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Energy & Fuels 2001, 15, 350-355
Co-liquefaction of Micro Algae with Coal Using Coal Liquefaction Catalysts Na-oki Ikenaga, Chiyo Ueda, Takao Matsui, Munetaka Ohtsuki, and Toshimitsu Suzuki* Department of Chemical Engineering, Faculty of Engineering, Kansai University, Suita, Osaka 564-8680, Japan Received June 12, 2000. Revised Manuscript Received November 28, 2000
Co-liquefaction of micro algae (Chlorella, Spirulina, and Littorale) with coal (Australian Yallourn brown coal and Illinois No. 6 coal) was carried out under pressurized H2 in 1-methylnaphthalene at 350-400 °C for 60 min with various catalysts. Co-liquefaction of Chlorella with Yallourn coal was successfully achieved with excess sulfur to iron (S/Fe ) 4), where sufficient amount of Fe1-xS, which is believed to be the active species in the coal liquefaction, was produced. The conversion and the yield of the hexane-soluble fraction were close to the values calculated from the additivity of the product yields of the respective homo-reactions. In the reaction with a one-to-one mixture of Chlorella and Yallourn coal, 99.8% of conversion and 65.5% of hexane-soluble fraction were obtained at 400 °C with Fe(CO)5 at S/Fe ) 4. When Littorale and Spirulina were used as micro algae, a similar tendency was observed with the iron catalyst. On the other hand, in the coliquefaction with Illinois No. 6 coal, which is known to contain a large amount of sulfur in the form of catalytically active pyrite, the oil yield in the co-liquefaction was close to the additivity of the respective reaction with Fe(CO)5-S, even at S/Fe ) 2. Ru3(CO)12 was also effective for the co-liquefaction of micro algae with coal.
Introduction Reduction of CO2, one of the greenhouse effect gases, in air is an important task. Fixation of CO2 by biomass, which is the only renewable organic energy source, through photosynthesis is considered to be one of the most promising methods. In general, the rate of CO2 fixation is very small, but recently fixing CO2 by cultivating micro algae with a high fixation rate is being investigated. However, biomass would be decomposed to CO2, H2O, and CH4 through microbacterial actions. Therefore, the development of the effective use of biomass is required. A large number of investigations on the conversion of biomass into fuel and chemical feedstock using liquefaction1-15 and gasification1,2,16-22 * Author to whom correspondence should be addressed. (1) Elliott, D. C.; Beckman, D.; Bridgwater, A. V.; Diebold, J. P.; Gevert, S. B.; Solantausta, Y. Energy Fuels 1991, 5, 399. (2) van Heek, K. H.; Strobel, B. O.; Wanzl, W. Fuel 1994, 73, 1135. (3) Yokoyama, S.; Ogi, T.; Koguchi, K. Sekiyu Gakkaishi 1985, 28, 239. (4) Yokoyama, S.; Ogi, T.; Koguchi, K. Sekiyu Gakkaishi 1986, 29, 262. (5) Yokoyama, S.; Ogi, T.; Koguchi, K.; Minowa, T. Sekiyu Gakkaishi 1989, 32, 21. (6) Yokoyama, S.; Ogi, T.; Dote, Y.; Minowa, T. Sekiyu Gakkaishi 1990, 33, 383. (7) Ogi, T.; Yokoyama, S. Sekiyu Gakkaishi 1993, 36, 73. (8) Yokoyama, S.; Kishimoto, M.; Okakura, T.; Minowa, T. Fuel 1995, 74, 1735. (9) Dote, Y.; Sawayama, S.; Inoue, S.; Minowa, T.; Yokoyama, S. Fuel 1994, 73, 1855. (10) Dote, Y.; Inoue, S.; Ogi, T.; Yokoyama, S. Biomass Bioenergy 1996, 11, 491. (11) Maldas, D.; Shiraishi, N. Biomass Bioenergy 1997, 12, 273. (12) Minowa, T.; Zhen, F.; Ogi, T.; Varhegyi, G. J. Chem. Eng. Jpn. 1997, 30, 186. (13) Minowa, T.; Zhen, F.; Ogi, T.; Varhegyi, G. J. Chem. Eng. Jpn. 1998, 31, 131. (14) Szabo, P.; Minowa, T.; Ogi, T. J. Chem. Eng. Jpn. 1998, 31, 571.
techniques have been reported. Yokoyama et al. reported a series of direct liquefactions of woody biomass and found that Na2CO3 was an effective catalyst in the presence of H2O at around 300 °C to give high oil yield.3-8 Dote et al. carried out liquefaction of Botryococcus braunii one of the micro algae, rich in hydrocarbons, under pressurized nitrogen using Na2CO3 in water for 60 min.9 A greater amount of oil than the content of hydrocarbons in B. braunii was obtained in the yield of 57-64% at 300 °C. Dote et al. reported the direct liquefaction of protein-containing biomass.10 They indicated that nitrogen-containing compounds from proteins were distributed into both the oil and aqueous phases and that nitrogen in the oil is very difficult to remove by hydrotreatment over nickel/molybdenum catalysts. Maldas et al. discussed the liquefaction of biomass in the presence of phenol and water using alkali.11 Minowa et at. decomposed woody biomass in hot-compressed water at around 300 °C and 10 MPa with and without Na2CO3.12-14 In our previous paper,15 we have reported that the liquefaction of micro algae Spirulina afforded more than 90% of THF-soluble products including gas and H2O and 60% of hexane-soluble fraction, in the reactions at 300(15) Matsui, T.; Nishihara, A.; Ueda, C.; Ohtsuki, M.; Ikenaga, N.; Suzuki, T. Fuel 1997, 76, 1043. (16) Rudiger, H.; Kicherer, A.; Greul, U.; Spliethoff, H.; Hein, K. R. G. Energy Fuels 1996, 10, 789. (17) Gil, J.; Aznar, M. P.; Caballero, M. A.; Frances, E.; Corella, J. Energy Fuels 1997, 11, 1109. (18) Wang, D.; Czernik, S.; Chornet, E. Energy Fuels 1998, 12, 19. (19) Dong, Y.; Borgwardt, R. H. Energy Fuels 1998, 12, 479. (20) Corella, J.; Orio, A.; Toledo, J.-M. Energy Fuels 1999, 13, 702. (21) Garcia, L.; Salvador, M. L.; Arauzo, J.; Bilbao, R. Energy Fuels 1999, 13, 851. (22) Marquevich, M.; Czernik, S.; Chornet, E.; Montane, D. Energy Fuels 1999, 13, 1160.
10.1021/ef000129u CCC: $20.00 © 2001 American Chemical Society Published on Web 01/25/2001
Co-liquefaction of Micro Algae with Coal
Energy & Fuels, Vol. 15, No. 2, 2001 351
Table 1. Elemental Analysis of Micro Algae and Coals micro algae
coal
Spirulina Chlorella Littorale Yallourn Illinois No. 6 C H O (diff) N S
46.1 7.4 41.4 4.8 0.4
47.3 7.2 37.6 8.2 0.7
35.5 5.4 53.1 6.0 -
67.2 4.8 27.3 0.5 0.2
79.7 5.4 10.3 1.4 3.3
protein fat fatty acid carbohydrate ash
57.5 12.0 1.0
