METHOD FOR PRODUCING BIODIESEL FROM ALGAL LIPID WITH DIMETHYL CARBONATE

Abstract

The present invention relates to a method for renewable energy production using biomass, more specifically, method for producing eco-friendly biodiesel with algal lipid and dimethyl carbonate.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to method for renewable energy production using biomass, more specifically, method for producing eco-friendly biodiesel with algal lipid and dimethyl carbonate.

2. Description of the Related Art

Technology for renewable energy production has been developed using food resources or waste wood as biomass sources. In recent years, renewable energy technology utilizing algal lipid has been proposed.

Algae captures carbon dioxide from the atmosphere through photosynthesis and has ecological positive functions to remove pollutants of eutrophication causes such as nitrogen and phosphorus in water. In addition, it can be obtained easily from a variety of marine and terrestrial environments in large quantities. Therefore, algae is an important life resource in renewable energy technology, especially biodiesel production technology. Recently, the technology removing nutrients in the wastewater and simultaneously culturing algae has been suggested for biodiesel production.

Conventional production method of biodiesel, a mixture of fatty acid methyl ester (FAME), a biodiesel, uses methanol in the transesterification reaction of algal lipid and makes glycerol as byproduct, as shown in following [Chemistry FIG. 1].

However, as methanol and hydrophobic algal lipid are immiscible, reaction rate of the transesterification is slow. Since glycerol is not suitable for biodiesel, additional removal step is essentially necessary as well.

There was different technology using solvents such as tetrahydrofuranare, yet, the use of these solvents was not eco-friendly. On the other hand, biodiesel production utilizing dimethyl carbonate (DMC), a eco-friendly solvent, has the advantage of producing no glycerol. The detailed reactions are described as follows:

The present inventors have already disclosed an algae Ankistrodesmus gracilis cultured in wastewater such as urban sewage or industrial wastewater (Jangho Lee and Joonhong Park, Journal of Korean Society of Environmental Engineering, 33(5), 2011).

In order to overcome the said problems, new technology is desperately needed to replace the existing material methanol used in the transesterification reaction of the algal lipid.

SUMMARY OF THE INVENTION

Accordingly, the object of the present invention is to provide a method for producing biodiesel from algal lipid with dimethyl carbonate.

The above object of the present invention was achieved by extracting algal lipid with DMC and transesterification reaction of the algal lipid with DMC.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is GC chromatogram of biodiesel obtained by transesterification reaction of algal lipid with DMC.

FIGS. 2a-b is a result showing qualitative analysis (a) and quantitative analysis (b) of biodiesel produced in the present invention.

FIG. 3 is recovery efficiency of algal lipid by DMC.

FIGS. 4a-b is a result of biodiesel production depending on the concentration of DMC (a: low concentration, b: high concentration).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention relates to a method for biodiesel production with algal lipid and dimethyl carbonate (DMC). As DMC, an eco-friendly solvent, is hydrophobic than methanol, hydrophobic algal lipid could be better mixed with DMC than with methanol. Additionally, DMC could be employed for lipid extraction from algal biomass instead of conventional organic solvents such as n-hexane. Due to said properties, the present invention has the advantage of increase in the reaction rate of transesterification for biodiesel production from algal lipid.

Algal biomass could be mixed with DMC by the ratio of 1:2 to 1:100 (g/mL) for extracting algal lipid. Preferably, the mixture ratio of biomass:DMC is 1:20 (g/mL).

Algal resources for the present invention are capable of being cultured in wastewater having high lipid content. More specifically, the algal resources could be selected from the genus Ankistrodesmus, the genus Scenedesmus, the genus Chlorella, the genus Anabaena, the genus Oscillatoria, the genus Botryococcus, the genus Neochloris, the genus Tetraselmis, the genus Porphyridium, the genus Phaeodactylum, the genus Nannochloropsis, the genus Ellipsoidion, the genus Isochrysis, the genus Pavlova, the genus Thalassiosira, the genus Skeletonema, the genus Chlorococcum, the genus Dunaliella, the genus Aphanizomenon, the genus Haematococcus, the genus Crypthecodinium and the genus Shizochytrium.

Hereinafter, the present invention will be described by the following examples in more detail. However, such examples are only to illustrate the invention and they do not restrict the present invention.

Example 1

Extraction and Transesterification Reaction of Algal Lipid with DMC

Ankistrodesmus gracilis SAG278-2 cultured in wastewater was utilized to extract algal lipid.

Fatty acid methyl esters (FAMEs) obtained from conventional 2-steps production process, which was hexane extraction/methanol transesterification, and the present invention, which was DMC extraction/DMC transesterification, were analyzed by Gas Chromatography (GC)-Flame Ionized Detector (FID).

The biomass 0.5 g of Ankistrodesmus gracilis SAG278-2 was finely chopped using a mortar. In order to extract the algal lipid, 10 mL of DMC was added into the above chopped algae and then mixed thoroughly for 2 hours. The mixture ratio of the biomass:DMC was 1:20 (g/mL). After adding 0.6% of H₂SO₄ (DMC:H₂SO₄, v/v) into DMC phase obtained from said extraction step, the DMC phase was reacted for 8 hours at 75° C. and then it was neutralized by pH 7.5 with 1M NaOH. To remove water left in the DMC phase, 3 g of Na₂SO₄ was added, and salt and residual sediment formed were filtered with Filter paper (Whatman No. 41). After evaporating DMC left, the algal biodiesel 0.194 g was obtained.

As shown in FIG. 1, glycerol carbonate and glycerol dicarbonate as byproducts were produced by transesterification reaction of the algal lipid with DMC. This indicated that the eco-friendly solvent DMC was effective in transesterification reaction.

FIGS. 2a and 2b represent FAMEs composition and those quantitative analysis, respectively. Compared the DMC biodiesel to the conventional methanol biodiesel, FAMEs composition of the DMC biodiesel was similar to the composition of the methanol biodiesel, showing comparable properties of both biodiesels (FIG. 2a).

Meanwhile, the conventional methanol biodiesel produces glycerol as byproduct in the transesterification reaction so that the glycerol needs to be separated and refined. However, glycerol carbonate and glycerol dicarbonate obtained from the transesterification reaction of algal lipid by DMC increased the yield of FAMEs without significant changes in biodiesel properties (FIG. 2b).

That is, the present invention found that the eco-friendly DMC could be applicable to not only algal lipid extraction but also transesterification reaction. Therefore, biodiesel produced from algal lipid with DMC has effects of more eco-friendly and fast production process compared to the conventional methanol biodiesel.

Example 2

Test of Lipid Content by DMC Extraction

To examine the lipid content by DMC extraction, Chlorella vulgaris AG10032 was used to extract the algal lipid. 1 g freeze-drying biomass of said algae was mixed with 10 mL DMC or hexane and then extracted for 2 hours.

As shown in FIG. 3, lipid content of the biomass was 6.84% for hexane extraction and 5.72% for DMC extraction. As a result, the solvent DMC showed a comparable effect with the solvent hexane which is one of available lipid extracting solvents.

Example 3

Test of Transesterification Rate of Algal Lipid by DMC

Using the above algae Chlorella vulgaris AG10032, the yield of DMC biodiesel was examined in time dependent manner. For this example, the conventional method used hexane for lipid extraction and methanol for the transesterification reaction.

As shown in FIG. 4a, the yield of the two types of biodiesel had no significant difference depending on the time at low concentration of catalyst (1.25%) even though the yield of methanol biodiesel was high at 5 min and the yield of DMC biodiesel was high at 30 min. However, as shown in FIG. 4b, the biodiesel yield appeared distinctly at high concentration of catalyst (2.5%). That is, methanol biodiesel showed high yield at 5 min yet DMC biodiesel had high yield at 30 min. Consequently, it was revealed that transesterification rate of the DMC biodiesel was slower than the rate of the methanol biodiesel within the initial 5 min, however faster within 30 min after 5 min as the reaction was completed.

Claims

1. A method for producing biodiesel from algal lipid with dimethyl carbonate.

2. The method of claim 1, wherein the algal lipid is extracted from an algae with dimethyl carbonate.

3. The method of claim 1, wherein the biodiesel is made by transesterification reaction of algal lipid and dimethyl carbonate.

4. The method of claim 2, wherein the algae is cultured in wastewater.

5. The method of claim 2, wherein the algae is selected from the genus Ankistrodesmus, the genus Scenedesmus, the genus Chlorella, the genus Anabaena, the genus Oscillatoria, the genus Botryococcus, the genus Neochloris, the genus Tetraselmis, the genus Porphyridium, the genus Phaeodactylum, the genus Nannochloropsis, the genus Ellipsoidion, the genus Isochrysis, the genus Pavlova, the genus Thalassiosira, the genus Skeletonema, the genus Chlorococcum, the genus Dunaliella, the genus Aphanizomenon, the genus Haematococcus, the genus Crypthecodinium and the genus Shizochytrium.

6. The method of claim 2, wherein the algal lipid is extracted by the mixture ratio of algal biomass:dimethyl carbonate=1:20 (g/mL).

7. A biodiesel without glycerol, produced according to the method of claim 1.