Feedstocks for fuels and chemicals from algae: Treatment of crude bio-oil over HZSM-5

Crude bio-oil produced from hydrothermal liquefaction of Nannochloropsis sp was reacted over HZSM-5 catalyst with high pressure H-2. The effects of reaction temperature (400-500 degrees C), reaction time (0.5-4 h), and catalyst loading (5-50 wt.%) on the composition and yields of the oil and gas products were determined. Treatment greatly reduced the heteroatom (N, O, and S) content in the oil. S was reduced to below detection limits (<0.1 wt.%) at all reaction conditions investigated. The lowest N/C ratio achieved is about 25% of the original N/C ratio in the crude bio-oil. The O/C ratio of the oil treated at 450 and 500 degrees C was an order of magnitude lower than that in the crude bio-oil. The carbon content of the oil increased at all reaction conditions investigated, but the H/C ratios of the oils treated at 450 and 500 degrees C fell below that of the crude bio-oil due to their high aromatic content and the migration of H atoms into the gaseous products. This study demonstrates the opportunities to engineer the composition of the products that emerge from this catalytic treatment of the crude bio-oil. Catalytic processing at 400 degrees C produced a paraffinic oil that was 95 wt.% C and H and retained 87% of the energy content of the crude bio-oil. This product would be useful as a feedstock for liquid transportation fuels. Catalytic processing at 500 degrees C, on the other hand, produced a freely flowing liquid mixture composed of aromatic hydrocarbons in 44 wt.% yield along with a hydrocarbon gas stream in 19 wt.% yield. These products, which could be useful as feedstocks for industrial chemicals, contained 70% of the carbon originally present in the crude bio-oil. (C) 2013 Elsevier B.V. All rights reserved.