(349b) Conversion of Algal and Duckweed Biomass to Liquid Fuels Through Catalytic Fast Pyrolysis

Microalgae and duckweed constitute a potentially viable alternative for replacing fossil fuels, given their economic and environmental benefits.  In this study fast pyrolysis of microalgae was studied to generate a third-generation bio-fuel, with the goal of producing a stable liquid fuel that has acceptable energy content and composition.  The impacts of the relevant process variables on the pyrolysis of microalgae and duckweed process were studied in detail.  The pyrolysis reactions were carried out in out in a continuous fixed bed reactor in which an auger screw feeder was used to feed biomass particles into the hot reaction zone set at a prescribed temperature.  Product vapors were condensed and collected for analysis employing a GCMS and elemental analyzer, while the post-condenser gas phase was evaluated by a combination of FTIR, GC, and FID.  The yields and chemical species distribution were shown to be dependent on both the feedstock type primarily and the pyrolysis processing conditions secondarily.  The analyses reveal that the pyrolytic liquid has a large fraction of oxygenated compounds which undermine the liquid chemical stability.  To this end, upgrading of the bio-oil is necessary to improve stability and the heating value.  Pyrolysis coupled with catalytic upgrading was utilized to achieve a pyrolitic oil with improved properties.  Several metal-exchanged MFI framework zeolites (e.g. Fe-ZSM-5, Cu-ZSM-5 and Ni-ZSM5) and H-ZSM-5 were compared in terms of the enhancement in the stability.  The catalyst performance studies showed an increase in the fraction of hydrocarbons and decrease of oxygenates, with H-ZSM-5 having the best performance.  Notably, this catalyst produce a higher bio-oil fraction compared to the other zeolites and, also, exhibited the least coking.  The effects of biomass weight hourly space velocity, and the comparison between zeolite powder and monolithic catalysts (i.e. synthesized with one or more layers of washcoated films containing the active catalyst) will also be presented.