Preparation of low-nitrogen and high-quality bio-oil from microalgae catalytic pyrolysis with zeolites and activated carbon

To reduce the N content and prepare low-nitrogen and high-quality bio-oil from microalgae, the catalytic effects of different zeolite catalysts (HZSM-5, H beta, HY) and activated carbon (AC) were studied. Zeolite catalysts and AC could effectively remove nitrogen from bio-oil and prepare the bio-oil enriched BTX. Zeolite catalysts promoted hydmdeoxygenation and hydrodenitrogenation of volatiles from microalgae pyrolysis and generated a mass of water, particularly HY, which had the most abundant acid sites. The bio-oil with HY catalyst had the lowest N content (1.25 wt%) and the highest mono-aromatics selectivity. Compared with zeolites, AC had more abundant microcellular structure, andaccelerated the deoxygenation of volatiles to form CO2 rather than H2O. The denitrification strengths on volatiles was as follows: HY > AC>HZSM-5>H beta. Besides, the production of oil reduced and gas yields increased with temperature increasing, the outputs of aromatics reached maximum value at 500 degrees C. And the N content of bio-oil reduced with temperature increasing, the N content of bio-oil from Nannochloropsis sp. (NS) and Spirulina platensis (SP) catalytic pyrolysis decreased to 0.82 and 1.82 wt% at 700 degrees C. Compared with NS, the BTX from SP catalytic pyrolysis were more stable at higher temperature (700 degrees C).

Automated summary

The use of zeolite catalysts and activated carbon effectively reduces nitrogen content in bio-oil and produces high-quality bio-oil. The denitrification strength of zeolite catalysts and activated carbon on volatiles varies at different temperatures, affecting oil yield and quality.