is an object of the present invention to provide a method for producing biofuel using seaweeds.

According to the present invention,

1) fermenting seaweed 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

And a method for producing biofuel from seaweed containing the same.

The method of producing mixed alcohol according to the present invention is not limited to the kind of seaweed used, unlike the glycation platform, and does not require the development of specific enzymes. In addition, it can be produced at high yields using all organic components such as proteins and fats other than carbohydrates Mixed alcohol can be produced. Further, the present invention is superior in productivity to methane gas production by conventional methane fermentation, and can produce more energy from the same biomass, and thus can contribute greatly to the production of bioenergy utilizing aquatic biomass in the future do.

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

Algae used in the present invention is not to be limited to their kinds are green algae, brown algae, can be used with all kinds of algae containing red algae, preferably seaweed in (Laminaria), wakame (Undaria pinnatifida ), moth ( Sargassum fulvellum ), corn ( Gracilaria verrucosa , Hizikia fusiforme or Gelidium amansii .

In the case of woody biomass, it is very hard due to the lignin contained in it. It requires acid pretreatment such as acid treatment, but since seaweed does not contain lignin, it can be treated immediately after a simple grinding process.

When the algae are fermented under anaerobic conditions, organic acids are produced by the anaerobic digestion process. Anaerobic digestion is the process of decomposing degradable organic matter in anaerobic conditions with little oxygen, and is finally converted to methane after hydrolysis and acid fermentation. At present, anaerobic digestion is applied to recover methane as energy at the same time as wastewater or waste treatment. In the present invention, organic acid is obtained from seaweeds using a part of a conventional anaerobic digestion process.

The anaerobic microorganisms used in the anaerobic digestion of the present invention are not limited to specific microorganisms and all anaerobic microorganisms capable of producing organic acids under anaerobic conditions can be used. In anaerobic conditions, the organisms that hydrolyze organic materials and produce organic acids include Clostridium sp., Acetobacterium wood woodii), Selena Nomo eggplant rumin tium (Selenomonas rumintium), propionic sludge tumefaciens arabinose breath (Propionibacterium a arabinosum), butynyl ribak teryum methyl trophy glutamicum (Butyribacterium methylotrophicum , Lactobacillus amylophilus , and the like.

The medium composition used for culturing the anaerobic microorganism is preferably used as a constituent component of the microorganism and includes inorganic salts which have an important function for controlling the pH and osmotic pressure of the medium. More preferably, a medium composition containing an ammonium salt, a calcium salt, a magnesium salt, a sodium salt and the like is used.

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

Along with the generation of organic acids by anaerobic digestion, carbon dioxide and hydrogen are also produced as byproducts. In the case of hydrogen generated, impurities can be removed with an adsorbent such as activated carbon or zeolite, or it can be separated at a high purity by using a suitable separation membrane. The separated hydrogen can be used for the hydrogenation reaction described later.

However, the methane generation process in which the organic acid is decomposed into methane and water by the methane-producing bacteria after the formation of the organic acid may proceed. In the present invention, however, only the organic acid is converted into alcohol through esterification and hydrogenation, It is desirable to inhibit the volatile methane production process. The methanogenesis process may be inhibited by adding a methane fermentation inhibitor to the medium composition, and the methane fermentation inhibitor may be iodoform, bromoform, bromoethanesulfonic acid, or the like. 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 becomes the main product.

The esterification process for converting the resulting organic acid into an ester is widely known and is represented by the following general formula (1).

The esterification consists of a liquid phase in the reactor, and the equilibrium constant of the reaction is approximately 4.0. As the acid catalyst for the esterification reaction, sulfuric acid, methane sulfonic acid, acid ion exchange resin, zeolite, carbonic acid produced by dissolution of CO ₂ and the like can be used. In addition, since the acid catalyst is capable of converting a carboxylic acid formed by anaerobic digestion into a carboxylate salt due to the presence of an inorganic salt in the culture medium, the acid catalyst is separated into a carboxylic acid, 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 migration, and the type of the alcohol used for the esterification is not limited. However, it is preferable from the viewpoint of cost to separate and recycle the high molecular weight alcohol which is low in value as a biofuel among the mixed alcohol finally produced by the production method of the present invention.

The obtained ester is converted into an alcohol by hydrogenation. The hydrogenation reaction is carried out in the presence of a catalyst according to the following general formula (2).

The hydrogenation reaction may be carried out in a liquid phase or a gas phase, and is preferably carried out at 150 to 250 ° C under a pressure of 15 to 40 atm. Also, in the above hydrogenation reaction, there may be used a catalyst such as reduced copper oxide-zinc oxide (CuO / ZnO), copper-chromite, nickel, Raney nickel, ruthenium, Platinum is preferably used, and copper oxide-zinc oxide, copper-chromium oxide, nickel and Raney nickel are preferably used. When the reaction is carried out in the liquid phase, it is preferable to use an alcohol solvent such as ethanol. In the case where the reaction is carried out in the gas phase, the produced ester is preferably vaporized and reacted with hydrogen gas, and then the temperature is lowered 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. However, in the present invention, it may be carried out by adding hydrogen generated in the step of fermenting seaweeds under anaerobic conditions to obtain an organic acid.

Finally, a mixed alcohol is produced by the hydrogenation reaction, and the mixed alcohol includes ethanol, propanol, butanol, pentanol, and a large number of alcohols. The resulting mixed alcohol is separated into a low molecular weight alcohol and a high molecular weight alcohol while passing through an alcohol separation column. The low molecular weight alcohol of ethanol, propanol, butanol and pentanol, which are valuable as biofuel, The alcohol is preferably used as an alcohol required for the esterification reaction.

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

Hereinafter, the present invention will be described in more detail with reference to examples, but the following examples are for illustrative purposes only and are not intended to limit the present invention.

[Example]

Example 1: Production of organic acid

In order to confirm the organic acid production by anaerobic digestion of each seaweed, the following experiment was carried out. Add 1 g of dried seaweed to a 250 mL Erlenmeyer flask, add 10 mL of the inorganic salt solution and 10 mL of pH 6.0 1M phosphate buffer solution as shown in Table 2 below, make a final volume of 100 mL with distilled water, and mix with 1 Minute. At this time, as a comparative example, sawdust having a dry weight of 1 g was used and the same experiment as above was carried out.

The pulverized mixed solution was again put into a flask and aerated with nitrogen gas for 10 minutes to remove oxygen in the solution. The total amount of total organic acids, including acetic acid, acetic acid, propionic acid, butyric acid, lactic acid, etc., produced by culturing in an agitation incubator adjusted at 100 rpm at 35 ° C for 3 days after adding 10 mL of the supernatant of anaerobic digestion sludge of Seongnam wastewater treatment plant Were measured. The microorganisms contained in the sludge supernatant of the used anaerobic digestion tank as a dominant species include Clostridium thermoaceticum , Clostridium formicoaceticum , Clostridium thermoautotropium ), Acetobacterium woodii , and Selenomonas rumintium . The results of measurement of the amount of the produced organic acid 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 Kokishigare ND ND 0.34 0.44 0.67 0.92 Moth 0.12 0.12 0.29 0.34 0.35 0.50 Top 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 above experiment, algae were fermented under anaerobic condition for 3 days to produce organic acid containing acetic acid at a high rate, but sawdust showed almost no fermentation. This is because sawdust has a high content of lignin and is dense in structure and relatively slow in decomposition.

Example 2: Production of organic acids and hydrogen by anaerobic digestion of seaweeds in a continuous reactor

100 g of kelp (moisture content 87% by weight, ignition loss 14.7%) was crushed finely with a blender and mixed with 100 mL of an inorganic salt solution having the composition shown in Table 2, followed by distilled water to make a total volume of 900 mL. The mixed solution was placed in a laboratory fermenter (Kobiotec) having a volume of 2 L and then aerated with nitrogen gas for 10 minutes to remove the mixed solution and oxygen in the reactor. 100 mL of the supernatant of anaerobic digestion sludge of the Seongnam wastewater treatment plant used in Example 1 was added and the reaction was carried out at 35 ° C with stirring at 100 rpm. The pH in the reactor was maintained at 6.0 by the addition of 100 mM caustic soda solution. After 3 days from the reaction, 200 mL of the reaction solution was removed per day, and 200 mL of a feed solution prepared by mixing 40 g of kelp and 20 mL of the inorganic salt solution of Table 2 and 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 after 10 days from the start of the stable result to 25 days. The concentration of organic acid including acetic acid was measured by HPLC (Shimadzu), and the volume and hydrogen content of the generated gas were measured by gas chromatography to obtain hydrogen production rate. The mean and standard deviation of the measured values are shown in Table 4 below.

Item Average Standard Deviation Volatile organic substance 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 production rate (mmol / day) ³⁾ 38 7.5 Gas production (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 - water content of kelp) x (1 - ignition loss)

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

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

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

Example 3: Esterification and Hydrogenation of Organic Acids

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

After the esterification reaction of the reaction liquid in which the organic acid is formed, the hydrogenation reaction proceeds in an ethanol solvent. The hydrogenation was carried out 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 amount of organic acid in the organic acid reaction solution and the amount of each alcohol in the finally produced mixed alcohol.

The organic acid used (g) The resulting mixed alcohol (g) ethanol Propanol Butanol Pentanol Etc 10.5 4.2 0.6 1.2 0.1 0.2

Through the above experiments, it was confirmed that the method of producing a mixed alcohol according to the present invention can produce alcohols which can be used as a fuel at a high yield from seaweeds.

FIG. 1 is a schematic diagram illustrating a process from algae to the generation of mixed alcohol.

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

Claims (9)

1) fermenting seaweed 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 ≪ RTI ID = 0.0 > 1. ≪ / RTI > 2. The method of claim 1, wherein the added hydrogen comprises hydrogen produced in the fermentation process of step (1). 3. The method 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 is subjected to the esterification Lt; / RTI > The method according to claim 1 or 2, wherein the fermentation in step 1) is carried out by culturing the anaerobic microorganism in a culture medium containing inorganic salts. 5. 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 selected from the group consisting of Clostridium thermoaceticum, Clostridium formicoaceticum, Clostridium thermoautotropium, But are not limited to, Acetobacterium woodii, Selenomonas rumintium, Propionibacterium arabinosum, Butyribacterium methylotrophicum and Lactobacillus amylophilus. , Wherein the microorganism is one or more microorganisms. The method according to claim 1 or 2, wherein the algae are brown algae, red algae or green algae.  The method according to claim 1 or 2, wherein the organic acid comprises acetic acid, propionic acid, butyric acid and lactic acid.  3. The process according to claim 1 or 2, wherein the finally produced mixed alcohol comprises ethanol, propanol and butanol.

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