(261b) Production of Light Olefins from Protein-Rich Microalgae By Hydrothermal Liquefaction and Sequential Catalytic Cracking

In recent years, biomass resources have gained increasing attention as sustainable feedstock for production of energy fuels and chemicals [1]. Algae is a very promising source as the third-generation biomass, following after the first-generation biomass (edible crops, sugars, and starches) and the second-generation biomass (inedible lignocellulose). Algal biomass can be converted into biofuels such as biogas, bioethanol, biodiesel, and bio-oils by anaerobic digestion, fermentation, gasification, liquefaction, pyrolysis, and so on [2]. Although hydrothermal liquefaction (HTL) is considered the most promising method for conversion of wet microalgae to often called â??bio-oilâ??, industrial viability of microalgae bio-oil production still has a lot of challenges to overcome [3]. In this study, we propose a unique method to produce light olefins such as ethylene, propylene, and butene from protein-rich microalgae.

Dry microalgae cells of Spirulina sp. was purchased from DIC LIFETEC Co., Ltd. (Tokyo, Japan). Spirulina sp. consisted of 4.7 wt% moisture, 6.1 wt% ash, 12.6 wt% carbohydrates, 7.8 wt% lipids, and 68.8 wt% protein. It contained 53.0 wt% C, 8.0 wt% H, 11.5 wt% N, 0.9 wt% S, and 26.6 wt% O (dry ash free). All other materials were purchased from commercial suppliers and used as received without any pretreatment or purification. Hydrothermal reaction experiments were carried out in a 100-mL hastelloy autoclave to obtain both water soluble and insoluble fractions. A fixed bed reaction system was used for catalytic cracking of water soluble fraction. The products were analysed using a gas chromatograph, high-performance liquid chromatographs, a total organic carbon analyser, a total nitrogen analyser, an elemental analyser, and etc. The yields of the products (mol%/C) were calculated based on the carbon content.

We demonstrated the hydrothermal liquefaction of Spirulina sp. at from 250 °C to 300 °C and sequential catalytic cracking using a HZSM-5 zeolite catalyst at 600 °C. We show that we obtained light olefins as major products along with aromatics and light alkanes as minor products in the presentation. The possible conversion pathways of carbohydrates, lipid, and protein to bio-oils in our system are also proposed. This research provides a useful production method of light olefins from protein-rich microalgae.

References

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[2] L. Brennan and P. Owende, Renewable & Sustainable Energy Reviews 2010, 14, 557-577.

[3] a) D. López Barreiro, W. Prins, F. Ronsse and W. Brilman, Biomass and Bioenergy 2013, 53, 113-127; b) Y. Guo, T. Yeh, W. Song, D. Xu and S. Wang, Renewable and Sustainable Energy Reviews 2015, 48, 776-790.